Process improvement and heat integration of rich gas ethane recovery

Abstract

The recovery of ethane from natural gas is an important measure to enhance the economic benefit and energy saving of oilfields. In the process of condensation, the gas‐rich ethane recovery process has the problems of high condensation, high methane content, difficult control of cold box pinch temperature, and high energy consumption. Based on the Recycle Split Vapor (RSV) process, two improved processes, Supplemental Rectification with Compression and Recycle Split Vapor (SRCR) and Recycle Split Vapor with Liquid Flashing (RSVL), are proposed. Energy consumption analysis shows that RSVL process has the lowest total compression power and lower investment cost than SRCR process. The heat integration analysis shows that the ratios R1 and R2 of the demethanizer side‐draw duty directly influence the temperature matching of the cold and hot streams in the main cold box. For rich gas, R1 is advised to set between .5 and .75, and R2 is advised to set between .6 and .8. The sensitivity analysis shows that the lower the feed gas pressure and the richer the gas, the higher the total compression power of the process, and the closer the composite curve of cold and heat in the main cold box. The higher the feed gas temperature, the greater the total compression power. The higher the CO2 content in the feed gas, the higher the total compression power of the RSVL process, and the smaller the CO2 freezing temperature in the demethanizer.