Process for separating a gas from a mixture of gases

Claim 2

A process for separating one gas from a mixture of said one gas and at least one other gas, comprising a. bringing said gas mixture at a varying flow rate into contact with one side of a membrane more permeable to said one gas than said other .. gas to allow said one gas to permeate through the membrane, said gas mixture being under a first pressure; and b. recovering said permeated one gas from the other side of said membrane, said permeated gas being at a second pressure lower than said first pressure such that there is a pressure differential across the membrane; characterised by c. varying said pressure differential with variations in said flow rate in such a manner that the ratio of change in said pressure differential to change in said flow rate remains substantially constant.

Claim 3

A process of Claim 1, wherein the product of said ratio and the effective surface area of said membrane is within the range of 1.5 to 10, where the pressure differential is expressed in terms of kg/cm 2 , the flow rate is expressed in terms of standard cubic meters per hour and said surface area is expressed in terms of square meters.

Claim 4

A process of either Claim 1 or Claim 2, wherein the membrane is in the form of hollow fibers.

Claim 5

A process of any of the preceding claims, wherein the flow rate of said feed gas varies within a range such that the maximum flow rate is no more than 20 times the minimum flow rate.

Claim 6

A process of Claim 4, wherein said maximum flow rate is no more than 10 times the minimum flow rate.

Claim 7

6 . A process of any of the preceding claims, wherein the second pressure is held substantially constant and the first pressure is varied to vary said pressure differential.

Claim 8

A process of any of the preceding claims, wherein said one gas is hydrogen.

Claim 9

A process of Claim 7, wherein said membrane has a separation factor of at least 10 for hydrogen in preference to at least one other gas in said gas. mixture.

Claim 10

A process of either Claim 7 or Claim 8, wherein said member has a permeability for hydrogen of at least about 1×10 -6 cc of hydrogen per square centimeter of membrane surface area per second at a partial pressure drop of 1 centimeter of mercury.

Claim 11

A process of any of Claims 7 to 9, wherein said other gas is at least one gas selected from the group consisting of nitrogen, carbon monoxide and hydrocarbon gases having one to five carbon atoms.

Claim 12

A process of any of the preceding claims, wherein flow rate variations are sensed and the pressure differential is changed in response to said sensed flow rate changes.

Claim 13

A process according to Claim 10 for recovering hydrogen .from a gas stream made up of a. mixture of hydrogen and said at least one other gas, comprising: a. bringing the gas stream at a varying flow rate into contact with the outer surface of a hollow fiber having a greater permeability for hydrogen than said at least one other gas so that said hydrogen permeates to the interior of the hollow fiber, said gas stream being under a first pressure; b. withdrawing the permeated hydrogen from the interior of the fiber under a second pressure, said second pressure being less than said first pressure such that a pressure differential exists between the exterior and interior of the fiber; c. sensing the flow rate of the gas stream to detect changes therein, and d. varying said pressure differential as aforesaid in proportion to changes detected in said flow rate.

Claim 14

A process of Claim 12, wherein the ratio selected is such that said product is within the range of 2 to 7.

Claim 15

A process of either Claim 12 or Claim 13, wherein both flow rate and gas mixture pressure are sensed, said flow rate being sensed at a first point upstream of the hollow fiber and said pressure being sensed at a second point downstream of said hollow fiber.