Heliotropin purification system

Abstract

The utility model provides a heliotropin purification system. The heliotropin purification system comprises a normal-pressure distillation device, a first negative-pressure rectification device, a second negative-pressure rectification device and a solvent circulation pipeline which are communicated in sequence, the first negative pressure rectification device comprises a first rectification tower, a first condenser, a first reflux tank, a first circulating pump and a first reboiler; the second negative pressure rectification device comprises a second rectification tower, a second condenser, a second reflux tank, a second circulating pump and a second reboiler; a feed port of the second rectification tower is communicated with a bottom discharge port of the first rectification tower through a second rectification pump; the solvent circulating pipeline comprises a benzodioxole circulating pipeline and a front distillation mixture pipeline, the inlet end of the benzodioxole circulating pipeline is communicated with the benzodioxole storage tank, the outlet end of the benzodioxole circulating pipeline is communicated with the heliotropin condensation reaction device, and the inlet end of the front distillation mixture pipeline is communicated with the front distillation mixture storage tank; and the outlet end of the front distillation mixture pipeline is communicated with the feeding hole of the first rectifying tower. According to the invention, efficient rectification of heliotropin is realized.

Description

Technical Field

[0001] This application relates to the technical field of chemical rectification and purification, and particularly relates to a piperonal purification system. Background Art

[0002] Piperonal has the fragrance of heliotropin, and is widely used in perfumes, spices, cherry and vanilla flavoring agents, and can also be used in the synthesis of organic compounds.

[0003] During the production process of piperonal, the crude piperonal needs to be rectified and purified to obtain pure piperonal. The existing rectification process is to input the crude piperonal into a vacuum tower for rectification. The crude product contains dichloroethane and dimethyl carbonate with lower boiling points, as well as piperylene, piperonal and still residues with higher boiling points. Since the light components dichloroethane and dimethyl carbonate have lower boiling points, during the negative pressure rectification process, it is easy to inhale the light components dichloroethane and dimethyl carbonate into the vacuum unit, resulting in serious liquid carry-over in the vacuum unit, so the stability of the tower is poor, and the rectification yield of the product piperonal is low.

[0004] Moreover, dichloroethane, dimethyl carbonate, piperylene and piperonal are pre-fractions. When the rectification temperature rises, the content of piperonal in the pre-fractions gradually increases until it reaches the index requirements before the post-fraction (piperonal product) can be withdrawn. The rectified pre-fraction is a mixture of four materials, and the pre-fraction is repeatedly applied to the rectification tower, resulting in a large load on the rectification tower, liquid hammer damage caused by the vacuum unit sucking in dichloroethane, and high load on the tail gas adsorption device through the vacuum unit discharging into the tail gas treatment device, and high energy consumption in the entire production rectification and purification process. Utility Model Content

[0005] This application provides a piperonal purification system to solve the above problems mentioned in the background art.

[0006] This application provides a piperonal purification system, including an atmospheric distillation device, a first negative pressure rectification device, a second negative pressure rectification device and a solvent circulation pipeline connected in sequence;

[0007] The first negative pressure rectification device includes a first rectification tower, a first condenser, a first reflux tank and a piperylene storage tank connected in sequence to the top gas phase outlet of the first rectification tower. The bottom of the first rectification tower is connected with a first circulation pump and a first reboiler in sequence. The gas phase outlet of the first reboiler is communicated with the steam inlet of the first rectification tower. The feed inlet of the first rectification tower is communicated with the bottom discharge outlet of the atmospheric distillation device through a first rectification pump. The first condenser is also connected with a first vacuum unit;

[0008] The second negative-pressure rectification device includes a second rectification column, a second condenser and a second reflux drum that are successively connected to the top gas-phase outlet of the second rectification column. The second reflux drum is respectively connected to a piperonal storage tank and a pre-fraction mixture storage tank. The bottom of the second rectification column is successively connected with a second circulation pump and a second reboiler. The gas-phase outlet of the second reboiler is connected to the steam inlet of the second rectification column. The feed inlet of the second rectification column is connected to the bottom discharge outlet of the first rectification column through a second rectification pump. The second condenser is also connected with a second vacuum unit;

[0009] The solvent circulation pipeline includes a piperylene circulation pipeline and a pre-fraction mixture pipeline. The inlet end of the piperylene circulation pipeline is connected to a piperylene storage tank, and the outlet end of the piperylene circulation pipeline is connected to a piperonal condensation reaction device. The inlet end of the pre-fraction mixture pipeline is connected to a pre-fraction mixture storage tank, and the outlet end of the pre-fraction mixture pipeline is connected to the feed inlet of the first rectification column.

[0010] Optionally, the atmospheric distillation device includes a distillation column and a third condenser connected to the top gas-phase outlet of the distillation column. The outlet of the third condenser is respectively connected to a dichloroethane storage tank and a dimethyl carbonate storage tank. The bottom discharge outlet of the distillation column is connected to the feed inlet of the first rectification column through a first rectification pump.

