Kinetics of high-pressure removal of hydrogen sulfide using calcium oxide powder

Sulfidation reaction of CaO at high pressure (up to 2 MPa) and high tempera ture (up to 900 degrees C) to remove H2S in a coal-fired gasifier was studi ed in a high-pressure and temperature differential-bed flow-through reactor . Experimental conditions selected are typical for pressurized gasifiers. E ffects of total pressure, H2S partial pressure, reaction temperature, fuel gas composition, and CaO surface ar ea on the extent of sulfur capture and sor bent conversions were determined The gasifier pressure affected the in- situ calcination of calcium carbonate particles through reduction in availa ble surface area and pore volume of CaO formed thus limiting the sulfidatio n conversion. Time-resolved conversion data of CaO sulfidation were analyze d using a modified grain model. The model incorporates external and interna l diffusion, surface reaction product layer diffusion, and the structural c hanges of the sulfiding CaO particle. The activation energy for the reactio n was 37 kcal/mol. The estimated product layer diffusivity was 8 X 10(-15) m(2)/s at 800 degrees C with an associated activation energy of 38.4 kcal/m ol- typical of solid state diffusion of ionic species through the product: layer: The extent of conversion increased with increasing initial surface a rea and porosity of CaO particles. The high-pressure sulfidation reaction d ata for CaO will be useful in understanding and optimizing the in-gasifier H2S capture using calcium-based sorbents.