A device and method for producing oxalic acid by utilizing oxalate as a byproduct of coal-to-ethylene glycol

Abstract

The present application relates to a kind of device and method for producing oxalic acid with oxalate byproduct of coal-to-ethylene glycol;Including oxalate feed tank connected with coal-to-ethylene glycol system, oxalate feed tank is connected with hydrolysis reactor with negative pressure induced draft unit, the liquid phase outlet of hydrolysis reactor is connected with oxalic acid storage tank through crystallization drying unit;The import of hydrolysis reactor is connected with raw material water tank;Hydrolysis reactor is equipped with first heat exchange jacket outside;With the advantages of simple structure, easy operation, reasonable process design, low energy consumption, low equipment purchase cost and production, low maintenance intensity in later period, not easy to occur side reaction and environment-friendly.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oxalic acid preparation, and particularly relates to a device and method for producing oxalic acid by utilizing oxalate produced in the process of producing ethylene glycol from coal. BACKGROUND

[0002] Oxalic acid, also known as ethanedioic acid, is one of the simplest organic diacids. Oxalic acid is an intermediate or necessary reagent for synthetic chemicals, and is mainly used for preparing various dyes, extractants, and intermediates of fine chemical products. In addition, oxalic acid is also a solvent for refining rare metals, a dye reducing agent, and a raw material for producing antibiotics and camphor, and has a wide market demand. Therefore, it is necessary to study and promote the production of oxalic acid.

[0003] Most domestic enterprises use sodium formate method and polysaccharide oxidation method to produce oxalic acid. However, the sodium formate method is restricted by process and environmental factors, and has been basically eliminated. The starch oxidation method uses grain crops such as corn as raw materials, and needs to be matched with a nitric acid plant, which has great cost and environmental pressure. Based on cost, market, and environmental protection, this preparation method also faces elimination. The most promising method for producing oxalic acid at present is the carbon monoxide gas phase coupling method, which mainly includes two steps: first, oxalic acid ester is generated by reacting raw material carbon monoxide with methyl nitrite or ethyl nitrite in an oxidative coupling reactor, and then oxalic acid is generated by hydrolysis reaction. In the whole production process, no other impurities or catalysts are added, so the purity of the oxalic acid product is high, and the impurities are few. The above-mentioned method uses CO, O2, methanol, and water as raw materials, and almost does not contain sulfate. However, the oxalic acid reaction prepared by the carbon monoxide oxidative carbonylation method is complex, the process is long, the investment is large, and it is not suitable for the preparation of oxalic acid alone, so it has been difficult to be large-scale industrialized. In recent years, with the large-scale production of coal-to-ethylene glycol devices, the production of by-product oxalate is increasing, and the production of oxalic acid by hydrolysis of by-product oxalate is becoming more and more industrialized. In order to solve the above problems, some enterprises try to use water to directly contact with oxalate for hydrolysis to produce oxalic acid, but the existing production system generally needs to use a packed tower, the internal structure of which is complex, the purchase cost is high, and in the use process, the use of packing increases the maintenance difficulty and increases the production cost. Moreover, the existing production system generally has problems of high energy consumption, long reaction process, easy to occur side reaction, and environmental pollution. SUMMARY

[0004] The purpose of the present application is to overcome the defects in the prior art, and to provide a device and method for producing oxalic acid by utilizing oxalate produced in the process of producing ethylene glycol from coal, which has the advantages of simple structure, convenient operation, reasonable process design, low energy consumption, low equipment purchase cost and production cost, low maintenance intensity in later period, not easy to occur side reaction, and environmental friendliness.

[0005] The purpose of the present application is to overcome the defects in the prior art, and to provide a device and method for producing oxalic acid by utilizing oxalate produced in the process of producing ethylene glycol from coal, which has the advantages of simple structure, convenient operation, reasonable process design, low energy consumption, low equipment purchase cost and production cost, low maintenance intensity in later period, not easy to occur side reaction, and environmental friendliness.

[0006] The device for producing oxalic acid by using oxalate as by-product in coal-to-ethylene glycol production comprises an oxalate feeding tank connected with a coal-to-ethylene glycol system, the oxalate feeding tank is connected with a hydrolysis reactor with a negative pressure induced draft unit, the liquid phase outlet of the hydrolysis reactor is connected with an oxalic acid storage tank through a crystallization and drying unit.

[0007] The inlet of the hydrolysis reactor is connected with a raw water tank; the outside of the hydrolysis reactor is provided with a first heat exchange jacket.

[0008] Preferably, the negative pressure induced draft unit comprises a heat exchanger connected with the gas phase outlet of the hydrolysis reactor, the first heat exchanger is connected with a gas-liquid separator, the gas phase outlet of the gas-liquid separator is connected with the gas inlet of a tail gas water washing tower through a vacuum pump.

[0009] Preferably, the liquid phase inlet of the gas-liquid separator is connected with a crude alcohol storage tank.

[0010] Preferably, the top of the tail gas water washing tower is provided with a gas discharge pipeline, the upper part of the tail gas water washing tower is provided with a water washing pipeline, and the bottom of the tail gas water washing tower is provided with a recovered water pipeline connected with the inlet of the raw water tank.

[0011] Preferably, the device further comprises a desalted water supplement pipeline connected with the water washing pipeline and the recovered water pipeline respectively.

[0012] Preferably, the crystallization and drying unit comprises a cooling crystallizer with a second heat exchange jacket connected with the liquid phase outlet of the hydrolysis reactor, the bottom outlet of the cooling crystallizer is connected with a solid-liquid separator and a dryer through a condenser, and the solid phase outlet of the dryer is connected with the oxalic acid storage tank.

[0013] Preferably, the liquid phase outlet of the solid-liquid separator is connected with the inlet of the hydrolysis reactor through a mother liquor tank; and the gas phase outlet of the dryer is connected with the gas inlet of the tail gas water washing tower.

[0014] Preferably, the hydrolysis reactor is provided with a hydrolysis reactor stirring device, and the cooling crystallizer is provided with a cooling crystallizer stirring device.