[0011] Optionally, the solvent circulation pipeline further includes a dichloroethane circulation pipeline and a dimethyl carbonate circulation pipeline. The dichloroethane circulation pipeline is connected between the dichloroethane storage tank and the piperonal extraction device, and the dimethyl carbonate circulation pipeline is connected between the dimethyl carbonate storage tank and the piperonal condensation solvent kettle.

[0012] Optionally, a first temperature sensor is arranged in the distillation column, a second temperature sensor is arranged in the first rectification column, and a third temperature sensor is arranged in the second rectification column.

[0013] Optionally, a plurality of trays with the same structure are arranged inside the first rectification column and the second rectification column along the tower body direction. The tray includes a tray plate, an overflow weir and a downcomer. Overflow weirs are arranged at positions close to both sides of the tray plate. A downcomer is connected to the lower part of one of the overflow weirs. The downcomers of every two adjacent tray plates are arranged staggeredly, and through holes are formed at positions between the two overflow weirs on the tray plate.

[0014] Optionally, the through hole includes a lower acceleration section, a direct flow section and a mixed flow section from bottom to top. The diameter of the acceleration section decreases from bottom to top. The diameter of the direct flow section is equal to the upper end diameter of the acceleration section and remains unchanged. The diameter of the mixed flow section increases from bottom to top, and the lower end diameter of the mixed flow section is equal to the diameter of the direct flow section.

[0015] Optionally, the ratio of the lower end diameter to the upper end diameter of the acceleration section is 1.3 - 1.6:1.

[0016] Optionally, a disturbance structure is further provided on the tray. The disturbance structure includes a spring seat, a vibration spring, and a disturbance plate. The spring seat is fixedly arranged on the tray surface of the tray. One end of the vibration spring is fixedly connected to the spring seat, and the other end of the vibration spring is connected to the central position of the disturbance plate.

[0017] The piperonal purification system provided by the present application realizes efficient rectification of piperonal. Compared with the prior art, it has the following beneficial effects:

[0018] (1) Low-boiling substances dichloroethane and dimethyl carbonate in the crude piperonal are distilled out through an atmospheric distillation device, and then the remaining crude piperonal is successively passed into a first negative-pressure rectification device for primary negative-pressure rectification to distill out piperylene in the crude product, and then the piperonal with a higher boiling point is distilled out through a second negative-pressure rectification device, realizing the rectification and purification of piperonal. Compared with directly subjecting the crude piperonal to negative-pressure rectification in the prior art, the purification system provided by the present application avoids the entry of light components dichloroethane and dimethyl carbonate into the negative-pressure unit during the rectification process, which is beneficial to maintaining the stability and efficiency of the overall purification system operation. By providing a solvent circulation pipeline, the piperylene in the piperylene storage tank is applied to the piperonal condensation reaction device through the piperylene circulation pipeline, and the piperonal and piperonal in the pre-fraction mixture storage tank are applied to the first rectification tower for further rectification. Such a setting reduces the waste of solvents, lowers the production cost, and only a small amount of piperylene and piperonal in the second rectification tower are applied to the first rectification tower for re-rectification. Compared with the prior art where the pre-fraction composed of dichloroethane, dimethyl carbonate, piperylene, and piperonal is all returned to the first rectification tower for re-rectification, the solution provided by the present application reduces the amount of fraction application, thereby avoiding the operation load of the first rectification tower and the second rectification tower, further avoiding the damage of light components to the negative-pressure unit, and reducing the treatment amount of the tail gas adsorption device for the tail gas from the negative-pressure unit, greatly reducing the system operation cost.

[0019] (2) Dichloroethane is transported to the piperonal extraction device through the dichloroethane circulation pipeline to participate in the extraction process of piperonal, reducing the waste of dichloroethane. At the same time, dimethyl carbonate is transported to the piperonal condensation solvent kettle for reuse of dimethyl carbonate, reducing the production cost and the waste water treatment load.

[0020] (3) The setting of the trays is conducive to the residence of the liquid phase on the trays, thereby increasing the gas-liquid contact time and improving the rectification efficiency. The overflow weir is used to form a liquid layer of a certain thickness on the tray, further increasing the gas-liquid contact time and contact area. The downcomer is used to guide the liquid on the upper tray to the lower tray, which is conducive to the continuous and stable operation of rectification. The downcomers of every two adjacent trays are staggered, that is, the downcomer of the upper tray is aligned vertically with the overflow weir of the lower tray that is not connected to the downcomer. This setting is conducive to the balanced force on the trays and the stable operation of the rectification column. The steam flowing upward from bottom to top in the first rectification column and the second rectification column enters the space above the tray through the through-hole, contacts the liquid on the tray, and mass and heat transfer occur, realizing the separation of the solvent.

