Conversion of refinery natural purge gases to liquid hydrocarbons in GTL loop with hydrogen-permselective membranes: An alternative to gas flaring

One of the main issues facing mankind in this century is the global warming which is induced by the increasing concentration of carbon dioxide and other greenhouse gases in the atmosphere. A promising process for controlling the atmospheric CO2 level is prevention of combustion in flares. In the present work, a novel GTL loop is proposed to convert the natural gas wasted by a gas refinery to higher molecular weight hydrocarbons. The process proposes an alternative method instead of conventional gas-burning flares, aims to minimize CO2 emissions and produce liquid fuel such as gasoline. For this purpose, purged natural gas is converted to synthesis gas in a novel hydrogen-permselective membrane reactor with recycle stream and then it is converted to liquid fuel in Fischer-Tropsch membrane reactor. In this configuration, a loop is constructed by returning and mixing a portion of the product with the original feed through a recycle stream. This approach produces large amounts of higher molecular weight hydrocarbons, hydrogen production and decreases environmental impacts owing to purge gases emission. The simulation results of the aforesaid loop, show decrease in CO2 emission rate with a value of 1/10 to that of flaring with production of 0.018 kgmol/s of hydrogen and more than 90 barrels per day of heavy fraction hydrocarbons containing gasoline and butane fraction for a specified value of (about 4 MMscfd) purge gases.

► Implementation of a GTL loop is suggested as an alternative to gas flaring. ► Effects of two important operating conditions on GTL loop performance are investigated. ► A significant reduction in CO2 emission is resulted comparing to other alternatives. ► Considerable amount of valuable hydrocarbons is produced from refinery purge gases.