A system and method for efficient utilization of light components in maleic anhydride refining

Abstract

The present invention relates to a system and method for efficiently utilizing light components of refined maleic anhydride. According to the characteristics of the light components of refined maleic anhydride, the light components are directly extracted, and light component impurities are removed by utilizing a novel box-type overflow reactor. Crude fumaric acid and a D,L-malic acid solution are simultaneously obtained through reaction in the reactor, flash evaporation, and filtration. The crude fumaric acid is crystallized and dried to obtain a fumaric acid product, and the D,L-malic acid solution is evaporated, crystallized, and dried to obtain a D,L-malic acid product. The method can effectively remove impurities of the light components of maleic anhydride during the reaction process, and can simultaneously produce products with high added value. The production process is continuous, simple, controllable, and highly operable, and has potential for industrial application.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and in particular to a system and method for efficiently utilizing light components of refined maleic anhydride. Background Art

[0002] Maleic anhydride is an important organic chemical raw material. The current production process contains trace impurities, resulting in poor quality stability of the finished product. Therefore, the crude maleic anhydride product produced by the device needs to be distilled. Although the light fraction of the distillation is of high purity, it cannot be sold. The rational use of this component has always been a difficulty in the industry. Patent CN204932911U proposes a continuous distillation device for maleic anhydride production. The device returns the light fraction discharged from the top of the refining tower to the device for repeated distillation. This will cause problems such as increased load on the refining device and poor operational stability, ultimately leading to unstable quality of maleic anhydride products. Patent CN110665450A reports a device for removing light components in maleic anhydride production. The device can collect acrylic acid polymers, the main component of light components, to avoid polymerization due to increased acrylic acid concentration, which can block tower plates and pipelines. However, the device only removes a small amount of light component impurities, and still needs to be returned to the device for repeated distillation, affecting the operational stability of the device. Summary of the Invention

[0003] The present invention addresses the above-mentioned technical problems and proposes a system and method for efficiently utilizing light components from refined maleic anhydride. The light components from refined maleic anhydride in this method are mainly maleic anhydride with a purity of 99.7%, and other impurities mainly include acetic acid, acrylic acid, maleic acid, etc. The present invention extracts the light components as a reaction raw material for high-value-added products, fundamentally solving the problem of light component utilization. The light components are mixed with water and reacted in a new box-type overflow reactor. After the reaction, the material is discharged under pressure, and impurities in the light components and the reaction part are removed by exhaust and flash evaporation. Crude fumaric acid is rapidly precipitated due to its low solubility, and a fumaric acid product is obtained through washing and drying. The reaction mother liquor contains a large amount of D,L-malic acid, and the D,L-malic acid product is obtained through distillation, multiple crystallizations, and drying.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A system for efficiently utilizing light components from refined maleic anhydride, the system comprising a first maleic anhydride distillation tower, a second maleic anhydride distillation tower, and a reactor;

[0006] The bottom of the crude maleic anhydride raw material storage tank is connected to the middle of the first maleic anhydride distillation tower, the bottom of the first maleic anhydride distillation tower is connected to the middle of the second maleic anhydride distillation tower, the tops of the first maleic anhydride distillation tower and the second maleic anhydride distillation tower are both connected to the top of the maleic anhydride light component storage tank, and the output end of the bottom of the maleic anhydride light component storage tank is connected to the reactor through a mixing tank and a high-pressure feed pump;

[0007] The top outlet channel of the reactor is connected to the flash gas collection tank through a stop valve and an exhaust pressure-stabilizing valve, and a bubble breaker is provided at the bottom of the reactor; the discharge port of the reactor is connected to the material flash tank, and the output end at the top of the material flash tank is connected to the flash gas collection tank.

[0008] In the technical solution of the present invention, the bottom output end of the material flash tank is connected to a rotary centrifuge, one output end of the rotary centrifuge is connected to an evaporator, a crystallizer and a dryer in sequence, and the other output end is connected to the dryer through the crystallizer.

[0009] In the technical solution of the present invention, the reactor contains 3 to 8 longitudinally parallel reaction chambers, which are separated by baffles 22. An overflow baffle is provided inside the reaction chamber. A stirring device is provided at the bottom of the baffle, and a bubble breaker is provided below the stirring device.