[0015] Preferably, a first regulating valve is arranged between the liquid phase outlet of the hydrolysis reactor and the cooling crystallizer, and a second regulating valve is arranged between the oxalate feeding tank and the hydrolysis reactor.

[0016] The method for producing oxalic acid by using oxalate as by-product in coal-to-ethylene glycol production comprises the following steps:

[0017] Step 1: the desalted water supplement pipeline supplements water to the raw water tank through the recovered water pipeline, so that the liquid level in the raw water tank reaches 30% to 80% of the raw water tank, and the liquid level in the raw water tank is ensured to be not lower than 30% during operation;

[0018] Step 2: The raw water in the raw water tank is sent to the hydrolysis reactor, the stirring device in the hydrolysis reactor is started, and the raw water in the hydrolysis reactor is heat-exchanged by the first heat exchange jacket, so that the temperature of the raw water is kept at 20-90℃ during operation;

[0019] Step 3: The by-product oxalate in the coal-to-ethylene glycol system enters the hydrolysis reactor through the oxalate feeding slot, and the second regulating valve is closed after the feeding is completed; the molar ratio of the oxalate to water is 1:2-5;

[0020] Step 4: The operating pressure is adjusted to 0.01-0.25 MPa by the vacuum pump and kept for 20-90 minutes, the first regulating valve is opened after the reaction is completed, and the material is sent to the cooling crystallizer; the generated methanol or ethanol is vaporized and transported to the heat exchanger by the vacuum pump for heat exchange and condensation;

[0021] Step 5: After the material enters the cooling crystallizer, the stirring device of the cooling crystallizer is started, the material in the cooling crystallizer is heat-exchanged by the second heat exchange jacket, the temperature of the material in the crystallizer is reduced to 30-40℃, and the material is kept for 10-30 minutes for crystallization, then the material is transported to the condenser and condensed to 15-25℃;

[0022] Step 6: The material condensed to 15-25℃ in step 5 is transported to the solid-liquid separator for solid-liquid separation, the solid oxalic acid is sent to the dryer for drying, and the liquid phase is sent to the mother liquor tank, which can be reused as raw water of the hydrolysis reactor in the later stage;

[0023] Step 7: The dried oxalic acid solid is sent to the oxalic acid storage tank for storage or directly packaged and stored;

[0024] Step 8: The gas phase of the dried oxalic acid solid in the dryer enters the tail gas water washing tower through the gas inlet of the tail gas water washing tower;

[0025] Step 9: The condensed methanol or ethanol in step four is sent to the gas-liquid separator for gas-liquid separation, the liquid phase after gas-liquid separation is sent to the crude alcohol storage tank for recovery, and the gas phase is transported to the gas inlet of the tail gas water washing tower by the vacuum pump;

[0026] Step 10: The dried gas phase in step 8 and the gas phase after gas-liquid separation in step 9 enter the tail gas water washing tower together, and the tail gas is washed by countercurrent contact with the desalted water in the water washing pipeline, and the washed gas phase is discharged through the gas discharge pipeline; the washed liquid phase enters the raw water tank through the bottom of the tail gas water washing tower, the recovered water pipeline and the inlet of the raw water tank for reuse.

[0027] The device and method for producing oxalic acid by-product oxalate in coal-to-ethylene glycol are prepared according to the above scheme, the first heat exchange jacket and negative pressure air induction unit arranged on the hydrolysis reactor can effectively improve the reaction speed, and avoid the methanol / ethanol from being directly evaporated and remaining in the hydrolysis reactor, thereby affecting the reaction rate and causing the occurrence of side reactions, the negative pressure provided by the negative pressure air induction unit can effectively reduce the boiling point of the methanol / ethanol, which can not only make the methanol / ethanol evaporate at a lower temperature, but also be beneficial to the recovery of the methanol / ethanol in the subsequent section, further, the stirring device arranged in the hydrolysis reactor can further improve the hydrolysis reaction efficiency and speed up the reaction process in cooperation with the working process of the first heat exchange jacket and the negative pressure air induction unit, the negative pressure air induction unit is also arranged in the application, the methanol / ethanol is recovered through secondary heat exchange, and the tail gas is transported to the water washing tower for water washing through the vacuum pump, so as to achieve the purpose of standard emission of the tail gas, further, the water washed in the water washing tower is recycled, which not only effectively saves water resources, prevents a small amount of methanol / ethanol from leaking and achieves the purpose of cyclic absorption, but also saves the purchase of subsequent treatment equipment for the water washing wastewater, meanwhile, the crystallization and drying unit is arranged in the application to achieve the purpose of rapid crystallization, drying and recovery of oxalic acid, specifically, the cooling crystallizer with the second heat exchange jacket and the stirring device is arranged to achieve rapid crystallization of the material, and the condenser is arranged to further crystallize the material, so as to improve the recovery rate of oxalic acid, meanwhile, the liquid phase in the solid-liquid separator can be recycled and utilized, and the tail gas generated by the dryer can be effectively treated, the hydrolysis reactor in the application adopts the form of the reactor, which has the characteristics of simple structure, low equipment cost, easy manufacturing and saving of later operation cost, the vacuum pump is used in the reaction process to reduce the pressure in the reactor, the methanol or ethanol generated in the reaction is evaporated from the reaction liquid at a lower temperature, which reduces energy consumption and side reactions, the tail gas is vented after water washing, which reduces pollution, the washing water can be reused as raw water, the whole reaction does not produce wastewater and waste residue, and the process is green, environmentally friendly and energy-saving, the green industrial production of oxalic acid can be realized, compared with the starch oxidation process for industrial production of oxalic acid, the following advantages are obtained: food is not used but the intermediate oxalate of coal-to-ethylene glycol is used, the raw material is cheap and easy to obtain; no supporting nitric acid production device is needed, which reduces equipment investment and energy consumption; no solid waste and wastewater are generated in the production process, the waste gas is mainly non-condensable gas, and the composition is mainly air and water, which is green, environmentally friendly and friendly to the environment; no catalyst is used in the reaction, water is not only the reaction raw material but also the solvent, which can be completely recycled and utilized, reduces impurities in the oxalic acid product, and improves the product purity; the reaction process is mild, without high temperature and high pressure conditions, which reduces the material requirement of the reaction equipment and improves the safety of the system; the methanol or ethanol generated in the hydrolysis reaction process is directly gasified, which makes the reaction continuously move in the positive direction, and the conversion rate of ammonium oxalate reaches 99.9% or more; the by-product methanol or ethanol can be directly used in the coal-to-ethylene glycol system as raw material, or can be directly sold as product, and the production cost can be reduced by 10-30% compared with the traditional process, and has good industrialization promotion prospect. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a structural schematic diagram of the present application. DETAILED DESCRIPTION

