Distillation waste liquid recovery equipment and TDI recovery method

Abstract

The invention relates to the technical field of material recovery, and discloses distillation waste liquid recovery equipment and a TDI recovery method.The distillation waste liquid recovery equipment comprises a drying device, a condensing device, a scraper and a rotating device, the condensing device is provided with a condensing cavity, the first end of a flow pipe communicates with the drying device, and the second end of the flow pipe communicates with the condensing cavity. The scraper at least partially penetrates through the flow pipe and is arranged in the length direction of the flow pipe. And the rotating device is connected with the scraper and is suitable for driving the scraper to circumferentially rotate along the inner wall of the flow pipe. When the distillation waste liquid recycling equipment is used for recycling TDI in TDI distillation waste liquid and gaseous TDI mixed with tar particles flows through the flow pipe, the rotating device is used for driving the scraper to rotate, and the tar particles in the gaseous TDI are not prone to deposition under the stirring action of the scraper. Therefore, tar particles are prevented from being deposited on the inner wall of the flow pipe and being excessively thick in coking, side reactions of TDI are reduced, the TDI recovery rate and the product purity are improved, the flow pipe is prevented from being blocked, and coking objects on the inner wall of the flow channel do not need to be cleaned through frequent inspection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material recycling, in particular to a distillation waste liquid recycling device and a TDI recycling method. BACKGROUND

[0002] Toluene diisocyanate (TDI) is an important basic chemical raw material, mainly used in the field of polyurethane. In the industrial production process of TDI, due to the existence of impurities in the raw material toluene diamine, insufficient phosgenation reaction and TDI polymerization at high temperature, TDI by-products are produced, which mainly include carbon urea group-containing compounds and chlorine-containing compounds, and have an adverse effect on the application performance of TDI products. Therefore, it is necessary to refine and purify the TDI crude product, thereby producing TDI distillation waste liquid. Since there is about 40-60 wt.% of TDI in the TDI distillation waste liquid, direct discharge will cause yield loss and environmental pollution.

[0003] At present, the mainstream of the industry adopts continuous vacuum drying technology to evaporate and recycle TDI in TDI distillation waste liquid, and then introduces the TDI gas phase flow into the washing tower through the pipeline, uses TDI circulating liquid to condense and capture the TDI gas phase flow, and uses the circulating pump to return the condensed and captured TDI to the front-end process of TDI for further refining. TDI gas phase flow and tar particles are produced after TDI distillation waste liquid is dried, and the TDI gas phase flow will carry the dried tar particles when flowing, and the tar particles will deposit and coking on the inner wall of the pipeline to form high-hardness coking material. On the one hand, TDI will adhere to the coking material to cause side reactions, thereby reducing the recovery rate of TDI and the purity of the product; on the other hand, the coking material is too thick to cause pipeline blockage, so it is necessary to frequently stop the drying equipment for disassembly and cleaning of the coking material on the inner wall of the pipeline.

[0004] Therefore, how to solve or improve the problem that the coking material of tar particles and TDI on the inner wall of the pipeline reduces the recovery rate of TDI and causes blockage has become an important technical problem to be solved by those skilled in the art. SUMMARY

[0005] Therefore, the present application provides a distillation waste liquid recycling device and a TDI recycling method to solve or improve the problem that the coking material on the inner wall of the pipeline reduces the recovery rate of TDI and causes blockage.

[0006] In a first aspect, the present application provides a distillation waste liquid recycling device, comprising:

[0007] a drying device adapted to dry the material in the distillation waste liquid into gaseous material;

[0008] a condensing device provided with a condensing cavity adapted to pass the gaseous material, the condensing device being adapted to condense the gaseous material into liquid state;

[0009] a flow pipe, a first end of which is in communication with the drying device and is used for passing the gaseous material, and a second end of which is in communication with the condensing cavity;

[0010] a scraper, which is at least partially arranged in the flow pipe and is arranged along the length direction of the flow pipe;

[0011] a rotating device, which is connected with the scraper and is adapted to drive the scraper to rotate circumferentially along the inner wall of the flow pipe.

[0012] Optionally, the application further comprises:

[0013] a connecting pipe, a first end of which is in communication with the condensing cavity, the first end of the connecting pipe is arranged opposite to the second end of the flow pipe, the rotating device is connected to the second end of the connecting pipe, and the scraper is arranged in the connecting pipe, the condensing cavity and the flow pipe in sequence.

[0014] Optionally, the application further comprises:

[0015] a stop ring, which is arranged in the connecting pipe and the outer wall of the stop ring is attached to the inner wall of the connecting pipe.

[0016] Optionally, the rotating device is provided with a through hole, and the flow pipe comprises:

[0017] a first flow pipe, a first end of which is in communication with the drying device, and a second end of which is connected to one side of the rotating device and is in communication with the through hole;

[0018] a second flow pipe, a first end of which is connected to the other side of the rotating device and is in communication with the through hole, and a second end of which is in communication with the condensing cavity.

[0019] Optionally, the flow pipe is arranged to be inclined upward in the direction away from the condensing device.

[0020] Optionally, the rotating speed α of the scraper satisfies:

[0021]

[0022] wherein d is the distance between the scraper and the inner wall of the flow pipe, F is the mass flow rate of the distillation waste liquid, C is the mass fraction of the material in the distillation waste liquid, T is the drying temperature of the drying device, P is the pressure inside the condensing cavity, and β is the inclination angle of the flow pipe.

