Evaluation of new equipments for utilization of waste heat in sponge iron industry

Abstract

The present work investigates the design modifications which can lead to efficient energy integration in coal-based sponge iron plant with a capacity of 500 t/day. For the present energy integration investigations, two scenarios: 1 and 2 are proposed and compared with the existing one. During the operation in coal-based sponge iron plant, a tremendous amount of heat is generated and a significant part of this heat, associated with the waste gas, remains unutilized. In scenario 1, the feed materials are preheated in a rotary drier with waste gas outside the rotary kiln. As a result of preheating, the intake capacity of the kiln is enhanced. The author takes this opportunity and increased the feed rate of iron ore by 10 % in scenario 2. For the purpose of energy integration, design and development of duct carrying waste gas and rotary drier is carried out. The comparative study based on capital investment, coal and energy consumption, water requirement, profit, and payback period, shows that scenario 2 is the best one. In scenario 2, production rate is increased by 10 % which consumes 17 % less coal, generates 24 % less waste gas, and consumes 30 % less water to produce 1 t direct reduced iron than that of the existing one and gives a profit of $31,000/day with a payback period of 34 days.