Feasibility of solar thermochemical natural gas desulphurization and hydrogen generation with a membrane reactor

Abstract Natural gas has enormous known reserves and is a relatively environment-friendly energy carrier compared to other fossil energy sources, but its utilization often is limited by the presence of impurities such as H2S. The traditional desulphurization processes for natural gas have several disadvantages, such as high energy costs, significant process complexity and expensive equipment maintenance requirements. In this study, a thermochemical system containing an H2 permeable membrane reactor driven by mid/low-temperature solar energy is proposed and analyzed. In this desulphurization process, solar energy is stored as hydrogen energy, while simultaneously carbon from CH4 is captured as CS2. The generated H2 is transported through an H2 permeable membrane reactor, which shifts the equilibrium of the H2S methane reformation (H2SMR) reaction forward and allows for conversion at a lower reaction temperature and thus a lower cost solar collector. A thermodynamic analysis of the desulphurization system was conducted in the temperature range of 300 °C to 700 °C under H2 permeate pressures of 10−2 bar to 10−5 bar and reaction pressures of 1 bar to 300 bar with a space velocity of 2.7 h−1. The CO2 emissions reduction of this system achieved 115 kg m−2 annually, and the first-law thermodynamic efficiency and solar-to-fuel efficiency of this system achieved maximums of 72.4% and 21.0%, respectively.