Effect of different components in cement raw meal on carbothermal reduction of NOx in flue gas: An experimental study

Abstract

In China, the cement industry is the third largest source of NO_x emissions after thermal power generation and transportation industries. Flue gas carbothermal reduction denitrification technology was proposed by the author team in previous research, and had been proved to be an effective method to cut NO_x emissions from coal-fired cement kiln. Based on previous research work, a series of tube furnace experiments were conducted to further clarify the impact laws of different components in cement raw meal (CRM) on NO_x reduction when using this method in the present work. Compared with the situation that only pulverized coal exists, adding only calcium carbonate had a slight inhibitory effect on NO reduction, and the maximum reduction efficiency of NO (η_max) dropped to 63.79% from 66.67%. The addition of oxides such as SiO₂, MgO, Al₂O₃ and Fe₂O₃ into the mixture of pulverized coal and CaCO₃ had an impact on the reduction of NO. Overall, metal oxides promoted the reduction of NO, while SiO₂ inhibited the reduction of NO. For positive promotion, Fe₂O₃ had the most significant effect on the reduction of NO, and η_max reached 89.71% when the addition amount was 4% compared to 63.79% before addition. The promoting effect of metal oxides on NO reduction is: Fe₂O₃>MgO>Al₂O₃. In addition to Fe₂O₃, the influencing law of addition amount of MgO and Al₂O₃ on NO reduction had also been revealed. The outputs achieved in this study will provide a reference for how to reasonably adjust the ratio of CRM when the flue gas carbothermal reduction denitrification technology is applied into cement industry.