Method and system for removing carbon dioxide from vinyl acetate feed gas

Abstract

The invention relates to a method and a system for removing carbon dioxide from vinyl acetate raw material gas. The method comprises the following steps: condensing a circulating gas material flow from a vinyl acetate generation system to form a gas-liquid two-phase material flow; the gas-liquid two-phase material is washed, a washed gas-phase material flow and a washed liquid-phase material are obtained, and the washing operation comprises the steps that vinyl acetate in the gas-liquid two-phase material flow is removed through an acetic acid aqueous solution, and acidic components in the gas-liquid two-phase material flow are removed through fresh water; one part of the washing gas-phase material flow is led out as exhaust gas, the other part of the washing gas-phase material flow is in countercurrent contact with CO2 removal liquid, and after carbon dioxide removal, the washing gas-phase material flow is sent back to a vinyl acetate generation system and used for participating in a vinyl acetate generation reaction; and carrying out recovery and regeneration treatment on the CO2 removal liquid participating in carbon dioxide removal. According to the invention, efficient removal of carbon dioxide in the feed gas circulated to the vinyl acetate generation system and recovery of vinyl acetate can be realized, so that the conversion rate of vinyl acetate is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon dioxide removal from vinyl acetate raw gas, and particularly relates to a method and system for removing carbon dioxide from vinyl acetate raw gas. BACKGROUND

[0002] Vinyl acetate is an important organic chemical raw material, which can be used to produce polyvinyl acetate, polyvinyl alcohol, vinyl acetate-ethylene copolymer emulsion and other derivatives, and is widely used in the fields of paint, adhesive, vinylon fiber and film. So far, the industrial production of vinyl acetate mainly adopts acetylene method and ethylene method. The synthesis of vinyl acetate is carried out by using ethylene, oxygen and acetic acid as raw materials, under the condition of palladium-gold (PdAu) catalyst and potassium acetate as co-catalyst, which is the mainstream process for the production of vinyl acetate in the world at present. The process involves engineering technical problems such as raw material recycling during development.

[0003] In the process of preparing vinyl acetate by ethylene gas phase method, the generation of the target product vinyl acetate is accompanied by a plurality of by-products (such as carbon dioxide, water, acetaldehyde, propylene aldehyde, propylene acid, methyl acetate, ethyl acetate, etc.). The carbon dioxide generated by the reaction of ethylene and oxygen is easy to accumulate in the circulating gas. The accumulated CO2 will be adsorbed on the surface of the catalyst, covering the active sites, resulting in the decrease of the activity of the catalyst; the existence of CO2 will change the partial pressure of the reaction system, promote the reverse movement of the chemical equilibrium, and inhibit the conversion rate of vinyl acetate. In addition, the unremoved CO2 will enter the circulation system with the unreacted raw materials, which will increase the load of the compressor and the energy consumption of separation, and damage the overall energy efficiency of the device. SUMMARY

[0004] In order to solve the technical problems existing in the prior art, the purpose of the present application is to provide a method and system for removing carbon dioxide from vinyl acetate raw gas, which can realize efficient removal of carbon dioxide in raw gas and recovery of vinyl acetate, and improve the conversion rate of vinyl acetate.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides a method for removing carbon dioxide from vinyl acetate raw gas, which comprises the following steps:

[0006] The circulating gas stream from the vinyl acetate generation system is subjected to condensation treatment to form a gas-liquid two-phase stream;

[0007] The gas-liquid two-phase material is subjected to water washing operation to obtain a water washing gas phase stream and a water washing liquid phase material, and the water washing operation comprises removing vinyl acetate in the gas-liquid two-phase stream by using an aqueous acetic acid solution, and removing acidic components in the gas-liquid two-phase stream by using fresh water;

[0008] Part of the water-washed gas phase stream is drawn off as exhaust gas, another part of the water-washed gas phase stream is contacted with CO2 removal liquid in counterflow, after carbon dioxide removal, is sent back to the vinyl acetate generation system for participating in the vinyl acetate generation reaction;

[0009] The CO2 removal liquid participating in carbon dioxide removal is recovered and regenerated.

[0010] According to one technical solution of the present application, the regeneration of the CO2 removal liquid comprises the following steps:

[0011] The CO2 removal liquid is subjected to pressure reduction to form a regenerated removal liquid gas phase stream and a regenerated removal liquid liquid phase stream;

[0012] The regenerated removal liquid gas phase stream is supplemented with fresh water, and then is subjected to condensation and gas-liquid separation, and CO2 is recovered from the separated gas phase;

[0013] The regenerated removal liquid liquid phase stream is supplemented with fresh CO2 removal liquid to obtain regenerated CO2 removal liquid.

[0014] According to one technical solution of the present application, CO2 is recovered from the separated gas phase, specifically comprising:

[0015] Fresh water is supplemented into the separated gas phase, and after condensation and gas-liquid separation, CO2 is recovered from the gas phase obtained by gas-liquid separation.

