Heat pump distillation for <50% light component in feed

Abstract

A process is presented for the separation of a hydrocarbon mixture having less than 50% of the light component in the feedstream. The process provides an energy efficiency through drawing off a vapor stream from the rectifying section of a distillation column, and using recompression of the vapor to provide a portion of the heat for reboiling a portion of the bottoms stream exiting the stripping section of the distillation column.

1 . A process for the separation of a light component from a mixture of hydrocarbons, comprising:
 passing a feedstream to a distillation column at a position between the rectifying section and the stripping section, wherein the feed comprises less than 50% light components, and wherein the distillation column has an overhead vapor stream and a bottoms liquid stream;   passing the overhead vapor stream to a first heat pump compressor, thereby creating a compressed overhead vapor stream;   passing the compressed overhead vapor stream to the vapor side of a first reboiler heat exchanger, thereby creating a partially condensed overhead stream;   drawing off a side vapor stream from the rectifying section at a draw off port, thereby creating a side draw stream;   passing the side draw stream to a second heat pump compressor, thereby creating a compressed side draw stream;   passing the compressed side draw stream to the vapor side of a second reboiler heat exchanger, thereby creating a cooled compressed side draw stream;   passing a first portion of the bottoms liquid stream to the liquid side of the first reboiler heat exchanger, thereby creating a first vapor bottoms stream; and   passing a second portion of the bottoms liquid stream to the liquid side of the second reboiler heat exchanger.   
     
     
         2 . The process of  claim 1  wherein the compressed overhead stream is totally condensed. 
     
     
         3 . The process of  claim 1  further comprising passing a portion of the condensed overhead stream to the top of the rectifying section. 
     
     
         4 . The process of  claim 1  further comprising partially condensing the compressed side draw stream, thereby creating a partially condensed compressed side draw stream. 
     
     
         5 . The process of  claim 4  further comprising passing the partially condensed compressed side draw stream back to the rectifying section. 
     
     
         6 . The process of  claim 1  further comprising passing the cooled compressed side draw stream back to the rectifying section. 
     
     
         7 . The process of  claim 6  wherein the cooled compressed side draw stream is passed to below the draw off port. 
     
     
         8 . The process of  claim 1  wherein the side draw stream is drawn from a tray positioned within 10 trays to the tray having the greatest temperature gradient per tray in the rectifying section. 
     
     
         9 . The process of  claim 8  wherein the side draw stream is drawn from a tray proximate to the tray having the greatest temperature gradient per tray in the rectifying section. 
     
     
         10 . The process of  claim 1  wherein the side draw stream is drawn from the lower half of the rectifying section. 
     
     
         11 . A process for the separation of a light component from a mixture of hydrocarbons, comprising:
 passing a feedstream to a distillation column at a position between the rectifying section and the stripping section, wherein the feed comprises less than 50% light components, and wherein the distillation column has a overhead vapor stream and a bottoms liquid stream;   passing the overhead vapor stream to a first heat pump compressor, thereby creating a compressed overhead vapor stream;   passing the compressed overhead vapor stream to the vapor side of a first reboiler heat exchanger, thereby creating a condensed overhead stream;   drawing off a side vapor stream from the rectifying section at a draw off port, thereby creating a side draw stream, wherein the draw off port is at a tray position that is within 10 trays of the tray having the greatest temperature gradient;   passing the side draw stream to a second heat pump compressor, thereby creating a compressed side draw stream;   passing the compressed side draw stream to the vapor side of a second reboiler heat exchanger, thereby creating a cooled compressed side draw stream, wherein the cooled compressed side draw stream is partially condensed;   passing a first portion of the bottoms liquid stream to the liquid side of the first reboiler heat exchanger, thereby creating a first vapor bottoms stream; and   passing a second portion of the bottoms liquid stream to the liquid side of the second reboiler heat exchanger.   
     
     
         12 . The process of  claim 11  further comprising passing a portion of the condensed overhead stream to the top of the rectifying section. 
     
     
         13 . The process of  claim 11  further comprising passing the partially condensed compressed side draw stream back to the rectifying section. 
     
     
         14 . The process of  claim 13  wherein the cooled compressed side draw stream is passed to below the draw off port. 
     
     
         15 . The process of  claim 11  further comprising totally condensing the compressed side draw stream. 
     
     
         16 . The process of  claim 15  further comprising passing the totally condensed compressed side draw stream back to the rectifying section. 
     
     
         17 . The process of  claim 16  wherein the cooled compressed side draw stream is passed to below the draw off port. 
     
     
         18 . The process of  claim 11  wherein the side draw stream is drawn from the lower half of the rectifying section. 
     
     
         19 . The process of  claim 11  wherein the side draw stream is drawn from a tray proximate to the tray having the greatest temperature gradient per tray in the rectifying section. 
     
     
         20 . The process of  claim 11  wherein the side draw stream is drawn from the lower half of the rectifying section.