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

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.