Design of waste heat recovery system in a sponge iron plant

Abstract

India is emerging as the leading producer of sponge iron among developing as well industrially developed nations. Sponge iron is produced by direct reduction of iron ore (DRI process) and is popular because of use of non-coking coal. The conventional blast furnace process uses coking coal. The DRI process doesn’t require coking coal and therefore is advantageous.
In the present work waste heat recovery system is designed to integrate the heat of waste gas in the sponge iron process. For this purpose a case study of typical sponge iron production process is considered. The waste gas from a sponge iron plant exits at a temperature of around 200-300C. A lot of sensible heat is lost with these gases. This heat is utilized to preheat the air entering to kiln. Further, the waste gas at reduced temperature is used to cool hot sponge iron which is previously carried out by water. Consequently, considerable energy and water savings is achived which increases the efficiency of the process manifold. The objective of this project is to design a suitable heat recovery system for above cases which can efficiently remove the sensible heat and put it to use.
The annual savings upon installing this system was found to be around Rs.95.3 lakh. The annual coal savings was calculated to be 620 tons, which is worth Rs.15.5 Lakh. The annual water savings was calculated to be 1.2 million tonnes, which is worth Rs.83 Lakhs.

Keywords: Waste Heat, Recovery, Waste Heat Utilisation, Design