what you need to know about rotary feeders in cement plants | precision machine and manufacturing

what you need to know about rotary feeders in cement plants | precision machine and manufacturing

This post begins with a look at the characteristics that make cement manufacturing so tough on material handling equipment. Following that is an examination of nine typical applications in a cement plant where rotary valves and feeders are proven problem-solvers.

Long-Cycle Operation Cement manufacturing is nearly a year-round, 24 hours per day business. Planned downtime is minimized. Unplanned downtime is not just inconvenient it is costly. The expectation is that equipment will run reliably from one outage to the next.

Materials Many of the precursors and inputs into the cement manufacturing process are inherently abrasive, including limestone, silica, slag, ash, and others. The critical intermediate cement form, clinker, is one of the most abrasive products in any process industry.

Volume The production scale required for economic, financially-viable cement manufacturing is enormous, and plants have gotten continuously larger over the years. Plants with a cement production capacity of 3 to 4 million tons per year are relatively common and far from the largest.

Particle/Piece Size At the front end of the process, quarried raw materials can arrive at the cement plant in a size equivalent to a softball. To continue the comparison, raw coal and clinker are usually in the tennis ball size category. Achieving the fine, powdered condition that is associated with cement is a continuous size reduction journey.

In North America, the majority of cement manufacturing plants use a vertical roller mill and an integrated separator (VRM) for grinding quarried limestone and other materials into raw meal. Throughput is usually in the range of 150-750 tons per hour. In raw mill feeding, a system of weigh-belts that discharge into the mill feeding device controls the material rate into the mill.

VRMs are fed either with a rotary feeder or a flap-gate system. In either, the primary role is to provide an airlock function to minimize the introduction of false air into the mill and separator.

A crucial consideration for cement plants is raw mill uptime. Rotary feeders, particularly new-generation designs such as the Precision PMCA Rotary Feeder, have proven to be much more reliable than flap-gates or older rotary feeders.

A Precision customer recently shared some illuminating statistics. Over a two-year operating cycle, accomplished without rebuilding the feeder, unplanned downtime was limited to less than 34 hours during planned production of 13,350 hours. 99.75% uptime!

A second significant advantage of rotary feeders over flap-gates is a much lower frequency and intensity of maintenance. The new generation of raw mill rotary feeders is made from heavier, thicker steel with a were building a tank attitude. Periodic maintenance is limited to an occasional visual inspection, bi-weekly or monthly lubrication, and little else.

VRMs are somewhat less common in finish mill applications. There are still many ball mills in use for cement grinding in North American. Functionally, the job of a finish mill feeder is the same as a raw mill feeder minimize false air passage into the mill: the airlock function. Finish mill feeders must handle large throughputs, 100-500 tons per hour rates are common.

For both rotary feeders and flap-gates, minimizing and controlling airflow into the mill despite the prolonged exposure to the sand-blasting effect is critical to performance. Improved rotary feeder designs, like the PMCA Rotary Feeder, and the use of abrasion-resistant steel can minimize gaps that allow false air infiltration.

Coal remains a common fuel choice for firing cement kilns in North America. Most plants receive their raw coal in a form that requires on-site grinding, using VRMs along with other mill types. Raymond bowl mills are particularly common.

Like the raw mill and finish mill applications, the infeed devices role here is as an airlock. A weigh belt system controls the feed rate. In most cases, coal mill feeders are smaller than raw mill or finish mill feeders with capacities of 10-100 tons per hour.

The #1 issue for coal mill operators is stickiness or coal build-up on all the material handling equipment, including the mill feeder. Raw coal, which is usually 3-4 inches or smaller, can have inherent moisture in it. If the plant receives its coal in open-top trucks or rail cars, surface moisture can accumulate. Surface moisture becomes even more problematic if the raw coal is stored outdoors.

Both conventional rotary feeders and especially flap-gates, struggle with handling raw coal. Maintenance and operations team members often spend hours trying to remove build-up to keep the system feeding and to maintain rate.

Cement plants have been substituting alternative fuels in place of coal for years. Liquid fuels and natural gas are outside the scope of this post. Solid fuels wood, tire shreds/chunks, carpet, plastics, nutshells, etc. are important fuel sources for cement plants, either year-round or in-season.

Rotary feeders in gravity-fed fuel systems segregate the negative pressure in the calciner from the atmospheric pressure outside to maintain balance in the calciner. The negative pressure is usually relatively modest. However, the potential for the system to go positive and push high-temperature gas back up into the rotary feeder means that the rotor-to-barrel clearance inside the rotary feeder must allow for a thermal shock. This increased clearance acts in opposition to what would otherwise be a tight clearance, low-leakage feeder.

