Research on two novel hydrogen-electricity-heat polygeneration systems using very-high-temperature gas-cooled reactor and hybrid-sulfur cycle

Abstract

The combination of the hybrid-sulfur (HyS) cycle with a very-high-temperature gas-cooled reactor (VHTR) presents a promising nuclear hydrogen production technology. This study proposes two novel hydrogen-electricity-heat polygeneration systems using VHTR and HyS cycle. A thermodynamic model is developed via energy and exergy analyses. Thermodynamic performance analysis and comparison are conducted on the two systems. For the two systems under design basis condition, the recommended variation range of the split ratio is 0–0.6395 and the hydrogen production rate is 0–55.7 mol/s. For systems 1 and 2, the energy utilization efficiencies are 65.91 % and 64.53 %, and the exergy efficiencies are 68.55 % and 67.36 %, at a hydrogen production rate of 55.7 mol/s. The process heat supply unit, steam generator (SG) and HyS cycle exhibit the top three largest exergy loss coefficients of 6.32 %, 6.26 % and 4.21 % at the split ratio of 0.5; therefore, they are key units for improving system performance. The intermediate heat exchanger's primary-side helium outlet temperature and SG's secondary-side main steam temperature both affect the variation range of split ratio. A slightly lower main steam temperature can increase the maximum hydrogen production rate and maximum energy utilization efficiency.