Vinyl acetate production method and system

Abstract

The invention relates to a vinyl acetate production method and system, and the method comprises the following steps: fully mixing oxygen, gas-phase acetic acid, shielding gas and a cocatalyst, feeding the mixture into a vinyl acetate reactor, and carrying out a reaction to generate a reaction product flow; the reaction product flow is cooled and then fed into a pre-dehydration tower, a vinyl acetate crude product is recovered at the tower bottom, and a reaction product gas-phase flow is recovered at the tower top; cooling the reaction product gas-phase material flow to enter a pre-dehydration tower gas-liquid separation tank, extracting a pre-dehydration tower gas-phase material flow from a gas-phase outlet of the pre-dehydration tower gas-liquid separation tank, and extracting a pre-dehydration liquid-phase material flow from a liquid-phase outlet of the pre-dehydration tower gas-liquid separation tank; separating an organic phase from a water phase of the pre-dehydrated liquid phase material flow through a pre-dehydration tower reflux tank, and enabling the obtained organic phase to flow back to the pre-dehydration tower; a gas-phase material flow of the pre-dehydration tower enters a recycle gas treatment device, a recycle gas material flow is formed after purge gas emission, vinyl acetate recovery through flash evaporation and pressurization, and after vaporization and gas-liquid separation, a gas phase is subjected to acetic acid supplementation and heating, and then is mixed with oxygen, shielding gas and a cocatalyst to be fed into the reactor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vinyl acetate production, in particular to a vinyl acetate production method and system. BACKGROUND

[0002] Vinyl acetate, also known as vinyl acetate (VAc for short), is a vinyl ester compound with α, β-unsaturated structure, with a molecular formula of C4H6O2 (CH3COOCH=CH2). As an important platform compound in the chemical industry, VAc is classified by the International Union of Pure and Applied Chemistry (IUPAC) as a vinyl ester monomer with conjugated double bond characteristics. The substance is colorless and transparent in liquid state (density 0.934 g / cm 3 , boiling point 72.7℃) under standard conditions, has typical ester volatility characteristics, and its flash point is as low as -8℃ (closed cup test), belonging to class IB flammable liquid. From the analysis of physical and chemical properties, vinyl acetate shows significant polar-nonpolar amphiphilic characteristics: it has good compatibility with most nonpolar organic solvents (such as benzene, acetone), but its solubility in water is temperature-dependent (solubility at 20℃ is 2.4wt%), and it can form binary azeotropic system with water (azeotropic point 66.5℃), methanol (62.1℃) and other solvents.

[0003] Vinyl acetate, as a basic organic chemical raw material, plays an important role in modern chemical industry. Its copolymerization characteristics make it a key synthesis monomer for a series of high polymer materials such as polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), ethylene-vinyl acetate copolymer resin (EVA), vinyl acetate-vinyl chloride copolymer (EVC), etc. According to market research data, China's total production capacity of vinyl acetate in 2024 is nearly 4 million tons / year, and its downstream applications cover synthetic fibers, adhesives, coatings, films and other fields, fully reflecting its basic role in modern industry.

[0004] The preparation of vinyl acetate by ethylene gas phase oxidation method is the dominant technical route for current industrial production. China has formed a full industrial chain layout from raw material supply to terminal application in the field of vinyl-based chemicals, but there is still significant room for improvement in the degree of self-determination of the core process. Looking back at the industrialization process, the vinyl acetate production system established through technology transfer in the 1970s laid the foundation for the industry, but its underlying technical architecture has a persistent technical gap with contemporary advanced processes. This generational difference is concentrated in key dimensions such as catalytic system energy efficiency, process intensification means and clean production level, directly leading to limitations in the development of downstream high-end products, especially in the field of high-value-added applications such as optical-grade polyvinyl alcohol film and special polymer materials that require precise control of monomer quality, and the local supply capacity has not achieved breakthrough progress.

[0005] In addition, in the existing ethylene gas phase oxidation method VAc production process, there are several technical bottlenecks to be solved: one is the optimization of raw material conversion efficiency; the second is the challenge of energy efficiency improvement in the separation process, and the mechanical balance limitation leads to the difficulty in separation of vinyl acetate, resulting in high energy consumption of separation; the utilization rate of high-grade heat of the device is insufficient, which leads to significant increase of CO2 equivalent emission, which directly conflicts with the current low-carbon production transformation requirements. SUMMARY

[0006] To solve the technical problems existing in the prior art, the purpose of the present application is to provide a vinyl acetate production method and system, which has the characteristics of less vinyl acetate by-product, low reaction energy consumption, high raw material utilization rate and high heat utilization rate.