[0016] According to one aspect of the present application, a vinyl acetate raw gas carbon dioxide removal system is provided, comprising:

[0017] A water washing unit for condensing and water washing a circulating gas stream from a vinyl acetate generation system;

[0018] A CO2 absorption unit for removing carbon dioxide by counterflow contacting of CO2 removal liquid with a water-washed gas phase stream output by the water washing unit;

[0019] A circulating gas treatment unit, the inlet end of which is connected with the gas phase outlet of the CO2 absorption unit, and the outlet end of which is connected with the circulating gas inlet end of the vinyl acetate generation system, for treating the gas phase material output by the CO2 absorption unit and inputting into the vinyl acetate generation system;

[0020] A CO2 desorption unit, the input end and the output end of which are connected with the removal liquid outlet end and the removal liquid inlet end of the CO2 absorption unit, for recovering and regenerating the liquid phase stream output by the CO2 absorption unit, and for supplying the CO2 removal liquid to the CO2 absorption unit;

[0021] The gas phase stream outlet of the water washing unit is connected with the inlet end of the CO2 absorption unit through a water washing gas phase stream pipeline, and an exhaust gas leading-out port is arranged on the water washing gas phase stream pipeline;

[0022] The water washing unit comprises:

[0023] A water washing tower pre-condenser, the inlet end of which is connected with the circulating gas stream output end of the vinyl acetate generation system;

[0024] A water washing tower, the middle part of which is provided with a circulating gas inlet, and the outlet end of the water washing tower pre-condenser is connected with the water washing tower; the water washing tower is provided with a fresh water spraying device and a water washing gas phase stream outlet at the top; and the middle part of the water washing tower is provided with a water-soluble acetic acid inlet.

[0025] According to one technical solution of the present application, the CO2 absorption unit comprises:

[0026] An absorption tower feed pre-heater, the inlet end of which is connected with the water washing gas phase stream outlet through the water washing gas phase stream pipeline;

[0027] A CO2 absorption tower, the feed inlet at the bottom of which is connected with the outlet end of the CO2 absorption tower feed pre-heater; and the CO2 absorption tower is provided with a CO2 removal liquid inlet at the top.

[0028] According to one technical solution of the present application, the water washing gas phase stream pipeline is provided with an ethane content detection device and a nitrogen content detection device, and when the ethane content detection device detects that the ethane content in the water washing gas phase stream pipeline is greater than or equal to 4.80wt%, or the nitrogen content detection device detects that the nitrogen content in the water washing gas phase stream pipeline is greater than 9.5wt%, the exhaust gas leading-out port is opened.

[0029] According to one technical solution of the present application, the circulating gas treatment unit comprises:

[0030] An absorption tower top condenser, the inlet end of which is connected with the top material outlet of the CO2 absorption tower;

[0031] An absorption tower gas-liquid separator, the inlet end of which is connected with the outlet end of the absorption tower top condenser; the gas phase outlet of the absorption tower gas-liquid separator is connected with the circulating gas reflux input end of the vinyl acetate generation system; and the liquid phase outlet of the absorption tower gas-liquid separator is connected with the CO2 desorption unit.

[0032] According to one technical solution of the present application, the CO2 desorption unit comprises:

[0033] A CO2 desorption tower, whose top inlet end is connected with the bottom liquid phase outlet end of the CO2 absorption tower; whose bottom inlet end is connected with the liquid phase outlet end of the absorption tower gas-liquid separator; whose bottom liquid phase outlet end is connected with the CO2 removal liquid feeding port; the top of the CO2 desorption tower is provided with a desorption tower gas phase discharge port; the bottom of the CO2 desorption tower is provided with a removal liquid reflux port, which is connected with the CO2 removal liquid feeding port;

[0034] A desorption tower bottom reboiler, which is connected with the bottom of the CO2 desorption tower, is used for converting the liquid phase of the bottom of the CO2 desorption tower into gas phase and refluxing to the bottom of the CO2 desorption tower;

[0035] A desorption tower top condenser, whose inlet end is connected with the desorption tower gas phase discharge port and a fresh water supplement source;

[0036] A desorption tower gas-liquid separator, whose inlet end is connected with the outlet end of the desorption tower top condenser; whose liquid phase outlet end is connected with the removal liquid reflux port; and whose gas phase outlet is used for recycling CO2;

[0037] A removal liquid supplement unit, which is connected with the removal liquid reflux port.

[0038] According to one technical solution of the present application, the operating temperature of the water washing tower pre-condenser is 35-45℃, and the operating pressure thereof is 900-1000kPaG;

[0039] The operating temperature of the bottom of the water washing tower is 30-35℃, and the operating temperature of the top thereof is 25-30℃; the operating pressure in the tower of the water washing tower is 850-900kPaG;

[0040] The operating temperature of the outlet end of the absorption tower top condenser is 40-50℃, and the operating pressure thereof is 750-850kPaG;

[0041] The operating temperature of the absorption tower gas-liquid separator is 40-50℃, and the operating pressure thereof is 750-850kPaG.

