Vinyl acetate reaction liquid degassing device

Abstract

The utility model relates to a vinyl acetate reaction liquid degassing device which comprises a degassing tower feed preheater, a degassing tower, a degassing tower circulating water condenser, a degassing tower chilled water condenser, a degassing tower kettle liquid pump, a degassing tower reflux pump and a degassing tower distillation pump. According to the device, the reaction liquid in the reaction liquid collecting tank is preheated by the degassing tower feeding preheater and then sent to the degassing tower for degassing, most of the tower bottoms of the degassing tower is fed into the first rectifying tower, and a small part of the tower bottoms of the degassing tower enters the degassing tower feeding preheater for heat exchange and then is sent to the reaction liquid storage tank, so that the tail gas amount of the reaction liquid storage tank is reduced by 90%; the problems of large tail gas amount and high calcium carbide consumption caused by the fact that reaction liquid is conveyed to a reaction liquid storage tank at present are solved; meanwhile, the acetylene content in the reaction liquid is reduced to 1-1.5%.

Description

Technical Field

[0001] The utility model belongs to the field of chemical equipment, and in particular relates to a degassing device for vinyl acetate reaction liquid. Background Art

[0002] Currently, the vinyl acetate reaction liquid produced in a fluidized bed synthesis reactor is first sent to a reaction liquid manifold, then pumped to a tank farm. From there, it is fed to the first distillation column, where it separates acetic acid, vinyl acetate, acetaldehyde, and acetylene gas. The offgas from the first distillation column is then returned to the synthesis water scrubber for water washing. Because the reaction liquid contains 1.8-2.3% acetylene, this not only produces large amounts of offgas, posing a safety hazard, but also leads to high consumption of calcium carbide, the raw material used to produce acetylene. Furthermore, the acetylene in this reaction liquid, once fed to the first distillation column, impairs the separation efficiency of the first distillation column and the condensation efficiency of the distillate condenser. This results in large offgas volumes from the first distillation column, high acetaldehyde levels in the bottom of the first distillation column, and high acetaldehyde levels in the distillate from the second distillation column (which separates the acetic acid and vinyl acetate separated in the first distillation column). In addition, due to the large amount of tail gas from the first distillation tower, the tail gas containing a large amount of vinyl acetylene (1.5%), acetaldehyde (more than 20%) and VAC (1.0%) returns to the water washing tower for water washing treatment, resulting in a vicious cycle and causing the water washing tower to operate at overload.

[0003] After in-depth research, the inventors discovered that the primary cause of the high volume of off-gas and high acetaldehyde and VAC contents in the first distillation tower is the presence of acetylene in the synthesis reaction liquid, which presents a challenge in separating acetylene and acetaldehyde. The original design of the first distillation tower likely failed to consider the acetaldehyde content in the off-gas, resulting in an acetaldehyde content exceeding 20% and a VAC content of 1.0%. This increased the tower load and created a vicious cycle of acetaldehyde and vinyl acetylene in the system. Because the first distillation tower process is difficult to control, increasing the evaporation rate to reduce the acetaldehyde content in the bottom of the tower results in high acetaldehyde and VAC contents in the off-gas of the first distillation tower, increasing the load on the water scrubber. Acetylene recovered from the top of the water scrubber contains VAC and acetaldehyde, resulting in poor acetylene purification and, ultimately, a sudden deterioration of the synthesis reaction. Utility Model Content

[0004] The first technical problem to be solved by the present invention is that after the current reaction liquid is sent to the reaction liquid storage tank, not only a large amount of tail gas is generated, which poses a safety hazard, but also the consumption of calcium carbide, a raw material for producing acetylene, is high. The second technical problem to be solved by the present invention is that after the current reaction liquid is sent to the first distillation tower for feeding, the acetylene in the reaction liquid affects the separation effect of the first distillation tower and the condensation effect of the distillation condenser, which not only causes a large amount of tail gas from the first distillation tower, but also causes a high acetaldehyde content in the bottom of the first distillation tower and a high acetaldehyde content in the distillate of the second distillation tower. The third technical problem to be solved by the present invention is that due to the large amount of tail gas from the first distillation tower, the tail gas containing a large amount of vinyl acetylene (1.5%), acetaldehyde (more than 20%) and VAC (1.0%) returns to the water washing tower for water washing treatment, resulting in a vicious cycle and causing the water washing tower to operate in overload. For this reason, the present invention provides a degassing device for vinyl acetate reaction liquid.

