A relief system for the polymerization of vinyl acetate

Abstract

The application discloses a kind of for vinyl acetate polymerization reaction relief system, which includes: reaction kettle, the inside of reaction kettle carries out the polymerization reaction of vinyl acetate;Pressure detection unit is used to detect the pressure in the inside of reaction kettle;Active relief unit is connected with reaction kettle pipeline and is connected with pressure detection unit signal, and active relief unit opens when the pressure in the inside of reaction kettle reaches first preset pressure value;Passive relief unit is connected with reaction kettle pipeline and is arranged in parallel with active relief unit, and passive relief unit is conducted through in the reaction kettle by reaction material ram when the pressure in the reaction kettle reaches second preset pressure value, and second preset pressure value is greater than first preset pressure value, so that active relief unit and passive relief unit are sequentially conducted through after the pressure in the reaction kettle reaches different limit values, avoid the polymerization reaction in the reaction kettle from out of control overpressure, to form effective protection to reaction kettle, and simple structure, high economic benefits.

Description

Technical Field

[0001] This invention relates to the field of chemical equipment safety technology, and more specifically to a venting system for vinyl acetate polymerization reactions. Background Technology

[0002] Vinyl acetate (VAc) is one of the world's most produced organic chemical raw materials. As an important organic chemical raw material, it is mainly used to produce derivatives such as polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), vinyl chloride-vinyl acetate copolymer (EVC), and polyacrylonitrile comonomer. These derivatives have a wide range of applications and can be used in the production of chemical products such as pharmaceuticals, coatings, slurries, adhesives, vinylon, films, vinyl copolymer resins, and acetal resins.

[0003] The polymerization of vinyl acetate is an exothermic reaction that occurs through the free radical polymerization of vinyl acetate monomers or other monomers in a methanol solution. If the conditions are not properly controlled, the polymerization reaction can run out of control and result in explosive polymerization. Explosive polymerization involves various polymerization processes, such as copolymerization of vinyl acetate with other monomers, self-polymerization of vinyl acetate, and self-polymerization of other monomers. The temperature rises rapidly, and the pressure in the reactor increases rapidly according to the saturated vapor pressure of the material (monomer or solvent), leading to overpressure in the reactor. If the pressure in the reactor is not released in time, once the pressure in the reactor exceeds the reactor's pressure-bearing capacity, the reactor will deform or even explode or rupture, leading to a safety accident. Summary of the Invention

[0004] The purpose of this invention is to provide a venting system for vinyl acetate polymerization. This venting system has a simple structure and can effectively vent overpressure runaway conditions in the vinyl acetate polymerization reaction vessel.

[0005] To achieve the above objectives, the present invention provides a venting system for vinyl acetate polymerization reactions, the venting system comprising:

[0006] The reactor is where the polymerization reaction of vinyl acetate takes place.

[0007] A pressure detection unit is used to detect the pressure inside the reactor.

[0008] The active venting unit is connected to the reactor pipeline and the pressure detection unit signal. The active venting unit is activated when the pressure inside the reactor reaches the first preset pressure value.

[0009] The passive venting unit is connected to the reactor pipeline and is set in parallel with the active venting unit. When the pressure in the reactor reaches the second preset pressure value, the passive venting unit is activated by the reaction material in the reactor. The second preset pressure value is greater than the first preset pressure value.

[0010] In an embodiment of the present invention, the passive discharge unit includes:

[0011] The safety valve pipeline includes a first pipeline connected to the reactor and a first safety valve installed on the first pipeline. The opening pressure of the first safety valve is a second preset pressure value.

[0012] The rupture disc pipeline and the safety valve pipeline are connected in parallel and include a second pipeline and multiple rupture discs installed on the second pipeline, wherein the bursting pressure of at least one rupture disc is greater than the opening pressure of the first safety valve.

[0013] In an embodiment of the present invention, the safety valve pipeline further includes a first auxiliary rupture disc and a second auxiliary rupture disc respectively disposed upstream and downstream of the first safety valve. The bursting pressure of the first auxiliary rupture disc is the same as the opening pressure of the first safety valve, and the bursting pressure of the second auxiliary rupture disc is less than the bursting pressure of the first auxiliary rupture disc.

[0014] In an embodiment of the present invention, the multiple rupture discs in the rupture disc pipeline include a main rupture disc, a third auxiliary rupture disc, and a fourth auxiliary rupture disc. The third auxiliary rupture disc and the fourth auxiliary rupture disc are respectively disposed upstream and downstream of the main rupture disc. The rupture pressure of the main rupture disc is the same as the rupture pressure of the third auxiliary rupture disc, and the rupture pressure of the fourth auxiliary rupture disc is less than the rupture pressure of the third auxiliary rupture disc.

