CN110606905A - Polypropylene production process and production device - Google Patents
Polypropylene production process and production device Download PDFInfo
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- CN110606905A CN110606905A CN201910869971.2A CN201910869971A CN110606905A CN 110606905 A CN110606905 A CN 110606905A CN 201910869971 A CN201910869971 A CN 201910869971A CN 110606905 A CN110606905 A CN 110606905A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/70—Filters with filtering elements which move during the filtering operation having feed or discharge devices
- B01D33/72—Filters with filtering elements which move during the filtering operation having feed or discharge devices for feeding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/80—Accessories
- B01D33/804—Accessories integrally combined with devices for controlling the filtration
- B01D33/808—Accessories integrally combined with devices for controlling the filtration by pressure measuring
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F10/02—Ethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F10/04—Monomers containing three or four carbon atoms
- C08F10/06—Propene
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Abstract
The invention relates to a polypropylene production process and a production device, wherein the production process is to polymerize liquid-phase propylene under the action of a catalyst in a liquid-phase reaction system; introducing a solid-liquid mixture generated by the polymerization reaction into a pressure separation system for solid-liquid separation under the condition of not carrying out other solid-liquid separation; sending filtrate obtained by solid-liquid separation into a liquid phase reaction system to be used as a propylene raw material; and (3) sending the solid separation material obtained by solid-liquid separation into a steaming system and a drying system for steaming, removing liquid and drying to form homopolymerized polypropylene powder. The production equipment comprises a corresponding liquid phase reaction system, a pressure separation system, a propylene feeding system, a steaming system, a drying system and the like. The invention has the advantages of less equipment quantity, short flow and high process operability, not only reduces the primary investment of project construction, but also solves the problem of huge energy consumption caused by discharge gasification, flash evaporation, propylene recompression, condensation and liquefaction of a liquid phase reactor in the traditional process.
Description
Technical Field
The invention provides a polypropylene production process based on liquid-phase bulk reaction and a corresponding production device, belonging to the technical field of olefin polymerization.
Background
Polypropylene is a thermoplastic synthetic resin with excellent performance, and has wide application in the fields of various industrial and civil plastic products such as injection molding, film blowing, coating, spinning, modified engineering plastics and the like. At present, the production process of polypropylene is classified into a solution process, a slurry process, a bulk process and a gas phase process and a bulk-gas phase combined process according to the type of polymerization. The solution method and the slurry method have long process flow and high operation and investment cost, so that the new and reconstructed large-scale polypropylene device does not adopt the process basically since the 80 s in the 20 th century.
The bulk method (bulk-gas phase method) has various process routes, which can be divided into a kettle type polymerization process and a ring tube type polymerization process, and currently, a Spheripol process of Basell company, a Hypol process of Japan Mitsui chemical company, a Borstar process of Borealis company and the like are more applied.
The Spheripol process is the most successful and widely applied polypropylene production process until now since the first industrialization in 1982. The process combines liquid-phase homopolymerization and gas-phase copolymerization, and adopts one or more loop reactors and one or more serially connected gas-phase fluidized bed reactors to perform homopolymerization and random copolymerization in the loop reactor to produce the impact copolymer in a gas-phase fluidized bed. Although the process is longer, the equipment is simple, the investment is not high, the operation is stable and reliable, and the product performance is good.
The Hypol process is successfully developed in the early stage of the 80 th in the 20 th century, and adopts HY-HS-II catalyst (TK-II) which is a multi-stage polymerization process. It integrates the advantages of bulk propylene polymerization process and gas phase polymerization process into one body, and is a combined process technology which has no solvent and does not need deashing and can produce various grades of polypropylene products.
Borstar is a bimodal polypropylene process, which is first put into production in 2005. It adopts the basic configuration of double reactors, when producing homopolymer and random copolymer, it adopts a loop reactor and connects a gas phase reactor in series; when producing impact copolymers, one or two further gas-phase reactors are connected in series. Depending on the rubber content of the product, for example in the production of impact copolymers having a very high rubber content, a second gas-phase reactor is required. The process is characterized in that the process is operated under the supercritical condition, the typical temperature of the loop reactor is 80-100 ℃, and the pressure is 5.0-6.0 MPaG; the gas phase reactor is operated at 80-100 deg.C and 2.5-3.5 MPaG. It can produce products ranging from very hard to very soft, and also can produce multimodal products.
