TDI distillation residue separation and recovery device and TDI distillation residue separation and recovery method

Abstract

The present invention belongs to the field of toluene diisocyanate separation and recovery, and specifically relates to a TDI distillation residue separation and recovery device and a TDI distillation residue separation and recovery method. The method comprises: a) passing the TDI distillation residue into a dryer for drying to obtain a high-temperature TDI vapor flow and flowing solid tar particles; the high-temperature TDI vapor flow is then passed into a novel gas chamber for separation; b) the separated high-temperature TDI vapor flow obtained in step a is conveyed through a gas phase conveying pipe into a spray tower for rapid cooling to obtain a gaseous vapor flow and a liquid material flow; c) a portion of the liquid material flow obtained in step b is cooled and circulated to the spray tower, and the remaining portion is conveyed downstream as a product. The method of the present invention not only ensures a high yield of the resulting TDI product, but also solves the problem of clogging of separation and refining-related equipment in the entire process, such as the drying device.

Description

Technical Field

[0001] The invention belongs to the field of separation and recovery of toluene diisocyanate, and particularly relates to a device for separating and recovering TDI distillation residue and a method for separating and recovering TDI distillation residue. Background Art

[0002] Yield loss occurs in the industrial production of toluene diisocyanate (TDI). This loss is partially due to incomplete phosgenation of toluenediamine (TDA) or the presence of impurities, which form TDI oligomers (primarily compounds containing carbodiimide and chlorine groups, generally referred to as tar), reducing TDI yield. Another reason is that TDI remains at elevated temperatures for extended periods, generating TDI oligomers. During the TDI refining stage, this tar product has a higher boiling point than TDI, making it difficult to completely separate TDI and tar through conventional distillation or rectification methods. Furthermore, the high viscosity of tar and the resulting high separation coefficient impair the flowability of the distillation / rectification column bottoms, which can easily lead to pipeline blockages. Consequently, the TDI refining stage produces a TDI distillation residue containing tar.

[0003] For the above problems, the currently known solutions are:

[0004] The distillation column bottoms stream containing the distillation residue can be burned continuously or discontinuously, which is technically simple to handle and can be used to generate steam if suitable heat utilization facilities are available. However, this method has the disadvantage that the distillation column bottoms stream containing the distillation residue always contains a certain amount of the useful product isocyanate, resulting in a yield loss.

[0005] In order to minimize the loss of isocyanate yield, the distillation column bottom stream can be transferred to a stirred and heated container and mixed with a high-boiling hydrocarbon (preferably pitch) to distill out the free isocyanate in the residue as much as possible (e.g., patent document EP0548685A2). The shortcoming of this method is that the introduction of foreign matter (pitch) and the long-term residence at high temperature can also cause isocyanate polymerization losses. In addition, the method of industrially available useful materials, such as the distillation column bottom stream containing the residue prepared from toluene diisocyanate, is separated after mixing with alkanolamines (e.g., patent document US 5902459) or with isocyanates of the diphenylmethane series (e.g., patent document DE 4211774A1, US 3694323).

[0006] Chinese patent application number CN201780079707.8 describes a method for drying an isocyanate distillation column bottoms stream containing ≥30% carbodiimide group-containing compounds at 200-270°C using a drying apparatus, evaporating and recovering the isocyanate, while the remaining impurities are converted into a solid product. This method offers the advantages of simplicity, stable operation, and economy. However, the patent does not address the issue of tar powder entrained in the evaporated and recovered isocyanate.

[0007] Chinese patent application number CN200610154191.2 describes a method for treating a crude isocyanate solution to obtain isocyanate and a residual material. The residual material is then processed in an evaporator or paddle dryer to recover the isocyanate from the residual material. This residual material is then purified in a dividing wall column to obtain the desired product, TDI. The remaining material is a highly viscous liquid or solid containing the desired product. This reduces the TDI content in the bottoms product. However, this method also produces a distillation bottoms stream containing isocyanate.

[0008] Chinese patent number CN210964533U describes a method for reducing impurities from entering the vacuum unit by installing a two-stage spray tower, thereby facilitating stable operation. Chinese patent number CN206970507U describes the use of a light solvent in a single-stage spray tower to reduce erosion and tar blockage in components such as the spray tower, spray cooler, and piping. However, the technical solutions disclosed in these patents do not address the problem of particle entrainment in the dryer.