[0015] In an embodiment of the present invention, the discharge area of ​​the first auxiliary rupture disc is the same as that of the second auxiliary rupture disc, and the discharge area of ​​the first safety valve is smaller than that of the first auxiliary rupture disc.

[0016] In an embodiment of the present invention, the venting area of ​​the third auxiliary rupture disc is the same as that of the fourth auxiliary rupture disc, and the venting area of ​​the main rupture disc is smaller than that of the third auxiliary rupture disc.

[0017] In an embodiment of the present invention, the active venting unit includes a third pipeline and a pressure control valve disposed on the third pipeline. The pressure control valve is signal-connected to a pressure detection unit, and the opening pressure of the pressure control valve is 50%-100% of a second preset pressure value.

[0018] In an embodiment of the present invention, the venting area of ​​the pressure control valve is smaller than the minimum venting area of ​​the passive venting unit.

[0019] In embodiments of the present invention, the venting system further includes a venting material collection unit disposed downstream of the active venting unit and the passive venting unit.

[0020] In an embodiment of the present invention, the venting system further includes a flare unit disposed downstream of the venting material collection unit.

[0021] Through the above technical solution, the venting system is equipped with an active venting unit and a passive venting unit connected to the reactor. The active venting unit is signal-connected to the pressure detection unit and is used to open and vent the pressure in the reactor when the pressure in the reactor reaches a first preset pressure value. The passive venting unit is activated by the pressure of the reactants in the reactor when the pressure in the reactor reaches a second preset pressure value. The second preset pressure value is greater than the first preset pressure value, so that the active venting unit and the passive venting unit are activated sequentially after the pressure in the reactor reaches different limit values. The pressure in the reactor where vinyl acetate polymerization is carried out is released sequentially, avoiding runaway and overpressure in the polymerization reaction in the reactor, thus effectively protecting the reactor. It also has the advantages of simple structure and high economic efficiency. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0023] Figure 1 This is a simplified structural diagram of the venting system in an embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures

[0025] 1. Reactor 2. Pressure Detection Unit

[0026] 3 Active Discharge Unit 301 Third Pipeline

[0027] 302 Pressure Control Valve 4 Passive Relief Unit

[0028] 401 First pipeline 402 First safety valve

[0029] 403 Second Pipeline 404 First Auxiliary Rupture Disc

[0030] 405 Second auxiliary blasting disc; 406 Main blasting disc

[0031] 407 Third auxiliary blasting disc; 408 Fourth auxiliary blasting disc

[0032] 409 First pressure sensor 410 Second pressure sensor

[0033] 411 Third pressure sensor 412 Fourth pressure sensor

[0034] 5. Discharge Material Collection Unit 501 Collection Tank

[0035] 502 Baffle; 503 Fourth Pipeline

[0036] 504 flow restrictor orifice plate; 505 fifth pipeline.

[0037] 506 Second safety valve 6 Flare unit Detailed Implementation

[0038] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0039] This invention provides a venting system for vinyl acetate polymerization. This venting system is suitable for various types of venting processes, such as single-phase or multi-phase venting; the phases include gas, liquid, second liquid, solid, and mixed phases. Figure 1As shown, the venting system includes a reactor 1, a pressure detection unit 2, an active venting unit 3, and a passive venting unit 4. The polymerization reaction of vinyl acetate takes place inside the reactor 1. The designed pressure venting value of the reactor 1 is a preset pressure venting value (obtained through theoretical calculation). In this embodiment, the gaseous reactants in the reactor 1 include non-condensable gases, olefins, vinyl acetate vapor, and solvent vapor; the liquid reactants include olefins, vinyl acetate, and solvents. The olefins include C2-C6 olefins, such as ethylene, propylene, and butene; the non-condensable gases include nitrogen, argon, oxygen, and methane; and the solvents include methanol, ethanol, ethylene glycol, glycerol, and other alcohols. The pressure detection unit 2 is used to detect the pressure in the reactor 1. The active venting unit 3 is connected to the reactor 1 via a pipeline and is connected to the pressure detection unit 2 to vent the pressure in the reactor 1. The venting system in this embodiment also includes a control unit, which, along with the pressure detection unit 2 and the passive venting unit 4, further vents the pressure in the reactor 1. The venting unit 3 is connected to the signal. When the pressure detection unit 2 detects that the pressure in the reactor 1 has reached the first preset pressure value, it transmits a signal to the control unit. The control unit controls the active venting unit 3 to start the venting function to control the pressure in the reactor 1 to be vented in advance. In this embodiment, the first preset pressure value is 50%-100% of the preset pressure venting value. Further, the first preset pressure value is preferably 70%-90% of the preset pressure venting value. The above range can better control the venting process of the ethyl acetate polymerization reaction. If the pressure in the reactor 1 is vented when it is below the above range, it may cause the reactants in the reactor 1 to be vented in advance, resulting in the loss of reactants and the shutdown of the venting system, which is not conducive to the stable operation of the venting system. If it is above the above range, it may cause the passive venting unit to be turned on. After the passive venting unit is turned on, its internal components (such as rupture discs) also need to be replaced, which will lead to unnecessary economic losses.

