Abstract: A multitubular heat exchanger for cooling a gas stream. including an inlet chamber: a bundle of tubes encased in a shell structure: and an outlet chamber, wherein (a) each tube has an inlet with a diameter of d1: a longitudinal middle part with a diameter of d2: an outlet: and (b) d1 is larger than d2.

Abstract: A reactor for carrying out a gas-phase olefin polymerization in the presence of a polymerization catalyst, made from or containing (i) a first polymerization zone adapted and arranged for growing polymer particles to flow upward under fast fluidization or transport conditions, (ii) a second polymerization zone adapted and arranged for the growing polymer particles to flow downward, and (iii) a set of bars for introducing feedstock or a barrier stream into the reactor, wherein each bar has (a) a hollow space along the length of the bar, (b) a particle deviating top, and (c) a multiplicity of openings arranged along the bottom half of the periphery of the bar.

Abstract: An apparatus for carrying out a gas-phase olefin polymerization having a first polymerization zone having a cylindrical segment of diameter D01, a second polymerization zone having a cylindrical upper part of diameter D05 and a cylindrical lower part of diameter D06, a separation zone of diameter D04, a first connecting element of diameter D03, which is a bend of radius R03 or has a bend part of radius R03, a gas recycle line of diameter D08, a transition segment of diameter D02, and a second connecting element of a diameter D09, which is a bend or has a bend part, wherein the ratio D04 to D05 is 1.0 to 1.5, the ratio D05 to D06 is 1.2 to 2, the ratio R03 to D03 is 1 to 6, the ratio D03 to D01 is 0.3 to 0.85, and the ratio D08 to D02 is 1.0 to 2.2.

Abstract: Apparatus for carrying out a catalytic gas-phase olefin polymerization having a first polymerization zone for growing polymer particles to flow upward under fast fluidization or transport conditions, a second polymerization zone for the growing polymer particles to flow downward, and a gas/solid separation zone; wherein the second polymerization zone has an upper part being connected to the separation zone and a lower part being connected to the upper part; wherein the ratio of the height H01 of the separation zone to the diameter D01 of the separation zone is 2.5 to 4.5.

Abstract: A process for the polymerization of olefins in gas phase carried out in a reactor having two interconnected polymerization zones, a first zone (riser) and a second zone (downcomer), wherein growing polymer particles: a) flow through the riser under fast fluidization conditions established by feeding a mixture of gas and liquid; b) leave the riser and enter the downcomer, through which the growing polymer particles flow downward in a densified form; and c) leave the downcomer and are reintroduced into the riser, thereby establishing a circulation of polymer between the riser and the downcomer; the reactor is operated at a temperature between 0° C. and 5° C. above the dew point of the riser gas at the operating pressure, and in the riser, besides the growing polymer particles and gas flow, an amount of liquid is present.

Abstract: A manhole for a polymerization unit having a through-hole formed with a shoulder matching a corresponding shoulder of a plug of a closure member operatively inserted in the through-hole. The through-hole can be closed with a minimum clearance, such that polymer particles do not deposit in the gap between the wall of the unit and the plug of the closure member.

Abstract: A gas-phase polymerization reactor for the gas-phase polymerization of olefins including a polymerization zone having a recycle line for (a) withdrawing reaction gas from the reactor, (b) leading the reaction gas through a heat-exchanger for cooling, and (c) feeding the reaction gas back to the reactor, wherein the recycle line has the heat-exchanger, a centrifugal compressor having variable guide vanes, and a butterfly valve, and a related process for preparing an olefin polymer in the gas-phase polymerization reactor.

Abstract: A gas-phase polymerization reactor for the gas-phase polymerization of olefins including a polymerization zone having a recycle line for (a) withdrawing reaction gas from the reactor, (b) leading the reaction gas through a heat-exchanger for cooling, and (c) feeding the reaction gas back to the reactor, wherein the recycle line has the heat-exchanger, a centrifugal compressor having variable guide vanes, and a butterfly valve, and a related process for preparing an olefin polymer in the gas-phase polymerization reactor.

Abstract: A manhole for a polymerization unit having a through-hole formed with a shoulder matching a corresponding shoulder of a plug of a closure member operatively inserted in the through-hole. The through-hole can be closed with a minimum clearance, such that polymer particles do not deposit in the gap between the wall of the unit and the plug of the closure member.

