screening 101

screening 101

Screening is the passing of material through definite and uniform apertures is the only true and accurate means of grading to a required particle size. Air separation and hydraulic classification depend upon gravity and particle shape, and result in the segregation and retention of material of higher specific gravity and lower surface area irrespective of size.

The use of Screens increases with the education and civilization of a people and with the improving and perfecting of an art. In our advanced civilization practically everything that we eat, wear and use has been in contact with, or dependent upon screens in some phase of its growth, development or processing. In this treatise, we are only concerned with the sorting, grading or sizing as accomplished with a mechanical screening device.

Some materials such as beach sands, clays, native chemicals, etc., occur in nature in a closely graded state resulting from a mechanical water sorting, precipitation or gravity deposition. They require only scalping or some form of treatment for removal of tramp coarse foreign elements. Others such as salt, sugar and various chemicals are crystallized or precipitated in their processing to fairly close limits of size. They require only such sorting or grading as is dictated by market preference and conditions of use.

In mechanical mixtures such as raw cement, finished fertilizers, stock feeds, etc., the ingredients are blended, ground and screened to a definite fineness. This maintains the intimate relationship by preventing segregation of a coarse constituent through automatic sorting. We have all noted how by piling an ungraded material the fines will segregate in the center of the pile and the coarse will automatically run to the outside and bottom. Metallic and non-metallic ores, stone and other aggregates, coal and coke, various furnace products, chemicals, cerealsetcetera, must be crushed, ground, disintegrated or pulverized before they can go on to further processing and ultimate use. In these fields screens are used for sorting into definite grades, top scalping for removal of coarse oversize and foreign material, bottom scalping for elimination of fines and dirt, and to return oversize to a crusher or grinder until it is reduced to a size finer than the opening of the screen. This latter practice is known as closed circuit crushing or grinding.

A nest of standard brass framed screens, with a definite ratio between openings, is used to sort a representative sample into the clean fractions retained on each screen. The tabulated resulting sieve analysis graphically shows the percentages of given sizes present in the sample. (Table I, p. 347). It indicates just what is available for recovery by screening through and over certain openings in a commercial production screening operation and also shows the reduction obtained by passage through crusher or grinding mill.

Another important factor in commercial screening that will be revealed by a sieve analysis is the percentage of near-mesh material present in the screen feed. If, for instance, it is observed that 40 percent of the sample had passed through the 8-mesh testing screen and was retained on 10- mesh and another 40 percent had passed through 10-mesh and was retained on 14-mesh, an efficient productionscreening operation at 10-mesh would require the maximum in screen area, particularly as to length. This preponderance of near-mesh, or go and no-go size of particle, obviously makes a difficult separation condition. In such cases unless the proper care is taken in the selection of the type of screening device and the specification of the wire cloth used on it, the openings may fill up and blind to a point where no separation is obtained.

In addition to the necessary sieve analysis, other factors must be known before a proper and intelligent recommendation can be made on any but the simplest of screening problems. Many cases require a laboratory test, simulating actual operating conditions, before the size and type of the screen can be determined and proper specification of screen cloth selected. The screen doctor must have the answer to the following questions before he can make proper diagnosis and prescribe treatment:

Capacity required in tons or gallons per hour? This should be expressed in both average and maximum, because peak loads, even of short duration, may result in spoiling of products previously graded or may upset subsequent steps in the operation, due to the drop in screening efficiency. Sufficient screen area should be provided to handle the maximum load.

Type of screening, wet or dry? How much water can be added? In the case of wet screening it is necessary to know if a definite density of the through screen product must be maintained and how much spray water can be added to rinse the oversize.

Percentage of moisture present in the feed? The maximum figure should be given here because different materials become unscreenable at varying degrees of moisture. To effect a separationat a given fineness it may be necessary to dry the material or add water and wash it through the screen.

Is material free-screening? An affirmative answer here obviates practically all other questions. Sticky? As clay, some food products, chemicals, etc. This determines if screening is practical and type of wire cloth recommended.

By closed circuit crushing or grinding it is meant that the product from a crusher or grinder is fed to a screen. The material that has been reduced to sufficient fineness passes through the openings and the oversize is returned to the breaker for further reduction. Escape from the circuit can only be through the screen so this product, the undersize, is equal in tonnage to the initial feed to the crusher or mill. The oversize returned for further work is known as the circulating load. It is a most important factor and can be extremely insidious. If the screen is inefficient and rejects finished material or if the crusher will not reduce the oversize fast enough, this load may build up, and rapidly, to a point beyond the capacity of the breaker, the screen or the conveying equipment, whicheverproves to be the neck of the bottle.

For greatest economy and efficiency, fines should be removed by means of a screen just as fast as they are created in each successive stage of crushing or grinding. Most every case must be handled on its own individual merits and proper balance worked out. In some cases a circulating load as high as 1,000 percent is considered economical. Picture how this would affect the requirement in screening capacity with eleven tons of material handled for every ton produced.

The percentage of circulating load can be readily determined from the sieve analyses of the screen feed, the oversize and the undersize (See Table 1). Samples should be taken simultaneously after circulating load has reached its peak. Conditions and analyses will be similar to those set forth in flowsheet at right. The formula can be expressed:

PercentCirculating Load=100 (B-C/A-C -1) A=Percent finer than required sizein the screen feed. B=Percent finer than required sizein the screen undersize. C=Percent finer than required sizein the screen oversize.

In the example, A equals 35.0,B equals 95.0, and C equals5.0. The value of 1 in the formula represents the initial feed to the circuit which is equivalentto the undersize, or product removed through the screen.

Percent Efficiency=100(100 F-D/AF) A=Percent finer than required size in the screen feed. D=Percent coarser than required size in the screen feed. F =Percent coarser than required size in the screen oversize.

There are different schools of thought on this subject and other formulae. Some operators are satisfied to simply use the percentage coarser than the screen opening in the overscreen product as the efficiency figure. This would be F in the above formula and 95 percent instead of 90.22 percent.

Dependent on the nature of the material and type of operation, screening may be accomplished through bars, perforated plate or woven wire screen. The bar screen is used for scalping extremely coarse material where definite sizing is of secondary importance and abrasion is severe. Perforated plate offers a smooth surface upon which heavy oversize will slide very easily, often too easily for good screening. Under some conditions it blinds less readily than woven wire screen. Objections to it are the fact that the openings wear gradually larger and larger, and the percentage of blank area is so high.

For most purposes woven wire screen, or wire cloth, is the best medium. With it the maximum in open area can be obtained. Various weights, metals and alloys, and shapes of openings are available to satisfy conditions of heavy load, abrasion, corrosion, screenability and capacity. Mesh in wire cloth is the number of openings per lineal inch and means nothing unless accompanied by the decimal designation of the wire diameter or the actual opening of the screen. It is best to specify the required screen opening as this can then be obtained in several meshes, dependentupon the weight of wire that is used. Obviously, for a given opening, the greater the mesh count and the finer the wire diameter, the higher will be the percentage of open area in the fabric.

Much as we might like to do so, we cannot have our cake and eat it, too. Therefore, the selection of a screen specification is usually a compromise. Dependent upon conditions, screen life is constantly being sacrificed for screenability and vice versa. For instance, a heavy and abrasive material suggests an extra heavy wire to secure maximum life. It is found, however, that the low percentage of open area restricts capacity and that the large wire diameter promotes blinding and lowers efficiency. A compromise is, therefore, made by easing off on the weight of the wire. Conversely, another material may, for instance, be damp and sticky, dictating the use of an extremely fine diameter of wire to minimize the surface upon which it may build up. Such a screen specification may last only a few hours and capacity and efficiency must be sacrificed in the interest of longer screen life.

Rectangular and elongated screen openings assist greatly in increasing capacity and eliminating blinding. The opening in a square mesh screen is shaped similar to a funnel and particles can be wedged into it to bear on all four sides. The rectangular opening limits this contact to three sides and thus minimizes the possibility of wedge blinding. When this slot is further elongated to many times the opening width, a springing of the long wires is possible and permanent blinding is eliminated. Naturally, these long openings can not be used for true sizing of anything but cubical or granular materials. Where flakes and slivers are present and cannot be tolerated in the screen under-size, square mesh cloth must be used at the sacrifice of capacity.

For abrasion resistance, high- carbon spring steel wire is available. Stainless steel and the non- ferrous alloys give a selection where rust and corrosion are a factor. The difference between success and failure of a screening operation may rest with the selection of the proper screen clothspecifications and this subject requires considerable thought and study, plus experience.

Reviewing the foregoing, it is readily understandable that a fixed table of screen capacities would be misleading and dangerous. There are so many variables that two neighbouring plants, working on the same deposit, may have entirely different screening conditions, due, for instance, to a difference in crushing practice. Larger tonnages can be handled on scalping operations, and in some cases with closed circuit crushing, than on close grading into specific fractions. On some materials a scalping deck over the sizing screen increases capacity by breaking and distributing the load and opening- up the mat of material. Washing increases capacity materially over so-called dry screening.

From the grizzly and trommel we have seen the development of screening devices through the shaking, knocking and bumping stages to the high speed vibrating screen of today. This development ran the range of eccentric head motions; knockers; cams; air, cam and electric vibrators; unbalanced shafts and eccentric flywheels; grasshopper motions, etc., up to the present positive-drive, high-speed, circle-throw, eccentric- shaft screen.

In this type the throw and speed must be properly specified and coordinated to secure the best screening action. Bearings should not be under shock and design should not be complicated with compensators and adjustments to eat power and tempt experimentation. The loading of the bearings should be so minimized that the equipment manufacturer evidences his confidence in his design by extending a generous guarantee.

In closing, it is recommended that the screen user select a proved and simple machine that will give uniform, continuous, care-free operation. Your supplier should qualify to consult with you on installation, operation, and selection of proper screen cloth specifications. Do not overlook this important service feature.

ore sintering - an overview | sciencedirect topics

ore sintering - an overview | sciencedirect topics

Iron ore sintering is a material preparation process employed worldwide in the production of iron and steel. According to statistical data on pollution, sintering plants rank second in terms of toxic emissions, after the incineration of municipal solid waste (Menad et al., 2006; Remus et al., 2013). Of the eight CORINAIR (Core Inventory of Air Emissions (environment)) standard gaseous compounds, all except ammonia are known to be emitted by sinter plants. As described in Chapter 14 on iron ore sintering, sintering involves the combustion of fossil fuels like coal and coke breeze to generate the heat required for sintering reactions. Therefore, emissions from the sintering process arise primarily from the combustion reactions in the sintering bed on the traveling sinter strand. The off-gas from the combustion reactions contains dust entrained directly from the strand along with combustion products such as CO, CO2, SOx, NOx, and particulate matter. The concentration of these substances varies with the quality of the fuel and raw materials used and the combustion conditions. Emissions also include volatile organic compounds (VOCs) formed from volatile material in the coke breeze and oily mill scale, and dioxins/furans formed in the presence of carbon, chlorine and metal catalysts, such as Cu, under certain operating conditions. While the majority of VOCs and dioxins/furans are vaporized, some of them may recondense and be trapped in the sinter bed. Metals are also volatilized from the raw materials used, and other acid vapors and high resistivity dusts are formed from the halides present in the raw materials. In addition, emissions also arise from material-handling operations, such as sinter discharge, crushing and screening, which result in airborne dust.

Original purpose of the iron-ore sintering process is to agglomerate fine ores into lump burdens for blast furnace (BF). Since sintering conditions, e.g., kinds of ores and used fluxing materials, and pregranulation processes, strongly affect the metallurgical properties of the produced sinter, many researches and developments on the sintering process have been made in order to achieve a stable and efficient BF operation. Major iron ores used in Asian and Oceanian countries are of Australia, Brazil, and India and they have relatively wide particle size ranges less than several millimeters. Some domestic ores are also used in China together with the imported ones, from which 45% of steel in the world is produced.

In the sintering process, iron ores are usually blended and mixed with fluxing materials, e.g., limestone and burnt lime, and fuels (so-called agglomeration agents), e.g., coke, anthracite, and some recycle dusts. Then, it is sent to a pregranulation process in which the mixture of raw materials is granulated with addition of water to have a size distribution less than about 10mm. The granulated materials are charged to a sintering machine to form the packed bed of granules with the care to give suitable segregations of granule size and coke content in the vertical direction. The granulation and charging are important operations, since they govern the coke combustion rate and temperature profile of the sintering bed through the influence on the permeability of the sintering bed.

