CN112812206B - Device and method for producing polyvinyl chloride by multi-kettle continuous polymerization - Google Patents
Device and method for producing polyvinyl chloride by multi-kettle continuous polymerization Download PDFInfo
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- 238000006116 polymerization reaction Methods 0.000 title claims abstract description 357
- 229920000915 polyvinyl chloride Polymers 0.000 title claims abstract description 88
- 239000004800 polyvinyl chloride Substances 0.000 title claims abstract description 88
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 33
- 239000002002 slurry Substances 0.000 claims abstract description 62
- 239000002245 particle Substances 0.000 claims abstract description 43
- 238000010992 reflux Methods 0.000 claims abstract description 38
- 238000007599 discharging Methods 0.000 claims abstract description 34
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 114
- 239000003999 initiator Substances 0.000 claims description 45
- 239000000498 cooling water Substances 0.000 claims description 31
- 239000002270 dispersing agent Substances 0.000 claims description 30
- 238000006243 chemical reaction Methods 0.000 claims description 27
- 239000003795 chemical substances by application Substances 0.000 claims description 24
- 238000011010 flushing procedure Methods 0.000 claims description 23
- 239000000178 monomer Substances 0.000 claims description 21
- 239000007788 liquid Substances 0.000 claims description 19
- 238000004140 cleaning Methods 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 11
- 239000011248 coating agent Substances 0.000 claims description 10
- 238000000576 coating method Methods 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 9
- 238000000926 separation method Methods 0.000 claims description 7
- 238000005086 pumping Methods 0.000 claims description 6
- 239000012066 reaction slurry Substances 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 29
- 230000008569 process Effects 0.000 abstract description 24
- 239000002351 wastewater Substances 0.000 abstract description 19
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 52
- 239000012752 auxiliary agent Substances 0.000 description 21
- 239000000047 product Substances 0.000 description 19
- 239000002518 antifoaming agent Substances 0.000 description 12
- 238000010438 heat treatment Methods 0.000 description 9
- 239000007787 solid Substances 0.000 description 9
- 229920005989 resin Polymers 0.000 description 8
- 239000011347 resin Substances 0.000 description 8
- 238000010557 suspension polymerization reaction Methods 0.000 description 8
- 239000000654 additive Substances 0.000 description 7
- 239000011164 primary particle Substances 0.000 description 7
- 230000000996 additive effect Effects 0.000 description 6
- 230000001276 controlling effect Effects 0.000 description 6
- 238000010612 desalination reaction Methods 0.000 description 6
- 239000008188 pellet Substances 0.000 description 6
- 238000012662 bulk polymerization Methods 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- 239000007791 liquid phase Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 239000007921 spray Substances 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 239000006286 aqueous extract Substances 0.000 description 4
- 238000007720 emulsion polymerization reaction Methods 0.000 description 4
- 239000012452 mother liquor Substances 0.000 description 4
- 239000004014 plasticizer Substances 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000003039 volatile agent Substances 0.000 description 4
- 230000001133 acceleration Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- 238000011437 continuous method Methods 0.000 description 3
- 238000010924 continuous production Methods 0.000 description 3
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 3
- 239000004615 ingredient Substances 0.000 description 3
- 238000007689 inspection Methods 0.000 description 3
- 230000002045 lasting effect Effects 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
- 238000011033 desalting Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 230000000379 polymerizing effect Effects 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- -1 sodium alkyl sulfonate Chemical class 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- 229920001730 Moisture cure polyurethane Polymers 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 238000006065 biodegradation reaction Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
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- 239000000701 coagulant Substances 0.000 description 1
- 238000010960 commercial process Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000003995 emulsifying agent Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 238000010907 mechanical stirring Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002609 medium Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000010526 radical polymerization reaction Methods 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000012257 stirred material Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- 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
- C08F14/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F14/02—Monomers containing chlorine
- C08F14/04—Monomers containing two carbon atoms
- C08F14/06—Vinyl chloride
-
- 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
- C08F2/00—Processes of polymerisation
- C08F2/01—Processes of polymerisation characterised by special features of the polymerisation apparatus used
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Polymerisation Methods In General (AREA)
Abstract
The invention discloses a device and a method for producing polyvinyl chloride by multi-kettle continuous polymerization, wherein the device comprises a premixing kettle for initial polymerization and a main polymerization kettle for main polymerization, which are connected with each other, the premixing kettle is connected with an inlet of the main polymerization kettle through a large-pipe-diameter pipeline, an outlet of the main polymerization kettle is sequentially connected with a cyclone of a classification device and a rotary cyclone centrifuge through a centrifugal pump, an underflow outlet pipe of the cyclone is connected with a discharging polymerization kettle for final polymerization, and an overflow pipeline of the cyclone is connected with the premixing kettle, a reflux polymerization kettle or the main polymerization kettle. According to the invention, the current PVC intermittent polymerization process is changed through multi-kettle operation, and the large-particle PVC in the PVC slurry is separated in time, so that the small-particle PVC slurry is returned to the premixing kettle or the main polymerization kettle for continuous polymerization, thus the continuous polymerization of VCM is realized to a certain extent, the production of process wastewater is reduced, the working intensity of the intermittent operation of the polymerization kettle is lightened, and the automatic control is facilitated.
Description
Technical Field
The invention relates to the technical field of polyvinyl chloride production, in particular to a device and a method for producing polyvinyl chloride by multi-kettle continuous polymerization.
Background
Polyvinyl chloride is one of five industrial general plastics, and is polymerized by VCM through different polymerization processes, and the following four PVC polymerization production processes are mainly available in the market at present:
the first suspension polymerization is produced by the process of polyvinyl chloride with the current industrial production of more than 90%, the mechanism of the suspension polymerization is free radical polymerization, the polymerization reaction is to initiate VCM monomer by an initiator, the VCM monomer which is insoluble in water is dispersed into liquid drops under the action of strong mechanical stirring in a polymerization kettle and is suspended in an aqueous medium dissolved with a dispersing agent, each liquid drop is equivalent to a small bulk polymerization system, and the initiator dissolved in the vinyl chloride monomer is decomposed into free radicals at the polymerization temperature (45-65 ℃) to initiate VCM polymerization.
In the current industrial production, only a small part of the wastewater is recycled, most of the wastewater is treated and discharged, a large amount of wastewater cannot be recycled, water resources are wasted, and a certain pollution is caused to the environment.
Disadvantages of suspension polymerization: (1) The polymerization process has an automatic acceleration function, water and VCM are mixed under the condition of using a dispersing agent, the dispersing agent is difficult to remove from a polymerization product after the polymerization is completed, and the residual dispersing agent can influence the performance of the polymerization product; (2) The wastewater amount is large, and the centrifugal mother liquor wastewater generated by producing 1 ton of PVC is about 3-4 t.
