A study on the effect mechanism of moisture content of the mixed material on denitrification in the sintering process

Abstract

The moisture content was a key factor affecting the permeability of the sintering granulation and the bed layer, and it promoted denitrification and combustion. This study investigated the influence of moisture content on denitrification, bed permeability, and the emissions of O₂ and CO in the sintering process through industrial trials on-site. By analyzing sintering reaction mechanisms and SPSS data, and combining CHEMKIN simulation, the mechanism of moisture content on NO emissions during sintering was obtained. The results showed that the moisture content of the sintering mixture could affect the emission of NO in the sintering flue gas by influencing the permeability of the bed and the O₂ and CO in the flue gas. As the moisture content of the mixture increased, the NO content in the sintering flue gas first decreased and then increased, while the permeability and CO content showed an initial increase followed by a decrease, and the volume fraction of O₂ in the flue gas gradually decreased. Eight factors, including permeability index, O₂ concentration, CO concentration, negative pressure, water vapor volume fraction, flue gas temperature, sintering trolley speed, and dust concentration, were significantly correlated with NO emissions, and a generalized linear model with NO emissions as the dependent variable was established. For a specific sintering industrial production, the moisture content of the sintering mixture determined the permeability. Apart from O₂ concentration, permeability had the greatest impact and was negatively correlated with NO emissions. Water vapor in the flue gas could promote the CO-NO reaction, and the higher the water vapor volume fraction, the higher the reduction rate of NO, but excessively high levels were detrimental to permeability. Taking into account the permeability of the sintering bed, O₂ and CO in the flue gas, the optimal moisture content (mass fraction) of the sintering mixture for denitrification during the sintering process ranged between 6.71% and 8.04%. In actual industrial sintering production, a water vapor volume fraction in the flue gas between 16% and 18% was most favorable for denitrification during the sintering process. These findings provided theoretical references for denitrification processes during sintering.