CN110548331A - method and device for separating polymer in slurry method polyethylene production process - Google Patents
method and device for separating polymer in slurry method polyethylene production process Download PDFInfo
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- CN110548331A CN110548331A CN201910869960.4A CN201910869960A CN110548331A CN 110548331 A CN110548331 A CN 110548331A CN 201910869960 A CN201910869960 A CN 201910869960A CN 110548331 A CN110548331 A CN 110548331A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
- B01D33/067—Construction of the filtering drums, e.g. mounting or sealing arrangements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/44—Regenerating the filter material in the filter
- B01D33/48—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
- B01D33/62—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
- B01D33/62—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying
- B01D33/66—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying by gases or by heating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/70—Filters with filtering elements which move during the filtering operation having feed or discharge devices
- B01D33/76—Filters with filtering elements which move during the filtering operation having feed or discharge devices for discharging the filter cake, e.g. chutes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F110/02—Ethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F6/00—Post-polymerisation treatments
- C08F6/06—Treatment of polymer solutions
- C08F6/10—Removal of volatile materials, e.g. solvents
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- Polymers & Plastics (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention relates to a method and a device for separating polymers in a slurry process polyethylene production process, wherein the method comprises the steps of carrying out polymerization reaction by a slurry process (slurry-gas phase process) process to generate a polymerization solid-liquid mixture, introducing the polymerization solid-liquid mixture into a pressure filter to obtain a filtrate and a filter cake, removing liquid from the filter cake in the filter, collecting the filtrate, gas after liquid removal and cleaning discharge liquid into a desorbent collecting tank, and feeding the filtrate, gas after liquid removal and cleaning discharge liquid into a reaction system together with a supplemented fresh desorbent to be used as the desorbent. The invention simplifies the process and the system structure, reduces the construction investment and reduces the energy consumption in the production.
Description
Technical Field
the invention relates to a method and a device for separating polymers in a slurry polyethylene production process, belonging to the technical field of chemical industry.
Background
Polyethylene is a thermoplastic resin prepared by polymerizing ethylene, also comprises a copolymer of ethylene and a small amount of alpha-olefin in industry, is odorless and nontoxic, has a wax-like hand feeling, has excellent low-temperature resistance, good chemical stability, can resist corrosion of most of acid and alkali, is insoluble in common solvents at normal temperature, and has small water absorption and excellent electrical insulation. Polyethylene is widely used, mainly for producing films, packaging materials, containers, pipes, monofilaments, electric wires and cables, daily necessities and the like, and can be used as a high-frequency insulating material for televisions, radars and the like.
Currently, the production process of polyethylene can be classified into a solution process, a slurry process, a gas phase process, and a slurry-gas phase process combined process according to the type of polymerization. Wherein, the slurry polymerization process is to mix ethylene and aliphatic hydrocarbon solvent, and add Ziegler-Natta, inorganic chromium or metallocene catalyst to initiate ethylene polymerization, and generate ethylene polymer to suspend in the solvent. The slurry polymerization process can be divided into 2 process methods of a loop and a kettle according to different reactor forms, wherein the loop slurry process comprises a Phillips loop process of Phillips corporation, an Innoveenes loop process of Enlish Enlis corporation, and a double loop slurry process improved on the basis of the Phillips loop reactor technology by Doudal France corporation; the tank slurry process includes the Hostalen process by LyondellBasell, the Netherlands, and the CX process by Mitsui, the Japan triple well chemical (Mitsui) company.
In the existing slurry process (slurry-gas phase process), ethylene is mixed in a diluent to realize polymerization in a liquid phase reactor, generally, jacket cooling is used for removing reaction heat, polyethylene powder generated by reaction, the diluent and unreacted ethylene are gasified or flash evaporated to form a gas-solid mixture, and then a filter, a cyclone separator and other equipment are used for separating the polyethylene powder. In order to ensure the power of the diluent and ethylene gasification and flash evaporation, a jacketed pipe is generally arranged on a pipeline for steam tracing, and the separated gas-phase diluent and ethylene are recycled in a reaction system through recovery processes such as compression, condensation and the like.