The second is the emulsion polymerization process, which is one of the earliest commercial processes for producing PVC. In emulsion polymerization, in addition to water and vinyl chloride monomer, surfactant such as sodium alkyl sulfonate is added as emulsifier to disperse the monomer into water phase to form emulsion, water soluble potassium persulfate or ammonium persulfate is used as initiator, and the polymerized product is emulsion with particle size of 0.05-2 microns and may be used directly or spray dried to form powdered resin.
The disadvantages of this method are: the polymer separation and precipitation process is complicated, and demulsifier or coagulant is required to be added; the wall of the reactor and the pipeline are easy to be glued and blocked; the variety of the auxiliary agent is large, the dosage is large, so that the residual impurities in the product are large, and the physical properties of the product can be influenced if the washing and the removal are not clean.
The third is a bulk polymerization method, the polymerization device is special, and compared with suspension polymerization and emulsion polymerization, the main characteristic is that the reaction does not need to add dispersing agent and initiator, and the bulk polymerization is carried out in two stages. The monomer and the initiator are pre-polymerized in a pre-polymerization kettle for a certain time to generate seed particles, the conversion rate reaches 8% -10%, and then the seed particles flow into a second-stage polymerization kettle, the monomer with the same amount as the pre-polymer is added, and the polymerization is continued. And (3) when the conversion rate reaches 85% -90%, discharging residual monomers, and then crushing and sieving to obtain a finished product. The particle size and shape of the resin are controlled by the stirring speed, and the reaction heat is brought out by the reflux condensation of the monomer.
Disadvantages of bulk polymerization: the thermal effect is relatively large, the automatic acceleration effect causes the product to have bubbles and color change, and when serious, the temperature is out of control, so that the explosion is caused, and the difficulty of reaching standards of the product is increased. Because the viscosity of the system is continuously increased along with polymerization, the mixing and heat transfer are difficult, and the phenomenon of automatic acceleration of the polymerization rate can sometimes occur, if the control is improper, the polymerization is initiated; the molecular weight distribution of the product is wide, unreacted monomers are difficult to remove, and the mechanical properties of the product are poor.
The fourth is solution polymerization, which is initiated by dissolving the VCM monomer in an organic solvent (e.g., n-butane or cyclohexane) and the polymer precipitates as the reaction proceeds.
Disadvantages of the solution polymerization process: the monomer is diluted by the solvent, the polymerization rate is slow, and the molecular weight of the product is low; the recovery treatment process of the solvent has high requirements and low equipment utilization rate, so that the cost is increased; the use of solvents causes environmental pollution problems.
Except for the suspension polymerization process, all three processes can realize continuous polymerization production, but emulsion polymerization, solution polymerization and bulk polymerization have various disadvantages.
The disadvantages of the centrifugal mother liquor wastewater of the suspension polymerization process of suspension polymerization are: (1) The water quantity is large, and the centrifugal mother liquor is produced by about 3-4 tons per 1 ton of PVC; (2) lower hardness and chloride (Cl-) concentration; (3) The turbidity is high, the mass concentration of suspended substances is 30-00 mg/L, and the suspended substances are mainly PVC particles; (4) The concentration of the organic matters is low, CODcr is generally 100-400 mg/L, and the wastewater belongs to low-concentration chemical wastewater; (5) The components are complex, and the traditional biodegradation method is difficult to process.
In view of the above, in order to make the most of the polymerization system, reduce the waste water discharge, and reduce the desalted water and the chemical consumed per ton of PVC, it is necessary to use continuous polymerization, and to design a device and a method for producing polyvinyl chloride by continuous polymerization.
Disclosure of Invention
The invention aims to solve the technical problems that the prior equipment for producing polyvinyl chloride has lower productivity, consumed desalted water, large usage amount of auxiliary agent and more wastewater is generated.
In order to solve the technical problems, the technical scheme adopted by the invention is to provide a device for producing polyvinyl chloride by multi-kettle continuous polymerization, which comprises a premixing kettle for initial polymerization and a main polymerization kettle for main polymerization, which are connected with each other, wherein the premixing kettle is connected with an inlet of the main polymerization kettle through a large-pipe-diameter pipeline, an outlet of the main polymerization kettle is connected with a cyclone through a centrifugal pump, an outflow pipe at the bottom of the cyclone is connected with a discharging polymerization kettle for final polymerization, overflow of the cyclone can return to the premixing kettle or the main polymerization kettle, a discharging pipe is connected between an outlet of the main polymerization kettle and the centrifugal pump, the discharging pipe is a pipeline with gradient, the pipeline is connected with a flushing water pipe and an anti-sticking kettle agent pipeline, the tail end of the pipeline is connected with the centrifugal pump and is provided with a discharging port, slurry of the main polymerization kettle is separated into large-particle PVC slurry and small-particle PVC slurry after entering the cyclone, the large-particle PVC slurry enters the discharging polymerization kettle to continue the reaction, and the small-particle PVC slurry returns to the premixing kettle to participate in the batch again or the main polymerization kettle to continue the batch.
In the scheme, the number of the premixing kettles and the number of the main polymerization kettles are respectively provided with a plurality of groups of polymerization devices, wherein the premixing kettles and the main polymerization kettles are in one-to-one correspondence, and the groups of polymerization devices are mutually connected in parallel.
In the scheme, one premixing kettle is arranged, two or more main polymerization kettles are arranged, and the main polymerization kettles are connected in parallel.
In the scheme, the outer walls of the premixing kettle and the main polymerization kettle are respectively provided with a coil pipe for introducing circulating water.
In the scheme, the cyclone is also connected with a reflux polymerization kettle.
In the scheme, the bottom outlet of the reflux polymerization kettle is connected with a diaphragm pump, and the reflux polymerization kettle is also connected with a reflux liquid inlet of the premixing kettle
The invention also provides a method for producing polyvinyl chloride by the multi-kettle continuous polymerization production polyvinyl chloride device, which comprises the following steps:
cleaning the main polymerization kettle by high-pressure water, and then carrying out steam coating kettle;
adding desalted water, VCM monomer, reflux liquid, dispersant, initiator, regulator, etc. into the main polymerization kettle;
after the materials mixed and stirred in the main polymerization kettle are heated to the inflection point temperature, circulating cooling water is switched, the flow of the circulating cooling water is automatically controlled by a program, and polymerization reaction is started;
after the polymerization reaction is carried out for a certain time, the premixing kettle starts to be washed by high-pressure water, the kettle is coated, the reaction materials enter the kettle, and the temperature is raised after stirring for a certain time;
after the materials in the main polymerization kettle continue to react for a certain time, slurry in the kettle flows out from an outlet of the main polymerization kettle, is pumped into a cyclone for separation, and enters a discharge polymerization kettle, and enters a reflux polymerization kettle or a premixing kettle, and the slurry in the premixing kettle flows into the main polymerization kettle, and simultaneously a certain amount of VCM is added to keep the water-oil ratio of the slurry in the main polymerization kettle in a certain range;
after the reaction slurry in the discharging polymerization kettle is polymerized for a certain time, adding a terminator to terminate the polymerization reaction, and pumping reflux liquid containing less PVC particles into a premixing kettle or a main polymerization kettle through a diaphragm pump to participate in the polymerization reaction.