[0007] To achieve the above-mentioned purpose of the application, the present application provides a vinyl acetate production method, comprising the following steps:

[0008] After the oxygen, gas phase acetic acid, protective gas and catalyst are fully mixed, they are sent to the vinyl acetate reactor to generate a reaction product stream.

[0009] The reaction product stream is sent to the pre-dehydration tower after cooling, and the crude vinyl acetate product is recovered at the bottom of the pre-dehydration tower, and the reaction product gas phase stream is recovered at the top of the pre-dehydration tower.

[0010] The reaction product gas phase stream enters the pre-dehydration tower gas-liquid separation tank after cooling, and the pre-dehydration tower gas phase stream is taken out from the gas phase outlet of the pre-dehydration tower gas-liquid separation tank, and the pre-dehydration liquid phase stream is taken out from the liquid phase outlet of the pre-dehydration tower gas-liquid separation tank.

[0011] After the pre-dehydration liquid phase stream is separated into organic phase and water phase in the pre-dehydration tower reflux tank, the obtained organic phase is refluxed to the pre-dehydration tower.

[0012] The pre-dehydration tower gas phase stream enters the circulating gas treatment device, and after venting, flash recovery of vinyl acetate and pressurization, a circulating gas stream is formed, and the gas phase after vaporization and gas-liquid separation of the circulating gas stream is mixed with oxygen, protective gas and catalyst after being supplemented with acetic acid and heated, and then sent into the reactor.

[0013] According to one technical solution of the present application, the reaction product stream and the circulating gas stream are heat exchanged to realize the cooling of the reaction product stream and the preheating of the circulating gas stream.

[0014] According to one technical solution of the present application, the protective gas is nitrogen, the catalyst is KOAc solution, and the catalyst is d-Au / SiO2.

[0015] According to one aspect of the present application, there is provided a vinyl acetate production system for implementing the above-mentioned vinyl acetate production method, comprising:

[0016] a mixer, a first inlet end of which is connected with a nitrogen source, an oxygen source and a promoter source;

[0017] an acetic acid separation device, a first inlet end of which is connected with an acetic acid source, and a gas phase outlet end of which is connected with a second inlet end of the mixer;

[0018] a reactor, a catalyst being arranged in a tube passage of the reactor, and an inlet end of the tube passage being connected with an outlet end of the mixer;

[0019] a pre-dehydration column, an inlet end of which is connected with an outlet end of the tube passage of the reactor, and a gas phase outlet end of which is used for tapping a pre-dehydration column gas phase stream, and a liquid phase outlet end of which is used for tapping a crude vinyl acetate product;

[0020] a pre-dehydration column gas phase stream cooler, which is used for cooling the pre-dehydration column gas phase stream;

[0021] a pre-dehydration column gas-liquid separation tank, an inlet end of which is connected with an outlet end of the pre-dehydration column gas phase stream cooler;

[0022] a pre-dehydration column reflux tank, an inlet end of which is connected with a liquid phase outlet of the pre-dehydration column gas-liquid separation tank, and an organic phase outlet of which is connected with a reflux port of the pre-dehydration column;

[0023] a circulating gas treatment device, an inlet end of which is connected with a gas phase outlet of the pre-dehydration column gas-liquid separation tank, which is used for venting, flash recovery of vinyl acetate and pressure treatment of the pre-dehydration column gas phase stream separated by the pre-dehydration column gas-liquid separation tank;

[0024] a circulating gas vaporization heating device, an inlet end of which is connected with an outlet end of the circulating gas treatment device, and an outlet end of which is connected with a second inlet end of the acetic acid separation device;

[0025] a liquid phase outlet end of the acetic acid separation device is used for recovering the crude vinyl acetate product, and the acetic acid separation device is used for gas-liquid separation of the stream output by the circulating gas vaporization heating device, and after supplementing acetic acid and heating of the gas phase after the separation, the gas phase is sent into the mixer.

[0026] According to one technical solution of the present application, the circulating gas treatment device comprises:

[0027] a circulating gas stripping column, an inlet end of which is connected with a gas phase outlet of the dehydration column gas-liquid separation tank, and a first gas phase outlet of which is connected with a venting device;

[0028] a stripping column flash tank, a second gas phase outlet of the circulating gas stripping column being connected with an inlet end of the stripping column flash tank; a liquid phase outlet of the stripping column flash tank being used to extract ethylene acetate crude product;

[0029] a circulating gas compressor, an inlet end of which being connected with a gas phase outlet of the stripping column flash tank, and being used to pressurize the gas phase stream extracted from the stripping column flash tank.

[0030] According to one technical solution of the present application, the gas output speed of the outlet end of the mixer is 33-66 m / s.

