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 inject ion in the combustor, reaction zone, and lean premixed Dry Low NOx (DL N) combustion. For ultralow emissions requirements, these must be comb ined with selective catalytic reduction (SCR) DeNO(x) systems in the g as 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 w ithin the gas turbine. The design of a catalytic combustion system usi ng natural gas fuel has been prepared for the GE model MS9OOIE gas tur bine. This machine has a turbine inlet temperature to the first rotati ng stage of over 1100 degrees C and produces approximately 105 MW elec trical output in simple cycle operation. The 508-mm-dia catalytic comb ustor designed for this gas turbine was operated at full-scale conditi ons in tests conducted in 1992 and 1994. The combustor was operated fo r twelve hours during the 1994 test and demonstrated very low NOx emis sions from the catalytic reactor. The total exhaust NOx level was appr oximately 12-15 ppmv and was produced almost entirely in the preburner ahead of the reactor. A small quantity of steam injected into the pre burner reduced the NOx emissions to 5-6 ppmv. Development of the combu stion system has continued with the objectives of reducing CO and UHC emissions, understanding the parameters affecting reactor stability an d spatial nonuniformities that were observed at low inlet temperature, and improving the structural integrity of the reactor system to a lev el required for commercial operation of gas turbines. Design modificat ions were completed and combustion hardware was fabricated for additio nal full-scale tests of the catalytic combustion system in March 1995 and January 1996. This paper presents a discussion of the combustor de sign, the catalytic reactor design, and the results of full-scale test ing of the improved combustor at MS9OO1E cycle conditions in the March 1995 and January 1996 tests. Major improvements in performance were a chieved with CO and UHC emissions of 10 ppmv and 0 ppmv at baseload co nditions. This ongoing program will lead to two additional full-scale combustion system tests in 1996. The results of these tests will be av ailable for at the June 1996 Conference in Birmingham.