Rate-Limiting Mechanism in Iron Ore Sintering Process with Waste Gas Recycling

Recycling waste gas through the sinter bed has an advantage of saving solid fuel. Depending upon the amount of waste gas recycled and its CO content, an equivalent quantity of solid fuel is saved. FeO is one of the key indicators of fuel needed for sintering; its optimization is critical to the consistency in sinter quality. Sinter pot tests were conducted to identify the effect of varying amounts of waste gas recycled. FeO and Tumbler Index increased with increasing waste gas up to 30%. Beyond 40% waste gas recycled, Tumbler Index decreased and the disintegration of the sinter was noticed. Incidental variation in the rate of solid fuel in an industrial scale Sinter Plant with waste gas recycling arrangement has resulted in a large variation in FeO than expected. Above 20%, productivity got adversely affected and Tumbler Index dropped as oxygen in the recycled gas started dropping below 19%. The rate-limiting mechanism has been identified as the underlying reason for low FeO. The deficiency of oxygen has affected the combustion efficiency of solid fuel, and hence, fresh airflow has been optimized to maintain the productivity and quality parameters. The variation in the carbon rate was restricted to 0.77 +/- 0.5 kg/t, and oxygen was maintained above 19% to achieve consistent performance.