Recent increase in the world steel production has made the deterioration of iron ore property apparent. In Australia, low-phosphorous Blockman ores, which are of hard hematite group, are being depleted and the ratio of goethite ores, which contains a larger amount of combined water, is increasing. There are mainly two types of goethite ores, i.e., Pisolite and Marra Mamba, and a part of latter has tended to export by blending with low-phosphorous Blockman ores [1]. In addition, a new type of ore called high-phosphorous Blockman ore will start to be exported in future. It also contains a significant amount of combined water, but has the possibility to be a major ore in future, since it has a large amount of deposit. A problem will be that preliminary removal of phosphorous component from this type of ores will not be easy, because it tends to coexist with goethite phase [1]. When using a larger amount of such ores, therefore, development of an efficient dephosphorous technology will be necessary during steel refining process.

The major agglomeration agent used for iron-ore sintering process is coke fine, which is undersize of coke charged to a BF. In the sintering process, coke combustion is one of the most important reactions, which affects temperature profile and structural change of the sintering bed and therefore governs strength and yield, productivity and metallurgical properties of the produced sinter. Besides coke, other heat sources are anthracite usually used for the reduction of NOx emissions, carbon contained in BF dust, and metallic iron and lower oxides of iron, i.e., FeO and Fe3O4, in mill scales. The sintering process is based on the reaction heats of the above solid fuels and the generated heats tend to accumulate in the lower bed with progress of the process. Therefore, the maximum temperature of the lower bed tends to be higher than that of the upper one. For more flexible control of the bed temperature profile, an injection technology of hydrocarbon gas from the top of the sintering bed has been developed [2]. On the other hand, utilization of biomass char has been also attempted as a carbon neutral fuel [35]. In the sintering process, selection of agglomeration agents and control of their reaction are important keys to reduce the CO2 emission.

Like other sintering processes, iron ore sintering converts iron ore fines of often 8mm sizing into larger agglomerates, namely, sinter, between 5 and 50mm particle size, which possess the physical and metallurgical characteristics and gas permeability required for efficient blast furnace operation. As shown in Figure 14.1, iron ore sintering is carried out in three stages: raw material preparation, ignition and firing, as well as cooling.

The sintering process begins with the preparation of a sinter mixture consisting of iron ore fines, fluxes, solid fuel (called bonding agents in Japan) such as coke breeze, and return fines from the sinter plant and blast furnace as well as recycled ferruginous materials from downstream iron and steelmaking processes. After being mixed in a rotating drum, water is then added to the mixture. Granulation is carried out in the same or a different rotating drum by controlling the moisture content and particle motion of the sinter mixture, sometimes with the help of binders, to form agglomerates of the sinter mixture or granules (also called micropellets, quasiparticles, or pseudoparticles). These granules are much coarser compared with the original sinter mixture and assist in obtaining optimum permeability of the sinter mixture during the sintering process.

The moistened granules of the sinter mixture are then loaded to a depth of typically 0.51m on a sinter strand, which is a continuous grate moving continuously at typically 23m/min. The sinter strand is normally about 46m wide with an effective sintering area of up to 600m2 and is covered generally with a layer of sized sinter screened out from the sinter product as a bedding material for the protection of the grates. After the granules are loaded and leveled on the sinter machine, the sinter bed passes a series of gas or oil burners, which heat the granules and ignite the coke particles at the surface of sinter bed. The heat generated from combustion of the coke particles continues to raise the temperature of successive layers of the sinter bed to generate a melt phase first from adhering fines and then by assimilation of coarse nucleus particles, which on cooling solidifies into a sinter matrix that bonds the initially loose iron ore particles into lumps of clinker-like material. The peak temperature of the burning coke layer (also called the flame front) reaches approximately 13001375C. The downdraft suction applied to the sinter bed helps to preheat the air sucked in from the top, to cool the sintered bed, and to heat and ignite the coke particles in the layer below the flame front. This allows the sintering of the iron ore granules on the grate to move downward with the flame front, while the grate proceeds horizontally toward the discharge point of the strand. The sinter strand speed and gas flow are so controlled that burn through (i.e., the point at which the flame front reaches the base of the strand) occurs just prior to the hot sinter being discharged.

At the end of the strand, the sintered product in the form of cake falls off the grate into a hot sinter breaker (primary crusher) where the hot sinter cake is crushed to a predetermined top particle size of typically 150200mm. The hot crushed sinter is sometimes screened to remove hot return fines and then discharged onto a straight or annular cooler, which cools the sinter down to about 150C. After the cooler, coarse sinter particles of larger than 5075mm are usually crushed by a secondary crusher and conveyed to the screening station where the product sinter, hearth material, and return fines are separated. The return fines, which are too fine and not suitable for use in blast furnaces (generally 5mm or under in particle size), are conveyed back to a bin for recycling in the sintering process.

The off-gas from selected zones of the sinter machine is sometimes mixed with cooler off-gas and/or ambient air and recirculated to the sinter machine by a sintering flue gas recirculation system or Emissions Optimized Sintering (EOS) system. This process not only allows savings in bonding agents due to the contribution of CO postcombustion and recirculated heat but also reduces the volume of waste gas and emissions from a sinter plant. For detailed information on EOS and sintering flue gas recirculation systems, please refer to Chapter 18 on sintering emissions and their mitigation technologies. The off-gas from other zones of the sinter machine is treated by a series of treatment steps after the primary dedusting step (e.g., an electrostatic precipitator or multi-cyclones) to reduce dust, acid gases, as well as harmful metallic and organic components. Selective catalytic reduction, where V2O5 is used as a catalyst to reduce NOx into N2, is often applied to remove NOx in the off-gas. SOx removal is achieved via installation of sintering flue gas desulfurization equipment. In addition to the conventional wet-type systems using limestone/lime, Mg(OH)2, or ammonia as absorbent, dry-type desulfurizing systems utilizing activated coke adsorption are now used. These systems not only are effective for desulfurization but also are effective for the removal of NOx and dioxins.

Denmark and the UK were the first European countries to introduce an Emission Trading System in 2000 and 2002, respectively. Now the European Directive 2003/87/CE has been approved introducing an E.U. Emission Trading System. According to this, since January 1, 2005, installations involved in activities listed in Annex I (see Appendix 1) must have a greenhouse gas emissions permit (the ability to measure and report emissions). Application can be made to the competent authority.

For each period (2005-2007, 2008-2012), member states develop a national plan to allocate the total quantity of allowances (Assigned Amount of UnitsAAUs). The National Plan must be approved by the Commission of the European Communities. At least 95% of the allocation will be free of charge in the 2005-2007 period and at least 90% in the 2008-2012 period. Allowances can be traded within the European Community. By April 30 of each year, starting from 2006, the owner of each installation will surrender a number of allowances equal to its emission in the previous year. For those who do not comply with the obligation, a penalty is applicable (40 euros per tonne in the 2005-2007 period, 100 euros per tonne in the 2008-2012 period). The member states will organize a registry for allowances issued, traded, and cancelled. The Commission shall designate a central administrator to maintain an independent transaction log recording the issue, transfer, and cancellation of allowances. The Directive 2003/87/CE does not allow participants to comply with obligations delivering other credits obtained through JI [Joint Implementation] and CDM [Clean Development Mechanism] projects. A Linking Directive, that amends the 2003/87 in order to make credits coming from Emission Reduction Units (ERUs) and credits relative to Certified Emission Reductions projects (CERs) valid for complying with the E.U. ETS obligation, has been recently approved.

This Black Certificate Market will join the GC and EEC markets in Italy, even though it will be at a European level while the latter two markets will be national. For some participants, Green and Black markets (i.e., electricity producers) will overlap, and it can be useful to have the same market platform to trade their certificates. In this sense, GME is going to organize an emission rights market where both Italian and other European operators can buy or sell their black certificates, providing a complete offer of environmental markets.

Production and Processing of Ferrous MetalsMetal ore (including sulphide ore) roasting or sintering installationsInstallations for the production of pig iron or steel (primary or secondary fusion) including continuous casting, with a capacity exceeding 2.5 tonnes per hour

Mineral IndustryInstallations for the production of cement clinker inrotary kilns with production capacity exceeding 500 tonnes per day, orlime in rotary kilns with production capacity exceeding 50 tonnes per day, orother furnaces with production capacity exceeding 50 tonnes per dayInstallations for the manufacture of glass including glass fiber with a melting capacity exceeding 20 tonnes per dayInstallations for the manufacture of ceramic products by firing (in particular, roofing tiles, bricks, refractory bricks, tiles, stoneware or porcelain) withproduction capacity exceeding 75 tonnes per day, and/orkiln capacity exceeding 4 m3 and setting density per kiln exceeding 300 kg/m3.

Installations for the production of cement clinker inrotary kilns with production capacity exceeding 500 tonnes per day, orlime in rotary kilns with production capacity exceeding 50 tonnes per day, orother furnaces with production capacity exceeding 50 tonnes per day

Installations for the manufacture of ceramic products by firing (in particular, roofing tiles, bricks, refractory bricks, tiles, stoneware or porcelain) withproduction capacity exceeding 75 tonnes per day, and/orkiln capacity exceeding 4 m3 and setting density per kiln exceeding 300 kg/m3.

The ore group iron ore textural classification scheme (Table 2.7 and Figures 2.7 and 2.8) has been developed to link ore texture to downstream processing performance including lump/fines ratio, beneficiation, blast furnace lump physical and metallurgical properties, or fine ore sintering quality (Clout, 2002). The Ore Group scheme defines textural groupings on the basis of similarities in mineralogy, ore texture, porosity, mineral associations, and hardness. Groups are also distinguished by what mineral forms the matrix and what is interstitial. Ore groups are the basic building blocks of iron ores. Textural characteristics are visible in hand specimen or under the petrographic microscope. Textures are often liberated from each other in both lump ore (40mm) and fine ore (6.3 to 0.06mm). The scheme follows a logical classification tree in the decision-making process (Figure 2.8) that can be defined numerically, measured objectively, and classified using automated optical image analysis (Donskoi et al., 2013). It groups together similar, but not perfectly, identical examples, with distinct processing characteristics. The scheme is easily adaptable to the introduction of new categories through the decision tree process and coding using three- or four-letter codes (Table 2.8).

Figure 2.7. Simplified iron ore classification scheme matrix. Note that hematite here can refer to either martite or microplaty hematite or both. Goethite may be the typical brown, hard or the yellow, ochreous variety.

Figure 2.8. The Iron Ore Group classification tree showing dominant mineral type, hardness, and texture steps. H, hematite; G, goethite; GB, brown goethite; OG, ochreous yellow goethite; GV, vitreous goethite; D, dense; P, porous; DH, dehydrated hematite.

The main ore texture groups (Table 2.7) include dense hematite (Figure 2.5a), dense martite-hematite (Figure 2.5b), microplaty hematite (Figures 2.3i and 2.5c and d), microplaty hematite-goethite (Figures 2.3j and 2.5e), martite-goethite (Figure 2.3g), goethite-martite (Figures 2.3f and 2.5g), and goethite-rich (Figures 2.3h and 2.5h). Different types of hematite are subdivided into martite, microplaty, specular, TextureX, and undifferentiated. TextureX is nanometer-sized platy hematite, typically has a deep red color, and is powdery (Trudu et al., 2004). The distinction between martite-goethite and goethite-martite textures is on the basis that the first mineral listed forms the matrix or supporting structure, while the latter is interstitial. Each group can be further subdivided into physically hard to softer subcategories.

The ore textural groups can be divided into those associated with primary replacement of BIF (groups 14; Figures 2.3el and 2.5ae) and secondary textures interpreted to have resulted from more recent modification by near-surface hydration or goethitization (groups 610; Figure 2.5g and h) or dehydration (group 5) and surface hard-capping (Figure 2.3d) processes (group 11) (Table 2.7).

Analogous ore textural groups have been documented from iron ore deposits in Australia, Brazil, and Africa (Clout, 2002, 2005). The principles of the ore group classification scheme formed the basis for the material-type classification used by Rio Tinto Iron Ore for logging of drill holes and geologic mapping (Box et al., 2002; Clout, 2002). In addition, recent automated optical microscopy techniques have enabled far more detailed, objective ore group abundance and porosity information to be collected than is possible with visual logging or SEM-based analysis (Donskoi et al., 2013).

