In natural gas transportation,low-temperature separation methods(J-T valve refrigeration,mechanical refrigeration)are often used to separate liquid hydrocarbons and water to control the dew point and ensure pipeline transportation safety.Given the significant differences between the two processes,we have simulated and analyzed the J-T valve refrigeration and mechanical refrigeration from both energy and economic aspects.The results show that the hydrocarbon dew point drop of the two processes is close,while the water dew point drop of the mechanical refrigeration process is higher.On the basis of exergy analysis,the J-T valve refrigeration process has a higher exergy destruction(5 159 kW)than the mechanical refrigeration process(1 961 kW).The mechanical refrigera-tion process has a higher system heat transfer efficiency,which makes its overall efficiency higher than J-T valve refrigeration.Detailed analysis shows that the avoidable energy destruction(69.8％)of the mechanical refrigera-tion process is higher than the J-T valve refrigeration process(66.7％),with greater improvement potential and lower cost.In terms of capital investment,the mechanical refrigeration process uses an external refrigeration system to provide cooling capacity,resulting in higher equipment purchase cost,but it retains the pressure energy of the feed gas.Under the same export conditions,the operating cost and the comprehensive investment cost of the mechanical refrigeration process is lower than the J-T valve refrigeration process.Over the whole operation cycle,the mechanical refrigeration process resulted in a cost advantage of 812.64 × 104 dollars.A sensitivity analysis of the two processes shows that the cooling performance of the refrigerant does not continue to increase with increasing flow rate.As the formation pressure decreases,the effect of using differential pressure of natural gas is less than that of external refrigerant refrigeration.
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