Equipment and process for dehydrating, recycling and recycling excessive alcohol in esterification reaction

Abstract

The invention provides dehydration recycling equipment and process for excessive alcohol in esterification reaction. The dehydration recycling equipment comprises a raw material pump, a first deacidification tower, a second deacidification tower, a preheater, an evaporator, a circulating pump, a heat supplementing device, a heat pump and membrane dehydration equipment. Due to the adoption of a heat pump pressurization mode, the heat pump is utilized to pressurize normal-pressure or micro-positive-pressure saturated material steam, so that the normal-pressure or micro-positive-pressure saturated material steam meets the dewatering working condition requirements of the pervaporation membrane. The pressurized raw material steam enters a pervaporation membrane for dehydration, and an anhydrous alcohol product is obtained. In the whole process, only a small amount of electric energy needs to be provided for the heat pump, public systems such as heating steam and cooling circulating water do not need to be provided externally, and stable and continuous production can be achieved. Alcohol recovered in the esterification reaction carries a small amount of organic acid, so that the service life of the inorganic molecular sieve membrane is shortened, and the organic acid in the raw materials is removed by using the deacidification tower, so that the service life of the inorganic molecular sieve membrane is ensured.

Description

Technical Field

[0001] The invention relates to the field of pharmaceutical chemicals, and in particular to a dehydration recovery device and process for excess alcohol in an esterification reaction. Background Art

[0002] In the esterification reaction, excess alcohol is added to ensure the complete reaction. After the reaction is completed and the product is extracted, this part of the excess alcohol needs to be recycled. This part of alcohol contains water produced in the esterification reaction and a small amount of unreacted or product hydrolyzed organic acid. In the recycling process, it is necessary to dehydrate and remove the organic acid. The traditional treatment solution is to use a distillation tower for dehydration and deacidification, which consumes a lot of steam. Alternatively, alkali is added to the stirred tank for neutralization, and then dehydrated with a pervaporation membrane dehydration device. The vaporization of the raw materials also consumes a lot of steam during the process, and the addition of alkali for neutralization is an intermittent operation, which cannot guarantee the continuous operation of the equipment. Summary of the invention

[0003] The present invention adopts a heat pump boosting method, and utilizes a heat pump to pressurize the saturated material steam at normal pressure or slightly positive pressure, so that it meets the requirements of the permeation vaporization membrane dehydration working condition. The pressurized raw material steam enters the permeation vaporization membrane for dehydration to obtain anhydrous alcohol products. The whole process only needs to provide a small amount of electric energy to the heat pump. After the heat pump operates normally, the steam valve of the supplementary heater is closed. No public systems such as heating steam and cooling circulating water are required to be provided by the outside world, and stable and continuous production can be achieved. Because the alcohol recovered in the esterification reaction will carry a small amount of organic acid, a large amount of inorganic molecular sieve membranes are used in the membrane dehydration equipment. This membrane has good selective permeability to water, but poor acid resistance. The organic acid in the raw material will reduce the service life of the inorganic molecular sieve membrane. The present invention utilizes a deacidification tower to remove the organic acid in the raw material, thereby ensuring the service life of the inorganic molecular sieve membrane.

[0004] The technical solution adopted by the present invention is as follows: A dehydration and recovery device for excess alcohol in an esterification reaction, comprising a deacidification tower, an evaporator, and a membrane dehydration device, wherein a heat pump is connected to the inlet pipeline of the membrane dehydration device; The heat pump is directly connected to the membrane dehydration equipment so that a relatively low-grade heat source can gasify the raw material at normal pressure; The membrane interception side of the membrane dehydration device is connected to the shell side of the evaporator to serve as a heat source for raw material gasification and to recover latent heat in product steam; The raw material is alcohol that needs to be recovered and reused after the product is extracted from the esterification reaction. It contains water produced in the esterification reaction and a small amount of unreacted or hydrolyzed organic acid, wherein the alcohol content is 85~95wt%, the water content is 5~15wt%, and the acid content is 25~60mg / L.