[0040] The passive venting unit 4 is connected to the pipeline of the reactor 1 and is set in parallel with the active venting unit 3. When the pressure in the reactor 1 reaches the second preset pressure value, the passive venting unit 4 is activated by the reaction material in the reactor 1. The second preset pressure value is greater than the first preset pressure value. Specifically, when the pressure in the reactor 1 does not reach the second preset pressure value, the passive venting unit 4 is in a non-flowing state, so that the active venting process takes place before the passive venting process. When the pressure in the reactor 1 reaches the second preset pressure value, it indicates that the polymerization reaction of vinyl acetate has reached an overpressure runaway state. At this time, the pressure in the reactor 1 rises sharply due to the violent reaction of the reaction material. The passive venting unit 4 is passively activated by the pressure (i.e., the blocking component set in the passive venting unit 4 opens or bursts under pressure) to release the pressure in the reactor 1, so that the pressure in the reactor 1 can be lower than the second preset pressure value, thereby effectively protecting the reactor 1 and preventing the polymerization reaction in the reactor 1 from running out of control and causing subsequent overpressure accidents.

[0041] In addition, in this embodiment, the total discharge area of ​​the passive discharge unit 4 is greater than the preset total discharge area of ​​the passive discharge unit 4, wherein the preset total discharge area is calculated based on the fluid state of the discharged material during the passive discharge process.

[0042] In one embodiment of the present invention, the passive discharge unit 4 includes:

[0043] The safety valve pipeline includes a first pipeline 401 connected to the reactor 1 and a first safety valve 402 installed on the first pipeline 401. The opening pressure of the first safety valve 402 is a second preset pressure value.

[0044] The rupture disc pipeline and the safety valve pipeline are connected in parallel and include a second pipeline 403 and multiple rupture discs installed on the second pipeline 403, wherein the bursting pressure of at least one rupture disc is greater than the opening pressure of the first safety valve 402.

[0045] Specifically, in this embodiment, the passive venting unit 4 includes a safety valve pipeline and a rupture disc pipeline connected in parallel. The bursting pressure of at least one rupture disc in the rupture disc pipeline is greater than the opening pressure of the first safety valve 402. That is, when the pressure in the reactor 1 reaches the second preset pressure value, the reactant first pressurizes the safety valve pipeline and makes it open. The pressure in the reactor 1 is effectively vented through the opening of the safety valve pipeline. If the pressure in the reactor 1 exceeds the second preset pressure value but does not continue to rise, that is, the rupture disc in the rupture disc pipeline is not pressurized to the point of rupture and the rupture disc pipeline is not damaged, then there is no need to replace the rupture disc, which helps to reduce the cost of the venting system and improve the economic performance of the venting system. When the pressure in the reactor 1 exceeds the second preset pressure value and continues to rise, the reactant in the reactor 1 will continue to pressurize the rupture disc in the rupture disc pipeline under the above-mentioned high pressure until multiple rupture discs rupture, so that the rupture disc pipeline is opened and the venting effect is further improved, so that the pressure in the reactor 1 is fully vented. Furthermore, in this embodiment, the first safety valve 402 can be reset after the discharge is completed.

[0046] Furthermore, the difference between the opening pressure of the first safety valve 402 in the safety valve pipeline and the bursting pressure of the rupture disc in the rupture disc pipeline is the first difference value. The range of the first difference value is 0.5-5 bar, and the range of the first difference value is preferably 1.5-4 bar. The above numerical range ensures that the pressure difference that needs to be conducted between the safety valve pipeline and the rupture disc pipeline is within a reasonable range. This can avoid both being conducted at the same time, resulting in overprotection, and also avoid the rupture disc pipeline not being able to be conducted, which would cause the rupture disc pipeline to fail to perform its pressure relief function and damage the reactor 1.