As described above, the existing slurry process (slurry-gas phase process) mainly has the following disadvantages:
1) The hydrocarbon solvent used as the diluent does not participate in the reaction in the process, but a large amount of steam heat tracing and cooling water condensation are needed in the processes of gasification, flash evaporation, compression and condensation, so that the consumption of public works is huge;
2) part of unreacted ethylene also consumes certain steam tracing heat and cooling water in the circulation process of gasification, flash evaporation, compression and condensation, so that the consumption of public works is increased;
3) the polyethylene powder is separated from the gasified diluent and ethylene by arranging a plurality of filters and separators, so that the equipment investment cost is high, the process flow is long, and the unreliability of the operation of the device is increased;
4) the compression of a large amount of diluent gas requires a large compressor capacity, which not only results in high equipment investment cost at one time, but also consumes a large amount of electric energy in the operation process.
disclosure of Invention
in order to overcome the defects in the prior art, the invention provides a method for separating polymers in a slurry method polyethylene production process and a device for separating polymers in the slurry method polyethylene production process, which simplifies the process and the system structure, reduces the construction investment and reduces the energy consumption in the production.
The technical scheme of the invention is as follows: the polymer separating process in slurry process of producing polyethylene includes the following steps:
Polymerization reaction: mixing ethylene in a diluent by adopting a slurry method or a slurry-gas phase method process to realize polymerization in a liquid phase reactor of a reaction system to form a polymerization solid-liquid mixture, wherein the polymerization solid-liquid mixture comprises powdered polyethylene, the diluent and ethylene dissolved in the diluent, and is led out from a discharge hole of the reaction system;
And (3) filtering: introducing a polymerization solid-liquid mixture generated by a reaction system into a pressure filter for filtering to form a filtrate and filter residues, wherein the filtrate mainly comprises a diluent and unreacted ethylene dissolved in the diluent, the filter residues mainly comprise powdery polyethylene, and the filter residues gradually fill a filter unit of the pressure filter to form a filter cake;
Removing liquid from a filter cake: moving the filter cake to a liquid removing area of the pressure filter, removing liquid from the filter cake by taking circulating ethylene gas of the system as liquid removing gas, and discharging gas after liquid removal, wherein the gas after liquid removal is a gas-liquid mixture containing ethylene and a diluent;
Discharging a filter cake: the filter cake after liquid removal is moved to a liquid removal area of the pressure filter, the filter cake is unloaded by self weight or the circulating ethylene gas of the system is used as the back blowing gas for unloading to carry out back blowing unloading, and the filter cake is sent out through an unloading pipeline of the pressure filter and is used as the filtered solid for discharging;
Cleaning a filter medium: cleaning the filter medium of the filter unit after unloading by using a pure diluent as a cleaning solution to realize regeneration of the filter medium and discharge cleaning discharge liquid;
And (3) recovering a diluent: the method comprises the following steps: introducing the filtrate into a diluent collection tank; introducing the liquid-removed gas into a condenser for condensation to obtain diluent condensate, and introducing the diluent condensate into a diluent collecting tank; introducing the purge effluent into a diluent collection tank;
And (3) recycling of a diluent: and sending the liquid collected by the diluent collecting tank to the reaction system to be recycled as the diluent, and introducing the supplemented fresh diluent into the diluent collecting tank when the fresh diluent needs to be supplemented.
the pressure filter is provided with a filtering area, a liquid removing area, a discharging area and a regeneration area which are sequentially distributed, wherein the filtering is implemented in the filtering area, the liquid removing of the filter cake is implemented in the liquid removing area, the discharging of the filter cake is implemented in the discharging area, and the cleaning of the filter medium is implemented in the regeneration area.
The pressure filter is a rotary drum type pressure filter.
the operating temperature of the rotary drum type pressure filter is 45-150 ℃, the operating pressure is 1.85-5.65 MPa, and the rotating speed is 0.3-10.0 r/min.
The rotational speed of the rotary drum filter press is preferably from 0.75 to 5.0 revolutions per minute.
The filtration pressure difference of the rotary drum type pressure filter can be 0.01MPa to 1.00MPa, and is preferably 0.1 MPa to 0.5 MPa.
The thickness of the filter cake is 15mm-180mm, preferably 60mm-130 mm.
