Energy integration of sponge iron production process

Abstract

The present work is an approach for conservation of energy in the coal based sponge iron industry by heat integration and incorporating certain design modifications without disturbing the SL/RN process technology involved in the sponge iron production. Although the making of sponge iron through direct reduction is being practiced in India, it still is having loopholes due to the non-optimal process parameters, high energy consumption and old running process technology motivation of the present work.The waste heat recovery in the process is done using waste gases exiting from ESP. For this purpose a case study of typical Indian sponge iron process of capacity 100 tpd is considered. After a complex reduction and combustion process waste gas exits the sponge iron plant at substantially higher temperature which is around 200-220C. At this range of temperature waste gas carries a lot of sensible heat which directly goes to the atmosphere through chimney.To apply heat integration on the sponge iron production process a solution technique has been developed. A complete material and energy balance is performed on the process to obtain theoretical oxygen and there by air demand of the process. Therefore air to coal ratio is calculated, which is kept fixed for entire integration process. A model is developed to calculate the theoretical coal demand of the process based on heat of reactions, feed preheating, sensible and radiation losses, etc. Then heat integration is applied by incorporating the proposed design modifications to preheat the kiln feed and air. This reduces the amount of coal consumption to 4.3%. In addition, due to decrease in the amount of air the waste gas amount is also decreased from 27.68155t/h to 26.3698 t/h.