A slurry process for the production of polyolefin systems

Abstract

The application discloses a kind of slurry method preparation polyolefin systems, including polymerization reaction unit, slurry solid-liquid separation unit, drying devolatilization unit, incondensable gas recovery unit and solvent refining unit.The application provides the system of slurry method preparation ethyl hexyl copolymer with pentane as solvent, which can be applied to large chemical industry.In the slurry solid-liquid separation unit of the application, slurry separation is carried out by pressure solid-liquid separation, polyethylene slurry from the reaction unit is directly introduced into pressure centrifuge for solid-liquid separation without cooling through heat exchanger, solvent loss is less, energy consumption can be effectively reduced, and the process is short, the number of equipment is less, which can reduce floor area.

Description

Technical Field

[0001] This invention relates to the field of slurry method for preparing polyolefins, and more particularly to a slurry method system for preparing polyolefins. Background Technology

[0002] In the slurry polyethylene process, hexane or butane solvents are typically used. However, when preparing ethylene-hexane copolymers, if hexane is used, it is difficult to separate hexene and hexane because their boiling points are close, making hexene unsuitable as a comonomer. If butane is used, it is highly volatile due to its low boiling point, requiring stringent reaction conditions.

[0003] Therefore, a process method for preparing ethylene-hexane copolymers is provided, with mild reaction conditions that are suitable for large-scale industrial production. Summary of the Invention

[0004] To achieve the above objectives, this invention uses pentane as a solvent and optimizes and matches the process flow based on the characteristics of pentane solvent, providing a system for preparing ethylene-hexane copolymers using pentane as a solvent via a slurry method.

[0005] This invention provides a slurry method system for preparing polyolefins using pentane as a solvent, comprising:

[0006] The polymerization reaction unit is connected to the catalyst feed pipe, hydrogen feed pipe, hexene feed pipe, solvent feed pipe, ethylene feed pipe, non-condensable gas outlet pipe, and slurry outlet pipe, respectively.

[0007] The slurry solid-liquid separation unit includes a mother liquor tank, a pressurized centrifuge, and a dryer; the end of the slurry discharge pipe furthest from the polymerization reaction unit is connected to the slurry solid-liquid separation unit.

[0008] The drying and devolatilization unit is connected to the slurry solid-liquid separation unit via an ethylene-hexyl copolymer pipe;

[0009] The solvent refining unit is connected to the slurry solid-liquid separation unit through the first mother liquor pipe, and to the polymerization reaction unit through the refined solvent pipe;

[0010] The non-condensable gas recovery unit is connected to the end of the reaction non-condensable gas outlet pipe away from the polymerization reaction unit; the solvent refining unit is connected to the non-condensable gas recovery unit through the refined non-condensable gas outlet pipe, and the non-condensable gas recovery unit is connected to the solvent refining unit through the solvent recovery pipe.

[0011] Preferably, in the slurry solid-liquid separation unit, the end of the slurry discharge pipe furthest from the polymerization reaction unit is connected to the pressurized centrifuge, and the pressurized centrifuge is connected to the dryer through the solid discharge pipe; the pressurized centrifuge is connected to the mother liquor tank through the mother liquor discharge pipe, the mother liquor tank is connected to the solvent refining unit through the first mother liquor pipe, the mother liquor tank is connected to the polymerization reaction unit through the second mother liquor pipe, and the mother liquor tank is connected to the moisture recovery unit through the mother liquor non-condensable gas discharge pipe.

[0012] Preferably, the slurry solid-liquid separation unit further includes a dryer screw feeder, the pressurized centrifuge is connected to the dryer screw feeder through a solid discharge pipe, and the dryer screw feeder is connected to the dryer.

[0013] Preferably, the solvent purification unit comprises:

[0014] The refining column is connected to the end of the first mother liquor pipe furthest from the mother liquor tank. The first mother liquor pipe is equipped with a powder remover and a mother liquor preheater sequentially from upstream to downstream. The refining column is equipped with a refining column top condenser, a refining column top reflux tank, a refining column top reflux pump, and a reboiler at the bottom of the refining column. The refining column is connected to the top condenser via a refining column top discharge pipe. The refining column top condenser is connected to the refining column top reflux tank via a pipeline. The refining column top reflux tank is connected to the refining column via a refining column top condensate pipe. The refining column is connected to a de-weighting tower or a polymerization monomer recovery unit via a refining column bottom discharge pipe.

[0015] The dehydration tower is connected to the refining tower via a branch of the condensate pipe at the top of the refining tower. The dehydration tower is equipped with a top condenser, a top aftercooler, a top condensate tank, a top reflux pump, and a reboiler. The top aftercooler is connected to the non-condensable gas recovery unit via a refining non-condensable gas outlet pipe. The dehydration tower is connected to a solvent buffer tank via a bottom discharge pipe, which is equipped with a bottom transfer pump and a bottom liquid cooler. The solvent buffer tank is connected to the polymerization solvent refiner via a pipeline, and the polymerization solvent refiner is connected to the polymerization reaction unit via a pipeline.

[0016] The heavy removal tower is connected to the refining tower via the reboiler outlet pipe of the refining tower. The top of the heavy removal tower is equipped 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 reboiler. The heavy removal tower top reflux tank is connected to the heavy removal tower via a heavy removal tower top condensate pipe, a branch of which is connected to the polymerization solvent refiner. The polymerization solvent refiner is connected to the polymerization reaction unit via a pipeline. The heavy removal tower is connected to the polymerization monomer recovery unit via the heavy removal tower reboiler outlet pipe.

[0017] Preferably, a branch of the discharge pipe at the top of the refining tower is connected to the inlet of the heat medium channel of the mother liquor preheater, and the outlet of the heat medium channel of the mother liquor preheater is connected to the reflux tank at the top of the refining tower via a pipeline.

[0018] Preferably, a branch of the discharge pipe at the top of the refining tower is connected to the inlet of the heat medium channel of the reboiler at the bottom of the dehydration tower, and the outlet of the heat medium channel of the reboiler at the bottom of the dehydration tower is connected to the reflux tank at the top of the refining tower via a pipeline.

