CN117619286A - System for preparing ethylene copolymer through slurry method and filter pressing process - Google Patents

Abstract

The invention discloses a system for preparing ethylene-hexane copolymer by a slurry method and a filter pressing process, which comprises a polymerization reaction unit, a slurry solid-liquid separation unit, a drying devolatilization unit, a noncondensable gas recovery unit and a solvent refining unit. The invention provides a system for preparing ethylene copolymer by using pentane as solvent, which can be applied to the large chemical industry and is prepared by a slurry method. In the slurry solid-liquid separation unit, continuous solid-liquid separation and solid drying are carried out by adopting a pressure filter mode. The mother liquid of recovered polymerization solvent is directly returned to the reactor for partial refining. The size of subsequent drying equipment of polyolefin resin can be reduced, equipment investment and occupied area are reduced, and meanwhile, part of polymerization solvent directly returns to the reactor without phase change, so that the separation energy consumption can be greatly reduced.

Description

System for preparing ethylene copolymer through slurry method and filter pressing process

Technical Field

The invention relates to the field of processes for preparing ethylene copolymer by a slurry method, in particular to a system for preparing ethylene copolymer by a slurry method and a filter pressing process.

Background

In the slurry polyethylene process, a hexane solvent or a butane solvent is generally used, but in the case of preparing a copolymer of ethylene, if a hexane solvent is used, hexene cannot be used as a comonomer because it is difficult to separate hexene and hexane due to their close boiling points. If butane solvent is adopted, the butane has very low boiling point, is very volatile, and has high requirements on reaction conditions.

Therefore, the process method is used for preparing the ethylene copolymer, has mild reaction conditions and can be suitable for industrial mass production.

Disclosure of Invention

In order to achieve the aim, the invention adopts pentane as a solvent, optimizes and matches the process flow aiming at the characteristics of the pentane solvent, and provides a system for preparing the ethylene copolymer by a slurry method by taking pentane as the solvent.

The invention provides a system for preparing ethylene-hexane copolymer by using pentane as solvent through a slurry method and a filter pressing process, which comprises

The polymerization reaction unit is respectively communicated with a catalyst feed pipe, a hydrogen feed pipe, a hexene feed pipe, a solvent feed pipe, an ethylene feed pipe, a reaction noncondensable gas outlet pipe and a slurry discharge pipe;

the slurry solid-liquid separation unit comprises a slurry cooling assembly, a mother liquor tank, a rotary pressure filter and a dry gas filtrate collecting tank; one end of the slurry discharging pipe, which is far away from the polymerization reaction unit, is communicated with the slurry solid-liquid separation unit;

the drying devolatilization unit is communicated with the slurry solid-liquid separation unit through a ethylene-propylene copolymer pipe;

the solvent refining unit is communicated with the slurry solid-liquid separation unit through a first mother liquor pipe and is communicated with the polymerization reaction unit through a refined solvent pipe;

The noncondensable gas recovery unit is communicated with one end of the reaction noncondensable gas outlet pipe, which is far away from the polymerization reaction unit; the solvent refining unit is communicated with the noncondensable gas recovery unit through a refined noncondensable gas outlet pipe, and the noncondensable gas recovery unit is communicated with the solvent refining unit through a solvent recovery pipe.

Preferably, in the slurry solid-liquid separation unit, one end of the slurry discharging pipe, which is far away from the polymerization reaction unit, is communicated with the rotary pressure filter, and a slurry cooling assembly is arranged on the slurry discharging pipe; the rotary pressure filter is communicated with the drying devolatilization unit through an ethylene-propylene copolymer pipe; the rotary pressure filter is communicated with the mother liquor tank through a mother liquor outlet pipe, the mother liquor tank is communicated with the solvent refining unit through the first mother liquor pipe, the mother liquor tank is communicated with the polymerization reaction unit through the second mother liquor pipe, and the mother liquor tank is communicated with the moisture recovery unit through the mother liquor noncondensable gas outlet pipe; the rotary pressure filter is communicated with the dry gas filtrate collecting tank through a dry gas outlet pipe, and the dry gas filtrate collecting tank is communicated with the moisture recovery unit through a separation non-condensable gas outlet pipe; the air outlet pipe for separating noncondensable gas is provided with a condenser, and the condenser is communicated with the dry gas filtrate collecting tank through a condensate pipe.

Preferably, the slurry solid-liquid separation unit further comprises a filter press flushing fluid inlet pipe and a filter press flushing fluid outlet pipe, wherein one end of the filter press flushing fluid outlet pipe, which is far away from the rotary pressure filter, is communicated with the polymerization reaction unit; and a cleaning liquid collecting tank is arranged on the flushing liquid outlet pipe of the filter press.

Preferably, the solvent refining unit includes:

the refining tower is communicated with one end of the first mother liquor pipe, which is far away from the mother liquor tank, and the first mother liquor pipe is sequentially provided with a powder remover and a mother liquor preheater from upstream to downstream; the refining tower is provided with a condenser at the top of the refining tower, a reflux tank at the top of the refining tower, a reflux pump at the top of the refining tower and a reboiler at the bottom of the refining tower; the refining tower is communicated with a condenser at the top of the refining tower through a discharge pipe at the top of the refining tower, the condenser at the top of the refining tower is communicated with a reflux tank at the top of the refining tower through a pipeline, the reflux tank at the top of the refining tower is communicated with the refining tower through a condensate pipe at the top of the refining tower, and the refining tower is communicated with a heavy-removal tower or a polymerized monomer recovery unit through a discharge pipe at the bottom of the refining tower;

the dehydration tower is communicated with the refining tower through a branch of a condensate pipe at the top of the refining tower; the dehydration tower is provided with a dehydration tower top condenser, a dehydration tower top aftercooler, a dehydration tower top condensate tank, a dehydration tower top reflux pump and a dehydration tower kettle reboiler, and the dehydration tower top aftercooler is communicated with the noncondensable gas recovery unit through a refined noncondensable gas outlet pipe; the dehydration tower is communicated with the solvent buffer tank through a dehydration tower kettle discharging pipe, and a dehydration tower kettle conveying pump and a dehydration tower kettle liquid cooler are arranged on the dehydration tower kettle discharging pipe; the solvent buffer tank is communicated with the polymerization solvent refiner through a pipeline, and the polymerization solvent refiner is communicated with the polymerization reaction unit through a pipeline;

The heavy-removal tower is communicated with the refining tower through a discharging pipe at the bottom of the refining tower; the top of the heavy-removal tower is provided with a heavy-removal tower top condenser, a heavy-removal tower top reflux tank, a heavy-removal tower top reflux pump and a heavy-removal tower kettle reboiler; the reflux tank at the top of the de-weighting tower is communicated with the de-weighting tower through a condensate pipe at the top of the de-weighting tower, a branch of the condensate pipe at the top of the de-weighting tower is communicated with the polymerization solvent refiner, and the polymerization solvent refiner is communicated with the polymerization reaction unit through a pipeline; the de-weighting tower is communicated with the polymerized monomer recovery unit through a discharging pipe at the bottom of the de-weighting tower.