[0005] The liquid material enters the evaporator and is heated to become saturated steam at normal pressure or slightly positive pressure, and the unvaporized raw material is continuously transported from the bottom of the evaporator to the top through a circulating pump. The saturated material steam at normal pressure or slightly positive pressure is pressurized by a heat pump to meet the working conditions of the permeation vaporization membrane dehydration. If the raw material is directly pressurized and vaporized in the evaporator to meet the working conditions, a higher-grade heat source is required, such as water vapor.

[0006] The present invention uses a lower-grade heat source to gasify the raw material at normal pressure. The residual heat of the product after the raw material is dehydrated by the pervaporation membrane can meet the working condition requirements. Then, a small amount of mechanical energy is provided by the heat pump to pressurize it to meet the working condition requirements. In this way, the consumption of water vapor required for the entire raw material gasification process can be saved by consuming a small amount of electric energy. The material steam at normal pressure is compressed by the heat pump to meet the working condition requirements of the pervaporation membrane and molecular sieve adsorption dehydration.

[0007] The anhydrous product steam that has been dehydrated by the membrane returns to the evaporator as a heat source for raw material gasification, recovering the latent heat in the product steam.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction also includes a preheater, a circulation pump, and a supplementary heater, and the deacidification tower, the cold side of the preheater, and the bottom feed port of the evaporator are connected in sequence by pipelines; The gas phase outlet at the bottom of the evaporator, the heat pump, the membrane dehydration equipment, the evaporator shell side, and the hot side of the preheater are connected in sequence by pipelines; the liquid phase outlet at the bottom of the evaporator, the circulation pump, the supplementary heat device, and the feed inlet at the top of the evaporator are connected in sequence by pipelines.

[0010] The anhydrous product liquefied after heat exchange in the shell side of the evaporator enters the preheater to exchange heat with the liquid raw material at room temperature, fully recovering the sensible heat in the anhydrous product.

[0011] Furthermore, the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction also includes a raw material pump, which is connected to the bottom feed pipeline of the deacidification tower.

[0012] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction, the deacidification tower is filled with deacidification resin.

[0013] The deacidification tower is filled with special deacidification resin to effectively remove organic acids in the raw materials and ensure the service life of the inorganic molecular sieve membrane.

[0014] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction, the deacidification resin is T300 deacidification resin, with a particle size of 0.45-1.25 mm, a density of 0.65-0.75 g / mL, and a functional group capacity of ≥5 mmol / g.

[0015] Furthermore, in the above-mentioned dehydration and recovery device for excess alcohol in esterification reaction, the membrane dehydration device is provided with an inorganic molecular sieve membrane. The raw material steam enters the membrane dehydration device, and the water in the alcohol is removed by utilizing the selective permeability of the inorganic molecular sieve membrane.

[0016] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction, there are two deacidification towers installed in parallel, and the inlet and outlet are respectively provided with valves.

[0017] Two deacidification towers are set up, which can be switched between for maintenance and replacement of deacidification resin to ensure continuous and stable operation of the equipment.

[0018] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in esterification reaction, the pore size of the inorganic molecular sieve membrane is 0.4 nanometers.

[0019] A dehydration and recovery process for excess alcohol in an esterification reaction, using the above-mentioned dehydration and recovery equipment for excess alcohol in an esterification reaction, the water-containing alcohol vapor is compressed by a heat pump and enters a membrane dehydration device, and the selective permeability of the membrane is used to separate alcohol and water, and high-purity anhydrous product vapor is obtained from the membrane interception side, and wastewater with an alcohol content of <0.5% on the membrane permeation side is discharged from the system; The anhydrous product steam enters the shell side of the evaporator and serves as a heat source for raw material vaporization, recovering the latent heat of vaporization. It is then condensed into a liquid phase and enters the preheater, where it serves as a heat source for raw material preheating again, fully recovering and utilizing its sensible heat.

