Influence of calcareous sorbents on particulate emissions from fluidized bed combustion of lignite

Abstract

The composition and morphology of coarse and fine fly ashes from atmospheric fluidized bed combustion of 2 lignites without additives or with hydrated lime and limestone as sorbents for sulfur dioxide removal were investigated. The ashes were separated and size segregated by cyclone and low pressure BLPI impactor. The properties of both coarse (sizes > 10 μm) and fine (sizes < 10 μm) particles were investigated using INAA, PIXE, and SEM. The application of sorbents increased the emissions of coarse particles, but reduced the emissions of fine particles. The increase was caused by additional carry over of particles of additives; the decrease of emission of fine particles probably resulted from the combined increase of scavenging of fine particles by particles of sorbents and reduction of their formation due to reduced concentrations of sulfur dioxide in flue gas. Most of the trace elements investigated in this study showed substantial enrichment in fine particles. However, due to simultaneous reduction of concentration of fine particles the emissions of most trace elements decreased.