[0005] The utility model cleverly designs a reaction liquid degassing system. After the reaction liquid is degassed (the kettle temperature of the degassing tower is controlled at 80±2°C), most of it is directly fed to the first distillation tower, and a small part is cooled through the degassing tower feed preheater and then sent to the reaction liquid storage tank, thereby solving the above technical problems.

[0006] The utility model is realized through the following technical solutions:

[0007] The utility model provides a degassing device for vinyl acetate reaction liquid, which comprises: a degassing tower feed preheater, a degassing tower, a degassing tower circulating water condenser, a degassing tower chilled water condenser, a degassing tower kettle liquid pump, a degassing tower reflux pump, and a degassing tower distillate pump, wherein a cold medium inlet of the degassing tower feed preheater is connected to a discharge pipeline of a reaction liquid collecting tank, a cold medium outlet of the degassing tower feed preheater is connected to an inlet of the degassing tower via a pipeline, a tower top outlet of the degassing tower is connected to an inlet of the degassing tower circulating water condenser via a pipeline, a condensate outlet pipeline of the degassing tower circulating water condenser is returned to the tower top of the degassing tower via the degassing tower reflux pump, a gas phase outlet of the degassing tower circulating water condenser is connected to an inlet of the degassing tower chilled water condenser via a pipeline, a top outlet of the degassing tower chilled water condenser is connected to an inlet pipeline of a water washing tower via a pipeline, and a tower kettle outlet pipeline of the degassing tower is connected to an inlet of a first distillation tower for separating acetic acid, vinyl acetate, acetaldehyde, and acetylene gas via the degassing tower kettle liquid pump. The degassing tower can remove acetylene and some acetaldehyde from the reaction liquid, thereby reducing the pressure on the first distillation tower to remove light components, which helps improve the separation efficiency of the first distillation tower. It can also remove some light components such as vinyl acetylene and other impurities from the tail gas, continuously improving system quality. The water scrubber is used to remove a small amount of acetaldehyde contained in the acetylene.

[0008] The reaction liquid in the present invention refers to vinyl acetate fluidized bed reaction liquid.

[0009] Furthermore, the bottom outlet pipe of the degassing tower chilled water condenser is connected to the inlet of the distillation tower for separating vinyl acetate and acetaldehyde through the degassing tower distillation pump.

[0010] Furthermore, in the vinyl acetate reaction liquid degassing apparatus, the degassing tower is a packed tower, and the packing material of the packed tower is selected from corrugated metal plates and / or wire mesh. The packing material serves to increase the heat exchange area between the hot and cold materials within the tower, and the heat exchange area of these two types of packing materials is larger than that of trays.

[0011] Furthermore, in the aforementioned vinyl acetate reaction liquid degassing apparatus, the distance between the degassing tower inlet and the tower bottom is 1 / 2 to 2 / 3 of the total height of the degassing tower. Since the feed primarily consists of acetic acid and vinyl acetate, a feed height that is too high may result in the distillation of acid and a large amount of vinyl acetate from the tower top.

[0012] Furthermore, in the above vinyl acetate reaction liquid degassing device, the degassing tower feed preheater is a plate heat exchanger. The plate heat exchanger has a compact structure, occupies a small space and has a large heat exchange area.

