MVR evaporation crystallization system for itaconic acid production

Abstract

The utility model relates to a kind of MVR evaporation crystallization system for itaconic acid production, including one-effect evaporator, two-effect evaporator, first steam compressor and second steam compressor, second steam compressor is compressed to the secondary steam after the temperature of first steam compressor compression, and the temperature and pressure of the compressed steam of second steam compressor are greater than the temperature and pressure of the compressed steam of first steam compressor, the compressed steam of first steam compressor is heated and evaporated as the heat source of one-effect evaporator to material, the compressed steam of second steam compressor is heated and evaporated as the heat source of two-effect evaporator to the material after evaporation concentration of one-effect evaporator, one-effect evaporator is multi-tube process falling film evaporator, and two-effect evaporator is forced circulation evaporator, one-effect evaporator and two-effect evaporator can make material have sufficient effective heat exchange temperature difference and evaporation intensity when different concentration, to effectively improve evaporation rate, reduce steam consumption, reduce concentration cost.

Description

Technical Field

[0001] This utility model relates to the technical field of itaconic acid production equipment, specifically to an MVR evaporation crystallization system for itaconic acid production. Background Technology

[0002] Itaconic acid, also known as methylene succinic acid, is an unsaturated acid containing conjugated double bonds and two carboxyl groups. It has been recognized as one of the top 12 value-added chemicals derived from biomass. At room temperature, it is a white crystalline powder or chemical book powder with a melting point of 165-168℃ and a specific gravity of 1.632. It is soluble in water, ethanol, and other solvents. Itaconic acid exhibits active chemical properties and can undergo various addition, esterification, and polymerization reactions.

[0003] Itaconic acid contains one unsaturated double bond and two active carboxyl groups, enabling it to undergo many chemical reactions. This also determines its wide range of applications. It is an industrial raw material for the production of chemical fibers such as acrylic fiber, synthetic resins, plastics, rubber, pharmaceuticals, surfactants, non-toxic food packaging materials, herbicides, descaling agents, dental adhesives, and more.

[0004] Currently, itaconic acid is generally produced using fermentation methods both domestically and internationally. This method mainly includes fermentation broth cultivation, separation of bacterial cells to obtain itaconic acid fermentation broth, ion exchange and activated carbon decolorization of the obtained itaconic acid fermentation broth to obtain itaconic acid filtrate, and evaporation concentration, coarse crystallization, and fine crystallization of the obtained itaconic acid filtrate to finally obtain itaconic acid crystals.

[0005] Currently, multi-effect continuous evaporation technology is commonly used for the evaporation and concentration of itaconic acid filtrate. For example, the Chinese utility model patent with patent number ZL201320636320.7, entitled "Energy-saving Four-Effect Concentration and Crystallization Device for Itaconic Acid," connects four evaporators in series according to the flow direction of the itaconic acid filtrate. The secondary steam separated from the previous evaporator enters the heater of the next evaporator and is used as the heat source for the heater of the next evaporator. Using live steam as the heat source, the itaconic acid filtrate is heated, evaporated, and concentrated using the four-effect evaporator to increase the concentration of the itaconic acid filtrate and provide conditions for the subsequent crystallization process. However, this multi-effect continuous evaporation technology has a large steam consumption, low energy utilization rate, and high concentration cost. Utility Model Content

[0006] In summary, to overcome the shortcomings of existing technologies, this utility model provides an MVR evaporation and crystallization system for itaconic acid production. It utilizes mechanical vapor recompression technology to evaporate and concentrate itaconic acid filtrate under vacuum conditions. The evaporation process, which combines a multi-pass falling film evaporator with a forced circulation evaporator, ensures that the material has sufficient effective heat exchange temperature difference and evaporation intensity at different concentrations, thereby effectively improving the evaporation rate, reducing steam consumption, and lowering concentration costs.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0008] An MVR evaporation crystallization system for itaconic acid production, comprising:

[0009] The feeding device includes a material tank for storing itaconic acid filtrate and a feed pump whose inlet is connected to the material tank.

[0010] The first-effect evaporator has its inlet connected to the outlet of the feed pump, its outlet connected to the inlet of the second-effect evaporator, its air inlet connected to the outlet of the first steam compressor, and its secondary steam outlet connected to the air inlet of the scrubbing tower.

[0011] The double-effect evaporator has its outlet connected to the inlet of the discharge pump, which in turn connects to the crystal slurry discharge pipeline. The inlet of the double-effect evaporator is connected to the outlet of the second steam compressor, and the secondary steam outlet of the double-effect evaporator is connected to the inlet of the scrubbing tower.

[0012] The scrubbing tower is used to wash the secondary steam separated from the first-effect evaporator and the second-effect evaporator. The outlet of the scrubbing tower is connected to the inlet of the first steam compressor, and the outlet of the scrubbing tower is connected to the feed inlet of the first-effect evaporator.

[0013] The first steam compressor is used to compress the secondary steam after cleaning in the scrubbing tower, increasing its pressure and temperature into high-grade compressed steam. The outlet of the first steam compressor is connected to the inlet of the second steam compressor and the inlet of the first-effect evaporator.

[0014] The second steam compressor is used to compress the compressed steam already compressed by the first steam compressor, further pressurizing and heating it.

[0015] A steam source is provided, which is connected via steam delivery pipelines to the air supply port of the first steam compressor, the air supply port of the second steam compressor, and the air inlet of the first-effect evaporator.

[0016] A surface condenser is used to condense the non-condensable gases discharged from the first-effect evaporator and the second-effect evaporator. The inlet of the surface condenser is connected to the non-condensable gas outlet of both the first-effect and second-effect evaporators.

