Sepor, Inc. began business in 1953 with the introduction of the Sepor Microsplitter , a Jones-type Riffle splitter, developed by geologist Oreste Ernie Alessio for his own use in the lab. Sepor grew over the next several decades to offer a complete line of mineral analysis tools, as well as pilot plant equipment for scaled operations.
This flowchart made of machinery icons explains or expresses in simple but clear terms the step of theCopper Mining and Copper Extraction Process. Starting from either open-pit or underground mining and using a different relevant treatment method for oxide or sulphide copper mineral (ore).
Havinga quick look now at how porphyry ores are treated and the metals extracted. There are two main process streams; one for sulfide ores and the other for ore that is being weathered to oxidize sulfides the so-called oxide ores. All ore in the pit is drilled and blasted and loaded into trucks and hauled for treatment if the ore is un-oxidized sulfidic ore then it needs to be crushed and milled to a fine slurry then it gets past through flotation cells in a concentrator to separate and concentrate the sulfides. The top picture shows the interior of a large concentrator with rows of individual flotation cells the floatation agent is added to the slurry and stirred. The floatation agent preferably sticks to the sulfide minerals rather than the waste minerals and then air is bubbled through the mixture and the floatation agent traps the fine bubbles which carry the sulfides to the surface of the cell where they are carried over aware and separated. From there they are dried to provide a concentrate which then goes on to a smelter. This is the same process for both copper and molybdenum porphyries. The smelter is basically a large furnace which melts the concentrate and drives off the sulfide to leave molten copper metal this is still contains impurities and it needs to be refined further to make it a salable product.
Returning to the overall process; that is the process for the sulfide ores and the oxide ore as I said are treated differently. Direct from the pit the oxide ore is piled onto large lined leach pads and the sulfuric acid. The top photo shows one of these leach pads with the new thick black plastic liner visible on the right of the pad. The copper oxide minimum minerals are dissolved by the acid to give a blue copper rich solution mainly of copper sulfate. This solution is tapped off from the bottom of the pad and placed into big tanks with steel plates an electrical current is passed from the tank to the steel which is then electroplated with pure copper. This process as the advantage of avoiding the smelting and refining stages required for sulfide ores.
As we look to the future, the mining industry faces a myriad of challenges. While demand for metals like copper, cobalt, lithium and iron ore is projected to reach record highs by 2050, ore grades are decreasing, orebodies are becoming more complex, and fewer tier 1 deposits are being discovered.
As metal prices increase, lower-grade orebodies are becoming economically feasible. But, with lower grades come higher tonnages to sustain production. Processing these deposits requires ever finer grinding for mineral liberation and significant flotation residence times. Lower grades mean that quantities of tailings and mine waste generated are also increasing. And, for many operations, their management is now a significant liability.
In many countries, water scarcity is a big constraint, and specific energy consumption and carbon emissions are rising as grades decrease; points that are at growing odds with mining companies efforts in improving their environmental, social and governance (ESG).
Given this backdrop, its pertinent to ask whether traditional beneficiation techniques like flotation, which have been a staple part of mineral processing circuits for more than 100 years and can, in some instances, be water, energy and time intensive, still serve the industrys needs?
Its not just flotation; mineral processing as a whole faces increased challenges, said Paolo Donnini, principal process engineer at SNC-Lavalin. We need to be smarter in how we go about extracting metals and minerals using less energy, smaller equipment, lesser footprints, less concrete everything really, he said.
Dr. Chris Anderson, specialist process engineer, and Marc Richter, AEM regional director for minerals processing at Hatch, agreed. Sustainable and effective changes in mining practices are essential to enable progress in value chain efficiencies, while recognizing the obligations to other important factors such as climate change, Richter said.
At a macro-level, efficiency in flotation can be driven using holistic engineering approaches. For example, Hatch offers two solutions Mine to Mill and Grade Engineering that aim to increase the overall efficiency of mineral processing operations, inclusive of flotation.
Richter explained: Mine to Mill is a consolidated approach focusing on optimizing mining operations across the value chain with a specific focus on mining (run-of-mine fragmentation), comminution and separation. Optimizing each stage in isolation can result in sub-optimal performance of the overall operation and reduce profitability. To get the best results, each stage is optimized considering the preceding and subsequent stages.
This approach increases plant throughput, reduces energy consumption and operating costs, and improves process efficiency. It can be applied to greenfield projects or business improvement initiatives on existing assets. Typical projects see noticeable throughput benefits with a short payback time.
In December 2020, Hatch announced it would commercialize Grade Engineering, an integrated and methodical approach for assessing the viability and implementation of coarse separation options in preconcentration.
Grade Engineering is designed to reject low-value material early in the extraction value chain to provide high-quality feed, Richter said. By reducing uneconomical material early in the process and improving the quality of the processed ore, Grade Engineering improves overall metal production and reduces water and energy intensities, while minimizing wet tailings.
Anderson added: Through Grade Engineering, we have worked with several clients to develop coarse particle flotation (CPF) circuits aimed at reducing energy consumption in comminution, while ensuring liberation of the valuable metals in the deposit. These projects included evaluating options for the recovery of coarse valuable-bearing composites in the primary grinding circuit and early gangue rejection; and recovery of coarse value-bearing composites lost to conventional flotation tailings.
In the right applications, CPF can offer a reduction in energy demand in preceding comminution stages, increased production rates, and result in coarser tailings streams, which are easier to handle and more geotechnically stable.
The limitations of conventional flotation cells can be overcome through the use of fluidized-bed flotation machines, like Eriezs HydroFloat, which are specifically engineered for the selective recovery of feeds containing very coarse particles. However, the coarsest particle size that can be floated will depend on the liberation of the valuable mineral.
Were also currently implementing a project in North America to install Woodgrove Staged Flotation Reactors (SFR) in a cleaner-scalper application, and several projects looking at Eriez StackCells as a retrofit to either a pre-rougher or rougher application where the client is seeking additional residence time in a constrained footprint, Anderson said.
Conventional flotation cells are known to be relatively inefficient in terms of promoting particle-bubble contacting. However, the historical approach is to compensate by adding a scale-up factor to the residence time obtained through bench-scale tests. This approach is increasingly limited in circuits, which are fine grained, requiring long residence times and complex cleaning circuits to achieve the necessary grade.
Technologies such as the Jameson cell and column cell have been substantially improved over the past 20 to 30 years and are increasingly viewed as mature technologies. The Jameson cell in particular can be used to develop compact full-plant solutions, which offer some attractive advantages. Newer technologies such as the Woodgrove SFR and Direct Flotation Reactor (DFR) cell are also gaining interest in large-scale installations.
The Eriez HydroFloat cell is seeing significant interest in coarse particle rejection applications in copper and PGMs (more on this later). If successful, CPF may eventually become a standard in flotation applications where gangue can be liberated at coarse sizes (~500 microns). Other technologies such as the NovaCell are also gaining traction in this space.
Anderson explained: Our role is to help the client through the process development and bring newer technologies into consideration as early as possible, particularly in the conceptual and prefeasibility phases.
Columns and Jameson cells can be simulated using traditional batch flotation tests and HydroFloat performance can be inferred based on mineralogy and liberation information. Ultimately, pilot-scale test work must be performed. However, the information derived from early mineralogy and bench-scale tests can be used for trade-off studies to focus in on high-value alternatives.
I think low-footprint technologies such as Jameson cells and Woodgrove cells may prove disruptive as they allow substantial throughputs with a low footprint. In the long term, these technologies may find applications closer to the mining face, especially for underground applications.
Like Richter and Anderson, Donnini has noticed a growing interest in novel flotation technologies over the past five years and, more importantly, a willingness from mining companies to consider their applicability and economic feasibility.
Were starting to dissect flotation, he said. Rather than trying to create huge cells of 500 cubic meters (m3) or more, vendors like Woodgrove and Eriez are trying to get greater efficiencies from smaller cells. And theyre doing that by looking at the fundamentals of flotation. For example, Woodgroves SFR splits the flotation process into three stages contacting, separation, and then removal of the froth and tails. Rather than looking at flotation as a macro process, its being looked at more closely as a micro process.
Likewise, classically in flotation, we try to embrace the whole particle size distribution of the feed material. But with technologies like Eriezs HydroFloat, theyre suggesting that we narrow the particle-size distribution to create more efficiency. Its a much more elegant, accurate and precise approach to the process.
With CPF, you dont have to grind the ore to the fine endpoint thats required for conventional flotation technology, he explained. You can separate ore from gangue at a size that is roughly twice the size of conventional technology. Which means you dont have to over grind and you dont have to waste any energy, which is very expensive. Also, mines dont have to worry about storing tailings that are very fine and unstable the material can be easily dewatered and you can reduce conventional flotation capacity as well.
It depends upon the ore and its density but, for copper, which were really focusing on, you get an acceptable recovery in conventional flotation up to about 120 or 130 microns. Certainly, it drops off before 200 microns.
With CPF, you can usually take that up to 400 microns, which reduces the amount of grinding needed by half. In grinding, the amount of energy required increases disproportionately as the material becomes finer the finer the material being ground, the more energy is required which is why ultra-fine grinding mills use a lot of energy.
According to a new report from Weir Group, Mining Energy Consumption 2021, comminution accounts for 25% of final energy consumption at the average mine site. Across the hard-rock mining sector, this equates to around 1% of total global energy consumption every year. The report author, Marc Allen, stated that a 5% incremental improvement in energy efficiency across comminution could result in GHG emission reductions of more than 30 million metric tons (mt) of CO2e. To put that into perspective, New Zealands total emissions stand at around 35 million mt of CO2e.
CPF is not a new concept. However, what is new is its application at a commercial scale in base metals. Eriez has been applying CPF in phosphate and potash for 20 years and, in the past eight years, has been working to bring the benefits into base metals operations, particularly copper.
We did a lot of pilot work at Rio Tinto Kennecott Utah Copper in the U.S., Wasmund said. And we discovered that CPF really suits tails scavenging. When we started looking at the tails of conventional plants, we realized the material being lost to tails wasnt spread across the entire size distribution. It was actually very low in the size distribution where conventional flotation is effective, which makes sense.
Where we see a big drop-off is where the material is too coarse, or where its too fine. And we found that its very easy to develop a business case for reprocessing tails from a conventional plant using the HydroFloat. You can make money just by reprocessing and treating the material that conventional flotation isnt good at recovering.
Conventional flotation is not efficient for coarse particles, explained Wasmund. But what if we put [these new flotation technologies] right into the mill circuit and remove a coarse product before we overgrind it? Then youd get all the benefits of having a coarse tail, a reduction in energy requirements, and you can reduce the size of your plant. Thats what were calling coarse gangue rejection and its being worked on by a number of mining companies right now.
Its an ore sorting technology, except it sorts material at maybe half a millimeter, as opposed to conventional sensor-based ore sorting, which decides whether a 6-in. rock can be differentiated and disposed of before it goes through the plant, Wasmund explained.
This is ore sorting on a much finer scale, and the benefit is that it produces a much higher recovery rate. Sensor-based ore sorting uses blasts of air to shoot rocks containing a certain percentage of gangue off of a conveyor belt. The cut-off grade means that a certain amount of ore is lost along the way. Whereas in coarse gangue rejection, because the material is much finer, the margin of recovery is that much higher.
Anglo American is trialing the use of coarse particle recovery or rejection at Mogalakwena in South Africa as part of its FutureSmart Mining program. The company is also using it in tails scavenging applications at mines like Quellaveco in Peru and El Soldado in Chile, and to generate coarse tails that can be co-deposited with fine material in a dry facility, without a water impoundment.
In a previous interview (Copper processing: the quest for efficiency at scale, December 2020), a spokesperson for Anglo said CPF is a key technology in closing the loop on its water usage too an initial step toward the companys goal of dry processing.
We did a study with Capstone Mining based on their Cozamin site using coarse gangue rejection. And found that we could reduce the ball mill requirement by 30%-50%, convert 30% of the tails to a coarse size (instead of 200 microns, they were 600 microns) and reduce the amount of conventional flotation by 40%, said Wasmund, proudly. All of these benefits are site specific. But CPF, as a tool, can be used in so many different ways. There could be exciting applications that we dont even know about yet!
Another concept that Eriez and others like Woodgrove are working on is staged flotation. Again, the technology is not new Eriez has been running its StackCell in coal applications for 15 years but the company has recently redesigned it to handle base metals.
People have known about this for a long time, but still prefer to do everything in a single stirred tank, Wasmund said. If you break the flotation process down into two steps, as with the StackCell, then you can reduce the amount of working volume needed by a factor of four to five. Thats been validated at a number of sites.
The StackCell, which is much smaller than a traditional flotation cell, can shrink the size of a flotation plant by 50%. The knock-on effect is that it also requires less concrete (smaller carbon footprint), less piping to connect the units, and fewer electrical connections and cable trays and pipe racks, thus reducing CAPEX and engineering times too. This makes it ideal for use in plant expansions or at projects where a minimal footprint is important.
In metal mines, orebody characteristics can vary significantly throughout the life of mine. Initial and ongoing test work are crucial to optimizing the reagents used in flotation circuits. Donnini believes there is much to be learned from the industrial minerals market in this regard.
We just finished an expansion study for an open-pit mine, he explained. Theyre looking at the material theyre going to be mining for the next 10 years, and its very different to what they have been mining for the past 15.
The challenge that creates in flotation is that a lot of factors can interfere with the surface chemistry; Ive known of flotation plants that were upset for weeks due to something that was present in the parts-per-million range. Its a continuously changing environment, and often chemicals are an afterthought.