Preferably, a branch of the outlet pipe of the refining tower is communicated with the inlet of the heating medium channel of the mother liquor preheater, and the outlet of the heating medium channel of the mother liquor preheater is communicated with the reflux tank at the top of the refining tower through a pipeline.

Preferably, a branch of the outlet pipe of the refining tower is communicated with a heating medium channel inlet of a tower kettle reboiler of the dehydration tower, and a heating medium channel outlet of the tower kettle reboiler of the dehydration tower is communicated with a reflux tank at the top of the refining tower through a pipeline.

Preferably, the solvent refining unit includes:

the refining tower is communicated with one end of the first mother liquor pipe, which is far away from the mother liquor tank, and the first mother liquor pipe is provided with a powder remover; the refining tower is provided with a condenser at the top of the refining tower, a reflux tank at the top of the refining tower, a reflux pump at the top of the refining tower, a reboiler at the bottom of the refining tower and a start-up reboiler at the bottom of the refining tower; the refining tower is communicated with a heating medium channel inlet of a tower kettle reboiler of the refining tower through a tower ejection material pipe of the refining tower, a heating medium channel outlet of the tower kettle reboiler of the refining tower is communicated with a tower top reflux tank of the refining tower through a pipeline, and the tower top reflux tank of the refining tower is communicated with the refining tower through a tower top condensate pipe of the refining tower; a heat pump is arranged on a tower ejection pipe of the refining tower; the refining tower is communicated with a heavy-removal tower or a polymerized monomer recovery unit through a discharging pipe at the bottom of the refining tower;

The dehydration tower is communicated with the refining tower through a branch of a condensate pipe at the top of the refining tower; the dehydration tower is provided with a dehydration tower top condenser, a dehydration tower top aftercooler, a dehydration tower top condensate tank, a dehydration tower top reflux pump and a dehydration tower kettle reboiler, and the dehydration tower top aftercooler is communicated with the noncondensable gas recovery unit through a refined noncondensable gas outlet pipe; the dehydration tower is communicated with the solvent buffer tank through a dehydration tower kettle discharging pipe, and a dehydration tower kettle conveying pump and a dehydration tower kettle liquid cooler are arranged on the dehydration tower kettle discharging pipe; the solvent buffer tank is communicated with the polymerization solvent refiner through a pipeline, and the polymerization solvent refiner is communicated with the polymerization reaction unit through a pipeline;

the heavy-removal tower is communicated with the refining tower through a discharging pipe at the bottom of the refining tower; the top of the heavy-removal tower is provided with a heavy-removal tower top condenser, a heavy-removal tower top reflux tank, a heavy-removal tower top reflux pump and a heavy-removal tower kettle reboiler; the reflux tank at the top of the de-weighting tower is communicated with the de-weighting tower through a condensate pipe at the top of the de-weighting tower, a branch of the condensate pipe at the top of the de-weighting tower is communicated with the polymerization solvent refiner, and the polymerization solvent refiner is communicated with the polymerization reaction unit through a pipeline; the de-weighting tower is communicated with the polymerized monomer recovery unit through a discharging pipe at the bottom of the de-weighting tower.

Preferably, a branch of the outlet pipe of the refining tower is communicated with a condenser at the top of the refining tower, and the condenser at the top of the refining tower is communicated with a reflux tank at the top of the refining tower through a pipeline.

Preferably, the refining column is a tray column.

Preferably, the heavy-removal tower is a plate tower.

Preferably, the cooling medium of the top condenser of the de-weight tower is cooling water.

Preferably, the heating medium of the reboiler of the refining tower kettle is steam.

Preferably, the heavy ends removal tower kettle reboiler is a thermosiphon reboiler.

Preferably, the drying devolatilization unit comprises a dryer and a wet gas scrubber, wherein one end of the ethylene-hexamethylene copolymer pipe, which is far away from the slurry solid-liquid separation unit, is communicated with the dryer, the dryer is communicated with the wet gas scrubber through a wet gas pipe, a top gas outlet pipe of the wet gas scrubber is sequentially communicated with a dry gas compressor, a dry gas condenser and a dry gas secondary condenser, a liquid outlet pipe of the dry gas secondary condenser is communicated with a dry gas sealing tank, and the dry gas sealing tank is communicated with the wet gas scrubber through a dry gas sealing tank; the wet gas scrubber is provided with a bottom liquid circulation pipe.

Preferably, an air outlet pipe of the drying gas secondary condenser is communicated with the noncondensable gas recovery unit through a pipeline.

Preferably, a branch of the bottom liquid circulation pipe is communicated with a solid-liquid separation unit, and the solid-liquid separation unit is communicated with the solvent refining unit.

Preferably, the polymerization reaction unit further comprises an ethylene refining unit which is communicated with one end of the ethylene feeding pipe far away from the polymerization reaction unit.

Preferably, the tail gas pipe of the noncondensable gas recovery unit is communicated with an ethylene recovery device.

Preferably, the discharging pipe of the drying devolatilization unit is communicated with the mixing air conveying unit through a pipeline.

Preferably, the pentane is n-pentane and/or isopentane.

Compared with the prior art, the invention has the following technical effects:

(1) The invention provides a system for preparing ethylene copolymer by using pentane as solvent, which can be applied to the large chemical industry and is prepared by a slurry method.

(2) The invention adopts a pressure filter mode to carry out continuous solid-liquid separation and solid drying. The mother liquid of recovered polymerization solvent is directly returned to the reactor for partial refining. The size of subsequent drying equipment of polyolefin resin can be reduced, equipment investment and occupied area are reduced, and meanwhile, part of polymerization solvent directly returns to the reactor without phase change, so that the separation energy consumption can be greatly reduced.

(3) Through the concrete design of the slurry solid-liquid separation unit, on the basis of efficiently drying the wet ethylene-propylene copolymer, non-condensable gas and solvent are collected for subsequent treatment, so that the utilization rate of energy sources is improved.

(4) The heavy-removal tower in the solvent refining unit can be used selectively, so that the solvent refining unit capable of producing products with ultrahigh molecular weight polyethylene, high density polyethylene and other brands is provided; in addition, on the basis of high-efficiency refining of the solvent, heavy components are separated, and residual monomers are further recovered for recycling.

(5) In the solvent refining unit, thermal coupling is considered, so that heat is fully utilized, and energy consumption is reduced.

