COREX Process of Iron Making - its Merits and Demerits

COREX Process and Technology of Ironmaking

The COREX technology is a cost efficient, environmentally friendly and industrially accomplished alternative to the blast furnace route for the production of hot metal from iron ore and coal. By fulfilling more stringent ecological regulations by law, utilization of low-cost, highly available low grade raw materials including fines, the COREX process has been accepted as a commercially proven technology for present and future iron making process. The COREX process was created by Siemens VAI and was elevated to industrial maturity by PRIMETALS. Primetals Technologies Limited, is a London (UK) based engineering and plant construction company established in 2015 by a joint venture of Siemens VAI Metals Technologies and Japan’s Mitsubishi Hitachi Metals Machinery (MHMM).

In a nutshell, COREX is a coal based SR (smelting reduction) process of making hot metal or pig iron by direct use of non-coking coal. The outputs can be used either by integrated mills or EAF (electric arc furnace) mills. The process gasifies non-coking coal in a smelting reactor, which also produces liquid iron. The gasified coal is then fed into a shaft furnace to remove oxygen from iron ore lumps, pellets or sinter and finally, this direct reduced iron (DRI) is fed to the smelting reactor. Compared with the traditional iron making process via the blast furnace route, the COREX process differs since non coking coal can be directly used for ore reduction and melting work, eliminating the need for coking plants. The use of lump ore or pellets also dispenses with the need for sinter plants.

Read: Steel Plants with COREX Process in Operation: A Quick Review 

Some Merits and Demerits of COREX Process

=> Conducive to production of high end and special steel required for sophisticated industrial and scientific applications with minimum damage to the environment at various stages of steel making and mining.

=> Unlike the conventional Blast furnace route for production of hot metal, it can accept high alkali containing ores without any build up inside the reactor.

=> It takes only half an hour to stop the plant and only four hours to restart it.

=> Specific melting capacity is higher than that in Blast Furnace; productivity around 3.5 t/m³/d can be achieved.

=> In 2009 Siemens first completed a life cycle assessment for pig iron production, looking at both conventional production in a blast furnace and the more environmentally friendly COREX and FINEX processes. Siemens claimed the COREX and FINEX processes can substantially reduce pollutant emissions when compared to traditional steel production, with its blast furnace and coking and sintering facilities.

=> The iron content of the feed should not be less than 50% as otherwise the slag volume produced will be too high.

=> As is the case in blast furnaces, over 90% of the phosphorous input reports to the hot metal. So, the phosphorous content of ore and coal should be as low as possible.

=> There are also reports that the COREX process cannot be operated without some amount of coke along with non-coking coal - at least around 10% of coke is required in the total reductant charge.

=> As far as coal is concerned, the non-coking coals having too high volatile matter (VM) or too low fixed carbon (FC) cannot be used in corex process of iron making.

=> The heat transfer plays a crucial role in the overall efficiency of the COREX process. This being a two stage process, i.e. reduction and smelting taking place in two separate units, post combustion of the gas generated in the smelting unit provides the heat to melt the DRI produced in the reduction unit. This calls for high heat transfer efficiency.

=> Unless the net export gas from any Corex plant (extent of generation around 1650 Nm³/thm) can be utilized, the process will not be economical. Because of many peripheral requirements, the total cost of a Corex project can be relatively high.   

=> The export gas generated in Corex technology can be used as a fuel gas in the downstream facilities to generate electricity or for the production of direct reduced iron in a region that has almost no resources of natural gas.

=> COREX plant emissions contain only insignificant amounts of NOx, SO2, dust, phenols, sulphides, and ammonium. Emission values are already far below the maximum values allowed by future standards. Also, waste-water emissions from the COREX process are far lower than those in the conventional blast-furnace route. These environmental features are key reasons for the attractiveness of the COREX process.

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The FINEX® Process: The Latest Smelting Reduction (SR) Ironmaking Technology

FINEX® Process, smelting reduction technology of ironmaking - Features, Merits and Limitations

28-June-2020
What is FINEX ?

The FINEX is the latest addition and an optimized fine-ore smelting reduction (SR) iron making process based on the direct use of the coal and iron ore fines. FINEX Process is a fluidized bed based process using ore fines instead using iron ore lumps and pellets. This is a process with great potential with regard to productivity and the low cost production of hot metal.

