With the increase of global energy demand, the natural gas will play a key role both for energy production and for transports. Typically, natural gas is extracted and liquefied in large-scale plants to be later transported by ship or, when it is possible, by pipeline. In this study, a plug & play solution for natural gas liquefaction to be directly installed at the vehicle’s filling stations, in order to avoid the transport costs of liquefied natural gas, is analyzed. The system analyzed in the paper consists in a single stage expansion process and the aim of the study is to improve the small-scale liquefaction process efficiency through the use of a cryogenic expander in replacement of a more common Joule-Thomson valve. A thermodynamic study has been carried out to optimize the process parameters with the aim of minimizing the energy consumption. This optimization study, starting from a reference case, allowed to identify an optimal case, which leads to a total energy saving of about 12% compared to the reference case. Furthermore, considerations relating to the cryogenic expander, which is a key component of the system, have been done. This device guarantees a higher thermodynamic efficiency than Joule-Thomson valve and it allows to integrate the produced shaft power into the process. This study represents a preliminary thermodynamic and parametric investigation on a low pressure LNG production process. The results of this study are the basis for the realization of a prototype which is actually under construction. Thus, further investigations by Authors will determinate the techno-economic feasibility of the optimized system also considering future experimental investigations.

随着全球能源需求的增加，天然气将在能源生产和运输中发挥关键作用。通常，天然气在大型工厂中被提取和液化，然后通过船或在可能的情况下通过管道运输。在本研究中，即插即用为了避免液化天然气的运输成本，分析了将天然气液化直接安装在车辆加气站的解决方案。本文分析的系统包括一个单级膨胀过程，该研究的目的是通过使用低温膨胀器代替更常见的焦耳-汤姆森阀来提高小规模液化过程的效率。为了最小化能量消耗，已经进行了热力学研究以优化工艺参数。从参考案例开始的优化研究可以确定最佳案例，与参考案例相比，可节省约12％的能源。此外，已经完成了与低温膨胀器有关的考虑，低温膨胀器是系统的关键组件。该设备保证了比焦耳-汤姆森阀更高的热力学效率，并且可以将产生的轴功率集成到过程中。这项研究代表了对低压液化天然气生产工艺的初步热力学和参数研究。这项研究的结果是实现实际在建造中的原型的基础。因此，作者的进一步研究将考虑未来的实验研究，从而确定优化系统的技术经济可行性。这项研究的结果是实现实际在建造中的原型的基础。因此，作者的进一步研究将考虑未来的实验研究，从而确定优化系统的技术经济可行性。这项研究的结果是实现实际在建造中的原型的基础。因此，作者的进一步研究将考虑未来的实验研究，从而确定优化系统的技术经济可行性。