(6) The invention uses n-pentane as solvent, the drying devolatilization unit does not use nitrogen as carrier gas, the nitrogen consumption is reduced, the energy consumption is reduced, and the generation of three wastes is reduced.

Drawings

FIG. 1 is a schematic flow chart of a system for preparing ethylene copolymer by slurry method and filter pressing process with pentane as solvent in the invention;

FIG. 2 is a process flow diagram of a slurry solid liquid separation unit;

FIG. 3 is a process flow diagram of a first solvent refining unit;

FIG. 4 is a process flow diagram of a second solvent refining unit;

FIG. 5 is a process flow diagram of a third solvent refining unit;

FIG. 6 is a process flow diagram of a fourth solvent refining unit;

FIG. 7 is a process flow diagram of a dry devolatilization unit;

the reference symbols in the drawings indicate the description:

a polymerization unit 10,

A slurry solid-liquid separation unit 20, a slurry cooling assembly 21, a mother liquor tank 22, a first mother liquor pipe 221, a second mother liquor pipe 222, a mother liquor noncondensable gas outlet pipe 223, a rotary pressure filter 23, a mother liquor outlet pipe 231, a dry gas outlet pipe 232, a filter press flushing liquid inlet pipe 233, a filter press flushing liquid outlet pipe 234, a cleaning liquid collecting tank 235, a dry gas filtrate collecting tank 24, a ethylene-propylene copolymer pipe 25, a noncondensable gas separating outlet pipe 26, a condenser 27, a condensate pipe 28,

A dry devolatilization unit 30, a dryer 31, a wet gas scrubber 32, a top gas outlet pipe 321, a bottom liquid circulation pipe 322, a dry gas compressor 33, a dry gas condenser 34, a dry gas secondary condenser 35, a dry gas airtight tank 36,

A solvent refining unit 40, a refining solvent pipe 41, a refining noncondensable gas outlet pipe 42,

Refining column 43, refining column top condenser 431, refining column top discharge pipe 432, refining column top reflux drum 433, refining column top reflux pump 434, refining column bottom reboiler 435, refining column top condensate pipe 436, refining column bottom discharge pipe 437, refining column bottom transfer pump 438, refining column bottom start-up reboiler 439,

A dehydration column 44, a dehydration column top condenser 441, a dehydration column top aftercooler 442, a dehydration column top condensate tank 443, a dehydration column top reflux pump 444, a dehydration column bottom reboiler 445, a dehydration column bottom discharge pipe 446, a dehydration column bottom conveying pump 447, a dehydration column bottom liquid cooler 448, a solvent buffer tank 449,

The heavy-duty removing tower 45, a condenser 451 at the top of the heavy-duty removing tower, a reflux tank 452 at the top of the heavy-duty removing tower, a reflux pump 453 at the top of the heavy-duty removing tower, a reboiler 454 at the bottom of the heavy-duty removing tower, a condensate pipe 455 at the top of the heavy-duty removing tower, a discharge pipe 456 at the bottom of the heavy-duty removing tower, a liquid outlet pipe 457 at the top of the heavy-duty removing tower,

A powder remover 46, a mother liquor preheater 47, a heat pump 48,

A noncondensable gas recovery unit 50, a solvent recovery pipe 51,

Blending air-sending unit 60, moisture recovery unit 70, polymerized monomer recovery unit 80, ethylene refining unit 90.

Detailed Description

The present invention will be described in detail and in detail by way of the following examples, which are not intended to limit the scope of the invention, for better understanding of the invention.

Example 1

Referring to FIG. 1, this example provides a system for preparing ethylene copolymer by slurry and pressure filtration using pentane as solvent, comprising

The polymerization reaction unit 10 is respectively communicated with a catalyst feed pipe, a hydrogen feed pipe, a hexene feed pipe, a solvent feed pipe, an ethylene feed pipe, a reaction noncondensable gas outlet pipe and a slurry discharge pipe;

a slurry solid-liquid separation unit 20 including a slurry cooling module 21, a mother liquor tank 22, a rotary pressure filter 23, and a dry gas filtrate collection tank 24; the end of the slurry discharging pipe far away from the polymerization reaction unit 10 is communicated with the slurry solid-liquid separation unit 20;

A dry devolatilization unit 30 connected to the slurry solid-liquid separation unit 20 through a ethylene-propylene copolymer pipe 25;

a solvent refining unit 40 which is connected to the slurry solid-liquid separation unit 20 through a first mother liquor pipe 221 and is connected to the polymerization reaction unit 10 through a refined solvent pipe 41;

a noncondensable gas recovery unit 50 which is communicated with one end of the reaction noncondensable gas outlet pipe far away from the polymerization reaction unit 10; the solvent refining unit 40 is communicated with the noncondensable gas recovery unit 50 through a refined noncondensable gas outlet pipe 42, and the noncondensable gas recovery unit 50 is communicated with the solvent refining unit 40 through a solvent recovery pipe 51.

In specific application, ethylene, hexene, pentane, hydrogen and a catalyst enter a polymerization reaction unit 10 to carry out a copolymerization reaction by a slurry method, polyolefin slurry obtained after the reaction is finished enters a slurry solid-liquid separation unit 20, a polyolefin solid material and a mother liquor are obtained through solid-liquid separation, the polyolefin solid material is further dried by a drying devolatilization unit 30 to obtain a polyolefin product, the mother liquor is refined by a solvent refining unit 40, and a solvent in the recovered mother liquor is applied to the polymerization reaction unit 10.

The noncondensable gas generated by the polymerization reaction unit 10, the noncondensable gas generated by the slurry solid-liquid separation unit 20 and the noncondensable gas generated by the solvent refining unit 40 are introduced into the noncondensable gas recovery unit 50, and the solvent and ethylene obtained by separation are recycled.

In a preferred embodiment, an ethylene refining unit 90 is also included in communication with the end of the ethylene feed line remote from the polymerization unit 10.

In a preferred embodiment, the tail gas pipe 52 of the non-condensable gas recovery unit 50 is in communication with an ethylene unit.

In a preferred embodiment, the discharge pipe of the dry devolatilization unit 30 is in communication with the blending air feed unit 60 via a pipe.

In a specific embodiment, the pentane is n-pentane and/or isopentane.

Example 2

Referring to fig. 2, the present embodiment provides a slurry solid-liquid separation unit using a pressure filter.

The slurry solid-liquid separation unit 20 includes a slurry cooling module 21, a mother liquor tank 22, a rotary pressure filter 23, a first mother liquor pipe 221, a second mother liquor pipe 222, a dry gas filtrate collecting tank 24, and a condenser 27.

