Investigation on the relationship between slurry droplet entrainment and fine particle emission in the limestone-gypsum WFGD system

Abstract

ABSTRACTThe entrainment of desulfurization slurry droplets out of the scrubber had a significant influence on the properties of fine particle emissions in the limestone-gypsum desulfurization system. Investigations on the relationship between entrainment of slurry droplets and generation of fine particles during the desulfurization process were carried out with an experimental system. The results showed that a large number of fine droplets and submicron particles existed in the flue gas out of the scrubber, which was attributed to the entrainment of slurry droplets during the desulfurization process. The entrained droplet sizes were closely connected with the slurry atomization characteristics, and majority of them were with sizes less than 20 μm. The mass ratio of solid contents in entrained and sprayed droplets ranged from 15% to 40%, and particles in the entrained droplets were much smaller. With the increase of superficial gas velocity, liquid–gas ratio, and desulfurization slurry concentration, the proportion of entrained micron droplets was significantly higher. Correspondingly, more fine particles were emitted with increased rates of number concentrations ranging from 20% to 50%. The optimizations of spray scrubber were beneficial for the reduction of entrained droplets and fine particles such as the adjustment of nozzle arrangement and the addition of spray layer. The decrease rate of emitted fine particle concentrations ranged from 10% to 30%.