[0047] In one embodiment of the present invention, the safety valve pipeline further includes a first auxiliary rupture disc 404 and a second auxiliary rupture disc 405 respectively disposed upstream and downstream of the first safety valve 402. The bursting pressure of the first auxiliary rupture disc 404 is the same as the opening pressure of the first safety valve 402, and the bursting pressure of the second auxiliary rupture disc 405 is less than the bursting pressure of the first auxiliary rupture disc 404.

[0048] Specifically, the first auxiliary rupture disc 404 is positioned upstream of the first safety valve 402 to isolate the reactants in the reactor 1, preventing the reactants from self-polymerizing at the first safety valve 402 and causing it to malfunction. Since the reactants released from the reactor 1 may contain flammable and explosive substances such as methanol and copolymer monomers, if the active release unit 3 and passive release unit 4 directly release these reactants at high altitude, a combustion explosion could easily occur at the high-altitude discharge port, polluting the surrounding environment. Therefore, in this embodiment, the release system also includes a release material collection unit 5 downstream of the active release unit 3 and passive release unit 4. The active release process precedes the passive release process, and after the active release is completed, the reactants are released into the release material collection unit 5, resulting in pressure within the collection unit 5. If the first safety valve 402 and the released material... If there is no obstruction between the collection units 5, the aforementioned pressure will affect the opening of the first safety valve 402. Therefore, the second auxiliary rupture disc 405 is placed downstream of the first safety valve 402 to isolate the first safety valve 402 from other components downstream of the first safety valve 402 (such as the discharge material collection unit 5), so that the rear side of the first safety valve 402 is in a normal pressure state, avoiding the first safety valve 402 from forming a pressure system directly with other downstream components (such as the discharge material collection unit 5) and affecting the opening of the first safety valve 402. In this embodiment, the bursting pressure of the second auxiliary rupture disc 405 is 50%-90% of the preset pressure discharge value. Further, the bursting pressure of the second auxiliary rupture disc 405 is preferably 60%-80% of the preset pressure discharge value. The above range allows the second auxiliary rupture disc 405 to easily burst during passive discharge and quickly open the safety valve pipeline.

[0049] In one embodiment of the present invention, the safety valve pipeline further includes a first pressure sensor 409, a second pressure sensor 410, a first drain line, and a second drain line (the first drain line and the second drain line are not shown in the figure). The first pressure sensor 409 and the first drain line are both disposed on the first pipeline 401 and located between the first auxiliary rupture disc 404 and the first safety valve 402. The second pressure sensor 410 and the second drain line are both disposed on the first pipeline 401 and located between the second auxiliary rupture disc 405 and the first safety valve 402, and are used to determine the working status of each rupture disc on the safety valve pipeline.

[0050] In one embodiment of the present invention, the discharge area of ​​the first auxiliary rupture disc 404 is the same as that of the second auxiliary rupture disc 405, and the discharge area of ​​the first safety valve 402 is smaller than that of the first auxiliary rupture disc 404. This structural design makes the location of the first safety valve 402 the position with the smallest diameter on the safety valve pipeline, which is beneficial to further improve the discharge efficiency of the safety valve pipeline.

[0051] In one embodiment of the present invention, the multiple rupture discs in the rupture disc pipeline include a main rupture disc 406, a third auxiliary rupture disc 407, and a fourth auxiliary rupture disc 408. The third auxiliary rupture disc 407 and the fourth auxiliary rupture disc 408 are respectively disposed upstream and downstream of the main rupture disc 406. The bursting pressure of the main rupture disc 406 is the same as the bursting pressure of the third auxiliary rupture disc 407, and the bursting pressure of the fourth auxiliary rupture disc 408 is less than the bursting pressure of the third auxiliary rupture disc 407.

