Yutaka Furuse

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.

Development of a catalytic combustor for a heavy-duty utility gas turbine

The most effective technologies currently available for controlling NO x emissions from heavy-duty industrial gas turbines are diluent injection in the combustor reaction zone, and lean premixed Dry Low NO x (DLN) combustion. For ultralow emissions requirements, these must be combined with selective catalytic reduction (SCR ) DeNO x systems in the gas turbine exhaust. An alternative technology for achieving comparable emissions levels with the potential for lower capital investment and operating cost is catalytic combustion of lean premixed fuel and air within the gas turbine. The design of a catalytic combustion system using natural gas fuel has been prepared for the GE model MS900IE gas turbine. This machine has a turbine inlet temperature to the first rotating stage of over 1100°C and produces approximately 105 MW electrical output in simple cycle operation. The 508-mm-dia catalytic combustor designed for this gas turbine was operated at full-scale conditions in tests conducted in 1992 and 1994. The combustor was operated for twelve hours during the 1994 test and demonstrated very low NO x emissions from the catalytic reactor. The total exhaust NO x level was approximately 12-15 ppmv and was produced almost entirely in the preburner ahead of the reactor. A small quantity of steam injected into the preburner reduced the NO x emissions to 5-6 ppmv. Development of the combustion system has continued with the objectives of reducing CO and UHC emissions, understanding the parameters affecting reactor stability and spatial nonuniformities that were observed at low inlet temperature, and improving the structural integrity of the reactor system to a level required for commercial operation of gas turbines. Design miodifications were completed and combustion hardware was fabricated for additional full-scale tests of the catalytic combustion system in March 1995 and January 1996. This paper presents a discussion of the combustor design, the catalytic reactor design, and the results of full-scale testing of the improved combustor at MS9001E cycle conditions in the March 1995 and January 1996 tests. Major improvements in performance were achieved with CO and UHC emissions of 10 ppmv and 0 ppmv at baseload conditions. This ongoing program will lead to two additional full-scale combustion system tests in 1996. The results of these tests will be available for discussion at the June 1996 Conference in Birmingham.

Design and Test of a Catalytic Combustor for a Heavy Duty Industrial Gas Turbine

The most effective technologies currently available for controlling NOx emissions from heavy duty industrial gas turbines are either diluent injection in the combustor reaction zone, or dry low NOx (DLN) combustion, coupled with selective catalytic reduction (SCR) De-NOx in the gas turbine exhaust. A competing technology with the potential for achieving comparable emissions levels at substantially lower capital investment and operating cost is catalytic combustion of lean premixed fuel and air within the gas turbine. A preliminary design of a catalytic combustion system using natural gas fuel has been prepared for the GE Model MS9001E gas turbine. A full scale test combustor has been constructed for a full pressure development test based upon this design work and was operated at the GE Power Generation Engineering Laboratory in Schenectady, New York. Discussion of the catalytic combustor design, the catalytic reactor design and laboratory development test results is presented.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

Development of Ceramic Rotor Blade for Power Generating Gas Turbine

To cope with the increasing demand of electric power, many research and development programs have been performed in the field of electric power industry. Among them, the application of highly thermal resistive ceramics to hot parts of the gas turbines is one of the most promising ways to raise the thermal efficiency of the gas turbine, and several projects have been executed in the U.S.A., Europe and Japan.Tokyo Electric Power Co., Inc. (TEPCO) also has been conducting a research project to apply ceramic components to hot parts of a 20MW class gas turbine with a turbine inlet temperature of 1300C. In this project. TEPCO and Hitachi have been conducting the cooperative research work to develop a first stage ceramic rotor blade.After several design modifications, it was decided to select ceramic blades attached directly to a metal rotor disc, and to insert metal pads between the dovetail of the ceramic blade and metal disc to convey the centrifugal force produced by the blade smoothly to the metal disc.The strength of this ceramic blade has been verified by a series of experiments such as tensile tests, room temperature spin tests, thermal loading tests, and high temperature spin tests using a high temperature gas turbine development unit (HTDU).In addition, the reliability of the ceramic blade under design and test conditions has been analyzed by a computer program GFICES (Gas turbine - Fine Ceramics Evaluation System) which was developed on the basis of statistical strength theory using two parameter Weibull probability distribution.These experiments and analyses demonstrate the integrity of the developed ceramic rotor blade.© 1994 ASME

