High temperature gas desulfurization with elemental sulfur production

Abstract

Preliminary results on the use of cerium oxide as a high-temperature desulfurization sorbent are presented. The primary advantage of cerium over current zinc-based sorbents is the potential to produce elemental sulfur during the regeneration phase of the process. Although CeO 2 is less effective for H 2S removal during sulfidation, the sulfided product, Ce 2O 2S, will react with SO 2 to produce elemental sulfur directly. Rapid and complete regeneration is possible over the range of 500 to 700°C, and only elemental sulfur is formed. Elemental sulfur concentrations (considered as S 2) as large as 20 mol% have been produced in the regeneration product. The sorbent has been subjected to ten sulfidation–regeneration cycles using a laboratory-scale fixed-bed reactor with negligible activity loss. Effectively complete conversion of CeO 2 to Ce 2O 2S during sulfidation and subsequent regeneration to CeO 2 was achieved in each cycle. A two-stage desulfurization process using CeO 2 for bulk H 2S removal followed by a zinc sorbent polishing step has been proposed to meet specifications of the integrated gasification combined cycle (IGCC) process. Economic comparison with a single-stage desulfurization process using zinc sorbent followed by elemental sulfur recovery using the direct sulfur recovery process (DSRP) shows that the two-stage cerium process may be less costly if the cerium sorbent is sufficiently durable.