A vinyl acetate purification device and process

Abstract

The present invention relates to a vinyl acetate purification device and process. The device comprises: a primary distillation tower, an extraction tower, a secondary distillation tower, a first condenser of the primary distillation tower, a reflux tank of the primary distillation tower, a second condenser of the primary distillation tower, and a distillate tank of the primary distillation tower. In the device, the overhead components of the primary distillation tower are secondary condensed into different distillate tanks, the primary condensate is refluxed to the primary distillation tower, and the secondary condensate is extracted to the extraction tower. This reduces the increase in energy consumption of the primary distillation tower caused by the acetaldehyde separated in the primary distillation tower being refluxed to the primary distillation tower again, while also improving the separation efficiency of the extraction tower and reducing energy consumption after cooling. The filtered supernatant is directly fed into the primary distillation tower and is separated from the reaction liquid feed, thereby solving the problem of crystallization of the filtered supernatant entering the reaction liquid pipeline before entering the primary distillation tower, causing pipeline blockage.

Description

Technical Field

[0001] The present invention belongs to the field of chemical equipment, and in particular relates to a vinyl acetate purification device and a process thereof. Background Art

[0002] Currently, vinyl acetate is produced primarily through the ethylene process and the acetylene process. The acetylene process primarily involves fluidized bed and fixed bed gas-phase synthesis. The fluidized bed gas-phase synthesis process involves reacting a mixture of acetylene and acetic acid at a constant temperature through a fluidized bed reactor using activated carbon as a carrier and zinc acetate as a catalyst. The resulting mixed gas exiting the reactor passes through a powder separator to separate the catalyst powder before entering a gas separation tower. The second stage of the separation tower produces the synthesis reaction liquid, while the first stage produces a filtrate containing a large amount of activated carbon powder and zinc acetate. However, in the fluidized bed gas-phase synthesis of vinyl acetate (VA) from the primary distillation tower, the distillate is condensed and cooled to condense components such as acetaldehyde, methyl acetate, vinyl acetate, and water. A portion of the condensate is then refluxed to the primary distillation tower, while a portion is withdrawn to the extraction tower. Cooling all the overhead components consumes significant energy, and the condensate contains a high VA content. This reflux increases the load and energy consumption of the primary distillation tower (because the refluxed condensate must be subjected to a further distillation to separate VA from components such as acetaldehyde). The condensate entering the extraction tower also increases the load on the extraction tower, impairing separation efficiency and hindering VAA recovery. Furthermore, the filtrate contains a large amount of activated carbon powder containing zinc acetate, which cannot be filtered through the filter and easily crystallizes and clogs the pipeline at temperatures below 60°C. The supernatant (referred to as the supernatant after distillation and filtration) enters the reaction liquid pipeline and then enters the primary distillation tower. Due to the low feed temperature, it is prone to crystallization, leading to pipeline clogging and the need to shut down the process for boiling and cleaning. Summary of the Invention

[0003] The first technical problem to be solved by the present invention is that in a fluidized bed gas-phase synthesis of vinyl acetate process, part of the condensate of the gas phase distilled from the primary distillation tower is refluxed to the primary distillation tower, while part is withdrawn to an extraction tower, resulting in high energy consumption after cooling and affecting the separation effect of the extraction tower. The second technical problem to be solved by the present invention is that in a fluidized bed gas-phase synthesis of vinyl acetate process, the filtered clear liquid (referred to as the filtered clear liquid after distillation and filtration) enters the reaction liquid pipeline and then enters the primary distillation tower, and is easily crystallized due to the low feed temperature, leading to pipeline blockage. To this end, the present invention provides a vinyl acetate purification device and further provides a vinyl acetate purification process using the device.

[0004] The present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a vinyl acetate purification device, comprising: a primary distillation tower, an extraction tower, a secondary distillation tower, a first condenser of the primary distillation tower, a reflux tank of the primary distillation tower, a second condenser of the primary distillation tower, a distillate tank of the primary distillation tower, a first condenser of the secondary distillation tower, a second condenser of the secondary distillation tower, and a distillate tank of the secondary distillation tower;

[0006] Among them, the reaction liquid feed pipeline, the filtered clear liquid pipeline and the top outlet pipeline of the extraction tower are all connected to the inlet of the primary distillation tower (preferably the middle inlet), the top outlet of the primary distillation tower is connected to the inlet of the first condenser of the primary distillation tower, the condensate outlet of the first condenser of the primary distillation tower is connected to the inlet of the reflux tank of the primary distillation tower, the outlet of the reflux tank of the primary distillation tower returns to the upper part of the primary distillation tower through the pipeline, the gas (gas phase) outlet of the first condenser of the primary distillation tower is connected to the inlet of the second condenser of the primary distillation tower, the condensate outlet of the second condenser of the primary distillation tower is connected to the inlet of the distillation tank of the primary distillation tower, the outlet of the distillation tank of the primary distillation tower is connected to the lower inlet of the extraction tower, and the upper inlet of the extraction tower is connected to the extractant (the extractant is synthetic acetaldehyde water or desalted water, preferably synthetic acetaldehyde water) feed The pipeline, the bottom outlet of the extraction tower is connected to the acetaldehyde water discharge pipeline, the (middle) inlet of the secondary distillation tower is connected to the bottom outlet of the primary distillation tower, the top outlet pipeline of the secondary distillation tower is divided into two routes, one route is connected to the inlet of the first condenser of the secondary distillation tower, and the other route is connected to the inlet of the second condenser of the secondary distillation tower. The bottom outlet of the secondary distillation tower is connected to the secondary distillation tower kettle liquid discharge pipeline, the gas phase outlet of the first condenser of the secondary distillation tower is also connected to the inlet of the second condenser of the secondary distillation tower, the condensate outlet pipeline of the first condenser of the secondary distillation tower and the condensate outlet pipeline of the second condenser of the secondary distillation tower are both connected to the inlet of the distillation tank of the secondary distillation tower, and the outlet pipeline of the distillation tank of the secondary distillation tower is divided into two routes, one route is connected to the vinyl acetate product discharge pipeline, and the other route returns to the top of the secondary distillation tower.

