Results on the cyclic calcination and recarbonation of calcined dolomite at atmospheric pressure and at 300 psig are presented. The effects of various reaction parameters (i.e., temperature, pressure, and gas composition) on the recarbonation rate and on the change in solid reactivity with cycling were explored. Addition of steam to the recarbonation atmosphere resulted in nearly a two order of magnitude increase in the recarbonation rate. Increasing the temperature and the partial pressure of carbon dioxide for calcination gave lower recarbonation rates and accelerated the loss of solid reactivity with cycling. Reactivation by subsequent calcination in nitrogen was demonstrated.

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w Kinetic data are given for the first time for reaction of half-calcined dolomite with H2S (55O-80O0C, 0.005-0.2 atm of H2S in gas at 1 atm). The reaction can be used to remove H2S from a fuel gas made by gasifying coal with air and steam at high pressure. Gas at 20 atm from a dilute-phase slagging gasifier can be desulfurized in an operation at about 920°C to reduce the SO2 emission from power generation to roughly that expected from coal containing 0.15 sulfur. Gas at 20 atm from an ash-agglomerating fluidized-bed gasifier can be desulfurized to an even greater extent in an operation at about 760°C. In light of data given here for 700" and 8OO"C, the reaction can be expected to proceed to completion under these conditions at a faster rate than that atforded by the reaction of fully calcined dolomite, reported earlier. Data at lower temperatures reveal kinetic curiosities which may prove important to understanding of the reverse reaction, useful in regenerating half-calcined dolomite and releasing H,S.quires (1967, 1968) proposed half-calcined dolomite as

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