Vinyl acetate refining system and method

Abstract

The invention relates to a vinyl acetate refining system and method, and the system comprises: an azeotropic tower for extracting a vinyl acetate azeotrope from the top of the azeotropic tower, extracting a water-containing acetic acid material flow from the bottom of the azeotropic tower, and extracting an ethyl acetate material flow from the side line of the azeotropic tower; the azeotrope tower reflux unit is used for separating the vinyl acetate azeotrope into an azeotrope organic phase and an azeotrope water phase; the dehydration unit is used for carrying out light component and vinyl acetate separation on an azeotrope organic phase output by the azeotropic tower reflux unit, so as to realize light component recovery and vinyl acetate finished product recovery; the ethyl acetate treatment unit is used for carrying out ethyl acetate separation and vinyl acetate component recovery on the ethyl acetate material flow through the ethyl acetate treatment unit; and the vinyl acetate material flow output end of the ethyl acetate treatment unit is connected with the input end of the azeotropic tower, so that the vinyl acetate material flow flows back to the azeotropic tower. The method provided by the invention can realize separation of each component in the vinyl acetate crude product, significantly improves process stability, reduces separation difficulty, and reduces energy consumption at the same time.

Description

Technical Field

[0001] This invention relates to the field of vinyl acetate refining and purification technology, and in particular to a vinyl acetate refining system and method. Background Technology

[0002] Vinyl acetate, as one of the most widely used organic chemicals globally, is increasingly prominent in the industrial sector due to its wide range of applications and importance. The main production methods for vinyl acetate (VAc) include the acetylene gas-phase process, the liquid-phase process, and the synthesis of vinyl glycolate. These processes each have advantages in terms of energy efficiency, cost control, and environmental friendliness. In industrial production, VAc is widely used to synthesize key polymer materials such as polyvinyl alcohol, polyvinyl acetate, and ethylene-vinyl acetate copolymers. These materials play an irreplaceable role in multiple industries due to their unique physicochemical properties. In recent years, the rapid development of the photovoltaic and network communication industries has led to a significant increase in demand for ethylene-vinyl acetate copolymers, a major raw material for photovoltaic films, wires, and cables, thereby driving the rapid development of the upstream vinyl acetate industry.

[0003] In the gas-phase process for preparing vinyl acetate from ethylene, the formation of the target product VAc is accompanied by the formation of various byproducts, including carbon dioxide, acetaldehyde, acrolein, acrylic acid, methyl acetate, ethyl acetate, vinyl acrylate, and ethylene glycol diacetate. Water is inevitably produced during the reaction. At the same time, vinyl acetate contains carbon-carbon double bonds, which are easy to polymerize, adding difficulty to the subsequent purification of vinyl acetate monomer. The core difficulty of the separation process lies in the fact that water and vinyl acetate form a binary azeotropic system containing 7 wt% water. The boiling points of the byproducts methyl acetate, ethyl acetate, and vinyl acrylate are close to those of vinyl acetate. They, along with unreacted acetic acid, light byproducts, and heavy components in the system, constitute a complex mixture with overlapping boiling points and multi-component azeotropic behavior. This results in several technical bottlenecks that urgently need to be addressed in the separation of vinyl acetate: (1) It is difficult to simultaneously achieve efficient recovery of acetic acid and removal of product water; (2) It is impossible to completely separate the vinyl acetate-water azeotrope from vinyl acrylate, which has a similar boiling point; (3) It is difficult to economically and feasiblely remove light / heavy component impurities to ensure the purity of the vinyl acetate product. The inherent complexity of this multi-component azeotropic system significantly increases the design difficulty and operating cost of the separation process, becoming a key bottleneck restricting the efficiency of ethylene gas-phase production. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention aims to provide a vinyl acetate refining system and method, which features high process stability, low separation difficulty, and low energy consumption.

[0005] To achieve the above-mentioned objectives, the present invention provides a vinyl acetate refining system, comprising:

[0006] An azeotropic column is used to collect the crude vinyl acetate product entering the azeotropic column, extract the vinyl acetate azeotrope from the top of the azeotropic column, extract the aqueous acetic acid stream from the bottom of the azeotropic column, and extract the ethyl acetate stream from the side stream of the azeotropic column.