Specifically, in the slurry solid-liquid separation unit 20, the end of the slurry discharge pipe away from the polymerization reaction unit 10 communicates with the rotary pressure filter 23; the rotary pressure filter 23 is communicated with the drying devolatilization unit 30 through an ethylene-propylene copolymer pipe 25; the rotary pressure filter 23 is communicated with the mother liquor tank 22 through a mother liquor outlet pipe 231, the mother liquor tank 22 is communicated with the solvent refining unit 40 through the first mother liquor pipe 221, the mother liquor tank 22 is communicated with the polymerization reaction unit 10 through the second mother liquor pipe 222, and the mother liquor tank 22 is communicated with the moisture recovery unit 70 through the mother liquor noncondensable gas outlet pipe 223; the rotary pressure filter 23 is communicated with the dry gas filtrate collecting tank 24 through a dry gas outlet pipe 232, and the dry gas filtrate collecting tank 24 is communicated with the moisture recovery unit 70 through a separation non-condensable gas outlet pipe 26; the separation noncondensable gas outlet pipe 26 is provided with a condenser 27, and the condenser 27 is communicated with the dry gas filtrate collecting tank 24 through a condensate pipe 28.

The polyolefin slurry provided by the polymerization unit 10, which contains polyolefin solids, polymerization solvent and related impurities, is fed to a rotary pressure filter 23. The solid-liquid separation and solid drying of the polyolefin solid and the mother liquid are carried out in the rotary pressure filter 23, the collected mother liquid enters the mother liquid tank 22, and the polyolefin solid material separated and dried by the rotary pressure filter 23 is sent to the polyolefin drying devolatilization unit 30 for further drying and devolatilization. The mother liquor in the mother liquor tank 22 is partially pumped to the polymerization reaction unit 10, and the other part is pumped to the solvent refining unit 40.

In a preferred embodiment, the slurry solid-liquid separation unit further comprises a filter press flushing fluid inlet pipe 233 and a filter press flushing fluid outlet pipe 234, wherein the end of the filter press flushing fluid outlet pipe 234 away from the rotary pressure filter 23 is communicated with the polymerization unit 10; the washing liquid collecting tank 235 is arranged on the washing liquid outlet pipe 234 of the filter press. The filter press rinse liquid is returned to the cleaning liquid collection tank 235 after washing the filter cloth, and the cleaning liquid collection tank 235 is provided with a corresponding pump to return the filter press rinse liquid to the polymerization reaction unit 10 for use as a solvent.

Example 3

Referring to fig. 3, the present embodiment provides a specific process flow of the first solvent refining unit 40. The method is suitable for a solvent refining system for solid-liquid separation under pressure/solid-liquid separation of a filter press.

The solvent refining unit 40 includes:

a refining tower 43 which is communicated with one end of the first mother liquor pipe 221 away from the mother liquor tank 22, wherein the first mother liquor pipe 221 is provided with a powder remover 46 and a mother liquor preheater 47 from upstream to downstream in sequence; the refining tower 43 is provided with a refining tower top condenser 431, a refining tower top reflux tank 433, a refining tower top reflux pump 434 and a refining tower bottom reboiler 435; the refining tower 43 is communicated with the refining tower top condenser 431 through a refining tower top discharge pipe 432, the refining tower top condenser 431 is communicated with the refining tower top reflux tank 433 through a pipeline, the refining tower top reflux tank 433 is communicated with the refining tower 43 through a refining tower top condensate pipe 436, and the refining tower 43 is communicated with the de-weight tower 45 or the polymerized monomer recovery unit 80 through a refining tower bottom discharge pipe 437;

a dehydration column 44 connected to the purification column 43 through a branch of a purification column overhead condensate pipe 436; the dehydration column 44 is provided with a dehydration column top condenser 441, a dehydration column top aftercooler 442, a dehydration column top condensate tank 443, a dehydration column top reflux pump 444 and a dehydration column bottom reboiler 445, wherein the dehydration column top aftercooler 442 is communicated with the non-condensable gas recovery unit 50 through a refined non-condensable gas outlet pipe 42; the dehydration tower 44 is communicated with the solvent buffer tank 449 through a dehydration tower kettle discharge pipe 446, and a dehydration tower kettle conveying pump 447 and a dehydration tower kettle liquid cooler 448 are arranged on the dehydration tower kettle discharge pipe 446; the solvent buffer tank 449 is in communication with a polymerization solvent refiner in communication with the polymerization reaction unit 10 through the refined solvent pipe 41;

A de-weight tower 45 which is communicated with the refining tower 43 through a discharging pipe 437 at the bottom of the refining tower; the top of the heavy-removal tower 45 is provided with a heavy-removal tower top condenser 451, a heavy-removal tower top reflux tank 452, a heavy-removal tower top reflux pump 453 and a heavy-removal tower kettle reboiler 454; the top reflux tank 452 of the de-weight tower is communicated with the de-weight tower 45 through a top condensate pipe 455 of the de-weight tower, a branch of the top condensate pipe 455 of the de-weight tower is communicated with the polymerization solvent refiner, and the polymerization solvent refiner is communicated with the polymerization reaction unit 10 through a pipeline; the de-weight tower 45 is communicated with the polymerized monomer recovery unit 80 through a discharging pipe 456 at the bottom of the de-weight tower.

In a preferred embodiment, a branch of the outlet pipe 432 of the refining tower is communicated with an inlet of a heating medium channel of the mother liquor preheater 42, and an outlet of the heating medium channel of the mother liquor preheater 42 is communicated with the reflux drum 433 of the top of the refining tower through a pipeline.

In a preferred embodiment, the branch of the outlet pipe 432 of the refining tower is communicated with the inlet of the heating medium channel of the reboiler 445 of the tower kettle of the dehydration tower, and the outlet of the heating medium channel of the reboiler 445 of the tower kettle of the dehydration tower is communicated with the reflux drum 433 of the tower top of the refining tower through a pipeline.

In particular applications, a portion of the mother liquor pumped into solvent refining unit 40 in mother liquor tank 22 is subjected to removal of small amounts of solids from the mother liquor by powder remover 46, and the solids-removed mother liquor is preheated by mother liquor preheater 47 and then sent to refining column 43 for refining. The top discharge is divided into three parts, one part is condensed by a condenser 431 at the top of the refining tower and then flows back to a reflux tank 433 at the top of the refining tower, the other part is used as a heat source to be sent to a mother liquor preheater 47 for heating mother liquor, the other part is used as a heat source to be sent to a dehydration tower reboiler 445 for heating tower bottom liquid of the dehydration tower, and the materials after heat exchange and condensation are returned to the reflux tank 433 at the top of the refining tower. A part of the condensate in the rectifying column top reflux drum 433 is returned to the rectifying column 43 by the rectifying column top reflux pump 434, and the other part is pumped to the dehydrating column 44. The bottoms are pumped to the de-heavies column 45 to remove heavies or directly to the polymerized monomer recovery unit 80.