[0021] (4) The through-hole includes a lower acceleration section, a straight-through section, and a mixed-flow section from bottom to top. The steam flows upward through the through-hole and enters the space above the tray. The diameter of the acceleration section decreases from bottom to top. This setting makes the flow cross-section of the steam decrease after entering the acceleration section, the pressure increase, and the flow velocity increase. The steam enters the straight-through section at a relatively high speed and is finally output from the mixed-flow section, so that the speed of the steam output from the mixed-flow section is greater than the speed of the steam entering the acceleration section. This enables the steam to contact the liquid on the tray with greater kinetic energy, and at the same time can stir the liquid, improving the gas-liquid mixing efficiency. At the same time, the shaking of the liquid surface will exert a force on the vibrating spring, causing the vibrating spring to undergo elastic deformation under the force, thereby driving the disturbance plate at the upper end of the vibrating spring to also produce slight movement, further disturbing the liquid, and thus improving the mass and heat transfer efficiency and the rectification efficiency. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 Structural schematic diagram of a piperonal purification system provided by an embodiment of the present application;

[0024] Figure 2 Structural schematic diagram of a piperonal purification system provided by another embodiment of the present application;

[0025] Figure 3 Structural schematic diagram of a tray provided by an embodiment of the present application;

[0026] Figure 4 Structural schematic diagram of a disturbance structure provided by an embodiment of the present application.

[0027] Description of the Reference Numerals:

[0028] 5: Tray, 101: First rectification pump, 110: First rectification column, 120: First condenser, 130: First reflux drum, 140: Piperylene storage tank, 150: First circulation pump, 160: First reboiler, 170: First vacuum unit, 180: Second temperature sensor, 201: Second rectification pump, 210: Second rectification column, 220: Second condenser, 230: Second reflux drum, 240: Piperonal storage tank, 241: Fore-fraction mixture storage tank, 250: Second circulation pump, 260: Second reboiler, 270: Second vacuum unit, 280: Third temperature sensor, 310: Piperylene circulation pipeline, 320: Fore-fraction mixture pipeline, 330: Dichloroethane circulation pipeline, 340: Dimethyl carbonate circulation pipeline, 410: Distillation column, 420: Third condenser, 430: Dichloroethane storage tank, 440: Dimethyl carbonate storage tank, 450: First temperature sensor, 510: Tray, 511: Spring seat, 512: Vibration spring, 513: Disturbance plate, 520: Overflow weir, 530: Downcomer, 540: Through hole, 541: Acceleration section, 542: Straight-through section, 543: Mixed-flow section. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts also belong to the scope of protection of the present application.

[0030] As Figure 1 shown, the present application provides a piperonal purification system, which includes an atmospheric distillation device, a first negative-pressure rectification device, a second negative-pressure rectification device and a solvent circulation pipeline that are connected in sequence;

[0031] The first negative-pressure rectification device includes a first rectification column 110, a first condenser 120, a first reflux drum 130 and a piperylene storage tank 140 that are connected in sequence to the top gas-phase outlet of the first rectification column 110. The feed inlet of the first rectification column 110 of the first rectification column 110 is connected to the bottom discharge outlet of the atmospheric distillation device through a first rectification pump 101, and the first condenser 120 is also connected to a first vacuum unit 170;

[0032] The second vacuum rectification device includes a second rectification column 210, a second condenser 220 and a second reflux drum 230 which are sequentially connected to the top gas phase outlet of the second rectification column 210. The second reflux drum 230 is respectively connected to a piperonal storage tank 240 and a fore-fraction mixture storage tank 241. The bottom of the second rectification column 210 is sequentially connected with a second circulation pump 250 and a second reboiler 260. The gas phase outlet of the second reboiler 260 is connected to the steam inlet of the second rectification column 210. The feed inlet of the second rectification column 210 is connected to the bottom discharge outlet of the first rectification column 110 through a second rectification pump 201. The second condenser 220 is also connected with a second vacuum unit 270;

[0033] The solvent circulation pipeline includes a piperylene circulation pipeline 310 and a fore-fraction mixture pipeline 320. The inlet end of the piperylene circulation pipeline 310 is connected to a piperylene storage tank 140, and the outlet end of the piperylene circulation pipeline 310 is connected to a piperonal condensation reaction device. The inlet end of the fore-fraction mixture pipeline 320 is connected to the fore-fraction mixture storage tank 241, and the outlet end of the fore-fraction mixture pipeline 320 is connected to the feed inlet of the first rectification column 110.

