Systems And Methods For Enhanced Recovery Of NGL Hydrocarbons

Abstract

Systems and methods for the enhanced recovery of ethane and heavier hydrocarbons using an absorbing agent. Typical absorbing agents include one or more C3+ alkanes. The systems and methods separate components of a feed gas containing methane and heavier hydrocarbons, which maximizes ethane recovery, without requiring appreciable increases in capital and operating costs, and improves the safety margin with respect to the risk of CO 2 freeze-out.

1 . A method for recovering ethane and heavier hydrocarbons from a hydrocarbon feed gas, which comprises:
 cooling an absorbing agent and an inlet stream comprising the feed gas in a heat exchanger to produce a cooled absorbing agent and a chilled inlet stream;   separating the chilled inlet stream in a separator to produce a liquid hydrocarbon stream and an overhead vapor stream;   combining the cooled absorbing agent with a portion of the overhead vapor stream to form a combined stream;   cooling the combined stream into a reflux exchanger to produce a subcooled liquid stream;   expanding another portion of the overhead vapor stream in an expander to produce a demethanizer feed stream; and   introducing the liquid hydrocarbon stream, the subcooled liquid stream and the demethanizer feed stream into a demethanizer column, wherein the ethane and heavier hydrocarbons are recovered as a bottom product in the demethanizer column and methane and lighter hydrocarbons are recovered as a top product in the demethanizer column.   
     
     
         2 . The method of  claim 1 , wherein the absorbing agent comprises one or more C3+ alkanes. 
     
     
         3 . The method of  claim 1 , wherein the hydrocarbon feed gas comprises methane and heavier hydrocarbons. 
     
     
         4 . The method of  claim 1 , wherein the absorbing agent and the inlet stream are cooled in the heat exchanger by indirect heat exchange with a residue stream, a side reboiling stream and a demethanizer reboiling stream. 
     
     
         5 . The method of  claim 1 , further comprising processing the methane and lighter hydrocarbons in the reflux exchanger, the heat exchanger and a boost compressor to produce a residue gas stream.