CN116236875A - Process and system for recycling vinyl chloride in PVC paste resin preparation process - Google Patents
Process and system for recycling vinyl chloride in PVC paste resin preparation process Download PDFInfo
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- CN116236875A CN116236875A CN202310530948.7A CN202310530948A CN116236875A CN 116236875 A CN116236875 A CN 116236875A CN 202310530948 A CN202310530948 A CN 202310530948A CN 116236875 A CN116236875 A CN 116236875A
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- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 238000000034 method Methods 0.000 title claims abstract description 53
- 239000011347 resin Substances 0.000 title claims abstract description 44
- 229920005989 resin Polymers 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 238000004064 recycling Methods 0.000 title claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 120
- 238000005406 washing Methods 0.000 claims abstract description 90
- 239000007791 liquid phase Substances 0.000 claims abstract description 39
- 238000009833 condensation Methods 0.000 claims abstract description 33
- 230000005494 condensation Effects 0.000 claims abstract description 33
- 239000000872 buffer Substances 0.000 claims abstract description 30
- 239000000178 monomer Substances 0.000 claims abstract description 30
- 238000001179 sorption measurement Methods 0.000 claims abstract description 28
- 239000012071 phase Substances 0.000 claims abstract description 27
- 230000006835 compression Effects 0.000 claims abstract description 20
- 238000007906 compression Methods 0.000 claims abstract description 20
- 238000011144 upstream manufacturing Methods 0.000 claims abstract description 11
- 230000003139 buffering effect Effects 0.000 claims abstract description 7
- 238000011084 recovery Methods 0.000 claims description 17
- 238000004519 manufacturing process Methods 0.000 claims description 16
- 239000007788 liquid Substances 0.000 claims description 2
- 238000005265 energy consumption Methods 0.000 abstract description 9
- 230000001105 regulatory effect Effects 0.000 abstract description 4
- 239000007789 gas Substances 0.000 description 81
- 239000004800 polyvinyl chloride Substances 0.000 description 27
- 229920000915 polyvinyl chloride Polymers 0.000 description 26
- 239000012535 impurity Substances 0.000 description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 11
- 238000006116 polymerization reaction Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 238000001816 cooling Methods 0.000 description 6
- 239000003995 emulsifying agent Substances 0.000 description 5
- 239000003999 initiator Substances 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 239000012267 brine Substances 0.000 description 4
- 239000004816 latex Substances 0.000 description 4
- 229920000126 latex Polymers 0.000 description 4
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 239000011534 wash buffer Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical group [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000004945 emulsification Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000010985 leather Substances 0.000 description 1
- 239000002649 leather substitute Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012946 outsourcing Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000007096 poisonous effect Effects 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
- B01D53/0462—Temperature swing adsorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1406—Multiple stage absorption
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1418—Recovery of products
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/389—Separation; Purification; Stabilisation; Use of additives by adsorption on solids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2256/00—Main component in the product gas stream after treatment
- B01D2256/26—Halogens or halogen compounds
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
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Abstract
The invention discloses a process and a system for recycling vinyl chloride in the preparation process of PVC paste resin, wherein the method comprises the steps of sequentially carrying out water washing, buffer tank buffering and compressor compression on gas to be recycled generated from the preparation of the upstream PVC paste resin to obtain second gas; the second gas is subjected to primary condensation to obtain a first gas phase and a first liquid phase, and the first gas phase is subjected to secondary condensation to obtain a second gas phase and a second liquid phase; and the first liquid phase and the second liquid phase are subjected to temperature swing adsorption operation to obtain a vinyl chloride monomer product. The invention eliminates the potential safety hazard of the traditional wet gas holder, and improves the safety and stability of the process and the system; the buffer tank is used for buffering and is combined with the compression operation of the compressor, the speed of the gas to be recovered in the condensation process is regulated and controlled, and the primary condensation and the secondary condensation can adopt circulating media which are close to normal temperature compared with the prior art, so that the energy consumption is remarkably saved.
Description
Technical Field
The invention relates to the technical field of polyvinyl chloride paste resin production, in particular to a process and a system for recycling vinyl chloride in the preparation process of polyvinyl chloride paste resin.