[0007] An azeotropic tower reflux unit is installed at the top of the azeotropic tower to separate the vinyl acetate azeotrope into an azeotropic organic phase and an azeotropic aqueous phase; the first organic phase output end of the azeotropic tower reflux unit is connected to the input end of the azeotropic tower.

[0008] The dehydration unit is connected to the second organic phase output end of the azeotropic tower reflux unit and is used to separate the light components and vinyl acetate from the azeotropic organic phase output by the azeotropic tower reflux unit, so as to realize the recovery of light components and vinyl acetate product.

[0009] An ethyl acetate processing unit, connected to the side stream of the azeotropic tower, is used to separate ethyl acetate and recover vinyl acetate components from the ethyl acetate stream.

[0010] The vinyl acetate stream output of the ethyl acetate processing unit is connected to the input of the azeotropic tower to enable the vinyl acetate stream to be refluxed back to the azeotropic tower.

[0011] According to one technical solution of the present invention, the azeotropic tower reflux unit includes:

[0012] An azeotropic tower top condenser is connected to the top of the azeotropic tower and is used to condense the vinyl acetate azeotrope.

[0013] An azeotropic tower reflux tank, connected to the top condenser of the azeotropic tower, is used to separate vinyl acetate azeotrope into an azeotropic organic phase and an azeotropic aqueous phase;

[0014] An azeotropic tower organic phase reflux pump has its input end connected to the organic phase output end of the azeotropic tower reflux tank, its first output end connected to the input end of the azeotropic tower, and its second output end connected to the input end of the dehydration unit.

[0015] According to one technical solution of the present invention, the dehydration unit includes:

[0016] A dehydration tower is connected to the output end of the organic phase reflux pump of the azeotropic tower, and is used to separate the light components and vinyl acetate from the organic phase of the azeotrope; the light component stream is output from the top of the tower, and the initial vinyl acetate product stream is output from the bottom of the tower.

[0017] The vinyl acetate product tower is connected to the bottom of the dehydration tower and is used to purify the primary vinyl acetate product stream; the top of the tower recovers vinyl acetate product, and the bottom of the tower is connected to the azeotropic tower reflux tank for returning the collected high / medium boiling point aggregate stream to the azeotropic tower reflux tank.

[0018] A light component removal tower, connected to the bottom of the dehydration tower, is used to recover vinyl acetate from the light component stream and to remove acetaldehyde, methyl acetate, and acrolein. The light component removal tower is a pressurized tower, with acetaldehyde stream collected from its top and acrolein and methyl acetate streams collected from its side streams. Its bottom is connected to the input end of the dehydration tower to return the collected light component vinyl acetate recovery stream to the dehydration tower.

[0019] According to one technical solution of the present invention, the dehydration unit further includes a dehydration tower reflux unit, comprising:

[0020] A condenser at the top of the dehydration tower is connected to the top of the dehydration tower;

[0021] The dehydration tower reflux tank has its inlet end connected to the outlet end of the dehydration tower top condenser, and is used to separate the light component stream into an organic phase and an aqueous phase.

[0022] A dehydration tower reflux pump is used to feed a portion of the organic phase of the light component stream into the dehydration tower and another portion into the light component removal tower.

[0023] According to one technical solution of the present invention, the bottom operating temperature of the azeotropic column is 130-140℃, the top operating temperature is 73-75℃, and the internal operating pressure of the azeotropic column is 30-85kPag.

[0024] The azeotropic tower has a total of 70 trays, of which the 30th tray is the feed tray; the 10th tray of the azeotropic tower is the side stream outlet; the total reflux ratio of the azeotropic tower is 4-6.

[0025] The operating temperature of the azeotropic tower top condenser is 35-42℃, and its operating pressure is 20-30kPag.

[0026] The operating temperature of the azeotropic tower reflux tank is 35-42℃, and its operating pressure is 20-30kPag.

[0027] According to one technical solution of the present invention, the bottom operating temperature of the dehydration tower is 85-89℃, the top operating temperature is 71-75℃, and the internal operating pressure of the dehydration tower is 25-60kPag.

[0028] The dehydration tower has a total of 40 trays, and the feed tray is the 30th tray; the total reflux ratio of the dehydration tower is 7-10.

[0029] The operating temperature of the condenser at the top of the dehydration tower is 40-45℃, and its operating pressure is 15-30kPag.

[0030] The operating temperature of the dehydration tower reflux tank is 40-45℃, and its operating pressure is 10-30kPag.

