Formation of Sodium Carbonate Sulfate Double Salts from Solid CaSO4 and Na2CO3

摘要

Fluidized bed combustion is a clean combustion technology for coal and other solid fuels. In fluidized bed combustors limestones are used as sorbent to capture SO2 in situ, via the following reactions: CaCO3 = CaO + CO2 (1) CaO + SO2 + ? O2 = CaSO4 (2) This process eliminates the need for costly flue gas desulfurization downstream of the boiler. Unfortunately, utilization of the limestones is low, typically below 40% of their CaO content. The low utilization is believed to be due to a sulfate shell formed on the sorbent particles. The shell is more compact than the porous CaO because of the larger molar volume of calcium sulfate [46 cm~3/(mol CaSO4) vs.17 cm~3/(mol CaO)] and retards mass transfer of reactants.