An Adaptive Sorbent for the Combined Desulfurization/Denitration Process Using a Powder-Particle Fluidized Bed

Abstract

This study is devoted to examining an adaptive sorbent for the combined desulfurization/denitration (DeSOx/DeNOx) process reported in work by Xu et al. (Trans. Inst. Chem. Eng. 1999, 77, Part B, 77−87). The so-called powder-particle fluidized bed (PPFB) is used by the process so that SOx in flue gas is absorbed by a continuously supplied fine DeSOx sorbent and NOx is reduced to N2 by ammonia under the catalysis of a coarse DeNOx catalyst, the fluidization medium particles (FMP). Experiments were conducted in a laboratory-scale PPFB reactor by using model flue gases containing SO2 and NO. It was found that the sodium carbonate supported by fine alumina particles (Na2CO3/Al2O3) had not only a high efficiency in absorbing SO2 but also little negative effect upon the simultaneous NOx reduction of the process. Using a DeNOx catalyst, such as V2O5·WO3/TiO2 or WO3/TiO2, to catalyze the DeNOx reactions, high SO2 absorption and NO reduction in excess of 95% were achieved for model gases free of CO2 at stoichiometric ratios of SO2 to sorbent (Na/S = 2.0) and NH3 to NO (NH3/NO = 1). As for the simulated flue gas SO2−NO−H2O−N2−air with an oxygen fraction of 2 vol % and a water vapor fraction of 5 vol %, such high removals of SO2 and NO were found available even in a shallow PPFB with a static catalyst packing height of 0.1 m. By using silica sand as FMP, the pure SO2 absorption by the sorbent Na2CO3/Al2O3 was also examined with respect to various influential factors, such as reaction temperature (523−673 K), flue gas composition (oxygen fraction and water vapor fraction), sorbent diameter, and operating conditions (gas velocity and FMP bed height).