Divalent cation removal from rich monoethylene glycol (meg) feed streams by ion exchange

Abstract

A system and process for removing divalent cations from a rich MEG feed stream is presented. An ion exchange bed containing a cation exchange resin adsorbs the divalent cations in the rich MEG feed stream as it flows through the ion exchange bed. After the divalent ions have been removed, the feed stream flows through a flash separator and a distillation column to reclaim MEG. Alternatively, the feed stream flows through a distillation column to regenerate MEG. The spent cation exchange resin may be regenerated in place using a regeneration brine comprised of sodium chloride and water. After use, the regeneration brine may be disposed as waste or recycled to the brine storage tank and re-used to regenerate the cation exchange resin.

What is claimed is: 
     
         1 . A system for removing divalent cations from a rich MEG feed stream, the system comprising:
 an ion exchange bed through which the rich MEG feed stream flows, the ion exchange bed containing a cation exchange resin that adsorbs the divalent cations in the rich MEG feed stream.   
     
     
         2 . A system according to  claim 1  further comprising a flash separator followed by a distillation column for reclaiming MEG from the rich MEG feed stream after the divalent cations have been removed. 
     
     
         3 . A system according to  claim 1  further comprising a distillation column for regenerating MEG from the rich MEG feed stream after the divalent cations have been removed. 
     
     
         4 . A system according to  claim 1  wherein a regeneration brine is used to regenerate the cation exchange resin without removing it from the ion exchange bed. 
     
     
         5 . A system according to  claim 4  wherein the regeneration brine is comprised of sodium chloride produced as the rich MEG feed stream is treated in the flash separator. 
     
     
         6 . A system according to  claim 4  wherein the regeneration brine is comprised of water produced as the rich MEG feed stream is treated in the distillation column. 
     
     
         7 . A system according to  claim 4  wherein the regeneration brine is held in a brine storage tank before it flows through the ion exchange bed. 
     
     
         8 . A system according to  claim 4  wherein the regeneration brine is routed to the brine storage tank after it flows through the ion exchange bed and re-used to regenerate the cation exchange resin. 
     
     
         9 . A system, comprising:
 an ion exchange unit with at least one ion exchange bed containing a cation exchange resin that absorbs divalent cations;   a source of rich MEG coupled to the ion exchange unit;   a flash separator coupled to the ion exchange unit; and   a source of regeneration brine coupled to the flash separator to receive salt from the flash separator and to the ion exchange unit to provide regeneration brine to the ion exchange unit.   
     
     
         10 . The system of  claim 9 , further comprising a distillation column coupled to the flash separator. 
     
     
         11 . The system of  claim 9 , wherein the source of rich MEG is coupled to the ion exchange unit to provide flow of rich MEG through the ion exchange unit in a first direction and the source of regeneration brine is coupled to the ion exchange unit to provide flow of regeneration brine through the ion exchange unit in a second direction opposite to the first direction. 
     
     
         12 . The system of  claim 10 , wherein an overhead of the distillation column is coupled to the source of regeneration brine. 
     
     
         13 . The system of  claim 9 , wherein the ion exchange unit has at least two ion exchange beds. 
     
     
         14 . The system of  claim 9 , wherein the ion exchange unit has a regeneration brine inlet and a brine outlet, and the brine outlet is coupled to the regeneration brine source. 
     
     
         15 . A system, comprising:
 an ion exchange unit with at least two ion exchange beds, each containing a cation exchange resin that absorbs divalent cations;   a source of rich MEG coupled to the ion exchange unit;   a distillation column to the ion exchange unit;   a source of regeneration brine coupled to to the ion exchange unit to provide regeneration brine to the ion exchange unit; and   a distillation column arranged to receive a stream depleted of divalent ions by the ion exchange unit, with an overhead of the distillation column coupled to the source of regeneration brine; and   a salt source coupled to the source of regeneration brine.   
     
     
         16 . The system of  claim 15 , wherein the salt source is a flash separator coupled to the ion exchange unit, the distillation column, and the source of regeneration brine.