[0034] Specifically, the crude piperonal contains dichloroethane, dimethyl carbonate, piperylene, piperonal and a small amount of high-boiling substances. The crude piperonal is subjected to atmospheric distillation through an atmospheric distillation device to distill out the low-boiling substances dichloroethane and dimethyl carbonate in the crude piperonal. Then the remaining crude piperonal is fed into a first vacuum rectification device for primary vacuum rectification to distill out the piperylene in the crude product and further purify the piperonal. After the primary vacuum rectification, the remaining piperonal, a small amount of piperylene and a small amount of high-boiling substances in the first vacuum rectification device are transported to a second vacuum rectification device for further rectification to distill out the piperonal with a higher boiling point, realizing the rectification and purification of piperonal. By first distilling out the light components dichloroethane and dimethyl carbonate through atmospheric distillation and then feeding the remaining crude piperonal into a vacuum rectification device for vacuum rectification, compared with directly subjecting the crude piperonal to vacuum rectification in the prior art, the piperonal purification system provided by the present application can prevent the light components dichloroethane and dimethyl carbonate from entering the vacuum unit during the rectification process, which is beneficial to the stable operation of the vacuum unit and also beneficial to maintaining the stability and high efficiency of the overall purification system operation.

[0035] First, the crude piperonal is fed into an atmospheric distillation unit for distillation to separate the light components, dichloroethane and dimethyl carbonate. The remaining crude piperonal after distillation is transported to the first rectification tower 110 through the first rectification pump 101. The remaining crude piperonal falls to the bottom of the first rectification tower 110 under the action of gravity. The first circulation pump 150 is started to pump the crude product at the bottom of the first rectification tower 110 into the first reboiler 160 for heating to vaporize piperylene. The obtained piperylene vapor enters the first rectification tower 110 through the vapor inlet of the first rectification tower 110 from the gas-phase outlet of the first reboiler 160. The vapor continuously rises to the top of the first rectification tower 110 and is condensed into piperylene liquid by the first condenser 120, then enters the first reflux drum 130 for temporary storage. Part of the piperylene in the first reflux drum 130 is pumped back to the first rectification tower 110 through the reflux pump to participate in rectification again. The refluxed piperylene moves from top to bottom, and the piperylene vapor moves from bottom to top. The two contact countercurrently for mass transfer and heat transfer to achieve further purification of piperylene. This process is repeated in a cycle, and finally, the obtained piperylene is transported to the piperylene storage tank 140 for storage, realizing the separation of piperylene.

[0036] The bottom liquid remaining in the bottom of the first rectification tower 110 is piperonal, a small amount of piperylene, and a small amount of high-boiling substances. The bottom liquid of the first rectification tower is transported into the second rectification tower 210 through the second rectification pump 201, falls to the bottom of the second rectification tower 210 under the action of gravity, and is transported to the second reboiler 260 through the second circulation pump 250 for heating and vaporization to obtain the vapor of a mixture of piperonal and a small amount of piperonal and piperylene. The vapor obtained by vaporization enters the second rectification tower 210 through the gas-phase outlet of the second reboiler 260 from the vapor inlet of the second rectification tower 210. The vapor continuously rises to the top of the second rectification tower 210, is condensed by the second condenser 220, and is temporarily stored in the second reflux drum 230. According to the different temperature sections in the second rectification tower 210, liquid piperonal, a mixed liquid of piperonal and piperylene are obtained, and are transported back to the second rectification tower 210 through the reflux pump to continue to participate in the rectification process. After multiple cycles of rectification, liquid piperonal is obtained and input into the piperonal storage tank 240 for temporary storage, and the obtained small amount of mixture of piperonal and piperylene is transported to the pre-fraction mixture storage tank 241 for temporary storage. In this way, the rectification and purification of piperonal are realized, and the purification system operates stably, can operate for a long period, greatly reduces the number of system repairs, and reduces the time cost and economic cost of system maintenance.

[0037] The piperonal purification system of the present application is also provided with a solvent circulation pipeline, which applies piperylene in the piperylene storage tank 140 to the piperonal condensation reaction device through the piperylene circulation pipeline 310, and applies piperonal and piperonal in the pre-fraction mixture storage tank 241 to the first distillation column 110 for further distillation, separating and recovering piperylene and piperonal therein. This setting reduces the waste of solvents and lowers the production cost. At the same time, only a small amount of piperylene and piperonal in the second distillation column 210 are applied to the first distillation column 110 for re-distillation. Compared with the prior art where all the pre-fractions composed of dichloroethane, dimethyl carbonate, piperylene, and piperonal are returned to the first distillation column 110 for re-distillation, the solution provided by the present application reduces the amount of fraction application, thereby avoiding the operating loads of the first distillation column 110 and the second distillation column 210, further avoiding the damage of light components to the vacuum unit, reducing the treatment amount of the tail gas adsorption device for the tail gas from the vacuum unit, and greatly reducing the system operating cost.