In 1992, POSCO and VAI, Austria signed an agreement to work together for a joint development of the FINEX Process. And accordingly, FINEX process was developed jointly by POSCO, Korea and Primetals Technologies to provide the iron making sector with the capability of producing (hot metal) at a reduced cost, lesser environmental pollutions and more flexibility in terms of operation and the choice of raw materials. Primetals Technologies Limited, is a joint venture of Siemens VAI Metals Technologies and Japan’s Mitsubishi Hitachi Metals Machinery (MHMM).

The present article contains about:

• What is Finex process
• Benefits or Merits of this technology
• Some limitations or disadvantages of Finex technology

To know more about the Steel plants with FINEX process in operation as how these FINEX plants were started and subsequent developments and changes brought in those FINEX plants, read: 

Development of FINEX Process and Steel Plants with FINEX in Operation

Fig: FINEX Technology (Flowsheet)

FINEX Process of Iron Making - An Overview

In the FINEX process the iron production is carried out in two separate Process steps. In a series of fluidized bed reactors, fine-grained iron oxides are reduced to direct-reduced iron, compacted and then transported to a melter gasifier. Coal and coal briquettes charged to the melter gasifier are gasified, providing the necessary energy for melting in addition to the reduction gas. Fine ore and additives (limestone and dolomite) are dried and then charged to a 3 or 4 stage fluidized bed system where the iron ores are progressively reduced in counter current flow with the reducing gas to fine DRI and the fine additives are partly calcined.

Reactors R4 and R3 are primarily used to preheat the ore fines to the reduction temperature, which can be adjusted by partial combustion of the off-gas (export gas) from R2. In R2 the fine ore is pre-reduced to reduction degree (RD) of about 30%. At the end of the production in R1, the final reduction to DRI takes place (RD about 90%). Operational pressure in R1 to R4 is approximately 4 - 5 bars. The fine DRI is compacted and then charged in the form of Hot Compacted Iron (HCI) into the melter gasifier. So, before charging to the melter gasifier unit of the FINEX unit, this material is compacted in a hot briquetting press to give hot compacted iron (HCI) since the melter gasifier cannot use fine material (to ensure permeability in the bed). Non-coking coal (lumpy and / or briquetted fines) is charged from the top of the melter gasifier, dried and degassed in the upper char bed area and finally the degassed coal (char) is gasified with pure oxygen which is blown in at the tuyere zone of the melter gasifier bed. The gasification supplies the energy required for the metallurgical reactions and for the melting of HCI and coal ash to hot metal and slag. Pulverized coal injection (PCI) system is provided to inject fine coal via the oxygen tuyeres. The gas generated in the melter gasifier of the FINEX unit is used to reduce the ore in the reactors preceding the melter gasifier. The generated FINEX off-gas is a highly valuable product and can be further used in power generation or heating processes. The DRI is charged in the melter gasifier in hot condition, where it is melted, fully reduced and carburized to hot metal. The hot metal and slag produced in the melter gasifier is frequently tapped from the hearth similar to the blast furnace and COREX operations. Also refer COREX Process of Iron Making - its Merits and Demerits.

FINEX Process - Merits and Benefits

In many respects FINEX process can be considered as an offshoot of COREX process and hence, bear the various advantages of the COREX and more as outlined below -  

Flexibility in Raw Materials

• No blending of ore & coal. Rather direct utilization of coal.
• Use of Low-grade ore & low-ranked coal. Integration of the coal briquetting technology increases the range of suitable coal blends for the FINEX application. Utilization of 100% coal briquettes offers the possibility to mix different coal qualities for the generation of coal briquettes.

Easy & Flexible Operation

• Independent control of reduction & melting processes
• Easy & hassle-free operational control

Environmental Friendliness

• Far less emission of SOx, NOx, phenols, sulphides, ammonia & dust because the FINEX process does not need sinter plant and the coke oven battery which are the actual sources of emission in a conventional blast furnace route.
• Applicability to the CO₂ sequestration.

Cost Competitiveness

• Lower cost in both capital investment & operation as compared to the blast furnace route, keeping the quality of the hot metal same.
• According to POSCO, the capital cost & operating cost of FINEX process are less than by 20 and 15 percent respectively of that of Blast Furnace route. 
• Need much less land as compared to conventional BF complex.
• Similar to the Corex export gas, FINEX export gas (with calorific value of 5,500 – 6,250 kJ/m3 STP) can be used to substitute natural gas, oil, coke and coal for metallurgical applications and power generations etc. Depending on the composition of coal and the decision whether gas recycling is applied or not, the amount and the composition of the export gas can vary within definite limits.

