Development of energy conservations scenarios for sponge iron industry using process integration

Abstract

This paper presents an approach to find the best modification in the coal-based sponge iron process with an aim to integrate energy in it. For this purpose, a few energy conservation cases are formulated by integrating unutilized energy present in possible areas of process flow sheet. When unutilized energy of the process is properly integrated, energy demand from outside sources can be reduced. It decreases coal consumption as coal is the only source of energy in this plant. For energy integration in sponge iron process pinch technology is applied on the actual data of plant. Based on this data, seven energy conservation cases are identified. Among these, two are selected for detailed analysis based on utility requirement. For these two cases capital investment required for energy integration, coal consumption, water requirement, energy consumption, profit, and payback period are compared. Based on these factors the best case is selected. The integrated design for the best case includes air preheating and cooling of kiln outlet using waste gas. Further, a modified case is discussed with preheating of feed to rotary kiln and air using waste gas. This case consumes 12.3% and 93.7% less energy and water, respectively, and gives 8.6% more profit in comparison to the previous case. Thus, the modified design is selected as the best option for energy integration. This design also satisfies the practical constraints of the process.