[0038] Through the above solution, the present application realizes the efficient rectification of piperonal. The crude piperonal is subjected to atmospheric distillation by an atmospheric distillation device to distill out the low-boiling substances dichloroethane and dimethyl carbonate in the crude piperonal. Then, the remaining crude piperonal is fed into a first negative-pressure rectification device for primary negative-pressure rectification to distill out piperylene in the crude product, and the piperonal is further purified. After the primary negative-pressure rectification, the remaining piperonal, a small amount of piperylene and a small amount of high-boiling substances in the first negative-pressure rectification device are transported to a second negative-pressure rectification device for further rectification to distill out the piperonal with a higher boiling point, realizing the rectification and purification of piperonal. By first distilling out the light components dichloroethane and dimethyl carbonate through atmospheric distillation and then feeding the remaining crude piperonal into the negative-pressure rectification device for negative-pressure rectification, compared with directly subjecting the crude piperonal to negative-pressure rectification in the prior art, the piperonal purification system provided by the present application avoids the light components dichloroethane and dimethyl carbonate from entering the negative-pressure unit during the rectification process, which is beneficial to the stable operation of the negative-pressure unit and is also conducive to maintaining the stability and efficiency of the overall purification system operation. By providing a solvent circulation pipeline, the piperylene in the piperylene storage tank is applied to the piperonal condensation reaction device through the piperylene circulation pipeline, and the piperonal and piperonal in the pre-fraction mixture storage tank are applied to the first rectification tower for further rectification to separate and recover the piperylene and piperonal therein. Such a setting reduces the waste of solvents and lowers the production cost. At the same time, only a small amount of piperylene and piperonal in the second rectification tower are applied to the first rectification tower for re-rectification. Compared with the prior art in which the pre-fraction composed of dichloroethane, dimethyl carbonate, piperylene and piperonal is all fed back to the first rectification tower for re-rectification, the solution provided by the present application reduces the amount of fraction application, thus avoiding the operating load of the first rectification tower and the second rectification tower, further avoiding the damage of the light components to the negative-pressure unit, and reducing the treatment amount of the tail gas adsorption device for the tail gas from the negative-pressure unit, greatly reducing the system operation cost.

[0039] As Figure 2 shown, optionally, the atmospheric distillation device includes a distillation tower 410 and a third condenser 420 connected to the gas-phase outlet at the top of the distillation tower 410. The outlet of the third condenser 420 is respectively connected to a dichloroethane storage tank 430 and a dimethyl carbonate storage tank 440. The bottom discharge port of the distillation tower 410 is connected to the feed port of the first rectification tower 110 through a first rectification pump 101.

[0040] Specifically, the crude piperonal is heated and distilled in the distillation column 410 to obtain the vapors of dichloroethane and dimethyl carbonate at different temperatures. Since the boiling point of dichloroethane is lower than that of dimethyl carbonate, during the distillation process, dichloroethane is distilled out first, and then dimethyl carbonate is distilled out. After the distilled vapors are condensed into liquids by the third condenser 420, first open the valve on the dichloroethane storage tank 430 to transfer the dichloroethane liquid to the dichloroethane storage tank 430 for storage, and then open the valve on the dimethyl carbonate storage tank 440 to transfer the dimethyl carbonate to the dimethyl carbonate storage tank 440 for temporary storage. The bottom liquid of the distillation column 410 is transferred to the first rectification column 110 through the first rectification pump 101 for further purification. By distilling out dichloroethane and dimethyl carbonate first, dichloroethane and dimethyl carbonate are avoided from entering the vacuum unit in the subsequent vacuum rectification stage, improving the operation stability of the system.

[0041] As Figure 2 shown, optionally, the solvent circulation pipeline further includes a dichloroethane circulation pipeline 330 and a dimethyl carbonate circulation pipeline 340. The dichloroethane circulation pipeline 330 is connected between the dichloroethane storage tank 430 and the piperonal extraction device, and the dimethyl carbonate circulation pipeline 340 is connected between the dimethyl carbonate storage tank 440 and the piperonal condensation solvent kettle.

[0042] Specifically, dichloroethane is transferred to the piperonal extraction device through the dichloroethane circulation pipeline 330 to participate in the extraction process of piperonal, reducing the waste of dichloroethane. At the same time, dimethyl carbonate is transferred to the piperonal condensation solvent kettle to recycle dimethyl carbonate, reducing the production cost and the wastewater treatment load.

[0043] Among them, the preparation process of piperonal in this application: after the condensation reaction of glyoxylic acid and piperylene, an oxidative decarboxylation reaction is carried out. Dimethyl carbonate is used as the solvent in the condensation reaction.

[0044] As Figure 2 shown, optionally, a first temperature sensor 450 is arranged in the distillation column 410, a second temperature sensor 180 is arranged in the first rectification column 110, and a third temperature sensor 280 is arranged in the second rectification column 210.

[0045] Specifically, the temperature in the distillation column 410 is detected by the first temperature sensor 450, and it is judged whether the distilled material is dichloroethane or dimethyl carbonate according to the reading of the first temperature sensor 450, and the valve on the corresponding storage tank is opened to collect the distillate. The second temperature sensor 180 is used to detect the temperature in the first rectification column 110, and the distillation temperature of piperylene is judged according to the boiling point of piperylene and the pressure of the vacuum unit. The third temperature sensor 280 is used to detect the temperature in the second rectification column 210, and it is judged whether to open the valve on the piperonal storage tank 240 or the pre-fraction mixture storage tank 241 according to the temperature reading, which helps the system to operate conveniently and efficiently.