[0019] Preferably, the solvent purification unit comprises:

[0020] A refining column is connected to the end of the first mother liquor pipe furthest from the mother liquor tank; the first mother liquor pipe is equipped with a powder remover. The refining column is equipped with a refining column top condenser, a refining column top reflux tank, a refining column top reflux pump, a refining column bottom reboiler, and a refining column bottom start-up reboiler. The refining column is connected to the inlet of the heat medium channel of the refining column bottom reboiler via a refining column top discharge pipe; the outlet of the heat medium channel of the refining column bottom reboiler is connected to the refining column top reflux tank via a pipeline; the refining column top reflux tank is connected to the refining column via a refining column top condensate pipe; a heat pump is installed on the refining column top discharge pipe; the refining column is connected to a de-heavyweighting column or a polymerization monomer recovery unit via the refining column bottom discharge pipe.

[0021] The dehydration tower is connected to the refining tower via a branch of the condensate pipe at the top of the refining tower. The dehydration tower is equipped with a top condenser, a top aftercooler, a top condensate tank, a top reflux pump, and a reboiler. The top aftercooler is connected to the non-condensable gas recovery unit via a refining non-condensable gas outlet pipe. The dehydration tower is connected to a solvent buffer tank via a bottom discharge pipe, which is equipped with a bottom transfer pump and a bottom liquid cooler. The solvent buffer tank is connected to the polymerization solvent refiner via a pipeline, and the polymerization solvent refiner is connected to the polymerization reaction unit via a pipeline.

[0022] The heavy removal tower is connected to the refining tower via the reboiler outlet pipe of the refining tower. The top of the heavy removal tower is equipped 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 reboiler. The heavy removal tower top reflux tank is connected to the heavy removal tower via a heavy removal tower top condensate pipe, a branch of which is connected to the polymerization solvent refiner. The polymerization solvent refiner is connected to the polymerization reaction unit via a pipeline. The heavy removal tower is connected to the polymerization monomer recovery unit via the heavy removal tower reboiler outlet pipe.

[0023] Preferably, a branch of the discharge pipe at the top of the refining tower is connected to the condenser at the top of the refining tower, and the condenser at the top of the refining tower is connected to the reflux tank at the top of the refining tower via a pipeline.

[0024] Preferably, the refining tower is a plate tower.

[0025] Preferably, the weight-removing tower is a plate tower.

[0026] Preferably, the cooling medium of the top condenser of the deweighting tower is cooling water.

[0027] Preferably, the heat medium for the reboiler in the refining tower is steam.

[0028] Preferably, the reboiler in the bottom of the deweighting tower is a thermosiphon reboiler.

[0029] Preferably, the drying and devolatilization unit includes a dryer and a wet scrubber. The end of the ethylene-hexyl copolymer pipe away from the slurry solid-liquid separation unit is connected to the dryer. The dryer is connected to the wet scrubber through a wet gas pipe. The top outlet pipe of the wet scrubber is sequentially connected to a dry gas compressor, a dry gas condenser, and a dry gas secondary condenser. The liquid outlet pipe of the dry gas secondary condenser is connected to a dry gas sealed tank. The dry gas sealed tank is connected to the wet scrubber. The wet scrubber is provided with a bottom liquid circulation pipe.

[0030] Preferably, the outlet pipe of the secondary condenser of the dry gas is connected to the non-condensable gas recovery unit via a pipeline.

[0031] Preferably, a branch of the bottom liquid circulation pipe is connected to the solid-liquid separation unit, and the solid-liquid separation unit is connected to the solvent refining unit.

[0032] Preferably, it further includes an ethylene refining unit, which is connected to the end of the ethylene feed pipe away from the polymerization reaction unit.

[0033] Preferably, the tail gas pipe of the non-condensable gas recovery unit is connected to the ethylene recovery device.

[0034] Preferably, the discharge pipe of the drying and devolatilization unit is connected to the mixing and pneumatic conveying unit via a pipeline.

[0035] Preferably, the pentane is n-pentane and / or isopentane.

[0036] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0037] (1) The present invention provides a slurry method for preparing ethylene-hexane copolymers using pentane as a solvent, which can be applied to large-scale chemical industries.

[0038] (2) In the slurry solid-liquid separation unit of the present invention, pressurized solid-liquid separation is adopted. The polyethylene slurry from the reaction unit does not pass through the heat exchanger for cooling, but directly enters the pressurized centrifuge for solid-liquid separation. Solvent loss is small, which can effectively reduce energy consumption. The process is short and the number of equipment is small, which can reduce the floor space.

[0039] (3) Through the specific design of the slurry solid-liquid separation unit, on the basis of efficient drying of wet ethylene-hexane copolymer, non-condensable gas and solvent are collected and processed for subsequent treatment, thereby improving the energy utilization rate.

[0040] (4) The solvent refining unit can be used to selectively produce ultra-high molecular weight polyethylene, high density polyethylene and other grade products. In addition, based on the efficient refining solvent, heavy components are separated and residual monomers are further recovered for recycling.

[0041] (5) In the solvent refining unit of the present invention, thermal coupling is taken into account to make full use of heat and reduce energy consumption.

[0042] (6) This invention uses n-pentane as a solvent and does not use nitrogen as a carrier gas in the drying and devolatilization unit, thereby reducing nitrogen consumption, energy consumption and the generation of waste. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of a slurry method for preparing polyolefins according to the present invention;

[0044] Figure 2 This is a process flow diagram of the slurry solid-liquid separation unit;

[0045] Figure 3 This is a process flow diagram for the first solvent refining unit;

[0046] Figure 4 This is a process flow diagram for the second solvent refining unit;

[0047] Figure 5 This is a process flow diagram for the third solvent refining unit;

[0048] Figure 6 This is the process flow diagram for the fourth solvent refining unit;

[0049] Figure 7 This is a process flow diagram for the drying and devolatilization unit;

[0050] The markings in the diagram indicate the following:

[0051] Polymerization reaction unit 10

[0052] Slurry solid-liquid separation unit 20, mother liquor tank 21, first mother liquor pipe 211, second mother liquor pipe 212, mother liquor non-condensable gas outlet pipe 213, pressurized centrifuge 22, solid discharge pipe 221, dryer screw feeder 23, dryer 24, ethylene-hexyl copolymer pipe 25.