[0009] During the actual operation of drying equipment in this field, the tar-containing TDI distillation residue is subjected to high temperature conditions. The TDI therein evaporates into a gaseous phase due to the heat, and the byproduct tar is carbonized into solid tar particles under the high-temperature drying conditions, simultaneously producing acidic gases and other halogen-containing compounds. Furthermore, when the drying equipment is agitated, the tar particles can shatter and generate dust. Small particles (in the form of powder) can escape along with the gaseous TDI, inevitably causing tar powder and halogen-containing compounds to be entrained in the TDI recovery liquid obtained through drying separation and evaporation separation. Consequently, the solid tar powder generated during the drying process of the tar-containing TDI distillation residue can cause scaling and clogging of the drying equipment. Furthermore, during the purification process of the tar-containing TDI recovery liquid from the drying equipment through distillation / rectification, the tar powder can also cause tower packing contamination, scaling of the circulating heating equipment, and reduced heat exchange efficiency, seriously affecting the operational stability of the equipment. At the same time, TDI is a heat-sensitive substance. When the TDI distillation residue containing tar is in the high-temperature drying treatment stage, or when the TDI recovery liquid containing tar powder is in the high-temperature distillation / rectification and other purification stages, impurities such as tar powder that reach a certain content will catalyze the self-polymerization reaction of TDI, which will cause more TDI product yield loss and affect the economic benefits of recovery and purification.

[0010] In view of this, continuing to explore ways to improve the problems existing in the methods and / or devices involved in the industrial preparation of toluene diisocyanate (TDI) has become a direction worthy of research. Summary of the Invention

[0011] The present invention aims to provide a TDI distillation residue separation and recovery device and a TDI distillation residue separation and recovery method. By further separating solid impurities such as tar powder from the high-temperature TDI gas phase material, the risk of dust blockage at the dryer outlet is reduced. At the same time, the loss of product yield caused by high-temperature TDI self-polymerization during the separation, recovery, and purification of the high-temperature TDI gas phase material is avoided. That is, while ensuring a high yield of the obtained TDI product, the problem of tar powder entrained in the recovered TDI distillation residue causing contamination and blockage of the corresponding processing equipment during the separation, recovery, and purification stages is solved. The advantages of the equipment being able to have a long continuous operation cycle and good stability are ensured. In addition, the content of halogen-containing compounds in the TDI product stream is reduced, which also solves the corrosion problem in the TDI purification equipment.

[0012] To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0013] In the first aspect, a separation and recovery device for TDI distillation residue is provided, which comprises: a dryer 101, a novel gas chamber 102, a gas phase conveying pipe 103, a spray tower 104, a cooler 106, and a return pipe 105; wherein,

[0014] The dryer 101 is used to dry the TDI distillation residue to be processed from the upstream of the device to obtain a high-temperature TDI vapor flow at the top of the dryer and solid tar particles at the bottom;

[0015] The novel gas chamber 102 is used to separate the high-temperature TDI vapor flow from the top of the dryer 101 to obtain a separated high-temperature TDI vapor flow. The novel gas chamber has a structure of an inverted frustum connected to a cylinder, with an outlet provided on the upper side of the cylinder and an inlet provided on the bottom. The top of the dryer 101 is connected to the inlet of the novel gas chamber 102.

[0016] The gas phase delivery pipe 103 is used to deliver the separated high-temperature TDI vapor flow into the spray tower 104; the gas phase delivery pipe is a beveled cylindrical structure, and its two ends are respectively connected to the novel gas chamber 102 and the spray tower 104;

[0017] The spray tower 104 is used to quench the separated high-temperature TDI vapor flow, so as to obtain a cooled liquid material flow at the bottom of the spray tower and a gaseous vapor flow at the top;

[0018] The return pipe 105 is used to circulate a portion of the liquid material flow from the bottom of the spray tower 104 back to the upper part of the spray tower as a circulating liquid material flow;

[0019] The cooler 106 is used to cool the circulating liquid flow from the return pipe 105.

[0020] According to the separation and recovery device provided by the present invention, in some embodiments, in the new air chamber, the (acute angle) angle between the hypotenuse of the inverted cone and the vertical line is not greater than 25° (such as 2°, 4°, 5°, 8°, 10°, 12°, 15°, 20°, 24°), and preferably not greater than 19°.

[0021] In some embodiments, in the gas phase transport pipe, the (acute angle) between the center line of the beveled cylinder and the horizontal line is 5-85° (e.g., 6°, 12°, 15°, 20°, 25°, 35°, 50°, 60°, 75°, 80°), preferably 10-30°.

[0022] In the present invention, the dryer can be a common drying equipment in the art, for example, the dryer is selected from a vacuum dryer with a horizontal axis having a heating and stirring function, a rotary tube, a disc dryer with a horizontal axis having a heating and stirring function, a belt dryer with a horizontal axis having a heating and stirring function, or a granulating screw device.

[0023] According to the separation and recovery device provided by the present invention, in some embodiments, a sprayer is provided above the interior of the spray tower; the number of the sprayers, for example, can be one group or multiple groups.

[0024] According to the separation and recovery device provided by the present invention, in some embodiments, a material delivery pump can be provided to deliver the remaining portion of the liquid material flow as a TDI product material flow to a downstream device.

