Experimental Study Of NO₂ Removal By Ca-Based Absorbent At Low Temperature

SO2 and NOx emissions from coal-fired power station have resulted in serious environment problems, and the traditional flue gas purification systems for desulfurization and denitrification simultaneously, are complex and of high operating cost. Desulfurization and denitrification technology with calcium-based absorbents by NO oxidation, which is on the basis of traditional desulfurization process, is an effective way to solve the above problems. At present, desulfurization technologies by calcium-based absorbents are mature, The effective removal of NOx becomes a hot issue of research. The characteristics and mechanisms of the NO2 removal by the calcium-based absorbents are investigated in this paper, the impacts of reaction conditions and flue gas components on NO2 absorption are analysised, the way of NO2 absorption by Ca-based absorbents is discussed at low temperature, and preliminary experimental study of Ca-based absorbents modification is investigated.In this paper, the characteristics of NO2 removal by Ca (OH)2 is studied by atmospheric pressure fixed-bed bench, which includes the impacts of simulated flue gas composition and reaction conditions on NO2 removal. It is found that: the presence of SO2 in the flue gas has great impact on the removal of NO2; the removal of NO2 first increases and then decreases as the concentration of H2O increases without SO2; The presence of O2 inhibites NO2 removal process in the simultaneous removal of SO2 and NO2. when relative humidity is constant, and the removal rate of NO2 decreases as the temperature increases.On the basis of above research, experimental study of Ca-based absorbents modification is investigated for improving NO2 removal, absorbents modified with NaOH, CaSO3 and fly ash as additives are prepared by the way of dry style digestion. NO2 removal rates of the modified absorbent of different preparation conditions are first studied. and then pore distribution and the surface microstructures of modified absorbent are studied. It indicates that NaOH as an additive is found to improve the surface alkalinity and pore size distribution, so it improves the removal rate of NO2; the addition of fly ash mades a lot of small Ca-based material adhere to the surface of large particles, which prevents absorbent agglomeration, and promotes the absorption of NO2.