[0020] Furthermore, in the above-mentioned dehydration and recovery process for excess alcohol in the esterification reaction, the alcohol containing water is removed from a small amount of organic acid in a deacidification tower, and then enters the evaporator through a preheater. After the evaporator reaches a certain liquid level, the circulation pump is turned on, and steam is passed through the shell side of the supplementary heater for heating. When a certain amount of material steam is generated, the heat pump is turned on. After the heat pump operates normally, the steam valve is closed, and the system can operate continuously without providing steam. The certain amount here refers to the vapor pressure rising to about 10kPa.

[0021] Furthermore, in the above-mentioned dehydration and recovery process for excess alcohol in the esterification reaction, most of the raw materials are vaporized during the process of running from the top to the bottom of the evaporator, and a small part that is not vaporized is transported to the top of the evaporator again through the circulation pump.

[0022] The compressed material vapor first enters the permeation vaporization membrane for dehydration to obtain anhydrous products.

[0023] The anhydrous alcohol product after dehydration is used as a heat source for raw material gasification, and its latent heat of gasification is recovered and utilized.

[0024] The anhydrous product after latent heat liquefaction is recovered and used again as a heat source for preheating the raw materials, fully recycling its sensible heat.

[0025] The invention discloses a dehydration and recovery device for excess alcohol in an esterification reaction, which is applicable to various alcohol systems, such as ethanol, ethylene glycol, propanol, butanol and the like.

[0026] The beneficial technical effects of the present invention are as follows: (1) In the present invention, the material steam at normal pressure is compressed by a heat pump to meet the dehydration working conditions of the permeation vaporization membrane, and the dehydrated anhydrous product can also be used as a heat source to continue to heat the gasification raw material, so that no additional water vapor is used in the gasification section, and no additional circulating water is used in the product condensation section; (2) The present invention uses a deacidification tower to remove organic acids in the raw material, thereby ensuring the service life of the inorganic molecular sieve membrane. (3) The equipment structure of the present invention is simpler and the energy consumption is low. When achieving the same dehydration effect, the steam consumption of the raw material gasification and the circulating water consumption of the product cooling are reduced, which greatly saves the equipment operation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a dehydration and recovery device for excess alcohol in an esterification reaction according to the present invention; In the figure: 1. raw material pump, 2. first deacidification tower, 3. second deacidification tower, 4. preheater, 5. evaporator, 6. circulation pump, 7. supplementary heat device, 8. heat pump, 9. membrane dehydration equipment, 10. water-containing raw material inlet, 11. permeate water outlet, 12. anhydrous product outlet. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the embodiments and drawings.

[0029] A dehydration and recovery device for excess alcohol in an esterification reaction, comprising a deacidification tower, an evaporator 5, and a membrane dehydration device 9, wherein a heat pump 8 is connected to the inlet pipe of the membrane dehydration device 9; The heat pump 8 is directly connected to the membrane dehydration device 9 so that the lower-grade heat source can gasify the raw material at normal pressure; The membrane interception side of the membrane dehydration device 9 is connected to the shell side of the evaporator 5 to serve as a heat source for raw material gasification and to recover the latent heat in the product steam; The raw material is alcohol that needs to be recovered and reused after the product is extracted from the esterification reaction. It contains water produced in the esterification reaction and a small amount of unreacted or hydrolyzed organic acid, wherein the alcohol content is 85~95wt%, the water content is 5~15wt%, and the acid content is 25~60mg / L.

[0030] Furthermore, the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction also includes a preheater 4, a circulation pump 6, and a supplementary heater 7, and the deacidification tower, the cold side of the preheater 4, and the bottom feed port of the evaporator 5 are connected in sequence by pipelines; The gas phase outlet at the bottom of the evaporator 5, the heat pump 8, the membrane dehydration equipment 9, the shell side of the evaporator 5, and the hot side of the preheater 4 are connected in sequence by pipelines; the liquid phase outlet at the bottom of the evaporator 5, the circulation pump 6, the supplementary heat device 7, and the top feed port of the evaporator 5 are connected in sequence by pipelines.

