Methods and system for heat recovery in a gasification system

Abstract

A tube and shell heat exchanger for a gasification system is provided. The heat exchanger includes a first shell-side inlet positioned proximate to a heat exchanger tube-side inlet. The first shell-side inlet is configured to receive a first portion of a scrubbed syngas flow therethrough. This first scrubbed syngas portion facilitates substantially preventing fouling at the heat exchanger inlet. The heat exchanger also includes a second shell-side inlet positioned proximate to a heat exchanger tube-side outlet. The second shell-side inlet is configured to receive a second portion of a scrubbed syngas flow therethrough.

1 . A tube and shell heat exchanger for a gasification system, said heat exchanger comprising:
 a first shell-side inlet positioned proximate to a heat exchanger tube-side inlet, said first shell-side inlet configured to receive a first portion of a scrubbed syngas flow therethrough, wherein said first scrubbed syngas portion facilitates substantially preventing fouling at said heat exchanger tube-side inlet; and   a second shell-side inlet positioned proximate to a heat exchanger tube-side outlet, said second shell-side inlet configured to receive a second portion of a scrubbed syngas flow therethrough.   
     
     
         2 . A tube and shell heat exchanger in accordance with  claim 1 , further comprising a plurality of shell-side baffles positioned within said heat exchanger configured to channel said first and second syngas flow portions to a shell side outlet. 
     
     
         3 . A tube and shell heat exchanger in accordance with  claim 2 , wherein said heat exchanger comprises at least one of a convective syngas cooler and an asymmetrical split flow exchanger. 
     
     
         4 . A tube and shell heat exchanger in accordance with  claim 2 , further comprising a split-feed shell-side tube system comprising a first flow path for channeling said first portion of a scrubbed syngas to said first shell-side inlet. 
     
     
         5 . A tube and shell heat exchanger in accordance with  claim 4 , wherein said split-feed shell-side tube system further comprises a second flow path configured to channel said second portion of a scrubbed syngas to said second shell-side inlet. 
     
     
         6 . A tube and shell heat exchanger in accordance with  claim 2 , further comprising a conduit configured to channel a quantity of carbon dioxide into said heat exchanger to facilitate subsequent cooling of at least a portion of the scrubbed syngas and facilitate recovering heat from the gasification system. 
     
     
         7 . A tube and shell heat exchanger in accordance with  claim 2 , wherein said heat exchanger is configured to produce a cooled raw syngas stream and a heated scrubbed syngas stream. 
     
     
         8 . A gasification system comprising:
 a gasifier configured to produce a flow of syngas;   a syngas cooler configured to receive said flow of syngas from said gasifier and reduce a temperature associated with said flow of syngas; and   a tube and shell heat exchanger comprising:
 a first shell-side inlet positioned proximate to a heat exchanger tube-side inlet, said first shell-side inlet configured to receive a first portion of a scrubbed syngas flow therethrough, wherein said first scrubbed syngas portion facilitates substantially preventing fouling at said heat exchanger tube-side inlet; and 
 a second shell-side inlet positioned proximate to a heat exchanger tube-side outlet, said second shell-side inlet configured to receive a second portion of a scrubbed syngas flow therethrough. 
   
     
     
         9 . A gasification system in accordance with  claim 8 , further comprising a split-feed shell-side tube system comprising a first flow path for channeling said first portion of a scrubbed syngas to said first shell-side inlet. 
     
     
         10 . A gasification system in accordance with  claim 9 , wherein said split-feed shell-side tube system further comprises a second flow path configured to channel said second portion of a scrubbed syngas to said second shell-side inlet. 
     
     
         11 . A gasification system in accordance with  claim 10 , further comprising a syngas scrubber configured to channel a stream of scrubbed syngas to said split-feed shell-side tube system for distribution into said heat exchanger. 
     
     
         12 . A gasification system in accordance with  claim 8 , further comprising a plurality of shell-side baffles positioned within said heat exchanger to channel said first and second syngas flow portions to a shell side outlet. 
     
     
         13 . The gasification system in accordance with  claim 8 , further comprising a conduit configured to channel a quantity of carbon dioxide into said heat exchanger to facilitate subsequent cooling of at least a portion of the scrubbed syngas and facilitate recovering heat from said gasification system. 
     
     
         14 . A method for operating a gasification system comprising:
 scrubbing a first stream of raw syngas to facilitate removing impurities therefrom;   producing a stream of scrubbed syngas from said scrubbed first stream;   transferring heat from a second stream of raw syngas to the stream of scrubbed syngas to produce a cooled raw syngas stream and a heated scrubbed syngas stream; and   channeling at least a portion of said stream of scrubbed syngas to facilitate substantially preventing fouling from the first stream of raw syngas.   
     
     
         15 . The method in accordance with  claim 14  wherein the first and second raw syngas streams are raw syngas. 
     
     
         16 . The method in accordance with  claim 15  further comprising:
 producing the first stream of raw syngas in a gasifier; and 
 cooling the first stream of raw syngas in a radiant syngas cooler prior to scrubbing. 
 
     
     
         17 . The method in accordance with  claim 14  wherein transferring heat is carried out in a convective syngas cooler. 
     
     
         18 . The method in accordance with  claim 17  wherein transferring heat is carried out in an asymmetrical split flow exchanger. 
     
     
         19 . The method in accordance with  claim 17  wherein transferring heat is carried out in a split flow exchanger with an isolated entrance section. 
     
     
         20 . The method in accordance with  claim 14  further comprising subsequently cooling of at least a portion of the scrubbed syngas heated in said tube and shell heat exchanger by heat exchange with recycled carbon dioxide to facilitate recovering heat from said gasification system.