[0023] Optionally, the condensing device comprises:

[0024] a container, which is internally provided with the condensing cavity;

[0025] a nozzle, which is arranged in the condensing cavity and is adapted to spray liquid;

[0026] a circulation pump having an inlet and an outlet, the inlet being in communication with the condensing cavity, the outlet being in communication with the nozzle;

[0027] a cooler disposed between the circulation pump and the nozzle and adapted to cool the liquid flowing from the circulation pump to the nozzle;

[0028] a filter disposed between the condensing cavity and the circulation pump and adapted to filter the liquid flowing from the condensing cavity to the circulation pump;

[0029] an outlet channel in communication between the circulation pump and the cooler.

[0030] Optionally, at least two circulation pumps are provided, the outlet of each of the circulation pumps being in communication with the nozzle, a filter being disposed between the inlet of each of the circulation pumps and the condensing cavity, and a valve being disposed between each filter and the condensing cavity.

[0031] In a second aspect, the present application provides a TDI recovery method, which is applicable to the distillation waste liquid recovery apparatuses described above, comprising:

[0032] passing the distillation waste liquid containing TDI into the drying device;

[0033] using the drying device to dry the TDI in the distillation waste liquid into gaseous TDI mixed with tar particles, the gaseous TDI flowing through the flow pipe into the condensing cavity;

[0034] using the rotating device to drive the scraper to rotate circumferentially along the inner wall of the flow pipe to scrape off part of the tar particles deposited on the inner wall of the flow pipe;

[0035] using the cooling device to condense the gaseous TDI into liquid for collection.

[0036] In a third aspect, the present application provides a TDI recovery method, which is applicable to the distillation waste liquid recovery apparatuses described above, the TDI recovery method comprising:

[0037] passing the distillation waste liquid containing TDI into the drying device;

[0038] using the drying device to dry the TDI in the distillation waste liquid into gaseous TDI mixed with tar particles, the gaseous TDI flowing through the flow pipe into the condensing cavity;

[0039] using the rotating device to drive the scraper to rotate circumferentially along the inner wall of the flow pipe to scrape off part of the tar particles deposited on the inner wall of the flow pipe;

[0040] The circulating pump is started, and the liquid TDI in the condensing cavity flows through the filter, and part of the liquid TDI flows through the cooler and then flows to the nozzle to be sprayed back to the condensing cavity, so as to condense the gaseous TDI in the condensing cavity into liquid TDI, and the other part of the liquid TDI is discharged from the discharge channel and collected.

[0041] The distillation waste liquid recovery equipment provided by the present application comprises a drying device, a condensing device, a flow pipe, a scraper and a rotating device. The condensing device is provided with a condensing cavity, and the flow pipe has a first end and a second end. The first end of the flow pipe is in communication with the drying device, and the second end of the flow pipe is in communication with the condensing cavity. The scraper is connected with the rotating device, the scraper is at least partially arranged in the flow pipe, and the scraper is arranged along the length direction of the flow pipe. When the rotating device drives the scraper to rotate, the scraper rotates along the inner wall of the flow pipe in the circumferential direction. When the distillation waste liquid recovery equipment is used to recover TDI in TDI distillation waste liquid, the TDI distillation waste liquid is introduced into the drying device, and the TDI in the TDI distillation waste liquid is dried into gaseous TDI mixed with tar particles. After the gaseous TDI enters the first end of the flow pipe, the gaseous TDI flows through the flow pipe and flows out from the second end of the flow pipe into the condensing cavity. Under the condensing effect of the condensing device, the gaseous TDI is condensed into liquid TDI.

[0042] When the gaseous TDI mixed with tar particles flows through the flow pipe, the rotating device is used to drive the scraper to rotate. Under the stirring effect of the scraper, the tar particles in the gaseous TDI are not easy to deposit. Even if part of the tar particles still deposit and coking on the inner wall of the flow pipe to form coking substances, under the scraping effect of the scraper when the scraper rotates, the thickness of the tar particle accumulation will not exceed the distance between the scraper and the inner wall of the flow pipe, so that the tar particles are not easy to deposit and coking on the inner wall of the flow pipe and the thickness of the coking is not too thick, which not only reduces the side reaction of TDI, improves the recovery rate of TDI and the purity of the product, but also avoids the blockage of the flow pipe, and the coking substances on the inner wall of the flow channel do not need to be cleaned frequently. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the specific embodiments or the related art, the drawings needed to be used in the specific embodiments or the related art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0044] Figure 1 FIG. 1 is a structural schematic view of a distillation waste liquid recovery equipment according to an embodiment of the present application;

[0045] Figure 2 FIG. 2 is a structural schematic view of another distillation waste liquid recovery equipment according to an embodiment of the present application;

[0046] Figure 3 FIG. 3 is a structural schematic view of a rotating device of a distillation waste liquid recovery equipment according to an embodiment of the present application;

[0047] Figure 4 FIG. 1 is a schematic diagram of an external structure of a rotating device of a distillation waste liquid recovery equipment according to an embodiment of the present application;

[0048] Figure 5 FIG. 2 is a flowchart of a TDI recovery method according to an embodiment of the present application;

[0049] Figure 6 FIG. 3 is a flowchart of another TDI recovery method according to an embodiment of the present application.

[0050] Legend of reference signs:

[0051] 1, drying device; 2, flow pipe; 201, maintenance window; 21, first flow pipe; 22, second flow pipe; 3, condensing device; 31, container; 311, exhaust port; 312, discharge port; 313, condensing cavity; 32, nozzle; 33, circulating pump; 34, cooler; 35, filter; 36, discharge channel; 4, scraper; 5, rotating device; 51, second motor; 52, box body; 53, driving shaft; 54, driving gear; 55, driven wheel; 551, through hole; 6, connecting pipe; 61, liquid guide port; 7, retaining ring; 8, liquid guide pipeline. DETAILED DESCRIPTION

[0052] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0053] The embodiments of the present application will be described below in conjunction with Figures 1 to 6 .

