Anticorrosion process and device for hydrolysis of methyl acetate and purification of acetic acid in the process of recovery of polyvinyl alcohol mother liquor

Abstract

The invention belongs to the field of chemical industry, and relates to an anti-corrosion process and device for hydrolysis of methyl acetate and refining of acetic acid in the process of recovering polyvinyl alcohol mother liquor. The anti-corrosion device comprises a methyl acetate concentration device, a methyl acetate dealdehyde device, a methyl acetate hydrolysis device, a hydrolyzate separation device, an acetic acid refining device and an isopropyl acetate recovery device. The methyl acetate hydrolysis and acetic acid refining process mainly comprises methyl acetate concentration, methyl acetate dealdehyde, methyl acetate hydrolysis, hydrolyzate separation, acetic acid refining and isopropyl acetate recovery. The ability to remove halogen-containing impurities is enhanced by arranging a mass transfer unit (i.e., a packing section) on the upper part of the side sampling port of the hydrolysis tower; by adding a precision filter, the broken resin entrained in the hydrolyzate is filtered, and the broken resin with sulfonic acid groups is prevented from entering the acetic acid refining system. The corrosion problem of acetic acid refining equipment is fundamentally solved, the problem of equipment corrosion in the acetic acid refining process is significantly solved, and the life of key equipment is extended by 1 to 5 times.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and specifically relates to a recovery device and process of a mother liquor recovery unit in a polyvinyl alcohol production process, and in particular to an anti-corrosion process and device for hydrolyzing methyl acetate and refining acetic acid in a polyvinyl alcohol mother liquor recovery process. Background Art

[0002] Polyvinyl alcohol (PVA) is a white powder, a water-soluble polymer with properties between plastic and rubber. It is widely used in the textile industry, construction and decoration industry, chemical industry, agriculture, daily cosmetics and high-frequency quenching agent. PVA is the only vinyl polymer that can be used as a carbon source and energy source by bacteria. It is a biodegradable polymer material that can be mass-produced by non-petroleum routes at a low price. It has outstanding oil resistance, solvent resistance and gas barrier properties, and has unique advantages in food and drug packaging.

[0003] In the process of producing polyvinyl alcohol by alcoholysis of polyvinyl acetate, a large amount of alcoholysis mother liquor is generated, which mainly consists of methanol, methyl acetate and sodium acetate, etc. These are important chemical raw materials and should be recycled. Methyl acetate is actually produced from raw materials acetic acid and methanol. About 1.5 tons of methyl acetate are produced for every ton of polyvinyl alcohol produced. Although methyl acetate is also a chemical raw material, the demand is small and it is generally not sold as a by-product. Methyl acetate needs to be hydrolyzed into acetic acid and methanol, which are separated and purified for use in vinyl acetate synthesis and polymerization. In the industrial production process, methyl acetate undergoes a hydrolysis reaction as shown in the following formula under the action of a strongly acidic cation exchange resin to produce acetic acid and methanol:

[0004] CH 3 COOCH 3 +H 2 O===CH 3 OH+CH 3 COOH

[0005] During the acetic acid refining process, high-temperature concentrated acetic acid containing impurities is often formed, causing serious equipment corrosion. The industry has tried to upgrade the equipment material from 316L stainless steel to deoxidized copper or even pure titanium. Although this can slightly extend the service life, it cannot completely solve the corrosion problem, which has long plagued the development of the PVA industry.

[0006] Literature reports (Mao Yongsheng, Research on Corrosion of Acetic Acid Concentration Tower, Master's Degree Thesis, 2000; Xu Zhiqiang, Research on Corrosion Mechanism and Protection Measures of Acetic Acid Tower in PVA Workshop, Petrochemical Equipment Technology, 2008, 29(5), 46) The main reason for the serious corrosion of the acetic acid refining tower is that the dilute acetic acid fed to the tower is mixed with halogen-containing impurities such as chloride ions. Under its operating conditions, halogen ions and hydrogen ions combine to form the corresponding hydride and water to form the highest azeotropic mixture. The azeotropic point is between the feed plate and the tower kettle temperature, causing halogen hydrides to accumulate in the tower. The accumulated halogen hydrides have a very obvious accelerating effect on the corrosion of metal materials in a high-concentration acetic acid and high-temperature environment, which can cause corrosion cracking in a very short time, greatly shortening the equipment service life. Ma Yuanzheng et al. (Ma Yuanzheng, Study on the Corrosion of Acetic Acid Concentrators in Polyvinyl Alcohol Production, Master's Thesis, 2005) proposed an anti-corrosion strategy of setting a side-line outlet in the chloride ion accumulation area of ​​the acetic acid refining tower to extract acetic acid containing chloride ions from the tower, thereby slowing down the accumulation of chloride ions. Although this method can alleviate the corrosion problem to a certain extent, it will form a large amount of chlorine-containing waste acetic acid that cannot be treated, and the problem has not been effectively solved.

[0007] At present, although the material of acetic acid refining equipment in some production units of polyvinyl alcohol industry has been upgraded to highly corrosion-resistant titanium, the problem of acetic acid corrosion has not been solved. Developing new process flow with enhanced anti-corrosion ability and eliminating impurities that enhance acetic acid corrosion from the source is of great significance to the long-term safe production of polyvinyl alcohol units, and it also has promotion value for similar units in other industries. Summary of the invention

[0008] The object of the present invention is to provide an anti-corrosion device and process for hydrolysis of methyl acetate and refining of acetic acid in the process of recovering mother liquor of PVA alcoholysis, and to eliminate impurities which enhance the corrosiveness of acetic acid from the source by reasonably setting a separation device and a process flow, so as to fundamentally prevent the corrosion of acetic acid refining equipment.

[0009] The anti-corrosion device for methyl acetate hydrolysis and acetic acid refining provided by the present invention comprises a methyl acetate concentration device, a methyl acetate dealdehyde device, a methyl acetate hydrolysis device, a hydrolyzate separation device, an acetic acid refining device and an isopropyl acetate recovery device;

[0010] The methyl acetate concentration device comprises an extractive distillation tower, the methyl acetate dealdehyde removal device comprises an acetaldehyde removal tower, the methyl acetate hydrolysis device comprises a hydrolysis tower, the hydrolyzate separation device comprises a hydrolyzate separation tower, the acetic acid refining device comprises an acetic acid refining tower, and the isopropyl acetate recovery device comprises an isopropyl acetate recovery tower;

[0011] The extractive distillation tower, acetaldehyde removal tower, hydrolysis tower, hydrolyzate separation tower, acetic acid refining tower and isopropyl acetate recovery tower are connected in series according to the material flow direction; preferably, the top of the extractive distillation tower is connected to the middle of the acetaldehyde removal tower, the bottom of the acetaldehyde removal tower is connected to the top of the hydrolysis tower, the bottom of the hydrolysis tower is connected to the middle of the hydrolyzate separation tower, the bottom of the hydrolyzate separation tower is connected to the middle of the acetic acid refining tower, and the top of the acetic acid refining tower is connected to the top of the isopropyl acetate recovery tower.

[0012] According to the device of the present invention, the methyl acetate concentration device also includes an extractive distillation tower condenser, an extractive distillation tower reflux tank, an extractive distillation tower reflux pump, and an extractive distillation tower reboiler;

[0013] The top of the extractive distillation tower is connected to the extractive distillation tower condenser, the extractive distillation tower reflux tank, and the extractive distillation tower reflux pump in sequence; the outlet of the extractive distillation tower reflux pump is connected to the top of the extractive distillation tower, and a branch connected to the acetaldehyde removal tower is arranged on the connecting pipeline;

[0014] The extractive distillation tower is provided with an extractive distillation tower reboiler in the tower kettle;

[0015] The bottom of the extractive distillation tower is also connected to a methanol refining system;

[0016] The methyl acetate concentration device further comprises an extraction water inlet and a methyl acetate inlet. Preferably, the extraction water inlet is connected to the top of the extractive distillation tower, and the methyl acetate inlet is connected to the middle of the extractive distillation tower.