[0031] According to one technical solution of the present invention, the bottom operating temperature of the light component removal tower is 98-103℃, the top operating temperature is 47-52℃, and the internal operating pressure is 145-180kPag; the light component removal tower has a total of 40 trays, and the feed tray of the light component removal tower is the 25th tray.

[0032] According to one embodiment of the present invention, the ethyl acetate treatment unit comprises:

[0033] An ethyl acetate column, whose inlet is connected to the side stream of the azeotropic column, is used to concentrate the ethyl acetate stream; the top of the column collects the ethyl acetate recovery stream; and the bottom of the column is the outlet of the vinyl acetate stream.

[0034] An ethyl acetate tower condenser, the inlet of which is connected to the top of the ethyl acetate tower;

[0035] An ethyl acetate tower reflux tank, whose inlet is connected to the outlet of the ethyl acetate tower condenser, is used to separate the organic phase and aqueous phase of the ethyl acetate recovery stream. A portion of the organic phase of the ethyl acetate recovery stream is refluxed back to the ethyl acetate tower, and the other portion is sent to the ethyl acetate storage tank.

[0036] According to one technical solution of the present invention, the bottom operating temperature of the ethyl acetate column is 118-122℃, the top operating temperature is 78-83℃, and the internal operating pressure of the dehydration column is 20-50 kPag.

[0037] The ethyl acetate column has a total of 20 trays, and the feed tray is the 10th tray; the total reflux ratio of the ethyl acetate column is 9-12.

[0038] According to one aspect of the present invention, a method for refining vinyl acetate is provided, comprising the following steps:

[0039] Crude vinyl acetate product enters an azeotropic column. Vinyl acetate azeotrope is collected from the top of the azeotropic column, aqueous acetic acid stream is collected from the bottom of the azeotropic column, and ethyl acetate stream is collected from the side stream of the azeotropic column.

[0040] The vinyl acetate azeotrope is separated into an azeotropic organic phase and an azeotropic aqueous phase by the azeotropic tower reflux unit. A portion of the azeotropic organic phase is refluxed back to the azeotropic tower, and the other portion of the azeotropic organic phase is separated from the light components and vinyl acetate by the dehydration unit, thereby realizing the recovery of light components and the recovery of vinyl acetate product.

[0041] The ethyl acetate stream is processed by an ethyl acetate treatment unit to separate ethyl acetate and recover vinyl acetate components; the recovered vinyl acetate stream is returned to the azeotropic tower.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention proposes a vinyl acetate refining system and method. Based on the material separation characteristics, acetic acid and water need to be removed first to ensure phase separation efficiency, achieving simultaneous separation of ethyl acetate and water in the initial runoff phase. The vinyl acetate azeotrope is collected from the top of the azeotropic tower, and the fraction collected in the 110-115℃ temperature range on the side stream of the azeotropic tower is sent to the ethyl acetate processing unit for ethyl acetate removal, preventing its subsequent accumulation in the system and entrainment by the aqueous phase. In the azeotropic tower reflux tank, the aqueous phase and the organic phase of vinyl acetate are separated, thus removing water. Furthermore, utilizing the ultra-low water content of the organic phase refluxed to the azeotropic tower, and through multi-stage gas-liquid equilibrium in the dehydration unit, deep dehydration is achieved, enabling efficient separation of vinyl acetate from light components such as methyl acetate, acetaldehyde, and acrolein in subsequent processes. This application significantly improves process stability, reduces separation difficulty, and reduces energy consumption by cutting off the entrainment path of ethyl acetate and water at the first moment of distillation and by utilizing the azeotropic properties of acetic acid and ethyl acetate and the easy separation of light components. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0045] Figure 1 The schematic diagram illustrates the structure of a vinyl acetate refining system provided in one embodiment of the present invention.