Abstract: A process for the polymerization of olefins in gas phase carried out in a reactor having two interconnected polymerization zones, a first zone (riser) and a second zone (downcomer), wherein growing polymer particles: a) flow through the riser under fast fluidization conditions established by feeding a mixture of gas and liquid; b) leave the riser and enter the downcomer, through which the growing polymer particles flow downward in a densified form; and c) leave the downcomer and are reintroduced into the riser, thereby establishing a circulation of polymer between the riser and the downcomer; the reactor is operated at a temperature between 0° C. and 5° C. above the dew point of the riser gas at the operating pressure, and in the riser, besides the growing polymer particles and gas flow, an amount of liquid is present.

Abstract: A process for the preparation of polyolefins carried out in the presence of an antistatic composition made from or containing: a) a compound of formula R—OH wherein R represents hydrogen or a linear or branched, saturated alkyl group having from 1 to 15 carbon atoms; and b) an oligomeric or polymeric organic compound having one or more terminal hydroxyl groups and a viscosity at 40° C. of at least about 20 mm2/sec (DIN 51562).

Abstract: A process for the preparation of polyolefins carried out in the presence of an antistatic composition made from or containing: a) a compound of formula R—OH wherein R represents hydrogen or a linear or branched, saturated alkyl group having from 1 to 15 carbon atoms; and b) an oligomeric or polymeric organic compound having one or more terminal hydroxyl groups and a viscosity at 40° C. of at least about 20 mm2/sec (DIN 51562).

Abstract: A gas-phase polymerization reactor having interconnected polymerization zones comprising:—a riser through which the polymer particles flow upwards under fast fluidization conditions or transport conditions;—a downcomer through which the polymer particles flow downward in a densified form under the action of gravity, the bottom of said downcomer being connected to the lower region of said riser by means of a transport section, said transport section being designed as a bend descending from the downcomer to the riser.

Abstract: A process for the gas-phase copolymerization of: (a) propylene, (b) at least one C4-C8 ?-olefin, and (c) optionally ethylene, the process being carried out in a reactor having 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, leave said downcomer and are reintroduced into said riser, thus establishing a circulation of polymer between the riser and the downcomer, the gas mixture present in the riser being at least partially prevented from entering the downcomer by introducing into the upper part of said downcomer a liquid barrier having a composition different from the gaseous mixture present in the riser and comprising at least one C4-C8 ?-olefin in a total amount of from 0.1% to 35% by mol.

Abstract: A gas-phase polymerization reactor having interconnected polymerization zones comprising:—a riser through which the polymer particles flow upwards under fast fluidization conditions or transport conditions—a dowcomer through which the polymer particles flow downward in a densified form under the action of gravity, the bottom of said downcomer being connected to the lower region of said riser by means of a transport section, said transport section being designed as a bend descending from the downcomer to the riser.

Abstract: A process for the gas-phase copolymerization of: (a) propylene, (b) at least one C4-C8 ?-olefin, and (c) optionally ethylene, the process being carried out in a reactor having 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, leave said downcomer and are reintroduced into said riser, thus establishing a circulation of polymer between the riser and the downcomer, the gas mixture present in the riser being at least partially prevented from entering the downcomer by introducing into the upper part of said downcomer a liquid barrier having a composition different from the gaseous mixture present in the riser and comprising at least one C4-C8 ?-olefin in a total amount of from 0.1% to 35% by mol.

Abstract: A process for the gas-phase polymerization of one or more alpha-olefins in the presence of a polymerization catalyst, the process comprising: at least a polymerization step wherein the polymer particles flow downward in densified form under the action of gravity so as to form a densified polymer bed; metering an anti-fouling agent in said polymerization step by means of at least N feeding lines placed at different heights of said densified polymer bed, N being the integer number satisfying the equation N?(1+0.08·H), where H is the height (expressed in meters) of the polymer bed.

Abstract: A process for the gas-phase polymerization of one or more alpha-olefins in the presence of a polymerization catalyst, the process comprising: at least a polymerization step wherein the polymer particles flow downward in densified form under the action of gravity so as to form a densified polymer bed; metering an anti-fouling agent in said polymerization step by means of at least N feeding lines placed at different heights of said densified polymer bed, N being the integer number satisfying the equation N?(1+0.08·H), where H is the height (expressed in meters) of the polymer bed.

Abstract: A process for the gas-phase polymerization of ?-olefins 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 Fp 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 polymerization of olefins carried out in a gas-phase reactor having interconnected polymerization zones, where the growing polymer particles flow upward through a first polymerization zone (riser) under fast fluidization or transport conditions, leave said riser and enter a second polymerization zone (downcomer) through which they flow downward under the action of gravity, leave said downcomer and are reintroduced into the riser, a gas recycle stream being withdrawn from said first polymerization zone, subjected to cooling below its dew point and then returned to said first polymerization zone, the process being characterized in that said gas recycle stream is cooled at a temperature Tc ranging from 0.05° C. to 3° C. below its dew point.