[0054] According to the embodiments of the present application, in one aspect, a distillation waste liquid recovery equipment is provided, which comprises a drying device 1, a condensing device 3, a flow pipe 2, a scraper 4 and a rotating device 5.

[0055] After the distillation waste liquid containing material is introduced into the drying device 1, the drying device 1 can dry the distillation waste liquid to dry the material into gaseous material.

[0056] The condensing device 3 is provided with a condensing cavity 313, and after the gaseous material enters the condensing cavity 313, the condensing device 3 can condense the gaseous material in the condensing cavity 313 into liquid.

[0057] The flow pipe 2 has a first end and a second end, the first end of the flow pipe 2 communicates with the drying device 1, so that the gaseous material discharged from the drying device 1 enters the flow pipe 2 from the first end of the flow pipe 2.

[0058] The second end of the flow pipe 2 is connected with the condensing device 3 and communicates with the condensing cavity 313, so that the gaseous material flows through the flow pipe 2 and is discharged from the second end of the flow pipe 2 and enters the condensing cavity 313.

[0059] The scraper 4 is connected with the rotating device 5, and the rotating device 5 can drive the scraper 4 to rotate. The scraper 4 is at least partially arranged in the flow pipe 2, and the scraper 4 is arranged along the length direction of the flow pipe 2, that is, the length direction of the scraper 4 is consistent with the extension direction of the flow pipe 2. When the rotating device 5 drives the scraper 4 to rotate, the scraper 4 rotates along the inner wall of the flow pipe 2 in the circumferential direction, that is, rotates around the axis of the flow pipe 2.

[0060] When the TDI in the TDI distillation waste liquid is recovered by using the distillation waste liquid recovery equipment, the TDI distillation waste liquid is introduced into the drying device 1, and the TDI in the TDI distillation waste liquid is dried into gaseous TDI by the drying device 1, and the gaseous TDI contains tar particles. After the gaseous TDI enters the first end of the flow pipe 2, it flows through the flow pipe 2 and flows out from the second end of the flow pipe 2 into the condensing cavity 313, and under the condensing action of the condensing device 3, the gaseous TDI is condensed into liquid state.

[0061] When the gaseous TDI containing tar particles flows through the flow pipe 2, the rotating device 5 is used to drive the scraper 4 to rotate, and under the stirring action of the scraper 4, the tar particles in the gaseous TDI are not easy to deposit. Moreover, even if part of the tar particles still deposit and coking on the inner wall of the flow pipe 2 to form coking matters, under the scraping action of the scraper 4 when rotating, the thickness of the tar particle accumulation will not exceed the distance between the scraper 4 and the inner wall of the flow pipe 2, so as to avoid the tar particles from depositing and coking too thick on the inner wall of the flow pipe 2, not only reducing the side reaction of TDI, improving the recovery rate of TDI and the purity of the product, but also avoiding the blockage of the flow pipe 2, without the need to frequently disassemble and inspect to clean the coking matters on the inner wall of the flow channel.

[0062] Wherein TDI is toluene diisocyanate.

[0063] The drying device 1 can be a vacuum drying machine, which has a feeding port and a discharging port, the feeding port is connected with a feeding pipeline, the TDI distillation waste liquid is introduced from the feeding pipeline, that is, enters the vacuum drying machine from the feeding port, and the vacuum drying machine is started to dry and evaporate the TDI distillation waste liquid, so as to dry the TDI into gaseous state and discharge from the discharging port. The first end of the flow pipe 2 communicates with the discharging port, so that the gaseous TDI discharged from the vacuum drying machine can enter the first end of the flow pipe 2.

[0064] The vacuum drier further has a waste discharge port. After the TDI distillation waste liquid is dried and evaporated by the vacuum drier, the TDI is dried into a gaseous state and tar particles are generated. The gaseous TDI mixed with some lighter tar particles when discharged from the discharge port. The remaining heavier tar particles are deposited in the vacuum drier and can be discharged from the waste discharge port for disposal.

[0065] The operating temperature of the vacuum drier is 100-300°C, preferably 250-290°C, such as 100°C, 250°C, 270°C, 290°C and 300°C.

[0066] The operating pressure of the vacuum drier is 0.1-15 kPa (abs), preferably 6-12 kPa (abs), such as 0.1 kPa (abs), 6 kPa (abs), 10 kPa (abs), 12 kPa (abs) and 15 kPa (abs).

[0067] The temperature in the condensation cavity 313 is 30-120°C, preferably 40-60°C, such as 30°C, 40°C, 50°C, 60°C and 120°C.

[0068] The pressure in the condensation cavity 313 is 0.1-15 kPa (abs), preferably 4-10 kPa (abs), such as 0.1 kPa (abs), 4 kPa (abs), 7 kPa (abs), 10 kPa (abs) and 15 kPa (abs).

[0069] The flow rate of the TDI distillation waste liquid is 500-2000 kg / h, preferably 1000-1800 kg / h, such as 500 kg / h, 1000 kg / h, 1500 kg / h, 1800 kg / h, 2000 kg / h.

[0070] The mass fraction of TDI in the TDI distillation waste liquid is 20-80 wt.%, preferably 40-60 wt.%, such as 20 wt.%, 40 wt.%, 50 wt.%, 60 wt.%, 80 wt.%.

[0071] The total content of carbodiimide group-containing compounds and chlorine-containing compounds in the TDI distillation waste liquid is not more than 80 wt.%, preferably not more than 60 wt.%, such as 40 wt.%, 60 wt.% or 80 wt.%.