[0025] In a second aspect, a method for separating and recovering TDI distillation residue using the separation and recovery device described above is provided, comprising the following steps:

[0026] a. Passing the TDI distillation residue 1 to be processed from the upstream of the device into the dryer for drying, obtaining a high-temperature TDI vapor flow at the top of the dryer and solid tar particles 4 at the bottom;

[0027] Then the high-temperature TDI vapor stream from the top of the dryer enters the novel gas chamber for separation to obtain a separated high-temperature TDI vapor stream 3;

[0028] b. The separated high-temperature TDI vapor stream 3 obtained in step a is introduced into the spray tower through a gas phase delivery pipe and brought into contact with a circulating liquid stream 7 circulating into the spray tower for rapid cooling and spraying, thereby obtaining a gaseous vapor stream 5 at the top of the spray tower and a purified liquid material stream 6 at the bottom;

[0029] c. The purified liquid material stream 6 obtained in step b is split, wherein a portion of the liquid material stream 6 is used as a circulating liquid material stream 7 and is transported back to the spray tower through a return pipe after cooling, and the separated high-temperature TDI vapor stream is quenched by spraying; the other portion of the liquid material stream 6 is sent to the downstream device as the TDI product material stream 2.

[0030] According to the method provided by the present invention, in some embodiments, in the novel air chamber, the angle between the hypotenuse of the frustum and the vertical line is not greater than 25°, preferably not greater than 19°.

[0031] In the present invention, after the TDI distillation residue to be processed enters the dryer for drying treatment, the solid tar particles formed are spherical solid small particles; the solid small particles can flow and be transported by the air flow, or flow downward along the wall in a new type of air chamber with an inclined angle. The high-temperature TDI vapor flow formed after treatment in the dryer is a mixture containing impurities such as TDI and halogen-containing group compounds. However, there is also the possibility that tar powder is entrained by a larger steam flow at the same time. To this end, the present invention can set the angle between the hypotenuse of the frustum and the vertical line within a suitable range by modifying the structure of the new type of air chamber connected to the dryer, which can reduce the entrainment of tar powder solids in the TDI gas phase material flow. That is, controlling the angle between the hypotenuse of the inverted cone and the vertical line in the new gas chamber can produce two effects: first, it can reduce the adhesion and coking of tar particles inside the equipment, thereby ensuring the long-term stable operation of the equipment; second, it can control the flow rate of the gaseous vapor flow in the new gas chamber within an appropriate range, thereby further reducing the tar powder content in the gaseous vapor flow; for example, in step a, by controlling the flow rate of the gaseous vapor flow leaving the new gas chamber to be no more than 30 m / s, such as 20 m / s, 10 m / s, 5 m / s, 3 m / s, 2 m / s, and 1 m / s, the tar powder content in the gaseous vapor flow can be completely controlled within 0.01 wt%-5 wt% (for example, 0.02 wt%, 0.06 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.8 wt%, 1 wt%, 2 wt%, and 4 wt%).

[0032] The separated high-temperature TDI vapor stream also includes some impurity components, such as tar powder and halogen-containing compounds. In some embodiments, the separated high-temperature TDI vapor stream 3 obtained in step a has a tar powder content of no more than 0.5 wt% (e.g., 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.45 wt%), preferably no more than 0.05 wt%, based on the total weight of the separated high-temperature TDI vapor stream; and a halogen-containing compound content of no more than 5.0 wt% (e.g., 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 4.5 wt%), preferably no more than 2.0 wt%.

[0033] In some embodiments, in step a, the flow rate of the high-temperature TDI vapor flow through the maximum inner diameter region of the novel gas chamber is no more than 30 m / s (e.g., 0.5 m / s, 1 m / s, 2 m / s, 3 m / s, 4 m / s, 8 m / s, 10 m / s, 15 m / s, 20 m / s, 25 m / s), preferably no more than 5 m / s.

[0034] According to the method provided by the present invention, in some embodiments, in the gas phase transport pipe, the angle between the central axis of the beveled cylinder and the horizontal line is 5-85°, preferably 10-30°.

[0035] By modifying the structure of the gas-phase conveying pipes connected to the new gas chamber and spray tower, respectively, and setting the angle (e.g., acute angle) between the beveled cylinder and the horizontal line within an appropriate range, it is possible to reduce the accumulation and clogging of the gas-phase conveying pipes by tar solids contained in the incoming gas phase and products that may form from TDI self-polymerization. Specifically, controlling the angle between the beveled cylinder and the horizontal line has two effects: first, it reduces the accumulation and clogging of solid impurities such as solid tar particles and TDI self-polymerization products within the gas-phase conveying pipes, reducing the frequency of pipe cleaning and ensuring long-term stable operation of the equipment; second, it reduces product yield losses caused by the high-temperature polymerization of TDI catalyzed by the contact of high-temperature tar particles with the TDI, thereby improving economic benefits.

