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Emerging Alternate Raw Materials and Processes for Steel Making

Prakash Tatia, Ravindra S. Borwankar, Vikram Ispat

29 Sep' 04

Introduction There are two(2) main routes for steel making. One is the "classical route", also called as "primary route" based on blast furnace (BF) and basic oxygen furnace (BOF) and the second is "modern route", also called as "secondary route", based on electric arc furnace (EAF), using steel scrap or sponge iron i.e. Direct Reduced Iron (DRI) as basic raw materials. Currently about 57% of the steel is produced through BF/BOF route. This route is very good for volume production. But the process requires high capital cost and substantial investments on infrastructures. As a way out of the shortcomings of BF/BOF route, EAF steel making was introduced about a century ago. Environment friendly and flexible to produce variety of value added grades of steel. The share of EAF steel making in the global output of crude steel has increased substantially from 26.6 per cent in 1998 to 35% in 2003 and is likely to go up in future. World Steel Production World's crude steel production from 2000 onwards has been growing faster with more growth in developing countries, although China remains the major growth driver. World Steel Forecast World finished steel consumption is forecast to rise from 808 MMT in 2002 to 894 MMT in 2007, an increase of 10.5% over the period. The early years of 21 st century have set the pattern for the future. Asia's share went up from 41.4% in year 2000 to in excess of 47% in year 2002. In terms of per capita consumption of the steel Chinese consumption has more than doubled within a decade. Looking to the low per capita consumption in India and Asia, there is good demand growth potential in this region. Metallics For EAFS EAFs mainly use following metallics for melting : Melting Scrap (Shredded/HMS etc.) Sponge Iron (HBI/DRI) Pig Iron Scrap and sponge iron are used by EAF as basic feedstock. However generation of scrap is gradually falling globally. DRI is a high quality metallic product, produced from Iron Ore/Pellets and used as a feedstock in the EAF and other steel making processes. HBI is a denser and compacted form of DRI, designed for ease of shipping, handling and storage. DRI is now recognized as a high purity, top quality charging material the world over. In comparison with scrap, the use of DRI/HBI offers many benefits like consistencies in composition, low tramp elements and environment friendliness. It has been predicted that supply of sponge iron globally will grow to 55 MMTPA in year 2010 as against about 45 MMTPA at present. Scrap Scenario There has been a spurt in scrap prices recently, mainly due to: Increase in demand in year on year terms owing to large global crude steel production increases. The Far East markets of China, South Korea & Taiwan continue, to drive prices upwards owing to high demand for scrap, based on strong increases in crude steel production rates. This has pushed up Rotterdam and US scrap export prices to such high level as currently. In the US, despite consolidation and Chapter 11 proceeding, capacity utilization rates have been higher than expected. In addition to this buoyant export demand from the US to China boosted prices in 2003. Overall US exports in 2003 were added by a weak dollar to the Asian market, causing tightness in US supply. Reduced scrap flow from CIS countries due to export restrictions Continued growth in steel production in China that will require iron units in the form of scrap or sponge iron. New EAF capacity in the Middle East which will absorb domestic scrap generation. The above factors will result in severe shortage of scrap and demand for alternate metallics i.e. sponge iron will continue to increase globally. With obsolete steel scrap recovery rates being high and with diminishing easy scrap availability, steel makers are facing a shortage of sourcing metallics Sponge Iron Sponge Iron is produced mainly by two routes Gas based (HYL, Midrex, etc) Coal based (SL/RN/CIRCORED, etc) World sponge iron production during calendar year 2002 was at 45.1 MMT an increase of 12% over 2001. With continuous decline in scrap generation, change of steel making route (EAF becoming popular) the sponge iron demand will continuously rise. Looking to this, lot of new DRI/HBI capacities are being added. In the current year (2003) USA is the largest importer of DRI besides being the world's largest export of ferrous scrap. A number of HR coil plants with EAF route were built in USA during 1990s. this resulted in increased global demand for cleaner raw material such as gas based sponge iron (HBI/DRI). It points to a trend of shift to