Hot coal-gas desulfurization with calcium-based sorbents in a pressurized moving-bed reactor

The performance of a pressurized moving bed on hot coal-gas desulfurization was analyzed for the countercurrent and cocurrent configurations. The behavior of several calcium-based sorbents, two limestones, and a dolomite was determined at temperatures in the range of 1073-1273 K and a pressure of 1 MPa. The limestones were used only under calcining conditions, whereas the dolomite was used under both calcining and noncalcining conditions. The desulfurization level and sorbent conversion, as well as the longitudinal H2S concentration profiles in the transference zone, were determined as a function of the main design and operating variables, including the Ca/S molar ratio, the bed height, the type of flow configuration (countercurrent or cocurrent), the temperature, the H2S concentration, and the particle size. The length of the transference zone, and then the reactor length necessary for full desulfurization, was highly dependent on the particle size and the solids velocity. In both countercurrent and cocurrent configurations, it was possible to reach high desulfurization levels with a H2S concentration at the gas outlet that were similar to the thermodynamic equilibrium. However, the countercurrent configuration was always more effective for desulfurization than the cocurrent configuration, and smaller reactors were necessary in the first case. The mathematical model developed to predict the experimental results obtained at small scale was used for design considerations of desulfurization reactors that use moving beds of calcium-based sorbents.