Utilization of Coke Oven Gas and Converter Gas in the Direct Reduction of Lump Iron Ore
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THE integrated steel plant typically consists of coke making, sintering plant, blast furnace, oxygen converter, secondary metallurgy, continuous casting, and rolling mill. Nowadays, a network connection consisting of different units in an integrated steel plant is being discussed more and more to reduce the energy consumption and CO2 emissions.[1,2] The use of off-gases from the integrated steel plant is important to increase the efficiency of the overall process. The production of DRI in the integrated steel route based on the utilization of available by-product gases has different benefits from both economic and environmental perspectives.[3–6] Among the off-gases that can be recovered and reused in the integrated steel mill are coke oven gas (COG) and basic oxygen furnace gas (BOFG). The COG has the higher net calorific value in the range of 16.4 to 18 MJ/ Nm3 (at standard temperature and pressure [STP]) than that of BOFG (~8.8 MJ/Nm3).[3] The specific amount of ELSAYED ABDELHADY MOUSA, Researcher, formerly with the Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan, Cairo, Egypt, is now with the Department of Ferrous Metallurgy, RWTH, Aachen University, D-52056 Aachen, Germany. Contact e-mail: [email protected] ALEXANDER BABICH, Associate Professor, and DIETER SENK, Professor, are with the Department of Ferrous Metallurgy, RWTH, Aachen University. Manuscript submitted June 26, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
COG is in the range of 410 to 560 Nm3/t coke depending on the charged coal.[5] The amount of BOFG is in the range of 50 to 100 Nm3/t steel in the suppressed combustion system, and it may reach to 500 to 1000 Nm3/t steel in the open combustion system.[7] In 2011, the worldwide coke production reached a new record with about 641 million tonnes, and the steel production by BOF reached to about 1050 million tonnes.[8,9] This production of coke and steel is estimated to be accompanied by about 310 billion Nm3 of COG and 0.5 to 1.0 billion Nm3 of BOFG, respectively.[10] The typical COG consists of about 58 pct H2, 27 pct CH4, 7 pct CO, and small amounts of CO2, N2, and other elements, while the typical composition of BOFG is about 55 pct CO, 15 pct CO2, and 28 pct N2, and small amounts of H2 and CH4.[11,12] The H2 content of COG can be increased to 77.7 pct by steam reforming of CH4 over a NiO/MgO catalyst.[10] The relatively high content of H2 and CO in COG and BOFG, respectively, has attracted much attention in the recent years for their utilization in the reduction processes.[13–19] Several of these works are focused on the evaluation of the economic benefits of DRI production in the integrated steel plant using off-gases, but little information was found on the efficiency of these gases in the reduction process.[20] Moreover, the economic production of DRI is mostly influenced by the cost of iron-bearing materials represented mainly in the form of pellets.[21] Increasing
the fraction of lump ore can decrease significantly the production cost of DRI, but the amount of lum
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