XU Sheng, ZHU Shaolong, FANG Song, QIU Limin, WANG Kai
Journal of Engineering Thermophysics. 2025, 46(10): 3143-3158.
Ortho-para hydrogen conversion is an indispensable process in hydrogen liquefaction system. This paper summarizes the experimental research progress of ortho-para hydrogen conversion, comprehensively compares the advantages and disadvantages of various ortho-para hydrogen conversion schemes, analyzes the differences between typical ortho-para hydrogen catalysts, such as iron hydroxide and oxide catalysts and supported nickel catalysts, in terms of the activation methods and catalytic efficiencies, and further summarizes various measurement methods for ortho-para hydrogen concentrations as well as their measurement principles. Regarding the selection of catalysts for ortho-para hydrogen conversion, the literature findings indicate that supported nickel-based catalysts have higher catalytic efficiencies, but taking full consideration of catalyst preparation, activation, deactivation, and liquefier operating requirements, iron hydroxide as well as its oxide catalysts are still the mainstream catalysts for application-oriented catalytic choices. Among the measurement methods of ortho-para hydrogen fractions, compared with spectroscopy, acoustic velocity measurement, nuclear magnetic resonance, enthalpy measurement, etc., the ortho-para hydrogen concentration measurement based on thermal conductivity method has comprehensive advantages in terms of accuracy, response speed, economy and operability, which can be used as the preferred solution for the measurement of ortho-para hydrogen concentration. As large-scale hydrogen liquefaction plants are developing towards the direction of higher efficiency, compactness and reliability, continuous conversion is the mainstream solution for ortho-para hydrogen conversion in the future hydrogen liquefaction processes. However, at present, most of the domestic studies on continuous ortho-para hydrogen conversion remain in conceptual analysis and process application, lacking data on hydrogen conversion, flow and heat transfer under cryogenic conditions, as well as relevant high-precision correlation equations. Based on the measured data of continuous catalysis and cooling of orthopara hydrogen, the development of high-precision correlations for heat transfer, pressure drop and catalysis of hydrogen eat exchangers, and the accurate design of heat exchangers for continuous ortho-para hydrogen conversion, will be an urgent task to be carried out in the future.