[0052] Specifically, the third auxiliary rupture disc 407 is positioned upstream of the main rupture disc 406 to isolate the reactants in the reactor 1, preventing premature rupture and failure of the main rupture disc 406 that could lead to premature venting. If there is no barrier between the main rupture disc 406 and the venting material collection unit 5, the pressure generated by the venting material collection unit 5 during the active venting process could affect the rupture of the main rupture disc 406. Therefore, the fourth auxiliary rupture disc 408 is positioned downstream of the main rupture disc 406 to isolate it from other components downstream of the main rupture disc 406 (such as the venting material collection unit 5), ensuring that the rear side of the main rupture disc 406 is under normal pressure. This prevents the main rupture disc 406 from directly forming a pressure system with other downstream components (such as the venting material collection unit 5) and affecting the rupture of the main rupture disc 406. In this embodiment, the burst pressure of the main rupture disc 406 is 90%-120% of the preset pressure relief value. More preferably, the burst pressure of the main rupture disc 406 is 98%-110% of the preset pressure relief value. This range effectively prevents premature bursting of the third auxiliary rupture disc 407 and the main rupture disc 406, which could lead to premature leakage of reactants and economic losses. It also prevents excessive pressure in the reactor 1 from causing damage or rupture. In this embodiment, the burst pressure of the fourth auxiliary rupture disc 408 is 50%-90% of the preset pressure relief value. More preferably, the burst pressure of the fourth auxiliary rupture disc 408 is 60%-80% of the preset pressure relief value. This range allows the fourth auxiliary rupture disc 408 to easily burst during passive relief, quickly opening the rupture disc pipeline.

[0053] In one embodiment of the present invention, the rupture disc pipeline further includes a third pressure sensor 411, a fourth pressure sensor 412, a third drain line, and a fourth drain line (the third drain line and the fourth drain line are not shown in the figure). The third pressure sensor 411 and the third drain line are both disposed on the second pipeline 403 and located between the third auxiliary rupture disc 407 and the main rupture disc 406. The fourth pressure sensor 412 and the fourth drain line are both disposed on the second pipeline 403 and located between the fourth auxiliary rupture disc 408 and the main rupture disc 406, and are used to determine the working status of each rupture disc on the rupture disc pipeline.

[0054] In one embodiment of the present invention, the venting area of ​​the third auxiliary rupture disc 407 is the same as that of the fourth auxiliary rupture disc 408, and the venting area of ​​the main rupture disc 406 is smaller than that of the third auxiliary rupture disc 407. This structural design makes the position of the main rupture disc 406 the position with the smallest diameter on the rupture disc pipeline, which is beneficial to further improve the venting efficiency of the rupture disc pipeline.

[0055] In one embodiment of the present invention, the active venting unit 3 includes a third pipeline 301 and a pressure control valve 302 disposed on the third pipeline 301. The pressure control valve 302 is signal-connected to the pressure detection unit 2, and the opening pressure of the pressure control valve 302 is 50%-100% of the second preset pressure value.

[0056] Specifically, in this embodiment, the venting unit also includes a display unit for displaying the pressure inside the reactor 1. The pressure detection unit 2, the control unit, and the display unit are integrated and installed on the third pipeline 301. When the pressure detection unit 2 detects that the pressure in the reactor 1 reaches the opening pressure of the pressure control valve 302, it transmits a signal to the control unit. The control unit controls the active venting unit 3 to activate the venting function to pre-vent the pressure in the reactor 1. The opening pressure of the pressure control valve 302 is the first preset pressure value, and the opening of the pressure control valve 302... The pressure is further preferably 70%-90% of the second preset pressure value. The above-mentioned value range makes it preferable for the active release unit 3 to release pressure than the passive release unit 4, and can better control the release process of the ethyl acetate polymerization reaction. In addition, when the valve opening of the pressure control valve 302 is 100%, the opening pressure of the pressure control valve 302 is 80%-100% of the preset pressure release value. Further, when the valve opening of the pressure control valve 302 is 100%, the opening pressure of the pressure control valve 302 is preferably 85%-95% of the preset pressure release value.

[0057] In one embodiment of the present invention, the discharge area of ​​the pressure control valve 302 is smaller than the minimum discharge area of ​​the passive discharge unit 4. Since the active discharge process is relatively gentle, this design can save manufacturing costs while meeting the active discharge requirements. Specifically, in this embodiment, the throat diameter of the pressure control valve 302 is 10%-60% of the minimum throat diameter of the passive discharge unit 4. Further, the throat diameter of the pressure control valve 302 is preferably 20%-40% of the minimum throat diameter of the passive discharge unit 4. The above numerical range can avoid the cross-section at the position of the pressure control valve 302 being too narrow, which would affect the efficiency of active discharge, and can also avoid excessive discharge of reactants during active discharge, which would affect the stability of the entire discharge system.

