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.
Easy & Flexible Operation
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 -
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:
For details 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 visit:
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
In the FINEX process the iron production is carried out in two separate Process steps. In a series