Alternative fuels have a diverse range of caloric contents, bulk densities, and sizes. Plant control systems can compensate for variations in the first two. Variations in material size usually require a knife-style rotary feeder, like the Precision PMR Rotary Feeder, to minimize feeding disruptions.

Knife-style rotary feeders shear off oversized solid fuel pieces that would otherwise jam-up a rotary feeder and interrupt fuel flow. This ability means that the plant can utilize minimally-prepared fuels that are less costly than other heavily pre-processed fuels.

The alternative fuels section of this post discussed one pneumatic conveying application, and there are numerous others. For most pneumatic conveying applications, the rotary valve or rotary feeder will function as an airlock, but some applications may demand both airlock and metering functionality.

Properly designed pneumatic conveying systems are balanced and require the consistent introduction of the material into the air stream. A rotary valve or feeder with excessive internal clearance, either when new or after use, will reduce transport efficiency. Excessive internal clearance leads to blow-by, where the conveying air passes through the valve or feeder and out of the conveying line.

Loss of efficiency will cause the blower to consume more power and material transport rates to fall below target. The conveying air that passes through a wide-clearance valve or feeder also can disrupt the material being fed. This disruption can manifest itself as a fluctuating feed rate material, particularly something light, may not drop into the valve or feeder at the designed or assumed rate. A further issue is the possibility of dusting when the leakage through the valve or feeder is so great that material is blown out of the top of the vessel.

Proper sizing and matching of the valve or feeder and the pneumatic line injector (a T-injector in Precisions parlance) is critical to proper feeding in a pneumatic conveying application. A very common concern is the operating pressure of the pneumatic system higher pressure will wear out all the conveying system components, including a valve or feeder, more quickly than a low-pressure system.

Excessive or increasing blow-by is the issue in pneumatic system feeding devices. A well-built rotary valve or feeder is preferred over a flap-gate in the cement industry. Tight initial clearance and resistance to clearance-widening wear in a rotary valve assure a lower level of blow-by than a flap-gate.

Common in storage silos or silo farms that hold raw meal, additives, finished cement, or a pulverized fuel, rotary valves in silo discharge applications are usually a metering device. The valve may also serve as an airlock function when a silo is discharging into a pneumatic line or air-slide. As the silo location may be in a less-traveled area, durability and reliability in the rotary valve are essential it may take time for personnel to notice if a valve isnt working or is leaking.

Silo discharge applications often require large capacity rotary valves. Units sized for 5 to 8 CFR (cubic feet per revolution) are reasonably common, which would produce a transfer rate of more than 7000 cubic feet per hour. Depending on the bulk density of the material in the silo, this could equate to 250 to 300 tons per hour. Very high throughput silo discharge applications dictate a robust, long-lived rotary valve.

Rotary valves, such as the Precision PMV Modular Rotary Valve, outperform flap-gates in this application, can be quickly activated and, with an inverter-duty motor, ramped up or down to meet required transfer rates.

The most common method of dosing pulverized coal or pet coke to the kiln main burner is to use a Pfister DRW rotor weighfeeder. A rotary feeder is often installed above the DRW to meter fuel, allowing the Pfister unit to be neither starved nor flooded. For accurate weighfeeding, the DRW must have a full-head of fuel available to it at all times.

The Precision PMV and other rotary valves in this application have to work without fail and operate over long operating cycles. Failure of the rotary valve would take down the DRW and the kiln. Durability is the key in this application, making rotary valves with upgraded materials of construction highly recommended. The successful operation also calls for an inverter-duty motor in the drive package the same signal relayed to the DRW for more or less fuel controls the rotor speed of the valve.

DSI (Dry Sorbent Injection) systems, which are sometimes known as FGD (Flue Gas Desulphurization) systems, are a specialized subset of pneumatic conveying. These systems treat flue gas to remove SOx and other contaminants. The most common sorbent is hydrated lime, but other sorbents, including trona, activated carbon, or some types of ash, are used.

This is another application where the rotary valve has to be available to run at all times. The treatment of flue gas is so vital that DSI systems are often set-up as a so-called dual train system with duplicate blowers, rotary valves, and metering devices. These pull from the same sorbent silo and discharge into the same pneumatic line that feeds the lances in the flue.

