Three-tower vacuum rectification system and process for recovering and purifying NMP

Abstract

The present application relates to the technical field of chemical equipment, and more particularly to a three-tower vacuum rectification recovery and purification NMP system, comprising: a recovery tower, a first dehydration tower, a second dehydration tower and a product tower arranged in sequence, wherein the recovery tower is provided with: a recovery mechanism for preliminary recovery of NMP waste gas, comprising a No. 1 collection tank arranged at the bottom of the recovery tower for collecting dissolved water; a circulating mechanism for multiple repeated recovery of NMP gas, comprising a mixing element located above the No. 1 collection tank and a shunt element arranged outside the recovery tower and in communication with the mixing element; a jet mechanism arranged around the mixing element in the circulating mechanism and used for fully mixing the waste gas and water droplets in cooperation with the circulating mechanism; the special mechanical structure of "three-tower vacuum rectification" combined with waste gas treatment forms a complete NMP purification system, improves the efficiency and quality of purification, and reduces energy consumption through three-tower rectification and step-by-step utilization of energy.

Description

Technical Field

[0001] This invention relates to the field of chemical equipment technology, and in particular to a three-tower vacuum distillation system and process for recovering and purifying NMP. Background Technology

[0002] The three-tower vacuum distillation process for recovering and purifying NMP uses waste NMP as raw material. Through distillation technology, impurities such as water and light and heavy components are removed from the NMP. Utilizing the boiling point differences between substances, a three-tower vacuum distillation process is employed. First, water is removed from the raw material through the first and second dehydration towers. Then, light and heavy components are removed from the raw material through the product tower, yielding qualified NMP. An intermittent product tower is added to further improve the recovery rate. Simultaneously, appropriate pretreatment such as neutralization and filtration is performed depending on the condition of the incoming waste liquid.

[0003] Patent document CN211752585U discloses a high-efficiency dehydration tower for NMP, comprising a tower base, a tower kettle, a tower body, and a tower top connected in sequence. The bottom of the tower kettle is connected to a discharge pipe, the side wall of the tower kettle is connected to a steam pipe, the tower top is connected to a gas outlet, the tower body is filled with packing, the middle of the tower body is provided with a feed pipe, a liquid distributor located inside the tower body is provided at the feed pipe, and a reflux pipe is provided at the top of the tower body, with a reflux distributor located inside the tower body at the reflux pipe.

[0004] However, existing technologies for NMP purification have poor purification effects and require a large amount of energy to purify. In addition, NMP waste gas needs to be recovered in advance, but the recovery efficiency of NMP waste gas is low, and the concentration of the recovered NMP solution is unstable, making it unsuitable to be directly introduced into the dehydration tower for dehydration and purification. Furthermore, the treatment of NMP waste liquid requires a large amount of energy. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by employing a "three-tower vacuum distillation" method combined with a special mechanical structure for the pre-treatment of NMP waste gas to form a complete NMP purification system. This system is supplemented by a recovery tower and subsequent three-tower multi-stage treatment to improve purification efficiency and quality. At the same time, through three-tower distillation and the cascade recovery and utilization of energy, the efficiency and quality of NMP purification are improved while reducing energy consumption.

[0006] To address the above technical issues, the following technical solution is adopted:

[0007] A three-tower vacuum distillation system for recovering and purifying NMP includes: a recovery tower, a first dehydration tower, a second dehydration tower, and a product tower arranged sequentially, wherein the recovery tower is equipped with:

[0008] The recycling mechanism is used for the preliminary recycling of NMP waste gas. The NMP waste liquid after the preliminary recycling is entered into the first dehydration tower. The recycling mechanism includes a No. 1 collection tank set at the bottom of the recycling tower for collecting dissolved water.

[0009] A circulation mechanism for repeatedly recovering NMP gas includes a mixing component disposed inside the recovery tower and above the first collection pool, and a diversion component disposed outside the recovery tower and connected to the mixing component.

[0010] The jetting mechanism is arranged around the mixing component in the circulation mechanism and is used to cooperate with the circulation mechanism to fully mix the exhaust gas and water droplets;

[0011] The NMP-containing waste gas enters the recovery tower and rises from bottom to top. During the ascent, it passes through the jetting mechanism, which guides the NMP waste gas on the outer circumference of the recovery tower towards the center of the mixing section. The NMP waste gas dissolves in water and enters the diversion section. After recovery, the residual gas is output from the top of the recovery tower. At the same time, some of the NMP in the mixing section returns to the top as the raw liquid for spraying and is recycled. The NMP solution in the diversion section, after being gradually recovered and increasing in concentration, flows back to the No. 1 collection tank below for collection and is output from the bottom of the recovery tower to the first dehydration tower for dehydration.

[0012] Preferably, the top of the product tower is provided with an insulated pipe that connects to a reboiler in the first dehydration tower and is used to reuse the top gas of the product tower through the reboiler in the first dehydration tower.

[0013] Preferably, the mixing component includes a second collection tank disposed above the demister and having a conical bottom, a second rotary sprayer disposed above the second collection tank for drawing the dissolved liquid from the second collection tank, multiple scrapers disposed at the bottom of the second collection tank, a first toothed ring rotatably connected to the second collection tank and having the scrapers fixedly connected to its lower end, a first bevel gear rotatably connected to the side wall of the second collection tank and meshing with the first toothed ring, a first motor connected to the first bevel gear via a belt, and multiple stirring rods rotatably connected to the side wall of the second collection tank and meshing with the first toothed ring.

[0014] Preferably, the jetting mechanism includes a guide plate arranged around the second collection pool to block the NMP exhaust gas from rising, multiple sets of jetting components arranged above the guide plate and horizontally positioned between the second collection pool and the second rotary sprayer, and a second gear ring that drives the jetting components to work via gear transmission.