Background
Polyvinyl chloride (PVC) paste resin belongs to an important branch of PVC resin, and is widely applied to various fields such as artificial leather, decorative materials, floor leather, wall wallpaper, industrial conveyor belts, sports fields, paint, adhesives, toys, medical disposable gloves, daily decorative materials, electrical instruments, electrical tools and the like due to the characteristics of stable performance, easy control, convenient use, good product performance, good chemical stability, certain mechanical strength, easy coloration and the like.
Vinyl chloride, the main raw material for synthesizing PVC paste resin, is a poisonous, harmful, inflammable, explosive, colorless and easy-to-liquefy gas. In the process for preparing PVC paste resin by vinyl chloride polymerization, no matter an emulsion method, a micro-suspension method or a mixing method is adopted, the raw material vinyl chloride can not be completely converted into PVC, and when the polymerization is finished, the vinyl chloride in the polymerization slurry is 5 multiplied by 10 -3 Left and right, if the part of monomers are directly discharged into the atmosphere, the environment is seriously polluted, and the human health is endangered; meanwhile, raw materials are wasted, and process loss is increased.
In the existing PVC paste resin production process, unreacted vinyl chloride needs to be subjected to self-pressing and forced recovery after the polymerization reaction is finished, the vinyl chloride gas is recovered to a gas holder, and the recovered vinyl chloride gas is refined through an independent compression and rectification system and then recycled. Specifically, gas output by a gas holder is compressed after being cooled before a machine, then liquid-phase chloroethylene obtained through primary cooling and secondary cooling enters a rectifying tower for refining, cold materials used for the primary cooling and the primary cooling in the process flow are saline water at 0 ℃, and deep-cooling saline water at-35 ℃ is used as the cold material for the secondary cooling. The existing chloroethylene recovery process has the following problems:
1. the wet type gas holder is low-pressure gas storage equipment, the design pressure is generally 4kPa, the height control difficulty of a gas holder bell jar under the process condition is high, if the water seal effect is weakened due to the fact that the bell jar is turned over easily due to the fact that the vinyl chloride leakage accident occurs, if the wet type gas holder is too low, the gas holder is not shrunken due to the fact that the recovery compressor is controlled, therefore, the potential safety hazard of the wet type vinyl chloride gas holder is more, intrinsic safety is difficult to achieve, and the safety accident of the multi-purpose vinyl chloride gas holder occurs in recent years. The intrinsic safety means a function of making production equipment or a production system itself safe by means of design or the like, and causing no accident even if an erroneous operation or a failure occurs.
2. Besides unpolymerized vinyl chloride, impurities such as resin with extremely low polymerization degree, residual initiator, emulsifier and the like are inevitably entrained in the recovered gas, a large amount of self-polymers can block equipment and pipelines of a compression and rectification system after long-term operation, production fluctuation and equipment damage are caused, and the condition that the equipment has to be stopped for cleaning is caused.
3. In addition, for the preparation process of producing paste resin by using outsourcing Vinyl Chloride Monomer (VCM), the equipment investment and occupation area of a vinyl chloride gas cabinet adopted by a recovery system are large, and the investment benefit is reduced.
Disclosure of Invention
In order to solve the problems, the invention provides a process and a system for recycling vinyl chloride in the preparation process of PVC paste resin, which avoid using a recycling gas holder to ensure the safety of the process, avoid the adverse effect of recycling vinyl chloride monomer on subsequent process pipelines and equipment, and improve the investment benefit.
In one aspect, the process for recovering vinyl chloride in the preparation process of the PVC paste resin comprises the following steps: the gas to be recovered, which is produced from the preparation of the upstream PVC paste resin, is buffered by a washing buffer tank and compressed by a compressor to obtain second gas; the second gas is subjected to primary condensation to obtain a first gas phase and a first liquid phase, and the first gas phase is subjected to secondary condensation to obtain a second gas phase and a second liquid phase; and the first liquid phase and the second liquid phase are subjected to temperature swing adsorption operation to obtain a vinyl chloride monomer product.