[0031] According to one technical solution of the present application, a circulating gas preheating heat exchanger is arranged between the circulating gas vaporization heating device and the circulating gas treatment device, an outlet end and an inlet end of a cold material cavity of the circulating gas preheating heat exchanger being connected with an inlet end of the circulating gas vaporization heating device and an outlet end of the circulating gas treatment device respectively, and an inlet end and an outlet end of a hot material cavity of the circulating gas preheating heat exchanger being connected with a tube side outlet end of the reactor and an inlet end of the predehydration column respectively.

[0032] According to one technical solution of the present application, the acetic acid separation device comprises:

[0033] an acetic acid gas-liquid separation tank, a first inlet end of which being connected with an outlet end of the circulating gas vaporization heating device, and a second inlet end of which being connected with an acetic acid source; a liquid phase outlet end of the acetic acid gas-liquid separation tank being used to extract ethylene acetate crude product;

[0034] a circulating gas material preheater, which is arranged on a gas phase outlet end of the acetic acid gas-liquid separation tank; an outlet end of the circulating gas material preheater being connected with a second inlet end of the mixer.

[0035] According to one technical solution of the present application, the operating temperature of the reactor is 150-180℃, and the operating pressure is 0.7-1.0 MPa;

[0036] the operating temperature of the cold material cavity of the circulating gas preheating heat exchanger is 140-160℃, and the operating pressure is 800-1000 kPa; the operating temperature of the hot material cavity of the circulating gas preheating heat exchanger is 130-180℃, and the operating pressure is 600-750 kPa;

[0037] the operating temperature of the cold material cavity of the circulating gas preheating heat exchanger is 70-170℃, and the operating pressure is 800-1100 kPa; the operating temperature of the hot material cavity of the circulating gas preheating heat exchanger is 85-150℃, and the operating pressure is 600-800 kPa;

[0038] the operating temperature of the top of the predehydration column is 90-100℃, the operating temperature of the column bottom is 110-130℃, the operating pressure of the top of the predehydration column is 680-720 kPa, and the pressure drop of a single plate is 0.4-0.75 kPa;

[0039] The operating temperature of the pre-dehydrated backflow tank is 40-50 DEG C, and the operating pressure is 500-700 kPa;

[0040] The operating temperature of the top of the circulating gas stripping tower is 35-45 DEG C, the operating temperature of the bottom is 40-50 DEG C, the operating pressure of the top is 500-600 kPa, and the single plate pressure drop is 0.60-0.80 kPa;

[0041] The operating temperature of the stripping tower flash tank is 40-50 DEG C, and the operating pressure is 150-300 kPa.

[0042] According to one of the technical solutions of the present application, the shell side of the reactor is connected with a low-pressure drum for withdrawing heat from the reactor.

[0043] Compared with the prior art, the present application has the following beneficial effects:

[0044] The present application provides a vinyl acetate production method and system, which is established through an efficient reaction system, improves the single-pass conversion rate of ethylene, simultaneously constructs a multi-tower rectification energy integration network, optimizes the mass transfer-heat transfer coupling efficiency, increases the cold energy utilization rate, reduces the comprehensive energy consumption, ensures the stability of the water content of the acetate product, simultaneously promotes the low-carbon upgrading of the process, through the directed recycling use of unreacted ethylene and the optimization of the whole process energy consumption, the carbon emission intensity is low, and the engineering verification is completed, the device is operated for more than 8000 hours per year, and a high-efficiency, low-carbon, economically sustainable acetate ethylene device solution is provided for the industry.

[0045] In the present application, nitrogen is introduced into the mixer, a circulation loop is established by circulation, nitrogen forms a protective atmosphere, and is always in a controlled device, thereby improving the safety and stability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0047] Figure 1 The flow chart of the vinyl acetate production method provided in one embodiment of the present application is schematically shown.

[0048] Among them, the correspondence between the component name and the reference sign is as follows:

[0049] M101: mixer; E102: recycle gas material preheater; R103: reactor; E104: recycle gas preheating heat exchanger; E105: acetic acid evaporator; T106: pre-dehydration tower; E107: crude vinyl acetate heat exchanger; E108: product cooling heat exchanger; V109: pre-dehydration tower gas-liquid separation tank; V110: pre-dehydration tower backflow tank; T111: recycle gas stripping tower; V112: stripping tower flash tank; C113: recycle gas compressor; V114: acetic acid gas-liquid separation tank. DETAILED DESCRIPTION

[0050] The description of the embodiments of the present specification should be combined with the corresponding drawings, which should be part of the complete specification. In the drawings, the shape or thickness of the examples can be exaggerated and simplified or facilitated. Furthermore, parts of the structures in the drawings will be described separately, and it should be noted that the elements not shown or not described by text in the drawings are in the form known to those skilled in the art.