[0017] According to the device of the present invention, the methyl acetate dealdehyde device also includes a deacetaldehyde tower condenser, a deacetaldehyde tower reflux tank, a deacetaldehyde tower reflux pump, a deacetaldehyde tower reboiler, and a deacetaldehyde tower kettle outlet pump;

[0018] The top of the acetaldehyde removal tower is connected to the acetaldehyde removal tower condenser, the acetaldehyde removal tower reflux tank, and the acetaldehyde removal tower reflux pump in sequence; the outlet of the acetaldehyde removal tower reflux pump is connected to the top of the acetaldehyde removal tower, and a branch connected to the acetaldehyde refining system is provided on the connecting pipeline;

[0019] The tower kettle of the acetaldehyde removal tower is provided with an acetaldehyde removal tower reboiler;

[0020] The tower kettle of the acetaldehyde removal tower is connected with the acetaldehyde removal tower kettle outlet pump and the top of the hydrolysis tower in sequence.

[0021] According to the device of the present invention, the methyl acetate hydrolysis device also includes a strongly acidic cation exchange resin bed, a hydrolysis tower condenser, a hydrolysis tower reflux tank, a hydrolysis tower reflux pump, a hydrolysis tower side extraction pump, a hydrolysis tower reboiler, a hydrolysis tower kettle outlet pump and a precision filter; the top of the hydrolysis tower is connected to the hydrolysis tower condenser, the hydrolysis tower reflux tank, and the hydrolysis tower reflux pump in sequence; the outlet of the hydrolysis tower reflux pump is connected to the top of the hydrolysis tower; the hydrolysis tower condenser is also connected to the middle of the acetaldehyde removal tower;

[0022] The upper side line production outlet of the hydrolysis tower is connected to the side production pump of the hydrolysis tower, the strong acid cation exchange resin bed, and the precision filter in sequence, and the outlet of the precision filter is connected to the middle of the hydrolysis tower;

[0023] Preferably, a packing section is provided in the hydrolysis tower, and the packing section is located above the upper side line production outlet;

[0024] Preferably, the packing section is equivalent to 5 to 10 theoretical plates;

[0025] Among them, at least one precision filter is provided, and the arrangement of the precision filters can be in parallel or in series; for example, a precision filter A and a precision filter B are provided in parallel, and a plurality of valves are installed on the connecting pipeline of the precision filter A and the precision filter B;

[0026] The tower kettle of the hydrolysis tower is provided with a hydrolysis tower reboiler;

[0027] The tower kettle of the hydrolysis tower is connected with the outlet pump of the hydrolysis tower kettle and the middle part of the hydrolyzate separation tower in sequence.

[0028] Furthermore, the methyl acetate hydrolysis device also includes a methyl acetate hydrolysis water inlet, which is arranged on the connecting pipeline between the acetaldehyde removal tower kettle and the top of the hydrolysis tower.

[0029] According to the device of the present invention, the hydrolyzed liquid separation device further comprises a hydrolyzed liquid separation tower condenser, a hydrolyzed liquid separation tower reflux tank, a hydrolyzed liquid separation tower reflux pump, a hydrolyzed liquid separation tower reboiler, and a hydrolyzed liquid separation tower kettle outlet pump;

[0030] The top of the hydrolyzate separation tower is provided with two branches, the first branch is connected to the middle of the extractive distillation tower, and the second branch is connected to the hydrolyzate separation tower condenser, the hydrolyzate separation tower reflux tank, and the hydrolyzate separation tower reflux pump in sequence; the outlet of the hydrolyzate separation tower reflux pump is connected to the top of the hydrolyzate separation tower;

[0031] The tower kettle of the hydrolyzed liquid separation tower is provided with a hydrolyzed liquid separation tower reboiler;

[0032] The tower kettle of the hydrolyzed liquid separation tower is connected with the outlet pump of the hydrolyzed liquid separation tower kettle and the middle part of the acetic acid refining tower in sequence.

[0033] According to the device of the present invention, the acetic acid refining tower also includes an acetic acid refining tower condenser, an acetic acid refining tower phase separator, an acetic acid refining tower reflux pump, an acetic acid refining tower reboiler, an acetic acid refining tower side extraction pump, and an acetic acid refining tower kettle outlet pump;

[0034] The top of the acetic acid refining tower is connected to the acetic acid refining tower condenser and the acetic acid refining tower phase separator in sequence, and the acetic acid refining tower phase separator is provided with an outlet 1 and an outlet 2, the outlet 1 is connected to the acetic acid refining tower reflux pump and the top of the acetic acid refining tower in sequence; the outlet 2 is connected to the isopropyl acetate recovery device;

[0035] The lower side line outlet of the acetic acid refining tower is connected to the side production pump of the acetic acid refining tower to produce acetic acid;

[0036] The kettle of the acetic acid refining tower is provided with an acetic acid refining tower reboiler;

[0037] The bottom of the acetic acid refining tower is connected to the bottom pump of the acetic acid refining tower to discharge residue and tar.

[0038] According to the device of the present invention, the isopropyl acetate recovery device also includes an isopropyl acetate recovery tower condenser, an isopropyl acetate recovery tower phase separator, an isopropyl acetate recovery tower distillation pump, an isopropyl acetate water phase receiving tank, an isopropyl acetate recovery tower feed pump, an isopropyl acetate recovery tower reboiler, and an isopropyl acetate recovery tower kettle outlet pump;

[0039] The acetic acid refining tower phase separator is provided with an oil phase outlet and a water phase outlet;

[0040] The outlet 2 of the phase separator of the acetic acid refining tower is connected in sequence with the isopropyl acetate water phase receiving tank, the isopropyl acetate recovery tower feed pump, and the top of the isopropyl acetate recovery tower;

[0041] The top of the isopropyl acetate recovery tower is connected to the isopropyl acetate recovery tower condenser and the isopropyl acetate recovery tower phase separator in sequence; the oil phase outlet of the acetic acid refining tower phase separator, the isopropyl acetate recovery tower distillation pump, and the acetic acid refining tower phase separator are connected in sequence; the water phase outlet of the acetic acid refining tower phase separator is connected to the isopropyl acetate water phase receiving tank;

[0042] The bottom of the isopropyl acetate recovery tower is provided with an isopropyl acetate recovery tower reboiler;

[0043] The kettle of the isopropyl acetate recovery tower is connected to the kettle outlet pump of the isopropyl acetate recovery tower to send out kettle drainage.

[0044] The present invention also provides the above-mentioned anti-corrosion process for hydrolysis of methyl acetate and refining of acetic acid. The anti-corrosion process is based on the above-mentioned anti-corrosion device, and the process mainly includes methyl acetate concentration, methyl acetate dealdehydeation, methyl acetate hydrolysis, hydrolyzate separation, acetic acid refining and isopropyl acetate recovery.

[0045] According to the process of the present invention, the methyl acetate concentration process unit includes the following operations:

[0046] (1) Crude methyl acetate enters an extractive distillation tower to separate methyl acetate from methanol;

[0047] (2) adding extraction water to the top of the extractive distillation tower, condensing, collecting, and pressurizing the methyl acetate vapor volatilized from the top of the extractive distillation tower, wherein a portion of the methyl acetate is refluxed from the top of the extractive distillation tower, and the rest is fed into the acetaldehyde removal tower as feed;

[0048] (3) The methanol-water solution produced in the bottom of the extraction distillation tower is sent to the methanol refining system for recovery;

[0049] Preferably, the sources of the crude methyl acetate include crude methyl acetate (concentration 60-75%, such as 75%) from a crude methyl acetate fractionation unit and crude methyl acetate distilled from the gas phase at the top of a hydrolyzate separation tower in a methyl acetate hydrolysis section;

[0050] Preferably, the temperature of the extraction water is 2 to 15°C, such as 4 to 10°C, and illustratively, the temperature is 10°C;

[0051] Wherein, the operating parameters of the extractive distillation tower are: pressure 0.085-0.15Mpa, for example 0.1MPa; tower top temperature 50-60°C, for example 55°C; tower bottom temperature 75-85°C, for example 82°C; tower top reflux flow rate / tower top production flow rate = 1.3-1.7, for example 1.4-1.6.

[0052] Among them, the above-mentioned process unit adopts the method of water addition extraction distillation to remove methanol from the alcoholysis solution, which destroys the azeotropic effect of methyl acetate and methanol and reduces the inhibitory effect of methanol on the subsequent hydrolysis process of methyl acetate.