[0053] Drying and de-volatile matter unit 30, dryer 31, moisture scrubber 32, top outlet pipe 321, bottom liquid circulation pipe 322, drying gas compressor 33, drying gas condenser 34, drying gas secondary condenser 35, drying gas sealed tank 36.

[0054] Solvent refining unit 40, refined solvent tube 41, refined non-condensable gas outlet tube 42.

[0055] 43. Refining column; 431. Refining column top condenser; 432. Refining column top discharge pipe; 433. Refining column top reflux tank; 434. Refining column top reflux pump; 435. Refining column reboiler; 436. Refining column top condensate pipe; 437. Refining column reboiler discharge pipe; 438. Refining column reboiler start-up pump; 439.

[0056] 44. Dehydration tower; 441. Dehydration tower top condenser; 442. Dehydration tower top aftercooler; 443. Dehydration tower top condensate tank; 444. Dehydration tower top reflux pump; 445. Dehydration tower reboiler; 446. Dehydration tower reboiler discharge pipe; 447. Dehydration tower reboiler transfer pump; 448. Dehydration tower reboiler liquid cooler; 449. Solvent buffer tank.

[0057] 45. Heavy removal tower, 451. Heavy removal tower top condenser, 452. Heavy removal tower top reflux tank, 453. Heavy removal tower top reflux pump, 454. Heavy removal tower reboiler, 455. Heavy removal tower top condensate pipe, 456. Heavy removal tower bottom discharge pipe, 457. Heavy removal tower top liquid outlet pipe.

[0058] Powder remover 46, mother liquor preheater 47, heat pump 48

[0059] Non-condensable gas recovery unit 50, solvent recovery pipe 51

[0060] The unit includes a blending air conveying unit 60, a moisture recovery unit 70, a polymer monomer recovery unit 80, and an ethylene refining unit 90. Detailed Implementation

[0061] The present invention will now be described in detail and specifically through specific embodiments to enable a better understanding of the invention. However, the following embodiments do not limit the scope of the invention.

[0062] Example 1

[0063] See Figure 1As shown in the illustration, this embodiment provides a slurry method system for preparing polyolefins using pentane as a solvent, comprising:

[0064] The polymerization reaction unit 10 is connected to the catalyst feed pipe, hydrogen feed pipe, hexene feed pipe, solvent feed pipe, ethylene feed pipe, non-condensable gas outlet pipe, and slurry outlet pipe, respectively.

[0065] The slurry solid-liquid separation unit 20 includes a mother liquor tank 21, a pressurized centrifuge 22, and a dryer 24; the end of the slurry discharge pipe away from the polymerization reaction unit 10 is connected to the slurry solid-liquid separation unit 20.

[0066] The drying and devolatilization unit 30 is connected to the slurry solid-liquid separation unit 20 via the ethylene-hexyl copolymer pipe 25;

[0067] The solvent refining unit 40 is connected to the slurry solid-liquid separation unit 20 through the first mother liquor pipe 211, and to the polymerization reaction unit 10 through the refined solvent pipe 41;

[0068] The non-condensable gas recovery unit 50 is connected to the end of the reaction non-condensable gas outlet pipe away from the polymerization reaction unit 10; the solvent refining unit 40 is connected to the non-condensable gas recovery unit 50 through the refined non-condensable gas outlet pipe 42, and the non-condensable gas recovery unit 50 is connected to the solvent refining unit 40 through the solvent recovery pipe 51.

[0069] In specific applications, ethylene, hexene, pentane, hydrogen, and catalyst enter the polymerization reaction unit 10 and undergo copolymerization via a slurry method. After the reaction, the resulting polyolefin slurry enters the slurry solid-liquid separation unit 20, where solid-liquid separation yields polyolefin solid material and mother liquor. The polyolefin solid material is further dried in the drying and devolatilization unit 30 to obtain the polyolefin product. The mother liquor is refined in the solvent refining unit 40, and the solvent in the mother liquor is recovered and applied to the polymerization reaction unit 10.

[0070] The non-condensable gas generated by the polymerization reaction unit 10, the non-condensable gas generated by the slurry solid-liquid separation unit 20, and the non-condensable gas generated by the solvent refining unit 40 are fed into the non-condensable gas recovery unit 50 to separate the solvent and ethylene for recycling.

[0071] In a preferred embodiment, the system further includes an ethylene refining unit 90, which is connected to the end of the ethylene feed pipe away from the polymerization reaction unit 10.

[0072] In a preferred embodiment, the tail gas pipe 52 of the noncondensable gas recovery unit 50 is connected to the ethylene plant.

[0073] In a preferred embodiment, the discharge pipe of the drying and devolatilization unit 30 is connected to the mixing and pneumatic conveying unit 60 via a pipeline.

[0074] In one specific embodiment, the pentane is n-pentane and / or isopentane.

[0075] Example 2

[0076] See Figure 2 As shown in the figure, this embodiment provides a slurry solid-liquid separation unit that employs a pressurized solid-liquid separation process.

[0077] The slurry solid-liquid separation unit 20 includes a mother liquor tank 21, a first mother liquor pipe 211, a second mother liquor pipe 212, a pressurized centrifuge 22, a dryer screw feeder 23, and a dryer 24.

