Process for safe membrane operation

A process for the removal of carbon dioxide from a hydrocarbon feed gas mixture comprising C.sub.1 to C.sub.6 hydrocarbons, C.sub.6.sup.+ hydrocarbons, and carbon dioxide to produce a sales gas stream, said process comprising:

• a) intermittently passing said feed gas mixture at separation conditions to a membrane separation zone having a non-permeate zone and a permeate zone to provide a non-permeate stream withdrawn from the non-permeate zone, said non-permeate stream comprising C.sub.6.sup.+ hydrocarbons and having a reduced amount of carbon dioxide relative to said feed gas mixture, and a permeate stream withdrawn from the permeate zone at a permeate pressure, said permeate stream enriched in carbon dioxide relative to said feed gas mixture;
• and
• b) passing a purge stream reduced in C.sub.6.sup.+ hydrocarbons to the non-permeate zone when said feed gas mixture is not passed to said membrane separation zone to prevent condensation of C.sub.6.sup.+ hydrocarbons.

A shut-down process for a membrane separation zone comprising at least one membrane separation module having a non-permeate side at a separation pressure and a permeate side at a permeate pressure for the removal of carbon dioxide from a hydrocarbon gas feed stream comprising light hydrocarbons including C.sub.1 to C.sub.4 hydrocarbons, C.sub.6.sup.+ hydrocarbons, a portion of said C.sub.6.sup.+ hydrocarbons being condensable at a saturation pressure, and carbon dioxide, said shut-down process comprising:

• a) terminating the flow of a pressurized hydrocarbon feed stream at a feed pressure to said membrane separation module to provide a first residual gas stream in said non-permeate side, said first residual gas stream comprising C.sub.6.sup.+ hydrocarbons and having a reduced amount of carbon dioxide relative to said feed gas stream, and a second residual gas stream in said permeate side enriched in carbon dioxide relative to said feed stream;
• and
• b) purging said membrane separation module by passing a purge stream essentially free of C.sub.6.sup.+ hydrocarbons to the non-permeate side at a pressure greater than said permeate pressure and recovering at least a portion of the first residual gas stream and withdrawing said second residual gas stream from said permeate side.