[0017] The vacuum pump's inlet is connected to the outlet of the surface condenser, and the outlet of the vacuum pump is used for venting.

[0018] Furthermore, the single-effect evaporator is a multi-pass falling film evaporator, including a single-effect heater, a single-effect separator, and multiple circulating pumps. The single-effect heater includes a shell, an upper support plate and a lower support plate located inside the shell, and a tube bundle connecting the upper and lower support plates. The inner cavity of the shell above the upper support plate is the feed chamber, and the inner cavity of the shell below the lower support plate is the discharge chamber. The inner cavity of the tube bundle connects the feed chamber and the discharge chamber. The feed chamber is provided with multiple upper baffles arranged vertically along the height direction of the shell, which divide the feed chamber into multiple non-communicating feed sub-chambers.

[0019] The discharge chamber is equipped with multiple lower baffles arranged vertically along the height of the shell. These lower baffles are circumferentially arranged within the discharge chamber, with gaps between the upper ends of the lower baffles and the lower support plates. The distances between the upper ends of the lower baffles and the lower support plates increase sequentially in a clockwise or counterclockwise direction. The lower baffles divide the discharge chamber into multiple discharge sub-chambers. Adjacent discharge sub-chambers are connected through the gaps between the upper ends of the lower baffles and the lower support plates. Material overflows through these gaps and flows sequentially through the discharge sub-chambers. Each lower baffle corresponds one-to-one with each upper baffle, ensuring a one-to-one correspondence between the discharge sub-chambers and the feed sub-chambers. Each discharge sub-chamber has a discharge port at its lower end and a feed port at its upper end. The discharge port of one discharge sub-chamber is connected to the feed port of its corresponding feed sub-chamber via a circulating pump.

[0020] The upper part of the discharge chamber is provided with a channel connecting to the first-effect separator. The channel is connected to the gap. The discharge port of the first-effect separator is connected to the feed port of the last circulating pump. The secondary steam outlet of the first-effect separator is connected to the air inlet of the washing tower.

[0021] Furthermore, in the plurality of discharge chambers, the last discharge chamber through which the material flows is equipped with a level gauge, and the pipeline connected to the outlet end of the feed pump is equipped with a feed valve. The level gauge is electrically connected to the feed valve, and the feed valve is adjusted according to the material level in the last discharge chamber.

[0022] Furthermore, the double-effect evaporator is a forced circulation evaporator, including a double-effect heater, a double-effect separator, and a forced circulation pump. The inlet of the lower end of the double-effect heater is connected to the outlet of the forced circulation pump, and the outlet of the upper end of the double-effect heater is connected to the inlet of the double-effect separator. The outlet of the double-effect separator is connected to the inlet of the forced circulation pump. The inlet of the forced circulation pump is connected to the outlet of the last circulation pump of the first-effect evaporator through the first-effect discharge pipeline. The outlet of the double-effect separator is connected to the inlet of the discharge pump through the double-effect discharge pipeline.

[0023] Furthermore, the double-effect separator is equipped with a double-effect level gauge, and the first-effect discharge pipe is equipped with a double-effect feed valve. The double-effect level gauge is electrically connected to the double-effect feed valve, and the double-effect feed valve is adjusted according to the material level in the double-effect separator.

[0024] Furthermore, the discharge port of the discharge pump is connected to the inlet of the forced circulation pump through a return pipeline, and a return valve is provided on the return pipeline.

[0025] Furthermore, a flow meter and a discharge valve are installed on the crystal slurry discharge pipeline. The flow meter and the discharge valve are electrically connected, and the discharge valve is adjusted according to the flow rate in the crystal slurry discharge pipeline.

[0026] Furthermore, it also includes a preheating system, which comprises a condensate preheater and a non-condensable gas preheater. The inlet of the condensate preheater is connected to the outlet of the feed pump, the outlet of the condensate preheater is connected to the inlet of the non-condensable gas preheater, and the outlet of the non-condensable gas preheater is connected to the inlet of the first-effect evaporator.

[0027] The preheating medium inlet of the condensate preheater is connected to the outlet of the condensate pump, and the preheating medium outlet of the condensate preheater is connected to the drainage system. The inlet of the condensate pump is connected to the outlet of a condensate tank for collecting and storing condensate. The inlet of the condensate tank is connected to the condensate outlets of the first-effect evaporator, the second-effect evaporator, the surface condenser, and the non-condensable gas preheater.

[0028] The inlet of the non-condensable gas preheater is connected to the non-condensable gas outlet of the first-effect evaporator and the non-condensable gas outlet of the second-effect evaporator.

[0029] The outlet of the non-condensable gas preheater is connected to the inlet of the surface condenser.

[0030] Furthermore, the condensate outlet of the first steam compressor is connected to the inlet of the first fan condensate tank, and the outlet of the first fan condensate tank is connected to the inlet of the condensate tank via the first fan condensate pump. The condensate outlet of the second steam compressor is connected to the inlet of the second fan condensate tank, and the outlet of the second fan condensate tank is connected to the inlet of the condensate tank via the second fan condensate pump. The first fan condensate tank is equipped with a first level gauge, which is electrically connected to the first fan condensate pump. The first fan condensate pump is adjusted according to the level of the first fan condensate tank. The second fan condensate tank is equipped with a second level gauge, which is electrically connected to the second fan condensate pump. The second fan condensate pump is adjusted according to the level of the second fan condensate tank.

[0031] Furthermore, the condensate tank is equipped with a third level gauge, and a condensate preheating regulating valve is installed on the pipeline connecting the preheating medium inlet of the condensate preheater and the outlet of the condensate pump. The third level gauge is electrically connected to the condensate preheating regulating valve, and the condensate preheating regulating valve is adjusted according to the liquid level in the condensate tank.