If we look at the work that Chinese phosphate manufacturers have done to develop reagent packages that are optimized for low-grade minerals they are developing the reagent package and then developing the flotation train based around that. The Phosphate Institute in Florida, which is largely supported by Mosaic, has done lots of work on this too.
I think one of the approaches that is necessary in the future is to identify the reagent package and how we want to use it in the process, and then build the flotation circuit around that package. Im sure others will say they do that already, but were not taking full advantage of the opportunity because most mines are using standard reagents.
I understand its expensive to do investigations and to invest in customized reagents. But at the same time, because of the challenges that are coming our way and theyre not coming, they are here already it makes total sense.
Dr. Kevin Brooks, APC global lead at Hatch, has pioneered the use of model predictive control (MPC) on flotation plants worldwide. Work with Anglo Platinum, FQML and Glencore has demonstrated that the combination of linear models derived from plant testing, and feedback from machine vision applications and/or online grade measurements yields significant benefits in grade, recovery and reagent usage.
Brooks explained: MPC is a technology developed in the oil refining industry more than 30 years ago. Its uptake in the minerals industry has been slow but has accelerated over the last five to 10 years. The technology slots right into the current thinking around Industry 4.0 and machine learning. The ability to optimize a unit in real-time yields paybacks in order of months leads to more consistent operation across shifts and allows plant operators to concentrate on the more manual areas of the unit.
Comminution is also an area where MPC yield benefits. Brooks sees a time when milling and flotation MPCs will be combined using a coordination model. This is the route to online control and optimization embracing the mine to mill concept, he said. Work is already being done to combine scheduling models with MPC to provide this wide scope of optimization and its associated benefits.
Donnini believes that, going forward, a more proactive approach is needed, one that encompasses prediction and automatic adjustment of plant parameters. Advanced process control and statistical process control will allow us to do a much better job of controlling the flotation process than we do today, he said.
In an operating environment, for a model to be useful, it must be able to accurately predict a reactive model is no use, Donnini said. That is a key element of the Industry 4.0 concept; mines need to be able to simulate their processes accurately enough so that they can predict whats going to happen in their processes, based on whats coming in.
Donnini believes advanced process control and neural networks offer a timely solution to predicting flotation performance today. The mathematical algorithms learn how a process operates and, using a certain number of inputs, take corrective action based upon experience.
To me, that is the solution to advanced process control in flotation, he said. I struggle to imagine somebody developing a model, being willing to spend the amount of money that it would take to collect all the data on factors that are likely to affect a flotation process. The alternative is that we learn (the machine learns). The more that machine is exposed to certain events, then the more accurately it can predict conditions.
Companies like Metso Outotec and FLSmidth have technologies that watch and measure froth properties, but I dont think anyone has closed the loop yet to allow those systems to initiate corrective action. Thats still left to the operator to do. But that will be an important step forward in controlling the flotation process.
Another important aspect, one that will be crucial to achieving all of the above, is continuous feed monitoring and particle size analysis. Today, this tends to be done in batches and the tests can take hours to return results. To install a laser scanner over a conveyor would provide a partial solution. However, the accuracy depends heavily on how a particle presents to the laser at a specific point in time.
Most particles are not spherical, but most models are created based on the assumption of spherical particles Again, in time, accurate, real time particle size analysis will improve our modelling capabilities as well.
What this article has shown is that flotation, as a technology, is not going anywhere. In fact, rather than being a limiting aspect of future flowsheets, one that could potentially be phased out over time, its going in quite the opposite direction.
Novel flotation technologies applied in new ways throughout flowsheets will prove invaluable in enabling ESG-conscious mining companies to meet future market demands while minding their resource consumption.
Anderson and Richter agreed. Flotation will remain a necessary portion of the flowsheet for the foreseeable future as a means of concentrating prior to roasting and leaching or even smelting, Anderson said. Dry technologies such as gravity, magnetic separation and electrostatic separation are unable to exploit the differences in surface characteristics which is a key separation method in mineral processing. However, its application may move closer to the mining face as time goes on.
Wasmund was pragmatic. Its important to put flotation into perspective with other extraction processes, he said. Its actually a very green technology, because it allows mines to separate valuable material from waste right after mining. If you compare that to other technologies
For instance, theres a big debate in the nickel market about where nickels going to come from for future electric vehicles. There are two main types of nickel resources: sulphides and laterites (oxides). Flotation can be used to concentrate sulphide nickels up to 30%, whereas laterites cannot be preconcentrated. The whole feed must be treated through high-pressure acid leaching (HPAL) or an electric arc furnace. And that increases the cost of production significantly, as well as the environmental footprint.
When were all driving electric vehicles and charging our cars at home with massive copper wires that connect up to our houses to get that copper and nickel were going to have to mine deposits that are much lower grade than those mined today. And the best way to do that is using more efficient forms of flotation.
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Since mid-1999, Kirunas haulage level at a depth of 775m has been replaced by the next level down at 1,045m and expansion is being carried out to increase the depth further, which will support production until 2030. The deepening requires relocation of the town and rail infrastructure.
In 2019, Kiruna produced 14.7Mt of iron ore products. The production in 2018 and 2017 was 15Mt and 14.8Mt, respectively. The mine produced 50,000t of ore feed material a day in June 2020. Mining at the site was briefly halted in 2019 after an earthquake of magnitude 4.1, the countrys biggest-ever, occurred in May that year.
The ore bed was then covered by further volcanic deposits (quartz porphyry) and sedimentary rocks before being tilted to its current dip of 50-60. The ore contains a very pure magnetite-apatite mix, containing more than 60% iron and an average of 0.9% phosphorus. Black ore contains less apatite than grey ore.
As of December 2019, the mine was estimated to contain 208Mt of proved reserves and 408Mt of probable reserves. The reserves decreased from the 2018 estimate of 624Mt of proven reserves and 62Mt of probable reserves due to the application of the Pan European Reserves and Resources Reporting Committee (PERC) reporting standard.
The mine is divided into eight production areas, each containing its own group of ore passes and ventilation systems. Mining the ventilation shafts for the current production level was carried out by SIAB using Indau 500 raise borers while Skanska Raise Drilling developed a total of 32 ore passes between the 775 and 1,045m levels using Tamrock and Robbins raise borers.
Ore is mined using sublevel caving, with sublevels spaced at 28.5m vertically. With a burden of 3.0m-3.5m per ring, this yields around 8,500t for each blast. LKAB subsidiary Kimit AB supplies the explosives and prepares the holes for blasting.
Seven 500t-capacity shuttle trains, controlled from the 775m level, collect ore from ten groups of ore passes and deliver it to one of four crushing stations. -100mm ore is then skip hoisted in two stages to the 775m level and then to surface.
After blasting, load-haul-dump machines (some of which are fully automated) carry the run-of-mine ore to the nearest ore pass, from which it is loaded automatically on to one of the trains operating on the 1,045m level.
After primary crushing, sampling using a Morgrdshammer automatic sampler to obtain the apatite and magnetite contents, and hoisting to surface, the ore is processed in Kirunas complex of a sorting plant, two concentrators and two pellet plants to give pellet and sinter fines products.
Ore is transported via remote-controlled shuttle trains to the crushing plant. The ore is then skip-hoisted approximately 1.4km vertically in two stages to the processing plant. Mining is carried out in ten production areas in stages between the current 1,045m level and the new 1,365m level.
The new level (KUJ1365) is the seventh since underground mining started. It is being developed in five stages. The first stage involved the construction of three groups of shafts. The first sections of the new main level were commissioned in May 2013. The remaining four stages will add more production areas, groups of shafts, trains, crushers and skip hoists for the new level.
The company also invested $925m in a third pelletising plant at Kiruna that was commissioned on 17 June 2008. The project also included a concentrator and ancillary equipment. The worlds largest grate-kiln pelletising plant, KK4 has an initial capacity of 5Mt/y of pellets, with the potential to increase its capacity to 6Mt/y.
With the contribution of the pelletising plants, the production capacity of LKAB increased by nearly 10Mtpa. Due to market slow down, one of the pelletising plants in Kiruna was closed in December 2009.
LKABs aim is to make Kiruna a one-product operation, with the focus exclusively on pellet production. As a result, it also invested in new flotation equipment for the Svappavaara concentrator that was inaugurated in May 2008.
The flotation enables it to produce pellet feed from some higher-phosphorus Kiruna ores. The project provides around 1Mtpa of additional output through efficiency savings. The company has been working on driving a 1,400m-long exploration drift northwards from the 1,365m level towards Luossavaara and the Per Geijer ores to the east of Luossavaara since November 2018. Several drill holes are planned to be drilled in 2020. LKAB expects to make decisions regarding a potential expansion involving a completely new production system in the mid-2020s.
Midroc Electro was contracted to provide fully automatic process control and train transportation systems for the new mining level. As a subcontractor to Mirdroc Electric, Bombardier Transportation is providing its fully automated driverless INTERFLO 150 train control technology to support the operations of the new level.
Prominer maintains a team of senior gold processing engineers with expertise and global experience. These gold professionals are specifically in gold processing through various beneficiation technologies, for gold ore of different characteristics, such as flotation, cyanide leaching, gravity separation, etc., to achieve the processing plant of optimal and cost-efficient process designs.
Based on abundant experiences on gold mining project, Prominer helps clients to get higher yield & recovery rate with lower running cost and pays more attention on environmental protection. Prominer supplies customized solution for different types of gold ore. General processing technologies for gold ore are summarized as below:
For alluvial gold, also called sand gold, gravel gold, placer gold or river gold, gravity separation is suitable. This type of gold contains mainly free gold blended with the sand. Under this circumstance, the technology is to wash away the mud and sieve out the big size stone first with the trommel screen, and then using centrifugal concentrator, shaking table as well as gold carpet to separate the free gold from the stone sands.
CIL is mainly for processing the oxide type gold ore if the recovery rate is not high or much gold is still left by using otation and/ or gravity circuits. Slurry, containing uncovered gold from primary circuits, is pumped directly to the thickener to adjust the slurry density. Then it is pumped to leaching plant and dissolved in aerated sodium cyanide solution. The solubilized gold is simultaneously adsorbed directly into coarse granules of activated carbon, and it is called Carbon-In-Leaching process (CIL).
Heap leaching is always the first choice to process low grade ore easy to leaching. Based on the leaching test, the gold ore will be crushed to the determined particle size and then sent to the dump area. If the content of clay and solid is high, to improve the leaching efficiency, the agglomeration shall be considered. By using the cement, lime and cyanide solution, the small particles would be stuck to big lumps. It makes the cyanide solution much easier penetrating and heap more stable. After sufficient leaching, the pregnant solution will be pumped to the carbon adsorption column for catching the free gold. The barren liquid will be pumped to the cyanide solution pond for recycle usage.
The loaded carbon is treated at high temperature to elute the adsorbed gold into the solution once again. The gold-rich eluate is fed into an electrowinning circuit where gold and other metals are plated onto cathodes of steel wool. The loaded steel wool is pretreated by calcination before mixing with uxes and melting. Finally, the melt is poured into a cascade of molds where gold is separated from the slag to gold bullion.
Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.
Optimal mineral recovery in a flotation circuit depends on the capacity to adapt to metallurgical variability in the ore being processed. Recognizing the need for a solution that addresses these challenges, Metso has made several advances in flotation design and technology.
Combining the benefits of circular cells with the unique features of the patented DV mechanism, the RCS (Reactor Cell System) flotation technology has been developed to create ideal conditions to maximize flotation performance for all roughing, cleaning and scavenging duties. The cell can be modified to handle high density slurries.
Maximize bubble-particle contact within the mechanism and the flotation tank leads to enhanced performance. Effective air dispersion and distribution throughout the cell volume helps in smooth froth surface and removal.
Our RCS flotation machines are built with efficient air and level controls with controlled aeration rate at each cell. The pneumatically operated dart valves help in effective pulp level control followed by accurate measurement with ultrasonic level sensor and float.
Metso offers the innovative circular tank concept to minimize slurry short circuiting as well as simplifying froth handling process. The compact and modular design proves to be very beneficial for quick construction, shipment and installation. Our internal dart valves also help to minimize footprint requirements.
Metso RCS flotation machines have extended wear life due to minimized local high velocity zones inside the tank. Impellers and diffusors supplied in high abrasion-resistant elastomers, and the impeller profile is design to minimize adsorbed power.
The mechanism design produces powerful radial slurry pumping to the cell wall and gives strong return flows to the underside of the impeller to minimize sanding. Additionally, it is the only mechanism to give maximum slurry recirculation to the upper part of the impeller.
The modular dart valve design provides flexibility to capacity changes without disturbances.Full suspension of the DV mechanism from the cell superstructure leads to very simplified routine maintenance. Along with our robust design, the RCS flotation machines are built to work for you!
Metso RCS flotation machines also are found as an essential piece to a regrind circuit. Rougher cells extract majority of the valuable mineral from the fresh ore. Meanwhile, scavenger cells are going to capture the remaining valuable mineral.
Revolutionary image analysis system for live measurement of multiple froth properties such as velocity, color, bubble size distribution, texture, stability and more. Higher froth recovery with continuous monitoring and analysis of flotation cells.
These ALL STAINLESS STEEL flotation machines are used to form banks of 2 cells. The can be arranged in series to accommodate small plants of up to 1 TPH (24 Ton/day). View the description below for a flotation cell capacity table you can use to estimate how many machines you need.
Look at the capacity you need in KPH (kilo/hour) or TPD (ton/day) and look for a number of machines, ideally, between 2 and 8. From this, select what cell size (volume) gives you that quantity of machines to form your flotation bank and circuit.