In the technical scheme, the process flow firstly carries out water washing operation on the input gas to be recovered so as to remove the impurities such as the initiator, the emulsifier, the latex and the like carried by the vinyl chloride monomer in the gas to be recovered, and the problem of equipment and pipeline blockage caused by the polymerization of the impurities in the subsequent process is avoided. The gas to be recovered is produced by preparing the upstream PVC paste resin and is recovered only through self-pressure or vacuum of a superior device.
In the above technical scheme, the pressure of the buffer tank is 0.4MPaG, which is far greater than the pressure of the gas to be recovered by 0-0.2 MPaG, so that the accidents of bell jar lifting or gas holder flattening caused by using a wet gas holder (the pressure is 4 kPa) in the prior art can be avoided. According to the technical scheme, the buffer tank is used for buffering, and the compressor is used for compressing, so that the speed of gas input into the subsequent process flow can be controlled, the technical effect of buffer balance of the recovery gas holder in the prior art is achieved, the safety of the whole process flow can be ensured, the recovery treatment efficiency is improved, the equipment investment and occupied area can be reduced, and the investment benefit is improved. In addition, the rate of the gas to be recovered, which is input into the subsequent treatment of the process flow of the invention, is further regulated and controlled by controlling the capacity of the compressor equipment, so that the production requirement is met.
In the technical scheme, the outlet pressure of the compressor is 0.4-0.6 MPaG. According to the invention, the compressor is used for compression, the primary condensation and the secondary condensation are combined, the second gas can be condensed by using a circulating medium with higher temperature than that of the brine cold material with the temperature of 0 ℃ in the prior art in the primary condensation operation through the compression of the compressor, the first gas phase can be condensed by using a circulating medium with the temperature close to the normal temperature than that of the brine cold material with the temperature of-35 ℃ in the prior art in the secondary condensation operation, so that the better effect of condensing and recycling the liquid-phase chloroethylene can be achieved, and the energy consumption of the circulating medium is obviously reduced. Optionally, the circulating medium is not limited in the invention, and the circulating medium meeting the condensing temperature requirement of the invention can be used in the invention, so that the formed technical scheme is within the protection scope of the invention; optionally, the circulating medium is brine cold charge, and further optionally is calcium chloride aqueous solution.
In a preferred embodiment of the invention, the outlet temperature of the primary condensation is 32 ℃ and the outlet temperature of the secondary condensation is 5 ℃, thereby remarkably reducing the energy consumption of the process and improving the production benefit. Wherein the first liquid phase and the second liquid phase are liquid phase chloroethylene which is a mixture of chloroethylene and water, and the second gas phase is discharged outside.
In the technical scheme, the invention combines the operations of compressor compression, primary condensation, secondary condensation and temperature swing adsorption, so that the first liquid phase and the second liquid phase meet the operation conditions of temperature swing adsorption; in addition, the temperature swing adsorption operation is adopted to remove the moisture and other impurities in the liquid-phase vinyl chloride monomer so as to achieve the refining purpose, and the use of a high-energy-consumption rectifying high-low tower in the prior art is replaced; the vinyl chloride monomer product subjected to temperature swing adsorption operation can be directly returned to a fresh vinyl chloride monomer system for recycling, so that secondary condensation after refining by a rectification high-low tower in the prior art is avoided, and the process energy consumption is further reduced.
In another aspect, the invention also provides a system for recycling vinyl chloride in the PVC paste resin preparation process, which comprises a water washing device, a buffer compression device, a condensing device and a temperature swing adsorption device, wherein
The water washing device comprises a water washing tower or two water washing towers, and when the water washing device comprises one water washing tower, the feed inlet of the water washing tower is connected with a recovery exhaust pipe and is used for inputting gas to be recovered generated by preparing the upstream PVC paste resin into the water washing device; when the water washing device comprises two water washing towers, the two water washing towers are a first water washing tower and a second water washing tower respectively, a feed inlet of the first water washing tower is connected with a recovery exhaust pipe and is used for inputting gas to be recovered generated by preparing the upstream PVC paste resin into the water washing device, and a discharge outlet of the first water washing tower is connected with a feed inlet of the second water washing tower;
the buffer compression device comprises a buffer tank and a compressor which are sequentially connected through a pipeline; when the water washing device comprises a water washing tower, a discharge port of the water washing tower is connected with the buffer tank through a pipeline; when the water washing device comprises two water washing towers, the two water washing towers are a first water washing tower and a second water washing tower respectively, and a discharge hole of the second water washing tower is connected with the buffer tank through a pipeline;
the condensing device comprises a first condenser, a second condenser and a chloroethylene collecting tank, wherein an outlet of the compressor is connected with an inlet of the first condenser through a pipeline, a gas phase outlet of the first condenser is connected with an inlet of the second condenser, and the second condenser is further provided with a gas phase outlet; the first condenser and the second condenser are respectively connected with a chloroethylene collecting tank through pipelines;
and a liquid outlet of the vinyl chloride collection tank is connected with an inlet of the temperature swing adsorption device through a pipeline, and vinyl chloride monomer products are extracted from an outlet of the temperature swing adsorption device.
