Recovery of hydrocarbons from a gaseous stream

Abstract

A process (10) for the recovery of hydrocarbons from a Fischer-Tropsch tail gas includes providing a hydrocarbon rich Fischer-Tropsch tail gas (30) which includes hydrocarbons and carbon dioxide, compressing (14) the hydrocarbon rich Fischer-Tropsch tail gas (30) to provide a compressed hydrocarbon rich Fischer-Tropsch tail gas (36, 54), and contacting the compressed hydrocarbon rich Fischer-Tropsch tail gas (36, 54) with a lean oil (64, 54) to recover the hydrocarbons from the compressed hydrocarbon rich Fischer-Tropsch tail gas (36, 54) and to produce a hydrocarbon rich oil (66). Carbon dioxide is stripped (20) from the hydrocarbon rich oil (66) at a pressure which is below the pressure at which the hydrocarbon rich Fischer-Tropsch tail gas (36, 54) is contacted with the lean oil (64, 54), to provide a stripped hydrocarbon oil product (86).

1 . A process for the recovery of hydrocarbons from a Fischer-Tropsch tail gas, the process including:
 providing a hydrocarbon rich Fischer-Tropsch tail gas which includes hydrocarbons and carbon dioxide;   compressing the hydrocarbon rich Fischer-Tropsch tail gas to provide a compressed hydrocarbon rich Fischer-Tropsch tail gas, the difference in pressure between the compressed hydrocarbon rich Fischer-Tropsch tail gas and the hydrocarbon rich Fischer-Tropsch tail gas being in the range of 10 bar to 40 bar;   contacting the compressed hydrocarbon rich Fischer-Tropsch tail gas with a lean oil to recover the hydrocarbons from the compressed hydrocarbon rich Fischer-Tropsch tail gas and to produce a hydrocarbon rich oil, the hydrocarbon rich oil also including carbon dioxide absorbed from the compressed hydrocarbon rich Fischer-Tropsch tail gas; and   stripping carbon dioxide from the hydrocarbon rich oil at a pressure which is below the pressure at which the hydrocarbon rich Fischer-Tropsch tail gas is contacted with the lean oil, thereby to provide a stripped hydrocarbon oil product which includes hydrocarbons recovered from the compressed hydrocarbon rich Fischer-Tropsch tail gas.   
     
     
         2 . The process according to  claim 1 , in which the compressed hydrocarbon rich Fischer-Tropsch tail gas is contacted with the lean oil in a sponge oil column. 
     
     
         3 . The process according to  claim 1 , in which the carbon dioxide is stripped from the hydrocarbon rich oil in a stripping column or desorber, thereby to provide the stripped hydrocarbon oil product. 
     
     
         4 . The process according to  claim 1 , which includes cooling the Fischer-Tropsch tail gas and separating the cooled Fischer-Tropsch tail gas into said hydrocarbon rich Fischer-Tropsch tail gas and a hydrocarbon condensate in a separator prior to compressing the hydrocarbon rich Fischer-Tropsch tail gas. 
     
     
         5 . The process according to  claim 1 , which includes cooling the compressed hydrocarbon rich Fischer-Tropsch tail gas prior to contacting the compressed, thus cooled hydrocarbon rich Fischer-Tropsch tail gas with the lean oil. 
     
     
         6 . The process according to  claim 5 , which includes separating a hydrocarbon condensate and a dirty water stream from the compressed, cooled hydrocarbon rich Fischer-Tropsch tail gas in a separator, prior to contacting the compressed, cooled hydrocarbon rich Fischer-Tropsch tail gas with the lean oil. 
     
     
         7 . The process according to  claim 1 , in which the lean oil is, or includes, a Fischer-Tropsch hydrocarbon condensate. 
     
     
         8 . The process according to  claim 1 , in which the stripped hydrocarbon oil product contains hydrocarbons predominantly in the range of from about C 3  to about C 30  hydrocarbons. 
     
     
         9 . The process according to  claim 2 , which includes cooling an overhead gas stream from the sponge oil column, and using at least a portion of the cooled overhead gas stream to cool the compressed hydrocarbon rich Fischer-Tropsch tail gas. 
     
     
         10 . The process according to  claim 1 , in which the carbon dioxide is stripped from the hydrocarbon rich oil at a pressure which is at least 10 bar or at least 15 bar or at least 20 bar or at least 25 bar below the pressure at which the hydrocarbon rich Fischer-Tropsch tail gas is contacted with the lean oil. 
     
     
         11 . The process according to  claim 2 , in which the hydrocarbon condensate, or at least a portion of the hydrocarbon condensate, is fed to the sponge oil column to form part of the lean oil.