Dry gas cleaning in coal gasification systems for fuel cells using composite sorbents

Abstract

Composite sorbents, for the simultaneous removal of sulfur compounds and alkali and heavy metals from coal gasifier products in an integrated gasification fuel cell (IGFC) system, were prepared. Iron oxide and zinc ferrite were selected as desulfurization sorbents and they were synthesized by precipitation from either ferric chloride, ferric nitride, or ferric and zinc nitride solution. In these solutions, fine oxide particles such as kaolinite, sepiolite, and activated clay, which have the capability of alkali and heavy metal absorption, were dispersed. These oxide particles effectively increased the surface area of synthesized iron oxide and zinc ferrite composite particles. In addition, they are expected to avoid the sintering or coking of the sorbents in the desulfurization and regeneration processes. Desulfurization tests were performed in a tube furnace by streaming a model gas containing H 2S. The desulfurization performance improved considerably in the case of composite sorbents with a high specific surface area. The desulfurization capacity and crystalline phases before and after desulfurization depended on the type of the oxide particle. The desulfurization rate of a composite sorbent was characterized accurately by the specific surface area.