[0042] According to one technical solution of the present application, the operating temperature of the bottom of the CO2 desorption tower is 110-120℃, and the operating temperature of the top thereof is 100-110℃; the operating pressure in the tower of the desorption tower is 50-80kPaG;

[0043] The operating temperature of the desorption tower gas-liquid separator is 40-50℃, and the operating pressure thereof is 50-80kPaG.

[0044] Compared with the prior art, the present application has the following beneficial effects:

[0045] The application provides a method and system for removing carbon dioxide from vinyl acetate raw gas, wherein the circulating gas material from a production system is first sent to a water washing tower pre-condenser for condensation, then enters the water washing tower, and the vinyl acetate in the raw gas is recovered by using an aqueous solution of acetic acid in the water washing tower, and the acidic impurities in the raw gas are absorbed by spraying fresh water at the top of the tower; in order to maintain the concentration of inert gases such as ethane and nitrogen in the reactor feed stream stable, a part of the gas at the top of the water washing tower is led out as exhaust gas; then the raw gas is preheated and enters a CO2 absorption tower, and the CO2 in the purified gas entering the tower bottom is absorbed by using potassium carbonate solution in countercurrent contact, then the water in the purified gas is removed by gas-liquid separation, and the raw gas returns to the circulating system, while the potassium bicarbonate aqueous solution obtained by the gas-liquid separation is sent to a desorption tower, and is decompressed to normal pressure to release CO2, which can be sent to a post-processing section, and the potassium carbonate solution after desorption is then recycled back to the CO2 absorption tower. The circulating raw gas is washed by water, the vinyl acetate product in the circulating gas is recovered, the acidic impurities in the circulating gas are removed to avoid affecting the subsequent operation of the device, the pressure in the raw gas is balanced, the composition of the raw gas is controlled, the CO2 impurities are removed by using CO2 absorption technology, and thus the process stability is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described in the following are only some of the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0047] Figure 1 A flow chart of a method for removing carbon dioxide from vinyl acetate raw gas provided in an embodiment of the present application is schematically shown.

[0048] In the drawings, the correspondence between the component names and the reference numerals is as follows:

[0049] E-101: water washing tower pre-condenser; T-102: water washing tower; E-103: absorption tower feed preheater; T-104: CO2 absorption tower; P-105: CO2 removal liquid feed pump; E-106: absorption tower overhead condenser; V-107: absorption tower gas-liquid separator; T-108: CO2 desorption tower; E-109: desorption tower overhead condenser; E-110: desorption tower bottom reboiler; P-111: desorption tower overhead reflux pump; P-112: potassium carbonate solution feed pump; V-113: desorption tower gas-liquid separator; V-114: potassium carbonate solution storage tank; V-115: potassium carbonate solution make-up tank. DETAILED DESCRIPTION

[0050] The description of the embodiments of this specification should be considered in connection with the accompanying drawings, which are incorporated in part herein. In the drawings, the dimensions or proportions of the various elements can be exaggerated for clarity. Further, portions of the structures and the like can be shown separately from each other and / or described with separate terminology, but it is to be understood that the features covered by such descriptive terms can be combined together under a general description.

[0051] The description of the embodiments herein makes any reference to a direction or an orientation only for the purpose of convenient description and does not imply any limitation on the protection scope of the present application. The following description of the preferred embodiments will refer to a combination of features that can exist independently from each other or in combination. The present application is not particularly limited to the preferred embodiments.

[0052] As shown in Figure 1 The present application provides a system for removing carbon dioxide from a vinyl acetate raw material gas, which comprises a water washing unit, a circulating gas treatment unit, a CO2 absorption unit and a CO2 desorption unit. The water washing unit is used to condense and wash the circulating gas stream from a vinyl acetate generation system. The CO2 absorption unit is used to remove carbon dioxide by countercurrent contact between the CO2 removal liquid and the water-washed gas phase stream output from the water washing unit. The inlet end of the circulating gas treatment unit is connected to the gas phase outlet of the CO2 absorption unit, and the outlet end of the circulating gas treatment unit is connected to the circulating gas inlet end of the vinyl acetate generation system, for processing the gas phase material output from the CO2 absorption unit and inputting it into the vinyl acetate generation system. The input end and the output end of the CO2 desorption unit are connected to the removal liquid outlet end and the removal liquid inlet end of the CO2 absorption unit, for recycling and regenerating the liquid phase stream output from the CO2 absorption unit and supplying CO2 removal liquid to the CO2 absorption unit. The gas phase stream outlet of the water washing unit is connected to the inlet end of the CO2 absorption unit through a water-washed gas phase stream pipeline, and a vent gas outlet is provided on the water-washed gas phase stream pipeline. A portion of the water-washed gas phase stream is drawn out from the water-washed gas phase stream pipeline through the vent gas outlet as vent gas, which can be sent to a incinerator for incineration, thereby maintaining the concentration of inert gases such as ethane and nitrogen in the raw material gas sent to the vinyl acetate generation system stable.