[0007] Furthermore, the reaction liquid feed line is connected to the inlet of the primary distillation column after passing through a heat exchanger or heater, wherein the heat exchanger is preferably an acetic acid refining column condenser to utilize the waste heat of the acetic acid refining column overhead distillate. The acetic acid refining column is used to refine the bottom liquid of the secondary distillation column. That is, the reaction liquid feed line is connected to the reaction liquid inlet of the acetic acid refining column condenser, the reaction liquid outlet of the acetic acid refining column condenser is connected to the inlet of the primary distillation column, and the top outlet pipe of the acetic acid refining column is connected to the acetic acid distillate inlet of the acetic acid refining column condenser. The acetic acid condensate emerges from the acetic acid distillate outlet of the acetic acid refining column condenser. In this way, the reaction liquid exchanges heat with the acetic acid distillate (the gas phase of the overhead distillate of the acetic acid refining column, with a temperature of 110-120°C) of the acetic acid refining column overhead, thereby being heated to 55-70°C. The reaction liquid temperature is between 10-40°C. If it is fed directly into the primary distillation tower, steam consumption will increase. At the same time, the temperature of the distillate gas phase from the acetic acid refining tower is 100-120°C, requiring circulating water for condensation, which increases circulating water usage. The reaction liquid feed, after passing through the acetic acid tower vapor phase heat exchange, raises the primary distillation tower feed temperature to 55-70°C, reducing both the primary distillation tower steam usage and the acetic acid refining tower circulating water usage.

[0008] Furthermore, a drain valve is provided at the bottom of the primary distillation tower reflux tank and / or the secondary distillation tower distillation tank. When water is carried over into the primary distillation tower or the secondary distillation tower, the water and vinyl acetate are separated in the primary distillation tower distillation tank after the water is carried over, and the water accumulates in the lower part of the distillation tank, which is not easy to be extracted from the primary distillation tower distillation tank, and the processing time is long (because the water will enter the primary distillation tower again with the reflux). When the primary distillation tower reflux tank is not provided, the water entering the primary distillation tower can only be discharged by increasing the overhead distillate volume and entering the extraction tower for treatment. The water carried over from the primary distillation tower enters the secondary distillation tower feed pipeline through the tower kettle pipeline, resulting in the production of unqualified vinyl acetate products, which need to be reprocessed into qualified vinyl acetate products. After adding the primary distillation tower reflux tank, there is no need to add a drain valve to the primary distillation tower distillation tank, and the primary distillation tower distillation tank is no longer used for reflux. Even if there is water in the primary distillation tower distillation tank, it will not affect the extraction tower. Drain valves are added to the bottom of the reflux tank of the primary distillation tower and the distillation tank of the secondary distillation tower. When there is abnormal water, the bottom water will be drained to reduce the amount of unqualified vinyl acetate (reduce the water from entering the vinyl acetate storage tank and causing unqualified vinyl acetate products).

[0009] Furthermore, the extraction tower is jacketed and cooled with chilled water. Because vinyl acetate has a low solubility in water at low temperatures and acetaldehyde dissolved in water can be prevented from escaping at low temperatures, the extraction tower is jacketed and cooled with chilled water to maintain a relatively low temperature throughout the tower (5-15°C), thereby improving the selectivity of water for acetaldehyde.

[0010] Furthermore, an interface regulator is provided in the extraction tower to adjust the interface formed in the tower by the acetaldehyde water and the vinyl acetate liquid due to the different densities to a specified position.

[0011] Furthermore, the filtered liquid pipeline is connected to the filter liquid outlet, the filter inlet is connected to the first stage outlet of the gas separation tower, and the gas separation tower is connected to the top outlet of the fluidized bed reactor.

[0012] Furthermore, the primary and secondary distillation towers have three inlets, one at the top, one at the middle, and one at the bottom, located in the middle of the towers. These inlets are adjusted based on the incoming material composition. When the light component content is high, the top inlet of the primary / secondary distillation tower is used; when the heavy component content is high, the bottom inlet of the primary / secondary distillation tower is used. This reduces energy consumption in the primary / secondary distillation towers and improves distillation separation efficiency.

[0013] The reaction solution described here refers to the reaction product of vinyl acetate synthesized by the calcium carbide acetylene method.

[0014] The fluidized bed gas-phase synthesis of vinyl acetate involves reacting a mixture of acetylene and acetic acid at a constant temperature through a fluidized bed reactor using activated carbon as a carrier and zinc acetate as a catalyst. The reacted gas exiting the reactor passes through a powder separator to separate the catalyst powder before entering a gas separation tower. The second stage of the separation tower produces a synthetic reaction liquid, while the first stage produces a filtrate containing a large amount of activated carbon powder containing zinc acetate. The filtrate then passes through a filter to remove the activated carbon powder, yielding a clear liquid.