FX Model Continuous Mechanical Flotation Machine is applicable to separation of minerals with float-free method in labs. It is a unit of several combinations of two cells with number of the cell being even, varying from two to ten cells. Left or right type flotation machine can be supplied as required by customer.
To adjust the level of slurry in the cell and the thickness of the scraped froth layer, use wall plates of the two cells to make intermediary cell;install slurry level regulator; and mount orifice plate onto the cover in the cell to avoid negative effects on the froth zone exerted by the chaotic motion of slurry, as well as to avoid the gangue from being taken into the concentrate by the machine.
Lining plates are installed at the cell so that the bottom of the cell will not be abraded. The lining plate can be replaced. On the outside of the cell bottom is a discharge mouth, which is used to discharge water during its cleaning. The slurry flows through the overflow mouth of wall panel into the intermediary cell and tail cell. It flows to the lower part of the intermediary cell and the duct covered by the lower part of the cell wall and then to the next cell. In this way, it can continue to flow through all the cells of flotation machine. It flows from the feed cell and is discharged from the discharge mouth of the tail cell. The front and back of the lower part of the cell is installed feeding mouth, to make it easy to change the process flow.
The impeller system is a disk impeller which is installed in the center of the cell in the flotation machine and whose blades are radially arranged. It is fixed onto the lower end of the impeller shaft and revolves around the vertical shaft pipe.
The upper end of the pipe lies above the pulp stone and the froth layer while its lower end is supported on the cover. When the impeller rotates, a large amount of air can be sucked along the vertical pipe. Below the cover is fixed protective disk. The gap between the safety disk and the impeller depends on the amount of sucked air. It can not be larger than 3mm at most. When the gap is too large, replace the abraded protective disc and make appropriate adjustment.The holes in the vertical pipe are used to circulate slurry as well as mix the slurry and air. The rolling shaft installed inside the bearing shell above the impeller shaft rotates. The bearing shell is installed on the crossbeam and belt pulley is fixed on the top of the shaft which rotates through the V-belt when the motor is turned on. The tension of the V-belt is adjusted through the nuts.
The froth is scraped along the flotation machine through rotary scraper. The scraper is installed outside the discharge mouth of cell. At one end of the scraping shaft is installed belt pulley which rotates through the drive of worm reducer and V-belt.
Improvement: Shallow groove, the stator lower than the impeller, large slurry circulation volume, low energy consumption; the stator is a cylinder with an elliptical hole which is conducive to the dispersion and mixing of pulp and air. Umbrella shaped dispersion cover with hole keeps the pulp surface stable.
JJF flotation machine(floatation cell) is a new type of flotation equipment advanced in China. It can be widely used in the selection of non-ferrous metals, ferrous metals and non-metallic minerals. It is suitable for rough selection and sweeping of large and medium-sized flotation plants.
Large clearance between impeller and stator, the stator is a cylinder with elliptic hole, and it is good for mixing and dispersing the gas and pulp. The height of stator is lower than the impeller, pulp circulation volume is large, and it can be reached at 2.5 times of others.
When the impeller rotates, eddy current is generated in the vertical cylinder and the draft tube. The eddy current forms a negative pressure, and the air is sucked from the intake pipe and sucked in the impeller and stator regions and through the draft tube. Mix the pulp. The slurry gas mixing flow is moved by the impeller in a tangential direction, and then converted into a radial motion by the action of the stator, and uniformly distributed in the flotation tank. The mineralized bubbles rise to the foam layer, and the unilateral or bilateral scraping is the foam product.
Flotation is the most widely used beneficiation method for fine materials, and almost all ores can be separated by flotation. Another important application is to reduce ash in fine coal and to remove fine pyrite from coal. The flotation machine is mechanical equipment for realizing the froth flotation process and separating target minerals from ore. At present nearly 2 billion tons of ore in the world are treated by the froth flotation process. According to rough statistics, about 90% of non-ferrous minerals are recovered by the flotation method, accounting for 50% proportion in the field of ferrous metal mineral separation.
Suitable material Sulfide minerals, oxide minerals, non-metallic minerals, silicate minerals, nonmetallic salt minerals, soluble salt minerals, rare earth minerals, etc., including gold, silver, copper, lead, zinc, galena, zinc blende, chalcopyrite, pyroxene, molybdenite, nickel pyrite, malachite, cerussite, smithsonite, hematite, cassiterite, wolframite, Ilmenite, beryl, spodumene, brimstone, graphite, diamond, quartz, mica, feldspar, fluorite, apatite, barite, and so on.
The flotation machine is composed of single or multiple flotation cells, by agitating and inflating the chemical reagent treated slurry, some mineral ore particles are adhered to the foam and float up, and then be scraped out, while the rest remains in the slurry.
Industrial flotation machines can be divided into 5 classes, mechanical agitation flotation machine, pneumatic flotation machines, flotation column, airlift flotation machine, froth separation flotation machines. At present, the mechanical flotation machine is the most commonly used in industry, followed by the column flotation which has recently set off hot spot, the pneumatic type and froth separation are not common.
Commonly used flotation models TankCell series, Wemco series, Agitair series, SuperCells, RCS(reactor cell system), Denver laboratory flotation, KYF, and XCF series flotation devices, laboratory flotation machine. Well-known flotation machine manufacturers have Outotec, Flsmidth, Metso, BGRIMM, JXSC flotation machine china; column flotation manufacturers or models have Jameson, CPT, Counter-flow inflatable flotation column.
Main parts: slurry tank, agitator device, mineralized froth discharging system, electromotor, etc. 1. Slurry tank: mainly consist of a slurry inlet, slurry tank and a gate device for controlling the slurry volume, welded with steel plate. 2. Agitator: slurry tank have a series of the mechanically driven impeller that disperses the air into the agitated pulp. 3. Mineralized forth discharging: the useful minerals are enriched in the foam, scraped out, dehydrated, and dried into concentrate products.
Whatever flotation machines design is selected, it must accomplish a series of complicated industrial requirements. 1. Good mixing function. a qualified flotation machine should mix the slurry uniformly and maintain the particles especially the target mineral particle in suspension with the pulp, maximum the froth-mineral probability. 2. Adequate ventilation and distribution of fine bubbles. Except for the flotation machine performance, the frother type and dosage also matter to the distribution of the bubbles. 3. Appropriate agitation control in the froth beds. It is should pay importance to keep froth zones smoothly, which ensures the suspension of collector coated particle.
1. The throughput capabilities of various cell designs will vary with the ore property (beneficiability, size, density, grade, pulp, PH, etc.). In the case of ore easy separated, and a small amount of air inflation required, may choose a mechanical flotation machine; if the minerals with coarse size, proper to choose the KYF, BS-F, ore CLF type; what's more, when in case of ore easy separated, fine particles, high grade, low PH, flotation column is the best, especially in the concentrating process. 2. There is a difference between the process of concentrating, rough selecting. Thin froth layer is better for separate mineral particles, thus may not choose a large air inflation flotation machine.
Mining Equipment Manufacturers, Our Main Products: Gold Trommel, Gold Wash Plant, Dense Media Separation System, CIP, CIL, Ball Mill, Trommel Scrubber, Shaker Table, Jig Concentrator, Spiral Separator, Slurry Pump, Trommel Screen.
Industrial flotation machines can be divided into four classes: (1) mechanical, (2) pneumatic, (3) froth separation, and (4) column. The mechanical machine is clearly the most common type of flotation machine in industrial use today, followed by the rapid growth of the column machine. Mechanical machines consist of a mechanically driven impeller, which disperses air into the agitated pulp. In normal practice, this machine appears as a vessel having a number of impellers in series. Mechanical machines can have open flow of pulp between each impeller or are of cell-to-cell designs which have weirs between each impeller. The procedure by which air is introduced into a mechanical machine falls into two broad categories: self-aerating, where the machine uses the depression created by the impeller to induce air, and supercharged, where air is generated from an external blower. The incoming slurry feed to the mechanical flotation machine is introduced usually in the lower portion of the machine.Figure 7 shows a typical industrial flotation cell of each air delivery type.
The most rapidly growing class of flotation machine is the column machine, which is, as its name implies, a vessel having a large height-to-diameter ratio (from 5 to 20) in contrast to mechanical cells. The mechanism behind this machine to is provide a countercurrent flow of air bubbles and slurry with a long contact time and plenty of wash water. As might be expected, the major advantage of such a machine is the high separation grade that can be achieved, so that column cells are often used as a final concentrate cleaning step. Special care has to be exercised in the generation of fine air bubbles and controlling the feed rate to column cells.
Good mixing of pulp. To be effective, a flotation machine should maintain all particles uniformly in suspension within the pulp, including those of relatively high density and/or size. Good mixing of pulp is required for maximizing bubble-particle collision frequency.
Appropriate aeration and dispersion of fine air bubbles. An important requirement of any flotation machine is the ability to provide uniform aeration throughout as large a volume of the machine as is possible. In addition, the size distribution of the air bubbles generated by the machine is also important, but experience has shown that the proper choice of frother type and dosage generally dominates the bubble size distributions being produced.
Sufficient control of pulp agitation in the froth zone. As mentioned earlier, good mixing in the machine is important; however, equally important is that near and in the actual froth bed at the top of the machine, sufficiently smooth or quiescent pulp conditions must be maintained to ensure suspension of hydrophobed (collector coated) particles.
Efficient mass flow-mechanisms. It is also necessary in any flotation machine that appropriate provisions be made for feeding pulp into the machine and also for the efficient transport of froth concentrate and tailing slurry out of the machine.
Probably the most significant area of change in mechanical flotation machine design has been the dramatic increase in machine size. This is typified by the data ofFig. 8, which shows the increase in machine (cell) volume size that has occurred with a commonly used cell manufactured by Wemco. The idea behind this approach is that as machine size increases, both plant capital and operating costs per unit of throughput decrease.
The throughput capabilities of various cell designs will vary with flotation residence time and pulp density. The number of cells required for a given operation is determined from standard engineering mass balance calculations. In the design of a new plant, the characterization of each cell's volume and flotation efficiency is generally calculated from performing a laboratory-scale flotation on the same type of equipment on the ore in question, followed by the application of empirically derived design (scale-up) factors. Research work is currently under way to improve the understanding and performance of commercial flotation cells. Currently, flotation-cell design is primarily a proprietary function of the various cell manufacturers.
Flotation plants are built in multiple cell configurations (called banks), and the flow through various banks is adjusted in order to optimize plant recovery of the valuable as well as the valuable grade of the total recovered mass from flotation. This recovery vs grade trade-off is economically important in flotation, as increased recovery of the valuable is associated with decreased grade. For example, a 95% recovery of copper in the feed ore might give a concentrate grade of 18% Cu in the total recovered mass, while 80% Cu recovery might give a grade of 25% in the concentrate. Obviously, the higher the valuable recovery is, the higher the potential income, but if this higher recovery requires a great deal more grinding and/or expensive downstream processing (including further flotation) in order to upgrade the concentrate for metal refining such as smelting, the increase in potential recovery income may actually cause a net loss of total income. This grade-recovery optimization is generally worked out by individual flotation operators in each plant (and each mineral) and sets the operating philosophy of that plant.Figure 9 shows a typical industrial recovery vs grade trade-off curve for a copper sulfide ore containing pyrite. The higher the copper recovery is, the greater the amount of undesired pyrite contained in the concentrate.
The various banks of flotation cells in an industrial plant are given special names to denote the particular purpose of the banks. The rougher bank is the first group of cells that the pulp sees after size reduction. The goal of the roughers is to produce a concentrate with as high a recovery of valuable as possible with generally low grade of the valuable. The rejected gangue material from any bank of cells is commonly denoted as the tails or tailings. Usually, rougher tails are discarded so that valuable mineral not recovered in the rougher bank is lost. The concentrate of the rougher bank can be further concentrated, sometimes after additional grinding, in banks of cells called cleaners or recleaners. The tailings from the cleaners or recleaners can be recirculated to a bank of cells known as scavengers in order not to lose any valuable material in the upgrading process. Various banks of cells are also sometimes known by the particle size of the particular pulps being floated. Coarse particles, fine or slime particles, and middle-sized particles, denoted as middlings, can all be treated in separate banks.
As to overall capacities of flotation plants, the range is quite variable, depending on the type and value of the mineral being processed, the amount of valuable mineral in the feed ore to flotation, the degree and cost of size reduction involved, and the relative response of the valuable(s) to the flotation process. Smaller plants ranging in size from 500 to 5000 metric tons of feed per day are common, with feed materials having high amounts of valuable per ton of feed ore (>40%), such as coal, phosphate, and oxide ores. On the other hand, the sulfide minerals that are typically a small percentage of the ore (<10% and often less than 1%) require much greater capacity in order to achieve a reasonable economic return on investment. Thus, typical copper sulfide plants have capacities in the range of 20,000 to more than 60,000 metric tons of feed ore per day.
Conventional flotation machines house two functions in a single vessel: an intense mixing region where bubbleparticle collision and attachment occurs, and a quiescent region where the bubbleparticle aggregates separate from the slurry. The reactor/separator machines decouple these functions into two separate (or sometimes more) compartments. The cells are typically considered high-intensity machines due to the turbulent mixing in the reactor (see Section 12.9.5). The role of the separator is to allow sufficient time for mineralized bubbles to separate from the tailing stream which generally requires relatively short residence time (when compared to mechanical cells or columns).
