High solids slurry polymerization

Abstract

An olefin polymerization process wherein monomer, diluent and catalyst are circulated in a continuous loop reactor and product slurry is recovered by means of a continuous product take off. The continuous product allows operating the reaction at significantly higher solids content in the circulating slurry. In a preferred embodiment, the slurry is heated in a flash line heater and passed to a high pressure flash where a majority of the diluent is separated and thereafter condensed by simple heat exchange, without compression, and thereafter recycled. Also an olefin polymerization process operating at higher reactor solids by virtue of more aggressive circulation.

1 . A process comprising: 
 polymerizing, in a loop reaction zone, at least one olefin monomer in a liquid diluent to produce a fluid slurry comprising liquid diluent and solid olefin polymer particles;    continuously withdrawing a portion of the slurry, comprising withdrawn liquid diluent and withdrawn solid polymer particles, as an intermediate product of said process;    passing the intermediate product of said process through a heated conduit to a first flash zone; and    exposing the intermediate product of said process to a pressure drop in the first flash zone, whereby a majority of the liquid diluent from the intermediate product is vaporized, producing a concentrated intermediate product and vaporized diluent;    wherein the rate of said continuously withdrawing is controlled so as to maintain the total reactor pressure within designated set points.    
     
     
         2 . The process of  claim 1 , wherein the concentrated intermediate product is exposed to a pressure drop in a second flash zone.  
     
     
         3 . The process of  claim 1 , wherein the vaporized diluent from the first flash zone contains entrained polymer particles and is subjected to a separation to separate the entrained polymer particles from the vaporized diluent.  
     
     
         4 . The process of  claim 1 , wherein the vaporized diluent from the first flash zone is condensed by indirect heat exchange.  
     
     
         5 . The process of  claim 2 , wherein the vaporized diluent from the second flash zone contains entrained polymer particles and is subjected to a separation to separate the entrained polymer particles from the vaporized diluent.  
     
     
         6 . The process of  claim 5 , wherein the vaporized diluent from the second flash zone is condensed by compression.  
     
     
         7 . The process of  claim 1 , wherein the temperature at which the intermediate product is heated in the heated conduit is below the melting point of the solid polymer particles.  
     
     
         8 . A process comprising: 
 polymerizing, in a loop reaction zone, at least one olefin monomer in a liquid diluent to produce a fluid slurry comprising liquid diluent and solid olefin polymer particles;    continuously withdrawing a portion of the slurry comprising withdrawn liquid diluent and withdrawn solid polymer particles as an intermediate product of said process;    passing the intermediate product of said process through a heated conduit to a first flash zone; and    exposing the intermediate product of said process to a pressure drop in the first flash zone, whereby a majority of the liquid diluent from the intermediate product is vaporized, producing a concentrated intermediate product and vaporized diluent;    wherein the amount of heat supplied to the intermediate product is at least sufficient to effect the vaporization of a majority of the liquid in the intermediate product in the flash.    
     
     
         9 . The process of  claim 8 , wherein the second slurry is exposed to a pressure drop in a second flash zone.  
     
     
         10 . The process of  claim 8 , wherein the vaporized diluent from the first flash zone contains entrained polymer particles and is subjected to a separation to separate the entrained polymer particles from the vaporized diluent.  
     
     
         11 . The process of  claim 8 , wherein the vaporized diluent from the first flash zone is condensed by indirect heat exchange.  
     
     
         12 . The process of  claim 9 , wherein the vaporized diluent from second flash zone contains entrained polymer particles and is subjected to a separation to separate the entrained polymer particles from the vaporized diluent.  
     
     
         13 . The process of  claim 12 , wherein the vaporized diluent from the second flash zone is condensed by compression.  
     
     
         14 . The process of  claim 8 , wherein the temperature at which the intermediate product is heated in the heated conduit is below the melting point of the solid polymer particles.  
     
     
         15 . A process comprising: 
 polymerizing at least one monomer in liquid diluent in a slurry reactor to produce a slurry of polymer solids in a liquid medium;    continuously discharging a portion of the slurry from the slurry reactor as polymerization effluent;    heating the polymerization effluent; and    flashing the heated polymerization effluent in a first flash to vaporize a majority of the liquid in the polymerization effluent to produce concentrated polymer effluent and vaporized liquid;    wherein the rate of discharge of the polymerization effluent from the slurry reactor is such as to maintain the total reactor pressure within designated set points.    
     
     
         16 . The process of  claim 15 , wherein the polymerization is conducted in a loop reactor.  
     
     
         17 . The process of  claim 15 , wherein the concentrated polymer effluent slurry is flashed in a second flash to vaporize liquid.  
     
     
         18 . The process of  claim 17 , wherein the vaporized liquid from the first flash contains entrained polymer solids and is subjected to a separation to separate polymer solids from the vaporized liquid.  
     
     
         19 . The process of  claim 18 , wherein the resulting separated, vaporized liquid from the first flash is condensed by indirect heat exchange.  
     
     
         20 . The process of  claim 19 , wherein the vaporized liquid from the second flash contains entrained polymer solids and is subjected to a separation to separate polymer solids from the vaporized liquid.  
     
     
         21 . The process of  claim 20 , wherein the vaporized liquid from the second flash is condensed by compression.  
     
     
         22 . The process of  claim 15 , wherein the temperature at which the polymerization effluent is heated is below the fusion temperature of the polymer.  
     
     
         23 . A process comprising: 
 polymerizing at least one monomer in liquid diluent in a slurry reactor to produce a slurry of polymer solids in a liquid medium;    continuously discharging a portion of the slurry from the slurry reactor as polymerization effluent;    heating the polymerization effluent; and    flashing the heated polymerization effluent in a first flash to vaporize a majority of the liquid in the polymerization effluent; and    wherein the amount of heat supplied to the polymerization effluent is at least sufficient to effect the vaporization of a majority of the liquid in the polymerization effluent in the flash.    
     
     
         24 . The process of  claim 23 , wherein the polymerization is conducted in a loop reactor.  
     
     
         25 . The process of  claim 23 , wherein the concentrated polymer effluent slurry is flashed in a second flash to vaporize liquid.  
     
     
         26 . The process of  claim 25 , wherein the vaporized liquid from the first flash contains entrained polymer solids and is subjected to a separation to separate polymer solids from the vaporized liquid.  
     
     
         27 . The process of  claim 26 , wherein the resulting separated, vaporized liquid from the first flash is condensed by indirect heat exchange.  
     
     
         28 . The process of  claim 27 , wherein the vaporized liquid from the second flash contains entrained polymer solids and is subjected to a separation to separate polymer solids from the vaporized liquid.  
     
     
         29 . The process of  claim 28 , wherein the vaporized liquid from the second flash is condensed by compression.  
     
     
         30 . The process of  claim 23 , wherein the temperature at which the polymerization effluent is heated is below the fusion temperature of the polymer.