[0015] In a second aspect, the present invention provides a vinyl acetate purification process, comprising the following steps: a reaction liquid for synthesizing vinyl acetate, preferably a reaction liquid for synthesizing vinyl acetate by a calcium carbide acetylene method, more preferably a reaction liquid containing the following components: 45-50% acetic acid, 45-50% vinyl acetate, 1.0-2.5% acetaldehyde, 0.8-1.8% acetylene, 0.01-0.1% water, a small amount of carbon powder and zinc acetate, at a temperature of 10-40°C; the reaction liquid enters the condenser from the reaction liquid inlet of the acetic acid refining tower, and is heat-exchanged with the distillate gas phase (110-120°C) of the acetic acid refining tower to 55 -70 ℃, the top distillate outlet of the acetic acid refining tower condenser obtains the acetic acid condensate after heat exchange, the reaction liquid (55-70 ℃) from the acetic acid refining tower condenser, the filtered clear liquid (components: acetic acid 85-95%, vinyl acetate 5-10%, water 0.01-0.1%, containing carbon powder and zinc acetate, temperature 85-95 ℃), the top outlet component of the extraction tower (components: vinyl acetate 80-90%, acetaldehyde 1.0-5.0%, water 0.5-1.5%, temperature 5-15 ℃) enter the middle part of the primary distillation tower (the function of the primary distillation tower is to extract the acetic acid from the top of the tower) The acetaldehyde in the reaction liquid is removed and the acetylene dissolved in the reaction liquid is desorbed and sent to the synthesis process for recycling). The temperature of the first distillation tower kettle is controlled at 90-105°C and the pressure is 50-60KPa. After distillation, the bottom outlet component of the first distillation tower (components: vinyl acetate 40-50%, acetic acid 50-60%, temperature 95-110°C) enters the middle part of the secondary distillation tower, and the top component of the first distillation tower (temperature 60-70°C) enters the inlet of the first condenser of the first distillation tower. After condensation by circulating water (temperature 25-35°C), the first condenser of the first distillation tower is discharged. The condensate outlet components of the condenser (components: vinyl acetate 90-95%, acetaldehyde 1.0-3.0%, a small amount of water 0.5-1.5%, temperature 30-45 ° C) enter the reflux tank of the primary distillation tower, and then return to the upper part of the primary distillation tower. The gas phase outlet components of the first condenser of the primary distillation tower (uncondensed gas) enter the second condenser of the primary distillation tower, after being condensed by chilled water (temperature of -6 to -3 ° C), the outlet components of the second condenser of the primary distillation tower (temperature 5-15 ° C, containing vinyl acetate 70.0-85.0%, acetaldehyde 8-10% and a small amount of water 1.0-2.0%, etc.) enters the distillation tank of the primary distillation tower and then enters the lower part of the extraction tower (the function of the extraction tower is to preliminarily separate acetaldehyde and vinyl acetate). The top inlet of the extraction tower is added with the extractant synthetic acetaldehyde water (low-temperature acetaldehyde water from the synthetic water washing tower, acetaldehyde content 2-5%, temperature 0-10°C). Because acetaldehyde is miscible with water, but the solubility of acetaldehyde in vinyl acetate and the solubility of vinyl acetate in water are very low, the distillate from the primary distillation tower is added from the lower part of the extraction tower. The vinyl acetate in it has a low density and moves upward, while the acetaldehyde in it gradually dissolves in the acetaldehyde water added from the upper part of the tower. It has a high density and moves downward. The two streams of materials alternately pass through the packing in the tower, in countercurrent contact, and the acetaldehyde gradually diffuses into the water and falls into the lower part of the tower. After extraction, the bottom components of the extraction tower (composition: water 80-90%, acetaldehyde 5.0-10.0%, vinyl acetate 1.0-5.0%, temperature 5-15°C) are connected to the acetaldehyde water discharge pipeline, and the top components of the extraction tower (vinyl acetate accumulates in the upper part of the tower, composition: vinyl acetate 80-90%, acetaldehyde 1.0-5.0%, water 0.5-1.5%, temperature 5-15°C) are returned to the middle part of the primary distillation tower. The function of the secondary distillation tower is to purify vinyl acetate. After being processed in the secondary distillation tower, the top component of the secondary distillation tower (vinyl acetate, temperature 66-76°C) is divided into two parts. One part enters the inlet of the first condenser of the secondary distillation tower. After condensation by circulating water (temperature, for example, 25-35°C), the condensate outlet component of the first condenser of the secondary distillation tower (vinyl acetate, temperature 45-55°C) enters the distillation tank of the secondary distillation tower. The gas phase outlet component of the first condenser of the secondary distillation tower (uncondensed gas and part of the gas phase distilled from the top of the tower) enters the inlet of the second condenser of the secondary distillation tower. The top component of the secondary distillation tower Another portion also enters the inlet of the second condenser of the secondary distillation tower. The outlet component of the second condenser of the secondary distillation tower (vinyl acetate, 35-50°C) enters the distillation tank of the secondary distillation tower. The bottom outlet component of the distillation tank of the secondary distillation tower is vinyl acetate. A portion of it is extracted, of which the qualified refined vinyl acetate (vinyl acetate ≥99.0%) is sent to the tank farm for sale or polymerization, and the unqualified product is returned for reprocessing. Another portion is returned to the top of the secondary distillation tower for reflux. The bottom outlet component of the secondary distillation tower (acetic acid containing impurities such as crotonaldehyde, 125-130°C) is discharged through the secondary distillation tower bottom liquid discharge pipeline.

[0016] In the above process, the feed to the primary distillation tower includes three parts of materials: the synthetic reaction liquid, the components at the top outlet of the extraction tower, and the filtered clear liquid. After being measured by the flow recording and regulating meter, they enter the primary distillation tower together with the reaction liquid after heat exchange.

[0017] In the above process, the non-condensable gas acetylene in the primary distillation tower carries along a small amount of acetaldehyde and returns to the acetylene gas recovery tank of the synthesis process.

[0018] In the above process, acetaldehyde water and vinyl acetate liquid form an interface in the tower due to their different densities. The interface between acetaldehyde water and vinyl acetate liquid is controlled at a specified position by an interface regulator in the extraction tower to prevent acetaldehyde water below the interface from being brought into the primary distillation tower when the vinyl acetate liquid is taken from the top outlet component of the extraction tower, thereby increasing the load and energy consumption of the primary distillation tower.

[0019] In the above process, the acetylene tail gas from the top of the extraction tower is returned to the synthesis process.

[0020] In the above process, the liquid phase of the first distillation tower kettle (temperature 95-110℃) is discharged from the first distillation tower, and the tower liquid level is controlled by the first distillation tower liquid level recording and adjustment table, and is pumped to the second distillation tower for feeding through the first distillation tower kettle liquid pump, and further separated in the second distillation tower.