As with other pneumatic conveying systems, excessive blow-by can be the major challenge in DSI systems. Flue gas treatment systems rely on a precise ratio of sorbent to gas. If some of the sorbent is not reaching the lances or nozzles in the flue, the system wont function properly. Hydrated lime presents unique problems due to its tendency to react chemically if over-heated and its tendency to build-up on metal surfaces if not kept very dry.

Tight-clearance rotary valves, such as the Precision PMV Modular Rotary Valve, are very desirable for DSI applications and are often equipped with optional upgrades to combat the issues with sorbents. These options include air purges, beveled rotor vanes, and zero speed sensors. Rotary valves for this application are generally small with capacities under 0.35 CFR (cubic feet per revolution.)

In many industries, rotary valves in dust collection systems can run for years and years with little attention as the products are mildly-abrasive, the loading is generally light, and there is minimal pressure drop. To some extent, these characteristics are similar in the cement industry except that products can be abrasive, particularly CKD (kiln dust), and at times at an elevated temperature.

While this application may be somewhat less demanding than others in a cement plant, it can be quite problematic if the rotary valves in a dust collector arent working. Housekeeping and clean-up can consume maintenance or operations man-hours if the valves arent working correctly or appropriately sized.

Rotary valves in dust collection systems are airlocks as they are discharging to atmospheric pressure usually to a screw conveyor or belt conveyor. The valves typically are relatively small with capacities generally less than 0.65 CFR; roughly a 12 valve.

There are numerous applications for rotary feeders and valves in cement manufacturing. The raw material and inputs, the existing process equipment, and the finished products at each plant vary considerably. So, it is difficult to apply hard-and-fast rules to selecting the best rotary valve or feeder for your application. However, here are some broad guidelines.

This is primarily a philosophical choice about costs. Smaller equipment running at a higher rate of speed usually requires a lower initial investment. However, the high speed will cause faster wear than a larger piece of equipment running more slowly. As a result, rebuilding or replacement costs will be incurred on a shorter cycle and measured over a medium-term horizon, overall equipment investment will be higher. Higher maintenance costs, for bearings, seals, and other components, also tend to correlate to operating speed further accentuating the expenses associated with the Small & Fast choice.

At Precision, our experience leads us to believe that valves and feeders will last longer and provide an improved total-cost-of-ownership if operated at 20 rpm or less and sized accordingly. We also have confidence that slower speeds and larger equipment will improve feeding performance. At higher speeds and with small diameter rotors, consistently filling the rotor pockets is difficult in Small & Fast.

Other valve and feeder manufacturers and some system design firms dont subscribe to the Large & Slow philosophy as the better choice. Our companys Mission Statement states, We provide solutions that deliver an exceptional return-on-investment and we are convinced that Large & Slow is a key to stronger ROI.

The hardest-to-know parameter in rotary valve or feeder sizing is pocket fill. For example, a dry, flowable material, coming out of a well-designed silo, with a consistently full-head of material in the silo, and into a valve with a sufficiently large inlet should fill the rotor pockets to at least 90%. Lots of qualifiers in that description, no?

Understanding all the details of the application is vitally important. Material moisture content can influence the fill assumption as can the tendency of the material to bridge. Particle size, specifically maximum dimensions, will have a significant impact.

Relatively small differences in pocket fill assumption can have an outsized impact on valve and feeder sizing. For example, in alternative fuels, changing the pocket fill assumption from 50% to 30% will push the feeder up at least one size larger or possibly two sizes. This change will impact equipment cost, the horsepower requirement, and the installation envelope.

Sizing for airlock-only applications is somewhat easier than for a combined airlock and metering device situation. In airlock-only apps, the sizing math is concerned with only the maximum anticipated throughput. Metering applications must consider minimum, maximum, and typical throughput rates and the turn-down that is achievable with the drive package.

In the cement industry, it is relatively common to run sizing calculations using the assumption of 30% pocket fill. This assumption provides for lots of growth in throughput in the future and provides reasonable assurance that the valve or feeder wont become a bottleneck.

One final subtlety regarding pocket fill assumptions in cement bears mentioning. Capacities are often provided to Precision in terms like 250 tons per hour. This sort of hourly rate is critical to proper sizing, but it does not describe the mini-surges or pulses that can develop in operation. Plant control systems frequently maintain feed rates within tight upper and lower bounds, but the potential for very short-term surges in rates are a reason not to assume a high-percentage pocket fill.

For many cement applications, particularly those where the sole function of the valve or feeder is as an airlock, the temptation is to assume that the tighter the internal clearances, the better. Up to a point, that is useful guidance.

