The present invention relates to a method for improving the cooling capacity of a gas solids olefin polymerization reactor by splitting the fluidization gas and returning part of the fluidization gas to the reactor into the bottom zone of the reactor and another part of the fluidization gas directly into the dense phase formed by particles of a polymer of the at least one olefin suspended in an upwards flowing stream of the fluidization gas in the middle zone of the reactor.

A process for preparing ethylene polymers including the step of polymerizing ethylene or copolymerizing ethylene and one or more comonomers at a temperature from 100° C. to 350° C. and a pressure of from 110 MPa to 350 MPa in a continuously operated tubular polymerization reactor, thereby yielding a reaction mixture, wherein the tubular polymerization reactor has a reactor cooling jacket for removing the heat of the reaction and a pressure control valve, the reaction mixture leaves the reactor through the pressure control valve, the reaction mixture then passes a post-reactor cooler equipped with a post-reactor cooling jacket, the reactor cooling jacket is provided with a reactor coolant having an inlet temperature and the post-reactor cooling jacket is provided with a post-reactor coolant having an inlet temperature, and the inlet temperature of the post-reactor coolant is independently controlled from the inlet temperature of the reactant coolant.

A process for preparing ethylene polymers including the step of polymerizing ethylene or copolymerizing ethylene and one or more comonomers at a temperature from 100° C. to 350° C. and a pressure of from 110 MPa to 350 MPa in a continuously operated tubular polymerization reactor, thereby yielding a reaction mixture, wherein the tubular polymerization reactor has a reactor cooling jacket for removing the heat of the reaction and a pressure control valve, the reaction mixture leaves the reactor through the pressure control valve, the reaction mixture then passes a post-reactor cooler equipped with a post-reactor cooling jacket, the reactor cooling jacket is provided with a reactor coolant having an inlet temperature and the post-reactor cooling jacket is provided with a post-reactor coolant having an inlet temperature, and the inlet temperature of the post-reactor coolant is independently controlled from the inlet temperature of the reactant coolant.

A process for preparing ethylene polymers including the step of polymerizing ethylene or copolymerizing ethylene and one or more comonomers at a temperature from 100° C. to 350° C. and a pressure of from 110 MPa to 350 MPa in a continuously operated tubular polymerization reactor, thereby yielding a reaction mixture, wherein the tubular polymerization reactor has a reactor cooling jacket for removing the heat of the reaction and a pressure control valve, the reaction mixture leaves the reactor through the pressure control valve, the reaction mixture then passes a post-reactor cooler equipped with a post-reactor cooling jacket, the reactor cooling jacket is provided with a reactor coolant having an inlet temperature and the post-reactor cooling jacket is provided with a post-reactor coolant having an inlet temperature, and the inlet temperature of the post-reactor coolant is independently controlled from the inlet temperature of the reactant coolant.

A method capable of stably performing continuous production of a propylene polymer with high productivity while reducing generation of agglomerates is described. In the method, a monomer(s) containing propylene is/are (co)polymerized in a presence of an olefin polymerization catalyst with a polymerization system containing two or more gas phase polymerization reactors or a polymerization system containing a liquid phase polymerization reactor(s) and a gas phase polymerization reactor(s) such that that the total number of liquid phase polymerization reactor(s) and gas phase polymerization reactor(s) is three or more. In at least one gas phase polymerization reactor, an average retention time τ.sub.G [hour] in the gas phase polymerization, an average particle diameter D.sub.pi [μm] of fed powder, and a total amount C.sub.o [wt %] of an ethylene-derived structural unit and C4-C12 α-olefin-derived structural units in a polymer in discharged powder are in a predetermined relationship.

Embodiments of a method for reducing unreacted ethylene monomer in a low density polyethylene (LDPE) polymerization process comprises: delivering a monomer feedstock comprising ethylene monomer to a compressor system to produce a pressurized feedstock having a pressure of at least 2000 bar; passing the pressurized feedstock to at least one free radical polymerization reactor to produce a reactor effluent comprising the LDPE and unreacted ethylene monomer; and delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, the third separation vessel having an operating pressure of less than or equal to 0.05 bar, wherein the third separation vessel produces a separation product comprising LDPE and less than or equal to 50 ppm of the unreacted ethylene monomer, wherein there is no stripping agent added upstream of the third separation vessel.

Embodiments of a method for reducing unreacted ethylene monomer in a low density polyethylene (LDPE) polymerization process comprises: delivering a monomer feedstock comprising ethylene monomer to a compressor system to produce a pressurized feedstock having a pressure of at least 2000 bar; passing the pressurized feedstock to at least one free radical polymerization reactor to produce a reactor effluent comprising the LDPE and unreacted ethylene monomer; and delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, the third separation vessel having an operating pressure of less than or equal to 0.05 bar, wherein the third separation vessel produces a separation product comprising LDPE and less than or equal to 50 ppm of the unreacted ethylene monomer, wherein there is no stripping agent added upstream of the third separation vessel.

This invention relates to a self cleaning reactor and to a process for the oligomerization of ethylene that employs a self-cleaning reactor. The reactor includes a mass of inert, particulate cleaning bodies that are entrained by the liquid in the reactor and scour the internal surfaces of the reactor during normal operation. This scouring action reduces the level of fouling on the reactor surfaces. Foulant material (polyethylene) is removed from the process on a continuous basis but the cleaning bodies remain within the reactor.

This invention relates to a self cleaning reactor and to a process for the oligomerization of ethylene that employs a self-cleaning reactor. The reactor includes a mass of inert, particulate cleaning bodies that are entrained by the liquid in the reactor and scour the internal surfaces of the reactor during normal operation. This scouring action reduces the level of fouling on the reactor surfaces. Foulant material (polyethylene) is removed from the process on a continuous basis but the cleaning bodies remain within the reactor.

It is provided a process for producing an ethylene copolymer comprising compressing ethylene monomer at a certain pressure; adding a fresh comonomer in liquid form and, optionally, a fresh modifier in liquid form at a certain pressure to the compressed ethylene monomer; introducing the resulting compressed mixture into an autoclave reactor having a first reaction zone and at least one more reaction zone, the first reaction zone having a volume that is greater than 50% of the total reactor volume, and, optionally, at least one additional reactor; adding at least one free radical initiator in order to start a polymerization reaction; and separating the ethylene copolymer from the reaction mixture; wherein all the compressed ethylene monomer or the compressed mixture are introduced into the first reaction zone of the autoclave reactor, and wherein the compressed mixture is introduced into the autoclave reactor and, optionally, into the at least one additional reactor at a temperature from −20° C. to 70° C.