Limitations (Demerits) of FINEX Process

As said FINEX, COREX, HISMELT are the latest alternative methods for producing liquid iron (Hot Metal) through Smelting Reduction (SR) process. Some of the limitations (disadvantages) are -

• Ease of obtaining FINEX technology is uncertain though POSCO has started to extend it.
• Both COREX and FINEX processes need a large amount of oxygen.
• The major criteria for an initial evaluation of coals or coal blends for the FINEX Process are: 1. Fix carbon content at a minimum of 55%, 2. Ash content up to 25%, 3.Volatile content lower than 35%, 4. Sulphur content lower than 1%
• Additional to these qualities the coal must have a good thermal stability to ensure the formation of a stable char bed in the melter gasifier. 

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Direct Reduction (DR) Processes - First No Coke Option for Iron Making

19-Dec-2009

The first no coke method of iron making units is Direct Reduction (DR Process). Direct reduction processes can be divided into those using non-coking coal (as in rotary kiln and rotary hearth furnace based processes) and those using natural gas (as in shaft furnace, fluidized bed furnace, and fixed bed furnace based processes). DR processes using coal have been found to be more suitable in areas, which have local sources of coal and ore but no natural gas. On the other hand in gas-rich areas, gas-based DR (larger in size and more energy efficient) is the automatic choice.

A large number of DR (direct reduction) processes are available today, which can be grouped as follows:

• Coal based direct reduction (DR processes) using rotary kilns such as SL/RN, DRC, TDR, Jindal, Codir, Accar, SIIL and OSIL. 
• Coal based direct reduction (DR processes) using rotary hearth furnaces such as Fastmet, Inmetco, Circofer and Sidcomet etc. 
• Batch type gas based processes using retorts - HyL I. 
• Continuous processes in a shaft furnace using reformed natural gas as the reductant such as Midrex and HyL III. 
• Gas based processes using a fluidized bed - Fior, Finmet, Circored.  
• Special processes for treating waste oxides such as Primus using a multi-hearth furnace.

We have described most of these DR (Direct Reduction) processes separately and individually in this Blog since, it will be too lengthy to put all of them at one place. To know more about each of the DR processes simply type the name of the process in the search box placed near the top of this Blog and search. Alternatively you may select and click on the name of the process from the list of KEYWORDS given in the sidebar.                 

ZERO Waste Steel Shop - The Most Innovative Metallurgical Process

28-Nov-2009

The ongoing boom in the iron and steel industry combined with scarcity in raw material supply, their availability has caused a dramatic increase of prices for raw materials and steel roducts. The whole chain of production from front-end side of iron making up to the finishing stage of steel products has to be observed and optimized continuously by introducing highly efficient new technologies, tools, and emission and residue free, environment-friendly processes for production of high value steel products. Among the various innovative iron making processes like Midrex, COREX®, FINEX®, Finmet, Fastmet, Romelt, Primus etc.

ZEWA (Zero Waste) is one such process. Here we are going to discuss in brief about the background and some features of ZEWA process.ZEWA (Zero Waste) is a new metallurgical process which converts blends of industrial waste materials and residues into hot metal and mineral products such as Hydraulic Binders for cement production, metallurgical powders for desulphurization practices and materials suitable for road construction. ZEWA (Zero Waste) process involves high temperature smelting reduction (SR) operations which are carried out in a specially designed, electrically operated reactor.

A demonstration plant with all necessary auxiliary facilities was erected at the Vitkovice Steel Works in the Czech Republic. An earlier report says that it took eleven test campaigns to prove the technical and economical feasibility of the process with respect to the generation of hot metal and useful mineral products from the residues of carbon and stainless steel production.

ZEWA (Zero Waste) Process - A Background

The basis for the development of the ZEWA (Zero Waste) process was laid at the Central Recherche Metallurgique (Center for Metallurgical Research) in Belgium where a laboratory scale smelting reduction process was developed to convert various residues from Steel Plants into valuable metallic and mineral products. Pilot plant tests using a hollow electrode for the pneumatic injection of residue materials into a furnace were then conducted by CRM, MSFOS (Sweden) and FEhS (German Research Institute) in the framework of the IBPM (Internal By-product Melting) project.

