Thermodynamic analysis of two novel very high temperature gas-cooled reactor-based hydrogen-electricity cogeneration systems using sulfur-iodine cycle and gas-steam combined cycle

In this paper, two novel system layouts are proposed to improve the thermodynamic performance of the conventional very high temperature gas-cooled reactor (VHTR)-based hydrogen-electricity cogeneration system using sulfur-iodine (S–I) cycle and gas-steam combined cycle (GSCC). The heat and electricity consumption data of the S–I cycle are obtained from our previous Aspen Plus simulation results, and the thermodynamic model of the entire hydrogen-electricity cogeneration system is established using energy and exergy analysis methods. The performance of the system under benchmark conditions is analyzed, and the effects of several key operating parameters on system performance are investigated. The results show that with these two new system layouts, the thermal efficiency and exergy efficiency of the conventional system are improved by 8.56%–10.27% and 9.01%–10.82%, respectively. The largest exergy loss of the system occurs in the VHTR, and the exergy efficiency of the S–I cycle is very low, only about 50.8%. Therefore, when the hydrogen production load is large, it is very important to optimize the process flow and operating parameters of the S–I cycle. Besides this, it is found that the S–I cycle-based nuclear hydrogen production efficiencies are lower than the GSCC-based nuclear power generation efficiencies.