[0046] As shown Figure 3 in the figure, optionally, a plurality of trays 5 with the same structure are arranged inside the first rectification column 110 and the second rectification column 210 along the tower body direction. The tray 5 includes a tray plate 510, an overflow weir 520, and a downcomer 530. Overflow weirs 520 are arranged at positions near both sides of the tray plate 510. A downcomer 530 is connected to the lower part of one of the overflow weirs 520. The downcomers 530 of every two adjacent tray plates 510 are arranged staggeredly, and through holes 540 are formed at positions between the two overflow weirs 520 on the tray plate 510.

[0047] Specifically, the tray 5 is used for mass transfer and heat transfer of gas and liquid during the rectification process. The arrangement of the tray plate 510 is conducive to the residence of the liquid phase on the tray plate 510, thereby increasing the gas-liquid contact time and improving the rectification efficiency. The overflow weir 520 is used to form a certain thickness of liquid on the tray plate 510, further increasing the gas-liquid contact time and contact area. The downcomer 530 is used to guide the liquid on the upper tray plate 510 to the lower tray plate 510, which is conducive to the continuous and stable progress of rectification. The downcomers 530 of every two adjacent tray plates 510 are arranged staggeredly, that is, the downcomer 530 of the upper tray plate 510 is aligned with the overflow weir 520 of the lower tray plate 510 that is not connected to the downcomer 530 in the vertical direction. This arrangement is conducive to the balanced force of the tray plate 510 and the stable operation of the rectification column. The steam flowing upward from the bottom in the first rectification column 110 and the second rectification column 210 enters above the tray plate 510 through the through holes 540, contacts the liquid on the tray plate 510, and performs mass transfer and heat transfer, realizing the separation of the solvent.

[0048] As shown Figure 4 in the figure, optionally, the through hole 540 includes a lower acceleration section 541, a straight flow section 542, and a mixed flow section 543 from bottom to top. The diameter of the acceleration section 541 decreases from bottom to top. The diameter of the straight flow section 542 is equal to the upper end diameter of the acceleration section 541 and remains unchanged. The diameter of the mixed flow section 543 increases from bottom to top, and the lower end diameter of the mixed flow section 543 is equal to the diameter of the straight flow section 542.

[0049] Specifically, the through hole 540 includes a lower acceleration section 541, a straight flow section 542, and a mixed flow section 543 from bottom to top. The steam flows upward through the through hole 540 and enters above the tray plate 510. The diameter of the acceleration section 541 decreases from bottom to top. This setting makes the flow cross-section of the steam decrease after entering the acceleration section 541, the pressure increase, and the flow velocity increase. The steam enters the straight flow section 542 at a faster speed and is finally output by the mixed flow section 543, so that the speed of the steam output by the mixed flow section 543 is greater than the speed of the steam entering the acceleration section 541. This enables the steam to contact the liquid on the tray plate 510 with greater kinetic energy, and at the same time can stir the liquid, improving the gas-liquid mixing efficiency, thereby improving the mass transfer and heat transfer efficiency and the rectification efficiency.

[0050] Optionally, the ratio of the lower end diameter to the upper end diameter of the acceleration section 541 is 1.3 - 1.6:1.

[0051] Specifically, if the ratio of the lower end diameter to the upper end diameter of the acceleration section 541 is too large, it will generate a large resistance to the rising steam. Therefore, it is necessary to keep the ratio of the lower end diameter to the upper end diameter at an appropriate value.

[0052] As Figure 4 shown, optionally, a disturbance structure is further provided on the tray 510. The disturbance structure includes a spring seat 511, a vibration spring 512, and a disturbance plate 513. The spring seat 511 is fixedly arranged on the tray surface of the tray 510. One end of the vibration spring 512 is fixedly connected to the spring seat 511, and the other end of the vibration spring 512 is connected to the central position of the disturbance plate 513.

[0053] Specifically, since the steam has a large kinetic energy and contacts the liquid on the tray 510, it causes the turbulent mixing of the liquid and the gas. The shaking of the liquid surface will exert a force on the vibration spring 512, causing the vibration spring 512 to undergo elastic deformation under the force, thereby driving the disturbance plate 513 at the upper end of the vibration spring 512 to also produce slight movement, thereby further disturbing the liquid, further increasing the contact time and area of the gas-liquid, improving the mass transfer and heat transfer efficiency, and further achieving the effect of improving the rectification efficiency.

[0054] Furthermore, the height of the disturbance plate 513 is lower than or equal to the height of the overflow weir 520, so that the disturbance plate 513 is placed below the liquid surface or flush with the liquid surface, which is helpful for the disturbance effect of the disturbance plate 513 on the liquid.