In 2000, Voest Alpine (VAI) teamed up with CRM and a large consortium of partners as part of a multi-national project team supported by the European Union. A process concept based on the previously tested pneumatic injection of residue materials into a furnace via an injection lance was chosen. The partnership within this so-called “Fifth Framework Programme” is as follows:

=> From the steel industry; CRM (project coordinator), VAI, ARCELOR, and Vitkovice Research team.

=> From the cement industry; LAFARGE

=> From the car dismantling industry; the Belgian SME Comestsambre.

=> From the coal industry; the ICPC (Institute for Chemical Processing of Coal, Poland)

This project works with a goal of developing a viable technology for the so-called ZEWA (from Zero-Waste) process and to test it on a demonstration scale. The main task to be carried out was thus the design and erection of a dedicated pilot plant, the performance of the pilot test campaigns and the final evaluation of the ZEWA as the basis for commercialization.   

The Principal of ZEWA (Zero Waste) Process

The ZEWA (Zero Waste) process is based on smelting reduction of suitable blends of basic and acidic residue materials from industrial production as follows:

=> From the steel industry basic steel making slags and dusts, and silica containing residues from scrap handling (mixtures of glass and plastics) in EAF plants;

=> Complementary acidic residues from another industrial sectors, such as fly ash from coal-fired power plants, automotive shredder residues (ASR) or bottom ash from urban incinerators (BI ash).

The main products are the refined slag (or mineral product) with targeted chemical composition, and hot metal or metal product to be recycled for steel production. For the smelting reduction (SR) process carbon based reductant (coke, anthracite, coal etc.) are added to the blend of residue materials. Depending on the raw material and the mineral product, small quantities of stronger reductants like ferro-silicon, or additives such as lime or bauxite, may also be added when necessary. Process dust with high zinc content is recovered in an off gas filtering unit. Targeted mineral products are a Portland clinker substitute for use in cement production and metallurgical powders for use in secondary steel refining units.       

ZEWA (Zero Waste) - The Process Technology

The smelting reduction in ZEWA or Zero Waste process is done in an electrically heated ladle-type furnace which is equipped to allow for top charging of liquid steel making slag and coarse solid materials into the foamy slag bath, and also for the deep pneumatic injection of powdery materials into the hot metal with a lance. Coarse solid materials like solid slags are charged by gravity, via a fibro-feeder or by a chute. Injected powdery materials are mainly steel making dusts, fly ash and reductants. Other features of the ladle include bottom stirring (to enhance mixing and reaction kinetics) and post combustion in the upper part of the slag bath (to recover chemical heat through the partial combustion of the CO from the reduction reactions). The ZEWA (Zero Waste) process technology is quite flexible with regards to the input materials, firstly because it allows for the charging of the liquid slag, and secondly because it can cope with highly variable charging ratios of liquid slag, coarse solids and powdery materials. Dry dusts can be directly used as a raw material. Sludges and other residue materials require only drying and micro granulation. No pelletization or briquetting is necessary, thus reducing the material pre-treatment costs substantially. Because of the filtering effect of thick foamy slag bath, ZEWA technology is also very efficient in terms of lowering dust emissions. Moreover, due to the low thermal losses by radiation from the arc and the metal bath, ZEWA process is very effective in lowering the energy consumption too.             

Primus - A Special DR (Direct Reduction) Process for Treating Waste Oxides using a Multi-hearth Furnace (MHF)

28-Nov-2009
About the Primus

The Primus process was developed by Paul Wurth, uses a multi-hearth furnace (MHF). The furnace volume and the number of hearth in any unit are variable and can be adapted to the requirements of the material to be processed. Coal fines and iron oxide fines are charged into the top hearth of the multi-hearth furnace and as per the need coal can also be added in the lower hearths. The furnace is operated at temperatures up to 1100^OC. The DRI (direct reduced iron) produced is discharged from the lowest hearth of the furnace at a temperature of 105-115^OC.

Primus - Some Features of the Process

=> High quality DRI can be produced using ore fines and low cost pulverized coal as the single energy source.

=> No preparation of the raw materials is required, and metallization level exceeding 95% can be easily achieved.

