基于Aspen Adsorption的氦气/甲烷吸附分离过程模拟优化

Optimization of helium/methane adsorption separation process based on Aspen Adsorption simulation

工业氦气主要通过深冷、膜分离和变压吸附(PSA)耦合从天然气提取,其中PSA是获得高纯He的关键。吸附过程模拟可以克服实验局限,有效指导工程设计、优化工艺条件。以体积分数90%的粗He为原料,利用AspenAdsorption软件建立He/CH4单塔PSA模型,获得穿透曲线。以此为基础,建立双塔分离流程,分析吸附、顺放、逆放、冲洗、升压步骤中吸附塔内气相组成的变化,五步最佳操作时间分别为60、180、30、60和180s。在三塔流程中,一个循环周期的最佳吸附时间和均压时间分别为135s和90s,产品纯度可达98.42%,回收率达60.45%。在五塔流程中,考虑到各步骤时间的匹配及生产的连续性,需要对一个周期内的循环时间进行优化。循环时间为300~340s时,产品纯度达到99.07%以上。

Industrial helium is mainly extracted from natural gas by cryogenic, membrane separation and pressure swing adsorption(PSA) coupling of which PSA is the key to obtain high purity helium. It is helpful to overcome experimental limitations via adsorption process simulation, which can effectively guide engineering design and optimize process conditions. A helium/methane single-column pressure swing adsorption model was established by Aspen Adsorption software to obtain breakthrough curves. Based on the results, a two-column PSA process was established. The optimal operation time of adsorption, forward, reverse, flush, and boost step is 60, 180, 30, 60 and 180 s, through analyzing the changes of the gas phase composition in the adsorption column. In three-column PSA process, the optimal time of adsorption and pressure equalization for one cycle are 135 s and 90 s, helium purity can reach 98.42% and the recovery is up to 60.45%. It is necessary to optimize the cycle time in one cycle by considering the matching of each step time and the continuity of production in five-tower PSA process. When cycle time is between 300 s and 340 s, purity of helium reaches 99.07%.