The gas phase process developed rapidly since the late 70 s of the 20 th century. The method is characterized in that propylene is directly subjected to gas phase polymerization reaction, the concentration of a monomer is far lower than that of liquid phase propylene, prepolymerization is not generally needed, and the pressure relief of a reactor is simpler and easier; regardless of the size of the scale, only 1 homopolymerization reactor and 1 impact reactor are required to be combined; most of PP powder after reaction is treated by one step by adopting a degassing bin and a purifying bin, so that the method has the advantages of short flow, less equipment, convenience in starting and stopping, suitability for impact-resistant copolymer production and the like. However, the gas phase reactor is prone to local overheating causing polymer agglomeration, resulting in plant shutdown, and thus its continuous operation cycle is not comparable to that of the loop plant.
In the existing bulk method (bulk-gas phase method) process, a liquid phase reactor is adopted to realize homopolymerization, reaction heat is removed by cooling through a jacket or an inner coil pipe, polypropylene powder generated by reaction and liquid phase polypropylene which does not participate in the reaction form a gas-solid mixture through gasification and flash evaporation of propylene, and then separation of the polypropylene powder and the gas phase propylene is realized by utilizing equipment such as a bag filter, a cyclone separator and the like. In order to ensure continuous flash evaporation and gasification, a jacketed pipe is generally arranged on a pipeline for steam tracing. The gas-phase propylene obtained by separation is compressed and condensed by a propylene compressor to obtain liquid-phase propylene, and the liquid-phase propylene enters a reactor for recycling. As mentioned above, this process has the following drawbacks:
1) the unreacted liquid phase propylene needs a large amount of steam heat tracing and cooling water condensation liquefaction in the cyclic process of gasification, flash evaporation, compression and condensation, which results in a large amount of public engineering consumption;
2) the separation of the propylene powder and the gasified propylene gas needs to be provided with a plurality of filters and separators, so that the equipment investment cost is high, the process flow is long, and the operation unreliability of the device is increased;
3) the compression of a large amount of circulating propylene gas requires a large compressor capacity, and the equipment investment cost is high; at the same time, the compression of a large amount of propylene gas consumes a large amount of electrical energy.
Disclosure of Invention
The invention aims to provide a polypropylene production process and a device thereof aiming at the defects in the prior art so as to shorten the prior process flow and reduce the consumption of heat tracing steam, cooling water and electric energy.
The technical scheme for realizing the aim of the invention is as follows: the polypropylene production process comprises the following steps:
1) in a liquid phase reaction system, polymerizing liquid phase propylene under the action of a catalyst to generate a solid-liquid mixture containing polypropylene particles and unreacted liquid propylene;
2) introducing a solid-liquid mixture generated in the polymerization reaction (step 1) into a pressure separation system for solid-liquid separation under the condition of not carrying out other solid-liquid separation to obtain a filtrate mainly composed of liquid propylene and a solid separation material (or called filter residue) mainly composed of polypropylene, wherein a small amount of hydrogen can be discharged together with the filtrate;
3) the filtrate obtained by the solid-liquid separation (step 2) is used as a feed for circulating propylene and is sent to a liquid phase reaction system to be used as a propylene raw material, if a small amount of hydrogen is also obtained in the solid-liquid separation process, the hydrogen obtained by the solid-liquid separation (step 2) can also be sent to the liquid phase reaction system;
4) feeding the solid-liquid separated material (step 2) into a steaming system for steaming to remove liquid, and feeding the steamed material into a drying system for drying to obtain dry powder, namely homopolymerized polypropylene powder; or sending the solid separation material obtained in the solid-liquid separation (step 2) into a fluidized reaction system for producing the polypropylene copolymer.
And 3, sending the hydrogen into a liquid phase reaction system through a hydrogen circulating compressor.
