Performance evaluation of biomass pretreated by demineralization and torrefaction for ash deposition and PM emissions in the combustion experiments

•Combustion characteristics of EFB and PKS pretreated by demineralization and torrefaction were investigated.•Torrefaction pretreatment lowered the char combustion reactivity.•Torrefaction pretreatment accelerated the ash deposition and PM emissions.•Demineralization pretreatment significantly reduced the ash deposition and PM emissions.