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Thailand has plenty of river sand resource which is high quality of silica sand, upto 99.6% SiO2. In the northest, the river sand had been proved that the high iron contaimination Fe2O3 upto 0.165% can be lowered down to 0.065% by high gradient magnetic separation technology.

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Wet magnetic separation is widely used in the purification of quartz sand, which has the characteristics of significant iron removal effect, large handling capacity and no dust pollution. In the primary stage of quartz sand purification, wet magnetic separation is generally considered to be an excellent way of iron removal purification, but in the stage of high-purity quartz cleaning, the conventional wet magnetic separation purification effect is not obvious, the reasons can be summarized as three points.

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direct-reduced iron - an overview | sciencedirect topics

DRI can be produced in powder, pellet, lump, or briquette form. The powder, pellets, and lumps retain the shape of the iron oxide material fed into the DR process. The removal of oxygen leaves voids, giving the DRI a spongy appearance when viewed through a microscope. Thus, DRI in these forms has a lower apparent density, greater porosity, and more surface area than iron ore. In the hot briquetted form, it is known as hot briquetted iron (HBI). Fluidized bed DRI is usually processed to HBI due to the difficulty of using fines in steelmaking, and the reactivity of fines to oxygen, even when cool. Typical physical properties of DRI forms are shown in Table 1.

HBI is produced by molding hot (ca. 700 C) DRI into pillow-shaped briquettes using a pocketed roll press. The lower surface area and higher density of HBI makes it 100 times more resistant to reoxidation. The high density, strength, and minimum water absorption make it ideally suited for merchant applications where shipping, handling, and storage characteristics are important.

DRI containing several percent C may be produced where the benefit of added carbon in steelmaking outweighs the added cost. The carbon can be as iron carbide (cementite, Fe3C), or graphitic carbon. The carbon contained in shaft-furnace DRI is typically over 90% Fe3C. Fluidized bed processes for producing iron carbide from ore fines have been developed, but none are presently operating.

DRI retains the chemical purity of the iron ore from which it is produced. It therefore tends to be very low in residual elements such as copper, chromium, tin, nickel, and molybdenum. Typical ranges of DRI chemistry are 9094% total iron, 8389% metallic iron, 6.59% iron oxide, 0.82.5% carbon, 2.86% gangue, 0.0050.09% phosphorus, and 0.0010.03% sulfur.

DRI normally has at least 90% of the oxygen removed, with the unreduced oxide present as wustite. Processes producing solid with <90% reduction are classified as prereduction processes. Prereduced iron is not acceptable for steelmaking, but can be used as a feed for ironmaking (e.g., feed for a BF).

Although it is theoretically possible to convert all the iron oxide to metal, it is not economically feasible. Reduction slows significantly in the last stages, and to complete the reduction would require low production rates. In practice, the DRI is discharged with a small amount of iron oxide remaining. In addition, during cooling prior to discharge, iron in the DRI reacts with the CO and CH4 in the cooling gas to form cementite according to:

The carbon content can be adjusted within limits by operating changes in the DR process, and is typically between 1% and 2.5% Calthough it can be higher by adjusting the composition and amount of cooling gas. During melting in an EAF, the iron oxide and carbon in the DRI react to form metallic iron and CO. The CO evolution enhances the steelmaking reactions, and the oxygen used to oxidize the extra carbon improves the energy balance. Most steelmakers prefer slightly more carbon than is required to balance the remaining iron oxide.

The gangue content of DRI is typically comprised of oxides such as SiO2, Al2O3, CaO, MgO, TiO2, K2O, Na2O, MnO, etc., and for gas-based processes, is dictated by the chemistry of the iron ore used. The phosphorus is normally in the form of P2O5. Sulfur content depends on the sulfur level in the ore and reductant, and the amount of sulfur released or absorbed by the DRI during reduction. The gangue content of DRI produced by coal-based processes may be considerably higher, owing to the retention of some of the coal ash by the DRI.

When handling, shipping, and storing DRI, care should be taken to avoid oxidation. This requires the material be kept cool and dry. If not, oxidation of DRI can take place by two mechanisms: corrosion and reoxidation. Corrosion occurs when the metallic iron in DRI is wetted with fresh or salt water, and reacts with oxygen from the air to form rust, Fe(OH)3. The corrosion reactions continue as long as water is present. Corrosion is very exothermic, but as long as water is present, the temperature does not reach much above 100 C. Reoxidation occurs when the warm metallic iron in corroding DRI reacts with oxygen in the air to form either Fe3O4 or Fe2O3. The reaction continues as long as the DRI remains hot, and oxygen is available. Owing to the exothermic nature of reoxidation, and the insulating nature of bulk DRI, the DRI temperature increases and accelerates the reoxidation rate. In comparison, HBI is almost twice as dense as DRI and thus does not absorb much water. It is much more resistant to corrosion and reoxidation. Several methods of passivating DRI have been developed, but none are as effective as hot briquetting.

