A comparative exergoenvironmental evaluation of chlorine-based thermochemical processes for hydrogen production

• Published in: International journal of hydrogen energy 2023-12, Vol.48 (95), p.37108-37123
• Main Authors: Razi, Faran, Hewage, Kasun, Sadiq, Rehan
• Format: Article
• Language: English
• Subjects: Copper-chlorine; Exergoenvironmental; Iron-chlorine; Magnesium-chlorine; Sustainable hydrogen; Thermochemical
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.06.154

Environmental impact assessment of energy generation processes is essential to evaluate their contributions toward the global carbon footprint. Even though hydrogen is a non-carbonaceous energy source, the pathways undertaken for its production can have harmful environmental implications. Thus, this study focuses on investigating the exergoenvironmental performances of the copper-chlorine, iron-chlorine, and magnesium-chlorine thermochemical hydrogen generation processes. This study also performs a comparative exergoenvironmental analysis of the three processes. The performances of the various processes are examined based on of the environmental impact rates of exergy destruction, component-related environmental impact rates, cumulative environmental impact rates, and exergoenvironmental factors. The global warming potentials of the thermochemical cycles are also evaluated and compared for various electricity sources to obtain hydrogen. The modeling and simulation of each process are performed using Aspen-plus by considering various heat recovery approaches for thermal management. The results suggest that the environmental impact rates of exergy destruction are relatively much higher compared to the environmental impact rates associated with the components for all processes. Furthermore, the hydrolysis step yields the highest component-associated environment impact rate for all thermochemical cycles considered (Fe–Cl: 3497 mPts/h, Cu–Cl: 1997 mPt/h, and Mg–Cl: 910 mPts/h). Moreover, the magnesium-chlorine cycle results in the highest environmental impact rate of exergy destruction (650,328 mPts/h) while the iron-chlorine cycle has the highest component-related environmental impact rate (5219 mPts/h) among the three cycles. In addition, the global warming potential of the magnesium-chlorine cycle is relatively higher compared to the copper-chlorine cycle for several electricity sources. [Display omitted] •An exergoenvironmental analyses of three thermochemical cycles is performed.•Each cycle is incorporated with thermal management schemes for higher efficiencies.•Industrial waste flue gases are considered as a heat source for hydrolysis reaction.•A hydrogen production capacity of 668 kg/h is considered for each cycle.•A comparison of global warming potential for various electricity sources is made.