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The COREX and FINEX Processes - reliable, environmental friendly and economical Hot Metal Production

K Wieder, C Bohm J Wurn, VOEST ALPINE Industrieanlagenbau GmBH & Co (VAI)

28 February' 2005

Summary Compared with the traditional hot metal production via the blast furnace route, only the COREX process offers the possibility to produce hot metal without BF quality coke on industrial scale. The operation results achieved from the operating COREX plants at POSCO, SALDANHA and jINDAL confirm this. Together with POSCO and RIST, both Korea, VAI currently is developing the FINEX process, a smelting reduction process based on direct charging of coal and fine ore in form of sinter feed. In May 2003 the FlNEX Demonstration plant with an annual nominal capacity of 600,000 t hot metal commenced operations. Based on the successful results, VAI was awarded a contract for the design of the first industrial FlNEX 1.5M plant with an annual capacity of 1,500,000 t of hot metal at POSCO Pohang Works All COREX developments of the last years aim at the optimization of the process, the increase of the productivity and the reduction of the specific consumption values. The developments done are mainly carried out in the field of coal and DRl charging into the melter gasifier, the charging of the burden, the injection of the reduction gases to the reduction shaft and the preparation of the raw materials. Specific notice was laid at the reduction of the specific coke consumption. Based on some of the new developments a nearly coke-free operation could be achieved at COREX/FINEX POSCO. Status of the COREX Projects SALDANHA STEEL, Saldanha Works, South Africa An Integrated Compact Mill (ICM), based on a COREX C-2000 unit in combination with a COREX Gas based Direct Reduction (DR) Plant, was started-up in mid I 999 at SALDANHA STEEL, on the west coast of South Africa. Export gas from the COREX plant is used for the production of direct reduced iron (DRI) in an adjacent DR plant using a MIDREXTM shaft furnace and LINDE Vacuum Pressure Swing Absorption plant (VPSA) for the removal of CO2. The DR plant is operated with a mixture of about 65 per cent SISHEN lump ore and 35 per cent CVRD pellets. Both the hot metal from the COREX plant and DRI from the DR plant are processed to high-quality steel in a twin-shell EAF, followed by thin slab casting and direct rolling to produce high-quality hot rolled coils (HRC). Roughly 50 per cent of the produced HRC are exported and 50 per cent are cold-rolled and further treated at DUFERCO STEEL PROCESSING, an adjacent cold-rolling complex also built by VAI on a turnkey basis. The cold-rolled coils are sold on domestic and international markets. The COREX plant at SALDANHA STEEL was started up on December 1998 and is operated with mainly indigenous iron ores comprising SISHEN lump ore (80 - 100%), CVRD pellets (0 - 20%) and indigenous coal from the VAN DIJKSDRIFT and GROOTELUK coal districts. All of the required additives are also supplied locally. The highlights of COREX/DR SALDANHA for 2004 (based on the production up to September 2004) are: Uninterrupted production output of approx 750,000 tons of hot metal for 2004 (forecast). Daily average production rate of 2,300 t (approx. 15% above nominal capacity or an increase of the average daily output compared to 2003 of approx. plus 200 t/d Plant availability (calendar utilization) of more than 92.5% A Reliable supply of gas to a COREX-gas-based DR plant, yielding in a production output of 700,000 tonnes of DRI Longest continuous uninterrupted operation 63 days Recovery in excess of 95% of all COREX slag sent to a slag granulation plant and sold to the cement industry Recycling of all available mill scale, roller-hearth-furnace steel scale and DR-plant classifier sands, as a COREX burden feedstock Recovery of all COREX, DR-plant, and steel-plant dust and sludge sent to a sludge granulation plant and used in the manufacture of cement During the last twelve months the COREX plant achieved the following records: Highest daily throughput of 2735 tons hot metal Highest monthly throughput of 66,985 tons hot metal The stability of the SALDANHA STEEL COREX plant played a major role in SALDANHA STEEL's achievement of 100% design capacity (1.25 mt HRC) production during the past year. Jindal Vijayanagar Steel, Toranagallu Works, India Please allow to quote out of a press release of JINDAL itself: [...] Realizing the importance of environment protection, resource conservation and sustainable development in a resource crunch country like India, the promoters of JINDAL VIJAYANAGAR Steel Ltd. has adopted COREX iron making technology in its integrated process route in India and is a leading technology steel producer. Two C-2000 modules of COREX are in operation in JVSL. Module-l was commissioned in August 1999 and Module-2 was commissioned in April 2001. This process has greater flexibility in operation, uses various types of non-coking coals as a primary fuel and requires raw materials of less stringent quality. The gas generated from the process is used for power generation, for the pellet plant and as a fuel in the integrated plant complex. The special features of COREX hot metal are high temperature (1480 - 1510o C), low sulphur, low nitrogen and least amount of impurities. Finally, it is more eco-friendly compared to the conventional Blast Furnace route due to exclusion of sinter plant and coke ovens. A total of 6,544,798 tons (3,810,507 tons from Module-l and 2,734,291 tons from Module-2) of hot metal was tapped from the time the plants were started up until the end of September 2004. The furnaces achieved the following performance during the last twelve months: Reliable uninterrupted production output of approx. 