[0053] According to the process of the present invention, the methyl acetate dealdehyde process unit comprises the following operations:

[0054] (1) Methyl acetate enters the acetaldehyde removal tower for gas-liquid mass transfer;

[0055] (2) After the steam distilled from the top of the acetaldehyde removal tower is condensed, collected, and pressurized, a portion of the acetaldehyde is refluxed from the top of the acetaldehyde removal tower, and the remaining acetaldehyde is sent for refining;

[0056] (3) the methyl acetate in the bottom of the tower is fed into the top of the hydrolysis tower as feed after being pressurized;

[0057] Preferably, the methyl acetate in step (1) comprises the methyl acetate stream distilled from the top of the extractive distillation tower and the gas phase impurity stream from the hydrolysis tower;

[0058] Wherein, the operating parameters of the acetaldehyde removal tower are: pressure 0.085-0.15MPa, for example 0.1MPa; tower top temperature 45-55°C, for example 50°C; tower bottom temperature 50-60°C, for example 55°C; reflux flow / feed flow = 1.2-1.7, for example 1.3-1.6.

[0059] The methyl acetate dealdehyde process unit is used to remove chloride ion, fluoride ion, bromide ion, iodine ion halogen impurities and acetaldehyde impurities brought into the system by the extraction water.

[0060] According to the process of the present invention, the methyl acetate hydrolysis process unit comprises the following operations:

[0061] (1) The methyl acetate flowing out of the acetaldehyde removal tower kettle enters the hydrolysis tower, and the steam distilled from the top of the hydrolysis tower is condensed, collected, and pressurized before being refluxed from the top of the hydrolysis tower. The uncondensed gas is fed into the acetaldehyde removal tower feed as a gas phase impurity stream;

[0062] (2) methyl acetate is extracted from the side line at the upper part of the hydrolysis tower, mixed with methyl acetate hydrolysis water after being pressurized, and sent to a strong acid cation exchange resin bed for hydrolysis reaction to generate acetic acid and methanol. The hydrolyzate is filtered to remove the broken resin entrained therein, and then returned to the lower part of the hydrolysis tower for separation;

[0063] Preferably, the methyl acetate extracted from the upper side line of the hydrolysis tower is treated by the packing section in the tower;

[0064] Wherein, the operating parameters of the hydrolysis tower are: pressure 0.085~0.15MPa, for example 0.1MPa; tower top temperature 55~65℃, for example 60℃; tower bottom temperature 80~85℃, for example 83℃; side line extraction temperature 60~65℃, for example 61℃; reflux flow / feed flow = 3.3~4.2, for example 3.5~4.0.

[0065] Preferably, the filtration is carried out using a precision filter, wherein the precision filter uses needle felt as a filter medium, which can effectively filter the broken resin and prevent the broken resin from entering the acetic acid concentration system;

[0066] Wherein, the operating parameters of the strongly acidic cation exchange resin bed are: feed temperature 65-75°C, for example 70°C.

[0067] Wherein, the operating conditions of the precision filter are: the pressure drop is less than 0.1MPa, such as 0.01-0.09MPa;

[0068] The thickness of the filter medium is 20 to 30 mm, and the pore size of the filter medium is less than 1 μm, such as 0.2 to 0.9 μm.

[0069] (3) The hydrolyzate in the kettle of the hydrolysis tower is pressurized and sent to a hydrolyzate separation tower for separation;

[0070] Preferably, the hydrolysis reaction solution mainly consists of acetic acid, methanol, water and methyl acetate;

[0071] In the methyl acetate hydrolysis process unit, the methyl acetate stream undergoing hydrolysis reaction in the strong acid cation exchange resin bed is extracted from the upper side line of the hydrolysis tower, and the halogen impurities and acetaldehyde in the system are concentrated by a mass transfer unit between the side line extraction port and the tower top, and then extracted in the gas phase to the methyl acetate dealdehyde unit, and the number of theoretical plates between the side extraction port and the tower top is 5 to 10;

[0072] The precision filter uses needle felt as the filter medium and adopts liquid precision clarification filtration to filter the hydrolysis reaction liquid. The filter medium of the precision clarification filtration has the characteristics of small capillary pore size, large porosity and thick filter medium layer, which intercepts solid particles in the internal pores of the filter medium layer.

[0073] According to the process of the present invention, the hydrolyzate separation process unit includes the following operations:

[0074] (1) The hydrolyzate flowing out of the hydrolysis tower kettle enters the hydrolyzate separation tower for separation, and the vapor portion of the tower top is blown into the extraction distillation tower, and the remaining portion is condensed, collected, pressurized, and then refluxed from the top of the hydrolyzate separation tower;

[0075] (2) The dilute acetic acid in the kettle of the hydrolyzate separation tower is pressurized and sent to the acetic acid refining tower for dehydration and refining.

[0076] Wherein, the operating parameters of the hydrolyzate separation tower are: pressure 0.085-0.15MPa, for example 0.1MPa; tower top temperature 60-70°C, for example 65°C; tower bottom temperature 110-115°C, for example 113°C, supplementary reflux flow / feed flow = 0.55-1.1, for example 0.6-1.0.

[0077] According to the process of the present invention, the acetic acid refining process unit includes the following operations:

[0078] (1) The dilute acetic acid flowing out of the bottom of the hydrolysis liquid separation tower enters the acetic acid refining tower, and the azeotrope of water and isopropyl acetate is distilled from the top of the tower. After condensation and phase separation, isopropyl acetate in the upper layer and separated water (containing a small amount of isopropyl acetate) in the lower layer are obtained;

[0079] Preferably, isopropyl acetate is used as an azeotropic agent in the acetic acid refining tower;

[0080] (2) the isopropyl acetate phase in the upper layer is sent to the top of the acetic acid refining tower for reflux after being pressurized, and the separated water (containing a small amount of isopropyl acetate) in the lower layer is collected and sent to the isopropyl acetate recovery tower;

[0081] (3) Acetic acid is extracted from the side line at the bottom of the acetic acid refining tower, and the residue and tar in the bottom of the tower are sent to the system.

[0082] Wherein, the operating parameters of the acetic acid refining tower are: pressure 0.085-0.15MPa, for example 0.1MPa; tower top temperature 70-80°C, for example 75°C; tower bottom temperature 120-125°C, for example 124°C; lower side line extraction temperature 120-125°C, for example 123.8°C; reflux flow rate / feed flow rate = 3.7-4.2, for example 3.8-4.1.

[0083] According to the process of the present invention, the isopropyl acetate recovery process unit comprises the following operations:

[0084] (1) The separated water from the acetic acid refining process unit enters the top of the isopropyl acetate recovery tower, and the top gas is condensed and phase-separated to obtain a water phase and an oil phase. The water phase is collected and returned to the top of the isopropyl acetate recovery tower, and the oil phase is returned to the acetic acid refining unit after being pressurized;

[0085] (2) The bottom water of the isopropyl acetate recovery tower is pressurized and then sent out of the system;

[0086] Preferably, the isopropyl acetate recovery tower is provided with only a stripping section;

[0087] The operating parameters of the isopropyl acetate recovery tower are as follows: pressure 0.085-0.15 MPa, for example 0.1 MPa; tower top temperature 90-100° C., for example 96° C.; tower bottom temperature 95-103° C., for example 100° C.;

[0088] Wherein, the operating temperature of the phase separation is 35-45°C.

[0089] The inventors of this application systematically studied the movement and distribution of halogen ions in the PVA alcoholysis mother liquor recovery system, and explored the accumulation mechanism of trace halogens in the system. Based on the above research, a method for removing trace halogen impurities from the system was developed, and a new separation process was constructed, thereby achieving the removal of halogen impurities with lower energy and material consumption.

[0090] The inventor of the present application unexpectedly discovered through a systematic study of methyl acetate hydrolysis and acetic acid refining devices that there are also broken strong acid ion exchange resin particles and powder in the acetic acid refining tower kettle. Further analysis found that the broken resin is brought with the hydrolysis liquid after the methyl acetate hydrolysis catalyst is broken. This type of resin is a high molecular polymer with a sulfonic acid group having a reticular three-dimensional structure. During use, due to mechanical external forces, repeated transformation, polymer molecule degradation, and regeneration, backwashing and extrusion, the polymer chains constituting the resin will be broken, and the strength of the resin will be easily weakened, resulting in breakage. The broken resin powder will enter the hydrolysis liquid separation tower and the acetic acid refining tower together with the hydrolysis reaction liquid, decompose organic acid molecules at a higher temperature, and synergize with acetic acid to form a strong corrosion source for the equipment. This discovery has not been reported in existing publicly published documents. Further research found that the broken resin has an extremely small particle size and the medium is corrosive, making it difficult to remove it from the system. Based on this discovery, the present application adds a precision filter at the outlet of the cation exchange resin bed of the hydrolysis reactor to filter the broken resin entrained in the hydrolyzate, preventing the broken resin with sulfonic acid groups from entering the acetic acid refining system, avoiding equipment corrosion caused by the broken resin, and effectively avoiding a source of corrosion.