Some of the earliest machine designs were of the reactor/separator-type. Figure 12.80 shows a design from a patent by Hebbard (1913). Feed slurry was mixed with entrained air in an agitation box (reactor) and flowed into the separation vessel where froth was collected as overflow. The design would be the basis for the Minerals Separation Corporation standard machine and early flotation cells used in the United States (Lynch et al., 2010).
The Davcra cell (Figure 12.81) was developed in the 1960s and is considered to be the first high-intensity machine. The cell could be thought of as a column or reactor/separator device. Air and feed slurry are contacted and injected into the tank through a cyclone-type dispersion nozzle, the energy of the jet of pulp being dissipated against a vertical baffle. Dispersion of air and collection of particles by bubbles occurs in the highly agitated region of the tank, confined by the baffle. The pulp flows over the baffle into a quiescent region designed for bubblepulp disengagement. Although not widely used, Davcra cells replaced some mechanical cleaner machines at Chambishi copper mine in Zambia, with reported lower operating costs, reduced floor area, and improved metallurgical performance.
Several attempts have been made to develop more compact column-type devices, the Jameson cell (Jameson, 1990; Kennedy, 1990; Cowburn et al., 2005) being a successful example (Figure 12.82). The Jameson cell was developed in the 1980s jointly by Mount Isa Mines Ltd and the University of Newcastle, Australia. The cell was first installed for cleaning duties in base metal operations (Clayton et al., 1991; Harbort et al., 1994), but it has also found use in coal plants and in roughing and preconcentrating duties. The original patent refers to the Jameson cell as a column method, but it can also be considered a reactor/separator machine: contact between the feed and the air stream is made using a plunging slurry jet in a vertical downcomer (the reactor), and the airslurry mixture flows downwards to discharge and disengage into a shallow pool of pulp in the bottom of a short cylindrical tank (the separator). The disengaged bubbles rise to the top of the tank to overflow into a concentrate launder, while the tails are discharged from the bottom of the vessel. Air is self-aspirated (entrained) by the action of the plunging jet. The air rate is influenced by jet velocity and slurry density and level in the separator chamber.
The Jameson cell has been widely used in the coal industry in Australia since the 1990s. Figure 12.83 shows a typical cell layout where fine coal slurry feeds a central distributor which splits the stream to the downcomers. Clean coal is seen overflowing as concentrate from the separation vessel. The major advantage of the cell in this application is the ability to produce clean concentrates in one stage of operation by reducing entrainment, especially when wash water is used. It also has a novel application in copper solvent extraction/electrowinning circuits, where it is used to recover entrained organic droplets from electrolyte (Miller and Readett, 1992).
The Contact cell (Figure 12.84) was developed in the 1990s in Canada. The feed slurry is placed in direct contact with pressurized air in an external contactor which comprises a draft tube and an orifice plate. The slurryair mixture is fed from the contactor to the column-type separation vessel, where mineralized bubbles rise to form froth. Contact cells employ froth washing similar to conventional flotation columns and Jameson cells. Contact cells have been implemented in operations in North America, Africa, and Europe.
The IMHOFLOT V-Cell (Figure 12.85(a)) was developed in the 19801990s and evolved from earlier designs developed in Germany in the 19601970s (Imhof et al., 2005; Lynch et al., 2010). Conditioned feed pulp is mixed with air in an external self-aeration unit above the flotation cell. The airslurry mixture descends a downcomer pipe and is introduced to the separation vessel via a distributor box and ring pipe with nozzles that redirect the flow upward in the cell. The separation vessel is fitted with an adjustable froth crowding cone which can be used to control mass pull. The concentrate overflows to an external froth launder, while the tailings stream exits at the base of the separation vessel. The V-Cell has been used to float sulfide and oxide ores with the largest operation being an iron ore application (Imhof et al., 2005).
The IMHOFLOT G-Cell (Figure 12.85(b)) was introduced in 2001 and employs the same external self-aerating unit as the V-Cell. The airslurry mixture which exits the aeration unit is fed to an external distributor box (located above the separation vessel) where pulp is split and fed to the separation vessel tangentially via feed pipes. The cell is unusual as an internal launder located at the center of the vessel collects froth. The centrifugal motion of the slurry enhances froth separation with residence times being ca. 30s.
The Staged Flotation Reactor (SFR) (Figure 12.86) is a recent development in the minerals industry. By sequencing the three processesparticle collection, bubble/slurry disengagement, and froth recoveryand assigning each to a purpose-built chamber, the SFR aims to optimize each of the three processes independently.
The SFR incorporates an agitator in the first (collection) chamber designed to provide high energy intensity (kWm3) and induce multiple particle passes through the high shear impeller zone, hence giving high collection efficiency. Slurry flows by gravity through the reactor stages, that is, there is no need to apply agitation to suspend solids, only for particle collection. As such, impeller speed can be adjusted online in correlation with desired recovery without sanding. The second tank is designed to deaerate the slurry (bubble disengagement) and rapidly recover froth to the launder without dropback. The froth recovery unit is tailored for use of wash water and for high solids flux. Efficient particle collection and high froth recovery translate into fewer, smaller cells, resulting in a smaller footprint and building height, with lower power consumption, and the potential for good selectivity in both roughing and cleaning applications.
Induced air flotation machines have gained a degree of popularity within certain sections of the minerals processing industry because of their ability to produce small bubbles at relatively high energy efficiency. The most common of such machines is the Jameson Cell. A downcomer protrudes out of the bubbly liquid in which is housed a plunging jet. Because this jet is at high velocity the pressure within the downcomer is low due to the Bernoulli equation, and air is induced into the downcomer creating a plume of bubbles within the liquid, which rise to form a foam. There are major problems with operating Jameson Cells because their high demand for surfactant causes downstream residual frother issues. (It is noted, as an aside, that frother strippers are being developed to remove residual frother in flotation circuits, and these are identical to foam fractionation units.) Notwithstanding that Jameson Cell technology has failed to live up to its promise, it has been successfully used as a pilot-scale foam reactor to effect the autothermal thermophilic aerobic digestion (ATAD) of high strength wastewater sludge produced at a chicken processing factory. The advantage that induced gas systems have over alternative pneumatic foam systems is their very high gasliquid surface area per unit volume of foam due to their small bubbles. This feature of the foams would also be an advantage in foam fractionation because it creates high flux of gasliquid surface. However, to the authors knowledge, no attempt has ever been made to use induced gas systems as foam fractionators.
The Denver DR flotation machine, which is an example of a typical froth flotation unit used in the mining industry, is illustrated in Figure 1.47. The pulp is introduced through a feed box and is distributed over the entire width of the first cell. Circulation of the pulp through each cell is such that, as the pulp comes into contact with the impeller, it is subjected to intense agitation and aeration. Low pressure air for this purpose is introduced down the standpipe surrounding the shaft and is thoroughly disseminated throughout the pulp in the form of minute bubbles when it leaves the impeller/diffuser zone, thus assuring maximum contact with the solids, as shown in Figure 1.47. Each unit is suspended in an essentially open trough and generates a ring doughnut circulation pattern, with the liquid being discharged radially from the impeller, through the diffuser, across the base of the tank, and then rising vertically as it returns to the eye of the impeller through the recirculation well. This design gives strong vertical flows in the base zone of the tank in order to suspend coarse solids and, by recirculation through the well, isolates the upper zone which remains relatively quiescent.
Froth baffles are placed between each unit mechanism to prevent migration of froth as the liquid flows along the tank. The liquor level is controlled at the end of each bank section by a combination of weir overflows and dart valves which can be automated. These units operate with a fully flooded impeller, and a low pressure air supply is required to deliver air into the eye of the impeller where it is mixed with the recirculating liquor at the tip of the air bell. Butterfly valves are used to adjust and control the quantity of air delivered into each unit.
Each cell is provided with an individually controlled air valve. Air pressure is between 108 and 124 kN/m2 (7 and 23 kN/m2 gauge) depending on the depth and size of the machine and the pulp density. Typical energy requirements for this machine range from 3.1 kW/m3 of cell volume for a 2.8 m3 unit to 1.2 kW/m3 for a 42 m3 unit.
In the froth flotation cell used for coal washing, illustrated in Figure 1.48, the suspension contains about 10 per cent of solids, together with the necessary reagents. The liquid flows along the cell bank and passes over a weir, and directly enters the unit via a feed pipe and feed hood. Liquor is discharged radially from the impeller, through the diffuser, and is directed along the cell base and recirculated through ports in the feed hood. The zone of maximum turbulence is confined to the base of the tank; a quiescent zone exists in the upper part of the cell. These units induce sufficient air to ensure effective flotation without the need for an external air blower.
Most of the industrial flotation machines used in the coal industry are mechanical, conventional cells. These machines consist of a series of agitated tanks (usually 48 cells) through which fine coal slurry is passed. The agitators are used to ensure that larger particles are kept in suspension and to disperse air that enters down through the rotating shaft assembly (Fig. 11.13). Air is either injected into the cell using a blower or drawn into the cell by the negative pressure created by the rotating impeller. For coal flotation, trough designs that permit open flow between cells along the bank are more common than cell-to-cell designs that are separated by individual weirs.
Some of the major manufacturers of flotation equipment include Wemco (FLSmidth), Metso, Svedala, and Outokumpu. The commercial units are very similar in basic design and function, although some slight variations exist in terms of cell geometry and impeller configuration. Machines with large specific surface areas are generally preferred for coal flotation, due to the fast flotation kinetics of coal and the large froth solids loadings. Flotation machines with individual cell volumes of up to 28m3 are commonly used due to advantages in terms of capital, operating and maintenance costs. Some manufacturers also offer tank machines, which consist of relatively short cylindrical tanks equipped with conventional impellers. The simplified structural design, which allows these machines to be much larger, can offer significant savings in terms of capital and power costs for some installations. Tank cells with volumes as large as 100m3 are already in operation at coal plants in Australia.
Unlike conventional, mechanically agitated flotation machines, which tend to use relatively shallow rectangular tanks, column cells used in the coal industry are usually tall vessels with heights typically ranging from 7 to 16m depending on the application. Unlike conventional flotation machines, columns do not use mechanical agitation and are typically characterized by an external sparging system, which injects air into the bottom of the column cell. The absence of intense agitation promotes higher degrees of selectivity and can aid in the recovery of coarse particles.
In general, feed slurry enters the column at one or more feed points located in the upper third of the column body and descends against a rising swarm of fine bubbles generated by the air sparging system (Fig. 11.14). Hydrophobic particles that collide with, and attach to, the bubbles rise to the top of the column, eventually reaching the interface between the pulp (collection zone) and the froth (cleaning zone). The location of this interface, which can be adjusted by the operator, is held constant by means of an automatic control loop that regulates a valve on the column tailings line. Varying the location of the interface will increase or decrease the height of the froth zone. The froth is transported from the froth zone into the product launder via mass action.
Methods of sparging in columns are numerous and include air lances, porous tubes, eductors, static mixers, and Cavitation-TubesTM. The air rate used in a column is selected according to the feed rate and concentrate-production requirements. This parameter typically has the largest effect on the operating point of the column with respect to the ash/yield curve. The bubbles generated by the air sparging system are sized to provide the maximum amount of bubble surface area given a constant energy input. In other words, the designs of the various sparging devices are engineered to provide the smallest size and largest number of bubbles possible.
For an equivalent volumetric capacity, the cross-sectional surface area of a column cell is much smaller than that of a conventional cell. This reduced area is beneficial for promoting froth stability and allowing deep froth beds to be formed. This is an important aspect of column flotation, as a deep froth bed facilitates froth washing for the removal of unwanted impurities from the float product. Wash water, added at the top of the column, percolates through the froth zone displacing dirty process water and non-selectively entrained particles trapped between the bubbles. In addition, froth wash water serves to stabilize and add mobility to the froth. Sufficient water must be added to ensure that all of the feed water that would otherwise normally report to the froth product is replaced with fresh or clarified water. It has been reported that less than 1% of the feed pulp and associated clays will report to the froth in a well-operated column (Luttrell et al., 1999). The ability to maintain and wash a deep froth layer is the main reason cited for the improved product grades when comparing column cells to conventional cells.
In contrast, conventional mechanical cells do not operate with deep froths. Therefore, these devices allow some portion of the ultrafine mineral slimes to be recovered with the water that reports to the froth. Consequently product quality is reduced by this non-selective hydraulic conveyance (i.e., entrainment) of gangue into the product launder. In fact, fine particles (<0.045mm) have a tendency to report to the froth concentrate in direct proportion to the amount of product water recovered. As such, the flotation operator is often forced to make the decision to either pull hard on the cells to maintain yield (e.g., wet froth), or run the cells less aggressively to maintain grade (e.g., dry froth).
The primary advantage of utilizing wash water is the ability to provide a superior product grade when compared to conventional flotation processes. This capability is illustrated by the test data summarized in Fig. 11.15, which compares column flotation technology with an existing bank of conventional cells. As shown, the separation data for the column cells utilizing wash water are far superior to those obtained from the conventional flotation bank. In fact, the data for the column cells tend to fall just below the separation curve predicted by release analysis (Dell et al., 1972). A release analysis is an indication of the ultimate flotation performance and is often regarded as wash-ability for flotation. This figure suggests that columns provide a level of performance that would be difficult to achieve even after multiple stages of cleaning by conventional machines.