[0029] In order to have a clearer understanding of the technical features, objects and effects of the present application, the specific embodiments of the present application will be described with reference to the drawings, and the same reference numerals in the drawings represent the same parts. In order to make the drawings simple, only the parts related to the present application are shown in the drawings, which do not represent the actual structure as a product.

[0030] As shown in Figure 1 , the present application is a device and method for producing oxalic acid by using oxalate as a by-product of coal-to-ethylene glycol, wherein the device comprises an oxalate feed tank 1 connected to a coal-to-ethylene glycol system, the oxalate feed tank 1 is connected to a hydrolysis reactor 2 with a negative pressure induced air unit, the liquid phase outlet of the hydrolysis reactor 2 is connected to an oxalic acid storage tank 3 through a crystallization and drying unit; the inlet of the hydrolysis reactor 2 is connected to a raw water tank 12; the outside of the hydrolysis reactor 2 is provided with a first heat exchange jacket 4. The present application can effectively save the purchase cost, production cost, and reduce the maintenance difficulty and intensity by setting the hydrolysis reactor 2, and can effectively improve the reaction rate by setting the first heat exchange jacket 4 and the negative pressure induced air unit, and ensure that the reaction continuously moves in the positive direction, which is not only beneficial to improve the reaction rate, but also can prevent the occurrence of side reactions, and is beneficial to improve the purity of the product (can reduce the boiling point of methanol / ethanol, and make methanol / ethanol timely removed, which creates conditions for subsequent recovery), further, the above reaction process is mild, without high temperature and high pressure conditions, which not only can reduce the material requirement of the reaction equipment, but also can improve the safety and stability of the system.

[0031] Further, the negative pressure induced air unit comprises a heat exchanger 5 connected to the gas phase outlet of the hydrolysis reactor 2, the first heat exchanger 5 is connected to a gas-liquid separator 6, and the gas phase outlet of the gas-liquid separator 6 is connected to the gas inlet of a tail gas water washing tower 8 through a vacuum pump 7. By setting the negative pressure induced air unit, the methanol / ethanol in the hydrolysis reactor 2 can be removed in time to avoid affecting the hydrolysis reaction, and at the same time, the recovery of methanol / ethanol and the problem of tail gas treatment can be solved.

[0032] Further, the liquid phase inlet of the gas-liquid separator 6 is connected with the crude alcohol storage tank 9. The present application realizes the recovery of the liquid phase material by lowering the temperature of the gas under negative pressure and cooperating with the gas-liquid separator 6, so as to improve the material recovery efficiency under the condition of reducing the recovery process, further lays the foundation for the subsequent water washing recovery of the tail gas, and ensures the purpose of standard emission of the subsequent tail gas.

[0033] Further, the top of the tail gas water washing tower 8 is provided with a gas exhaust pipeline 10, the upper part of the tail gas water washing tower 8 is provided with a washing pipeline 11, and the bottom of the tail gas water washing tower 8 is provided with a recovered water pipeline 13 connected with the raw water tank 12 inlet. Through the above setting, not only the countercurrent contact of the desalinated water and the tail gas is realized to improve the washing effect, but also the recycling and recovery of the soluble gas are realized to save resources and achieve the purpose of environmental friendliness.

[0034] Further, it further includes a desalinated water supplement pipeline 14 connected with the washing pipeline 11 and the recovered water pipeline 13. The desalinated water in the present application can be supplied in a unified manner, which can ensure the effective supply of desalinated water during system operation and the effective allocation of desalinated water as a whole, not only has the advantages of convenient operation control, but also can realize the purpose of effective utilization of water resources.

[0035] Further, the crystallization and drying unit includes a cooling crystallizer 16 connected with the liquid phase outlet of the hydrolysis reaction kettle 2 and provided with a second heat jacket 15, the bottom outlet of the cooling crystallizer 16 is connected with a solid-liquid separator 18 and a dryer 19 through a condenser 17, and the solid phase outlet of the dryer 19 is connected with the oxalic acid storage tank 3. The present application realizes the crystallization and drying of the material after the hydrolysis reaction through the crystallization and drying unit, and produces oxalic acid solid; in the above process, the second heat jacket 15 and the condenser 17 are arranged to realize the uniform and rapid cooling of the material, so as to realize the purpose of rapid completion of the crystallization reaction.

[0036] Further, the liquid phase outlet of the solid-liquid separator 18 is connected with the inlet of the hydrolysis reaction kettle 2 through a mother liquor tank 20, and the gas phase outlet of the dryer 19 is connected with the gas inlet of the tail gas water washing tower 8. Through the above structure, the recovery and reuse of the mother liquor in the solid-liquid separator 18 are realized, and the gas phase outlet of the dryer 19 is connected with the tail gas water washing tower 8, which can realize the water washing of the tail gas, not only can realize the characteristics of standard emission, but also can realize the characteristics of recycling and recovery of the soluble gas.

[0037] Further, the hydrolysis reactor 2 is provided with a hydrolysis reactor stirring device 23, and the cooling crystallizer 16 is provided with a cooling crystallizer stirring device 24. By providing stirring devices in the hydrolysis reactor 2 and the cooling crystallizer 16, the mixing of the materials can be accelerated, and the reaction rate can be improved by cooperating with the corresponding auxiliary equipment.