[0021] In the above process, the bottom liquid of the secondary distillation tower is acetic acid (125-130℃) containing impurities such as crotonaldehyde. The bottom liquid level of the secondary distillation tower is controlled by the bottom liquid level recording and adjustment table. When the bottom liquid is qualified, it is directly fed to the acetic acid refining tower through the bottom liquid pump.

[0022] In the above process, primary separation is performed through primary distillation, acetaldehyde and other water-soluble impurities are separated by liquid-liquid extraction, and vinyl acetate product is obtained through secondary distillation.

[0023] In the above process, the light components at the top of the primary distillation tower pass through an extraction tower, where acetaldehyde and other water-soluble impurities are separated by liquid-liquid extraction to recover vinyl acetate.

[0024] In the above process, the heavy components in the bottom of the primary distillation tower are separated and refined for the second time in the secondary distillation tower to obtain the vinyl acetate product.

[0025] In the above process, the reaction liquid feed is heated by the acetic acid refining tower gas phase, raising the feed temperature of the primary distillation tower to 55-70°C, thereby reducing the steam consumption of the primary distillation tower and the circulating water consumption of the acetic acid refining tower condenser.

[0026] In the above process, the top of the primary distillation tower contains acetylene, acetaldehyde, methyl acetate, vinyl acetate, water and other components. The distillate contains a high content of vinyl acetate. Reflux increases the load and energy consumption of the primary distillation tower, and distillation increases the load of the extraction tower, affecting the extraction effect. The load and energy consumption of the primary distillation tower are reduced by secondary condensing the distillate gas phase of the primary distillation tower into different distillation tanks, that is, the primary condensate (components: vinyl acetate 90-95%, acetaldehyde 1.0-3.0%, a small amount of water 0.5-1.5%, temperature 30- The secondary condensate (components: vinyl acetate 70.0-85.0%, acetaldehyde 8-10% and a small amount of water 1.0-2.0%, etc., temperature 5-15°C) is withdrawn to the extraction tower. This can reduce the acetaldehyde content in the material flowing back to the primary distillation tower, reduce the load and energy consumption of the primary distillation tower, and at the same time ensure that the temperature of the material entering the extraction tower is appropriate, reduce the consumption of chilled water in the extraction tower, increase the acetaldehyde content in the material entering the extraction tower, and improve the extraction effect of the extraction tower.

[0027] In the above process, a portion of the distillate gas phase from the secondary distillation tower enters the first condenser of the secondary distillation tower to exchange heat with the feed of the acetaldehyde refining tower, so that the temperature of the distillate gas phase from the secondary distillation tower can be used to increase the feed temperature of the acetaldehyde refining tower and reduce the amount of circulating water; a portion of the distillate gas phase from the secondary distillation tower condenses after heat exchange in the first condenser of the secondary distillation tower and enters the distillation tank of the secondary distillation tower. In order to prevent the self-polymerization of vinyl acetate in the distillation tank of the secondary distillation tower (vinyl acetate is prone to self-polymerization at high temperatures), the two condensates are mixed; the non-condensable gas from the first condenser of the secondary distillation tower and another portion of the distillate gas phase from the secondary distillation tower enter the second condenser of the secondary distillation tower and are condensed using circulating water.

[0028] The technical solution of the present invention has the following advantages:

[0029] (1) The vinyl acetate purification apparatus of the present invention comprises components such as acetylene, acetaldehyde, methyl acetate, vinyl acetate, and water at the top of the primary distillation tower. The primary distillation tower is subjected to secondary condensation (secondary condensation), and the condensate is treated differently, for example, entering different distillation tanks. The primary condensate (primary condensate) is mainly vinyl acetate and water, which is refluxed to the primary distillation tower (reducing the amount of acetaldehyde refluxed to the primary distillation tower, reducing the load and energy consumption of the primary distillation tower). The secondary condensate (secondary condensate) has an increased acetaldehyde content and a decreased vinyl acetate content compared to the primary condensate, and is withdrawn to the extraction tower. This reduces the vinyl acetate content entering the extraction tower, allows the water in the extraction tower to absorb more acetaldehyde, reduces interference from vinyl acetate, and improves the efficiency of the extraction tower.

[0030] (2) In the vinyl acetate purification device of the present invention, the filtered supernatant directly enters the primary distillation tower and is fed separately from the reaction liquid. This solves the problem that the filtered supernatant enters the reaction liquid pipeline and then enters the primary distillation tower. Since the temperature of the reaction liquid is lower than that of the filtered supernatant, the two streams of materials mix and cause zinc acetate crystals in the filtered supernatant, resulting in clogging of the pipeline. This provides favorable conditions for continuous production.

[0031] (3) In the vinyl acetate purification device of the present invention, a drain valve is provided at the bottom of the reflux tank of the primary distillation tower and / or the distillation tank of the secondary distillation tower. When abnormal water is present, the water is drained through the bottom, thereby reducing the amount of unqualified vinyl acetate produced.

[0032] (4) In the vinyl acetate purification device of the present invention, the reaction liquid feed is passed through the acetic acid refining tower for gas phase heat exchange, thereby raising the feed temperature of the primary distillation tower to 55-70° C., thereby reducing the steam consumption of the primary distillation tower and the circulating water consumption of the acetic acid refining tower.

[0033] (5) The vinyl acetate purification device of the present invention is provided with a jacketed extraction tower, through which chilled water is passed for cooling, thereby maintaining a relatively low temperature throughout the tower, improving the selectivity of water for acetaldehyde, and preventing the escape of acetaldehyde dissolved in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0035] Figure 1 This is a schematic structural diagram of a vinyl acetate purification device according to Example 1 of the present invention.

[0036] Among them: 1—primary distillation tower, 2—extraction tower, 3—secondary distillation tower, 4—acetic acid refining tower condenser, 5—first condenser of primary distillation tower, 6—reflux tank of primary distillation tower, 7—second condenser of primary distillation tower, 8—distillation tank of primary distillation tower, 9—first condenser of secondary distillation tower, 10—second condenser of secondary distillation tower, 11—distillation tank of secondary distillation tower. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments 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.