[0015] The insulation pipe is arranged around the middle of the side wall of the recovery tower and is used to continuously insulate the side wall of the recovery tower near the air guide plate. At the same time, a filter element is also provided at the tail end of the insulation pipe.

[0016] The filter element includes a deflector plate rotatably connected to the end of the insulation pipe and having a flow tube inside, a filter frame rotatably connected to the deflector plate and fixedly connected to the furnace wall of the recovery tower, and a filter tube fixedly connected to the filter frame and having a vertical filter element groove in the middle.

[0017] Preferably, the jet assembly includes:

[0018] An air chamber is located above the air guide plate and is used to contain waste gas and collect and release it.

[0019] Piston, which is slidably connected inside the air chamber;

[0020] A connecting rod, which is fixedly connected to the piston and has a sliding groove on it;

[0021] Preferably, the air chamber has a jet nozzle at one end near the second collection pool and is horizontally offset from the jet nozzles of the air chambers located on both sides of the second collection pool. An air inlet pipe is provided at the bottom of the air chamber near the jet nozzle, which connects to the bottom of the air guide plate. A first baffle plate hinged to the side wall of the air inlet pipe and used to control the gas flow direction of the air inlet pipe and a second baffle plate hinged to the side wall of the jet pipe and used to control the gas flow direction of the jet pipe are provided inside the air chamber.

[0022] Preferably, the diversion component includes a first liquid storage tank and a second liquid storage tank. The first liquid storage tank and the second liquid storage tank are both connected to the second collection pool at the top and to the first collection pool at the bottom. The flow direction of the liquid is controlled by a solenoid valve. A concentration meter is installed in both the first liquid storage tank and the second liquid storage tank. A filter assembly with the same structure as the filter of the jet mechanism is installed on the connecting pipe between the first liquid storage tank, the second liquid storage tank and the first collection pool.

[0023] Preferably, the recovery and purification process of the three-tower vacuum distillation system for recovering and purifying NMP includes the following steps:

[0024] A. Waste gas recovery process in the recovery tower;

[0025] B. In the first dehydration process, the raw material is neutralized and filtered before entering the preheater for heat exchange. It then enters the first dehydration tower from the middle, where most of the water is removed. The liquid phase of the gas at the top of the tower after condensation enters the reflux tank, where part of it is refluxed and part is collected as wastewater. The liquid at the bottom of the tower then enters the second dehydration tower.

[0026] C. The second dehydration process involves a second dehydration treatment of the bottom liquid of the first dehydration tower to obtain the required initial NMP product. The liquid phase after condensation of the vapor phase at the top of the second dehydration tower enters the reflux tank. Part of it is refluxed, and part of it is mixed with the raw materials and returned to the first dehydration tower. The bottom liquid with a water content of <100ppm enters the product tower.

[0027] In the D.NMP refining process, the top condenser of the product tower and the reboiler of the first dehydration tower are double-effect thermally coupled. The top gas of the product tower serves as the heat source for the reboiler of the first dehydration tower. The top gas phase of the product tower is condensed by the condenser-reboiler and the tail cooler. The condensed liquid phase enters the reflux tank, with part being refluxed and part being collected to the intermediate tank for removing light components. NMP product is collected from the upper part of the product tower, enters the preheater and exchanges heat with the raw materials, and is then cooled by circulating water before entering the intermediate tank for the product. Qualified product is sent out of the boundary area, while unqualified product is returned to the raw material tank in the tank area for further processing. The bottom of the product tower is heated by steam, and the bottom liquid is NMP and heavy components to be removed from the intermediate tank for heavy components.

[0028] As a preferred embodiment, the recovery and purification process of the three-tower vacuum distillation system for recovering and purifying NMP includes the following steps in the waste gas recovery process of the recovery tower:

[0029] Step 1, preliminary recovery step: NMP waste gas is introduced into the recovery tower. After passing through the recovery mechanism, the NMP in the NMP waste gas dissolves into water droplets and falls into the No. 1 collection tank. When the dissolved liquid in the No. 1 collection tank reaches the set concentration, the dissolved liquid in the No. 1 collection tank is fed into the first dehydration tower.

[0030] Step two, the mixing and recovery step: the waste gas that was not recovered in the initial recovery step rises again, is blocked by the guide plate, and stays below the guide plate. At this time, the first motor starts to drive the stirring rod to rotate and simultaneously drive the second toothed ring to rotate. The second toothed ring drives the chain to rotate, causing the piston to move in the gas chamber. The piston draws the waste gas below the guide plate into the gas chamber and sprays it out through the jet nozzle. The sprayed waste gas comes into contact with the sprayed water droplets and falls into the second collection tank. With continuous jetting, the concentration in the second collection tank gradually increases. During the recovery process, the heat source in the product tower is transported through the pipeline to the reboiler of the first dehydration tower by the heat insulation pipe. During the process of transporting the heat source, the side wall of the recovery tower is heated in a zone.

[0031] Step 3, Filtration and Switching: The solution in Collection Pool 2 enters the First Storage Tank and is filtered before entering the First Storage Tank. When the solution in the First Storage Tank reaches a certain concentration, the pipe connecting Collection Pool 2 to the First Storage Tank is closed while the pipe connecting to the Second Storage Tank is opened. The solution in the First Storage Tank flows to Collection Pool 1. During the flow of the solution from Collection Pool 2 to the First and Second Storage Tanks, it is filtered by the filtration assembly. The liquid passes through the filter tube, which is equipped with a filter element to filter the solution. When it is necessary to switch the filter element, the deflector plate rotates, causing the liquid to flow to another filter tube. The filter element of the used filter tube is replaced manually.

[0032] Alternatively, the two ends of the insulation pipe are connected to the gas outlet of the product tower and the reboiler of the first dehydration tower, respectively, so that the light components released in the product tower are introduced into the reboiler of the first dehydration tower through the insulation pipe.

