Membrane nitrogen with temperature tracking

Claim 1

An improved gas separation process for the operation of high permeability membranes having optimum operating temperatures above cool ambient temperatures prevailing during a portion of an operating year at a gas separation location, the optimum operating temperature being below the ambient temperature during the remainder of the operating year, comprising the steps of: (a) compressing feed gas to a predetermined feed gas operating pressure in a feed gas compressor of a feed gas compresser/membrane gas separation system combination at a plant location in which cool ambient temperature conditions prevail during a portion of the year, with higher ambient conditions prevailing during the remainder of the year, a design feed gas operating pressure being a desired feed gas pressure pertaining to said cool ambient temperature conditions; (b) adjusting the feed gas at said predetermined feed gas operating pressure, using an aftercooler unit of the feed gas compressor and heater means to maintain a desired optimum operating temperature above said cool ambient temperature conditions during the portion of the year in which said cool ambient temperature conditions prevail; (c) passing the feed gas, at said predetermined feed gas operating pressure and adjusted to a desired optimum operating temperature in step (b) above, to said membrane gas separation system for the isothermal separation of a less permeable component thereof at said desired optimum operating temperature, said membrane gas separation system being capable of selectively permeating the more permeable component of feed gas and comprising membrane separation material having a desired optimum operating temperature above said cool ambient temperature conditions; (d) recovering non-permeate gas and permeate gas from the membrane gas separation system at said optimum operating temperature above said cool ambient temperature conditions; (e) adjusting the thus compressed feed gas, using the aftercooler unit of the feed gas compressor and heater means, but allowing the operating temperature to rise in response to higher ambient temperature conditions in the portion of the year in which the ambient temperature rises to above the optimum operating temperature conditions prevailing during the other portion of the year; (f) decreasing the feed gas operating pressure below said predetermined feed gas operating pressure that prevails at said cool ambient temperature conditions during the portion of the year in which the operating temperature is allowed to rise in step (e), in response to higher ambient temperature conditions, so as to maintain desired product conditions in step (d), whereby membrane gas separation operations are carried out for the production of product gas under varying ambient temperature conditions without the use of external refrigeration and at desirable reduced power consumption levels.