The total energy use distribution [24] by various units of the steel plant (coke ovens, sinter plant, blast furnaces, steel shop, rolling mills, and power plant) is shown in Figure 4.2.8. It can be noted that the major share (72%) of energy is required during iron making which includes coke making (12%), iron ore sintering (6%), and blast furnaces (54%). The steel making needs very little share (4%) as the process is exothermic in nature. The thermal energy used in power generation and hot rolling account for 8% and 11%, respectively. The cold rolling needs 5% energy mainly as electricity.

The total energy input is partly (52%) used to meet chemical, thermal, and process needs of the plant and the rest (48%) is wasted. This energy used and wasted is illustrated [24] in Figure 4.2.9. The efforts are made to recover the waste heat to improve the efficiency of the process. The amount of sensible heat available [25] in various units is indicated in Figure 4.2.10.

This group of compounds, polychlorinated dibenzo-p-dioxins (PCDD), and polychlorinated dibenzofurans (PCDF), is known collectively as dioxins. Their molecular structure consists of two benzene rings joined at their meta positions by oxygen links, and the molecules may contain chlorine atoms substituted in positions 19. The extent of chlorination ranges from one to eight atoms, so that there are 75 isomers of PCDD and 135 of PCDF. Dioxins and furans are concentrated by the food chain and accumulate in dairy food, meat, fish and human fat.

Dioxins are found in low concentrations in nature, but now mostly find their way into the environment via combustion systems containing chlorine, for example, incinerators, iron ore sintering, metal processing and recovery, and even diesel motors. They were also formed as a by-product from the preparation of 2,4,5-T, a herbicide once used for crop spraying.

Only those molecules with four or more Cl atoms are found to be toxic, that is, 17 in total, with the most toxic being the symmetrical tetrachloro dioxin (TCDD). When toxicities are reported, TCDD is given a value of 1 and the other congeners are rated in proportion to TCDD. The total concentration is thus reported as a TCDD equivalent, or TEQ. They are extremely toxic to some animals and their long-term effects on humans are still being investigated. Cancer and interference with the immune system are likely effects.

There are dioxin-like chlorinated compounds such as co-planar polychlorinated biphenyls (PCB) which are also allocated toxic equivalents. These are formed in flames along with dioxins, but generally contribute far less to the TEQ values of power station emissions and ambient air. There are over 100 such compounds, but only seven are considered of environmental significance (Cleverly et al., 2007).

PCDD and PCDF can be formed in flames when carbon, oxygen and chlorine are present. They form from organic precursors in the gas phase at temperatures between 550C and 900C, and on ash surfaces at temperatures between 200C and 400C when a suitable metal catalyst, particularly copper, is available. The carbon source for formation on the ash is generally elemental carbon and the formation is called de novo. In some circumstances when the chlorophenol and chlorobenzene concentrations in the gas phase are high, they can adsorb onto the ash and form PCDD/F. This route is known as precursor formation.

Since only some members of the two groups of compounds PCDD and PCDF are toxic, their concentrations are generally reported as toxic equivalents or I-TEQ of 2,3,7,8-tetrachloro-dibenzo-p-dioxin, which is the most toxic (ngI-TEQ g1 for ash and ngI-TEQ Nm3 for gas). For wood ash, the ratio of total mass of PCDD/F to the mass of I-TEQ is about 50, similar to the value for MSW ash.

The reactions which produce PCDD/F are complex, and the extent of I-TEQ release in flue gases is determined by a number of factors. Regarding the feed material, the amounts of precursors, chlorine and copper (or to a lesser extent iron) are important. The PCDD/F products in the flyash are concentrated on the finer particles. The combustion conditions which favour formation are high ash loadings (particularly of finer particles) and long residence times in the appropriate temperature zones. Temperatures above 900C will quickly destroy PCDD/F in the gas phase, and temperatures above 400C will destroy it on the solid phase.

During de novo synthesis, if chlorine is present only at low concentration as in coal, it will probably be incorporated into PCDD/F via metal chlorides in the solid (ash) phase. Copper is particularly active in catalysing the reaction. The copper can also act as a shuttle for chlorine between the gas and solid phases. It has been found that sulphur- and nitrogen-containing compounds can inhibit the formation of PCDD/F during combustion, presumably by poisoning the catalytic sites. For instance, the addition of coal to the solid feed of MSW incinerators leads to a significant fall in PCDD/F emissions. A correlation between PCDD/F formation in combustion systems and the (copper + chlorine) and sulphur contents of the fuel has been produced by Thomas and McCreight (2008).

The emission of PCDD/F from a combustion system is the sum of two parts the gas phase material and the solid phase material present on the ash. The latter is determined by the product of the ash loading of the gas (g Nm3) and the PCCD/F concentration on the ash (ng g1). Ash concentrations of PCDD/F have frequently been measured, but the ash loading in the stack depends on the type of combustion system, the fuel and the efficiency of any particulate removal system. Because of the cost of the sampling/analysis procedures, most reports of PCDD/F content do not separate the gas and ash results, but combine the two extracts together for analysis. Efficient gas cleaning to remove particulates is important for low emission values of PCDD/F.

The legislated emission limit for much of the world is 0.1ngI-TEQ Nm3 of dry fluegas. The individual measurements reported in the literature span a wide range, from 0.41pgITEQ per Nm3 (Fernndez-Martnez, 2004) to 120pgI-TEQ Nm3 of dry fluegas (Lin et al., 2007). From a study of a range of power stations, in the year 2000 the US EPA produced an emission factor for utility power generation of 0.079ngITEQ per kg of fuel combusted (Thomas and McCreight, 2008), or about 7pgITEQ Nm3. For a 25MJ kg1 coal burned to produce electricity at 40% overall efficiency, this amounts to 28.5 gITEQ per GWh produced. An Australian Report gives 7% of emissions to air from this source.

The formation of PAHs, including dioxins, in power station boilers is low because of the high temperature of the flame. If there is any change resulting from the move to USC boilers, it most likely to be in a negative direction.

First, let us take a solid material, such as a desk or a bookshelf, and imagine the stress situations in the material by arbitrarily selecting a virtual cube inside the material and by checking both normal and tangential stresses acting on its six planes. In some parts of solid materials, the tangential stress can be non-zero and/or normal stress can be negative, i.e., tensile stress, to make them stand upright keeping their form as they are. In contrast, a fluid is a state of material in which tangential stresses are absent at rest and in which normal stresses are always pressure, i.e., not tensile stress (cf. Imai, 1974).

Particulate matter can also be either solid-like or fluid-like. In nature, some mountains, cliffs and particularly sandy beaches are made of solid-like particulate matter. It is possible to stand and walk on a sandy beach, which indicates that the mass of sand particles that it is made up of are macroscopically in the solid-like condition due to gravity and some surface forces. However, this situation can be changed to a fluid-like state by the application of counteracting forces. Suppose air or water is introduced flowing upward far below the surface of the beach. The gravitational force acting downward on the sand particles can be counter-balanced at a certain velocity by the upward fluid drag force. Then, the local particle assemblies are broken (which are rather particle shape dependent), followed by the breakage of particle-to-particle contact bridges (liquid or solid bridges), if they exist. When all static forces between the contacting particles disappear, the bed of sand particles start behaving like a fluid, at which point we could even enjoy a dusty swim. In this fluidized condition, i.e., fluid-like condition, we can put a bar or a stick into the bed of solids with little resistance and stir the solids with it. If the bar or stick is made of a material of density lighter than that of the bed, it can float upon it.

Thus, a bed of particles in such a fluid-like condition is called a fluidized bed. If not in this condition, it is called a fixed bed. If all the particles are suspended and carried by the fluid, we call the group of particles an entrained bed by convention, even though there no longer exists any bedlike behaviour of the particles. For fine, light, dusty and sometimes fibrous particles, say less than 10m in diameter in an air atmosphere, such clear phase changes between fluidized bed and entrained bed modes as noted above do not exist, since their weight is so light that they can be suspended and float with only small turbulence or convective flow in the fluid.

Fluidization can be said to be the most powerful method to handle a variety of solid particulate materials in industry. For decades fluidization has been a key technology in fluid catalytic cracking (FCC) to make gasoline in the petroleum industry; in catalytic processes such as partial oxidation of ammonia to acrylonitrile to prepare acrylic resin; in gas phase polymerization processes of polyethylene and polypropylene; in the chlorination process of metals such as silicon for purification in the semiconductor industry; in the granulation process for the pharmaceutical industry; in fluidized bed combustion (FBC) of solid fuels (coal, wastes and biomass) to generate steam for boilers; in waste incineration of solids and sludge; and in other simpler operations including drying, dip powder coating, thermal treatment of metals by hot or cold sands, and even a bed of seriously burnt patients in hospitals. By the 1950s fluidization had become a technical principle of a domain of technology, using the terminology of W.B. Arthur (2009), that can be applied to any technological field.

The most important feature of gas-solid fluidized beds in industrial processes is their temperature uniformity, which is generated as a result of frequent particle collisions microscopically and of good solid mixing macroscopically by bubble motion and/or solid circulation. Temperature uniformity is a critical demand of exothermic catalytic reactions to avoid dangerous chain reactions or to avoid melting of product polymer particles in polymerization. With this temperature uniformity, ash melting and clinker formation can be avoided in fluidized bed combustion and gasification. In fluidized bed combustion, the burning fuel particles are individually surrounded by non-combustible solid particles (bed materials) and the temperature differences between them are 100200C (Ross and Davidson, 1981). Heat generated by combustion is taken out continuously through the repeated contact of the bed materials onto the heat exchanger surfaces either immersed in the bed or placed vertically over the combustor wall. Since gaseous combustibles derived from solid or liquid fuels are always surrounded by hot particles, they can continue stable burning as long as oxygen is present. However, since the residence time of gas is much shorter than solids in a fluidized bed, the mixing of gaseous reactants, i.e., gaseous combustibles and oxygen in the case of combustion, is crucial in fluidized bed reactions.

In contrast, in fixed bed combustion, a sharp temperature non-uniformity ranging from the room temperature up to 1000C over less than 1/2min can easily be generated as in the case of iron ore sintering. There the heat generated is transferred to the flowing gas, which then gives the heat to the still cold solids that are waiting for ignition. In such situations no direct heat recovery from solids is possible but only through the flowing gas as the heat carrier. However, even in a fluidized bed combustor, some particles are defluidized due to insufficiency of fluidizing air supply, which provides a condition for fixed bed combustion, causing agglomeration and clinkering troubles. In entrained bed combustion, typical in pulverized coal combustion, individual particles burn while being separately entrained by the gas with no particle-to-particle collisions and with poor cooling by the surroundings. This is why fly ash particles from a pulverized coal furnace have a spherical shape, indicating that their temperature went up above ash melting temperature.

Another aspect of fixed bed combustion is the tar issue. With the sharp temperature gradient in fixed bed combustion, the combustible tar gases derived from pyrolysis of solid fuels are easily cooled down and removed from the combustion zone. This is the way people can enjoy an unburned flavour from smoking cigarettes with the problem of inhaling toxic tar. This is also one of the reasons for using coke instead of coal in a blast furnace for iron making, to avoid tar production and softening of the bed. Coke is able to support tons of iron ore without being crushed. Raw coal would fall to pieces, be softened by heat and in any case block the air flow.

One of the most troubling but interesting aspects of fluidization engineering is the management of particle properties and their changes in the course of physical collisions, thermochemical reactions and/or agglomeration. Also in some reactors very fine particles are formed through attrition, fragmentation, condensation or deposition. In such a mixed particle bed, the coarser and heavier fraction of particles may tend to settle on the column bottom while fine particles are flowing through the bed of coarser particles, entrained and carried out or elutriated from the reactor. However, it should also be noted here that there exists a non-uniformity of gas velocity distribution in fluidized beds, particularly around the distributor, where solid dead zone is formed due to the local gas velocity being insufficient for fluidization. In dead zones, some weak gas flow still exists and this ensures localized fixed bed combustion and resulting clinker formation troubles.

Fluidization is essentially a natural phenomenon that can be seen anywhere. For instance, every day we may encounter a sort of fluidization in settling sugar particles in a teacup. When particles settle in liquid or in gas, their velocity reaches an equilibrium or steady velocity. The steady settling velocity is determined by Stokes law in the viscous regime if the particle volume fraction is very low, say below 0.001, where particles are almost completely isolated from each other. We call this velocity the terminal velocity. The terminal velocity is a function of both particle and fluid properties.