Tighter clearances do reduce blow-by. For example, a Precision PMV-12 with a rotor-to-barrel clearance of 0.005 has 44% less blow-by than an identical valve with 0.010 rotor-to-barrel clearance, reducing blow-by from 108 CFM to 61 CFM.

Tight internal clearance (rotor-to-barrel) in rotary valves and feeders will reduce the pathways for blow-by or false air to migrate. Minimizing airflow is, by definition, the valve or feeders job as an airlock and will result in improved material handling and transport.

Rotary valves and feeders, once purchased and installed, become the responsibility of the plant maintenance team. Most cement industry insiders would agree that maintenance is the most overloaded department. Troublesome, maintenance-intensive equipment is something that they could happily do without.

Chief among these design features are such things as replaceable rotor tips, adjustable rotor tips, and feeder inlet flaps. Each has a certain theoretical appeal and can have a beneficial impact on performance when new.However, the downsides of frequent maintenance attention and the difficulty of even accessing these components to adjust them or change them out seem to us to strongly outweigh any benefits.

Heavy steel body panel inserts, bulletproof glass, and other Up-Armoring features increase occupant protection in limousines used by presidents, prime ministers, and other dignitaries. The same concept protects rotary valves and rotary feeders against abrasive wear.

Up-Armoring has its place in material handling equipment. However, too often, the Up-Armoring lacks a coordinated, thoughtful design. For example, Stellite-tipped rotors sound like a robust, durable feature. However, if that Stellite-tipped rotor is running inside an ordinary cast-iron valve housing, the gain in durability will be illusory or non-existent.

Up-Armoring should be one part of a product plan that includes excellent manufacturing workmanship, proper sizing, consideration of system design, and site-specific factors. Otherwise, it is just slapping expensive materials onto a valve or feeder for marketing purposes.

The kilns, the mills, and the control systems receive much attention in cement manufacturing. Rightfully so, as they are the keys to producing a saleable product. Weve described some of the considerations and complications in several feeding applications that, if not done correctly, have the potential to bring cement manufacturing to a halt, significantly disrupt production, or needlessly consume energy, fuel, and manpower.

Precisions strongly-held position is that rotary valves and feeders cost-effectively address all of the applications discussed here. If youd like to learn more about our solutions, please contact us. Precision is focused on solving the toughest cement industrys material handling challenges. Wed be delighted to help you overcome the material handling challenges in your plant.

pfister

pfister

PFISTER has established its name through a vast number of technical innovations for many applications and lines of business. PFISTER is an international leader in rotor weighfeeder technology for precise dosing of various materials.

One of the many advantages of this technology: The systems can be applied multifariously in different lines of business and for various purposes. In cement manufacturing e.g. PFISTER technologies are useful in all stages of production: from the raw mill, the kiln plant to the finish mill and cement preloading.

The PFISTER product range consists of classical linear dosing systems consisting of belt weighfeeders as well as the famous rotor weighfeeders and measuring scales. The performance range of these technologically advanced systems spans from dosing of fine products such as cement, coal dust, alternative fuels, raw meal or fly ashes to dosing of coarse materials such as clinker, raw coal or additives.

Especially in the field of dosing alternative fuels such as fluff, plastic, RDF, animal meal, tetra pack, bio masses etc., the rotor weighfeeder finds a broad field of employment as a multi-fuel system. Whether the materials to be dosed are pulverised, flaky or fibrous: PFISTER dosing systems are adjusted individually to the needs of the customer and each individual application.

In the pro-active rotor weighfeeder, the material mass is measured before it leaves the rotor weighfeeder. That means that the speed of the rotor is adjusted before the material is discharged into the system. The result is extremely high short and long-term accuracy.

Even long after the start-up of a PFISTERsolution, you can rely on our experienced service technicians for first-class service. A 24-hour hotline and online trouble-shooting provide worldwide support.

Constant efforts in R&D are key to our success In order to provide high-end dosing solutions to our customers now and in the future, PFISTER allocates substantial resources to research and development.For customers, applying PFISTERsystems means an investment for the future: The systems enable optimal production and add to our customers competitive advantage.All relevant PFISTERproducts and systems are certified to ATEX, which provides the technical requirements to be applied to equipment intended for use in potentially explosive environments.

Ludwig Pfister Wag-Fabrik (Ludwig Pfister Weighing Company) was founded in 1894 by blacksmith Ludwig Pfister. The companys first products were scales used for a number of different industrial and agricultural applications.