[0038] Further, the first regulating valve 21 is arranged between the liquid phase outlet of the hydrolysis reactor 2 and the cooling crystallizer 16, and the second regulating valve 22 is arranged between the oxalate feeding tank 1 and the hydrolysis reactor 2.

[0039] A method for producing oxalic acid by utilizing oxalate as a byproduct of coal-to-ethylene glycol production, the method comprising the following steps:

[0040] Step 1: The desalination water supplement pipeline 14 supplements the raw water tank 12 through the recovery water pipeline 13, so that the liquid level in the raw water tank 12 reaches 30% to 80% of the raw water tank 12, and the liquid level in the raw water tank 12 is ensured to be not lower than 30% during operation;

[0041] Step 2: The raw water in the raw water tank 12 is sent to the hydrolysis reactor 2, the hydrolysis reactor stirring device 23 is turned on, and the raw water in the hydrolysis reactor 2 is heat-exchanged through the first heat-exchange jacket 4, so that the temperature of the raw water is ensured to be 20℃ to 90℃ during operation;

[0042] Step 3: The byproduct oxalate in the coal-to-ethylene glycol system enters the hydrolysis reactor 2 through the oxalate feeding tank 1, and the second regulating valve 22 is closed after the feeding is completed; the molar ratio of the oxalate to water is 1:2 to 5;

[0043] Step 4: The operating pressure is adjusted to 0.01 to 0.25 MPa by the vacuum pump 7, and maintained for 20 to 90 minutes, the first regulating valve 21 is opened after the reaction is completed, and the materials enter the cooling crystallizer 16; the generated methanol or ethanol is vaporized and transported to the heat exchanger 5 for heat exchange and condensation by the vacuum pump 7 during the reaction;

[0044] Step 5: After the materials enter the cooling crystallizer 16, the cooling crystallizer stirring device 24 is turned on, and the materials in the cooling crystallizer 16 are heat-exchanged through the second heat-exchange jacket 15, so that the temperature of the materials in the crystallizer is reduced to 30℃ to 40℃, and the materials are kept for 10 to 30 minutes for crystallization, and then the materials are transported to the condenser 17 and condensed to 15 to 25℃;

[0045] Step 6: The material condensed to 15-25 DEG C in step 5 is transported to the solid-liquid separator 18 for solid-liquid separation, and the oxalic acid solid after the solid-liquid separation is sent to the dryer 19 for drying, and the liquid phase is sent to the mother liquor tank 20, and the mother liquor in the mother liquor tank 20 is reused as the raw water of the hydrolysis reactor 2 later;

[0046] Step 7: The oxalic acid solid after drying in the dryer 19 is sent to the oxalic acid storage tank 3 for storage or directly packaged and stored;

[0047] Step 8: The gas phase after drying of the oxalic acid solid in the dryer 19 enters the tail gas water washing tower 8 from the gas inlet of the tail gas water washing tower 8;

[0048] Step 9: The methanol or ethanol after condensation in step four is subjected to gas-liquid separation in the gas-liquid separator 6, and the liquid phase after the gas-liquid separation is recycled into the crude alcohol storage tank 9, and the gas phase is transported to the gas inlet of the tail gas water washing tower 8 through the vacuum pump 7;

[0049] Step 10: The gas phase after drying in step 8 and the gas phase after gas-liquid separation in step 9 are jointly introduced into the tail gas water washing tower 8, and the tail gas is washed by countercurrent contact with the desalted water in the water washing pipeline 11, and the gas phase after washing is discharged through the gas discharge pipeline 10; the liquid phase after washing enters the raw water tank 12 through the bottom of the tail gas water washing tower 8, the recovered water pipeline 13 and the inlet of the raw water tank 12 for reuse.

[0050] The present application is based on the existing coal-based ethylene glycol system and realizes the reuse of the by-product oxalate, has the characteristics of wide raw material source and low production cost, reduces the consumption of food, and at the same time, the present application discards the traditional hydrolysis reaction which needs to use large consumable equipment such as packing tower, and adopts the form of reaction kettle, through the setting of the first heat exchange jacket 4, the stirring device and the negative pressure air induction unit, the full mixing of the material, the meeting of the needs of the hydrolysis reaction and the reduction of the influence of methanol / ethanol on the hydrolysis reaction can be realized, at the same time, through the setting of the negative pressure air induction unit, the recovery of methanol / ethanol and the timely treatment of the tail gas can be realized; the whole production process of the present application does not produce solid waste and waste water, the waste gas is mainly non-condensable gas, and the composition is mainly air and water, which is green and environmentally friendly; the reaction does not need to use catalyst, water is the reaction raw material and can also be used as solvent, which can realize complete recycling and utilization, reduces the impurities in the oxalic acid product, and the product purity is high; the reaction process is mild, without high temperature and high pressure conditions, which reduces the material requirement of the reaction equipment and improves the safety of the system; the methanol or ethanol generated in the hydrolysis reaction process is directly gasified, so that the reaction continuously moves in the positive direction, and the conversion rate of ammonium oxalate is more than 99.9%; the by-product methanol or ethanol can be directly used as raw material in the coal-based ethylene glycol system, or can be directly sold as product, and the production cost can be reduced by 10-30% compared with the traditional process, which has good industrialization popularization prospect.