[0051] The description of the embodiments herein, any reference to direction and orientation, is only for the convenience of description, and cannot be understood as any limitation on the scope of protection of the present application. The following description of the preferred embodiments will refer to combinations of features, which can exist independently or in combination, and the present application is not particularly limited to the preferred embodiments. The scope of the present application is defined by the claims.

[0052] The vinyl acetate (VA) process is to react ethylene, acetic acid and oxygen as raw materials to generate vinyl acetate, carbon dioxide and water under the action of noble metal Pd-Au bimetallic catalyst. The molecular formula of the reaction process is as follows:

[0053] C2H4+CH3COOH+1 / 2O2→CH3COOCH2CH2+H2O

[0054] Catalyst: Pd-Au / SiO2

[0055] Catalyst: Pd-Au / SiO2

[0056] Reaction conditions: temperature 150-180℃, pressure 0.7-1.0 MPa.

[0057] At the same time, the process exists the main side reaction of ethylene generating carbon dioxide:

[0058] C2H4+3O2→2CO2+2H2O

[0059] Therefore, in order to ensure the continuous reaction, ethylene is first supplemented to the recycle gas in the reaction system.

[0060] The present application provides a vinyl acetate production method, comprising the following steps:

[0061] The oxygen, the gaseous acetic acid, the protective gas and the cocatalyst are mixed sufficiently and then sent to the vinyl acetate reactor to generate a reaction product stream through the vinyl acetate production reaction;

[0062] The reaction product stream is cooled and then sent to the pre-dehydration tower, and the crude vinyl acetate product is recovered at the bottom of the pre-dehydration tower, and the reaction product gaseous stream is recovered at the top of the pre-dehydration tower;

[0063] The reaction product gaseous stream is cooled and then enters the pre-dehydration tower gas-liquid separation tank, the pre-dehydration tower gaseous stream is collected from the gaseous phase outlet of the pre-dehydration tower gas-liquid separation tank, and the pre-dehydration liquid stream is collected from the liquid phase outlet of the pre-dehydration tower gas-liquid separation tank;

[0064] The pre-dehydration liquid stream is separated into an organic phase and an aqueous phase in the pre-dehydration tower reflux tank, and the obtained organic phase is refluxed to the pre-dehydration tower;

[0065] The pre-dehydration tower gaseous stream enters the circulating gas treatment device, is discharged through the vent gas, and then the vinyl acetate is recovered through flash evaporation and is pressurized to form a circulating gas stream, and the gaseous phase after vaporization and gas-liquid separation of the circulating gas stream is mixed with oxygen, a protective gas and a cocatalyst after being supplemented with acetic acid and heated, and then is sent to the reactor.

[0066] In some embodiments of the present application, further, the reaction product stream and the circulating gas stream are heat exchanged to achieve cooling of the reaction product stream and preheating of the circulating gas stream.

[0067] As shown in Figure 1 The present application also provides a vinyl acetate production system for realizing the above-mentioned vinyl acetate production method, which comprises:

[0068] A mixer M101, a first inlet end of which is connected with a nitrogen source, an oxygen source and a cocatalyst source outside the zone;

[0069] An acetic acid separation device, a first inlet end of which is connected with an acetic acid source, and a gaseous phase outlet end of which is connected with a second inlet end of the mixer;

[0070] A reactor R103, a tube passage of which is provided with a catalyst, and an inlet end of the tube passage of which is connected with an outlet end of the mixer M101;

[0071] A pre-dehydration tower T106, an inlet end of which is connected with an outlet end of the tube passage of the reactor R103, a gaseous phase outlet end of which is used to collect a pre-dehydration tower gaseous stream, and a liquid phase outlet end of which is used to collect a crude vinyl acetate product;

[0072] A pre-dehydration tower gaseous stream cooler, which comprises a crude vinyl acetate heat exchanger E107 and a product cooling heat exchanger E108 connected in series, and is used to cool the pre-dehydration tower gaseous stream;

[0073] a pre-dehydration tower gas-liquid separation tank V109, an inlet end of which is connected with an outlet end of the pre-dehydration tower gas phase stream cooler;

[0074] a pre-dehydration tower reflux tank V110, an inlet end of which is connected with a liquid phase outlet of the pre-dehydration tower gas-liquid separation tank V109, for separating an organic phase and a water phase of the pre-dehydration tower gas phase stream; an organic phase outlet of which is connected with a reflux port of the pre-dehydration tower T106; and a water phase inlet of which is connectable with the refined unit azeotrope reflux tank.

