By a News Reporter-Staff News Editor at Journal of Technology -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Fouarge, Louis (Dilbeek, BE); Horre, Annelies (Temse, BE); Nauwelaerts, Geert (Zoersel, BE); Tanghe, Rudi (St.-Lenaarts, BE); Janssens, Johan (Grobbendonk, BE); Beuckelaers, Steven (Breendonk, BE); Richet, Marc (Oignies en Thierache, BE); Wilderiane, Pascal (Biercee, BE), filed on January 21, 2014, was published online on September 19, 2017.
The assignee for this patent, patent number 9765165, is TOTAL RESEARCH & TECHNOLOGY FELUY (Seneffe, BE).
Reporters obtained the following quote from the background information supplied by the inventors: "Olefin polymerizations such as ethylene polymerization are frequently carried out using monomer, diluent and optional catalyst and optionally co-monomers in a loop reactor. The polymerization is usually performed under slurry conditions, wherein the product consists usually of solid particles and is in suspension of a diluent. The slurry contents of the reactor are circulated continuously with a pump to maintain efficient suspension of the polymer solid particles in the liquid diluent, the product being often taken off by means of settling legs which operate usually on a batch principle to recover the product. Settling in the legs is used to increase the solids concentration of the slurry finally recovered as product slurry. The product is further either transferred to another reactor or discharged to a flash tank, through flash lines, where most of the diluent and unreacted monomers are flashed off and recycled. The polymer particles are dried, additives can be added and finally the polymer is extruded and pelletized.
"In these polymerization processes, settling legs, however, do present some problems. They represent the imposition of a 'batch' or 'discontinuous' technique onto a basic continuous process. Each time a settling leg reaches the stage where it 'discharges' or 'fires' accumulated polymer slurry it causes interferences on the pressure in the loop reactor, which is thereby not kept constant. Pressure fluctuations in the loop reactor may be larger than 1 bar. At very high monomer concentration, such pressure fluctuations may generate several problems such as the creation of gas bubbles that may cause trouble in the operation of the circulation pump. They may also provoke perturbations in the control scheme of the reactor pressure.
"Various alternative product removal techniques are known. EP 0891990 describes an olefin polymerization process wherein the product slurry is recovered by means of a continuous product take off, more in particular by means of an elongated hollow appendage provided on the reactor, wherein, said hollow appendage is in direct fluid communication with a heated flash line, and thus being adapted for continuous removal of product slurry.
"However the above-described apparatus and processes have the disadvantage that the suspension discharged from the reactor still contains a large amount of diluent and of other reactants, such as the monomer, which it is then necessary to subsequently separate from the polymer particles and to treat for the purpose of reusing it in the reactor. Another disadvantage of the above-described apparatus and processes is their lack of flexibility during the phase or reaction start-up or in response to large disruptions in the normal behavior of the reactor, like sudden interruption of one of the feed streams. Furthermore, reliability of the discharge of the polymer slurry from the loop reactor is not high enough.
"It is therefore an object of the present invention to provide a polymerization process occurring in a loop reactor wherein the polymer slurry is efficiently and continuously removed from the loop reactor. More in particular, it is an object of the invention to optimize the residence time in the settling legs. Another object of the present invention is to improve efficiency of separation of olefin polymer, reactants and diluent. It is further an object of the present invention to improve polymerization process' operability and reliability."
In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "These present objects are achieved by the processes according to the present invention.
"The present invention relates to a process for the preparation of a polyolefin in at least one slurry loop reactor provided with one or more settling legs, comprising the steps of: introducing into said loop reactor one or more olefin reactants, diluents, polymerization catalyst and optional ingredients and while circulating said olefin reactants, diluents and polymerization catalyst in said loop reactor; polymerizing said one or more olefin reactants to produce a polymer slurry comprising liquid diluent and solid olefin polyolefin particles; continuously withdrawing polyolefin slurry comprising polyolefin particles and diluent from said reactor, via said one or more settling legs and transferring said withdrawn solid olefin polymer particles from said loop reactor to a recovery section; wherein each settling leg has an inlet connected to the reactor and an outlet connected to the recovery section, and wherein at least one settling leg is continuously open allowing continuous withdrawal of said polyolefin slurry from said loop reactor, and wherein each outlet of said one or more settling legs is connected to the recovery section by means of at least one conduit provided with a pressure control device, and wherein the pressure in said loop reactor is controlled by operating said pressure control device.
"Surprisingly, the present inventors have found that the process according to the present invention improved the operability/reliability by avoiding polymer stagnation and optimizing residence time in the settling legs. Furthermore, the process according to the present invention further improves efficiency of polymer/reactants/diluent separation by minimizing the amount of reactants/diluent transferred to recovery sections and reduces the complexity of the known processes.
"The process according to the present invention does not require take-off point to be located at specific location(s) in the reactor or to have complex shape, and do not need to extend into the circulation path.
"The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description and drawings, which illustrate, by way of example, the principles of the invention."
For more information, see this patent: Fouarge, Louis; Horre, Annelies; Nauwelaerts, Geert; Tanghe, Rudi; Janssens, Johan; Beuckelaers, Steven; Richet, Marc; Wilderiane, Pascal. Olefin Polymerization Process with Continuous Discharging. U.S. Patent Number 9765165, filed January 21, 2014, and published online on September 19, 2017. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=9765165.PN.&OS=PN/9765165RS=PN/9765165
Keywords for this news article include: TOTAL RESEARCH & TECHNOLOGY FELUY.
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