The present paper addresses the plant configuration, the thermodynamic performance and the economics of combined cycle power plants, having the following characteristics: (i) CO2 emissions reduced by at least one order of magnitude, (ii) utilization of hydrogen produced by natural gas as the fuel for the gas turbine, (iii) acceptable NOx emissions. Two plant configurations are discussed, based on high pressure reformers heated up by: (i) gas turbine exhausts with hydrogen firing, (ii) oxygen combustion of carbonated purge gases from a pressure-swing-absorber. In the first case CO2 is separated by a chemical absorption plant, in the second from the reformer exhausts after water condensation. The fuel dilution by water/steam or nitrogen was properly kept into account, to achieve NOx emission of about 30-45 ppmvd with a flame temperature of 2300 K. The two plant schemes show a net efficiency of about 48% (including CO2 liquefaction) vs. 56% of the reference combined cycle having the same gas turbine and cycle technology, with a remarkable increase of the net power output (based on the same gas turbine unit). The ability of removing CO2 from the exhausts yields to a 25-30% increase of the cost of electricity, i.e. 40-45 $/ton of CO2 sequestrated.

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