Research on integrated energy system for hydrogen production and liquefaction from LNG cold energy generation

Objective In order to achieve the multiple objectives of LNG cold energy recycling, green hydrogen production and liquid hydrogen storage and transportation, an integrated energy system which utilizes LNG cold energy to power generation as a power source for hydrogen production from electrolytic water and hydrogen liquefaction, and meanwhile LNG roles as hydrogen liquefaction pre-refrigerant is proposed.

Methods The process of LNG cold energy power generation and hydrogen liquefaction by HYSYS is simulated and calculated. A mathematical model of the relationship between materials in each unit and the distribution of electric energy is established. The annual liquefied hydrogen production are obtained for three power generation modes of direct expansion, Rankine cycle and combined cycle under different export pressures by solving the model.

Result When the annual LNG receiving capacity is 3 million tons, the liquid hydrogen output of the integrated energy system is about 1 420-3 790 tons per year.

Conclusions It is found that under the same export pressure and efficiency, the hydrogen production benefit of combined cycle power generation is mostly obvious. When other conditions are same, the hydrogen production decreases with the increase of export pressure, and the benefit of PEM electrolysis is better than that of alkaline electrolysis.