基于LNG接收站的氢气液化流程设计与优化

Design and optimization of hydrogen liquefaction process based on LNG terminals

针对氢气液化存在的高能耗、低效率问题,提出了基于液化天然气(LNG)接收站的氢气液化流程。该流程利用LNG冷能预冷、混合制冷剂制冷,将25℃、2.1 MPa和仲氢浓度(物质的量分数,下同)25.00%的氢气转化为-252.4℃、130 kPa和仲氢浓度98.01%的液氢,50 t/d处理量可供5×10^(4)~10×10^(4)辆氢能源汽车使用。该流程在保证天然气入网压力不变的条件下,通过天然气压力能膨胀做功,降低了氢气液化能耗。采用Aspen HYSYS软件对该流程进行了模拟,以比能耗最低为目标函数,结合MATLAB软件,对流程关键参数进行了优化;以㶲效率、品质因数和制冷性能系数作为评价指标,对系统进行了能量分析。结果表明,优化后流程的比能耗(5.257 kW·h/kg)降低了28.09%,相比欧洲IDEALHY项目降低了17.86%,低于文献报道的同类型流程;㶲效率、品质因数和制冷性能系数分别为45.73%、0.4573和0.2346,相较优化前分别提高了39.04%、39.04%和39.06%,其中㶲效率高于多数文献报道的同类型流程;氢气液化压力低,对设备制造和安全运行更为友好。本流程较为合理、性能较高,可为LNG接收站开展氢气液化提供参考。

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 × 10^(4) to 10 × 10^(4) 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.