[0053] The water washing unit comprises a water washing tower pre-condenser E-101 and a water washing tower T-102. The inlet end of the water washing tower pre-condenser E-101 is connected with the circulating gas stream output end of the raw material gas circulating system in the vinyl acetate generation system. The middle part of the water washing tower T-102 is provided with a circulating gas inlet connected with the outlet end of the water washing tower pre-condenser E-101. The water washing tower T-102 is provided with a fresh water spraying device at the top and a water washing gas phase stream outlet. The middle part of the water washing tower T-102 is provided with a vinyl acetate aqueous solution inlet. The fresh water spraying device is connected with a fresh water supply source to supply fresh water into the water washing tower T-102 for removing the acidic components in the circulating gas.

[0054] A small amount of circulating gas from the raw material gas circulating system enters the water washing tower pre-condenser E-101 and is condensed into gas-liquid two-phase and then enters the tower kettle of the water washing tower T-102 through the bottom of the water washing tower T-102. The middle section of the water washing tower T-102 enters the vinyl acetate aqueous solution for absorbing the vinyl acetate product in the circulating raw material gas, and the fresh water is sprayed in the tower kettle of the water washing tower T-102 to remove the acidic components in the circulating gas. The acidic components in the raw material gas are removed to prevent them from affecting the absorption of CO2 by the subsequent potassium carbonate solution. In order to maintain the stable concentration of inert gases such as ethane and nitrogen in the reactor feed stream, a part of the gas at the top of the water washing tower T-102 is led out as exhaust gas and finally sent to the incinerator for treatment. The remaining part of the purified gas enters the absorption tower feed pre-heater E-103. The vinyl acetate-containing acetic acid solution obtained from the tower kettle of the water washing tower T-102 is sent to the refining system. Further, the water washing gas phase stream pipeline is provided with an ethane content detection device and a nitrogen content detection device. When the ethane content detection device detects that the ethane content in the water washing gas phase stream pipeline is greater than or equal to 4.80wt%, or the nitrogen content detection device detects that the nitrogen content in the water washing gas phase stream pipeline is greater than 9.5wt%, the exhaust gas outlet is opened to realize the leading out of the exhaust gas.

[0055] The CO2 absorption unit comprises an absorption tower feed pre-heater E-103 and a CO2 absorption tower T-104. The inlet end of the absorption tower feed pre-heater E-103 is connected with the water washing gas phase stream outlet through the water washing gas phase stream pipeline. The feed inlet at the bottom of the CO2 absorption tower T-104 is connected with the outlet end of the CO2 absorption tower T-104 feed pre-heater E-103. The CO2 removal liquid inlet is arranged at the top of the CO2 absorption tower T-104.

[0056] The circulating gas treatment unit comprises an absorption tower overhead condenser E-106 and an absorption tower gas-liquid separator V-107. The inlet end of the absorption tower overhead condenser E-106 is connected to the overhead material outlet of the CO2 absorption tower T-104. The inlet end of the absorption tower gas-liquid separator V-107 is connected to the outlet end of the absorption tower overhead condenser E-106. The gas phase outlet of the absorption tower gas-liquid separator is connected to the circulating gas reflux input end of the vinyl acetate generation system; the liquid phase outlet of the absorption tower gas-liquid separator is connected to the CO2 desorption unit.

[0057] The CO2 desorption unit comprises a CO2 desorption tower T-108, a desorption tower bottom reboiler E-110, a desorption tower overhead condenser E-109, a desorption tower gas-liquid separator V-113 and a removal liquid supplement unit. The overhead inlet end of the CO2 desorption tower T-108 is connected to the liquid phase outlet end of the CO2 absorption tower T-104, the bottom inlet end of the CO2 desorption tower T-108 is connected to the liquid phase outlet end of the absorption tower gas-liquid separator V-107, and the bottom liquid phase outlet end of the CO2 desorption tower T-108 is connected to the CO2 removal liquid feed port. The overhead of the CO2 desorption tower T-108 is provided with a desorption tower gas phase discharge port. The desorption tower bottom reboiler E-110 is connected to the tower bottom of the CO2 desorption tower T-108, for converting the liquid phase in the tower bottom of the CO2 desorption tower T-108 into a gas phase and refluxing to the tower bottom of the CO2 desorption tower T-108, and through the reverse contact of the refluxed gas phase with the CO2 removal liquid entering from the overhead inlet end of the CO2 desorption tower T-108, releasing carbon dioxide. The bottom of the CO2 desorption tower T-108 is provided with a removal liquid reflux port, which is connected to the CO2 removal liquid feed port. The inlet end of the desorption tower overhead condenser E-109 is connected to the desorption tower gas phase discharge port and a fresh water supplement source. The inlet end of the desorption tower gas-liquid separator V-113 is connected to the outlet end of the desorption tower overhead condenser E-109. The liquid phase outlet end of the desorption tower gas-liquid separator V-113 is connected to the removal liquid reflux port. The gas phase outlet of the desorption tower gas-liquid separator V-113 is used for recovering CO2. The removal liquid supplement unit is connected to the removal liquid reflux port on the CO2 absorption tower T-104 through a CO2 removal liquid feed pump P-105, for supplementing the removal liquid.