Compared with the prior art, the process and the system for recycling the chloroethylene in the preparation process of the PVC paste resin have the following beneficial effects:
(1) By setting the pressure of the buffer tank to be 0.4MPaG, the potential safety hazard of 4kPa of the design pressure of the traditional wet gas holder is eliminated, and the safety and stability of the process and the system are improved.
(2) The pressure of the compressor is set to be 0.4-0.6 MPaG, and the buffer tank is used for buffering and the compression operation of the compressor is combined, so that the speed of the gas to be recovered in the condensation process is regulated and controlled, and the primary condensation and the secondary condensation can adopt a circulating medium which is close to normal temperature compared with the prior art, thereby obviously saving energy consumption.
(3) The invention carries out water washing operation on the input gas to be recovered to remove impurities carried by vinyl chloride monomer in the gas to be recovered, thereby avoiding the problem of equipment and pipeline blockage caused by the polymerization of the impurities in the subsequent process.
(4) The invention combines the operations of compressor compression, primary condensation, secondary condensation and temperature swing adsorption to remove water and other impurities, thereby further reducing the process energy consumption.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is a block diagram of a system for recovering vinyl chloride in the process of preparing a PVC paste resin according to the present invention.
Wherein the above figures include the following reference numerals:
11-a first water scrubber, 12-a second water scrubber, 21-a buffer tank, 22-a compressor, 31-a first condenser, 32-a second condenser, 33-a vinyl chloride collection tank, and 4-a temperature swing adsorption device.
Detailed Description
In order to facilitate an understanding of the present invention, the present invention will be described in further detail below with reference to the drawings by way of specific embodiments. It should be understood that these examples are for the purpose of more detailed description only and should not be construed as limiting the invention in any way, i.e., not intended to limit the scope of the invention. Unless defined otherwise, technical terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which the inventive concepts pertain. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
It should be noted that, in this embodiment, relational terms such as "first," "second," "first," "second," and the like are used solely to distinguish one from another component having the same name, and do not necessarily require or imply any actual relationship or order between the components. Features defining "first," "second," "primary," "secondary," etc. may include one or more of the features, either explicitly or implicitly, etc.
In the description of the invention, the term "coupled" is to be interpreted broadly, as being either a fixed connection, a removable connection, or an integral connection, unless clearly indicated and defined otherwise; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the creation of the present invention can be understood by those of ordinary skill in the art in a specific case.
Example 1
A process for recovering vinyl chloride in the preparation process of PVC paste resin, which comprises the following steps: the gas to be recovered produced from the upstream PVC paste resin preparation is buffered by a water washing buffer tank 21 and compressed by a compressor 22 to obtain a second gas; the second gas is subjected to primary condensation to obtain a first gas phase and a first liquid phase, and the first gas phase is subjected to secondary condensation to obtain a second gas phase and a second liquid phase; the first liquid phase and the second liquid phase are subjected to temperature swing adsorption operation to obtain a vinyl chloride monomer product, and the second gas phase is discharged outside the boundary.
Wherein the temperature of the gas to be recovered is about 60 ℃ or less, the pressure of the gas is about 0-0.2 MPaG, and the composition of the gas comprises less than 90% of chloroethylene gas by mass, more than 10% of water by mass, and trace amounts of latex, initiator, emulsifier, ammonia gas, nitrogen gas and the like.