[0038] In the description of the invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "provided with," "connected," etc., should be understood broadly. For example, "connected" may refer to a fixed connection, a detachable connection, or an integral connection; it may refer to a mechanical connection, a direct connection, an indirect connection via an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0039] like Figure 1 As shown, the vinyl acetate purification device of the present invention comprises: a primary distillation tower 1, an extraction tower 2, a secondary distillation tower 3, a first condenser 5 of the primary distillation tower, a reflux tank 6 of the primary distillation tower, a second condenser 7 of the primary distillation tower, a distillation tank 8 of the primary distillation tower, a first condenser 9 of the secondary distillation tower, a second condenser 10 of the secondary distillation tower, and a distillation tank 11 of the secondary distillation tower;

[0040] Among them, the reaction liquid feed pipeline, the filtered clear liquid pipeline and the top outlet pipeline of the extraction tower 2 are all connected to the inlet of the primary distillation tower 1 (preferably the middle inlet), the top outlet of the primary distillation tower 1 is connected to the inlet of the first condenser 5 of the primary distillation tower, the condensate outlet of the first condenser 5 of the primary distillation tower is connected to the inlet of the reflux tank 6 of the primary distillation tower, and the outlet of the reflux tank 6 of the primary distillation tower is returned to the upper part of the primary distillation tower 1 through a pipeline, the gas phase outlet of the first condenser 5 of the primary distillation tower is connected to the inlet of the second condenser 7 of the primary distillation tower, the condensate outlet of the second condenser 7 of the primary distillation tower is connected to the inlet of the distillation tank 8 of the primary distillation tower, the outlet of the distillation tank 8 of the primary distillation tower is connected to the lower inlet of the extraction tower 2, the upper inlet of the extraction tower 2 is connected to the synthetic acetaldehyde water feed pipeline, and the bottom outlet of the extraction tower 2 is connected to the acetaldehyde water The discharge pipeline is connected, the (middle) inlet of the secondary distillation tower 3 is connected to the bottom outlet of the primary distillation tower 1, and the top outlet pipeline of the secondary distillation tower 3 is divided into two paths, one path is connected to the inlet of the first condenser 9 of the secondary distillation tower, and the other path is connected to the inlet of the second condenser 10 of the secondary distillation tower. The bottom outlet of the secondary distillation tower 3 is connected to the secondary distillation tower bottom liquid discharge pipeline, and the gas phase outlet of the first condenser 9 of the secondary distillation tower is also connected to the inlet of the second condenser 10 of the secondary distillation tower. The condensate outlet pipeline of the first condenser 9 of the secondary distillation tower and the condensate outlet pipeline of the second condenser 10 of the secondary distillation tower are both connected to the inlet of the secondary distillation tower distillation tank 11. The outlet pipeline of the secondary distillation tower distillation tank 11 is divided into two paths, one path is connected to the vinyl acetate product discharge pipeline, and the other path returns to the top of the secondary distillation tower 3.

[0041] In a preferred embodiment, the reaction liquid feed line is connected to the inlet of the primary distillation tower 1 after passing through the acetic acid refining tower condenser 4, wherein the acetic acid refining tower is used to refine the bottom liquid of the secondary distillation tower. In this way, the reaction liquid is heated to 55-70°C by heat exchange with the acetic acid refining tower overhead distillate acetic acid (the overhead distillate gas phase of the acetic acid refining tower, the temperature is 110-120°C). The acetic acid refining tower condenser 4 here can be replaced by any heat exchanger or heater, as long as the reaction liquid is heated to 55-70°C. In the case where a heat exchanger, heater or acetic acid refining tower condenser 4 is not provided, it is also possible to control the bottom temperature of the primary distillation tower 1 (for example, the bottom temperature is 90-105°C and the pressure is 50-60KPa).

[0042] In another preferred embodiment, the secondary distillation column 3 is a guided sieve plate column.

[0043] In another preferred embodiment, a drain valve is provided at the bottom of the primary distillation tower reflux tank 6 and / or the secondary distillation tower distillation tank 11.

[0044] In another preferred embodiment, the extraction tower 2 is provided with a jacket and cooled by chilled water.

[0045] In another preferred embodiment, an interface regulator is provided in the extraction column 2 .

[0046] The clear liquid filter pipeline is connected to the clear liquid outlet of the filter, the filter inlet is connected to the outlet of the first stage of the gas separation tower, and the gas separation tower is connected to the top outlet of the fluidized bed reactor. The process for the gas-phase synthesis of vinyl acetate in a fluidized bed involves reacting a mixture of acetylene and acetic acid at a certain temperature through a fluidized bed reactor using activated carbon as a carrier and zinc acetate as a catalyst. The reacted mixed gas exiting the reactor passes through a powder separator to separate the catalyst powder before entering the gas separation tower. The second stage of the separation tower produces the synthesis reaction liquid, while the first stage produces a filtrate containing a large amount of activated carbon powder containing zinc acetate. The filtrate passes through a filter to remove the activated carbon powder, resulting in a clear liquid.

[0047] Example 1

[0048] like Figure 1 As shown, the vinyl acetate purification device of this embodiment includes: a primary distillation tower 1, an extraction tower 2, a secondary distillation tower 3, an acetic acid refining tower condenser 4, a primary distillation tower first condenser 5, a primary distillation tower reflux tank 6, a primary distillation tower second condenser 7, a primary distillation tower distillate tank 8, a secondary distillation tower first condenser 9, a secondary distillation tower second condenser 10 and a secondary distillation tower distillate tank 11;