[0033] The beneficial effects of this invention are:

[0034] 1. This invention employs "thermal coupling multi-effect distillation technology," which reuses the waste gas released from the product tower through an insulated pipe to provide a heat source for the reboiler of the first dehydration tower. Simultaneously, during the process of guiding the heat source's movement, the waste gas in the product tower is used as a heat source to heat and insulate the sidewall of the recovery tower. This prevents NMP in the waste gas accumulated below the guide plate from condensing due to temperature changes, thus reducing steam consumption, cooling water consumption, and electricity consumption, thereby lowering production costs.

[0035] 2. In this invention, by setting up a "three-tower vacuum distillation", efficient and precise control of the dehydration and distillation process is achieved, increasing product purity, improving the quality of the final NMP product, and improving product recycling rate while increasing product purity, reducing waste discharge and protecting the environment;

[0036] 3. In this invention, by setting up a jet assembly, the exhaust gas is blocked, and at the same time, the piston and the gas chamber are used to extract and spray the exhaust gas. By changing the flow path of the gas, the gas and water droplets can be fully contacted, which is conducive to the rapid separation and recovery of the remaining NMP in the exhaust gas.

[0037] 4. In this invention, by setting up a recovery mechanism and cooperating with a circulation mechanism and a jetting mechanism, NMP waste gas is efficiently recovered, allowing the NMP waste gas to contact water droplets and dissolve in them. Water droplets are sprayed out by a rotating sprayer, and waste gas is sprayed toward the water droplets by the jetting assembly, thereby mixing the waste gas and water droplets, increasing the contact area between the waste gas and water droplets, which is conducive to the rapid dissolution of NMP in the waste gas, significantly reducing the NMP content in the waste gas. Furthermore, the concentration of the NMP solution is monitored, and when it reaches the set concentration range, it is input into the first dehydration tower to ensure the concentration of the solution and improve the dehydration efficiency.

[0038] 5. In this invention, by setting up a multi-layer circulation mechanism and a jetting mechanism, the gas can be recovered multiple times. At the same time, the flow of the dissolved liquid in each layer of the circulation mechanism is controlled by the flow divider, and the concentration of the dissolved liquid is controlled according to the number of layers, so as to achieve efficient utilization of the dissolved liquid and improve the recovery efficiency. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A schematic diagram of the overall process for a three-tower vacuum distillation system to recover and purify NMP.

[0041] Figure 2 A schematic diagram of the overall structure of a three-tower vacuum distillation system for the recovery and purification of NMP.

[0042] Figure 3 A partial structural diagram of a three-tower vacuum distillation system for the recovery and purification of NMP.

[0043] Figure 4 This is a schematic diagram of the demister structure.

[0044] Figure 5 This is a schematic diagram showing the flow direction of waste and dissolved water within the device.

[0045] Figure 6 This is a schematic diagram of the relevant structure of the No. 2 collection pool.

[0046] Figure 7 This is a schematic diagram of the relevant structure of the first toothed ring.

[0047] Figure 8 This is a schematic diagram of the jet mechanism.

[0048] Figure 9 This is a schematic diagram showing the relative positions of the air guide plate and the No. 2 collection pool.

[0049] Figure 10 This is a schematic diagram of the relevant structure of the insulation pipe.

[0050] Figure 11 This is a schematic diagram of the filter element.

[0051] Figure 12 This is a schematic diagram of the jet assembly.

[0052] Figure 13 for Figure 12 A magnified schematic diagram of the structure of A in the middle.

[0053] Figure 14 for Figure 12 A magnified schematic diagram of the structure of B in the middle.

[0054] Figure 15 This is a schematic diagram of the gas flow direction of the jet assembly.

[0055] Figure 16Schematic diagram of gas flow direction of jet assembly

[0056] Figure 17 This is a schematic diagram of the flow divider.

[0057] Figure 18 A schematic diagram of the process for recovering and purifying NMP using a three-tower vacuum distillation system. Detailed Implementation

[0058] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0059] Example 1

[0060] like Figure 1-5 As shown, a three-tower vacuum distillation system for recovering and purifying NMP includes a recovery tower 11, a first dehydration tower 01, a second dehydration tower 02, and a product tower 03 arranged sequentially. The recovery tower 11 is equipped with:

[0061] The recycling mechanism 1 is used for the preliminary recovery of NMP waste gas. The NMP waste liquid after the preliminary recovery is entered into the first dehydration tower 01. The recycling mechanism 1 includes a first collection tank 12 set at the bottom of the recycling tower 11 for collecting dissolved water.

[0062] The circulation mechanism 2 is used to repeatedly recover NMP gas. It includes a mixing component 21 disposed inside the recovery tower 11 and above the first collection pool 12, and a diverting component 22 disposed outside the recovery tower 11 and communicating with the mixing component 21.

[0063] The jetting mechanism 3 is arranged around the mixing component 21 in the circulation mechanism 2 and is used to cooperate with the circulation mechanism 2 to fully mix the exhaust gas and water droplets;

[0064] The NMP-containing waste gas enters the recovery tower 11 and rises from bottom to top. During the rise, it passes through the jetting mechanism 3, which guides the NMP waste gas on the outer circumference of the recovery tower 11 towards the center of the mixing component 21. The NMP waste gas dissolves in water and enters the diversion component 22. After recovery, the residual gas is output from the top of the recovery tower 11. At the same time, some of the NMP in the mixing component 21 returns to the top as the raw liquid for spraying and is recycled. The NMP solution in the diversion component 22, after being gradually recovered and increasing in concentration, flows back to the first collection tank 12 below for collection and is output from the bottom of the recovery tower 11 to the first dehydration tower 01 for dehydration.

[0065] Simultaneously, a wind equalizer 13 is installed above the No. 1 collection pool 12, a No. 1 rotary sprayer 14 is installed above the wind equalizer 13 and connected to the No. 1 collection pool 12, and a demister 15 is installed above the No. 1 rotary sprayer 14.