In step 3, the feed recycled propylene and fresh propylene are fed, with or without intermixing, to the propylene feed pump of the liquid phase reaction system.
In step 4, the solid separation material is steamed to further remove liquid, and then the steamed solid separation material is dried by heated inert gas to obtain the dry powder material.
Other solid-liquid separation such as gasification, flash evaporation and the like is not needed in the whole production process.
The liquid phase reaction system may consist of one or more liquid phase reactors in series.
The liquid phase reactor is preferably a loop reactor or the like.
The polymerization conditions of the liquid phase reactor can be that the polymerization temperature is 45 ℃ and ~ 120 ℃ and the polymerization pressure is 1.85MPa and ~ 5.65.65 MPa;
the pressure separation system preferably employs a rotary drum type pressure filter (may be simply referred to as a rotary drum type pressure filter).
The operating temperature of the drum filter is 45 ℃ ~ 150 ℃, the operating pressure is 1.85MPa ~ 5.65.65 MPa, the filtering pressure difference is 0.01MPa ~ 1.0.0 MPa, and the rotating speed is 0.3 ~ 10.0.0 r/min.
The drum-type pressure filter is characterized in that a filtering area, a liquid removing area, a discharging area and a regeneration area are sequentially arranged in the drum-type pressure filter, pressure filtering separation of solid-liquid mixture is carried out in the filtering area to form filtrate and filter cakes (solid separation materials accumulated into cakes), liquid removing is carried out on the filter cakes in the liquid removing area by liquid removing gas, the filter cakes after liquid removing are output in the discharging area through a discharging pipeline, and a filtering medium of the filter is cleaned and regenerated in the regeneration area by cleaning liquid.
The filter cake is preferably subjected to liquid removal by using gas-phase propylene compressed by a propylene compressor as a liquid removal gas. The liquid removal may be one liquid removal or a plurality of liquid removal, for example, preferably twice liquid removal.
The unreacted propylene contained in the filter cake only accounts for 2 to 15 percent of the unreacted propylene;
a sealed discharging device can be arranged on a discharging pipeline of the rotary drum type pressure filter, sealed discharging is carried out through the sealed discharging device, and the back pressure of the filter is guaranteed.
Steaming of the solid separated material may be performed using a steamer.
The operating pressure range of the steamer is from normal pressure to 1.0MPa, the entrainment amount of propylene in the solid separation material entering the steamer is from 0.5 percent to 15 percent, and the preferential range is 2.0 ~ 8.0.0 percent, and the gas formed by steaming enters a propylene circulating system as circulating propylene gas.
Introducing a filtrate from the pressure separation system into a propylene feed tank, introducing a purge effluent of a filter medium of the filter into the propylene feed tank, introducing fresh liquid-phase propylene for supplementing a propylene raw material into the propylene feed tank, mixing the liquids introduced into the propylene feed tank, and connecting to a propylene feed pump of a liquid-phase reaction system.
And the gas (gas-liquid mixture) after liquid removal discharged by the liquid removal of the filter can be condensed, and the condensed propylene liquid obtained by condensation is introduced into a propylene feeding tank.
The propylene feeding tank is provided with a stirrer.
The operating pressure of the propylene feed tank is 1.85MPa ~ 5.5.5 MPa and the operating speed of the stirrer is 5.0 ~ 100rpm, preferably 10 ~ 50 rpm.
The sealed blanking device adopts a rotary blanking valve.
The rotary blanking valves are in one-stage or multi-stage, and all rotary blanking valves in the multi-stage rotary blanking valves are sequentially arranged on the discharging pipeline.
