Experimental and modeling studies of SO 3 homogeneous formation in the post-flame region

Abstract

SO 3 exists in the atmosphere in the form of sulfuric acid aerosol, heavily polluting the environment and decreasing the safety of boiler equipment. This study focuses on the homogeneous formation mechanism of SO 3 in the post-flame region. We conducted experiments and simulations to investigate the influence of various combustion parameters on SO 3 generation. The formation of SO 3 was affected by factors such as temperature and the concentrations of O 2 , SO 2 , NO, and H 2 O. With a rise in temperature, the SO 3 concentration initially increased but then decreased, reaching its maximum at about 1000°C, which indicates that SO 2 can promote the formation of SO 3 over a certain temperature range. An increase in the O 2 concentration promoted the formation of O and OH radicals, which enhanced the generation of SO 3 from SO 2 . The presence of NO resulted in direct and indirect interactions between NO x and SO x species for different reaction sets, potentially enhancing SO 3 generation. With an increase in the H 2 O concentration, SO 3 formation initially increased rapidly before plateauing. ROP (rate of production) and sensitivity analyses suggest that adding H 2 O will produce O and OH, which strongly influence SO 3 formation. Furthermore, the sensitivity analysis indicated that radicals and the direct reaction between SO 2 and NO 2 play significant roles in SO 3 formation.