[0072] The distance between the scraper 4 and the inner wall of the flow pipe 2 is 2-20 mm, preferably 5-10 mm, such as 2 mm, 5 mm, 8 mm, 10 mm or 20 mm.

[0073] In this way, the thickness and hardness of the coking in the gap are increased due to the excessive distance between the scraper 4 and the inner wall of the flow pipe 2, and the contact friction between the scraper 4 and the inner wall of the flow pipe 2 is avoided due to the excessive distance between the scraper 4 and the inner wall of the flow pipe 2.

[0074] The scraper 4 is made of metal material, and the material grade is one of 304, 316, 316L, 35 steel, 45 steel, 40Cr, 65Mn, Cr12, D2, DC53, HT150, HT200, Q235A, Q345R, SKD11, SKH-9, and ASP-23, preferably one of 65Mn, DC53, SKH-9, and ASP-23. The toughness and wear resistance of the scraper 4 are improved by optimizing the material, the good toughness can avoid plastic deformation or fracture of the scraper 4 when blocked by high adhesion coking, and the good wear resistance can reduce the wear rate of the scraper 4 and prolong the service life of the scraper 4.

[0075] The cross-sectional shape of the scraper 4 is one of rectangular, rhombic, trapezoidal, and triangular, preferably trapezoidal, the lower base of the trapezoidal is close to the inner wall of the flow pipe 2, and the lower base angle of the trapezoidal is 20°-70°, preferably 30°-60°, such as 20°, 30°, 45°, 60°, or 70°.

[0076] By optimizing the lower base angle of the scraper 4, it is easier to cut and remove the coking attached to the inner wall of the flow channel, and avoid plugging or jamming when the scraper 4 contacts coking with high hardness and strong adhesion, causing the scraper 4 to stop running.

[0077] The longest side of the cross section of the scraper 4 is 10-100mm, preferably 30-50mm, such as 10mm, 30mm, 40mm, 50mm, or 100mm.

[0078] In an optional embodiment, the flow pipe 2 is provided with an inspection window 201 to facilitate the inspection of the inside of the flow pipe 2.

[0079] As an optional embodiment, the distillation waste liquid recovery device further comprises a connecting pipe 6, the connecting pipe 6 has a first end and a second end. The first end of the connecting pipe 6 is in communication with the condensing cavity 313 and is arranged opposite to the second end of the flow pipe 2. The first end of the connecting pipe 6 is aligned with the second end of the flow pipe 2, and the extension directions of the connecting pipe 6 and the flow pipe 2 are the same.

[0080] After connecting one end of the scraper 4 to the rotating device 5, the other end of the scraper 4 is inserted from the second end of the connecting pipe 6, passes through the connecting pipe 6, and then passes out from the first end of the connecting pipe 6 and into the condensing cavity 313, and then passes through the condensing cavity 313 and into the flow pipe 2 from the second end of the flow pipe 2, and then the rotating device 5 is connected to the second end of the connecting pipe 6.

[0081] In this way, when the rotating device 5 drives the scraper 4 to rotate, the part of the scraper 4 located in the flow pipe 2 can rotate along the circumference of the inner wall of the flow pipe 2.

[0082] In the embodiment, the rotating device 5 can be a first motor, the motor shaft of the first motor is coaxial with the axis of the flow pipe 2, and the scraper 4 is eccentrically connected with the motor shaft of the motor, so that the first motor can drive the scraper 4 to rotate around the axis of the flow pipe 2, i.e., to rotate along the circumference of the inner wall of the flow pipe 2.

[0083] In the alternative embodiment, the distillation waste liquid recovery device further comprises a baffle 7. The baffle 7 is arranged in the connecting pipe 6, and the outer wall of the baffle 7 is attached to the inner wall of the connecting pipe 6. Thus, the baffle 7 forms a ring-shaped protrusion on the inner wall of the connecting pipe 6.

[0084] In this way, after the gaseous TDI is condensed into liquid in the condensing cavity 313, even if part of the liquid TDI enters the connecting pipe 6, most of it will be blocked by the baffle 7, so as to avoid the liquid TDI from contacting the rotating device 5 and to avoid the sealing failure and leakage caused by the contact, thereby prolonging the service life of the rotating device 5 and reducing the maintenance cost.

[0085] To this end, the inner diameter of the connecting pipe 6 is 50-200 mm larger than the inner diameter of the flow pipe 2, preferably 50-100 mm. For example, it can be 50 mm, 80 mm, 100 mm or 200 mm.

[0086] The height of the baffle 7 is 20-100 mm, preferably 50-80 mm, for example, it can be 20 mm, 50 mm, 60 mm, 80 mm or 100 mm.

[0087] In order to facilitate the liquid TDI entering the connecting pipe 6 to be guided out, a liquid guiding opening 61 is formed on the wall of the connecting pipe 6, and a liquid guiding pipe 8 is connected with the liquid guiding opening 61, and the end of the liquid guiding pipe 8 away from the liquid guiding opening 61 is connected back to the condensing cavity 313.

[0088] In this way, after the liquid TDI entering the connecting pipe 6 flows out of the connecting pipe 6 from the liquid guiding opening 61, it flows back to the condensing cavity 313 through the liquid guiding pipe 8.

[0089] In the embodiment, the nominal diameter of the liquid guiding opening 61 and the liquid guiding pipe 8 is not less than 25 mm, preferably 50-150 mm, for example, it can be 25 mm, 50 mm, 120 mm or 150 mm. This can avoid the problem of tar particles blocking the liquid guiding pipe 8.