[0066] In this embodiment, the NMP exhaust gas is recovered multiple times by setting up the circulation mechanism 2 and the jet mechanism 1, and the NMP in the exhaust gas is recovered into the solution. The NMP exhaust gas is initially recovered by passing it into the recovery mechanism 1. The NMP that is not completely absorbed in the recovery mechanism 1 continues to rise into the jet mechanism 1, and is recycled again by the cooperation of the jet mechanism 1 and the circulation mechanism 2.

[0067] In detail, NMP exhaust gas is introduced into recovery tower 11, where it rises evenly via air distributor 13. Rotary sprayer 14 opens, spraying water droplets. These droplets contact the NMP exhaust gas, dissolving the NMP in the water droplets, which then fall into collection tank 12 under gravity. Simultaneously, rotary sprayer 14 continuously draws and sprays the dissolved solution from collection tank 12, gradually increasing its concentration. When the concentration reaches 85%-90%, and the optimal output concentration of the NMP solution is 85%, the solution is transported to first dehydration tower 01 for further dehydration. At this point, the composition of the solution is as follows:

[0068]

[0069] Note: The above serves as the basis for simulation calculations.

[0070] During the spraying and recovery process, the exhaust gas continues to rise, passing through the demister 15 to block water droplets in the gas, and continues to rise. The recovery mechanism 1 first recovers NMP from the exhaust gas, producing a certain concentration of NMP solution. Some of the NMP exhaust gas that is not fully absorbed by the recovery mechanism 1 continues to rise, is extracted by the jetting mechanism 3 and sprayed out in a predetermined direction, and is simultaneously recovered again by the circulation mechanism 2, becoming a lower concentration solution. When the solution in the recovery mechanism 1 reaches a certain concentration, it is input into the first dehydration tower 01, and the solution in the circulation mechanism 2 reaches a certain level and is input into the recovery mechanism 1. The NMP exhaust gas is recovered through layer-by-layer circulation absorption.

[0071] It should be noted that multi-layer absorption of NMP waste gas is used to achieve full recovery of NMP waste gas, while ensuring that the NMP solution is at a certain concentration to facilitate subsequent dehydration and distillation steps.

[0072] It is worth mentioning that by setting up the jet mechanism 3, the flow path of the exhaust gas is changed, so that the exhaust gas can fully contact the sprayed water droplets, thereby improving the efficiency of dissolution and recovery.

[0073] Furthermore, such as Figure 15As shown, the top of the product tower 03 is provided with an insulated pipe 34 that is connected to the reboiler of the first dehydration tower 01 and is used to reuse the top gas of the product tower 03 through the reboiler of the first dehydration tower 01.

[0074] The "thermal coupling multi-effect distillation technology" is adopted, which uses the top gas of product tower 03 to provide a heat source for the first dehydration tower 01, and recovers and utilizes its heat. This not only reduces steam consumption, but also reduces the amount of cooling circulating water used and reduces power consumption. The "energy cascade utilization technology" is adopted, which reduces steam consumption by utilizing the heat of high-temperature NMP products and steam energy in a cascade manner. The steam consumption is equivalent to 0.37-0.5t per ton of raw material, which is far lower than the 1.0-1.3t of the same industry, and the energy consumption is reduced by 50%.

[0075] Furthermore, such as Figure 6 , 7 As shown, the mixing component 21 includes a second collection tank 211 disposed above the demister 15 and with a conical bottom, a second rotary sprayer 217 disposed above the second collection tank 211 to extract the dissolved liquid in the second collection tank 211, multiple scrapers 212 disposed at the bottom of the second collection tank 211, a first toothed ring 213 rotatably connected to the second collection tank 211 and fixedly connected to the scrapers 212 at its lower end, a first bevel gear 214 rotatably connected to the side wall of the second collection tank 211 and meshing with the first toothed ring 213, a first motor 215 connected to and driving the first bevel gear 214 via a belt, and multiple stirring rods 216 rotatably connected to the side wall of the second collection tank 211 and meshing with the first toothed ring 213.

[0076] In this embodiment, by setting up a scraper 212 and a stirring rod 216, the solution in the second collection tank 211 is stirred. The first motor 215 simultaneously drives the scraper 212 and the stirring rod 216 to work, stirring the solution in the second collection tank 211 and promoting the full mixing of NMP in the second collection tank 211. At the same time, the scraper 212 scrapes and cleans the bottom of the second collection tank 211 to prevent condensation from forming at the bottom for a long time.

[0077] In detail, the first motor 215 drives the first bevel gear 214 to rotate, the first bevel gear 214 drives the first gear ring 213 to rotate, the rotation of the first gear ring 213 drives the scraper 212 to move at the bottom of the second collection tank 211, and at the same time drives multiple stirring rods 216 to rotate. The rotation of the stirring rods 216 promotes the flow of the solution and makes the solution fully mixed. The scraper 212 scrapes and cleans the bottom of the second collection tank 211.

[0078] It should be noted that multiple stirring rods 216 are provided and are obliquely rotatably connected to the side wall of the second collection tank 211. When the rotating rod is driven, it rotates along its own axis.

[0079] It is worth mentioning that the first toothed ring 213 is horizontally rotatably connected to the side wall of the second collection tank 211 and rotates along the axis of the second collection tank 211. The first toothed ring 213 drives the scraper 212 to rotate along the bottom of the second collection tank 211, scraping away the condensate at the bottom of the second collection tank 211.

[0080] Furthermore, such as Figure 8-11 As shown, the jet mechanism 3 includes a guide plate 31 arranged around the second collection pool 211 to block the NMP exhaust gas from rising, multiple sets of jet components 32 arranged above the guide plate 31 and horizontally positioned between the second collection pool 211 and the second rotary sprayer 217, and a second gear ring 33 that drives the jet components 32 to work by gear transmission.