The innovation point of the invention is that:
(1) Separating a polymerization product by using a separation device, adding a terminator into slurry with higher PVC particle solid content to terminate the reaction, and adding raw materials into a polymerization kettle in batches to realize continuous polymerization of vinyl chloride and improve the productivity of the polymerization kettle;
(2) Because the reflux liquid containing desalted water and the initiator is applied to the ingredients, the consumption of desalted water and the auxiliary agent is reduced, the generation of waste water is reduced, and the consumption of the auxiliary agent is reduced;
(3) The intermittent PVC production process with polymerization kettles includes flushing, adding assistant, heating, etc. and the continuous polymerization process with several kettles has less operation strength and automatic control.
Drawings
FIG. 1 is a schematic view of the external shape of the present invention;
FIG. 2 is an enlarged schematic view of the structure of a discharge pipe at the bottom of the main polymerizer according to the present invention;
FIG. 3 is a schematic view of a first preferred embodiment of the present invention;
FIG. 4 is a schematic view of a second preferred embodiment of the present invention;
FIG. 5 is a schematic view of a third preferred embodiment of the present invention;
FIG. 6 is a schematic diagram of a fourth preferred embodiment of the present invention;
fig. 7 is a schematic view of a fourth preferred embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
The invention discloses a device and a method for producing polyvinyl chloride by multi-kettle continuous polymerization, and the technical parameters can be properly improved by a person skilled in the art by referring to the content of the invention. It is to be particularly pointed out that all similar substitutes and modifications apparent to those skilled in the art are deemed to be included in the invention and that the relevant person can make modifications and appropriate alterations and combinations of what is described herein to make and use the technology without departing from the spirit and scope of the invention.
In the present invention, unless otherwise indicated, scientific and technical terms used herein have the meanings commonly understood by one of ordinary skill in the art.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
It should be noted that in the description of the present invention, the terms "first," "second," and the like are merely used for convenience in describing the various elements and are not to be construed as indicating or implying a sequential relationship, relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.
The PVC resin produced by the suspension polymerization process is white particles with the particle size of 75-250 mu m, the outer skin of the particles is connected with primary particles or agglomerates in the particles, the distance between the primary particles or agglomerates is very small, the size of the agglomerates is 1.5-3 mu m, the agglomerates are formed by condensing more than ten primary particles, the particle size of the primary particles is 0.7 mu m, finer particles forming the primary particles are about 230nm and are formed by condensing macromolecules with the particle size of 5nm, and finally the formed PVC resin particles are formed by stacking sub-particles, agglomerates and primary particles.
The VCM polymerization reaction is finished in a polymerization kettle by an industrial suspension method, and the duration from feeding to discharging is 4-6 hours, and the whole polymerization period can be divided into an induction period, an initial polymerization period, a middle polymerization period and a later polymerization period. At the beginning of the polymerization, the chain growth rate of the monomer is slower, the polymer dissolves in the monomer, and the polymerization exotherm increases as the amount of VCM converted to PVC increases.
As shown in fig. 1, the device for producing polyvinyl chloride by multi-kettle continuous polymerization provided by the invention comprises a premixing kettle 1 and a main polymerization kettle 2, wherein the premixing kettle 1 and the main polymerization kettle 2 are connected with each other and are used for initial polymerization, a coil pipe 10 for introducing circulating water is respectively arranged on the outer walls of the premixing kettle 1 and the main polymerization kettle 2, the outlets of the premixing kettle 1 are connected with the inlet of the main polymerization kettle 2, the tops of the premixing kettle 1 and the main polymerization kettle 2 are respectively provided with a raw material inlet A, A1, the outlet of the main polymerization kettle 2 is sequentially connected with a classification device such as a cyclone 4 through a centrifugal pump 3, the cyclone 4 is connected with a discharge polymerization kettle 6 used for final polymerization, an underflow outlet E of the cyclone 4 is connected with the inlet of the discharge polymerization kettle 6, and an outlet F is arranged at the bottom of the discharge polymerization kettle 6. Stirring devices are respectively arranged at the tops of the premixing kettle 1, the main polymerization kettle 2 and the discharging polymerization kettle 6. The components of the invention are communicated through a plurality of pipelines.
The cyclone 4 is also connected with an inlet D of the reflux polymerizer 5 through a pipeline, a diaphragm pump 7 is connected with the bottom outlet of the reflux polymerizer 5, and the reflux polymerizer 5 is also connected with a reflux liquid inlet G of the premixing kettle 1 through a pipeline. The cyclone 4 is not always in an operation state, the cyclone 4 is put into operation when PVC slurry of the main polymerization kettle 2 is graded, steam is needed to spray anti-sticking agent on the cyclone 4 before the cyclone is operated for the first time, high-pressure flushing water is needed to be introduced to flush the cyclone after the cyclone is operated for a plurality of times, cleaning fluid does not enter the reflux polymerization kettle, and the anti-sticking agent is needed to be sprayed after the high-pressure flushing water.
A discharging pipe 9 is sequentially connected between an outlet C of the main polymerization kettle 2 and the centrifugal pump 3, the discharging pipe 9 is connected with a flushing water pipe and an anti-sticking kettle agent pipe, and the discharging pipe 9 is connected with the centrifugal pump 3 through a straight pipe 8 and is provided with a discharging hole W1.
As shown in FIG. 1, the invention also provides a method for producing polyvinyl chloride by the multi-kettle continuous polymerization of the polyvinyl chloride production device, which comprises the following steps:
the main polymerization kettle 2 is subjected to high-pressure cleaning and then is subjected to steam coating;
VCM monomer, reflux liquid, dispersing agent, regulator and the like are added from an inlet B of a main polymerization kettle 2;
after the stirred materials of the main polymerization kettle 2 are mixed and stirred and heated to the inflection point temperature, circulating cooling water is switched, and the flow rate of the circulating cooling water is automatically controlled by a program;
after the polymerization reaction is carried out for a certain time, the premixing kettle 1 starts to be washed, coated and proportioned, and the temperature is raised after the initiator is added to start the polymerization reaction;
after the materials in the main polymerization kettle 2 continue to react for a certain time, slurry in the kettle flows out from an outlet C of the main polymerization kettle 2, is pumped into a cyclone 4 for separation through a centrifugal pump 3, and enters a discharge polymerization kettle 6, and enters a reflux polymerization kettle 5, and simultaneously, slurry in a premixing kettle 1 flows into the main polymerization kettle 2 to keep the water-oil ratio in the main polymerization kettle 2 in a certain range;
after the reaction slurry in the discharge polymerization kettle 6 is polymerized for a certain time, the polymerization reaction is stopped after the terminator is added, and the reflux liquid of the reflux polymerization kettle 5 is pumped into the premixing kettle 1 or the main polymerization kettle 2 through the diaphragm pump 7 to participate in the batching again.