[0091] Beneficial effects of the present invention:

[0092] The present invention is based on the movement and distribution laws of chloride ions, fluoride ions, bromide ions, iodide ions and broken resins in methyl acetate hydrolysis and acetic acid refining systems discovered by the inventors, establishes efficient removal measures, and effectively controls the impurity content in high-temperature concentrated acetic acid.

[0093] Specifically, on the one hand, the present invention enhances the removal capacity of halogen-containing impurities by arranging a mass transfer unit (i.e., a packing section) on the upper part of the side production port of the hydrolysis tower, and controls the content of hydrides formed by chloride ions, fluoride ions, bromide ions, iodide ions and hydrogen in the hydrolyzed liquid in the tower bottom of the post-transmission system to be below 10 ppm, thereby avoiding the accumulation of local high-concentration areas in the acetic acid refining tower due to the formation of the highest azeotrope; while the prior art produces methyl acetate from the top of the hydrolysis tower, and the halogen impurities enter the cation exchange resin bed of the hydrolysis reactor together with the reaction stream, and enter the acetic acid refining tower together with the generated acetic acid, and accumulate continuously.

[0094] On the other hand, the present invention adds a precision filter at the outlet of the cation exchange resin bed of the hydrolysis reactor to filter the broken resin entrained in the hydrolyzate, thereby preventing the broken resin with sulfonic acid groups from entering the acetic acid refining system.

[0095] Through the above two measures, the effective removal of impurities that aggravate the corrosiveness of high-concentration acetic acid can be achieved under low energy consumption conditions, fundamentally solving the corrosion problem of acetic acid refining equipment, thereby significantly solving the problem of equipment corrosion in the acetic acid refining process and extending the life of key equipment by 1 to 5 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Figure 1 Schematic diagram of the structure of the device for hydrolyzing methyl acetate and refining acetic acid described in Example 1 of the present invention;

[0097] Figure symbols: 01-extractive distillation tower, 02-acetaldehyde removal tower, 03-hydrolysis tower, 04-strong acid cation exchange resin bed, 05A-precision filter A, 05B-precision filter B, 06-hydrolyzate separation tower, 07-acetic acid refining tower, 08-isopropyl acetate recovery tower, 09-extractive distillation tower condenser, 10-extractive distillation tower reflux tank, 11-extractive distillation tower reflux pump, 12-extractive distillation tower reboiler, 13-acetaldehyde removal tower condenser, 14-acetaldehyde removal tower reflux tank, 15-acetaldehyde removal tower reflux pump, 16-acetaldehyde removal tower reboiler, 17-acetaldehyde removal tower kettle outlet pump, 18-hydrolysis tower condenser, 19-hydrolysis tower reflux tank, 20-hydrolysis tower reflux pump, 21-hydrolysis tower side production pump, 22-hydrolysis tower reboiler, 23-hydrolysis tower kettle outlet pump, 24-hydrolysis liquid separation tower condenser, 25-hydrolysis liquid separation tower reflux tank, 26-hydrolysis liquid separation tower reflux pump, 27-hydrolysis liquid separation tower reboiler, 28 hydrolysis liquid separation tower kettle outlet pump, 29-acetic acid refining tower condenser, 30-acetic acid refining tower phase separator, 31-acetic acid refining tower reflux pump, 32-acetic acid refining tower reboiler, 33-acetic acid refining tower side sampling pump, 34-acetic acid refining tower kettle outlet pump, 35-isopropyl acetate recovery tower condenser, 36-isopropyl acetate recovery tower phase separator, 37-isopropyl acetate recovery tower distillation pump, 38-isopropyl acetate water phase receiving tank, 39-isopropyl acetate recovery tower feed pump, 40-isopropyl acetate recovery tower reboiler, 41-isopropyl acetate recovery tower kettle outlet pump. DETAILED DESCRIPTION

[0098] The following will further describe the device structure and process of the present invention in detail in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope of protection of the present invention.

[0099] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0100] Example 1

[0101] like Figure 1 The anti-corrosion device for methyl acetate hydrolysis and acetic acid refining with anti-corrosion function shown includes a methyl acetate concentration device, a methyl acetate dealdehyde device, a methyl acetate hydrolysis device, a hydrolyzate separation device, an acetic acid refining device and an isopropyl acetate recovery device;

[0102] The methyl acetate concentration device includes an extractive distillation tower 01, the methyl acetate dealdehyde device includes an acetaldehyde removal tower 02, the methyl acetate hydrolysis device includes a hydrolysis tower 03, the hydrolyzate separation device includes a hydrolyzate separation tower 06, the acetic acid refining device includes an acetic acid refining tower 07, and the isopropyl acetate recovery device includes an isopropyl acetate recovery tower 08;

[0103] Among them, the extractive distillation tower 01, the acetaldehyde removal tower 02, the hydrolysis tower 03, the hydrolyzate separation tower 06, the acetic acid refining tower 07 and the isopropyl acetate recovery tower 08 are connected in series according to the material flow direction; the top of the extractive distillation tower 01 is connected to the middle of the acetaldehyde removal tower 02, the bottom of the acetaldehyde removal tower 02 is connected to the top of the hydrolysis tower 03, the bottom of the hydrolysis tower 03 is connected to the middle of the hydrolyzate separation tower 06, the bottom of the hydrolyzate separation tower 06 is connected to the middle of the acetic acid refining tower 07, and the top of the acetic acid refining tower 07 is connected to the top of the isopropyl acetate recovery tower 08.

[0104] The methyl acetate concentration device includes an extractive distillation tower 01, an extractive distillation tower condenser 09, an extractive distillation tower reflux tank 10, an extractive distillation tower reflux pump 11, and an extractive distillation tower reboiler 12;

[0105] The top of the extractive distillation tower 01 is connected to the extractive distillation tower condenser 09, the extractive distillation tower reflux tank 10, and the extractive distillation tower reflux pump 11 in sequence; the outlet of the extractive distillation tower reflux pump 11 is connected to the top of the extractive distillation tower 01, and a branch connected to the acetaldehyde removal tower 02 is arranged on the connecting pipeline; the tower kettle of the extractive distillation tower 01 is provided with an extractive distillation tower reboiler 12 as a heat source; the tower kettle of the extractive distillation tower 01 is also connected to the methanol refining system;

[0106] The methyl acetate concentration device further includes an extraction water inlet and a methyl acetate inlet. The extraction water inlet is connected to the top of the extraction distillation tower 01 , and the methyl acetate inlet is connected to the middle of the extraction distillation tower 01 .

[0107] The methyl acetate dealdehyde removal device includes a deacetaldehyde tower 02, a deacetaldehyde tower condenser 13, a deacetaldehyde tower reflux tank 14, a deacetaldehyde tower reflux pump 15, a deacetaldehyde tower reboiler 16, and a deacetaldehyde tower kettle outlet pump 17; the top of the deacetaldehyde tower 02 is connected to the deacetaldehyde tower condenser 13, the deacetaldehyde tower reflux tank 14, and the deacetaldehyde tower reflux pump 15 in sequence; the outlet of the deacetaldehyde tower reflux pump 15 is connected to the top of the deacetaldehyde tower 02, and a branch connected to the acetaldehyde refining system is provided on the connecting pipeline;

[0108] The tower kettle of the acetaldehyde removal tower 02 is provided with an acetaldehyde removal tower reboiler 16 as a heat source;

[0109] The kettle of the acetaldehyde removal tower 02 is connected to the acetaldehyde removal tower kettle outlet pump 17 and the top of the hydrolysis tower 03 in sequence.

[0110] The methyl acetate hydrolysis device includes a hydrolysis tower 03, a strongly acidic cation exchange resin bed 04, a hydrolysis tower condenser 18, a hydrolysis tower reflux tank 19, a hydrolysis tower reflux pump 20, a hydrolysis tower side extraction pump 21, a hydrolysis tower reboiler 22, a hydrolysis tower kettle outlet pump 23 and a precision filter;

[0111] The top of the hydrolysis tower 03 is connected to the hydrolysis tower condenser 18, the hydrolysis tower reflux tank 19, and the hydrolysis tower reflux pump 20 in sequence, and the outlet of the hydrolysis tower reflux pump 20 is connected to the top of the hydrolysis tower 03;

[0112] The upper side line production outlet of the hydrolysis tower 03 is connected to the hydrolysis tower side production pump 21, the strong acid cation exchange resin bed 04, and the precision filter in sequence, and the outlet of the precision filter is connected to the middle of the hydrolysis tower 03;

[0113] A packing section is provided in the hydrolysis tower 03, and the packing section is located above the upper side line production outlet, and the packing section is equivalent to 5 to 10 theoretical plates;

[0114] The precision filter includes a precision filter 05A and a precision filter 05B connected in parallel. Several valves are installed on the connecting pipeline between the precision filter 05A and the precision filter 05B. Under normal circumstances, one valve is used and the other is spare.

