US2018361310A1PendingUtilityA1

Method and system for purification of natural gas using membranes

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Assignee: AIR LIQUIDE ADVANCED TECH US LLCPriority: Dec 3, 2015Filed: Aug 22, 2018Published: Dec 20, 2018
Est. expiryDec 3, 2035(~9.4 yrs left)· nominal 20-yr term from priority
Inventors:Sandeep K. KarodeYong Ding
B01D 53/261B01D 71/56B01D 53/268B01D 53/225C10L 3/104C10L 2290/08B01D 53/229B01D 71/80B01D 2053/224C10L 3/101B01D 53/72B01D 2325/20B01D 71/52C10L 3/106C10L 2290/548C10L 2290/542B01D 69/08B01D 71/5222Y02C20/40B01D 53/228B01D 2257/504B01D 53/227B01D 2256/245B01D 53/226B01D 2257/80B01D 2311/14
61
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Claims

Abstract

Natural gas may be purified by removing C 3+ hydrocarbons and CO 2 in respective first and second gas separation membrane stages to yield conditioned gas lower in C 3+ hydrocarbons and CO 2 in comparison to the un-conditioned natural gas.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
         1 . A method for purification of natural gas including methane, CO 2 , and C 3+  hydrocarbons, comprising the steps of:
 feeding a feed gas consisting of the natural gas to a first gas separation membrane stage comprising one or more membranes in series or parallel having a selective layer that is selective for C 3+  hydrocarbons over methane; 
 withdrawing a first permeate stream from the membrane(s) of the first stage that is enriched in C 3+  hydrocarbons in comparison to the feed gas; 
 withdrawing a first retentate stream from the membrane(s) of the first stage that is deficient in C 3+  hydrocarbons in comparison to the feed gas; 
 feeding the first retentate stream to a second gas separation membrane stage comprising one or more membranes in series or parallel having a selective layer that is selective for CO 2  over methane; 
 withdrawing a second permeate stream from the membrane(s) of the second stage that is enriched in CO 2  in comparison to the feed gas; and 
 withdrawing a first retentate stream from the membrane(s) of the first stage that is deficient in CO 2  in comparison to the feed gas. 
 
     
     
         2 . The method of  claim 1 , further comprising removing water from the feed gas prior to feeding the feed gas to the first gas separation membrane stage. 
     
     
         3 . The method of  claim 2 , wherein said step of removing water comprises feeding the feed gas to a molecular sieve adapted and configured to remove water from fluids. 
     
     
         4 . The method of  claim 2 , wherein said step of removing water comprises feeding the feed gas to a dehydration gas separation membrane. 
     
     
         5 . The method of  claim 1 , further comprising the step of combusting the first and/or the second permeate streams as a flare gas. 
     
     
         6 . The method of  claim 1 , wherein the feed gas is obtained from natural gas extracted from a subterranean or subsea geological formation and said step further comprises injecting the first and/or second stage permeate streams into the geological formation. 
     
     
         7 . The method of  claim 6 , further comprising dehydrating the first and/or second permeate streams prior to injection into the geological formation such that a water content in the first and/or second permeate stream injected into the geological formation is no more than 50 ppm (vol/vol). 
     
     
         8 . The method of  claim 1 , wherein the one or membranes of the first gas separation membrane stage have a separation layer made of a copolymer or block polymer of tetramethylene oxide, and/or propylene oxide, or ethylene oxide. 
     
     
         9 . The method of  claim 8 , wherein a pressure drop between a pressure of the feed gas and a pressure of the retentate gas is less than 50 psi (3.45 bar). 
     
     
         10 . The method of  claim 8 , wherein a pressure drop between a pressure of the feed gas and a pressure of the retentate gas is less than 30 psi (2.07 bar). 
     
     
         11 . The method of  claim 8 , wherein a pressure drop between a pressure of the feed gas and a pressure of the retentate gas is less than less than 20 psi (1.38 bar). 
     
     
         12 . The method of  claim 8 , wherein the one or more membranes of the first gas separation membrane stage have a methane permeance of less than 68 gas permeation units (22.4 mol/m 2 ·sec·Pa). 
     
     
         13 . The method of  claim 8 , wherein the one or more membranes of the first gas separation membrane stage have a methane permeance of less than 34 GPU. 
     
     
         14 . The method of  claim 8 , wherein the one or more membranes of the first gas separation membrane stage have a methane permeance of less than 20 GPU. 
     
     
         15 . The method of  8 , wherein the one or membranes of the first gas separation membrane stage have a separation layer made of a copolymer or block polymer of the formula: 
       
         
           
           
               
               
           
         
       
       where PA is an aliphatic polyamide having 6 or 12 carbon atoms and PE is either poly(ethylene oxide) poly(tetramethylene oxide). 
     