Development of a Catalytic Combustor for a Heavy-Duty Utility Gas Turbine

The most effective technologies currently available for controlling NOx emissions from heavy-duty industrial gas turbines are either diluent injection in the combustor reaction zone, or lean premixed Dry Low NOx (DLN) combustion. For ultra low emissions requirements, these must be combined with selective catalytic reduction (SCR) DeNOx systems in the gas turbine exhaust. An alternative technology for achieving comparable emissions levels with the potential for lower capital investment and operating cost is catalytic combustion of lean premixed fuel and air within the gas turbine. The design of a catalytic combustion system using natural gas fuel has been prepared for the GE model MS9OOIE gas turbine. This machine has a turbine inlet temperature to the first rotating stage of over 1100°C and produces approximately 105 MW electrical output in simple cycle operation. The 508 mm diameter catalytic combustor designed for this gas turbine was operated at full-scale conditions in tests conducted in 1992 and 1994. The combustor was operated for twelve hours during the 1994 test and demonstrated very low NOx emissions from the catalytic reactor. The total exhaust NOx level was approximately 12–15 ppmv and was produced almost entirely in the preburner ahead of the reactor. A small quantity of steam injected into the preburner reduced the NOx emissions to 5–6 ppmv.Development of the combustion system has continued with the objectives of reducing CO and UHC emissions, understanding the parameters affecting reactor stability and spatial non-uniformities which were observed at low inlet temperature, and improving the structural integrity of the reactor system to a level required for commercial operation of gas turbines. Design modifications were completed and combustion hardware was fabricated for additional full-scale tests of the catalytic combustion system in March 1995 and January 1996. This paper presents a discussion of the combustor design, the catalytic reactor design and the results of full-scale testing of the improved combustor at MS9OOIE cycle conditions in the March 1995 and January 1996 tests. Major improvements in performance were achieved with CO and UHC emissions of 10 ppmv and 0 ppmv at base load conditions.This ongoing program will lead to two additional full-scale combustion system tests in 1996. The results of these tests will be available for discussion at the June 1996 Conference in Birmingham.Copyright

Development of Air-Cooled Ceramic Nozzles for a Power Generating Gas Turbine

The development of air-cooled ceramic nozzle vanes for a power generating gas turbine has been reported. To make up the limited temperature resistance of present ceramic materials, the utilization of a small amount of cooling air has been studied for the first stage nozzle vanes of a 1500°C class gas turbine.A series of cascade tests were carried out for the designed air-cooled Si3N4 nozzle vanes under 6 ata and 1500°C conditions. It was confirmed that the maximum ceramic temperature can be maintained below 1300°C by a small amount of cooling air. In spite of the increased thermal stresses by local cooling, all Si3N4 nozzle vanes survived in the cascade tests including both steady state and transients of emergency shutdown and the possibility of air cooled ceramic nozzle was demonstrated for a 1500°C class gas turbine application.Copyright

A Study of Cycle Performance of Ceramic Gas Turbines

A study has been carried out to assess the performance improvement of a combined cycle used for an industrial power plant when ceramic turbine components are employed. This paper presents the details of this study. Performance improvement is obtained as a result of reduced blade cooling air. In this study four different kinds of combined cycles were investigated and these are listed below:A. Combined cycle with a simple gas turbine.B. Combined cycle with an inter-cooled gas turbine.C. Combined cycle with a reheat gas turbine.D. Combined cycle with an inter-cooled reheat gas turbine.Results of this study indicate that the combined cycle with a simple gas turbine is the most practical of the four cycles studied with an efficiency of higher than 60%. The combined cycle with reheat gas turbine has the highest efficiency if a higher compressor exit air temperature and a high gas temperature (over 1000°C) to reheat the combustion system are used. A higher pressure ratio is required to optimize the cycle performance of the combined cycle with the ceramic turbine components than that with the metal turbine components because of reduced blade cooling air. To minimize leakage air for these higher pressure ratios, advanced seal technology should be applied to the gas turbines.Copyright

Development of ceramic components for a power generating gas turbine

A research program has been conducted to apply ceramics for hot parts of a power generating gas turbine to improve thermal efficiencies of gas-steam combined cycle power generating plants. The first objective of this program is to verify adaptability of Si-based monolithic ceramics to the combustor, the first and second stage nozzles, and the first stage rotor of a 20MW class gas turbine with turbine inlet temperature(TIT: Temperature at combustor outlet) of 1300°(1573K). Combustion tests on the combustor(SiC) and cascade tests on the nozzles(SiC and/or Si3N4) were conducted under full-pressure and full-temperature conditions. Hot spin tests were conducted on rotor(Si3N4) after confirming the validity of design by cold spin tests and thermal loading cascade tests in a static test rig. The soundness of ceramic components was verified by these tests simulating the actual gas turbine conditions and a positive prospect for an application of ceramics to gas turbine components was obtained. Further efforts have been conducted to apply ceramics for a gas turbine with higher TIT. Silicon nitride nozzle-vanes along with a small amount of cooling air showed a possibility of the first stage ceramic nozzle with TIT of 1500°(1773K).

Investigation of R-curve Behavior and Its Effect on Strength for Advanced Ceramics

Three kinds of tests, including compact tension (CT) test, SEPB test and indentation flaw resistance test, were carried out on advanced ceramics for gas turbine components in order to investigate R-curve behavior and its effect on strength. Rising R-curve behaviors were observed not only in ceramic matrix composite but also in monolithic ceramics. KRmax value of each sample was nearly equal to its KIC value that was obtained by SEPB method. This was related to the large pre-crack used in SEPB method in which process zone would grow up sufficiently. Indentation flaw resistance of composite was higher than that of monolithic materials. The KIC value obtained by indentation induced flaw (IIF) method increased with increasing the length of flaw introduced by Vickers indentation. This result indicates that the KIC value can be related to the pre-crack length and its process zone length growing with extension crack. Distribution of strength was simulated by Monte Carlo method in both flat and rising R-curve cases using the same flaw distribution. It was found that the Weibull modulus of rising R-curve case was higher than that of flat R-curve case.