[0078] Specifically, in the slurry solid-liquid separation unit 20, the end of the slurry discharge pipe away from the polymerization reaction unit 10 is connected to the pressurized centrifuge 22 via a pipe; the pressurized centrifuge 22 is connected to the dryer 24 via the solid discharge pipe 221; the pressurized centrifuge 22 is connected to the mother liquor tank 21 via the mother liquor discharge pipe; the mother liquor tank 21 is connected to the solvent refining unit 40 via the first mother liquor pipe 211; the mother liquor tank 21 is connected to the polymerization reaction unit 10 via the second mother liquor pipe 212; and the mother liquor tank 21 is connected to the moisture recovery unit 70 via the mother liquor non-condensable gas discharge pipe 213.

[0079] The polyolefin slurry provided by polymerization unit 10 contains polyolefin solids, polymerization solvents, and related impurities. The slurry is sent to pressurized centrifuge 22. Solid-liquid separation of the polyolefin solids and mother liquor is performed in pressurized centrifuge 22. The collected mother liquor enters mother liquor tank 21. The polyolefin solids separated by pressurized centrifuge 22 are sent to dryer 24 for drying. The dried polyolefin solids are sent to polyolefin drying and devolatilization unit 30 for further drying and devolatilization. A portion of the mother liquor in mother liquor tank 21 is pumped to polymerization unit 10, and the other portion is pumped to solvent purification unit 40.

[0080] In a preferred embodiment, the slurry solid-liquid separation unit 20 further includes a dryer screw feeder 23, the pressurized centrifuge 22 is connected to the dryer screw feeder 23 through a solid discharge pipe 221, and the dryer screw feeder 23 is connected to the dryer 24.

[0081] Example 3

[0082] See Figure 3 As shown in the illustration, this embodiment provides a specific process flow for the first solvent refining unit 40. It is applicable to solvent refining systems involving pressurized solid-liquid separation.

[0083] The solvent refining unit 40 includes:

[0084] The refining tower 43 is connected to the end of the first mother liquor pipe 211 away from the mother liquor tank 21. The first mother liquor pipe 211 is equipped with a powder remover 46 and a mother liquor preheater 47 from upstream to downstream. The refining tower 43 is equipped with a refining tower top condenser 431, a refining tower top reflux tank 433, a refining tower top reflux pump 434, and a reboiler 435. The refining tower 43 is connected to the refining tower top condenser 431 through the refining tower top discharge pipe 432. The refining tower top condenser 431 is connected to the refining tower top reflux tank 433 through a pipeline. The refining tower top reflux tank 433 is connected to the refining tower 43 through the refining tower top condensate pipe 436. The refining tower 43 is connected to the de-heavyweight tower 45 or the polymerization monomer recovery unit 80 through the refining tower bottom discharge pipe 437.

[0085] The dehydration tower 44 is connected to the refining tower 43 via a branch of the refining tower top condensate pipe 436. The dehydration tower 44 is equipped 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 bottom reboiler 445. The dehydration tower top aftercooler 442 is connected to the non-condensable gas recovery unit 50 via the refining non-condensable gas outlet pipe 42. The dehydration tower 44 is connected to the solvent buffer tank 449 via the dehydration tower bottom discharge pipe 446. The dehydration tower bottom discharge pipe 446 is equipped with a dehydration tower bottom transfer pump 447 and a dehydration tower bottom liquid cooler 448. The solvent buffer tank 449 is connected to the polymerization solvent refiner via a pipeline. The polymerization solvent refiner is connected to the polymerization reaction unit 10 via the refining solvent pipe 41.

[0086] The deweight removal tower 45 is connected to the refining tower 43 via the refining tower bottom outlet pipe 437. The top of the deweight removal tower 45 is equipped with a deweight removal tower top condenser 451, a deweight removal tower top reflux tank 452, a deweight removal tower top reflux pump 453, and a deweight removal tower bottom reboiler 454. The deweight removal tower top reflux tank 452 is connected to the deweight removal tower 45 via a deweight removal tower top condensate pipe 455. A branch of the deweight removal tower top condensate pipe 455 is connected to the polymerization solvent refiner. The polymerization solvent refiner is connected to the polymerization reaction unit 10 via a pipeline. The deweight removal tower 45 is connected to the polymerization monomer recovery unit 80 via the deweight removal tower bottom outlet pipe 456.

[0087] In a preferred embodiment, a branch of the top discharge pipe 432 of the refining tower is connected to the inlet of the heat medium channel of the mother liquor preheater 42, and the outlet of the heat medium channel of the mother liquor preheater 42 is connected to the top reflux tank 433 of the refining tower via a pipeline.

[0088] In a preferred embodiment, a branch of the top discharge pipe 432 of the refining tower is connected to the inlet of the heat medium channel of the reboiler 445 of the dehydration tower, and the outlet of the heat medium channel of the reboiler 445 of the dehydration tower is connected to the reflux tank 433 at the top of the refining tower via a pipeline.

[0089] In specific applications, a portion of the mother liquor pumped from mother liquor tank 21 to solvent refining unit 40 undergoes a small amount of solid removal via powder remover 46. The mother liquor after solid removal is preheated by mother liquor preheater 47 and then sent to refining tower 43 for further refining. The top discharge from the tower is divided into three streams: one stream is condensed by refining tower top condenser 431 and returned to refining tower top reflux tank 433; one stream is used as a heat source to heat the mother liquor in mother liquor preheater 47; and the other stream is used as a heat source to heat the bottom liquid in dehydration tower reboiler 445. All materials after heat exchange and condensation are returned to refining tower top reflux tank 433. A portion of the condensate in refining tower top reflux tank 433 is returned to refining tower 43 via refining tower top reflux pump 434, while the other portion is pumped to dehydration tower 44. The bottom discharge is pumped to heavy component removal tower 45 for removal of heavy components or directly pumped to polymerization monomer recovery unit 80.

