CN115475581A

CN115475581A - Multi-reactor olefin polymerization system and polymerization method

Info

Publication number: CN115475581A
Application number: CN202110663106.XA
Authority: CN
Inventors: 高静; 魏梦怡; 马桂荣; 苏洪; 宁波
Original assignee: China Petroleum and Chemical Corp; Sinopec Engineering Inc
Current assignee: China Petroleum and Chemical Corp; Sinopec Engineering Inc
Priority date: 2021-06-15
Filing date: 2021-06-15
Publication date: 2022-12-16

Abstract

The invention belongs to the technical field of olefin polymerization, and discloses a multi-reactor olefin polymerization system and a polymerization method. The polymerization system comprises a feeding subsystem, a reaction subsystem and a separation subsystem; the reaction subsystem comprises a ring pipe prepolymerization reactor, a liquid phase ring pipe reactor group, a high-pressure gas-solid separation unit and a vertical gas-phase fluidized bed reactor group which are connected in sequence; the feeding subsystem comprises a raw material refining unit, a catalyst preparation and feeding unit and a monomer feeding unit; the catalyst preparation and feeding unit is connected with the ring pipe prepolymerization reactor; the monomer feeding unit is respectively connected with the loop prepolymerization reactor, the liquid-phase loop reactor group and the vertical gas-phase fluidized bed reactor group. The invention can greatly increase the addition of ethylene, butene and hexene in the vertical gas-phase fluidized bed reactor, obviously increase the rubber phase content of the impact-resistant copolymerization product, and obtain the low-modulus ultra-flexible in-kettle alloy polypropylene product and the polyolefin product with lower heat sealing temperature.

Description

Multi-reactor olefin polymerization system and polymerization method

Technical Field

The invention belongs to the technical field of olefin polymerization, and particularly relates to a multi-reactor olefin polymerization system and a polymerization method.

Background

The industrial production of polypropylene in China began in 1971, and in recent years, along with the development of the process technologies such as the process of preparing olefin from methanol, the dehydrogenation of propane and the like, the polypropylene source is in a diversified state. With the rapid development of the application field of polypropylene, major enterprises expand the polypropylene capacity. According to statistics, the domestic polypropylene production capacity is increased by 205 million tons/year in 2010-2020 on average. In 2019, the global production capacity of the polypropylene reaches 8857 ten thousand tons, and by the end of 2020, the production capacity of the polypropylene in China reaches 3339 ten thousand tons/year. It is estimated that 17 sets of polypropylene devices are planned to be added in China in 2021, and the scale increase reaches 580 million tons per year. At present, china is the world polypropylene maximum supply area, although the polypropylene self-sufficiency rate of China will continuously rise in the future, the newly increased capacity is mainly homogeneous and low-end general materials, and high-end materials still highly depend on imports. With the competition of common polypropylene materials tending to be fierce, the uncertainty factor of the domestic and foreign macroscopic situation increases, the release of domestic new production energy and the diversification of the production technical route in the future, chinese polypropylene enterprises improve the added value of polypropylene products, relieve the inventory of low-end polypropylene products and improve the competitive strength of enterprises by researching and developing special materials for high-end polypropylene, such as polypropylene for high-melting fibers, polypropylene for thin-wall injection molding and the like.

Since Montectini corporation applied a series of patents in the world from the end of the 50's to the beginning of the 60's of the 20 th century, regarding the production of polypropylene and the preparation of polypropylene catalysts, polypropylene production technology has begun to develop rapidly and has been developed as the most active polymer material. At present, twenty kinds of technological routes for producing polypropylene exist, and various technological processes can be classified into solution process, slurry process (also called solvent process), bulk process, gas phase process and bulk and gas phase combined production process according to polymerization type. More than half of the global polypropylene production devices adopt a body and gas phase combined production process.

The combined production process of the body and the gas phase comprises a Spheripol process, a Chinese petrochemical ring pipe method polypropylene process, a HypoII and Hypol process and a Borstar process.

The Spheripol process employs one or two series loop reactors to produce polypropylene homopolymer and random copolymer, and then a gas phase reactor to produce impact copolymer.

The Chinese petrochemical ring tube method polypropylene technology relies on the catalyst technology and the newly developed asymmetric external electron donor and propane-butadiene copolymerization technology, and the development of acid-alkali-resistant high-performance tube materials, homopolymerized high-speed BOPP special materials, high-melt-strength and high-melt-index impact-resistant polypropylene and other commercial products is realized.

The three well oiling company developed the HypoIII process using a loop reactor and a gas phase kettle in series. The residence time of the two loop reactors is 1-1.5 h, and the gas phase reactor adopts a fluidized bed reactor with a wall-scraping stirrer at the lower part. The major difference between the HypoLII process and the Spheripol process is the gas phase reactor design, and the other units, including the catalyst and the prepolymerization, are essentially the same as in the Spheripol process.

The Borstar process technology uses a loop reactor in series with a gas phase reactor to produce homopolymer and random copolymer, and one or two gas phase reactors in series to produce impact copolymer, depending on the rubber content of the final product, with a second gas phase copolymerization reactor being required to produce impact copolymer of high rubber content. The Borstar process adopts BC1 series catalysts of Borealis company, can adapt to higher polymerization temperature, and can produce products with narrow molecular weight distribution and wide molecular weight distribution.