As shown in fig. 2, the discharging pipe at the bottom of the main polymerization kettle provided by the invention is matched with the production process of the invention as follows:
(1) Under the condition that the inspection of public and auxiliary equipment meets the running conditions, the operation of cleaning the polymerization kettle and coating the anti-sticking kettle agent by high-pressure water is started, the high-pressure water is opened to flush the kettle wall in the main polymerization kettle 2, hot water is circulated in the coil pipe 10 to heat the main polymerization kettle 2, the temperature of the main polymerization kettle 2 is kept at 50-80 ℃, a steam valve is opened to blow for tens of seconds, a pipeline valve of the anti-sticking kettle agent is opened, the anti-sticking kettle agent valve and the steam valve are closed after the duration of 10-15 minutes, and the high-pressure water is pumped again to flush.
(2) And (3) feeding desalted water, opening a valve of a desalted water pipeline on the top of the main polymerization kettle 2, and feeding a certain amount of desalted water.
(3) Adding an auxiliary agent, starting an auxiliary agent pump, adding a dispersing agent, a defoaming agent and a regulator, wherein the dispersing agent dosage is about 0.2-0.5% of the VCM, the defoaming agent dosage is 0.1-0.5%, and the regulator is 0.1-0.2%.
(4) And adding an initiator, wherein the amount of the initiator is 0.1-0.5%, and the initiator is a certain amount by opening a valve of an initiator pipeline at the top of the main polymerization kettle 2.
(5) And feeding VCM, opening a valve of a VCM pipeline on the top of the main polymerization kettle 2, and feeding a certain amount of VCM.
(6) Heating up, accelerating the circulation flow rate of hot water in the coil pipe 10, and increasing the liquid temperature of the main polymerization kettle 2 to 2 ℃ under the set temperature.
(7) Switching cooling water, automatically controlling by a program as the temperature rises to a set temperature, and introducing circulating cooling water at 20-30 ℃ by the program, wherein the cooling water quantity is automatically controlled by the program so as to maintain the polymerization temperature stable;
(8) After a certain period of reaction, the premixing kettle 1 is cleaned under high pressure, sprayed with an anti-sticking kettle agent, a certain amount of liquid-phase VCM is added, then a regulator, a dispersing agent, an initiator and the like are added, the dispersing agent is about 0.2% -0.5% of the VCM, the defoaming agent is about 0.1% -0.5%, the regulator is about 0.1% -0.2%, after a certain period of stirring, hot water is introduced into a coil pipe of the premixing kettle to heat the slurry, and then the polymerization reaction is started.
(9) The main polymerization kettle is polymerized, the flow rate of cooling water in the coil pipe 10 of the main polymerization kettle 2 is automatically controlled by a program, and the temperature of the main polymerization kettle 2 is controlled to be near the set temperature.
(10) And (3) discharging, after reacting for a certain time, feeding the slurry in the main polymerization kettle 2 into a discharge polymerization kettle 6 in a grading manner, discharging the slurry with higher solid content into the discharge polymerization kettle 6, and feeding the slurry with lower solid content into a reflux polymerization kettle 5.
(11) After discharging, according to the reaction condition of the premixing kettle, the slurry in the premixing kettle 1 is put into a main polymerization kettle 2, and VCM monomer is supplemented, and the water-oil ratio in the main polymerization kettle is kept within 1.1-1.5. .
(12) And (3) after 30-90 min of polymerization, adding a terminator to the slurry in the discharge polymerization kettle 6 to stop polymerization, wherein the reflux polymerization kettle can be independently matched with monomers, desalted water and auxiliary agents to independently perform polymerization reaction, and the slurry can also be returned to the premixing kettle 1 to participate in preparation of the reaction raw materials of the next batch.
The PVC pellets produced by the above apparatus were subjected to the process indexes shown in Table 1.
Table 1 technical index for producing PVC particles by continuous process
| Project | Numerical value |
| Average degree of polymerization | 1100～1000 |
| Impurity particle count (number) | 58～65 |
| Volatiles (including water) (%) | 0.5 |
| Apparent density (g/m L) | 0.40 |
| 0.25mm mesh | 6～10 |
| 0.63mm mesh | 80～83 |
| 100g resin plasticizer absorption (g) | 46～55 |
| Whiteness (160 ℃ C., after 10 min') | 70～78 |
| Conductivity of aqueous extract (s/m) | — |
Under the continuous polymerization production condition, the additive amount, the desalination water amount, the flushing water amount and the wastewater production amount of each ton of products are greatly reduced, and the specific indexes are shown in Table 2.
Table 2 Single set polymerization apparatus (48 m) 3 ) PVC ton consumption index
| Sequence number | Project | Batch polymerization | Continuous polymerization |
| 1 | Daily output (t) | ～43 | ～65 |
| 2 | Water consumption (t/t-PVC) | 3～4 | 1.5～2.5 |
| 3 | Initiator consumption (kg/t-PVC) | 2～5 | 1～5 |
| 4 | Dispersant consumption (kg/t-PVC) | 1～2 | 0.5～0.8 |
Example 1
According to the first embodiment provided by the invention, as shown in fig. 3, according to the suspension continuous polymerization process, the outlets of 1 premixing kettles 1 are connected with inlets of two main polymerization kettles 2 in parallel through Y-shaped electric valves, slurry in the premixing kettles 1 is controlled by the Y-shaped electric valves to go to the main polymerization kettles 2, the 2 main polymerization kettles 2 share a set of reflux polymerization kettles 5 and discharge polymerization kettles 6, and the outlets of the two main polymerization kettles 2 are respectively connected with a centrifugal pump 3 through two sets of discharge pipes 9 and straight pipes 8 which are configured in the same way.
The volume of the premixing kettle 1 is 30m 3 The volume of the 2 main polymerization kettles 2 is 48m 3 The volume of the reflux polymerization kettle 5 and the discharge polymerization kettle 6 is 30m 3 。
Before the first kettle is put into operation, the main polymerization kettle 2 is cleaned under high pressure, then a steam coating kettle is carried out, auxiliary agents such as dispersing agents, regulators, initiators and the like are added into the main polymerization kettle 2, after the temperature is raised, cooling water is switched to start the polymerization reaction, after the reaction is carried out for a certain time, the premixing kettle 1 starts to be washed and fed, after various reaction raw materials are added, the temperature is raised to start the polymerization, then a discharge pump 3 of the main polymerization kettle 2 is started, slurry is pumped into a cyclone 4 for classification, underflow separated by the cyclone 4 enters a discharge tank 6 to continue the polymerization, a terminator is added to terminate the polymerization reaction after a certain time of polymerization, most overflows containing less PVC particles separated by the cyclone 4 return to the main polymerization kettle 2, and a part overflows into the premixing kettle 1 to participate in the batching.