The top discharge of the dehydration column 44 is subjected to two-stage condensation by a dehydration column top condenser 441 and a dehydration column top post-cooler 442 and then is sent to a dehydration column top condensate tank 443 for gas-liquid two-phase separation. The noncondensable gas is sent to a noncondensable gas recovery unit 50. The dehydration column overhead reflux pump 444 in the dehydration column overhead condensate tank 443 reflux to the dehydration column 44. The dehydration column 44 is equipped with a reboiler using the gas at the top of the refining column 43 as a heat source, and the polymerization solvent after refining the discharged material of the column is sent to a dehydration column bottom liquid cooler 448 for cooling by a dehydration column bottom conveying pump 447 and then enters a solvent buffer tank 449. The solvent in solvent buffer tank 449 is pumped to a polymerization solvent refiner for further dehydration and then to individual users.

The noncondensable gas at the top of the heavy-duty removal column 45 is sent to a top condenser 451 of the heavy-duty removal column, and the gas-liquid two phases are subjected to gas-liquid separation in a top reflux tank 452 of the heavy-duty removal column. Part of the condensate in the top reflux tank 452 of the de-weight tower is returned to the de-weight tower 45 through the top reflux pump 453 of the de-weight tower, the other part is pumped into a polymerization solvent refiner for refining, and the refined solvent is sent to the polymerization reaction unit 10. The bottom discharge of the de-weight tower 45 contains oligomerization products, residual monomers with boiling point higher than that of the polymerization solvent, and the like, and is pumped to the polymerization monomer recovery unit 80, and the residual monomers with boiling point higher than that of the polymerization solvent are obtained through rectification and the like for recycling.

The path of the bottom discharge of the column can be selected according to the needs of the product type, for example, when ultra-high molecular weight polyethylene products are produced, the weight removing column 45 is not used, the refining column 43 can bear the function of the weight removing column 45, and the bottom discharge of the refining column 43 is directly pumped to the polymerized monomer recovery unit 80 for recovery.

In a preferred embodiment, the refining column 43 is a tray column; the weight removing tower 45 is a plate tower.

In a specific embodiment, the cooling medium of the top condenser 451 of the de-weight tower is cooling water; the heating medium of the reboiler 435 of the refining tower kettle is steam; the de-heavies column bottoms reboiler 454 is a thermosiphon reboiler.

Example 4

Referring to fig. 4, the present embodiment provides a specific process flow of the second solvent refining unit 40. The solvent refining unit 40 provided in this example is based on example 3, except that the mother liquor directly enters the refining column 43 without cooling, and the heat pump 48 is used to utilize the heat of the refining column 43, including the reboiler 439 at the bottom of the refining column.

Specifically, in this embodiment, the refining tower 43 is communicated with an end of the first mother liquor pipe 221 away from the mother liquor tank 22, and the first mother liquor pipe 221 is provided with a powder remover 46; the refining tower 43 is provided with a refining tower top reflux tank 433, a refining tower top reflux pump 434, a refining tower kettle reboiler 435 and a refining tower kettle start-up reboiler 439; the refining tower 43 is communicated with the inlet of a heating medium channel of a reboiler 435 of the tower kettle of the refining tower through a top outlet pipe 432 of the refining tower, the outlet of the heating medium channel of the reboiler 435 of the tower kettle of the refining tower is communicated with a reflux tank 433 of the tower top of the refining tower through a pipeline, and the reflux tank 433 of the tower top of the refining tower is communicated with the refining tower 43 through a condensate pipe 436 of the tower top of the refining tower; a heat pump 48 is arranged on the refining tower ejection pipe 432; the refining tower 43 is communicated with the weight removing tower 45 or the polymerized monomer recovery unit 80 through a discharging pipe 437 at the bottom of the refining tower;

Part of the mother liquor pumped into the solvent refining unit 40 in the mother liquor tank 22 is subjected to removal of a small amount of solids in the mother liquor by the powder remover 46, and the mother liquor after removal of the solids is sent to the refining tower 43 for refining. The discharged material from the top of the refining tower is heated by a heat pump and then is used as a heat source to be sent to a reboiler 435 of the tower bottom of the refining tower to heat the tower bottom liquid of the refining tower 43, and the material after heat exchange and condensation is returned to a reflux tank 433 of the top of the refining tower. A part of the condensate in the rectifying column top reflux drum 433 is returned to the rectifying column 43 by the rectifying column top reflux pump 434, and the other part is pumped to the dehydrating column 44. The bottoms are pumped to the de-heavies column 45 to remove heavies or directly to the polymerized monomer recovery unit 80.

Example 5

Referring to fig. 5, the present embodiment provides a specific process flow of the third solvent refining unit 40. The solvent refining unit 40 provided in this example is based on example 4, except that: the branch of the refining tower top outlet pipe 432 is communicated with the refining tower top condenser 431, and the refining tower top condenser 431 is communicated with the refining tower top reflux drum 433 through a pipeline.

Part of the mother liquor pumped into the solvent refining unit 40 in the mother liquor tank 22 is subjected to removal of a small amount of solids in the mother liquor by the powder remover 46, and the mother liquor after removal of the solids is sent to the refining tower 43 for refining. The top discharge of the refining tower is divided into two parts, one part is condensed by a condenser 431 at the top of the refining tower and then flows back to a reflux tank 433 at the top of the refining tower, the other part is heated by a heat pump and then is used as a heat source to be sent to a reboiler 435 at the bottom of the refining tower to heat the bottom liquid of the refining tower 43, and the material after heat exchange and condensation is returned to the reflux tank 433 at the top of the refining tower. A part of the condensate in the rectifying column top reflux drum 433 is returned to the rectifying column 43 by the rectifying column top reflux pump 434, and the other part is pumped to the dehydrating column 44. The bottoms are pumped to the de-heavies column 45 to remove heavies or directly to the polymerized monomer recovery unit 80.

Example 6

Referring to fig. 6, the present embodiment provides a specific process flow of the solvent refining unit 40 including only the weight removing column 45 and the dehydrating column 44 for preparing ultra-high molecular weight ethylene copolymer.