[0013] Furthermore, in the above-mentioned vinyl acetate reaction liquid degassing device, the outlet pipe of the degassing tower bottom liquid pump is provided with a branch connected to the heat medium inlet of the degassing tower feed preheater, and the heat medium outlet of the degassing tower feed preheater is connected to the reaction liquid storage tank feed pipeline.

[0014] Furthermore, in the above-mentioned vinyl acetate reaction liquid degassing device, a first valve for changing the liquid flow direction is provided on the branch line between the heat medium inlet of the degassing tower feed preheater and the outlet of the degassing tower bottom liquid pump.

[0015] Furthermore, in the vinyl acetate reaction liquid degassing apparatus, the outlet pipe of the degassing tower reflux pump includes a branch line connected to the inlet of the distillation tower for separating vinyl acetate and acetaldehyde. This arrangement is implemented because the liquid level in the condenser needs to be stabilized by discharging the reflux pump after the reflux rate is fixed.

[0016] Furthermore, in the above-mentioned vinyl acetate reaction liquid degassing device, a second valve for changing the liquid flow direction is provided on the branch line between the outlet of the degassing tower reflux pump and the inlet of the distillation tower for separating vinyl acetate and acetaldehyde.

[0017] Furthermore, in the vinyl acetate reaction liquid degassing apparatus, a polymerization inhibitor feed line is provided on the pipeline between the degassing tower reflux pump and the top of the degassing tower. Preferably, a line for feeding TDA (thiodiphenylamine) or a line for feeding hydroquinone is provided, and more preferably, a line for feeding TDA (thiodiphenylamine). The polymerization inhibitor is added to the degassing tower to prevent VAC from self-polymerizing in the upper portion of the degassing tower. The polymerization inhibitor can be added at a rate of 40-80 L / h.

[0018] Furthermore, in the above-mentioned vinyl acetate reaction liquid degassing device, a nitrogen addition pipeline is provided at the bottom of the degassing tower. Nitrogen replacement is performed before the degassing tower is started to prevent the oxygen and acetylene gas in the tower from forming an explosive gas.

[0019] Furthermore, in the vinyl acetate reaction liquid degassing apparatus, a nitrogen blanketing system is installed on the tail gas vent line of the first distillation tower. Although the acetylene dissolved in the reaction liquid is almost completely removed in the degassing tower, a small amount of acetylene (the supernatant filtered from the first distillation tower feed contains a small amount of acetylene) and vinyl acetylene, other flammable and explosive gases, still remain in the tail gas of the first distillation tower. Therefore, for safety reasons, a nitrogen blanketing system is installed on the vent line of the first distillation tower tail gas acetylene recovery step.