     
         16 . The method of  claim 8 , wherein one or membranes of the first gas separation membrane stage have a separation layer made of repeating units of the following monomers: 
       
         
           
           
               
               
           
         
       
     
     
         17 . The method of  claim 8 , wherein the one or more membranes of the first gas separation membrane stage are formed as flat films or as a plurality of hollow fibers. 
     
     
         18 . The method of  claim 8 , wherein each of the one or more membranes of the first gas separation membrane stage has a separation layer that is supported by a support layer. 
     
     
         19 . The method of  claim 18 , wherein each of the support layers is made of a polyimide, polysulfone, or polyether ether ketone. 
     
     
         20 . The method of  claim 19 , wherein each of the support layers is porous and is made of polyether ether ketone. 
     
     
         21 . The method of  claim 1 , wherein each of the membranes of the second gas separation membrane stage is made of cellulose acetate, a polysulfone, or a polyimide. 
     
     
         22 . A system for purification of natural gas including methane, CO2, and C 3+  hydrocarbons, comprising:
 a source of natural gas; 
 a first gas separation membrane stage comprising one or more membranes fluidly in series or parallel communicating with said source, each membrane of the first gas separation membrane stage having a selective layer that is selective for C 3+  hydrocarbons over methane; and 
 a second gas separation membrane stage comprising one or more membranes in series or parallel fluidly communicating with a retentate outlet(s) of the membranes of the first gas separation membrane stage so as to receive retentate from the first gas separation membrane stage as a feed gas in the second gas separation membrane stage, each membrane of the second gas separation membrane stage having a selective layer that is selective for CO 2  over methane. 
 
     
     
         23 . The system of  claim 22 , further comprising a water removal apparatus adapted and configured to remove water from the feed gas prior to feeding the feed gas to the first gas separation membrane stage. 
     
     
         24 . The system of  claim 23 , wherein said water removal apparatus is a molecular sieve adapted and configured to remove water from fluids. 
     
     
         25 . The system of  claim 23 , wherein said water removal apparatus is a dehydration gas separation membrane. 
     
     
         26 . The system of  claim 22 , wherein each of the one or membranes of the first gas separation membrane stage has a separation layer made of a copolymer or block polymer of tetramethylene oxide, and/or propylene oxide, or ethylene oxide. 
     
     
         27 . The system of  claim 26 , wherein each of the one or membranes of the first gas separation membrane stage exhibits a pressure drop between a pressure of the feed gas and a pressure of the retentate gas is less than 50 psi (3.45 bar). 
     
     
         28 . The system of  claim 26 , wherein each of the one or membranes of the first gas separation membrane stage exhibits a pressure drop between a pressure of the feed gas and a pressure of the retentate gas is less than 30 psi (2.07 bar). 
     
     
         29 . The system of  claim 26 , wherein each of the one or membranes of the first gas separation membrane stage exhibits a pressure drop between a pressure of the feed gas and a pressure of the retentate gas is less than less than 20 psi (1.38 bar). 
     
     
         30 . The system of  claim 26 , wherein each of the one or membranes of the first gas separation membrane stage exhibits a methane permeance of less than 68 gas permeation units (22.4 mol/m 2 ·sec·Pa). 
     
     
         31 . The system of  claim 26 , wherein each of the one or membranes of the first gas separation membrane stage exhibits a methane permeance of less than 34 GPU. 
     
     
         32 . The system of  claim 26 , wherein each of the one or membranes of the first gas separation membrane stage exhibits a methane permeance of less than 20 GPU. 
     
     
         33 . The system of  claim 26 , wherein the one or membranes of the first gas separation membrane stage have a separation layer made of a copolymer or block polymer of the formula: 
       
         
           
           
               
               
           
         
       
       where PA is an aliphatic polyamide having 6 or 12 carbon atoms and PE is either poly(ethylene oxide) poly(tetramethylene oxide). 
     
     
         34 . The system of  claim 26 , wherein one or membranes of the first gas separation membrane stage have a separation layer made of repeating units of the following monomers: 
       
         
           
           
               
               
           
         
       
     
     
         35 . The system of  claim 26 , wherein the one or more membranes of the first gas separation membrane stage are formed as flat films or as a plurality of hollow fibers. 
     
     
         36 . The system of  claim 26 , wherein each of the one or more membranes of the first gas separation membrane stage has a separation layer that is supported by a support layer. 
     
     
         37 . The system of  claim 36 , wherein each of the support layers is made of a polyimide, polysulfone, or polyether ether ketone. 
     
     
         38 . The system of  claim 37 , wherein each of the support layers is porous and is made of polyether ether ketone. 
     
     
         39 . The system of  claim 22 , wherein each of the membranes of the second gas separation membrane stage is made of cellulose acetate, a polysulfone, or a polyimide.

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