[0032] Furthermore, it also includes a cleaning system, which includes a cleaning water supply pipe and a drain pipe. The inlet end of the cleaning water supply pipe is connected to the outlet of the condensate pump, and the outlet end of the cleaning water supply pipe is connected to the cleaning port of the first-effect evaporator, the cleaning port of the second-effect evaporator, the inlet of the washing tower, and the inlet of the discharge pump, respectively. The inlet end of the drain pipe is connected to the drain port of the first-effect evaporator, the drain port of the second-effect evaporator, the drain port of the condensate tank, the drain port of the first fan condensate tank, and the drain port of the second fan condensate tank, respectively. The outlet end of the drain pipe is connected to the drain system. A cleaning valve is provided on the cleaning water supply pipe near the inlet end, and a washing valve is provided on the outlet end of the cleaning water supply pipe connected to the washing tower.

[0033] Furthermore, the cleaning system also includes a cleaning water supply pipe, the inlet end of which is connected to the water supply system, and the outlet end of which is connected to the cleaning water supply pipe.

[0034] The beneficial effects of this utility model are as follows:

[0035] 1. This utility model utilizes mechanical vapor recompression technology to evaporate and concentrate itaconic acid filtrate under vacuum conditions. The evaporation process using a multi-pass falling film evaporator combined with a forced circulation evaporator ensures that the material has sufficient effective heat exchange temperature difference and evaporation intensity at different concentrations, thereby effectively improving the evaporation rate, reducing steam consumption, and lowering concentration costs.

[0036] 2. This utility model is equipped with two steam compressors. The second steam compressor further pressurizes and heats the secondary steam compressed and heated by the first steam compressor. Therefore, the temperature and pressure of the compressed steam flowing out of the second steam compressor are greater than those of the compressed steam flowing out of the first steam compressor. The compressed steam flowing out of the first steam compressor serves as the heat source for the first-effect evaporator to heat and evaporate the preheated itaconic acid filtrate. The preheated itaconic acid filtrate has a low concentration, good fluidity, and a minimal increase in boiling point. Therefore, a falling film evaporator is used for its evaporation and concentration. The itaconic acid filtrate concentrated by the first-effect evaporator... As the concentration of the clear liquid increases, its fluidity decreases, and its boiling point rises. Therefore, the compressed steam from the second steam compressor is used as the heat source for the second-effect evaporator to heat and evaporate the itaconic acid filtrate concentrated by the first-effect evaporator. The itaconic acid filtrate is then concentrated by using compressed steam at a higher temperature. At this point, the concentration of the itaconic acid filtrate increases, and its fluidity decreases. Therefore, the second-effect evaporator adopts a forced circulation evaporator. The combination of the multi-pass falling film first-effect evaporator and the forced circulation second-effect evaporator can ensure that the itaconic acid filtrate has a sufficient effective heat exchange temperature difference and evaporation intensity at different concentrations, which can effectively improve the evaporation efficiency.

[0037] 3. This utility model uses two steam compressors, both of which are low-speed direct-drive steam compressors. Compared with traditional high-speed gearbox steam compressors, low-speed direct-drive steam compressors have the advantages of high compression efficiency, low energy consumption, and low operating temperature.

[0038] 4. The single-effect evaporator of this utility model adopts a multi-pass falling film evaporator. Its single-effect heater divides the feed chamber inside the shell into multiple non-interconnected feed sub-chambers through an upper partition plate, and divides the discharge chamber into multiple discharge sub-chambers through a lower partition plate. The feed sub-chambers and discharge sub-chambers correspond one-to-one. The corresponding feed sub-chambers and discharge sub-chambers are connected inside the shell through a partial tube bundle, and connected outside the shell through a circulating pump, thereby realizing the circulating heating of the material. The corresponding feed sub-chambers, discharge sub-chambers, tube bundles and a circulating pump constitute one pass of the single-effect heater. The multiple discharge sub-chambers achieve material flow through overflow, thereby realizing material flow between tube passes. The single-effect evaporator of this utility model has a simple structure and ingenious design. Multiple evaporation and concentration of materials can be achieved in one heater. One evaporator can achieve the effect of multi-effect evaporation, which can effectively improve evaporation efficiency and reduce equipment costs.

[0039] 5. This utility model is equipped with a preheating system, which uses condensate and non-condensable gas to preheat the itaconic acid filtrate in sequence. This can increase the temperature of the itaconic acid filtrate entering the first-effect evaporator, so that the material and steam in the first-effect evaporator have an effective heat exchange temperature difference, improve the evaporation efficiency, and also effectively recover the heat in the condensate and non-condensable gas, saving energy and reducing costs.

[0040] 6. This utility model is equipped with a cleaning system that can clean the first-effect evaporator and the second-effect evaporator with condensate and / or primary water after production is completed and / or before the next production. This avoids corrosion and damage caused by the presence of itaconic acid in pipes and equipment, and can also effectively prevent the deposition and scaling caused by the presence of itaconic acid, thus ensuring the service life of this utility model. At the same time, it can also prevent cross-contamination between materials and ensure the purity of the harvested itaconic acid.

[0041] 7. The surface condenser of this utility model is equipped with a pressure sensor, which detects the pressure inside the surface condenser, i.e., the vacuum level. A gas supply line is provided on the pipeline connecting the gas outlet of the surface condenser and the gas inlet of the vacuum pump. A vacuum regulating valve is provided on the gas supply line. The pressure sensor is electrically connected to the vacuum regulating valve. The vacuum regulating valve is adjusted by controlling the pressure inside the surface condenser, thereby realizing the adjustment and control of the vacuum level, so that this utility model can operate under suitable vacuum conditions and ensure the stability of equipment operation.