[0090] As an optional embodiment, the rotating device 5 is provided with a through hole 551, and the flow pipe 2 comprises a first flow pipe 21 and a second flow pipe 22, which are located on two sides of the rotating device 5 respectively. The first flow pipe 21 has a first end and a second end, and the first end of the first flow pipe 21 is communicated with the drying device 1, so that the gaseous material is discharged from the drying device 1 and enters the first flow pipe 21 from the first end of the first flow pipe 21. The second end of the first flow pipe 21 is connected with one side of the rotating device 5 and communicated with the through hole 551, so that the gaseous material flows through the first flow pipe 21 and enters the through hole 551.

[0091] The second flow pipe 22 has a first end and a second end, and the first end of the second flow pipe 22 is connected with the other side of the rotating device 5 and communicated with the through hole 551, so that the gaseous material flows through the through hole 551 and enters the first end of the second flow pipe 22. The second end of the second flow pipe 22 is connected with the condensing device 3 and communicated with the condensing cavity 313, so that the gaseous material flows through the second flow pipe 22, is discharged from the second end of the second flow pipe 22 and enters the condensing cavity 313.

[0092] The scraper 4 can be an integral body or divided into a first scraper 4 and a second scraper 4.

[0093] In the case that the scraper 4 is an integral body, the scraper 4 is arranged in the through hole 551, and the parts of the scraper 4 located outside the two ends of the through hole 551 are arranged in the first flow pipe 21 and the second flow pipe 22 respectively, and the part of the scraper 4 located in the through hole 551 is connected with the rotating device 5, so that when the rotating device 5 drives the scraper 4 to rotate, the parts of the scraper 4 located outside the two ends of the through hole 551 rotate along the inner walls of the first flow pipe 21 and the second flow pipe 22 respectively.

[0094] In the case that the scraper 4 is divided into the first scraper 4 and the second scraper 4, the first scraper 4 is arranged in the first flow pipe 21, and the second scraper 4 is arranged in the second flow pipe 22. One end of the first scraper 4 close to the rotating device 5 is connected with the rotating device 5, and one end of the second scraper 4 close to the rotating device 5 is connected with the rotating device 5, so that the rotating device 5 can drive the first scraper 4 and the second scraper 4 to rotate simultaneously, so that the first scraper 4 rotates along the inner wall of the first flow pipe 21 and the second scraper 4 rotates along the inner wall of the second flow pipe 22.

[0095] The rotating device 5 comprises a second motor 51, a box body 52, a driving shaft 53, a driving gear 54 and a driven wheel 55. The driving shaft 53 and the driven wheel 55 are both rotatably connected to the box body 52. The driving shaft 53 is connected with the driving gear 54. The outer wall of the driven wheel 55 is provided with teeth, and the driving gear 54 is engaged with the teeth on the outer wall of the driven wheel 55. The driving shaft 53 is in transmission connection with the motor shaft of the second motor 51.

[0096] A through hole 551 is formed in the driven wheel 55. The second end of the first flow pipe 21 is connected to the box 52 and communicates with the through hole 551. The first end of the second flow pipe 22 is connected to the box 52 and communicates with the through hole 551. Thus, the gaseous material can pass through the first flow pipe 21, the through hole 551 and the second flow pipe 22 in sequence. The scraper 4 is connected to the driven wheel 55.

[0097] In this way, the motor shaft of the second motor 51 rotates to drive the driving shaft 53 and the driving gear 54 to rotate, thereby driving the driven wheel 55 to rotate. When the driven wheel 55 rotates, the scraper 4 is driven to rotate.

[0098] As an optional embodiment, the flow pipe 2 is inclined, i.e., the axis of the flow pipe 2 forms an angle with the horizontal line, and the flow pipe 2 is inclined upward in the direction away from the condensing device 3. This prevents the liquid TDI in the condensing cavity 313 of the condensing device 3 from flowing back into the flow pipe 2 and entering the drying device 1, which causes the drying device 1 to have excessive processing load or even stop.

[0099] The inclination angle of the flow pipe 2 is 5-60°, preferably 10-45°, such as 5°, 10°, 30°, 45° or 60°.

[0100] Selecting a suitable inclination angle of the flow channel is beneficial for the coking matter falling off from the flow pipe 2 to gradually move to the condensing cavity 313 and enter the bottom of the condensing cavity 313 under the action of gravity and the disturbance of the scraper 4.

[0101] As an optional embodiment, the condensing device 3 includes a container 31, a nozzle 32, a circulating pump 33, a cooler 34, a filter 35 and a discharge passage 36. The inside of the container 31 is provided with a condensing cavity 313. The nozzle 32 is suspended in the condensing cavity 313 and is used to spray low-temperature TDI liquid to condense the gaseous TDI. The container 31 can be a scrubbing tower.

[0102] A first interface communicating with the condensing cavity 313 is formed in the side wall of the container 31. The second end of the flow pipe 2 is connected to the first interface, so that the flow pipe 2 communicates with the condensing cavity 313. In the case that the rotating device 5 is connected to the connecting pipe 6, a second interface communicating with the condensing cavity 313 is also formed in the side wall of the container 31. The first end of the connecting pipe 6 is connected to the second interface.

[0103] The first interface and the second interface are sequentially arranged along the extension direction of the flow pipe 2.

[0104] A discharge port 312 communicating with the condensing cavity 313 is formed in the bottom of the container 31. The low-temperature TDI liquid sprayed from the nozzle 32 and the condensed TDI liquid are discharged from the discharge port 312 in the bottom of the container 31.