[0051] In order to explain the application in more detail, the application will be further described in conjunction with the embodiments. The specific embodiments are as follows:

[0052] Example 1

[0053] A device for producing oxalic acid by utilizing oxalate as a byproduct of coal-to-ethylene glycol, comprising an oxalate feed tank 1 connected to a coal-to-ethylene glycol system, the oxalate feed tank 1 being connected to a hydrolysis reactor 2 with a negative pressure induced draft unit, the liquid phase outlet of the hydrolysis reactor 2 being connected to an oxalic acid storage tank 3 through a crystallization and drying unit; the inlet of the hydrolysis reactor 2 being connected to a raw water tank 12; the outside of the hydrolysis reactor 2 being provided with a first heat exchange jacket 4. The negative pressure induced draft unit comprises a heat exchanger 5 connected to the gas phase outlet of the hydrolysis reactor 2, the first heat exchanger 5 being connected to a gas-liquid separator 6, the gas phase outlet of the gas-liquid separator 6 being connected to the gas inlet of a tail gas water washing tower 8 through a vacuum pump 7. The liquid phase inlet of the gas-liquid separator 6 is connected to a crude alcohol storage tank 9. The top of the tail gas water washing tower 8 is provided with a gas discharge pipeline 10, the upper part of the tail gas water washing tower 8 is provided with a water washing pipeline 11, and the bottom of the tail gas water washing tower 8 is provided with a recovered water pipeline 13 connected to the inlet of the raw water tank 12. It further comprises a desalinated water supplement pipeline 14 connected to the water washing pipeline 11 and the recovered water pipeline 13 respectively. The crystallization and drying unit comprises a cooling crystallizer 16 with a second heat exchange jacket 15 connected to the liquid phase outlet of the hydrolysis reactor 2, the bottom outlet of the cooling crystallizer 16 being connected to a solid-liquid separator 18 and a dryer 19 through a condenser 17, the solid phase outlet of the dryer 19 being connected to the oxalic acid storage tank 3. The liquid phase outlet of the solid-liquid separator 18 is connected to the inlet of the hydrolysis reactor 2 through a mother liquor tank 20; the gas phase outlet of the dryer 19 is connected to the gas inlet of the tail gas water washing tower 8. The hydrolysis reactor 2 is provided with a hydrolysis reactor stirring device 23, and the cooling crystallizer 16 is provided with a cooling crystallizer stirring device 24. A first regulating valve 21 is arranged between the liquid phase outlet of the hydrolysis reactor 2 and the cooling crystallizer 16, and a second regulating valve 22 is arranged between the oxalate feed tank 1 and the hydrolysis reactor 2.

[0054] A method for producing oxalic acid by utilizing oxalate as a byproduct of coal-to-ethylene glycol, comprising the following steps:

[0055] Step 1: The desalinated water supplement pipeline 14 supplements water to the raw water tank 12 through the recovered water pipeline 13, so that the liquid level in the raw water tank 12 reaches 30% to 50% of the raw water tank 12, and the liquid level in the raw water tank 12 is ensured to be not lower than 30% during operation;

[0056] Step 2: The raw water in the raw water tank 12 is sent to the hydrolysis reactor 2, the hydrolysis reactor stirring device 23 is turned on at the same time, and the raw water in the hydrolysis reactor 2 is heat exchanged through the first heat exchange jacket 4, so that the temperature of the raw water is ensured to be 20℃ during operation;

[0057] Step 3: The byproduct oxalate in the coal-to-ethylene glycol system enters the hydrolysis reactor 2 through the oxalate feed tank 1, and the second regulating valve 22 is closed after the feeding is completed; the molar ratio of the oxalate to water is 1:2;

[0058] Step 4: The operating pressure is adjusted to 0.01 MPa by the vacuum pump 7, and maintained for 90 minutes, and the first regulating valve 21 is opened after the reaction is completed, and the material enters the cooling crystallizer 16; the methanol or ethanol generated during the reaction is vaporized and transported to the heat exchanger 5 by the vacuum pump 7 for heat exchange and condensation;

[0059] Step 5: After the material enters the cooling crystallizer 16, the cooling crystallizer stirring device 24 is turned on, and the material in the cooling crystallizer 16 is heat exchanged by the second heat exchange jacket 15 to reduce the temperature of the material in the crystallizer to 30℃, and the material is crystallized for 10 minutes, and after the crystallization of the material in the cooling crystallizer 16 is completed, the material is transported to the condenser 17 and condensed to 15℃;

[0060] Step 6: The material condensed to 15℃ in step 5 is transported to the solid-liquid separator 18 for solid-liquid separation, the solid oxalic acid is sent to the dryer 19 for drying, and the liquid phase is sent to the mother liquor tank 20, and the mother liquor in the mother liquor tank 20 can be reused as the raw water of the hydrolysis reactor 2 in the later stage;

[0061] Step 7: The solid oxalic acid is dried in the dryer 19 and then sent to the oxalic acid storage tank 3 for storage or directly packaged and stored;

[0062] Step 8: The gas phase of the solid oxalic acid dried in the dryer 19 enters the tail gas water washing tower 8 through the gas inlet of the tail gas water washing tower 8;

[0063] Step 9: The condensed methanol or ethanol in step four is subjected to gas-liquid separation in the gas-liquid separator 6, the liquid phase after gas-liquid separation is recycled into the crude alcohol storage tank 9, and the gas phase is transported to the gas inlet of the tail gas water washing tower 8 through the vacuum pump 7;

[0064] Step 10: The gas phase after drying in step 8 and the gas phase after gas-liquid separation in step 9 enter the tail gas water washing tower 8 together, and the desalted water in the water washing pipeline 11 is countercurrently contacted to wash the tail gas, and the gas phase after washing is discharged through the gas discharge pipeline 10; the liquid phase after washing enters the raw water tank 12 through the bottom of the tail gas water washing tower 8, the recovered water pipeline 13 and the inlet of the raw water tank 12 for reuse.