[0046] The correspondence between component names and reference numerals in the accompanying drawings is as follows:

[0047] T-101: Azeotropic column; P-102: Azeotropic column organic phase reflux pump; P-103: Ethyl acetate column feed pump; P-104: Azeotropic column aqueous phase reflux pump; V-105: Azeotropic column reflux tank; E-106: Azeotropic column condenser; E-107: Azeotropic column reboiler; T-108: Ethyl acetate column; E-109: Ethyl acetate column reboiler; E-110: Ethyl acetate column condenser; V-111: Ethyl acetate column reflux tank; P-112: Azeotropic column side-stream reflux pump; P-113: Ethyl acetate column reflux pump; T-114: Dehydration column; E-115: Dehydration column condenser; V- 116: Dehydration tower condenser; P-117: Dehydration tower reflux pump; E-118: Dehydration tower reboiler; T-119: Light component tower; E-120: Light component tower reboiler; P-121: Light component tower bottom pump; T-122: Vinyl acetate product tower; E-123: Product tower condenser; V-124: Product tower reflux tank; P-125: Product tower reflux pump; E-126: Product tower reboiler; E-127: Product condenser; P-128: Product tower bottom pump; P-129: Acetic acid circulation pump; E-130: Dehydration tower feed preheater; P-131: Product tower feed pump. Detailed Implementation

[0048] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0049] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0050] like Figure 1 As shown, the present invention provides a vinyl acetate refining system, comprising:

[0051] Azeotropic tower T-101 is used to collect the crude vinyl acetate product entering the azeotropic tower T-101, extract the vinyl acetate azeotrope from the top of the azeotropic tower T-101, extract the aqueous acetic acid stream from the bottom of the azeotropic tower T-101, and extract the ethyl acetate stream from the side stream of the azeotropic tower T-101.

[0052] The azeotropic tower reflux unit is located at the top of the azeotropic tower T-101 and is used to separate the vinyl acetate azeotrope into an azeotropic organic phase and an azeotropic aqueous phase. The first organic phase output end of the azeotropic tower reflux unit is connected to the input end of the azeotropic tower T-101.

[0053] The dehydration unit is connected to the second organic phase output end of the azeotropic tower reflux unit and is used to separate the light components and vinyl acetate from the azeotropic organic phase output from the azeotropic tower reflux unit, so as to realize the recovery of light components and vinyl acetate product.

[0054] The ethyl acetate processing unit is connected to the side line of the azeotropic tower T-101 and is used to separate ethyl acetate and recover vinyl acetate components from the ethyl acetate stream.

[0055] The vinyl acetate stream output of the ethyl acetate processing unit is connected to the input of the azeotropic tower T-101 to enable the vinyl acetate stream to be refluxed back to the azeotropic tower T-101.

[0056] According to one technical solution of the present invention, the azeotropic tower reflux unit includes:

[0057] The azeotropic tower top condenser E-106 is connected to the top of the azeotropic tower T-101 and is used to condense the vinyl acetate azeotrope.

[0058] The reflux tank V-105 of the azeotropic tower is connected to the top condenser E-106 of the azeotropic tower and is used to separate the vinyl acetate azeotrope into an azeotropic organic phase and an azeotropic aqueous phase.

[0059] The azeotropic tower organic phase reflux pump P-102 has its input end connected to the organic phase output end of the azeotropic tower reflux tank V-105, its first output end connected to the input end of the azeotropic tower T-101, and its second output end connected to the input end of the dehydration unit.

[0060] Furthermore, the dehydration unit includes:

[0061] The dehydration tower T-114 is connected to the output end of the organic phase reflux pump P-102 of the azeotropic tower and is used to separate the light components and vinyl acetate from the azeotropic organic phase; the light component stream is output from the top of the tower and the initial vinyl acetate product stream is output from the bottom of the tower.

[0062] The vinyl acetate product tower T-122 is connected to the bottom of the dehydration tower T-114 and is used to purify the primary vinyl acetate product stream. The top of the tower recovers vinyl acetate product, and the bottom of the tower is connected to the azeotropic tower reflux tank V-105 to return the collected high / medium boiling point aggregate stream to the azeotropic tower reflux tank V-105.

[0063] The light component removal tower T-119 is connected to the bottom of the dehydration tower T-114 and is used to recover vinyl acetate from the light component stream, as well as to remove acetaldehyde, methyl acetate, and acrolein. The light component removal tower T-119 is a pressurized tower, with acetaldehyde stream collected from the top and acrolein and methyl acetate streams collected from its side stream. Its bottom is connected to the input end of the dehydration tower T-114 to return the collected light component vinyl acetate recovery stream to the dehydration tower T-114.

[0064] Furthermore, the dehydration unit also includes a dehydration tower reflux unit, comprising:

[0065] The top condenser E-115 of the dehydration tower is connected to the top of the dehydration tower T-114;

[0066] The dehydration tower reflux tank V-116 has its inlet end connected to the outlet end of the dehydration tower top condenser E-115, and is used to separate the light component stream into the light component stream organic phase and the light component stream aqueous phase.

