Comparison of calcium-based sorbents for coal gas desulfurization
Book
·
OSTI ID:257037
- Lawrence Berkeley Lab., CA (United States)
H{sub 2}S sorption by small (0.4 mm) particles of three different calcium-based sorbents (limestone, dolomitic limestone and dolomite) was tested under simulated coal gas in a differential tube reactor. Two fundamentally different behaviors were observed. Above the calcination temperature of CaCO{sub 3}, T {sub c}, complete conversion of CaCO{sub 3} to CaS can be achieved with all three sorbents; the reaction rate increases as the Mg/Ca ratio increases in the sorbent and the reaction rate is controlled by the diffusion of H{sub 2}S through the CaS product layer and (near T{sub c}) by the kinetics of the calcination of CaCO{sub 3} to CaO. However, below T{sub c} (about 900 C under 1 bar of CO{sub 2}), only about 10% of the CaCO{sub 3} in limestone can be converted to CaS compared to 100% in dolomite. Dolomitic limestone is found to consist of regions of nearly pure dolomite (MgCO{sub 3}{center_dot}CaCO{sub 3}) interspersed with regions of nearly pure calcite (CaCO{sub 3}). During sulfidation, all of the calcium atoms associated with the dolomite regions can be converted to CaS whereas only about 20% of those associated with the calcite can be converted. Above 710 C, the sulfidation rate of dolomite and dolomitic limestone is controlled by the diffusion of H{sub 2}S through the product layer. Below 710 C, both the rate of the calcination of MgCO{sub 3} and the rate of the reaction between CaCO{sub 3} and H{sub 2}S limit the overall reaction kinetics.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 257037
- Report Number(s):
- CONF-950952--
- Country of Publication:
- United States
- Language:
- English
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