With increased particle loading, the particle volume fraction increases so that the same fluid drag force can be achieved at a settling velocity much lower than the terminal velocity. This is because of the increased interstitial gas velocity due to the decreased area for fluid to flow around the particles. Among settling particles there is no static remnant stress. They are in a fluidized condition. Conversely, any particles, dusts, mists, etc., blown by air are fluidized. This is why a cloud flows in a fluid-like manner, although in the majority it consists of solids, i.e., ice particles. More can be found on clouds in Houze (1993). The violent convective flow in a cloud, particularly in a large cumulonimbus cloud that reaches as high as 10,000m, can be so strong that ice particles can take sufficient time to circulate in the cloud to collide with each other, to agglomerate and grow to become hail particles several millimeters in diameter. Precipitation takes place once the balance between the draft strength and particle gravity is lost. A hailstorm occurs if there is no sufficient heat supply.

Other fluidization phenomena observed in nature include avalanche and pyroclastic flows (for the latter, see Salatino, 2005). They can give us violent disastrous effects because of their fluid-like nature, i.e., flowability. In the case of an avalanche, its sliding speed is so rapid that air is taken into it from its front nose. The air is then distributed inside the bed of snow and ice particles and fluidizes them. The same mechanism takes place in the sliding period of pyrocrastic flow, i.e., the flow of very hot rock fragments followed by the eruption column collapse or explosion of a lava dome of a volcano. However, these deadly hot rocks can keep flowing even over long stretches of flat ground, since they can continuously self-supply the required up-drafting fluidizing gases through the flash evaporation of surface water with their own heat.

As described, fluidization is quite a fundamental phenomenon but related to a wide variety of scientific and engineering areas. Forces related to it include gravitational forces, fluid mechanical forces, elastic/plastic collision forces, electromagnetic forces, surface forces, yield forces of materials, etc. To understand fluidization, in reality we need to have knowledge of almost all the areas mentioned above. Accordingly, fluidization science has been a platform where scientists and engineers from different fields can meet, exchange ideas and in many cases change even their subjects or professions. Indeed, the fluidization community has been a place of gathering for people who know particles, fluids, mechanics, heat transfer, reaction kinetics, simulation and a variety of phenomena, engineering processes and even society.

Fluidized bed combustion and gasification share most of the technological advantages of fluidization with other applications. In this respect, this overview intends not to limit the subject within the realm of combustion and gasification but to provide an understanding that can further lead the coming decades of scientific progress and technological and social innovations by interpreting them from historical and philosophical viewpoints.

Ferrous metallurgy offers one of the best examples of how a traditional iconic polluter, particularly as far as the atmospheric emissions were concerned, can clean up its act, and do so to such an extent that it ceases to rank among todays most egregious offenders. But environmental impacts of iron- and steelmaking go far beyond the release of airborne pollutants, and I will also review the most worrisome consequences in terms of waste disposal, demand for water, and water pollution. And while iron and steel mills are relatively compact industrial enterprises that do not claim unusually large areas of flat land (many of them, particularly in Japan, are located on reclaimed land), extraction of iron ores has major local and regional land use impacts in areas with large-scale extraction, above all in Western Australia and in Par and Minas Gerais in Brazil.

All early cokemaking, iron smelting, and steelmaking operations could be easily detected from afar due to their often voluminous releases of air pollutants whose emissions were emblematic of the industrial era: particulate matter (both relatively coarse with diameter of at least 10m, as well as fine particles with diameter of less than 2.5m that can easily penetrate into lungs), sulfur dioxide (SO2), nitrogen oxides (NOx, including NO and NO2), carbon monoxide (CO) from incomplete combustion, and volatile organic compounds. Where these uncontrolled emissions were confined by valley locations with reduced natural ventilation, the result was a chronically excessive local and regional air pollution: Pittsburgh and its surrounding areas were perhaps the best American illustration of this phenomenon.

Recent Chinese rates and totals illustrate both the significant contribution of the sector to national pollution flows and the opportunities for effective controls. Guo and Xu (2010) estimated that the sector accounted for about 15% of total atmospheric emissions, 14% of all wastewater and waste gas, and 6% of solid waste, and they put the nationwide emission averages in the year 2000 (all per tonne of steel) at 5.56kg SO2, 5.1kg of dust, 1.7kg of smoke, and 1kg of chemical oxygen demand (COD). But just 5 years later spreading air and water pollution controls and higher conversion efficiencies reduced the emissions of SO2 by 44%, those of smoke and COD by 58%, and those of dust by 70%.

Particulates are released at many stages of integrated steelmaking, during ore sintering, in all phases of integrated steelmaking as well as from EAFs and from DRI processes, but efficient controls (filters, scrubbers, baghouses, electrostatic precipitators, cyclones) can reduce these releases to small fractions of the uncontrolled rates (USEPA, 2008). Sintering of ores emits up to about 5kg/t of finished sinter, but after appropriate abatement maximum EU values in sinter strand waste gas are only about 750g of dust per tonne of sinter, and minima are only around 100g/t, but there are also small quantities of heavy metals, with maxima less than 1g/t of sinter and minima of less than 1mg/t (Remus et al., 2013). In the United States, modern agglomeration processes (sintering and pelletizing) emit just 125 and up to 250g of particulates per tonne of enriched ore (USEPA, 2008). Similarly, air pollution controls in modern coking batteries limit the dust releases to less than 300g/t of coke and SOx emissions (after desulfurization) to less than 900g/t, and even to less than 100g/t.

Smelting in BFs releases up to 18kg of top gas dust per tonne of pig iron, but the gas is recovered and treated. Smelting in BOFs and EAFs can generate up to 1520kg of dust per tonne of liquid steel, but modern controls keep the actual emissions from BOFs to less than 150g/t or even to less than 15g/t, and from EAFs to less than 300g/t (Remus et al., 2013). Long-term Swedish data show average specific dust emissions from the countrys steel plants falling from nearly 3kg/t of crude steel in 1975 to 1kg/t by 1985 and to only about 200g/t by 2005 (Jernkontoret, 2014).

But there is another class of air pollutants that is worrisome not because of its overall emitted mass but because of its toxicity. Hazardous air pollutants originate in coke ovens, BFs, and EAFs. Hot coke gas is cooled to separate liquid condensate (to be processed into commercial by-products, including tar, ammonia, naphthalene, and light oil) and gas (containing nearly 30% H2 and 13% CH4) to be used or sold as fuel. Coking is a source of particulates, volatile organic compounds, and polynuclear aromatic hydrocarbons: uncontrolled emissions per tonne of coke are up to 7kg of particulate matter, up to 6kg of sulfur oxides, around 1kg of nitrogen oxides, and 3kg of volatile organics. Ammonia is the largest toxic pollutant emitted from cokemaking, and relatively large volumes of hydrochloric acid (HCl) originate in pickling of steel, when the acid is used to remove oxide and scale from the surface of finished metal. Manganese, essential in ferrous metallurgy due to its ability to fix sulfur, deoxidize, and help in alloying, has the highest toxicity among the released metallic particulates, with chromium, nickel, and zinc being much less worrisome.

But, again, modern controls can make a substantial difference: USEPAs evaluations show that the sectors toxicity score (normalized by annual production of iron and steel) declined by almost half between 1996 and 2005 and that the mass of all toxic chemicals was reduced by 66% (USEPA, 2008). And these improvements have continued since that time. Water used in coke production and for cooling furnaces is largely recycled, and wastewater volumes that have to be treated are relatively small, typically just 0.10.5m3/t of coke and 0.36m3/t of BOF steel. Wastewater from BOF gas treatment is processed by electrical flocculation while mill scale and oil and grease have to be removed from wastewater from continuous casting. EAFs produce only small amounts of dusts and sludges, usually less than 13kg/t of steel (WSA, 2014a). Dust and sludge removed from escaping gases have high iron content and can be reused by the plant, while zinc oxides captured during EAF operation can be resold.

But solid waste mass generated by iron smelting in BFs is an order of magnitude larger, typically about 275kg/t of steel (extremes of 250345kg/t), and steelmaking in BOFs adds another 125kg/t (85165kg/t). The BF/BOF route thus leaves behind about 400kg of slag per tonne of metal, and the global steelmaking now generates about 450Mt of slag a yearand yet this large mass poses hardly any disposal problems. Concentrated and predictably constant production of the material and its physical and chemical qualities, that make it suitable for industrial and agricultural uses, mean that slag is not just another bothersome waste stream but a commercially useful by-product.

The material is marketed in several different forms which find specific uses (NSA, 2015; WSA, 2014b). Granulated slag is produced by rapid water cooling; it is a sand-like material whose principal use is incorporation into standard (Portland) cement. Air-cooled slag is hard, dense, and chunky material that is crushed and screened to produce desirable sizes used as aggregates in precast and ready-mixed concrete, in asphalt mixtures or as a railroad ballast and permeable fill for road bases, in septic fields, and for pipe beds. Pelletized (expanded) slag resembles a volcanic rock, and its lightness and (when ground) excellent cementitious properties make it a perfect aggregate to make cement or to be added to masonry. Expanded slag is now widely used in the construction industry, and Lei (2011) reported that in 2010 Chinas cement industry used all available metallurgical slag (about 223Mt in that year). Brazilian figures for 2011 show 60% of slag used in cement production, 16% put into road bases, and 13% used for land leveling (CNI, 2012).

High content of free lime prevents the use of some slag in construction, but after separation both materials become usable, with lime best used as fertilizer. Because of its high content of basic compounds (typically about 38% CaO and 12% MgO), ordinary slag is an excellent fertilizer used to control soil pH in field cropping as well as in nurseries and parks and for lawn maintenance and land recultivation; slag also contains several important plant micronutrients, including copper, zinc, boron, and molybdenum.

Iron ore sintering process is an important sector for iron and steel industry as well as a major pollution emission source of PCDD/Fs. The PCDD/Fs emission of sintering process has not been properly controlled because the flue gas presents the following characteristics, including large amount, remarkable flow fluctuations and lower concentration. The generation mechanism of PCDD/Fs in the iron ore sintering was discussed systematically and the new developments and technologies of PCDD/Fs emission reduction were also summarized from the source, process and the end treatments. Commonly, the PCDD/Fs formed in drying and preheating zone is transferred to the lower part of the material layer which is a chemical transfer process in the iron ore sintering. Finally, the potential future development of PCDD/Fs emission reduction in the iron ore sintering was also pointed out.

iron ore processing | home

iron ore processing | home

The mid-sized company JOEST GmbH + Co. KG from Duelmen in Germany is installing a high-tech system for processing iron ore pellets in Narvik, Norway. Kiruna, the northernmost city of Sweden, is home to an iron ore mine of the same name, which processes and stores pellets. These iron ore pellets are transported from Sweden to Norway for shipping. In 1902, a train line was built all the way to Narvik for this purpose. At the time this was the most northern train line in the world. The trains using this route pull up to 68 rail carts and transport around 33 million tons of iron ore per year.

Narvik is situated at the Ofotfjord, north of the Arctic Circle, and has an average annual temperature of around 4 C. Thanks to these temperatures, which are influenced by the Gulf Stream, the fjord remains free of ice almost all year round. This is where the processing plant of Scandinavias biggest iron ore producer is located, with a facility for direct loading of iron ore pellets onto ships. The existing plant has a processing rate of 6,000 t/h, and a new plant with a processing rate of an additional 9,000 t/h had to be added.

The new screening plant system consists of a storage bunker system, six large double-decker vibrating screens with chutes, various connecting belt conveyors as well as a crusher. The scope of delivery also included the entire steel structure, detailed planning, project management as well as installation and start-up.

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1.600 m3 Eisenerzpellets zwischen zu lagern. Die 11-16 mm groen Pellets knnen ber drei verschiedene Bnder, aus unterschiedlichen Lagersystemen, dem Bunker zugefhrt werden. Durch einen Trichter wird das Material auf ein reversierbares Band aufgegeben. Durch den Einsatz von Fallstufen wird die optimale Befllung des Bunkers gewhrleistet.

Der ca. 350 Tonnen schwere Stahlbunker ist in sechs gleiche Einheiten gegliedert. Auch hier sorgen Fallstufen fr einen mglichst schonenden Transport der Pellets. Jedes Bunkerabteil besitzt zwei hydraulische Nadelschieber mit den Maen 800 x 800 mm die als Notverschluss dienen.

