Optimization Of The Heat Exchange Network In The Condensation Separation Of A Natural Gas Processing Station With Daily Output Of 20×10~4 Nm~3

Based on the different target products of natural gas recovering,different processes have been developed.According to the gas properties of the HSZ gas field,two processes for recovering ethane and liquefied petroleum gas（LPG）have been proposed for treating low pressure natural gas,respectively.In the process of natural gas separation,the problem of opmizing heat exchang network is common focused.The analysis of the heat exchang network aiming to different products,and the resulting optimization strategies are significant to improve the economic,rationality and efficiency of the natural gas treatment.This dissertation attempted to analyze the literatures of natural gas condension separation and condensate recovery,and then calculate the Direct Heat Exchange Process（DHX）for the recovery of liquefied petroleum gas as well as the Liquid Subcooled Process（LSP）for ethane.The simulation of DHX process leads to a high recovery rate of liqufied petroleum gas at 98.16%,and a high yield of C₃ at 97.64%,which meet the requirement of the design.The recovery rate of ethane and LPG in LSP is 94.21%and 99.17%,respectively,which meet the requirement of the design.Based on the caculation,the income of the DHX process is 268,000 yuan/day,and the income of the LSP process is 298,000 yuan/day.The system energy consumption of the DHX process is 3288.2 k W,and the value for the LSP process is 5818.0 k W.Based on the analysis of the heat exchang networks of the two above processes,the heat transfer across the pinch points has been obtained.The heat exchang network was redesigned using the pinch matching principle to obtain the heat exchang flow which is matched with zero heat transfer across the pinch point.After optimization,the cold utility of the DHX process is reduced from 939.7 k W to 886.2 k W,the thermal utility is reduced from 90.41 k W to 36.8 k W,leading to a reduction of the total cost from 983.6Cost/s to 972.8 Cost/s.The cold utility of the LSP process is reduced from 1699.0 k W to 1510.0 k W,and the thermal utility is reduced from 112.9 k W to 22.9 k W,leading to a reduction of the total cost from 2089 Cost/s to 2022 Cost/s.The calculated total cost together with the utility load analysis,the best recycling process should be the DHX process,which mainly produces dry gas,extracts liquefied petroleum gas and stabilizes light hydrocarbons.Based on the analysis of a heat exchang network of a practical recover of liquefied petroleum gas by the DHX process,the cross-pinch heat transfer phenomenon can not be observed,which proves the rationality of the optimization of the heat exchange network.Thus,the strategy without the cross-pinch heat transfer is suitable for the heat exchang network for the HSZ gas field.