1,600,000 tons of hot metal Typical plant availability (calendar utilization) of 92.5% Average specific fuel and oxygen 1050 kg/t HM and 540 Nm3/t HM Reliable gas supply to power plant and as a fuel in the integrated plant complex. Recovery in excess of 94 per cent of COREX slag sent to slag granulation plant and used in the manufacture of cement. Recycling of most of the metallurgical waste j such as coke fines, mill scale, iron ore fines, LD Slag, limestone and dolomite fines etc as a COREX burden feedstock. During the last twelve months, the COREX plants achieved the following records: Highest monthly throughput of hot metal 77516 tons from Module 2. Highest monthly plant calendar utilization 99.36% in Module 1 and 95.85% in Module 2. Lowest monthly specific fuel and oxygen consumption - fuel rate 945 kg/t HM and oxygen rate 492 Nm3 /t HM in Module 1 and fuel rate 970 kg/t HM and oxygen rate 510 Nm3/t HM in Module 2. JVSL has got certain unique operational features like various fines addition directly into the melter gasifier, recycling of various metallurgical wastes to an extent, high melting rate operation etc. JVSL COREX has surpassed its rated capacity by about 15 - 20 per cent, producing quality hot metal for steel making. However, with increasing operational experiences in COREX, a number of areas have been uncovered, where there are still possibilities of improvement in terms of productivity, equipment availability and reduction in hot metal cost [...]. POSCO, Pohang Works, Republic of Korea The COREX plant at POSCO Pohang Works, Republic of Korea, which started up in 1995 adjacent to the five existing blast furnaces, has since produced approximately 5.7 million tons of high-quality hot metal (as of September 2004) and is operated since May 2003 in "FINEX process mode". The FINEX Process The FINEX Process, a smelting-reduction technology based on the direct use of coal and fine ore is now jointly developed by POSCO and VAL The direct use of fine ore for the production of hot metal and DRI will be one of the driving forces behind future developments. COREX Coals A wide range of non-coking coals can be used in the COREX process. If these requirements for COREX coals are compared to the requirements for blast furnace coals, it can be concluded that the requirements are lower. COREX coals are more available and it does not have to be emphasized that the use of more widely available and thus lower cost coals lead to lower cost operations. Currently, this is of high importance as metallurgical coal can only be secured on the world market at increased prices due to non-availability, whereas "COREX" coal prices kept widely constant during the last year. The price gap between COREX@ coal price and metallurgical coal price that have been traded internationally has opened from approximately 20 USD/t to approx. 35 USD/t. Coke Consumption All developments over the last years aimed to optimize the process, increase the production and to minimize the consumption figures. Special attention was put on the coke consumption. Whereas P~SCO showed that it is possible to operate the COREX plant at zero coke for long periods (coke consumption in total 1999 in average 19 kg/t HM) by a careful operation and treatment of the raw materials, SALDANHA and JINDAL could not do similar for different reasons. However, still ongoing developments on the process and on related equipment resulted in coke quantities in the operating plants in the range of approximately 2-10 % of the coal charge. As not all the developments currently available could be implemented effectively in the operating COREX plants (e.g. material distribution equipment) this figure will considerably drop in future COREX plants. Another important aspect has to be taken into account regarding to the required coke quality: In case coke is charged to the COREX plant, the coke quality is different to the coke qualities as being typically used in the blast furnace. In terms of blast furnace operation, only low quality coke is required for COREX, which has also a tremendous effect to the specific coke price. It is equal to coke breeze. Finally, coke can be seen as an "additive" for the process to be only a minor economical issue as to the most extent thermal coal is directly used. Latest Equipment Developments/ Optimizations in the COREX Process Equipment Changes Based on the experience of the producing COREX plants that are operated at very different conditions