The state of sodium and potassium in the pressurized fluidized-bed combustion and gasification of peat

Multicomponent multiphase equilibrium calculations were carried out for pressurized fluidized-bed combustion and gasification conditions to determine the relative distribution of the alkali methals (sodium and potassium) in the gas and condensed phases. The dependence of alkali volatilization on operating temperature, pressure, total alkali content and chlorine content of the feedstock was studied. Alkali release in the vapour phase may be much higher than is acceptable to a gas turbine, especially in gasification conditions. Therefore the need to remove the volatilized alkali metal compounds is more acute in gasification than in combustion. The results are also compared with the measured alkali content of the effluent stream of a pressurized fluidized-bed combustor.