Die Siebmaschinen klassieren das aufgegebene Material in Pellets, Fein- und Grobmaterial. Die Pellets werden direkt auf das Band zur Schiffsbeladung aufgegeben. Das Feinmaterial mit einer Gre von 0 6 mm wird durch einen Feinkorntrichter gesondert abgefhrt und in einem weiteren Prozess wiederum zu Pellets verarbeitet. Das 20 50 mm groe Grobmaterial wird zum Oversize Material Handling weiter gefrdert.

Copper Mountain Mining Corp. ( ist ein mittelstndisches Kupfer-Bergbau Unternehmen aus Vancouver, British Columbia, Kanada, mit einer Haupt-Bergbau-Anlage in der Nhe von Princeton im Sden von British Columbia. Nach dem Start der Arbeiten in 2011, hat Copper Mountain Ende 2013 erkannt, dass die Installation eines Sekundr-Zerkleinerers ein strategisch wichtiges Projekt ist und beschleunigte die Konstruktion und Installation des neuen Zerkleinerungskreislaufes. Der Sekundr-Zerkleinerer ist das grte betriebene Modell in West-Kanada. Das System wurde pnktlich und im Budget installiert und konnte bereits im August 2014 das erste Erz verarbeiten.

Die Aufgabe des JST Siebes ist es, die Aufgabe auf den Sekundr-Zerkleinerer zu reduzieren. Aufgestellt vor dem Zerkleinerer separiert das Sieb 3000t/h Kupfererz in die Fraktionen < 50 mm und > 50 mm. Material, das grer als 50 mm ist, wir in den Zerkleinerer gefrdert. Material, welches kleiner als 50 mm ist, bentigt keine weitere Verarbeitung und umgeht den Zerkleinerer. Dies steigert die Kapazitt des Zerkleinerers deutlich und verlngert die Abnutzungsdauer der Maschine deutlich. JST wurde aufgrund der Erfahrung beim Bauen hnlicher Siebe fr Copper Mountain, aber auch hnlicher Erz-Zerkleinerungs-Anlagen, der technischen Fhigkeit ein solch groes Sieb zu konstruieren und zu bauen und im Zeitplan zu liefern, als Lieferant ausgewhlt.

JST entwickelte ein Doppel-Deck-Sieb um die Leistungsanforderungen zu erfllen. Aufgrund der hohen Kapazitt knnte ein Ein-Deck-Sieb die geforderte Siebleistung nicht erreichen. Ein Bananensieb nutzt verschiedene Neigungen des Siebdecks, um die Siebeffektivitt zu maximieren. Der erste Teil des Siebes hat eine hhere Neigung, um so eine hhere Produktgeschwindigkeit zu erreichen und reduziert dadurch die Materialschicht auf der Sieboberflche. Dies ermglicht kleineren Teilen den schnellen Weg nach unten und durch diese Sieboberflche kann die eigentliche Siebung so schnell wie mglich beginnen. Das Oberdeck des JST Siebes wird als Entlastungsdeck verwendet, um Material grer 75 mm zu trennen, whrend das Unterdeck die finale Trennung bis zu 50 mm bernimmt.

Wenn sich das Material auf der Sieboberflche nach unten bewegt, reduziert sich die Neigung, um das Material zu verlangsamen und die Verweildauer zu erhhen. Da ein Teil des Produktes bereits das Sieb passiert hat, wird die Schichtdicke gering gehalten. Am Auslauf des Siebes ist die Neigung nochmals verringert, um die Siebung weiter zu maximieren und die Geschwindigkeit des Materials bei Auslaufen aus dem Sieb zu Verringern.

Das JST firmeneigene Siebberechnungsprogram kalkuliert den Effekt der verndernden Neigungen auf die Siebeffektivitt, um so das Siebdesign zu optimieren. Um die Sieboberflche zur vergrern, wurden die Untersttzungstraversen bei 45 zur Sieboberflche montiert, um so dem Sammeln von Material an den Traversen vorzubeugen. Dieses Sieb ist eines von vier JOEST US Sieben fr die nordamerikanische Bergbauindustrie.

Copper Mountain Mining Corp. ( ist ein mittelstndisches Kupfer-Bergbau Unternehmen aus Vancouver, British Columbia, Kanada, mit einer Haupt-Bergbau-Anlage in der Nhe von Princeton im Sden von British Columbia. Nach dem Start der Arbeiten in 2011, hat Copper Mountain Ende 2013 erkannt, dass die Installation eines Sekundr-Zerkleinerers ein strategisch wichtiges Projekt ist und beschleunigte die Konstruktion und Installation des neuen Zerkleinerungskreislaufes. Der Sekundr-Zerkleinerer ist das grte betriebene Modell in West-Kanada. Das System wurde pnktlich und im Budget installiert und konnte bereits im August 2014 das erste Erz verarbeiten.

Die Aufgabe des JST Siebes ist es, die Aufgabe auf den Sekundr-Zerkleinerer zu reduzieren. Aufgestellt vor dem Zerkleinerer separiert das Sieb 3000t/h Kupfererz in die Fraktionen < 50 mm und > 50 mm. Material, das grer als 50 mm ist, wir in den Zerkleinerer gefrdert. Material, welches kleiner als 50 mm ist, bentigt keine weitere Verarbeitung und umgeht den Zerkleinerer. Dies steigert die Kapazitt des Zerkleinerers deutlich und verlngert die Abnutzungsdauer der Maschine deutlich. JST wurde aufgrund der Erfahrung beim Bauen hnlicher Siebe fr Copper Mountain, aber auch hnlicher Erz-Zerkleinerungs-Anlagen, der technischen Fhigkeit ein solch groes Sieb zu konstruieren und zu bauen und im Zeitplan zu liefern, als Lieferant ausgewhlt.

JST entwickelte ein Doppel-Deck-Sieb um die Leistungsanforderungen zu erfllen. Aufgrund der hohen Kapazitt knnte ein Ein-Deck-Sieb die geforderte Siebleistung nicht erreichen. Ein Bananensieb nutzt verschiedene Neigungen des Siebdecks, um die Siebeffektivitt zu maximieren. Der erste Teil des Siebes hat eine hhere Neigung, um so eine hhere Produktgeschwindigkeit zu erreichen und reduziert dadurch die Materialschicht auf der Sieboberflche. Dies ermglicht kleineren Teilen den schnellen Weg nach unten und durch diese Sieboberflche kann die eigentliche Siebung so schnell wie mglich beginnen. Das Oberdeck des JST Siebes wird als Entlastungsdeck verwendet, um Material grer 75 mm zu trennen, whrend das Unterdeck die finale Trennung bis zu 50 mm bernimmt.

Wenn sich das Material auf der Sieboberflche nach unten bewegt, reduziert sich die Neigung, um das Material zu verlangsamen und die Verweildauer zu erhhen. Da ein Teil des Produktes bereits das Sieb passiert hat, wird die Schichtdicke gering gehalten. Am Auslauf des Siebes ist die Neigung nochmals verringert, um die Siebung weiter zu maximieren und die Geschwindigkeit des Materials bei Auslaufen aus dem Sieb zu Verringern.

Das JST firmeneigene Siebberechnungsprogram kalkuliert den Effekt der verndernden Neigungen auf die Siebeffektivitt, um so das Siebdesign zu optimieren. Um die Sieboberflche zur vergrern, wurden die Untersttzungstraversen bei 45 zur Sieboberflche montiert, um so dem Sammeln von Material an den Traversen vorzubeugen. Dieses Sieb ist eines von vier JOEST US Sieben fr die nordamerikanische Bergbauindustrie.

Die Siebe wurden entsprechend der Standards der Nahrungsmittelindustrie konstruiert und gefertigt. Besonders interessant sind die feinen Siebgewebe, die aus magnetischem Edelstahl bestehen und somit ein Sonderwerkstoff sind.

Die Konstruktion weist einige spezielle Details auf, um der groen schwingenden Masse und der hohen Kapazitt zu entsprechen. Insbesondere die Siebdecktraversen sind ein besonderes JST Design, das sich ber Jahrzehnte bewhrt hat.

Drei leistungsstarke JST Richterregerantriebe vom Typ JR 818 versetzen das Sieb in die notwendige Schwingung. Die Siebmaschine wurde mit einer nahezu staubdichten stationren Abdeckung geliefert, in der die Aufgabeanschlsse, Entstaubungsstutzen und groe Inspektionsklappen integriert sind. Newmont ist mit der Siebleistung sehr zufrieden und betonte, dass JST wegen seiner langjhrigen Erfahrung im Bau von Grosiebmaschinen, der berdurchschnittlichen Siebeffizienz und Zuverlssigkeit als Lieferant ausgewhlt wurde.

Mit ber 90 Jahren Erfahrung ist JST eines der weltweit fhrenden Unternehmen auf dem Gebiet der Schwingungstechnik und Schttgutaufbereitung mit Tochtergesellschaften und Vertretungen in der ganzen Welt

Fr ein groes Kohlekraftwerk in Vietnam hat JST zwei Bananensiebmaschinen mit speziellen Siebeinstzen konstruiert und gebaut. Der Kunde setzt diese Siebe zur Nachklassierung seiner Kohle ein. Mit diesen Hochleistungssiebmaschinen erhlt die Kohle eine maximale Krnung von 20-40 mm und wird somit optimal fr den Verbrennungsprozess aufbereitet.Der JST Kunde setzt diese Siebe fr 2 seiner Ofenbeschickungslinien ein. Die Bananensiebmaschinen besitzen jeweils eine Siebflche von 25 qm und haben einen Durchsatz von 1.400 t/h. Mit einer Lnge von fast 10 m und einer Breite von knapp 3 m war der Transport von Dlmen nach Vietnam eine logistische Herausforderung. Ebenso gestaltete sich die Installation in ein sehr enges Siebhaus als schwierig. Aufgrund der langjhrigen JST Erfahrung als einer der weltweit fhrenden Hersteller von Grosiebmaschinen werden diese Schwierigkeiten dank des erfahrenen JST Personals vor Ort problemlos gemeistert.Whrend der Regenzeit in Vietnam weist die Kohle eine erhhte Feuchte auf. Um diese optimal sieben zu knnen, wurde eine Kombination aus einem speziellen Stangensiebbelag und einem Siebgewebe mit Selbstreinigungsfunktion gewhlt. Diese Kombination verbessert die Siebeffizienz durch die Mglichkeit einer schnellen Absiebung der Feinanteile.Die Bananensiebmaschinen wurden mit einer absolut staubdichten stationren Abdeckung ausgestattet, in der die Aufgabeanschlsse, Entstaubungsstutzen und groe Inspektionsklappen integriert sind. Auch die bergnge von Fein- und Grobgut sind komplett abgedichtet. Einmal mehr konnte JST durch langjhrige Erfahrung und Know-how eine passgenaue und effiziente Lsung bieten.

The total weight of each screen is approx. 12 tons with a length of 5000 mm, a width of 2700 mm and a height of 3400 mm. The rooftop of the customers plant had to be opened to install the machines with the help of a crane.

The screens have been constructed and manufactured according to the standards of the food industry. Of particular interest are the fine screen cloths which consist of special material magnetic stainless steel.

This screen is specially designed to process limestone using salt water for the wet screening process. Special design details and coating are required for a long term successful and reliable operation.

JOEST has designed and built two banana screens with special screen decks for a large coal power plant in Vietnam. The customer is using the screens for the preparation of the coal before the furnaces. These high-performance screens process coal with a maximum granulation of 20-40mm, ensuring it is optimally prepared for the combustion process.

The customer is using the screens on two furnace feed lines. The banana screens each have a screening area of 25 sqm and a throughput of 1,400 t/h. With a length of nearly 10m and a width of almost 3m, transporting the screens from Dlmen to Vietnam presented a considerable logistical challenge. The installation in a very narrow screening plant was a challenge JST had to manage. Thanks to JOESTs long-standing experience as one of the worlds leading manufacturers of industrial screens, these difficulties were successfully overcome by experienced JOEST personnel on site.

During the rainy season in Vietnam, the coals moisture content is higher than normal. Therefore, a combination of a special finger screen and a screen deck with a self-cleaning function was chosen for optimal screening. This combination improves the screening efficiency by allowing fast screening of the smaller material.

The banana screens are equipped with a completely dust-tight cover, dust extraction nozzles and large inspection openings. The transfer points for both fine and coarse material were also completely sealed.