[0049] Among them, the discharge line of the kettle of the secondary distillation tower 3 is connected to the acetic acid refining tower, the reaction liquid feed line is connected to the reaction liquid inlet of the acetic acid refining tower condenser 4, the heat exchange raw material outlet of the acetic acid refining tower condenser 4 is connected to the acetic acid condensate pipeline, the top distillate (acetic acid) inlet of the acetic acid refining tower condenser 4 is connected to the top discharge pipeline of the acetic acid refining tower (not shown in the figure), the reaction liquid outlet pipeline of the acetic acid refining tower condenser 4, the filtered clear liquid pipeline and the top outlet pipeline of the extraction tower 2 are all connected to the primary distillation tower The middle inlet of the primary distillation tower 1 is connected, the top outlet of the primary distillation tower 1 is connected to the inlet of the first condenser 5 of the primary distillation tower, the condensate outlet of the first condenser 5 of the primary distillation tower is connected to the inlet of the reflux tank 6 of the primary distillation tower, the outlet of the reflux tank 6 of the primary distillation tower returns to the upper part of the primary distillation tower 1 through a pipeline, the gas phase outlet of the first condenser 5 of the primary distillation tower is connected to the inlet of the second condenser 7 of the primary distillation tower, and the condensate outlet of the second condenser 7 of the primary distillation tower is connected to the inlet of the distillation tank 8 of the primary distillation tower The outlet of the distillation tank 8 of the primary distillation tower is connected to the lower inlet of the extraction tower 2, the upper inlet of the extraction tower 2 is connected to the synthetic acetaldehyde water feed pipeline, the bottom outlet of the extraction tower 2 is connected to the acetaldehyde water discharge pipeline, the middle inlet of the secondary distillation tower 3 is connected to the bottom outlet of the primary distillation tower 1, and the top outlet pipeline of the secondary distillation tower 3 is divided into two routes, one route is connected to the inlet of the first condenser 9 of the secondary distillation tower, and the other route is connected to the inlet of the second condenser 10 of the secondary distillation tower. The bottom outlet of the secondary distillation tower 3 is connected to the inlet of the first condenser 9 of the secondary distillation tower, and the other route is connected to the inlet of the second condenser 10 of the secondary distillation tower. The outlet of the first condenser 9 of the secondary distillation tower is connected to the liquid discharge line of the kettle of the secondary distillation tower, the gas phase outlet of the first condenser 9 of the secondary distillation tower is also connected to the inlet of the second condenser 10 of the secondary distillation tower, the condensate outlet pipeline of the first condenser 9 of the secondary distillation tower and the condensate outlet pipeline of the second condenser 10 of the secondary distillation tower are both connected to the inlet of the distillation tank 11 of the secondary distillation tower, and the outlet pipeline of the distillation tank 11 of the secondary distillation tower is divided into two routes, one route is connected to the vinyl acetate product discharge pipeline, and the other route returns to the top of the secondary distillation tower 3.

[0050] Among them, the secondary distillation tower 3 is a guided sieve plate tower.

[0051] Wherein, a drain valve is provided at the bottom of the primary distillation tower reflux tank 6 and / or the secondary distillation tower distillation tank 11.

[0052] The extraction tower 2 is provided with a jacket and is cooled by chilled water.

[0053] The extraction tower 2 is provided with an interface regulator for adjusting the interface formed in the tower by acetaldehyde water and vinyl acetate liquid due to different densities at a predetermined position.

[0054] The above device is used to purify vinyl acetate according to the following process:

[0055] The reaction liquid of the synthesis of vinyl acetate by the calcium carbide acetylene process (components: 45-50% acetic acid, 45-50% vinyl acetate, 1.0-2.5% acetaldehyde, 0.8-1.8% acetylene, 0.01-0.1% water, a small amount of carbon powder and zinc acetate, temperature 10-40°C) enters the acetic acid refining tower condenser 4 from the reaction liquid inlet of the acetic acid refining tower condenser 4, is heat-exchanged to 55-70°C by the distillate gas phase (110-120°C) of the acetic acid refining tower (not shown in the figure, the acetic acid refining tower is used to refine the bottom liquid of the secondary distillation tower), and the top distillate outlet of the acetic acid refining tower condenser 4 is heated to 55-70°C. The acetic acid condensate obtained after heat exchange in the acetic acid refining tower is fed into the middle of the primary distillation tower 1 (the function of the primary distillation tower 1 is to remove acetaldehyde from the reaction liquid and desorb acetaldehyde from the top of the tower). The acetylene dissolved in the reaction liquid is sent to the synthesis process for recycling. The temperature of the first distillation tower kettle is controlled at 90-105°C and the pressure is controlled at 50-60KPa. After distillation, the bottom outlet component of the first distillation tower 1 (components: 40-50% vinyl acetate, 50-60% acetic acid, temperature 95-110°C) enters the middle of the secondary distillation tower 3, and the top component of the first distillation tower 1 (temperature 60-70°C) enters the inlet of the first condenser 5 of the first distillation tower. After condensation with circulating water (temperature 25-35°C), the condensate outlet component of the first condenser 5 of the first distillation tower is The gaseous phase of the first condenser 5 (composition: vinyl acetate 90-95%, acetaldehyde 1.0-3.0%, a small amount of water 0.5-1.5%, temperature 30-45 ℃) enters the reflux tank 6 of the primary distillation tower, and then returns to the upper part of the primary distillation tower 1. The gaseous phase outlet components (uncondensed gas) of the first condenser 5 of the primary distillation tower enter the second condenser 7 of the primary distillation tower, and after condensation by chilled water (temperature of -6 to -3 ℃), the gaseous phase outlet components (temperature of 5-15 ℃, containing vinyl acetate 70.0-85.0%, acetaldehyde 8-10% and a small amount of water 1.0-2.5%) are discharged from the lower part of the second condenser 7 of the primary distillation tower.0%, etc.) enters the distillation tank 8 of the primary distillation tower and then enters the lower part of the extraction tower 2 (the function of the extraction tower 2 is to preliminarily separate acetaldehyde and vinyl acetate). The top inlet of the extraction tower 2 is added with the extractant synthetic acetaldehyde water (low-temperature acetaldehyde water from the synthetic water washing tower, acetaldehyde content 2-5%, temperature 0-10°C). Because acetaldehyde is miscible with water, but the solubility of acetaldehyde in vinyl acetate and the solubility of vinyl acetate in water are very low, the distillate from the primary distillation tower is added from the lower part of the extraction tower. The vinyl acetate therein has a low density and moves upward, and the acetaldehyde therein gradually dissolves in the acetaldehyde added from the upper part of the tower. The density of acetaldehyde water is large and it moves downward. The two streams of materials alternately pass through the packing in the tower and contact each other in countercurrent. Acetaldehyde gradually diffuses into the water and falls into the lower part of the tower. After extraction, the bottom component of the extraction tower 2 (components: water 80-90%, acetaldehyde 5.0-10.0%, vinyl acetate 1.0-5.0%, temperature 5-15°C) is connected to the acetaldehyde water discharge pipeline, and the top component of the extraction tower 2 (components: vinyl acetate 80-90%, acetaldehyde 1.0-5.0%, water 0.5-1.5%, temperature 5-15°C) is returned to the middle of the primary distillation tower 1, and the secondary distillation tower 3 is connected to the secondary distillation tower 3. The top component (vinyl acetate, temperature 66-76 ° C) is divided into two parts, one part enters the upper inlet of the first condenser 9 of the secondary distillation tower, and after condensation by circulating water (temperature 25-35 ° C), the condensate outlet component (vinyl acetate, temperature 45-55 ° C) of the first condenser 9 of the secondary distillation tower enters the distillation tank 11 of the secondary distillation tower, the gaseous phase outlet component (uncondensed gas and part of the gas phase distilled from the top of the tower) of the first condenser 9 of the secondary distillation tower enters the inlet of the second condenser 10 of the secondary distillation tower, and the other part of the top component of the secondary distillation tower 3 also enters the second condenser of the secondary distillation tower. The outlet components of the second condenser 10 (vinyl acetate, 35-50°C) from the inlet of the condenser 10 enter the distillation tank 11 of the secondary distillation tower. The bottom outlet component of the distillation tank 11 of the secondary distillation tower is vinyl acetate. A portion of this is extracted, with qualified refined vinyl acetate (vinyl acetate ≥ 99.0%) sent to the tank farm for sale or polymerization, while unqualified products are returned for reprocessing. Another portion is returned to the top of the secondary distillation tower for reflux. The bottom outlet component of the secondary distillation tower 3 (acetic acid containing impurities such as crotonaldehyde, 125-130°C) is discharged through the secondary distillation tower bottom liquid discharge pipeline.