Direct reduced iron is iron ore in the form of lumps, fines or pellets that have had the oxygen removed by using hydrogen and carbon monoxide. Typical sources of carbon monoxide are natural gas, coal gas, and coal. Other energy inputs into the production process often include oil and electricity. Since much of the energy used is in the form of natural gas (e.g., Mexico produces virtually all its direct reduced iron with natural gas), most direct reduced iron is produced where low cost natural gas is available and where adequate capacities exist to access iron ore shipments. Use of natural gas not only reduces the need for coal and coke, but also reduces the associated emissions, such as sulfur oxides and carbon dioxide into the atmosphere.

In direct reduction the ore is heated to temperatures below its melting point. Direct energy requirements per net ton of direct reduced iron are in the order of 10,000MJ. The product is 90 to 95% metallized and hence is suitable as a charge in blast, basic oxygen, and electric arc furnaces.

By using direct reduced iron, steel makers can dilute lower grade ores and lower cost ferrous scrap to attain acceptable levels of contamination in the mix. If direct reduced iron pellets are substituted for pelletized ores in blast furnaces, the amount of coke per ton of pig iron would be cut. However, reductions in the coke rate could result in shortages of coke byproducts, while natural gas requirements would increase considerably.

Coal can also be directly used as a reducing agent without going through the gasification process. Processes based on the RHF and RK utilize coal as the reductant. Generally, the processes based on the RHF utilize self-reducing iron oxide and coal composite pellets, where iron ore concentrate, coal, additives, and binder are mixed together. At elevated temperatures, the carbon and hydrogen present in self-reducing pellets interact with oxygen to produce reducing gases CO and H2. In the case of the RK, iron oxide pellets, coal, and flux are fed into the furnace at the elevated end. Here again, the carbon and hydrogen components of the coal react with oxygen and iron oxide at elevated temperatures, with gaseous reduction of the oxide occurring. Key chemical and physical characteristics of the coal used in these processes are considered below, with the technologies themselves discussed in Section 1.2.3.

The DRI processes based on the RK usually do not require a very fine size of coal; the particles can vary from 5 to 20mm for different processes [38]. However, processes based on the RHF require very fine particle sizes, typically 70% below 325-mesh (45m), since the coal will be blended with fine ore and pelletized.

In general, a high level of fixed carbon in the coal is always preferable and desirable. It should be noted that fixed carbon and total carbon are usually not the same. Total carbon represents the carbon present in the coal under normal conditions. Fixed carbon is determined by heating the coal to 900C in the absence of air, thus burning away all volatiles (including carbon in hydrocarbons). The carbon remaining after this treatment is called fixed carbon. When it comes to using coal as a solid reductant, fixed carbon is more important than total carbon.

The processes based on the rotary hearth usually require high fixed carbon compared to processes based on a RK. Since RHF-based processes use composite pellets, a minimum level of carbon in coal is required. Low levels of fixed carbon mean higher amounts of coal in composite pellets, which will reduce the overall productivity of the process. In reduction using RKs, lump coal and iron oxide pellets are added separately and the amount of coal can be easily varied. Also the char formed during the process is recycled and used as feed as well. Processes based on RKs are more flexible when it comes to fixed carbon level or even overall coal composition. Processes such as Krupp-CODIR, Direct Reduction Corporation (DRC), ACCAR/OSIL, and SL/RN have utilized coal with fixed carbon levels varying from 34% to 75% carbon by weight [32,33].

Volatiles are basically the material present in coal that is burnt away when coal is heated to 900C without air being present. Coal with low volatile matter is preferred since any chemical or calorific value in the volatiles is typically wasted, though it is sometimes possible to capture some of that value. RK-based processes can handle coal with higher volatile matter (ranging from 6% to 40%) as volatiles are already burnt away before they enter the kiln. RHF-based processes prefer coal with less than 25% volatiles [38,39].

Regardless of the ironmaking process, sulfur and phosphorus are generally undesirable elements in any raw material, since they can make the final steel product brittle and weak. Often limestone (CaCO3) or dolomite (CaMg(CO3)2) is added with the feed to an RK and mixed with iron ore concentrate to act as a desulfurizing agent. The specification for sulfur in RK-grade coal in India is a maximum of 1% [38]. The maximum moisture content allowed in the same coals is 7%.

One disadvantage of the coal-based technologies is that they often bring significant levels of impurities with them, as part of the coal ashfor the low-grade Indian coals, ash can be as high as 27.5% of the coal [38]. This ash is typically made up of common slag-forming components such as SiO2, Al2O3, CaO, MgO, and FeO, though other oxides and sulfides are often present. The exact mix of components in a particular coal ash can be criticalfor example, ash containing more than 70% silica can react with ferrous oxide (FeO) to form a low-melting point compound (fayalite, Fe2SiO4) that interferes with the reduction process [39].

Char is a substance that is produced by partial combustion of a carbonaceous material. Coal char reactivity is an ability to produce carbon monoxide (CO) after reacting with carbon dioxide (CO2) [40]. RK-based processes prefer high coal char reactivity since only low operating temperatures are required to fully utilize these coals [39,41]. Typically, RHF-based processes do not mention the reactivity index as a material characteristic of the coal used.

