DEVELOPMENT OF A HYBRID CATALYTIC COMBUSTOR FOR A 1300-DEGREES-C CLASS GAS-TURBINE

The hybrid catalytic combustor concept proposed by the authors has an advantage concerned with catalyst durability, because the catalyst is maintained below 1000 degrees C even for application to 1300 degrees C class gas turbines. A full-scale hybrid catalytic combustor has been designed for a 200 MW (1300 degrees C) class gas turbine. The catalyst bed was 450 mm in diameter and consisted of a Pd/alumina washcoat on a cordierite monolith. In experiments, the combustor has demonstrated the capability of meeting the NOx emission level of SCR (selected cata lytic reduction) during atmospheric pressure testing. To predict the c atalyst performance at an elevated pressure, the characteristics of th e catalyst were studied using a small scale reactor test, and a materi al property test using a DTA/TGA-Q.MASS system. The catalyst showed a higher activity in the oxidized state (PdO) than in the metallic state (Pd). This activity difference was governed by the equilibrium of the oxygen release from PdO in bulk. It was considered that oxidation rat e of the metallic Pd in bulk was not so high and this caused self-osci llation for the Pd catalyst around the temperature of the oxygen relea se equilibrium. Even below the temperature of the oxygen release equil ibrium, both surface and bulk (lattice) oxygen of the PdO was consumed by the methane oxidation reaction, and resulted in a lack of surface oxygen on the catalyst. This caused a reversible decrease in the catal yst activity during combustion testing, and indicated that the oxygen dissociation step was a rate limiting step in the catalytic combustion .