[0105] The circulating pump 33 has an inlet and an outlet, the inlet of the circulating pump 33 is communicated with the discharge port 312 through a pipeline, and the outlet of the circulating pump 33 is communicated with the nozzle 32 through a pipeline. The circulating pump 33 can pump the liquid TDI at the bottom of the condensation cavity 313 to the nozzle 32 to form a circulation when the circulating pump 33 is started.

[0106] The cooler 34 is arranged on the connecting pipeline between the circulating pump 33 and the nozzle 32, and is used for cooling the liquid TDI flowing between the circulating pump 33 and the nozzle 32.

[0107] In this way, the liquid TDI discharged from the outlet of the circulating pump 33 is cooled to low-temperature liquid TDI by the cooler 34 first, and then flows to the nozzle 32 to be sprayed out. This facilitates the condensation of the gaseous TDI.

[0108] The cooler 34 can be a liquid cooling heat exchanger.

[0109] The filter 35 is arranged on the connecting pipeline between the condensation cavity 313 and the circulating pump 33, and is used for filtering the liquid flowing from the condensation cavity 313 to the circulating pump 33.

[0110] The discharge passage 36 is communicated with the connecting pipeline between the circulating pump 33 and the cooler 34, and a switch should be arranged on the discharge passage 36.

[0111] In this way, after the circulating pump 33 is started, the liquid TDI at the bottom of the container 31 is first filtered by the filter 35 to form TDI products, and then part of the TDI products is pumped to the nozzle 32 by the circulating pump 33 to be sprayed out. The TDI products are cooled by the cooler 34 in the process of flowing to the nozzle 32, so that the TDI products sprayed out of the nozzle 32 have a lower temperature, and the gaseous TDI entering the condensation cavity 313 can be condensed into liquid, and then falls to the bottom of the container 31 to form a circulating liquid path. The other part of the TDI products is discharged through the discharge passage 36 for collection. The switch on the discharge passage 36 should be at a proper opening degree to ensure that the TDI products not passing through the discharge passage 36 can meet the circulation requirements.

[0112] The TDI products are the filtered liquid TDI.

[0113] The filter 35 can be a commonly used filter 35 on a pipeline, which is composed of a cylinder, a filter screen and a blowdown part. After the impurities are filtered by the stainless steel filter screen, the blowdown part can be opened to clean the impurities.

[0114] In an optional embodiment, at least two circulating pumps 33 are arranged, each of which is communicated with the nozzle 32 through a connecting pipeline 6, and is connected with the discharge port 312 of the container 31 and communicated with the condensation cavity 313 through a connecting pipeline 6. A filter 35 is arranged between each circulating pump 33 and the condensation cavity 313.

[0115] In this way, the two circulating pumps 33 can work simultaneously, and the liquid TDI discharged from the discharge port 312 of the container 31 can be filtered by the filter 35 and then sprayed from the spray head, so that the flow efficiency of the TDI product is higher.

[0116] A valve is arranged between each filter 35 and the condensation cavity 313. In this way, after each circulating pump 33 is started for a period of time, a large amount of coke particles are filtered out by each filter 35. At this time, one of the circulating pumps 33 can be closed, and then the valve between the circulating pump 33 and the condensation cavity 313 is closed. Then, the filter 35 is disassembled, the filtered coke particles are cleaned, the filter 35 is reassembled, the valve is opened, and the circulating pump 33 is restarted. In this process, the other circulating pump 33 can still work normally and circulate the TDI product, so that the filter 35 can be cleaned without stopping.

[0117] The same method can be used to clean the other filter 35 without stopping, and details are not repeated.

[0118] In an optional embodiment, the top of the container 31 is provided with an exhaust port 311, which is in communication with the condensation cavity 313, for discharging waste gas. The exhaust port 311 should be connected to a waste gas treatment device to avoid pollution caused by discharging waste gas to the outside.

[0119] As an optional embodiment, the rotating speed α of the scraper 4 satisfies:

[0120]

[0121] Where d is the distance between the scraper 4 and the inner wall of the flow pipe 2; F is the mass flow rate of the distillation waste liquid; C is the mass fraction of the material in the distillation waste liquid; T is the drying temperature of the drying device 1; P is the pressure in the cooling cavity; and β is the inclination angle of the flow pipe 2.

[0122] The formation rate, shedding rate, hardness, adhesion strength of the coking material on the inner wall of the flow pipe 2 and the TDI side reaction rate are mainly affected by the above factors. By calculating and controlling the rotating speed of the scraper 4 through the above dynamic control formula, on the one hand, the shedding rate of the coking material is greater than its formation rate, so that the flow pipe 2 is not blocked, and on the other hand, the rotating speed of the scraper 4 is prevented from being too fast, and the abnormal wear failure of the scraper 4 system caused by over-speed operation is inhibited.

[0123] After the dynamic control formula is used to calculate and control the rotating speed of the scraper 4, the TDI product obtained has a tar particle content of ≤0.05wt.%, a total content of a carbodiimide group-containing compound and a chlorine-containing compound of ≤0.05wt.%, a TDI content of ≥99.9wt.%, a TDI recovery rate of ≥99.5%, i.e., a ratio of the mass of TDI in the TDI product to the mass of TDI in the TDI distillation waste liquid of ≥99.5%.

[0124] The following further verifies and illustrates by combining three combined examples and two comparative examples:

[0125] Example One

[0126] Referring to the distillation waste liquid recovery equipment as shown in Figure 1 and recovering the TDI distillation waste liquid by the distillation waste liquid recovery equipment to obtain a TDI product; wherein the relevant parameters and material stream information are shown in Table 1 and Table 2:

[0127] Table 1, main equipment parameter information in Example One

[0128]

[0129] Table 2, main material stream information in Example One

[0130]

[0131]

[0132] In Example One, the distillation waste liquid recovery equipment is used to recover and treat the TDI distillation waste liquid, the purity of the TDI product is 99.92wt.%, the recovery rate of the TDI product is 99.65%, and the continuous operation cycle of the vacuum dryer is 392 days.

