Hydrocarbon recovery and light product purity when processing gases with physical solvents

Abstract

A process and apparatus for separating the components of a multi-component gas stream comprising light and intermediate volatility components. The process includes contacting the multi-component gas stream with a lean solvent in an absorber to produce a light component overhead stream and a rich solvent bottoms stream, flashing the rich solvent bottoms stream in at least one reduced pressure stage, recycling the lean solvent to the absorber, heat exchange cooling of the light component overhead stream, using at least one pressure reduction device for auto-refrigeration cooling, vapor/liquid separating the light component overhead stream in a vapor/liquid separator, reheating a vapor product stream from the vapor/liquid separator against the light component overhead stream, and removing the condensed intermediate component liquid from the vapor/liquid separator. The apparatus for separating the components of a multi-component gas stream containing hydrocarbons including an absorption tower containing internal equipment for contacting a feed gas with a lean solvent stream to create an light component overhead stream and a rich solvent bottom stream, a heat exchanger in contact with the light component overhead stream and a purified product stream, a vapor/liquid separator in contact with the light component overhead stream, and a pressure reduction device in contact with the light component overhead stream.

1 . A process for separating the components of a multi-component gas stream comprising light and intermediate volatility components, the process comprising:
 contacting the multi-component gas stream with a lean solvent in an absorber to produce a light component overhead stream and a rich solvent bottoms stream;   flashing the rich solvent bottoms stream in at least one reduced pressure stage;   recycling the lean solvent to the absorber;   heat exchange cooling of the light component overhead stream, using at least one pressure reduction device for auto-refrigeration cooling;   vapor/liquid separating the light component overhead stream in a vapor/liquid separator;   reheating a vapor product stream from the vapor/liquid separator against the light component overhead stream; and   removing the condensed intermediate component liquid from the vapor/liquid separator.   
     
     
         2 . The process of  claim 1 , wherein a pressure of the light component overhead stream is at least about 200 psig. 
     
     
         3 . The process of  claim 1 , wherein a pressure of the vapor/liquid separator is greater than about 150 psig. 
     
     
         4 . The process of  claim 1 , wherein a pressure of an outlet of the pressure reduction device is about 200 psi to about 600 psi. 
     
     
         5 . The process of  claim 1 , wherein the multi-component gas stream comprises hydrogen, nitrogen, helium, argon, oxygen, carbon dioxide, hydrogen sulfide, methane, ethylene, ethane, heavier saturated and unsaturated hydrocarbons, and mixtures thereof. 
     
     
         6 . The process of  claim 1 , wherein a temperature of the vapor/liquid separator is about −50° F. to about −220° F. 
     
     
         7 . The process of  claim 1 , wherein a temperature of the vapor/liquid separator is greater than about −175° F. 
     
     
         8 . The process of  claim 1 , wherein the condensed intermediate component liquid is one of the components of the multi-component gas stream. 
     
     
         9 . The process of  claim 1 , further comprising controlling flow by using a second control valve between vapor/liquid separating the light component overhead stream in a vapor/liquid separator and reheating a vapor product stream from the vapor/liquid separator against the light component overhead stream. 
     
     
         10 . The process of  claim 1 , further comprising separating a portion of the light component overhead stream with a split that provides a stream to the vapor/liquid absorber and a heat exchanger bypass. 
     
     
         11 . The process of  claim 10 , wherein the pressure of the vapor/liquid absorber is greater than about 350 psig. 
     
     
         12 . The process of  claim 1 , further comprising
 controlling flow by using a second pressure reducing valve between vapor/liquid separating the light component overhead stream in a vapor/liquid separator and reheating a vapor product stream from the vapor/liquid separator against the light component overhead stream; and   separating a portion of the light component overhead stream with a split that provides a stream to the vapor/liquid separator and a heat exchanger bypass.   
     
     
         13 . The process of  claim 1 , wherein the pressure reducing device is a turbo-expander. 
     
     
         14 . The process of  claim 1 , wherein the cooling and separating are multiple, sequential steps. 
     
     
         15 . The process of  claim 1 , wherein removing the condensed intermediate component liquid from the vapor/liquid separator includes returning condensed liquid to a rich solvent pressure reduction stage vapor/liquid separator. 
     
     
         16 . The process of  claim 1 , wherein the condensed intermediate component liquid cools the multi-component gas stream. 
     
     
         17 . The process of  claim 1 , wherein a hydrocarbon or mixed hydrocarbon stream with a carbon number of three of greater is added to the light component overhead stream to facilitate condensation and recovery of components in the light component stream. 
     
     
         18 . An apparatus for separating the components of a multi-component gas stream containing hydrocarbons, the apparatus comprising:
 an absorption tower containing internal equipment for contacting a feed gas with a lean solvent stream to create an light component overhead stream and a rich solvent bottom stream;   a heat exchanger in contact with the light component overhead stream and a purified product stream;   a vapor/liquid separator in contact with the light component overhead stream; and   a pressure reduction device in contact with the light component overhead stream.   
     
     
         19 . The apparatus of  claim 18 , wherein the pressure reduction device is located between the heat exchanger and the separator. 
     
     
         20 . The apparatus of  claim 18 , wherein the pressure reduction device is an expander. 
     
     
         21 . The apparatus of  claim 18 , wherein the pressure reduction device is located on a conduit between the vapor/liquid separator and the heat exchanger. 
     
     
         22 . The apparatus of  claim 18 , further comprising a split that provides a stream to the vapor/liquid separator and a heat exchanger bypass.