摘要
Abstract
The content(mole fraction)of ethane and helium in the natural gas of a domestic gas field is increasing year by year,and the recovery value is highlighted.A process of helium extraction and ethane co-production by nitrogen double expansion refrigeration was proposed.The process was simulated by HYSYS software,and the influences of the key parameters of the process(temperature of the cryogenic separator,reflux ratio of the demethanizer top,feed temperature of the secondary helium extraction tower,reflux ratio of the secondary helium extraction tower top,inlet pressure of the nitrogen expansion end,outlet pressure of the nitrogen expansion end and flow rate of the nitrogen refrigerant)on the process indexes were investigated.Based on the optimisation theory,the Back Propagation(BP)neural network algorithm was used to optimise the key parameters with the objectives of minimising the total energy consumption of the unit when the C2 yield and the secondary crude helium concentration were maximised.The results show that the total energy consumption of the unit is mainly affected by temperature of the cryogenic separator,the outlet pressure of the nitrogen expansion end and the flow rate of the nitrogen refrigerant,and the C2 yield is mainly affected by temperature of the cryogenic separator and the reflux ratio of the demethanizer top,and the helium yield is mainly affected by the feed temperature of the secondary helium extraction tower.The optimal combination of key parameters is as follows:Temperature of the cryogenic separator is-95.30 ℃,flow rate of the nitrogen refrigerant is 1549.22 kmol/h,inlet pressure of the nitrogen expansion end is 3.25 MPa,outlet pressure of the nitrogen expansion end is 0.44 MPa,reflux ratio of the demethanizer top is 0.13,feed temperature of the secondary helium extraction tower is-150.57 ℃,and eflux ratio of the secondary helium extraction tower top is 0.80.Compared with the pre-optimization,the total energy consumption of the optimized unit is reduced by 1.46％,the C2 yield is increased by 5.64％,and the secondary crude helium concentration(mole fraction)is increased by 1.81％.关键词
氮气双膨胀制冷/天然气提氦/乙烷回收/联产工艺/参数优化/BP神经网络算法Key words
nitrogen double expansion refrigeration/helium extraction from natural gas/ethane recovery/co-production process/parameter optimization/BP neural network algorithm分类
石油、天然气工程
