Process and device for refining glyoxylic acid

Abstract

The present invention relates to a process method and device for refining glyoxylic acid, which is a process method and device for producing a glyoxylic acid aqueous solution product after quenching and absorbing glyoxylic acid methyl ester process gas, and producing a methanol product as a by-product through hydrolysis and concentration operations. The entire device at least comprises seven towers, namely, a pre-fractionation tower T110, an absorption tower T120, a hydrolysis tower T130, a concentration tower T140, a methanol rectification tower T150, a recovery tower T160 and a tail gas absorption tower T170, and their supporting equipment. The present invention can be perfectly combined with the process route of preparing glyoxylic acid methyl ester by oxidation of methyl glycolate, further hydrolyze and concentrate to produce glyoxylic acid, and reduce the operating energy consumption to the greatest extent, which can overcome the defects of the prior art, has significant practicality and economic benefits, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to a process method and device for refining glyoxylic acid, which is a process method and device for producing a glyoxylic acid aqueous solution product by condensing and absorbing glyoxylic acid methyl ester from a glycolate oxidation reaction product, and then hydrolyzing and concentrating the product, and producing a methanol product as a by-product. Background Art

[0002] Glyoxylic acid, referred to as GLA, is a white crystal with an unpleasant odor. Its aqueous solution is a colorless or light yellow transparent liquid and is slightly soluble in ethanol, ether and benzene.

[0003] Glyoxylic acid is the simplest keto acid (aldehyde acid) with the properties of both acid and aldehyde. It is an important raw material for fine chemicals and can be used as an intermediate for varnish raw materials, fragrances, medicines, dyes, plastics and household chemicals. Glyoxylic acid is widely used in medicine (mainly used in broad-spectrum antibiotic amoxicillin, oral penicillin, antihypertensive drug atenolol, cosmetic additive allantoin, high value-added aromatic aldehydes, p-hydroxybenzoic acid, etc.), water quality stabilizer, fragrance (vanillin, ethyl vanillin, etc.), flavoring agent and fixative, pesticide intermediate, etc.

[0004] The main domestic methods for preparing glyoxylic acid are: glyoxal oxidation method, oxalic acid electrolytic reduction method, maleic anhydride ozone oxidation method and dichloroacetic acid hydrolysis method.

[0005] The glyoxal oxidation method is to oxidize glyoxal with nitric acid. Crude glyoxylic acid can be obtained in one step. After post-treatment, a small amount of oxalic acid and glyoxal are removed, and finally concentrated to produce glyoxylic acid products of a certain specification. It is currently the most mature production method in the world, but the raw material price of this method is relatively high, the amount of by-product oxalic acid is large, the pollution is relatively large, the equipment is severely corroded, and the product purity is relatively low.

[0006] The disadvantages of the oxalic acid electrolytic reduction method are poor and unstable product quality, high energy consumption, high investment and production costs, and poor continuity.

[0007] The disadvantages of maleic anhydride ozone oxidation method are large equipment investment, reliance on ozone technology and high electricity consumption.

[0008] The dichloroacetic acid hydrolysis method has a long process route, many operating steps, high production cost, and uses strong alkaline substances, which cause serious corrosion to equipment.

[0009] With the rapid development of coal-to-ethylene glycol technology, its derivative methyl glycolate has been better developed and utilized. Among them, the production of glyoxylic acid by oxidation and hydrolysis of methyl glycolate has more competitive advantages than existing process technologies.

[0010] At present, China has no patent on the supporting purification process for producing glyoxylic acid by hydrolyzing methyl glyoxylate, the product of methyl glycolate oxidation reaction.

[0011] Chinese patent CN100369882C discloses a "process method for purifying and refining glyoxylic acid", which provides a process method for purifying and refining glyoxylic acid, which is directed to oxalic acid electrolytic reduction method, glyoxal oxidation method, etc., and the crude product generated is further purified and refined. This process removes inorganic acids, salts and oxalic acid through ion exchange, and then obtains anhydrous glyoxylic acid product through reduced pressure concentration, low-temperature crystallization and drying.

[0012] Chinese patent CN102786409A discloses "a method for refining glyoxylic acid", which provides a method for refining glyoxylic acid. This method uses a calcifying agent to remove oxalic acid from crude glyoxylic acid, and the filtered filtrate is concentrated under reduced pressure, crystallized at low temperature, centrifuged and dried under vacuum to obtain high-purity solid glyoxylic acid.

[0013] Chinese patent CN203227316U discloses "a glyoxylic acid refining device", which provides a glyoxylic acid refining device. The device removes glyoxal, oxalic acid and other impurities step by step through a vacuum intermittent distillation method to obtain a high-concentration glyoxylic acid product.

[0014] The above patent documents are all directed to the process of refining crude glyoxylic acid obtained by oxalic acid electrolytic reduction or glyoxal oxidation, which is not suitable for the process of producing glyoxylic acid by methyl glycolate oxidation and hydrolysis. In addition, the operation energy consumption in the method is high and the material is highly corrosive, resulting in high equipment investment. Summary of the invention

[0015] The present invention relates to a process method and device for refining glyoxylic acid, which is a process method and device for producing a glyoxylic acid aqueous solution product after condensing and absorbing methyl glyoxylate from a methyl glycolate oxidation reaction product, and producing a methanol product as a by-product through hydrolysis and concentration operations. The process method and device can be perfectly combined with a process route for preparing methyl glyoxylate by using methyl glycolate and its oxidation, and glyoxylic acid can be produced by further hydrolyzing and concentrating methyl glyoxylate, thereby greatly reducing operating energy consumption, overcoming the defects of the prior art, having significant practicality and economic benefits, and having broad application prospects.

[0016] The present invention provides a process and device for refining glyoxylic acid, which comprises at least seven towers, namely, a pre-fractionation tower T110, an absorption tower T120, a hydrolysis tower T130, a concentration tower T140, a methanol distillation tower T150, a recovery tower T160 and a tail gas absorption tower T170, and mainly comprises the following steps:

[0017] (S1) Pre-fractionation: The process gas containing methyl glyoxylate from the reaction system enters the lower part of the pre-fractionation tower T110, and sequentially contacts with the circulating flow at the lower part of the tower and the absorbent at the top of the tower in countercurrent flow, so as to separate methyl glyoxylate from heavy components. Except for a small amount of methyl glyoxylate and water, all heavy components in the process gas are condensed and captured at the bottom of the tower and discharged from the bottom of the tower; most of the methyl glyoxylate, water and uncondensed gas phase in the process gas are discharged from the top of the pre-fractionation tower T110;

