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 polymerization process comprising: 
 polymerizing, in a loop reactor, at least one monomer in a liquid diluent to produce a fluid slurry comprising liquid diluent and solid polymer particles;    continuously withdrawing a portion of said slurry as an intermediate product of said process;    exposing said intermediate product to a pressure drop in a high pressure flash zone such that a major portion of said withdrawn liquid diluent is vaporized and thus separated from said withdrawn solid polymer particles;    condensing the thus separated withdrawn liquid diluent without compression; and    operating the loop reactor more efficiently.    
     
     
         2 . A process for producing polymer comprising: 
 polymerizing in liquid diluent at least one monomer in a loop reactor to produce a slurry of polymer solids;    continuously discharging a portion of the slurry from the loop reactor as polymerization effluent;    flashing the polymerization effluent in a first flash to vaporize from about 50% to about 100% of the liquid medium to produce concentrated polymer effluent and vaporized liquid;    condensing at least a portion of the vapor obtained in the first flash without compression; and    operating the loop reactor more efficiently.    
     
     
         3 . The process of  claim 2 , wherein the monomer is an olefin monomer.  
     
     
         4 . A polymerization 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slurry comprising liquid diluent and solid olefin polymer particles;    continuously withdrawing said slurry comprising withdrawn liquid diluent and withdrawn solid polymer particles, as an intermediate product of said process;    exposing the intermediate product of said process to a pressure drop in a high pressure flash zone, such that a major portion of the liquid diluent from the intermediate product is vaporized and thus separated from said withdrawn solid polymer particles;    condensing the thus separated withdrawn liquid diluent without any compression; and    operating the loop reaction zone at an efficiency of 2.13 lbs/hr-gal or greater.    
     
     
         5 . A process for producing polymer comprising: 
 polymerizing in liquid diluent at least one monomer in a loop reactor to produce a slurry of polymer solids;    continuously discharging a portion of the slurry from the loop reactor as polymerization effluent;    flashing the polymerization effluent in a first flash to vaporize from about 50% to about 100% of the liquid medium to produce concentrated polymer effluent and vaporized liquid;    condensing at least a portion of the vapor obtained in the first flash without compression; and    operating the loop reactor at a space time yield greater than 2.13 lbs/hr-gal.    
     
     
         6 . The process of  claim 5 , wherein the monomer is an olefin monomer.  
     
     
         7 . The process of  claim 5 , wherein the concentrated polymer effluent is flashed in a second flash to vaporize liquid.  
     
     
         8 . The process of  claim 7 , wherein the vapor from the first flash is condensed by heat exchange.  
     
     
         9 . The process of  claim 7 , wherein the slurry is circulated within the loop reactor by more than one pump and the loop reactor volume is greater than 20,000 gallons.  
     
     
         10 . The process of  claim 9 , wherein the loop reactor has more than eight vertical legs.  
     
     
         11 . The process of  claim 9 , wherein the loop reactor is operated at a total recirculating pumping head/reactor distance of greater than 0.07 ft/ft.  
     
     
         12 . The process of  claim 11 , wherein the loop reactor is operated with a total pumping head of greater than or equal to 92.4 ft.  
     
     
         13 . The process of  claim 5 , further comprising heating the polymerization effluent.  
     
     
         14 . The process of  claim 13 , wherein the polymerization effluent is heated to a temperature below the fusion temperature of the polymer.  
     
     
         15 . The process of  claim 13 , wherein the quantity of heat supplied to the polymerization effluent is at least equal to that quantity of heat which equals the heat of vaporization of the liquid medium which is to be flashed in the first flash.  
     
     
         16 . A polymerization 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 said slurry comprising withdrawn liquid diluent and withdrawn solid polymer particles, as an intermediate product of said process;    exposing the intermediate product of said process to a pressure drop in a high pressure flash zone, such that a major portion of the liquid diluent from the intermediate product is vaporized and thus separated from said withdrawn solid polymer particles;    condensing at least a portion of the vaporized diluent without any compression; and    operating the loop reaction zone at a polymer production rate of at least 39,900 lbs/hr.    
     
     
         17 . The polymerization process of  claim 17 , wherein the volume of the loop reaction zone is 18,700 gallons.  
     
     
         18 . A process for producing polymer comprising: 
 polymerizing in liquid diluent at least one monomer in a loop reactor to produce a slurry of polymer solids;    continuously discharging a portion of the slurry from the loop reactor as polymerization effluent;    flashing the polymerization effluent in a first flash to vaporize from about 50% to about 100% of the liquid medium to produce concentrated polymer effluent and vaporized liquid;    condensing at least a portion of the vapor obtained in the first flash without compression; and    operating the loop reactor at a polymer production rate of at least 39,900 lbs/hr.    
     
     
         19 . The process of  claim 19 , wherein the volume of the loop reactor is 18,700 gallons.  
     
