Separating carbon dioxide and hydrogen sulfide from a natural gas stream using co-current contacting systems

Abstract

Systems and methods for separating CO 2 and H 2 S from a natural gas stream are provided herein. The system includes a first loop of co-current contacting systems configured to remove H 2 S and CO 2 from a natural gas stream and a second loop of co-current contacting systems configured to remove the H 2 S from the CO 2 .

What is claimed is: 
     
         1 . A system for separating H 2 S and CO 2  from a natural gas stream, comprising:
 a first loop of co-current contacting systems configured to remove H 2 S and CO 2  from a natural gas stream; and   a second loop of co-current contacting systems configured to remove the H 2 S from the CO 2 .   
     
     
         2 . The system of  claim 1 , wherein the first loop of co-current contacting systems comprises:
 a first series of co-current contacting systems configured to remove the H 2 S and the CO 2  from the natural gas stream by contacting the natural gas stream with a solvent stream, providing for incorporation of the H 2 S and the CO 2  from the natural gas stream into the solvent stream;   a second series of co-current contacting systems configured to remove the H 2 S and the CO 2  from the solvent stream, wherein the solvent stream is recirculated to the first series of co-current contacting systems.   
     
     
         3 . The system of  claim 2 , wherein the second loop of co-current contacting systems comprises:
 a third series of co-current contacting systems configured to remove the H 2 S from the CO 2  by contacting the H 2 S and the CO 2  with an H 2 S-selective solvent stream, providing for incorporation of the H 2 S into the H 2 S-selective solvent stream; and   a fourth series of co-current contacting systems configured to remove the H 2 S from the H 2 S-selective solvent stream, wherein the H 2 S-selective solvent stream is recirculated to the third series of co-current contacting systems.   
     
     
         4 . A method for separating CO 2  and H 2 S from a natural gas stream, comprising:
 contacting a sour natural gas stream comprising CO 2  and H 2 S with a lean solvent stream within a first series of co-current contacting systems, generating a sweetened natural gas stream and a rich solvent stream comprising the CO 2  and the H 2 S;   contacting the rich solvent stream with a stripping gas within a second series of co-current contacting systems, regenerating the lean solvent stream and generating a first gas stream comprising the CO 2 , the H 2 S, and the stripping gas;   recirculating the lean solvent stream to the first series of co-current contacting systems;   contacting the first gas stream with a lean H 2 S-selective solvent stream within a third series of co-current contacting systems, generating a rich H 2 S-selective solvent stream comprising the H 2 S and a second gas stream comprising the CO 2  and the stripping gas;   contacting the rich H 2 S-selective solvent stream with a stripping gas within a fourth series of co-current contacting systems, regenerating the lean H 2 S-selective solvent stream and generating a third gas stream comprising the H 2 S and the stripping gas; and   recirculating the lean H 2 S-selective solvent stream to the third series of co-current contacting systems.   
     
     
         5 . The method of  claim 4 , comprising producing liquefied natural gas (LNG) from the sweetened natural gas stream. 
     
     
         6 . The method of  claim 4 , comprising removing the CO 2  from the second gas stream to recover a final CO 2  product. 
     
     
         7 . The method of  claim 6 , comprising recirculating the stripping gas from the second gas stream to the second series of co-current contacting systems. 
     
     
         8 . The method of  claim 6 , comprising injecting the final CO 2  product into a subterranean reservoir for enhanced oil recovery (EOR) operations. 
     
     
         9 . The method of  claim 4 , comprising removing the H 2 S from the third gas stream to recover a final H 2 S product. 
     
     
         10 . The method of  claim 9 , comprising recirculating the stripping gas from the third gas stream to the fourth series of co-current contacting systems. 
     
     
         11 . The method of  claim 9 , comprising recovering elemental sulfur from the final H 2 S product within a Claus sulfur recovery unit. 
     
     
         12 . The method of  claim 4 , wherein contacting the sour natural gas stream with the lean solvent stream within a first series of co-current contacting systems comprises progressively sweetening the sour natural gas stream via contact with the lean solvent stream within each of a plurality of co-current contacting systems connected in series. 
     
     
         13 . The method of  claim 4 , wherein contacting the rich solvent stream with the stripping gas within the second series of co-current contacting systems comprises progressively removing the CO 2  and the H 2 S from the rich solvent stream via contact with the stripping gas within each of a plurality of co-current contacting systems connected in series. 
     
     
         14 . The method of  claim 4 , wherein contacting the first gas stream with the lean H 2 S-selective solvent stream within the third series of co-current contacting systems comprises progressively removing the H 2 S from the first gas stream via contact with the lean H 2 S-selective solvent stream within each of a plurality of co-current contacting systems connected in series. 
     
     
         15 . The method of  claim 4 , wherein contacting the rich H 2 S-selective solvent stream with the stripping gas within the fourth series of co-current contacting systems comprises progressively removing the H 2 S from the rich H 2 S-selective solvent stream via contact with the stripping gas within each of a plurality of co-current contacting systems connected in series. 
     