[0018] (S2) Absorption: The gas phase discharged from the top of the pre-fractionation tower T110 enters the lower part of the absorption tower T120. The absorption tower T120 is provided with a plurality of circulating cooling sections. An absorbent is introduced into the top of the tower to absorb the methyl glyoxylate in the ascending gas phase in the absorption tower into the liquid phase. The gas phase substantially free of methyl glyoxylate is discharged from the top of the tower; the methyl glyoxylate aqueous solution is discharged from the bottom of the absorption tower T120 to the pre-hydrolysis kettle V1301, or part of the methyl glyoxylate aqueous solution can be discharged from the bottom of the absorption tower T120 to the pre-hydrolysis kettle V1301, or part of the methyl glyoxylate aqueous solution is simultaneously extracted from the bottom of the absorption tower and the bottom to the pre-hydrolysis kettle V1301; the remaining material flow from the bottom of the absorption tower T120 is sent to the top of the pre-fractionation tower T110 as the reflux liquid of the pre-fractionation tower T110;

[0019] (S3) Prehydrolysis: The methyl glyoxylate absorption liquid discharged from the lower part of the absorption tower T120, the kettle liquid of the methanol distillation tower T150, and the methyl glyoxylate recovered by the recovery tower T160 are mixed and preheated and then enter the prehydrolysis kettle V1301. The liquid above the feed position of the hydrolysis tower T130 also enters the prehydrolysis kettle V1301; 50-99% of the methyl glyoxylate is hydrolyzed in the prehydrolysis kettle V1301, and the gas and liquid phases after the prehydrolysis are respectively fed into the hydrolysis tower T130;

[0020] (S4) hydrolysis: the methyl glyoxylate not hydrolyzed in the pre-hydrolysis reactor V1301 is further hydrolyzed in the hydrolysis tower T130, and a mixture of methanol, water and methyl glyoxylate is distilled off at the top of the tower, and a glyoxylic acid aqueous solution is obtained in the bottom of the tower;

[0021] (S5) Concentration: The glyoxylic acid aqueous solution from the bottom of the hydrolysis tower T130 is further dehydrated and concentrated in the concentration tower T140 to obtain a glyoxylic acid aqueous solution product with a qualified concentration;

[0022] (S6) Methanol distillation: The top material of the hydrolysis tower T130 enters the methanol distillation tower T150, and methanol with a purity of more than 99% (mass percentage, the same below) is distilled from the top of the tower. The bottom of the tower is a methyl glyoxylate aqueous solution, which goes to the pre-hydrolysis kettle V1301;

[0023] (S7) Recovery: The materials in the bottom of the pre-fractionation tower T110 are fed into the recovery tower T160. The top of the recovery tower T160 is methyl glyoxylate containing a small amount of water, which is sent to the pre-hydrolysis kettle V1301. The heavy component discharge device in the bottom of the recovery tower T160 is used;

[0024] (S8) Tail gas absorption: Part of the gas phase from the top of the absorption tower T120 is returned to the reaction system, and the other part is used as purge gas to enter the tail gas absorption tower T170. The vacuum non-condensable gas from other towers in the system also enters the tail gas absorption tower T170. The purified gas is discharged after being absorbed and purified by process water, and the absorption liquid in the tower bottom is sent to the pre-hydrolysis kettle V1301 or the discharge device.

[0025] The pre-fractionation tower T110 described in step (S1) is provided with several heat exchangers so that the heavy components are completely condensed and absorbed, and most of the methyl glyoxylate and water in the process gas are discharged from the top of the pre-fractionation tower T110 along with the uncondensed gas phase. The typical heat exchanger arrangement of the pre-fractionation tower T110 is as follows: the upper part, the lower part, and the tower kettle are provided with a circulating cooling section; the upper part and the lower part are provided with a circulating cooling section, and the tower kettle is provided with a stripping section; the temperature of the tower kettle of the pre-fractionation tower T110 is 15 to 160°C.

[0026] In step (S2), the typical absorbent is water; the absorption tower T120 is provided with 1 to 4 circulating cooling sections, and the typical circulating cooling sections are provided at the top, middle and bottom of the tower; the temperature of the bottom of the absorption tower T120 is 5 to 100° C., and the concentration of the methyl glyoxylate aqueous solution discharged from the bottom of the absorption tower T120 to the prehydrolysis kettle V1301 is 5 to 45%.

[0027] According to the process method provided by the present invention, the pre-fractionation tower T110 and the absorption tower T120 described in step (S1) and step (S2) can be connected in series into one tower to save floor space; the pre-fractionation tower T110 and the absorption tower T120 can also be split into three or more tower equipment. One or more heat exchangers can be set in the pre-fractionation tower T110 and the absorption tower T120 as needed and for structural convenience. Technicians in the relevant fields can make corresponding arrangements and combinations according to the process method and flow chart provided by the present invention. It should be particularly noted that the arrangements and combinations of different numbers of heat exchangers and / or heat exchange positions are all local optimizations of the process method provided by the present invention, which are obvious to those skilled in the art and are regarded as within the spirit, scope and content of the present invention.

[0028] According to the process provided by the present invention, in step (S3), the operating temperature of the pre-hydrolysis kettle V1301 is 35-150°C; in step (S4), the operating temperature of the hydrolysis tower T130 is 35-150°C, and the glyoxylic acid concentration in the bottom of the hydrolysis tower T130 is 10-60%. The concentration of the typical glyoxylic acid aqueous solution product 24 in the bottom of the concentration tower T140 is 20-70%, and the above-listed concentrations do not constitute any limitation to the present invention.

[0029] According to the process provided by the present invention, in step (S5), the glyoxylic acid aqueous solution in the bottom of the hydrolysis tower T130 can be concentrated to the target concentration by a single-effect concentration, a double-effect concentration or a multi-effect concentration process, and the typical glyoxylic acid aqueous solution product concentration is 20-70%. It should be noted that whether a single-effect, double-effect or multi-effect concentration process is adopted, or a conventional evaporator, a thin film evaporator with a scraper, a falling film evaporator or a tower concentration device is adopted, it does not constitute a limitation to the process provided by the present invention, and relevant technicians in this professional field can fully implement this concentration process according to the known heating and / or concentration methods.

[0030] According to the process provided by the present invention, a hydrolysis kettle V1401 can be added between step (S4) and step (S5) as needed, that is, the material in the bottom of the hydrolysis tower T130 is introduced into the hydrolysis kettle V1401 to ensure that methyl glyoxylate is completely hydrolyzed, and the material in the hydrolysis kettle V1401 is then concentrated in step (S5) to obtain a glyoxylic acid aqueous solution product with a qualified concentration.

[0031] According to the process provided by the present invention, step (S5) can be omitted, and a glyoxylic acid aqueous solution product with qualified purity can be directly obtained from the hydrolysis tower T130 kettle or the hydrolysis kettle V1401.

[0032] According to the process provided by the present invention, the prehydrolysis kettle V1301, the hydrolysis tower T130 and the hydrolysis kettle V1401 can be filled with catalysts to accelerate the hydrolysis rate of methyl glyoxylate; a heater is provided inside the prehydrolysis kettle V1301 to maintain a suitable hydrolysis temperature.

[0033] According to the process provided by the present invention, the gas phase returned to the reaction system from the top of the absorption tower T120 can be first dehydrated by a drying unit and then returned to the reaction system. The drying unit can be a molecular sieve adsorption dehydration, or triethylene glycol (TEG) or ethylene glycol (EG) dehydration.