In the actual project approx. 80 t/h green yard waste have to be screened. A mixture of branches, leaves, grass, soil and sand with particle sizes between 0 and 30 mm are fed onto the screen. This is not yet the peak performance of the screen. The customer has the possibility to increase the capacity significantly.

Since the green waste decomposes rapidly and thus the product properties are changing, the material must be processed promptly and the screen must be flexible. The fractions between 0 and 10 mm are screened from the material mixture mentioned above. This fraction will be used for the preparation of potting soil later.

OSCILLA is a vibratory screen based on a resonance system. The inner frame of the screen is set in motion as a result of the motion of the screen body putting the screen panels in a high vertical motion. The linear or circular motion of the screen is producing an acceleration of the screen deck which can be higher than any other screen before (> 50g).

This leads to a tensioning and release of the elastic screen coverings. This causes the material to be thrown up vertically to the screen area and loosened. The screen mats have perforations through which material with smaller dimensions falls. The fine material falls out of the machine.

Copper Mountain Mining Corp. (TSX:CUM, is a mid-tier copper mining company headquartered in Vancouver, British Columbia, Canada with its flagship mining operations near Princeton in Southern BC. Commencing operations in 2011, Copper Mountain identified the installation of a secondary crusher as a strategically important project in late 2013 and fast-tracked the design and installation of the new crushing circuit. The secondary crusher is the largest operating model in Western Canada. The system was installed on schedule and on budget, processing the first ore in August 2014.

The purpose of the screen is to reduce the loading of the secondary crusher. Situated before the secondary crusher, the screen separates 3,000 MT/hr of copper ore into plus and minus 50 mm (2 inch) fractions. Material larger than 50 mm is sent to the crusher. Material smaller than 50 mm does not require further size reduction and bypasses the crusher. This significantly increases the crusher capacity and improves the crushers wear life. JOEST was selected as the screen supplier because of experience building similar screens for Copper Mountain, Other similar ore crushing equipment, the technological ability to engineer and build such a large screen, and to design and deliver the equipment within the project schedule Joest designed a double deck screen to meet the performance requirements of the project. Due to the high capacity, a single deck screen could not provide the required screening efficiencies. A banana screen uses different slopes on the screen decks to maximize the screening efficiency. The first portion of the screen deck has a higher slope to achieve a higher product speed, reducing the thickness of the material layer on the screen surface. This allows smaller particles to quickly work their way down to and then through the screen surface to start the screening as quickly as possible. The top deck of the JOEST screen is used as a relief deck to remove material greater than 75 mm while the bottom deck does the final sizing down to 50 mm.

As the material moves down the screen surface, the slope is reduced to slow the product and increase the residence time. Since some of the product has already passed through the screen, the layer thickness is kept low. On the discharge end of the screen, the slope is reduced further to maximize the screening and reduce the velocity of material moving off the end of the screen. JOESTs proprietary screen sizing program calculates the effect of the changing slopes on the screen performance to optimize the screen design.

A modular rubber deck was used for both the top and bottom screening surfaces, including steel-backed bolt- in rubber panels at the high impact inlet end of the screen and rail-mounted, easily replaceable panels for the remainder. To maximize the screen surfaces, the support beams that hold up the screen deck are mounted at 45 degrees to the screen surface, preventing material from collecting on the beams.

This screen is one of four built by Joest US for the North American mining industry. JOEST USs parent company JOEST Germany and JOEST Australia have also built screens this size and bigger for operations around the world.

The steel bunker, which weighs approx. 350 t, is split into six equal segments. Another special design was developed to make sure that the pellets are transported as careful as possible to avoid loss of product. Each part of the bunker consists of two hydraulic needle gates, which serve as an emergency shut off systems.

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iron ore

iron ore

The major rock types mined for the production of metallic iron are massive hematite, pisolitic goethite/limonite, which provide a 'high-grade' ore, and banded metasedimentary ironstone, magnetite-rich metasomatite, to a much lesser degree, rocks rich in siderite, rocks rich in chamosite and taconite which provide a 'low-grade' ore.

Hematite is named from the Greek word for blood, haima, because of its reddish colour. The ore has very high iron content, and although the iron content of hematite itself is lower than that of magnetite, the mineral sometimes occurs in higher-grade deposits, often referred to as direct-shipping ore (DSO). This means that, due to its high iron content, such hematite ores may be mined and extracted with a fairly simple crushing and screening process prior to shipping for further industrial uses.

Magnetite ores most distinctive property is its magnetism. It is the most magnetic mineral in the world. Additionally, obtaining iron from hematite ore can produce a great deal of carbon emissions, and the process for magnetite ore is much less harmful. End products made from this type of iron ore are also of higher quality than that produced from hematite ore. The former has fewer impurities, making it a premium product that can be sold to steelmakers for higher prices. In this way, the elevated cost of processing magnetite ore can be balanced out.

Ore bearing rock is reduced by blasting into product which, through a sequential crushing process in ball mills, is reduced to powder fine consistency. Magnetic rollers extract the iron concentrate and the waste is transferred to a tailings facility.

iron ore | bhp

iron ore | bhp

Air that has been heated to around 1,200 degrees Celsius is injected into the furnace, creating a flame temperature of 2,000 degrees. This converts the iron ore to molten pig iron and slag.

Then, impurities are removed and alloying elements are added. The steel is then cast, cooled and rolled for use in finished products.

Our Western Australia Iron Ore business in the Pilbara region of Western Australia contains five mines, four processing hubs and two port facilities, all of which are connected by more than 1,000 kilometres of rail infrastructure.

iron ore processing,crushing,grinding plant machine desgin&for sale | prominer (shanghai) mining technology co.,ltd

iron ore processing,crushing,grinding plant machine desgin&for sale | prominer (shanghai) mining technology co.,ltd

After crushing, grinding, magnetic separation, flotation, and gravity separation, etc., iron is gradually selected from the natural iron ore. The beneficiation process should be as efficient and simple as possible, such as the development of energy-saving equipment, and the best possible results with the most suitable process. In the iron ore beneficiation factory, the equipment investment, production cost, power consumption and steel consumption of crushing and grinding operations often account for the largest proportion. Therefore, the calculation and selection of crushing and grinding equipment and the quality of operation management are to a large extent determine the economic benefits of the beneficiation factory.

There are many types of iron ore, but mainly magnetite (Fe3O4) and hematite (Fe2O3) are used for iron production because magnetite and hematite have higher content of iron and easy to be upgraded to high grade for steel factories.

Due to the deformation of the geological properties, there would be some changes of the characteristics of the raw ore and sometimes magnetite, hematite, limonite as well as other types iron ore and veins are in symbiosis form. So mineralogy study on the forms, characteristics as well as liberation size are necessary before getting into the study of beneficiation technology.

1. Magnetite ore stage grinding-magnetic separation process The stage grinding-magnetic separation process mainly utilizes the characteristics of magnetite that can be enriched under coarse grinding conditions, and at the same time, it can discharge the characteristics of single gangue, reducing the amount of grinding in the next stage. In the process of continuous development and improvement, the process adopts high-efficiency magnetic separation equipment to achieve energy saving and consumption reduction. At present, almost all magnetic separation plants in China use a large-diameter (medium 1 050 mm, medium 1 200 mm, medium 1 500 mm, etc.) permanent magnet magnetic separator to carry out the stage tailing removing process after one stage grinding. The characteristic of permanent magnet large-diameter magnetic separator is that it can effectively separate 3~0mm or 6~0mm, or even 10-0mm coarse-grained magnetite ore, and the yield of removed tails is generally 30.00%~50.00%. The grade is below 8.00%, which creates good conditions for the magnetic separation plant to save energy and increase production.

2.Magnetic separation-fine screen process Gangue conjoined bodies such as magnetite and quartz can be enriched when the particle size and magnetic properties reach a certain range. However, it is easy to form a coarse concatenated mixture in the iron concentrate, which reduces the grade of the iron concentrate. This kind of concentrate is sieved by a fine sieve with corresponding sieve holes, and high-quality iron concentrate can be obtained under the sieve.

There are two methods for gravity separation of hematite. One is coarse-grained gravity separation. The geological grade of the ore deposit is relatively high (about 50%), but the ore body is thinner or has more interlayers. The waste rock is mixed in during mining to dilute the ore. For this kind of ore, only crushing and no-grinding can be used so coarse-grained tailings are discarded through re-election to recover the geological grade.

The other one is fine-grain gravity separation, which mostly deals with the hematite with finer grain size and high magnetic content. After crushing, the ore is ground to separate the mineral monomers, and the fine-grained high-grade concentrate is obtained by gravity separation. However, since most of the weak magnetic iron ore concentrates with strong magnetic separation are not high in grade, and the unit processing capacity of the gravity separation process is relatively low, the combined process of strong magnetic separation and gravity separation is often used, that is, the strong magnetic separation process is used to discard a large amount of unqualified tailings, and then use the gravity separation process to further process the strong magnetic concentrate to improve the concentrate grade.

Due to the complexity, large-scale mixed iron ore and hematite ore adopt stage grinding or continuous grinding, coarse subdivision separation, gravity separation-weak magnetic separation-high gradient magnetic separation-anion reverse flotation process. The characteristics of such process are as follows:

(1) Coarse subdivision separation: For the coarse part, use gravity separation to take out most of the coarse-grained iron concentrate after a stage of grinding. The SLon type high gradient medium magnetic machine removes part of the tailings; the fine part uses the SLon type high gradient strong magnetic separator to further remove the tailings and mud to create good operating conditions for reverse flotation. Due to the superior performance of the SLon-type high-gradient magnetic separator, a higher recovery rate in the whole process is ensured, and the reverse flotation guarantees a higher fine-grained concentrate grade.

(2) A reasonable process for narrow-level selection is realized. In the process of mineral separation, the degree of separation of minerals is not only related to the characteristics of the mineral itself, but also to the specific surface area of the mineral particles. This effect is more prominent in the flotation process. Because in the flotation process, the minimum value of the force between the flotation agent and the mineral and the agent and the bubble is related to the specific surface area of the mineral, and the ratio of the agent to the mineral action area. This makes the factors double affecting the floatability of minerals easily causing minerals with a large specific surface area and relatively difficult to float and minerals with a small specific surface area and relatively easy to float have relatively consistent floatability, and sometimes the former has even better floatability. The realization of the narrow-level beneficiation process can prevent the occurrence of the above-mentioned phenomenon that easily leads to the chaos of the flotation process to a large extent, and improve the beneficiation efficiency.

(3) The combined application of high-gradient strong magnetic separation and anion reverse flotation process achieves the best combination of processes. At present, the weak magnetic iron ore beneficiation plants in China all adopt high-gradient strong magnetic separation-anion reverse flotation process in their technological process. This combination is particularly effective in the beneficiation of weak magnetic iron ore. For high-gradient strong magnetic separation, the effect of improving the grade of concentrate is not obvious. However, it is very effective to rely on high-gradient and strong magnetic separation to provide ideal raw materials for reverse flotation. At the same time, anion reverse flotation is affected by its own process characteristics and is particularly effective for the separation of fine-grained and relatively high-grade materials. The advantages of high-gradient strong magnetic separation and anion reverse flotation technology complement each other, and realize the delicate combination of the beneficiation process.

The key technology innovation of the integrated dry grinding and magnetic separation system is to "replace ball mill grinding with HPGR grinding", and the target is to reduce the cost of ball mill grinding and wet magnetic separation.

HPGRs orhigh-pressure grinding rollshave made broad advances into mining industries. The technology is now widely viewed as a primary milling alternative, and there are several large installations commissioned in recent years. After these developments, anHPGRsbased circuit configuration would often be the base case for certain ore types, such as very hard, abrasive ores.

The wear on a rolls surface is a function of the ores abrasivity. Increasing roll speed or pressure increases wear with a given material. Studs allowing the formation of an autogenous wear layer, edge blocks, and cheek plates. Development in these areas continues, with examples including profiling of stud hardness to minimize the bathtub effect (wear of the center of the rolls more rapidly than the outer areas), low-profile edge blocks for installation on worn tires, and improvements in both design and wear materials for cheek plates.

With Strip Surface, HPGRs improve observed downstream comminution efficiency. This is attributable to both increased fines generation, but also due to what appears to be weakening of the ore which many researchers attribute to micro-cracking.

As we tested , the average yield of 3mm-0 and 0.15mm-0 size fraction with Strip Surface was 78.3% and 46.2%, comparatively, the average yield of 3mm-0 and 0.3mm-0 with studs surface was 58.36% and 21.7%.