A polypropylene production apparatus comprising a liquid phase reaction system for propylene polymerization, further comprising:
the pressure separation system is used for carrying out solid-liquid separation on a liquid-solid mixture formed after propylene polymerization reaction to form filtrate and solid separation materials, and is provided with a continuous working drum type pressure filter, a feed pipe of the drum type pressure filter is connected with a discharge pipe of the liquid phase reaction system, no solid-liquid separation device is arranged between the liquid phase reaction system and the pressure separation system, the solid-liquid separation is carried out on the discharge material (solid-liquid mixture) of the liquid phase reaction system by the drum type pressure filter under the condition of no other solid-liquid separation, a sealed discharging device is arranged on a discharging and discharging pipeline of the drum type pressure filter, and the solid material (solid separation material after liquid removal) is output by adopting a sealed discharging mode;
the propylene supply system is used for supplying or supplementing liquid phase propylene raw materials to the liquid phase reaction system, and is provided with a propylene supply tank, a filtrate output pipe and a cleaning discharge liquid output pipe of the rotary drum type pressure filter are connected into the propylene supply tank, the propylene supply tank is used for recovering liquid phase propylene discharged by each part of the device, fresh liquid phase propylene is mixed with the recovered liquid phase propylene, and formed mixed propylene liquid is used as the liquid phase propylene raw materials of the reaction system;
the system comprises a steaming system and/or a fluidized reaction system, wherein the steaming system is provided with a steamer and is used for steaming solid materials (liquid-removed solid separation materials) output by a pressure separation system so as to further remove liquid, the fluidized reaction system is used for polypropylene copolymerization reaction and is provided with a fluidized bed reactor, and the solid materials output by a discharge pipeline of a rotary drum type pressure filter are sent into the steamer and/or the fluidized bed reactor;
the steaming system is matched with a polypropylene drying system and is used for drying steamed solid materials, a dryer is arranged, the solid materials output by the steaming system are connected into the dryer, and the dry powder output by the dryer is corresponding homopolymerized polypropylene powder (product);
the propylene circulating system is used for cyclic utilization of propylene and is provided with a propylene compressor, an inlet of the propylene compressor is connected with a propylene gas output pipeline of the steaming system and/or a propylene gas output pipeline of the fluidized reaction system, an outlet of the propylene compressor is connected with a liquid removal gas input pipe of the rotary drum type pressure filter and/or a condensation inlet (an inlet of a condensed medium) of a condensation heat exchanger, and a condensate output pipeline of the condensation heat exchanger is connected into the propylene feed tank.
The drum-type pressure filter is internally provided with a filtering area, a liquid removing area, a discharging area and a regeneration area which are sequentially arranged, pressure filtration of solid-liquid mixture is carried out in the filtering area to form filtrate and filter cakes, liquid removal is carried out on the filter cakes in the liquid removing area by liquid removing gas, the filter cakes after liquid removal are output in the discharging area through a discharging pipeline, and cleaning and regeneration are carried out on a filtering medium in the regeneration area by cleaning liquid.
The drum type pressure filter is provided with a liquid removing gas input pipe, a cleaning liquid input pipe, a liquid removing gas output pipe, a filtrate output pipe, a cleaning discharge liquid output pipe and a discharge pipeline, and is provided with or not provided with a discharge back-blowing gas input pipe.
And the liquid removing gas input pipe of the rotary drum type pressure filter is used for connecting liquid removing gas, is connected with a propylene pipeline at the outlet side of the propylene compressor, and removes liquid from a filter cake in the filter by taking the pressurized propylene gas as the liquid removing gas.
The cleaning liquid input pipe of the rotary drum type pressure filter is used for connecting fresh liquid phase propylene used as cleaning liquid to clean the filter medium of the filter.
The discharge back-blowing gas input pipe of the rotary drum type pressure filter is used for accessing discharge back-blowing gas, is connected with a propylene pipeline at the outlet side of the propylene compressor, and takes the pressurized propylene gas as the back-blowing gas during discharging.
And the liquid-removed gas output pipe of the rotary drum type pressure filter is used for outputting a gas-liquid mixture generated by liquid removal, and propylene in the gas-liquid mixture is condensed into propylene condensate through the condensing heat exchanger to be reused in a liquid phase reaction system as a source of a propylene raw material.
The filtrate outlet line of the drum filter is used for outputting filtrate which can be used as a feed for circulating propylene to the liquid phase reaction system as a source of propylene raw material.