The existing process technology for producing polypropylene has the development prospect of combining a bulk method and a gas phase method.

The main difference of the bulk method according to different process routes is the difference of reactors, which is mainly divided into a tank reactor and a loop reactor. The tank reactor removes reaction heat by using latent heat of liquid evaporation, most of evaporated gas returns to the reactor after circulating and condensing, and uncondensed gas is circulated to the reactor after being boosted by a compressor. The loop reactor utilizes an axial flow pump to circulate the slurry at a high speed, and the slurry is cooled and removed heat through a jacket. Compared with a kettle reactor, the circular tube method has four advantages that: 1. the space-time yield of the reactor is high, and the volume of the loop reactor of the device with the same scale is smaller; 2. the reactor has simple structure, and because the pipe diameter is small, the wall thickness is not very thick even the design pressure is high, the manufacturing cost is lower, and the localization is realized; 3. the loop reactor removes heat through jacket water, has large heat transfer area and good heat removal effect, and the temperature is easy to control, so the volume yield of the unit reactor is high, and the energy consumption is low; 4. the slurry in the loop reactor is circulated at high speed by the axial flow pump, so that polymer slurry can be uniformly mixed, a catalyst system is uniformly distributed, the polymerization reaction condition is easy to control and can be controlled to be very accurate, the product quality is uniform, hot spots are not easy to generate, the wall is not easy to stick, and the energy consumption of the axial flow pump is lower. It also has some drawbacks: since the polymerization monomer is present in liquid form in the loop reactor, the amount of monomer stored per unit volume is large as compared with a gas phase reactor, and therefore the amount of flare discharge is larger than that of a gas phase reactor of the same scale, and so on.

The main difference between the gas phase process is the difference between the reactors and the stirring modes thereof, and the gas phase process is mainly divided into a stirred bed reactor and a fluidized bed reactor. The stirred bed reactor adopts forced stirring to ensure that powder is uniformly distributed and hot spots are not easy to generate in a bed layer; however, the reactor and the stirrer have complex structures, the inner wall of the reactor and the stirrer need to be polished, the clearance between the stirrer and the inner wall of the reactor has strict requirements, the manufacturing precision is high, and the cost is high; the contact area between the reactor and the stirrer is large, the diameter of mechanical seal is large, and the mechanical seal difficulty is large; the rotating parts and the matching system have complex design, high manufacturing difficulty and high cost. The gas-phase fluidized bed reactor not only can uniformly mix materials and has relatively low caking probability of products, but also contains a certain amount of liquid-phase propylene below a sieve plate of the reactor and can effectively remove reaction heat. In addition, catalysts such as Unipol's SHAC (ultra high activity catalyst) series do not require pretreatment or prepolymerization. Meanwhile, the first reactor circulating gas compressor is provided with an accident turbine, the first reactor circulating gas compressor can be kept to operate at a low speed in an accident state, the terminating agents can be fully mixed in the reactor, and the reactor is prevented from caking. Many fluidized bed reactors employ a unique advanced control system (APC) to direct process operations, which is simple, flexible, economical, and safe.

The process technology combining the bulk method and the gas phase method has the advantages of simple process flow, less equipment, low production cost, less three wastes, capability of removing low molecular weight random polymers and catalyst residues which have adverse effects on product properties, capability of obtaining high-quality products in the aspect of product cleanliness and the like, and can also realize the advantages of capability of adjusting product varieties in a wide range, suitability for producing impact-resistant polypropylene, good safety, convenience in driving and the like of the gas phase method.

In addition, Z-N catalysts have undergone tremendous growth in catalyst terms since the k.ziegler and g.natta co-earned nobel chemical prize in 1963. So far, the commercial catalyst of aluminum alkyl-TiCl 3 suitable for polypropylene isotactic polymerization to prepare iPP is quite different from the original catalyst. The existing fourth and fifth generation catalysts with high activity and high performance, supported and electron donor are developed, the catalytic activity is improved by hundreds of times, the product does not need to be deashed, and the economic benefit is greatly improved.

The polymerization reaction has double bond breakage and single bond formation, which cause energy absorption and release, so the reaction is not stable in the environment temperature and the microscopic state. Therefore, the propylene monomer has inconsistent polymerization rate around the catalyst, the reaction near the active center is faster, the faster polymerization reaction brings larger temperature fluctuation, the polymerization reaction rate of the active center is accelerated, the rapid polymerization in the central area of the catalyst and the slow polymerization in the peripheral area are more easily caused, the polymer is easy to break, and fine powder is generated. Therefore, the pre-polymerization process can prevent the initial reaction from being too violent, properly reduce the shrinkage during polymerization, effectively control the polymerization reaction rate and reduce the generation of fine powder. However, the conventional tank-type prepolymerization reactor cannot efficiently remove heat in time in many cases in the case where the exothermic property of the highly active catalyst is severe.

