| With the work of improving quality and efficiency in major oil and gas fields in China,the recovery of ethane in natural gas is a new development direction.The ethane content in rich natural gas is high,and recycling it can effectively improve the comprehensive utilization of natural gas condensate resources.Through the investigation and analysis of the domestic ethane recovery equipment,it is found that the domestic oilfield associated gas treatment has a small scale and low external pressure,and the LSP process is mostly used.The process is simple,but the energy consumption is high.So it is necessary to improve the process to enhance the recovery rate of ethane and increase the economic income.By comparing the RSV.SRC and SRX ethane recovery processes suitable for large scale and high external pressure,The process characteristics of the three processes show that the reflux of the top of the demethanizer in the RSV process is lean,the ethane recovery rate is high,and the gas phase load distribution in the demethanizer is relatively uniform and reasonable,meeting the requirement of anti-CO2 freeze,so the treatment scale is large.The working conditions with high external pressure and the RSV process are selected as the basis for process improvement.Based on the idea of increasing the ethane recovery rate by the lean gas reflux at the top of the tower,the LSP process was improved,and two improved processes of GLSP and FGSP were proposed.With a number of many simulations,the GLSP process with 94%ethane recovery and the lowest total shaft power of the plant was selected as an improved ethane recovery scheme with low external pressure and small treatment scale.Through the characteristic analysis of the improved process,it is concluded that the ethane recovery rate of the improved process is between 93%and 95%.The boost pressure varies from feed gas.With the increase of GPM of feed gas,the boost pressure decrease gradually.When the GPM of feed gas increases from 5.3 to 9.2,the recommended boost pressure range is between 4.0 and 4.6 MPa.The GLSP process shows good adaptability under different feed gas,both with different GPM and CO2 content,and the ethane recovery rate can reach more than 93%,but when the feed gas becomes rich the total shaft power of the device increases.Based on the idea of continuously reducing the methane content in the liquid phase of the cryogenic separator and increasing the supercooling of the gas phase,two improved processes of RSVL and RSVR were proposed by multi-stage separation and multi-strand reflux at the top of the column.By a large number of simulation analysis,the ethane recovery rate of the two improved processes was increased to 95%,and the RSVL and RSVR total shaft power were reduced by 563 kW and 327 kW,respectively.The characteristics of the feed gas of different GPM in the RSVL process were analyzed.It was concluded that with the increase of GPM,the pressure of the demethanizer decreased and the temperature of the cryogenic separator increased.The RSVL process shows good adaptability under different temperament GPM and CO2 content,and the ethane recovery rate can reach more than 95%,but when the feed gas becomes rich and the total shaft power of the device increases.The demethanizer is the equipment with the highest energy consumption and the largest equipment investment in the ethane recovery unit.Based on the sensitivity analysis and enthalpy analysis technology,the optimal theoretical number of plates for the demethanizer,the optimal feed position for multiple streams and the side reboiling drawing position is optimized to further reduce the thermal load of the demethanizer in the ethane unit.Finally,the hydraulic performance of the demethanizer is analyzed.No hydraulic problems such as leakage and flooding detected in each layer of the tower,which means the demethanizer has a good condition for fluid contacting and can be operated safely and effectively. |
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