等压开式制冷天然气凝液回收工艺优化研究

Optimization of isobaric open refrigeration process for natural gas liquid recovery

关键词:  天然气凝液回收  开式制冷  混合冷剂 

Key words:  natural gas liquid recovery  open refrigeration  mixed refrigerant

摘要:

等压开式制冷工艺是一种较新的天然气凝液回收工艺技术,与目前广泛采用的直接换热工艺相比,该工艺所需设备数量少,投资和运行费用低。以长庆油田典型伴生气为例,对该工艺进行了模拟研究,分析并优化了影响该工艺C⁺₃回收率以及能耗的主要工艺参数。计算结果表明:①C⁺₃回收率随原料气预冷温度的降低而增加,当原料气预冷温度低于-30 ℃后,C⁺₃回收率随温度变化的增幅变缓；②混合冷剂节流压力对C⁺₃回收率以及脱乙烷塔塔底重沸器热负荷的影响不显著,但节流压力降低会增加混合冷剂压缩机的能耗；③混合冷剂冷却温度越低,C⁺₃回收率越高。最优操作条件为:原料气预冷温度-30 ℃,混合冷剂节流压力500 kPa,混合冷剂冷却温度-30 ℃。此时,C⁺₃回收率可达96.1%。 

Abstract:

Isobaric open refrigeration process is a new NGL-recovery technology. Compared with the traditional direct heat exchange process, this new process requires less equipment, and has lower capital and operating costs. In this study, associated gas from Changqing Oilfield is taken as an example. The process is simulated, and the process parameters affecting C⁺₃ recovery and energy consumption are investigated and optimized. The results indicate that:①C⁺₃ recovery increases as the feed gas temperature decreases, however when the feed gas temperature is below -30 ℃, C⁺₃ recovery increases slowly; ②refrigerant throttle pressure has little influence on C⁺₃ recovery and de-ethanizer reboiler duty, but a lower refrigerant throttle pressure means a larger mixed refrigerant compressor duty required; ③C⁺₃ recovery increases with the decrease of refrigerant cooling temperature. The optimum operating conditions are as follows:feed gas temperature is -30 ℃, refrigerant throttle pressure is 500 kPa, refrigerant cooling temperature is -30 ℃. Under these conditions, the C⁺₃ recovery can reach 96.1%.