Development and Characterization of Steam Regenerable Sorbents for Hot Gas Desulphurization in Coal Gasification Based Combined Cycle Plant

Abstract

A process and sorbents have been developed for the desulphurization of coal gases at temperatures above 350°C. Characteristic features of these sorbents are the utilization of the reversible gas solid reaction

$$ {\text{H}}_{\text{2}} {\text{ + H}}_{\text{2}} {\text{S + SnO}}_{\text{2}} {\text{ = 2H}}_{\text{2}} {\text{O + SnS}} $$

which has an equilibrium constant close to 400 at 400°C. A low sulphur emission can be achieved when using tin-sorbents for the cleaning of coal gases. As the reaction is reversible, steam can be used to oxidize SnS back to SnO₂ and this is typically done at 450°C to 500°C.

The sorbents have been examined for other possible reactions in the coal gas. Whereas the sorbents have high catalytic activity for carbonyl sulphide conversion, they have a vanishing catalytic activity for the water gas shift reaction and the hydrocarbon synthesis reaction.

With respect to mechanical properties, repeated sulphidation and regeneration in steam have not resulted in deterioration of strength or mechanical breakdown.

Application of sorbent based upon tin dioxide in IGCC (Integrated Gasification Combined Cycle) plants along with other units processes needed in a hot gas cleaning train result in an improvement of the thermal efficiency by several percent compared to systems based upon wet scrubbers.