To the present day, PFISTER are specialists in dosing technology and runs offices worldwide. PFISTERis still headquartered in Germany, including departments for research, development, engineering, assembly, sales, service and management.

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.

coal pulverizer maintenance improves boiler combustion

coal pulverizer maintenance improves boiler combustion

Coal pulverizers are the heart of a pulverized coal-fueled boiler. Often, the root causes of nonoptimized combustion lie with the pulverizers. Capacity; reliability; and environmental issues such as slagging, fouling, and higher-than-desired CO or NOx emissions; overheated superheater and reheater tube metals; and cinder fouling of selective catalytic reduction catalyst and air heaters have all, at times, been linked to poor pulverizer performance.

It is common in our experience to find pulverizers that are performing poorly, yet the degree to which unit reliability, efficiency, capacity, and environmental emissions are affected by them is often underappreciated. However, there are steps that can be taken to measure, quantify, and monitor pulverizer operation so that changes can be made to improve performance.

Obtaining representative samples of coal fineness and fuel distribution is the first step. The best method we have found to do this is by using an isokinetic coal sampler. All fuel lines must be sampled and the fineness sieved from each coal pipe separately. The fuel mass flow to each burner must also be measured.

An isokinetic sampler similar to the one shown in Figure 1 can be used with a dirty-air velocity probe to establish the proper sample extraction rate. The fuel line velocities that are measured are used to compute the primary airflow and air/fuel (A/F) ratios of each coal pipe. The velocities and A/F ratios are valuable for diagnosing combustion issues.

Tuning improvements can only be implemented after the true current performance is measured. Sampling single pipes, or sampling at a single location, is totally unacceptable in our experience. All fuel pipes must be sampled and sieved individually for best accuracy.

The fuel lines must be tested/sampled under normal operating conditions. Often during testing, we have observed that operating conditions are changed. For example, we have seen primary airflow reduced, classifiers reset for best fineness, and fuel flow brought back to mill design fuel flow rates. In other words, the assessment is not representative of normal operation. Testing under special conditions proves nothing. Only testing under normal operational conditions enables a useful diagnosis.

Acceptable standards for best low-NOx burner performance are coal fineness of 75% passing a 200-mesh sieve and less than 0.1% remaining on a 50-mesh sieve. Fuel balance should be within the range of plus or minus 10%. However, in our experience, it is common to find fuel fineness that is well below 65% passing through a 200-mesh sieve and more than 1% remaining on a 50-mesh sieve. Furthermore, it is common to see fuel imbalances that exceed plus or minus 30% to the burners.

2. Lopsided fuel distribution. This test data shows pulverizer fuel flow rates measured during an actual test. The fuel distribution is poor in this case. It should be balanced within plus or minus 10%. Source: Storm Technologies

Once the data are compiled, out-of-specification readings must be investigated. An internal inspection should be completed to check the wear of grinding elements and classifier housings, vanes, and other internal components. Also, check for foreign matter that might be blocking fuel flow paths. Any problems identified should be corrected.

Achieving best fuel balance is done by first balancing the system resistance in all of the fuel lines using orifices and then increasing fuel fineness. Figure 3 shows the typical results of this approach to fuel balancing. Of course, internal pulverizer blue printing to best mechanical tolerances and optimizing an accurate and repeatable air/fuel ration is also important.

There are various adjustments and mechanical tuning measures that can be completed to improve the performance of a modern coal pulverizer. Locations identified on Figure 4 are keyed to the following improvements (journal pressures listed are for a #943-size pulverizer):

Install synchronized straight vane coarse particle guide blades (A). The retrofit lengthens the classifier blades, improves material to 3/8-inch-thick AR400 or better, and implements critical synchronization of the classifier blades for fuel/air two-phase mixture homogenization.

Install orifice housings (E) to support future balancing efforts. The change offers two advantages: It is easier for maintenance personnel to change out orifice plates, and it speeds testing and balancing efforts.

Verify that roll-to-ring clearances (I) are absolutely no greater than 1/4-inch over the full grinding length of the rolls and that the clearance is parallel to the bowl for the full width of the rolls.

Additionally, ensure that venturi sensing lines, connections, and transmitters are all in good condition. Tempering air dampers should be stroked and corrections made to ensure that they close at least 99%. This should also be done for hot air dampers.

All internal mill surfaces must be smooth so that the swirl of the coal/air mixture may enter and leave the classifier without spoiling or turbulence caused by double layer tiles, welded pad eyes, or other internal surface discontinuities. This, combined with precise primary airflow measurement and control, is important for uniform fuel distribution at the classifier outlet. All internal dimensions should be verified and technically directed by a qualified service engineer during installation of performance parts and before closing the mill.