[0081] The insulation pipe 34 is arranged around the side wall of the recovery tower 11 in the middle and is used to continuously insulate the side wall of the recovery tower 11 near the air guide plate 31. At the same time, a filter element 35 is also provided at the tail end of the insulation pipe 34.

[0082] The filter element 35 includes a deflector plate 351 rotatably connected to the end of the insulation pipe 34 and having a flow tube inside, a filter frame 352 rotatably connected to the deflector plate 351 and fixedly connected to the furnace wall of the recovery tower 11, and a filter tube 353 fixedly connected to the filter frame 352 and having a vertical filter element groove 354 in the middle.

[0083] In this embodiment, by setting the air guide plate 31 and the jet assembly 32, the upward path of the exhaust gas is changed. The jet assembly 32 is driven by the second bevel gear and the second gear ring 33 to collect the gas blocked below the air guide plate 31 into the jet assembly 32. The heat source in the product tower 03 led out by the heat insulation pipe 34 is used to heat the side wall of the recovery tower 11 to avoid the exhaust gas from condensing due to the temperature drop of the side wall of the recovery tower 11. At the same time, the steam in the heat insulation pipe 34 is filtered by the filter element 35.

[0084] In detail, the exhaust gas from the demister 15 continues to rise and is blocked by the guide plate 31, stopping below it. Simultaneously, the first motor 215 drives the second gear ring 33 to rotate, which in turn drives the jet assembly 32. The heat-insulating pipe 34 is located below the guide plate 31 at the gas stopping point. Heating this point prevents NMP in the gas from condensing and adhering to the sidewalls or guide plate 31 due to prolonged gas residence time. The deflector plate 351 and filter pipe 353 control the flow direction of the dissolved liquid, directing it through the flow tube in the deflector plate 351 to one of the filter pipes 353. A filter element is installed in the vertical filter groove of the filter pipe 353, filtering out impurities from the dissolved liquid. When the filter element needs replacement, the motor drives the deflector plate 351 to switch the flow direction of the dissolved liquid, and the filter element in the empty filter pipe 353 is replaced manually.

[0085] It should be noted that the air guide plate 31 is arc-shaped and set around the second collection tank 211. In conjunction with the conical setting at the bottom of the second collection tank 211, the exhaust gas is guided to the area below the air guide plate 31. The deflecting plate 351 is controlled by a motor and has a flow tube inside to allow the dissolved liquid to flow. By rotating the plate 351, one of the filter tubes 353 can be connected, and the other filter tube 353 will be stopped from use.

[0086] It is worth mentioning that a filter element is installed in the vertical filter element groove 354 in the filter tube 353. The vertical arrangement of the vertical filter element groove 354 ensures that impurities are blocked below the filter element groove. A certain space is reserved below the filter element groove to prevent impurities from clogging the filter tube 353 and causing a decrease in the flow rate of the dissolving liquid.

[0087] Furthermore, such as Figure 12-14 As shown, the jet assembly 32 includes:

[0088] Air chamber 321, which is located above the air guide plate 31 and is used to contain waste gas and collect and release waste gas;

[0089] Piston 322, which is slidably connected inside air chamber 321.

[0090] A connecting rod 323 is fixedly connected to a piston 322 and a sliding groove is provided on the connecting rod 323.

[0091] A chain 324 is also provided, on which a traction block is fixed in the groove of the connecting rod 323, a sprocket 325 for driving the chain 324 to rotate, a third bevel gear 328 fixedly connected to the sprocket 325, a fourth bevel gear 329 meshing with the third bevel gear 328, and a first gear 340 fixedly connected to the fourth bevel gear 329 and meshing with the second toothed ring 33.

[0092] In this embodiment, by setting the chain 324 and the piston 322 rod, the piston 322 is moved, so that the piston 322 reciprocates in the air chamber 321, thereby completing the air intake-air ejection process of the air chamber 321, drawing the exhaust gas below the air guide plate 31 into the air chamber 321 and ejecting it.

[0093] In detail, the rotation of the second gear ring 33 drives the first gear 340 and the fourth bevel gear 329 to rotate. The fourth bevel gear 329 drives the third bevel gear 328 and the sprocket 325 to rotate. The sprocket 325 drives the chain 324 to move. The traction block fixed on the chain 324 is set in the groove of the connecting rod 323, which drives the connecting rod 323 and the piston 322 to move together. It should be noted that multiple sets of jet components 32 are arranged along the circumference of the second collection pool 211. The jet components 32 are divided into two batches to adjust the movement of their pistons 322, so that when one batch of jet components 32 inhales air, the other batch of jet components 32 sprays air, ensuring that exhaust gas is continuously sprayed into the second rotary sprayer 217 in the middle.

[0094] It is worth mentioning that, regarding the setting of the jet nozzles of the multiple jet assembly 32, the jet nozzles of the jet assembly 32 located on both sides of the No. 2 collection pool 211 are staggered and not directly opposite each other, so as to avoid collision between the gas ejected from both sides, resulting in a higher gas density and further improving the dissolution effect of gas and water droplets.

[0095] Furthermore, such as Figure 15 , 16 As shown, the air chamber 321 has a jet nozzle at one end near the second collection pool 211, and the jet nozzles of the air chambers 321 on both sides of the second collection pool 211 are horizontally offset. The bottom of the air chamber 321 near the jet nozzle is provided with an air inlet pipe that connects to the bottom of the air guide plate 31. The air chamber 321 is provided with a first baffle plate 326 hinged to the side wall of the air inlet pipe and used to control the gas flow direction of the air inlet pipe, and a second baffle plate 327 hinged to the side wall of the jet pipe and used to control the gas flow direction of the jet pipe.

[0096] In this embodiment, by setting the first baffle plate 326 and the second baffle plate 327, the air inlet and outlet of the air chamber 321 are controlled, so that the air chamber 321 can draw the exhaust gas below the guide plate 31 and spray the exhaust gas toward the middle of the mixing component 21, thereby reducing the chaos of the gas flow.

