Design and optimization of hydrogen liquefaction process based on LNG terminals
To address the high energy consumption and low efficiency of hydrogen liquefaction,a novel hydrogen liquefaction process based on liquefied natural gas(LNG)terminals is proposed.The process utilizes LNG cold energy for precooling and mixed refrigerants for cooling,converting hydrogen at 25 ℃,2.1 MPa with parahydrogen concentration(mole fraction,the same below)of 25.00％into liquid hydrogen at-252.4 ℃,130 kPa with parahydrogen concentration of 98.01％.The process,with a handling capacity of 50 t/d,can support 5 × 104 to 10 × 104 hydrogen-powered vehicles.By leveraging the pressure energy of natural gas expansion while maintaining the gas grid entry pressure,the energy consumption of hydrogen liquefaction is reduced.The process was simulated using Aspen HYSYS software.With minimized specific energy consumption as the objective function,MATLAB software was used to optimize key process parameters.Exergy efficiency,figure of merit and coefficient of performance were used as evaluation indicators for energy analysis of the system.The results show that the optimized process reduces specific energy consumption(5.257 kW·h/kg)by 28.09％,which is 17.86％lower than the European IDEALHY project and below the levels reported for similar processes in the literature.The exergy efficiency,figure of merit and coefficient of performance are 45.73％,0.4573,and 0.2346,respectively,which increase by 39.04％39.04％and 39.06％compared to before optimization.The exergy efficiency is higher than that reported for most similar processes in the literature.The lower liquefaction pressure of hydrogen is more favorable for equipment manufacturing and safe operation.The process is reasonable and highly efficient,which can provide a reference for hydrogen liquefaction at LNG terminals.
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