[0042] 8. This utility model has a simple structure, is easy to use, has a novel design, and is low in cost. It can effectively improve the concentration efficiency of itaconic acid filtrate, reduce the amount of steam used during the evaporation and concentration of itaconic acid filtrate, reduce energy consumption, reduce the production cost of itaconic acid, and reduce the burden on enterprises. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings.

[0045] like Figure 1 As shown, an MVR evaporation and crystallization system for itaconic acid production includes a material tank 1 for storing itaconic acid filtrate, a feed pump 2 for conveying and feeding itaconic acid filtrate, a preheating system for preheating itaconic acid filtrate, a first-effect evaporator 5 and a second-effect evaporator 6 for heating and evaporating itaconic acid filtrate, a washing tower 7 for washing the secondary steam separated from the first-effect evaporator 5 and the second-effect evaporator 6, a first steam compressor 8 and a second steam compressor 9 for compressing and increasing the pressure and temperature of the washed secondary steam, a condensate tank 10 for recovering condensate, a condensate pump 11 for conveying condensate, a vacuum pump 12 for creating a vacuum, and a steam source 13 and a steam conveying pipeline 25 for providing live steam to the entire system.

[0046] The inlet of the feed pump 2 is connected to the material tank 1, and the outlet of the feed pump 2 is connected to the preheating system. The preheating system includes a condensate preheater 3 and a non-condensable gas preheater 4. The inlet of the condensate preheater 3 is connected to the outlet of the feed pump 2, the outlet of the condensate preheater 3 is connected to the inlet of the non-condensable gas preheater 4, the outlet of the non-condensable gas preheater 4 is connected to the inlet of the first-effect evaporator 5, the preheating medium inlet of the condensate preheater 3 is connected to the outlet of the condensate pump 11, and the preheating medium outlet of the condensate preheater 3 is connected to the drainage system.

[0047] The feed inlet of the first-effect evaporator 5 is connected to the discharge outlet of the non-condensable gas preheater 4. The first-effect evaporator 5 is a double-pass falling film evaporator, including a first-effect heater 501, a first-effect separator 502, and two circulating pumps. The first-effect heater 501 includes a shell, an upper support plate and a lower support plate located inside the shell, and a tube bundle connecting the upper support plate and the lower support plate. The inner cavity of the shell above the upper support plate is the feed chamber, and the inner cavity of the shell below the lower support plate is the discharge chamber. The inner cavity of the tube bundle connects the feed chamber and the discharge chamber. An upper baffle 505 is arranged vertically along the height direction of the shell in the feed chamber. 505 divides the feeding chamber into two non-communicating feeding sub-chambers, namely the left feeding sub-chamber 503 and the right feeding sub-chamber 504. The discharging chamber is provided with a lower partition 506 arranged vertically along the height direction of the shell. There is a gap between the upper end of the lower partition 506 and the lower support plate. The lower partition 506 divides the discharging chamber into two discharging sub-chambers, namely the left discharging sub-chamber 507 and the right discharging sub-chamber 508. The left discharging sub-chamber 507 and the right discharging sub-chamber 508 are connected through the gap between the upper end of the lower partition 506 and the lower support plate. Material overflows over the lower partition 506 and exits from the lower partition 506. The gap above allows material to enter the right discharge chamber 508 from the left discharge chamber 507. The lower partition 506 corresponds to the upper partition 505, aligning the left discharge chamber 507 with the left feed chamber 503 and connecting them through the inner cavity of a portion of the tube bundle within the housing, forming the left tube side of the single-effect heater 501. The right discharge chamber 508 corresponds to the right feed chamber 504 and connects it through the inner cavity of another portion of the tube bundle within the housing, forming the right tube side of the single-effect heater 501. Both the left and right discharge chambers 507 and 508 have discharge ports at their lower ends. The left and right feed chambers 503 and 508... The upper end of each of the 504 sections is provided with a feed inlet. Outside the shell, the discharge port of the left discharge chamber 507 is connected to the feed port of the left feed chamber 503 through the left circulation pump 509. The discharge port of the right discharge chamber 508 is connected to the feed port of the right feed chamber 504 through the right circulation pump 510. The upper part of the discharge chamber is provided with a channel connecting to the first-effect separator 502. The channel is connected to the gap between the lower partition plate 506 and the lower support plate. The discharge port of the first-effect separator 502 is connected to the feed port of the right circulation pump 510. The secondary steam outlet of the first-effect separator 502 is connected to the air inlet of the scrubbing tower 7. A first-effect level gauge 511 is installed on the right discharge chamber 508. A first-effect feed valve 512 is installed on the pipeline connecting the outlet end of the feed pump 2 to the inlet of the condensate preheater 3. The first-effect level gauge 511 is electrically connected to the first-effect feed valve 512, and the first-effect feed valve 512 is adjusted according to the material level in the right discharge chamber 508. The outlet of the right circulation pump 510 is connected to the second-effect evaporator 6 through the first-effect discharge pipeline 513.