[0090] The top discharge from dehydration tower 44 undergoes two-stage condensation via dehydration tower top condenser 441 and dehydration tower top aftercooler 442 before being sent to dehydration tower top condensate tank 443 for gas-liquid two-phase separation. Non-condensable gas is sent to non-condensable gas recovery unit 50. The top reflux pump 444 in dehydration tower top condensate tank 443 returns the gas to dehydration tower 44. The bottom of dehydration tower 44 is equipped with a reboiler using the top gas from purification tower 43 as a heat source. The purified polymerization solvent from the bottom is sent by dehydration tower bottom transfer pump 447 to dehydration tower bottom liquid cooler 448 for cooling before entering solvent buffer tank 449. The solvent in solvent buffer tank 449 is pumped to the polymerization solvent refiner for further dehydration before being delivered to various users.

[0091] The non-condensable gas from the top of the de-condensation tower 45 is sent to the top condenser 451, where the gas and liquid phases undergo gas-liquid separation in the top reflux tank 452. Part of the condensate in the top reflux tank 452 is returned to the de-condensation tower 45 via the top reflux pump 453, while the other part is pumped to the polymerization solvent purifier for purification. The purified solvent is then sent to the polymerization reaction unit 10. The bottom product of the de-condensation tower 45 contains oligomers and residual monomers with boiling points higher than the polymerization solvent. This product is pumped to the polymerization monomer recovery unit 80, where residual monomers with boiling points higher than the polymerization solvent are obtained through distillation or other methods for recycling.

[0092] The discharge path of the tower bottom can be selected according to the needs of the product type. For example, when producing ultra-high molecular weight polyethylene products, the deweighting tower 45 is not used, and the refining tower 43 can also perform the function of the deweighting tower 45. The discharge from the refining tower 43 is directly pumped to the polymer monomer recovery unit 80 for recovery.

[0093] In a preferred embodiment, the refining tower 43 is a plate tower; the deweight removal tower 45 is a plate tower.

[0094] In one specific embodiment, the cooling medium of the top condenser 451 of the deweighting tower is cooling water; the heat medium of the reboiler 435 of the refining tower is steam; and the reboiler 454 of the deweighting tower is a thermosiphon reboiler.

[0095] Example 4

[0096] See Figure 4 As shown in the figure, this embodiment provides a specific process flow for the second solvent refining unit 40. The solvent refining unit 40 provided in this embodiment is based on embodiment 3, the difference being that the mother liquor enters the refining tower 43 directly without cooling, and the heat of the refining tower 43 is utilized by a heat pump 48, including a reboiler 439 for starting up the refining tower.

[0097] Specifically, in this embodiment, the refining column 43 is connected to the end of the first mother liquor pipe 211 away from the mother liquor tank 21, and the first mother liquor pipe 211 is equipped with a powder remover 46; the refining column 43 is equipped with a refining column top reflux tank 433, a refining column top reflux pump 434, a refining column bottom reboiler 435, and a refining column bottom start-up reboiler 439; the refining column 43 is connected to the refining column bottom reboiler 439 via the refining column top discharge pipe 432. The inlet of the heat medium channel of the reboiler 435 of the refining tower is connected, and the outlet of the heat medium channel of the reboiler 435 of the refining tower is connected to the reflux tank 433 at the top of the refining tower through a pipeline. The reflux tank 433 at the top of the refining tower is connected to the refining tower 43 through the condensate pipe 436 at the top of the refining tower. A heat pump 48 is installed on the discharge pipe 432 at the top of the refining tower. The refining tower 43 is connected to the de-weighing tower 45 or the polymerization monomer recovery unit 80 through the discharge pipe 437 at the bottom of the refining tower.

[0098] A portion of the mother liquor pumped from mother liquor tank 21 to solvent refining unit 40 is passed through powder remover 46 to remove small amounts of solids. The mother liquor after solid removal is sent to refining tower 43 for further refining. The top discharge from the refining tower is heated by a heat pump and used as a heat source to heat the bottom liquid of the refining tower 43 in reboiler 435. The material after heat exchange and condensation is returned to the refrigerant tank 433 at the top of the refining tower. Part of the condensate in the refrigerant tank 433 is returned to the refining tower 43 via refrigerant pump 434, and the other part is pumped to dehydration tower 44. The bottom discharge is pumped to de-heavy component removal tower 45 or directly pumped to monomer recovery unit 80.

[0099] Example 5

[0100] See Figure 5As shown in the figure, this embodiment provides a specific process flow for the third solvent refining unit 40. The solvent refining unit 40 provided in this embodiment is based on embodiment 4, with the difference that: a branch of the discharge pipe 432 at the top of the refining tower is connected to the condenser 431 at the top of the refining tower, and the condenser 431 at the top of the refining tower is connected to the reflux tank 433 at the top of the refining tower through a pipeline.

[0101] A portion of the mother liquor pumped from mother liquor tank 21 to solvent refining unit 40 is processed by powder remover 46 to remove small amounts of solids. The mother liquor after solid removal is then sent to refining tower 43 for further refining. The top discharge from the refining tower is split into two streams: one stream is condensed by refining tower top condenser 431 and returned to refining tower top reflux tank 433; the other stream is heated by a heat pump and used as a heat source to heat the reboiler 435 of the refining tower bottom liquid. The material after heat exchange and condensation is returned to refining tower top reflux tank 433. A portion of the condensate in refining tower top reflux tank 433 is returned to refining tower 43 via refining tower top reflux pump 434, while the other portion is pumped to dehydration tower 44. The bottom discharge is pumped to heavy component removal tower 45 for removal of heavy components or directly pumped to polymerization monomer recovery unit 80.

[0102] Example 6

[0103] See Figure 6 As shown in the figure, this embodiment provides a specific process flow for the solvent purification unit 40, which includes only a deweighting tower 45 and a dehydration tower 44, for preparing ultra-high molecular weight ethylene-hexyl copolymer.