The discharge pipeline of the rotary drum type pressure filter is used for outputting solid separation materials after liquid removal, and after the solid separation materials are subjected to subsequent steaming and drying, the formed dry powder is polypropylene powder (product), and can also be directly used in a fluidized reaction system as a copolymerization raw material;
and a liquid-removed gas output pipe of the rotary drum type pressure filter is connected to a condensation inlet of the condensation heat exchanger so as to realize condensation of the gaseous propylene.
The rotary drum type pressure filter is provided with one-time liquid removal or multiple-time liquid removal. For example, preferably, the drum-type filter press is provided with twice liquid removal, the liquid removal gas input pipeline comprises a primary liquid removal gas input pipe and a secondary liquid removal gas input pipe, and the secondary liquid removal gas input pipe is positioned at the subsequent stage of the primary liquid removal gas input pipe, namely, the primary liquid removal gas is firstly introduced into a filter cake in the filter unit for carrying out primary liquid removal, and then the secondary liquid removal gas is introduced into the filter cake for carrying out secondary liquid removal in the rotating process of the drum.
The sealed blanking device can adopt a rotary blanking valve.
The rotary blanking valve is one-stage or multi-stage.
Each stage of rotary blanking valves in the multi-stage rotary blanking valves are sequentially arranged on the discharging pipeline.
The filter medium of the rotary drum type pressure filter can be filter cloth made of metal materials and nonmetal materials.
The condensing heat exchanger can adopt cooling water as a condensing medium, is a water-cooled condenser and is provided with a cooling water supply pipe and a cooling water return pipe.
The propylene feeding tank is provided with a feeding tank stirrer, and the feeding tank stirrer can adopt an electric stirrer.
The steamer may be provided with a steamer stirrer, which may be an electric stirrer.
The liquid phase reaction system may consist essentially of one or more liquid phase reactors in series.
The liquid phase reactor is preferably a loop reactor or a vertical stirred reactor.
The liquid phase reaction system is provided with a catalyst inlet.
When the liquid phase reaction system mainly comprises a plurality of liquid phase reactors connected in series, the catalyst inlet is arranged on at least the first liquid phase reactor.
And a top gas outlet of the propylene feed tank is connected into a liquid phase reactor in the liquid phase reaction system through a hydrogen circulating compression pump.
The invention has the following beneficial effects:
1) according to the invention, through the device and the process flow, the production conditions of homo-polypropylene or co-polypropylene powder are met, and through the addition and adjustment of related equipment, the separation method after the traditional liquid phase reaction is changed, the separation efficiency of the device is improved, and the one-time investment and the operation cost of the device are obviously reduced;
2) the pressure separation system is arranged to replace the liquid-phase propylene gasification and flash evaporation process in the prior art, and the polypropylene powder and the unreacted liquid-phase polypropylene are separated, so that the energy required by the liquid-phase propylene gasification and flash evaporation in the prior art is saved;
3) a propylene circulating gas compressor is arranged to boost the pressure of trace propylene entrained in propylene powder, and part of high-pressure propylene gas is used for removing liquid from a filter cake of a pressure separator to reduce the entrainment of propylene in the filter cake; the other part is condensed and then circularly enters a reaction system for use;
4) the production process and the device of the polypropylene can obviously reduce the running cost and the investment cost of the device from the following 4 aspects:
a) heating energy required by the gasification and flash evaporation of the propylene after the reaction is completely saved;
b) the circulating flow of the gas propylene is greatly reduced, and the energy consumption in the compression process and the condensation process is saved;
c) the delivery lift of the propylene feed pump is greatly reduced, and the energy consumption in the conveying process is saved;
d) the equipment such as a separator, a filter and the like in the original process are eliminated, the rated capacity of the equipment such as a propylene compressor, a propylene feed pump, a steaming system and the like is obviously reduced, and the one-time investment of the device is reduced.
The invention uses the pressure separation technology to replace the traditional bulk method (bulk-gas phase method) process which uses gasification and flash evaporation to realize the separation process, and simultaneously greatly reduces the circulating flow of gas propylene in the device.
The invention is also suitable for the slurry method polyethylene production process or other similar occasions, wherein the liquid phase reaction system which is correspondingly produced is adopted in the liquid phase reaction system, and the same effect can be achieved.