[0133] Example Two

[0134] Referring to the distillation waste liquid recovery equipment as shown in Figure 2 and recovering the TDI distillation waste liquid by the distillation waste liquid recovery equipment to obtain a TDI product; wherein the relevant parameters and material stream information are shown in Table 3 and Table 4:

[0135] Table 3, main equipment parameter information in Example Two

[0136]

[0137]

[0138] Table 4, main material stream information in Example Two

[0139]

[0140] In Example Two, the distillation waste liquid recovery device was used to recover the TDI distillation waste liquid, the purity of the TDI product was 99.94wt.%, the recovery rate of the TDI product was 99.72%, and the continuous running period of the vacuum drying machine was 427 days.

[0141] Example Three:

[0142] Referring to the distillation waste liquid recovery device as shown in Figure 1 , and recovering the TDI distillation waste liquid by the distillation waste liquid recovery device to obtain a TDI product; wherein the relevant parameters and material flow information are shown in Table 5 and Table 6:

[0143] Table 5, main equipment parameter information in Example Three

[0144]

[0145] Table 6, main material flow information in Example Three

[0146]

[0147] In Example Three, the distillation waste liquid recovery device was used to recover the TDI distillation waste liquid, the purity of the TDI product was 99.95wt.%, the recovery rate of the TDI product was 99.74%, and the continuous running period of the vacuum drying machine was 553 days.

[0148] Comparative Example One:

[0149] Referring to the recovery device as shown in Figure 1 , and recovering the TDI distillation waste liquid by the distillation waste liquid recovery device to obtain a TDI product; the difference is that the rotating speed α of the scraper 4 is not obtained by the calculation formula, and its value is far greater than the appropriate range of the rotating speed; wherein the relevant equipment parameters and material flow information are shown in Table 7 and Table 8:

[0150] Table 7, main equipment parameter information in Comparative Example One

[0151]

[0152] Table 8, main material flow information in Comparative Example One

[0153]

[0154]

[0155] In the comparative example 1, the TDI distillation waste liquid was recovered, the purity of the TDI product was 99.93 wt.%, the recovery rate of the TDI product was 99.75%, and the continuous running period of the vacuum drying machine was 181 days. The continuous running period of the vacuum drying machine in the comparative example 1 was lower than that of each of the examples.

[0156] Comparative example 2

[0157] Referring to the recovery device as shown in Figure 1 , and recovering the TDI distillation waste liquid by using the distillation waste liquid recovery device to obtain a TDI product; the difference lies in that the rotating device 5 and the scraper 4 are not arranged; wherein the related device parameters and material flow information are shown in Table 9 and Table 10:

[0158] Table 9, main device parameter information in comparative example 2

[0159]

[0160] Table 10, main material flow information in comparative example 2

[0161]

[0162] In the comparative example 2, the TDI distillation waste liquid was recovered, the purity of the TDI product was 98.41 wt.%, the recovery rate of the TDI product was 96.92%, and the continuous running period of the vacuum drying machine was 25 days. The purity of the TDI product, the recovery rate of the TDI product, and the continuous running period of the vacuum drying machine in the comparative example 2 were all significantly lower than those of each of the examples of the present application.

[0163] According to the embodiments of the present application, in another aspect, a TDI recovery method is also provided, which is suitable for any of the above recovery devices. The TDI recovery method is as follows:

[0164] Passing the TDI-containing distillation waste liquid into the drying device 1;

[0165] Using the drying device 1 to dry the TDI in the TDI distillation waste liquid into gaseous TDI, the gaseous TDI mixed with tar particles, the gaseous TDI flowing through the flow pipe 2 after entering the first end of the flow pipe 2, and flowing out from the second end of the flow pipe 2 into the condensation cavity 313;

[0166] Using the rotating device 5 to drive the scraper 4 to rotate along the axial direction of the inner wall of the flow pipe 2 to scrape off part of the tar particles deposited on the inner wall of the flow pipe 2;

[0167] Under the condensation effect of the condensation device 3, the gaseous TDI in the condensation cavity 313 is condensed into liquid state.

[0168] When the gaseous TDI mixed with tar particles flows through the flow pipe 2, the rotating device 5 is used to drive the scraper 4 to rotate, and under the stirring action of the scraper 4, the tar particles in the gaseous TDI are not easy to deposit. Moreover, even if some tar particles are still deposited and coked on the inner wall of the flow pipe 2 to form coke, under the scraping action of the scraper 4 when rotating, the thickness of the tar particle accumulation will not exceed the distance between the scraper 4 and the inner wall of the flow pipe 2, so as to avoid the deposition and coking of the tar particles on the inner wall of the flow pipe 2 to be too thick, not only reducing the side reaction of TDI and improving the recovery rate and product purity of TDI, but also avoiding the blockage of the flow pipe 2, and there is no need to frequently disassemble and clean the coke on the inner wall of the flow channel.

[0169] According to the embodiments of the present application, in another aspect, a TDI recovery method suitable for the distillation waste liquid recovery device is also provided, and the TDI recovery method is as follows:

[0170] The distillation waste liquid containing TDI is introduced into the drying device 1;

[0171] The TDI in the TDI distillation waste liquid is dried into gaseous TDI by using the drying device 1, the gaseous TDI mixed with tar particles, and the gaseous TDI enters the first end of the flow pipe 2, flows through the flow pipe 2, and flows out from the second end of the flow pipe 2 into the condensation cavity 313;

[0172] The rotating device 5 is used to drive the scraper 4 to rotate along the axial direction of the inner wall of the flow pipe 2 to scrape off part of the tar particles deposited on the inner wall of the flow pipe 2.