[0115] The hydrolysis tower 03 has a hydrolysis tower reboiler 22 as a heat source;

[0116] The kettle of the hydrolysis tower 03 is connected in sequence with the outlet pump 23 of the hydrolysis tower kettle and the middle of the hydrolyzate separation tower 06;

[0117] The methyl acetate hydrolysis device also includes a methyl acetate hydrolysis water inlet, which is arranged on the connecting pipeline between the bottom of the acetaldehyde removal tower 02 and the top of the hydrolysis tower 03.

[0118] The hydrolyzate separation device includes a hydrolyzate separation tower 06, a hydrolyzate separation tower condenser 24, a hydrolyzate separation tower reflux tank 25, a hydrolyzate separation tower reflux pump 26, a hydrolyzate separation tower reboiler 27, and a hydrolyzate separation tower kettle outlet pump 28;

[0119] The top of the hydrolyzate separation tower 06 is provided with two branches, the first branch is connected to the middle of the extraction distillation tower 01, and the second branch is connected to the hydrolyzate separation tower condenser 24, the hydrolyzate separation tower reflux tank 25, and the hydrolyzate separation tower reflux pump 26 in sequence; the outlet of the hydrolyzate separation tower reflux pump 26 is connected to the top of the hydrolyzate separation tower 26;

[0120] The bottom of the hydrolyzed liquid separation tower 06 is provided with a hydrolyzed liquid separation tower reboiler 27 as a heat source;

[0121] The bottom of the hydrolyzed liquid separation tower 06 is connected to the hydrolyzed liquid separation tower bottom outlet pump 28 and the middle of the acetic acid refining tower 07 in sequence.

[0122] The acetic acid refining device includes an acetic acid refining tower 07, an acetic acid refining tower condenser 29, an acetic acid refining tower phase separator 30, an acetic acid refining tower reflux pump 31, an acetic acid refining tower reboiler 32, an acetic acid refining tower side extraction pump 33, and an acetic acid refining tower kettle outlet pump 34;

[0123] The top of the acetic acid refining tower 07 is connected to the acetic acid refining tower condenser 29 and the acetic acid refining tower phase separator 30 in sequence. The acetic acid refining tower phase separator 30 is provided with an outlet 1 and an outlet 2. The outlet 1 is connected to the acetic acid refining tower reflux pump 31 and the top of the acetic acid refining tower 07 in sequence.

[0124] The lower side line of the acetic acid refining tower 07 is connected to the acetic acid refining tower side production pump 33 to produce acetic acid;

[0125] The acetic acid refining tower 07 is provided with an acetic acid refining tower reboiler 32 as a heat source;

[0126] The bottom of the acetic acid refining tower 07 is connected to the acetic acid refining tower bottom outlet pump 34 to discharge residue and tar.

[0127] The isopropyl acetate recovery device includes an isopropyl acetate recovery tower 08, an isopropyl acetate recovery tower condenser 35, an isopropyl acetate recovery tower phase separator 36, an isopropyl acetate recovery tower distillation pump 37, an isopropyl acetate water phase receiving tank 38, an isopropyl acetate recovery tower feed pump 39, an isopropyl acetate recovery tower reboiler 40, and an isopropyl acetate recovery tower kettle outlet pump 41;

[0128] The acetic acid refining tower phase separator 36 is provided with an oil phase outlet and a water phase outlet;

[0129] The outlet 2 of the acetic acid refining tower phase separator 30 is connected in sequence to the isopropyl acetate water phase receiving tank 38, the isopropyl acetate recovery tower feed pump 39, and the top of the isopropyl acetate recovery tower 08;

[0130] The top of the isopropyl acetate recovery tower 08 is connected to the isopropyl acetate recovery tower condenser 35 and the isopropyl acetate recovery tower phase separator 36 in sequence; the oil phase outlet of the acetic acid refining tower phase separator 36, the isopropyl acetate recovery tower distillation pump 37, and the acetic acid refining tower phase separator 30 are connected in sequence; the water phase outlet of the acetic acid refining tower phase separator 36 is connected to the isopropyl acetate water phase receiving tank 38;

[0131] The bottom of the isopropyl acetate recovery tower 08 is connected to the isopropyl acetate recovery tower bottom outlet pump 41 to send out the bottom water.

[0132] The following combination Figure 1 The process flow of the anti-corrosion device for methyl acetate hydrolysis and acetic acid refining is described in detail:

[0133] Methyl acetate concentration process unit: 75% crude methyl acetate from the previous process section and crude methyl acetate distilled from the top gas phase of the hydrolyzate separation tower 06 enter the extraction distillation tower 01 to separate methyl acetate from methanol. Extraction water cooled to 10°C is added from the top of the extraction distillation tower 01 to destroy the azeotropic effect of methyl acetate and methanol and increase the relative volatility of methyl acetate and methanol. The top steam of the extraction distillation tower 01 is condensed by the extraction distillation tower condenser 09 and enters the extraction distillation tower reflux tank 10. Part of it is pressurized by the extraction distillation tower reflux pump 11 and returned to the extraction distillation tower 01 for reflux, and the rest is sent to the acetaldehyde removal tower 02 for feeding. The heat source of the tower bottom is provided by the extraction distillation tower reboiler 12. The tower bottom is a methanol-water solution, which is sent to the methanol refining system for refining and recovery.

[0134] Methyl acetate deacetaldehyde process unit: the methyl acetate stream distilled from the top of the extractive distillation tower 01 and the gas phase impurity stream from the hydrolysis tower 03 enter the deacetaldehyde tower 02 for vapor-liquid mass transfer. The top vapor is condensed by the deacetaldehyde tower condenser 13 and enters the deacetaldehyde tower reflux tank 14. After being pressurized by the deacetaldehyde tower reflux pump 15, a part of it is refluxed, and the rest is sent to the acetaldehyde refining system for treatment, so that the chloride ion, fluoride ion, bromide ion, iodine ion halogen impurities and acetaldehyde impurities are removed from the system. The heat source of the tower bottom of the deacetaldehyde tower 02 is provided by the deacetaldehyde tower reboiler 16, and the tower bottom is fed to the top of the hydrolysis tower 03 by the liquid deacetaldehyde tower bottom outlet pump 17.

[0135] Methyl acetate hydrolysis process unit: After the steam at the top of the hydrolysis tower 03 is partially condensed by the hydrolysis tower condenser 18, all the condensate enters the hydrolysis tower reflux tank 19 and returns to the hydrolysis tower 03 through the hydrolysis tower reflux pump 19 for reflux, and the uncondensed gas is sent to the acetaldehyde removal tower 02 as a waste stream to remove the acetaldehyde of the catalytic hydrolysis system and the chloride ion, fluoride ion, bromide ion, and iodine ion halogen impurities brought in by the extraction water. The material extracted from the upper side line of the hydrolysis tower 03 is pressurized by the hydrolysis tower side extraction pump 21 and mixed with the methyl acetate hydrolysis water, and then sent to the strong acid cation exchange resin bed 04 for hydrolysis reaction. A high-efficiency packing section equivalent to 8 theoretical plates is set above the side line extraction outlet to achieve the key technical measures for the effective removal of halogen impurities and aldehydes. In 04, methyl acetate and water are partially hydrolyzed to generate acetic acid and methanol under the catalytic action of the cation exchange resin. The hydrolyzate is filtered by the precision filter 05 and returned to the lower part of the hydrolysis tower 03 for separation. The hydrolyzate precision filter uses needle felt as the filter medium to effectively filter the broken resin and prevent the broken resin from entering the acetic acid concentration system. The hydrolysis reaction liquid in the hydrolysis tower 03 is mainly composed of acetic acid, methanol, water and methyl acetate, which are pumped out of the hydrolysis tower to the hydrolysis tower separation tower 06 for separation. The heat source of the hydrolysis tower 03 is provided by the hydrolysis tower reboiler 22.

