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.

What is FASTMET Process of Ironmaking ?

11-Sept-2009
Fastmet – The Process Concept and References  

This is a direct reduction process using a Rotary Hearth Furnace (RHF) which was derived from the work done in USA by Midland Ross and Surface Combustion, in the ‘Heat Fast’ process, treated in 1960s. It is a solid reductant based process in which iron ore concentrate, pulverized coal and a binder are mixed together and pelletized. The resulting green pellets are fed either to a drier or directly to a rotary hearth furnace where the pellets are heated to 1250 - 1400^OC and reduced to metallic iron. Burners and post-combustion the CO evolved provide the heat required to raise the pellets to the reduction temperature.

The first commercial Fastmet plant was commissioned at the Hirohata Works No.1 of Nippon Steel in April, 2000 and Hirohata Works No.2 in February, 2005 with material processing capacities of 190000 tpa each plant. The second plant established was Kobe’s Steel’s Kakogawa Works started from April, 2001 having a material processing capacity of 16000 tpa.  The Fastmet process has allowed the Kakogawa Works to achieve a zero emission rating of steel mill waste. Waste utilization is the principal application of the Fastmet process in Japan.       

FASTMET Process - Flowchart

Advantages of Fastmet

Some of the advantages of Fastmet process as have been reported are summarized as follows:

=> A wide variety of iron ore as well as steel mill wastes including BF dust, BF Sludge, BOF dust, Sinter dust, EAF dust, mill scale, and etc. can be used as the oxide feed.

=> Elimination of waste disposal cost and landfill liability as wastes is changed to a quality source of iron (DRI).

=> Recovery of Zinc contained in wastes (Zn deriving from scrap) which can be sold to zinc producer. Zinc removal: 95% or higher.

=> A wide variety of energy sources can be utilized including natural gas, LPG, coke oven gas, heavy oil, coke breeze and carbon bearing wastes or pulverized non-coking coal.

=> The short reduction time of less than 12 minutes enables easy plant starting and shut-down, and quick adjustment of production rate.

=> Reclamation of carbon is possible. Carbon contained in dusts will be used as reductant. The carbon content of DRI can be adjusted as per the customer’s requirement.

 Related Articles – 

• COREX® : An Innovative Ironmaking Metallurgical Process
• The FINEX® Process: The Latest Smelting Reduction (SR) Ironmaking Technology 
• What is Finmet Process of Ironmaking ?

What is Finmet Process (Technology) of Ironmaking ?

9-Sept-2009
What is Finmet ?

Finmet is a fluidized bed iron ore reduction process developed jointly by Fior de Venezuela and Voest Alpine (VAI) of Austria in 1991 based on the original Fior process operated in Venezuela. Two Finmet plants are currently in operation - one 2 Mtpa plant at Puerto Ordaz, Venezuela and another 2 Mtpa plant at Port Headland, Western Australia operated by BHP (now Bluescope).

Fig: Flow-chart of Finmet Process

Finmet – The Process Concept

The Finmet process uses a train of four fluid bed reactors marked (A) in the adjacent figure with counter-current gas/solids contacting down the reactor train. The feed concentrate (iron ore fines of less than 12 mm size) is charged to the reactor train via a pressurized lock hopper system. The upper lock hopper in this system cycles continuously from ambient to reactor pressure to feed the ore continuously to the reactors maintained at the reactor pressure of 11-13 bars. The feed enters the topmost reactor (R4) where it is pre-heated to 550-570^OC by the reducing gas leaving reactor (R3). Pre-heating, dehydration, decrepitation and reduction of hematite to magnetite take place in reactors R4, R3 and R2. The temperature in R1 is around 780-800^OC and final reduction to 93% metallization is accomplished in this reactor accompanied by carburization of some of the Fe to iron carbide. The hot fine DRI (at 650^OC) is then transported by a sealed system to the briquetting machine (D) to attain a briquette density of around 5 gm/cm³. The product from any Finmet plant is hence, HBI (Hot Briquetted Iron).

The gas required for reduction is a mixture of recycled top gas and fresh reformer make-up gas processed in a standard steam reformer from natural gas. The recycled gas (taken from the top gas leaving R4), is first quenched to 40-50^OC and scrubbed in a wet scrubber to remove dust and water. The make-up gas required to balance the gas consumed by the reduction reactions is supplied from a conventional steam reformer system (C).          

Finmet: Advantages and Disadvantages

Some of the advantages and disadvantages of Finmet process of iron making are :

=> It can use very large reserves of iron ore fines as feed stock unlike Midrex and HyL, which can use maximum 5% fines.

=> The output from a Finmet plant is HBI with Fe content varying from 91-94%, carbon 1-1.5% (or 3% maximum), metallization 91-93%.

=> Finmet’s operating pressure is as high as 12 bars to ensure higher degree of metallization. It has been reported that continuous operation at such high pressures has been a major problem in both the Finmet plants.    

Related Articles – 

• COREX® : An Innovative Ironmaking Metallurgical Process
• The FINEX® Process: The Latest Smelting Reduction (SR) Ironmaking Technology
• Iron Making in Mini Blast Furnace (MBF) 
• Blast Furnace (BF) - Design and Ironmaking 
• Blast Furnace - Refractory Lining Pattern