The technical characteristics of removing impurities in the recovered gas are firstly provided in the process flow, and specifically, the input gas to be recovered is washed to remove impurities such as an initiator, an emulsifying agent, latex and the like carried by chloroethylene in the recovered gas, so that the condition that equipment and pipelines are blocked due to impurity polymerization in the subsequent process flow is avoided.
Optionally, the washing operation comprises primary washing and secondary washing, and two-stage washing is adopted to ensure the washing effect, so that impurities in the gas to be recovered are effectively removed; in addition, the primary water washing and the secondary water washing are respectively and independently carried out by adopting clear water or alkaline water, and the alkaline water can be used for washing instead of the clear water according to specific working conditions so as to achieve better washing effect. The alkaline water used in the invention is weak alkaline water; further optionally, weak alkaline water with a pH value of 8-12 is used.
After the water washing process, the temperature of the gas to be recovered is about 50 ℃ or less, the pressure of the gas is about 0-0.2 MPaG, and the gas comprises less than 90% of chloroethylene gas by mass, more than 10% of water by mass and trace nitrogen.
The process can realize the technical effect of buffer balance of the recovery gas holder in the prior art by combining water washing, buffer tank 21 buffering and compressor compression, thereby regulating and controlling the rate of gas input into the subsequent process flow, improving the recovery treatment efficiency of the chloroethylene and ensuring the safety of the whole process flow.
Alternatively, in the actual process flow, in order to save equipment investment, the buffer tank can adopt a smaller volume, so that the equipment investment and the occupied area investment can be saved.
The second gas output from the compressor outlet has a temperature of about 50 ℃ or less and a pressure of 0.4-0.6 MPaG, and comprises less than 90% by mass of vinyl chloride gas, more than 10% by mass of water, and a trace amount of nitrogen.
The process combines the compressor compression, the primary condensation and the secondary condensation, so that a circulating medium with higher temperature than the prior art is used in the primary condensation and the secondary condensation, the better effect of condensing and recycling the liquid-phase chloroethylene can be achieved, and meanwhile, the pre-machine condensation operation before the compression operation is omitted, thereby reducing the energy consumption and improving the benefit.
Alternatively, the outlet temperature of the primary condensate is 32 ℃ and the outlet temperature of the secondary condensate is 5 ℃, which significantly reduces the energy consumption compared with the 0 ℃ brine cold material and the-35 ℃ water cold material used in the prior art, and the technical characteristics will produce considerable economic benefit in the production process of the general quantity of PVC paste resin.
In the process of the present invention, the first liquid phase and the second liquid phase are fed to the vinyl chloride collection tank 33 and then to the temperature swing adsorption apparatus 4 for temperature swing adsorption. Alternatively, the liquid phase vinyl chloride fed into the vinyl chloride collection tank 33 has a temperature of about not more than 32℃and a pressure of 0.4 to 0.6MPaG, and comprises vinyl chloride monomer (liquid phase), water content of 500ppm or less, and a trace amount of nitrogen. The second gas phase is vented outside the boundary.
It should be noted that the temperature swing adsorption apparatus 4 employed in the present invention removes moisture and other impurities from the liquid phase vinyl chloride monomer obtained after condensation. Wherein the temperature of the liquid-phase vinyl chloride monomer input from the temperature swing adsorption device 4 is normal temperature, the pressure is 0.4-0.6 MPaG, the water content is less than or equal to 500ppm, and the liquid-phase vinyl chloride monomer also comprises trace nitrogen; the vinyl chloride monomer product is obtained after variable temperature adsorption, the water content of the vinyl chloride monomer product is less than or equal to 100ppm, the pressure is 0.4-0.6 MPaG, and the vinyl chloride monomer product can be directly returned to a fresh vinyl chloride monomer system for recycling.
The temperature swing adsorption device 4 of the invention is characterized in that water in liquid-phase vinyl chloride (a mixture of vinyl chloride and water) is adsorbed by selecting an adsorbent, and water in the liquid-phase vinyl chloride is removed through adsorption, decompression, temperature swing and purging to obtain a vinyl chloride monomer product.