Therefore, in order to solve the problems of low rubber phase content and low impact strength of the copolymerization product in the bulk polypropylene process, difficulty in controlling the polymer morphology in the gas-phase polypropylene process, easy agglomeration in the reactor, and the problem that the conventional kettle-type prepolymerization reactor cannot transfer heat efficiently in time under many circumstances, a new multi-reactor olefin polymerization system and a polymerization method are urgently needed.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a multi-reactor olefin polymerization system and a polymerization method. The polymerization system and the polymerization method are a multi-reactor olefin polymerization system and a polymerization method consisting of a liquid phase ring pipe and a vertical gas-phase fluidized bed, can realize the ideal target of producing various products of polypropylene process by using one set of polymerization system, obviously improve the particle shape of polymer, reduce the content of polymer fine powder, simultaneously reduce the caking phenomenon in the operation process of a polymerization reactor, and greatly improve the adding amount of ethylene, butylene and hexene in the vertical gas-phase fluidized bed reactor, thereby obviously improving the rubber phase content of an impact-resistant copolymerization product, and obtaining an in-kettle alloy polypropylene product with low modulus and super flexibility and a polyolefin product with lower heat sealing temperature.

In order to achieve the above objects, one aspect of the present invention provides a multi-reactor olefin polymerization system comprising a feed subsystem, a reaction subsystem, and a separation subsystem;

the reaction subsystem comprises a loop prepolymerization reactor, a liquid-phase loop reactor group, a high-pressure gas-solid separation unit and a vertical gas-phase fluidized bed reactor group which are sequentially connected;

the feeding subsystem comprises a raw material refining unit and a catalyst preparation and feeding unit; the catalyst preparation and feeding unit is connected with the loop prepolymerization reactor; the raw material refining unit is respectively connected with the loop prepolymerization reactor, the liquid-phase loop reactor group and the vertical gas-phase fluidized bed reactor group.

In another aspect of the present invention, there is provided a multi-reactor olefin polymerization method using the multi-reactor olefin polymerization system, comprising the steps of:

s1: preparing a catalyst mixture in a catalyst preparation and feeding unit, and feeding the catalyst mixture and a polymerization monomer into the loop prepolymerization reactor together for prepolymerization;

s2: feeding the discharged material of the ring pipe prepolymerization reactor into the liquid phase ring pipe reactor group, and supplementing polymerization monomers and hydrogen into the liquid phase ring pipe reactor group for polymerization reaction;

s3: feeding the discharge of the liquid phase loop reactor group into the high-pressure gas-solid separation unit and the vertical gas-phase fluidized bed reactor group in sequence, supplementing a polymerization monomer into the vertical gas-phase fluidized bed reactor group, and continuing the polymerization reaction;

s4: and treating the discharged material of the vertical gas-phase fluidized bed reactor by the separation subsystem to obtain a polyolefin product.

The technical scheme of the invention has the following beneficial effects:

(1) The invention improves the rubber phase content of the copolymer by combining the liquid phase loop reactor group and the vertical gas phase fluidized bed reactor group, realizes the production of products with ultrahigh impact resistance, transparent impact resistance and stress whitening resistance, and solves the problem that reaction monomers among different reactors are in series and are not beneficial to accurately controlling the product characteristics.

(2) According to the invention, the form of the polymer is effectively controlled through prepolymerization, and the molecular weight of the polymer generated in different reactors is adjustable through accurately controlling the concentration of hydrogen among different reactors, so that the molecular weight distribution range of the final product is expanded to the greatest extent; the invention can make different reactors produce multi-polymers with different structures by accurately controlling the composition of the polymerized monomers in different reactors, thereby obtaining various polyolefin products, such as high melt strength and high melt index impact polypropylene, high transparent propylene/butylene random copolymer with low heat sealing temperature, ternary random copolymer polyolefin with lower heat sealing temperature, block copolymer polyolefin with higher impact strength and other commercial products.

(3) The invention provides a multi-reactor polymerization process comprising continuous prepolymerization, liquid-phase bulk ring polymerization and vertical gas-phase fluidized polymerization, which can be used for adjusting the stereospecificity, hydrogen regulation sensitivity, copolymerization performance and the like of a catalyst and realizing the production of high-performance and full-range polypropylene products by combining the adjustment of polymerization process conditions.

(4) The invention is a combined multi-reactor olefin polymerization system composed of a loop prepolymerization reactor, a liquid phase loop reactor group and a vertical gas-phase fluidized bed reactor group, which comprises 1 loop prepolymerization reactor, at most 2 liquid phase loop reactors and at most 3 vertical gas-phase fluidized bed reactors, and can flexibly adjust the production process according to the market demand for product brands in the actual production operation process, select a proper liquid phase loop reactor group and a vertical gas-phase fluidized bed reactor group, and select a proper connection form of the loop prepolymerization reactor, the liquid phase loop reactor group and the vertical gas-phase fluidized bed reactor group, so as to produce a beautiful product meeting the market demand, thereby realizing the maximum benefit of a production device and producing products belonging to various polyolefin processes by using one polymerization system, and having high comprehensive investment rate, flexible brand switching and high operation efficiency, thereby realizing the ideal goal that one device covers various polyolefin processes and products.