[0104] The solvent refining unit 40 includes:

[0105] The heavy removal tower 45 is connected to the end of the flash evaporation wet gas pipe 232 away from the high-pressure flash tank 23. The flash evaporation wet gas pipe 232 is equipped with a powder removal bag 46 and a mother liquor preheater 47. The top of the heavy removal tower 45 is equipped 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 bottom reboiler 454. The heavy removal tower 45 is connected to the heavy removal tower top condenser 451 through a heavy removal tower top liquid outlet pipe 457. The reflux tank 452 at the top of the deweighting tower is connected to the deweighting tower 45 via the condensate pipe 455 at the top of the deweighting tower. The first branch of the condensate pipe 455 at the top of the deweighting tower is connected to the polymerization solvent purifier, and the second branch of the condensate pipe 455 at the top of the deweighting tower is connected to the dehydration tower 44. The polymerization solvent purifier is connected to the polymerization reaction unit 10 via a pipeline. The deweighting tower 45 is connected to the polymerization monomer recovery unit 80 via the bottom discharge pipe 456 of the deweighting tower.

[0106] The dehydration tower 44 is connected to the de-heavy tower 45 via a second branch of the condensate pipe 455 at the top of the de-heavy tower. The dehydration tower 44 is equipped 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 bottom reboiler 445. The dehydration tower top aftercooler 442 is connected to the non-condensable gas recovery unit 50 via a refined non-condensable gas outlet pipe 42. The dehydration tower 44 is connected to the solvent buffer tank 449 via a dehydration tower bottom discharge pipe 446. The dehydration tower bottom discharge pipe 446 is equipped with a dehydration tower bottom transfer pump 447 and a dehydration tower bottom liquid cooler 448. The solvent buffer tank 449 is connected to the polymerization solvent purifier via a pipeline. The polymerization solvent purifier is connected to the polymerization reaction unit 10 via the refined solvent pipe 41.

[0107] In a preferred embodiment, a branch of the top discharge pipe 432 of the refining tower is connected to the inlet of the heat medium channel of the mother liquor preheater 47, and the outlet of the heat medium channel of the mother liquor preheater 47 is connected to the top reflux tank 452 of the de-weighting tower via a pipeline.

[0108] In a preferred embodiment, a branch of the top discharge pipe 432 of the refining tower is connected to the inlet of the heat medium channel of the reboiler 445 of the dehydration tower, and the outlet of the heat medium channel of the reboiler 445 of the dehydration tower is connected to the top reflux tank 452 of the de-weighting tower via a pipeline.

[0109] In specific applications, 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 by the powder remover 46. The mother liquor after solid removal is preheated by the mother liquor preheater 47 and then sent to the de-consolidation tower 45 for refining. The top discharge from the tower is divided into three streams: one stream is condensed by the de-consolidation tower top condensate pipe 455 and returned to the de-consolidation tower top reflux tank 452; the second stream is sent as a heat source to the dehydration tower reboiler 445 to heat the dehydration tower bottom liquid; and the third stream is sent as a heat source to the mother liquor preheater 47 to preheat the mother liquor. All materials after heat exchange and condensation are returned to the de-consolidation tower top reflux tank 452. A portion of the condensate in the de-consolidation tower top reflux tank 452 is returned to the de-consolidation tower 45 via the de-consolidation tower top reflux pump 453, a second portion is pumped to the dehydration tower 44, and a third portion is pumped to the polymerization solvent refiner. The bottom product is pumped to the monomer recovery unit 80.

[0110] The top discharge from dehydration tower 44 undergoes two-stage condensation via top condenser 441 and top aftercooler 442 before being sent to top condensate tank 443 for gas-liquid two-phase separation. Non-condensable gas is sent to non-condensable gas recovery unit 50. The condensate in top condensate tank 443 is returned to dehydration tower 44 via top reflux pump 444. The bottom of dehydration tower 44 is equipped with a reboiler using the top gas from de-heavy tower 45 as a heat source. The refined polymerization solvent from the bottom of dehydration tower is sent to bottom liquid cooler 448 via bottom transfer pump 447 for cooling before entering solvent buffer tank 449. The solvent in solvent buffer tank 449 is pumped to polymerization solvent refiner for further dehydration before being distributed to various users.

[0111] Example 7

[0112] See Figure 7 As shown in the figure, this embodiment provides a specific process flow for the drying and devolatilization unit 30.

[0113] Specifically, the drying and devolatilization unit 30 includes a dryer 31 and a wet scrubber 32. The end of the ethylene-hexyl copolymer pipe 25 away from the slurry solid-liquid separation unit 20 is connected to the dryer 31. The dryer 31 is connected to the wet scrubber 32 through a wet air pipe 311. The top outlet pipe 321 of the wet scrubber 32 is sequentially connected to a dry gas compressor 33, a dry gas condenser 34, and a dry gas secondary condenser 35. The liquid outlet pipe of the dry gas secondary condenser 35 is connected to a dry gas sealed tank 36. The dry gas sealed tank 36 is connected to the wet scrubber 32. The wet scrubber 32 is provided with a bottom liquid circulation pipe 322.

[0114] In one specific embodiment, the moisture scrubber 32 contains low-temperature pentane.

[0115] In practical applications, the moisture evaporated from the dryer 31 is sent to the moisture scrubber 32 for gas-liquid separation. The separated gas exits from the top of the moisture scrubber 32, is compressed by the dry gas compressor 33, and then sent to the dry gas condenser 34 and the secondary dry gas condenser 35 for condensation. The condensate in the secondary dry gas condenser 35 flows to the dry gas sealing tank 36, and the condensate in the dry gas sealing tank 36 is then returned to the moisture scrubber 1 for recycling.

[0116] In a preferred embodiment, the outlet pipe of the dry gas secondary condenser 35 is connected to the non-condensable gas recovery unit 50 via a pipeline.

[0117] In a preferred embodiment, a branch of the bottom liquid circulation pipe 322 is connected to a solvent recovery unit.

[0118] Application Example 1:

[0119] This application example uses the slurry method for preparing polyolefins with pentane as a solvent provided in Example 1 to prepare ultra-high molecular weight ethylene-hexane copolymers.

[0120] In this application example, in the solvent refining unit 40, the refining tower 43 is connected to the polymerization monomer recovery unit 80 through the refining tower bottom discharge pipe 437, without passing through the deweighting tower 44.