[0136] Hydrolyzed liquid separation process unit: the hydrolyzed liquid in the bottom of the hydrolyzed liquid separation tower 03 is sent to the hydrolyzed liquid separation tower 06 for separation through the hydrolyzed liquid separation tower bottom outlet pump 23, the vapor portion of the top of the tower is blown into the extraction distillation tower 01, and the rest is condensed by the hydrolyzed liquid separation tower condenser 24 and enters the hydrolyzed liquid separation tower reflux tank 25, and returns to the tower for reflux through the hydrolyzed liquid separation tower reflux pump 26; the dilute acetic acid in the bottom of the hydrolyzed liquid separation tower 06 is sent to the acetic acid refining tower 07 for dehydration and refining through the hydrolyzed liquid separation tower bottom outlet pump 28. The heat source of the hydrolyzed liquid separation tower 06 bottom is provided by the hydrolyzed liquid separation tower reboiler 27.

[0137] Acetic acid refining process unit: The acetic acid refining tower 07 uses isopropyl acetate as an azeotropic agent, and utilizes the azeotropic effect of isopropyl acetate and water to distill the azeotrope of water and isopropyl acetate from the top of the tower. The gas phase mixture at the top of the tower is condensed and cooled by the acetic acid refining tower condenser 29, and then enters the acetic acid refining tower phase separator 30 for phase separation. The upper isopropyl acetate phase is sent to the top of the acetic acid refining tower 07 for reflux through the acetic acid refining tower reflux pump 31; the separated water (containing a small amount of isopropyl acetate) at the bottom of the acetic acid refining tower phase separator 30 is collected in the isopropyl acetate water phase receiving tank 38, and then sent to the isopropyl acetate recovery tower 08 for feeding, and the isopropyl acetate therein is recovered. The acetic acid refining tower 07 extracts the finished acetic acid from the lower side line through the acetic acid refining tower side extraction pump 33, and the tower bottom liquid is the residue and tar, which are sent out of the system by the acetic acid refining tower bottom outlet pump 34. The heat source for the bottom of the acetic acid refining tower 07 is provided by the acetic acid refining tower reboiler 32.

[0138] Isopropyl acetate recovery process unit: the separated water from the acetic acid refining tower phase separator 30 is sent to the top of the isopropyl acetate recovery tower 08 for feeding through the isopropyl acetate water phase receiving tank 38 and the isopropyl acetate recovery tower feed pump 39 to recover the isopropyl acetate dissolved in the separated water. The tower is only provided with a stripping section. After the top gas is condensed by the isopropyl acetate recovery tower condenser 35, the condensate enters the isopropyl acetate recovery tower phase separator 36 for phase separation. The water phase is sent to the isopropyl acetate water phase receiving tank 38, and the oil phase is sent to the oil phase side feed of the acetic acid refining tower phase separator 30 by the isopropyl acetate recovery tower distillation pump 37. The heat source of the tower bottom of the isopropyl acetate recovery tower 08 is provided by the isopropyl acetate recovery tower reboiler 40, and the kettle drainage is sent out of the system by the isopropyl acetate recovery tower bottom outlet pump 41.

[0139] Example 2

[0140] The invention discloses an anti-corrosion process for hydrolysis of methyl acetate and refining of acetic acid, which mainly includes continuous operation of methyl acetate concentration, methyl acetate dealdehydeation, methyl acetate hydrolysis, hydrolyzate separation, acetic acid refining and isopropyl acetate recovery.

[0141] The methyl acetate concentration process unit includes the following operations:

[0142] (1) 75% of the crude methyl acetate from the methyl acetate crude fractionation unit and the crude methyl acetate distilled from the top gas phase of the hydrolyzate separation tower in the methyl acetate hydrolysis stage enter the extractive distillation tower to separate methyl acetate from methanol;

[0143] (2) adding 10° C. extraction water to the top of the extractive distillation tower, condensing, collecting, and pressurizing the methyl acetate vapor volatilized from the top of the extractive distillation tower, wherein a portion of the methyl acetate is refluxed from the top of the extractive distillation tower, and the rest is fed into the acetaldehyde removal tower as feed; reflux flow rate / tower top extraction flow rate = 1.4;

[0144] (3) The methanol-water solution produced in the bottom of the extraction distillation tower is sent to the methanol refining system for recovery.

[0145] The methyl acetate dealdehyde process unit includes the following operations:

[0146] (1) Methyl acetate (the methyl acetate stream distilled from the top of the extractive distillation tower and the gas phase impurity stream from the hydrolysis tower) enters the acetaldehyde removal tower for vapor-liquid mass transfer;

[0147] (2) After the steam distilled from the top of the acetaldehyde removal tower is condensed, collected and pressurized, a portion of the acetaldehyde is refluxed from the top of the acetaldehyde removal tower, and the remaining acetaldehyde is sent to refining; reflux flow rate / feed flow rate = 1.3;

[0148] (3) The methyl acetate in the bottom of the tower is pressurized and fed into the top of the hydrolysis tower as feed.

[0149] The methyl acetate hydrolysis process unit includes the following operations:

[0150] (1) The methyl acetate flowing out of the acetaldehyde removal tower kettle enters the hydrolysis tower, and the steam distilled from the top of the hydrolysis tower is condensed, collected, and pressurized before being refluxed from the top of the hydrolysis tower. The uncondensed gas is fed into the acetaldehyde removal tower feed as a gas phase impurity stream; reflux flow rate / feed flow rate = 3.4;

[0151] (2) After being treated in the packing section in the tower (the packing section is equivalent to 8 theoretical plates), methyl acetate is extracted from the side line at the upper part of the hydrolysis tower, mixed with methyl acetate hydrolysis water after being pressurized, and sent to a strong acid cation exchange resin bed (feed temperature 65-75° C.) for hydrolysis reaction to generate acetic acid and methanol. The hydrolyzate is filtered to remove the broken resin entrained therein, and then returned to the lower part of the hydrolysis tower for separation;

[0152] The filtration adopts a precision filter with needle felt as the filter medium, the filter medium thickness is 30 mm, the filter medium pore size is less than 1 μm, and the pressure drop is less than 0.1 MPa; (3) the hydrolyzate (mainly composed of acetic acid, methanol, water and methyl acetate) in the kettle of the hydrolysis tower is pressurized and then sent to the hydrolyzate separation tower for separation.

[0153] The hydrolyzate separation process unit includes the following operations:

[0154] (1) The hydrolyzate flowing out of the hydrolysis tower kettle enters the hydrolyzate separation tower for separation, and the vapor portion of the tower top is blown into the extraction distillation tower in gas phase, and the remaining portion is condensed, collected, and pressurized before being refluxed from the top of the hydrolyzate separation tower, with the reflux flow rate / feed flow rate = 0.6;

[0155] (2) The dilute acetic acid in the kettle of the hydrolyzate separation tower is pressurized and sent to the acetic acid refining tower for dehydration and refining.

[0156] The acetic acid refining process unit includes the following operations:

[0157] (1) The dilute acetic acid flowing out of the bottom of the hydrolysis liquid separation tower enters the acetic acid refining tower, in which isopropyl acetate is used as an azeotropic agent, and the azeotropic product of water and isopropyl acetate is distilled from the top of the tower. After condensation and phase separation, isopropyl acetate in the upper layer and separated water (containing a small amount of isopropyl acetate) in the lower layer are obtained;

[0158] (2) The isopropyl acetate phase in the upper layer is sent to the top of the acetic acid refining tower for reflux after being pressurized, and the separated water (containing a small amount of isopropyl acetate) in the lower layer is collected and sent to the isopropyl acetate recovery tower; reflux flow rate / feed flow rate = 3.8;

[0159] (3) Acetic acid is extracted from the side line at the bottom of the acetic acid refining tower, and the residue and tar in the bottom of the tower are sent to the system.

[0160] The isopropyl acetate recovery process unit includes the following operations:

[0161] (1) The separated water from the acetic acid refining process unit enters the top of the isopropyl acetate recovery tower (the recovery tower only has a stripping section), the top gas is condensed and phase-separated at 45° C. to obtain a water phase and an oil phase, the water phase is collected and returned to the top of the isopropyl acetate recovery tower, and the oil phase is pressurized and returned to the acetic acid refining unit;

[0162] (2) The bottom water of the isopropyl acetate recovery tower is pressurized and then sent out of the system.