[0067] The dehydration tower reflux pump P-117 is used to send a portion of the organic phase of the light component stream into the dehydration tower T-114, and the other portion into the light component removal tower T-119.

[0068] Furthermore, the bottom operating temperature of the azeotropic tower T-101 is 130-140℃, and the top operating temperature is 73-75℃; the internal operating pressure of the azeotropic tower T-101 is 30-85kPag.

[0069] The azeotropic tower T-101 has a total of 70 trays, of which the 30th tray is the feed tray; the 10th tray of the azeotropic tower T-101 is the side stream outlet; the total reflux ratio of the azeotropic tower T-101 is 4-6.

[0070] The operating temperature of the E-106 azeotropic column top condenser is 35-42℃, and its operating pressure is 20-30kPag.

[0071] The operating temperature of the azeotropic tower reflux tank V-105 is 35-42℃, and its operating pressure is 20-30kPag.

[0072] Furthermore, the bottom operating temperature of the dehydration tower T-114 is 85-89℃, the top operating temperature is 71-75℃, and the internal operating pressure of the dehydration tower T-114 is 25-60kPag.

[0073] The dehydration tower T-114 has a total of 40 trays, and the feed tray of the dehydration tower T-114 is the 30th tray; the total reflux ratio of the dehydration tower T-114 is 7-10.

[0074] The operating temperature of the E-115 top condenser of the dehydration tower is 40-45℃, and its operating pressure is 15-30kPag.

[0075] The operating temperature of the dehydration tower reflux tank V-116 is 40-45℃, and its operating pressure is 10-30kPag.

[0076] Furthermore, the bottom operating temperature of the light component removal tower T-119 is 98-103℃, the top operating temperature is 47-52℃, and the internal operating pressure is 145-180kPag. The light component removal tower T-119 has a total of 40 trays, and the feed tray is the 25th tray.

[0077] Furthermore, the ethyl acetate processing unit includes:

[0078] Ethyl acetate column T-108 has its inlet connected to the side line of azeotropic column T-101 for concentrating the ethyl acetate stream; the top of the column produces a recovered ethyl acetate stream; and the bottom of the column is the outlet for the vinyl acetate stream.

[0079] The ethyl acetate tower condenser E-110 has its inlet end connected to the top of the ethyl acetate tower T-108;

[0080] The ethyl acetate tower reflux tank V-111 is connected at its inlet to the outlet of the ethyl acetate tower condenser E-110. It is used to separate the organic phase and aqueous phase of the ethyl acetate recovery stream. A portion of the organic phase of the ethyl acetate recovery stream is refluxed back to the ethyl acetate tower T-108, and the other portion is sent to the ethyl acetate storage tank.

[0081] Furthermore, the bottom operating temperature of the ethyl acetate tower T-108 is 118-122℃, and the top operating temperature is 78-83℃; the internal operating pressure of the dehydration tower T-114 is 20-50 kPag.

[0082] The ethyl acetate tower T-108 has a total of 20 trays, with the feed tray being the 10th tray. The total reflux ratio of the ethyl acetate tower T-108 is 9-12.

[0083] According to one aspect of the present invention, a method for refining vinyl acetate is provided, comprising the following steps:

[0084] Crude vinyl acetate enters azeotropic tower T-101. Vinyl acetate azeotrope is collected from the top of azeotropic tower T-101, aqueous acetic acid stream is collected from the bottom of azeotropic tower T-101, and ethyl acetate stream is collected from the side stream of azeotropic tower T-101.

[0085] Vinyl acetate azeotrope is separated into an azeotropic organic phase and an azeotropic aqueous phase by the azeotropic tower reflux unit. A portion of the azeotropic organic phase is refluxed back to the azeotropic tower T-101, while the other portion of the azeotropic organic phase is separated from vinyl acetate by the dehydration unit, thereby achieving the recovery of light components and vinyl acetate product.

[0086] The ethyl acetate stream undergoes separation of ethyl acetate and recovery of vinyl acetate components in the ethyl acetate processing unit; the recovered vinyl acetate stream from the ethyl acetate stream is refluxed to the azeotropic tower T-101.