Overhauling Stock gravimetric feeders can also be worthwhile. The refurbishment should include calibrating load cells properly, installing modern microprocessors, adjusting belt tension appropriately, and completing accurate speed calibration.

Another pulverizer performance monitoring technique is to observe the drive motor power input in correlation with the coal feed rate. The relationship of ton/hour to kWh power input is a very helpful leading indicator (Figure 5). A reduction in the power used by a coal pulverizer does not usually result in an improved heat rate. Instead, more grinding power nearly always correlates with better coal fineness. The only exception is with a ball tube mill.

Pulverizer capacity is not simply a measure of coal throughput; capacity refers to a certain coal throughput at a given fineness, raw coal sizing, HGI (Hardgrove Grindability Index), and moisture. Often, if the desired coal throughput or load response is not achieved, the primary airflow will be elevated to higher flow rates than are best for capacity. However, increased throughput achieved in this way sacrifices fuel fineness (Figure 6).

6. A negative correlation. The three main factors that constitute pulverized capacity are Hardgrove Grindability Index (HGI), fineness, and coal throughput. Increasing throughput will adversely affect fineness. Source: Storm Technologies

This is very common. When the primary airflow is higher than optimum, it creates entrainment of larger-than-desired coal particles leaving the mills, promotes poor fuel distribution, lengthens flames, and impairs low-NOx burner performance. We have found that targeting an A/F ratio around 1.8 lb of air per lb of fuel is best. For some pulverizer types, such as ball tube mills and high-speed attrition mills, often a 1.6 A/F ratio is optimum. Never have we observed good combustion conditions or good mill performance with A/F ratios of 2.5 or greater. However, it is common to find A/F ratios of 2.2 to 2.5 during baseline testing.

Results of as-found airflow to fuel flow testing from a sample plant are shown in Figure 7. In this particular case, the A/F ratios tested were well above the desired A/F ramp. When operators bias the primary airflow up, above the optimum, it may improve wet-coal drying, load response, and reduce coal spillage from the grinding zone, but it is not good for the furnace burner belt performance.

7. Missing the mark. The air-to-fuel (A/F) flows shown in this graph are much higher than optimum. Installing properly sized rotating throats is often required to achieve targeted A/F ratios. Source: Storm Technologies

All combustion airflow inputs should be measured and controlled, if possible. We prefer to use the tried and proven venturi or flow nozzles for this purpose because they are rugged, reliable, offer repeatable results, and are less prone to impulse line plugging.

Several components can be retrofitted to improve the performance of MPS mills. The changes may cost a significant amount of money, but the work will usually pay for itself through improved heat rate. One 450-MW coal-fired unit in the Midwest spent $750,000 on testing, changes, and tuning, but calculated that it saved millions by improving heat rate and by allowing higher-slagging fuel to be used at a reduced cost, which greatly increased its market competitivness.

8. Extending component lives. Getting 8,000 hours per year performance requires condition-based maintenance utilizing periodic isokinetic coal sampling and venturi hot K testing and calibration. Source: Storm Technologies

Cold air has a different density than hot air, which can result in a variance in measured velocity at similar mass flow rates. Because the K-factor will vary, we prefer to conduct Hot-K airflow calibrations that use typical operational air or gas density when developing an average K-factor. That information is important when developing a pulverizer primary airflow curve and when measuring all combustion airflows.

Most instrumentation technicians can calibrate and check using the Hot-K method to verify calibration accuracy. As previously mentioned, high primary airflows are one of the most common root causes of poor pulverizer performance, in our experience, so obtaining accurate and representative measurements is very important.

The goal is to obtain the best possible burner belt combustion because it improves heat rate, reduces slagging/fouling, lowers emissions, and reduces cost. All of the following actions can help improve burner belt combustion:

dosing of raw coal with rotor weighfeeder pfister trw-k | flsmidth

dosing of raw coal with rotor weighfeeder pfister trw-k | flsmidth

In 2009 Holcim Spain started a project to improve thepet-coke grinding performance in order to obtain safe andreliable coal mill feeding and to improve the coal mill grindingperformance. The start-up of this installation took placein 2010. With rotor weighfeeder Pfister TRW-K FLSmidth

The project included the replacement of the old raw coalfeeding equipment to the mill, which consisted of an apronfeeder, for the new design of rotor weighfeeder PfisterTRW-K.Rotor weighfeeder Pfister TRW-K installed in Carbonerasis the first reference installation of raw coal and pet cokemill feeding in the cement industry. The know-how of thisspecific technology was transferred from the power industrywhere rotor weighfeeder systems Pfister TRW-K have beensuccessfully in operation since 2003.