[0058] In one embodiment of the present invention, the first end of the third pipeline 301 is connected to the outlet at the top of the reactor 1, and the second end of the third pipeline 301 is connected to the discharge material collection unit 5. The diameters of the outlet at the top of the reactor 1 and the third pipeline 301 are both larger than the throat diameter of the pressure control valve 302, so as to avoid the discharge efficiency of the active discharge unit 3 being affected by the outlet at the top of the reactor 1 and / or the third pipeline 301.

[0059] In one embodiment of the present invention, the discharge material collection unit 5 includes a collection tank 501 and baffles 502 disposed in the collection tank 501. Specifically, the upper half of the collection tank 501 is provided with a first inlet connected to the active discharge unit 3, and the active discharge unit 3 discharges the reactant material into the collection tank 501 through the first inlet; the bottom of the collection tank 501 is provided with a second inlet and a third inlet connected to the passive discharge unit 4, and the passive discharge unit 4 discharges the reactant material into the collection tank 501 through the second inlet and the third inlet. There are two baffles 502, which are respectively disposed at intervals above the second inlet and the third inlet to prevent the reactant material entering the collection tank 501 through the second inlet and the third inlet from impacting the top of the collection tank 501.

[0060] In one embodiment of the present invention, the venting system further includes a flare unit 6 disposed downstream of the venting material collection unit 5. Specifically, the top of the collection tank 501 is provided with a first outlet and a second outlet. The first outlet and the second outlet are respectively connected to the flare unit 6 via a fourth pipe 503 and a fifth pipe 505. The flare unit 6 is used to treat combustible and / or toxic gases in the vented reaction materials that cannot be recovered and reprocessed, thereby avoiding environmental pollution. The fourth pipe 503 is provided with a flow-limiting orifice plate 504, and the flow rate of the flow-limiting orifice plate 504 is consistent with the maximum processing capacity of the flare unit 6, so as to prevent the gas flowing out of the collection tank 501 from impacting the flare unit 6, and also to prevent the flare unit 6 from incompletely treating the above-mentioned discharged gas. The fifth pipe 505 is provided with a second safety valve 506, which is used to passively open the fifth pipe 505 when the pressure in the collection tank 501 is too high, so that the gas in the collection tank 501 can enter the flare unit 6 for treatment through the fifth pipe 505.

[0061] In this embodiment, the venting system is used for polymerization reactions between vinyl acetate and different reactants. Various parameters, such as the preset venting pressure, the first preset pressure, and the second preset pressure, vary. For example, in the first example, when the capacity of reactor 1 is 100L and its withstand pressure is 10MPa, with a simulated design pressure of 7MPa, the venting process, based on experiments and venting design, is a unidirectional steam-type venting, with a preset total venting area of ​​14.8mm². 2 The preset pressure relief value is 4 MPa; in the active relief unit 3, the opening pressure of the pressure control valve 302 is 5 MPa (i.e., the first preset pressure value is 5 MPa); when the valve opening of the pressure control valve 302 is 100%, the opening pressure of the pressure control valve 302 is 6.3 MPa, and the relief area of ​​the pressure control valve 302 is 3 mm². 2 In the passive relief unit 4, the opening pressure of the first safety valve 402 and the burst pressure of the first auxiliary rupture disc 404 are both 6.7 MPa, the burst pressure of the second auxiliary rupture disc 405 is 3 MPa, and the relief area of ​​the first safety valve 402 is 8 mm². 2 The burst pressure of the main rupture disc 406 and the third auxiliary rupture disc 407 is 7 MPa, the burst pressure of the fourth auxiliary rupture disc 408 is 3 MPa, and the relief area of ​​the main rupture disc 406 is 8 mm. 2 The volume of the collection tank 501 is 100L. The outlet of the collection tank 501 is first connected to the gas-liquid separator, and then the gas-liquid separator is connected to the flare unit 6.

[0062] Vinyl acetate, ethylene, and methanol solvent are added to reactor 1, with the liquid phase reactants accounting for 60% of the volume. After adding excess initiator, the reaction temperature in reactor 1 reaches 50°C (reactor 1 is equipped with a temperature detection unit connected to the control unit). When the pressure reaches 4MPa, polymerization begins. Raising the temperature in reactor 1 to 70°C will cause the reaction to runaway. The pressure in reactor 1 rises to 5MPa, after which the control unit opens the pressure control valve 302. The reaction in reactor 1 continues to runaway, and the pressure rises rapidly to 7MPa. This pressure causes the first safety valve 402 pipeline and the rupture disc pipeline to be simultaneously opened to release the pressure in reactor 1, causing the pressure in reactor 1 to drop instantly. The released reactants enter the collection tank 501 of the material collection unit. The gas and a small amount of liquid from the reactants entering the collection tank 501 are discharged through the first outlet and / or the second outlet of the collection tank 501. A small amount of liquid remains at the bottom of the collection tank 501.

