Low-emission gas turbines using catalytic combustion

Gas turbines are being increasingly used for electric power generation and other applications. Gas turbines are efficient and clean-burning, but without emission controls they emit far more nitrogen oxides (NOx) than regulations permit. Commercial NOx control techniques, such as dry low NOx (DLN), wet diluent injection (WDI), and selective catalytic reduction (SCR), are generally uneconomical for achieving NOx emissions of 10 ppm or less, which are, or will soon be, required in many industrialized regions of the world. In the thermal combustion of natural gas (methane), NOx emissions are very low up to about 1400 degrees C, but increase sharply to more than 160 ppm at the typical flame temperature of about 1800 degrees C. In catalytic combustion, which occurs at 1300-1400 degrees C, NOx emissions can be as low as 2-5 ppm, which are one to two orders of magnitude less than the emissions from thermal combustion and are in compliance with current and foreseeable regulatory standards worldwide. Catalytic combustion turbine technology is at the field demonstration stage of development and is expected to be commercialized by the late 1990s. Catalytic combustion systems can be built in to new gas turbines and retrofitted to some existing turbines. Catalytic combustion turbines will initially be used primarily for electric power generation, including cogeneration and combined-cycle power generation. Subsequent major applications might also include aircraft, rail locomotives, motor vehicles, ships, and gas pipeline compressors. (C) 1997 Elsevier Science Ltd.