The installation supplied by FLSmidth Pfister GmbH consistsof a vibrating hopper (1m), a shut-off gate and a rotorweighfeeders Pfister TRW-K (4.18/5).The installation is a raw coal system to feed the coal mill.It consist of a 70 m3 hopper where the raw coal is stored.The vibrating hopper ensures the constant flow of thematerial. Installed below there is a dosing system (rotorweighfeeder Pfister TRW-K) and a drag chain conveyorbehind the airlock at the mill inlet. The chain conveyor transportsthe material either to the mill inlet or to another feedpoint for truck transport. The performance of rotor weighfeederPfister TRW-K is laid out to use up to 40 t/h of rawcoal with a range of 10 - 100% nominal and a precision of+/- 1%. Due to ATEX requirements, the design of theinstallation is pressure- shock resistant. The vibration hooper,shut off gate and Pfister weighfeeder are pressure shockresistant up to 3,5 bar.

The outstanding compact design of the gravimetric rotorweighfeeder Pfister TRW-K permits a minimum installationin terms of height. It also results in less maintenancework and a longer life of operation owing to the followingfeatures:

Pfister rotor weighfeeder TRW-K is a very reliable equipment,robust and free of spillages. Due to the exact and stablecoal and pet-coke dosing for mill feeding the mill grindingperformance is increased and mill vibrations decreased.

In order to obtain safe and reliable coal mill feeding, thestability and precision of raw coal dosing to the mill are keyelements. With its rotor weighfeeder Pfister TRW-Kconcept, FLSmidthPfister offers a future-oriented technologywith more than 50 units running successfully in operationsince 2003.

FLSmidth Pfister GmbH does not only supply the singledosing machines. FLSmidth Pfisters know-how includesthe complete setup and surrounding of the installation likesilo engineering, intermediate material transport and safetyequipment. That ensures that customers get all engineeringfrom one experience partner and one single source.In the meantime Holcim Cement Australia has also installeda rotor weighfeeder Pfister TRW-K at their coal mill,feeding 20 t/h.

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.

operations and maintenance training for ball mills

operations and maintenance training for ball mills

Learn how to optimise your ball mill systems in this 5-day training seminar focused on best practices for operations and maintenance (preventive and reactive) to achieve energy savings, reduced maintenance costs and overall improved productivity of the ball mill systems. Ball mills are used for many applications in cement production: raw meal grinding, coal and petcoke grinding as well as finish cement grinding. Each of these systems have their similarities and differences. This ball mill seminar is designed to train your personnel on the overall technology, operation and maintenance of your ball mill cement grinding system. The seminar focuses on the latest best practices for the operation and maintenance of ball mill systems to allow for optimal cement production, energy savings, reduced maintenance costs as well as the continuous improvement of the overall equipment operation. The course offers classroom instruction from our FLSmidth ball mill specialists and case studies based on real situations at different ball mill installations. Working sessions are scheduled to allow for a thorough study of the design and function of the main equipment, including but not limited to the latest methods for optimisation and possibilities for upgrades and modernisation of the current systems and operations. Maintenance training is focused on routine preventive maintenance to minimize downtime in ball mill systems, as well as developing preventive maintenance programmes and troubleshooting techniques to quickly identify and fix problems. Beyond what you will learn about your ball mill systems, this seminar provides excellent networking opportunities with our specialists as well as your counterparts from the cement industry.

Learn how to optimise your ball mill systems in this 5-day training seminar focused on best practices for operations and maintenance (preventive and reactive) to achieve energy savings, reduced maintenance costs and overall improved productivity of the ball mill systems.

Ball mills are used for many applications in cement production: raw meal grinding, coal and petcoke grinding as well as finish cement grinding. Each of these systems have their similarities and differences. This ball mill seminar is designed to train your personnel on the overall technology, operation and maintenance of your ball mill cement grinding system.

The seminar focuses on the latest best practices for the operation and maintenance of ball mill systems to allow for optimal cement production, energy savings, reduced maintenance costs as well as the continuous improvement of the overall equipment operation.

The course offers classroom instruction from our FLSmidth ball mill specialists and case studies based on real situations at different ball mill installations. Working sessions are scheduled to allow for a thorough study of the design and function of the main equipment, including but not limited to the latest methods for optimisation and possibilities for upgrades and modernisation of the current systems and operations.

