Alternative Coke from Inferior Coal for Ferro-Alloy Industry
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lternative Coke from Inferior Coal for Ferro-Alloy Industry M. Gangopadhyaya,*, Gautam K. Bayena, M. Kumara, and A. Mukherjeea a Central
Institute of Mining and Fuel Research, Carbonisation Section, Post Office FRI, Dhanbad, Jharkhand, Digwadih-828108 India *e-mail: [email protected]
Received May 22, 2020; revised May 22, 2020; accepted July 22, 2020
Abstract– Carbothermic reduction of iron oxide is an important reaction in Ferro-alloy production process. Coke and bio-char are the main resource carbon for these industries. Carbon not only takes part in reduction reaction but also have important role in maintaining required carbon percentage in metal and contribution in energy supply for the process. Thus the price of carbonaceous material has significant contribution to the overall cost of Ferro-alloy production. Suitable low cost carbon materials are always in demand for such industries. In the present study low rank Indian coal has been carbonised in medium temperature level for producing an alternative semi-coke for this purpose. The coal sample has been first fractionated in two parts based on particle size distribution. Larger size samples are directly carbonised in a laboratory scale coke oven using non-recovery type coke making technique. Finer fractions are first carbonised, then agglomerated into small briquettes and subsequently de-volatilised for lowering volatile matter content, enhancement of fixed carbon and improvement of other properties. Keywords: semi-coke, Ferro-alloy, carbonisation, Indian coal DOI: 10.3103/S0361521920060038
INTRODUCTION Ferroalloys are very important for manufacturing of various alloys and steel with special properties like corrosion resistance, hardness, abrasion resistance etc. [1]. The production of ferroalloys is dependent on carbothermic reduction processes, where carbonaceous materials are used as reductant in electric arc furnace. The primary Ferro-alloys are Ferro-manganese, Ferro-silicon, and Ferro-chrome, etc. [2, 3]. Different types of carbonaceous materials are used for production of ferroalloys, and it has a large impact on overall cost, energy consumption and quality of the final product [4]. The key purpose of the carbon materials is reduction of the metal oxides; however it is also the source of carbon in the Ferro-alloy, which acts as trap for SiO gas and maintaining required electrical resistivity [5, 6]. The most common reductants are coal, coke, charcoal, pet coke etc. The selection of carbon materials for ferroalloy industry depends on their availability, properties and cost [7]. It is reported about 35–40% of total cost of production arises due to reductant material. High price of bio-char and scarcity of good coking coal force industries to find out alternative raw materials [8]. Low ash non coking coal may be a good alternative. Globally there is increasing trend of utilizing non-coking coal for metallurgical purpose. India has a
vast coal reserve, but suffers from the main demerit of its high ash content. Among this only ~14% is coking coal va
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