Ash fusion temperature is the temperature at which the ash present in the coal begins to soften or melt. In general, a high ash fusion temperature is preferred, to avoid deposition of sticky ash inside the kiln. It is usually measured at four different temperatures under oxidizing and reducing atmospheres: initial deformation (IT), softening temperature, hemispherical temperature, and fluid temperature [41]. Typically ash fusion temperatures (IT) 130150C above the reduction temperature are preferred for good productivity [41].

Free swelling index is a measurement of increase in volume when coal is heated under specified conditions. A standard method (ASTM D720-91 (2010)) can be used to measure this characteristic. Although it is still not completely clear what affects the free swelling index of coal, it is believed to relate to the coals plastic properties. The free swelling index tends to be higher if coal exhibits plastic properties and contains high volatiles. Anthracite coal typically has a low free swelling index, which makes it preferable in most instances over typical bituminous coal [42].

Coal can be coking or noncoking; this is partially determined by the caking property of coal. Caking is determined by heating the coal to a certain temperature in the absence of air and, if it leaves a solid residue behind upon cooling, it is considered caking coal [40,43,44]. The caking property of coal is usually referred to as the Caking Index; the standard method ISO15585:2006 is one of the methods used to determine this property [40]. A noncaking coal is always noncoking but a caking coal does not always make good coke. Solid-based DRI processes prefer a noncaking and noncoking coal, but a coking coal is desirable for BF operation [39,40]. For RK-grade coal in India, the specification for Caking Index is a maximum of 3 [38].

Calorific value is basically a measurement of energy or heat released (kJ or kcal) when 1kg of coal is completely combusted in the presence of air or oxygen. The calorific value of coal increases directly with its carbon and hydrogen contents, while oxygen content reduces calorific value. For DR processes based on both types of furnace, coal with a high calorific value is preferred.

The Circofer process is a coal-based direct reduction process developed by Outotec GmbH. Fine ore is pre-reduced to DRI in a CFB (circulating fluidised bed) reactor (Fig.12.14). Char and hot reducing gas are produced as by-products.

In the CFB reactor, preheated iron ore is pre-reduced to a degree of metallisation of up to 85% with CO and H2 out of in situ coal gasification. The reactor off gas is used in one or two preheating stages (depending on desired off gas temperature) to preheat the cold iron ore making use of the sensitive heat in the gas. After that, it is cooled and cleaned and the reaction products water and carbon dioxide are removed (Born et al., 2011).

Coal is fed directly into the integrated heat generator where it is partially combusted with pure oxygen. Unburnt coal and char are transferred into the CFB where the pre-reduction takes place at around 950C, using the Boudouard reaction to produce CO from coal. The DRI product is continuously discharged from the reactor and fed into a subsequent smelting reduction process. This can either be a shaft furnace, a submerged arc furnace or a smelting reduction process like HIsmelt (Orth et al., 2004), Fig.12.14, or Auslron (Laumann et al, 2010). The carbon content of the material is 68%.

For the production of highly metallised DRI, the CFB is followed by a bubbling fluidised bed reactor (FB) where the pre-reduced material is further reduced by recycled gas containing mainly CO and H2, to a degree of metallisation of over 90%. After the discharge of the DRI from the FB, the remaining carbon is removed in a hot magnetic separator. The hot DRI can be used directly in electric smelting furnaces. The off gas from the FB is fed into the CFB making full use of the remaining reduction potential. The recirculated off gas is used for fluidisation of the solids in the reactors. Primarily, reduction occurs with carbon monoxide: Fe. O3+3 CO=2Fe+3CO2. After heat recovery in a boiler, the de-dusted, quenched and CO2stripped gas is returned to the fluidised bed reactors.

In the Circofer process any coal having an ash melting temperature of >1050C and volatile matter content of 1040% can be used. A coal with ash content <15% is preferable in order to keep the circulating load in the reactor, and in the case of direct charging into a smelter the slag volume to a minimum (von Bitter et al., 1999).

cooling stage. DRI is cooled by transferring its heat to a cold reducing gas (72% H2 and 17% CO). The reducing gas leaving the vessel is regenerated by quenching and scrubbing to remove humidity, CO2, and dust. The regenerated gas is then injected into stage 2.

primary stage. Wustite (FeO) is reduced to metallic iron. The reducing gas leaving the vessel is once more regenerated by quenching and scrubbing to remove humidity, CO2, and dust. The regenerated gas is then injected into stage 3.

secondary stage. Hematite (Fe2O3) is reduced to wustite. The reducing gas leaving the vessel is regenerated by quenching and scrubbing to remove humidity, CO2, and dust. The regenerated gas is then reformed to its initial reducing strength of 72% H2 and 17% CO.

During reduction the lump iron ore or pellets are stationary in the reactor and therefore the risk of sticking is high. A DRI removal tool is used to break the superficial bonds among DRI pieces. The DRI product must also be briquetted to avoid reoxidation.