[0121] The final product was subjected to physical property testing. The ultra-high molecular weight polyethylene (ethylene homopolymer, copolymer of ethylene and comonomers) had a viscosity-average molecular weight of 1.5-8 million g / mol, preferably 3-7 million g / mol, a metal element content of 0-40 ppm, preferably 0-30 ppm, a bulk density of 0.30-0.55 g / cm3, preferably 0.33-0.52 g / cm3, a comonomer molar insertion rate of 0-2.0%, preferably 0-1.0%, a tensile yield strength greater than 21 MPa, preferably greater than 23 MPa, a tensile breaking strength greater than 33 MPa, preferably greater than 35 MPa, and an ash content of less than 200 ppm, preferably less than 150 ppm.

[0122] Application Example 2:

[0123] This application example uses the slurry method for preparing polyolefins with pentane as a solvent provided in Example 1 to prepare high-density ethylene-hexane copolymers or multi-peak polyethylene products.

[0124] In this application example, in the solvent refining unit 40, the refining tower 43 is connected to the deweight removal tower 44 through the refining tower bottom discharge pipe 437.

[0125] The final product was subjected to physical property testing. It is a high-density ethylene polymer with an average particle size of 50-3000 μm, preferably 100-1000 μm; a weight-average molecular weight of 20,000 g / mol to 400,000 g / mol, preferably 50,000 g / mol to 300,000 g / mol; a molecular weight distribution of 1.8-10, preferably 2.0-8.0; and a comonomer molar insertion rate of 0.01-5 mol%, preferably 0.05-2.5 mol%. Preferably, the melt index at 2.16 kg load and 190 °C is 0.01-2500 g / 10 min, preferably 0.1-20. 0.00 g / 10 min, more preferably 0.1-1000 g / 10 min, bulk density 0.28-0.55 g / cm3, preferably 0.32-0.50 g / cm3, true density 0.930-0.980 g / cm3, preferably 0.940-0.970 g / cm3, more preferably 0.942-0.970 g / cm3, crystallinity 30-90%, preferably 40-80%, melting point 105-147℃, preferably 110-143℃, processing index in blown film test 4.0-6.0, preferably 4.5-5.9, more preferably 5.0-5.8.

[0126] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A slurry method system for preparing polyolefins, using pentane as a solvent, characterized in that, include The polymerization reaction unit (10) is connected to the catalyst feed pipe, hydrogen feed pipe, hexene feed pipe, solvent feed pipe, ethylene feed pipe, non-condensable gas outlet pipe, and slurry outlet pipe, respectively. The slurry solid-liquid separation unit (20) includes a mother liquor tank (21), a pressurized centrifuge (22), and a dryer (24); the end of the slurry discharge pipe away from the polymerization reaction unit (10) is connected to the slurry solid-liquid separation unit (20); The drying and devolatilization unit (30) is connected to the slurry solid-liquid separation unit (20) via an ethylene-hexyl copolymer pipe (25); The solvent refining unit (40) is connected to the slurry solid-liquid separation unit (20) through the first mother liquor pipe (221) and to the polymerization reaction unit (10) through the refined solvent pipe (41); The non-condensable gas recovery unit (50) is connected to the end of the reaction non-condensable gas outlet pipe away from the polymerization reaction unit (10); the solvent refining unit (40) is connected to the non-condensable gas recovery unit (50) through the refined non-condensable gas outlet pipe (42), and the non-condensable gas recovery unit (50) is connected to the solvent refining unit (40) through the solvent recovery pipe (51).

2. The slurry method for preparing polyolefins according to claim 1, characterized in that, In the slurry solid-liquid separation unit (20), the end of the slurry discharge pipe away from the polymerization reaction unit (10) is connected to the pressurized centrifuge (22), and the pressurized centrifuge (22) is connected to the dryer (24) through the solid discharge pipe (221); the pressurized centrifuge (22) is connected to the mother liquor tank (21) through the mother liquor discharge pipe, the mother liquor tank (21) is connected to the solvent refining unit (40) through the first mother liquor pipe (211), the mother liquor tank (21) is connected to the polymerization reaction unit (10) through the second mother liquor pipe (212), and the mother liquor tank (21) is connected to the moisture recovery unit (70) through the mother liquor non-condensable gas discharge pipe (213).

3. The slurry method for preparing polyolefins according to claim 2, characterized in that, The slurry solid-liquid separation unit (20) also includes a dryer screw feeder (23). The pressurized centrifuge (22) is connected to the dryer screw feeder (23) through a solid discharge pipe (221). The dryer screw feeder (23) is connected to the dryer (24).

4. The slurry method for preparing polyolefins according to claim 1, characterized in that, The solvent refining unit (40) includes: The refining column (43) is connected to the end of the first mother liquor pipe (211) away from the mother liquor tank (21). The first mother liquor pipe (221) is equipped with a powder remover (46) and a mother liquor preheater (47) from upstream to downstream. The refining column (43) is equipped with a refining column top condenser (431), a refining column top reflux tank (433), a refining column top reflux pump (434), and a reboiler (435) at the bottom of the refining column. The refining column (43) is connected to the end of the first mother liquor pipe (211) away from the mother liquor tank (21). The top discharge pipe (432) of the refining tower is connected to the top condenser (431) of the refining tower. The top condenser (431) of the refining tower is connected to the top reflux tank (433) of the refining tower through a pipe. The top reflux tank (433) of the refining tower is connected to the refining tower (43) through the top condensate pipe (436) of the refining tower. The refining tower (43) is connected to the de-weighting tower (45) or the polymerization monomer recovery unit (80) through the bottom discharge pipe (437) of the refining tower. The dehydration tower (44) is connected to the refining tower (43) via a branch of the refining tower top condensate pipe (436); the dehydration tower (44) is equipped 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 bottom reboiler (445). The dehydration tower top aftercooler (442) is connected to the refining tower (43) via the refining non-condensable gas outlet pipe (42). The non-condensable gas recovery unit (50) is connected; the dehydration tower (44) is connected to the solvent buffer tank (449) through the dehydration tower bottom discharge pipe (446), and the dehydration tower bottom discharge pipe (446) is equipped with a dehydration tower bottom transfer pump (447) and a dehydration tower bottom liquid cooler (448); the solvent buffer tank (449) is connected to the polymerization solvent purifier through a pipeline, and the polymerization solvent purifier is connected to the polymerization reaction unit (10) through a pipeline; The deweight removal tower (45) is connected to the refining tower (43) via the refining tower bottom outlet pipe (437); the top of the deweight removal tower (45) is equipped with a deweight removal tower top condenser (451), a deweight removal tower top reflux tank (452), a deweight removal tower top reflux pump (453), and a deweight removal tower bottom reboiler (454); the deweight removal tower top reflux tank (452) is connected to the deweight removal tower (45) via the deweight removal tower top condensate pipe (455), a branch of the deweight removal tower top condensate pipe (455) is connected to the polymerization solvent purifier, and the polymerization solvent purifier is connected to the polymerization reaction unit (10) via a pipeline; the deweight removal tower (45) is connected to the polymerization monomer recovery unit (80) via the deweight removal tower bottom outlet pipe (456).