[0055] The technical solution of the present application will be described in detail below with specific embodiments as examples.

[0056] In the present embodiment, the operation process of the piperonal purification system during specific operation is as follows:

[0057] The crude piperonal is heated and distilled in the distillation column 410. The temperature inside the distillation column 410 is detected by the first temperature sensor 450, and the vapors of dichloroethane and dimethyl carbonate obtained at different temperatures are judged according to the reading of the first temperature sensor 450. Since the boiling point of dichloroethane is lower than that of dimethyl carbonate, during the distillation process, dichloroethane is distilled out first, and then dimethyl carbonate is distilled out. After the distilled vapors are condensed into liquids by the third condenser 420, the valve on the dichloroethane storage tank 430 is first opened to transfer the dichloroethane liquid to the dichloroethane storage tank 430 for storage, and then the valve on the dimethyl carbonate storage tank 440 is opened to transfer the dimethyl carbonate to the dimethyl carbonate storage tank 440 for temporary storage. The bottom liquid of the distillation column 410 is transferred to the first rectification column 110 through the first rectification pump 101 for further purification. Dichloroethane is transferred to the piperonal extraction device through the dichloroethane circulation pipeline 330 to participate in the extraction process of piperonal, reducing the waste of dichloroethane. At the same time, dimethyl carbonate is transferred to the piperonal condensation solvent kettle.

[0058] The bottom liquid of the distillation column 410 is transferred to the first rectification column 110 through the first rectification pump 101. The remaining crude piperonal falls to the bottom of the first rectification column 110 under the action of gravity. The first circulation pump 150 is started to pump the crude product at the bottom of the first rectification column 110 into the first reboiler 160 for heating to vaporize piperylene. The obtained piperylene vapor enters the first rectification column 110 through the gas-phase outlet of the first reboiler 160 and the steam inlet of the first rectification column 110. The steam continuously rises to the top of the first rectification column 110 (the extraction temperature is 75 - 85 °C), and after being condensed into piperylene liquid by the first condenser 120, it enters the first reflux tank 130 for temporary storage. Part of the piperylene in the first reflux tank 130 is pumped back to the first rectification column 110 through the reflux pump to participate in the rectification again. The refluxed piperylene moves from top to bottom, and the piperylene vapor moves from bottom to top. The two contact countercurrently for mass transfer and heat transfer to achieve the further purification of piperylene. This process is repeated in a cycle, and finally the obtained piperylene is transferred to the piperylene storage tank 140 for storage, realizing the separation of piperylene.

[0059] The bottoms liquid remaining in the reboiler of the first rectification column 110 is piperonal, a small amount of piperylene, and a small amount of high boilers. The bottoms liquid of the first rectification column is transported into the second rectification column 210 by the second rectification pump 201 for rectifying piperonal. The bottoms liquid of the first rectification column falls to the reboiler of the second rectification column 210 under the action of gravity and is transported to the second reboiler 260 by the second circulation pump 250 for heating and vaporization, obtaining vapor of piperonal (drawing temperature 100 - 120 °C) and a mixture of a small amount of piperonal and piperylene (drawing temperature 85 - 95 °C). The vapor obtained by vaporization is input into the second rectification column 210 from the gas-phase outlet of the second reboiler 260 through the vapor inlet of the second rectification column 210. The vapor continuously rises to the top of the second rectification column 210, is condensed by the second condenser 220, temporarily stored in the second reflux drum 230, and due to the different temperature sections in the second rectification column 210, liquid piperonal and a mixture of liquid piperonal and piperylene are obtained and are transported back into the second rectification column 210 by the reflux pump to continue participating in the rectification process. After multiple cycles of rectification, liquid piperonal is input into the piperonal storage tank 240 for temporary storage and is applied to the piperonal condensation reaction device through the piperylene circulation pipeline 310. The obtained mixture of a small amount of piperonal and piperylene is transported to the fore-fraction mixture storage tank 241 for temporary storage and is applied to the first rectification column 110 for further rectification.