[0063] In the second example, when the capacity of reactor 1 is 100L and its pressure tolerance is 10MPa, with a simulated design pressure of 3MPa, the venting process, based on experiments and venting design, is a steam-type two-phase flow venting, with a preset total venting area of ​​32mm². 2 The preset pressure relief value is 1 MPa; in the active relief unit 3, the opening pressure of the pressure control valve 302 is 2.5 MPa (i.e., the first preset pressure value is 2.75 MPa); when the valve opening of the pressure control valve 302 is 100%, the opening pressure of the pressure control valve 302 is 6.3 MPa, and the relief area of ​​the pressure control valve 302 is 5 mm². 2 In the passive relief unit 4, the opening pressure of the first safety valve 402 and the burst pressure of the first auxiliary rupture disc 404 are both 2.8 MPa, the burst pressure of the second auxiliary rupture disc 405 is 1 MPa, and the relief area of ​​the first safety valve 402 is 16 mm². 2 The burst pressure of the main rupture disc 406 and the third auxiliary rupture disc 407 is 3 MPa, and the burst pressure of the fourth auxiliary rupture disc 408 is 1 MPa. The venting area of ​​the main rupture disc 406 is 16 mm². 2 ;

[0064] Vinyl acetate was added to reactor 1 for polymerization. The pressure in reactor 1 rose to 2.5 MPa, and the reaction became uncontrollable. The control unit opened the pressure control valve 302. The reaction in reactor 1 continued to run out of control, and the pressure rose rapidly to 3 MPa. The pressure caused the first safety valve 402 pipeline and the rupture disc pipeline to be opened simultaneously to release the pressure in reactor 1. The pressure in reactor 1 continued to rise to 3.3 MPa and then began to decrease. The released reaction material entered the collection tank 501 of the material collection unit. The gas and a small amount of liquid of the reaction material that entered the collection tank 501 were discharged through the first outlet and / or the second outlet of the collection tank 501. A certain amount of liquid remained at the bottom of the collection tank 501.

[0065] In the third example, when the capacity of reactor 1 is 100L and its pressure tolerance is 10MPa, with a simulated design pressure of 5MPa, the venting process, based on experiments and venting design, is a steam-type two-phase flow venting, with a preset total venting area of ​​7.4mm². 2 The preset pressure relief value is 2.5 MPa; in the active relief unit 3, the opening pressure of the pressure control valve 302 is 4 MPa (i.e., the first preset pressure value is 4 MPa); when the valve opening of the pressure control valve 302 is 100%, the opening pressure of the pressure control valve 302 is 4.5 MPa, and the relief area of ​​the pressure control valve 302 is 0.74 mm². 2 In the passive relief unit 4, the opening pressure of the first safety valve 402 and the burst pressure of the first auxiliary rupture disc 404 are both 4.8 MPa, the burst pressure of the second auxiliary rupture disc 405 is 3.5 MPa, and the relief area of ​​the first safety valve 402 is 2 mm². 2 The burst pressure of the main rupture disc 406 and the third auxiliary rupture disc 407 is 5 MPa, and the burst pressure of the fourth auxiliary rupture disc 408 is 2 MPa. The relief area of ​​the main rupture disc 406 is 3.5 mm. 2 ;

[0066] Vinyl acetate and hexene are added to reactor 1 for polymerization. When the pressure in reactor 1 rises to 4 MPa, the reaction becomes uncontrollable. The control unit opens the pressure control valve 302, and the reaction in reactor 1 continues to run uncontrollably. The pressure rises rapidly to 5 MPa. This pressure causes the first safety valve 402 line and the rupture disc line to be opened simultaneously to release the pressure in reactor 1. When the pressure in reactor 1 continues to rise to 7 MPa, the pressure in reactor 1 exceeds 110% of the preset pressure release value. After that, the pressure in reactor 1 begins to drop, and the released reactants enter the collection tank 501 of the material collection unit. The gas and a small amount of liquid from the reactants entering the collection tank 501 are discharged through the first outlet and / or the second outlet of the collection tank 501. A certain amount of liquid remains at the bottom of the collection tank 501.