The shaft seal structure of the rotary drum type pressure filter preferably adopts a packing and mechanical seal combined structure.
and compressing the circulating ethylene gas by using a circulating ethylene gas compressor to increase the pressure and the temperature of the circulating ethylene gas, and using the circulating ethylene gas after increasing the temperature and the pressure as the liquid removing gas and/or the discharging back blowing gas.
the pressure control value of the liquid removing gas can be higher than the backpressure of the pressure filter by 0.1 ~ 0.8.8 MPa (the specific backpressure is higher by 0.1 ~ 0.8.8 MPa), and preferably higher than the backpressure of the pressure filter by 0.3-0.6 MPa.
The pressure control value of the discharging back-blowing gas can be higher than the backpressure of the pressure filter by 0.002MPa ~ 0.050.050 MPa, and preferably higher than the backpressure of the pressure filter by 0.005 ~ 0.025.025 MPa;
the mass percentage control value of the diluent in the filtered solid discharge is 1.0-15.0%, preferably 2.0-8.0%.
the diluent collection tank is mechanically agitated by an agitator to prevent the entrained polyethylene powder from settling.
The diluent collection tank has an operating pressure of 1.85MPa to 5.50MPa and an operating speed of 5.0 to 100rpm, preferably 10 to 50rpm, of the stirrer.
the polymer separation device in the slurry method polyethylene production process comprises:
the reaction system is a polymerization reaction system adopting a slurry method or a slurry-gas phase method, is provided with a liquid phase reactor, and generates a polymerization solid-liquid mixture, wherein the polymerization solid-liquid mixture comprises powdered polyethylene, a diluent and ethylene dissolved in the diluent;
the system comprises a pressure filter, a mother liquor feeding pipe, a cleaning liquid input pipe, a liquid removing gas input pipe, a filtrate output pipe, a liquid removing gas output pipe, a cleaning discharge liquid output pipe and a solid discharge pipeline, wherein the pressure filter is used for filtering and separating a polymerization solid-liquid mixture formed by a polymerization reaction system to form filtrate and filter residues (filter cakes), the pressure filter is provided with the mother liquor feeding pipe, the cleaning liquid input pipe, the filtrate output pipe, the liquid removing gas output pipe and the solid discharge pipeline, the mother liquor feeding pipe is used for connecting a discharge port of the reaction system and is connected with the polymerization solid-liquid mixture generated by the reaction system, the cleaning liquid input pipe is used for connecting a fresh diluent used as the cleaning liquid, the liquid removing gas input pipe is used for connecting;
The diluent collecting tank is used for collecting diluent discharged by the system and is provided with a fresh diluent input pipe and a circulating diluent output pipe, the fresh diluent is connected into the fresh diluent which is used for being connected into the system to be supplemented, the circulating diluent output pipe is connected into the reaction system through a diluent feeding pump and serves as diluent raw materials, a filtrate output pipe of the pressure filter is connected into the diluent collecting tank, a cleaning discharge liquid output pipe is connected into the diluent collecting tank, a liquid removing gas output pipe is connected into a condenser to be condensed, and a condensate output pipe of the condenser is connected into the diluent collecting tank.
the reaction system is provided with a liquid phase reactor suitable for slurry process or slurry-gas phase process polymerization, and is used for generating polyethylene by adopting slurry process or slurry-gas phase process polymerization and outputting a polymerization solid-liquid mixture, wherein the polymerization solid-liquid mixture mainly comprises powder polyethylene, diluent and unreacted ethylene dissolved in the diluent.
the pressure filter is internally provided with a filtering area, a liquid removing area, a discharging area and a regeneration area which are distributed in sequence.
The pressure filter adopts a rotary drum type pressure filter.
The shaft seal structure of the rotary drum type pressure filter preferably adopts a packing and mechanical seal combined structure.
the filter medium of the rotary drum type pressure filter is made of metal and nonmetal filter cloth, preferably nonmetal filter cloth, and further preferably PEEK (polyetheretherketone) filter cloth.
And a discharge pipeline of the rotary drum type pressure filter is provided with a sealed discharging device.
the sealed blanking device of the rotary drum type pressure filter adopts a rotary blanking valve.
the number of the rotary blanking valves is one or more, and the rotary blanking valves are arranged in series.
The diluent collection tank is provided with a stirrer.
The stirrer is an electric mechanical stirrer.
The electric mechanical stirrer is provided with an electric control device so as to control the whole operation of the system through a unified electric control cabinet.
the condenser is a water-cooled condenser, and cooling water is used as a condensing medium (heat absorbing medium).
