Methods and systems for natural gas purification integrated with gas compression

Abstract

Methods and systems are disclosed to compress raw, liquids-rich natural gas to high pressures while removing heavier hydrocarbons and water through inter-stage gas processing. Some variations provide a method for purifying and compressing natural gas, comprising: conveying a methane-containing input stream to first-compression stages; generating an initial compressed gas stream at a first pressure; conveying the initial compressed gas stream to a low-temperature separation sub-system configured to remove liquid contaminants, thereby generating an intermediate compressed gas stream at a second pressure; conveying the intermediate compressed gas stream to second-compression stages, to generate a compressed gas product stream at a third pressure; recovering purified and compressed natural gas; and feeding the compressed gas product stream into a mobile container. The sub-systems are preferably integrated into a single unit. The invention solves several problems associated with processing and transporting raw natural gas from initial production locations to end markets for final use.

What is claimed is: 
     
         1 . A method for purifying and compressing natural gas, said method comprising:
 (a) providing a methane-containing input stream;   (b) conveying said methane-containing input stream to a first compression sub-system configured with one or more first-compression stages;   (c) compressing said methane-containing input stream, in said first compression sub-system, to generate an initial compressed gas stream at a first pressure from about 100 psig to about 4500 psig and a first temperature from about 100° F. to about 500° F.;   (d) conveying at least a portion of said initial compressed gas stream to a low-temperature separation sub-system configured to cool said initial compressed gas stream to a second temperature from about −50° F. to about 70° F., wherein at least one liquid contaminant is removed from said low-temperature separation sub-system, thereby generating an intermediate compressed gas stream at a second pressure from about 100 psig to about 2000 psig;   (e) conveying said intermediate compressed gas stream to a second compression sub-system configured with one or more second-compression stages, to generate a compressed gas product stream at a third pressure from about 2000 psig to about 5000 psig and a third temperature that is higher than said second temperature;   (f) recovering said compressed gas product stream containing purified natural gas; and   (g) feeding said compressed gas product stream into a mobile container.   
     
     
         2 . The method of  claim 1 , wherein said methane-containing input stream is at an input pressure from about 1 psig to about 300 psig. 
     
     
         3 . The method of  claim 1 , wherein said first compression sub-system is configured with a single first-compression stage. 
     
     
         4 . The method of  claim 1 , wherein said first compression sub-system is configured with at least two first-compression stages. 
     
     
         5 . The method of  claim 1 , wherein said first compression sub-system is configured with at least three first-compression stages. 
     
     
         6 . The method of  claim 1 , wherein said first compression sub-system is configured with four or more first-compression stages. 
     
     
         7 . The method of  claim 1 , wherein said low-temperature separation sub-system utilizes Joule-Thomson cooling of said initial compressed gas stream, and wherein said Joule-Thomson cooling is integrated within said low-temperature separation sub-system. 
     
     
         8 . The method of  claim 7 , wherein said Joule-Thomson cooling causes said initial compressed gas stream to reach said second pressure. 
     
     
         9 . The method of  claim 1 , wherein said method utilizes Joule-Thomson cooling of said initial compressed gas stream between steps (c) and (d). 
     
     
         10 . The method of  claim 9 , wherein said Joule-Thomson cooling causes said initial compressed gas stream to reach a treatment pressure that is from about 100 psig to about 1000 psig, and wherein said treatment pressure is lower than said first pressure. 
     
     
         11 . The method of  claim 1 , wherein said low-temperature separation sub-system utilizes refrigeration. 
     
     
         12 . The method of  claim 1 , wherein said low-temperature separation sub-system utilizes both refrigeration and Joule-Thomson cooling. 
     
     
         13 . The method of  claim 1 , wherein said low-temperature separation sub-system utilizes one or more heat exchangers interfacing with said intermediate compressed gas stream. 
     
     
         14 . The method of  claim 1 , wherein said low-temperature separation sub-system utilizes one or more heat exchangers interfacing with one or more liquid streams downstream of said low-temperature separation sub-system. 
     
