A study on integrated HTR-PM driven hydrogen production using thermochemical cycles

Abstract

This present study aims to design a nuclear-based hydrogen production system by using the three- and four-step magnesium-chloride cycles, and compares the three-step magnesium-chloride cycle integrated nuclear-based system and the four-step magnesium-chloride cycle integrated nuclear-based system. Within the scope of this study, four units of high-temperature gas-cooled-pebble bed modular nuclear reactor are employed, where a total of 1 GW thermal energy (heat) is secured from these four reactors. All of the heat generated by the reactors is used to drive the power generation and hydrogen production cycles. The proposed system, along with its cycles and processes, are examined by using mass, energy, entropy, and exergy balance equations. The modeling and simulations for the three- and four-step magnesium-chloride cycles are carried out via the Aspen Plus software package. The results are compared for two hydrogen production methods, and sensitivity analysis is assessed for various steam/MgCl2 ratios, as well as different reactor temperatures and pressures for each reaction in the cycles. While the three-step magnesium-chloride cycle integrated nuclear-based system produces 2.43 kg/s hydrogen, 2.13 kg/s hydrogen is produced by the four-step magnesium-chloride cycle integrated nuclear-based system. As a consequence of this present study, energy and exergy efficiencies are calculated as 54.2% and 60.9% for the three-step magnesium-chloride cycle, while these values are 48.0% and 54.0% for the four-step magnesium-chloride cycle. Additionally, while the energy and exergy efficiencies of the three-step magnesium-chloride cycle integrated overall system are 29.2% and 40.3%, these values are 25.6% and 35.2% for the four-step magnesium-chloride cycle integrated system, respectively.