Tomiaki Furuya

Development of a hybrid catalytic combustor for a 1300°C class gas turbine

Abstract The hybrid catalytic combustor concept proposed by the authors has an advantage concerned with catalyst durability, because the catalyst is maintained below 1000°C even for application to 1300°C class gas turbines. A full-scale hybrid catalytic combustor has been designed for a 200 MW (1300°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 NO x emission level of SCR (selected catalytic reduction) during atmospheric pressure testing. To predict the catalyst performance at an elevated pressure, the characteristics of the catalyst were studied using a small scale reactor test, and a material 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 rate of the metallic Pd in bulk was not so high and this caused self-oscillation for the Pd catalyst around the temperature of the oxygen release equilibrium. Even below the temperature of the oxygen release equilibrium, 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 catalyst activity during combustion testing, and indicated that the oxygen dissociation step was a rate limiting step in the catalytic combustion.

Hybrid Catalytic Combustion for Stationary Gas Turbine: Concept and Small Scale Test Results

Catalytic combustion for gas turbine applications has been investigated. Its significant advantages in reducing combustor emissions, particularly nitrogen oxides (NOx), have been shown. One of the main problems in regard to developing a catalytic combustor is the durability of catalysts, because the catalysts deteriorate during high temperature operation, which is normal for current gas turbines and near future gas turbines. The hybrid catalytic combustion concept has advantages concerned with catalyst durability. This paper shows its concept and small scale test results. This hybrid catalytic combustion concept comprises the following steps; premix fuel and air for a catalyst-packed zone; operate catalysts at rather low temperatures, to prolong catalyst life; add fresh fuel into the stream at the catalyst-packed zone outlet, where gas phase combustion occurs completely without a catalyst; add dilution air into the stream at the gas phase combustion zone outlet with a by-pass valve. Experimental data and analyses indicated that this hybrid catalytic combustion has a potential of being applicable to current gas turbines (turbine inlet temperature is about 1100°C) and near future gas turbines (turbine inlet temperature is about 1300°C).Copyright

Feasibility Study on Honeycomb Ceramics for Catalytic Combustor

This paper contains results of a structural feasibility study on honeycomb ceramic materials used for catalytic combustors in power gas turbines. Extruded cordierite honeycomb substrates are widely used as catalyst carriers in automotive exhaust systems, because of their excellent thermal shock resistance. For gas turbines, however, the ceramic catalyst carriers should retain the reliability at high temperature.In a hybrid catalytic combustor, which handles both catalysis and gas phases combustion, cordierite honeycomb structures (melt at 1445°C) can be adopted as the catalyst carrier, because the auxiliary gas phase combustion makes catalyst temperature lower than the conventional catalytic combustor.During this study, cordierite honeycomb (200 square cells/in2) tensile tests were carried out at high temperatures up to 1000°C. Using the finite element method, stresses in a cell wall were analyzed. The honeycomb cell wall mechanical strength was derived by comparing the experimental and analytical results. Also, combustor honeycomb cell stresses were calculated under typical oprerating conditions. Consequently, it was shown that it is sufficiently feasible to use the cordierite honeycomb structure as a catalyst carrier for hybrid catalytic combustors.Copyright