There are a significant number of full-scale column installations currently in commercial service around the world. The most popular brands of columns include the CPT CoalPro (Eriez), Jameson, and Microcel columns. Although the Jameson cell does not have the traditional column geometry, it is included since it typically uses wash water to improve ash rejection. Details related to the specific design features of the various column technologies are available in the literature (McKay et al., 1988; Finch and Dobby, 1990; Yoon et al., 1992; Manlapig et al., 1993; Davis et al., 1995; Rubinstein, 1995; Wyslouzil, 1997). The primary difference between the various columns used in the coal industry is the type of air sparging system employed. These include porous bubblers, static mixers, and dynamic air injectors. Details related to the features and operation of these systems have been discussed extensively in the literature (Dobby and Finch, 1986a; Xu and Finch, 1989; Huls et al., 1991; Groppo and Parekh, 1992; Yoon et al., 1992; Finch, 1995). Ideally, the spargers should produce small, uniformly sized bubbles at a desired aeration rate. Other factors, such as equipment costs, mechanical reliability, wear resistance, and serviceability also need to be carefully considered prior to selecting an industrial sparging system.
Due to economy of scale, recent trends in the coal industry have shifted away from the installation of large numbers of smaller units toward fewer, large units with diameters up to 5m or more. Although most column installations involve the treatment of particles finer than 0.150mm, several recent column operations have been installed to treat coarser particles, such as minus 1mm feeds or deslimed 0.1500.045mm feeds. Additionally, a move to more economical cells in terms of energy efficiency has been realized as manufacturers focus on the generation of the required air bubble dispersions while using significantly less power than traditional approaches. One such device is the Eriez StackCell, which utilizes both pre-aeration methods in conjunction with traditional froth washing (Davis et al., 2011) to maximize efficiency with regard to both installation and operating cost.
The two most important requirements of laboratory flotation machines are reproducibility and performance similar to commercial operations. These two criteria are not always satisfied. The basic laboratory machines are scaled down replicas of commercial machines such as Denver, Wemco and Agitair. In the scale down, there are inevitable compromises between simplification of manufacture and attempts to simulate full scale performance. There are scaling errors, for example, in the number of impeller and stator blades and various geometric ratios. Reproducibility in semi-batch testing requires close control of impeller speed, air flow rate, pulp level and concentrate removal.
Until now, deaeration tanks always had to be placed underneath the flotation machine and also frequently in the cellar of a facility in order to ensure a sufficient height difference for the conveyance of foam. In addition, the tanks are open on top and can overflow with excess foam. That is now a thing of the past with the Deaeration Foam Pump (DFP) 4000. The new pump can be linked directly to the deinking machine and forms a clean and closed disposal system. Because it can be placed at the same level as the flotation cells, the entire flotation system saves more space than previous systems. A cellar or an additional floor height for the flotation is no longer required. The deaeration results are very impressive with the DFP 4000 from Voith Paper. The air content of the foam mass is reduced when passing through the pump from 80% to an average of 8%. Conventional deaeration systems offer approximately 12%. In addition, by using the DFP 4000, upstream foam destroyers, downstream long piping as well as pumps with high head pressures to overcome the floor height can be dispensed. With the DFP 4000, it is possible to deaerate and convey the foam, which is loaded with inks and other impurities, within a single machine. As a compact unit, it fully replaces the foam destroyer, foam tank stirring unit, and pump of previous deaeration systems. This means a clear reduction in investment costs for the tank, stirring unit, pipes, pumps, and floor space.
The DFP 4000, developed by Voith, is a compact unit that integrates several elements of the flotation deinking system. This combines the pump and deaeration machine into one unit. The deaeration foam pump replaces the foam destroyer, foam tank, stirring unit, and pump and costs less than the current suite of equipment. The DFP 4000 achieves better deaeration of the foam than conventional systems.
The DFP 4000 has two parts. In the upper part, foam is predeaerated by a mechanical foam destroyer. In the lower part, centrifugal force produced by a quick rotational movement further deaerates the foam. The resulting low-air-content suspension is brought to the required pressure so that it can be conveyed out of the machine to the next process stage. The air released during deaeration is conveyed out of the machine through a special air chamber on the side so that the airflow does not prevent the foam entering from above (Dreyer,2010).
The new pump can be linked directly to the deinking machine, forming a clean and closed disposal system. Because the deaeration pump can be placed at the same level as the flotation cells, the entire system requires less space than previous systems, so a cellar (or additional floor height) is no longer required to accommodate the system. When the foam mass passes through the DFP 4000, the foams air content is reduced from 80% to an average of 8% (Voith,2011a). Conventional deaeration systems reduce the air content to approximately 12%. The first DFP 4000 operating in a paper mill has been in service since September 2009 (Dreyer,2010). The benefits of the DFP 4000 are summarized in Table11.9 (Dreyer,2010; Voith,2011a).
Batch testing has been carried out using a specially designed 21 tumbler for mixing, and a standard Denver flotation machine for separation. A typical charge of the soil sample ranged from 200 to 600g, and the amount of coal varied depending on the contaminant concentration.
Figure 1 shows the block diagram of the 6T/day continuous unit. A slurry of contaminated soil and coal is fed at optimal solids concentration to a specially designed tumbler. In the front section of the tumbler, as a result of rotary motion, the solids are mixed and dispersed. In another section of the tumbler, layering, compaction and abrasion take place. After being discharged from the tumbler, the contents are screened into two streams. The 1mm particle size stream is directed to a high shear mixer where the oil-wetted coal particles are conditioned. The slurry is then transfered to flotation cells, where the coal microagglomerates, in the form of froth, are separated from clean soil. To facilitate dewatering and improve handleability of the combustible product, the froth can be subsequently fed into the low shear mixer for further agglomeration.
Flotation has progressed and developed over the years; recent trends to achieve better liberation by fine grinding have intensified the search for more advanced means of improving selectivity. This involves not only more selective flotation agents but also better flotation equipment. Since the froth product in conventional flotation machines contains entrained fine gangue, which is carried into the froth with feed water, the use of froth spraying was suggested in the late 1950s to eliminate this type of froth contamination. The flotation column patented in Canada in the early 1960s and marketed by the Column Flotation Company of Canada, Ltd., combines these ideas in the form of wash water supplied to the froth. The countercurrent wash water introduced at the top of a long column prevents the feed water and the slimes that it carries from entering an upper layer of the froth, thus enhancing selectivity.
The microbubble flotation column (Microcel) developed at Virginia Tech is based on the basic premise that the rate (k) at which fine particles collide with bubbles increases as the inverse cube of the bubble size (Db), i.e., k1/Db3. In the Microcel, small bubbles in the range of 100500m are generated by pumping a slurry through an in-line mixer while introducing air into the slurry at the front end of the mixer. The microbubbles generated as such are injected into the bottom of the column slightly above the section from which the slurry is with drawn for bubble generation. The microbubbles rise along the height of the column, pick up the coal particles along the way, and form a layer of froth at the top section of the column. Like most other columns, it utilizes wash water added to the froth phase to remove the entrained ash-forming minerals. Advantages of the Microcel are that the bubble generators are external to the column, allowing for easy maintenance, and that the bubble generators are nonplugging. An 8-ft diameter column uses four 4-in. in-line mixers to produce 56 tons of clean coal from a cyclone overflow containing 50% finer than 500 mesh.
Another interesting and quite different column was developed at Michigan Tech. It is referred to as a static tube flotation machine, and it incorporates a packed-bed column filled with a stack of corrugated plates. The packing elements arranged in blocks positioned at right angles to each other break bubbles into small sizes and obviate the need for a sparger. Wash water descends through the same flow passages as air (but countercurrently) and removes entrained particles from the froth product. It was shown in both the laboratory and the process demonstration unit that this device handles extremely well fine below 500-mesh material.
Another novel concept is the Air-Sparged Hydrocyclone developed at the University of Utah. In this device, the slurry fed tangentially through the cyclone header into the porous cylinder to develop a swirl flow pattern intersects with air sparged through the jacketed porous cylinder. The froth product is discharged through the overflow stream.
The process is carried out in a flotation cell or tank, of which there are two basic types, mechanical and pneumatic. Within each of these categories, there are two subtypes, those that operate as a single cell, and those that are operated as a series or bank of cells. A bank of cells (Fig. 8) is preferred because this makes the overall residence times more uniform (i.e., more like plug flow), rather than the highly diverse residence times that occur in a single (perfectly mixed) tank.
FIGURE 8. Flotation section of a 80,000t/d concentrating plant, showing the arrangement of the flotation cells into banks. A small part of the grinding section can be seen through the gap in the wall. [Courtesy Joy Manufacturing Co.]
The purpose of the flotation cell is to attach hydrophobic particles to air bubbles, so that they can float to the surface, form a froth, and can be removed. To do this, a flotation machine must maintain the particles in suspension, generate and disperse air bubbles, promote bubbleparticle collision, minimize bypass and dead spaces, minimize mechanical passage of particles to the froth, and have sufficient froth depth to allow nonhydrophobic (hydrophilic) particles to return to the suspension.
Pneumatic cells have no mechanical components in the cell. Agitation is generally by the inflow of air and/or slurry, and air bubbles are usually introduced by an injector. Until comparatively recently, their use was very restricted. However, the development of column flotation has seen a resurgence of this type of cell in a wider, but still restricted, range of applications. While the total volume of cell is still of the same order as that of a conventional mechanical cell, the floor space and energy requirements are substantially reduced. But the main advantage is that the cell provides superior countercurrent flow to that obtained in a traditional circuit (see Fig. 11), and so they are now often used as cleaning units.
Mechanical cells usually consist of long troughs with a series of mechanisms. Although the design details of the mechanisms vary from manufacturer to manufacturer, all consist of an impeller that rotates within baffles. Air is drawn or pumped down a central shaft and is dispersed by the impeller. Cells also vary in profile, degree of baffling, the extent of walling between mechanisms, and the discharge of froth from the top of the cell.
Selection of equipment is based on performance (represented by grade and recovery), capacity (metric tons per hour per cubic meter); costs (including capital, power, maintenance), and subjective factors.
Walker mining supply single cell laboratory flotation machine . XFDI,XFDII,XFDIII is represent 3 generation single cell flotation cell. XFDII equipment frequency adjust function compared with XFDI, XFDIII is equipped additional heating function compared with XFDII. D12 flotation cell is muti-cell flotation machine . it is Denver type machine .but the price is much lower than Denver D12 .
XFD-12 laboratory multi-cell floatation machine is applicable to floatation of non-ferrous andferrous metals, nonmetals and coal with the size fraction less than -35 meshes and can be used in floatation test of 125-3000g floatation samples. For D12 lab flotation ,we have 3 models D12I,D12II,D12III,below sheet is difference between them.
Structure Introduction XFD-12 laboratory multi-cell floatation machine consists of the following main components: elevating mechanism , mechanical stepless variable-speed mechanism , machine head part, stator and rotor part and control switch . All components are coupled to the column body. The main shaft rotates in a clockwise direction. The movement is driven by the motor to rotate the impeller through the main shaft, and the gear wheel can be rotated to adjust the impeller speed. Adjust the inverter knob to set the impeller speed. The main body of the main shaft is lifted and lowered by the motor to drive the gear through the gear box and drive the lift to the desired position. When descending, press the down button. Because there is a travel switch, it will automatically stop when it reaches the bottom. The trough body is fixed on the square hole of the base by four cylindrical pins under the groove Note: When lifting and lowering, you must make sure that you can switch the lifting work after pressing the stop button. Do not stay away from the operator during lifting operations
The floatation machine is installed on the workbench and its levelness can be adjusted using four base screws. Check for its rotation direction before the motor is powered on. The main shaft impeller driven by the motor is required to rotate clockwise The speed of the flotation machine is regulated by the frequency converter. The speed can also be adjusted while the machine is running; the speed can be displayed on the LCD meter of the control panel. In addition, the machine is equipped with a rocking handle, which can also be used or fine-tuned to adapt to the stirring conditions. It should be noted that before the electric lift, the handle should be pulled out and then folded to the inside of the rocker to prevent injury to the personnel in the electric lift. Do not approach the rocker during the electric lift. The impeller, stator and hollow shaft can be replaced. The impeller is connected with the right-handed screw of the main shaft, the stator is connected with the left-handed screw of the hollow sleeve, and the hollow shaft is connected with the machine head on a left-handed basis. Pay attention to the rotation direction during replacement. The circulating cylinder (13) is connected with the stator uniformly using three rubber belts.
The valve on the hollow shaft is the main valve for switching off/on the air circuit. The valve on the flowmeter is a fine adjustment valve. Pay attention to the starting/closing sequence and prevent ore pulp from rushing into the flowmeter. The starting sequence: start the motoropen the main valveopen the fine adjustment valve; the shutdown sequence: close the main valvestop the motor. The seal ring at the upper end of the hollow shaft shall be checked regularly to prevent ore pulp leakage into the bearing caused by seal ring damage from damaging the bearing Check for air tightness in clear water during initial running after installation and repair. That is, after closing the main valve and starting the main shaft, there shall be no air bubble out of the periphery of the stator, the added clear water volume shall be in line with the nominal volume of the cell, and the speed is the highest speed in case of not exhausting air from the circulating cylinder. There is no special requirement for lubrication of the machines moving part. Inject instrument oil to the tachometer regularly. After the flowmeter is detached from the system, the air inflow of the machine will vary very greatly. Pay attention to this during use.
Stawell gold mine in co-operation with Outotec Services completed a flotation circuit upgrade on time and on budget last year that, instead of the projected 3.5% improvement, resulted in an increase of 4.5% since the project was completed. Payback was also impressive, occurring within less than four months.
Flotation has been at the heart of the mineral processing industry for over 100 years, addressing the sulphide problem of the early 1900s, and continues to provide one of the most important tools in mineral separation today. The realisation of the effect of a minerals hydrophobicity on flotation all those years ago has allowed us to treat oxides, sulphides and carbonates, coals and industrial minerals economically, and will continue to do so in the future.