[0020] The vinyl acetate reaction liquid degassing device of the utility model is degassing according to the following process flow: the reaction liquid in the reaction liquid collecting tank (i.e. the reaction liquid obtained after the reaction of acetylene gas and acetic acid, the main components of which are 45-55% acetic acid, 35-45% vinyl acetate, 1.5-2.5% acetaldehyde, and 2.0-2.5% acetylene (acetylene is a volume percentage), 5-10°C) first enters the degassing tower feed preheater for preheating (the feed temperature is about 15°C, and is raised to 30-50°C by heat exchange, preferably by The heat exchange reaches 30-35℃), and then enters the degassing tower for degassing (the degassing tower is used to analyze the acetylene dissolved in the reaction liquid by heating). The top gas of the degassing tower (mainly acetylene gas and acetaldehyde) (acetylene gas comes out from the top of the condenser to the water scrubber, and part of the condensed acetaldehyde returns to the tower to cool the gas in the degassing tower by reflux) is first condensed in the circulating water condenser of the degassing tower (circulating water temperature is 20~26℃). Most of the condensate in the circulating water condenser of the degassing tower (for example, 80~90%) (The condensate is mainly vinyl acetate and a small amount of acetaldehyde. It returns to the tower to cool the rising gas in the tower through reflux) It returns to the top of the degassing tower through the degassing tower reflux pump. The remaining part of the condensate (for example, 10~20%) is fed to the distillation tower for vinyl acetate and acetaldehyde separation (the distillation tower is fed during normal operation). It can also be added to the inlet of the degassing tower reflux pump when the system is just started. The uncondensed gas (mainly acetylene gas and a small amount of CO2, N2, etc.) of the degassing tower circulating water condenser enters the degassing tower chilled water condensation The condensate from the degassing tower chilled water condenser (mainly acetaldehyde and a small amount of vinyl acetate) is fed to the distillation tower for separating vinyl acetate and acetaldehyde through the degassing tower distillation pump. The uncondensed gas (acetylene gas containing acetaldehyde and vinyl acetate, including 65% acetylene, 23% acetaldehyde, 10.7% vinyl acetate, 1.3% other impurities, and no acetic acid) is sent to the acetylene recovery tank for water washing in the water washing tower. When the device is started, stopped or abnormal, the tail gas is vented through a flame arrester and nitrogen filling. Most (e.g. 70-80%) of the bottom liquid of the degassing tower (the main components of the bottom liquid are acetic acid 50-55%, vinyl acetate 40-45%, acetaldehyde 1-2.5%, acetylene 1-1.5% (acetylene is by volume), 80-90°C) is fed through the degassing tower bottom liquid pump to the first distillation tower for separating acetic acid, vinyl acetate, acetaldehyde and acetylene gas (the top distillate gas of the first distillation tower is acetylene gas and acetaldehyde, and the bottom liquid acetic acid and vinyl acetate are sent to the second distillation tower for separating acetic acid and vinyl acetate, the top distillate gas of the second distillation tower is vinyl acetate, and the bottom liquid is acetic acid). A small part (e.g. 20-30%) of the bottom liquid enters the degassing tower feed preheater for heat exchange with the reaction liquid and is then sent to the reaction liquid storage tank (due to fluctuations in the bottom liquid volume, only a part of the bottom liquid is used for heat exchange in order to ensure the feeding temperature).

[0021] In the present application, the feed to the first distillation tower is the reaction liquid of vinyl acetate, which is the liquid obtained by the reaction of acetylene gas and acetic acid. The main components are acetic acid (45-55%), vinyl acetate (35-45%), acetaldehyde (1.5-2.5%), and acetylene (2.0-2.5%) (acetylene is the volume percentage). The first distillation tower is used to separate acetic acid, vinyl acetate, acetaldehyde, and acetylene gas, and the second distillation tower is used to separate the acetic acid and vinyl acetate separated by the first distillation tower.

[0022] In this application, the distillation column for separating vinyl acetate and acetaldehyde is a device in an existing vinyl acetate reaction liquid purification process, used to separate vinyl acetate and acetaldehyde, and the water scrubber is a water scrubber in the existing process. In the existing process, the feed to the distillation column for separating vinyl acetate and acetaldehyde is distilled from the first distillation column, and the feed mainly contains vinyl acetate, acetaldehyde, and water.

[0023] The technical solution of the utility model has the following beneficial effects:

[0024] (1) The vinyl acetate reaction liquid degassing device of the present invention preheats the reaction liquid from the reaction liquid collecting tank through the degassing tower feed preheater and then sends it to the degassing tower for degassing. Most of the bottom liquid of the degassing tower is fed to the first distillation tower, and a small part enters the degassing tower feed preheater for heat exchange with the reaction liquid and then is sent to the reaction liquid storage tank. This can reduce the acetylene content in the reaction liquid to 1-1.5%, so that the tail gas volume of the reaction liquid storage tank is reduced by 90% compared with the current level, and at the same time reduces the consumption of calcium carbide, a raw material for producing acetylene, thereby solving the current problem that after the reaction liquid is sent to the reaction liquid storage tank, not only a large amount of tail gas is generated, which poses a safety hazard, but also leads to high consumption of calcium carbide.