5. The slurry method for preparing polyolefins according to claim 4, characterized in that, The branch of the discharge pipe (432) at the top of the refining tower is connected to the inlet of the heat medium channel of the mother liquor preheater (47), and the outlet of the heat medium channel of the mother liquor preheater (47) is connected to the reflux tank (433) at the top of the refining tower through a pipeline.

6. The slurry method for preparing polyolefins according to claim 4, characterized in that, The branch of the top discharge pipe (432) of the refining tower is connected to the inlet of the heat medium channel of the reboiler (445) of the dehydration tower, and the outlet of the heat medium channel of the reboiler (445) of the dehydration tower is connected to the reflux tank (433) at the top of the refining tower through a pipeline.

7. The slurry method for preparing polyolefins according to claim 1, characterized in that, The solvent refining unit (40) includes: The refining column (43) is connected to the end of the first mother liquor pipe (221) away from the mother liquor tank (22), and the first mother liquor pipe (221) is equipped with a powder remover (46); the refining column (43) is equipped with a refining column top condenser (431), a refining column top reflux tank (433), a refining column top reflux pump (434), a refining column bottom reboiler (435), and a refining column bottom start-up reboiler (439); the refining column (43) is connected to the refining column bottom reboiler through the refining column top discharge pipe (432). The inlet of the reboiler (435) is connected to the heat medium channel, and the outlet of the heat medium channel of the reboiler (435) in the refining tower is connected to the reflux tank (433) at the top of the refining tower through a pipeline. The reflux tank (433) at the top of the refining tower is connected to the refining tower (43) through the condensate pipe (436) at the top of the refining tower. A heat pump (48) is installed on the discharge pipe (432) at the top of the refining tower. The refining tower (43) is connected to the de-weighting tower (45) or the polymerization monomer recovery unit (80) through the discharge pipe (437) at the bottom of the refining tower. The dehydration tower (44) is connected to the refining tower (43) via a branch of the condensate pipe (436) at the top of the refining tower; the dehydration tower (44) is equipped 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 bottom reboiler (445). The dehydration tower top aftercooler (442) is connected to the refining tower (43) via the refining non-condensable gas outlet pipe (42). The non-condensable gas recovery unit (50) is connected; the dehydration tower (44) is connected to the solvent buffer tank (449) through the dehydration tower bottom discharge pipe (446), and the dehydration tower bottom discharge pipe (446) is equipped with a dehydration tower bottom transfer pump (447) and a dehydration tower bottom liquid cooler (448); the solvent buffer tank (449) is connected to the polymerization solvent purifier through a pipeline, and the polymerization solvent purifier is connected to the polymerization reaction unit (10) through a pipeline; The deweight removal tower (45) is connected to the refining tower (43) via the refining tower bottom outlet pipe (437); the top of the deweight removal tower (45) is equipped with a deweight removal tower top condenser (451), a deweight removal tower top reflux tank (452), a deweight removal tower top reflux pump (453), and a deweight removal tower bottom reboiler (454); the deweight removal tower top reflux tank (452) is connected to the deweight removal tower (45) via the deweight removal tower top condensate pipe (455), a branch of the deweight removal tower top condensate pipe (455) is connected to the polymerization solvent purifier, and the polymerization solvent purifier is connected to the polymerization reaction unit (10) via a pipeline; the deweight removal tower (45) is connected to the polymerization monomer recovery unit (80) via the deweight removal tower bottom outlet pipe (456).

8. The slurry method for preparing polyolefins according to claim 7, characterized in that, A branch of the discharge pipe (432) at the top of the refining tower is connected to the condenser (431) at the top of the refining tower, and the condenser (431) at the top of the refining tower is connected to the reflux tank (433) at the top of the refining tower through a pipeline.

9. The slurry method for preparing polyolefins according to claim 1, characterized in that, The drying and devolatilization unit (30) includes a dryer (31) and a wet scrubber (32). The end of the ethylene-hexyl copolymer pipe (25) away from the slurry solid-liquid separation unit (20) is connected to the dryer (31). The dryer (31) is connected to the wet scrubber (32) through a wet air pipe (311). The top outlet pipe (321) of the wet scrubber (32) is connected in sequence to the dry gas compressor (33), the dry gas condenser (34), and the dry gas secondary condenser (35). The liquid outlet pipe of the dry gas secondary condenser (35) is connected to the dry gas sealed tank (36). The dry gas sealed tank (36) is connected to the wet scrubber (32). The wet scrubber (32) is provided with a bottom liquid circulation pipe (322).

10. The slurry method system for preparing polyolefins according to claim 9, characterized in that, The outlet pipe of the dry gas secondary condenser (35) is connected to the non-condensable gas recovery unit (50) via a pipeline.

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