Example 2
A system for recovering vinyl chloride in the process of preparing PVC paste resin is shown in figure 1, which comprises a water washing device, a buffer compression device, a condensing device and a temperature swing adsorption device 4, wherein
The water washing device comprises a water washing tower or two water washing towers, and when the water washing device comprises the water washing tower, the feed inlet of the water washing tower is connected with a recovery exhaust pipe for inputting the gas to be recovered generated by the preparation of the upstream PVC paste resin into the water washing device; when the water washing device comprises two water washing towers, the two water washing towers are a first water washing tower and a second water washing tower respectively, a feed inlet of the first water washing tower 11 is connected with a recovery exhaust pipe and is used for inputting gas to be recovered generated by preparing the upstream PVC paste resin into the water washing device, and a discharge outlet of the first water washing tower 11 is connected with a feed inlet of the second water washing tower 12; the system for recovering vinyl chloride in the process of preparing PVC paste resin comprising two water washing towers shown in fig. 1, namely, comprises a first water washing tower 11 and a second water washing tower 12.
The buffer compression device comprises a buffer tank 21 and a compressor which are connected in sequence through a pipe; when the water washing device comprises a water washing tower, a discharge hole of the water washing tower is connected with the buffer tank 21 through a pipe; when the water washing device comprises two water washing towers, the two water washing towers are a first water washing tower and a second water washing tower respectively, and a discharge port of the second water washing tower 12 is connected with the buffer tank 21 through a pipe;
the condensing device comprises a first condenser 31, a second condenser 32 and a vinyl chloride collection tank 33, wherein an outlet of the compressor is connected with an inlet of the first condenser 31 through a pipeline, a gas phase outlet of the first condenser 31 is connected with an inlet of the second condenser 32, and the second condenser 32 is also provided with a gas phase outlet; the first condenser 31 and the second condenser 32 are respectively connected with a vinyl chloride collection tank 33 through pipelines;
the outlet of the vinyl chloride collection tank 33 is connected to the inlet of the temperature swing adsorption apparatus 4 via a pipe, and the vinyl chloride monomer product is withdrawn from the outlet of the temperature swing adsorption apparatus 4.
Example 3
In this embodiment, the process flow of recovering vinyl chloride in the process of preparing PVC paste resin by using the system as shown in embodiment 2 is shown in a specific working condition, and it should be noted that this embodiment is only a showing of a preferred flow, and does not limit the protection scope of the present invention.
Taking a PVC paste resin production process line with annual production of 6 ten thousand tons as an example, after the polymerization reaction of the process line is completed, unreacted vinyl chloride monomer enters a vinyl chloride recovery processing device through a polymerization recovery system and a recovery buffer separation tank, the air inlet temperature of the recovered gas to be processed is less than 60 ℃, the air inlet pressure is less than 0.2MPaG, the content of the vinyl chloride monomer in the gas is 92wt% at maximum, the water content is 8wt% at minimum, and the gas also contains trace amount of impurities such as an initiator, an emulsifying agent, latex and the like.
Wherein the first water scrubber 11 is cleaned by clean water, and the second water scrubber 12 is cleaned by clean water or pH value of about 1%; the input gas to be recovered is washed by the secondary water washing tower and then is input into the buffer tank 21 for buffering, and then is input into the compressor for compression. Wherein the pressure of the second gas at the outlet of the compressor is 0.4-0.6 MPaG.
The second gas is input into the first condenser 31 to be condensed to obtain a first gas phase and a first liquid phase, wherein the first gas phase is input into the second condenser 32 to be continuously condensed to obtain a second gas phase and a second liquid phase. Wherein the outlet temperature of the first condenser 31 is less than or equal to 40 ℃, and the outlet temperature of the second condenser 32 is less than or equal to 5 ℃. The first liquid phase and the second gas phase are fed to the vinyl chloride collection tank 33, the second gas phase being excluded from the boundary. The temperature of the liquid phase vinyl chloride at the inlet of the vinyl chloride collection tank 33 is +.32deg.C, the pressure is 0.4-0.6 MPaG, the water content is about 8wt%, and a small amount of nitrogen is included.