Integrating gasification-produced syngas with DRI/HBI in an optimised way offers a technically viable alternative to natural-gas based processes. The process allows a range of feedstocks to be used giving it considerable fuel flexibility. Opportunity fuels such as petcoke are being produced at an increasing rate, thereby ensuring a cheap, abundant supply. Gasification technology offers a way to process these feedstocks while at the same time meeting the most stringent environmental requirements. The process is especially adept at handling high sulphur fuels, with sulphur being recovered in its elemental form or as sulphuric acid. A marketable slag is produced. Carbon dioxide is captured as part of the process and can be used if a suitable use is available

Cost comparisons are highly site specific. In the case studied here, it was found that operating costs are quite competitive with the gas-based processes, with costs being equivalent atUS$ 2.00/GJ for gas versus US$ 20/t for petcoke. Notwithstanding the great advances made in capital cost reduction in the development of the quench design, this is still a significant factor. For the recovery factors selected, the cost of capital contribution lifts the equivalent gas price toUS$ 3.00/GJ. This contribution is highly sensitive to the local interest rate and can be reduced by appropriate financing, but efforts to reduce capital cost should still be a major thrust of future work.

The RHF process was originally developed as an alternative to gas-based direct reduction, making DRI from iron ore and coal. The process started from the patent of D. Beggs applied by Midland-Ross Corporation in 1965 [144]. This process was known as Heat Fast [145]. Tests to reduce fine iron ore were carried out using a pilot plant (2tons/h) in Minnesota, USA in 1965.

The DRI made from iron ore reduced by using coal as the reducing agent is not suitable for use in EAFs due to the large amount of slag and high sulfur content. As a result, the coal-based direct reduction process is utilized today mainly for steel mill dust treatment.

Figure 4.5.82 shows the development history of the RHF process in subsequent years. The processes such as FASTMET, INMETCO, and DRyIron, which have been put to practical use as RHF processes today, have been developed from the Heat Fast process.

In a DR process, iron ore pellets and/or lump iron ores are reduced by a reducing gas to produce DRI or hot briquetted iron (HBI). Depending on the generation of the reducing gas, two different DR processes are commercially available: gas-based and coal/oil-based. In the gas-based DR process, the reducing gas is produced by chemically reforming a mixture of natural gas and off-gas from the reducing furnace to produce a gas that is rich in hydrogen and carbon monoxide. Typical examples of the gas-based DR process include MIDREX and HYL, which are often the preferred technology in countries where natural gas is abundant. However in the coal/oil-based DR process, the reducing gas is generated from hydrocarbons (primarily coal, but sometimes oil and natural gas) in the reduction zone of the furnace, which is typically a rotary kiln. Typical examples of the coal-based process include the SL/RN and ACCAR processes. The coal-based DR process is more popular in India and China. Different types of reactors, such as shaft furnaces, fluidized beds, rotary kilns, and rotary hearth furnaces, have been used in different variations of the processe to achieve the metallization required.

Based on statistics (Anon 3, 2014), India is the world leader in DRI production producing about 17.8Mt of DRI in 2013, approximately one-forth of world DRI production. The gas-based DR processes are producing almost 80% of the world's DRI. MIDREX is the key variant of the gas-based DR processes accounting for about 63.2% of world DRI production in 2013, followed by HYL (15.4%). Therefore, the following discussion focuses mainly on the MIDREX process.

For most steelmaking operations, refining in the EAF is limited to dephosphorization, decarburization, and temperature adjustment. Phosphorus in the charge could be at higher than usual levels for DRI, HBI, pig iron, and hot metal, depending on the iron ore source. Some steels require particularly low P levels to avoid too high ductile/brittle transition temperature or tempering brittleness. From the equilibrium point of view, lower temperatures, high slag basicity, and high oxidation of the bath favor dephosphorization. Slag/metal interaction is important from a kinetic point of view but is not always attainable in the EAF.

Reversion of phosphorus from slag to steel may take place when heating to the aimed temperature, close to the end of the process. Then, if there is some slag carry over to the ladle, and steel and slag have a low oxidation level, P reversion is again possible. Therefore, in such phosphorus critical cases slag carry over to the ladle should be carefully prevented. That can be done by slag detectionslag stopping system or by EBT, which is stopped before the end of the steel. In such a hot heel practice, a significant fraction of liquid steel is left in the furnace for the next heat. Hot heel practice not only prevents steel from rephosphorization, but also speeds up the melting process; however, it has a smaller charge weight in the ladle as a drawback.

Different equations were tested by calculating final P contents using plant data [19] and comparing with analyzed P contents in Figure 1.5.11. It was found that the distribution by Turkdogan equation was closest to the mean value, but showed somewhat bigger scatter than both Suitos and Healys models.

Decarburization is carried out as a refining task. If the charge is 100% scrap, carbon in the metallic charge should be relatively low. This is not the case when charging a high percentage of DRI (if produced in a gas-based unit), HBI, pig iron, or hot metal, with carbon contents between 1.6 and 4.5.

