Initial layer-induced slagging characteristics of a biomass-fired grate boiler: A combined experimental and simulation study

Abstract

The higher alkali contents in the biomass lead to condensation occurring on the heating surfaces, which form an initial layer and induces severe slagging in biomass-fired boiler. To clarify the slagging mechanism and carry out further simulation prediction, the initial layer-induced slagging characteristics of a biomass-fired grate boiler have been investigated. The analysis was performed based on the collected slagging samples, and the melting adhesion characteristics of the initial layer have been calculated by thermodynamic equilibrium calculation. The results show that the viscous capture of initial layer formed by K condensation, and the molten ash adhesion constitute the slagging mechanism in high-temperature superheater. While viscous deposition weakens the effect of flue gas velocity on deposition distribution and promotes the deposition of large particle. K/Ca sulfate condensation and non-molten fly ash inertial deposition dominates the slagging in medium-temperature superheater. More serious slagging in the high-temperature superheater and the NH₄Cl found in the tail flue indicates that the influence of boiler power rating and parameters, fuel characteristics and soil impurities on slagging cannot be ignored. This study can provide a basis for the prediction of initial layer-induced slagging of biomass-fired grate boiler.