[0036] According to the method provided by the present invention, the circulating liquid stream 7 conveyed through the return pipe is sprayed into the spray tower through a sprayer. In some embodiments, the mass flow ratio of the separated high-temperature TDI vapor stream to the circulating liquid stream 7 conveyed through the return pipe is 1:20-1:500 (e.g., 1:30, 1:50, 1:80, 1:120, 1:140, 1:200, 1:300, 1:400), preferably 1:100-1:150.

[0037] By controlling the mass flow ratio of the gaseous vapor flow and the liquid material flow transported by the return pipe (such as 1:20-1:500) for reverse contact quenching, the appropriate spray density can improve the cooling effect of the high-temperature gaseous vapor flow, and at the same time increase the separation effect of halogen-containing gas impurities, thereby improving the purity of the TDI product material flow.

[0038] In some embodiments, in order to enhance the separation effect of halogen-containing compound impurities, nitrogen gas 8 can be introduced into the return pipe through a pipeline.

[0039] In some embodiments, in step a, the process conditions for the drying treatment include: a temperature of 150-350°C (e.g., 180°C, 200°C, 250°C, 300°C, 320°C); a pressure of 0.1-90mbar (e.g., 0.5mbar, 1mbar, 5mbar, 10mbar, 50mbar, 80mbar).

[0040] In some embodiments, in the novel gas chamber of step a, the separation process conditions include: temperature of 150-350°C (e.g., 180°C, 200°C, 250°C, 300°C, 320°C); pressure of 0.1-90mbar (e.g., 0.5mbar, 1mbar, 5mbar, 10mbar, 50mbar, 80mbar).

[0041] In some embodiments, in the gas phase transport pipe of step b, the internal temperature is 140-340°C (e.g., 150°C, 200°C, 250°C, 320°C), preferably 180-280°C; the internal pressure is 0.1-90 mbar (e.g., 0.2 mbar, 0.5 mbar, 1 mbar, 4 mbar, 8 mbar, 10 mbar, 30 mbar, 50 mbar, 80 mbar), preferably 5-15 mbar.

[0042] In some embodiments, in step b, the bottom temperature of the spray tower is 30-100°C (e.g., 30°C, 50°C, 80°C, 100°C); the top pressure is 0.1-90 mbar (e.g., 0.2 mbar, 0.5 mbar, 1 mbar, 4 mbar, 8 mbar, 15 mbar, 30 mbar, 50 mbar, 80 mbar), preferably 5-10 mbar. Treating the material in the spray tower under vacuum enhances the separation efficiency and effectiveness of the halogen compound-containing impurity gas in the high-temperature steam stream.

[0043] The liquid material stream 6 obtained at the bottom of the spray tower includes components such as TDI, halogen-containing compound impurities, and tar powder. In some embodiments, after the treatment in step b, the content of tar powder in the liquid material stream obtained at the bottom of the spray tower, based on the total weight of the liquid material stream, is not greater than 0.5 wt% (e.g., 0.001 wt%, 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.45 wt%), preferably not greater than 0.05 wt%; the content of halogen-containing compound is not greater than 0.2 wt% (e.g., 0.001 wt%, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%), preferably not greater than 0.02 wt%.

[0044] In some embodiments, in step c, the process conditions for cooling in the cooler include: the material inlet temperature is 30-100°C (for example, 40°C, 60°C, 80°C), and the outlet temperature is 20-90°C (for example, 30°C, 50°C, 70°C).

[0045] In some embodiments, in step c, the content of tar powder in the TDI product material stream 2, based on the total weight of the TDI product material stream, is not greater than 0.5 wt% (e.g., 0.001 wt%, 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.45 wt%), preferably not greater than 0.05 wt%; the content of halogen group-containing compounds is not greater than 0.2 wt% (e.g., 0.001 wt%, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%), preferably not greater than 0.02 wt%.

[0046] In step c, when the TDI product stream 2 is sent to the downstream for processing, attention should be paid to the impact of a small amount of solid particulate impurities in the TDI product stream on the downstream separation equipment. If necessary, it is preferred to operate according to the method described in CN114470812A.

[0047] In the present invention, the method of obtaining the TDI distillation residue containing tar entering the dryer or the method of preparing TDI is not important. For example, it can be prepared by phosgenating toluenediamine (TDA) or by phosgenating toluenediamine hydrochloride or carbamate.

[0048] In addition to TDI to be recovered as a product, the TDI distillation residue stream typically also includes: halogen-containing compounds and carbodiimide-containing compounds. In some embodiments, the TDI distillation residue to be processed has a halogen-containing compound content of no greater than 30 wt% (e.g., 25 wt%, 20 wt%, 15 wt%, 10 wt%, 5 wt%, 4 wt%, 2 wt%, 1 wt%, 0.1 wt%), preferably no greater than 5 wt%, based on the total weight of the TDI distillation residue; a carbodiimide-containing compound content of 20-70 wt% (e.g., 25 wt%, 30 wt%, 35 wt%, 40 wt%, 44 wt%, 50 wt%, 55 wt%, 65 wt%), preferably 45-60 wt%, based on the total weight of the TDI distillation residue; and the remainder is TDI.