(5) The invention adopts a ring pipe prepolymerization reactor, adopts jacket water cooling, can efficiently remove reaction heat especially under the condition of high-activity catalyst, and has better heat transfer performance compared with the traditional kettle type prepolymerization; the small loop prepolymerization allows high solids concentration operation, avoiding severe limitations of mixing and heat transfer of high concentration large size particles compared to tank prepolymerization.

(6) The liquid phase loop reactor is utilized in the polymerization reaction, and has the advantages of simple structure, less investment, better heat transfer and mass transfer performance, high conversion per pass of propylene, easy grade switching in the product, short time, uniform product quality, less plasticizing blocks in the product and the like; and the combination with the strong back mixing of the vertical gas-phase fluidized bed reactor results in less material monomer storage.

(7) According to the invention, a plurality of vertical gas-phase fluidized bed reactors are connected in series, so that the rubber phase content in the polymer is increased, the gas lock system can realize mutual isolation of polymerized monomers among different vertical gas-phase fluidized bed reactors, the polymerized monomer composition in different reactors can be adjusted according to the product characteristic requirements, and the hydrogen equilibrium concentration can be increased to the required hydrogen equilibrium concentration more quickly so as to remarkably improve the melt index of the homopolymerized polyolefin. A wide range of different products are available, including homopolymers, random copolymers, impact copolymers, propylene ethylene butene terpolymers, propylene hexene copolymers, propylene ethylene hexene terpolymers, etc.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.

FIG. 1 shows a schematic diagram of a multiple reactor olefin polymerization system provided in example 1 of the present invention.

The reference numerals are explained below:

1-loop prepolymerization reactor; 2.1-a first liquid phase loop reactor; 2.2-a second liquid phase loop reactor; 3-high pressure gas-solid separation unit; 4.1-a first vertical gas-phase fluidized-bed reactor; 4.2-a second vertical gas-phase fluidized-bed reactor; 4.3-a third vertical gas-phase fluidized-bed reactor; 5-a raw material refining unit; 6-catalyst preparation and feeding unit; 7-airlock unit; 8-a separation subsystem; .

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In one aspect, the present invention provides a multiple reactor olefin polymerization system comprising a feed subsystem, a reaction subsystem, and a separation subsystem;

the reaction subsystem comprises a ring pipe prepolymerization reactor, a liquid-phase ring pipe reactor group, a high-pressure gas-solid separation unit and a vertical gas-phase fluidized bed reactor group which are sequentially connected;

According to the present invention, preferably, said liquid phase loop reactor battery comprises a plurality of liquid phase loop reactors connected in series.

According to the present invention, preferably, the loop prepolymerization reactor is a continuous reactor; the volume of the loop prepolymerization reactor is smaller than the volume of the liquid phase loop reactor (i.e. small loop reactors of smaller volume as known to the person skilled in the art); preferably, the volume of the loop prepolymerization reactor is 750-800L smaller than the volume of the liquid phase loop reactor; the loop prepolymerization reactor is provided with a cold water jacket.

According to the present invention, preferably, the vertical gas-phase fluidized bed reactor group comprises a plurality of vertical gas-phase fluidized bed reactors connected in series or in parallel, and the vertical gas-phase fluidized bed reactors are connected with each other through a gas lock unit.

According to the invention, the vertical gas-phase fluidized bed reactors are used for conveying polymer powder among the vertical gas-phase fluidized bed reactors through the gas lock system, the gas lock system completes the discharge of each vertical gas-phase fluidized bed reactor through sequential control operations such as pressurization, blowing, discharging, pressure relief and the like, and ensures that the materials among the vertical gas-phase fluidized bed reactors are not mixed with each other.

According to the present invention, preferably, the catalyst preparation and feeding unit comprises a catalyst in-line mixer and a catalyst feeding pump connected to each other, the catalyst feeding pump being connected to the loop prepolymerization reactor.

According to the present invention, preferably, the raw material refining unit includes an ethylene refining subunit, a propylene refining subunit, a butene refining subunit, a hexene refining subunit, and a hydrogen feeding unit.

According to the present invention, preferably, said liquid phase loop reactor battery comprises 1-2 of said liquid phase loop reactors; the vertical gas-phase fluidized bed reactor group comprises 1-3 vertical gas-phase fluidized bed reactors.

According to the invention, preferably, the separation subsystem comprises a low-pressure gas-solid separation unit, a steaming unit, a drying unit, a granulation unit, a granule conveying and blending unit and a packaging and stacking unit which are connected in sequence; and the low-pressure gas-solid separation unit is connected with a discharge port of the vertical gas-phase fluidized bed reactor group.

In the present invention, as a preferable mode, the steaming unit includes a steam tank, and the drying unit includes a dryer connected to the steam tank.

In the invention, the low-pressure gas-solid separation unit is used for low-pressure gas-solid separation, and the low-pressure gas-solid separation refers to: the discharged polymer of the vertical gas-phase fluidized bed reactor group still adsorbs a small amount of polymerized monomer, and the polymer is added into a low-pressure bag filter under the action of pressure difference to remove the residual hydrocarbon polymerized monomer.

According to the invention, preferably, the granulation unit comprises an additive metering sub-unit and an extrusion granulator set.