[0034] According to the process provided by the present invention, when the temperature of the bottom of the pre-fractionation tower T110 is properly controlled and the content of methyl glyoxylate in the bottom of the tower is very low, the recovery tower T160 can be omitted to simplify the process flow.

[0035] According to a typical glyoxylic acid refining device provided by the present invention, Figure 1 As shown, it goes through the following steps:

[0036] The process gas 1 containing methyl glyoxylate from the methyl glycolate oxidation reaction system enters the bottom of the pre-fractionation tower T110.

[0037] A circulating cooling section S1101 is provided at the bottom of the pre-fractionation tower T110, and the pre-fractionation tower circulating cooler E1101 is used for cooling; the liquid phase material 3 in the bottom of the pre-fractionation tower T110 enters the lower part of the recovery tower T160; the gas phase 2 at the top of the pre-fractionation tower T110 enters the bottom of the absorption tower T120.

[0038] The process water 4 enters the top of the absorption tower T120; the absorption tower T120 is provided with the first circulation cooling section S1201 at the bottom of the tower, the second circulation cooling section S1202, the purification section, and the third circulation cooling section S1203 at the top of the tower from bottom to top; the first circulation cooling section S1201 at the bottom of the absorption tower T120 is cooled by the first circulation cooler E1201 of the absorption tower; the liquid phase material 9 in the bottom of the absorption tower T120 enters the top of the pre-fractionation tower T110; the second circulation cooling section S120 of the absorption tower T120 202 is cooled by the second circulating cooler E1202 of the absorption tower; the liquid material 8 taken out from the lower side line of the second circulating cooling section S1202 of the absorption tower T120 enters the hydrolysis preheater E1301; the third circulating cooling section S1203 at the top of the absorption tower T120 is cooled by the third circulating cooler E1203 of the absorption tower; the gas phase 5 at the top of the absorption tower T120 is divided into two streams, one of which is sent out as the circulating gas 6 to return to the reaction system, and the other 7 enters the kettle of the tail gas absorption tower T170.

[0039] The mixed stream 10 of the liquid material 8 produced from the side line of the second circulating cooling section S1202 of the absorption tower T120, the liquid material 33 produced from the top of the recovery tower T160 and the liquid material 37 produced from the bottom of the tail gas absorption tower T170 enters the hydrolysis preheater E1301, and the preheated stream 11 enters the prehydrolysis kettle V1301; the top gas phase 12 and the bottom liquid phase 13 of the prehydrolysis kettle V1301 respectively enter the upper part of the hydrolysis tower T130.

[0040] The bottom of the hydrolysis tower T130 is heated by the hydrolysis tower reboiler E1302; the liquid material 19 in the bottom of the hydrolysis tower T130 enters the bottom of the concentration tower T140; the liquid material 18 taken out from the side line above the feed position of the hydrolysis tower T130 enters the pre-hydrolysis kettle V1301; the condensate 15 of the top gas phase 14 of the hydrolysis tower T130 after condensation by the hydrolysis tower condenser E1303 is divided into two streams, one of which is directly returned to the top of the hydrolysis tower T130 as the reflux liquid 16, and the other condensate 17 enters the middle part of the methanol distillation tower T150.

[0041] The bottom of the concentration tower T140 is heated by the concentration tower reboiler E1401; the liquid phase material in the bottom of the concentration tower T140 is used as the delivery device of the glyoxylic acid aqueous solution product 24; the condensate 21 of the top gas phase 20 of the concentration tower T140 after condensation by the concentration tower condenser E1402 is divided into two streams, one of which is directly returned to the top of the concentration tower T140 as the reflux liquid 22, and the other condensate 23 enters the top of the absorption tower T120.

[0042] The bottom of methanol distillation tower T150 is heated by methanol distillation tower reboiler E1501; liquid material 29 in the bottom of methanol distillation tower T150 enters pre-hydrolysis kettle V1301; condensate 26 of top gas phase 25 of methanol distillation tower T150 after condensation by methanol distillation tower condenser E1502 is divided into two streams, one stream is directly returned to the top of methanol distillation tower T150 as reflux liquid 27, and the other stream of condensate is sent out of the device as methanol product 28.

[0043] The bottom of the recovery tower T160 is heated by the recovery tower reboiler E1601; the liquid phase material in the bottom of the recovery tower T160 is sent out as the heavy component 34; the condensate 31 of the top gas phase 30 of the recovery tower T160 after condensation by the recovery tower condenser E1602 is divided into two streams, one of which is directly returned to the top of the recovery tower T160 as the reflux liquid 32, and the other condensate 33 is mixed with the liquid phase material 8 taken from the side line below the second circulation cooling section S1202 of the absorption tower T120 and then enters the hydrolysis preheater E1301.

[0044] The process water 35 enters the top of the tail gas absorption tower T170; the vacuum non-condensable gas 38 in the system enters the bottom of the tail gas absorption tower T170, and the liquid phase material 37 in the bottom of the tail gas absorption tower T170 goes to the hydrolysis preheater E1301; the top gas phase of the tail gas absorption tower T170 is used as the purified gas 36 to send out the device.

[0045] The process provided by the present invention mainly involves the following two reactions:

[0046] (1) Methyl glycolate is oxidized to produce methyl glyoxylate and water:

[0047]

[0048] (2) Methyl glyoxylate is hydrolyzed to produce glyoxylic acid and methanol:

[0049]

[0050] The process gas of the methyl glycolate oxidation reaction is separated from the heavy components by the pre-fractionation tower T110, and the top stream of the pre-fractionation tower T110 is then absorbed by the absorption tower T120, and the methyl glyoxylate is hydrolyzed by the pre-hydrolysis kettle and the hydrolysis tower to obtain the glyoxylic acid aqueous solution. The process method and device provided by the present invention can be perfectly combined with the process route of preparing methyl glyoxylate by using methyl glycolate and its oxidation, and glyoxylic acid is produced by further hydrolysis and concentration of methyl glyoxylate, which has the advantages of simple process flow, low operation energy consumption, low equipment corrosion, can overcome the defects of the prior art, has significant practicality and economic benefits, and has broad application prospects.

[0051] According to the process provided by the present invention, in addition to adopting the above process to purify glyoxylic acid, other processes can also be used to purify glyoxylic acid.

[0052] Deformation process method 1: Figure 2 As shown, relative Figure 1 In the process provided, a second circulating cooling section S1102 is added to the lower part of the pre-fractionation tower T110, and the second circulating cooler E1102 of the pre-fractionation tower is used for cooling; a third circulating cooling section S1103 is added to the top of the pre-fractionation tower T110, and the third circulating cooler E1103 of the pre-fractionation tower is used for cooling. Figure 1 According to the provided process, the third circulating cooling section S1203 at the top of the absorption tower T120 cancels the circulating cooling and changes it into a purification section.

