小型撬装式天然气液化流程模拟与分析

Simulation and analysis of liquefaction process for small-scale liquefied natural gas plants in skid-mounted packages

基于中国绝大多数天然气田储量不大,而且分布较分散,离天然气管道较远,因此小型撬装式天然气装置在中国具有广阔的应用前景。小型撬装式天然气装置要求设备少、结构紧凑、操作简单、可靠性高、适应性强、操作弹性大。这对于净化与液化流程提出了更高的要求。采用化工流程软件HYSYS,对单阶混合制冷剂流程,氮气膨胀流程和带丙烷预冷氮气膨胀流程三种工艺流程进行了模拟分析,并以单位能耗为指标对上述三种流程进行了优化。结果发现带丙烷预冷氮气膨胀流程换热平均温差较小,而且能耗较低、流程简单、启动快、操作与维护方便,是比较适合于小型撬装式液化天然气装置的流程。

Based on the fact that the majority of the natural gas fields in China have small reserves, dispersed distribution and are far away from the natural gas pipelines, small - scale LNG （ Liquefied Natural Gas） plants in skid - mounted packages have a broad application prospect in China. Small -scale LNG （Liquefied Natural Gas） plants in skid -mounted packages have many advantages, including less equipments, compact structure, high reliability and adaptability, simple and flexible operation. Therefore, it sets higher requirements for the purification and liquefaction process. In this paper, three liquefaction processes, including mixed refrigerant process, nitrogen expansion process and nitrogen expansion process with propane pre -cooling, were designed and simulated by the software Aspen HYSYS, and optimized with the unit product liquefaction power consumption as the major index. The results show that the liquefaction process adopting a nitrogen expansion process with propane pre - cooling is suitable for small- scale LNG （Liquefied Natural Gas） plants in skid -mounted packages due to its simplicity, small tempera- ture difference in heat exchanger, low unit product liquefaction power consumption, quick startup and convenient maintenance.