The production process comprises the following steps:
(1) After the main polymerization kettle 2 is washed and coated, under the condition that the inspection of public and auxiliary equipment meets the operation condition, the temperature of the main polymerization kettle 2 is kept at 50-80 ℃, a steam valve and an anti-sticking kettle agent valve are opened, the valve is closed after 10-15 min, and after half an hour of delay, the other main polymerization kettle 2 starts to be washed, coated and the like.
(2) And (3) feeding water, opening a desalted water pipeline valve at the top of the main polymerization kettle 2, and adding 20-23 t of desalted water.
(3) Adding an auxiliary agent, starting an auxiliary agent pump, adding a dispersing agent, a defoaming agent, a regulator and an initiator, wherein the dispersing agent dosage is about 0.2-0.5% of the VCM, the defoaming agent dosage is 0.05-0.1%, and the regulator is 0.1-0.2%.
(4) Initiator was added and the top initiator line valve of the main polymerizer 2 was opened and an initiator solution of about 0.1% of the amount of VCM was added.
(5) Feeding VCM, opening a VCM pipeline valve at the top of the main polymerization kettle 2, adding 18-20 t of VCM, and increasing the stirring speed for 15min.
(6) The temperature is raised, the circulation flow rate of hot water in the coil pipe 10 is accelerated, and the liquid temperature of the main polymerization kettle 2 is raised to 55 ℃.
(7) Switching cooling water, and automatically controlling the flow of the cooling water by a program along with the temperature rising to the inflection point temperature of 57 ℃;
(8) After 1 hour of reaction, 0.5m of the mixture was introduced into the main polymerizer 2 3 Intermediate cooling water of/h;
(9) After 2 hours of reaction, adding desalted water, dispersing agent and the like into the premixing kettle 1 to heat;
(10) After 3 hours of reaction, stopping adding intermediate cooling water, starting a centrifugal pump 3, pumping slurry in a main polymerization kettle 2 into a cyclone 4 for classification, enabling underflow of the cyclone 4 to enter a discharge polymerization kettle 6, enabling overflow of the cyclone 4 to return to enter a reflux polymerization kettle 5, stopping the centrifugal pump 3 after discharging is finished, closing a discharge valve at the bottom of the main polymerization kettle 2, closing an inlet and outlet valve of the cyclone 4, opening a flushing water valve, flushing the interior of the main polymerization kettle, and spraying anti-sticking kettle agent by steam;
(11) After the material is fed into the main polymerization kettle 2, a discharge valve at the bottom of the premixing kettle 1 is opened, slurry in the premixing kettle 1 is discharged into the main polymerization kettle 2, a VCM pipeline at the top of the main polymerization kettle 2 is opened, and a valve is closed after a certain amount of liquid phase VCM is added.
(12) And (3) feeding the slurry in the discharge polymerization kettle 6, adding a terminator after polymerization for 30-90 min, stopping polymerization, feeding the slurry into a next stripping process, and independently adding desalted water, VCM and an auxiliary agent into a reflux polymerization kettle to continue polymerization until discharge.
(13) The emptied premixing kettle 1 is opened with a VCM feeding pipe and a mother liquor return pipe again, auxiliary agents are added for batching, and polymerization reaction in the main polymerization kettle 2 is carried out for a certain time and then discharged again.
The PVC pellets produced by the above apparatus were subjected to the process indexes shown in Table 3.
Table 3 technical index for producing PVC particles by continuous process
| Project | Numerical value |
| Average degree of polymerization | 900～1000 |
| Impurity particle count (number) | 95 |
| Volatiles (including water) (%) | 0.8 |
| Apparent density (g/m L) | 0.42 |
| 0.25mm mesh | 9.2 |
| 0.63mm mesh | 75 |
| 100g resin plasticizer absorption (g) | 75 |
| Whiteness (160 ℃ C., after 10 min') | 66 |
| Conductivity of aqueous extract (s/m) | — |
Under the continuous polymerization production condition, the additive amount, the desalination water amount, the flushing water amount and the wastewater production amount of each ton of products are greatly reduced, and the specific indexes are shown in table 4.
TABLE 4 Single set continuous polymerization apparatus (48 m) 3 ) PVC ton consumption index
| Sequence number | Project | Technological index |
| 1 | Daily output (t) | ～52 |
| 2 | Water consumption (t/t-PVC) | 1.8 |
| 3 | Initiator consumption (kg/t-PVC) | 5 |
| 4 | Dispersant consumption (kg/t-PVC) | 11 |
Example 2
As shown in FIG. 4, in order to reduce the equipment amount of continuous polymerization and simplify the operation, the second embodiment provided by the invention adopts 3 main polymerization kettles 2 and 3 pre-mixing kettles with smaller volumes to realize semi-continuous polymerization, 3 main polymerization kettles 2 adopt intermittent feeding and discharging, 3 groups of polymerization devices are formed between the pre-mixing kettles 1 and the main polymerization kettles 2 in a one-to-one correspondence manner, the groups are mutually connected in parallel, 1 pre-mixing kettle serves as a discharging polymerization kettle 6,1 pre-mixing kettle serves as a standby kettle 11, the outlet of a centrifugal pump 3 is connected to the standby kettle 11, and the polymerization reaction is terminated in the discharging polymerization kettle 6.
The production process comprises the following steps:
(1) And (3) sequentially cleaning each main polymerization kettle 2 and each premixing kettle 1 by high-pressure water, sequentially opening a steam valve and an anti-sticking kettle agent valve at the top of the main polymerization kettle 2 under the condition that the inspection of public and auxiliary equipment meets the operation conditions, closing the anti-sticking kettle agent valve and the steam valve after lasting for 10-15 min, and then opening spray water for secondary cleaning.
(2) And (3) feeding water, opening a desalted water pipeline valve at the top of the main polymerization kettle 2, and feeding desalted water for 20-23 t.
(3) Adding an auxiliary agent, starting an auxiliary agent pump, adding a dispersing agent, a defoaming agent and a regulating agent, wherein the dispersing agent dosage is about 0.2% -0.5% of the VCM, the defoaming agent dosage is 0.1% -0.2%, and the regulating agent dosage is 0.1% -1%.
(4) And adding an initiator, opening an initiator pipeline valve at the top of the main polymerization kettle 2, and feeding a certain amount of initiator, wherein the amount of the initiator is 0.1-0.2%.
(5) And feeding VCM, opening a valve of a VCM pipeline at the top of the main polymerization kettle 2, and feeding the VCM of 18-20 t.
(6) Heating, namely introducing a certain amount of steam into hot water, increasing the hot water temperature of the coil 10, accelerating the circulation flow rate of the hot water in the coil of the polymerization kettle, and increasing the kettle liquid temperature to 2 ℃ under the set reaction temperature.
(7) Switching cooling water, automatically controlling by a program as the temperature rises to a set temperature, and introducing cooling water at 20-30 ℃ and automatically controlling the cooling water quantity by the program;
(8) And in the polymerization stage of the main polymerization kettle, the flow rate of cooling water in the coil pipe 10 is automatically controlled by a program, and the temperature of the main polymerization kettle 2 is controlled to be near the set temperature.
