Investigation of combined SO{sub 2}/NO{sub x} removal by ceria sorbents. Quarterly technical progress report, [April--June 1995]

Simultaneous removal of SO{sub 2} and NO{sub x} 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 SO{sub 2} and NO{sub x} 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 the sulfation of the sorbent and to obtain a rate expression for the regeneration of alumina-supported CeO{sub 2} sorbents. In this quarter runs for methane regeneration were completed. The data obtained were evaluated and interpreted. When the sulfated sorbent was regenerated with methane coke formation on the sorbent was observed. Treatment of fresh sorbent with methane also resulted in coking. Coke formed on the sorbent disappeared very rapidly after the methane flow was replaced with nitrogen. The order of the regeneration reaction with respect to methane was estimated as 0:76 and the activation energy of the reaction was estimated as 130 kJ/mol. During repeated sulfation-regeneration cycles the decrease in the sulfur capacity after the first cycle was slightly more when regeneration was done with methane compared to that observed with hydrogen regeneration. In the subsequent 4 cycles, the ceria sorbent preserved its sulfur capacity. The regenerated sorbent was able to capture 1.5 sulfur atoms per cerium atom in less than an hour of sulfation, compared to S/Ce of 2.5 for fresh sorbents and 2 for sorbents regenerated with hydrogen