There have been a number of important changes in the industry over the years as flotation technology and equipment have advanced. Xstrata Technology considers the most noticeable has been the increase in sizes of the flotation machines, from the multiple small square cells that were initially used, to the 300 m round cells used today that are the norm in large scale plants.
Other changes have been more subtle, but equally as important. One of these has been the design of the flotation circuit to make the most of the liberation and surface chemistry effects of the minerals. In a lot of these situations it is not a matter of bigger is better, that will make the process work, but being smarter in the application of flotation technology.
Xstrata Technology is one company that believes the smarter use of flotation machines can deliver big improvements in plant performance. Through its use of the naturally aspirated Jameson Cell, Xstrata Technology has been making inroads into the processing of more complex ores. Having a small footprint, and using the high intensity mixing environment of slurry and naturally induced air in a simple downcomer, the Jameson Cell provides an ideal environment for the separation of hydrophobic particles and gangue, it says. The small footprint of the cells also makes them ideal to retrofit into a circuit especially where space is tight.
While the cell has been included in some flotation applications as the only flotation technology such as coal and SX-EW, the main applications in base metals have seen the cell operating in conjunction with conventional cells. The combination of the two technologies enables the Jameson Cell to target the quicker floating material, while the conventional cells target the slower floating material. Such a combination provides a superior overall grade recovery response for the whole circuit, than just one technology type on its own, Xstrata Technology says. Below are some of the duties for which the Jameson Cell can be used.
Jameson Cells in a scalping operation target fast floating liberated minerals, and produce a final grade concentrate from them. The wash water added to the Jameson Cell assists in obtaining the required concentrate grade due to washing out the entrained gangue. Scalping can be done at the head of the cleaner (also known as pre cleaning), or at the head of the rougher (also known as pre roughing), and minimises the downstream flotation capacity using conventional cells needed to recover the slower floating minerals.
Sometimes deleterious elements found in the orebody are naturally highly hydrophobic, and need to be removed at the start of flotation, otherwise they will report with the valuable minerals to the concentrate and effect concentrate grade. Mineral species such as talc, carbon and carbon associated minerals, such as carbonaceous pyrite, can all be difficult to depress in a flotation circuit. On the other hand, floating them off in a prefloat circuit before the rougher is an easier way to handle them. Jameson Cells acting as a prefloat cell at the head of a rougher circuit, or treating the hydrophobic gangue as a prefloat rougher cleaner, is an ideal way to produce a throw away product before flotation of the valuable minerals, minimising reagent use and circulating loads.
Jameson Cells can be used in cleaning circuits to produce consistent final grade concentrates. The ability of the cell to keep a constant pulp level, even with up stream disturbances or loss of feed, enables a constant grade to be obtained.
Xstrata Technology concludes: Importantly in a lot of these circuits, it is not the selection of one type of technology that produces therequired grade and recovery, but the selection of several technologies to get the best results. The interaction of slow floating and fast floating minerals, entrainment, hydrophobic gangue and a myriad of other variables make it rare for just one type of technology to prevail, but the combination of different flotation machines can achieve the required outcome more efficiently, as well as make the circuit robust enough to handle variations in feed quality.
Clariant Mining Solutions service engineers develop custom formulated reagents for each ore to be processed, while collectors and frothers are carefully selected for mutual compatibility. Clariant is investing considerably in mining chemicals and in support services for its customers all over the world.
The Jameson Cell has benefitted from over 20 years of continuous development. Early this year, the 300th cell was sold into Capcoals Lake Lindsay coal operation in the Bowen Basin of Australia. Around this time there were a number of coal projects taking in new Jameson Cells, including expansion projects for Wesfarmers Curragh and Gloucester Coals Stratford operations (both in Australia), Riversdales Benga project in Mozambique and Energy Resources Ukhaa Khudag coking coal project in Mongolia.
Le Huynh, Jameson Cell Manager, said the interest for coal preparation plants has remained strong, where operators needed dependable and reliable technology to treat fine coal, an important source of revenue. During 2010, the Jameson Cell business also found success in other applications, including recovering organic from a copper raffinate stream at Xstrata-Anglo Americans Collahuasi copper SX-EW plant in Chile.
Le said the consistent generation of very fine bubbles and the high intensity mixing in the Jameson Cell, was ideal for recovering very low concentrations of organic from raffinate streams, typically less than several hundred ppm. High throughput in a small footprint, simple operation and extremely low maintenance due to no moving parts in the cell are distinct advantages in this application.
The cell is designed with features specific to suit such hydrometallurgy applications including specialist materials, a flat-bottomed flotation tank with integrated pump box and tailings recycle system, and large downcomers. The Collahuasi cell was the first of its type in Chile, though there are many other large cells installed in SX-EW plants in Mexico, USA and Australia to treat both raffinate and electrolyte streams.
Dominic Fragomeni, Manager Process Mineralogy, Xstrata Process Support (XPS), notes that accurate, rapid development of a milling and flotation flowsheet for a new orebody is key to successful mine development. Time honoured conventional practice has typically favoured the extraction of a bulk sample of up to several hundred tonnes for conventional pilot plant campaigns which could operate at several hundred kilograms per hour. Where sample extraction is limited, much reliance has been placed on locked cycle tests alone to produce design basis criteria. These approaches can be lengthy, expensive, carry scale up risk, and have seen a wide range of successes and failures at commissioning and during life of a mine.
XPS has miniaturised the pilot plant process. At the same time, it has improved the representativeness of results from the pilot plant campaign by using exploration drill core to formulate the pilot plant sample. This Flotation Mini Pilot Plant (MPP) was developed in collaboration with Eriez subsidiary Canadian Processing Technologies (CPT) and operates in fully continuous mode either around the clock or can be made to demonstrate unit operations on a shift basis. The feed samples are in the range of 0.5-5 t and can consist of exploration NQ drill core which improves the sample representativeness. The MPP operates in the range of 7-20 kg/h, an order of magnitude lower in sample mass and typically at a lower cost when compared to conventional pilot plants.
XPS has developed and validated a representative sampling strategy, an appropriate quality control model for metallurgical results and has accurately demonstrated operations results using Raglan and Strathcona ores and flowsheets. These validation campaigns, in scale down mode from the full scale plants, have produced actual mill recoveries to within 0.5% at the same concentrate grade with internal material balance consistent with the plant.
When designing a plant to recover copper, Scott Kay, Process Engineer with METS suggests (in METS Gazette, issue 32, October 2011) it would be prudent to perform some mineralogical analysis test work such as QEMSCAN (Quantitative Evaluation of Mineral by Scanning electron microscopy) to provide some knowledge on the proportion of sulphide and oxide minerals present, the grain sizes of each mineral and a suggested grind size before jumping into the bulk of the beneficiation test work.
Ideally, the characteristics of the copper bearing minerals should suggest an appropriate grinding circuit P80 of between 100 and 200 m (0.1 and 0.2 mm), which can be controlled by cyclones, or in some cases fine screens.
The Delkor BQR flotation machine (formally Bateman BQR) here at Messina Mowana Copper mine in Botswana. 15 x 50BQR and 16 x 200BQR flotation cells for Copper roughing, cleaning & re-cleaning. Oxide / Sulphide
Flotation reagent selection is paramount and test work is necessary to ensure the optimum reagent suite is utilised. If the ore contains a low amount of iron sulphides, xanthate collectors are often suitable to float copper sulphideminerals. If native gold is present, dithiophosphates can be used which are less selective to iron sulphides. Increasing and controlling the pH within the flotation vessel to between 10 and 12 causes the process to become more selective, away from iron sulphide gangue minerals such as pyrite to produce a cleaner copper mineral concentrate. Depending on the ore mineralogy, activators and depressants may be required to achieve the optimum reagent suite.
Recovery of copper oxide minerals can be achieved with flotation by sulphidising the ore. In essence, this creates a thin layer of copper sulphide (chalcocite) on the oxide grains which can then be activated and collected in the froth. When employed, this occurs after the sulphide flotation stage, however, this is not commonly used as other beneficiation processes, such as leaching and SX-EW are often more cost effective for copper oxide minerals.
A common flotation circuit usually includes a rougher/scavenger and a cleaner stage. As most copper orebodies exhibit an in-situ grade of less than 1% Cu, the mass pull to the rougher froth is often low. This means that the throughput of the cleaner stage is significantly less than the throughput of the rougher stage which imparts a relatively low capital and operating cost to the flotation circuit.
To counteract the possible absence of a scavenger stage, a slightly higher mass pull to the rougher froth is targeted (although still low overall) to increase overall copper recovery. The rougher froth can then be reground to increase the liberation of the copper sulphides from the iron sulphides before being fed to the cleaner flotation vessels. This results in a significant upgrade in copper in the cleaner froth whilst still achieving a high copper recovery. The final flotation concentrate usually contains between 25 and 40% Cu.
Alain Kabemba, Flotation Process Specialist at Delkor notes the major trend to treating lower-grade and more finely disseminated ores and lately the re-treatment of tailings. He also points to the broad applicability of size to below 10 m.
Real systems do not fulfil ideal conditions, mainly because of feed variation or disturbances. Before considering disturbances to flotation specifically, Kabemba says it is important to emphasise the interlock between grinding and flotation, not only with respect to particle size effects, but equally to flotation feed rate variations. The grinding circuit is usually designed to produce the optimum size distribution established in testing and given in the design criteria. When the product size alters from this optimum, control requires either changing feed tonnage to the circuit or changing product volume, with either causing changes in flotation feed rates.
While grindability changes due to the variation in ore properties are disturbances to the grinding circuit, they generate feed rate changes as disturbances to the flotation circuit. The variations in ore properties which affect flotation from those assumed in the design criteria must therefore necessarily include grindability changes.
This reflects important differences in flotation machine characteristics between the two processes. Grinding circuits are built and designed with fixed total mill volumes and energy input, so the grinding intensity is not a controllable variable, instead grinding retention time is changed by variation of feed rates. In contrast, the flotation circuit is provided both with adjustable froth and pulp volume for variation of flotation intensity by aeration rate or hydrodynamic adjustment. Reagent levels and dosages provide a further means for intensity control.
One recent trend has been towards larger, metallurgical efficient and more cost effective machines. These depart from the simpler tank/mechanism combination towards design which segregates and directs flow and towards providing an external air supply for types which had been self aerating and towards the application of hydrodynamic principles to cell design, like the Delkor BQR range of flotation machines, initially the Bateman BQR Float Cells.
Bateman has steadily developed the BQR flotation cells which have been in application for the past 30 years, and with its acquisition of Delkor in 2008, decided to rebrand the equipment into the Delkor equipment range. Kabemba explains that BQR cell capacities range from 0.5 to 150 m3 currently installed, and can be used in any application as roughers, scavengers and in cleaning and re-cleaning circuits.
Provide good contact between solid particles and air bubbles Maintain a stable froth/pulp interface Adequately suspend the solid particles in the slurry Provide sufficient froth removal capacity Provide adequate retention time to allow the desired recovery of valuable constituent.
Highest possible effective volume and reduced the froth travel distance Improved metallurgical performances in terms of grade recovery and reduced capital and operating costs based on reduced fabrication material and ease of maintenance
Kabemba says there are not many differences in terms of design between BQR Flotation cells; however, from the BQR1000 upwards, the flotation cells have internal launders to maintain the design objectives and benefits highlighted.
Operating variables, such as impeller speed, air rate, pulp and froth depths have to be adjustable over a sufficient range to provide optimum results with a given ore, grind and chemical treatment, but adjustment should not extend beyond the hydrodynamic regime in which good flotation is possible.
The largest current BQR flotation machine is shown in the table. In the near future the BQR2000 (200 m3) and BQR3000 (300 m3) will be available to the market. Kabemba also explained that circular cells reduce the amount of dead volume when compared to square cells. This enables a much higher effective pulp volume, hence increasing the effective energy input into the flotation cell. In addition tank type cells offer enhanced froth removal due to the uniform shape of the circular launders. He concluded that fully automated flotation cells are becoming more and more common with the aid of smart control and advances in software in the marketplace.
FLSmidths flotation team notes that fundamental flotation models suggest that a relationship exists between fine particle recovery and turbulent dissipation energy1. Conversely, increased turbulence in the rotorstator region is theoretically related to higher detachment rates of the coarser size range2. Conceptually, the suggested modes of recovery for the extreme size distribution regions appear to be diametrically opposed.
Industrial applications have previously confirmed that imparting greater power to flotation slurries yields significant improvements in fine particle recovery. However, recovery of the coarser size class favours an opposing approach, the FLSmidthteam believe. An improvement in the kinetics of the fine and coarse size classes, provided there is no adverse metallurgical influence on the intermediate size ranges, is obviously beneficial to the overall recovery response. Managing the local energy dissipation, and hence the power imparted to the slurry, offers the benefit of targeting the particle size ranges exhibiting slower kinetics.
New concept, Hybrid Energy FlotationTM (HEFTM),was recently introduced by FLSmidth. In principle it decouples regimes where fine and coarse particles are preferentially floated. HEF includes three sections:
This subject will be expanded upon at the 5th International Flotation Conference (Flotation 11) in Cape Town, South Africa. The fundamental parameters that influence fine and coarse particle recovery will be reviewed. The potential dual recovery benefit is then presented in terms of its practical implementation in a scavenging application. HEF is proposed as the preferred methodology of recovering these slow-floating size ranges; a method that opposes the traditional approach of residence time compensation.
