The Application of an Electronic Computer to the Calculation of the Recovery of Natural Gasoline by Refrigeration

A study of the recovery of natural gasoline from natural gas by refrigeration was made with the aid of an IBM 650 computer. A form of the familiar "flash" equation, chosen to minimize calculation time, was employed to determine the natural gasoline recovery. An eight-component system can be solved in about 30 seconds for each pressure and temperature combination. The ranges of the variables studied aregasoline content (isobutane and heavier) of the wet gas, 0.891 to 3.293 gal/Mcf,pressure, 50 psia to 1,000 psia, andtemperature, −20 degrees F to +40 degrees F. For the gases considered the gasoline content of the discharge gas decreases more or less linearly with pressure to about 300 psia and then levels off. For all but the leanest gas, the gasoline content of the discharge gas can be reduced to 0.45 gal/Mcf at 400 psia and 0 degrees F. Under certain conditions of pressure and temperature the gasoline content can be reduced to as low as 0.25 gal/Mcf. In this case a large penalty is paid in the excessive recovery of propane and lighter in the liquid, The extraction efficiency is often a more satisfactory measure of the utility of the process than is the gasoline content of the discharge gas. The extraction efficiency increases more or less linearly to about 300 psia and then levels out beyond 600 psia. For all but the leanest wet-gas the isobutane and heavier extraction efficiency exceed 70 per cent at 400 psia and 0 degrees F. Under certain conditions the efficiency may exceed 90 per cent. At a given pressure and temperature, the richer the wet gas, the higher is the extraction efficiency. Introduction The recovery of natural gasoline from natural gas by refrigeration is a special field processing method. A study was made to establish the area of application of the method. The first step was to determine the ultimate physical recovery of liquid product, and the second step, to determine the economic recovery of liquid product. This paper will deal only with the first step. It describes in some detail the program for solving the flash equation with the aid of the IBM 650 computer and reports the calculated results. A somewhat similar study has been reported by Stamm, McCarty, Allen and Moore, but for a more limited range of wet-gas compositions and operating conditions.