Oxidation of sulfided limestone under the conditions of pressurized fluidized bed combustion

During coal gasification, the removal of H2S from the hot product gases usi ng limestone generates calcium sulfide, a potentially hazardous chemical re quiring treatment before disposal. One approach is to convert the CaS to Ca SO4 via oxidation in a topping cycle pressurized fluidized bed combustion. In this work, the oxidation behavior of sulfided limestone particles was ex amined under the conditions of pressurized fluidized bed combustion using a pressurized thermogravimetric analyzer. Experiments were conducted ensurin g that the partial pressure of CO2 in the reaction gas mixtures exceeded th e equilibrium pressure for CaCO3 calcination. The effects of total pressure , O-2 partial pressure and temperature were examined to determine their inf luence on the conversion of CaS to CaSO4 and on the amount of CaCO3 formed during the oxidation process. The total pressure was shown to have only a r elatively weak influence on the degree of conversion to sulfate, in spite o f the fact that the conversion of CaS to CaSO4 increased to a certain exten t with increasing pressure at a constant oxygen volume fraction. However, o ver the 0.1-2.0 MPa range, temperature had a strong influence on the CaS ox idation, its effect being more pronounced at lower pressures. Furthermore, the reaction of CaS with CO2 occurred above 550 degreesC and the solid prod uct was primarily CaCO3. (C) 2001 Elsevier Science Ltd. All rights reserved .