[0010] In the technical solution of the present invention, the bubble breaker is a micron-pore tube array 24 .

[0011] In the technical solution of the present invention: the discharge port of the reactor is located at 1 / 2 to 3 / 4 of the height of the chamber baffle.

[0012] In the technical solution of the present invention, the bubble breaker is connected to the nitrogen high-pressure pump, and a defoamer is also provided on the upper part of the reactor.

[0013] A method for achieving efficient utilization of light components from maleic anhydride purification using the above system comprises the following steps:

[0014] (1) The refined light component of maleic anhydride is directly extracted into the maleic anhydride light component storage tank, and then the raw material maleic anhydride light component and water are stirred and mixed in a mixing tank and added to the reactor through a high-pressure pump;

[0015] (2) Turn on the nitrogen high-pressure pump and the exhaust stop valve, the pressure in the kettle gradually increases, and adjust the exhaust pressure-stabilizing valve to maintain the pressure in the kettle at a constant pressure of 0.1 to 2 MPa. During the exhaust process, the light component impurities of maleic anhydride and the light component impurities produced by the reaction are discharged to the flash gas collection tank along with the nitrogen, and a small amount of water vapor in the kettle is also discharged, thereby increasing the concentration of the reaction solution. After the reaction, the discharge pressure-stabilizing valve is used to control the discharge of the material at a constant pressure and constant speed in the kettle;

[0016] (3) After discharge, the concentration of D, L-malic acid in the material tank can reach 40-60%. Since the solubility of fumaric acid is extremely low, it precipitates instantly after flash evaporation, and the material is in a slurry state. The slurry enters a rotary centrifuge for solid-liquid separation. The filter residue is the crude fumaric acid product. After washing the crystallizer and drying the fumaric acid product, the filtrate is concentrated multiple times by an evaporator, crystallized by a crystallizer, and dried by a dryer to obtain the D, L-malic acid product.

[0017] In the above method: in step (1), the maleic anhydride light component and water are stirred and mixed in a mixing tank 5 at a mass ratio of 1 to 0.6:1.

[0018] In the above method: the liquid phase temperature of the reactor in step (2) is set to 160-200°C, and the reactor is heated at 0.4-1.5m 3 / h constant speed discharge.

[0019] Preferably: in step (2), the liquid phase temperature of the reactor is set to 170-190°C, and the reactor is heated at 0.75-1.5m 3 / h constant speed discharge.

[0020] In the above method: in step (2), the pressure in the kettle is maintained at a constant pressure of 0.5 to 1.2 MPa.

[0021] As a preference: in step (2), the pressure in the kettle is maintained at a constant pressure of 0.6 to 1 MPa.

[0022] In the technical solution of the present invention, the lining material of the reactor is titanium, the reactor body is heated by a steam jacket, each cavity has an independent steam temperature control, the reaction liquid flows in a curve in each cavity to increase the residence time of the reaction liquid, a stirring paddle and a bubble breaker are provided below the inner cavity wall of the reactor, the main mass transfer mode is stirring, the bubble breaker has the functions of assisting mass transfer, maintaining an inert gas atmosphere in the reactor, and taking away light component volatile impurities, etc. The bubble breaker is composed of a sintered tube containing micropores, and nitrogen is pressed into the bubble breaker by a high-pressure nitrogen pump. The gas passes through the tube to form dense bubbles with a diameter of ≤10μm. The bubbles are driven by the stirring paddle, and the reactants perform high-speed random motion in the reactor, the molecules are fully in contact with each other, the diffusion rate between molecules is increased, and thus the reaction efficiency is improved.

[0023] A vent is installed at the top of the reaction chamber to ensure uniform and stable pressure in each chamber. A demister is installed at the top of the reactor to prevent excessive foaming during the reaction. A gas outlet and a pressure-stabilizing valve are located at the top of the reactor to stabilize the pressure within the reactor and expel light impurities. The reactor discharge port is located at 1 / 2 to 3 / 4 of the chamber baffle height to prevent the discharge of large amounts of gas, which could cause pressure fluctuations and abnormal discharge. This reactor achieves efficient reactions. The reactor is in an inert gas atmosphere. The exhaust port can discharge light impurities, reducing impurity generation. During the entire reaction process, some water vapor can be discharged through the exhaust port, concentrating the solution in the reactor and reducing energy consumption for subsequent evaporation and crystallization.

