Modeling and Evaluation of Ash-Forming Element Fate and Occurrence in Woody Biomass Combustion in an Entrained-Flow Burner

Biomass combustion equipment is often susceptibleto ash deposition due to the relatively significant quantities ofpotassium, silicon, and other ash-forming elements in biomass. Toevaluate the propensity for ash deposition resulting from biomasscombustion, a biomass combustion model was integrated with achemical equilibrium model to predict the fate and occurrence ofash-forming elements in a pilot-scale entrained-flow burner. Theintegrated model simulated the combustion of white wood (virginwood) and recycled wood (treated wood) previously combusted inthe burner. The key advantage of this model in comparison to amodel with general equilibrium assumed is that it was able toconsider the rate of release of trace and minor species with time,the local equilibrium in the particles, and separately, that in thecontinuum phase (which also included any solid or liquid materials nucleating). The simulation generated the fate and occurrenceprofiles of each ash-forming element along the burner. The qualitative comparisons between the modeled profiles and the previousexperimentalfindings under similar operating conditions show reasonable agreement. The concentrations of ash-forming elementsreleased from the burner were also compared with the experimental online inductively coupled plasma readings. However, the lattercomparison shows overestimation using the modeled results and might suggest that further considerations of other parameters suchas ash nucleation and coagulation are required. Nonetheless, based on the ongoing performance of the integrated model, future useof the model might be expanded to a broader range of problematic solid fuels such as herbaceous biomass or municipal solid waste.