Slurry loop reactors

Abstract

An apparatus defined as a set of loop reactors suitable for the polymerization process of a monomer, preferably ethylene and optionally an olefin comonomer, comprising for each of said reactors: a plurality of interconnected pipes P defining a flow path for a polymer slurry, said slurry consisting essentially of ethylene, optionally a comonomer, a polymerization catalyst, liquid diluent and solid olefin polymer particles, means for feeding monomer, optionally a co-monomer, diluent and optionally hydrogen in the reactor, means for feeding a polymerization catalyst in the reactor, a pump suitable for maintaining the polymer slurry in circulation in such reactor, one or more settling legs connected to the pipes P of such reactor for settling of polymer slurry, one or more control valves connected to the outlet of such settling legs, and one or more flash lines for discharging settled polymer slurry out of the reactor characterized in that each of said loop reactors comprises a three-or-more-way valve defining three-or-more ends, one end A being positioned at the outlet of said one or more control valves. A method to switch from series to parallel configuration a set of loop reactors. The use of the apparatus to switch polymerization reactors from parallel to series configuration and vice-versa.

1 - 13 . (canceled) 
   
   
       14 . A reactor system suitable for the polymerization of an olefin monomer comprising first and second loop reactors effective for the polymerization of an olefin monomer;
 a) each of said reactors having at least one settling leg connected to said reactor for receiving polymer slurry from said reactor and sequentially discharging settled polymer from said at least one settling leg to withdraw said polymer slurry from said reactor;   b) a transfer line extending from the outlet at least one first reactor settling leg to an inlet for said second loop reactor;   c) a flash line extending from said transfer line at a valve location intermediate said first reactor settling leg and said inlet for said second reactor;   d) a multiway valve located in said transfer line at said valve location intermediate said first reactor settling leg and the inlet to said second reactor and having one position in which said multiway valve provides for the flow of polymer slurry through said transfer line to said second reactor and another position in which said first reactor settling leg is connected to said flash line for the discharge of polymer slurry from said first reactor settling leg to said flash line and removal of said polymer from said polymer system.   
   
   
       15 . The system of  claim 14  further comprising a supply line connected to said transfer line adjacent said valve location in order to supply diluent liquid to said transfer line. 
   
   
       16 . The system of  claim 15  wherein said supply line is located intermediate said valve location and the inlet to said second reactor. 
   
   
       17 . The system of  claim 14  further comprising a flash tank for said first reactor and wherein the flash line extending from said transfer line is connected to said flash tank. 
   
   
       18 . The system of  claim 17  wherein the ratio of the length of said flash line extending from said transfer line to said first reactor divided by the length of said transfer line extending from the settling leg outlet to the inlet of said second loop reactor is within the range of 6 to 14. 
   
   
       19 . The system of  claim 18  wherein said ratio is within the range of 8 to 12. 
   
   
       20 . The system of  claim 17  further comprising a second flash tank for said second reactor and a second flash line extending from a settling leg of said second reactor to said second reactor flash tank. 
   
   
       21 . A multi-reactor polymerization process for the production of an olefin polymer comprising:
 a) introducing an olefin monomer, a polymerization catalyst and a diluent carrier liquid into a first reactor of a multi-reactor polymerization system and circulating said diluent liquid and monomer in said first reactor to polymerize said monomer in the presence of said catalyst system to produce a slurry of polymer particles in said diluent carrier liquid;   b) introducing an olefin monomer, a polymerization catalyst and a diluent carrier liquid into a second reactor of said multi-reactor polymerization system and circulating said diluent liquid and monomer in said second reactor to polymerize said monomer in the presence of said catalyst system to produce a second slurry of polymer particles in said diluent carrier liquid;   c) directing said polymer slurry in said first reactor into a settling leg connected to said first reactor; and   d) periodically transferring polymer slurry from said settling leg of said first reactor into a transfer line having a multi-position valve having a first position in which said transfer line is open to an inlet of said second reactor and a second position in which said transfer line is closed to the inlet of said first reactor and open to a flash line providing an exit for the withdrawal of polymer slurry from said process;   e) operating said multi-position valve in said transfer line in said first position to provide for a series mode of operation of said first and second reactors or in said second position in which said first and second reactors are operated in a parallel mode of operation;   f) directing polymer slurry in said second reactor into a settling leg connected to said second reactor; and   g) transferring polymer slurry from said second reactor settling leg into a flash line for withdrawal of polymer slurry from said second reactor.   
   
   
       22 . The method of  claim 21  further comprising switching said multi-position valve from one of said first and second positions to the other of said first and second positions to change the operation of said first and second reactors from one of said modes of operation to the other of said modes of operation. 
   
   
       23 . The method of  claim 22  wherein prior to switching said valve to transition said process from one mode of operation to another mode of operation, terminating the operation of said reactors and circulating a diluent liquid through said reactors for at least 8 hours before switching said valve to transition from one mode to another mode of operation. 
   
   
       24 . The method of  claim 22  further comprising supplying a diluent liquid to a portion of said multi-position valve to which polymer slurry is not flowing after switching said valve to transition said process from one mode of operation to another.