Effects of trace components in cement raw materials on NO_x reduction by selective non-catalytic reduction in precalciner

Effects of trace Al₂O₃, MgO, Fe₂O₃, CaSO₄, and CaF₂ in cement raw materials on NO_x reduction by selective noncatalytic reduction (SNCR) were studied in a simulated precalciner atmosphere. It was found that when there is only one trace component, Al₂O₃ and MgO exert no significant effects on NO_x reduction. Fe₂O₃ reduces the NO_x reduction efficiency at low temperatures. CaSO₄ promotes the SNCR process to a slight extent. CaF₂ significantly improves the NO_x reduction efficiency. When Al₂O₃, MgO, Fe₂O₃, and CaSO₄ coexist in the solid material, the main effect is to inhibit NO_x reduction at low temperatures, and the promoting effect of CaSO₄ is curtailed. Therefore, in the new dry process for cement production, in order to mitigate the negative effects of trace components on NO_x reduction, the Fe₂O₃ content in the raw materials should be reduced to curtail effects on cement properties. In addition, positioning of the reducing agent injecting points at low-temperature areas in the precalciner should be avoided.