[0048] The double-effect evaporator 6 is a forced circulation evaporator, including a double-effect heater 601, a double-effect separator 602, and a forced circulation pump 603. The inlet of the lower end of the double-effect heater 601 is connected to the outlet of the forced circulation pump 603, and the outlet of the upper end of the double-effect heater 601 is connected to the inlet of the double-effect separator 602. The outlet of the double-effect separator 602 is connected to the inlet of the forced circulation pump 603. The inlet of the forced circulation pump 603 is connected to the outlet of the right circulation pump 510 of the first-effect evaporator 5 through the first-effect discharge pipe 513. The double-effect separator 602 is equipped with a double-effect level gauge 604, and the first-effect discharge pipe 513 is equipped with a double-effect feed valve 605. The double-effect level gauge 604 is electrically connected to the double-effect feed valve 605, and the double-effect feed valve 605 is adjusted according to the material level in the double-effect separator 602. The discharge port of the double-effect separator 602 is connected to the inlet of the discharge pump 19 via the double-effect discharge pipeline 606. The discharge port of the discharge pump 19 is connected to the inlet of the forced circulation pump 603 via the return pipeline 20. The return pipeline 20 is equipped with a return valve 21. The discharge port of the discharge pump 19 is connected to the crystal slurry discharge pipeline 22. The crystal slurry discharge pipeline 22 is equipped with a discharge flow meter 23 and a discharge valve 24. The discharge flow meter 23 is electrically connected to the discharge valve 24, and the discharge valve 24 is adjusted according to the material flow rate in the crystal slurry discharge pipeline 22.

[0049] The steam source 13 is connected to the air supply port of the first steam compressor 8, the air supply port of the second steam compressor 9, and the air inlet of the first-effect heater 501 of the first-effect evaporator 5 via the steam delivery pipeline 25. The secondary steam outlet of the first-effect separator 502 of the first-effect evaporator 5 is connected to the air inlet of the scrubbing tower 7. The air outlet of the scrubbing tower 7 is connected to the air inlet of the first steam compressor 8. The first steam compressor 8 is used to compress the secondary steam after cleaning by the scrubbing tower 7, so that it is pressurized and heated into high-grade compressed steam. The air outlet of the first steam compressor 8 is connected to the air inlet of the second steam compressor 9 and the air inlet of the first-effect heater 501. The second steam compressor 9 is used to compress the compressed steam compressed by the first steam compressor 8, so that it is pressurized and heated again. The air outlet of the second steam compressor 9 is connected to the air inlet of the second-effect heater 601 of the second-effect evaporator 6. The secondary steam outlet of the second-effect separator 602 of the second-effect evaporator 6 is connected to the air inlet of the scrubbing tower 7. The outlet of the washing tower 7 is connected to the inlet of the first-effect heater 501 of the first-effect evaporator 5.

[0050] The non-condensable gas outlet of the second-effect heater 601 is connected to the inlet of the first-effect heater 501. The non-condensable gas outlet of the first-effect heater 501 is connected to the inlet of the non-condensable gas preheater 4. The outlet of the non-condensable gas preheater 4 is connected to the inlet of the surface condenser 14. The outlet of the surface condenser 14 is connected to the inlet of the vacuum pump 12. The outlet of the vacuum pump 12 is vented. The surface condenser 14 is equipped with a pressure sensor 26, which detects the pressure inside the surface condenser 14, i.e., the vacuum degree. A gas supply line is provided on the pipeline connecting the outlet of the surface condenser 14 and the inlet of the vacuum pump 12. A vacuum regulating valve 27 is provided on the gas supply line. The pressure sensor 26 is electrically connected to the vacuum regulating valve 27. The vacuum regulating valve 27 is adjusted by controlling the pressure inside the surface condenser 14, thereby realizing the adjustment and control of the vacuum degree in the entire evaporation crystallization system.

[0051] The condensate outlet of the first steam compressor 8 is connected to the inlet of the first fan condensate tank 15. The outlet of the first fan condensate tank 15 is connected to the inlet of the condensate tank 10 via the first fan condensate pump 16. The condensate outlet of the second steam compressor 9 is connected to the inlet of the second fan condensate tank 17. The outlet of the second fan condensate tank 17 is connected to the inlet of the condensate tank 10 via the second fan condensate pump 18. The first fan condensate tank 15 is equipped with a first level gauge 28, which is electrically connected to the first fan condensate pump 16. The first fan condensate pump 16 is adjusted according to the level of the first fan condensate tank 15. The second fan condensate tank 17 is equipped with a second level gauge 29, which is electrically connected to the second fan condensate pump 18. The second fan condensate pump 18 is adjusted according to the level of the second fan condensate tank 17.

[0052] The condensate outlet of the first-effect heater 501 is connected to the inlet of the condensate tank 10, and the condensate outlet of the second-effect heater 601 is also connected to the inlet of the condensate tank 10. The exhaust port of the condensate tank 10 is connected to the inlet of the non-condensable gas preheater 4 via a pipeline. The outlet of the condensate tank 10 is connected to the inlet of the condensate pump 11, and the outlet of the condensate pump 11 is connected to the preheating medium inlet of the condensate preheater 3. A third level gauge 30 is provided on the condensate tank 10. A condensate preheating regulating valve 31 is provided on the pipeline connecting the preheating medium inlet of the condensate preheater 3 and the outlet of the condensate pump 11. The third level gauge 30 is electrically connected to the condensate preheating regulating valve 31, and the condensate preheating regulating valve 31 is adjusted according to the liquid level in the condensate tank 10.

[0053] The water outlet of the surface condenser 14 is connected to the inlet of the condensate pump 11 via a pipeline, and a one-way valve is provided on the pipeline.

[0054] The system also includes a cleaning system comprising a cleaning water supply pipe 32, a drain pipe 33, and a cleaning water replenishment pipe. The inlet end of the cleaning water supply pipe 32 is connected to the outlet of the condensate pump 11. The outlet ends of the cleaning water supply pipe 32 are respectively connected to the cleaning ports of the first-effect evaporator 5, the second-effect evaporator 6, the inlet of the washing tower 7, and the inlet of the discharge pump 19. The inlet end of the drain pipe 33 is respectively connected to the drain ports of the first-effect evaporator 5, the second-effect evaporator 6, the condensate tank 10, the first fan condensate tank 15, and the second fan condensate tank 17. The outlet end of the drain pipe 33 is connected to the drainage system. A cleaning valve is installed near the inlet end of the cleaning water supply pipe 32, and a washing valve 34 is installed at the outlet end of the cleaning water supply pipe 32 connected to the washing tower 7. The inlet end of the cleaning water replenishment pipe is connected to the water supply system, and the outlet end of the cleaning water replenishment pipe is connected to the cleaning water supply pipe 32.