[0049] In industrial production, TDI is synthesized from meta-toluenediamine (MTDA) and phosgene using either the gas-phase or liquid-phase phosgene process. The reaction product is then separated and removed using a separation device to remove substances such as HCl, phosgene, and solvent, yielding a crude TDI product containing tar. This crude TDI product is then purified and processed through conventional distillation methods, such as distillation towers, to produce a purified TDI product and a TDI distillation residue. Typically, this TDI distillation residue is treated in a drying device (such as a dryer) to produce a vapor-phase TDI stream. After cooling, it is returned to the separation device or fed into a distillation tower or other distillation equipment for purification to recover the TDI material.

[0050] When conventional recovery methods are used to process the resulting TDI distillation residue, tar particles carried over from the gaseous stream obtained after drying in the dryer can clog the dryer outlet pipeline, shortening the dryer's cleaning cycle (typically 1-2 months). If the untreated recovered TDI material is further returned to the system for refining, the entrained tar particles can also clog the packing or trays of the separation device or the distillation tower used for refining, affecting separation and recovery efficiency and shortening the overall process cycle to typically 6-11 months. In light of these issues, the present invention provides improved technical solutions. Using the separation and recovery device and separation and recovery method of the present invention to process TDI distillation residue, while ensuring high purity and yield of the resulting TDI product, the operating cycle of the drying device in an industrial TDI production system can be extended by 100-500%, and the operating cycle of the separation and recovery device or refining equipment, such as the distillation tower, can be extended by 20-200%.

[0051] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0052] 1. By installing a new gas chamber and a specially designed gas phase conveying pipe, the velocity of the high-temperature TDI vapor flow is significantly reduced under the same feed conditions as the dryer, thereby reducing the entrainment of tar powder. Furthermore, the angles of the beveled edges of the frustum and the beveled cylinder are adjusted according to the physical properties of impurities such as tar particles in the high-temperature TDI vapor flow. This reduces the adhesion and coking of solid particles inside the equipment, significantly improving the continuous operation cycle and stability of the dryer and other related equipment. It also reduces the yield loss caused by tar particles in the catalytic thermal polymerization of high-temperature TDI, significantly increasing the TDI product yield. Furthermore, it avoids the problem of liquid materials containing tar powder contaminating separation equipment or evaporation equipment (such as tower internals) during further conventional processing, significantly improving the continuous operation cycle and stability of the entire device.

[0053] 2. By installing a spray tower to rapidly cool the high-temperature TDI vapor stream, the residence time of TDI at high temperatures is reduced, thereby minimizing TDI product losses. Simultaneously, the vacuum spray tower enhances the separation efficiency of halogen-containing impurity gases in the high-temperature vapor stream, ensuring a high-purity TDI product. This ensures a high-purity TDI product stream while significantly improving the continuous operating cycle and stability of the drying unit and the entire device, as well as the TDI product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is an example of an embodiment of the separation and recovery device of the present invention;

[0055] Figure 2 for Figure 1 The structure of the new gas chamber and the gas phase conveying pipe connected thereto in the separation and recovery device shown is an example, wherein the angle (acute angle) between the hypotenuse of the frustum and the vertical line is 15°; the angle (acute angle) between the center line of the beveled cylinder and the horizontal line is 15°.

[0056] The description of the accompanying drawings is as follows:

[0057] Name of the material flow:

[0058] 1. TDI distillation residue to be treated;

[0059] 2. TDI product material flow;

[0060] 3. High-temperature TDI vapor stream after separation;

[0061] 4. Solid tar particles;

[0062] 5. Gaseous steam flow;

[0063] 6. Liquid material flow;

[0064] 7. Circulating liquid stream;

[0065] 8. Nitrogen;

[0066] Device Name:

[0067] 101-dryer; 102-new gas chamber; 103-gas phase conveying pipe; 104-spray tower; 105-return pipe; 106-cooler; 107-material conveying pump. DETAILED DESCRIPTION

[0068] In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0069] In some embodiments of the present invention, the separation and recovery device refers to Figure 1 As shown, it includes: a dryer 101, a new gas chamber 102, a gas phase conveying pipe 103, a spray tower 104, a material conveying pump 107, a cooler 106, and a return pipe 105; wherein,

[0070] The dryer 101 is used to dry the TDI distillation residue 1 to be processed from the upstream device, obtaining a high-temperature TDI vapor flow (gas phase) at the top of the dryer and flowable solid tar particles 4 (solid phase) at the bottom. The dryer can be a commonly used device in the art.