=> In a stationary state, the Primus process does not require any additional energy supply; burners are only required to preheat the furnace. The high degree of post combustion, the counter-current flow of the off-gas and the relatively low process temperatures, make the Primus process energy-efficient.  

At first, in co-operation with Paul Arbed, Paul Wurth built a pilot plant designed for a throughput of ½ t/h in the steel works of Esch-Belval in Luxembourg. Several trial campaigns were carried out to melt the DRI produced on the basis of iron ore and EAF dust since September 2000. All the trials successfully demonstrated the feasibility of the process on a continuous basis which paved way for the successful implementation of the Primus process later in many other plants.    

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HYL III and SL/RN - The two widely accepted Direct Reduction (DR) Processes of ironmaking

10-Oct-2009

Direct Reduced Iron (DRI) is obtained by reducing lumps as well as fines of iron ore in solid state at a relatively low temperature of around 1000^OC. A large number of DR processes are available today. SL/RN and HYL are two such DR processes. While HYL is a batch-type gas based process and uses a countercurrent shaft-furnace, the SL/RN process utilizes rotary kiln to reduce lump ore, pellets and sand iron with coal. Here we will discuss about some key features, including advantages and disadvantages of these two DR processes.

HYL III

Fig: HYL III Process Scheme

The HYL process was developed in Mexico and was the forerunner of the HYL III direct reduction technology. In HYL I process, a mixture of gases containing about 89% of reducing compounds is used. Each reduction module in HYL plant consists of four units - three “in line” and the fourth in “turn around” mode. The principal change made over HYL I in HYL III was the modification of the four fixed bed reactors by a single moving bed reactor, utilizing the same gas reforming plant, auxiliary equipment and quenching towers.  Actually HYL III technology is characterized by its wide flexibility for adapting to special needs, depending on available reducing gases, energy use and melt-shop requirements. Use of spent gases from direct ironmaking processes, coal gasification, energy optimization in DR plants and technology developments aimed to improve EAF productivity have been the objective of HYL. Some distinctive features of HYL III process are:

Fig: HYL III - COREX Off-Gas Process Scheme

=> The H₂/CO of the reformed gas is 3, the temperature is about 930^OC, the inside pressure of the countercurrent shaft-furnace is 450 kilopascals and the energy required for the reduction is basically the same as in the MIDREX process.

=> The selective elimination of H₂O and CO₂ from the reducing gas circuit allows maximum recycle of the reducing gases to the reduction reactor. Hence, the reducing gas make-up and the process natural gas consumption are minimized.

=> The reducing gas generation and the reduction sections of a HYL III unit are independent from an operational point of view. This feature offers important flexibility for adapting to different reducing gas sources. The process schemes based on use of alternative reducing gases from different sources and other DR/ Ironmaking sources have been proven in HYL III plants. Such alternate sources of reducing gas can be -

• Coal gasification processes.
• Coke oven gas.
• Gases from Hydrocarbon gasification.
• Partially spent gases from another DR plant.
• COREX off-gases.

=> High pressure operation (4 atmospheres or more) enables the effective control of process conditions, with smaller equipment size for gas handling and lower energy requirements (9.0 - 10.0 GJ/t).

=> The process is much flexible as far as raw material use is concerned - while it operates best with 100% pellets, even 100% lump ore of a suitable type has been used, but it is suggested to use a mixture of pellets and lump ores.   

=> This technology offers the unique flexibility to produce three different product forms depending on the specific requirements of each user - Cold DRI, HBI and HYTEMP iron. Metallization can be controlled up to 95% and Carbon content 5.0%.

=> When combined with COREX off-gas as a source of reducing gas, the HYL III DR plant offers high productivity using available spent gas and benefits in steel production using HYTEMP® iron together with hot metal in EOF/BOF based steel mills.

=> The HYL III process features the flexibility of generating electric power, taking advantage of high pressure steam produced in the natural gas-steam reforming unit which can be used in a turbo generator or in a set of turbines, at a high generation capacity.

According a data of recent past, around 11 million tones of direct reduced iron (DRI) was produced in 2003 by this process in India, Grasim’s HYL plant at Raigad (Orissa) produced 0.75 million tones of HBI.     

