Evaluation of the impact of hydrogen blending on the process characteristics of a cold energy power generation system

Abstract

As an efficient and clean energy carrier, the use of hydrogen can not only reduce the dependence on fossil fuels, alleviate the problem of energy shortages, but also help the realization of the global carbon neutrality goal, becoming a necessary way to solve the energy crisis. However, the sale of hydrogen is limited by the transportation volume and the transportation radius. Receiving stations are responsible for receiving, gasifying and exporting natural gas, which coincides with the transportation of hydrogen. If the hydrogen near the port can be delivered to the LNG receiving terminal, and the natural gas can be blended with hydrogen and exported from the terminal, the market can be expanded and the comprehensive benefits can be enhanced. Based on this, a power generation system using LNG and H₂ cold energy is constructed in this paper, which not only has the functions of gasification of LNG, blending of natural gas and hydrogen and exporting, and capturing of CO₂ in the flue gas, but also pumps warm seawater, which is utilized as waste heat, to a thermal power plant, where it is exchanged with the hot steam in the condenser to obtain heat, and then transported to the system for reuse, which avoids the impact of waste heat of thermal power plant on the power plant, and thus prevents the waste heat of the thermal power plant from causing damage to the power plant. In this way, the waste heat of the thermal power plant is avoided to pollute the sea, and the whole process is cleaner and more environmentally friendly. In this paper, the effects of different hydrogen blending ratios, flue gas inlet pressure and temperature on separation of water in flue gas, and the effects of different hydrogen blending ratios, flue gas outlet temperature and compressor pressurization on CO₂ collection were investigated, and the system as a whole and each component were thermodynamically analyzed. It was found that the effects of hydrogen blending ratio on separation of water in flue gas and CO₂ collection were the most important. when the hydrogen blending ratio was increased from 0% to 100%, the energy efficiency, cold recovery efficiency, exergy efficiency, and power generation of the system increased by 22.5%, 31.3%, 24.6%, and 36609 kW, respectively. Compared with the pure natural gas delivery, 30% hydrogen blending with natural gas can increase the energy efficiency of the system by 10.8% and the exergy efficiency by 8.6%, and the annual power generation of the whole process can produce an economic benefit of 1.58 × 10⁷$, while the CO₂ can be fixed up to 1.82 × 10⁵t. With the increase in the ratio of hydrogen blending, the performance indexes of the system as a whole and locally have been improved.