[0071] The novel gas chamber 102 is used to separate the high-temperature TDI vapor flow from the top of the dryer 101 to obtain the separated high-temperature TDI vapor flow 3; Figure 2 As shown, the novel air chamber 102 is a structure in which an inverted frustum is connected to a cylinder, and the angle between the hypotenuse of the inverted frustum and the vertical line is not greater than 25°; a discharge port is provided on the side of the cylinder of the novel air chamber, and an inlet is provided at the bottom;

[0072] The top of the dryer 101 is connected to the feed port of the novel gas chamber 102. The high-temperature TDI vapor stream carrying solid tar powder distilled from the top of the dryer 101 is directly passed into the novel gas chamber 102 for separation. The resulting separated high-temperature TDI vapor stream 3 passes through the discharge port and enters the spray tower 104 from the bottom through the gas phase conveying pipe 103.

[0073] The gas phase delivery pipe 103, such as Figure 2 As shown, it is connected to the discharge port of the new gas chamber; the angle between the center line of the beveled cylinder of the gas phase conveying pipe 103 and the horizontal line is 5-85°;

[0074] The spray tower 104 is used to cool the separated high-temperature TDI vapor stream 3 transported from the vapor phase delivery pipe 103. A sprayer is provided at the top of the spray tower 104. A portion of the liquid material stream 6 discharged from the bottom of the spray tower is cooled in a cooler 106 as a circulating liquid material stream 7 and then returned to the sprayer through a return pipe 105. The gas phase material stream (high-temperature TDI vapor stream 3) entering from the bottom of the spray tower 104 is cooled in the spray tower by spraying. After treatment, a gaseous vapor stream 5 is obtained at the top of the spray tower 104, and a liquid material stream 6 is obtained at the bottom. A portion of the liquid material stream 6 is discharged by a material delivery pump 107, and the remaining portion is returned to the sprayer.

[0075] The return pipe 105 is used to transport a portion of the liquid stream 6 obtained from the bottom of the spray tower 104 back to the spray tower 104 as a circulating liquid stream 7;

[0076] The cooler 106 is used to cool the circulating liquid flow 7 in the return pipe 105, such as using warm water or circulating water as a refrigerant.

[0077] In some embodiments of the present invention, using Figure 1 The process flow and separation and recovery device shown in the figure are used to separate and recover TDI distillation residue, including the following steps:

[0078] a. The TDI distillation residue 1 from the upstream device enters the dryer 101, and the TDI distillation residue 1 to be treated is dried in the dryer 101; wherein,

[0079] In the TDI distillation residue 1, the content of the halogen group compound is not more than 30wt%, the content of the carbodiimide group compound is 20-70wt%, and the balance is TDI;

[0080] The process conditions of the drying process include: temperature of 150-350°C; pressure of 0.1-90mbar;

[0081] After drying, a high-temperature TDI vapor stream is obtained at the top of the dryer 101, and flowable solid tar particles 4 are obtained at the bottom. The high-temperature TDI vapor stream then enters a new gas chamber 102 connected to the top of the dryer 101 for further separation, obtaining a separated high-temperature TDI vapor stream 3.

[0082] In the new gas chamber, the separation process conditions include: temperature 150-350℃; pressure 0.1-90mbar; reference Figure 2 As shown, the new air chamber is a structure in which an inverted frustum is connected to a cylinder, and the angle between the hypotenuse of the inverted frustum and the vertical line is no greater than 25°;

[0083] The gas flow rate of the high-temperature TDI vapor flow passing through the maximum inner diameter area of ​​the novel gas chamber 102 is no more than 30 m / s; the obtained separated high-temperature TDI vapor flow 3 contains, in addition to the TDI component, impurities such as tar powder and halogen-containing group compounds, wherein the content of the tar powder is 0.01-0.5 wt%, and the content of the halogen-containing group compounds is 0.1-5 wt%;

[0084] b. The separated high-temperature TDI vapor stream 3 obtained in step a is transported to the lower part of the spray tower 104 through the gas phase transport pipe 103. A portion of the liquid material stream 6 returned from the return pipe 105 is cooled as the circulating liquid material stream 7 and then enters the upper part of the spray tower 104 through a provided sprayer. Optionally, nitrogen 8 can be introduced into the return pipe 105. The circulating liquid material stream 7 contacts the high-temperature TDI vapor stream in a spraying manner to be rapidly cooled. The material formed after cooling enters the bottom of the spray tower 104, thereby obtaining a gaseous vapor stream 5 at the top of the spray tower 104 and a liquid material stream 6 at the bottom.

