Quantitative Analysis of the Effects of Catalytic Ortho-Para Hydrogen Conversion on the Hydrogen Liquefaction Process

The catalytic conversion of the ortho-para (o-p) hydrogen is a key issue in the design and operation of the high-efficient hydrogen liquefaction process. Continuous conversion is considered to be the most efficient conversion method in the hydrogen liquefaction process compared to isothermal conversion and adiabatic conversion. However, there are few quantitative analyses and studies on the effects of different catalytic o-p hydrogen conversion methods. In this paper, a theoretical model is developed based on the thermodynamic properties of hydrogen. The model can reflect the difference in the distribution of the cooling capacity requirements of the hydrogen liquefaction process due to the different catalytic o-p hydrogen conversion methods. Meanwhile, the minimum work for the hydrogen liquefaction process of different o-p hydrogen conversion methods is calculated by MATLAB based on this model. In addition, a comparative analysis is performed to quantify the effects of the o-p hydrogen conversion methods on the hydrogen liquefaction process. The results show that when the parahydrogen percentage in the liquid hydrogen is 95%, the minimum work of the continuous conversion is decreased by 4.71% and 22.97%, compared to that of the five-stage adiabatic conversion and of the isothermal conversion, respectively.