According to the present invention, preferably, said loop prepolymerization reactor is directly connected to said vertical gas phase fluidized bed reactor battery by means of a pipeline.

In another aspect, the present invention provides a multi-reactor olefin polymerization method, which employs the multi-reactor olefin polymerization system, including the following steps:

in the invention, the high-pressure gas-solid separation unit carries out a high-pressure gas-solid process, wherein the high-pressure gas-solid process is as follows: since a large amount of liquid-phase monomer is discharged out of the liquid-phase loop reactor together with the polymer, it is necessary to recover this portion of liquid-phase monomer. The liquid monomer is first completely vaporized by heating at a relatively high pressure, and then the solid powder is separated from the gas by means of a high-pressure bag filter. And discharging the solid powder discharged from the bottom of the high-pressure bag filter into the vertical gas-phase fluidized bed reactor group under the material level control.

S4: and treating the discharge of the vertical gas-phase fluidized bed reactor by the separation subsystem to obtain a polyolefin product.

According to the present invention, preferably, in step S1,

the catalyst mixture comprises a catalyst raw material and an auxiliary catalyst; the raw material of the catalyst is a polyolefin catalyst; the auxiliary catalyst comprises white oil, grease, triethyl aluminum and an electron donor;

the method for preparing the catalyst mixture comprises the steps of feeding the white oil and the grease into the catalyst in-line mixer for first stirring; then feeding the triethyl aluminum and the electron donor into the catalyst online mixer, mixing with the mixture of the white oil and the grease, and stirring for the second time; and feeding the catalyst raw material into the catalyst on-line mixer, and stirring and cooling the catalyst raw material and the mixture in the catalyst on-line mixer for the third time to obtain the catalyst mixture.

According to the invention, preferably, the volume ratio of said white oil to said fat is (0.9-1.1): (0.9-1.1), wherein the sum of the dosage of the white oil and the dosage of the grease is 18-24L; preferably, the dosage of the triethyl aluminum is 80-100mL, and the dosage of the electron donor is 3-10mL; preferably, the catalyst starting material is used in an amount of 450 to 550g.

According to the invention, preferably, the temperature of the first stirring is 65-75 ℃, and the time of the first stirring is 100-150min; preferably, the time of the second stirring is 20-50min; preferably, the time for the third stirring is 30-90min.

According to the present invention, preferably, the cooling comprises reducing the temperature of the catalyst in-line mixer to room temperature using jacketed cooling water.

According to the invention, preferably, the catalyst mixture is fed to the loop prepolymerization reactor in an amount ranging from 80 to 120mL/h;

according to the invention, the prepolymerization is preferably carried out at a temperature of 18 to 22 ℃ and a pressure of 3.3 to 4.4MpaG. In the invention, the heat is removed through the cold water jacket of the loop prepolymerization reactor to ensure that the polymerization monomer is polymerized at 18-22 ℃, thereby better controlling the form of the polymer.

According to the present invention, preferably the polymerized monomer in the loop prepolymerization reactor is liquid phase propylene.

According to the invention, preferably, the average residence time of the catalyst mixture in the loop prepolymerization reactor is in the range of 15 to 25min, determined by the feed amount of the prepolymerized monomer.

According to the present invention, preferably, in step S2,

the polymerization reaction temperature in the liquid phase loop reactor group is 60-80 ℃, and the pressure is 3.2-4.4MPaG;

the polymerization monomer in the liquid-phase loop reactor group is at least one of liquid-phase propylene, ethylene, hexene and butene;

the feed concentration of hydrogen is 1000-2000ppm.

According to the present invention, preferably, in step S3,

the operating pressure of the high-pressure gas-solid separation unit is 2.0-2.1MPaG;

the temperature of the polymerization reaction in the vertical gas-phase fluidized bed reactor group is 60-90 ℃, the pressure is always lower than the saturated vapor pressure of the materials at the corresponding polymerization temperature, and the preferred pressure is 1.4-3.6MPaG;

the polymerization monomer in the vertical gas-phase fluidized bed reactor group is at least one of liquid-phase propylene, ethylene, hexene and butene.

According to the present invention, preferably, in step S4, the processing of the separation subsystem includes sending the output of the vertical gas-phase fluidized-bed reactor to a low-pressure gas-solid separation unit, a steaming unit, a drying unit, a granulation unit, a granule conveying and blending unit and a packaging and stacking unit in sequence to obtain the polyolefin product.

The present invention is specifically illustrated by the following examples.