The invention has the following beneficial effects:
1) the pressure filtration technology is adopted to replace the gasification, flash evaporation, additional bag type filtration and cyclone separation technologies in the traditional slurry method polyethylene production technology, so that the energy required by the gasification and flash evaporation of the diluent and the ethylene in the original technology is saved, and the defects of long process flow and multiple redundant operations in the prior art are overcome;
2) The filter cake of the pressure filter is subjected to liquid removal by using the circulating ethylene gas, so that the entrainment of the diluent in the filter cake is reduced, and the load is further reduced for the subsequent drying operation;
3) Compared with the prior art, the investment cost, the operation cost and the operation energy consumption of the device are obviously reduced from the following 4 aspects:
a) heating energy required by gasification and flash evaporation of the liquid phase diluent and the ethylene after the reaction is avoided;
b) The circulation flow of the diluent and the ethylene gas is greatly reduced, and the energy consumption in the compression process and the condensation process is saved;
c) The lift of a diluent circulating pump in the prior art is greatly reduced, and the energy consumption in the conveying process is saved;
d) the equipment such as a cyclone separator, a bag filter, a large-scale heat exchanger and the like in the original process are eliminated, the specifications of a circulating compressor, a diluent circulating pump, heat exchange equipment and steaming drying system equipment are obviously reduced, and the one-time investment of the device is reduced.
The invention adopts the pressure filtration technology to replace the processes of diluent gasification, flash evaporation, additional filtration and cyclone separation in the prior slurry method polyethylene production process, realizes the separation of polyethylene powder, and greatly reduces the circulation flow of diluent gas and ethylene gas in the device. By means of the invention, the equipment quantity in the existing slurry process technology can be greatly reduced, the consumption of heat tracing steam, cooling water and electric energy in the technological process is reduced, and the requirements of energy conservation and emission reduction as an optimized economic structure and promotion of green cycle low-carbon development are met.
drawings
FIG. 1 is a schematic diagram of the system configuration and process flow of the present invention.
Detailed Description
Referring to fig. 1, the apparatus of the present invention mainly comprises: a liquid phase reactor (not shown), a pressure filter 10, a sealed blanking device 20, a condenser 30, a diluent collecting tank 40, a stirrer 50, a mother liquid feeding pipe 11 of the filter, a cleaning liquid input pipe 12, liquid removing gas input pipes 13 and 14, a discharging back-blowing gas input pipe 15, a circulating gas phase ethylene pipeline 16, a fresh diluent input pipe 17, a filtrate output pipe 21, a gas output pipe (control pipeline) 22 after liquid removing, a filter discharging pipeline 23, a cleaning discharge liquid output pipe 24 and a circulating diluent output pipe 25.
the method can be implemented by adopting the device of the invention, taking a device adopting a rotary drum type pressure filter (hereinafter referred to as a filter for short) as an example, the process flow of the invention comprises the following steps:
1) Generating polyethylene powder in a liquid phase reactor by using raw material ethylene in the presence of a diluent to form a polymerization solid-liquid mixture (or called mother liquor) comprising the polyethylene powder, the diluent and unreacted ethylene;
2) The polymerization solid-liquid mixed liquid formed by the liquid phase reactor enters a pressure filter 10 through a mother liquid feeding pipe 11 of the filter under the action of system pressure, after being filtered by a filter medium in a filtering area of the pressure filter, a diluent and unreacted ethylene dissolved in the diluent form a filtrate, polyethylene powder forms filter residues, and the filter residues are continuously accumulated into a cake shape in a filtering unit and can also be called as a filter cake;
3) The filtrate enters a diluent collecting tank 40 through a filtrate output pipe 21 by a filter control head;
4) After a filter unit of the filter 10 is filled with polyethylene powder to form a filter cake, the filter cake enters a liquid removing area along with the rotation of a rotary drum, circulating ethylene gas is compressed by a circulating compressor and then is heated and pressurized, a liquid removing gas input pipe 13 is connected through a circulating gas phase ethylene pipeline 16 and enters the liquid removing area through the liquid removing gas input pipe 13, the circulating ethylene gas passes through the filter cake under the pushing of pressure, and a diluent and ethylene dissolved in the diluent and the polyethylene powder in pores of the filter cake are continuously removed, so that the liquid removing of the filter cake is realized;
5) After primary liquid removal, secondary liquid removal can be carried out according to the process requirement, a filter cake after primary liquid removal enters the next area (which can be regarded as a secondary liquid removal area) of the liquid removal area along with the rotation of the rotary drum, circulating ethylene gas enters the secondary liquid removal area through a liquid removal gas input pipe 14 after temperature rise and pressure rise in a circulating gas phase ethylene pipeline 16, and diluent and ethylene in the filter cake are further removed according to the same mode;