     
         15 . The method of  claim 1 , wherein said at least one liquid contaminant is water or a C 2+  hydrocarbon. 
     
     
         16 . The method of  claim 1 , wherein low-temperature separation sub-system is configured to dehydrate said initial compressed gas stream using a liquid solution that absorbs water out of said initial compressed gas stream to generate a water-absorbed liquid solution. 
     
     
         17 . The method of  claim 16 , wherein said liquid solution is a glycol solution. 
     
     
         18 . The method of  claim 17 , wherein said glycol solution contains ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, or a combination thereof. 
     
     
         19 . The method of  claim 16 , wherein said method utilizes a flash unit to purge flash gas from said water-absorbed liquid solution to regenerate said liquid solution for reuse in step (d). 
     
     
         20 . The method of  claim 19 , wherein free water is removed from said water-absorbed liquid solution in said flash unit. 
     
     
         21 . The method of  claim 19 , wherein free water is removed from said water-absorbed liquid solution in another unit that is distinct from said flash unit. 
     
     
         22 . The method of  claim 1 , wherein said at least one liquid contaminant is a C 2+  hydrocarbon, wherein a C 2+  liquid stream is generated from said low-temperature separation sub-system, and wherein said C 2+  liquid stream is stabilized. 
     
     
         23 . The method of  claim 22 , wherein said C 2+  liquid stream is stabilized by cascading said C 2+  liquid stream countercurrently with gas through said low-temperature separation sub-system and/or through said first compression sub-system. 
     
     
         24 . The method of  claim 22 , wherein said C 2+  liquid stream is stabilized by processing said C 2+  liquid stream through a stabilization or de-ethanization tower. 
     
     
         25 . The method of  claim 1 , wherein said second compression sub-system is configured with a single second-compression stage. 
     
     
         26 . The method of  claim 1 , wherein said second compression sub-system is configured with at least two second-compression stages. 
     
     
         27 . The method of  claim 1 , wherein said third temperature is from about 40° F. to about 140° F. 
     
     
         28 . The method of  claim 1 , wherein said method utilizes an acid gas separation unit for removing carbon dioxide and/or hydrogen sulfide from said initial compressed gas stream. 
     
     
         29 . The method of  claim 28 , wherein said acid gas separation unit is contained within said low-temperature separation sub-system. 
     
     
         30 . The method of  claim 28 , wherein said acid gas separation unit is distinct from said low-temperature separation sub-system, wherein said first compression sub-system, said low-temperature separation sub-system, and said second compression sub-system are integrated into a single unit, and wherein said acid gas separation unit is integrated into said single unit. 
     
     
         31 . The method of  claim 1 , wherein said method further utilizes an acid gas purification unit for removing carbon dioxide and/or hydrogen sulfide from said compressed gas product stream. 
     
     
         32 . The method of  claim 31 , wherein said first compression sub-system, said low-temperature separation sub-system, and said second compression sub-system are integrated into a single unit, and wherein said acid gas purification unit is integrated into said single unit. 
     
     
         33 . The method of  claim 1 , wherein said methane-containing input stream is obtained from a geological formation. 
     
     
         34 . The method of  claim 1 , wherein said methane-containing input stream is obtained from anaerobic digestion of biomass or animal waste, an industrial compost facility, or a landfill. 
     
     
         35 . The method of  claim 1 , wherein method is conducted continuously or semi-continuously. 
     
     
         36 . The method of  claim 1 , wherein said first compression sub-system and said second compression sub-system are driven by a single engine or motor. 
     
     
         37 . The method of  claim 1 , wherein said first compression sub-system, said low-temperature separation sub-system, and said second compression sub-system are integrated into a single unit. 
     
     
         38 . The method of  claim 1 , wherein said method further comprises feeding said compressed gas product stream into a stationary container. 
     
     
         39 . The method of  claim 1 , wherein said method further comprises feeding said compressed gas product stream into a pipeline. 
     
     
         40 . The method of  claim 1 , wherein said method further comprises directly or indirectly converting said purified natural gas into one or more chemicals or fuels.