Example 1

This example provides a multiple reactor olefin polymerization system, as shown in fig. 1, comprising a feed subsystem, a reaction subsystem, and a separation subsystem;

the reaction subsystem comprises a ring pipe prepolymerization reactor 1, a first liquid phase loop reactor 2.1, a second liquid phase loop reactor 2.2, a high-pressure gas-solid separation unit 3, a first vertical gas phase fluidized bed reactor 4.1, a second vertical gas phase fluidized bed reactor 4.2 and a third vertical gas phase fluidized bed reactor 4.3 which are connected in sequence;

the first liquid phase loop reactor 2.1 and the second liquid phase loop reactor 2.2 are connected in series and have the same size;

the first vertical gas-phase fluidized bed reactor 4.1, the second vertical gas-phase fluidized bed reactor 4.2 and the third vertical gas-phase fluidized bed reactor 4.3 are connected in series and have the same size;

the loop prepolymerization reactor 1 is a continuous reactor, and is a loop reactor with a small volume relative to the volume of the first liquid phase loop reactor 2.1, the volume of the loop prepolymerization reactor is 5L, and the first liquid phase loop reactor 2.1 is a loop polymerization reactor with an inner diameter of 200mm, a total length of 12000mm, and a total volume of 760L. The loop prepolymerization reactor 1 is provided with a cold water jacket (not shown); each vertical gas-phase fluidized bed reactor is connected with each other through an airlock unit 8; the total volume of each vertical gas-phase fluidized bed reactor is 1000L, and the length-diameter ratio is 4.

The feeding subsystem comprises a raw material refining unit 5 and a catalyst preparation and feeding unit 6;

the raw material refining unit 5 comprises an ethylene refining subunit, a propylene refining subunit, a butene refining subunit, a hexene refining subunit and a hydrogen feeding unit.

The catalyst preparation and feeding unit 6 is connected to the loop prepolymerization reactor 1, and specifically, the catalyst preparation and feeding unit 6 comprises a catalyst in-line mixer (not shown) and a catalyst feeding pump (not shown) which are connected with each other, and the catalyst feeding pump (not shown) is connected to the loop prepolymerization reactor 1;

the raw material refining unit 5 is respectively connected with the loop prepolymerization reactor 1, each liquid phase loop reactor and each vertical gas phase fluidized bed reactor.

The separation subsystem 9 comprises a low-pressure gas-solid separation unit, a steaming unit, a drying unit, a granulation unit, a granule conveying and blending unit and a packaging and stacking unit which are connected in sequence; the low-pressure gas-solid separation unit is connected with a discharge hole of a third vertical gas-phase fluidized bed reactor 4.3. The granulation unit comprises an additive metering sub-unit and an extrusion granulator set.

The method for carrying out multi-reactor olefin polymerization by adopting the system comprises the following steps:

s1: a catalyst mixture was formulated in the catalyst preparation and feed unit 6: feeding 20L of white oil and grease with equal volume ratio into the catalyst on-line mixer, and stirring at 70 deg.C for 120min; then feeding triethyl aluminum and an electron donor into the catalyst on-line mixer, mixing with the mixture of the white oil and the grease, and stirring for 30min; feeding 500g of special catalyst for polypropylene into the catalyst on-line mixer, stirring the special catalyst for the polypropylene and the mixture in the catalyst on-line mixer for 60min, and cooling the temperature in the catalyst on-line mixer to room temperature by using jacket cooling water to obtain the catalyst mixture; feeding the catalyst mixture and liquid phase propylene into the loop prepolymerization reactor 1 through a catalyst feeding pump at a feeding amount of 100mL/h for prepolymerization reaction; the average residence time of the catalyst mixture in the loop prepolymerization reactor 1 was set to 20min by adjusting the amount of the propylene entering in the liquid phase. The temperature of the prepolymerization reaction is 18-22 ℃, and the pressure is 3.3-4.4MpaG.

S2: the discharge material of the ring pipe prepolymerization reactor 1 is sent into a first liquid phase loop reactor 2.1 under the push of liquid phase propylene, and polymerization monomers and hydrogen are supplemented into the first liquid phase loop reactor 2.1 for polymerization reaction; additional polymerized monomers include: the feeding amount is 360kg/h of liquid phase propylene and 30kg/h of hexene; the feed concentration of hydrogen was 1500ppm; the polymerization temperature was controlled at 70 ℃ and the polymerization pressure was controlled at 3.8MPaG.

The discharge of the first liquid phase loop reactor 2.1 enters the second liquid phase loop reactor 2.2 through the upper span line of the first liquid phase loop reactor, and polymerization monomers and hydrogen are supplemented into the second liquid phase loop reactor 2.2 for polymerization reaction; additional polymerized monomers include: the feeding amount is 180kg/h of liquid phase propylene and 20kg/h of butylene; the feed concentration of hydrogen was 1800ppm; the polymerization temperature was controlled to 68 ℃ and the polymerization pressure was controlled to 3.8MPaG.

S3: feeding the discharge of a second liquid phase loop reactor 2.2 into the high-pressure gas-solid separation unit 3, flashing and filtering more than 95% of hydrocarbons under the pressure of 2.0-2.1MPaG, allowing gas-phase propylene to escape from the top end of a high-pressure bag filter, allowing polypropylene particles carrying a small amount of gas-phase olefins to enter a first vertical gas-phase fluidized bed reactor 4.1 through a discharge valve bank of the high-pressure gas-solid separation unit 3, supplementing polymerization monomers into the first vertical gas-phase fluidized bed reactor 4.1, and continuing polymerization; the additional polymerized monomers include: the feed rate was 30kg/h of vapor phase propylene, the feed rate was 25kg/h of ethylene; the temperature of the polymerization reaction is controlled to be 75-80 ℃, and the pressure of the polymerization reaction is controlled to be 1.7-1.8MPaG.