[0085] The discharge port of the novel gas chamber 102 is connected to the spray tower 104 through the gas phase conveying pipe 103. Figure 2 As shown, the gas phase delivery pipe 103 is a structure of an oblique cylinder, and the angle between the center line of the oblique cylinder and the horizontal line is 5-85°;

[0086] The temperature of the circulating liquid material in the return pipe 105 is regulated by the cooler 106, and the bottom temperature of the spray tower 104 is finally controlled to be 30-100°C, and the top pressure of the spray tower 104 is controlled to be 0.1-90mbar;

[0087] c. The liquid material stream 6 obtained at the bottom of the spray tower 104 is split. That is, a portion of the liquid material stream 6 from the bottom of the spray tower 104 is cooled in a cooler through a return pipe 105 as a circulating liquid material stream 7 and then transported back to the spray tower 104 in a spraying manner; and the remaining liquid material stream 6 at the bottom of the spray tower 104 is used as a product material stream 2 and transported to a downstream processing step.

[0088] The content of tar powder in the liquid material stream 6 (i.e., the circulating liquid material stream 7, the product material stream 2) is not more than 0.5 wt%, preferably not more than 0.05 wt%, and the content of the halogen group-containing compound is not more than 0.2 wt%, preferably not more than 0.02 wt%;

[0089] The mass flow ratio of the separated high-temperature TDI vapor stream 3 to the circulating liquid stream 7 transported by the return pipe 105 is 1:20-1:500.

[0090] The present invention is further described below with reference to Examples and Comparative Examples.

[0091] Example 1:

[0092] Refer to Figure 1 The separation and recovery device and its separation process are shown in the figure, and the TDI distillation residue 1 is separated and recovered through the process steps described above to obtain the product material stream 2; wherein, the relevant equipment parameters and logistics information are shown in the following Tables 1 and 2:

[0093] Table 1 Main logistics information of each step in Example 1

[0094]

[0095] In Example 1, the yield of TDI product was 99.90%.

[0096] Table 2 Parameter information of each main device in Example 1

[0097]

[0098]

[0099] In Example 1, the experimental results regarding operating cycles show that using the separation and recovery apparatus and method of the present invention to separate and recover TDI distillation residue can extend the operating cycle of the dryer in an industrial TDI production system by 400%, and the operating cycle of the separation apparatus or distillation tower in the entire process can be extended by 120%.

[0100] Example 2:

[0101] Refer to Figure 1The separation and recovery device and its separation process diagram are shown, and the TDI distillation residue is separated and recovered through the process steps described above to obtain product material stream 2; wherein, the relevant equipment parameters and logistics information are shown in Tables 3 and 4 below:

[0102] Table 3 Main logistics information of each step in Example 2

[0103]

[0104]

[0105] In Example 2, the yield of TDI product was 99.78%.

[0106] Table 4 Parameter information of each main device in Example 2

[0107]

[0108] In Example 2, experimental results regarding operating cycles show that by using the separation and recovery method of the present invention to separate and recover TDI distillation residue, the operating cycle of the dryer in an industrial TDI production system can be extended by 370%, and the operating cycle of the separation device or distillation tower in the entire process can be extended by 90%.

[0109] Example 3:

[0110] Refer to Figure 1 The separation and recovery device and its separation process diagram are shown, and the TDI distillation residue is separated and recovered through the process steps described above to obtain product material stream 2; wherein the relevant equipment parameters and logistics information are shown in Tables 5 and 6 below:

[0111] Table 5 Main logistics information of each step in Example 3

[0112]

[0113]

[0114] In Example 3, the yield of TDI product was 99.63%.

[0115] Table 6 Parameter information of each main device in Example 3

[0116]

[0117] In Example 3, the experimental results regarding the operating cycle show that by using the separation and recovery method of the present invention to separate and recover TDI distillation residue, the operating cycle of the dryer in an industrial TDI production system can be extended by 100%, and the operating cycle of the separation device or distillation tower in the entire process can be extended by 80%.

[0118] Comparative Example 1:

[0119] Refer to Figure 1 The separation and recovery apparatus and its separation process diagram shown in the figure separate and recover TDI distillation residue. The difference is that the separation and recovery apparatus does not have the novel gas chamber 102 and gas phase conveying pipe 103. Instead, the dryer 101 is connected to the conventional horizontal gas phase pipeline 103' of the dryer. After the TDI distillation residue is dried, the resulting high-temperature gas phase stream is directly introduced into the spray tower through the conventional horizontal gas phase pipeline. The relevant equipment parameters and logistics information are shown in Tables 7 and 8 below:

[0120] Table 7 Main logistics information of each step in Comparative Example 1

[0121]

[0122] In Comparative Example 1, the yield of TDI product was 97.58%.

[0123] Table 8 Parameter information of each main equipment in comparative example 1

[0124]

[0125] In Comparative Example 1, the experimental results regarding the operating cycle show that when this separation and recovery method is used to separate and recover TDI distillation residue, the operating cycle of the dryer in an industrial TDI production system is relatively short, with the conventional horizontal gas phase pipeline of the dryer generally requiring cleaning every one to two months. The operating cycle of the separation device or distillation tower in the entire process is approximately six to nine months.

