Structural studies in limestone sulfidation

Study of Calcium-Based Sorbents for High-Temperature H2S Removal. 1. Kinetics of H2S Sorption by Uncalcined Limestone

“…Morphological Study. SEM pictures of the external surface of the particles reveal the same "smoothness" previously observed in the pictures of sintered CaS powder (Fenouil, 1992). The original limestone-particle surface has lost most of its sharp angles.…”

“…A close correlation between the color, or rather the tone of gray, and the chemical composition of the samples was demonstrated earlier (Fenouil, 1992). A white spot coincides with an area containing at least 1% sulfur atoms: a lighter tone of gray corresponds to a zone very rich in CaS, whereas the darkest gray is associated with the original calcium carbonate.…”

“…The internal surface of the faults appears very smooth. These kinds of fractures have been observed in several different sulfided samples, whereas they were never seen to this extent in fresh limestone samples that were simply heated to the same temperature under an inert atmosphere (Fenouil, 1992).…”

“…The rest of the gas phase was CO2 (87.5%), CO (4.6%), H20 (4.6%), and H2 (1.5%)). The CO2 fraction in the gas feed was kept very high so that the variations of the reactor temperature would have minimal influence on the gas-phase composition over the limestone samples after thermodynamic equilibrium was reached (Fenouil, 1992). As mentioned above, each point in Figure 3 is the average of four to six experiments.…”

“…Ultimately, as the sintering is completed, the CaS surface would become flat again, with a thickness of ho/2. The sharp-edged cubic shape of the partially sintered crystals does not provide a very realistic description of the actual shape of the CaS surface, which quickly loses its sharp features (Fenouil, 1992). However, it approximates the surface area evolution while sintering is occurring.…”