The solvent refining unit 40 includes:

the de-weight tower 45 is communicated with one end of the flash wet gas pipe 232, which is far away from the high-pressure flash tank 23, and the flash wet gas pipe 232 is provided with a powder removing bag 46 and a mother liquor preheater 47; the top of the heavy-removal tower 45 is provided with a heavy-removal tower top condenser 451, a heavy-removal tower top reflux tank 452, a heavy-removal tower top reflux pump 453 and a heavy-removal tower kettle reboiler 454; the de-weight tower 45 is communicated with a de-weight tower top condenser 451 through a de-weight tower top liquid outlet pipe 457, a de-weight tower top reflux tank 452 is communicated with the de-weight tower 45 through a de-weight tower top condensate pipe 455, a first branch of the de-weight tower top condensate pipe 455 is communicated with the polymerization solvent refiner, and a second branch of the de-weight tower top condensate pipe 455 is communicated with the de-weight tower 44; the polymerization solvent refiner is communicated with the polymerization reaction unit 10 through a pipeline; the de-weight tower 45 is communicated with the polymerized monomer recovery unit 80 through a discharging pipe 456 at the bottom of the de-weight tower.

A dehydration column 44, which is communicated with the de-weight column 45 through a second branch of a de-weight column top condensate pipe 455; the dehydration column 44 is provided with a dehydration column top condenser 441, a dehydration column top aftercooler 442, a dehydration column top condensate tank 443, a dehydration column top reflux pump 444 and a dehydration column bottom reboiler 445, wherein the dehydration column top aftercooler 442 is communicated with the non-condensable gas recovery unit 50 through a refined non-condensable gas outlet pipe 42; the dehydration tower 44 is communicated with the solvent buffer tank 449 through a dehydration tower kettle discharge pipe 446, and a dehydration tower kettle conveying pump 447 and a dehydration tower kettle liquid cooler 448 are arranged on the dehydration tower kettle discharge pipe 446; the solvent buffer tank 449 is in communication with a polymerization solvent refiner in communication with the polymerization reaction unit 10 through the refined solvent pipe 41;

in a preferred embodiment, a branch of the top outlet pipe 432 of the refining tower is communicated with an inlet of a heating medium channel of the mother liquor preheater 47, and an outlet of the heating medium channel of the mother liquor preheater 47 is communicated with a reflux tank 452 at the top of the de-weight tower through a pipeline.

In a preferred embodiment, the branch of the outlet pipe 432 of the refining tower is communicated with the inlet of the heating medium channel of the reboiler 445 of the dehydration tower, and the outlet of the heating medium channel of the reboiler 445 of the dehydration tower is communicated with the reflux tank 452 of the top of the de-weight tower through a pipeline.

In a specific application, the moisture in the high-pressure flash tank 23 is sent to the solvent refining unit 40 through the flash moisture pipe 232, a small amount of solids in the mother liquor is removed through the powder remover 46, and the mother liquor after the solids removal is sent to the heavy-duty removal tower 45 for refining after being preheated by the mother liquor preheater 47. The top discharge of the tower is divided into three strands, one strand is condensed by a condensate pipe 455 at the top of the heavy-duty removing tower and then flows back to a reflux tank 452 at the top of the heavy-duty removing tower, and the second strand is taken as a heat source and sent to a reboiler 445 at the bottom of the dehydration tower to heat the bottom liquid of the dehydration tower; the third stream is used as a heat source and sent to the mother liquor preheater 47 to preheat the mother liquor, and the materials after heat exchange and condensation are returned to the top reflux tank 452 of the de-duplication tower. A part of the condensate in the top reflux tank 452 of the de-weight tower is returned to the de-weight tower 45 through the top reflux pump 453 of the de-weight tower, the second part is pumped to the dehydration tower 44, and the third part is pumped to the polymeric solvent refiner. The bottoms discharge is pumped to a polymerized monomer recovery unit 80.

The top discharge of the dehydration column 44 is subjected to two-stage condensation by a dehydration column top condenser 441 and a dehydration column top post-cooler 442 and then is sent to a dehydration column top condensate tank 443 for gas-liquid two-phase separation. The noncondensable gas is sent to a noncondensable gas recovery unit 50. Condensate in the dehydration column overhead condensate tank 443 is refluxed to the dehydration column 44 by a dehydration column overhead reflux pump 444. The dehydration column 44 is equipped with a reboiler using the top gas of the heavy-duty removal column 45 as a heat source, and the polymerization solvent after refining the discharged material of the dehydration column is sent to a dehydration column bottom liquid cooler 448 for cooling by a dehydration column bottom conveying pump 447 and then enters a solvent buffer tank 449. The solvent in solvent buffer tank 449 is pumped to a polymerization solvent refiner for further dehydration and then to individual users.

Example 7

Referring to fig. 7, the present embodiment provides a specific process flow of the dry devolatilization unit 30.

Specifically, the dry devolatilization unit 30 includes a dryer 31 and a wet gas scrubber 32, wherein an end of the ethylene-propylene copolymer pipe 25, which is far away from the slurry solid-liquid separation unit 20, is communicated with the dryer 31, the dryer 31 is communicated with the wet gas scrubber 32 through a wet gas pipe 311, a top gas outlet pipe 321 of the wet gas scrubber 32 is sequentially communicated with a dry gas compressor 33, a dry gas condenser 34 and a dry gas secondary condenser 35, a liquid outlet pipe of the dry gas secondary condenser 35 is communicated with a dry gas seal tank 36, and the dry gas seal tank 36 is communicated with the wet gas scrubber 32; the wet gas scrubber 32 is provided with a bottom liquid circulation pipe 322.

In one particular embodiment, low temperature pentane is stored in the wet gas scrubber 32.

In a specific application, the wet gas evaporated by the dryer 31 is sent to the wet gas scrubber 32, gas and liquid are separated, the separated gas is discharged from the top of the wet gas scrubber 32, compressed by the dry gas compressor 33 and sent to the dry gas condenser 34 and the dry gas secondary condenser 35 for condensation. The condensate in the dry gas secondary condenser 35 flows to the dry gas seal tank 36, and the condensate in the dry gas seal tank 36 flows back to the wet gas scrubber 1 for recycling.

In a preferred embodiment, the outlet pipe of the dry gas secondary condenser 35 is in communication with the noncondensable gas recovery unit 50 via a conduit.

In a preferred embodiment, the branches of the bottom liquid circulation tube 322 are in communication with a solvent recovery unit.

Application example 1:

the ultra-high molecular weight ethylene copolymer was prepared by using the system for preparing ethylene copolymer by slurry method and filter pressing process using pentane as solvent provided in example 1.

In the solvent refining unit 40 of this embodiment, the refining column 43 is connected to the polymerized monomer recovery unit 80 via the discharge pipe 437 at the bottom of the refining column, without passing through the de-weight column 44.