(9) After 3 hours of reaction, adding desalted water and an auxiliary agent into a premixing kettle 1 of which the coating kettle is finished, and heating after the addition is finished;
(10) And after a certain period of time is reacted, starting a centrifugal pump 3, sequentially pumping the slurry in the 3 main polymerization kettles 2 into a cyclone 4 for classification, enabling the underflow to flow into a discharge polymerization kettle 6, enabling the overflow slurry containing small particles to fully return to 1 premixing kettle, closing a discharge valve after discharging, and starting flushing water to flush the cyclone 4.
(11) And (3) placing the slurry in the premixing kettle 1 into a main polymerization kettle 2, and simultaneously supplementing a certain amount of liquid phase VCM into the polymerization kettle according to the online analysis data of the reflux slurry, and adjusting the water-oil ratio to continue the polymerization reaction.
(12) After the liquid phase VCM ingredients are added, the temperature of the premix kettle 1 for storing all the reflux liquid starts to rise, and the polymerization reaction is continued in the premix kettle 1.
(13) And (3) discharging the slurry in the polymerization kettle 6, polymerizing for 30-90 min, and then adding a terminator to stop the polymerization.
The PVC pellets produced by the apparatus described above were subjected to the process indicated in Table 5.
Table 5 technical index for producing PVC particles by continuous process
Under the continuous polymerization production condition, the additive amount, the desalination water amount, the flushing water amount and the wastewater production amount of each ton of products are greatly reduced, and the specific indexes are shown in Table 6.
TABLE 6 Multi-pot continuous polymerization apparatus (48 m) 3 ) PVC ton consumption index
| Sequence number | Project | Technological index |
| 1 | Daily output (t) | ～48 |
| 2 | Water consumption (t/t-PVC) | 1.8 |
| 3 | Initiator consumption (kg/t-PVC) | 5.5 |
| 4 | Dispersant consumption (kg/t-PVC) | 13 |
Example 3
As shown in FIG. 5, in order to accelerate the polymerization reaction and shorten the polymerization time, a composite initiator can be used to avoid the phenomenon of "flying temperature" in the polymerization reaction, so that a sectional initiator mode is adopted, a high-efficiency initiator CNP is added in a premixing kettle, a common initiator EHP is added in a main polymerization kettle 2, the addition of the high-efficiency initiator can promote the generation of primary particles in a liquid phase of VCM in a short time, the addition of the high-efficiency initiator can shorten the reaction time and improve the productivity of a single kettle, meanwhile, the process is applied to a polymerization kettle matched with a tower top condenser, a reflux condenser 12 is used for condensing the gas-phase VCM in the kettle, heat in the kettle is transferred away through circulating water, and the heat transfer area of the main polymerization kettle 2 can be increased by the reflux condenser 12. Shortens the polymerization period and improves the productivity of the polymerization kettle.
The production process comprises the following steps:
(1) After the public and auxiliary equipment checks that the operation conditions are met, checking the valve action, cleaning the polymerization kettle and the premixing kettle by high-pressure water, sequentially opening a steam valve and an anti-sticking kettle agent valve, starting the steam coating kettle, and closing the anti-sticking kettle agent valve and the steam valve after lasting 10-15 min.
(2) And (3) feeding water, opening a desalted water pipeline valve at the top of the main polymerization kettle 2, and feeding desalted water for 20-23 t.
(3) Adding an auxiliary agent, starting an auxiliary agent pump, adding a dispersing agent, a defoaming agent, a regulator and an initiator, wherein the dispersing agent dosage is about 0.2-0.5% of the VCM, the defoaming agent dosage is 0.1-0.2%, the regulator is 0.1-1%, and the initiator dosage is 0.1-0.5%.
(4) Feeding VCM, opening a valve of a VCM pipeline at the top of the main polymerization kettle 2, feeding the VCM for 18-20 t, and stirring for 10-20 min after the material is added.
(5) And opening an initiator pipeline valve at the top of the main polymerization kettle 2, and adding 10 kg-20 kg of common initiator solution.
(6) Heating, namely, introducing a certain amount of steam into hot water, increasing the temperature of the hot water of the coil pipe 10, accelerating the circulation flow rate of the hot water in the coil pipe 10, and increasing the liquid temperature of the main polymerization kettle 2 to 2 ℃ under the set temperature.
(7) Switching cooling water, automatically controlling by a program as the temperature rises to a set temperature, and introducing circulating cooling water at 20-30 ℃ into the jacket of the main polymerization kettle, wherein the cooling water quantity is automatically controlled by a temperature control program;
(8) After a certain period of reaction, opening an intermediate cooling water valve, and introducing intermediate cooling water into the main polymerization kettle, wherein the flow is 1-2 m 3 And (h) simultaneously starting circulating water of a condenser on the top of the main polymerization kettle 2, wherein the circulating water flow is automatically controlled by a program;
(9) And (3) performing polymerization preparation of the premixing kettle 1, starting to coat the kettle, cleaning with high-pressure water, adding desalted water, a dispersing agent and a high-efficiency initiator CNP, stirring for 20min, and heating to the reaction temperature to perform polymerization reaction.
(10) Discharging, after reacting for 4 hours, closing a valve on a cooling water pipeline, starting a centrifugal pump 3, pumping slurry in the main polymerization kettle 2 into a cyclone 4 for classification, discharging slurry with higher solid content into a discharging polymerization kettle 6, returning slurry containing small particles into the main polymerization kettle 2, and after the slurry is pumped, introducing high-pressure flushing water into the cyclone 4 for flushing, wherein the flushing water does not enter the main polymerization kettle 2.
(11) The slurry of the premixing kettle 1 is completely discharged into a main polymerization kettle 2, desalted water and VCM are continuously and quantitatively added into the main polymerization kettle 2, and the water-oil ratio is adjusted.
(12) The temperature in the main polymerization kettle is increased to the reaction temperature by switching cold and hot circulating water, and then 10 kg-20 kg of common initiator solution is added.
(13) And (3) discharging the slurry in the polymerization kettle 6, polymerizing for 30-90 min, and then adding a terminator to stop the polymerization.
The PVC pellets produced by the apparatus described above were subjected to the process indicated in Table 7.
Table 7 technical index for producing PVC particles by continuous method
Under the continuous polymerization production condition, the additive amount, the desalination water amount, the flushing water amount and the wastewater production amount of each ton of products are greatly reduced, and the specific indexes are shown in Table 8.
