The development of a small skid-mounted natural gas liquefaction plant can economically, environmentally-friendly, and efficiently collect natural gas in mountainous areas where are not easy to lay pipelines. A propane and iso-butane pre-cooled mixed refrigerant liquefaction process (C₃&C₄-MR) is proposed in this paper. Compared with the propane pre-cooled mixed refrigerant liquefaction process, the improved liquefaction process can reduce system energy consumption and increase exergy efficiency greatly. Genetic algorithm is applied to optimize energy consumption of C₃&C₄-MR process. The optimized specific energy consumption $S_{\mathit{Total}}$ is 0.301 kW·h/kg, which is 18.0% lower than the optimized C₃-MR process. And compared with the optimized R410a pre-cooled mixed refrigerant liquefaction process, $S_{\mathit{Total}}$ of C₃&C₄-MR process is 5.64% lower than that of R410a-MR process. Besides, mixed propane and isobutane as pre-coolant is easier to obtain from the feed gas. By analyzing the temperature sensitivity of mixed refrigerant and calculating the unit compression power consumption of a single refrigerant, the guidance and recommendations for mixed refrigerant ratio are summarized. Due to the property of iso-butane, the optimal percentage of iso-butane in the pre-coolant was analyzed. In conclusion, C₃&C₄-MR process is energy-saving and advanced in terms of system operating costs to recycle scattered natural gas in remote areas.

在不易铺设管道的山区开发小型的撬装式天然气液化厂可以经济，环保并有效地收集天然气。本文提出了丙烷和异丁烷的预冷混合制冷剂液化工艺（C ₃＆C ₄ -MR）。与丙烷预冷混合制冷剂液化工艺相比，改进后的液化工艺可以降低系统能耗，提高火用效率。应用遗传算法优化C ₃＆C ₄ -MR工艺的能耗。优化的单位能耗${\mathrm{小号}}_{\mathit{总}}$为0.301 kW·h / kg，比优化的C ₃ -MR工艺低18.0％。与优化的R410a预冷混合制冷剂液化工艺相比，${\mathrm{小号}}_{\mathit{总}}$与R410a-MR工艺相比，C ₃＆C ₄ -MR工艺的效率降低了5.64％。此外，从进料气中更容易获得混合的丙烷和异丁烷作为预冷却剂。通过分析混合制冷剂的温度敏感性并计算单个制冷剂的单位压缩功率消耗，总结了混合制冷剂比例的指导和建议。由于财产异丁烷，最优比例ISO在预冷却液丁烷进行了分析。总之，C ₃＆C ₄ -MR工艺是节能的，并且在系统运行成本方面先进，可以回收偏远地区的分散天然气。