Sorbent materials for removing pollutants from gases in a fluidized bed combustor

摘要

Emissions of both sulfur and nitrogen oxides can be reduced adding sorbents in a fluidized bed combustion. Feeding limestone (CaCO{sub}3) or dolomite (CaMg(CO{sub}3){sub}2 as sorbents it is likely to achieve the task of reducing pollutants from the combustion gases. In order to understand the phenomena occurring in the combustor we developed a thermodynamic analysis for the chemical equilibrium and compared it with the literature when it was possible. The thermodynamic properties such as standard heat of formation (ΔH°{sub}f) and the standard Gibbs free energy of formation (ΔG°{sub}f) of several chemical compounds were calculated at temperatures between 298.15 and 1273 K. The thermodynamic analysis was done regarding non-ideal system take into account Peng-Robinson equation of state (or virial equation) for representing vapor phase. Both of them showed the same results for equilibrium composition. There was no influence of the system pressure in the results working in atmospheric pressure and under 20 atm. We concluded that: the capture of SO{sub}2 in the fluidized bed by dolomite and limestone is most likely by direct formation of calcium sulfate. In the conditions considered in this study (1 atm, 850 °C) nitrogen oxides do not react with any sorbent materials. The addition of MgO did not contribute to the decreasing of SO{sub}2 in the atmospheric bed combustor. Finally, the disagreements in the literature can be ended.