cleaner DRI with increased production of higher value steel products and preference for use of DRI over scrap. Recent Innovations & Future Trend In Steel Making A First At Vikram Ispat Vikram Ispat is the world's first Gas based sponge iron plant to produce both HBI & DRI from the same reactor successfully. The plant is based on HYL-III technology. Vikram Ispat started as a merchant producer of HBI with an installed capacity of 0.9 MMTPA. The plant used 3 lines of HBI briquetting machines and had a provision for a 4th line. In order to serve the domestic market for conventional DRI, the plant installed a 4th STREAM as DRI line. Looking at growing shortage of gas based DRI in domestic market, this development provided a flexibility to produce either HBI or DRI as per the market needs. At later stage Vikram Ispat can go for hot DRI discharge for steel making from same reactor. This development opened up new possibilities for future DRI plants and the route adopted for steel making. The above innovation will have a long term impact on the future of steel making and will help increase the already growing acceptance of the more environment friendly electric arc furnace route. Current Steel Making & Energy Usage The globalization of steel industry has ushered in a new era of cost competitiveness. Steel industry is a single biggest energy consumer with a consumption of about 4% of world's energy consumption. The energy used is a major cost factor for the steel industry. In developed countries, cost of energy is between 15 to 20% of the over all cost of production. While in India it is between 30 to 33%. In steel industry the greatest saving in energy is achieved through improvement in Iron & Steel making technologies. In current route through DRI to EAF, first cold DRI/HBI is produced at ambient temperature. This is then fed to EAF to produce steel. This involves loss of substantial energy due to multiple heating and cooling and is a potential source of energy saving. Various scrap- preheating technologies are now available, however preheating of DRI cannot be accomplished applying conventional off-gas preheating systems. A variety of systems have been designed to convey hot DRI from DRI reactor to EAF. These systems include mechanical conveyors, transport vessels (rail or truck) and pneumatic conveying systems. Savings Due To Hot Charging DRI There are two primary benefits of hot charging of DRI to an EAF Lower energy consumption for melting and Increased productivity due to shorter tap to tap time. The energy savings occur because less energy is required to heat DRI to melting temperature. As a thumb rule, power consumption can be reduced by about 20 kwh/ton of liquid steel for each 100% increase in the composite charge temperature. Also in addition there is saving in electrode consumption of 0.004 kg/Kwh due to its linear relationship with power consumption. At 80% hot DRI charging the savings in electrode works out to Rs.50 PMT at current electrode prices. Future Trend However using only hot DRI charging involves the difficulty of matching a continuous process (DRI plant) with a batch process (EAF PLANT). To partially overcome this difficulty a hot DRI surge bin may be used, located between DRI furnace and EAF. However for a more viable solution as proved at Vikram Ispat, the same reactor may have flexibility to produce simultaneously HBI and/or cold DRI for merchant sale, and charge hot DRI to EAF directly. It is anticipated that the future DRI projects will be based on this model. Hot DRI/EAF route will be competitive even over hot metal (MBF)/EAF route which will be subject to uncertainty as regards availability & prices of coke. Conclusion Looking to following aspects, alternate raw materials like DRI will play an important role in shaping the future steel making processes. Natural Gas being a critical input, sufficient improvement in availability of NG/LNG all over the world, is expected. In India also, import of LNG has already commenced. Spiraling prices of pig iron, scrap and coke. Continuous growth of EAF's globally. Decline of scrap generation globally. New Steel making capacities in Middle East based on EAF route. With recent technological developments it is now possible to set up fully integrated DRI plants which use hot DRI for melting into steel & produce cold DRI/HBI to service market needs. Such a model provides flexibility to produce as per market needs. The HAMIL STEEL DR-EAF combination coming up in Dubai, UAE will be world's first plant to utilize the patented and proprietary HOTLlNK@ Technology. About half of the DRI will be fed directly to the EAF and balance will be for the production of HBI FOR MERCHANT SALE. This plant will have 6.0 Lac MT p.a. capacity.