StackCell offers column-like performance in a substantially smaller footprint than conventional cells. These compact, stackable units provide considerable savings for new installations and are ideal for expanding capacity in an existing plant
Eriez Flotation Group introduced the StackCell flotation concept in 2009. This innovative technology recovers fine particles more efficiently than mechanical flotation cells. Weve taken the inherent advantages of mechanical flotation and adapted them to a new design that is significantly smaller and requires less energy, explained Eriez Vice President Mike Mankosa. We focused on reducing the retention time and energy consumption by implementing a completely different approach to the flotation process. This new approach provides all the performance advantages of column flotation while greatly reducing capital, installation and operation costs.
At the core of the StackCell technology is a proprietary feed aeration system that concentrates the energy used to generate bubbles and provides bubble/particle contacting in a relatively small volume. An impeller in the aeration chamber located in the centre of the cell shears the air into extremely fine bubbles in the presence of feed slurry, thereby promoting bubble/particle contact. Unlike conventional, mechanically agitated flotation cells, the energy imparted to the slurry is used solely to generate bubbles rather than to maintain particles in suspension. This leads to reduced mixing in the cell and shorter residence time requirements.
The StackCell sparging system operates with low pressure, energy efficient blowers that decrease power consumption by 50% compared to air compressors or multi-stage blowers used in other flotation devices.
The low-profile StackCell design features an adjustable water system for froth washing and also takes advantage of a cell-to-cell configuration to minimise short-circuiting and improve recovery rates. Space requirements for the StackCell design are approximately half of equivalent column circuits, with corresponding reductions in weight leading to reductions in installation costs. Units can be shipped fully assembled and lifted into place without the need for field fabrication.
This technology can provide recoveries and product qualities comparable to column flotation systems while using a low profile design. Not intended to replace the need forcolumn flotation, it does provide an alternative method to column-like performance where space and/or capital is limited. The small size and low weight of the new StackCell makes possible lower cost upgrades where a single cell or series of cells may be placed into a currently overloaded flotation circuit with minimal retrofit costs.
Steve Flatman, General Manager of Maelgwyn Mineral Services (MMS) also comments on the trend of moving towards a finer grind to improve mineral liberation. Unfortunately conventional tank flotation cells are relatively inefficient in recovering these metal fines below 30 m and very inefficient at the ultra fine grind sizes below 15 m. The incorporation of regrind mills on rougher concentrates has further exacerbated this problem. To date the conventional flotation tank cell manufacturers have attempted to counter this fall off in recovery of fine particles by inputting increasing amounts of energy (bigger agitation motors) into the system to improve bubble particle contact. Unfortunately this tends to compromise coarse particle recovery.
He says the solution is MMSs Imhoflot pneumatic flotation technology and specifically the Imhoflot G-Cell. Recent pilot plant test work at a nickel operation with a three stage Imhoflot G-Cell pilot plant enabled an additional 30% nickel to be recovered from the conventional flotation tank cell final plant tails. The recovery was predominantly associated with the minus-11 m fraction indicating that this improved recovery was not just related to additional residence time. The above results are in line with an earlier pilot plant trial using G-Cells on a zinc operation where an additional 10-20% zinc was recovered from cleaner tailings this time being associated with minus 7 m material.
It is postulated that the above improvements are related to the order of magnitude increase in terms of air rate (m/min/m pulp)for the G-Cells due to their principle of operation where forced bubble particle contact takes place in the aeration chamber rather than the cell itself with the cell merely acting as a froth separation chamber. Typically in percentage terms the G-Cell air rates are five to ten times that of conventional flotation although the overall or total air usage is approximately half.
When this additional targeted energy input is combined with the centrifugal action of the GCell and small bubbles benefits are obtained in both the flotation rate (kinetics) and overall recovery. The improved kinetics results in a much lower residence time than conventional flotation facilitating a double benefit of both reduced footprint and improved recovery.
Metso notes a main drawback of column cells being low recovery performance, typically resulting in bigger circulating loads. Its CISA sparger is derived from the patented MicrocelTM technology and enhances metallurgical performance by allowing flexibility on the graderecovery curve. Metso Cisa says the main advantages of its column technology include:
At the bottom of the column, the sparger system raises mineral recovery by increased carrying capacity due to finer bubble sizes. This maximises the bubble surface area flux which is a standard parameter in evaluating flotation device performance. It also provides maximum particle-bubble contacts within the static mixers and effective reagent activation from the mechanical operation of the pump.
It is well known that coarse particles behave poorly in a conventional flotation cell and were previously regarded as non-floatable. However, recent laboratory work demonstrates that Fluidised Bed Froth (FBF) flotation extends the upper size limit of flotation recovery by a factor of 2-3 resulting in significant concentrator performance benefits. AMIRAs P1047 project, Improved Coarse Particle Recovery by FBF Flotation, is expected to commence in 2012, and will be structured in two phases.
Early rejection of gangue with minimum mineral loss. Potential for significant increase in concentrator throughput or significant improvement in capital efficiency Reduced energy consumption. Independent modelling predicts that if particles of 1 mm can be floated, comminution energy consumption will be lowered by at least 20%. Better management of water requirement. FBF cells can take product straight from the milling circuit without dilution, and the feed to the FBF cell could be up to 80% w/w solids, which could lead to significant savings in process water demand. Improve recovery of metallic and other dense minerals. In a continuous FBF Cell, dense mineral particles will tend to sink to the bottom and accumulate in the cell, thus they can be recovered in a concentrated form by emptying the cell periodically. This could be a significant benefit where the concentration of the heavy metallic material is too low to warrant a separate treatment plant to recover them.
In Australia, Northgate Minerals Stawell gold mine recently completed a project through which it aimed to increase recoveries by 3.5% by upgrading the flotation plant. This upgrade was implemented after Stawell changed its production profile to process lower grade ore at higher throughput rates.
Instead of the projected 3.5% improvement, the upgrade from Outotec Services has resulted in an increase of 4.5% since the project was completed on time and on budget last year, despite the wettest seasonal weather in recorded history. Payback was also impressive, occurring within less than four months. The projected payback was 5.5 months, so it was a pleasant surprise when it happened so soon explains Jodie Hendy, senior metallurgist at Stawell.
The project has also achieved payback in less than four months and has delivered further ongoing benefits, including easier operation and reduced maintenance costs, says Outotec Services, which worked in close partnership with Stawell Gold to ensure the site remained fully operational during
The mine, which has produced more than 2 Moz in its 26-year history, previously employed a flotation circuit consisting of a bank of eight mechanical trough cells in the rougher circuit, followed by two banks of 2 x OK3 Outotec cells as cleaners. The feed rate to the cells was between 90-105 t/h, at 50-55% solids. The overall flotation circuit was not performing at optimal rate due to entrainment problems in the rougher cells when feed density increased from 45% to 55% solids, typically at 105 t/h.
In anticipation of future production levels and as part of Stawells focus on operational excellence, it was decided to upgrade the flotation circuit. Following a site audit from Outotec Services, a 2 x TankCell -20 configuration equipped with larger TankCell -30 mechanisms was proposed to help optimise flotation. The larger mechanisms would allow operation at very high percent solids (50% and over).
The TankCell design also allows a much deeper froth depth and better concentrate grade through optimised launder lip length and surface area. These cells known for great performance, ease of operation and reduced power and air consumption. Outotec Services was commissioned to handle the complete turnkey solution of the new rougher circuit, including design, supply, installation and commissioning.
The schedule was demanding but achievable, in just 30 weeks. It was decided to adopt the partnering approach between Stawell and Outotec Services, because this collaborative method ensured open communication, with all parties having greater ownership of the project and its aims. This close teamwork resulted in meticulous planning and site remaining fully operational at all times. Pipework and electrical easement ducts, for example, were rerouted early in the project. Tie-in points for new cells and rerouting of pipework were also planned upfront in the project and all disruptive work was completed during shutdowns.
The project overcame a number of challenges, including an extremely limited footprint, which was adjacent to a gabion wall, close to the runof-mine pad and also close to a reagents shed, which could not be moved. Additionally, existing process requirements at Stawell required specific elevations for the new TankCells. Structural stability was the main issue when designing the tank support structure due to the height of the tanks and the limited footprint. Sufficient stiffness was required such that the operation frequencies of the TankCells would not interfere with the natural frequency of the tank support structure. Through FE modelling of the structure, section sizes and bracing orientations were optimised to produce the required stiffness.
Despite the challenges, the turnkey installation of the new rougher circuit, along with blowers for the complete flotation circuit, was completed within deadlines. Because all tie-in points had been already carefully planned upfront, commissioning was a seamless exercise.
Designed to cope with projected increases in production and considerably more operator friendly than its predecessor, the new TankCell 20 cells have quickly proved their worth at site. The air demand for the old rougher cells, for example, was estimated at over 3,000 Am3/h, whereas the estimated air demand on the Outotec TankCells is a maximum of 992 Am3/h.
The Outotec FloatForce rotor-stator mechanism, with its unique design, delivers enhanced flotation cell hydrodynamics and improved wear life and maintenance. Maintenance on the Outotec TankCells has also been minimal since the upgrade, Hendy commented. Basically we check the cells during shutdowns but there has been no maintenance required in the nine months since commissioning. The TankCells have really delivered on their reputation. Basically, they do exactly what they are supposed to do.
Turning to flotation reagents, Frank Cappuccitti, President of Flottec explains that Flottec and Cidra are working very hard jointly on developing instruments that will measure hydrodynamics in the flotation cell and circuit in a bid for better flotation control. This would be a great step forward in using a combination of reagents and sensors to optimise flotation systems. It brings together the knowledge we have developed in both how reagents effect hydrodynamics and measuring the hydrodynamics to maintain optimum conditions. He explains that back in the 1990s, when he worked at a well-known mining chemicals supplier, we spent most of our research on trying to find the best collectors. The thinking was that we could try to develop collectors with absolute specificity. In other words, we could develop a collector that would float only specific minerals and provide clients with an almost perfect flotation separation. This was our approach to flotation optimisation. Unfortunately, we discovered that there was no such thing as absolute specificity. In fact, we had trouble measuring any improvements in the circuits because they were multi-variant and highly complex. Every change made was always a trade off between grade, recovery and cost. Changing one thing in the circuit seemed to improve something but always got a negative response in some other variable. It was also very hard to measure the performance of the flotation circuit because the only real parameters you could measure on line were concentrate grades and tails of the circuits, which were always after the fact. There was little ability and understanding about what real time measurements we could take other than air rates, cell levels and flow rates. So even if we got an improvement or a response to a change, we never knew if that was a response to a change or a natural variation in the system. Every test needed long term statistical trials to get some confidence in any real change.
So, I wrote a paper in the 1990s that basically said that until we could measure the real time variables in a flotation system and learned to really understand and control the system, we were limited in our ability to work on continuous improvement in reagent optimisation. We needed new sensors that could measure the performance of the flotation circuit so we could learn to control it. Once we got this, then we could actually measure improvements and use this to develop reagents.
Fortunately, with the advent of strong computing power and software, we have moved forward tremendously in the last decade in understanding the flotation circuit. Froth cameras that tried to measure froth grade and velocity were one of the first new sensors developed to assist in optimising circuits. Through the work of universities such as McGill and organisations like JKtech, new sensors have been developed that could actually measure reliably and in real time the hydrodynamic parameters in the flotation cell. Flotation cell hydrodynamics (gas dispersion parameters) is critical to the performance of the cell. When we talk about these parameters, we are talking about measuring what is happening in a flotation cell. Flotation is really about making bubbles and using the surface area of the bubble to do the work of transporting hydrophobic minerals to the froth. In flotation cells, we add air, create bubbles of a certain size and speed that provide the surface area to do the flotation. The more bubbles and the smaller the bubble, the more surface area we have to do the work. This surface area we create is known as the surface bubble flux (Sb) and controls the kinetics of flotation. Now that we have instruments that can measure the air into a cell (known as Jg), measure the size of the bubble diameter (Db) and the gas hold up (Eg), we can figure out how the relationship between these parameters and how they affect the Sb and flotation circuit performance. We can also now do research on how reagents can be used to control these parameters as well.
Research of the last few years has shown that frothers actually play a much more important role in flotation hydrodynamics than once thought. Frothers perform two major functions. They create and maintain small bubbles in the pulp to transport the minerals and they create the froth on top of the cell to hold the minerals until they can be recovered. The froth is created because frothers allow a film of water to form on the bubbles which makes them stable enough not to break when they reach the surface of the cell. Fortunately, the water drains over a short period of time and the froth will eventually break down. Froth breakdown is essential for cleaning and transporting the concentrates. Small bubbles are essential in making flotation efficient. For the same volume of air in a cell, smaller bubbles give much higher surface area, which in turn gives much higher kinetics.
We now know that as you increase the concentration of frothers to the cell, the bubble size gets smaller, and the film of water on the bubble gets bigger. But bubble size does not keep getting smaller forever. The frother will reduce the bubble down to a certain size, which is about the same for all frothers in the same set of conditions. The concentration of frother where the bubble is at a minimum is known as the critical coalescence concentration or CCC.
Each frother has a different CCC. Each frother also has a different ability to add water to the bubble and hence provides different froth stability. This also changes with concentration. We have learned in the last few years that each frother has a hydrodynamic curve which relates the bubble size with the froth stability. Strong frothers give very high froth stability at the CCC, while weak frothers give very low stability of the froth at the CCC.