The physical properties of the final product were examined, and an ultra-high molecular weight polyethylene (ethylene homopolymer, copolymer of ethylene and comonomer) having a viscosity average molecular weight of 150 to 800 g/mol, preferably 300 to 700 g/mol, a metal element content of 0 to 40ppm, preferably 0 to 30ppm, a bulk density of 0.30 to 0.55g/cm3, preferably 0.33 to 0.52g/cm3, a comonomer molar insertion rate of 0 to 2.0%, preferably 0 to 1.0%, a tensile yield strength of more than 21MPa, preferably more than 23MPa, a tensile breaking strength of more than 33MPa, preferably more than 35MPa, an ash content of less than 200ppm, preferably less than 150ppm was obtained.

Application example 2:

this application example prepares a high density ethylene copolymer or multimodal polyethylene product with the system provided in example 1 for preparing ethylene copolymer by slurry process and pressure filtration process using pentane as solvent.

In the solvent refining unit 40 in this application example, the refining tower 43 is connected to the de-weight tower 44 through the discharging pipe 437 at the bottom of the refining tower.

The final product is subjected to physical property detection, and a high-density ethylene polymer having an average particle diameter of 50 to 3000 μm, preferably 100 to 1000 μm, a weight average molecular weight of 2 to 40 g/mol, preferably a weight average molecular weight of 5 to 30 g/mol, a molecular weight distribution of 1.8 to 10, preferably 2.0 to 8.0, a comonomer molar insertion rate of 0.01 to 5mol%, preferably 0.05 to 2.5mol%, preferably a melt index of 0.01 to 2500g/10min, preferably 0.1 to 2000g/10min, more preferably 0.1 to 1000g/10min, a bulk density of 0.28 to 0.55g/cm3, preferably 0.32 to 0.50g/cm3, a true density of 0.930 to 0.980g/cm3, preferably 0.940 to 0.970g/cm3, more preferably 0.942 to 0.970g/cm3, a crystallinity of 0.01 to 90 ℃, preferably 0.5 to 5.147 g/10min, a melt index of the film at 190 ℃ of 2.16Kg load of 0.01 to 90 ℃, preferably 0.28 to 0.55g/cm3, preferably 0.32 to 0.52 g/cm3, and a blowing index of 5 to 5.5.5, preferably to 5.5.147 g/8.

The above description of the specific embodiments of the present invention has been given by way of example only, and the present invention is not limited to the above described specific embodiments. Any equivalent modifications and substitutions for the present invention will occur to those skilled in the art, and are also within the scope of the present invention. Accordingly, equivalent changes and modifications are intended to be included within the scope of the present invention without departing from the spirit and scope thereof.

Claims (10)

1. A system for preparing ethylene-hexane copolymer by slurry method and press filtration process, which uses pentane as solvent, is characterized by comprising

The polymerization reaction unit (10) is respectively communicated with a catalyst feed pipe, a hydrogen feed pipe, a hexene feed pipe, a solvent feed pipe, an ethylene feed pipe, a reaction noncondensable gas outlet pipe and a slurry discharge pipe;

a slurry solid-liquid separation unit (20) comprising a slurry cooling assembly (21), a mother liquor tank (22), a rotary pressure filter (23) and a dry gas filtrate collection tank (24); one end of the slurry discharging pipe far away from the polymerization reaction unit (10) is communicated with the slurry solid-liquid separation unit (20);

a dry devolatilization unit (30) in communication with the slurry solid-liquid separation unit (20) through a ethylene-co-polymer pipe (25);

A solvent refining unit (40) which is communicated with the slurry solid-liquid separation unit (20) through a first mother liquor pipe (221) and is communicated with the polymerization reaction unit (10) through a refined solvent pipe (41);

the noncondensable gas recovery unit (50) is communicated with one end of the reaction noncondensable gas outlet pipe, which is far away from the polymerization reaction unit (10); the solvent refining unit (40) is communicated with the noncondensable gas recovery unit (50) through a refined noncondensable gas outlet pipe (42), and the noncondensable gas recovery unit (50) is communicated with the solvent refining unit (40) through a solvent recovery pipe (51).

2. The system for preparing a co-ethylene by a slurry process and a pressure filtration process according to claim 1, characterized in that in the slurry solid-liquid separation unit (20), the end of the slurry discharge pipe remote from the polymerization unit (10) is in communication with the rotary pressure filter (23); the rotary pressure filter (23) is communicated with the drying devolatilization unit (30) through an ethylene-propylene copolymer pipe (25); the rotary pressure filter (23) is communicated with the mother liquor tank (22) through a solvent discharging pipe, the mother liquor tank (22) is communicated with the polymerization reaction unit (10) through the first mother liquor pipe (221), the mother liquor tank (22) is communicated with the solvent refining unit (40) through the second mother liquor pipe (222), and the mother liquor tank (22) is communicated with the moisture recovery unit (70) through the mother liquor noncondensable gas outlet pipe (223); the rotary pressure filter (23) is communicated with the dry gas filtrate collecting tank (24) through a dry gas outlet pipe (232), and the dry gas filtrate collecting tank (24) is communicated with the moisture recovery unit (70) through a separation non-condensable gas outlet pipe (26); the separation noncondensable gas outlet pipe (26) is provided with a condenser (27), and the condenser (27) is communicated with the dry gas filtrate collecting tank (24) through a condensate pipe (28).

3. The system for preparing a copolymer ethylene by a slurry process and a pressure filtration process according to claim 2, characterized in that in the slurry solid-liquid separation unit (20), there are also included a filter press flushing fluid inlet pipe (233) and a filter press flushing fluid outlet pipe (234), the end of the filter press flushing fluid outlet pipe (234) remote from the rotary pressure filter (23) being in communication with the polymerization unit (10); and a cleaning liquid collecting tank (235) is arranged on the flushing liquid outlet pipe (234) of the filter press.

4. The system for preparing a co-ethylene by a slurry process and a pressure filtration process according to claim 1, characterized in that the solvent refining unit (40) comprises:

a refining tower (43) communicated with one end of the first mother liquor pipe (221) far away from the mother liquor tank (22), wherein the first mother liquor pipe (221) is provided with a powder remover (46) and a mother liquor preheater (47) from upstream to downstream in sequence; the refining tower (43) is provided with a refining tower top condenser (431), a refining tower top reflux tank (433), a refining tower top reflux pump (434) and a refining tower kettle reboiler (435); the refining tower (43) is communicated with the refining tower top condenser (431) through a refining tower top discharge pipe (432), the refining tower top condenser (431) is communicated with the refining tower top reflux tank (433) through a pipeline, the refining tower top reflux tank (433) is communicated with the refining tower (43) through a refining tower top condensate pipe (436), and the refining tower (43) is communicated with the de-heavy tower (45) or the polymerized monomer recovery unit (80) through a refining tower bottom discharge pipe (437);