6) the filter cake after liquid removal enters an unloading area along with the rotation of the rotary drum, the polyethylene powder is unloaded by the gravity of the polyethylene powder or is unloaded under the back blowing of the unloading back blowing gas according to the requirement, the unloading back blowing gas adopts the circulating ethylene gas after the temperature rise and the pressure rise in a circulating gas phase ethylene pipeline 16, and the circulating ethylene gas is connected into the unloading area through an unloading back blowing gas input pipe 15 for back blowing;
7) the solid material falling from the discharge pipeline 23 is discharged out of the filter after being decompressed to low pressure or normal pressure through the sealed blanking device 20, which can be called as filtered solid discharge, the solid component of the filtered solid discharge is polyethylene powder, a small amount of diluent remains, and the filtered solid discharge can be dried by adopting the prior art subsequently, or used in other production processes, or used as corresponding products;
8) the gas after liquid removal discharged by the liquid removal is a gas-liquid mixture taking ethylene as a main material and carrying a diluent, enters the condenser 30 through the control pipeline 22 for condensation, and then enters the diluent collecting tank 40;
9) The filter unit for removing the filter cake enters a regeneration zone along with the rotation of the rotary drum, the filter medium is washed and regenerated by pure diluent accessed by a cleaning liquid input pipe 12, cleaning discharge liquid generated by washing enters a diluent collecting tank 40 through a control head through a cleaning discharge liquid output pipe 24, and the pure diluent used as the cleaning liquid can adopt fresh diluent required to be supplemented by a system or clean liquid-phase diluent circulated in the device;
10) The diluent collecting tank 40 receives the filtrate (diluent and ethylene dissolved therein) from the filter 10, the condensate formed by the gas after liquid removal and the cleaning discharge liquid, the components in the liquid are basically the diluent and the ethylene dissolved therein, the liquid is conveyed to the liquid phase reactor for recycling through the circulating diluent output pipe 25, the fresh diluent outside the battery limits can be connected through the fresh diluent input pipe 17 of the diluent collecting tank according to the process requirements, the diluent in the system is supplemented, the diluent collected from the system is mixed, and the mixed diluent is sent to the liquid phase reactor through the circulating diluent output pipe 25. The diluent collection tank 40 is provided with an agitator 50 for agitation to prevent polyethylene powder entrained in the diluent from settling at the bottom of the tank.
The technical means disclosed by the invention can be combined arbitrarily to form a plurality of different technical schemes except for special description and the further limitation that one technical means is another technical means.
Claims (10)
1. The polymer separating process in slurry process of producing polyethylene includes the following steps:
polymerization reaction: mixing ethylene into a diluent by adopting a slurry method or a slurry-gas phase method process to realize polymerization in a liquid phase reactor of a reaction system to form a polymerization solid-liquid mixture, wherein the polymerization solid-liquid mixture comprises powdered polyethylene, the diluent and ethylene dissolved in the diluent;
and (3) filtering: introducing a polymerization solid-liquid mixture generated by a reaction system into a pressure filter for filtering to form a filtrate and filter residues, wherein the filtrate mainly comprises a diluent and unreacted ethylene dissolved in the diluent, the filter residues mainly comprise powdery polyethylene, and the filter units of the pressure filter are gradually filled with the filter residues to form a filter cake;
removing liquid from a filter cake: moving the filter cake to a liquid removing area of the pressure filter, removing liquid from the filter cake by taking circulating ethylene gas of the system as liquid removing gas, and discharging gas after liquid removal, wherein the gas after liquid removal is a gas-liquid mixture containing ethylene and a diluent;
Discharging a filter cake: the filter cake after liquid removal is moved to a discharging area of the pressure filter, the filter cake is discharged by self weight or the circulating ethylene gas of the system is used as the discharging back-blowing gas for back-blowing discharging, and the filter cake is sent out through a discharging pipeline of the pressure filter and is discharged as the filtered solid;
Cleaning a filter medium: cleaning the filter medium of the filter unit after unloading by using a pure diluent as a cleaning solution to realize regeneration of the filter medium and discharge cleaning discharge liquid;
and (3) recovering a diluent: introducing the filtrate into a diluent collection tank; introducing the liquid-removed gas into a condenser for condensation to obtain diluent condensate, and introducing the diluent condensate into a diluent collecting tank; introducing the purge effluent into a diluent collection tank;
and (3) recycling of a diluent: and sending the liquid collected by the diluent collecting tank to the reaction system to be recycled as the diluent, and introducing the supplemented fresh diluent into the diluent collecting tank when the fresh diluent needs to be supplemented.
