Investigation of Combined S02/N0x Removal by Ceria Sorbents

Simultaneous removal of S02 and NOX using a regenerable solid sorbent will constitute an important improvement over the use of separate processes for the removal of these two pollutants from stack gases and possibly eliminate several shortcomings of the individual S02 and NOX removal operations. Recent studies at PETC considered cerium oxide as an alternate sorbent to CUO. The present study aims to determine the effects of ammonia on ihe sulfation of the sorbent and to obtain a rate expression for the regeneration of alumina-supported CeOa sorbents. In the past quarter the effect of cerium content of the sorbent on its performance through four sulfation-regeneration cycles were investigated and the analysis of the economics of a commercial scale ceria process wcs sub-contracted to TECOGEN. It was found that all ceria sorbents did not show any capacity loss after the first cycle and, in fact, their performance improved slightly after the third cycle. Increasing cerium loading appears to reduce the S/Cc ratio to about 2 as monolayer coverage is approached. It was found that the sulfation rate for the sorbents containing 9.28% and 7.64% cerium were first order with respect to cerium oxide up to 90% conversion. The sorbents containing 4.39% and 1.59 showed first order kinetics up to only about 40% conversion. The effects of product layer diffusion and gas phase diffusion are currently being considered for these sorbents