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.    

Related Articles 

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

What is Finmet Process of Ironmaking ?

What is Fastmet Process of Ironmaking ?

Blast Furnace - Refractory Lining Pattern

ZERO Waste Steel Shop - The Most Innovative Metallurgical Process

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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ROMELT - Another No Coke Alternative Smelting Reduction (SR) Process of Ironmaking

19-Nov-2009
ROMELT - The Process

This process was developed by the Moscow Institute of Steel and Alloys (MISA) in the mid-eighties to produce liquid iron from iron-bearing ores (lumps and fines) as well as waste iron oxides generated in an integrated plant using non-coking coal and oxygen. ROMELT is the only single stage SR process.

Unlike COREX and most other SR processes, the strength of this process is that it is a single stage concept. That is why ROMELT is a robust and simple process, which is also very much environment-friendly, since it operates under a slight negative pressure. As a result the area around a ROMELT plant is extremely clean. However, the process has a few inherent weaknesses being a single stage process, it uses large amounts of coal (1.3 - 1.5 t/thm) as well as oxygen (1100 - 1200 Nm³/thm) and it generates a very rich exit gas, which has to be utilized effectively e.g. in power generation to meet the demand of oxygen plant to make the hot metal production economic.        

ROMELT Process - The Advantages

=> This process can accept iron ore in a wide range of sizes (0 - 20 mm) without any pre-treatment. This would allow operating units to use slimes and other iron-bearing wastes which can be a big advantage for many reasons.

=> Non-cocking coals of size 0 - 20 mm with moisture content less than 10% are acceptable for this process. Although it is preferable to restrict the VM content of the coal up to 20%, higher VM coals can also be used. Then, no separate coal preparation is required.

=> The ROMELT process is capable of achieving fairly high degrees of post-combustion (even more than 70%) of the melter gas (primarily CO and H₂) before it leaves the reactor, thus ensuring satisfactory utilization of energy even though it is a single stage process.

=> The quality of ROMELT iron is excellent - Carbon 4%, Silicon 0.6%, Manganese 0.05%, Sulphur 0.04% and temperature 1400 - 1450^OC. The process offers particular advantage  in terms of phosphorous in hot metal because in the ROMELT process, instead of 100% phosphorous going to metal (as is the case in Blast furnace), only 60% phosphorous is reported to be in the hot metal while 30% goes to the slag, and 10% forms a part of exit gas.

=> Small scale production of 200000 to 1000000 tpa of hot metal is possible along with flexibility in production. The capacity of the rectangular ROMELT reactor (productivity in the range of 0.95 t/m² of hearth area) is limited by the penetration of oxygen from the side-wall tuyeres into the bath. Thus, ROMELT unit may be ideal for supplying hot metal in EAF based mini steel plants.

=> The specific investment in a ROMELT plant is not likely to be as high as in many other SR processes because the equipment is simple and easy to operate. For the same reason, the plant availability should be high.