[0097] In detail, when piston 322 compresses the air in air chamber 321, the gas is ejected from the jet nozzle. At this time, the first baffle plate 326 blocks the air inlet pipe. When piston 322 draws out the air, the second baffle plate 327 blocks the jet nozzle, and the gas below the guide plate 31 is drawn into air chamber 321.

[0098] Furthermore, such as Figure 17 As shown, the diversion component 22 includes a first liquid storage tank 221 and a second liquid storage tank 222. The first liquid storage tank 221 and the second liquid storage tank 222 are both connected to the second collection pool 211 above and to the first collection pool 12 below. The flow direction of the liquid is controlled by a solenoid valve. A concentration meter is installed in both the first liquid storage tank 221 and the second liquid storage tank 222. A filter assembly with the same structure as the filter element 35 of the jet mechanism 3 is installed on the connecting pipe between the first liquid storage tank 221, the second liquid storage tank 222 and the first collection pool 12.

[0099] In this embodiment, the flow of the solution between the first collection pool 12 and the second collection pool 211 is achieved by setting the first storage tank 221 and the second storage tank 222. Switching between the first storage tank 221 and the second storage tank 222 allows a certain concentration of solution to be input into the first collection pool 12.

[0100] In detail, during use, the first storage tank 221 is connected to the second collection tank 211. The solution flows into the first storage tank 221. When the solution in the first storage tank 221 reaches a certain concentration, the valve controls the connection between the second collection tank 211 and the second storage tank 222 to recover the gas. At the same time, the solution in the first storage tank 221 flows into the first collection tank 12 for reuse.

[0101] It should be noted that the first storage tank 221 and the second storage tank 222 are set up to switch and divert the solution in the second collection tank 211. Both the first storage tank 221 and the second storage tank 222 are equipped with concentration meters to monitor the concentration of the solution. The concentration of the solution in the second collection tank 211 is lower than the concentration of the solution in the first collection tank 12.

[0102] Furthermore, such as Figure 1 As shown, the jetting mechanism 3 and the circulation mechanism 2 are arranged in multiple sets from bottom to top to recycle NMP exhaust gas multiple times.

[0103] In this embodiment, multiple sets of jetting mechanisms 3 and multiple sets of circulation mechanisms 2 are set to achieve layer-by-layer recovery of exhaust gas;

[0104] In detail, the recovery tower 11 is equipped with multiple layers, each layer having an air jet mechanism 3 and a circulation mechanism 2. By setting up the air jet mechanism 3 and the circulation mechanism 2, the absorption effect of NMP in the exhaust gas is improved.

[0105] It should be noted that the storage tank in each layer is connected to the collection pool of the layer below, and the concentration of the solution released must be lower than the concentration set by the layer below. The concentration of the solution recovered layer by layer must reach more than 85% before being released into the first dehydration tower 01.

[0106] It is worth mentioning that the insulation pipe 34 also needs to be set according to the number of layers of the recovery tower so that the insulation pipe 34 can provide insulation and heating for the side walls of the multi-layer recovery tower 11.

[0107] Furthermore, such as Figure 10 As shown, the two ends of the insulation pipe 34 are connected to the gas outlet of the product tower 03 and the reboiler of the first dehydration tower 01, respectively. The hot steam released in the product tower 03 is introduced into the reboiler of the first dehydration tower 01 through the insulation pipe 34.

[0108] In detail, the heat insulation pipe 34 is arranged around the side wall of the reactor, and the heat source is released into the product tower 03 to heat the side wall of the recovery tower 11, and finally flows into the reboiler of the first dehydration tower 01.

[0109] It is worth mentioning that by eliminating the reboiler steam and changing the heat source to the top gas of product column 03, steam consumption can be effectively reduced by 50%.

[0110] Example 2

[0111] Furthermore, such as Figure 18 As shown, a recovery and purification process for an NMP system using a three-tower vacuum distillation method includes the following steps:

[0112] A. Waste gas recovery process in the recovery tower;

[0113] B. In the first dehydration process, the raw material is neutralized and filtered before entering the preheater for heat exchange. It enters the first dehydration tower 01 from the middle, where most of the water is removed. The liquid phase of the gas at the top of the tower after condensation enters the reflux tank. Part of it is refluxed and part is collected as wastewater. The liquid at the bottom of the tower then enters the second dehydration tower 02.

[0114] C. The second dehydration process involves a second dehydration treatment of the bottom liquid of the first dehydration tower 01 to obtain the NMP initial product that meets the requirements. The liquid phase after condensation of the gas phase at the top of the second dehydration tower 02 enters the reflux tank. Part of it is refluxed, and part of it is mixed with the raw materials and returned to the first dehydration tower 01. The bottom liquid with a water content of <100ppm enters the product tower 03.

[0115] In the D.NMP refining process, the top condenser of product tower 03 and the reboiler of the first dehydration tower 01 are double-effect thermally coupled. The top gas of product tower 03 serves as the heat source for the reboiler of the first dehydration tower 01. The gas phase at the top of product tower 03 is condensed by the condenser-reboiler and the tail cooler. The condensed liquid phase enters the reflux tank, with part being refluxed and part being collected to the intermediate tank for removing light components. NMP product is collected from the upper part of product tower 03, enters the preheater and exchanges heat with the raw materials, and is then cooled by circulating water before entering the intermediate tank. Qualified product is sent out of the boundary area, while unqualified product is returned to the raw material tank in the tank area for further processing. The bottom of product tower 03 is heated by steam, and the liquid in the bottom of the tower is NMP and heavy components that are sent to the intermediate tank for removing heavy components.

