Experimental Characterization of a Hydrogen Fuelled Combustor With Reduced NOx Emissions for a 10 MW Class Gas Turbine

In the frame of a research project launched in 2006 (partly funded by Regione Veneto, a local institution in the North-East of Italy), ENEL and Nuovo Pignone are developing an innovative “zero emission” gas turbine cycle suitable for power generation. The gas turbine, a GE10-1 model, is manufactured by Nuovo Pignone and will be installed at ENEL’s coal-fired Fusina power plant, near Venice. The turbine, rated for 11 MWe, is equipped with a diffusive flame combustor and is suitable for operation with 100% hydrogen as main fuel over the entire load range. Hydrogen is available at Fusina site as by-product of petrochemical plants. Natural gas will be used as start-up and back-up fuel, and NOx emission abatement will be achieved by means of steam injection. Load operation will be possible with hydrogen only, with methane or hydrogen-methane mixtures (in case of reduced availability of hydrogen) and with or without steam injection. In order to support the combustion system’s design, experimental activities have been carried over a prototypical combustor, installed on a combustion test rig at ENEL’s experimental facility, located in Sesta (Tuscany). The test rig has been upgraded in order to permit full-scale combustor operation. Tests have been planned with the aim of providing a complete screening of combustion system’s sensitivity to minor hardware modification (three different burners and two different liners, designed for diffusive combustion, have been available) and operating conditions (sensitivity to cycle parameters and effect of steam injection). Special instrumentations have been installed for a detailed monitoring of hot parts’ metal temperature, combustion-driven pressure oscillations and pollutant emissions. A water-cooled camera has been installed for direct flame visualization. The experimental campaign is still on-going and only the default combustor configuration has been tested so far. However, collected results indicate safe combustor operation in both hydrogen and methane combustion mode: metal temperatures have never exceeded warning limits and pressure pulsation have been extremely quiet. NOx emission during hydrogen operation in dry combustion mode have been proven to be roughly 3 times higher than in dry methane combustion mode. Steam injection has been proven to be effective in reducing NOx emissions down to contractual values. Additional efforts are in progress to obtain a further reduction of emission level. Finally, experimental results have been processed in order to set up a simple NO_x emissions’ model, accounting for NOx production in any possible operating mode.