[0056] Comparative Example 1

[0057] Compared to Example 1, Comparative Example 1 lacked a primary distillation column reflux tank. Condensate from the first condenser of the primary distillation column flowed directly into the primary distillation column distillate tank. Drain valves were not installed in the primary distillation column distillate tank or the secondary distillation column distillate tank. The reaction liquid pipeline and the filtered supernatant liquid pipeline entered the primary distillation column through the same feed line. The reaction liquid feed was heated by steam. The remaining equipment and pipeline connections were identical to those in Example 1.

[0058] It can be seen from the above examples that in the vinyl acetate purification device and process of this embodiment, the top component of the primary distillation tower is subjected to secondary condensation (i.e., two-stage condensation) and enters different distillation tanks, and the primary condensate is refluxed to the primary distillation tower, reducing the amount of acetaldehyde refluxed to the primary distillation tower by 1560.8 t / year, reducing the load and energy consumption of the primary distillation tower, and reducing the steam consumption by 1598.4 t / year. The secondary condensate is extracted to the extraction tower, and the acetaldehyde content of the secondary condensate is increased by 3% compared with the secondary condensate of Comparative Example 1. The amount of acetaldehyde in this part is 1560.8 t / year, and the vinyl acetate content is reduced by 1560.8 t / year. It is extracted to the extraction tower, which improves the separation effect of the extraction tower and reduces the energy consumption after cooling. In Example 1, the filtered supernatant enters the primary distillation tower directly, separate from the reaction liquid feed. This solves the problem of crystallization of the filtered supernatant entering the primary distillation tower after entering the reaction liquid pipeline. In Comparative Example 1, the reaction liquid pipeline and the filtered supernatant pipeline enter the primary distillation tower through the same feed line, resulting in blockage at least once per quarter. Each blockage requires system shutdown and steam cleaning of the feed line for 8-16 hours, affecting system stability. Compared with Comparative Example 1, in this embodiment, drain valves are installed at the bottom of the primary distillation tower reflux tank and / or the secondary distillation tower distillation tank. In the event of abnormal water contamination, draining is done through the bottom, reducing the amount of substandard vinyl acetate produced by approximately 960 tons / year. In addition, in this embodiment, the reaction liquid feed is heated by the acetic acid refining tower after vapor phase heat exchange, raising the primary distillation tower feed temperature to 55-70°C, reducing the primary distillation tower steam consumption by 1300-1500 tons / year and the acetic acid refining tower circulating water consumption by 84,500-97,500 tons / year.