[0024] In the technical solution of the present invention: the pressures mentioned are all gauge pressures.

[0025] Beneficial effects of the present invention:

[0026] The present invention uses light components as raw materials, reacts and co-produces fumaric acid and D,L-malic acid, which are high-value-added products. The light component impurity removal rate is over 95%, which significantly reduces the load of a maleic anhydride distillation device, improves the stability of the device, and reduces the quality fluctuation of the maleic anhydride product. The purity of the fumaric acid and D,L-malic acid products reaches over 99.5%, and the total molar yield of fumaric acid and D,L-malic acid reaches over 98.0%, with significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the system of the present invention.

[0028] Among them: 1. Crude maleic anhydride raw material storage tank; 2. Maleic anhydride distillation tower 1; 3. Maleic anhydride distillation tower 2; 4. Maleic anhydride light component storage tank; 5. Mixing tank; 6. High-pressure feed pump; 7. High-pressure nitrogen pump; 8. Bubble breaker; 9. Stop valve; 10. Exhaust pressure-stabilizing valve; 11. Reactor; 12. Discharge pressure-stabilizing valve; 13. Material flash tank; 14. Flash gas collection tank; 15. Rotary centrifuge; 16. Crystallizer; 17. Dryer; 18. Evaporator; 19. Crystallizer; 20. Dryer; 21. Micropore tube; 22. Baffle; 23. Overflow partition; 24 is a demister. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the embodiments, but the protection scope of the present invention is not limited thereto:

[0030] like Figure 1 , a system for efficiently utilizing light components of maleic anhydride purification, the system comprising a first maleic anhydride distillation tower 2, a second maleic anhydride distillation tower 3 and a reactor 11;

[0031] The bottom of the crude maleic anhydride raw material storage tank 1 is connected to the middle of the first maleic anhydride distillation tower 2, the bottom of the first maleic anhydride distillation tower 2 is connected to the middle of the second maleic anhydride distillation tower 3, the tops of the first maleic anhydride distillation tower 2 and the second maleic anhydride distillation tower 3 are both connected to the top of the maleic anhydride light component storage tank, and the output end of the bottom of the maleic anhydride light component storage tank is connected to the reactor 11 through a mixing tank 5 and a high-pressure feed pump 6;

[0032] The top outlet channel of the reactor 11 is connected to the flash gas collection tank 14 through a stop valve 9 and an exhaust pressure-stabilizing valve 10. A bubble breaker 8 is provided at the bottom of the reactor 11. The discharge port of the reactor 11 is connected to the material flash tank 13, and the output end at the top of the material flash tank 13 is connected to the flash gas collection tank 14.

[0033] The bottom output end of the material flash tank 13 is connected to the rotary centrifuge 15. One output end of the rotary centrifuge 15 is connected to the evaporator 18, the crystallizer 19 and the dryer 20 in sequence, and the other output end is connected to the dryer 17 through the crystallizer 16.

[0034] Reactor 11 contains six longitudinally parallel reaction chambers, separated by baffles 22. An overflow baffle 23 is installed inside the reaction chambers. A stirring device is located at the bottom of the overflow baffle, and a bubble breaker 8 is located below the stirring device. Bubble breaker 8 is connected to a high-pressure nitrogen pump 7. A defoamer is also located on the top of reactor 11.

[0035] The bubble breaker 8 is a micron-pore tube array 24. The discharge port on the top of the reactor is located at 1 / 2 of the height of the chamber baffle. The bubble breaker 8 is connected to the nitrogen high-pressure pump 7. A defoamer is also provided on the top of the reactor 11.