Drawings
FIG. 1 is a block diagram of the equipment configuration and process flow of the present invention;
FIG. 2 is a schematic diagram of the apparatus configuration and process flow of the present invention.
Detailed Description
Referring to fig. 1 and 2, this propylene production apparatus includes:
a liquid-phase reaction system 10 for liquid-phase homopolymerization;
a pressure separation system 20 for separating, removing, discharging and sealing the polypropylene powder and the propylene liquid;
a fluidized bed reaction system (or called fluidized reaction system) 30 for realizing the copolymerization reaction of the polypropylene copolymer and other monomers to produce the polypropylene copolymer;
a steaming system 40 for pre-drying the polypropylene;
a propylene recycle system 50 for recovery and recycle of propylene and other monomers;
a polypropylene drying system 60;
a propylene feed system 70.
The working process is as follows:
the prepared catalyst is injected into a liquid phase reactor (liquid phase bulk reactor) 12 through a catalyst inlet 11 of a liquid phase reaction system 10, and a liquid phase propylene pump 75 of a propylene supply system 70 is used to pump the liquid phase propylene into the reactor 12, and the liquid phase propylene is polymerized in the liquid phase reactor 12 in the presence of a certain amount of hydrogen to produce homopolypropylene.
The prepared catalyst and the solvent have homopolymerization reaction with propylene in a liquid phase reaction system, and the reactor for polymerization is any reactor which can meet the requirements of full mixing and reaction cooling, including a stirring reactor, a loop reactor and the like; the powder (tiny particle) polypropylene generated by the reaction and the unreacted liquid phase propylene form a liquid-solid mixture, the obtained liquid-solid mixture of the polypropylene and the propylene enters a pressure separation system under the action of the self pressure, and the process and equipment for separating the unreacted liquid phase propylene and hydrogen are not required to be arranged in the middle of the system, and the process of gasification and flash evaporation are not required.
The generated polypropylene powder is separated from the unreacted liquid-phase polypropylene by the drum-type pressure filter 21 in the pressure separation system 20 to obtain propylene liquid (filtrate containing trace hydrogen) and polypropylene powder (filter cake containing a small amount of liquid-phase propylene), or other suitable pressure filtration or solid-liquid separation equipment can be used to replace the drum-type pressure filter to realize the required solid-liquid separation, and the unreacted liquid-phase polypropylene enters the propylene feeding tank 71 in the propylene feeding system 70.
Meanwhile, the solid phase polypropylene powder (solid separation material, which is in a cake shape in the filter and can be called as a filter cake) in the drum type pressure filter is subjected to liquid removal by using high-pressure and high-temperature propylene gas in the propylene circulating system 50; the solid-phase polypropylene powder is decompressed by a sealing and blanking device 22 and then sent out for entering the subsequent process.
The solid-phase polypropylene powder output by the pressure separation system can enter a steaming system 40 to finally obtain the homo-polypropylene powder; and/or, the polypropylene copolymer powder is finally obtained after entering the fluidized reaction system 30:
a) the solid-phase polypropylene powder from the pressure separation system 20 can be directly fed into the fluidized bed reactor 31 of the fluidized reaction system 30 as required, the copolymerization reaction is carried out in the fluidized bed reactor 31 by adopting a process technology well known in the art, the solid-phase polypropylene powder is fed into a subsequent process through a polypropylene copolymer discharge 33, the tail gas treatment unit 32 of the fluidized reaction system can adopt the prior art, and the discharged propylene gas is compressed by a propylene compressor 51 in a propylene circulation system 50 and condensed by a cooling heat exchanger 52, and then is conveyed into a propylene feed tank 71 of a propylene feed system 70 by a propylene conveying pump 53.
b) If the polypropylene powder from the pressure separation system 20 enters the steaming system 40, a process flow known in the art, such as a Spheripol process, is adopted, propylene entrained in the polypropylene powder is removed in the steamer 41 under the action of steam and a steamer stirrer 42, a steam distributor is arranged in the steamer and the steamer stirrer with multiple layers of blades is arranged, and the propylene entrained in the polypropylene powder is removed by heating with the steam under the stirring action of the steamer stirrer; then, the steaming treatment unit 43 is utilized to condense the steam in the steaming tail gas to separate out pure hydrocarbon monomers, so that the hydrocarbons in the tail gas can be completely recycled, and the consumption of the monomers is reduced; the hydrocarbons in the tail gas are compressed by a propylene compressor 51 in the propylene circulating system 50 and condensed by a cooling heat exchanger, and then are conveyed to a propylene feeding system 70 by a propylene conveying pump 53.
