Application of coalbed methane assisted iron ore sintering: Injection effect, pollutant abatement and economic evaluation

Abstract

Hydrogen-rich gas injection, which has garnered widespread attention from academia and industry, is an effective method for reducing CO2 emissions during the sintering process and for improving sinter quality. Coalbed methane (CBM) is a cost-effective and reliable hydrogen-rich gas resource in China. In this study, we investigated the injection effect of CBM in assisting iron ore sintering. Additionally, we determined the appropriate injection parameters by systematic sintering pot tests and compared it with coke oven gas (COG). The impacts of CBM injection on pollutant abatement and combustion efficiency were analyzed based on the variations in the sintering flue gas composition, and a comprehensive economic evaluation was conducted. The results showed that injecting 0.51 vol.% CBM between 5 and 13 min after ignition with 0.3 wt.% coke breeze ratio reduction could significantly improve the sintering index and the uniformity of heat distribution within the sinter bed. Excessive injection would affect the bed permeability. CBM took advantage over COG at a gas–solid heat transfer ratio of 1:1.28. The four-stage cascade mode with a gradient of 0.18 vol.% and the intermittent mode with an intermittent time of 0.5 min could optimize the injection effect. However, the cascade mode performed better. Besides, injecting CBM increased the emission reduction rates of CO and NOx and improved combustion efficiency by 5.72%, 4.47%, and 1.46%, respectively. Overall, the cost-savings were CNY 2.19 per ton sinter, and the annual production cost could be reduced by approximately CNY 6.71 million for a 265 m2 sintering machine. The profits achieved because of CBM injection can be further improved by increasing the bed permeability and mixed injecting with other gas media. This study provides an effective path for green transformation of sintering production.