The discharge of the first vertical gas-phase fluidized bed reactor 4.1 enters an airlock unit 8, after all volatile components brought by the first vertical gas-phase fluidized bed reactor 4.1 are isolated, polypropylene powder enters the second vertical gas-phase fluidized bed reactor 4.2, a polymerization monomer is supplemented into the second vertical gas-phase fluidized bed reactor 4.2, and polymerization reaction is continued; the additional polymerized monomers include: the feed rate was 17kg/h of vapor phase propylene, the feed rate was 15kg/h of ethylene; controlling the temperature of the polymerization reaction to be 75-80 ℃ and the pressure of the polymerization reaction to be 1.5-1.6MPaG, so that the residual special catalyst for the polypropylene generates high molecular weight polymer in the reactor.

The discharge of the second vertical gas-phase fluidized bed reactor 4.2 enters an airlock unit 8, after all volatile components brought by the second vertical gas-phase fluidized bed reactor 4.2 are isolated, polypropylene powder enters the third vertical gas-phase fluidized bed reactor 4.3, a polymerization monomer is supplemented into the third vertical gas-phase fluidized bed reactor 4.3, and polymerization reaction is continued; the additional polymerized monomers include: the feed rate was 12kg/h of vapor phase propylene, the feed rate was 10kg/h of ethylene; controlling the temperature of the polymerization reaction to be 75-80 ℃ and the pressure of the polymerization reaction to be 1.5-1.6MPaG, so that the special catalyst for the residual polypropylene generates high molecular weight polymers in the reactor.

S4: and (3) discharging the material from the third vertical gas-phase fluidized bed reactor 4.3, and sequentially feeding the material into a low-pressure gas-solid separation unit, a steaming unit, a drying unit, a granulating unit, a granule conveying and mixing unit and a packaging and stacking unit for treatment to obtain a polypropylene product (the copolymer of the propylene, the butylene and the hexylene) with higher polymer material strength.

Example 2

This example provides a multiple reactor olefin polymerization system, which differs from example 1 only in that: this example comprises 1 liquid phase loop reactor. The polymerization monomers replenished in the liquid phase loop reactor and the vertical gas phase fluidized bed reactor set are shown in Table 1.

The procedure for the multiple reactor olefin polymerization using the above system is the same as in example 1.

Example 3

Example 4

This example provides a multiple reactor olefin polymerization system, differing from example 1 only in that: this example comprises 1 liquid phase loop reactor and 2 vertical gas phase fluidized bed reactors. The polymerization monomers replenished in the liquid phase loop reactor and the vertical gas phase fluidized bed reactor set are shown in Table 1.

Example 5

This example provides a multiple reactor olefin polymerization system, differing from example 1 only in that: this example comprises 1 liquid phase loop reactor and 3 vertical gas phase fluidized bed reactors; the first vertical gas-phase fluidized bed reactor 4.1, the second vertical gas-phase fluidized bed reactor 4.2 and the third vertical gas-phase fluidized bed reactor 4.3 are connected in parallel, and the liquid-phase loop reactor is connected with the 3 vertical gas-phase fluidized bed reactors in series. The polymerization monomers replenished in the liquid phase loop reactor and the vertical gas phase fluidized bed reactor set are shown in Table 1.

Table 1 examples 1-5 polymerization monomer feed conditions

Wherein: r1 represents a first liquid phase loop reactor 2.1; r2 represents a first liquid phase loop reactor 2.2; r3 represents a first vertical gas phase fluidized bed reactor 4.1; r4 represents a first vertical gas phase fluidized bed reactor 4.2; r5 denotes the first vertical gas-phase fluidized-bed reactor 4.3.

Comparative example 1

This comparative example provides a multiple reactor olefin polymerization system, differing from example 1 only in that: and replacing the loop prepolymerization reactor with a kettle-type prepolymerization reactor.

The rest was the same as in example 1.

Comparative example 2

This comparative example provides a multiple reactor olefin polymerization system, differing from example 5 only in that: and replacing the loop prepolymerization reactor with a kettle-type prepolymerization reactor.

The rest was the same as in example 5.

Test example

This test example measured the contents of ethylene, 1-butene and 1-hexene in the polymers obtained in examples 1 to 5 and comparative examples 1 to 2 by infrared spectroscopy; the melt index, notched Izod impact strength, and heat seal initiation temperature of the polymers obtained in each of the examples and comparative examples were measured using ASTM test standards, and the test results are shown in Table 2 below.

TABLE 2 test results

As can be seen from the results in table 2 above: the invention realizes the production of multiphase copolymerization olefin polymers such as propylene, butene, hexene, ethylene and the like by adopting small loop prepolymerization and combining a liquid phase loop reactor with a vertical gas phase reactor. The combination of different loop reactors and a vertical gas phase reactor can be used for producing propylene homopolymer, ethylene-propylene-diene copolymer, propylene-butylene-diene copolymer, propylene-hexylene-diene copolymer, ethylene-propylene-butylene terpolymer, propylene-butylene-hexylene-terpolymer and propylene-butylene-hexylene-propylene-copolymer products, greatly improving the impact strength of the products and obtaining ultra-flexible in-kettle alloy products (polyolefin products) with low heat sealing temperature and low modulus.