The polypropylene powder obtained from the steaming unit 40 enters a polypropylene drying system 60 and is dried to obtain the homopolypropylene powder by a process known in the art. The drying system may employ a process known in the art and may be provided with a dryer 61, and the obtained dry polypropylene powder is output through a homo-polypropylene discharge port 62 for further processing in a further processing unit.
The gas phase mixture from the top of the steamer can be treated by the existing process, and the obtained propylene gas is compressed and condensed by a propylene circulating system and then is conveyed to a propylene feeding tank.
The circulating gas from the top of the fluidized bed reactor can be treated by the prior art, and the separated hydrocarbon gas is compressed by a propylene circulating system, condensed and liquefied and then conveyed to a propylene feeding system.
In the process of treating the solid-liquid mixture output from the liquid phase reaction system, propylene recovered from each process step is collected in a propylene feed system, and the recovered liquid phase propylene is mixed with fresh propylene from a fresh liquid phase propylene input pipe 74 in a propylene feed tank and then is sent to the liquid phase reaction system by a propylene feed pump 75 for recycling.
The propylene feed tank is provided with a stirrer 72 to prevent the deposition of entrained polypropylene powder in the liquid.
The gas (mainly hydrogen) at the top of the propylene feed tank in the propylene feed system is compressed by a hydrogen compressor 73 and then enters the liquid phase reaction system for recycling.
Claims (10)
1. The polypropylene production process comprises the following steps:
in a liquid phase reaction system, polymerizing liquid phase propylene under the action of a catalyst to generate a solid-liquid mixture containing polypropylene particles and unreacted liquid propylene;
introducing a solid-liquid mixture generated by polymerization reaction into a pressure separation system for solid-liquid separation under the condition of not carrying out other solid-liquid separation to obtain a filtrate mainly composed of liquid propylene and a solid separation material mainly composed of polypropylene;
circulating propylene by taking a filtrate obtained by solid-liquid separation as a feed, and sending the feed into a liquid phase reaction system to be used as a propylene raw material;
feeding a solid separation material obtained by solid-liquid separation into a steaming system for steam removal of liquid, and feeding the steamed material into a drying system for drying to obtain dry powder, namely homo-polypropylene powder; or sending the solid separation material obtained by solid-liquid separation into a fluidized reaction system for producing the polypropylene copolymer.
2. The polypropylene production process according to claim 1, wherein the pressure separation system comprises a drum filter press, the drum filter press comprises a filtering zone, a liquid removing zone, a discharging zone and a regeneration zone, the filtering zone is sequentially provided with a filtering zone, a liquid removing zone, a discharging zone and a regeneration zone, the filtering zone is used for pressure filtering and separating the solid-liquid mixture to form filtrate and filter cake, the liquid removing zone is used for removing liquid from the filter cake with liquid removing gas, the discharging zone is used for outputting the filter cake after liquid removing through a discharging pipeline, and the regeneration zone is used for cleaning and regenerating the filtering medium of the filter press by using cleaning liquid.
3. The polypropylene production process according to claim 2, wherein the filter cake is subjected to liquid removal by using vapor phase propylene compressed by a propylene compressor as a liquid removal gas, a discharge pipeline of the rotary drum type filter press is provided with a sealed discharging device, sealed discharging is performed through the sealed discharging device, and steaming of the solid separation material is performed by using a steamer.
4. The process for producing polypropylene according to claim 1, wherein the liquid phase reaction system comprises one or more liquid phase reactors connected in series.