[0075] a circulating gas treatment device, an inlet end of which is connected with a gas phase outlet of the pre-dehydration tower gas-liquid separation tank V109, for discharging a vent gas, recovering the ethylene acetate by flash evaporation, and pressurizing treatment of the pre-dehydration tower gas phase stream separated from the pre-dehydration tower gas-liquid separation tank V109;

[0076] a circulating gas vaporization heating device, which is an acetate evaporator E105, an inlet end of the acetate evaporator E105 being connected with an outlet end of the circulating gas treatment device, and an outlet end of the acetate evaporator E105 being connected with a second inlet end of the acetate separation device;

[0077] a liquid phase outlet end of the acetate separation device being used for recovering the ethylene acetate crude product, the acetate separation device being used for gas-liquid separation of the stream output by the circulating gas vaporization heating device, and after supplementing acetate and heating, the gas phase after separation is sent to a mixer.

[0078] In some embodiments of the present application, further, the circulating gas treatment device comprises:

[0079] a circulating gas stripping tower T111, an inlet end of which is connected with a gas phase outlet of the dehydration tower gas-liquid separation tank V109; and a first gas phase outlet of which is connected with a vent gas device;

[0080] a stripping tower flash tank V112, a second gas phase outlet of the circulating gas stripping tower T111 being connected with an inlet end of the stripping tower flash tank V112, and a circulating gas buffer tank can be arranged between the second gas phase outlet of the circulating gas stripping tower T111 and the stripping tower flash tank V112, so as to ensure stable pressure in the system; and a liquid phase outlet of the stripping tower flash tank V112 being used for recovering the ethylene acetate crude product;

[0081] a circulating gas compressor C113, an inlet end of which is connected with a gas phase outlet of the stripping tower flash tank, for pressurizing the gas phase stream recovered by the stripping tower flash tank V112.

[0082] In some embodiments of the present application, further, a circulating gas preheating heat exchanger E104 is arranged between the circulating gas vaporization heating device and the circulating gas treatment device, the outlet end and the inlet end of the cold material cavity of the circulating gas preheating heat exchanger E104 are connected with the inlet end of the acetic acid evaporator E105 and the outlet end of the circulating gas compressor in the circulating gas treatment device respectively, and the inlet end and the outlet end of the hot material cavity of the circulating gas preheating heat exchanger E104 are connected with the outlet end of the tube side of the reactor and the inlet end of the pre-dewatering tower respectively, so as to realize heat exchange between the reaction product stream and the circulating gas stream, and further realize the temperature reduction of the reaction product stream and the preheating of the circulating gas stream.

[0083] In some embodiments of the present application, further, the acetic acid separation device comprises:

[0084] An acetic acid gas-liquid separation tank V114, the inlet end of which is connected with the outlet end of the circulating gas vaporization heating device; the liquid phase outlet end of which is used to extract the vinyl acetate crude product to be sent to the vinyl acetate refining section;

[0085] A circulating gas material preheater E102 is arranged on the gas phase outlet end of the acetic acid gas-liquid separation tank V114, the first inlet end of which is connected with the gas phase outlet end of the acetic acid gas-liquid separation tank V114, and the second inlet end of which is connected with the external acetic acid source; the outlet end of the circulating gas stream preheater E102 is connected with the second inlet end of the mixer M101. The heat of the circulating gas material preheater E102 is provided by the medium-pressure steam from the utility.

[0086] In some embodiments of the present application, further, the supplemental oxygen is mixed into the circulating raw material of the supplemental acetic acid by the mixer, so that the oxygen concentration at the outlet of the mixer is the highest. In order to avoid explosion, the gas output speed at the outlet end of the mixer is 33 m / s-66 m / s. In the case of low flow rate, inert nitrogen can be mixed into the oxygen to maintain the speed.

[0087] In some embodiments of the present application, further, the operating temperature of the reactor R103 is 150-180℃, and the operating pressure is 0.7-1.0 MPa; the vinyl acetate reaction is carried out in the gas phase. Since higher temperature will cause the catalyst to be inactivated and shorten its service life, the reactor R103 should be controlled at an appropriate temperature, and gradually increased as the reaction proceeds and the catalyst ages, so as to increase the reaction temperature to compensate for the lower catalyst activity.

[0088] The operating temperature of the cold material cavity of the circulating gas preheating heat exchanger E104 is 140-160℃, and the operating pressure is 800-1000 kPa; the operating temperature of the hot material cavity of the circulating gas material preheater E102 is 130-180℃, and the operating pressure is 600-750 kPa.