[0053] Deformation process method 2: Figure 3 As shown, relative Figure 2 In the provided process, the circulating cooling section S1101 at the bottom of the pre-fractionation tower T110 is changed into the stripping section S1104, and the pre-fractionation tower circulating heater E1104 is used for heating; the process gas is fed between the second circulating cooling section S1102 and the stripping section S1104; the third circulating cooling section S1103 at the top of the pre-fractionation tower T110 is cancelled. By adopting this modified process method, the content of non-condensable gas and methyl glyoxylate in the discharge of the pre-fractionation tower T110 can be reduced, the yield of methyl glyoxylate at the top of the pre-fractionation tower T110 can be increased, the processing capacity of the recovery tower T160 can be reduced, the equipment investment can be reduced, and the operating energy consumption can be reduced.

[0054] Deformation process method three: Figure 4 As shown, relative Figure 1 In the provided process, the pre-fractionation tower T110 and the absorption tower T120 described in step (S1) and step (S2) can be connected in series into one tower to save floor space.

[0055] Deformation process method 4: Figure 5 As shown, relative Figure 1 In the provided process, the hydrolysis tower T130 kettle is not heated, the hydrolysis tower reboiler E1302 is omitted, and a hydrolysis kettle V1401 is added. The liquid phase material 19 of the hydrolysis tower T130 kettle enters the hydrolysis kettle V1401; the bottom of the hydrolysis kettle V1401 is heated by the hydrolysis kettle reboiler E1403; the liquid phase material 40 at the bottom of the hydrolysis kettle V1401 enters the kettle of the concentration tower T140; the gas phase material 39 at the top of the hydrolysis kettle V1401 enters the kettle of the hydrolysis tower T130. The tail gas absorption tower T170 bottom absorption liquid 37 discharge device.

[0056] Deformation process method 5: Figure 6 As shown, it is Figure 1As a further supplement to the provided process, a drying unit is added so that the gas phase 6 diverted from the top of the absorption tower T120 is dehydrated and then returned to the reaction system. The gas phase 6 first enters the bottom of the drying tower T180, contacts the absorbent in the tower in countercurrent, removes moisture, and then passes through the demister D1801 to remove the mist and foam entrainment, and the dry circulating gas 41 returns to the reaction system. The bottom stream 42 of the drying tower T180 is heat exchanged with the bottom stream 49 of the solvent regeneration tower T190 through the solvent regeneration tower feed preheater E1802, and then enters the upper part of the solvent regeneration tower T190. The bottom of the solvent regeneration tower T190 is heated by the solvent regeneration tower reboiler E1901; the liquid phase material 49 in the bottom of the solvent regeneration tower T190 is heat exchanged and the logistics 50 is used as the regenerated solvent, and then the logistics 51 after cooling by the solvent cooler E1801 enters the upper part of the drying tower T180; the condensate 45 of the top gas phase 44 of the solvent regeneration tower T190 is condensed by the solvent regeneration tower condenser E1902 and is divided into two streams, one of which is directly returned to the top of the solvent regeneration tower T190 as the reflux liquid 46, and the other condensate is the desorbed waste water 47. The waste water 47 goes to the top of the absorption tower T120 or the discharge device, and is treated as waste water. Typical dehydration solvents can be triethylene glycol (TEG), ethylene glycol (EG), etc. The supplementary solvent 48 preferably enters the inlet of the solvent regeneration tower reboiler E1901, and can also directly enter the top of the drying tower T180, the bottom of the drying tower T180, the bottom of the solvent regeneration tower T190, the middle of the solvent regeneration tower T190, the feed of the solvent regeneration tower T190, etc.

[0057] In order to highlight the process method for refining glyoxylic acid provided by the present invention, some heat exchangers in the process are omitted. According to the process method provided by the present invention, technicians in the relevant professional field can fully implement appropriate system internal logistics heat exchange methods according to specific device conditions, and various evolutionary process flows formed thereby should be regarded as within the spirit, scope and content of the present invention. The heat exchangers in the process diagram are for illustration only, and their specific structural types do not constitute any limitation to the present invention.

[0058] According to the process provided by the present invention, the typical operating conditions of the main equipment are:

[0059] The operating pressure range of the top of the pre-fractionation tower T110 is 60-500 kPa;

[0060] The operating pressure range of the absorption tower T120 top is 50~450kPa;

[0061] The operating pressure of the prehydrolysis kettle V1301 is 5~300kPa;

[0062] The operating pressure range of the hydrolysis tower T130 top is 5~200kPa;

[0063] The operating pressure range of the top of the concentration tower T140 is 5 to 150 kPa.

[0064] The top operating pressure range of methanol distillation tower T150 is 20~400kPa.

[0065] The operating pressure range of the top of recovery tower T160 is 3 to 150 kPa.

[0066] The top operating pressure range of tail gas absorption tower T170 is 100~300kPa.

[0067] Unless otherwise specified, all pressures in the present invention refer to absolute pressures.

[0068] According to the process provided by the present invention, the preferred operating conditions of the main equipment are:

[0069] The top operating pressure of the pre-fractionation tower T110 is 150-200 kpa, the top operating temperature is 10-60°C, and the bottom operating temperature is 15-160°C;

[0070] The top operating pressure of absorption tower T120 is 150-200 kPa, the top operating temperature is 3-45°C, and the bottom operating temperature is 5-100°C;

[0071] The operating pressure of the prehydrolysis kettle V1301 is 8-200 kPa, and the operating temperature is 35-130°C;

[0072] The top operating pressure of hydrolysis tower T130 is 8-100 kPa, the top operating temperature is 35-85°C, and the bottom operating temperature is 50-110°C;

[0073] The top operating pressure of the concentration tower T140 is 5-70 kpa, the top operating temperature is 30-90°C, and the bottom operating temperature is 35-110°C.

[0074] The top operating pressure of methanol distillation tower T150 is 30-150kpa, the top operating temperature is 35-75℃, and the bottom operating temperature is 75-120℃.

[0075] The top operating pressure of recovery tower T160 is 5-50kpa, the top operating temperature is 30-80℃, and the bottom operating temperature is 50-120℃.

[0076] The top operating pressure of the tail gas absorption tower T170 is 100-200 kpa, the top operating temperature is 10-45°C, and the bottom operating temperature is 15-70°C.

[0077] The present invention provides a device for refining glyoxylic acid, which is characterized by mainly comprising seven towers including a pre-fractionation tower T110, an absorption tower T120, a hydrolysis tower T130, a concentration tower T140, a methanol distillation tower T150, a recovery tower T160 and a tail gas absorption tower T170, as well as connecting pipelines:

[0078] The process gas supply line of the raw material methyl glyoxylate is connected to the bottom of the pre-fractionation tower T110; the process water supply lines are respectively connected to the top of the absorption tower T120 and the top of the tail gas absorption tower T170.