These intelligently engineered units are ideal for classifying coarser cuts ranging from 50 to 200 mesh. The feed material is dropped into the top of the classifier. It falls into a continuous feed curtain in front of the vanes, passing through low velocity air entering the side of the unit. The air flow direction is changed by the vanes from horizontal to angularly upward, resulting in separation and classification of the particulate. Coarse particles dropps directly to the product and fine particles are efficiently discharged through a valve beneath the unit. The micro fines are conveyed by air to a fabric filter for final recovery.

Air Magnetic Separation Cluster is a special equipment developed for dry magnetic separation of fine size (-3mm) and micro fine size(-0.1mm) magnetite. The air magnetic separation system can be combined according to the characteristic of magnetic minerals to achieve effective recovery of magnetite.

After rough grinding, adopt appropriate separation method, discard part of tailings and sort out part of qualified concentrate, and re-grind and re-separate the middling, is called stage grinding and stage separation process.

According to the characteristics of the raw ore, the use of stage grinding and stage separation technology is an effective measure for energy conservation in iron ore concentrators. At the coarser one-stage grinding fineness, high-efficiency beneficiation equipment is used to advance the tailings, which greatly reduces the processing volume of the second-stage grinding.

If the crystal grain size is relatively coarse, the stage grinding, stage magnetic separation-fine sieve self-circulation process is adopted. Generally, the product on the fine sieve is given to the second stage grinding and re-grinding. The process flow is relatively simple.

If the crystal grain size is too fine, the process of stage grinding, stage magnetic separation and fine sieve regrind is adopted. This process is the third stage of grinding and fine grinding after the products on the first and second stages of fine sieve are concentrated and magnetically separated. Then it is processed by magnetic separation and fine sieve, the process is relatively complicated.

At present, the operation of magnetic separation (including weak magnetic separation and strong magnetic separation) is one of the effective means of throwing tails in advance; anion reverse flotation and cation reverse flotation are one of the effective means to improve the grade of iron ore.

In particular, in the process of beneficiation, both of them basically take the selected feed minerals containing less gangue minerals as the sorting object, and both use the biggest difference in mineral selectivity, which makes the two in the whole process both play a good role in the process.

Based on the iron ore processing experience and necessary processing tests, Prominer can supply complete processing plant combined with various processing technologies, such as gravity separation, magnetic separation, flotation, etc., to improve the grade of TFe of the concentrate and get the best yield. Magnetic separation is commonly used for magnetite. Gravity separation is commonly used for hematite. Flotation is mainly used to process limonite and other kinds of iron ores

Through detailed mineralogy study and lab processing test, a most suitable processing plant parameters will be acquired. Based on those parameters Prominer can design a processing plant for mine owners and supply EPC services till the plant operating.

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.

iron ore screening

iron ore screening

Iron ore screening equipmentfromMultotecis made from polyurethane or rubber screening media. Our screening equipment is ideal for high, medium or low grade profiles,reduce plant footprint by more than 33%and materials of construction ensure along lifeatreduced costwithlow maintenancerequirements.

Our polyurethane and rubber iron ore screening solutions are manufactured using state-of-the-art injection moulding and rubber compression moulding machines. Aperture sizes and panel materials are tailored for use with all types of screening, from coarse, heavy-duty to ultra-fine applications.

Our screening solutions manufacturing technique, combined with our in-depth understanding of mineral processing industry flow sheets, four decades of industry experience and dedication to research and development, ensures the best iron ore screening solution for your application.

Our hammer samplers provide representative, cross belt samples of particulate material from a moving conveyor belt. They are manufactured in South Africa according to ISO 9001:2000 standards, and can be set up to suit all conveyor belt installations from 450 mm to 2 100 mm wide.

The Longi-Multotec heavy media drum separator (HMDS) for screening improves grade and recovery in dense medium recovery processes. We combine leading magnet technology, an established, application-specific experience in mineral processing and high-quality configurations, materials and parts, to improve the performance of dense media mineral recovery operations

Multotec has designed and optimised screening spiral concentrators for minerals, including iron ore, supplied with steel rubber-lined or PVC/polyurethane pipe launder systems, ideal for iron ore screening.

Multotecs polyurethane screens are made with self-relieving apertures resulting in the unrestricted downward movement of any sized particle eliminating pegging and blinding from your iron ore screening.

We manufacture three varied dimensions of static and reversible sievebend housing units for iron ore screening. Both units are suited to polyurethane sievebends and have 3 standard dimensions, varying from 800 mm arc length to 1 600 mm arc length

iron processing | britannica

iron processing | britannica

iron processing, use of a smelting process to turn the ore into a form from which products can be fashioned. Included in this article also is a discussion of the mining of iron and of its preparation for smelting.

Iron (Fe) is a relatively dense metal with a silvery white appearance and distinctive magnetic properties. It constitutes 5 percent by weight of the Earths crust, and it is the fourth most abundant element after oxygen, silicon, and aluminum. It melts at a temperature of 1,538 C (2,800 F).

Iron is allotropicthat is, it exists in different forms. Its crystal structure is either body-centred cubic (bcc) or face-centred cubic (fcc), depending on the temperature. In both crystallographic modifications, the basic configuration is a cube with iron atoms located at the corners. There is an extra atom in the centre of each cube in the bcc modification and in the centre of each face in the fcc. At room temperature, pure iron has a bcc structure referred to as alpha-ferrite; this persists until the temperature is raised to 912 C (1,674 F), when it transforms into an fcc arrangement known as austenite. With further heating, austenite remains until the temperature reaches 1,394 C (2,541 F), at which point the bcc structure reappears. This form of iron, called delta-ferrite, remains until the melting point is reached.

The pure metal is malleable and can be easily shaped by hammering, but apart from specialized electrical applications it is rarely used without adding other elements to improve its properties. Mostly it appears in iron-carbon alloys such as steels, which contain between 0.003 and about 2 percent carbon (the majority lying in the range of 0.01 to 1.2 percent), and cast irons with 2 to 4 percent carbon. At the carbon contents typical of steels, iron carbide (Fe3C), also known as cementite, is formed; this leads to the formation of pearlite, which in a microscope can be seen to consist of alternate laths of alpha-ferrite and cementite. Cementite is harder and stronger than ferrite but is much less malleable, so that vastly differing mechanical properties are obtained by varying the amount of carbon. At the higher carbon contents typical of cast irons, carbon may separate out as either cementite or graphite, depending on the manufacturing conditions. Again, a wide range of properties is obtained. This versatility of iron-carbon alloys leads to their widespread use in engineering and explains why iron is by far the most important of all the industrial metals.

There is evidence that meteorites were used as a source of iron before 3000 bc, but extraction of the metal from ores dates from about 2000 bc. Production seems to have started in the copper-producing regions of Anatolia and Persia, where the use of iron compounds as fluxes to assist in melting may have accidentally caused metallic iron to accumulate on the bottoms of copper smelting furnaces. When iron making was properly established, two types of furnace came into use. Bowl furnaces were constructed by digging a small hole in the ground and arranging for air from a bellows to be introduced through a pipe or tuyere. Stone-built shaft furnaces, on the other hand, relied on natural draft, although they too sometimes used tuyeres. In both cases, smelting involved creating a bed of red-hot charcoal to which iron ore mixed with more charcoal was added. Chemical reduction of the ore then occurred, but, since primitive furnaces were incapable of reaching temperatures higher than 1,150 C (2,100 F), the normal product was a solid lump of metal known as a bloom. This may have weighed up to 5 kilograms (11 pounds) and consisted of almost pure iron with some entrapped slag and pieces of charcoal. The manufacture of iron artifacts then required a shaping operation, which involved heating blooms in a fire and hammering the red-hot metal to produce the desired objects. Iron made in this way is known as wrought iron. Sometimes too much charcoal seems to have been used, and iron-carbon alloys, which have lower melting points and can be cast into simple shapes, were made unintentionally. The applications of this cast iron were limited because of its brittleness, and in the early Iron Age only the Chinese seem to have exploited it. Elsewhere, wrought iron was the preferred material.

Although the Romans built furnaces with a pit into which slag could be run off, little change in iron-making methods occurred until medieval times. By the 15th century, many bloomeries used low shaft furnaces with water power to drive the bellows, and the bloom, which might weigh over 100 kilograms, was extracted through the top of the shaft. The final version of this kind of bloomery hearth was the Catalan forge, which survived in Spain until the 19th century. Another design, the high bloomery furnace, had a taller shaft and evolved into the 3-metre- (10-foot-) high Stckofen, which produced blooms so large they had to be removed through a front opening in the furnace.

The blast furnace appeared in Europe in the 15th century when it was realized that cast iron could be used to make one-piece guns with good pressure-retaining properties, but whether its introduction was due to Chinese influence or was an independent development is unknown. At first, the differences between a blast furnace and a Stckofen were slight. Both had square cross sections, and the main changes required for blast-furnace operation were an increase in the ratio of charcoal to ore in the charge and a taphole for the removal of liquid iron. The product of the blast furnace became known as pig iron from the method of casting, which involved running the liquid into a main channel connected at right angles to a number of shorter channels. The whole arrangement resembled a sow suckling her litter, and so the lengths of solid iron from the shorter channels were known as pigs.

Despite the military demand for cast iron, most civil applications required malleable iron, which until then had been made directly in a bloomery. The arrival of blast furnaces, however, opened up an alternative manufacturing route; this involved converting cast iron to wrought iron by a process known as fining. Pieces of cast iron were placed on a finery hearth, on which charcoal was being burned with a plentiful supply of air, so that carbon in the iron was removed by oxidation, leaving semisolid malleable iron behind. From the 15th century on, this two-stage process gradually replaced direct iron making, which nevertheless survived into the 19th century.

By the middle of the 16th century, blast furnaces were being operated more or less continuously in southeastern England. Increased iron production led to a scarcity of wood for charcoal and to its subsequent replacement by coal in the form of cokea discovery that is usually credited to Abraham Darby in 1709. Because the higher strength of coke enabled it to support a bigger charge, much larger furnaces became possible, and weekly outputs of 5 to 10 tons of pig iron were achieved.

Next, the advent of the steam engine to drive blowing cylinders meant that the blast furnace could be provided with more air. This created the potential problem that pig iron production would far exceed the capacity of the finery process. Accelerating the conversion of pig iron to malleable iron was attempted by a number of inventors, but the most successful was the Englishman Henry Cort, who patented his puddling furnace in 1784. Cort used a coal-fired reverberatory furnace to melt a charge of pig iron to which iron oxide was added to make a slag. Agitating the resultant puddle of metal caused carbon to be removed by oxidation (together with silicon, phosphorus, and manganese). As a result, the melting point of the metal rose so that it became semisolid, although the slag remained quite fluid. The metal was then formed into balls and freed from as much slag as possible before being removed from the furnace and squeezed in a hammer. For a short time, puddling furnaces were able to provide enough iron to meet the demands for machinery, but once again blast-furnace capacity raced ahead as a result of the Scotsman James Beaumont Nielsens invention in 1828 of the hot-blast stove for preheating blast air and the realization that a round furnace performed better than a square one.

The eventual decline in the use of wrought iron was brought about by a series of inventions that allowed furnaces to operate at temperatures high enough to melt iron. It was then possible to produce steel, which is a superior material. First, in 1856, Henry Bessemer patented his converter process for blowing air through molten pig iron, and in 1861 William Siemens took out a patent for his regenerative open-hearth furnace. In 1879 Sidney Gilchrist Thomas and Percy Gilchrist adapted the Bessemer converter for use with phosphoric pig iron; as a result, the basic Bessemer, or Thomas, process was widely adopted on the continent of Europe, where high-phosphorus iron ores were abundant. For about 100 years, the open-hearth and Bessemer-based processes were jointly responsible for most of the steel that was made, before they were replaced by the basic oxygen and electric-arc furnaces.

Apart from the injection of part of the fuel through tuyeres, the blast furnace has employed the same operating principles since the early 19th century. Furnace size has increased markedly, however, and one large modern furnace can supply a steelmaking plant with up to 10,000 tons of liquid iron per day.