regarding raw material input and process control and on the experience from the in-house blast furnace know-how, many investigations (e.g. CFD calculations that show the tendencies and effects after implementation of certain charging equipment) were carried out regarding the distribution of the materials charged to the melter gasifier. Two major optimization points were identified: charging of DRI to the melter gasifier and charging of coal to the me Iter gasifier. Based on the results of the investigations new equipment is designed and applied at single operating COREX plants and will be applied in future COREX plants. Installation of new DRI distribution device This new DRI distribution system that is already installed at the COREX. SALDANHA plant (Figure 9) is to distribute the DRI evenly onto the melter-gasifier bed surface in a "doughnut" form, at a radius of 2 m to 4 m from the center. Tests during stable production indicated that the DRI flaps have a dramatic effect on melter performance. When the -deflection flaps were moved away from the DRI stream, an almost immediate deterioration in melter performance was observed and stave heat losses peaked. Coke addition had to be increased during the tests by 4% to maintain liquid iron temperature. After the first start-ups of the COREX plants at SALDANHA and JINDAL it was found that charging of coal did not take place as desired. Due to the horizontal discharge speed of the coal at the coal screw outlet, the main coal stream was placed approximately 1 m off the center on the top of the char bed in the melter gasifier. By centralizing the coal stream, the situation improved. Due to the fact that the coal was charged in one stream and no coal distribution took place, major volumes of not-pyrolised coal came into hot areas of the melter gasifier resulting in pressure peaks. After installing a static coal distribution device (coal riffler), that distributed the coal over a wider area of the char bed surface, the pressure peaks situation improved considerably. Based on an almost pressure peak free operation the process pressure and the char bed height could be increased resulting in a more stable hot metal temperature and composition, leading to decreased specific consumption values and smoother process operation. Already the static coal distribution improves the coal distribution. An even better result will be achieved with a dynamic coal distribution system at COREX SALDANHA that looks similar to a rotating chute of the blast furnace. Such a system will be installed at SALDANHA to achieve a distribution. Raw Material Preparation Changes Based on the fact that COREX charges mainly lumpy coal into the process, also applications for fine coal generated during the coal transport and storage had to be found. Besides charging fine coal to a certain percentage directly into the COREX melter gasifier, or using it in the coke oven process, in a power plant or cement plant, at POSCO a coal briquetting technology was also developed that suited for the COREX process. During charging higher amounts of briquettes, it was found that in case the briquettes contain certain amounts of metallurgical coal, these briquettes supported a coke free COREX@ operatio~. This fact is of importance. As the above-mentioned equipment measures (distribution issues) that have already shown at SALDANHA a considerably improved operation, are not all yet applied at COREX POSCO. Conclusion Based on the experience of the four operating COREX plants and the 10 years of operational experience of the ISCOR COREX* C-I000 Plant, a considerable knowledge base has been accumulated with respect to engineering and operation. This knowledge and subsequent investigations result in a most competitive hot metal production compared with the blast-furnace route. As the development optimization of COREX technology is still underway, additional economical and technological potentials are anticipated. Major developments are currently carried out at the material distribution devices for charging of these materials into the main aggregates of the COREX process - the melter gasifier and the reduction shaft. Due to the well-proven plant concept, new process features and the highly competitive production costs, VAI is confident that the COREX Process will account for an increasing share of future investments in iron making facilities. As a consequence of a tight raw material supply for the blast furnace, the COREX process enables operators to produce hot metal based on raw materials that are still not tight in supply and are available at "reasonable" prices. The FINEX Process is under development and will provide hot metal production based on the direct use of coal and fine ore. Currently the COREX plant of POSCO is part of the FINEX Demonstration Plant with an annual nominal hot metal capacity of 600,000 t/a. The next step in the development will be the design and erection of the FINEX 1.5M plant with an annual capacity of 1.5 million t/a hot metal. The direct use of fine ore for the production of hot metal and DRI will be one of the driving forces behind future developments.