KINETIC AND STRUCTURAL STUDIES OF CALCIUM-BASED SORBENTS FOR HIGH-TEMPERATURE COAL-GAS DESULFURIZATION

摘要

The absorption of H_2S by large particles of limestone, dolomitic limestone and dolomite (average mass-radius of 0.40 mm) was tested under simulated coal gases. Below the calcination temperature of CaCO_3 (about 900℃ under 1 bar of CO_2), complete conversion of the calcium carbonate to calcium sulfide can only be achieved with dolomite. Above the calcination temperature of CaCO_3, the conversion to CaS is complete for all three sorbents in about one hour when 10,000 ppm H_2S is present in the gas phase. Large panicles of limestone thus appear to be a suitable sorbent for high-temperature coal-gas desulfurization (above about 900℃). A mathematical model based on the kinetic information collected in this work predicts the desulfurization performance of a packed or moving bed of limestone particles. Finally, a low-temperature regeneration scheme for the spent sorbent (CaS) in which sulfur can be subsequently recovered as the element is suggested.