TABLE 8 Multi-pot continuous polymerization apparatus (48 m) 3 ) PVC ton consumption index
| Sequence number | Project | Technological index |
| 1 | Daily output (t) | ～56 |
| 2 | Water consumption (t/t-PVC) | 1.5 |
| 3 | Initiator consumption (kg/t-PVC) | 4.5 |
| 4 | Dispersant consumption (kg/t-PVC) | 13 |
Example 4
As shown in FIG. 6, in order to increase the productivity of the polymerization kettle, the fourth embodiment provided by the invention increases the proportion of size particle separation, namely, slurry in the main polymerization kettle 2 is pumped into a cyclone 4 in the later stage of the polymerization process, overflows and returns to the main polymerization kettle 2, and underflow enters a discharge polymerization kettle 6 to continue to carry out polymerization reaction under heat preservation.
The specific operation process flow is as follows:
(1) After checking that the parameters of the public and auxiliary equipment and the materials meet the operation conditions, cleaning the main polymerization kettle 2 by high-pressure water, checking the action of a process valve after checking, starting the steam coating kettle procedure, sequentially opening a steam valve and an anti-sticking kettle agent valve, closing the anti-sticking kettle agent valve and the steam valve after lasting for 10-15 min, and then pumping low-pressure water for spray cleaning.
(2) And (3) feeding water, opening a desalted water pipeline valve at the top of the main polymerization kettle 2, and feeding desalted water for 20-23 t.
(3) Adding an auxiliary agent, starting an auxiliary agent pump, adding a dispersing agent, a defoaming agent and a regulating agent, wherein the dispersing agent dosage is about 0.2% -0.5% of the VCM, the defoaming agent dosage is 0.1% -0.2%, and the regulating agent dosage is 0.1% -1%.
(4) And feeding VCM, opening a VCM pipeline valve at the top of the main polymerization kettle 2, and feeding 18-20 t of VCM.
(5) Opening an initiator pipeline valve at the top of the main polymerization kettle 2, and adding 20 kg-40 kg of initiator solution.
(6) After stirring for 10min, heating is started, a certain amount of steam is introduced into the circulating hot water in the coil pipe 10, the temperature of the hot water entering the coil pipe 10 is increased, the circulating flow rate of the hot water in the coil pipe 10 is accelerated, and the liquid temperature of the main polymerization kettle 2 is increased to 2 ℃ under the set reaction temperature.
(7) As the temperature rises to the inflection point temperature, the program automatically controls the cooling water to be switched, the circulating hot water is switched into cold water, and the cooling water quantity is automatically controlled by the temperature control program;
(8) After a certain period of reaction, the pre-mixing kettle 1 is prepared for polymerization, and the operations of coating kettle, water inlet, auxiliary agent inlet, VCM monomer and the like are started, wherein hot desalted water with the temperature of 60-70 ℃ is adopted, and after raw materials are added, the temperature of the pre-mixing kettle is raised, and the polymerization reaction is started.
(9) In the polymerization stage, the flow rate of cooling water in the coil pipe 10 of the main polymerization kettle 2 is automatically controlled by a program, and after the pressure and the temperature in the polymerization kettle are stable, an intermediate cooling water pump is started to control the temperature and the pressure of the main polymerization kettle 2 within a set range.
(10) After polymerization for 3-4 hours, a discharge pump is started, slurry in the kettle is pumped into a cyclone 4 for classification, underflow enters a discharge polymerization kettle 6, overflow returns to a main polymerization kettle 2 or enters another polymerization kettle 5 (a reflux polymerization kettle), the centrifugal pump 3 is stopped after the discharge of the main polymerization kettle 2 reaches a certain liquid level, a valve is closed, and high-pressure water is pumped into the cyclone for flushing and steam spraying of anti-sticking kettle agents.
(11) And opening a valve on a feed pipe from the premixing kettle 1 to the main polymerization kettle 2, placing slurry into the main polymerization kettle 2, opening a desalting water valve and a VCM valve on the top of the main polymerization kettle according to feed data, adjusting the water-oil ratio, and starting the polymerization reaction of the second batch.
(12) And after the slurry in the discharge polymerization kettle 6 reacts for a certain time, adding a terminator, stopping polymerization, and conveying the polymerized PVC slurry to a stripping process. The high-pressure flushing water is introduced into the cyclone 4 for flushing.
The PVC pellets produced by the apparatus described above were subjected to the process indicated in Table 9.
Table 9 technical index for producing PVC particles by continuous method
| Project | Numerical value |
| Average degree of polymerization | 950～1100 |
| Impurity particle count (number) | 100～120 |
| Volatiles (including water) (%) | 0.9 |
| Apparent density (g/m L) | 0.52 |
| 0.25mm mesh | 7～13 |
| 0.63mm mesh | 72～80 |
| 100g resin plasticizer absorption (g) | 30～48 |
| Whiteness (160 ℃ C., after 10 min') | 72～80 |
| Conductivity of aqueous extract (s/m) | — |
Under the continuous polymerization production condition, the additive amount, the desalination water amount, the flushing water amount and the wastewater production amount of each ton of products are greatly reduced, and the specific indexes are shown in Table 10.
Table 10 Multi-pot continuous polymerization apparatus (48 m) 3 ) PVC ton consumption index
Example 5
As shown in fig. 7, in a fifth embodiment provided by the invention, a rotary cyclone centrifuge is adopted to grade the slurry in the later stage of PVC polymerization, the slurry with smaller solid content after grading returns to the main polymerization kettle 2, and the slurry with larger solid content enters a discharge chute.
The specific operation process flow is as follows:
(1) After checking that the public and auxiliary equipment meets the operation condition, starting high-pressure water to clean the main polymerization kettle 2, introducing hot water after flushing to heat the polymerization kettle to 90 ℃, opening a steam valve, placing a valve on a kettle agent pipeline of the adhesive kettle, and closing for 5-10 min;
(2) Opening a high-pressure cleaning water valve to clean the inside of the main polymerization kettle;
(3) Opening a desalting water valve, putting 20-21 t desalted water, respectively adding a regulator, a dispersing agent, an initiator and the like into a polymerization kettle, wherein the dispersing agent is about 0.2-0.5% of the amount of VCM, the amount of a defoaming agent is 0.1-0.2%, and the regulator is 0.1-1%;
(4) Stirring for 10-30 min, introducing hot water into the jacket of the polymerization kettle, heating the polymerization kettle to about 55 ℃, switching the hot water into cooling water, starting polymerization reaction by VCM, introducing intermediate cooling water into the polymerization kettle, and controlling the flow to be 1.5m 3 /h；
(5) After the reaction is carried out for 4 hours, starting to prepare the feed of the premixing kettle 1, and cleaning the kettle wall under high pressure, and then coating the kettle, feeding, adding additives and the like (except for an initiator);
(6) After the reaction is carried out for 5 hours, a valve at the bottom of the main polymerization kettle 2 is opened, a centrifugal pump 3 is started, a rotary cyclone centrifuge 8 is started, slurry in the main polymerization kettle 2 is pumped into the rotary cyclone centrifuge, the slurry with larger solid content enters a discharge chute, and the slurry with lower solid content returns to the main polymerization kettle 2.