[0079] A circulating cooling section S1101 is arranged at the bottom of the pre-fractionation tower T110; the bottom of the pre-fractionation tower T110 is respectively connected to the hot side inlet of the pre-fractionation tower circulating cooler E1101 and the middle of the recovery tower T160, and the hot side outlet of the pre-fractionation tower circulating cooler E1101 is connected to the top of the pre-fractionation tower T110 circulating cooling section S1101; the top of the pre-fractionation tower T110 is connected to the kettle of the absorption tower T120.

[0080] The absorption tower T120 is provided with the first circulation cooling section S1201 at the bottom of the tower, the second circulation cooling section S1202, the purification section, and the third circulation cooling section S1203 at the top of the tower in sequence from bottom to top; the bottom of the absorption tower T120 is respectively connected to the hot side inlet of the first circulation cooler E1201 of the absorption tower and the top of the pre-fractionation tower T110, and the hot side outlet of the first circulation cooler E1201 of the absorption tower is connected to the first circulation cooling section S1201 of the absorption tower T120; the side line outlet under the second circulation cooling section S1202 of the absorption tower T120 is respectively connected to the second circulation cooler E1201 of the absorption tower and the third circulation cooling section S1203 of the absorption tower. The hot side inlet of the cooler E1202 is connected to the pipe inlet of the hydrolysis preheater E1301, and the hot side outlet of the second circulating cooler E1202 of the absorption tower is connected to the second circulating cooling section S1202 of the absorption tower T120; the side line outlet below the third circulating cooling section S1203 of the absorption tower T120 is connected to the hot side inlet of the third circulating cooler E1203 of the absorption tower, and the hot side outlet of the third circulating cooler E1203 of the absorption tower is connected to the top of the absorption tower T120; the top of the absorption tower T120 is respectively connected to the circulating gas production pipeline and the kettle of the tail gas absorption tower T170.

[0081] The outlet of the hydrolysis preheater E1301 is connected to the top of the prehydrolysis kettle V1301; the top and bottom outlet pipelines of the prehydrolysis kettle V1301 are respectively connected to the middle of the hydrolysis tower T130.

[0082] The bottom of the hydrolysis tower T130 is respectively connected to the inlet of the hydrolysis tower reboiler E1302 pipe side and the bottom of the concentration tower T140, and the outlet of the hydrolysis tower reboiler E1302 pipe side is connected to the bottom of the hydrolysis tower T130; the side line outlet above the feed position of the hydrolysis tower T130 is connected to the top of the pre-hydrolysis kettle V1301; the top of the hydrolysis tower T130 is connected to the hydrolysis tower condenser E1303, and the condensate outlet of the hydrolysis tower condenser E1303 is respectively connected to the top of the hydrolysis tower T130 and the middle of the methanol distillation tower T150.

[0083] The bottom of the concentrator tower T140 is respectively connected to the inlet of the concentrator tower reboiler E1401 tube side and the glyoxylic acid aqueous solution product extraction pipeline, and the outlet of the concentrator tower reboiler E1401 tube side is connected to the bottom of the concentrator tower T140; the top of the concentrator tower T140 is connected to the concentrator tower condenser E1402, and the condensate outlet of the concentrator tower condenser E1402 is respectively connected to the top of the concentrator tower T140 and the top of the absorption tower T120.

[0084] The bottom of the methanol distillation tower T150 is respectively connected to the inlet of the methanol distillation tower reboiler E1501 pipe side and the top of the prehydrolysis kettle V1301, and the outlet of the methanol distillation tower reboiler E1501 pipe side is connected to the bottom of the methanol distillation tower T150; the top of the methanol distillation tower T150 is connected to the methanol distillation tower condenser E1502, and the condensate outlet of the methanol distillation tower condenser E1502 is respectively connected to the top of the methanol distillation tower T150 and the methanol product extraction pipeline.

[0085] The bottom of the recovery tower T160 is respectively connected to the recovery tower reboiler E1601 pipe side inlet and the heavy component extraction pipeline, and the recovery tower reboiler E1601 pipe side outlet is connected to the bottom of the recovery tower T160; the top of the recovery tower T160 is connected to the recovery tower condenser E1602, and the condensate outlet of the recovery tower condenser E1602 is respectively connected to the top of the recovery tower T160 and the hydrolysis preheater E1301 pipe side inlet.

[0086] The bottom of the tail gas absorption tower T170 is connected to the inlet of the hydrolysis preheater E1301 pipe line; the top of the tail gas absorption tower T170 is connected to the purified gas production pipeline.

[0087] The invention relates to a process method and device for refining glyoxylic acid, which is a process method and device for producing a glyoxylic acid aqueous solution product through hydrolysis and concentration operations after quenching and absorbing glyoxylic acid methyl ester process gas, and producing a methanol product as a by-product. The process method and device can be perfectly combined with a process route for preparing glyoxylic acid methyl ester by oxidation of methyl glycolate, further hydrolyze and concentrate to produce glyoxylic acid, and reduce operating energy consumption to the greatest extent, thereby overcoming the defects of the prior art, having significant practicality and economic benefits, and having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 The present invention provides a typical seven-tower device for rapidly cooling and absorbing methyl glyoxylate process gas, followed by hydrolysis and concentration operations to produce a glyoxylic acid aqueous solution product and a by-product methanol product.

[0089] Figure 2 yes Figure 1 An evolutionary process method, namely deformation process method 1, is relatively Figure 1In the process provided, a second circulating cooling section S1102 is added to the lower part of the pre-fractionation tower T110, and the second circulating cooler E1102 of the pre-fractionation tower is used for cooling; a third circulating cooling section S1103 is added to the top of the pre-fractionation tower T110, and the third circulating cooler E1103 of the pre-fractionation tower is used for cooling. Figure 1 According to the provided process, the circulating cooling of the third circulating cooling section S1203 at the top of the absorption tower T120 is cancelled and replaced with a purification section.

[0090] Figure 3 yes Figure 2 An evolutionary process method, namely deformation process method 2, is relatively Figure 2 In the provided process, the circulating cooling section S1101 at the bottom of the pre-fractionation tower T110 is changed into the stripping section S1104, and the pre-fractionation tower circulating heater E1104 is used for heating; the process gas is fed between the second circulating cooling section S1102 and the stripping section S1104; the third circulating cooling section S1103 at the top of the pre-fractionation tower T110 is cancelled. By adopting this modified process method, the content of non-condensable gas and methyl glyoxylate in the discharge of the pre-fractionation tower T110 can be reduced, the yield of methyl glyoxylate at the top of the pre-fractionation tower T110 can be increased, the processing capacity of the recovery tower T160 can be reduced, the equipment investment can be reduced, and the operating energy consumption can be reduced.

[0091] Figure 4 yes Figure 1 An evolutionary process method, namely deformation process method three, is relatively Figure 1 In the provided process, the pre-fractionation tower T110 and the absorption tower T120 described in step (S1) and step (S2) can be connected in series to form one tower.

[0092] Figure 5 yes Figure 1 An evolutionary process method, namely deformation process method 4, is relatively Figure 1 In the process provided, a hydrolysis kettle V1401 is added between the hydrolysis tower T130 and the concentration tower T140. The bottom of the tail gas absorption tower T170 is changed to an absorption liquid discharge device.

