The Regeneration of High Temperature Sulfur Dioxide Sorbents: the CO Reduction of Supported Alkali Sulfates

The chemical reactions involved in the regeneration step of a high temperature SO2 removal process have been investigated. In particular, the CO reduction of supported alkali sulfates has been studied. Thermogravimetric measurements have yielded the time-resolved composition of sorbent and gaseous products during reduction with 10% CO at 700 and 800°C. FTIR was used to identify reaction intermediates . A flow microreactor was used to compare gaseous product selectivity between SO2, COS and elemental sulfur of sorbents reduced with 1 and 10% CO at 700 and 800°C. The experimental results show regeneration; i.e., sulfur removal is greatly increased by the presence of lithium in the sorbent material. Reaction between the support and the alkali material greatly influences the degree of regeneration. Support materials are apparently active in the catalysis of the reduction of SO2 to elemental sulfur and the reaction between elemental sulfur and CO to form COS, and therefore, influences the product selectivity. A reaction scheme which qualitatively explains the experimental results is proposed.