Combustion of biomass or coal is known to yield aerosols and condensed alkali minerals that affect boiler heat transfer performance.In this work,alkali behavior in the pressurized oxyfuel co-combustion of coal and biomass is predicted by thermodynamic and chemical kinetic calculations.Existence of solid minerals is evaluated by X-ray diffraction (XRD) analysis of ashes from pressure thermogravimetric combustion.Results indicate that a rise in pressure affects solid alkali minerals negligibly,but increases their contents in the liquid phase and decreases them in the gas phase,especially below 900 ℃.Thus,less KCl will condense on the boiler heat transfer surfaces leading to reduced corrosion.Increasing the blend ratio of biomass to coal will raise the content of potassium-based minerals but reduce the sodium-based ones.The alkali-associated slagging in the boiler can be minimized by the synergistic effect of co-combustion of sulphur-rich coal and potassium-rich biomass,forming stable solid K2SO4 at typical fluidized bed combustion temperatures.Kinetics modelling based on reaction mechanisms shows that oxidation of SO2 to SO3 plays a major role in K2SO4 formation but that the contribution of this oxidation decreases with increase in pressure.