2. the process according to claim 1, wherein the pressure filter is provided with a filtration zone, a liquid removal zone, a discharge zone and a regeneration zone, which are arranged in this order, the filtration being carried out in the filtration zone, the cake liquid removal being carried out in the liquid removal zone, the cake discharge being carried out in the discharge zone, and the filtration medium washing being carried out in the regeneration zone.
3. The process according to claim 2, wherein the pressure filter is a rotary drum pressure filter.
4. A process according to any one of claims 1 to 3, wherein the recycle ethylene gas is compressed by a recycle ethylene gas compressor to raise the pressure and temperature of the recycle ethylene gas, and the raised and raised pressure recycle ethylene gas is used as said liquid-removing gas and/or said blow-back-discharge gas.
5. A method according to any of claims 1 to 3, wherein the diluent collection tank is mechanically agitated by means of an agitator to prevent the settling of entrained polyethylene powder.
6. the polymer separating device in the slurry process polyethylene production process comprises a reaction system, wherein the reaction system is a polymerization reaction system adopting a slurry process or a slurry-gas phase process and is provided with a liquid phase reactor,
it is characterized by comprising:
a pressure filter used for filtering and separating a polymerization solid-liquid mixture formed by a polymerization reaction system, which is provided with a mother liquor feeding pipe, a cleaning solution input pipe, a liquid removing gas input pipe, a filtrate output pipe, a liquid removing gas output pipe, a cleaning discharge liquid output pipe and a solid discharge pipeline, with or without a discharge back-blowing gas input pipe, the mother liquor feeding pipe is used for connecting a discharge port of the reaction system and is connected with a polymerization solid-liquid mixture generated by the reaction system, the cleaning liquid input pipe is used for being connected with a diluent used as a cleaning liquid, the diluent used as the cleaning liquid can be a fresh diluent or a diluent filtered by a system, it can be determined according to actual conditions that the liquid removal gas input pipe is used for connecting a circulating gas phase ethylene pipeline at the outlet side of a circulating ethylene compressor, the discharge back-blowing gas input pipe is used for connecting a circulating gas-phase ethylene pipeline on the outlet side of the circulating ethylene compressor;
The diluent collecting tank is used for collecting diluent discharged by the system and is provided with a fresh diluent input pipe and a circulating diluent output pipe, the fresh diluent is connected into the fresh diluent which is used for being connected into the system to be supplemented, the circulating diluent output pipe is connected into the reaction system through a diluent feeding pump and serves as diluent raw materials, a filtrate output pipe of the pressure filter is connected into the diluent collecting tank, a cleaning discharge liquid output pipe is connected into the diluent collecting tank, a liquid removing gas output pipe is connected into a condenser to be condensed, and a condensate output pipe of the condenser is connected into the diluent collecting tank.
7. The apparatus according to claim 6, wherein the pressure filter is a rotary drum pressure filter.
8. The apparatus according to claim 7, wherein the shaft seal structure of the rotary drum type pressure filter is a combined structure of packing and mechanical seal.
9. the apparatus as claimed in claim 7, wherein the discharge duct of the rotary drum filter press is provided with a sealed blanking device.
10. An apparatus according to any one of claims 6 to 9, wherein the diluent collection tank is provided with an agitator.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111912170A (en) * | 2020-07-24 | 2020-11-10 | 北方华锦化学工业股份有限公司 | Method for recycling and comprehensively utilizing purge gas of high-density polyethylene device |
| CN114907505A (en) * | 2021-02-08 | 2022-08-16 | 中国科学院上海有机化学研究所 | Production process of ultrahigh molecular weight polyethylene |
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