[0025] (2) The degassing device for vinyl acetate reaction liquid of the utility model can separate the acetylene and part of the acetaldehyde in the reaction liquid in advance in the degassing tower to reduce the pressure of the first distillation tower in removing the light components, which is beneficial to improving the separation effect of the first distillation tower. It can also take part of the light components such as vinyl acetylene and other impurities out of the system from the tail gas. The acetaldehyde content of the first distillation tower system is greatly reduced (reduced to 40-50%), the top temperature of the first distillation tower is increased from 60°C to 65°C, and the steam consumption of the first distillation tower can be reduced by about 10%. It solves the problem that after the reaction liquid is sent to the first distillation tower for feeding, the acetylene in the reaction liquid affects the separation effect of the first distillation tower and the condensation effect of the distillation condenser, which not only causes a large amount of tail gas from the first distillation tower, but also causes a high acetaldehyde content in the bottom of the first distillation tower and a high acetaldehyde content in the distillate of the second distillation tower;

[0026] (3) The vinyl acetate reaction liquid degassing device of the utility model can reduce the acetylene content in the reaction liquid to 1-1.5%. The tail gas of the first distillation tower is directly discharged to reduce impurities in the system and reduce the operating load of the water washing tower. It solves the problem that the tail gas of the first distillation tower is large, and the tail gas containing a large amount of vinyl acetylene (1.5%), acetaldehyde (more than 20%) and VAC (1.0%) returns to the water washing tower for water washing treatment, resulting in a vicious cycle and causing the water washing tower to operate overloaded. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the content of the utility model easier to understand, the utility model is further described in detail below based on the specific embodiments of the utility model in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 This is a schematic structural diagram of a vinyl acetate reaction liquid degassing device according to Example 1 of the present utility model;

[0029] Figure 2 This is a schematic structural diagram of a vinyl acetate reaction liquid purification device according to Comparative Example 1 of the present invention;

[0030] Among them: 1. Degassing tower feed preheater; 2. Degassing tower; 3. Degassing tower circulating water condenser; 4. Degassing tower chilled water condenser; 5. Degassing tower kettle liquid pump; 6. Degassing tower reflux pump; 7. Degassing tower distillate pump; 8. First valve; 9. Second valve; 101. Reaction liquid collecting tank; 102. Reaction liquid collecting tank delivery pump; 103. Reaction liquid storage tank; 104. Reaction liquid storage tank delivery pump; 105. First distillation tower; 106. Condenser. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] In the description of the utility model, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, an indirect connection through an intermediate medium, or a connection between the two components. The terms "upper", "middle", "outer", "inner", "lower", "surrounding", "left", "right", "front", "back", "top", "bottom", etc. indicate directions or positional relationships. They are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the utility model. For those of ordinary skill in the art, the specific meanings of the above terms in the utility model can be understood according to specific circumstances.

[0033] like Figure 1 As shown, the utility model of the vinyl acetate reaction liquid degassing device includes: a degassing tower feed preheater 1, a degassing tower 2, a degassing tower circulating water condenser 3, a degassing tower chilled water condenser 4, a degassing tower kettle liquid pump 5, a degassing tower reflux pump 6, and a degassing tower distillate pump 7, wherein the cold medium inlet of the degassing tower feed preheater 1 is connected to the discharge pipeline of the reaction liquid collecting tank 101, the cold medium outlet of the degassing tower feed preheater 1 is connected to the inlet of the degassing tower 2 through a pipeline, the top outlet of the degassing tower 2 is connected to the top inlet of the degassing tower circulating water condenser 3 through a pipeline, and the condensate outlet pipe of the degassing tower circulating water condenser 3 is connected to the top inlet of the degassing tower The gas is returned to the top or upper part of the degassing tower 2 through the degassing tower reflux pump 6, the gas phase outlet of the degassing tower circulating water condenser 3 is connected to the inlet of the degassing tower chilled water condenser 4 through a pipeline, the top outlet of the degassing tower chilled water condenser 4 is connected to the inlet pipeline of the water washing tower (not shown) through a pipeline, the bottom outlet pipeline of the degassing tower chilled water condenser 4 is connected to the inlet of the distillation tower (not shown) for separating vinyl acetate and acetaldehyde through the degassing tower distillate pump 7, and the tower bottom outlet pipeline of the degassing tower 2 is connected to the inlet of the first distillation tower 105 for separating acetic acid, vinyl acetate, acetaldehyde and acetylene gas through the degassing tower bottom liquid pump 5.