A dehydration column (44) which is communicated with the refining column (43) through a branch of a condensate pipe (436) at the top of the refining column; the dehydration tower (44) is provided with a dehydration tower top condenser (441), a dehydration tower top aftercooler (442), a dehydration tower top condensate tank (443), a dehydration tower top reflux pump (444) and a dehydration tower kettle reboiler (445), and the dehydration tower top aftercooler (442) is communicated with the noncondensable gas recovery unit (50) through a refined noncondensable gas outlet pipe (42); the dehydration tower (44) is communicated with a solvent buffer tank (449) through a dehydration tower kettle discharging pipe (446), and a dehydration tower kettle conveying pump (447) and a dehydration tower kettle liquid cooler (448) are arranged on the dehydration tower kettle discharging pipe (446); the solvent buffer tank (449) is communicated with a polymerization solvent refiner through a pipeline, and the polymerization solvent refiner is communicated with the polymerization reaction unit (10) through a pipeline;

the weight removing tower (45) is communicated with the refining tower (43) through a discharging pipe (437) at the bottom of the refining tower; the top of the de-weight tower (45) is provided with a de-weight tower top condenser (451), a de-weight tower top reflux tank (452), a de-weight tower top reflux pump (453) and a de-weight tower kettle reboiler (454); the top reflux tank (452) of the de-weight tower is communicated with the de-weight tower (45) through a top condensate pipe (455) of the de-weight tower, a branch of the top condensate pipe (455) of the de-weight tower is communicated with the polymerization solvent refiner, and the polymerization solvent refiner is communicated with the polymerization reaction unit (10) through a pipeline; the de-weighting tower (45) is communicated with the polymerized monomer recovery unit (80) through a discharging pipe (456) at the bottom of the de-weighting tower.

5. The system for preparing ethylene copolymer by slurry process and pressure filtration process according to claim 4, wherein the branch of the refining column top outlet pipe (432) is communicated with the inlet of the heating medium channel of the mother liquor preheater (42), and the outlet of the heating medium channel of the mother liquor preheater (42) is communicated with the reflux drum (433) at the top of the refining column by a pipeline.

6. The system for preparing ethylene copolymer by slurry process and pressure filtration process according to claim 4, wherein the branch of the refining column top outlet pipe (432) is communicated with the heat medium channel inlet of the dehydration column bottom reboiler (445), and the heat medium channel outlet of the dehydration column bottom reboiler (445) is communicated with the refining column top reflux drum (433) through a pipeline.

7. The system for preparing a co-ethylene by a slurry process and a pressure filtration process according to claim 1, characterized in that the solvent refining unit (40) comprises:

a refining tower (43) communicated with one end of the first mother liquor pipe (221) far away from the mother liquor tank (22), wherein the first mother liquor pipe (221) is provided with a powder remover (46); the refining tower (43) is provided with a refining tower top condenser (431), a refining tower top reflux tank (433), a refining tower top reflux pump (434), a refining tower kettle reboiler (435) and a refining tower kettle start-up reboiler (439); the refining tower (43) is communicated with a heating medium channel inlet of a reboiler (435) at the bottom of the refining tower through a material outlet pipe (432) of the refining tower, a heating medium channel outlet of the reboiler (435) at the bottom of the refining tower is communicated with a reflux tank (433) at the top of the refining tower through a pipeline, and the reflux tank (433) at the top of the refining tower is communicated with the refining tower (43) through a condensate pipe (436) at the top of the refining tower; a heat pump (48) is arranged on the refining tower ejection pipe (432); the refining tower (43) is communicated with a weight removing tower (45) or a polymerized monomer recovery unit (80) through a discharging pipe (437) at the bottom of the refining tower;

A dehydration column (44) which is communicated with the refining column (43) through a branch of a condensate pipe (436) at the top of the refining column; the dehydration tower (44) is provided with a dehydration tower top condenser (441), a dehydration tower top aftercooler (442), a dehydration tower top condensate tank (443), a dehydration tower top reflux pump (444) and a dehydration tower kettle reboiler (445), and the dehydration tower top aftercooler (442) is communicated with the noncondensable gas recovery unit (50) through a refined noncondensable gas outlet pipe (42); the dehydration tower (44) is communicated with a solvent buffer tank (449) through a dehydration tower kettle discharging pipe (446), and a dehydration tower kettle conveying pump (447) and a dehydration tower kettle liquid cooler (448) are arranged on the dehydration tower kettle discharging pipe (446); the solvent buffer tank (449) is communicated with a polymerization solvent refiner through a pipeline, and the polymerization solvent refiner is communicated with the polymerization reaction unit (10) through a pipeline;

the weight removing tower (45) is communicated with the refining tower (43) through a discharging pipe (437) at the bottom of the refining tower; the top of the de-weight tower (45) is provided with a de-weight tower top condenser (451), a de-weight tower top reflux tank (452), a de-weight tower top reflux pump (453) and a de-weight tower kettle reboiler (454); the top reflux tank (452) of the de-weight tower is communicated with the de-weight tower (45) through a top condensate pipe (455) of the de-weight tower, a branch of the top condensate pipe (455) of the de-weight tower is communicated with the polymerization solvent refiner, and the polymerization solvent refiner is communicated with the polymerization reaction unit (10) through a pipeline; the de-weighting tower (45) is communicated with the polymerized monomer recovery unit (80) through a discharging pipe (456) at the bottom of the de-weighting tower.

8. The system for preparing a ethylene copolymer by a slurry process and a pressure filtration process according to claim 7, wherein the branch of the refining column top outlet pipe (432) is in communication with the refining column top condenser (431), and the refining column top condenser (431) is in communication with the refining column top reflux drum (433) through a pipe.

9. The system for preparing the ethylene copolymer by a slurry process and a filter pressing process according to claim 1, wherein the dry devolatilization unit (30) comprises a dryer (31) and a wet gas scrubber (32), one end of an ethylene copolymer pipe (25) which is far away from the slurry solid-liquid separation unit (20) is communicated with the dryer (31), the dryer (31) is communicated with the wet gas scrubber (32) through a wet gas pipe (311), a top gas outlet pipe (321) of the wet gas scrubber (32) is sequentially communicated with a dry gas compressor (33), a dry gas condenser (34) and a dry gas secondary condenser (35), a liquid outlet pipe of the dry gas secondary condenser (35) is communicated with a dry gas seal tank (36), and the dry gas seal tank (36) is communicated with the wet gas scrubber (32); the wet gas scrubber (32) is provided with a bottom liquid circulation pipe (322).

10. The system for preparing ethylene copolymer by slurry process and pressure filtration process according to claim 1, characterized in that the outlet pipe of the dry gas secondary condenser (35) is in communication with the noncondensable gas recovery unit (50) through a pipe.