Development of Granular Catalysts and Natural Gas Combustion Technology for Small Gas Turbine Power Plants

Abstract

Gas turbine power plants (GTPPs) of low power (tens of kW to 1.5-2 MW) are promising autonomous sources of energy and heat. The application of gas turbine technologies saves fuel, solves heat supply and water shortage problems. The nominal efficiency of GTTPs belonging to different generations varies from 24% to 38% (average weighted efficiency – 29%). This is 1.5 times higher than that of combined heat power plants. The main GTPP drawback is significant emission of toxic nitrogen oxides due to high temperature combustion of the gas fuel. The main approach used today to decrease the emission of nitrogen oxides from GTPPs is based on the use of the so-called homogeneous combustion chambers working with premixed lean fuel-air mixtures with two-fold excess of air. The decrease of NOx formation is principally the result of the low flame temperatures that are encountered under lean conditions (Correa 1992). This technology makes it possible to decrease significantly the temperature in the combustion zone relative to traditional GTPP combustion chambers with separate supply of fuel and air to the combustion zone. As a result, the concentration of nitrogen oxides in the flue gases decreases from 100 ppm to 1020 ppm. The downside of this approach is, however, that it results in low heat release rates, which, in turn, may negatively affect combustion stability. The most efficient way to decrease emissions of nitrogen oxides in GTPPs is to use catalytic combustion of fuel (Trimm, 1983; Pfefferle & Pfeferle., 1987; Ismagilov & Kerzhentsev 1990; Parmon et al., 1992; Ismagilov et al., 1995; Ismagilov & Kerzhentsev, 1999; Ismagilov et al., 2010). In the catalytic chamber, efficient combustion of homogeneous fuel-air mixture is achieved at larger excess of air and much lower temperatures in the zone of chemical reactions compared to modern homogeneous combustion chambers. In the last decade, the obvious advantages of the catalytic combustion chambers in GTPPs initiated intense scientific and applied studies in the USA (Catalytica) and Japan (Kawasaki Heavy Industries) which are aimed at development of such chambers for GTPPs for various applications (Dalla Betta et al., 1995; Dalla Betta & Tsurumi, 1995; Dalla Betta & RostrupNielsen, 1999; Dalla Betta & Velasco, 2002).