[0089] The operating temperature of the pre-dehydrating tower T106 is 90-100°C, the operating temperature of the tower bottom is 110-130°C, the operating pressure of the tower top is 680-720 kPa, and the single plate pressure drop is 0.4-0.75 kPa;

[0090] The operating temperature of the pre-dehydrating tower reflux tank V110 is 40-50°C, and the operating pressure is 500-700 kPa;

[0091] The operating temperature of the circulating gas stripping tower T111 is 35-45°C, the operating temperature of the tower bottom is 40-50°C, the operating pressure of the tower top is 500-600 kPa, and the single plate pressure drop is 0.60-0.80 kPa;

[0092] The operating temperature of the stripping tower flash tank V112 is 40-50°C, and the operating pressure is 150-300 kPa.

[0093] In some embodiments of the present application, further, the shell side of the reactor R103 is connected with a low-pressure steam drum for heat removal of the reactor R103. The vinyl acetate reaction is an exothermic reaction, and therefore, in order to control the reaction temperature and maintain the catalyst activity, the reactor is cooled through the low-pressure steam drum so as to recover heat from the reactor and generate steam as the reboiler steam of the rectifying tower.

[0094] The technical solutions of the present application are described in detail below in combination with the drawings and examples of the specification.

[0095] Example 1

[0096] The oxygen, recycle gas, protective gas nitrogen and KOAc solution out of the catalyst are mixed in mixer M101 and then sent to the vinyl acetate reactor R103. The oxygen feed is 11000 kg / h and the acetic acid feed is 26500 kg / h. The reaction temperature of the vinyl acetate reactor R103 is 170°C and the operating pressure is 720 kPa. The reaction product is cooled in the recycle gas preheating heat exchanger E104 at a temperature of 140°C and a pressure of 710 kPa. It is then sent to the pre-dehydration tower T106. The overhead temperature of the pre-dehydration tower T106 is 95°C and the pressure is 700 kPa. The bottom temperature is 130°C and the pressure is 712 kPa. The overhead of the pre-dehydration tower T106 is the pre-dehydration tower gas phase stream, which is a mixture of the gas phase light components and vinyl acetate. The pre-dehydration tower gas phase stream is cooled in two stages in the vinyl acetate heat exchanger E107 and the product cooling heat exchanger E108. The temperature of the pre-dehydration tower gas phase stream is reduced to 41°C and the pressure is 620 kPa. A gas-liquid mixture is obtained. The gas-liquid mixture is separated in the pre-dehydration tower gas-liquid separation tank V109. The gas phase component is sent to the recycle gas stripping tower T111 for recycle gas treatment. The liquid phase outlet of the pre-dehydration tower gas-liquid separation tank V109 is the water-liquid phase containing vinyl acetate, which is sent to the pre-dehydration tower reflux tank V110. The water phase and the organic phase vinyl acetate are obtained in the pre-dehydration tower reflux tank V110. The organic phase is refluxed to the recycle gas stripping tower T111 and the water phase is sent to the subsequent section for treatment. The overhead temperature of the recycle gas stripping tower T111 is 40°C and the pressure is 550 kPa. The bottom temperature is 44°C and the pressure is 600 kPa. The concentration of the vinyl acetate at the bottom of the recycle gas stripping tower T111 is 60.5 wt%.

[0097] Example 2

[0098] The oxygen, recycle gas, protective gas nitrogen and KOAc solution from the catalyst are mixed in mixer M101 and then sent to the vinyl acetate reactor R103. The oxygen feed is 8000 kg / h and the acetic acid feed is 20000 kg / h. The reaction temperature in the vinyl acetate reactor R103 is 175°C and the pressure is 750 kPa. The reaction product is cooled in the recycle gas preheating heat exchanger E104 at a temperature of 142°C and a pressure of 720 kPa. It is then sent to the pre-dehydration tower T106. The overhead temperature is 94°C and the pressure is 695 kPa. The bottom temperature is 128°C and the pressure is 705 kPa. The overhead of the pre-dehydration tower T106 is the pre-dehydration tower gas phase stream, which is a mixture of the gas phase light components and vinyl acetate. The pre-dehydration tower gas phase stream is cooled in two stages in the vinyl acetate heat exchanger E107 and the product cooling heat exchanger E108. The temperature of the pre-dehydration tower gas phase stream is reduced to 40°C and the pressure is 610 kPa. A gas-liquid mixture is obtained. The gas-liquid mixture is separated in the pre-dehydration tower gas-liquid separation tank V109. The gas phase component is sent to the recycle gas stripping tower T111 for recycle gas treatment. The liquid phase outlet of the pre-dehydration tower gas-liquid separation tank V109 is the vinyl acetate-containing water liquid phase, which is sent to the pre-dehydration tower reflux tank V110. The water phase and the organic phase vinyl acetate are obtained in the pre-dehydration tower reflux tank V110. The organic phase is refluxed to the recycle gas stripping tower T111 and the water phase is sent to the subsequent section for treatment. The overhead temperature of the recycle gas stripping tower T111 is 40°C and the pressure is 555 kPa. The bottom temperature is 45°C and the pressure is 610 kPa. The vinyl acetate concentration at the bottom of the tower is 60.2 wt%.

