Energy recovery from mother liquid in paraxylene crystallization process

Abstract

Methods for recovering energy from a mother liquor stream in paraxylene crystallization processes are disclosed herein. The low temperature energy from the mother liquor is optimally utilized to reduce the refrigeration burden on the crystallization process.

1 . A method for recovering energy from a mother liquor in a PX crystallization process, said method comprising:
 providing a feed stream to a PX crystallization unit;   providing a first crystallizer or heat exchanger to recover low temperature energy from low temperature mother liquor;   providing a second heat exchanger to recover energy from intermediate temperature mother liquor; and   providing a third heat exchanger to recover energy from high temperature mother liquor;   wherein the feed stream is cooled down by the mother liquor.   
     
     
         2 . The method of  claim 1 , wherein said low temperature mother liquor temperature is −50° C. to −70° C. 
     
     
         3 . The method of  claim 1 , wherein said first crystallizer or heat exchanger is a screw type crystallizer, scrape surface crystallizer, or part of the crystallizer in the main PX crystallization section. 
     
     
         4 . The method of  claim 1 , wherein said first crystallizer or heat exchanger comprises multiple crystallizers operated in serial. 
     
     
         5 . The method of  claim 1 , wherein said first crystallizer or heat exchanger comprises multiple crystallizers operated in parallel. 
     
     
         6 . The method of  claim 1 , wherein said second heat exchanger is a heat shell/tube type heat exchanger. 
     
     
         7 . The method of  claim 1 , wherein said second heat exchanger is a double pipe heat exchanger. 
     
     
         8 . A method for recovering energy from a mother liquor in a PX crystallization process, said method comprising:
 providing a feed stream to a PX crystallization unit;   providing a first crystallizer or heat exchanger to recover low temperature energy from low temperature mother liquor;   providing a second heat exchanger to recover energy from intermediate temperature mother liquor;   providing a third heat exchanger to recover energy from high temperature mother liquor;   and providing a fourth heat exchanger that reduces the temperature of the feed stream.   
     
     
         10 . The method of  claim 8 , wherein said low temperature mother liquor temperature is −50° C. to −70° C. 
     
     
         11 . The method of  claim 8 , wherein said first crystallizer or heat exchanger is a screw type crystallizer, scrape surface crystallizer, or part of the crystallizer in the main PX crystallization section. 
     
     
         12 . The method of  claim 8 , wherein said first crystallizer or heat exchanger comprises multiple crystallizers operated in serial. 
     
     
         13 . The method of  claim 8 , wherein said first crystallizer or heat exchanger comprises multiple crystallizers operated in parallel. 
     
     
         14 . The method of  claim 8 , wherein said second heat exchanger is a heat shell/tube type heat exchanger. 
     
     
         15 . The method of  claim 8 , wherein said second heat exchanger is a double pipe heat exchanger.