Comparative analysis of H 2/O 2 cycle power plants based on different hydrogen production systems from fossil fuels

Abstract

In this paper, two options for H 2 production by means of fossil fuels are presented and their performances are evaluated when integrated with H 2/O 2 cycles. The investigation has been developed with reference to two different schemes, both representative of advanced technology (TIT=1350°C) and of futurist technology (TIT=1700°C). The two methods, here considered, to produce H 2 are: • Coal gasification: it permits transformation of a solid fuel into a gaseous one, by means of partial combustion reactions; • Steam–methane reforming: it is the simplest and potentially the most economic method for producing hydrogen in the foreseeable future. These hydrogen production plants require material and energy integrations with the power section, and the best connections must be investigated in order to obtain good overall performance. The overall efficiencies are very poor, especially those of the power plants coupled with the steam methane reforming; their mean values are about 21% for the first reference case and about 25% for the second one. The overall efficiencies of the power plants, coupled with the coal gasification, are little better than the previous ones but always rather low: their mean values are about 28% for the first reference case and about 33% for the second one. The CO 2 specific emissions depend on the fossil fuel typology and the overall efficiency: adopting a removal efficiency of 90% in the CO 2 absorption systems, the CO 2 emission reduction is 87% and 82% in the coal gasification and in the steam-methane reforming, respectively.