[0093] Figure 6 yes Figure 1 A supplementary process method, namely deformation process method 5, is relatively Figure 1 The process provided is provided with an additional drying unit so that the gas phase 6 diverted from the top of the absorption tower T120 can be dehydrated and then returned to the reaction system. DETAILED DESCRIPTION

[0094] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but are only for illustration rather than limitation of the present invention.

[0095] Unless otherwise specified, the composition and structure of the process equipment such as tower parts, materials (connecting pipelines between tower parts, etc.), reagents, etc. not specifically used in the examples can be obtained from commercial sources or by methods known to those skilled in the art. The specific experimental methods and operating conditions involved are usually based on conventional process conditions and conditions described in the manual, or according to the conditions recommended by the manufacturer.

[0096] Application Example 1:

[0097] The typical composition of the process gas containing methyl glyoxylate from the reaction system is as follows:

[0098]

[0099] The above raw material composition range does not constitute any limitation to the present invention. The present invention can be used for the process of rapid cooling, absorption, hydrolysis and concentration of glyoxylate methyl ester process gas raw materials of various compositions to produce glyoxylic acid aqueous solution product and by-produce methanol product.

[0100] like Figure 1 As shown, the process gas 1 containing methyl glyoxylate from the methyl glycolate oxidation reaction system enters the bottom of the pre-fractionation tower T110.

[0101] A circulating cooling section S1101 is provided at the bottom of the pre-fractionation tower T110, and the pre-fractionation tower circulating cooler E1101 is used for cooling; the liquid phase material 3 in the bottom of the pre-fractionation tower T110 enters the lower part of the recovery tower T160; the gas phase 2 at the top of the pre-fractionation tower T110 enters the bottom of the absorption tower T120.

[0102] The process water 4 enters the top of the absorption tower T120; the absorption tower T120 is provided with the first circulation cooling section S1201 at the bottom of the tower, the second circulation cooling section S1202, the purification section, and the third circulation cooling section S1203 at the top of the tower from bottom to top; the first circulation cooling section S1201 at the bottom of the absorption tower T120 is cooled by the first circulation cooler E1201 of the absorption tower; the liquid phase material 9 in the bottom of the absorption tower T120 enters the top of the pre-fractionation tower T110; the second circulation cooling section S120 of the absorption tower T120 202 is cooled by the second circulating cooler E1202 of the absorption tower; the liquid material 8 taken out from the lower side line of the second circulating cooling section S1202 of the absorption tower T120 enters the hydrolysis preheater E1301; the third circulating cooling section S1203 at the top of the absorption tower T120 is cooled by the third circulating cooler E1203 of the absorption tower; the gas phase 5 at the top of the absorption tower T120 is divided into two streams, one of which is sent out as the circulating gas 6 to return to the reaction system, and the other 7 enters the kettle of the tail gas absorption tower T170.

[0103] The mixed stream 10 of the liquid material 8 produced from the side line of the second circulating cooling section S1202 of the absorption tower T120, the liquid material 33 produced from the top of the recovery tower T160 and the liquid material 37 produced from the bottom of the tail gas absorption tower T170 enters the hydrolysis preheater E1301, and the preheated stream 11 enters the prehydrolysis kettle V1301; the top gas phase 12 and the bottom liquid phase 13 of the prehydrolysis kettle V1301 respectively enter the upper part of the hydrolysis tower T130.

[0104] The bottom of the hydrolysis tower T130 is heated by the hydrolysis tower reboiler E1302; the liquid material 19 in the bottom of the hydrolysis tower T130 enters the bottom of the concentration tower T140; the liquid material 18 taken out from the side line above the feed position of the hydrolysis tower T130 enters the pre-hydrolysis kettle V1301; the condensate 15 of the top gas phase 14 of the hydrolysis tower T130 after condensation by the hydrolysis tower condenser E1303 is divided into two streams, one of which is directly returned to the top of the hydrolysis tower T130 as the reflux liquid 16, and the other condensate 17 enters the middle part of the methanol distillation tower T150.

[0105] The bottom of the concentration tower T140 is heated by the concentration tower reboiler E1401; the liquid phase material in the bottom of the concentration tower T140 is used as the delivery device of the glyoxylic acid aqueous solution product 24; the condensate 21 of the top gas phase 20 of the concentration tower T140 after condensation by the concentration tower condenser E1402 is divided into two streams, one of which is directly returned to the top of the concentration tower T140 as the reflux liquid 22, and the other condensate 23 enters the top of the absorption tower T120.

[0106] The bottom of methanol distillation tower T150 is heated by methanol distillation tower reboiler E1501; liquid material 29 in the bottom of methanol distillation tower T150 enters pre-hydrolysis kettle V1301; condensate 26 of top gas phase 25 of methanol distillation tower T150 after condensation by methanol distillation tower condenser E1502 is divided into two streams, one stream is directly returned to the top of methanol distillation tower T150 as reflux liquid 27, and the other stream of condensate is sent out of the device as methanol product 28.

[0107] The bottom of the recovery tower T160 is heated by the recovery tower reboiler E1601; the liquid phase material in the bottom of the recovery tower T160 is sent out as the heavy component 34; the condensate 31 of the top gas phase 30 of the recovery tower T160 after condensation by the recovery tower condenser E1602 is divided into two streams, one of which is directly returned to the top of the recovery tower T160 as the reflux liquid 32, and the other condensate 33 is mixed with the liquid phase material 8 taken from the side line below the second circulation cooling section S1202 of the absorption tower T120 and then enters the hydrolysis preheater E1301.

[0108] The process water 35 enters the top of the tail gas absorption tower T170; the vacuum non-condensable gas 38 in the system enters the bottom of the tail gas absorption tower T170, and the liquid phase material 37 in the bottom of the tail gas absorption tower T170 goes to the hydrolysis preheater E1301; the top gas phase of the tail gas absorption tower T170 is used as the purified gas 36 to send out the device.

[0109] The cooling medium used by the pre-fractionation tower circulating cooler E1101, the first circulating cooler of the absorption tower E1201, the second circulating cooler of the absorption tower E1202, the third circulating cooler of the absorption tower E1203, the hydrolysis tower condenser E1303, the concentration tower condenser E1402, the methanol distillation tower condenser E1502, the recovery tower condenser E1602, etc. can be circulating water, low-temperature water, chilled water or other cooling media such as low-temperature materials inside the system.

[0110] The heat sources used by the hydrolysis preheater E1301, the hydrolysis tower reboiler E1302, the concentration tower reboiler E1401, the methanol distillation tower reboiler E1501, the recovery tower reboiler E1601, etc. can be fresh steam, heat transfer oil or material steam generated inside the system.

