Review of the continuous catalytic ortho-para hydrogen conversion technology for hydrogen liquefaction

In order to meet rapidly growing demand of liquid hydrogen in the future hydrogen industry and energy structure, the continuous catalytic ortho-para hydrogen conversion technology (CCOPHCT) has been once again proposed and has become an important choice to improve the hydrogen liquefaction units (HLUs). The origin, concept, and research progress of the CCOPHCT are systematically reviewed for the first time in this paper. However, the research depth and breadth of the CCOPHCT are insufficient to support its current application. To solve it, for the continuous catalytic ortho-para hydrogen conversion plate-fin heat exchanger (CCOPHC-PFHE) with better comprehensive performances, this paper comprehensively summarizes the research achievements in the related fields from the perspective of the unit analysis, including the ortho-para hydrogen conversion (OPHC), packing layer and plate-fin heat exchanger (PFHE), which to provide further thinking for the development of the CCOPHC-PFHE. Further, some suggestions for the CCOPHCT are proposed based on the existed research foundations, including preparing the effective ortho-para hydrogen conversion catalyst (OPHCC), developing the accurate OPHC dynamical model, revealing the coupling mechanism in the packing layer filled with the OPHCC and establishing an effective design method and standard of the CCOPHC-PFHE. In addition, considering the special conditions on the CCOPHC-PFHE, the importance of the experimental research is emphasized. And based on the established hydrogen experimental platform with the comprehensive supporting implementations, the experimental device of the CCOPHC-PFHE has been completed and a series of experimental tests are currently in progressing.