Usually, due to productivity reasons, steelmakers prefer to achieve a carbon content of around 0.05 before tapping. Lower contents may imply a too high oxidation level. In Figure 1.5.12, the theoretical CO equilibrium is compared with plant values. The equilibrium calculation was performed by using FactSage 6.2 Program Package and FToxide and FactSage databases.

An alternative strategy is catch-carbon practice in which carbon content is targeted at somewhat under the final value, to be reached with alloys addition. This practice can bring material savings in alloying and deoxidation, but needs strict individual process control for each heat. For this reason, it is not so good for productivity, and if final carbon is maintained high, dephosphorization could be problematic.

Desulphurization is usually carried out at tapping and during ladle metallurgy, as in those stages the steel is deoxidized and the slag has high basicity and low oxygen potential (low content of oxidizing components, FeO, MnO, etc.). Nowadays, all other refining operations, except decarburization and dephosphorization, are performed in ladles and the electric arc furnace can act as a fast melting machine.

Before moving to a brief review of state-of-the-art steelmaking practices, I must devote a few pages to describing the only major practical alternative to BF ironmaking, direct reduced iron (DRI). This group of techniques obviates the use of metallurgical coke as it reduces iron ores in their solid state at temperatures well below the metals melting point. In principle, DRI could be thought of as a modern, efficient replication of the preindustrial, artisanal production of spongy iron masses in bloomeries, the process described in this books first chapter. Between 1869 and 1877, William Siemens experimented with a variant of DRI by attempting to reduce a mixture of crushed high-quality iron ore and coal in rotating cylindrical furnaces, and during the 1920s two Swedish processes were employed in a small-scale local production of iron powders. One of them (Hgans process) is still used for that purpose by an eponymous Swedish company and by other enterprises (Hgans, 2015).

Commercialization of DRI began only during the late 1960s, and by the mid-1970s there was a choice of nearly 100 designs combining different reactors (furnaces, kilns, retorts, fluidized-bed reactors) with a number of reducing agents, including coal, graphite, char, liquid and solid hydrocarbons, and gases (Anameric & Kawatra 2015; Hasanbeigi, Price, & Arens, 2013). DRI processes can be classified according to the kind and source of reducing gas or type of reactor used, and the DRI process that has been so far the most commercially successful relies on natural gas and hence it has been most commonly installed in locations and in countries where this fuel has been inexpensive and readily available. Natural gas is reformed by a catalytic steam process (CH4 + H2O CO +3H2) and it reduces iron pellets or fines as it ascends, mixed with crushed limestone, in a shaft (Anameric & Kawatra, 2015). The Mexican Hojalata y Lamina was the pioneering design (with later versions marketed as HYL-III), and the most successful US contribution, MIDREX process, uses shaft furnaces, while Fior/Finmet, Iron Carbide, and Circored use fluidized-bed reactors.

MIDREX has earned its leadership in direct reduction because its plants are the industrys most productive and most reliable (often operating for more than 8000 hours a year) and can use a range of reductants and raw materials (MIDREX, 2015). Plants can produce reducing gas from the energy source that is either locally, or most readily, available or that is most competitively priced, be it natural gas (reformed to yield CO), syngas from coal, petroleum coke ore heavy refinery residue (processed in a gasifier), or coke oven gas. Furnaces can work either with lump ore or iron oxide pellets (or their mixture), and the process itself is simple (involving the countercurrent descent of iron-bearing material loaded at the top of a cylindrical vessel lined with refractories and ascent of reducing gases).

MIDREX DRI is in the form of a solid sponge, vulnerable to reoxidation and unsuitable for transportation, and since 1984 this sponge iron has been first converted into hot-briquetted iron (HBI), produced by discharging hot DRI into roller presses that mold it into dense, pillow-shaped briquettes highly suitable as EAF charge. The other products are cold DRI (cooled before discharging) and hot DRI in the form of dense (bulk density of 2.53t/m3) briquettes containing 9094% Fe and each weighing up to 3kg. When compared to blast furnace smelting, the process has three other key advantages besides doing away with coke. First, its specific energy requirement (GJ/t) is approximately only half of those for BF operation (for details see the penultimate section of the next chapter). Second, as a result, its specific carbon emission is also much lower (see the last section of the next chapter). Third, there is a much greater flexibility in designing plant capacities: while the economies of scale for the standard BFBOF choice demand annual output of at least 2Mt, DRI plants associated with a mini-mill can produce as little as 0.5Mt/year.

Corex, the most successful smelting-reduction process, was originally developed by Voest-Alpine Industrieanlagenbau (VAI), and it is now marketed by Siemens under the name SIMETAL Corex (Siemens VAI, 2011). It requires two separate process reactors, the first being a reduction shaft charged with lump ore or pellets and additives to produce DRI in a counterflow reaction, and the second being a melter gasifier where the reduction is completed and hot metal and slag are tapped, much as in conventional BF. The first Corex plant began to operate in Pretoria in 1989, and subsequent installations included Saldanha in South Africa, Pohang in South Korea, at Chinas Baosteel (two units), and five units in India (JSW Steel and Essar Steel).

