Characterization of unburned carbon from ash after bituminous coal and lignite combustion in CFBs

This paper deals with the characterisation of carbon (UC) from bottom ash (BA) and fly ash (FA) samples from two fluidised-bed power stations burning bituminous coal and lignite. The laboratory results for the carbon determinations and its mass balances are evaluated. Chemical and mineral analyses and textural characteristics (specific surface area and pore-size distribution) are presented. Depletion/enrichment of selected elements (S, Cl, V, Cr, Ni, Cu, Zn, As, Se, Sb, Hg, and Pb) in carbon from the bottom ash are compared with both ash compostions. The strong positive relationships between the concentrations of some trace element contents (Hg, Se, As, Cu, Ni, V and Cl) in fly ash with the content of carbon and the specific surface area of FA are presented and expressed by regression equations with very high correlation coefficients. Laser ablation-ICP–MS has been used to obtain an insight into element distributions within carbon grains from the bottom ash.