[0065] Example 2

[0066] The utility model relates to a device for producing oxalic acid by using oxalate byproduct of coal-to-ethylene glycol, which comprises an oxalate feeding tank 1 connected with a coal-to-ethylene glycol system, the oxalate feeding tank 1 is connected with a hydrolysis reactor 2 with a negative pressure induced draft unit, the liquid phase outlet of the hydrolysis reactor 2 is connected with an oxalic acid storage tank 3 through a crystallization and drying unit; the inlet of the hydrolysis reactor 2 is connected with a raw water tank 12; the outside of the hydrolysis reactor 2 is provided with a first heat exchange jacket 4. The negative pressure induced draft unit comprises a heat exchanger 5 connected with the gas phase outlet of the hydrolysis reactor 2, the first heat exchanger 5 is connected with a gas-liquid separator 6, the gas phase outlet of the gas-liquid separator 6 is connected with the gas inlet of a tail gas water washing tower 8 through a vacuum pump 7. The liquid phase inlet of the gas-liquid separator 6 is connected with a crude alcohol storage tank 9. The top of the tail gas water washing tower 8 is provided with a gas discharge pipeline 10, the upper part of the tail gas water washing tower 8 is provided with a water washing pipeline 11, and the bottom of the tail gas water washing tower 8 is provided with a recovered water pipeline 13 connected with the inlet of the raw water tank 12. The device further comprises a desalted water supplement pipeline 14 connected with the water washing pipeline 11 and the recovered water pipeline 13 respectively. The crystallization and drying unit comprises a cooling crystallizer 16 connected with the liquid phase outlet of the hydrolysis reactor 2 and provided with a second heat exchange jacket 15, the bottom outlet of the cooling crystallizer 16 is connected with a solid-liquid separator 18 and a dryer 19 through a condenser 17, and the solid phase outlet of the dryer 19 is connected with the oxalic acid storage tank 3. The liquid phase outlet of the solid-liquid separator 18 is connected with the inlet of the hydrolysis reactor 2 through a mother liquor tank 20, and the gas phase outlet of the dryer 19 is connected with the gas inlet of the tail gas water washing tower 8. The hydrolysis reactor 2 is provided with a hydrolysis reactor stirring device 23, and the cooling crystallizer 16 is provided with a cooling crystallizer stirring device 24. A first regulating valve 21 is arranged between the liquid phase outlet of the hydrolysis reactor 2 and the cooling crystallizer 16, and a second regulating valve 22 is arranged between the oxalate feeding tank 1 and the hydrolysis reactor 2.

[0067] A method for producing oxalic acid by using oxalate byproduct of coal-to-ethylene glycol, which comprises the following steps:

[0068] Step 1: the desalted water supplement pipeline 14 supplements water to the raw water tank 12 through the recovered water pipeline 13, so that the liquid level in the raw water tank 12 reaches 30% to 60% of the raw water tank 12, and the liquid level in the raw water tank 12 is ensured to be not lower than 30% during operation;

[0069] Step 2: the raw water in the raw water tank 12 is sent to the hydrolysis reactor 2, the hydrolysis reactor stirring device 23 is started at the same time, and the raw water in the hydrolysis reactor 2 is heat exchanged through the first heat exchange jacket 4, so that the temperature of the raw water is ensured to be 90℃ during operation;

[0070] Step 3: the byproduct oxalate in the coal-to-ethylene glycol system enters the hydrolysis reactor 2 through the oxalate feeding tank 1, the second regulating valve 22 is closed after the feeding is completed; the molar ratio of the oxalate and water is 1:5;

[0071] Step 4: Adjust the vacuum pump 7 to make the operating pressure 0.25 MPa, and keep for 20 minutes, after the reaction is finished, open the first regulating valve 21, and make the material enter the cooling crystallizer 16; the methanol or ethanol generated in the reaction is vaporized and transported to the heat exchanger 5 by the vacuum pump 7 to exchange heat and condense;

[0072] Step 5: After the material enters the cooling crystallizer 16, open the cooling crystallizer stirring device 24, and exchange heat of the material in the cooling crystallizer 16 through the second heat exchange jacket 15, so that the temperature of the material in the crystallizer is reduced to 40℃, and keep for 30 minutes, after the material in the cooling crystallizer 16 is crystallized, the material is transported to the condenser 17 and condensed to 25℃;

[0073] Step 6: The material condensed to 25℃ in step 5 is transported to the solid-liquid separator 18 for solid-liquid separation, the oxalic acid solid after solid-liquid separation is sent to the dryer 19 for drying, and the liquid phase is sent to the mother liquor tank 20, the mother liquor in the mother liquor tank 20 can be reused as the raw material water of the hydrolysis reaction kettle 2 in the later stage;

[0074] Step 7: The oxalic acid solid after drying in the dryer 19 is sent to the oxalic acid storage tank 3 for storage or directly packaged and stored;

[0075] Step 8: The gas phase of the oxalic acid solid after drying in the dryer 19 enters the tail gas water washing tower 8 from the gas inlet of the tail gas water washing tower 8;

[0076] Step 9: The methanol or ethanol condensed in step four is made to enter the gas-liquid separator 6 for gas-liquid separation, the liquid phase after gas-liquid separation enters the crude alcohol storage tank 9 for recovery, and the gas phase is transported to the gas inlet of the tail gas water washing tower 8 by the vacuum pump 7;

[0077] Step 10: The gas phase after drying in step 8 and the gas phase after gas-liquid separation in step 9 enter the tail gas water washing tower 8 together, and are countercurrently contacted with the desalted water in the water washing pipeline 11 to wash the tail gas, the gas phase after washing is discharged through the gas discharge pipeline 10; the liquid phase after washing enters the raw material water tank 12 through the bottom of the tail gas water washing tower 8, the recovered water pipeline 13 and the inlet of the raw material water tank 12 for reuse.

