Lean Reflux Process for High Ethane Recovery

The recently patented lean reflux process (LRP) was developed to achieve high recovery levels of ethane in a natural gas feed without the addition of substantial amounts of recompression and/or external refrigeration horsepower. This new process utilizes a slipstream from the cold separator or feed gas to generate an essentially ethane-free stream as a lean reflux to the demethanizer. The introduction of a lean reflux considerably reduces equilibrium loss, thereby leading to high ethane recovery while maintaining the demethanizer at a relatively high operating pressure. The process overcomes deficiencies in the commonly-used gas subcooled reflux process in which ethane recovery levels are ultimately restricted to approximately 90 percent due to equilibrium loss, or otherwise demand a lower demethanizer pressure and a higher recompression and/or refrigeration HP. The enhancement in operational efficiency coupled with reduced capital cost becomes even more profound in gas processing plants requiring deep ethane recovery, particularly in excess of 95%, or with an ethane content typically greater than 5% in the feed gas. The IPSI enhancement package (US Patent No. 5,992,175) features a self-refrigeration and stripping gas add-on skid to most leading NGL recovery technologies.  The package can also be adapted for rich gas feed where additional external refrigeration is deemed necessary, thus replacing conventional and costly processes, such as propane refrigeration.

Figure 6: Lean Reflux Process for High Ethane Recovery

For a printable PDF, please click here.