High-temperature desulfurization of coal-fired fuel gases is an essential process in emerging power generation technologies, such as the Integrated Gasification Combined Cycle (IGCC), aiming to improve both the efficiency and environmental performance of power generation from coal. Hot gas desulfurization may be accomplished by using solid sorbents such as oxides of those metals that form stable sulfides. The effectiveness of a desulfurizing sorbent in treating such gases is related to the predicted equilibrium partial pressure of hydrogen sulfide (H2S), which will be present in a combination of the reduced form of the sulfide and oxide phases. The external desulfurization approach consists of passing the hot fuel gases through beds of regenerable sorbents. These sorbents are invariably oxides, which are converted to sulfides during a sulfur loading stage under reducing hot fuel gas conditions and then regenerated by oxidation of the sulfides to oxides and a by-product stream of sulfur dioxide (SO2). Regeneration is crucial to the commercial acceptance of external sorbents since they are often made from relatively expensive materials.
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