Our steel manufacturing facility is strategically located in Gamharia, Jharkhand which comprises a pellet plant, sinter plant, oxygen plant, lime kiln plant, coke oven, sponge iron plant consisting of five kilns, two blast furnaces and a steel melting shop. The pellet plant (using the grate kiln technology) is used to agglomerate and indurate iron ore fines into pellets, while the sinter making enables us to agglomerate iron ore fines into a coarse product, i.e. the sinter. Hard and semi-hard coking coal is heated in the coke oven facility which consists of two batteries containing 48 ovens each. Produce from the 5 DRI kilns of 350 tpd each is primarily used for merchant purpose while some quantity is also fed into the Electric Arc Furnace, depending upon the cost benefit analysis.
The two blast furnaces have capacities of 280 m3 and 380 m3. Three Electric Arc Furnaces (EAFs) are operated at the steel melting shop, two of which have a capacity of 40 MT each and one of 70 MT, to produce liquid steel. In addition to these, the finished steel section comprises a wire rod mill, bloom mill and a bar mill, where bars, billets, blooms, etc. are reshaped and resized into products of various dimensions. The company has access to its own captive railway siding for all its inbound raw materials and outbound finished products, in an efficient and cost effective manner. Our continuous access to cheaper power at the steel manufacturing facility is facilitated by two coal based captive power plants (having power generation capacity of 25 MW and 30 MW, respectively), two waste heat recovery based captive power plants (having power generation capacity of 30 MW each) and a coal – gas hybrid captive power plant (having power generation capacity of 15 MW).
Process of Steel Operation
Iron ore fines & lumps and coking coal are the prime raw materials for the production of steel.
Firstly, hard & semi-hard coking coal are heated in the coke oven in the absence of air to produce metallurgical coke. Simultaneously, iron ore fines are agglomerated into sinter and pellets through the sinter and pellet plants, respectively, and iron ore lumps are reduced to DRI in the sponge iron kilns. The sinter, pellets, metallurgical coal and quartzite are fed into the blast furnace where the mixture, through a reaction with preheated air, is reduced into liquid hot metal and pig iron. Thereafter, the hot metal, DRI, scrap and lime are charged into the electric arc furnace, and an electric current is passed through the electrodes to form an arc. The heat produced by the arc melts the mixture into liquid steel.
The liquid steel is then reheated into the ladle refining furnace, and alloying metals such as manganese, nickel, chromium, ferro manganese, ferro silicon, ferro chrome and vanadium are added to the same to produce different grades of steel. The filled ladle is taken to the vacuum degassing facility, where gases such as nitrogen, oxygen and hydrogen are extracted from the liquid steel. Later, the liquid steel, through the process of continuous casting, is solidified into semi-finished billets or blooms for subsequent rolling in the finishing mills. The billets or blooms are then passed through the wire rod mill, bloom mill and bar mill, as the case may be,, where the sizes are reduced depending upon the desired end product. The finished materials are then shifted to the conditioning and finishing department for final inspection and allied activities
Sponge Iron (DRI)
Besides the 5 DRI kilns at Gamharia, the company also operated 3 more kilns at Bileipada, near Joda, in the Keonjhar district of Odisha, two of which have a nameplate capacity of 375 each and one 500 TPD, to produce sponge iron. However, as against its annual capacity, this plant has already achieved a total capacity of 112%.
The state of the art technology, coupled with innovative operative techiques, have helped this unit to be recognized as one of the best managed sponge iron plants in India. With the implementation of significant digitization initiatives, the production process aims to achieve greater efficiency and cost reduction without compromising on quality. This unit is gearing up to achieve a target capacity of 450,000 tpa as against its nameplate capacity of 390,000 tpa. To utilize the waste heat generated during the process of kiln operation, 2 waste heat recovery based power plants have been established which collectively has a capacity of 26 MW – a consistent source of ‘green’ power. After meeting the captive power requirements, surplus power is sold to the Ferro Alloys Plan of Tata Steel, which provides a steady source of revenue. To facilitate the sale and transmission of power, a dedicated overhead tower line of around seven kilometres has been laid. Like Gamharia, the company has also developed its own railway siding for sourcing raw materials as well as dispatching the finished goods.
Process of DRI Operation
Iron ore and non-coking coal are the prime raw materials for the production of sponge iron.
These are charged into a rotary kiln in requisite proportions, along with some dolomite. Coal serves as a reductant as well as fuel for providing heat to maintain the requisite temperature inside the kiln at 950-1050°C. Unlike in a blast furnace, the reduction process occurs in solid state here. The crucial factor in this reduction process is the controlled combustion of coal and its conversion to carbon monoxide to remove oxygen from the iron ore.
The overall process of direct reduction takes about 10 to 12 hours inside the kiln. During this time, iron ore is optimally reduced and the hot reduced sponge iron along with semi-burnt coal/char is discharged to a rotary cooler for indirect cooling to a temperature of between 100°C to 120°C. Sponge iron being magnetic in nature, the discharge from cooler consisting of sponge iron, char and other contaminations are routed through electromagnetic separators, to separate other impurities (i.e. non-magnetics) from sponge iron.The product is then screened in size fractions of lump (>3 mm) and fines (0-3 mm). Separate bins are installed to preserve its quality, prevent re-oxidation and facilitate faster loading on to the trucks. Automatic bagging machines have been installed just below the bunkers for bagging sponge iron, which are then sent to customers through rakes from our captive railway siding or through trucks, as per customers’ preference.
Power Generation through DRI making
During DRI operation, waste hot gasses at a temperature of about 800 to 1000°C emanate from the sponge iron kilns. Our three WHRBs in Joda and , together with the electrostatic precipitators and turbines, enable us to utilize the aforesaid waste heat and convert it into ‘green’ power. As mentioned earlier, the power requirement at our steel manufacturing facility is met through two coal based captive power plants, two waste heat recovery based captive power plants and a coal – gas hybrid captive power plant.