[0059] 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 appreciate that other variations or modifications can be made based on the above description. 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 vinyl acetate purification device, characterized in that: The device comprises: a primary distillation tower (1), an extraction tower (2), a secondary distillation tower (3), a first condenser (5) of the primary distillation tower, a reflux tank (6) of the primary distillation tower, a second condenser (7) of the primary distillation tower, and a distillation tank (8) of the primary distillation tower; The reaction liquid feed pipeline and the filtered clear liquid pipeline are both connected to the inlet of the primary distillation tower (1), the top outlet of the primary distillation tower (1) is connected to the inlet of the first condenser (5) of the primary distillation tower, the condensate outlet of the first condenser (5) of the primary distillation tower is connected to the inlet of the reflux tank (6) of the primary distillation tower, the outlet of the reflux tank (6) of the primary distillation tower returns to the upper part of the primary distillation tower (1) through the pipeline, and the gas phase outlet of the first condenser (5) of the primary distillation tower is connected to the inlet of the second condenser (7) of the primary distillation tower. Then, the condensate outlet of the second condenser (7) of the primary distillation tower is connected to the inlet of the distillation tank (8) of the primary distillation tower, the outlet of the distillation tank (8) of the primary distillation tower is connected to the lower inlet of the extraction tower (2), the upper inlet of the extraction tower (2) is connected to the extractant feed pipeline, the inlet of the secondary distillation tower (3) is connected to the bottom outlet of the primary distillation tower (1), and the top outlet pipeline of the secondary distillation tower (3) is divided into two routes, one route is connected to the vinyl acetate product discharge pipeline, and the other route returns to the top of the secondary distillation tower (3); The device further comprises: a first condenser (9) of a secondary distillation tower, a second condenser (10) of a secondary distillation tower and a distillation tank (11) of a secondary distillation tower; wherein the top outlet pipeline of the secondary distillation tower (3) is divided into two routes, one route is connected to the inlet of the first condenser (9) of the secondary distillation tower, and the other route is connected to the inlet of the second condenser (10) of the secondary distillation tower; the bottom outlet of the secondary distillation tower (3) is connected to the secondary distillation tower bottom liquid discharge pipeline; the gas phase outlet of the first condenser (9) of the secondary distillation tower is also connected to the inlet of the second condenser (10) of the secondary distillation tower; the condensate outlet pipeline of the first condenser (9) of the secondary distillation tower and the condensate outlet pipeline of the second condenser (10) of the secondary distillation tower are both connected to the inlet of the distillation tank (11) of the secondary distillation tower; the outlet pipeline of the distillation tank (11) of the secondary distillation tower is divided into two routes, one route is connected to the vinyl acetate product discharge pipeline, and the other route returns to the top of the secondary distillation tower (3).

2. The vinyl acetate purification device according to claim 1, characterized in that: A drain valve is provided at the bottom of the primary distillation tower reflux tank (6) and / or the secondary distillation tower distillation tank (11).

3. The vinyl acetate purification device according to claim 1, characterized in that: The reaction liquid feed pipeline is connected to the inlet of the primary distillation tower (1) after passing through a heat exchanger or heater.

4. The vinyl acetate purification device according to claim 3, characterized in that: The heat exchanger is an acetic acid refining tower condenser (4), wherein the acetic acid refining tower is used to refine the bottom liquid of the secondary distillation tower.

5. The vinyl acetate purification device according to claim 1, characterized in that: The extraction tower (2) is provided with a jacket and is cooled by chilled water.

6. The vinyl acetate purification device according to claim 1, characterized in that: An interface regulator is provided in the extraction tower (2).

7. The vinyl acetate purification device according to claim 1, characterized in that: The primary distillation tower (1) and the secondary distillation tower (3) are respectively provided with upper, middle and lower inlets.

8. The vinyl acetate purification device according to any one of claims 1 to 7, characterized in that: The top outlet pipeline of the extraction tower (2) is also connected to the inlet of the primary distillation tower (1).

9. The vinyl acetate purification device according to claim 8, characterized in that: The reaction liquid feed pipeline, the filtered clear liquid pipeline and the top outlet pipeline of the extraction tower (2) are all connected to the middle inlet of the primary distillation tower (1).

10. The vinyl acetate purification device according to any one of claims 1 to 7, characterized in that: The bottom outlet of the extraction tower (2) is connected to the acetaldehyde water discharge pipeline.

11. A vinyl acetate purification process, characterized in that: The vinyl acetate purification device according to any one of claims 1 to 10 comprises the following steps: the reaction liquid for synthesizing vinyl acetate enters a primary distillation tower (1), after distillation, the top component of the primary distillation tower (1) enters a first condenser (5) of the primary distillation tower, after condensation, the condensate outlet component of the first condenser (5) of the primary distillation tower returns to the primary distillation tower (1), the gas phase outlet component of the first condenser (5) of the primary distillation tower enters a second condenser (7) of the primary distillation tower, after condensation, the condensate outlet component of the second condenser (7) of the primary distillation tower enters an extraction tower (2) for extraction, an extractant is added to the top inlet of the extraction tower (2), the bottom outlet component of the primary distillation tower (1) enters a secondary distillation tower (3) for distillation treatment, and the top component of the secondary distillation tower (3) is divided into two parts, one part is extracted, and the other part is returned to the top of the secondary distillation tower (3) for reflux; The top component of the secondary distillation tower (3) is divided into two parts. One part enters the inlet of the first condenser (9) of the secondary distillation tower. After condensation by circulating water, the condensate outlet component of the first condenser (9) of the secondary distillation tower enters the distillation tank (11) of the secondary distillation tower. The gas phase outlet component of the first condenser (9) of the secondary distillation tower enters the inlet of the second condenser (10) of the secondary distillation tower. Another part of the top component of the secondary distillation tower (3) also enters the inlet of the second condenser (10) of the secondary distillation tower. The condensate outlet component of the second condenser (10) of the secondary distillation tower enters the distillation tank (11) of the secondary distillation tower. The outlet component of the distillation tank (11) of the secondary distillation tower is vinyl acetate, one part of which is extracted and the other part is returned to the top of the secondary distillation tower (3) for reflux. The bottom outlet component of the secondary distillation tower (3) is discharged through the secondary distillation tower bottom liquid discharge pipeline.

12. The process according to claim 11, characterized in that The bottom component of the extraction tower (2) is connected to the acetaldehyde water discharge pipeline.

13. The process according to claim 11, characterized in that The components at the top outlet of the extraction tower (2) also enter the middle part of the primary distillation tower (1).

14. The process according to any one of claims 11 to 13, characterized in that The reaction liquid for synthesizing vinyl acetate enters the condenser (4) of the acetic acid refining tower through the reaction liquid inlet of the condenser, exchanges heat with the distillate gas of the acetic acid refining tower, and obtains the acetic acid condensate after heat exchange at the top distillate outlet of the acetic acid refining tower condenser (4). The reaction liquid coming out of the acetic acid refining tower condenser (4) enters the middle part of the primary distillation tower (1).

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