[0163] The process provided in this example achieves effective removal of impurities that aggravate the corrosion of high-concentration acetic acid under low energy consumption conditions, significantly alleviates the problem of equipment corrosion in the acetic acid refining process, and extends the life of key equipment by 4 to 5 times.

[0164] The process flow of this comparative example is similar to that of Example 2, except that

[0165] (1) The process parameters are slightly different (see Table 1);

[0166] (2) The packing section in the hydrolysis tower is equivalent to 3 theoretical plates;

[0167] (3) No precision filter is installed.

[0168] The operating conditions of the main equipment in Example 2 and Comparative Example 1 are shown in Table 1.

[0169] Table 1. Main equipment operating conditions

[0170]

[0171] It can be seen from Example 2 and Comparative Example 1 that strictly controlling the theoretical plate number and operating parameters of the hydrolysis tower packing section can enhance the removal capacity of halogen impurities and aldehydes. Specifically, when the F - , Cl - When the concentrations of acetaldehyde and F in the hydrolysis tower kettle material of Example 2 were 134ppm, 281ppm and 150ppm respectively. - and Cl - The concentrations were 7ppm and 2ppm respectively, and the acetaldehyde concentration in the side-extracted material of the hydrolysis tower was 1ppm. - , Cl - The concentrations are 30ppm and 20ppm respectively, and the acetaldehyde concentration in the side-collected material of the hydrolysis tower is 10ppm. The setting of the precision filter can effectively filter the broken resin entrained in the hydrolyzate, thereby preventing the broken resin from entering the acetic acid concentration system and causing equipment corrosion. Specifically, in Example 2, the resin content in the feed of the precision filter is 1000ppm, and the resin content in the output of the precision filter after filtration is reduced to 1ppm. Correspondingly, the resin concentration in the output of the hydrolysis tower kettle is 1ppm; while in Comparative Example 1, because no precision filter is set, the resin concentration in the hydrolysis tower kettle material is 1000ppm. F in the hydrolyzate of Comparative Example 1 - , Cl - The resin concentration is significantly higher than that in Example 2, which shows that the technical measures of the present invention have achieved good beneficial effects.

[0172] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. The antiseptic process of hydrolyzing methyl acetate and refining acetic acid is characterized in that: The anti-corrosion process adopts the following anti-corrosion device, which includes a methyl acetate concentration device, a methyl acetate dealdehyde device, a methyl acetate hydrolysis device, a hydrolyzate separation device, an acetic acid refining device and an isopropyl acetate recovery device; The methyl acetate concentration device comprises an extractive distillation tower, the methyl acetate dealdehyde removal device comprises an acetaldehyde removal tower, the methyl acetate hydrolysis device comprises a hydrolysis tower, a hydrolysis tower side sampling pump, a strong acid cation exchange resin bed and a precision filter, the hydrolyzate separation device comprises a hydrolyzate separation tower, the acetic acid refining device comprises an acetic acid refining tower, and the isopropyl acetate recovery device comprises an isopropyl acetate recovery tower; The top of the extractive distillation tower is connected to the middle of the acetaldehyde removal tower, the bottom of the acetaldehyde removal tower is connected to the top of the hydrolysis tower, the bottom of the hydrolysis tower is connected to the middle of the hydrolyzate separation tower, the bottom of the hydrolyzate separation tower is connected to the middle of the acetic acid refining tower, and the top of the acetic acid refining tower is connected to the top of the isopropyl acetate recovery tower; the upper side line production outlet of the hydrolysis tower is connected to the side production pump of the hydrolysis tower, the strong acid cation exchange resin bed, and the precision filter in sequence, and the outlet of the precision filter is connected to the middle of the hydrolysis tower; A packing section is provided in the hydrolysis tower, and the packing section is located above the upper side line production outlet; the packing section is equivalent to 5 to 10 theoretical plates; The precision filter uses needle felt as the filter medium, the thickness of the filter medium is 20 to 30 mm, and the pore size of the filter medium is less than 1 μm; The anti-corrosion process mainly includes a methyl acetate concentration process unit, a methyl acetate dealdehyde process unit, a methyl acetate hydrolysis process unit, a hydrolyzate separation process unit, an acetic acid refining process unit and an isopropyl acetate recovery process unit; The methyl acetate dealdehyde process unit comprises the following operations: (1) Methyl acetate enters the acetaldehyde removal tower for gas-liquid mass transfer; The methyl acetate comprises a methyl acetate stream distilled from the top of an extractive distillation tower and a gas phase impurity stream from a hydrolysis tower; (2) After the steam distilled from the top of the acetaldehyde removal tower is condensed, collected, and pressurized, a portion of the acetaldehyde is refluxed from the top of the acetaldehyde removal tower, and the remaining acetaldehyde is sent for refining; (3) the methyl acetate in the bottom of the tower is fed into the top of the hydrolysis tower as feed after being pressurized; The methyl acetate hydrolysis process unit comprises the following operations: (1) The methyl acetate flowing out of the acetaldehyde removal tower kettle enters the hydrolysis tower, and the steam distilled from the top of the hydrolysis tower is condensed, collected, and pressurized before being refluxed from the top of the hydrolysis tower. The uncondensed gas is fed into the acetaldehyde removal tower feed as a gas phase impurity stream; (2) methyl acetate is extracted from the side line at the upper part of the hydrolysis tower, mixed with methyl acetate hydrolysis water after being pressurized, and sent to a strong acid cation exchange resin bed for hydrolysis reaction to generate acetic acid and methanol. The hydrolyzate is filtered to remove the broken resin entrained therein, and then returned to the lower part of the hydrolysis tower for separation; The methyl acetate extracted from the upper side line of the hydrolysis tower is treated by the packing section in the tower; The operating conditions of the precision filter are: the pressure drop is less than 0.1 MPa; (3) The hydrolyzed liquid in the kettle of the hydrolysis tower is pressurized and sent to a hydrolyzed liquid separation tower for separation; the hydrolysis reaction liquid mainly consists of acetic acid, methanol, water and methyl acetate.

2. The anti-corrosion process according to claim 1, characterized in that: The methyl acetate concentration device also includes an extractive distillation tower condenser, an extractive distillation tower reflux tank, an extractive distillation tower reflux pump, and an extractive distillation tower reboiler; The top of the extractive distillation tower is connected to the extractive distillation tower condenser, the extractive distillation tower reflux tank, and the extractive distillation tower reflux pump in sequence; the outlet of the extractive distillation tower reflux pump is connected to the top of the extractive distillation tower, and a branch connected to the acetaldehyde removal tower is arranged on the connecting pipeline; And / or, the extractive distillation tower kettle is provided with an extractive distillation tower reboiler; And / or, the bottom of the extractive distillation tower is also connected to a methanol refining system; And / or, the methyl acetate concentration device further comprises an extraction water inlet and a methyl acetate inlet, the extraction water inlet is connected to the top of the extraction distillation tower, and the methyl acetate inlet is connected to the middle of the extraction distillation tower.

3. The anti-corrosion process according to claim 1, characterized in that: The methyl acetate dealdehyde removal device also includes a deacetaldehyde tower condenser, a deacetaldehyde tower reflux tank, a deacetaldehyde tower reflux pump, a deacetaldehyde tower reboiler, and a deacetaldehyde tower kettle outlet pump; The top of the acetaldehyde removal tower is connected to the acetaldehyde removal tower condenser, the acetaldehyde removal tower reflux tank, and the acetaldehyde removal tower reflux pump in sequence; the outlet of the acetaldehyde removal tower reflux pump is connected to the top of the acetaldehyde removal tower, and a branch connected to the acetaldehyde refining system is provided on the connecting pipeline; The tower kettle of the acetaldehyde removal tower is provided with an acetaldehyde removal tower reboiler; The kettle of the acetaldehyde removal tower is connected to the acetaldehyde removal tower kettle outlet pump and the top of the hydrolysis tower in sequence; And / or, the operating parameters of the acetaldehyde removal tower are: pressure 0.085-0.15 MPa; tower top temperature 45-55° C.; tower bottom temperature 50-60° C.; reflux flow / feed flow=1.2-1.

7.