Rotary hearth furnaces (RHFs) have been used for decades in heat treating metals and high-temperature recovery of nonferrous metals, and hence their use in ironmaking has been a matter of specific application and appropriate process control. RHFsdeveloped and marketed under proprietary labels of Fastmet, Fastmelt, Redsmelt, Sidcomet, Primus, and lTmlk3now constitute the largest class of new direct reduction processes but account for a minority of global DRI output (Anameric & Kawatra, 2015; Guglielmini & Degel, 2007; McCelland, 2002; Sohn & Fruehan, 2006). Their flat refractory hearths rotate inside high-temperature circular tunnel kilns lined with refractories, with iron ore and reductant in a single- or multi-layer bed, and with temperature controlled by burners (using natural gas, fuel oil, or pulverized coal) along the wall and on the roof. Mixed ore-and-coal pellets are subjected to temperatures up to 1300C, mostly for just 612min.

The product is not liquid and, inevitably, it contains relatively large amounts of ash and nonmetallic residues from the processed coalore mixture, and it must be melted in EAF. The process requires constant feeding and has limited productivity. The first commercial RHF, designed to recycle wastes containing Ni and Cr at INMETCO in Elwood, PA, went into operation in 1997 (INMETCO, 2015). MIDREX began developing an RHF process concurrently with its countercurrent reactor, using reformed natural gas, abandoned the quest in favor of the latter technique, and returned to it by 1992 with the development of the Fastmet process. The first Japanese plant has been operating since the year 2000 at Hirohata Works, and there are now six plants with combined annual capacity of nearly 1Mt (Kobelco, 2015a). The process is particularly suitable for converting such iron- and steelmaking wastes as blast furnace dusts and sludges and EAF dust and mill scale.

Obvious drawbacks are the need for constant feeding and a limited productivity. Fastmelt is Fastmet with an added electric iron melting furnace to produce hot DRI. Currently the most advanced RHF design (which can be seen as a variation of Fastmet) is the ITmk3 (Ironmaking Technology Mark 3, BF being the first, and gas-fueled DRI the second generation) process developed by Kobelco Steel (Harada & Tanaka, 2011; Kobelco, 2015b).

Iron ore concentrate (magnetite or hematite or their mixtures) and noncoking coal mixed in pellets are processed for 10min by a single-stage heat treatment in an RHF, yielding high-quality (9697% Fe), slag-free iron nuggets. These nuggets are easier to handle than DRI or hot-briquetted iron and are processed in EAF or (after remelting) in BOF. Because nearly all combustible gases generated by the reactions are burnt within the furnace, the process can reduce specific CO2 emissions by 817% compared to BF. The first plant, at Hoyt Lakes, MN, began operating in 2010 and it had an annual capacity of 500,000t.

Not surprisingly, during the early years of its commercialization DRI received enthusiastic reception and there were high expectations for its continuing strong expansion, if not an eventual dominance of primary iron production. Global DRI production rose nearly 10-fold during the 1970s (to 7.1Mt), and Miller (1976) forecast the output of 120Mt by 1985but the global capacity in that year was just over 20Mt, and actual sales were only 11Mt (MIDREX, 2014a). Expectations shifted, as slow but steady growth came to represent DRI success. Global output rose to 31Mt in 1995, 43Mt in 2000, and 75.22Mt in 2013, and DRIs share of the global primary iron production (excluding the output of RHFs using recovered mill wastes) rose from 1% in 1980 to 4.7% in 2013.

In 2013, there were more than 120 DRI plants worldwide and MIDREX (now owned by Kobe Steel) remains the premiere DRI licensor as its plants have been supplying 60% of all DRI for more than two decades and produced 63% of all DRI in 2013 (MIDREX, 2014b). In 2013, the largest of the 56 plants were in Mobarakeh in Iran (capacity of 3.2Mt in five modules) and in Corpus Christi, TX (2Mt). The other leading shaft reduction process (HYL/Energiron) supplied about 15% of all DRI in 2013, while coal-based RHFs delivered about 21%. Maximum annual capacity of MIDREX installations grew from less than 0.5Mt (Series 400) to more than 3Mt (MEGAMOD series), and the oldest MIDREX reactors have been in service for more than 40 years (MIDREX, 2014b). The Middle East is the leading (natural gas-based) producer with nearly 40% of the global total; India, with more than 40 (mostly coal-based) plants, is the leading nation (nearly 25% of the total), and both the United States and the EU are only negligible producers.

gold processing,extraction,smelting plant design, equipment for sale | prominer (shanghai) mining technology co.,ltd

Prominer maintains a team of senior gold processing engineers with expertise and global experience. These gold professionals are specifically in gold processing through various beneficiation technologies, for gold ore of different characteristics, such as flotation, cyanide leaching, gravity separation, etc., to achieve the processing plant of optimal and cost-efficient process designs.