5. The polypropylene production process according to any one of claims 1 to 4, wherein the filtrate from the pressure separation system is introduced into a propylene feed tank, the purge effluent of the filter medium of the filter is introduced into the propylene feed tank, fresh liquid phase propylene for supplementing the propylene raw material is introduced into the propylene feed tank, the liquids introduced into the propylene feed tank are mixed, and a propylene feed pump of the liquid phase reaction system is connected.
6. A polypropylene production apparatus comprising a liquid phase reaction system for propylene polymerization, characterized by further comprising:
the pressure separation system is used for carrying out solid-liquid separation on a liquid-solid mixture formed after propylene polymerization reaction to form filtrate and solid separation materials, and is provided with a continuously working drum type pressure filter, a feed pipe of the drum type pressure filter is connected with a discharge pipe of the liquid phase reaction system, no solid-liquid separation device is arranged between the liquid phase reaction system and the pressure separation system, the solid-liquid separation is carried out on the discharge material of the liquid phase reaction system by the drum type pressure filter under the condition that other solid-liquid separation is not carried out, and a discharge pipeline of the drum type pressure filter is provided with a sealed blanking device;
the propylene supply system is used for supplying or supplementing liquid phase propylene raw materials to the liquid phase reaction system, and is provided with a propylene supply tank, a filtrate output pipe and a cleaning discharge liquid output pipe of the rotary drum type pressure filter are connected into the propylene supply tank, the propylene supply tank is used for recovering liquid phase propylene discharged by each part of the device, fresh liquid phase propylene is mixed with the recovered liquid phase propylene, and formed mixed propylene liquid is used as the liquid phase propylene raw materials of the reaction system;
the system comprises a steaming system and/or a fluidized reaction system, wherein the steaming system is provided with a steamer and is used for steaming solid materials output by a pressure separation system so as to further remove liquid, the fluidized reaction system is used for polypropylene copolymerization reaction and is provided with a fluidized bed reactor, and the solid materials output by a discharge pipeline of a rotary drum type pressure filter are sent into the steamer and/or the fluidized bed reactor;
the steaming system is matched with a polypropylene drying system and is used for drying steamed solid materials, a dryer is arranged, the solid materials output by the steaming system are connected into the dryer, and the dry powder output by the dryer is corresponding homopolymerized polypropylene powder;
the propylene circulating system is used for cyclic utilization of propylene and is provided with a propylene compressor, an inlet of the propylene compressor is connected with a propylene gas output pipeline of the steaming system and/or a propylene gas output pipeline of the fluidized reaction system, an outlet of the propylene compressor is connected with a liquid removal gas input pipe of the rotary drum type pressure filter and/or a condensation inlet of a condensation heat exchanger, and a condensate output pipeline of the condensation heat exchanger is connected to the propylene feed tank.
7. The apparatus for producing polypropylene according to claim 6, wherein the liquid removing gas inlet pipe of the rotary drum type pressure filter is used for introducing liquid removing gas, and is connected to an outlet side propylene pipe of the propylene compressor, pressurized propylene gas is used as the liquid removing gas to remove liquid from the filter cake in the filter, and the cleaning liquid inlet pipe is used for introducing fresh liquid phase propylene used as a cleaning liquid to clean the filter medium of the filter, and the discharge back-blowing gas inlet pipe is used for introducing discharge back-blowing gas, and is connected to the outlet side propylene pipe of the propylene compressor, and pressurized propylene gas is used as the back-blowing gas during discharge.
8. The polypropylene production apparatus according to claim 7, wherein the drum type pressure filter is provided with two times of liquid removal, and the liquid removal gas feed line comprises a primary liquid removal gas feed line and a secondary liquid removal gas feed line, the secondary liquid removal gas feed line being positioned in the subsequent stage of the primary liquid removal gas feed line.
9. The polypropylene production apparatus according to claim 8, wherein the sealing and discharging device employs a rotary discharging valve, and the condensing heat exchanger employs cooling water as a condensing medium and is a water-cooled condenser.
10. The polypropylene production apparatus according to any one of claims 6 to 9, wherein the liquid phase reaction system consists essentially of one or more liquid phase reactors connected in series, the liquid phase reactor being a loop reactor or a vertical stirred reactor.
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