[0078] Example 3

[0079] The utility model relates to a device for producing oxalic acid by using oxalate byproduct of coal-to-ethylene glycol, which comprises an oxalate feeding tank 1 connected with a coal-to-ethylene glycol system, the oxalate feeding tank 1 is connected with a hydrolysis reactor 2 with a negative pressure induced draft unit, the liquid phase outlet of the hydrolysis reactor 2 is connected with an oxalic acid storage tank 3 through a crystallization and drying unit; the inlet of the hydrolysis reactor 2 is connected with a raw water tank 12; the hydrolysis reactor 2 is externally provided with a first heat exchange jacket 4. The negative pressure induced draft unit comprises a heat exchanger 5 connected with the gas phase outlet of the hydrolysis reactor 2, the first heat exchanger 5 is connected with a gas-liquid separator 6, the gas phase outlet of the gas-liquid separator 6 is connected with the gas inlet of a tail gas water washing tower 8 through a vacuum pump 7. The liquid phase inlet of the gas-liquid separator 6 is connected with a crude alcohol storage tank 9. The top of the tail gas water washing tower 8 is provided with a gas discharge pipeline 10, the upper part of the tail gas water washing tower 8 is provided with a water washing pipeline 11, and the bottom of the tail gas water washing tower 8 is provided with a recovered water pipeline 13 connected with the inlet of the raw water tank 12. The device further comprises a desalted water supplement pipeline 14 connected with the water washing pipeline 11 and the recovered water pipeline 13 respectively. The crystallization and drying unit comprises a cooling crystallizer 16 connected with the liquid phase outlet of the hydrolysis reactor 2 and provided with a second heat exchange jacket 15, the bottom outlet of the cooling crystallizer 16 is connected with a solid-liquid separator 18 and a dryer 19 through a condenser 17, and the solid phase outlet of the dryer 19 is connected with the oxalic acid storage tank 3. The liquid phase outlet of the solid-liquid separator 18 is connected with the inlet of the hydrolysis reactor 2 through a mother liquor tank 20, and the gas phase outlet of the dryer 19 is connected with the gas inlet of the tail gas water washing tower 8. The hydrolysis reactor 2 is provided with a hydrolysis reactor stirring device 23, and the cooling crystallizer 16 is provided with a cooling crystallizer stirring device 24. A first regulating valve 21 is arranged between the liquid phase outlet of the hydrolysis reactor 2 and the cooling crystallizer 16, and a second regulating valve 22 is arranged between the oxalate feeding tank 1 and the hydrolysis reactor 2.

[0080] A method for producing oxalic acid by using oxalate byproduct of coal-to-ethylene glycol, which comprises the following steps:

[0081] Step 1: The desalted water supplement pipeline 14 supplements water to the raw water tank 12 through the recovered water pipeline 13, so that the liquid level in the raw water tank 12 reaches 30% to 80% of the raw water tank 12, and the liquid level in the raw water tank 12 is ensured to be not lower than 30% during operation;

[0082] Step 2: The raw water in the raw water tank 12 is sent to the hydrolysis reactor 2, the hydrolysis reactor stirring device 23 is started at the same time, and the raw water in the hydrolysis reactor 2 is heat exchanged through the first heat exchange jacket 4, so that the temperature of the raw water is ensured to be 55℃ during operation;

[0083] Step 3: The byproduct oxalate in the coal-to-ethylene glycol system enters the hydrolysis reactor 2 through the oxalate feeding tank 1, the second regulating valve 22 is closed after the feeding is completed; the molar ratio of the oxalate and water is 1:3.5;

[0084] Step 4: Adjust the vacuum pump 7 to make the operating pressure 0.13 MPa, and keep for 50 minutes, after the reaction is completed, open the first regulating valve 21, and make the material enter the cooling crystallizer 16; the methanol or ethanol generated during the reaction is vaporized and transported to the heat exchanger 5 by the vacuum pump 7 for heat exchange and condensation;

[0085] Step 5: After the material enters the cooling crystallizer 16, the cooling crystallizer stirring device 24 is started, and the material in the cooling crystallizer 16 is heat exchanged by the second heat exchange jacket 15 to make the temperature of the material in the crystallizer drop to 35℃, and keep crystallization for 20 minutes, after the crystallization of the material in the cooling crystallizer 16 is completed, the material is transported to the condenser 17 and condensed to 20℃;

[0086] Step 6: The material condensed to 20℃ in step 5 is transported to the solid-liquid separator 18 for solid-liquid separation, the solid oxalic acid is sent to the dryer 19 for drying, and the liquid phase is sent to the mother liquor tank 20, the mother liquor in the mother liquor tank 20 can be reused as the raw material water of the hydrolysis reactor 2 in the later stage;

[0087] Step 7: After the oxalic acid solid is dried in the dryer 19, it is sent to the oxalic acid storage tank 3 for storage or directly packaged and stored;

[0088] Step 8: The gas phase of the oxalic acid solid dried in the dryer 19 enters the tail gas water washing tower 8 through the gas inlet of the tail gas water washing tower 8;

[0089] Step 9: The methanol or ethanol condensed in step four is made to enter the gas-liquid separator 6 for gas-liquid separation, the liquid phase after gas-liquid separation enters the crude alcohol storage tank 9 for recovery, and the gas phase is transported to the gas inlet of the tail gas water washing tower 8 through the vacuum pump 7;

[0090] Step 10: The gas phase after drying in step 8 and the gas phase after gas-liquid separation in step 9 enter the tail gas water washing tower 8 together, and are countercurrently contacted with the desalted water in the water washing pipeline 11 to wash the tail gas, the gas phase after washing is discharged through the gas discharge pipeline 10; the liquid phase after washing enters the raw water tank 12 through the bottom of the tail gas water washing tower 8, the recovered water pipeline 13 and the inlet of the raw water tank 12 for reuse.

