Method and System for Membrane-Based Gas Recovery

Abstract

A fast gas is recovered from a feed gas containing a fast gas and at least one slow gas using a gas separation membrane. A controller may control a control valve associated with a partial recycle of a permeate gas from the membrane for combining with the feed gas. A controller may control a control valve associated with the backpressure of a residue gas from the membrane.

What is claimed is: 
     
         1 . A system for recovering a gas of interest from a process producing a varying flow rate of an exhaust gas, comprising:
 a plurality of sources of an exhaust gas, the exhaust gas comprising a fast gas and a slow gas;   a feed gas conduit in selective fluid communication with the plurality of sources;   a compressor having an inlet in fluid communication with the feed gas conduit and an outlet;   a primary gas separation membrane having an inlet, a permeate outlet and a residue outlet, the inlet of the primary gas separation membrane being in fluid communication with the compressor outlet, the primary gas separation membrane being preferentially permeate to the gas of interest;   a primary permeate conduit in fluid communication with the permeate outlet of the primary gas separation membrane;   a product gas conduit in fluid communication with the primary permeate conduit;   a recycle conduit in fluid communication between the primary permeate conduit and the compressor inlet;   a recycle control valve in fluid communication with the primary permeate conduit, the recycle conduit, and the product gas conduit, the recycle control valve being adapted to adjust a proportion of permeate gas that is allowed to flow from the primary permeate conduit to the recycle conduit versus the product gas conduit; and   a controller adapted to control the proportionate adjustment by the recycle control valve.   
     
     
         2 . The system of  claim 1 , further comprising:
 a secondary gas separation membrane having an inlet in fluid communication with the residue outlet of the primary gas separation membrane, a secondary residue outlet, and a secondary permeate outlet; and   a secondary permeate conduit in fluid communication between the permeate outlet of the secondary gas separation membrane the recycle conduit.   
     
     
         3 . The system of  claim 1 , further comprising a secondary gas separation membrane having an inlet in selective fluid communication with the plurality of sources, a secondary residue outlet, and a secondary permeate outlet in fluid communication with the feed gas conduit. 
     
     
         4 . The system of  claim 1 , further comprising a device sensing whether or not one or more of the sources are actively producing the exhaust gas, wherein the controller is further adapted to receive a signal from the sensing device representative of the number of sources that are actively producing the exhaust gas and control the proportionate adjustment by the recycle control valve based upon the signal. 
     
     
         5 . The system of  claim 1 , wherein the controller is further adapted to:
 receive a signal from a sensing device that is representative of a recovery of the fast gas that is achieved by operation of said system; and   control the proportionate adjustment by the recycle control valve based upon the recovery signal.   
     
     
         6 . The system of  claim 1 , further comprising a sensing device adapted to measure a concentration of the fast gas in product gas in the product gas conduit and send a signal to the controller representative of the measured concentration, wherein the controller is further adapted to:
 receive the concentration signal from the sensing device; and   control the proportionate adjustment by the recycle control valve based upon the concentration signal.   
     
     
         7 . The system of  claim 1 , further comprising:
 a secondary gas separation membrane having an inlet in fluid communication with the residue outlet of the primary gas separation membrane, a secondary residue outlet, and a secondary permeate outlet; and   a secondary permeate conduit in fluid communication between the permeate outlet of the secondary gas separation membrane the recycle conduit, wherein the sources are optical fiber cooling towers and the fast gas is Helium.