Hydrogen production system with near-zero carbon dioxide emissions enabled by complementary utilization of natural gas and electricity

Abstract

The complementary utilization of different energy sources is a promising strategy for consuming excess electricity and improving system efficiency. In this study, complementary utilization of electricity and natural gas is proposed for a hydrogen production system based on chemical recuperation. The system uses electrolysis technology to convert excess electricity generated from intermittent and fluctuating renewable energy into green hydrogen. It also utilizes the by-product oxygen for oxy-fuel combustion to achieve near-zero carbon dioxide emissions after subsequent compression, transportation, and storage. The system uses natural gas for steam methane reforming to generate hydrogen. A portion of flue gas generated by the combustor is introduced into the reformer, replacing high-temperature steam for reforming with methane. In addition, the waste heat from the flue gas is introduced into the electrolysis cell to save electricity. Energy and exergy analyses of the proposed and reference systems were performed. The results revealed that the energy and exergy efficiencies of the proposed system are 81.20% and 73.29% at near-zero carbon dioxide emission, representing an improvement of 7.09 and 6.41 percentage points, respectively, compared to the reference system. It also appeared that 98.68% in situ oxygen consumption was achieved. The hydrogen mass flow generated by the proposed system is 33.83 kg/h, which is 8.78% higher than the 30.88 kg/h of the reference system. This study introduces a promising method for developing a hydrogen production system with high efficiency and near-zero carbon dioxide emissions.