[0036] The method for realizing efficient utilization of light components in maleic anhydride refining by using the above system is as follows:

[0037] Example 1

[0038] Each batch of raw materials, maleic anhydride refined light component 376kg, water 565kg, were stirred and mixed in a mixing tank, and then added to the reactor through a high-pressure feed pump. The reactor liquid phase temperature was set at 170℃, and the flow rate of the material discharge was controlled at 0.75m 3 / h, open the nitrogen high-pressure pump, exhaust shut-off valve and discharge pressure regulating valve, adjust the exhaust pressure regulating valve and discharge pressure regulating valve to maintain the pressure in the kettle at 0.6MPa, and continuously discharge under this pressure condition. After discharge, collect the reaction slurry in the flash kettle, filter the reaction slurry to obtain filter residue and filtrate, the filter residue is crude fumaric acid, which is crystallized and dried to obtain fumaric acid product with a purity of 99.7%, and the filtrate is D,L-malic acid solution, which is evaporated, crystallized and dried to obtain D,L-malic acid product with a purity of 99.5%. The total molar yield of fumaric acid and D,L-malic acid is 98.4%

[0039] Example 2

[0040] Each batch of raw materials, maleic anhydride refined light component 376kg, water 565kg were stirred and mixed in a mixing tank, and then added to the reactor through a high-pressure feed pump. The reactor liquid phase temperature was set to 185℃, and the material flow rate was controlled to 1.5m 3 / h, open the nitrogen high-pressure pump, exhaust shut-off valve and discharge pressure regulating valve, adjust the exhaust pressure regulating valve and discharge pressure regulating valve to maintain the pressure in the kettle at 1.0MPa, and continuously discharge under this pressure condition. After discharge, collect the reaction slurry in the flash kettle, filter the reaction slurry to obtain filter residue and filtrate, the filter residue is crude fumaric acid, crystallize and dry to obtain fumaric acid product with a purity of 99.6%, the filtrate is D, L-malic acid solution, evaporate, crystallize and dry to obtain D, L-malic acid product with a purity of 99.5%. The total molar yield of fumaric acid and D, L-malic acid is 97.9%

[0041] Example 3

[0042] Each batch of raw materials, 446 kg of refined light components of maleic anhydride and 565 kg of water, were stirred and mixed in a mixing tank and added to the new reactor through a high-pressure feed pump. The liquid phase temperature of the reactor was set to 170 ° C and the material flow rate was controlled to 0.75 m 3 / h, open the nitrogen high-pressure pump, exhaust shut-off valve and discharge pressure regulating valve, adjust the exhaust pressure regulating valve and discharge pressure regulating valve to maintain the pressure in the kettle at 0.6MPa, and continuously discharge under this pressure condition. After discharge, collect the reaction slurry in the flash kettle, filter the reaction slurry to obtain filter residue and filtrate, the filter residue is crude fumaric acid, crystallize and dry to obtain fumaric acid product with a purity of 99.6%, the filtrate is D, L-malic acid solution, evaporate, crystallize and dry to obtain D, L-malic acid product with a purity of 99.5%. The total molar yield of fumaric acid and D, L-malic acid is 97.0%

[0043] Example 4

[0044] Each batch of raw materials, including 181 kg of refined light components of maleic anhydride, 230 kg of fumaric acid, and 565 kg of water, were stirred and mixed in a mixing tank and then added to the new reactor through a high-pressure feed pump. The liquid phase temperature of the reactor was set to 170 ° C, and the material flow rate was controlled to 0.75 m 3 / h, open the nitrogen high-pressure pump, exhaust shut-off valve and discharge pressure regulating valve, adjust the exhaust pressure regulating valve and discharge pressure regulating valve to maintain the pressure in the kettle at 0.6MPa, and continuously discharge under this pressure condition. After discharge, collect the reaction slurry in the flash kettle, filter the reaction slurry to obtain filter residue and filtrate, the filter residue is crude fumaric acid, crystallize and dry to obtain fumaric acid product with a purity of 99.5%, the filtrate is D, L-malic acid solution, evaporate, crystallize and dry to obtain D, L-malic acid product with a purity of 99.5%. The total molar yield of fumaric acid and D, L-malic acid is 98.3%

[0045] Comparative Examples 1-2

[0046] The conditions of Comparative Example 1 are the same as those of Example 1, except that the pressure control method in the kettle is different.

[0047] The conditions of Comparative Example 2 are the same as those of Example 1, except that the pressure control method in the kettle is different.

[0048]

[0049]

[0050] Comparative analysis shows that the pressure control of the reactor by the pressure-stabilizing valve can significantly improve the product purity and total molar yield, and the operation is relatively easy and controllable.