[0055] During initial startup, the live steam provided by steam source 13 is used as a heat source to evaporate and concentrate the itaconic acid filtrate. Vacuum pump 12 is started, and under its action, live steam enters the shell side of the first-effect heater 501 of the first-effect evaporator 5 via steam delivery pipeline 25. The itaconic acid filtrate stored in material tank 1 enters the tube side of the first-effect heater 501 of the first-effect evaporator 5 under the action of feed pump 2. In the first-effect heater 501, live steam heats the itaconic acid filtrate, causing it to evaporate and concentrate. The secondary steam separated by the first-effect separator 502 of the first-effect evaporator 5 is washed by washing tower 7 and then enters the first steam compressor 8, which pressurizes the secondary steam. The steam is heated to become primary compressed steam. Part of the primary compressed steam re-enters the shell side of the first-effect heater 501, while the other part enters the second steam compressor 9. Under the pressurization effect of the second steam compressor 9, it becomes secondary compressed steam. The secondary compressed steam enters the shell side of the second-effect heater 601 of the second-effect evaporator 6. The itaconic acid filtrate flowing out of the first-effect evaporator 5 enters the tube side of the second-effect heater 601. In the second-effect heater 601, the itaconic acid filtrate is heated by the secondary compressed steam to evaporate and concentrate it. The secondary steam separated by the second-effect separator 602 of the second-effect evaporator 6 is also washed by the scrubbing tower 7 before entering the first steam compressor 8.

[0056] After the present invention has been operating stably, the secondary steam generated by the first-effect evaporator 5 and the secondary steam generated by the second-effect evaporator 6 are used as heat sources to evaporate and concentrate the itaconic acid filtrate. The live steam from the steam source 13 is used as a supplementary heat source. The itaconic acid filtrate with a concentration of about 8% and a temperature of about 40°C stored in the material tank 1 enters the condensate preheater 3 under the action of the feed pump 2. The itaconic acid filtrate is preheated for the first time using condensate. The condensate preheater 3 can preheat the itaconic acid filtrate to about 60°C. The itaconic acid filtrate after the first preheating enters the non-condensable gas preheater 4. In the non-condensable gas preheater 4, the itaconic acid filtrate is further concentrated using non-condensable gas. The second preheating process raises the temperature of the itaconic acid filtrate to approximately 65°C. After the second preheating, the itaconic acid filtrate enters the left feed chamber 503 of the first-effect heater 501 of the first-effect evaporator 5, and then flows along the inner cavity of the tube bundle into the left discharge chamber 507. Under the action of the left circulation pump 509, it re-enters the left feed chamber 503, and so on. When the material level in the left discharge chamber 507 is higher than the height of the lower baffle 506, the itaconic acid filtrate overflows into the right discharge chamber 508, and then enters the right feed chamber 504 under the action of the right circulation pump 510. After a delay, it re-enters the right discharge chamber 508 along the inner cavity of the tube bundle, and so on. The primary compressed steam, which is about 70°C, flows out from the first steam compressor 8 and enters the shell side of the first-effect heater 501. Inside the first-effect heater 501, the primary compressed steam heats the itaconic acid filtrate, causing it to evaporate and concentrate. The first-effect evaporator 5 can increase the concentration of the itaconic acid filtrate to about 32%.

[0057] The itaconic acid filtrate flowing out of the first-effect evaporator 5 enters the tube side of the second-effect heater 601 under the action of the forced circulation pump 603. Secondary compressed steam at approximately 78°C, generated by the second steam compressor 9, enters the shell side of the second-effect heater 601. The itaconic acid filtrate is heated in the second-effect heater 601 using this secondary compressed steam. The heated itaconic acid filtrate then enters the second-effect separator 602, where gas-liquid separation occurs. The separated itaconic acid filtrate is then re-entered into the tube side of the second-effect heater 601 under the action of the forced circulation pump 603 for further heating. This cycle continues, allowing the second-effect evaporator 6 to increase the concentration of the itaconic acid filtrate to approximately 80% crystal slurry. The discharge pump 19 is started, and the discharge valve 24 is opened. Under the action of the discharge pump 19, the itaconic acid crystal slurry is discharged along the crystal slurry discharge pipe 22, thus completing the evaporation and concentration of the itaconic acid filtrate.

[0058] During system operation, the material flow direction is: material tank 1 → feed pump 2 → condensate preheater 3 → non-condensable gas preheater 4 → first-effect evaporator 5 → second-effect evaporator 6 → discharge pump 19.

[0059] The non-condensable gas flowing out of the shell side of the second-effect heater 601 of the double-effect evaporator 6 enters the shell side of the first-effect heater 501, where it participates in the heating of the itaconic acid filtrate by the first-effect heater 501. The non-condensable gas flowing out of the first-effect heater 501 enters the non-condensable gas preheater 4, where the heat in the non-condensable gas is used to preheat the itaconic acid filtrate. After the temperature of the non-condensable gas decreases, it enters the surface condenser 14, where cooling water is used to cool the non-condensable gas. After it cools down, it is discharged by the vacuum pump 12.

