Hot and Warm Gas Cleanup

The major sorbents reported for high or mild temperature desulfurization of the raw syngas are the solid metal oxides. Metal oxides, such as ZnO, MnO, Zn Ti O, Cu-Zn I i O, Co Fc O, Ce02, and La203, have been reported to remove H2S from nature gas, reformate, and other gas mixtures.4 113 174 178 180 The process is based on the reaction of the metal oxides with H2S to form metal sulfides. For ZnO sorbent, the reaction is shown below  

The regeneration of the spent sorbent is based on the oxidation reaction of the metal sulfide  

The low temperature is thermodynamically favored. However, since the reaction rate is low at low temperature, the process usually prefers to conduct at higher temperature in the practical application to increase the reaction rate. A review in the gas desulfurizaton sorbents is made in Section 5.4. The major problems in high or mild temperature desulfurization sorbents and processes are summarized below  

Consequently, none of the proposed sorbent materials have become commercially viable.203 No any hot or warm gas desulfurization process has been demonstrated.180 The only two large-scale hot gas desulfurization systems installed in the U.S. (both in DOE CCT IGCC demonstration projects), but have never been dem- 

The ODS of hydrocarbon fuels consists of the conversion of sulfur compounds in the fuels by oxidation to element sulfur, sulfur oxides, sulfoxides, and/or sulfones followed by adsorption or abstraction separation of the oxidized sulfur compounds from the hydrocarbon fuels. The potential advantages for ODS are (a) the process does not need to use H2 gas (b) ODS takes place at relatively mild operating conditions in comparison with HDS or even at ambient conditions and (c) ODS is able to remove some refractory sulfur compounds, such as 4,6-DMDBT, that are difficult to be removed by HDS or selective adsorption. 

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