Maintenance training is focused on routine preventive maintenance to minimize downtime in ball mill systems, as well as developing preventive maintenance programmes and troubleshooting techniques to quickly identify and fix problems.

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.

improving the coal-feeding conveying system in a holcim cement plant

improving the coal-feeding conveying system in a holcim cement plant

AERZEN, as a specialist in cement applications, has improved the pneumatic conveying coal feeding system to the main burner at the Holcim Colombia plant. The plant is located in Nobsa, a small town 2.5 hours away from Bogot. The plant capacity is about 3Mt/year of cement and has a market share in Colombia of 12%, with high growth expectations following the establishment of the Lafarge Holcim joint venture in 2015.

In 2014, Aerzen USA optimised the pneumatic coal-conveying transport to the main burner, also known as the Pfister system. In this application, two AERZEN GM 35S tri-lobe blowers from the 90s were in operation. Each machine operated at an intake volume flow of 37.4m/min, differential pressure of 600mbar and with a 75kW (100HP) electric motor. The noise generated was calculated at 102dB as the machines didnt have acoustic hoods (local Colombian regulations define 80dB as the maximum allowed noise level). Power consumption demand for the system was measured at an average of 54kW per machine, which represented an annual energy cost of USD 78,000 (considering a kW cost of 0.1 USD and 20,000 hours MTBR - Mean Time Between Repairs).

Javier Forero, Pfister Area Manager, indicates the results 10% energy consumption reduction, about 20% noise level reduction in the operating area thanks to the improved acoustic hoods, better control of the coal flow into the burner which improves our kiln operation.

AERZENs commitment as an application specialist presented a solution with Delta Hybrid rotary lobe compressors, model D62S, that were selected specifically for this application with the primary purpose of improving the following aspects: noise level reduction to comply with the Colombian regulation of 80dB maximum. The D62S blowers operate at 72dB under the same operational conditions with a 10% energy consumption reduction, which represents annual savings of around USD 7,800.Installed power reduction was achieved with the Delta Hybrid performance by replacing the existing 75kW motors for 55kW IE3 premium efficiency motors. Process stability improved due to the Delta Hybrids operating principle that reduces pulsations when the flow is conveyed, delivering a more laminar flow, which makes the burning process smoother.In addition to the obvious advantages which came from upgrading the technology, for Holcim it was also important to have a TCO (Total Cost of Ownership) evaluation of the new machines in the system. AERZEN delivered a 5-year projection which indicated that by using the Delta Hybrid rotary lobe compressors operational costs would be reduced by 40% and would operate at 40,000 hours MTBR, with 50% better performance than could be achieved with conventional tri-lobe blowers.Javier Forero, Pfister Area Manager, sums up the results after one year of operation with the new technology: 10% energy consumption reduction, about 20% noise level reduction in the operating area thanks to the improved acoustic hoods, better control of the coal flow into the burner, which improves our kiln operation.

The AERZEN subsidiary Aerzen USA started operations in Colombia in 2008 with the primary purpose of supporting existing customers, such as Holcim, with AERZEN machinery in their processes.The Holcim Colombia plant uses AERZEN technology in all eight main applications that required oil-free, low-pressure air supply, from raw mill pneumatic conveying to the raw meal silos up to the bagging systems for finished cement. Thanks to AERZENs specific knowledge in cement applications, an upgrade was successfully implemented in the coal feeding system to the main burner that brings savings in energy consumption, noise reduction and more stable and laminar air flow that helps improve the burners stability.

Aerzener Maschinenfabrik GmbH successfully sold its product division rotary piston gas meters to RMA Rheinau GmbH at the end of 2018.The AERZEN rotary piston gas meter has been a product rich in tradition at Aerzener Maschinenfabrik since 1930. Due to their design, however, demand and sales of measuring instruments were concentrated primarily on the German market. On the basis of the companys international growth strategy, which mainly focuses on compressor technology and application specialisation, the AERZEN gas meter no longer fits in with the future target orientation. Against this background, the management decided to sell this product division to another company in the industry with good know-how.For AERZEN it was very important to find a buyer who would offer the product range to our long-standing customers with the usual high quality, says the CEO, Klaus-Hasso Heller. We are very pleased that we have now found a reliable partner in RMA, based in Rheinau, who will not only continue the AERZEN technology, but will also develop it further in this way, adds Klaus-Hasso Heller.

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