High temperature gas desulfurization with elemental sulfur production

摘要

Preliminary results on the use of cerium oxide as a high-temperature desulfurization sorbent are pressented.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 degC,and only elemental sulfur is formed.Elemental sulfur concentrations(considered as S_2)as large as 20mol% have been droduced 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 ineach cycle.A two-stage desulfurization process using CeO_2 for bulk H_2S removal followed by a zinc sorben polishing step has been proposed to meet specifications of the integrated gasification combined cycle(IGCC) process.Economic comparison with a single-stage dusulfurization 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.