This new understanding of how frothers affect flotation cell hydrodynamics has lead to new methodologies to optimise flotation circuits. Flottec has worked on an optimisation system where a frother is added to a circuit at the CCC (which guarantees maximum kinetics or maximum Sb) and the performance is measured. Then frothers of different strength are added (always at the CCC) until the right strength for maximum performance is determined. Adding the frother at the CCC is the critical optimisation difference. By doing this you are always guaranteed to have maximum kinetics. If the frother used is too strong, the dosage will have to be cut back below the CCC or the froth will be too persistent. This lowers flotation kinetics. If the frother is too weak, too much has to be added to get the froth strength and this increases cost and likely reduces recovery. Flottec has been conducting research withMcGill University to develop the hydrodynamic curves and CCC for all families of frothers in order to implement the new methodology of frother optimisation in plants.
The next step in this research is to be able to use new sensor technology to measure and control the flotation system by controlling the hydrodynamics in the cell. With our current knowledge of how air rate, cell levels, and frother addition affect bubble size, water recovery and gas hold up, we can use these control variables to maintain the optimum hydrodynamics in the cell resulting in the optimum flotation circuit performance. Flottec is working with companies like Cidra to develop new sensors that can provide real time information on cell hydrodynamics (gas dispersion parameters) and on froth stability properties in order for us to optimise the reagents and operating strategies used in a plant. This will bring flotation performance to the next level.
Clariant Mining Solutions business is investing considerably in mining chemicals. It has opened a new laboratory at its US headquarters in Houston, Texas, dedicated to the development and optimisation of chemical solutions for North American customers. The laboratory is part of a planned multi-million dollar investment into Clariants global Mining Solutions business, which includes establishing several new Mining Solutions laboratories around the world. This network is intended to enable the business to better support customer needs and address regional challenges. Most recently, Clariant has opened new mining labs in South Africa (Johannesburg) and in China (Guangzhou). The new laboratories will complement existing facilities in Europe and Latin America.
As part of Clariant Mining Solutions global investment, new mining labs have been established in South Africa and China, to complement those already operating in Brazil, Chile, Peru, Australia, North America, Russia and Germany
Mining is a strategic focus area for Clariant, said Christopher Oversby, Global Head of Clariants Oil & Mining Services business unit. This investment further demonstrates Clariants ongoing commitment to providing innovative technologies and solutions for our mining customers around the world.
The Houston laboratory will process ore samples from customers in the USA and Canada. These samples were previously handled in Clariants mining laboratories located in South America and at the companys global research facility in Frankfurt, Germany. We are very excited about the new mining laboratory and the opportunity it provides us for offering our North American mineral processing customers even more localised services and attention, said Paul Gould, Global Head of Marketing and Application Development for Clariant Mining Solutions. The Houston lab will allow Clariant technicians to more efficiently develop optimised reagent solutions for our US and Canadian customers.
Additionally, Clariant is in the process of developing a new Innovation Center in Frankfurt at a cost of 50 million. Employing nearly 500 people and covering 30,000 m2, the facility will focus on customers using an integrated multidisciplinary approach to problem solving. Clariant says an open innovation approach on joint ventures with external partners will ensure the acceleration of the idea-to-market process. Mining research and development will also be part of this facility.
Axis House has been developing reagent technologies for the past 10 years, at its flotation laboratory in Cape Town, South Africa and more recently at it metallurgical labs in Sydney and Melbourne. These were acquired when Axis House bought the oxide flotation reagent technology from Ausmelt Chemicals. A practical application technology strategy was followed with Axis House providing a complimentary suite selection and optimisation service to its clients, who were then mainly interested in the Axis developed technology of combining fatty acids, hydroxamates and sulphidisation suites to effectively and economically float oxide minerals.
Early on the focus was on developing reagents to float complex ores which contained multiple minerals with varying flotation kinetics. Often the limiting factor was not only the sluggish flotation kinetics of the minerals but the process plants own equipment limitations, like flotation and conditioning times. Developing a reagent that floated a certain mineral was simply not enough. The solution was to develop suites of reagents which could function synergistically. By altering the types of collectors and the dosages, the company could optimise both the use of the processing equipment and the collecting power. It says this approach has successfully been applied to various types of base metal oxide ores.
It is now taking this innovative approach into the field of rare earth element (REE) flotation. This fits into the Axis House business plan as the chemistries are quite similar to what is in existence at Axis already. Of course some tweaks will have to be made to the reagents as well as the laboratories this process has already started, with the first batch of REE test material having arrived at Cape Town, and new reagent samples at the ready. There are a large number of REE projects coming online in the next few years. Most of these orebodies have not been previously treated at industrial level and so will face difficulties when scaling up. REO (Rare Earth Oxides) are often difficult to float and the development of multiple collector systems for these ore types would help increase the viability of these projects.
Jerry Sullivan, Global Marketing Manager-Mineral Processing, Cytec Industries Inc, discussed collectors, which contain mineralselective functional groups. They have a hydrophobic hydrocarbon tail. Changing the molecules functional group changes the preference for what mineral it will adsorb on to. Changing the length of the hydrocarbon chain changes the hydrophobicity of the molecule. This is related to the strength of the collector.
Within the collector molecule, there are donor atoms whose goal is to form bonds with acceptor atoms within the ore. Nitrogen, oxygen, and sulphur are the most important donor atoms in all reagent chemistry. Sulphur is the most important donor in sulphide collectors. Nitrogen and oxygen are additional donor atoms. Phosphorous and carbon are central atoms carrying the donors. They only have indirect participation in interactions. He noted the general characteristics of sulphide collectors to be:
Ionic collectors are stronger and less selective Neutral, oily collectors are weaker, more selective Higher homologues (more carbons) are stronger than lower homologues (fewer carbons) Cytecs NCPs are very selective collectors
There is a strong case for formulated products (or blends), he continued That is because mineralogy is complex. Plant performance is also inherently variable. Mineralogy changes routinely. In addition, different minerals have different affinities for reagents. Various minerals will compete for a given reagent. Modifiers used will also influence reagent partitioning. Particle size distribution will also affect recoveries (recovery losses in coarse and fine size range). A single collector will not be sufficiently robust. Indeed, most plants use two or more collectors. The goal is to pick reagents that will get to the right minerals. Utilising a collector blend can balance cost and performance.
Cytec has multiple collectors and collector blends that are continuously being developed to tailor to the customers application. A few of the collector families that have recently been introduced to the market include the new XR Series Xanthate Replacement Collectors, developed to meet the desire to replace xanthates. This new series of collectors are cost competitive with xanthates and are strong collectors but with high selectivity. In addition, they are safer and vastly improves handling and level of toxic exposure of the personnel to product, stock safety management and simplifies plant operations.
The XD 5002 blends were developed to operate in a broad pH range 8-12 and be highly selective in Cu/Mo, Cu/Au sulphide ores, enhance Mo recovery in Cu/Mo bulk float and enhance Au recovery in Cu/Au ores. The MAXGOLDTM blends were introduced to float primary Au ores; auriferous pyrite, arsenopyrite, and tellurides and are also capable of enhancing recovery in Cu/Au ores.
It is now possible to use measurement devices based on impedance tomography to create realtime 3D images. The technology opens up entirely new possibilities in controlling flotation processes. With Flotation Watch the operator can see what takes place underneath the surface. Flotation Watch measures several parameters at the same time, on-line. The sensor can measure the stiffness of the froth, the thickness of the froth, analyse the interface area between the froth and the slurry and it can analyse the slurry too depending on the customer needs, says Jukka Hakola, Numcores Vice President of Sales and Marketing.
With Numcore measurement devices, the size and quantity of air bubbles and the solid matter content of the froth bed can be monitored by means of electric conductivity distribution. With Flotation Watch the stiffness of the flotation froth can be measured and this helps to keep the recovery in higher level. The signals for the production failures, such as hardening and collapse of the froth bed, can be seen beforehand and avoided. This way we can help to minimise the losses in the flotation process, says Hakola.
Real-time characteristics are a key in this technology; in other words, the system continuously provides the operator with factual data on what is happening in the flotation cells, for example the location of minerals and the bottom surface of the froth bed. Because it has not been possible to look inside tanks, controlling a mineral concentration process has largely been based on experience-derived knowhow. Now that operators can look inside the process, it is possible for them to maintain an optimal mix all the time, says Hakola.
Numcore has, in close co-operation with a few key customers, developed measurement technology to better serve everyday work. We have now delivered several Flotation Watch sensors to flotation cells in several markets and for different metals such as copper, zinc and gold. One of the main benefits is that contamination of the probe is taken into account in mathematical formula and the measurement probe does not need to be cleaned. Our sensor has been in a zinc rougher flotation cell for nine months and is giving accurate results to the operator. We can now offer automated control for flotation process with Flotation Watch and see that this can bring new benefits for our customers, he promises.
Numcores measurement technology is currently in test use at Inmets Pyhsalmi copper-zinc mine (IM, April 2010, pp10-18), among others. According to Seppo Lhteenmki, Processing Mill Manager, the system has provided accurate information on the condition of the froth bed, and the technology has functioned reliably. We have tested the device for a few months, and it has provided clear benefits for those operators who have received operator training for it and actively monitored the data provided by the system. The device appears to be so useful, in fact, that we are seriously considering buying it after the test period, he says.
Mettler Toledo notes that pH greatly determines the efficiency of the flotation, which minerals will float, or even if there will be any flotation at all. The critical pH value for efficient flotation depends on the mineral and the collector. Below this value the mineral will float, above it, it will not (or, in some cases, vice versa).
In a recent white paper www.mt.com/pro-phflotation, the company says in order to overcome difficulties with the hostile environment in flotation cells, sensor manufacturers are very creative in their choice of sensor design. It is possible to find pH electrodes with a ceramic, plastic, rubber or even a wood reference diaphragm. Still, their performance can be severely limited as the colloidal particles and sulphides interfere almost instantly with the reference system. The sensors maintenance requirement is therefore high, requiring very frequent cleaning and calibration, and usually sensor life is short.
Mettler Toledo has acknowledged this issue and to combat it has designed the InPro 4260i pH electrode with Xerolyt Extra solid polymer electrolyte. The InPro 4260i does not have a diaphragm and instead features an open junction, which is an opening that allows direct contact between the process medium and the electrolyte. Contrary to the miniscule capillaries of any other type of diaphragm in conventional pH electrodes, the diameter of the open junction is extremely large and much less susceptible to clogging or fouling. Another significant difference is in the choice of polymer electrolyte. Xerolyt Extra was designed specifically for service in tough environments to provide a strong and lasting barrier against sulphide poisoning.
The companys Intelligent Sensor Management (ISM) is a platform based on sensors with embedded digital technology for better pH management. The integrated system consists of a digital sensor and ISM-compatible transmitter. The key to the technology is a microprocessor which is contained within the sensor head and is powered by and read through the transmitter. Critical sensor information such as identification, calibration data, time in operation and process environment exposure are all recorded and used to continuously monitor the health of the sensor.
By constantly keeping track of process pH value, temperature and operating hours, ISM calculates when sensor calibration, cleaning or replacement will be needed. Any need for maintenance is recognised at an early stage.
In recent years, researchers at Imperial College have been focusing on measuring air recovery in industrial flotation cells and have found that a peak in metallurgical performance (improvements in both grade and recovery) corresponds well with a peak in air recovery. Major platinum and copper operations have already observed the benefits of using this methodology as developed by the researchers. JKTech is now licensed by Imperial Innovations to commercially provide this methodology and associated benefits to the global minerals industry.
The PAR technique comprises two stages evaluation and implementation. The evaluation stage involves determining the effect of the technology at a mine site, typically determining the peak air recovery for a bank (or banks) of flotation cells and evaluating the resultant metallurgical performance. The implementation stage involves setting the air rates to those that maximise the air and/or metal recovery, and support and training of site personnel including operating manuals. The implementation stage requires an end-user license to be obtained by the sites through Imperial Innovations.
GIW Industries has launched its new High Volume Froth (HVF) pump. Unlike any other pump on the market, GIW says, the HVF pump can pump froth without airlocks. It provides continuous operation without shutdown or operator intervention. The new hydraulic design actually removes air from the impeller eye while the pump is running, so you can keep
Designed for air-entrained slurries, the pump can be used in phosphate mining, hard rock mining and oil sands. The pump offers improved efficiency and is environmentally friendly and cost effective, GIW reports
The GIW HVF can be retrofit into many existing froth applications. The pumps deaeration system includes a patent-pending vented impeller and airlock venting. This helps to eliminate sump overflow due to pump airlock; reduce downtime; and allow water use to be restricted to the bare minimum. Fewer pumps are required for less capital expense, requiring less water and power usage.
The HVF pump has been fully tested on froth and viscous liquids. The pump exceeded expectations at a large phosphate company in Finland. The companys existing pumps were not able to provide the required flow and were airlocking at only one-third of process design capacity. After installing an HVF pump, the company achieved a flow of 415 m3/h.
Traditional slurry pumps are prone to airlock when working with slurries that incorporate froth. A pump works by pulling in a liquid at a certain pressure and adding mechanical force to expel the liquid at a higher pressure. The air in the froth does not want to move to a higherpressure zone, and it is prone to build up at the lower-pressure pump entrance. The accumulation of air can eventually block the pump entrance completely, leading to airlock, which requires pump shutdown or operator intervention to avoid sump overflow.
How is GIWs HVF pump different? The main innovation is in the impeller design. Typically, air bubbles gather at the centre of the impeller as the heavier fluids are spun to the outer edges. The HVF pumps de-aeration system includes the vented impeller and airlock venting. In the HVF pump, small holes in the centre of the impeller allow air bubbles to pass through to a separate port. The port vents air up and out of the pump to normal atmospheric pressure.Get in Touch with Mechanic