The liquid phase vinyl chloride output from the vinyl chloride collection tank 33 is input into the temperature swing adsorption device 4 for moisture removal, the temperature of the vinyl chloride monomer product extracted from the outlet of the temperature swing adsorption device 4 is normal temperature, the pressure is 0.38-0.658 MPaG, and the water content is less than 100ppm. The vinyl chloride monomer product is input into a fresh vinyl chloride monomer system for recycling.
The foregoing is a further detailed description of the invention in connection with specific embodiments, and it is not intended that the invention be limited to such description. It will be apparent to those skilled in the art that several simple modifications and adaptations of the invention can be made without departing from the spirit of the invention and are intended to be within the scope of the invention.
Claims (10)
1. A process for recycling vinyl chloride in the preparation process of PVC paste resin is characterized in that gas to be recycled, which is produced from the preparation of the upstream PVC paste resin, is subjected to water washing, buffer tank buffering and compressor compression in sequence to obtain second gas; the second gas is subjected to primary condensation to obtain a first gas phase and a first liquid phase, and the first gas phase is subjected to secondary condensation to obtain a second gas phase and a second liquid phase; and the first liquid phase and the second liquid phase are subjected to temperature swing adsorption operation to obtain a vinyl chloride monomer product.
2. The process for recovering vinyl chloride in the process of preparing PVC paste resin according to claim 1, wherein the pressure of the gas to be recovered is 0 to 0.2mpa g.
3. The process for recovering vinyl chloride in the process of preparing PVC paste resin according to claim 1, wherein the water washing includes a primary water washing and a secondary water washing, which are independently rinsed with clear water or alkaline water, respectively.
4. The process for recovering vinyl chloride in the production of PVC paste resin according to claim 1, wherein the pressure of the buffer tank is 0.4MPaG.
5. The process for recovering vinyl chloride in the production of PVC paste resin according to claim 1, wherein the pressure of the compressor is 0.4 to 0.6MPaG.
6. The process for recovering vinyl chloride in the production of PVC paste resin according to claim 1, wherein the temperature of the primary condensation is 32 ℃ and the temperature of the secondary condensation is 5 ℃.
7. The process for recovering vinyl chloride in the production of PVC paste resin according to claim 1, wherein the water content of the vinyl chloride monomer product is not more than 100ppm.
8. A system for recycling vinyl chloride in PVC paste resin preparation process is characterized by comprising a water washing device, a buffer compression device, a condensing device and a temperature swing adsorption device (4), wherein
The water washing device comprises a water washing tower, a feed inlet of the water washing tower is connected with a recovery exhaust pipe, and the water washing device is used for inputting gas to be recovered generated by preparing the upstream PVC paste resin;
the buffer compression device comprises a buffer tank (21) and a compressor (22) which are sequentially connected through a pipeline, and a discharge hole of the water washing device is connected with the buffer tank (21) through a pipeline;
the condensing device comprises a first condenser (31), a second condenser (32) and a chloroethylene collecting tank (33), wherein the outlet of the compressor (22) is connected with the inlet of the first condenser (31) through a pipeline, the gas phase outlet of the first condenser (31) is connected with the inlet of the second condenser (32), and the second condenser (32) is also provided with a gas phase outlet; the first condenser (31) and the second condenser (32) are respectively connected with a chloroethylene collecting tank (33) through pipelines;
the liquid outlet of the vinyl chloride collection tank (33) is connected with the inlet of the temperature swing adsorption device (4) through a pipe, and vinyl chloride monomer products are extracted from the outlet of the temperature swing adsorption device (4).
9. The system for recovering vinyl chloride in the production of PVC paste resin according to claim 8, wherein,
the water washing device comprises a first water washing tower (11) and a second water washing tower (12), wherein a feed inlet of the first water washing tower (11) is connected with a recovery exhaust pipe and is used for inputting gas to be recovered generated by preparing the upstream PVC paste resin into the water washing device, and a discharge outlet of the first water washing tower (11) is connected with a feed inlet of the second water washing tower (12); the feed inlet of the second water washing tower (12) is connected with the buffer tank (21) through a pipe.
10. The system for recovering vinyl chloride in the process of preparing PVC paste resin according to claim 9, wherein the first water washing tower (11) and the second water washing tower (12) are rinsed with clear water or alkaline water, respectively, independently.
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