4. The anti-corrosion process according to claim 1, characterized in that: The methyl acetate hydrolysis device also includes a hydrolysis tower condenser, a hydrolysis tower reflux tank, a hydrolysis tower reflux pump, a hydrolysis tower reboiler and a hydrolysis tower kettle outlet pump; The top of the hydrolysis tower is connected to the hydrolysis tower condenser, the hydrolysis tower reflux tank, and the hydrolysis tower reflux pump in sequence; the outlet of the hydrolysis tower reflux pump is connected to the top of the hydrolysis tower; the hydrolysis tower condenser is also connected to the middle of the acetaldehyde removal tower; And / or, a hydrolysis tower reboiler is provided in the tower kettle of the hydrolysis tower; And / or, the kettle of the hydrolysis tower is connected in sequence with the outlet pump of the kettle of the hydrolysis tower and the middle part of the hydrolyzate separation tower; And / or, the methyl acetate hydrolysis device further comprises a methyl acetate hydrolysis water inlet, which is arranged on a connecting pipeline between the acetaldehyde removal tower kettle and the top of the hydrolysis tower; And / or, the operating parameters of the hydrolysis tower are: pressure 0.085-0.15 MPa; tower top temperature 55-65°C; tower bottom temperature 80-85°C; side line extraction temperature 60-65°C; reflux flow / feed flow = 3.3-4.2; And / or, the operating parameters of the strongly acidic cation exchange resin bed are: feed temperature 65-75°C.

5. The anti-corrosion process according to claim 1, characterized in that: The hydrolyzate separation device also includes a hydrolyzate separation tower condenser, a hydrolyzate separation tower reflux tank, a hydrolyzate separation tower reflux pump, a hydrolyzate separation tower reboiler, and a hydrolyzate separation tower kettle outlet pump; The top of the hydrolyzate separation tower is provided with two branches, the first branch is connected to the middle of the extractive distillation tower, and the second branch is connected to the hydrolyzate separation tower condenser, the hydrolyzate separation tower reflux tank, and the hydrolyzate separation tower reflux pump in sequence; the outlet of the hydrolyzate separation tower reflux pump is connected to the top of the hydrolyzate separation tower; And / or, a hydrolyzed liquid separation tower reboiler is provided in the tower kettle of the hydrolyzed liquid separation tower; And / or, the bottom of the hydrolyzate separation tower is connected in sequence with the bottom outlet pump of the hydrolyzate separation tower and the middle part of the acetic acid refining tower.

6. The anti-corrosion process according to claim 1, characterized in that: The acetic acid refining tower also includes an acetic acid refining tower condenser, an acetic acid refining tower phase separator, an acetic acid refining tower reflux pump, an acetic acid refining tower reboiler, an acetic acid refining tower side extraction pump, and an acetic acid refining tower kettle outlet pump; The top of the acetic acid refining tower is connected to the acetic acid refining tower condenser and the acetic acid refining tower phase separator in sequence, the acetic acid refining tower phase separator is provided with an outlet 1 and an outlet 2, and the outlet 1 is connected to the acetic acid refining tower reflux pump and the top of the acetic acid refining tower in sequence; And / or, the lower side line outlet of the acetic acid refining tower is connected to the side production pump of the acetic acid refining tower to produce acetic acid; And / or, the kettle of the acetic acid refining tower is provided with an acetic acid refining tower reboiler; And / or, the bottom of the acetic acid refining tower is connected to an outlet pump of the bottom of the acetic acid refining tower to discharge residue and tar.

7. The anti-corrosion process according to claim 6, characterized in that: The isopropyl acetate recovery device also includes an isopropyl acetate recovery tower condenser, an isopropyl acetate recovery tower phase separator, an isopropyl acetate recovery tower distillation pump, an isopropyl acetate water phase receiving tank, an isopropyl acetate recovery tower feed pump, an isopropyl acetate recovery tower reboiler, and an isopropyl acetate recovery tower kettle outlet pump; The acetic acid refining tower phase separator is provided with an oil phase outlet and a water phase outlet; The outlet 2 of the phase separator of the acetic acid refining tower is connected in sequence with the isopropyl acetate water phase receiving tank, the isopropyl acetate recovery tower feed pump, and the top of the isopropyl acetate recovery tower; The top of the isopropyl acetate recovery tower is connected to the isopropyl acetate recovery tower condenser and the isopropyl acetate recovery tower phase separator in sequence; the oil phase outlet of the acetic acid refining tower phase separator, the isopropyl acetate recovery tower distillation pump, and the acetic acid refining tower phase separator are connected in sequence; the water phase outlet of the acetic acid refining tower phase separator can be connected to the isopropyl acetate water phase receiving tank; And / or, the bottom of the isopropyl acetate recovery tower is provided with an isopropyl acetate recovery tower reboiler; And / or, the bottom of the isopropyl acetate recovery tower is connected to an outlet pump of the bottom of the isopropyl acetate recovery tower to discharge the water from the bottom of the tower.

8. The anti-corrosion process according to claim 1, characterized in that: The methyl acetate concentration process unit comprises the following operations: (1) Crude methyl acetate enters an extractive distillation tower to separate methyl acetate from methanol; (2) adding extraction water to the top of the extractive distillation tower, condensing, collecting, and pressurizing the methyl acetate vapor volatilized from the top of the extractive distillation tower, wherein a portion of the methyl acetate is refluxed from the top of the extractive distillation tower, and the rest is fed into the acetaldehyde removal tower as feed; (3) The methanol-water solution produced in the bottom of the extraction distillation tower is sent to the methanol refining system for recovery.

9. The anti-corrosion process according to claim 8, characterized in that: The sources of the crude methyl acetate include crude methyl acetate from a methyl acetate crude separation unit and crude methyl acetate distilled from the gas phase at the top of a hydrolyzed liquid separation tower in a methyl acetate hydrolysis section; And / or, the temperature of the extraction water is 2 to 15°C; And / or, the operating parameters of the extractive distillation tower are: pressure 0.085-0.15 MPa, tower top temperature 50-60°C, tower bottom temperature 75-85°C, tower top reflux flow rate / tower top production flow rate = 1.3-1.

7.

10. The anti-corrosion process according to claim 1, characterized in that: The hydrolyzate separation process unit comprises the following operations: (1) The hydrolyzate flowing out of the hydrolysis tower kettle enters the hydrolyzate separation tower for separation, and the vapor portion of the tower top is blown into the extraction distillation tower, and the remaining portion is condensed, collected, pressurized, and then refluxed from the top of the hydrolyzate separation tower; (2) The dilute acetic acid in the kettle of the hydrolyzate separation tower is pressurized and sent to the acetic acid refining tower for dehydration and refining.

11. The anti-corrosion process according to claim 10, characterized in that: The operating parameters of the hydrolyzate separation tower are: pressure 0.085-0.15 MPa, tower top temperature 60-70°C, tower bottom temperature 110-115°C, supplementary reflux flow / feed flow = 0.55-1.

1.

12. The anti-corrosion process according to claim 1, characterized in that: The acetic acid refining process unit includes the following operations: (1) The dilute acetic acid flowing out of the bottom of the hydrolysis liquid separation tower enters the acetic acid refining tower, and the azeotrope of water and isopropyl acetate is distilled from the top of the tower. After condensation and phase separation, isopropyl acetate in the upper layer and separated water in the lower layer are obtained; Isopropyl acetate is used as an azeotropic agent in the acetic acid refining tower; (2) the isopropyl acetate phase in the upper layer is sent to the top of the acetic acid refining tower for reflux after being pressurized, and the separated water in the lower layer is collected and sent to the isopropyl acetate recovery tower; (3) Acetic acid is extracted from the side line at the bottom of the acetic acid refining tower, and the residue and tar in the bottom of the tower are sent to the system.

13. The anti-corrosion process according to claim 12, characterized in that: The operating parameters of the acetic acid refining tower are: pressure 0.085-0.15 MPa, tower top temperature 70-80°C, tower bottom temperature 120-125°C, lower side line extraction temperature 120-125°C, reflux flow / feed flow = 3.7-4.

2.

14. The anti-corrosion process according to claim 1, characterized in that: The isopropyl acetate recovery process unit comprises the following operations: (1) The separated water from the acetic acid refining process unit enters the top of the isopropyl acetate recovery tower, and the top gas is condensed and phase-separated to obtain a water phase and an oil phase. The water phase is collected and returned to the top of the isopropyl acetate recovery tower, and the oil phase is returned to the acetic acid refining unit after being pressurized; (2) The bottom water of the isopropyl acetate recovery tower is pressurized and then sent out of the system.

15. The anti-corrosion process according to claim 14, characterized in that: The operating parameters of the isopropyl acetate recovery tower are: pressure 0.085-0.15 MPa, tower top temperature 90-100° C., tower bottom temperature 95-103° C.; And / or, the operating temperature of the phase separation is 35-45°C.

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