[0067] This invention provides a venting system for vinyl acetate polymerization. The system includes an active venting unit and a passive venting unit connected to the reactor. The active venting unit is signal-connected to a pressure detection unit and is activated to release pressure in the reactor when the pressure reaches a first preset pressure value. The passive venting unit is activated by the reactants in the reactor when the pressure reaches a second preset pressure value. The second preset pressure value is greater than the first preset pressure value, allowing the active and passive venting units to sequentially activate after reaching different pressure limits in the reactor. This sequentially releases pressure in the reactor undergoing vinyl acetate polymerization, preventing runaway polymerization and overpressure, thus effectively protecting the reactor. The system also features a simple structure and high economic efficiency.

[0068] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

[0069] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0070] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A vent system for the polymerization of vinyl acetate characterized in that, The venting system includes: The reaction vessel (1) is used for the polymerization reaction of vinyl acetate. Pressure detection unit (2) is used to detect the pressure inside the reactor (1); The active venting unit (3) is connected to the pipeline of the reactor (1) and is signal-connected to the pressure detection unit (2). The active venting unit (3) is activated when the pressure inside the reactor (1) reaches a first preset pressure value. A passive venting unit (4) is connected to the reactor (1) via pipeline and is arranged in parallel with the active venting unit (3). When the pressure in the reactor (1) reaches a second preset pressure value, the passive venting unit (4) is activated by the reaction material in the reactor (1) through pressure. The second preset pressure value is greater than the first preset pressure value. The passive venting unit (4) includes a safety valve pipeline and a rupture disc pipeline. The safety valve pipeline includes a first pipeline (401) connected to the reactor (1) and a first safety valve (402) installed on the first pipeline (401). The opening pressure of the first safety valve (402) is the second preset pressure value. The safety valve pipeline also includes a first auxiliary rupture disc (404) and a second auxiliary rupture disc (405) respectively installed upstream and downstream of the first safety valve (402). The bursting pressure of the first auxiliary rupture disc (404) is related to the opening pressure of the first safety valve (402). The opening pressures are consistent, and the bursting pressure of the second auxiliary rupture disc (405) is less than that of the first auxiliary rupture disc (404); the multiple rupture discs on the rupture disc pipeline include a main rupture disc (406), a third auxiliary rupture disc (407), and a fourth auxiliary rupture disc (408), the third auxiliary rupture disc (407) and the fourth auxiliary rupture disc (408) are respectively disposed upstream and downstream of the main rupture disc (406), the bursting pressure of the main rupture disc (406) is consistent with that of the third auxiliary rupture disc (407), and the bursting pressure of the fourth auxiliary rupture disc (408) is less than that of the third auxiliary rupture disc (407); the rupture disc pipeline and the safety valve pipeline are connected in parallel and include a second pipeline (403) and multiple rupture discs disposed on the second pipeline (403), and the bursting pressure of at least one of the rupture discs is greater than the opening pressure of the first safety valve (402).

2. The vent system for the vinyl acetate polymerization reaction according to claim 1, characterized by, The discharge area of ​​the first auxiliary rupture disc (404) is the same as that of the second auxiliary rupture disc (405), and the discharge area of ​​the first safety valve (402) is smaller than that of the first auxiliary rupture disc (404).

3. The vent system for the vinyl acetate polymerization reaction according to claim 2, characterized by, The venting area of ​​the third auxiliary rupture disc (407) is the same as that of the fourth auxiliary rupture disc (408), and the venting area of ​​the main rupture disc (406) is smaller than that of the third auxiliary rupture disc (407).

4. The vent system for the vinyl acetate polymerization reaction according to claim 3, characterized by, The active bleed unit (3) comprises a third pipeline (301) and a pressure control valve (302) arranged on the third pipeline (301), the pressure control valve (302) is signal connected with the pressure detection unit (2), and the opening pressure of the pressure control valve (302) is 50%-100% of the second preset pressure value.

5. The vent system for the vinyl acetate polymerization reaction according to claim 4, characterized by, The bleed area of the pressure control valve (302) is smaller than the minimum bleed area of the passive bleed unit (4).

6. The vent system for the vinyl acetate polymerization reaction according to claim 1, characterized by, The bleed system further comprises a bleed material collecting unit (5) arranged downstream of the active bleed unit (3) and the passive bleed unit (4).

7. The vent system for the vinyl acetate polymerization reaction according to claim 6, characterized by, The bleed system further comprises a flare unit (6) arranged downstream of the bleed material collecting unit (5).

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