Abstract:
A gas-phase process for polymerizing one or more α-olefins in a fluidized bed reactor in the presence of a polymerization catalyst, said fluidized bed reactor being equipped with a fluidization grid arranged at its base, and external means for recycling and cooling the unreacted gas from the top of said reactor to said fluidization grid, the process being characterized by: (i) a continuous pneumatic recycle of polymer by means of a circulation loop connecting said fluidization grid to the upper region of the fluidized bed reactor; (ii) a continuous discharge of polymer from a zone of said circulation loop having a polymer concentration higher than the polymer concentration inside the fluidized polymer bed.
Abstract:
The present disclosure relates to a manhole for a gas-phase polymerization unit having a through-hole formed with a shoulder (28) matching a corresponding shoulder (38) of a plug of a closure member (30) operatively inserted in said through-hole. In some embodiments, the through-hole is closed with a minimum clearance (47) so that polymer particles do not deposit in the gap between the wall (10) of the unit and the plug of the closure member (30). In further embodiments, retrofitting of standard manholes using the manhole disclosed herein is performed.
Abstract:
A process for the gas-phase polymerization of α-olefms carried out in two interconnected polymerization zones, wherein the growing polymer particles flow through the first of said polymerization zones (riser) under fast fluidization conditions, leave said riser and enter the second of said polymerization zones (downcomer) through which they flow downward in a densified form, the process being characterized in that: (a) the gas mixture present in the riser is totally or partially prevented from entering the downcomer by introducing into the upper part of said downcomer a liquid stream LB having a composition different from the gaseous mixture present in the riser; (b) the ratio R between the flow rate F p of polymer circulated between said downcomer and said riser and the flow rate LB of said liquid being adjusted in a range from 10 to 50.
Abstract:
A process for the multistage polymerization of olefins comprising a gas-phase polymerization carried out in at least two serially connected gas-phase reactors, the continuous discharge of polymer and gas reaction mixture from an upstream reactor into a transfer device and the continuous feeding of polymer from said transfer device to a downstream reactor, said transfer device comprising: a) a separation chamber in which said gas reaction mixture is removed from the polymer; b) at least a couple of lock hoppers working intermittently in parallel, where one of said lock hoppers is continuously filled with the polymer coming from step a), while simultaneously the other one is continuously pressurized by means of a gas comprising the reaction mixture coming from said downstream reactor.
Abstract:
A process for the slurry polymerization of one or more α-olefins in a sequence of at least two loop reactors interconnected by means of a transfer line, the transfer of polymer from a first loop reactor to a second loop reactor comprising the steps: i) establishing a recycle of polymer slurry to the second loop reactor by means of said transfer line, whereby a fraction of polymer slurry S1 withdrawn from said second loop reactor is continuously recycled back to it; ii) discharging a fraction of polymer slurry produced in the first loop reactor into a discharge line connected to said transfer line;
Abstract:
An apparatus for the liquid-phase polymerization of one or more α-olefins comprising: a first reactor selected from a loop reactor or a continuously stirred tank reactor; at least a downstream loop reactor; a connection line for transferring a polymer slurry from said first reactor to said downstream loop reactor, said connection line comprising: one or more adjacent pipes arranged at progressively increasing heights, each pipe forming with a horizontal direction (x) an angle α greater than the angle of rest of the obtained polymer; an on-off valve positioned flush with the wall of said downstream loop reactor.
Abstract:
An apparatus for drying polymer particles by means of an inert gas comprising: - a first drying chamber, placed above a first distribution grid, having an annular shape, where the polymer is maintained in fluidized conditions by a first stream of inert gas; - a second drying chamber comprising a tubular body running inside said first drying chamber and protruding downwardly below said first distribution grid.
Abstract:
A gas distribution grid comprising a plurality of trays arranged to form the lateral walls of an inverted cone, said plurality of trays being attached each other to form slots in the overlapping area of adjacent trays.
Abstract:
A polymerization process for preparing heterophasic propylene copolymers in two or more gas-phase reactors connected in series, in the presence of a polymerization catalyst comprising a catalytic component based on a titanium compound supported on magnesium halide, the process comprising the following steps: - contacting said catalytic component with an organo-Aluminum compound at a temperature from 5°C to 30°C and a weight ratio propylene/(catalytic component) ranging from 0 to 2.0; - prepolymerizing the catalyst from A) with propylene, optionally in the presence of an inert hydrocarbon solvent; - polymerizing propylene, optionally with an another -olefin comonomer in an amount lower than 15% by weight, to prepare a semicrystalline polymer component; - successively copolymerizing two or more alpha-olefin comonomers C 2 -C 10 to prepare one or more olefin copolymers having a solubility in xylene higher than 15% by weight; the process being characterized in that the bulk density of the semi-crystalline component of step C) is adjusted at a value lower than 0.40 g/cm 3 .
Abstract:
A process to perform the finishing of a polyolefin produced by polymerization of one or more α-olefins, the process comprising: (1) contacting a polyolefin discharged from a polymerization reactor with a counter-current flow of saturated steam, so as to strip away the gases from said polyolefin and to form condensed steam on the particles of said polyolefin; (2) drying the polyolefin particles by means of a counter-current flow of a dry inert gas, said flow of dry inert gas maintaining the polyolefin particles in fluidization conditions, the evaporation of said condensed steam cooling the polyolefin.