[0087] The technical solution of the present invention will be described below with reference to the accompanying drawings and specific embodiments.

[0088] Example 1

[0089] like Figure 1 As shown, Example 1 provides a vinyl acetate refining system and method. During acetic acid refining, the crude vinyl acetate product first enters an azeotropic column T-101. The vinyl acetate / water azeotrope is distilled from the top of the azeotropic column T-101, while the aqueous acetic acid stream is collected from the bottom of the azeotropic column T-101. The azeotropic column T-101 has 70 trays. An ethyl acetate stream is collected from the side stream of the 10th tray at the bottom of the column and pumped to the ethyl acetate column T-108 via the ethyl acetate column feed pump P-103 for concentration of the ethyl acetate.

[0090] The top vapor of the azeotropic tower T-101 is condensed by the azeotropic tower condenser E-106 and enters the azeotropic tower reflux tank V-105. In the azeotropic tower reflux tank V-105, the condensed liquid is separated into an organic phase and an aqueous phase, forming an azeotrope organic phase and an azeotropic aqueous phase.

[0091] The azeotropic organic phase contains a high concentration of vinyl acetate, which is pumped back to the azeotropic tower T-101 via the azeotropic tower organic phase reflux pump P-102. The remaining portion is sent to the subsequent dehydration tower T-114. The aqueous phase is discharged to the outside treatment area via the azeotropic tower aqueous phase reflux pump P-104.

[0092] The aqueous acetic acid stream at the bottom of the azeotropic tower T-101 is mainly composed of acetic acid, which is pumped by the acetic acid circulation pump P-129 to the upstream section for further processing (such as recycling to the vinyl acetate reactor for reuse).

[0093] One primary function of the ethyl acetate tower T-108 is to remove ethyl acetate from the ethyl acetate stream. Another function is to recover and reuse acetic acid from the side stream of the azeotropic tower T-101. The acetic acid is concentrated in the bottom of the tower and then pumped back to the azeotropic tower T-101 via the azeotropic tower side stream reflux pump P-112. The ethyl acetate tower T-108 has 20 trays. Ethyl acetate, water, and vinyl acetate are enriched in the ethyl acetate tower reflux tank V-111. In the ethyl acetate tower reflux tank V-111, the organic phase is separated from the liquid phase. The aqueous phase is transported to the subsequent wastewater treatment section, while the organic phase is sent to the light component storage tank.

[0094] The organic phase output from the azeotropic tower organic phase reflux pump P-102 is preheated by the dehydration tower feed preheater E-130 before entering the dehydration tower T-114. Dehydration tower T-114 has 40 trays used to remove water and light components such as acetaldehyde, methyl acetate, and acrolein from the azeotropic tower reflux tank V-101. Vinyl acetate containing small amounts of high- and medium-boiling-point substances is distilled from the bottom of dehydration tower T-114 and then pumped by the ethyl acetate tower reflux pump P131 to the vinyl acetate product tower T-122 for further purification. The vapor stream at the top of dehydration tower T-114 contains acetaldehyde, methyl acetate, acrolein, water, and vinyl acetate. It is condensed by dehydration tower condenser E-115 and enters dehydration tower condenser V-116. In dehydration tower condenser V-116, the liquid is separated into an organic phase and an aqueous phase. The aqueous phase is sent to the preceding process for use, part of the organic phase is used as reflux for dehydration tower T-114, and the remainder is sent to dehydration tower T-114.

[0095] Light component removal tower T-119 is used to recover vinyl acetate and remove acetaldehyde, methyl acetate, and acrolein. T-119 has 40 trays and is a pressurized tower operating at 150 kPag. In T-119, acetaldehyde accumulates at the top and is collected therefrom. Acrolein and methyl acetate are collected from the side streams, while vinyl acetate is collected at the bottom and pumped back to dehydration tower T-114 via the light component tower bottom pump P-121.

[0096] The vinyl acetate product tower T-122 aims to remove trace amounts of high and medium boiling point substances from the bottom liquid of the dehydration tower T-114, purifying vinyl acetate to meet product specifications. The vinyl acetate product tower T-122 has 40 trays. Trace amounts of high and medium boiling point substances in the bottom liquid accumulate at the bottom and are pumped back to the azeotropic tower reflux tank V-105 via the product tower bottom pump P-128. The finished vinyl acetate is collected at the top of the tower, cooled by the finished product condenser E-127, and then sent to the finished product storage tank.