[0111] A typical operating condition of each major device in Example 1 is given below:

[0112] The operating pressure of the pre-fractionation tower T110 is 155kpa, the top of the tower is 39℃, and the bottom of the tower is 52℃;

[0113] The top operating pressure of absorption tower T120 is 150kpa, the top temperature is 10℃, and the bottom temperature is 16℃;

[0114] The operating pressure of prehydrolysis reactor V1301 is 32 kPa and the operating temperature is 60 °C;

[0115] The top operating pressure of hydrolysis tower T130 is 30kpa, the top is 55℃, and the bottom is 73℃;

[0116] The operating pressure of the top of the concentration tower T140 is 20kpa, the top of the tower is 60℃, and the bottom of the tower is 65℃;

[0117] The operating pressure of the methanol distillation tower T150 is 50kpa, the top of the tower is 48℃, and the bottom of the tower is 83℃;

[0118] The operating pressure of the recovery tower T160 is 8kpa, the top of the tower is 38℃, and the bottom of the tower is 60℃;

[0119] The top operating pressure of tail gas absorption tower T170 is 150kpa, the top temperature is 25℃, and the bottom temperature is 35℃;

[0120] The typical content of methyl glyoxylate in the methyl glyoxylate solution in the bottom of the pre-fractionation tower T110 is about 8%.

[0121] The typical operating range of the glyoxylic acid methyl ester concentration of the side-line material 8 taken out from the lower part of the absorption tower T120 is 23%. The typical operating range of the glyoxylic acid concentration of the bottom material 19 of the hydrolysis tower T130 is 20-40%; the typical concentration of the glyoxylic acid aqueous solution product 24 in the bottom of the concentration tower T140 is 50%.

[0122] The process method and device for refining glyoxylic acid provided by the present invention can be perfectly combined with the process route of preparing glyoxylic acid methyl ester by oxidation of methyl glycolate, further hydrolyze and concentrate to produce glyoxylic acid, and reduce the operating energy consumption to the greatest extent, thereby overcoming the defects of the prior art, having significant practicality and economic benefits, and having broad application prospects.

[0123] Application Example 2:

[0124] like Figure 2 As shown, it is Figure 1 An evolutionary process method, relatively Figure 1 In the process provided, a second circulating cooling section S1102 is added to the lower part of the pre-fractionation tower T110, and the second circulating cooler E1102 of the pre-fractionation tower is used for cooling; a third circulating cooling section S1103 is added to the top of the pre-fractionation tower T110, and the third circulating cooler E1103 of the pre-fractionation tower is used for cooling. Figure 1 According to the provided process, the circulating cooling of the third circulating cooling section S1203 at the top of the absorption tower T120 is cancelled and replaced with a purification section.

[0125] Application Example 3:

[0126] like Figure 3 As shown, it is Figure 2 An evolutionary process method, relatively Figure 2 In the provided process, the circulating cooling section S1101 at the bottom of the pre-fractionation tower T110 is changed into the stripping section S1104, and the pre-fractionation tower circulating heater E1104 is used for heating; the process gas is fed between the second circulating cooling section S1102 and the stripping section S1104; the third circulating cooling section S1103 at the top of the pre-fractionation tower T110 is cancelled. By adopting this modified process method, the content of non-condensable gas and methyl glyoxylate in the discharge of the pre-fractionation tower T110 can be reduced, the yield of methyl glyoxylate at the top of the pre-fractionation tower T110 can be increased, the processing capacity of the recovery tower T160 can be reduced, the equipment investment can be reduced, and the operating energy consumption can be reduced.

[0127] Application Example 4:

[0128] like Figure 4 As shown, it is Figure 1 An evolutionary process method, relatively Figure 1 In the provided process, the pre-fractionation tower T110 and the absorption tower T120 described in step (S1) and step (S2) can be connected in series into one tower to save floor space.

[0129] Application Example 5:

[0130] like Figure 5 As shown, it is Figure 1 An evolutionary process method, relatively Figure 1In the provided process, the kettle of hydrolysis tower T130 is not heated, the hydrolysis tower reboiler E1302 is omitted, and a hydrolysis kettle V1401 is added. The liquid-phase material 19 in the kettle of hydrolysis tower T130 enters the top of hydrolysis kettle V1401; the bottom of hydrolysis kettle V1401 is heated by hydrolysis kettle reboiler E1403; the liquid-phase material 40 in the bottom of hydrolysis kettle V1401 enters the kettle of concentration tower T140; the gas-phase material 39 at the top of hydrolysis kettle V1401 enters the kettle of hydrolysis tower T130.

[0131] Application Example 6:

[0132] like Figure 6 As shown, it is Figure 1 As a further supplement to the provided process, a drying unit is added so that the gas phase 6 diverted from the top of the absorption tower T120 is dehydrated and then returned to the reaction system. The gas phase 6 first enters the bottom of the drying tower T180, contacts the absorbent in the tower in countercurrent, removes moisture, and then passes through the demister D1801 to remove the mist and foam entrainment, and the dry circulating gas 41 returns to the reaction system. The bottom stream 42 of the drying tower T180 is heat exchanged with the bottom stream 49 of the solvent regeneration tower T190 through the solvent regeneration tower feed preheater E1802, and then enters the upper part of the solvent regeneration tower T190. The bottom of the solvent regeneration tower T190 is heated by the solvent regeneration tower reboiler E1901; the liquid phase material 49 in the bottom of the solvent regeneration tower T190 is heat exchanged and the logistics 50 is used as the regenerated solvent, and then the logistics 51 after cooling by the solvent cooler E1801 enters the upper part of the drying tower T180; the condensate 45 of the top gas phase 44 of the solvent regeneration tower T190 is condensed by the solvent regeneration tower condenser E1902 and is divided into two streams, one of which is directly returned to the top of the solvent regeneration tower T190 as the reflux liquid 46, and the other condensate is the desorbed wastewater 47. The wastewater 47 goes to the top of the absorption tower T120 or the discharge device, and is treated as wastewater. Typical dehydration solvents can be triethylene glycol (TEG), ethylene glycol (EG), etc. The supplementary solvent 48 enters the inlet of the solvent regeneration tower reboiler E1901.

[0133] The present invention provides a process method and device for refining glyoxylic acid, which is a process method and device for producing a glyoxylic acid aqueous solution product after quenching and absorbing glyoxylic acid methyl ester process gas, and producing a methanol product as a by-product through hydrolysis and concentration operations. The entire device at least includes seven towers, including a pre-fractionation tower T110, an absorption tower T120, a hydrolysis tower T130, a concentration tower T140, a methanol rectification tower T150, a recovery tower T160, and a tail gas absorption tower T170, and their supporting equipment. The present invention can be perfectly combined with the process route of preparing glyoxylic acid methyl ester by oxidation of methyl glycolate, further hydrolyze and concentrate to produce glyoxylic acid, and reduce the operating energy consumption to the greatest extent, which can overcome the defects of the prior art, has significant practicality and economic benefits, and has broad application prospects.

[0134] The invention is specifically described in conjunction with the embodiments, and persons skilled in the relevant art can fully implement the technology by making appropriate changes or modifications and combinations according to the method provided by the invention. It should be particularly noted that all these similar changes or modifications and recombinations of the process provided by the invention are obvious to those skilled in the art and are considered to be within the spirit, scope and content of the invention.

