Critical review of predictive coefficients for biomass ash deposition tendency

Abstract

Energy production by solid biofuel combustion is the most commonly used biomass-to-energy technology. Nevertheless, the ash generated from the combustion process leads to problematic phenomena. Depending on the origin and chemical characteristics of the biomass used, the combustion technology and conditions, and the melting temperature of the ash, there may be considerable sinter and slag formation during biomass combustion. A great number of coefficients developed for coal ash have been applied to approximately predict the slagging and fouling tendencies of biomass ash. However, because biomass composition is significantly different from that of coal, such formulas are not accurate when applied to the prediction of a biomass ash melting point.This paper presents an overview of indices or coefficients commonly used in the literature to predict biomass slagging and fouling tendencies in order to compare them and apply them to several types of biomass having different origins. The results show no relationship or predictive trend among the existing indices when applied to biomass fuels. Indeed, the contradictory findings come to demonstrate that further research and experimental tests under real conditions are needed to create or validate any of these indices. These coefficients should base on results from real combustion experiences, considering the influence of the combustion conditions and technologies, the heterogeneity of solid biomass fuels, and their physicochemical characterization.