[0097] Using the vinyl acetate refining system and method provided in Example 1, the purity of the generated vinyl acetate product is 99.98 wt%.

[0098] Example 2

[0099] This embodiment provides a vinyl acetate refining system and method. The structure of the vinyl acetate refining system and the process of the vinyl acetate refining method are the same as in Example 1. The difference lies in the operating parameters of the azeotropic tower T-101, ethyl acetate tower T-108, dehydration tower T-114, light component removal tower T-119, and vinyl acetate product tower T-122, which are different from those in Example 1. Specific parameters are shown in Table 1. Using the vinyl acetate refining system and method provided in Example 1, the purity of the generated vinyl acetate product is 99.955 wt%.

[0100] Example 3

[0101] This embodiment provides a vinyl acetate refining system and method. The structure of the vinyl acetate refining system and the process of the vinyl acetate refining method are the same as in Example 1. The difference lies in the operating parameters of the azeotropic tower T-101, ethyl acetate tower T-108, dehydration tower T-114, light component removal tower T-119, and vinyl acetate product tower T-122, which are different from those in Example 1. Specific parameters are shown in Table 1. Using the vinyl acetate refining system and method provided in Example 1, the purity of the generated vinyl acetate product is 99.977 wt%.

[0102] The device operating parameters for each embodiment are shown in Table 1 below.

[0103]

[0104]

[0105] Finally, it should be noted that the above description represents a preferred embodiment of the present invention. It should be pointed out that although preferred embodiments have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles described herein. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

Claims

1. A vinyl acetate refining system, characterized in that, include: An azeotropic column is used to collect the crude vinyl acetate product entering the azeotropic column, extract the vinyl acetate azeotrope from the top of the azeotropic column, extract the aqueous acetic acid stream from the bottom of the azeotropic column, and extract the ethyl acetate stream from the side stream of the azeotropic column. An azeotropic tower reflux unit is installed at the top of the azeotropic tower to separate the vinyl acetate azeotrope into an azeotropic organic phase and an azeotropic aqueous phase; the first organic phase output end of the azeotropic tower reflux unit is connected to the input end of the azeotropic tower. The dehydration unit is connected to the second organic phase output end of the azeotropic tower reflux unit and is used to separate the light components and vinyl acetate from the azeotropic organic phase output by the azeotropic tower reflux unit, so as to realize the recovery of light components and vinyl acetate product. An ethyl acetate processing unit, connected to the side stream of the azeotropic tower, is used to separate ethyl acetate and recover vinyl acetate components from the ethyl acetate stream. The vinyl acetate stream output of the ethyl acetate processing unit is connected to the input of the azeotropic tower to enable the vinyl acetate stream to be refluxed back to the azeotropic tower.

2. The vinyl acetate refining system according to claim 1, characterized in that, The azeotropic tower reflux unit includes: An azeotropic tower top condenser is connected to the top of the azeotropic tower and is used to condense the vinyl acetate azeotrope. An azeotropic tower reflux tank, connected to the top condenser of the azeotropic tower, is used to separate the vinyl acetate azeotrope into an azeotropic organic phase and an azeotropic aqueous phase. An azeotropic tower organic phase reflux pump has its input end connected to the organic phase output end of the azeotropic tower reflux tank, its first output end connected to the input end of the azeotropic tower, and its second output end connected to the input end of the dehydration unit.

3. The vinyl acetate refining system according to claim 2, characterized in that, The dehydration unit includes: A dehydration tower is connected to the output end of the organic phase reflux pump of the azeotropic tower, and is used to separate the light components and vinyl acetate from the organic phase of the azeotrope; the light component stream is output from the top of the tower, and the initial vinyl acetate product stream is output from the bottom of the tower. The vinyl acetate product tower is connected to the bottom of the dehydration tower and is used to purify the primary vinyl acetate product stream; the top of the tower recovers vinyl acetate product, and the bottom of the tower is connected to the azeotropic tower reflux tank for returning the collected high / medium boiling point aggregate stream to the azeotropic tower reflux tank. A light component removal tower, connected to the bottom of the dehydration tower, is used to recover vinyl acetate from the light component stream and to remove acetaldehyde, methyl acetate, and acrolein. The light component removal tower is a pressurized tower, with acetaldehyde stream collected from its top and acrolein and methyl acetate streams collected from its side streams. Its bottom is connected to the input end of the dehydration tower to return the collected light component vinyl acetate recovery stream to the dehydration tower.