[0058] The main component of the liquid phase at the bottom of the CO2 absorption tower T-104 is potassium bicarbonate solution, and the main component of the liquid phase of the absorption tower gas-liquid separator V-107 is water. The liquid phase of the absorption tower gas-liquid separator V-107 enters the CO2 desorption tower T-108, and since the CO2 desorption tower T-108 is operated under reduced pressure, and the CO2 desorption tower T-108 has a desorption tower bottom reboiler E-110, the water in the gas-liquid separation tank will be converted from the liquid phase to the gas phase. The gas phase upwardly contacts the potassium bicarbonate solution from the top of the CO2 absorption tower T-104, and releases carbon dioxide. The gas phase stream from the top of the CO2 desorption tower T-108 will carry a portion of water vapor into the subsequent CO2 recovery section, causing the concentration of the potassium bicarbonate solution in the CO2 desorption tower T-108 to change. By supplementing fresh water to the desorption tower gas phase stream of the desorption tower top condenser E-109, the problem of water loss in the desorption tower can be solved, thereby achieving the effect of maintaining the concentration of the potassium bicarbonate solution in the system stable. The ratio of the fresh water supplement to the water vapor content in the desorption tower gas phase stream is 1:64-65, in mass ratio.

[0059] Further, the removal liquid can be potassium carbonate solution. The removal liquid supplementing unit can include a potassium carbonate solution supplementing tank V-115 and a potassium carbonate solution storage tank V-114. The inlet end of the potassium carbonate solution supplementing tank V-115 is connected to the fresh potassium carbonate and fresh water, and a 20% potassium carbonate aqueous solution is prepared by mixing and stirring in the tank. The outlet end of the potassium carbonate solution supplementing tank V-115 is connected to the fresh potassium carbonate solution storage tank V-114. The outlet end of the potassium carbonate solution storage tank V-114 is connected to the CO2 desorption tower T-108 through a potassium carbonate solution feeding pump P-112, and enters the CO2 desorption tower T-108, and the regenerated potassium carbonate solution is circulated to the CO2 absorption tower T-104.

[0060] The raw material gas is circulated into the CO2 absorption tower T-104 after being preheated by the CO2 absorption tower T-104 feeding preheater E-103, and the purified gas from the top of the water washing tower T-102 is sent to the bottom of the CO2 absorption tower T-104.

[0061] In the CO2 absorption column T-104, the potassium carbonate solution (K2CO3) from the top is contacted countercurrently with the purified gas from the bottom, so that CO2 is absorbed by the solution. The solution containing CO2 is discharged from the bottom to the CO2 desorption column T-108. The treated gas enters the absorption column top condenser E-106, and after condensation enters the absorption column gas-liquid separator V-107. The gas phase obtained is the raw material gas from which CO2 has been removed, and is returned to the raw material gas circulation system of the vinyl acetate production system. The liquid phase water is sent to the bottom of the CO2 desorption column T-108. The CO2 absorption column T-104 column bottom stream enters the top of the CO2 desorption column T-108. In the CO2 desorption column T-108, the solution containing potassium bicarbonate is released from reduced pressure to normal pressure, releasing CO2. Heat is provided by the desorption column column bottom reboiler E-110, and the potassium bicarbonate is regenerated into potassium carbonate. The heating and regeneration process simultaneously releases the absorbed CO2. The regenerated potassium carbonate solution is recycled back to the CO2 absorption column T-104 by the CO2 removal liquid feed pump P-105, and the CO2 separated out enters the desorption column top condenser E-109, and is then sent to the desorption column gas-liquid separator V-113. The gas phase CO2 produced by the desorption column gas-liquid separator V-113 is sent to the subsequent processing section, and the liquid phase water is recycled back to the CO2 desorption column T-108 by the desorption column top reflux pump P-111. To compensate for the loss of water caused by the discharge of CO2 gas, fresh water is added before the CO2 desorption column T-108 condenser.

[0062] Further, the operating temperature of the water washing column pre-condenser E-101 is 35-45°C, and the operating pressure thereof is 900-1000 kPaG.

[0063] Further, the column bottom operating temperature of the water washing column T-102 is 30-35°C, and the column top operating temperature thereof is 25-30°C; the operating pressure in the water washing column T-102 is 850-900 kPaG.

[0064] Further, the operating temperature at the material outlet end of the absorption column feed pre-heater E-103 is 85-90°C, and the operating pressure thereof is 850-900 kPaG.

