Investigation on minerals migration during co-firing of different straw/coal blending ratios

Highlights: • The blending ratios of coal/straw caused inhibited or promoted ash quantity effects. • The chlorine element had great influence on ash quantity and ash components. • The minerals coupling reaction was verified by the newborn stable compounds. • The 40 wt.% coal-blending ratio was significant in the prevention of slagging and corrosion. - Abstract: A set of experiments on biomass/coal co-combustion were performed to investigate the ashing behavior in a tube furnace and a Muffle furnace respectively. The eight blending samples in terms of coal contents were 0, 5, 15, 20, 40, 60, 90, and 100 wt.%. The blending ratios of coal/straw caused different ash quantity effects, ash quantity was inhibited when the coal ratio was from 5 wt.% to 15 wt.%, and promoted when higher coal ratios. Combined the morphology analysis, mineral analysis, and chlorine equilibrium analysis, the chlorine content in the drop-tube furnace ash rapidly decreased when the coal ratio was from 5 wt.% to 15 wt.%, and the Cl content of the fly ash from 40 wt.% coal blend was very low at 0.49%. In the ash from the 40 wt.% coal blend, the CaCO3 and CaSO4 contents were very low for coupling reaction between the biomass and coal minerals under high temperature, the new and stable CaAl2Si2O8, K2Fe4Si12O30, and KAlSi3O8 minerals were produced, which accompanied the ash promotion effect. The ashing behavior of 40 wt.% coal-blending is largely significant in preventing slagging and corrosion during straw co-firing and coal plant operation