[0116] E. Light and heavy component processing: After the materials in the light component intermediate tank and the heavy component intermediate tank accumulate to a certain amount, they are respectively sent to batch distillation columns for recovery and processing; the heavy component material is heated and distilled, and the product output at the top of the column is the product. After condensation, it enters the NMP tank of the batch distillation column. After inspection, the qualified product is pumped into the product tank for temporary storage, and the unqualified product is returned to the raw material buffer tank; the light component material is heated and distilled, and the light component is first collected from the top of the column into the light component tank of the batch distillation column, and then the middle fraction is collected into the middle component tank of the batch distillation column. When the top of the column contains no light component, NMP is collected into the NMP tank of the batch distillation column.

[0117] F. Vacuum and tail gas treatment: Non-condensable gases from the top of the first dehydration tower 01, the second dehydration tower 02, the product tower 03, and the batch distillation tower enter the vacuum buffer tank along the vacuum pipeline for gas-liquid separation. The gas is extracted by the vacuum system and enters the tail gas pipeline, where it merges and enters the tail gas absorption tower. NMP is recovered through two-stage circulation absorption. After exiting the tower, the tail gas enters the activated carbon adsorption device for further removal of NMP before being discharged in compliance with standards. The activated carbon adsorption device system is equipped with a fan to meet the pressure loss from the vacuum system to the tail gas discharge.

[0118] The waste gas recovery process of the recovery tower includes the following steps:

[0119] Step 1, preliminary recovery step: NMP exhaust gas is introduced into recovery tower 11, and rotary sprayer 14 is activated. The exhaust gas rises through the air distributor 13 and combines with the sprayed water droplets. Due to gravity, it falls into collection tank 12. When the dissolved solution in collection tank 12 reaches the set concentration, i.e., 80%-90%, the dissolved solution in collection tank 12 is fed into the first dehydration tower 01. The optimal NMP dissolved solution output concentration is 85%.

[0120] Step two, the mixing and recovery step: the waste gas that was not recovered in the preliminary recovery step rises again, passes through the demister 15, continues to rise, is blocked by the guide plate 31, and stops below the guide plate 31. At this time, the first motor 215 starts to drive the stirring rod 216 to rotate and simultaneously drive the second toothed ring 33 to rotate. The second toothed ring 33 drives the chain 324 to rotate, causing the piston 322 to move in the gas chamber 321. The piston 322 draws the waste gas below the guide plate 31 into the gas chamber 321 and sprays it out through the jet nozzle. The sprayed waste gas comes into contact with the sprayed water droplets and falls into the second collection pool 211. With continuous jetting, the concentration in the second collection pool 211 gradually increases. During the recovery process, the heat source in the product tower 03 is transported through the pipeline to the reboiler of the first dehydration tower 01. During the process of transporting the heat source, the heat source in the heat insulation pipe 34 heats the side wall of the recovery tower 11.

[0121] Step 3, Filtration and Switching: The solution in the second collection tank 211 enters the first storage tank 221 and is filtered before entering the first storage tank 221. When the solution in the first storage tank 221 reaches a certain concentration, the pipe connecting the second collection tank 211 to the first storage tank 221 is closed, while the pipe connecting to the second storage tank 222 is opened. The solution in the first storage tank 221 flows to the first collection tank 12. During the process of the solution in the second collection tank 211 flowing to the first and second storage tanks 221 and 222, it is filtered by the filtration assembly. The liquid passes through the filter tube 353, which is equipped with a filter element to filter the solution. When it is necessary to switch the filter element, the deflector plate 351 rotates, causing the liquid to flow to another filter tube 353. The filter element of the used filter tube 353 can be replaced manually.

[0122] In the description of this invention, it should be understood that the terms "front and back", "left and right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0123] Of course, those skilled in the art should understand that the term "a" should be understood as "at least one" or "one or more". That is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple. The term "a" should not be understood as a limitation on the quantity.

[0124] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art under the technical guidance of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A three-tower vacuum distillation system for recovering and purifying NMP, characterized in that, It includes a recovery tower, a first dehydration tower, a second dehydration tower and a product tower arranged sequentially. The recovery tower is equipped with a recovery mechanism for preliminary recovery of NMP exhaust gas, a circulation mechanism for repeated recovery of NMP gas, and a jetting mechanism for fully mixing exhaust gas and water droplets in conjunction with the circulation mechanism. The bottom material collection pipeline of the recovery tower is connected to the first dehydration tower, the bottom material collection pipeline of the first dehydration tower is connected to the second dehydration tower, the bottom material collection pipeline of the second dehydration tower is connected to the inlet of the product tower, a heat exchange reboiler is installed at the bottom of the first dehydration tower, and the top gas of the product tower is connected to the shell-side inlet of the heat exchange reboiler of the first dehydration tower through the collection pipeline. The jetting mechanism is arranged around the mixing component in the circulation mechanism and includes a guide plate arranged around the second collection pool to block the NMP exhaust gas from rising, multiple sets of jetting components arranged above the guide plate and horizontally positioned between the second collection pool and the second rotary sprayer, and a second gear ring that drives the jetting components to work through gear transmission. The middle part of the insulation pipe is arranged around the side wall of the recovery tower and is used to continuously insulate the side wall of the recovery tower near the air guide plate. At the same time, a filter element is also provided at the end of the insulation pipe. The jet assembly includes: An air chamber is located above the air guide plate and is used to contain waste gas and collect and release it. Piston, which is slidably connected inside the air chamber; A connecting rod is fixedly connected to the piston and has a sliding groove on it. The connecting rod is driven to move by a chain and sprocket. The air chamber has a jet nozzle at one end near the No. 2 collection pool and is horizontally offset from the jet nozzles of the air chambers located on both sides of the No. 2 collection pool. An air inlet pipe is provided at the bottom of the air chamber near the jet nozzle, which connects to the bottom of the air guide plate. A first baffle plate hinged to the side wall of the air inlet pipe and used to control the gas flow direction of the air inlet pipe and a second baffle plate hinged to the side wall of the jet pipe and used to control the gas flow direction of the jet pipe are provided inside the air chamber. The recovery mechanism is used for the preliminary recovery of NMP waste gas. The NMP waste liquid after the preliminary recovery is completed enters the first dehydration tower. The recovery mechanism includes a No. 1 collection tank set at the bottom of the recovery tower for collecting dissolved water. The circulation mechanism includes a mixing component disposed inside the recycling tower and above the No. 1 collection pool, and a diversion component disposed outside the recycling tower and communicating with the mixing component; The top of the product tower is equipped with a reboiler that connects to the first dehydration tower and is used to reuse the top gas of the product tower through the reboiler of the first dehydration tower.