4. The vinyl acetate refining system according to claim 3, characterized in that, The dehydration unit further includes a dehydration tower reflux unit, comprising: A condenser at the top of the dehydration tower is connected to the top of the dehydration tower; The dehydration tower reflux tank has its inlet end connected to the outlet end of the dehydration tower top condenser, and is used to separate the light component stream into an organic phase and an aqueous phase. A dehydration tower reflux pump is used to feed a portion of the organic phase of the light component stream into the dehydration tower and another portion into the light component removal tower.

5. The vinyl acetate refining system according to claim 2, characterized in that, The bottom operating temperature of the azeotropic column is 130-140℃, and the top operating temperature is 73-75℃; the internal operating pressure of the azeotropic column is 30-85 kPag. The azeotropic tower has a total of 70 trays, of which the 30th tray is the feed tray; the 10th tray of the azeotropic tower is the side stream outlet; the total reflux ratio of the azeotropic tower is 4-6. The operating temperature of the azeotropic tower top condenser is 35-42℃, and its operating pressure is 20-30kPag. The operating temperature of the azeotropic tower reflux tank is 35-42℃, and its operating pressure is 20-30kPag.

6. The vinyl acetate refining system according to claim 4, characterized in that, The operating temperature of the bottom of the dehydration tower is 85-89℃, and the operating temperature of the top of the tower is 71-75℃; the operating pressure inside the dehydration tower is 25-60 kPag. The dehydration tower has a total of 40 trays, and the feed tray is the 30th tray; the total reflux ratio of the dehydration tower is 7-10. The operating temperature of the condenser at the top of the dehydration tower is 40-45℃, and its operating pressure is 15-30kPag. The operating temperature of the dehydration tower reflux tank is 40-45℃, and its operating pressure is 10-30kPag.

7. The vinyl acetate refining system according to claim 3, characterized in that, The operating temperature of the bottom of the light component removal tower is 98-103℃, the operating temperature of the top of the tower is 47-52℃, and the operating pressure inside the tower is 145-180kPag. The light component removal tower has a total of 40 trays, and the feed tray of the light component removal tower is the 25th tray.

8. The vinyl acetate refining system according to claim 1, characterized in that, The ethyl acetate processing unit includes: An ethyl acetate column, whose inlet is connected to the side stream of the azeotropic column, is used to concentrate the ethyl acetate stream; the top of the column collects the ethyl acetate recovery stream; and the bottom of the column is the outlet of the vinyl acetate stream. An ethyl acetate tower condenser, the inlet of which is connected to the top of the ethyl acetate tower; An ethyl acetate tower reflux tank, whose inlet is connected to the outlet of the ethyl acetate tower condenser, is used to separate the organic phase and aqueous phase of the ethyl acetate recovery stream. A portion of the organic phase of the ethyl acetate recovery stream is refluxed back to the ethyl acetate tower, and the other portion is sent to the ethyl acetate storage tank.

9. The vinyl acetate refining system according to claim 8, characterized in that, The bottom operating temperature of the ethyl acetate column is 118-122℃, and the top operating temperature is 78-83℃; the internal operating pressure of the dehydration column is 20-50 kPag. The ethyl acetate column has a total of 20 trays, and the feed tray is the 10th tray; the total reflux ratio of the ethyl acetate column is 9-12.

10. A method for refining vinyl acetate, characterized in that, Includes the following steps: Crude vinyl acetate product enters an azeotropic column. Vinyl acetate azeotrope is collected from the top of the azeotropic column, aqueous acetic acid stream is collected from the bottom of the azeotropic column, and ethyl acetate stream is collected from the side stream of the azeotropic column. The vinyl acetate azeotrope is separated into an azeotropic organic phase and an azeotropic aqueous phase by the azeotropic tower reflux unit. A portion of the azeotropic organic phase is refluxed back to the azeotropic tower, and the other portion of the azeotropic organic phase is separated from the light components and vinyl acetate by the dehydration unit, thereby realizing the recovery of light components and the recovery of vinyl acetate product. The ethyl acetate stream is processed by an ethyl acetate treatment unit to separate ethyl acetate and recover vinyl acetate components; the recovered vinyl acetate stream is returned to the azeotropic tower.

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