Helium Recovery From Natural Gas Streams

Abstract

A system and methods for recovering helium from a natural gas stream are disclosed. The system may include a cold box configured to chill a feed stream and a cryogenic stripper column configured to separate the feed stream into a gaseous top stream and a liquid bottom stream. The gaseous top stream includes an enhanced concentration of helium. A Joule-Thompson (J-T) valve is configured to flash at least a portion of the liquid bottom stream into a first gaseous stream into a heat exchanger in a cold box to chill the feed stream.

What is claimed is: 
     
         1 . A method for removing helium from natural gas (LNG), comprising:
 flowing a compressed natural gas stream through a cold box to condense liquids;   metering the cooled stream into a cryogenic stripper column;   removing a raw helium product from the top of the cryogenic stripper column; and   removing a liquid product stream from the bottom of the cryogenic stripper column, wherein the temperature in the cold box is controlled by:
 flashing a first portion of the liquid product stream into the cold box to form a first flash gas stream; 
 flashing a second portion of the liquid product stream into the cold box to form a second flash gas stream; and 
 controlling the ratio of the first portion to the second portion to adjust the temperature in the cold box. 
   
     
     
         2 . The method of  claim 1 , comprising feeding the raw helium product through the cold box to provide further cooling. 
     
     
         3 . The method of  claim 1 , comprising feeding the raw helium product through a cryogenic concentrator to increase the helium concentration. 
     
     
         4 . The method of  claim 1 , comprising:
 compressing the first flash gas stream to substantially match a pressure of the second flash gas stream;   combining the first flash gas stream and the second flash gas stream to form a combined stream; and   compressing the combined stream to form a product stream.   
     
     
         5 . The method  claim 1 , comprising producing a product stream comprising a low BTU natural gas. 
     
     
         6 . The method of  claim 5 , comprising generating electrical power from the product stream. 
     
     
         7 . The method of  claim 1 , comprising providing the raw helium product to a marketplace through a pipeline. 
     
     
         8 . A system for recovering helium from a natural gas stream, comprising:
 a cold box configured to chill a feed stream;   a cryogenic stripper column configured to separate the feed stream into a gaseous top stream and a liquid bottom stream, wherein the gaseous top stream comprises an enhanced concentration of helium; and   a Joule-Thompson (J-T) valve configured to flash at least a portion of the liquid bottom stream into a first gaseous stream into a heat exchanger in a cold box to chill the feed stream.   
     
     
         9 . The system of  claim 8 , comprising a cryogenic distillation. 
     
     
         10 . The system of  claim 8 , comprising a Ryan-Holmes cryogenic distillation. 
     
     
         11 . The system of  claim 8 , comprising a warm-gas processing plant. 
     
     
         12 . The system of  claim 8 , comprising a helium concentrator, wherein the helium concentrator comprises:
 a second cold box configured to chill an overhead gas stream from a cryogenic stripper column to form a second chilled stream;   a J-T valve configured to flash the second chilled stream to form a two phase stream; and   a separation vessel configured to separate gas and liquid components from the two phase stream.   
     
     
         13 . The system of  claim 8 , comprising a product heat exchanger configured to chill plant streams in a cryogenic purification plant using cold from the liquid bottom stream. 
     
     
         14 . The system of  claim 8 , comprising a second J-T valve configured to flash a second portion of the liquid bottoms stream into a second gaseous stream, wherein the ratio of the flows through the J-T valve and the second J-T valve is used to control the temperature of the cold box. 
     
     
         15 . The system of  claim 8 , comprising a compressor configured to boost the pressure of the first gaseous stream to a sales pressure. 
     
     
         16 . The system of  claim 14 , comprising a compressor configured to boost the pressure of the second gaseous stream to match a pressure of the first gaseous stream. 
     
     
         17 . The system of  claim 8 , comprising an electrical generation plant configured to burn a low-BTU natural gas comprising at least the first gaseous stream. 
     
     
         18 . A method for using low-BTU natural gas from a field, comprising:
 harvesting a low-BTU natural gas from a well;   dehydrating the low-BTU natural gas to remove at least a portion of a water vapor;   removing at least a portion of natural gas liquids from the low-BTU natural gas;   removing at least a portion of acid gases from the low-BTU natural gas;   removing at least a portion of helium from the low-BTU natural gas in a cryogenic stripper column, wherein the energy to lower a temperature for the helium removal is provided by flashing at least a portion of a liquid bottoms stream from the cryogenic stripper column through a cold box; and   providing the low-BTU natural gas to customers.   
     
     
         19 . The method of  claim 18 , comprising adjusting the temperature of the cold box by controlling a ratio between two portions of the liquid bottoms stream that are each being flashed, wherein one portion is flashing at a first pressure, and another portion is flashing at a lower pressure. 
     
     
         20 . The method of  claim 19 , comprising removing a further portion of the helium from the low-BTU natural gas using a helium concentrator.