[0065] Further, the column bottom operating temperature of the CO2 absorption column T-104 is 100-110°C, and the column top operating temperature thereof is 110-120°C; the operating pressure in the CO2 absorption column T-104 is 750-850 kPaG.

[0066] Further, the operating temperature at the outlet end of the absorption column top condenser E-106 is 40-50°C, and the operating pressure thereof is 750-850 kPaG.

[0067] Further, the operating temperature of the gas-liquid separator V-107 is 40-50℃, and the operating pressure is 750-850kPaG.

[0068] Further, the operating temperature of the bottom of the CO2 desorption tower T-108 is 110-120℃, and the operating temperature of the top is 100-110℃; the operating pressure in the tower is 50-80kPaG.

[0069] Further, the operating temperature of the gas-liquid separator V-113 is 40-50℃, and the operating pressure is 50-80kPaG.

[0070] The application provides a method for removing CO2 from a vinyl acetate raw gas, which comprises the following steps:

[0071] The circulating gas stream from the vinyl acetate generating system is condensed to form a gas-liquid two-phase stream;

[0072] The gas-liquid two-phase stream is subjected to water washing to obtain a water-washed gas-phase stream and a water-washed liquid-phase stream, wherein the water washing comprises removing vinyl acetate from the gas-liquid two-phase stream by using an aqueous acetic acid solution and removing acidic components from the gas-liquid two-phase stream by using fresh water;

[0073] Part of the water-washed gas-phase stream is discharged as exhaust gas, and the other part of the water-washed gas-phase stream is subjected to countercurrent contact with a CO2 removal liquid, and after CO2 removal, is sent back to the vinyl acetate generating system to participate in the vinyl acetate generating reaction;

[0074] The CO2 removal liquid participating in the CO2 removal is recovered and regenerated.

[0075] Further, the regeneration of the CO2 removal liquid comprises the following steps:

[0076] The CO2 removal liquid is subjected to decompression to form a regenerated removal liquid gas-phase stream and a regenerated removal liquid liquid-phase stream;

[0077] The regenerated removal liquid gas-phase stream is supplemented with fresh water, and then subjected to condensation and gas-liquid separation, and CO2 is recovered from the separated gas phase;

[0078] The regenerated removal liquid liquid-phase stream is supplemented with fresh CO2 removal liquid to obtain regenerated CO2 removal liquid.

[0079] Further, the CO2 is recovered from the separated gas phase, specifically comprising:

[0080] Fresh water is supplemented into the separated gas phase, and after condensation and gas-liquid separation, CO2 is recovered from the gas phase obtained by the gas-liquid separation.

[0081] The technical solutions of the present application will be described in detail below in combination with the drawings and examples of the specification.

[0082] Example 1

[0083] A small amount of circulating gas from the raw material gas circulating system enters the water washing tower pre-condenser, is condensed into gas-liquid two phases, and then enters the water washing tower T-102 tower kettle.

[0084] The middle section of the water washing tower T-102 enters the acetic acid aqueous solution, which is used to absorb the vinyl acetate product in the circulating raw material gas. Fresh water is sprayed in the water washing tower kettle to remove the acidic components in the circulating gas. The acidic components in the raw material gas are removed to prevent them from affecting the absorption of CO2 by the potassium carbonate solution in the subsequent process. In order to maintain the stable concentration of inert gases such as ethane and nitrogen in the reactor feed stream, a portion of the gas at the top of the water washing tower is discharged as exhaust gas and finally sent to the incinerator for treatment. The remaining portion of the purified gas enters the absorption tower feed preheater E-103. The acetic acid solution containing vinyl acetate obtained from the water washing tower T-102 kettle is sent to the refining system.

[0085] After being preheated by the absorption tower feed preheater E-103, the circulating raw material gas enters the CO2 absorption tower T-104, and the purified gas from the top of the water washing tower is sent to the bottom of the CO2 absorption tower T-104.

[0086] In the CO2 absorption tower T-104, the potassium carbonate solution K2CO3 from the top of the tower is in countercurrent contact with the purified gas entering from the bottom, allowing CO2 to be absorbed by the solution. The solution containing CO2 is discharged from the bottom to the CO2 desorption tower T-108. The treated gas enters the CO2 absorption tower top condenser E-106, is condensed, and then enters the absorption tower gas-liquid separator V-107. The obtained gas phase is the raw material gas purified and removed of CO2, which is returned to the raw material gas circulating system. The liquid phase water is sent to the bottom of the CO2 desorption tower T-108. The CO2 absorption tower T-104 kettle stream enters the CO2 desorption tower T-108. The solution containing potassium bicarbonate is reduced from vacuum to atmospheric pressure, releasing CO2. Heat is provided by the desorption tower kettle reboiler E-110 to regenerate the potassium bicarbonate into potassium carbonate. The potassium carbonate solution is circulated back into the CO2 absorption tower T-104 by the CO2 removal liquid feed pump P-105. The CO2 that separates out enters the desorption tower top condenser E-109 for condensation, and then is sent to the desorption tower gas-liquid separator V-113, producing gaseous CO2 which is sent to the subsequent processing section. The liquid phase water is circulated back to the CO2 desorption tower T-108 by the desorption tower top reflux pump P-111.