Based on abundant experiences on gold mining project, Prominer helps clients to get higher yield & recovery rate with lower running cost and pays more attention on environmental protection. Prominer supplies customized solution for different types of gold ore. General processing technologies for gold ore are summarized as below:

For alluvial gold, also called sand gold, gravel gold, placer gold or river gold, gravity separation is suitable. This type of gold contains mainly free gold blended with the sand. Under this circumstance, the technology is to wash away the mud and sieve out the big size stone first with the trommel screen, and then using centrifugal concentrator, shaking table as well as gold carpet to separate the free gold from the stone sands.

CIL is mainly for processing the oxide type gold ore if the recovery rate is not high or much gold is still left by using otation and/ or gravity circuits. Slurry, containing uncovered gold from primary circuits, is pumped directly to the thickener to adjust the slurry density. Then it is pumped to leaching plant and dissolved in aerated sodium cyanide solution. The solubilized gold is simultaneously adsorbed directly into coarse granules of activated carbon, and it is called Carbon-In-Leaching process (CIL).

Heap leaching is always the first choice to process low grade ore easy to leaching. Based on the leaching test, the gold ore will be crushed to the determined particle size and then sent to the dump area. If the content of clay and solid is high, to improve the leaching efficiency, the agglomeration shall be considered. By using the cement, lime and cyanide solution, the small particles would be stuck to big lumps. It makes the cyanide solution much easier penetrating and heap more stable. After sufficient leaching, the pregnant solution will be pumped to the carbon adsorption column for catching the free gold. The barren liquid will be pumped to the cyanide solution pond for recycle usage.

The loaded carbon is treated at high temperature to elute the adsorbed gold into the solution once again. The gold-rich eluate is fed into an electrowinning circuit where gold and other metals are plated onto cathodes of steel wool. The loaded steel wool is pretreated by calcination before mixing with uxes and melting. Finally, the melt is poured into a cascade of molds where gold is separated from the slag to gold bullion.

Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.

contact multotec

Whatever your mineral processing challenges, Multotec engineers and metallurgists are on hand to help you optimise plant performance and lower your cost per ton. Multotec is active across the world, with branches and representatives in South Africa, Africa, Australia, North America, South America and China. Our presence in these areas is tailored to the specific requirements of local mineral processing applications, where local experts draw on international technology and one of the worlds largest ranges of mineral processing equipment to help customers optimise recoveries and reduce total cost of ownership. Whether you need to upgrade existing equipment or introduce process optimisation plant-wide or at a particular plant site, our engineers and metallurgists are on hand to help you.

Multotec branches are conveniently located near strategic mining areas, ensuring we can respond rapidly to your requirements for products and equipment, service and support. Equipped with relevant fabrication services and tailored technology portfolios, local Multotec technical and product specialists possess the experience to develop tailored solutions to meet your unique requirements, no matter where you are or what your processing challenge entails.

multotec | mineral processing

For over 45 years, weve been driven by one primary goal: helping customers get more from their ore. We partner with our clients to drive continuous process optimisation to their plant with application-specific mineral processing solutions that:

For over 45 years, weve helped the worlds biggest mining houses maximise process efficiency and plant uptime, increase levels of product quality, consistency and reliability, and enhance product speed to market.

Multotec is active across the world. Through our global presence, we deliver local expertise, with engineered solutions and services tailored to the unique mineral processing requirements of each region.

iron ore magnetic separator plant

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Engenium, a project delivery and engineering consultant to Australias mining sector, was tasked with providing a feasibility study to design new magnetic separation technology. The technology will increase iron-ore production at an existing plant in the Pilbara region of Western Australia. The plan needed to include the type of equipment, concept arrangement, budget development, and schedule delivery. Engeniums two key challenges included delivering the project on a fast track and compressing the feasibility study timeline to reach an investment decision for project execution. The design also needed to focus on layout tie-ins, key equipment, new building footprints and levels, piping routes, and new substation facilities. The layouts would be refined and optimized during detail design. Brownfield tie-ins, new process buildings, and multiple process and layout options were also included in the project scope.

To meet the requirements, Engenium used OpenPlant Modeler and ProSteels 3D plant modeling and digital workflows to develop the feasibility plant designs and pass them on to the owner-operator for review and approval. Engenium also used 3D design models to determine the amount of budget needed to complete the project. The team established a collaborative working environment to determine the process and layout options, while the 3D multidiscipline plant models included tie-ins to the existing plant that produced multiple options to enable value engineering and to support the investment. Engenium also generated critical options analysis and capital estimates using information from the design model. Moreover, identifying the preferred option enabled a fast-track project delivery.

With the project requiring a collaborative design workflow among the multidiscipline design team, implementing an integrated solution using 3D multidiscipline plant models provided significant benefits. Engeniums use of digital workflows enabled the team to deliver the feasibility study in less than two months, saving at least 50% when compared to other projects. Additionally, by using the software, the amount of engineering hours spent on the project were well below the benchmark for an over USD 50 million mining project.

