A single flash integrated gas turbine-geothermal power plant with non-condensable gas combustion

In this work the possibility of increasing the performances of the 20 MW ENEL (Italian Electric Company) standard geothermal power plants, by the addition of a flash separator and by recovering the gas turbine exhaust heat, have been analyzed in the “Monte Amiata - Piancastagnaio” geothermal field (Bidini et al., 1997). In this place the geothermal fluid is saturated steam with a water fraction about the 30 - 50% in mass and a non condensable gasses content of about 8% in mass. The non condensable gasses are represented mainly by the CO2, about the 95% by weigh, H2S, H2, Hg, NH3 and CH4. In many cases the emission of this gasses in the environment represent a polluant source due to the high concentration mainly of H2S and ammonia. To overcome this problem some exhaust gasses cleaning device must be adopted increasing the plant capital costs with no performances increase. Anyway the methane, the H2, and the H2S are an energetic source due to their high LHV. For this matter it is possible to send them in the combustion chamber of the gas turbine, by reducing the fossil fuel consumption and the environmental impact. In the following the performances of the single flash gas turbine - geothermal power plant with non condensable gasses combustion have been examinated and discussed.