Claims

1. A process for refining glyoxylic acid, characterized in that The process includes at least a pre-fractionation tower (T110), an absorption tower (T120), a hydrolysis tower (T130), a concentration tower (T140), a methanol distillation tower (T150), a recovery tower (T160) and a tail gas absorption tower (T170), and mainly includes the following steps: (S1) Pre-fractionation: The process gas containing methyl glyoxylate from the reaction system enters the lower part of the pre-fractionation tower (T110), and sequentially contacts the circulating flow at the lower part of the tower and the absorbent at the top of the tower in countercurrent to separate methyl glyoxylate from heavy components. Except for a small amount of methyl glyoxylate and water, all heavy components in the process gas are condensed and captured at the bottom of the tower and discharged from the bottom of the tower; most of the methyl glyoxylate, water and uncondensed gas phase in the process gas are discharged from the top of the pre-fractionation tower (T110); The pre-fractionation tower (T110) described in step (S1) is provided with a plurality of heat exchangers so that the heavy components are completely condensed and absorbed, and most of the methyl glyoxylate and water in the process gas are discharged from the top of the pre-fractionation tower (T110) along with the uncondensed gas phase; the pre-fractionation tower (T110) heat exchanger is arranged in the following manner: the upper part, the lower part and the tower kettle are provided with a circulating cooling section; the upper part and the lower part are provided with a circulating cooling section, and the tower kettle is provided with a stripping section; the temperature of the tower kettle of the pre-fractionation tower (T110) is 15-160° C.; (S2) Absorption: The gas phase discharged from the top of the pre-fractionation tower (T110) enters the lower part of the absorption tower (T120), and the absorption tower (T120) is provided with a plurality of circulating cooling sections. An absorbent is introduced into the top of the tower to absorb the methyl glyoxylate in the ascending gas phase in the absorption tower into the liquid phase, and the gas phase substantially free of methyl glyoxylate is discharged from the top of the tower; The methyl glyoxylate aqueous solution is discharged from the lower part of the absorption tower (T120) to the pre-hydrolysis kettle (V1301), or part of the methyl glyoxylate aqueous solution is discharged from the tower kettle of the absorption tower (T120) to the pre-hydrolysis kettle (V1301); or part of the methyl glyoxylate aqueous solution is simultaneously extracted from the lower part and the tower kettle of the absorption tower to the pre-hydrolysis kettle (V1301); the remaining material flow from the tower kettle of the absorption tower (T120) is sent to the top of the pre-fractionation tower (T110) as the reflux liquid of the pre-fractionation tower (T110); In step (S2), the absorbent is water; The absorption tower (T120) is provided with 1 to 4 circulating cooling sections, and the circulating cooling sections are provided at the top, the middle and the bottom of the tower; the bottom temperature of the absorption tower (T120) is 5 to 100° C., and the concentration of the methyl glyoxylate aqueous solution discharged from the bottom of the absorption tower (T120) to the prehydrolysis kettle (V1301) is 5 to 45%; (S3) Pre-hydrolysis: the methyl glyoxylate absorption liquid discharged from the lower part of the absorption tower (T120), the kettle liquid of the methanol distillation tower (T150), and the methyl glyoxylate recovered by the recovery tower (T160) are mixed and preheated and then enter the pre-hydrolysis kettle (V1301), and the liquid above the feed position of the hydrolysis tower (T130) also enters the pre-hydrolysis kettle (V1301); 50-99% of the methyl glyoxylate is hydrolyzed in the pre-hydrolysis kettle (V1301), and the gas and liquid phases after the pre-hydrolysis are respectively fed into the hydrolysis tower (T130); In step (S3), the operating temperature of the prehydrolysis reactor (V1301) is 35 to 150°C; (S4) hydrolysis: the unhydrolyzed methyl glyoxylate in the pre-hydrolysis reactor (V1301) is further hydrolyzed in the hydrolysis tower (T130), and a mixture of methanol, water and methyl glyoxylate is distilled off at the top of the tower, and a glyoxylic acid aqueous solution is obtained in the bottom of the tower; In step (S4), the operating temperature of the hydrolysis tower (T130) is 35 to 150° C., and the glyoxylic acid concentration in the bottom of the hydrolysis tower (T130) is 10 to 60%; (S5) Concentration: The glyoxylic acid aqueous solution from the bottom of the hydrolysis tower (T130) is further dehydrated and concentrated in the concentration tower (T140) to obtain a glyoxylic acid aqueous solution product with a qualified concentration; In step (S5), the glyoxylic acid aqueous solution in the bottom of the hydrolysis tower (T130) is concentrated to a target concentration by a single-effect concentration or a multi-effect concentration process, wherein the glyoxylic acid aqueous solution product concentration is 20 to 70%; (S6) Methanol distillation: The top material of the hydrolysis tower (T130) enters the methanol distillation tower (T150), and methanol with a purity of more than 99% is distilled from the top of the tower. The bottom of the tower is a methyl glyoxylate aqueous solution, which goes to the pre-hydrolysis kettle (V1301); (S7) Recovery: the materials in the bottom of the pre-fractionation tower (T110) enter the recovery tower (T160), the top of the recovery tower (T160) is methyl glyoxylate containing a small amount of water, and goes to the pre-hydrolysis kettle (V1301); the heavy component discharge device of the bottom of the recovery tower (T160); (S8) Tail gas absorption: Part of the gas phase from the top of the absorption tower (T120) is returned to the reaction system, and the other part is sent to the tail gas absorption tower (T170) as the purge gas. The vacuum non-condensable gas from other towers in the system also enters the tail gas absorption tower (T170). The purified gas is discharged after being purified by process water absorption, and the absorption liquid in the tower bottom is sent to the pre-hydrolysis kettle (V1301) or the discharge device.

2. The process according to claim 1, characterized in that: A hydrolysis kettle (V1401) is added between step (S4) and step (S5), that is, the materials in the bottom of the hydrolysis tower (T130) are introduced into the hydrolysis kettle (V1401) to ensure that methyl glyoxylate is completely hydrolyzed. The materials in the hydrolysis kettle (V1401) are then concentrated in step (S5) to obtain a glyoxylic acid aqueous solution product with a qualified concentration.

3. The process according to claim 1, characterized in that: The prehydrolysis kettle (V1301), the hydrolysis tower (T130) or the hydrolysis kettle (V1401) is filled with a catalyst to accelerate the hydrolysis rate of methyl glyoxylate; a heater is arranged inside the prehydrolysis kettle (V1301) to maintain a suitable hydrolysis temperature.

4. The process according to claim 1, characterized in that: The gas phase returned to the reaction system from the top of the absorption tower (T120) is first dehydrated by a drying unit and then returned to the reaction system; the drying unit is a molecular sieve adsorption dehydration, or triethylene glycol or ethylene glycol dehydration.

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