[0034] In a preferred embodiment, the degassing tower 2 is a packed tower, and the packing of the packed tower is selected from corrugated metal plates and / or wire mesh.

[0035] In another preferred embodiment, the distance between the inlet of the degassing tower 2 and the bottom of the tower is 1 / 2 to 2 / 3 of the total height of the degassing tower 2.

[0036] In yet another preferred embodiment, the degassing tower feed preheater 1 is a plate heat exchanger.

[0037] In another preferred embodiment, the outlet pipe of the degassing tower bottom liquid pump 5 is provided with a branch connected to the heat medium inlet of the degassing tower feed preheater 1, and the heat medium outlet of the degassing tower feed preheater 1 is connected to the feed pipeline of the reaction liquid storage tank 103.

[0038] In another preferred embodiment, a first valve 8 for changing the flow direction of the liquid is provided on the branch line between the heat medium inlet of the degassing tower feed preheater 1 and the outlet of the degassing tower bottom liquid pump 5 .

[0039] In another preferred embodiment, the outlet pipe of the degassing tower reflux pump 6 includes a branch connected to the inlet of the distillation tower for separating vinyl acetate and acetaldehyde. This is done because the reflux volume needs to be sent out to stabilize the liquid level in the condenser after it is fixed.

[0040] In another preferred embodiment, a second valve 9 for changing the flow direction of the liquid is provided on the branch line between the outlet of the degassing tower reflux pump 6 and the inlet of the distillation tower for separating vinyl acetate and acetaldehyde.

[0041] In another preferred embodiment, a polymerization inhibitor feeding line is provided on the pipeline between the degassing tower reflux pump 6 and the top of the degassing tower 2, preferably a thiopheneamine feeding line or a hydroquinone feeding line, more preferably a thiopheneamine feeding line.

[0042] In another preferred embodiment, a nitrogen adding pipeline is provided at the bottom of the degassing tower 2 . Example 1

[0043] The vinyl acetate reaction liquid degassing device of this embodiment includes: a degassing tower feed preheater 1, a degassing tower 2, a degassing tower circulating water condenser 3, a degassing tower chilled water condenser 4, a degassing tower kettle liquid pump 5, a degassing tower reflux pump 6, and a degassing tower distillate pump 7, wherein the cold medium inlet of the degassing tower feed preheater 1 is connected to the discharge pipeline of the reaction liquid collecting tank 101, the cold medium outlet of the degassing tower feed preheater 1 is connected to the inlet of the degassing tower 2 through a pipeline, the top outlet of the degassing tower 2 is connected to the top inlet of the degassing tower circulating water condenser 3 through a pipeline, the condensate outlet pipeline of the degassing tower circulating water condenser 3 is returned to the top of the degassing tower 2 through the degassing tower reflux pump 6, the gas phase outlet of the degassing tower circulating water condenser 3 is connected to the inlet of the degassing tower chilled water condenser 4 through a pipeline, and the top outlet of the degassing tower chilled water condenser 4 is connected to the degassing tower reflux pump 6. The pipeline is connected to the inlet pipeline of the water washing tower, and the bottom outlet pipeline of the degassing tower chilled water condenser 4 is connected to the inlet of the distillation tower for separating vinyl acetate and acetaldehyde through the degassing tower distillate pump 7. The outlet pipeline of the degassing tower reflux pump 6 includes a branch connected to the inlet of the distillation tower for separating vinyl acetate and acetaldehyde, and a second valve 9 for changing the flow direction of the liquid is provided on the branch. The bottom outlet pipeline of the degassing tower 2 is connected to the inlet of the first distillation tower 105 for separating acetic acid, vinyl acetate and acetaldehyde and acetylene gas through the degassing tower bottom liquid pump 5. The outlet pipeline of the degassing tower bottom liquid pump 5 is provided with a branch connected to the heat medium inlet of the degassing tower feed preheater 1, and a first valve 8 for changing the flow direction of the liquid is provided on the branch. The heat medium outlet of the degassing tower feed preheater 1 is connected to the feed pipeline of the reaction liquid storage tank 103.