[0060] The condensate produced by the shell side of the first-effect heater 501 enters the condensate tank 10 for storage. The condensate produced by the shell side of the second-effect heater 601 also enters the condensate tank 10 for storage. The condensate from the fan of the first steam compressor 8 enters the first fan condensate tank 15 for storage, and then enters the condensate tank 10 under the action of the first fan chilled water pump. The condensate from the fan of the second steam compressor 9 enters the second fan condensate tank 17 for storage, and then enters the condensate tank 10 under the action of the second fan chilled water pump. The condensate produced by the non-condensable gas preheater 4 also enters the condensate tank 10 for storage. The condensate stored in the condensate tank 10 enters the condensate preheater 3 under the action of the condensate pump 11 to preheat the itaconic acid filtrate.

[0061] The washing tower 7 of this invention uses the condensate stored in the condensate tank 10 to wash the secondary steam separated from the first-effect evaporator 5 and the second-effect evaporator 6. When the cleaning valve and the washing valve 34 are opened, the condensate in the condensate tank 10 enters the cleaning water supply pipe 32 and enters the water inlet of the washing tower 7 under the action of the condensate pump 11.

[0062] When the system needs cleaning after production is completed, the cleaning valve is opened. The condensate in the condensate tank 10 enters the cleaning water supply pipe 32 under the action of the condensate pump 11. A first-effect cleaning valve is installed at the outlet end of the cleaning water supply pipe 32, which connects to the cleaning port of the first-effect evaporator 5. A second-effect cleaning valve is installed at the outlet end of the cleaning water supply pipe 32, which connects to the cleaning port of the second-effect evaporator 6. During cleaning, both the first-effect and second-effect cleaning valves are opened, and the condensate flows through the cleaning water supply pipe 32 into the first-effect evaporator 5 and the second-effect evaporator 6 respectively, cleaning the first-effect evaporator 5, the second-effect evaporator 6, and the pipelines. The wastewater from the cleaning well is discharged into the wastewater treatment system via the sewage discharge pipe 33. In the initial operation of this invention or when the condensate in the condensate tank 10 is insufficient, the system can be cleaned through the cleaning water replenishment pipe and the water supply system.

[0063] It should be noted that the above-described embodiments are illustrative of the technical solution of this utility model and not limiting. Equivalent substitutions or other modifications made by those skilled in the art based on the prior art, as long as they do not exceed the concept and scope of the technical solution of this utility model, should be included within the scope of the claims of this utility model.

Claims

1. An MVR evaporation crystallization system for itaconic acid production, characterized in that: include The feeding device includes a material tank (1) for storing itaconic acid filtrate and a feed pump (2) whose inlet end is connected to the material tank (1). The first-effect evaporator (5) has its inlet connected to the outlet of the feed pump (2), its outlet connected to the inlet of the second-effect evaporator (6), its air inlet connected to the outlet of the first steam compressor (8), and its secondary steam outlet connected to the air inlet of the scrubbing tower (7). The discharge port of the second-effect evaporator (6) is connected to the inlet of the discharge pump (19), the discharge port of the discharge pump (19) is connected to the crystal slurry discharge pipeline (22), the air inlet of the second-effect evaporator (6) is connected to the air outlet of the second steam compressor (9), and the secondary steam outlet of the second-effect evaporator (6) is connected to the air inlet of the scrubbing tower (7). The washing tower (7) is used to wash the secondary steam separated from the first-effect evaporator (5) and the second-effect evaporator (6). The outlet of the washing tower (7) is connected to the inlet of the first steam compressor (8), and the outlet of the washing tower (7) is connected to the feed inlet of the first-effect evaporator (5). The first steam compressor (8) is used to compress the secondary steam after cleaning by the scrubbing tower (7), pressurizing and heating it into high-grade compressed steam. The outlet of the first steam compressor (8) is connected to the inlet of the second steam compressor (9) and the inlet of the first-effect evaporator (5). The second steam compressor (9) is used to compress the compressed steam that has been compressed by the first steam compressor (8), and to pressurize and heat it again. A steam source (13) is connected to the air supply port of the first steam compressor (8), the air supply port of the second steam compressor (9), and the air inlet of the first-effect evaporator (5) via a steam delivery pipeline (25). A surface condenser (14) is used to condense the non-condensable gases discharged from the first-effect evaporator (5) and the second-effect evaporator (6). The inlet of the surface condenser (14) is connected to the non-condensable gas outlet of the first-effect evaporator (5) and the non-condensable gas outlet of the second-effect evaporator (6). Vacuum pump (12), the air inlet of vacuum pump (12) is connected to the air outlet of surface condenser (14), and the air outlet of vacuum pump (12) is vented.

2. The MVR evaporation crystallization system for itaconic acid production according to claim 1, characterized in that: The single-effect evaporator (5) is a multi-pass falling film evaporator, including a single-effect heater (501), a single-effect separator (502), and multiple circulating pumps. The single-effect heater (501) includes a shell, an upper support plate and a lower support plate located inside the shell, and a tube bundle connecting the upper support plate and the lower support plate. The inner cavity of the shell above the upper support plate is the feed chamber, and the inner cavity of the shell below the lower support plate is the discharge chamber. The inner cavity of the tube bundle connects the feed chamber and the discharge chamber. Multiple upper partitions (505) are arranged vertically along the height direction of the shell in the feed chamber. The multiple upper partitions (505) divide the feed chamber into multiple non-communicating feed sub-chambers. The discharge chamber is provided with multiple lower partitions (506) arranged vertically along the height of the shell. The multiple lower partitions (506) are arranged circumferentially in the discharge chamber. There is a gap between the upper end of the lower partition (506) and the lower support plate. The distance between the upper end of the multiple lower partitions (506) and the lower support plate increases sequentially in a clockwise or counterclockwise direction. The multiple lower partitions (506) divide the discharge chamber into multiple discharge sub-chambers. Two adjacent discharge sub-chambers are connected by the lower partitions (506). 506) The gap between the upper end and the lower support plate is connected, and the material overflows through the gap and flows sequentially through the discharge chamber. Multiple lower partitions (506) correspond one-to-one with multiple upper partitions (505), so that multiple discharge chambers correspond one-to-one with multiple feed chambers. The lower end of the discharge chamber is provided with a discharge port, and the upper end of the feed chamber is provided with a feed port. The discharge port of one discharge chamber is connected to the feed port of the corresponding feed chamber through a circulating pump. The upper part of the discharge chamber is provided with a channel connecting the first-effect separator (502), the channel is connected to the gap, the discharge port of the first-effect separator (502) is connected to the feed port of the last circulating pump, and the secondary steam outlet of the first-effect separator (502) is connected to the air inlet of the washing tower (7).

