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Combustion of biofuel mixtures for heat and power production is often combined with ash related operational problems. Their reliable prediction is therefore essential in order to improve boiler performance and availability. In this work, an ash behavior prediction tool based on computational fluid dynamics and advanced fuel analysis is used to predict the ash deposition tendencies in a 295 MW_th bubbling fluidized bed boiler fired with mixtures of peat and forest residue. The work focuses especially on two new modeling approaches for fuel distribution and bubbling bed. The overall combustion and deposition prediction results agree well with conditions in a real boiler.