[0044] The degassing tower 2 is a packed tower, the packing of which is a corrugated metal plate, and the distance between the inlet and the bottom of the degassing tower 2 is 1 / 2 of the total height of the degassing tower 2.

[0045] Among them, the degassing tower feed preheater 1 is a plate heat exchanger.

[0046] Wherein, a thiodiphenylamine feeding pipeline is provided on the pipeline between the degassing tower reflux pump 6 and the top of the degassing tower 2 .

[0047] Wherein, a nitrogen adding pipeline is provided at the bottom of the degassing tower 2.

[0048] The vinyl acetate reaction liquid degassing device of this embodiment is degassing according to the following process flow: the reaction liquid in the reaction liquid collecting tank 101 (i.e., the reaction liquid obtained after the reaction of acetylene gas and acetic acid, the main components of which are 45-55% acetic acid, 35-45% vinyl acetate, 1.5-2.5% acetaldehyde, and 2.0-2.5% acetylene (acetylene is a volume percentage), 5-10°C) first enters the degassing tower feed preheater 1 to be preheated to about 30-50°C, and then enters the degassing tower 2 for degassing. The top gas of degassing tower 2 (mainly acetylene gas and acetaldehyde) is first condensed by degassing tower circulating water condenser 3 (circulating water temperature 20~26℃), and most of the condensate in degassing tower circulating water condenser 3 is returned to the top of degassing tower 2 through degassing tower reflux pump 6. The remaining part of the condensate is fed to the distillation tower for separation of vinyl acetate and acetaldehyde. The uncondensed gas in degassing tower circulating water condenser 3 enters degassing tower chilled water condenser 4 for condensation (chilled water Temperature -6.5~-5℃), the condensate of the chilled water condenser 4 of the degassing tower is fed to the distillation tower for separating vinyl acetate and acetaldehyde through the degassing tower distillation pump 7, and the uncondensed gas (acetylene gas containing acetaldehyde and VAC, including acetylene 65%, acetaldehyde 23%, VAC 10.7%, other impurities 1.3%, and no acetic acid) is sent to the acetylene recovery tank and sent to the water washing tower for washing. Most of the bottom liquid of the degassing tower 2 (the main components of the bottom liquid are acetic acid and vinyl acetate, 80-90℃) is washed by the degassing tower 2. The degassing tower bottom liquid pump 5 is used to feed the first distillation tower 105 for separating acetic acid, vinyl acetate, acetaldehyde and acetylene gas (the top distillate gas of the first distillation tower is acetylene gas and acetaldehyde, and the bottom liquid acetic acid and vinyl acetate are sent to the second distillation tower for separating acetic acid and vinyl acetate, and the top distillate gas of the second distillation tower is vinyl acetate, and the bottom liquid is acetic acid). A small part of the bottom liquid enters the degassing tower feed preheater 1, exchanges heat with the reaction liquid, and is then sent to the reaction liquid storage tank 103, and then as shown in FIG. Figure 2 In this way, the product is transported to the first distillation tower 105 by a pump. Comparative Example 1

[0049] This comparative example is an existing vinyl acetate reaction liquid purification device, such as Figure 2 As shown, the vinyl acetate reaction liquid is first sent to the reaction liquid collecting tank 101, and then sent to the reaction liquid storage tank 103 through the reaction liquid collecting tank delivery pump 102, and then fed to the first distillation tower 105 through the reaction liquid storage tank delivery pump 104. The top gas (i.e., tail gas) of the first distillation tower 105 passes through the condenser 106 and then returns to the water washing tower for water washing treatment.