[0087] When the mass ratio of potassium bicarbonate to carbon dioxide in the circulating gas is less than 6.7, fresh potassium carbonate solution is supplied to the CO2 desorption tower V-114 through the potassium carbonate solution make-up tank V-115 and the potassium carbonate solution storage tank V-114. The fresh potassium carbonate solution and the regenerated potassium carbonate solution are circulated to the CO2 absorption tower T-104.

[0088] The system and method for removing carbon dioxide from the ethylene acetate raw gas provided in this embodiment 1 is used to remove carbon dioxide from the raw gas with a CO2 content of 6.00wt%.

[0089] Embodiment 2

[0090] This embodiment provides a technology for removing carbon dioxide from the ethylene acetate raw gas, and the structural process of the technology for removing carbon dioxide from the ethylene acetate raw gas is the same as that of embodiment 1, except that in this embodiment, the operating parameters of the water washing tower T-102, the CO2 absorption tower T-104 and the CO2 desorption tower V-107 are different from those of embodiment 1, and the specific parameters are shown in Table 1. The system and method for removing carbon dioxide from the ethylene acetate raw gas provided in this embodiment 1 is used to remove carbon dioxide from the raw gas with a CO2 content of 5.45wt%.

[0091] Embodiment 3

[0092] This embodiment provides a technology for removing carbon dioxide from the ethylene acetate raw gas, and the structural process of the technology for removing carbon dioxide from the ethylene acetate raw gas is the same as that of embodiment 1, except that in this embodiment, the operating parameters of the water washing tower T-102, the CO2 absorption tower T-104 and the CO2 desorption tower V-107 are different from those of embodiment 1, and the specific parameters are shown in Table 1. The system and method for removing carbon dioxide from the ethylene acetate raw gas provided in this embodiment 1 is used to remove carbon dioxide from the raw gas with a CO2 content of 5.00wt%.

[0093] The device operating parameters of each embodiment are shown in Table 1 below.

[0094]

[0095] Finally, it should be noted that the above description is a preferred embodiment of the present application, and it should be pointed out that although the preferred embodiment of the present application has been described, for those skilled in the art, once the basic creative concept of the present application is known, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application. Therefore, the appended claims are intended to be interpreted as including the preferred embodiment and all changes and modifications falling within the scope of the embodiments of the present application.

Claims

1. A method for removing carbon dioxide from vinyl acetate feed gas, characterized in that, Includes the following steps: The circulating gas stream from the vinyl acetate generation system is condensed to form a gas-liquid two-phase stream. The gas-liquid two-phase material is subjected to a water washing operation to obtain a water-washed gas phase stream and a water-washed liquid phase material. The water washing operation includes removing vinyl acetate from the gas-liquid two-phase stream using an aqueous acetic acid solution and removing acidic components from the gas-liquid two-phase stream using fresh water. A portion of the water-washed gaseous material is led out as exhaust gas, and another portion of the water-washed gaseous material is contacted countercurrently with CO2 removal liquid to remove carbon dioxide. After removal, it is sent back to the vinyl acetate generation system to participate in the vinyl acetate generation reaction. The CO2 removal liquid that participated in carbon dioxide removal is recovered and regenerated.

2. The method for removing carbon dioxide from vinyl acetate feed gas according to claim 1, characterized in that, The regeneration treatment of the CO2 removal liquid includes the following steps: The CO2 removal liquid is subjected to depressurization treatment to form a regenerated removal liquid gas phase stream and a regenerated removal liquid liquid liquid phase stream; After replenishing the regenerated desorbed liquid-gas phase stream with fresh water, condensation and gas-liquid separation are performed to recover CO2 from the separated gas phase; Fresh CO2 removal liquid is added to the regenerated CO2 removal liquid liquid stream to obtain the regenerated CO2 removal liquid.

3. The method for removing carbon dioxide from vinyl acetate feed gas according to claim 2, characterized in that, The recovery of CO2 from the separated gas phase specifically includes: Fresh water is added to the separated gas phase, and after condensation and gas-liquid separation, CO2 is recovered from the gas phase obtained from the gas-liquid separation.