[0031] Furthermore, the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction also includes a raw material pump 1, and the raw material pump 1 is connected to the bottom feed pipeline of the deacidification tower.

[0032] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction, the deacidification tower is filled with deacidification resin.

[0033] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction, the deacidification resin is T300 deacidification resin, with a particle size of 0.45-1.25 mm, a density of 0.65-0.75 g / mL, and a functional group capacity of ≥5 mmol / g.

[0034] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction, the membrane dehydration equipment 9 is provided with an inorganic molecular sieve membrane, and the pore size of the inorganic molecular sieve membrane is 0.4 nanometers.

[0035] Furthermore, in the above-mentioned dehydration and recovery equipment for excess alcohol in the esterification reaction, there are two deacidification towers installed in parallel, and the inlet and outlet are respectively provided with valves.

[0036] A dehydration and recovery process for excess alcohol in an esterification reaction, using the above-mentioned dehydration and recovery equipment for excess alcohol in an esterification reaction, the water-containing alcohol vapor is compressed by a heat pump 8 and enters a membrane dehydration device 9, and the selective permeability of the membrane is used to separate alcohol and water, and high-purity anhydrous product vapor is obtained from the membrane retention side, and wastewater with an alcohol content of <0.5% on the membrane permeation side is discharged from the system; The anhydrous product steam enters the shell side of the evaporator 5 and serves as a heat source for raw material vaporization, recovering the latent heat of vaporization. It is then condensed into a liquid phase and enters the preheater 4, where it serves as a heat source for raw material preheating again, fully recovering and utilizing its sensible heat.

[0037] Furthermore, in the above-mentioned dehydration and recovery process for excess alcohol in the esterification reaction, the alcohol containing water is removed from a small amount of organic acid in the deacidification tower, and then enters the evaporator 5 through the preheater 4. After the evaporator 5 reaches a certain liquid level, the circulation pump 6 is turned on, and at the same time, the shell side of the supplementary heat device 7 is heated by steam. When a certain amount of material steam is generated, the heat pump 8 is turned on. After the heat pump 8 operates normally, the steam valve is closed, and the system can operate continuously without providing steam. The certain amount here refers to the vapor pressure rising to about 10kPa.

[0038] Furthermore, in the above-mentioned dehydration and recovery process for excess alcohol in the esterification reaction, most of the raw materials are vaporized during the process of running from the top to the bottom of the evaporator 5, and a small amount that is not vaporized is transported to the top of the evaporator 5 again through the circulation pump 6.

[0039] The dehydration and recovery equipment for excess alcohol in esterification reaction described in any one of the above items is used for dehydration and recovery of ethanol, ethylene glycol, propanol or butanol system.

[0040] Example 1 A dehydration and recovery device for excess alcohol in an esterification reaction, comprising a raw material pump 1, a first deacidification tower 2, a second deacidification tower 3, a preheater 4, an evaporator 5, a circulation pump 6, a supplementary heater 7, a heat pump 8, and a membrane dehydration device 9; The first deacidification tower 2 and the second deacidification tower 3 are installed in parallel, and the inlet and outlet are respectively provided with valves; the raw material pump 1, the deacidification tower, the cold side of the preheater 4, and the bottom feed port of the evaporator 5 are connected in sequence by pipelines; The bottom gas phase outlet of the evaporator 5, the heat pump 8, the membrane dehydration equipment 9, the shell side of the evaporator 5, and the hot side of the preheater 4 are connected in sequence by pipelines; The liquid phase outlet at the bottom of the evaporator 5, the circulation pump 6, the supplementary heat device 7, and the feed inlet at the top of the evaporator 5 are connected in sequence by pipelines.