OpenPlant Modeler and ProSteel were used to refine and optimize the layouts at the detailed design stage and, along with Navigator, established new workflows using iModels to implement a collaborative workflow across the multidiscipline design team. Bentley View and Navigator enabled team members to review the design among project stakeholders, allowing them to provide feedback to the modeling team. LumenRT assisted the client with visual presentations of the project to outside stakeholders. iModels were used to make the design file sizes smaller, allowing information sharing across the multidiscipline design team.

Bentley software allowed us to deliver exceptional value and results for our client through the development of [a] multidiscipline design, in parallel, under tight schedule expectations. [We did this] through the deployment of a [single] design and review environment for the whole project team.

Qinghai Kexin Electric Power applied 3D modeling technology on a substation design project, reducing the error rate and enhancing design depth by 90% and 50%, respectively.

Using Bentleys digital twin technology, AAEngineering Group saved 30% in design time to deliver a gold production facility that ensured interoperability with existing infrastructure.

Northern Engineering & Technology Corporation, MCC used Bentleys building information modeling (BIM) applications to simulate a modular design and construction environment on Australias largest monomer mining project, reducing design changes by 80 percent.

AMEC Foster Wheeler used Bentley applications to create data-rich 3D models for the largest undeveloped gold deposit in Australia.

Hatch uses MineCycle Material Handling to optioneer a lump rescreening plant for an existing iron export terminal in Whyalla, Australia, improving design efficiency by 33 percent.

African Consulting Surveyors and GESS use laser surveying to capture over 221 million points along a 640-meter tunnel haulage route 3.5 kilometers underground to ensure clearance for substation equipment.

Ausenco seamlessly brings together disparate teams from across three countries to create a process for future project management and engineering projects.

ENFIs first full 3D engineering effort with Bentley software delivers accurate 3D design model of 338-hectare molybdenum ore mining operation in Mongolia

China Nerin Engineering uses ProjectWise with PlantSpace Design Series to reduce design time by 20 percent for worlds largest copper smelting plant.

Hatch sets up Bentley-based, data-centric environment to model and modify massive dehydration facility transported from Canada to China.

Kumba Iron Ore used Bentley Map to develop integrated data management system that saves time, money, and the environment at South African iron ore mine.

Petra Diamonds replaced legacy systems with Bentley software-based GIS that served a dual purpose: mine data management and town utility billing.

dry magnetic separation of iron ore of the bakchar deposit - sciencedirect

Currently, the development of iron ore of the Bakchar deposit (Tomsk region) is considered promising because of the extremely large reserves of iron ore. Ores of this deposit are related to the high-grade type and expected to have a magnetic concentration for iron extraction. The main task of magnetic separation is to increase the total iron content in concentrates to a value which allows its further metallurgical processing. Ferruginous ore particles have a rounded shape that facilitates a separation process. The paper considers the influence of technological parameters on the magnetic concentrate yield and recovery rate of iron-containing fractions.

iron ore, gold ore, copper magnetic separator machine by china manufacture

Iron Ore, Gold Ore, Copper Magnetic Separator by China Manufacture Foshan Wandaye Machinery Company Limited is a national high-tech enterprise,owns a number of invention patents, with research and development production,major products are: magnetic separator for non-metallic mineral raw materials, ceramic glaze, metal, plastics, food and all kinds of industries.The main products are: electromagnetic Slurry separator, electromagnetic powder machine, permanent magnetic separator vertical ring electromagnetic separator,vertical ring permanent magnetic separator and different sizes of magnetic plates, magnetic rod, drawer type magnetic separator etc; Our company possesses professional technical team and sophisticated laboratory,can be customized for magnetic separator. Wandaye Limited since 2014 get involved in domestic and international mineral processing engineering technology and the fields of whole line project design etc . Product characteristic Magnetic separator are arranged in stainless steel tanks, according to a certain distance and height,is widely used in ceramic glaze, pulp, chemical industry, food industry such as iron removed liquid raw materials.(magnetic rod can be customized) Working principle Raw material into the 2.5 inch pipe inlet, through the a30 mm gap below the adjustable damper, and then into the iron box and be captured, and finally, raw material slowly rising. Application scope The magnetic bar is widely used in the following industries such as mine, raw material of ceramic, chemical, medicine, mechatronics, paint and pigment, food processing.

Foshan Wandaye Machinery Company Limited is a national high-tech enterprise,owns a number of invention patents, with research and development production,major products are: magnetic separator for non-metallic mineral raw materials, ceramic glaze, metal, plastics, food and all kinds of industries.The main products are: electromagnetic Slurry separator, electromagnetic powder machine, permanent magnetic separator vertical ring electromagnetic separator,vertical ring permanent magnetic separator and different sizes of magnetic plates, magnetic rod, drawer type magnetic separator etc; Our company possesses professional technical team and sophisticated laboratory,can be customized for magnetic separator. Wandaye Limited since 2014 get involved in domestic and international mineral processing engineering technology and the fields of whole line project design etc .

Magnetic separator are arranged in stainless steel tanks, according to a certain distance and height,is widely used in ceramic glaze, pulp, chemical industry, food industry such as iron removed liquid raw materials.(magnetic rod can be customized)