(U.S. Patent No. 6116050 Issued 9/12/2000)
The recently patented Improved Propane Recovery (IPR) method was developed to achieve high recovery levels (in excess of 98%) of propane in a natural gas feed without the addition of substantial amounts of recompression and/or refrigeration HP. The IPR method employs sequentially configured first and second distillation columns, e.g. a demethanizer tower followed by a deethanizer tower. A cooled gas feed condensate is separtated in the first column into methane and a liquid phase comprising ethane and heavier hydrocarbons. The liquid phase is separated in the second column into a gas phase primarily comprising ethane and a second liquid phase primarily comprising the desired C3+ hydrocarbons. At least a portion of the second gas phase is introduced into the first distillation column as a propane free overhead reflux stream to improve the separation of C3+ hydrocarbons. The process permits separation and recovery of more than about 99% of the C3+ hydrocarbons in the gas feed at higher than normal operating pressures. Further, by cooling the second gas phase with a liquid condensed in a lower tray of the first column, significant capital and operating costs may be saved. By employing the self refrigeration system (see Improved Propane Recovery Methods), the need for external refrigeration is eliminated and the separation efficiency is improved in the first column. Accordingly, the IPR method results in achievement of higher liquid recovery levels with lower capital requirements and significant savings in operation.