The prediction of behaviour of ashes from five different solid fuels in fluidised bed combustion

The behavior of different ashes was predicted by the combination of extended fuel anal. with advanced global thermodn. equil. calcns.  The extended fuel anal. is a fractionation method that consists of sequential leaching of a solid fuel with water, ammonium acetate and hydrochloric acid.  In order to cover a broad spectrum of fuels a coal, a peat, a forest residue and Salix (i.e. willow) were studied.  The last was taken with and without soil contamination, i.e. with a high and low content of silica, resp.  Results from the fractionation showed clear differences in mineral distribution in the fuels.  More ash-​forming elements were present as included minerals in the older fuels.  In relatively young fuels, almost half of the inorg. material was found in the sol. fractions after leaching with water and ammonium acetate.  Fouling and slagging predictions based on the combined use of the extended fuel anal. and the advanced global equil. anal. indicated that no ash-​related problems should be expected in FBC boilers firing the studied coal.  The peat that was studied could cause minor ash depositions in the flue gas channel at temps. above 700°C.  The studied forest residue could form fly ash deposits in the flue gas channel at temps. between 600 and 860°C.  The Salix could cause fly ash depositions at temps. between 840 and approx. 1000°C.  If soil contamination was present as well, Salix could cause bed sintering at temps. above 1030°C.