     
         20 . A polymerization 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 said slurry comprising withdrawn liquid diluent and withdrawn solid polymer particles, as an intermediate product of said process, wherein said intermediate product of said process is exposed to a pressure drop in a high pressure flash zone such that a major portion of said withdrawn liquid diluent is vaporized and thus separated from said withdrawn solid polymer particles, the thus separated withdrawn liquid diluent thereafter being condensed without any compression; and    maintaining a concentration of solid olefin polymer particles in said fluid slurry in said loop reaction zone of greater than 40 weight percent based on the weight of said polymer particles and the weight of said liquid diluent.    
     
     
         21 . The polymerization process of  claim 20  wherein the intermediate product of said process is continuously passed through a heating zone wherein said intermediate product is heated before being exposed to the pressure drop in the high pressure flash zone.  
     
     
         22 . The polymerization process of  claim 21 , wherein the intermediate product is heated to an extent such that a major portion of the withdrawn liquid diluent is vaporized.  
     
     
         23 . The polymerization process of  claim 22 , wherein the vaporized diluent is condensed for recycle by heat exchange.  
     
     
         24 . The polymerization process of  claim 23 , wherein the vaporized diluent is condensed for recycle by heat exchange with a fluid having a temperature within the range of about 40 degrees F. to about 130 degrees F.  
     
     
         25 . The polymerization process of  claim 20  whereby said loop reaction zone is operated at a high polymer production rate.  
     
     
         26 . The polymerization process of  claim 20  whereby said loop reaction zone is operated at a polymer production rate of at least 39,900 lb/hr.  
     
     
         27 . The polymerization process of  claim 20  whereby said loop reaction zone is operated at an efficiency of at least 2.13 lb/hr-gal.  
     
     
         28 . A polymerization 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 said slurry comprising withdrawn liquid diluent and withdrawn solid polymer particles, as an intermediate product of said process,    exposing the intermediate product of said process to a pressure drop in high pressure flash zone, such that a major portion of the liquid diluent from the intermediate product is vaporized and thus separated from said withdrawn solid polymer particles;    condensing the thus separated withdrawn liquid diluent without any compression; and    maintaining a concentration of solid olefin polymer particles in said fluid slurry in said loop reaction zone of greater than 40 weight percent based on the weight of said polymer particles and the weight of said liquid diluent.    
     
     
         29 . The polymerization process of  claim 28  whereby said loop reaction zone is operated at a high polymer production rate.  
     
     
         30 . The polymerization process of  claim 28  whereby said loop reaction zone is operated at a polymer production rate of at least 39,900 lb/hr.  
     
     
         31 . The polymerization process of  claim 28  whereby said loop reaction zone is operated at an efficiency of at least 2.13 lb/hr-gal.  
     
     
         32 . The polymerization process of  claim 28  wherein the intermediate product of said process is continuously passed through a heating zone wherein said intermediate product is heated before being exposed to the pressure drop in the high pressure flash zone.  
     
     
         33 . The polymerization process of  claim 28 , wherein the intermediate product is heated to an extent sufficient to vaporize a major portion of the withdrawn liquid diluent.  
     
     
         34 . The polymerization process of  claim 28 , further comprising heating the intermediate product before the high pressure flash zone.  
     
     
         35 . The polymerization process of  claim 28 , further comprising exposing the solid polymer particles separated and withdrawn from said liquid diluent in said high pressure flash zone to a pressure drop in a low pressure flash zone to vaporize additional liquid diluent.  
     
     
         36 . A process for producing polymer comprising: 
 polymerizing in liquid diluent at least one monomer in a loop reactor to produce a slurry of polymer solids;    continuously discharging a portion of the slurry from the loop reactor as polymerization effluent;    flashing the polymerization effluent in a first flash to vaporize from about 50% to about 100% of the liquid medium to produce concentrated polymer effluent and vaporized liquid;    condensing at least a portion of the vapor obtained in the first flash without compression; and    operating the loop reactor at a concentration of solid polymer particles in said slurry of greater than 40 weight percent.    
     
     
         37 . The process of  claim 36 , wherein the monomer is an olefin monomer.  
     
     
         38 . The process of  claim 36 , further comprising passing the polymerization effluent of said process through a heated conduit to the first flash.  
     
     
         39 . The process of  claim 36  whereby said loop reaction zone is operated at a high polymer production rate.  
     
     
         40 . The process of  claim 36  whereby said loop reaction zone is operated at a polymer production rate of at least 39,900 lb/hr.  
     
     
         41 . The process of  claim 36  whereby said loop reaction zone is operated at an efficiency of at least 2.13 lb/hr-gal.  
     
     
         42 . A process for producing polymer comprising: 
 polymerizing in liquid diluent at least one monomer in a loop reactor to produce a slurry of polymer solids;    continuously discharging a portion of the slurry from the loop reactor as polymerization effluent;    flashing the polymerization effluent in a first flash to vaporize from about 50% to about 100% of the liquid medium to produce concentrated polymer effluent and vaporized liquid; and    condensing a major portion of the vapor obtained in the first flash without compression.