Study on mechanisms of aerosol formation in wet ammonia-based desulfurization process

Abstract

A simulation ammonia wet flue gas desulfurization (WFGD) platform was built to simulate separately the two different aerosol formation mechanisms in ammonia WFGD process of inhomogeneous reaction and entrainment. The aerosol concentration and size distribution along with the morphology features and the chemical composition were tested and investigated with the electrical low-pressure impactor (ELPI), the pollutant PM sampler, the field emission scanning electron microscope (FESEM), and the aerosol mass spectrometer (AMS). The comparison was made of the numerical concentration size distribution of aerosols generated under the two different formation mechanisms and the typical ammonia WFGD process. The results showed that the inhomogeneous reaction mechanism is the dominating one of the two in ammonia WFGD, which produced the majority of the aerosols emitted from the scrubber, the most of which, if counted in numerical concentration, were submicron particles with the chemical ingredients consisting mainly of sulfates and ammonium and the size distribution based on numerical concentration being a bimodal one. While the entrainment mechanism had minor influences on aerosol formation in the ammonia WFGD, the aerosols generated under this mechanism were much larger than those generated under the inhomogeneous reaction. Great differences were found between the aerosols formed under the two mechanisms.