To reduce NOx emissions significantly, a catalytic combustor was developed. Full scale tests of catalytic combustors designed for application in Kawasaki S1A-O2 type gas trubines were conducted. The combustor consisted of a pre-combustion zone, a premixing zone, a catalytic combustion zone, and a variable geometry dilution zone. Liquefied Natural Gas (LNG) was burned in combustor rig tests and results indicated low NOx emissions and high combustion efficiencies over a wide range of air/fuel ratios and that the catalytic combustor can be applied to the engine tests.

As described previously in ASME papers, an effort has been underway to apply catalytic combustion for small gas turbines. To improve combustion efficiency at the engine operating conditions, two catalytic combustors have been developed. Both combustors showed high combustion efficiency and low NOx emissions in combustor rig tests. In engine tests, Type A combustor achieved the NOx goal of 15 ppmv as corrected to 5 percent oxygen (5.6 ppmv at 15 percent oxygen) for base load operation. Combustion efficiency was greater than 98 percent for the fresh catalyst, however, it decreased rapidly with catalyst deactivation.

As a final step of the Catalytic Combustor Development Program, a catalytic combustor developed was tested in a 150-kW gas turbine-generator unit. A digital control system was developed to improve its controllability for a transient operation, and a 200-hr continuous operation test was performed to asses the durability of the catalyst. During the test, an excellent performance of the control system was verified, and a very high combustion efficiency of more than 99% and a ultra-low NOx level of less than 5.6 ppm (at 15% O2) were achieved at a 150-kW generator output. In addition, the combustion efficiency has been maintained at over 98% for 200 hours of operation. However, the catalyst exposed to 200 hours of operation showed signs of deactivation.

To meet strict NOx regulations, Kawasaki Heavy Industries, Ltd. has been conducting a development program of dry, low-NOx combustion system since 1989. In a first step of the development program, a multi-burner type, can combustor has been developed. The test engine, with an output of 1.5 MW, demonstrated NOx emissions below 42 ppm at 15% O2. Following the engine performance tests, a 500 cycle endurance test and a 300 hour test at full load have been conducted to assess the reliability of the combustion system developed. During these tests, no mechanical durability issues arose.

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