SL/RN

SL/RN is the most widely accepted coal based DR process. It was jointly developed by Stelco, Lurgi Chemie, Republic Steel Company and National Lead Corporation in 1964. In this process, the materials charged into the kiln gravitate towards the discharge end during which they are progressively heated to the temperature of reduction of around 1000 - 1100^OC. The product discharged from the kiln is cooled in an extremely cooled rotary cooler around 100^OC before being subjected to magnetic separation to separate sponge iron from coal ash and char. Waste gases leaving the kiln at the inlet end pass through a dust chamber and a post combustion chamber, before being cooled and cleaned in electrostatic precipitators, scrubbers or bag filters. In SL/RN technology the clean gases can be used in waste heat boilers to recover the sensible heat and the steam generated can be utilized for heating purpose or for electric power generation. Some distinctive features of SL/RN process include:

=> Flexibility with regard to the type of iron bearing materials which can be used such as lump ore, pellets, ilmanite, iron sands and steel plant wastes.

=> Use of a wide variety of solid fuels ranging from anthracite to lignite and charcoal.

=> Improved heating of the charge by submerged air injection in pre-heating zone of the kiln. This process suffers, however, from relatively big heat loss and facility size.

=> SL/RN technology provides optimized coal injection facilities at the discharge end of the kiln.

=> Waste gas conditioning by controlled post combustion followed by power generation (the power generated is more than the requirement of the plant).

The original SL/RN process has been modified in a variety of ways, particularly in India where rotary kiln DR technology has been widely applied.            

MIDREX - The Most Widely accepted Direct Reduction (DR) Process of Ironmaking

2-Oct-2009

Midrex the most widely accepted direct reduction (DR) process of ironmaking in the world was developed by Midland Ross Corporation of Cleveland, USA in 1967 , has the following distinctive features:

Recommended Natural Gas Composition for MIDREX Plants

Components	Vol %	Effects
CH4 C2H6 C3H8 C4H10 +C4 (Hydrocarbon) CO2 N2 S	75 - 100 0 - 25 0 - 4 0 - 2 0 - 0.5 20 max 20 max 20 ppm. (max Wt.)	-- -- Above 4% C3H8, water vapour content should be increased. -- Above 20% CO2, export fuel is produced. For every 10% of N2, fuel consumption increases by 2%. Above 20 ppm, carbon deposition on catalyst.

MIDREX Process - Some Features

=> It allows the production of highly metalized DRI (exceeding 92%, see adjacent Table showing typical composition of Midrex DRI) and the carbon content of can be controlled in the range of about 1.0 - 2.0%.

=> Although originally developed for use with high grade pellets, the Midrex shaft furnace is now able to use some amount of lump ores. Optimum process conditions are often obtained by mixing 30-50% of an appropriate type of lump ore with high grade pellets. See adjacent Table showing Physical Characteristics of Pellets and Lump Ores used in the MIDREX Process.  

=> Fuel utilization in Midrex process has steadily decreased from an average of 12.5 - 14 GJ/t of DRI to 9.5 - 10.5 GJ/t. This improvement in energy efficiency has been the result of higher reduction temperatures, enrichment of reduction gas with methane, utilization of in-situ reforming, and pre-heating of the process gas utilizing waste heat from the reformer.

=> Following the advent of in-situ reforming, oxygen carriers from an external source are now not required in the production of reformed gas. Therefore, the investment cost and operating costs of Midrex units have been reduced.

=> The DRI produced is relatively active towards re-oxidation, particularly when moisture is present. Hence it must be deactivated if it is to be stored or transported over a long distance.    

Physical Characteristics of Oxide Feeds

(Pellets and Lump Ores) used in the MIDREX Plants

	Pellets	Lump Ores
Screen analysis (wt %) 50 - 31.75 mm 31.75 - 6.3 mm + 15 mm 8 - 15 mm – 8 mm – 6.3 mm Bulk Density (t/m3) Compressive Strength (kg/pellet) ISO Tumbler Test (wt%) + 6.3 mm – 0.5 mm	-- -- 10% max 85% max 5% max -- 2.0 - 2.1 270 min 95% min 4% max	5% max. 93% max. -- -- -- 7% max 2.0 - 2.6 -- -- --

Typical Product Composition of Midrex DRI

Content	Wt %
Fe (total) Fe (metallic) Metallization SiO2 Al2O3 CaO MgO S P	92 -93 84 - 88 93 - 95 2.0 - 3.5 0.5 - 1.5 0.2 - 1.6 0.3 - 1.1 0.005 - 0.015 0.02 - 0.04

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