Size Distribution of Fine Particle Emissions from a Steam Plant with a Fluidized-Bed Coal Combustor

Abstract

The size distribution of fly ash emitted from an atmospheric fluidized-bed coal combustor (AFBC) with a 20- m² cross-section bed equipped with cyclones and a baghouse system to control the particulate emission is described. The Georgetown AFBC was designed to produce a maximum of 100,000 pounds/h of saturated steam at 275 or 625 psig to support space heating and to supply hot water to the university. A 2-cyclone dust collector was used to remove large fly ash particles from the effluent stream, and a baghouse system was used for fine control of the particulate emissions before discharging to the atmosphere. The fly ash concentration and size distribution before and after the baghouse dust control system were measured, and the collection efficiency of the baghouse system was determined. A bimodal size distribution of fly ash was observed. The mass fraction of submicron particles was 4.3% before the baghouse and increased to 18% at the stack because the collection efficiency of the baghouse was size dependent. The high collection efficiency (99.98%) of the newly installed baghouse removed most of the fly ash; therefore, the emission factor for particles was below the new source performance standards required by the EPA. Comparison of fly ash size distributions obtained in several fluid-bed coal combustors are discussed.