Abstract A thermodynamic process is investigated and designed for hydrogen liquefaction system to utilize the cold energy of liquefied natural gas (LNG). This study is an initial effort of newly launched five-year governmental project in Korea, aiming at efficient hydrogen liquefiers. Since Korea is a major LNG import country, the cold energy is abundantly available and could be useful in reducing the liquefaction cost. Hydrogen gas at ambient temperature is pre-cooled by LNG and then fed into a closed-cycle Brayton refrigerator. Rigorous thermodynamic analysis is carried out on the process with standard or modified Brayton cycles for the optimal condition to minimize the power consumption. It is revealed that LNG at atmospheric pressure is much more effective in pre-cooling than pressurized LNG (for pipeline distribution), because of the temperature pinch problem in heat exchanger. By taking into consideration the efficiency and other factors such as safety, compactness, and simplicity of operation, 2-stage expansion cycle with LNG pre-cooling is identified as most suitable for the pilot system with a capacity of 0.5 ton/day. Full details of liquefaction process are presented with the optional use of catalysts for ortho-para conversion.

中文翻译：

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利用 LNG 冷能的布雷顿制冷循环制氢工艺

摘要 研究并设计了氢气液化系统利用液化天然气(LNG)冷能的热力学过程。这项研究是韩国新启动的五年政府项目的初步努力，旨在开发高效的氢气液化器。由于韩国是液化天然气的主要进口国，冷能资源丰富，可用于降低液化成本。常温下的氢气由 LNG 预冷，然后送入闭式循环布雷顿制冷机。使用标准或改进的布雷顿循环对过程进行严格的热力学分析，以获得最佳条件，以最大限度地降低功耗。结果表明，常压 LNG 在预冷方面比加压 LNG（用于管道分配）更有效，因为热交换器中的温度夹点问题。综合考虑效率和安全性、紧凑性、操作简便性等因素，LNG预冷二级膨胀循环最适合0.5吨/天的中试系统。液化过程的全部细节都可以选择使用用于邻位对位转化的催化剂。