Throughout the 20th century, many new iron-making processes were proposed, but it was not until the 1950s that potential substitutes for the blast furnace emerged. Direct reduction, in which iron ores are reduced at temperatures below the metals melting point, had its origin in such experiments as the Wiberg-Soderfors process introduced in Sweden in 1952 and the HyL process introduced in Mexico in 1957. Few of these techniques survived, and those that did were extensively modified. Another alternative iron-making method, smelting reduction, had its forerunners in the electric furnaces used to make liquid iron in Sweden and Norway in the 1920s. The technique grew to include methods based on oxygen steelmaking converters using coal as a source of additional energy, and in the 1980s it became the focus of extensive research and development activity in Europe, Japan, and the United States.

the iron ore transportation process | usa truckload shipping

the iron ore transportation process | usa truckload shipping

If youre in Michigan or Minnesota and mining valuable minerals, theres a chance you have a vested interest in the iron ore transportation process. In the area around Lake Superior, it is a huge industry but one where the production still needs to go elsewhere to be turned into steel.

Learning more about iron ore transportation and how it can help your operations reach their financial goals is invaluable. In the iron ore trade, youll need to be concerned with the raw material being transported multiple times before its turned into usable steel. Read more below about how to handle this.

Also, consider partnering with a reputable third-party logistics (3PL) company like R+L Global Logistics. Finding a good fit to take over the hauling of your raw iron ore can make a huge difference, both in the way your business is able to run and also on the money side of things.

The state of Minnesota leads the country in iron ore production by a wide margin. In fact, 98 percent of the iron ore mined in America in 2018 came from the Lake Superior region of both Minnesota and Michigan. Even so, Minnesota does the vast majority of that 98 percent.

Besides these two U.S. behemoths, there is not any other substantial iron ore production in the country. While that wasnt always the case think Birmingham, Alabama in the 20th century it is currently. Since iron is not a renewable resource, once a place has been stripped of its iron ore, it is done for good.

With underground mining, there are a variety of different ways to transfer the metal. The resource is hoisted to the surface up a shaft and shipped to processing plants in myriad ways. First the ore is loaded onto trains that take it to Lake Superior, where it is then put onto ships. The reason ships are used is because no taconite mine in the U.S. is located more than 100 miles from the Great Lakes and shipping by boat is considered a low-cost mode of transport.

A less common method of iron ore movement during this phase is the use of a slurry pipeline. This is a special kind of pipeline that is a mixture of iron ore and water that moves over a long distance. Once the slurry gets to the processing plant, the water is drained and the ore is then ready for processing.

Before it reaches steel mills, iron ore is not always shipped in giant, raw chunks. A large portion of the iron ore we get now comes from taconite, which is a type of iron formation that also contains other minerals like quartz, carbonate or chert. Even iron that is pure is never truly pure and needs at least a base level of beneficiation

Iron usually comprises 25 percent of taconite, so it needs to be heavily processed before it reaches steel mills. Both to separate the iron from the other minerals but to shape it in a way for the steel-making process to be able to properly use it.

This is the point where the taconite is shaped into pellets, which satisfies both of those requirements. The beneficiation process removes impurities in the ore and improves the quality. In this case, the iron ore is agglomerated into pellets, which is the most common form that iron is introduced to steel-making blast furnaces.

The reason agglomeration is preferred to other methods is makes the ore permeable so that gases during the transformation into steel can pass through the pellets. There are three types of agglomeration, the one used in this case is called pelletizing.

Pelletizing sees the taconite ground into a fine power and then heated up to form marble-sized balls. Binders are then added to make sure the newly formed pellet retains its shape during shipping and at the steel mills.

Truck: Loading your iron ore onto a tractor trailer is a good all-around mode of transportation since it can reach any part of the continental United States with little issue. The freight hauling industry strikes the perfect balance between ubiquity and affordability that other modes of transportation would be hard-pressed to match.

Rail: Shipping by rail has seen an uptick in recent years since it is viewed as a sometimes cheaper, always cleaner and readily available form of transport. This involves your items going onto into a shipping container and being loaded onto the train platform.

Ship: In the United States, since so much of the currently mined iron ore is located near one of the Great Lakes, there is a huge incentive to use ships for at least part of the journey from the mine or pit to the steel mills. Part of this, besides the convenience, is the inexpensive cost relative to the same trip taking place via truck or rail.

Pipeline: As described earlier, a slurry pipeline is one that transports a mix of iron ore and water over long distances. It is not used as a primary shipping method by itself and it most likely will run to a body of water to be loaded onto a ship to complete its journey to the steel mill.

A downside to this method is that pipelines are susceptible to rupturing, which can completely shut down the movement of iron ore temporarily while the pipeline is fixed, or permanently if it is a bad enough incident or the pipeline has been problematic multiple times.

A trucking company can also offer expedited shipping for times when you need something there earlier than usual. While you may have to pay an additional fee for this, its at least an option for times when you find yourself in a bind. With a train that is carrying the loads of other customers, the rail choice cant offer such a service.

Fuel efficiency is probably the biggest drawback to shipping by truck. A train is always going to be more fuel efficient than a truck and depending on the market price for diesel fuel at a given moment, it can also be more expensive to ship by truck than rail.

There are also times when, for a variety of reasons, it might be hard to find a truckload. There might be less drivers available for instance, which will also make it harder (and more expensive) to find an empty tractor-trailer to ship in.

Rail shipping can ship more at a time than a single truck can. Yes, youll have to pay for the number of cars used on a train but you dont have to worry about multiple trucks carrying multiple loads at possibly different times. Your loads on the rails will also show up at the same time. Many times, containers can also be double stacked as well. While this doesnt reduce the weight, it allows a train to haul more freight in a space of the same length and width something a truck cant compete with.

Rail shipping doesnt have to worry as much about closures, traffic or other outside forces as traditional road vehicles do. Also, trains are more fuel efficient than trucks. Not only is that better for the environment, but since less fuel is being burned, it should lead to savings for you, the customer.

In truth, most loads shipped by rail especially over longer distances will end up using trucks for some portion of the journey. Train tracks rarely have a stop right at a business, meaning the load will have to be shifted to a truck or boat at the beginning and end of each trip.

This is referred to as intermodal transportation, where containers or loads are sent between two points using more than one type of transportation, whether it be trucks, planes, trains or ships. This type of moving freight has grown because it is more efficient than solely trucks in the U.S. and impossible to use just one mode of transport when shipping overseas.

While it can be seen as a positive overall, intermodal transportation is not a pro for shipping entirely by rail. A truck can make a delivery from point A to point B by itself in nearly every domestic case, but a train cannot do that same.

Overweight or oversized trucking shipments are only allowed for items that have to be shipped in one piece. Since a load of iron can be easily separated, an overweight load would be unnecessary and also illegal.

The definition of an overweight load is one where the total weight of the vehicle is in excess of 80,000 pounds. The only way a load is allowed to be shipped as overweight would be if it is not able to be divided.

Once the worlds largest producer of steel, the United States production has waned from its peak in the 1950s. Still, America is the fourth-largest producer of steel behind China, India and Japan and ahead of South Korea and Russia.

Of the nine currently operating integrated steel mills, five are in Indiana, one is in Pennsylvania and two are in Ohio. The three companies that run those nine mills are AK Steel, ArcelorMittal and US Steel.

Once the iron ore is transformed into steel, it can be used to build a variety of products in different industries. The two biggest ones are the construction industry and the transportation industry which includes cars, airplanes, railroads and trains.

But in actuality, the use of steel extends into many facets of life as its used in the energy field as well as modern appliances like refrigerators, washer and dryer machines, dishwashers, sinks and more.

Just focusing on construction and the transportation industry, since it needs a lot of steel to make its products, lets break down how it would be moved. As mentioned previously, steel is able to be divided, so it can be transported by any available means of transport. That could be by truck, train or boat, and your operation will have to figure out which one to use depending on its convenience, reliability and cost.

Automobile manufacturers will be a relatively easy business to deliver to since theyre highly likely to have the facilities to receive large shipments of steel for either immediate use or storage. The same goes for the aviation industry.

Construction sites, on the other hand, are all different and out in the open. Delivering steel to them comes with a different set of potential dangers since construction sites are active places with workers constantly moving around. While you want an experienced company for any of your deliveries, you especially want one when having to deliver to construction sites.

Once the iron ore transportation process has become clear to you and youre ready to ship, look to do so with the trusted 3PL company R+L Global Logistics. We can easily, efficiently and quickly ship your unprocessed ore to the steel mills to have them turned into a strong, durable product.

With our 99.5 percent on-time rate and industry-leading customer service, R+L Global Logistics is well positioned to be both speedy and helpful during the entire course of shipping your load. Also included with each of our trucks is real-time freight visibility so you can track your minerals journey from start to finish.

When the regular timeframe simply wont do for your business needs, R+L Global Logistics can offer expedited shipping at an additional cost. This can drop the turnaround time by a day or two in most cases.

So when youre prepared to engage in iron ore transportation or even ship refrigerated freight like cranberries, check out the heavy haul trucking competitive pricing at R+L Global Logistics. For a free freight shipping quote today with no obligation, call us at (866) 353-7178.

screening media | mineral screening multotec

screening media | mineral screening multotec

From wedge wire sieve bends and centrifuge baskets to completely optimised composite screen decks, Multotec is a leading screening media technology solutions provider for the global minerals processing industry.

We supply products covering the full range of screening applications, including sizing, dewatering, scalping and desliming. Refined over 45 years experience in mineral screening applications, Multotec manufactures one of the worlds largest ranges of rubber, polyurethane, wedge wire, steel and composite screening media.

Your local Multotec branch provides turnkey screening media solutions, with short lead times on screening media products, and engineering and field services to ensure your screening plant is optimised for your processing conditions, material and the output targets.

Multotec screening media has been developed in response to the worlds toughest mineral screening applications. We offer this global technology to the worlds mining and mineral processing houses through an established worldwide footprint that includes a complete network of branches and distributors in almost 100 countries on 6 continents.

Your local Multotec experts offer complete turnkey solutions for screening media installations, including design and engineering, installation and commissioning, and wear monitoring and field service support. Our teams will ensure the optimum screening media solution is supplied according to your specific plant and process parameters and requirements, such as feed tonnage required, the average particle size and the particle shape.

Multotec can design and build completely customised screening decks. Drawing on one of the worlds largest ranges of purpose-specific screen panels from materials including rubber, polyurethane, steel, woven-wire, ceramics, Hardox, fibreglass and combinations of these materials we can optimise each area of your screen deck to suit the conditions, your material and output targets.

A popular composite deck configuration is to place a set of panels with highly impact-resistant material at the feed end of the screen, where the impact of material from the feed box or chute is highest.

Weve supplied composite screen decks with over a dozen different types of panels, with each panel fulfilling a specific function. The apertures will be chosen according to the screens purpose and factors like the feed tonnage required, the average particle size and the particle shape. That way, we can ensure maximum mineral screening efficiency at the lowest overall cost.

Our monitoring software Hawkeye provides complete real time and historical intelligence of the condition of your screening media. Through accurately indicating screen media wear, Hawkeye helps optimise wear-related maintenance and reduces downtime, while ensuring your screening media reliably delivers the cut size your plant required.

By enabling plant operations and technical teams to systematically manage and analyse wear data from the screening deck, Hawkeye also provides a powerful planning system for on-going application improvement. By tracking the performance over time of the various panel types on each deck in operation, the screening requirements in each part of the deck can be constantly refined.

Multotec screen panels are manufactured standard with visual wear indicators. These wear indicators comprise four or five moulded cavities in the body of the panel, spaced at predetermined intervals below the upper wear surface. As the panel surface is worn away, so the individual cavities become visible, the final cavity of which indicates that a replacement must be conducted or planned shortly.

This simple but innovative system, patented by Multotec, not only indicates when replacement needs to take place, but can be used as a data source to measure the rate of wear so that a future replacement time can be predicted and planned.

Blinding occurs when dirt, minerals and other substances adhere and bridge across the apertures of your screening surface, creating a stubborn paste that blocks material from screening through. Pegging describes the presence of irregular material lodged in the screen apertures, and occurs when stones are about the same size as the holes.

Multotec, in partnership with universities across the globe, is constantly developing and testing new innovations and technologies to respond the challenges our customers face in processing minerals more efficiently, and at a lower cost. Our screening equipment of today reflects over 45 years of innovation and optimisation in the worlds largest mining and mineral processing operations.

Roy has been involved in mining and metallurgy since 1981, and has vast global experience in both the production and sales side of the industry, across Africa, Australia and South America. His commitment to product development, business development and customer satisfaction has made Roche one of the worlds leading experts in screening media solutions.

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