4. A system for removing carbon dioxide from vinyl acetate feedstock, characterized in that, include: A water washing unit is used to condense and wash the circulating gas stream from the vinyl acetate generation system. The CO2 absorption unit is used to remove carbon dioxide by having the CO2 removal liquid come into countercurrent contact with the water washing gas stream output from the water washing unit. The circulating gas treatment unit has its inlet end connected to the gas phase outlet of the CO2 absorption unit and its outlet end connected to the circulating gas inlet end of the vinyl acetate generation system. It is used to process the gas phase material output from the CO2 absorption unit and then input it into the vinyl acetate generation system. The CO2 desorption unit has its input and output ends connected to the desorbed liquid outlet and desorbed liquid inlet of the CO2 absorption unit. It is used to recover and regenerate the liquid phase stream output by the CO2 absorption unit and to supply the CO2 desorbed liquid to the CO2 absorption unit. The gas phase flow outlet of the water washing unit is connected to the inlet of the CO2 absorption unit through a water washing gas phase flow pipeline, and the water washing gas phase flow pipeline is provided with an exhaust gas outlet. The water washing unit includes: The inlet end of the water washing tower pre-condenser is connected to the output end of the circulating gas stream of the vinyl acetate generation system. The water washing tower has a circulating gas inlet in its middle section, which is connected to the outlet end of the pre-condenser of the water washing tower; a fresh water spray device and a water washing gas phase stream outlet are provided at the top of the water washing tower; and an acetic acid aqueous solution inlet is provided in the middle section of the water washing tower.

5. The vinyl acetate feed gas decarbonization system according to claim 4, characterized in that, The water washing gas phase flow pipeline is equipped with an ethane content detection device and a nitrogen content detection device. When the ethane content detection device detects that the ethane content in the water washing gas phase flow pipeline is greater than or equal to 4.80 wt%, or the nitrogen content detection device detects that the nitrogen content in the water washing gas phase flow pipeline is greater than 9.5 wt%, the exhaust gas outlet is opened.

6. The vinyl acetate feed gas decarbonization system according to claim 4, characterized in that, The CO2 absorption unit includes: The inlet end of the absorber feed preheater is connected to the outlet of the water washing gas stream through the water washing gas stream pipeline. The CO2 absorption tower has a feed inlet at the bottom connected to the outlet of the CO2 absorption tower feed preheater; and a CO2 removal liquid feed inlet is provided at the top of the CO2 absorption tower.

7. The vinyl acetate feed gas decarbonization system according to claim 6, characterized in that, The recirculating gas treatment unit includes: The condenser at the top of the absorption tower has its inlet end connected to the material outlet at the top of the CO2 absorption tower. The inlet of the gas-liquid separator in the absorption tower is connected to the outlet of the condenser at the top of the absorption tower; the gas phase outlet of the gas-liquid separator is connected to the reflux input of the circulating gas of the vinyl acetate generation system; and the liquid phase outlet of the gas-liquid separator is connected to the CO2 desorption unit.

8. The vinyl acetate feed gas decarbonization system according to claim 7, characterized in that, The CO2 desorption unit includes: The CO2 desorption tower has its top inlet connected to the bottom liquid outlet of the CO2 absorption tower; its bottom inlet connected to the liquid outlet of the gas-liquid separator of the absorption tower; its bottom liquid outlet connected to the CO2 removal liquid inlet; a desorption tower gas phase outlet is provided at the top of the CO2 desorption tower; and a removal liquid reflux port is provided at the bottom of the CO2 desorption tower, which is connected to the CO2 removal liquid inlet. A reboiler for the bottom of a desorption tower is connected to the bottom of the CO2 desorption tower and is used to convert the liquid phase in the bottom of the CO2 desorption tower into a gas phase and reflux it back to the bottom of the CO2 desorption tower. The inlet end of the desorption tower top condenser is connected to the gas phase outlet of the desorption tower and the fresh water supply source. The desorption tower gas-liquid separator has its inlet end connected to the outlet end of the top condenser of the desorption tower; the liquid phase outlet end of the desorption tower gas-liquid separator is connected to the desorbed liquid reflux port; and the gas phase outlet of the desorption tower gas-liquid separator is used to recover CO2. The descaling fluid replenishment unit is connected to the descaling fluid return port.

9. The vinyl acetate feed gas decarbonization system according to claim 7, characterized in that, The operating temperature of the pre-condenser of the water washing tower is 35-45℃, and its operating pressure is 900-1000kPaG. The operating temperature of the bottom of the water washing tower is 30-35℃, and the operating temperature of the top of the tower is 25-30℃; the operating pressure inside the water washing tower is 850-900 kPaG. The operating temperature at the outlet of the top condenser of the absorption tower is 40-50℃, and its operating pressure is 750-850 kPaG. The operating temperature of the gas-liquid separator in the absorption tower is 40-50℃, and its operating pressure is 750-850 kPaG.

10. The vinyl acetate feed gas decarbonization system according to claim 8, characterized in that, The operating temperature of the bottom of the CO2 desorption tower is 110-120℃, and the operating temperature of the top of the tower is 100-110℃; the operating pressure inside the desorption tower is 50-80 kPaG. The operating temperature of the desorption tower gas-liquid separator is 40-50℃, and its operating pressure is 50-80 kPaG.

Images