2. The three-tower vacuum distillation system for recovering and purifying NMP according to claim 1, characterized in that, The mixing component includes a second collection tank located above the demister and with a conical bottom, a second rotary sprayer located above the second collection tank to extract the dissolved liquid from the second collection tank, multiple scrapers located at the bottom of the second collection tank, a first toothed ring rotatably connected to the second collection tank and with the scrapers fixedly connected to its lower end, a first bevel gear rotatably connected to the side wall of the second collection tank and meshing with the first toothed ring, a first motor connected to the first bevel gear via a belt, and multiple stirring rods rotatably connected to the side wall of the second collection tank and meshing with the first toothed ring.

3. The three-tower vacuum distillation system for recovering and purifying NMP according to claim 1, characterized in that, The filter element includes a deflector plate rotatably connected to the end of the insulation pipe and having a flow tube inside, a filter frame rotatably connected to the deflector plate and fixedly connected to the furnace wall of the recovery tower, and a filter tube fixedly connected to the filter frame and having a vertical filter element groove in the middle.

4. The three-tower vacuum distillation system for recovering and purifying NMP according to claim 1, characterized in that, The diversion component includes a first liquid storage tank and a second liquid storage tank. The first liquid storage tank and the second liquid storage tank are both connected to the second collection pool at the top and to the first collection pool at the bottom. The flow direction of the liquid is controlled by a solenoid valve. A concentration meter is installed in both the first liquid storage tank and the second liquid storage tank. A filter assembly with the same structure as the filter of the jet mechanism is installed on the connecting pipe between the first liquid storage tank, the second liquid storage tank and the first collection pool.

5. The recovery and purification process of a three-tower vacuum distillation system for recovering and purifying NMP according to any one of claims 1 to 4, characterized in that, Includes the following steps: A. Waste gas recovery process in the recovery tower; B. In the first dehydration process, the raw material is neutralized and filtered before entering the preheater for heat exchange. It then enters the first dehydration tower from the middle, where most of the water is removed. The liquid phase of the gas at the top of the tower after condensation enters the reflux tank, where part of it is refluxed and part is collected as wastewater. The liquid at the bottom of the tower then enters the second dehydration tower. C. The second dehydration process involves a second dehydration treatment of the bottom liquid of the first dehydration tower to obtain the required initial NMP product. The liquid phase after condensation of the vapor phase at the top of the second dehydration tower enters the reflux tank, where part of it is refluxed and part is mixed with the raw material and returned to the first dehydration tower. The bottom liquid with a water content of <ppm enters the product tower. In the D.NMP refining process, the top condenser of the product tower and the reboiler of the first dehydration tower are double-effect thermally coupled. The top gas of the product tower serves as the heat source for the reboiler of the first dehydration tower. The top gas phase of the product tower is condensed by the condenser-reboiler and the tail cooler. The condensed liquid phase enters the reflux tank, with part being refluxed and part being collected to the intermediate tank for removing light components. NMP product is collected from the upper part of the product tower, enters the preheater and exchanges heat with the raw materials, and is then cooled by circulating water before entering the intermediate tank for the product. Qualified product is sent out of the boundary area, while unqualified product is returned to the raw material tank in the tank area for further processing. The bottom of the product tower is heated by steam, and the bottom liquid is NMP and heavy components removed to the intermediate tank for heavy components.

6. The recovery and purification process of a three-tower vacuum distillation system for recovering and purifying NMP according to claim 5, wherein the waste gas recovery process of the recovery tower specifically includes the following steps: Step 1, preliminary recovery step: NMP waste gas is introduced into the recovery tower. After passing through the recovery mechanism, the NMP in the NMP waste gas dissolves into water droplets and falls into the No. 1 collection tank. After the dissolved liquid in the No. 1 collection tank reaches the output standard concentration range, the dissolved liquid in the No. 1 collection tank is input into the first dehydration tower. Step two, the mixing and recovery step: the waste gas that was not recovered in the initial recovery step rises again, is blocked by the guide plate, and stays below the guide plate. At this time, the first motor starts to drive the stirring rod to rotate and drive the piston to move in the gas chamber. The piston draws the waste gas under the guide plate into the gas chamber and sprays it out through the jet nozzle. The sprayed waste gas comes into contact with the sprayed water droplets and falls into the second collection tank. With the continuous jetting, the concentration in the second collection tank gradually increases. During the recovery process, the heat source in the product tower is transported to the reboiler of the first dehydration tower through the pipeline. During the heat source transportation process, the heat source in the heat insulation pipe heats the side wall of the recovery tower in a specific area. Step 3, Filtration and Switching: The solution in Collection Pool 2 enters the First Storage Tank and is filtered before entering the First Storage Tank. When the solution in the First Storage Tank reaches a certain concentration, the pipe connecting Collection Pool 2 to the First Storage Tank is closed while the pipe connecting to the Second Storage Tank is opened. The solution in the First Storage Tank flows to Collection Pool 1. During the flow of the solution from Collection Pool 2 to the First and Second Storage Tanks, it is filtered by the filtration assembly. The liquid passes through the filter tube, which is equipped with a filter element to filter the solution. When it is necessary to switch the filter element, the deflector plate rotates, causing the liquid to flow to another filter tube, and then the filter element of the used filter tube is replaced.

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