[0050] Compared with Comparative Example 1, Example 1 has a large operating load and stable operation.

[0051] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A degassing device for vinyl acetate reaction liquid, characterized in that: The degassing tower comprises a feed preheater (1), a degassing tower (2), a circulating water condenser (3), a chilled water condenser (4), a kettle liquid pump (5), a reflux pump (6), and a distillate pump (7). The cold medium inlet of the feed preheater (1) is connected to the discharge pipeline of the reaction liquid collecting tank (101), the cold medium outlet of the feed preheater (1) is connected to the inlet of the degassing tower (2) via a pipeline, and the top outlet of the degassing tower (2) is connected to the outlet of the circulating water condenser (3) of the degassing tower via a pipeline. The condensate outlet pipe of the degassing tower circulating water condenser (3) is returned to the top of the degassing tower (2) through the degassing tower reflux pump (6), the gas phase outlet of the degassing tower circulating water condenser (3) is connected to the inlet of the degassing tower chilled water condenser (4) through a pipe, the top outlet of the degassing tower chilled water condenser (4) is connected to the water washing tower inlet pipeline through a pipe, and the tower bottom outlet pipe of the degassing tower (2) is connected to the inlet of the first distillation tower (105) for separating acetic acid, vinyl acetate and acetaldehyde and acetylene gas through the degassing tower bottom liquid pump (5).

2. The vinyl acetate reaction liquid degassing device according to claim 1, characterized in that: The bottom outlet pipe of the degassing tower chilled water condenser (4) is connected to the inlet of the distillation tower for separating vinyl acetate and acetaldehyde through the degassing tower distillation pump (7).

3. The vinyl acetate reaction liquid degassing device according to claim 1 or 2, characterized in that: The degassing tower (2) is a packed tower, wherein the packing of the packed tower is selected from corrugated metal plates and / or wire mesh; and / or The distance between the inlet of the degassing tower (2) and the bottom of the tower is 1 / 2 to 2 / 3 of the total height of the degassing tower (2).

4. The vinyl acetate reaction liquid degassing device according to claim 1 or 2, characterized in that: The degassing tower feed preheater (1) is a plate heat exchanger.

5. The vinyl acetate reaction liquid degassing device according to claim 1 or 2, characterized in that: The outlet pipe of the degassing tower kettle liquid pump (5) is provided with a branch connected to the heat medium inlet of the degassing tower feed preheater (1), and the heat medium outlet of the degassing tower feed preheater (1) is connected to the feed pipeline of the reaction liquid storage tank (103).

6. The vinyl acetate reaction liquid degassing device according to claim 5, characterized in that: A first valve (8) for changing the flow direction of liquid is provided on a branch line between the heat medium inlet of the degassing tower feed preheater (1) and the outlet of the degassing tower kettle liquid pump (5).

7. The vinyl acetate reaction liquid degassing device according to claim 1 or 2, characterized in that: The outlet pipeline of the degassing tower reflux pump (6) includes a branch connected to the inlet of the distillation tower for separating vinyl acetate and acetaldehyde.

8. The vinyl acetate reaction liquid degassing device according to claim 7, characterized in that: A second valve (9) for changing the flow direction of the liquid is provided on the branch line between the outlet of the degassing tower reflux pump (6) and the inlet of the distillation tower for separating vinyl acetate and acetaldehyde.

9. The vinyl acetate reaction liquid degassing device according to claim 1 or 2, characterized in that: A polymerization inhibitor supply line is provided on the pipeline between the degassing tower reflux pump (6) and the top of the degassing tower (2).

10. The vinyl acetate reaction liquid degassing device according to claim 1 or 2, characterized in that: A nitrogen adding pipeline is provided at the bottom of the degassing tower (2).

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