3. The MVR evaporation crystallization system for itaconic acid production according to claim 2, characterized in that: In the multiple discharge chambers, the last discharge chamber through which the material flows is equipped with a level gauge (511), and a feed valve (512) is provided on the pipeline connected to the outlet end of the feed pump (2). The level gauge (511) and the feed valve (512) are electrically connected, and the feed valve (512) is adjusted according to the material level in the last discharge chamber.

4. The MVR evaporation crystallization system for itaconic acid production according to claim 1, characterized in that: The double-effect evaporator (6) is a forced circulation evaporator, including a double-effect heater (601), a double-effect separator (602), and a forced circulation pump (603). The inlet of the lower end of the double-effect heater (601) is connected to the outlet of the forced circulation pump (603), and the outlet of the upper end of the double-effect heater (601) is connected to the inlet of the double-effect separator (602). The outlet of the double-effect separator (602) is connected to the inlet of the forced circulation pump (603). The inlet of the forced circulation pump (603) is connected to the outlet of the last circulation pump of the first-effect evaporator (5) through the first-effect discharge pipe (513). The outlet of the double-effect separator (602) is connected to the inlet of the discharge pump (19) through the double-effect discharge pipe (606).

5. The MVR evaporation crystallization system for itaconic acid production according to claim 4, characterized in that: The double-effect separator (602) is equipped with a double-effect level gauge (604), and the first-effect discharge pipeline (513) is equipped with a double-effect feed valve (605). The double-effect level gauge (604) is electrically connected to the double-effect feed valve (605), and the double-effect feed valve (605) is adjusted according to the material level in the double-effect separator (602).

6. The MVR evaporation crystallization system for itaconic acid production according to claim 1, characterized in that: The discharge port of the discharge pump (19) is connected to the inlet of the forced circulation pump (603) through the return pipe (20), and the return pipe (20) is equipped with a return valve (21).

7. The MVR evaporation crystallization system for itaconic acid production according to claim 1, characterized in that: The crystal slurry discharge pipeline (22) is equipped with a discharge flow meter (23) and a discharge valve (24). The discharge flow meter (23) is electrically connected to the discharge valve (24), and the discharge valve (24) is adjusted according to the flow rate in the crystal slurry discharge pipeline (22).

8. The MVR evaporation crystallization system for itaconic acid production according to claim 1, characterized in that: It also includes a preheating system, which includes a condensate preheater (3) and a non-condensable gas preheater (4). The inlet of the condensate preheater (3) is connected to the outlet of the feed pump (2), the outlet of the condensate preheater (3) is connected to the inlet of the non-condensable gas preheater (4), and the outlet of the non-condensable gas preheater (4) is connected to the inlet of the first-effect evaporator (5). The inlet of the preheating medium of the condensate preheater (3) is connected to the outlet of the condensate pump (11), and the outlet of the preheating medium of the condensate preheater (3) is connected to the drainage system. The inlet of the condensate pump (11) is connected to the outlet of the condensate tank (10) for collecting and storing condensate. The inlet of the condensate tank (10) is connected to the condensate outlet of the first-effect evaporator (5), the condensate outlet of the second-effect evaporator (6), the condensate outlet of the surface condenser (14), and the condensate outlet of the condensate preheater (3). The inlet of the non-condensable gas preheater (4) is connected to the non-condensable gas outlet of the first-effect evaporator (5) and the non-condensable gas outlet of the second-effect evaporator (6). The outlet of the non-condensable gas preheater (4) is connected to the inlet of the surface condenser (14).

9. The MVR evaporation crystallization system for itaconic acid production according to claim 1, characterized in that: The condensate outlet of the first steam compressor (8) is connected to the inlet of the first fan condensate tank (15), and the outlet of the first fan condensate tank (15) is connected to the inlet of the condensate tank (10) through the first fan condensate pump (16). The condensate outlet of the second steam compressor (9) is connected to the inlet of the second fan condensate tank (17), and the outlet of the second fan condensate tank (17) is connected to the inlet of the condensate tank (10) through the second fan condensate pump (18). A first level gauge (28) is provided on a fan condensate tank (15). The first level gauge (28) is electrically connected to a first fan condensate pump (16). The first fan condensate pump (16) is adjusted according to the level of the first fan condensate tank (15). A second level gauge (29) is provided on a second fan condensate tank (17). The second level gauge (29) is electrically connected to a second fan condensate pump (18). The second fan condensate pump (18) is adjusted according to the level of the second fan condensate tank (17).

10. The MVR evaporation crystallization system for itaconic acid production according to claim 8, characterized in that: The condensate tank (10) is equipped with a third level gauge (30). The condensate preheating medium inlet of the condensate preheater (3) is connected to the outlet of the condensate pump (11) via a pipeline. The third level gauge (30) is electrically connected to the condensate preheating regulating valve (31). The condensate preheating regulating valve (31) is adjusted according to the liquid level in the condensate tank (10).

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