[0091] In the description of the present application, it should be noted that unless specifically stated and limited otherwise, the terms "connected", "connected", and the like should be understood broadly, for example, can be fixedly connected, integrally connected, or detachably connected; can be internal communication of two elements; can be directly connected, or indirectly connected through an intermediate medium; for those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. The above examples are only specific descriptions of the feasible embodiments of the present application, and they are not intended to limit the protection scope of the present application. Any equivalent embodiments, changes and modifications made without departing from the spirit of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing oxalic acid using coal-to-ethylene glycol coproduct oxalate, the method comprising: The method comprises the following steps: ​ Step 1: the desalted water supplement pipeline (14) supplements the raw water tank (12) through the recovery water pipeline (13), so that the liquid level in the raw water tank (12) reaches 30% to 80% of the raw water tank (12), and the liquid level in the raw water tank (12) is ensured to be not lower than 30% during operation; Step 2: the raw water in the raw water tank (12) is sent to the hydrolysis reaction kettle (2), and the hydrolysis reaction kettle stirring device (23) is started at the same time, and the raw water in the hydrolysis reaction kettle (2) is heat-exchanged through the first heat exchange jacket (4), so that the temperature of the raw water is ensured to be 20℃ to 90℃ during operation; Step 3: the by-product oxalate ester in the coal-to-ethylene glycol system enters the hydrolysis reaction kettle (2) through the oxalate ester feeding groove (1), and the second adjusting valve (22) is closed after the feeding is completed; the molar ratio of the oxalate ester and water is 1:2 to 5; Step 4: the operation pressure of the vacuum pump (7) is adjusted to be 0.01 to 0.25 MPa, and is kept for 20 to 90 minutes, the first adjusting valve (21) is opened after the reaction is completed, and the material enters the cooling crystallizer (16); the generated methanol or ethanol is vaporized, is transported to the heat exchanger (5) through the vacuum pump (7), and is heat-exchanged and condensed; Step 5: after the material enters the cooling crystallizer (16), the cooling crystallizer stirring device (24) is started, the material in the cooling crystallizer (16) is heat-exchanged through the second heat exchange jacket (15), the temperature of the material in the crystallizer is reduced to 30℃ to 40℃, and the material is kept for 10 to 30 minutes for crystallization, after the crystallization of the material in the cooling crystallizer (16) is completed, the material is transported to the condenser (17) and is condensed to 15 to 25℃; Step 6: the material condensed to 15 to 25℃ in step 5 is transported to the solid-liquid separator (18) for solid-liquid separation, the solid oxalic acid after the solid-liquid separation is sent to the dryer (19) for drying, and the liquid phase is sent to the mother liquor tank (20); the mother liquor in the mother liquor tank (20) can be reused as raw water of the hydrolysis reaction kettle (2) in the later period; Step 7: the solid oxalic acid after the drying in the dryer (19) is sent to the oxalic acid storage tank (3) for storage or is directly packaged and stored; Step 8: the gas phase of the solid oxalic acid after the drying in the dryer (19) enters the tail gas water washing tower (8) through the gas inlet of the tail gas water washing tower (8); Step 9: the condensed methanol or ethanol in step four is sent to the gas-liquid separator (6) for gas-liquid separation, the liquid phase after the gas-liquid separation is sent to the crude alcohol storage tank (9) for recovery, and the gas phase is transported to the gas inlet of the tail gas water washing tower (8) through the vacuum pump (7); Step 10: the gas phase after the drying in step 8 and the gas phase after the gas-liquid separation in step 9 enter the tail gas water washing tower (8) together, and are countercurrently contacted with the desalted water in the water washing pipeline (11) to wash the tail gas, the gas phase after the washing is discharged through the gas discharge pipeline (10); the liquid phase after the washing is discharged through the bottom of the tail gas water washing tower (8), the recovery water pipeline (13) and the inlet of the raw water tank (12), and is reused in the raw water tank (12).

2. The method for producing oxalic acid by-product oxalate from coal-to-glycol according to claim 1, characterized in that: It comprises an oxalate feeding tank (1) connected with a coal-to-ethylene glycol system, the oxalate feeding tank (1) is connected with a hydrolysis reactor (2) with a negative pressure induced draft unit, the liquid phase outlet of the hydrolysis reactor (2) is connected with an oxalic acid storage tank (3) through a crystallization and drying unit; The inlet of the hydrolysis reactor (2) is connected with a raw water tank (12); the outside of the hydrolysis reactor (2) is provided with a first heat exchange jacket (4); The negative pressure induced draft unit comprises a heat exchanger (5) connected with the gas phase outlet of the hydrolysis reactor (2), the first heat exchanger (5) is connected with a gas-liquid separator (6), the gas phase outlet of the gas-liquid separator (6) is connected with the gas inlet of a tail gas water washing tower (8) through a vacuum pump (7).

3. The method for producing oxalic acid by using coal-to-ethylene glycol by-product oxalate according to claim 2, characterized in that: The liquid phase inlet of the gas-liquid separator (6) is connected with a crude alcohol storage tank (9).

4. The method for producing oxalic acid by using coal-to-ethylene glycol by-product oxalate according to claim 2, characterized in that: The top of the tail gas water washing tower (8) is provided with a gas discharge pipeline (10), the upper part of the tail gas water washing tower (8) is provided with a water washing pipeline (11), and the bottom of the tail gas water washing tower (8) is provided with a recovered water pipeline (13) connected with the inlet of the raw water tank (12).

5. The method for producing oxalic acid with oxalate as by-product in the production of ethylene glycol from coal according to claim 2, characterized in that: It also comprises a desalinated water supplement pipeline (14) connected with the water washing pipeline (11) and the recovered water pipeline (13) respectively.

6. The method for producing oxalic acid with oxalate as by-product in the production of ethylene glycol from coal according to claim 2, characterized in that: The crystallization and drying unit comprises a cooling crystallizer (16) connected with the liquid phase outlet of the hydrolysis reactor (2) and provided with a second heat exchange jacket (15), the bottom outlet of the cooling crystallizer (16) is connected with a solid-liquid separator (18) and a dryer (19) through a condenser (17), and the solid phase outlet of the dryer (19) is connected with the oxalic acid storage tank (3).

7. The method for producing oxalic acid with oxalate as by-product in the production of ethylene glycol from coal according to claim 6, characterized in that: The liquid phase outlet of the solid-liquid separator (18) is connected with the inlet of the hydrolysis reactor (2) through a mother liquor tank (20); and the gas phase outlet of the dryer (19) is connected with the gas inlet of the tail gas water washing tower (8).

8. The method for producing oxalic acid with oxalate as by-product in the production of ethylene glycol from coal according to claim 6, characterized in that: The hydrolysis reactor (2) is provided with a hydrolysis reactor stirring device (23), and the cooling crystallizer (16) is provided with a cooling crystallizer stirring device (24).

9. The method for producing oxalic acid with oxalate as by-product from coal-to-ethylene glycol according to claim 6, characterized in that: A first regulating valve (21) is arranged between the liquid phase outlet of the hydrolysis reactor (2) and the cooling crystallizer (16), and a second regulating valve (22) is arranged between the oxalate feeding tank (1) and the hydrolysis reactor (2). A first regulating valve (21) is arranged between the liquid phase outlet of the hydrolysis reactor (2) and the cooling crystallizer (16), and a second regulating valve (22) is arranged between the oxalate feeding tank (1) and the hydrolysis reactor (2).

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