Fractionation system and method including depropanizer column and bottoms stripping column

Abstract

Fractionation systems utilizing a rectifying column with a stripping column are described. The liquid from the rectifying column bottoms is sent to the first tray of the stripping column, while the overhead stream from the stripping column is sent to the bottom of the rectifying column. Processes for separating feed streams are also described.

What is claimed is: 
     
         1 . A fractionation system comprising:
 a rectifying column having a feed inlet between a top and a bottom tray, a reflux inlet at the top tray, a fluid inlet at the bottom tray, an overhead product outlet at the first tray, and a bottoms outlet at the bottom tray;   a rectifying column reboiler in communication with the rectifying column;   a stripping column having a fluid inlet at a top tray, an overhead outlet at the top tray, and a bottoms outlet at a bottom tray, the bottoms outlet of the rectifying column being in fluid communication with the fluid inlet of the stripping column, the overhead outlet of the stripping column being in fluid communication with the fluid inlet of the rectifying column; and   a stripping column reboiler in communication with the stripping column.   
     
     
         2 . The fractionation system of  claim 1  wherein the rectifying column and the stripping column are in separate vessels. 
     
     
         3 . The fractionation system of  claim 1  wherein the rectifying column and the stripping column are in a single vessel, the rectifying column being positioned above the stripping column, the rectifying column having a diameter, and the stripping column having a diameter less than the diameter of the rectifying column. 
     
     
         4 . The fractionation system of  claim 3  wherein the rectifying column is separated from the stripping column by a liquid accumulator tray. 
     
     
         5 . The fractionation system of  claim 1  further comprising a condenser having an inlet in fluid communication with the product overhead outlet of the rectifying column, and an outlet in fluid communication with the reflux inlet of the rectifying column. 
     
     
         6 . The fractionation system of  claim 1  wherein at least a portion of a heat source for the rectifying column reboiler is a stream from a heat pump compressor. 
     
     
         7 . The fractionation system of  claim 6  wherein an outlet and an inlet for the rectifying column reboiler are in a space below the bottom tray and above the bottom of the rectifying column, the rectifying column reboiler outlet being positioned above the rectifying column reboiler inlet. 
     
     
         8 . The fractionation system of  claim 6  wherein the heat pump compressor is in fluid communication with a splitter column, the splitter column being downstream of a reactor, the reactor being in fluid communication with the overhead product outlet of the rectifying column. 
     
     
         9 . The fractionation system of  claim 6  wherein the rectifying column reboiler further comprises a valve to control flow of a recycle stream to the rectifying column reboiler. 
     
     
         10 . The fractionation system of  claim 1  wherein the overhead product outlet of the rectifying column is in fluid communication with a reactor. 
     
     
         11 . The fractionation system of  claim 1  wherein the overhead product outlet of the rectifying column is above the top tray of the rectifying column, the reflux inlet of the rectifying column is above the top tray of the rectifying column and below the overhead product outlet, the overhead outlet of the stripping column is above the top tray of the stripping column, the fluid inlet of the stripping column is above the top tray of the stripping column and below the overhead outlet of the stripping column, and the fluid inlet of the rectifying column is below the bottom tray of the rectifying column and above the bottoms outlet of the rectifying column. 
     
     
         12 . The fractionation system of  claim 1  wherein the rectifying column reboiler is a thermosyphon reboiler. 
     
     
         13 . A process of separating a feed stream comprising:
 introducing the feed stream into a feed inlet of a rectifying column, the feed inlet between a top tray and a bottom tray, the rectifying column having a reflux inlet at the top tray, a fluid inlet at the bottom tray, an overhead product outlet at the first tray, and a bottoms outlet at the bottom tray;   separating the feed stream in the rectifying column into an overhead product stream and a bottoms stream;   introducing the bottoms stream from the rectifying column into a fluid inlet in a stripping column, the fluid inlet at a top tray of the stripping column, the stripping column having an overhead outlet at the top tray, and a bottoms outlet at a bottom tray;   separating the bottoms stream from the rectifying column into an overhead stream and a bottoms stream in the stripping column;   introducing the overhead stream from the stripping column into the fluid inlet of the rectifying column;   refluxing a portion of the overhead product stream from the rectifying column to the reflux inlet of the rectifying column;   reheating at least a portion of the bottoms stream from the rectifying column in a rectifying column reboiler; and   reheating at least a portion of the bottoms stream from the stripping column in a stripping column reboiler.   
     
     
         14 . The process of  claim 13  wherein reheating at least the portion of the bottoms stream from the rectifying column in the rectifying column reboiler comprises:
 placing at least the portion of the bottoms stream from the rectifying column in thermal communication with a stream from a heat pump compressor. 
 
     
     
         15 . The process of  claim 14  further comprising:
 introducing a second portion of the overhead product stream from the rectifying column into a reactor; 
 separating the reactor effluent in a splitter column; and 
 condensing an overhead stream from the splitter column in the heat pump compressor forming a compressed stream, wherein a portion of the compressed stream comprises the stream from the heat pump compressor. 
 
     
     
         16 . The method of  claim 13  wherein an outlet and an inlet for the rectifying column reboiler are in a space below the bottom tray of the rectifying column reboiler and above the bottom of the rectifying column, the rectifying column reboiler outlet being positioned above the rectifying column reboiler inlet. 
     
     
         17 . The process of  claim 13  wherein the rectifying column and the stripping column are in separate vessels. 
     
     
         18 . The process of  claim 13  wherein the rectifying column and the stripping column are in a single vessel, the rectifying column being positioned above the stripping column, the rectifying column having a diameter, and the stripping column having a diameter less than the diameter of the rectifying column. 
     
     
         19 . The process of  claim 18  wherein the rectifying column and the stripping column are separated by a liquid accumulator tray, and wherein introducing the bottoms stream from the rectifying column into the fluid inlet in the stripping column comprises introducing the bottoms stream through a downcomer in the fluid accumulator tray, and wherein introducing the overhead stream from the stripping column into the fluid inlet of the rectifying column comprises introducing the overhead stream through a vapor riser in the liquid accumulator tray. 
     
     
         20 . The process of  claim 19  wherein reheating at least a portion of the bottoms stream from the rectifying column further comprises returning the portion of the bottoms stream from the rectifying column to the liquid accumulator tray.