[0041] During the operation of the present invention, a deacidification tower is selected, the inlet and outlet valves are opened, and the water-containing alcohol is transported from the water-containing raw material inlet 10 to the deacidification tower through the raw material pump 1 to remove a small amount of organic acid, and then enters the evaporator 5 through the preheater 4. After the evaporator 5 reaches a certain liquid level, the circulation pump 6 is turned on, and at the same time, the shell side of the supplementary heater 7 is heated by steam. After a certain amount of material steam is generated, the heat pump 8 is turned on. After the heat pump 8 operates normally, the steam valve of the supplementary heater 7 is closed, and the system can operate continuously without providing steam. In the process of the raw material running from the top to the bottom of the evaporator 5, most of it is vaporized, and a small part that is not vaporized is transported to the top of the evaporator 5 again through the circulation pump 6. The certain amount here means that the vapor pressure rises to about 10kPa.

[0042] The water-containing alcohol vapor is compressed by the heat pump 8 and then enters the membrane dehydration device 9. The selective permeability of the membrane is used to separate the alcohol and water, and high-purity anhydrous product vapor is obtained from the anhydrous product outlet 12 on the membrane retention side. Wastewater with an alcohol content of <0.5% is discharged from the permeate water outlet 11 on the membrane permeation side.

[0043] The anhydrous product vapor enters the shell side of the evaporator 5 and serves as a heat source for raw material vaporization, recovering the latent heat of vaporization. It is then condensed into a liquid phase and enters the preheater 4, where it serves as a heat source for raw material preheating again, fully recovering and utilizing its sensible heat. Finally, the condensed anhydrous product is discharged from the anhydrous product outlet 12.

[0044] The whole process only needs to provide a small amount of electric energy to the heat pump 8. After the heat pump 8 operates normally, the steam valve of the supplementary heater 7 is closed. There is no need for the outside to provide public systems such as heating steam and cooling circulating water, and stable and continuous production can be achieved.

[0045] The deacidification tower needs to be filled with special deacidification resin, and the deacidification resin should be replaced regularly according to the different acidity of the material. When replacing, switch to another deacidification tower through the valve to ensure the deacidification effect of the material and the stable and continuous operation of the equipment.

[0046] Application Example 1 The project produces 20,000 tons of diethyl maleate per year and processes 50,000 tons of ethanol per year. The water content of the raw materials is 7wt.%, the ethanol content is 93wt.%, and the acetic acid content is 40~45mg / L. After passing through the deacidification tower, it is reduced to 7~10mg / L, reaching the tolerance range of the inorganic molecular sieve membrane; after membrane dehydration, the water content of the product is 0.4wt.%.

[0047] Although the present specification uses more terms such as raw material pump 1, first deacidification tower 2, second deacidification tower 3, preheater 4, evaporator 5, circulation pump 6, supplementary heat device 7, heat pump 8, membrane dehydration equipment 9, etc., it does not exclude the possibility of using other terms. These terms are used only to more conveniently describe the essence of the present invention. It is contrary to the spirit of the present invention to interpret them as any additional limitations.

[0048] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0049] It should be understood that the above description of the preferred embodiment is relatively detailed and cannot be regarded as limiting the scope of patent protection of the present invention. Under the enlightenment of the present invention, ordinary technicians in this field can also make substitutions or modifications without departing from the scope of protection of the claims of the present invention, which all fall within the scope of protection of the present invention. The scope of protection requested for the present invention shall be based on the attached claims.