While embodiments of the present invention have been described above, the above description is illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A multiple reactor olefin polymerization system, the polymerization system comprising a feed subsystem, a reaction subsystem, and a separation subsystem;

2. The multiple reactor olefin polymerization system of claim 1,

the liquid phase loop reactor group comprises a plurality of liquid phase loop reactors connected in series;

the ring pipe prepolymerization reactor is a continuous reactor; the volume of the loop prepolymerization reactor is less than that of the liquid phase loop reactor; preferably, the volume of the loop prepolymerization reactor is 750-800L smaller than the volume of the liquid phase loop reactor; the ring pipe prepolymerization reactor is provided with a cold water jacket;

the vertical gas-phase fluidized bed reactor group comprises a plurality of vertical gas-phase fluidized bed reactors connected in series or in parallel, and the vertical gas-phase fluidized bed reactors are connected through an airlock unit;

the catalyst preparation and feeding unit comprises a catalyst online mixer and a catalyst feeding pump which are connected with each other, and the catalyst feeding pump is connected with the loop prepolymerization reactor;

the raw material refining unit comprises an ethylene refining subunit, a propylene refining subunit, a butene refining subunit, a hexene refining subunit and a hydrogen feeding unit.

3. The multiple reactor olefin polymerization system of claim 1, wherein the liquid phase loop reactor bank comprises 1-2 of the liquid phase loop reactors; the vertical gas-phase fluidized bed reactor group comprises 1-3 vertical gas-phase fluidized bed reactors.

4. The multiple reactor olefin polymerization system of claim 1, wherein the separation subsystem comprises a low pressure gas-solid separation unit, a steaming unit, a drying unit, a pelletizing unit, a pellet conveying and blending unit, and a packing and palletizing unit which are connected in sequence; the low-pressure gas-solid separation unit is connected with a discharge hole of the vertical gas-phase fluidized bed reactor group;

preferably, the granulation unit comprises an additive metering sub-unit and an extrusion granulator set.

5. A multi-reactor olefin polymerization system according to any one of claims 1 to 4, wherein the loop prepolymerization reactor is connected directly to the vertical gas phase fluidized bed reactor train by means of a pipeline.

6. A multiple reactor olefin polymerization process using the multiple reactor olefin polymerization system of any one of claims 1-5, comprising the steps of:

s3: feeding the discharged materials of the liquid phase ring pipe reactor group into the high-pressure gas-solid separation unit and the vertical gas phase fluidized bed reactor group in sequence, supplementing polymerized monomers into the vertical gas phase fluidized bed reactor group, and continuing the polymerization reaction;

7. The multiple reactor olefin polymerization process according to claim 6, wherein, in step S1,

the method for preparing the catalyst mixture comprises feeding the white oil and the grease into the catalyst in-line mixer for a first stirring; then feeding the triethyl aluminum and the electron donor into the catalyst online mixer, mixing with the mixture of the white oil and the grease, and stirring for the second time; feeding the catalyst raw material into the catalyst on-line mixer, and carrying out third stirring and cooling on the catalyst raw material and the mixture in the catalyst on-line mixer to obtain the catalyst mixture;

preferably, the volume ratio of the white oil to the fat is (0.9-1.1): (0.9-1.1), wherein the sum of the dosage of the white oil and the grease is 18-24L; preferably, the dosage of the triethyl aluminum is 80-100mL, and the dosage of the electron donor is 3-10mL; preferably, the amount of the catalyst raw material is 450 to 550g;

preferably, the temperature of the first stirring is 65-75 ℃, and the time of the first stirring is 100-150min; preferably, the time of the second stirring is 20-50min; preferably, the time for stirring for the third time is 30-90min;

preferably, the cooling comprises reducing the temperature of the catalyst in the in-line mixer to room temperature with jacketed cooling water;

the feeding amount of the catalyst mixture fed into the loop prepolymerization reactor is 80-120mL/h;

the temperature of the prepolymerization reaction is 18-22 ℃, and the pressure is 3.3-4.4MPaG;

the polymerization monomer in the ring pipe prepolymerization reactor is liquid phase propylene;

the average residence time of the catalyst mixture in the loop prepolymerization reactor is determined by the feed of the prepolymerized monomer and is between 15 and 25min.

8. The multiple reactor olefin polymerization process according to claim 6, wherein, in step S2,

the temperature of the polymerization reaction in the liquid-phase loop reactor group is 60-80 ℃, and the pressure is 3.2-4.4MPaG;

the feed concentration of hydrogen is 1000-2000ppm.

9. The multiple reactor olefin polymerization process of claim 6, wherein, in step S3,

the temperature of the polymerization reaction in the vertical gas-phase fluidized bed reactor group is 60-90 ℃, and the pressure is 1.4-3.6MPaG;

10. The multiple reactor olefin polymerization process of claim 6, wherein, in step S4, the processing of the separation subsystem comprises feeding the discharge of the vertical gas-phase fluidized-bed reactor sequentially into a low-pressure gas-solid separation unit, a steaming unit, a drying unit, a pelletizing unit, a pellet conveying and blending unit and a packaging and palletizing unit to obtain the polyolefin product.