     
         16 . A system for separating CO 2  and H 2 S from a natural gas stream, comprising:
 a first series of co-current contacting systems configured to contact a sour natural gas stream comprising CO 2  and H 2 S with a lean solvent stream to generate a sweetened natural gas stream and a rich solvent stream comprising the CO 2  and the H 2 S;   a second series of co-current contacting systems configured to contact the rich solvent stream with a stripping gas to regenerate the lean solvent stream and generate a first gas stream comprising the CO 2 , the H 2 S, and the stripping gas, wherein the lean solvent stream is recirculated to the first series of co-current contacting systems;   a third series of co-current contacting systems configured to contact the first gas stream with a lean H 2 S-selective solvent stream to generate a rich H 2 S-selective solvent stream comprising the H 2 S and a second gas stream comprising the CO 2  and the stripping gas; and   a fourth series of co-current contacting systems configured to contact the rich H 2 S-selective solvent stream with a stripping gas to regenerate the lean H 2 S-selective solvent stream and generate a third gas stream comprising the H 2 S and the stripping gas, wherein the lean H 2 S-selective solvent stream is recirculated to the third series of co-current contacting systems.   
     
     
         17 . The system of  claim 16 , wherein each of the first series of co-current contacting systems, the second series of co-current contacting systems, the third series of co-current contacting systems, and the fourth series of co-current contacting systems comprises a plurality of co-current contacting systems connected in series. 
     
     
         18 . The system of  claim 17 , wherein each of the plurality of co-current contacting systems comprises:
 a co-current contactor located in-line within a pipe, the co-current contactor comprising:
 a mixer, comprising:
 an annular support ring configured to maintain the mixer within the pipe; 
 a plurality of radial blades configured to allow a liquid stream to flow into the mixer; and 
 a central gas entry cone configured to allow a gas stream to flow through a hollow section within the mixer; and 
 
 a mass transfer section downstream of the mixer;
 wherein the mixer and the mass transfer section provide for efficient incorporation of liquid droplets formed from the liquid stream into the gas stream; and 
 
   a separation system configured to remove the liquid droplets from the gas stream.   
     
     
         19 . The system of  claim 18 , wherein the separation system comprises a cyclonic separator. 
     
     
         20 . The system of  claim 18 , wherein a downstream portion of the central gas entry cone comprises a blunt ended cone. 
     
     
         21 . The system of  claim 18 , wherein a downstream portion of the central gas entry cone comprises a tapered ended cone. 
     
     
         22 . The system of  claim 16 , wherein the H 2 S-selective solvent stream comprises a tertiary amine. 
     
     
         23 . The system of  claim 16 , wherein the H 2 S-selective solvent stream comprises a sterically-hindered amine. 
     
     
         24 . The system of  claim 16 , wherein the stripping gas comprises nitrogen. 
     
     
         25 . The system of  claim 16 , wherein the system comprises a CO 2  separation system configured to remove the CO 2  from the second gas stream to recover a final CO 2  product. 
     
     
         26 . The system of  claim 25 , wherein the stripping gas from the second gas stream is recirculated to the second series of co-current contacting systems. 
     
     
         27 . The system of  claim 16 , wherein the system comprises a H 2 S separation system configured to remove the H 2 S from the third gas stream to recover a final H 2 S product. 
     
     
         28 . The system of  claim 27 , wherein the stripping gas from the third gas stream is recirculated to the fourth series of co-current contacting systems. 
     
     
         29 . A method for selectively removing one gaseous component from a multi-component gas stream, comprising:
 flowing a lean solvent stream into a mixer of a co-current contactor via an annular support ring and a plurality of radial blades extending from the annular support ring, wherein the annular support ring secures the mixer in-line within a pipe;   flowing a multi-component gas stream comprising a first gaseous component and a second gaseous component into the mixer via a central gas entry cone that is supported by the plurality of radial blades, wherein a first portion of the multi-component gas stream flows through the central gas entry cone and a second portion of the multi-component gas stream flows around the central gas entry cone between the plurality of radial blades;   contacting the multi-component gas stream with the lean solvent stream within the mixer and a mass transfer section of the co-current contactor to provide for incorporation of liquid droplets formed from the lean solvent stream into the multi-component gas stream, wherein the liquid droplets comprise the first gaseous component from the multi-component gas stream; and   separating the liquid droplets from the multi-component gas stream within a separation system, generating a rich solvent stream comprising the first gaseous component and a gas stream comprising the second gaseous component.   
     
     
         30 . The method of  claim 29 , wherein the first gaseous component comprises H 2 S, the second gaseous component comprises CO 2 , and the solvent stream comprises an H 2 S-selective solvent stream. 
     
     
         31 . The method of  claim 30 , wherein the H 2 S-selective solvent stream comprises a tertiary amine. 
     
     
         32 . The method of  claim 30 , wherein the H 2 S-selective solvent stream comprises a sterically-hindered amine. 
     
     
         33 . The method of  claim 29 , comprising flowing the multi-component gas stream through a plurality of co-current contactors and corresponding separation systems connected in series within the pipe. 
     
     
         34 . The method of  claim 29 , comprising regenerating the lean solvent stream from the rich solvent stream within a separate co-current contactor and corresponding separation system.