[0099] Example 3

[0100] The oxygen, recycle gas, protective gas nitrogen and KOAc solution from the catalyst are mixed in mixer M101 and then sent to the vinyl acetate reactor R103. The oxygen feed is 5000 kg / h and the acetic acid feed is 13100 kg / h. The reaction temperature in the vinyl acetate reactor is 172°C and the pressure is 710 kPa. The reaction product is cooled in the recycle gas preheating heat exchanger E104 at a temperature of 140°C and a pressure of 690 kPa. It is then sent to the pre-dehydration tower T106. The overhead temperature is 93°C, the pressure is 705 kPa, the bottom temperature is 131°C and the pressure is 715 kPa. The overhead from the pre-dehydration tower T106 is a pre-dehydration tower gas phase stream which is a mixture of the gas phase light components and the vinyl acetate. This stream is cooled in two stages in the vinyl acetate heat exchanger E107 and the product cooling heat exchanger E108. The temperature of the pre-dehydration tower gas phase stream is reduced to 40°C and the pressure is 615 kPa. A gas-liquid mixture is obtained which is separated in the pre-dehydration tower gas-liquid separation tank V109. The gas phase component is sent to the recycle gas stripping tower T111 for recycle gas treatment. The liquid phase from the pre-dehydration tower gas-liquid separation tank V109 is sent to the pre-dehydration tower reflux tank V110. The water phase and the organic phase vinyl acetate are obtained in the pre-dehydration tower reflux tank V110. The organic phase is refluxed to the recycle gas stripping tower T111 and the water phase is sent to the subsequent section for treatment. The overhead temperature in the recycle gas stripping tower T111 is 41°C, the pressure is 560 kPa, the bottom temperature is 45°C and the pressure is 605 kPa. The vinyl acetate concentration in the bottom is 61.0 wt%.

[0101] Finally, it should be noted that the above description is of preferred embodiments of the application. It will be apparent, however, to those skilled in the art that many modifications and improvements can be made to the preferred embodiments without departing from the scope of the inventive concept as set forth in the principles of the application. Therefore, the appended claims are intended to cover all such modifications and improvements as falling within the scope of the application.

Claims

1. A method for producing vinyl acetate, characterized in that, Includes the following steps: After oxygen, gaseous acetic acid, protective gas and co-catalyst are thoroughly mixed, they are sent to the vinyl acetate reactor to carry out the vinyl acetate preparation reaction and generate the reaction product stream. The reaction product stream is cooled and then fed into a pre-dehydration tower, where crude vinyl acetate is recovered at the bottom and the gaseous reaction product stream is recovered at the top. The gaseous product of the reaction is cooled and enters the gas-liquid separator of the pre-dehydration tower. The gaseous product of the pre-dehydration tower is collected from the gas phase outlet of the gas-liquid separator, and the pre-dehydrated liquid product is collected from the liquid phase outlet of the gas-liquid separator. The pre-dehydrated liquid phase stream is separated into organic and aqueous phases in the pre-dehydration tower reflux tank, and the resulting organic phase is refluxed back to the pre-dehydration tower. The gaseous stream from the pre-dehydration tower enters the circulating gas treatment device, where it is discharged as purge gas, flash-evaporated to recover vinyl acetate, and pressurized to form a circulating gas stream. The gaseous stream, after vaporization and gas-liquid separation, is supplemented with acetic acid and heated before being mixed with oxygen, protective gas, and co-catalyst and sent into the reactor.

2. The method for producing vinyl acetate according to claim 1, characterized in that, The reaction product stream and the circulating gas stream exchange heat to achieve cooling of the reaction product stream and preheating of the circulating gas stream.

3. The method for producing vinyl acetate according to claim 2, characterized in that, The protective gas is nitrogen, the co-catalyst is KOAc solution, and the catalyst is d-Au / SiO2.