Claims

1. A dehydration and recovery device for excess alcohol in esterification reaction, characterized in that: It comprises a deacidification tower, an evaporator (5), and a membrane dehydration device (9), and a heat pump (8) is connected to the inlet pipeline of the membrane dehydration device (9); The heat pump (8) is directly connected to the membrane dehydration device (9) so that a relatively low-grade heat source can be used to gasify the raw material at normal pressure; The membrane interception side of the membrane dehydration device (9) is connected to the shell side of the evaporator (5) to serve as a heat source for gasification of the raw material and to recover the latent heat in the product steam; The raw material is alcohol that needs to be recovered and reused after the product is extracted from the esterification reaction. It contains water produced in the esterification reaction and a small amount of unreacted or hydrolyzed organic acid, wherein the alcohol content is 85~95wt%, the water content is 5~15wt%, and the acid content is 25~60mg / L.

2. The dehydration and recovery equipment for excess alcohol in esterification reaction according to claim 1, characterized in that: It also includes a preheater (4), a circulation pump (6), and a supplementary heater (7), wherein the deacidification tower, the cold side of the preheater (4), and the bottom feed port of the evaporator (5) are connected in sequence by pipelines; The gas phase outlet at the bottom of the evaporator (5), the heat pump (8), the membrane dehydration device (9), the shell side of the evaporator (5), and the hot side of the preheater (4) are sequentially connected by pipelines; the liquid phase outlet at the bottom of the evaporator (5), the circulation pump (6), the supplementary heat device (7), and the feed inlet at the top of the evaporator (5) are sequentially connected by pipelines.

3. The dehydration and recovery equipment for excess alcohol in esterification reaction according to claim 1, characterized in that: It also comprises a raw material pump (1), wherein the raw material pump (1) is connected to the bottom feed pipeline of the deacidification tower.

4. The dehydration and recovery equipment for excess alcohol in esterification reaction according to claim 1, characterized in that: The deacidification tower is filled with deacidification resin.

5. The dehydration and recovery equipment for excess alcohol in esterification reaction according to claim 1, characterized in that: The membrane dehydration device (9) is provided with an inorganic molecular sieve membrane.

6. The dehydration and recovery equipment for excess alcohol in esterification reaction according to claim 1, characterized in that: There are two deacidification towers, which are installed in parallel and have valves in the inlet and outlet respectively.

7. A dehydration and recovery process for excess alcohol in an esterification reaction, characterized in that: Using the dehydration and recovery equipment for excess alcohol in the esterification reaction as described in claim 2, the water-containing alcohol vapor is compressed by a heat pump (8) and then enters a membrane dehydration device (9), and the selective permeability of the membrane is used to separate alcohol and water, and high-purity anhydrous product vapor is obtained from the membrane retention side, and wastewater with an alcohol content of less than 0.5% on the membrane permeation side is discharged from the system; The anhydrous product vapor enters the shell side of the evaporator (5) and serves as a heat source for raw material vaporization, recovering the latent heat of vaporization. It is then condensed into a liquid phase and enters the preheater (4) and serves as a heat source for raw material preheating again, fully recovering and utilizing its sensible heat. Finally, the condensed anhydrous product is discharged from the anhydrous product outlet.

8. A dehydration and recovery process for excess alcohol in esterification reaction according to claim 7, characterized in that: The alcohol containing water passes through a deacidification tower to remove a small amount of organic acid, and then passes through a preheater (4) to enter an evaporator (5). When the evaporator (5) reaches a certain liquid level, a circulation pump (6) is turned on, and steam is passed through the shell side of the supplementary heat exchanger (7) for heating. When a certain amount of material steam is generated, a heat pump (8) is turned on. After the heat pump (8) operates normally, the steam valve is closed. The system can operate continuously without providing steam.

9. A dehydration and recovery process for excess alcohol in esterification reaction according to claim 7, characterized in that: In the process of the raw material running from the top to the bottom of the evaporator (5), most of it is vaporized, and a small amount that is not vaporized is transported to the top of the evaporator (5) again through the circulation pump (6).

10. The dehydration and recovery device for excess alcohol in esterification reaction according to any one of claims 1 to 6 is used for dehydration and recovery of ethanol, ethylene glycol, propanol or butanol system.

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