An adaptive sorbent for the combined desulfurization/denitration process using a powder-particle fluidized bed

This study is devoted to examining an adaptive sorbent for the combined desulfurization/denitration (DeSO x /DeNO x ) 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 SO x in flue gas is absorbed by a continuously supplied fine DeSO x sorbent and NO x is reduced to N 2 by ammonia under the catalysis of a coarse DeNO x catalyst, the fluidization medium particles (FMP). Experiments were conducted in a laboratory-scale PPFB reactor by using model flue gases containing SO 2 and NO. It was found that the sodium carbonate supported by fine alumina particles (Na 2 CO 3 /Al 2 O 3 ) had not only a high efficiency in absorbing SO 2 but also little negative effect upon the simultaneous NO x reduction of the process. Using a DeNO x catalyst, such as V 2 O 5 .WO 3 /TiO 2 or WO 3 /TiO 2 , to catalyze the DeNO x reactions, high SO 2 absorption and NO reduction in excess of 95% were achieved for model gases free of CO 2 at stoichiometric ratios of SO 2 to sorbent (Na/S=2.0) and NH 3 to NO (NH3/NO=1). As for the simulated flue gas SO 2 -NO-H 2 O-N 2 -air with an oxygen fraction of 2 vol% and a water vapor fraction of 5 vol%, such high removals of SO 2 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 SO 2 absorption by the sorbent Na 2 CO 3 /Al 2 O 3 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).