4. A vinyl acetate production system, characterized in that, A method for producing vinyl acetate as described in any one of claims 1 to 3, comprising: The mixer has its first inlet end connected to a nitrogen source, an oxygen source, and a co-catalyst source; An acetic acid separation device, wherein its first inlet is connected to an acetic acid source; and its gas phase outlet is connected to the second inlet of the mixer. The reactor has a catalyst inside its tube side, and the inlet end of its tube side is connected to the outlet end of the mixer. The inlet of the pre-dehydration tower is connected to the tube outlet of the reactor; its gas phase outlet is used to collect the gas phase stream from the pre-dehydration tower, and its liquid phase outlet is used to collect the crude vinyl acetate product. A pre-dehydration tower gas phase stream cooler is used to cool the gas phase stream from the pre-dehydration tower. The inlet end of the pre-dehydration tower gas-liquid separator is connected to the outlet end of the pre-dehydration tower gas phase stream cooler; The inlet end of the pre-dehydration tower reflux tank is connected to the liquid phase outlet of the pre-dehydration tower gas-liquid separator; its organic phase outlet is connected to the reflux port of the pre-dehydration tower. A circulating gas treatment device, the inlet end of which is connected to the gas phase outlet of the pre-dehydration tower gas-liquid separator, is used to release the pre-dehydration tower gas phase stream separated by the pre-dehydration tower gas-liquid separator, flash evaporate and recover vinyl acetate, and pressurize it. The inlet end of the circulating gas vaporization heating device is connected to the outlet end of the circulating gas treatment device, and the outlet end is connected to the second inlet end of the acetic acid separation device. The liquid phase outlet of the acetic acid separation device is used to recover crude vinyl acetate. The acetic acid separation device is used to perform gas-liquid separation on the stream output from the circulating gas vaporization heating device, and after adding acetic acid and heating the separated gas phase, it is sent to the mixer.

5. The vinyl acetate production system according to claim 4, characterized in that, The circulating gas treatment device includes: The inlet of the circulating gas stripping tower is connected to the gas phase outlet of the gas-liquid separator of the dehydration tower; its first gas phase outlet is connected to the venting gas device. A stripping tower flash tank is provided, wherein the second gas phase outlet of the circulating gas stripping tower is connected to the inlet end of the stripping tower flash tank; the liquid phase outlet of the stripping tower flash tank is used to extract crude vinyl acetate product. A circulating gas compressor, the inlet of which is connected to the gas phase outlet of the stripping tower flash tank, is used to pressurize the gas phase stream collected from the stripping tower flash tank.

6. The vinyl acetate production system according to claim 4, characterized in that, The gas output velocity at the outlet of the mixer is 33m / s-66m / s.

7. The vinyl acetate production system according to claim 4, characterized in that, A circulating gas preheating heat exchanger is provided between the circulating gas vaporization heating device and the circulating gas treatment device. The outlet and inlet ends of its cold material chamber are connected to the inlet end of the circulating gas vaporization heating device and the outlet end of the circulating gas treatment device, respectively. The inlet and outlet ends of its hot material chamber are connected to the tube outlet end of the reactor and the inlet end of the pre-dehydration tower, respectively.

8. The vinyl acetate production system according to claim 4, characterized in that, The acetic acid separation device includes: The acetic acid gas-liquid separator has a first inlet end connected to the outlet end of the circulating gas vaporization heating device, and a second inlet end connected to the acetic acid source; its liquid phase outlet end is used to collect crude vinyl acetate product. A circulating gas material preheater is installed at the gas phase outlet end of the acetic acid gas-liquid separator; the outlet end of the circulating gas material preheater is connected to the second inlet end of the mixer.

9. The vinyl acetate production system according to claim 8, characterized in that, The reactor operates at a temperature of 150-180℃ and a pressure of 0.7–1.0 MPa. The operating temperature of the cold chamber of the circulating gas preheating heat exchanger is 140-160℃, and the operating pressure is 800-1000kPa; the operating temperature of the hot chamber of the circulating gas preheating heat exchanger is 130-180℃, and the operating pressure is 600-750kPa. The operating temperature of the cold chamber of the circulating gas preheating heat exchanger is 70-170℃ and the operating pressure is 800-1100kPa, while the operating temperature of its hot chamber is 85-150℃ and the operating pressure is 600-800kPa. The pre-dehydration tower has an operating temperature of 90-100℃ at the top, an operating temperature of 110-130℃ at the bottom, an operating pressure of 680-720 kPa at the top, and a single-plate pressure drop of 0.4-0.75 kPa. The operating temperature of the pre-dehydration tower reflux tank is 40-50℃, and the operating pressure is 500-700kPa; The operating temperature at the top of the circulating gas stripping tower is 35-45℃, the operating temperature at the bottom of the tower is 40-50℃, the operating pressure at the top of the tower is 500-600kPa, and the pressure drop per plate is 0.60-0.80kPa. The operating temperature of the stripping tower flash tank is 40-50℃, and the operating pressure is 150-300kPa.

10. The vinyl acetate production system according to claim 6, characterized in that, The shell side of the reactor is connected to a low-pressure steam drum for heat removal from the reactor.

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