(7) After a certain amount of material is discharged, the valve is closed, the centrifugal pump 3 and the rotary cyclone centrifuge 13 are closed, and high-pressure water is pumped into the kettle to flush and steam spray the anti-sticking agent.
(8) And opening a valve at the lower part of the premixing kettle, putting slurry in the premixing kettle into the main polymerization kettle 2, and supplementing a certain amount of VCM monomer according to calculation to ensure that the water-oil ratio in the polymerization kettle is in a certain range.
(9) After the PVC slurry in the discharge chute is continuously polymerized for a certain time, a terminator is added, and after the polymerization reaction is stopped, the PVC slurry is sent to a stripping process.
The PVC pellets produced by the apparatus described above were subjected to the process indicated in Table 9.
Table 11 technical index for producing PVC particles by continuous method
| Project | Numerical value |
| Average degree of polymerization | 900～1080 |
| Impurity particle count (number) | 90～110 |
| Volatiles (including water) (%) | 0.9 |
| Apparent density (g/m L) | 0.47 |
| 0.25mm mesh | 10～15 |
| 0.63mm mesh | 63～78 |
| 100g resin plasticizer absorption (g) | 32～38 |
| Whiteness (160 ℃ C., after 10 min') | 65～76 |
| Conductivity of aqueous extract (s/m) | — |
Under the continuous polymerization production condition, the additive amount, the desalination water amount, the flushing water amount and the wastewater production amount of each ton of products are greatly reduced, and the specific indexes are shown in Table 10.
TABLE 12 Multi-pot continuous polymerization apparatus (48 m) 3 ) PVC ton consumption index
| Sequence number | Project | Technological index |
| 1 | Daily output (t) | ～52 |
| 2 | Water consumption (t/t-PVC) | 1.5 |
| 3 | Initiator consumption (kg/t-PVC) | 4.0～4.6 |
| 4 | Dispersant consumption (kg/t-PVC) | 15～17 |
The innovation point of the invention is that:
(1) The polymerization product is separated by using a separation device, a terminator is added into the slurry with higher solid content of PVC particles to terminate the reaction, the PVC slurry with small particle size is returned to the polymerization kettle, continuous polymerization is realized to a certain extent, and the productivity of the polymerization kettle is improved;
(2) Because the reflux liquid containing desalted water and the initiator is applied to ingredients, the use of desalted water and auxiliary agents is reduced, and the generation of wastewater is reduced;
(3) The intermittent PVC production process with polymerization kettles includes flushing, adding assistant, heating, etc. and the continuous polymerization process with several kettles has less work strength and easy control.
The present invention is not limited to the above-mentioned preferred embodiments, and any person who can learn about the structural changes made under the teaching of the present invention can be within the scope of the present invention if the present invention has the same or similar technical solutions.
Claims (5)
1. The device is characterized by comprising a premixing kettle for initial polymerization and a main polymerization kettle for main polymerization, which are connected with each other, wherein the premixing kettle is connected with an inlet of the main polymerization kettle through a large-diameter pipeline, an outlet of the main polymerization kettle is connected with a cyclone through a centrifugal pump, an outflow pipe at the bottom of the cyclone is connected with a discharging polymerization kettle for final polymerization, an overflow pipeline of the cyclone is connected with the premixing kettle or the main polymerization kettle, a discharging pipe is connected between an outlet of the main polymerization kettle and the centrifugal pump, the discharging pipe is a pipeline with a gradient, the pipeline is connected with a flushing water pipe and an anti-sticking agent pipeline, the tail end of the pipeline is connected with the centrifugal pump and is provided with a discharging port, slurry of the main polymerization kettle is separated into large-particle PVC slurry and small-particle PVC slurry after entering the cyclone, the large-particle PVC slurry enters the discharging polymerization kettle to continue polymerization, and the small-particle PVC slurry returns to the premixing kettle to participate in the batching again, or the main polymerization kettle continues to batching;
the number of the premixing kettles and the number of the main polymerization kettles are respectively provided with a plurality of groups of polymerization devices, wherein the premixing kettles and the main polymerization kettles are in one-to-one correspondence, and the groups of polymerization devices are mutually connected in parallel;
the premixing kettles are provided with one main polymerization kettle, two or more main polymerization kettles are arranged, and the main polymerization kettles are mutually connected in parallel.
2. The apparatus for producing polyvinyl chloride by multi-kettle continuous polymerization according to claim 1, wherein the outer walls of the pre-mixing kettle and the main polymerization kettle are respectively provided with a coil pipe for introducing circulating water.
3. The apparatus for producing polyvinyl chloride by multi-pot continuous polymerization according to claim 1, wherein the cyclone is further connected to a reflux polymerization pot.
4. The apparatus for producing polyvinyl chloride by multi-kettle continuous polymerization according to claim 3, wherein a diaphragm pump is connected to a bottom outlet of the reflux polymerization kettle, and the reflux polymerization kettle is further connected to a reflux inlet of the pre-mixing kettle.
5. A method for producing polyvinyl chloride in a multi-pot continuous polymerization apparatus for producing polyvinyl chloride as claimed in any one of claims 1 to 4, comprising the steps of:
cleaning the main polymerization kettle by high-pressure water, and then carrying out steam coating kettle;
adding desalted water, VCM monomer, reflux liquid, dispersant, initiator and regulator into the main polymerization kettle;
after the materials mixed and stirred in the main polymerization kettle are heated to the inflection point temperature, the program control is performed to switch the circulating cooling water, and the program automatically controls the circulating cooling water flow to start the polymerization reaction;
after the polymerization reaction is carried out for a certain time, the premixing kettle starts to be washed by high-pressure water, the kettle is coated, the reaction materials enter the kettle, and the temperature is raised after stirring for a certain time;
after the materials in the main polymerization kettle continue to react for a certain time, slurry in the kettle flows out from an outlet of the main polymerization kettle, is pumped into a cyclone for separation, and enters a discharge polymerization kettle, and enters a reflux polymerization kettle or a premixing kettle, and the slurry in the premixing kettle flows into the main polymerization kettle, and simultaneously a certain amount of VCM is added to keep the water-oil ratio of the slurry in the main polymerization kettle in a certain range;
after the reaction slurry in the discharging polymerization kettle is polymerized for a certain time, adding a terminator to terminate the polymerization reaction, and pumping reflux liquid containing less PVC particles into a premixing kettle or a main polymerization kettle through a diaphragm pump to be re-compounded to participate in the polymerization reaction.
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| CN214636371U (en) * | 2021-02-25 | 2021-11-09 | 华阳新材料科技集团有限公司 | Device for producing polyvinyl chloride by multi-kettle continuous polymerization |
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| JPS6051705A (en) * | 1983-08-31 | 1985-03-23 | Toyo Soda Mfg Co Ltd | Vapor phase polymerization of vinyl chloride |
| JPH0632806A (en) * | 1992-05-19 | 1994-02-08 | Shin Etsu Chem Co Ltd | Continuous polymerization apparatus |
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