Claims

1. A system for efficiently utilizing light components from maleic anhydride purification, characterized by: The system comprises a first maleic anhydride distillation tower (2), a second maleic anhydride distillation tower (3) and a reactor (11); The bottom of the crude maleic anhydride raw material storage tank (1) is connected to the middle of the first maleic anhydride distillation tower (2), the bottom of the first maleic anhydride distillation tower (2) is connected to the middle of the second maleic anhydride distillation tower (3), the tops of the first maleic anhydride distillation tower (2) and the second maleic anhydride distillation tower (3) are both connected to the top of the maleic anhydride light component storage tank (4), and the output end of the bottom of the maleic anhydride light component storage tank is connected to the reactor (11) through a mixing tank (5) and a high-pressure feed pump (6); The top outlet channel of the reactor (11) is connected to the flash gas collection tank (14) through a stop valve (9) and an exhaust pressure stabilizing valve (10), and a bubble breaker (8) is provided at the bottom of the reactor (11); the discharge port of the reactor (11) is connected to the material flash tank (13), and the output end at the top of the material flash tank (13) is connected to the flash gas collection tank (14).

2. The system according to claim 1, wherein: The bottom output end of the material flash tank (13) is connected to the rotating centrifuge (15), and one output end of the rotating centrifuge (15) passes through the evaporator (18), the crystallizer (19) and The first output end is connected to the dryer (20), and the other output end is connected to the dryer (17) through the crystallizer (16).

3. The system according to claim 1, wherein: The reactor (11) contains 3 to 8 longitudinally parallel reaction chambers, which are separated by baffles (22). An overflow baffle (23) is provided inside the reaction chamber. A stirring device is provided at the bottom of the baffle (22), and a bubble breaker (8) is provided below the stirring device.

4. The system according to claim 1, wherein: The bubble breaker (8) is a micron-pore tube array (24).

5. The system according to claim 1, wherein: The discharge port of the reactor is located at 1 / 2~3 / 4 of the height of the chamber baffle.

6. The system according to claim 1, wherein: The bubble breaker (8) is connected to the nitrogen high-pressure pump (7), and a defoamer is also provided on the upper part of the reactor (11).

7. A method for achieving efficient utilization of light components from maleic anhydride purification using the system of claim 1, characterized in that: The method comprises the following steps: (1) The refined light component of maleic anhydride is directly pumped out to the maleic anhydride light component storage tank (4), and then the raw material maleic anhydride light component and water are stirred and mixed in a mixing tank (5), and then added to the reactor (11) through a high-pressure pump (6); (2) Open the nitrogen high-pressure pump (7) and the exhaust stop valve (9), and the pressure in the kettle gradually increases. Adjust the exhaust pressure-stabilizing valve (10) to maintain the pressure in the kettle at a constant pressure of 0.1~2Mpa. During the exhaust process, the maleic anhydride light component impurities and the light component impurities generated by the reaction are discharged to the flash gas collection tank (14) along with the nitrogen, and a small amount of water vapor in the kettle is also discharged, so that the concentration of the reaction solution is increased. After the reaction, the discharge pressure-stabilizing valve (12) is used to control the discharge of the kettle at a constant pressure and constant speed; (3) After discharge, the D,L-malic acid concentration in the material tank (13) can reach 40-60%. Since the solubility of fumaric acid is extremely low, it precipitates instantly after flash evaporation, and the material is in a slurry state. The slurry enters the rotary centrifuge (15) for solid-liquid separation. The filter residue is the crude fumaric acid product. After washing the crystallizer (16) and the dryer (17), the fumaric acid product is obtained. The filtrate is concentrated multiple times in the evaporator (18), crystallized in the crystallizer (19), and dried in the dryer (20) to obtain the D,L-malic acid product.

8. The method according to claim 7, wherein: In step (1), the maleic anhydride light component and water are stirred and mixed in a mixing tank (5) at a mass ratio of 1 to 0.6:

1.

9. The method according to claim 7, wherein: In step (2), the liquid phase temperature of the reactor is set to 160-200°C, and the reactor is heated at 0.4-1.5 m 3 / h constant speed discharge.

10. The method according to claim 9, wherein: In step (2), the liquid phase temperature of the reactor is set to 170-190°C, and the reactor is heated at 0.75-1.5 m 3 / h constant speed discharge.

11. The method according to claim 7, wherein: In step (2), the pressure in the kettle is maintained at a constant pressure of 0.5~1.2Mpa.

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