Characterization of Ash Deposition During Co-Combustion of Coal With Refuse-Derived Fuels in a Pilot FBC Facility

This paper presents data from a recent investigation of the character of ash deposition in the convective zone (547°C to 338°C) in a 0.1 MW_th bench-scale FBC system at Western Kentucky University. The ash deposit samples were collected during co-firing experiments using two coals with various blends of a refuse-derived fuel (RDF). A low sulfur coal, a high sulfur coal, and commercially available RDF sample were selected to investigate the influence of sulfur and chlorine in the fuels on the formation of ash deposits. Limestone was added to the combustor as the bed material and desulfurization sorbent. The results showed that the formation of ash deposits had a close relationship to the active fine lime particles produced from the limestone. An increase in the concentration of SO_x in the flue gas restricts the formation of the ash deposits because of the reaction between SO_x and the fine lime particles, which drops the adhesive force of the fine lime particles by reducing the contact area among the particles. With an increase in the content of the RDF in the fuels, the rate of deposit of ash decreased because of the higher content of chlorine and aluminum, which also decreased the contact area among the particles, leading to a low deposition rate of the fly ash.