[0173] The circulating pump 33 is started, and the liquid TDI in the condensation cavity 313 flows through the filter 35, part of which flows through the cooler 34 and then flows out from the nozzle 32 back to the condensation cavity 313 to condense the gaseous TDI in the condensation cavity 313 into liquid, and the other part is discharged from the discharge channel 36 for collection.

[0174] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the present application.

Claims

1. A distillation waste liquid recovery device, characterized in that, include: Drying device (1) is suitable for drying materials in distillation waste liquid into gaseous materials; The condensing device (3) is provided with a condensing chamber (313) suitable for introducing the gaseous material, and the condensing device (3) is suitable for condensing the gaseous material into a liquid state; The flow tube (2) has its first end connected to the drying device (1) and used to introduce the gaseous material, and its second end connected to the condensation chamber (313). A scraper (4) is at least partially inserted through the flow tube (2) and is arranged along the length of the flow tube (2); A rotating device (5) is connected to the scraper (4) and is adapted to drive the scraper (4) to rotate circumferentially along the inner wall of the flow tube (2).

2. The distillation waste liquid recovery equipment according to claim 1, characterized in that, Also includes: The first end of the connecting pipe (6) is connected to the condensing chamber (313), and the first end of the connecting pipe (6) is opposite to the second end of the flow pipe (2). The rotating device (5) is connected to the second end of the connecting pipe (6), and the scraper (4) is sequentially inserted through the connecting pipe (6), the condensing chamber (313), and the flow pipe (2).

3. The distillation waste liquid recovery equipment according to claim 2, characterized in that, Also includes: A retaining ring (7) is disposed inside the connecting pipe (6), and the outer wall of the retaining ring (7) is in contact with the inner wall of the connecting pipe (6).

4. The distillation waste liquid recovery equipment according to claim 1, characterized in that, The rotating device (5) is provided with a through hole (551), and the flow tube (2) includes: The first flow tube (21) has its first end connected to the drying device (1), and its second end is connected to one side of the rotating device (5) and connected to the through hole (551). The second flow tube (22) has its first end connected to the other side of the rotating device (5) and communicates with the through hole (551); the second end of the second flow tube (22) is communicated with the condensation chamber (313).

5. The distillation waste liquid recovery equipment according to claim 1, characterized in that, The flow tube (2) is inclined upward in a direction away from the condenser (3).

6. The distillation waste liquid recovery equipment according to claim 5, characterized in that, The rotational speed α of the scraper (4) satisfies: Wherein, d is the distance between the scraper (4) and the inner wall of the flow tube (2); F is the mass flow rate of the distillation waste liquid; C is the mass fraction of the material in the distillation waste liquid; T is the drying temperature of the drying device (1); P is the pressure inside the condensation chamber (313); and β is the tilt angle of the flow tube (2).

7. The distillation waste liquid recovery equipment according to claim 1, characterized in that, The condensation device (3) includes: The container (31) has the condensation chamber (313) inside; A nozzle (32) is disposed in the condensation chamber (313) and is adapted to spray liquid; A circulating pump (33) has an inlet and an outlet, the inlet being connected to the condensation chamber (313) and the outlet being connected to the nozzle (32); A cooler (34) is disposed between the circulation pump (33) and the nozzle (32) and is adapted to cool the liquid flowing from the circulation pump (33) to the nozzle (32); A filter (35) is disposed between the condenser (313) and the circulation pump (33) and is adapted to filter the liquid flowing from the condenser (313) to the circulation pump (33); The discharge channel (36) is connected between the circulating pump (33) and the cooler (34).

8. The distillation waste liquid recovery equipment according to claim 7, characterized in that, At least two circulation pumps (33) are provided, and the outlet of each circulation pump (33) is connected to the nozzle (32). A filter (35) is provided between the inlet of each circulation pump (33) and the condensing chamber (313), and a valve is provided between each filter (35) and the condensing chamber (313).

9. A method for TDI recovery, characterized in that, The distillation waste liquid recovery equipment according to any one of claims 1-8 comprises: The distillation waste liquid containing TDI is passed into the drying device (1); The drying device (1) is used to dry the TDI in the distillation waste liquid into gaseous TDI mixed with tar particles, and the gaseous TDI flows through the flow tube (2) into the condensation chamber (313). The rotating device (5) is used to drive the scraper (4) to rotate circumferentially along the inner wall of the flow tube (2) to scrape off part of the tar particles deposited on the inner wall of the flow tube (2); The gaseous TDI is condensed into a liquid state using a cooling device and collected.

10. A method for TDI recovery, characterized in that, The TDI recovery method, applicable to the distillation waste liquid recovery equipment of claim 7, comprises: The distillation waste liquid containing TDI is passed into the drying device (1); The drying device (1) is used to dry the TDI in the distillation waste liquid into gaseous TDI mixed with tar particles, and the gaseous TDI flows through the flow tube (2) into the condensation chamber (313). The rotating device (5) is used to drive the scraper (4) to rotate circumferentially along the inner wall of the flow tube (2) to scrape off part of the tar particles deposited on the inner wall of the flow tube (2); Start the circulation pump (33) so that the liquid TDI in the condensation chamber (313) flows through the filter (35), and part of it flows through the cooler (34) and then flows to the nozzle (32) to be sprayed back into the condensation chamber (313) to condense the gaseous TDI in the condensation chamber (313) into liquid. The other part is discharged and collected from the discharge channel (36).

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