[0060] During the rectification process, the vapor runs from bottom to top and enters the space above the tray 510 through the through-hole 540. The acceleration section 541 decreases in diameter from bottom to top, so that the flow cross-section of the vapor decreases after entering the acceleration section 541, the pressure increases, the flow rate increases, the vapor enters the straight-through section 542 at a relatively high speed, and finally is output by the mixed-flow section 543, making the speed of the vapor output by the mixed-flow section 543 greater than the speed of the vapor entering the acceleration section 541, so that the vapor has a greater kinetic energy to contact the liquid on the tray 510, and at the same time can agitate the liquid, improving the gas-liquid mixing efficiency, thereby improving the mass transfer and heat transfer efficiency and the rectification efficiency. At the same time, the sloshing of the liquid surface will exert a force on the vibrating spring 512, causing the vibrating spring 512 to undergo elastic deformation under the force, thereby driving the disturbing plate 513 at the upper end of the vibrating spring 512 to also produce slight movement, further disturbing the liquid.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A piperonal purification system, characterized in that, It includes an atmospheric distillation unit, a first vacuum rectification unit, a second vacuum rectification unit and a solvent circulation pipeline that are connected in sequence; The first vacuum rectification unit includes a first rectification tower (110), a first condenser (120), a first reflux tank (130) and a piperylene storage tank (140) that are connected in sequence to the top gas phase outlet of the first rectification tower (110). The bottom of the first rectification tower (110) is sequentially connected to a first circulation pump (150) and a first reboiler (160). The gas phase outlet of the first reboiler (160) is connected to the steam inlet of the first rectification tower (110). The feed inlet of the first rectification tower (110) is connected to the bottom discharge outlet of the atmospheric distillation unit through a first rectification pump (101). The first condenser (120) is also connected to a first vacuum unit (170); The second vacuum rectification unit includes a second rectification tower (210), a second condenser (220) and a second reflux tank (230) that are connected in sequence to the top gas phase outlet of the second rectification tower (210). The second reflux tank (230) is respectively connected to a piperonal storage tank (240) and a fore-fraction mixture storage tank (241). The bottom of the second rectification tower (210) is sequentially connected to a second circulation pump (250) and a second reboiler (260). The gas phase outlet of the second reboiler (260) is connected to the steam inlet of the second rectification tower (210). The feed inlet of the second rectification tower (210) is connected to the bottom discharge outlet of the first rectification tower (110) through a second rectification pump (201). The second condenser (220) is also connected to a second vacuum unit (270); The solvent circulation pipeline includes a piperylene circulation pipeline (310) and a fore-fraction mixture pipeline (320). The inlet end of the piperylene circulation pipeline (310) is connected to the piperylene storage tank (140). The outlet end of the piperylene circulation pipeline (310) is connected to a piperonal condensation reaction device. The inlet end of the fore-fraction mixture pipeline (320) is connected to the fore-fraction mixture storage tank (241). The outlet end of the fore-fraction mixture pipeline (320) is connected to the feed inlet of the first rectification tower (110).

2. The piperonal purification system according to claim 1, wherein, The atmospheric distillation unit includes a distillation tower (410) and a third condenser (420) that is connected to the top gas phase outlet of the distillation tower (410). The outlet of the third condenser (420) is respectively connected to a dichloroethane storage tank (430) and a dimethyl carbonate storage tank (440). The bottom discharge outlet of the distillation tower (410) is connected to the feed inlet of the first rectification tower (110) through a first rectification pump (101).

3. The piperonal purification system according to claim 2, wherein The solvent circulation pipeline also includes a dichloroethane circulation pipeline (330) and a dimethyl carbonate circulation pipeline (340). The dichloroethane circulation pipeline (330) is connected between the dichloroethane storage tank (430) and a piperonal extraction device. The dimethyl carbonate circulation pipeline (340) is connected between the dimethyl carbonate storage tank (440) and a piperonal condensation solvent kettle.

4. The piperonal purification system according to claim 3, wherein A first temperature sensor (450) is provided inside the distillation column (410), a second temperature sensor (180) is provided inside the first rectification column (110), and a third temperature sensor (280) is provided inside the second rectification column (210).

5. The piperonal purification system according to any one of claims 1-4, characterized in that, A plurality of trays (5) with the same structure are arranged inside the first rectification column (110) and the second rectification column (210) along the tower body direction. The tray (5) includes a tray plate (510), an overflow weir (520), and a downcomer (530). The overflow weirs (520) are arranged at positions close to both sides of the tray plate (510). The downcomer (530) is connected to the lower part of one of the overflow weirs (520). The downcomers (530) of every two adjacent tray plates (510) are arranged staggeredly, and through holes (540) are formed at positions between the two overflow weirs (520) on the tray plate (510).

6. The piperonal purification system according to claim 5, characterized in that, The through hole (540) includes a lower acceleration section (541), a direct flow section (542), and a mixed flow section (543) from bottom to top. The diameter of the acceleration section (541) decreases from bottom to top. The diameter of the direct flow section (542) is equal to the upper end diameter of the acceleration section (541) and remains unchanged. The diameter of the mixed flow section (543) increases from bottom to top, and the lower end diameter of the mixed flow section (543) is equal to the diameter of the direct flow section (542).

7. The piperonal purification system according to claim 6, wherein, The ratio of the lower end diameter to the upper end diameter of the acceleration section (541) is 1.3 - 1.6:

1.

8. The piperonal purification system according to claim 7, wherein, A disturbance structure is further arranged on the tray plate (510). The disturbance structure includes a spring seat (511), a vibration spring (512), and a disturbance plate (513). The spring seat (511) is fixedly arranged on the plate surface of the tray plate (510). One end of the vibration spring (512) is fixedly connected to the spring seat (511), and the other end of the vibration spring (512) is connected to the central position of the disturbance plate (513).

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