[0126] The experimental results of the above embodiments and comparative examples show that the separation and recovery devices of the embodiments, by providing a novel gas chamber structure and gas phase conveying pipeline with a special structure, as well as designing the bevel angle of the frustum and the inclination angle of the beveled cylinder, reduce the adhesion and coking of tar particles inside the dryer and other equipment, significantly improving the long-term and stable operation of the dryer and related equipment during the recovery and separation process. At the same time, this also reduces the yield loss caused by the thermal autopolymerization of high-temperature TDI by solid tar particles, significantly improving the TDI product yield. In addition, by providing a spray tower to quench the high-temperature TDI vapor flow, not only can a TDI feed liquid with high purity and high recovery rate be obtained, but also the problem of tar powder causing equipment (such as tower internals) in conventional refining processes is avoided, resulting in a long and stable continuous operation cycle of the separation device or refining device in the entire process.

[0127] In the comparative example, however, no novel gas chamber and / or gas phase conveying pipeline is provided, and the yield of the recovered liquid is significantly reduced. At the same time, the entrained tar particles may also cause clogging of the packing or trays of the drying device and the separation device or distillation tower in the entire process, thereby affecting the separation efficiency, resulting in a short operating cycle of the drying device and the entire process, or insignificant improvement in the operating cycle of the device.

[0128] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A TDI distillation residue separation and recovery device, characterized in that: The separation and recovery device comprises: a dryer (101), a novel gas chamber (102), a gas phase conveying pipe (103), a spray tower (104), a cooler (106), and a return pipe (105); wherein, The dryer (101) is used to dry the TDI distillation residue to be processed from the upstream of the device to obtain a high-temperature TDI vapor flow at the top of the dryer and solid tar particles at the bottom; The novel air chamber (102) is used to separate the high-temperature TDI vapor flow from the top of the dryer (101) to obtain a separated high-temperature TDI vapor flow; the novel air chamber is a structure in which an inverted frustum is connected to a cylinder, and a discharge port is provided on the upper side of the cylinder and a feed port is provided on the bottom; the top of the dryer (101) is connected to the feed port of the novel air chamber (102); The gas phase delivery pipe (103) is used to deliver the separated high-temperature TDI vapor flow into the spray tower (104); the gas phase delivery pipe is a beveled cylindrical structure, and its two ends are respectively connected to the novel gas chamber (102) and the spray tower (104); The spray tower (104) is used to perform quench spraying on the separated high-temperature TDI vapor flow, so as to obtain a cooled liquid material flow at the bottom of the spray tower and a gaseous vapor flow at the top; The return pipe (105) is used to circulate a portion of the liquid material flow from the bottom of the spray tower (104) back to the upper part of the spray tower as a circulating liquid material flow; The cooler (106) is used to cool the circulating liquid flow from the return pipe (105).

2. The separation and recovery device according to claim 1, characterized in that: In the novel air chamber, the angle between the hypotenuse of the frustum and the vertical line is no greater than 25°.

3. The separation and recovery device according to claim 1, characterized in that: In the novel air chamber, the angle between the hypotenuse of the frustum and the vertical line is no greater than 19°.

4. The separation and recovery device according to claim 1, characterized in that: In the gas phase conveying pipe, the angle between the central axis of the oblique cylinder and the horizontal line is 5-85°.

5. The separation and recovery device according to claim 1, characterized in that: In the gas phase conveying pipe, the angle between the central axis of the oblique cylinder and the horizontal line is 10-30°.

6. A method for separating and recovering TDI distillation residue using the separation and recovery device according to claim 1, characterized in that: The steps include: a. Passing the TDI distillation residue (1) to be processed from the upstream of the device into the dryer for drying, obtaining a high-temperature TDI vapor flow at the top of the dryer and solid tar particles (4) at the bottom; Then the high-temperature TDI vapor flow from the top of the dryer enters the novel gas chamber for separation to obtain a separated high-temperature TDI vapor flow (3); b. The separated high-temperature TDI vapor stream (3) obtained in step a is passed through a gas phase delivery pipe into the spray tower and brought into contact with a circulating liquid stream (7) circulating into the spray tower for rapid cooling and spraying, thereby obtaining a gaseous vapor stream (5) at the top of the spray tower and a purified liquid stream (6) at the bottom; c. The purified liquid material flow (6) obtained in step b is split, wherein a portion of the liquid material flow (6) is used as a circulating liquid material flow (7) and is transported back to the spray tower through a return pipe after cooling, and the separated high-temperature TDI vapor flow is quenched by spraying; the other portion of the liquid material flow (6) is sent to a downstream device as a TDI product material flow (2).

7. The method according to claim 6, characterized in that In the separated high-temperature TDI vapor stream (3) obtained in step a, the content of tar powder is not more than 0.5 wt % and the content of halogen group-containing compounds is not more than 5.0 wt %, based on the total weight of the separated high-temperature TDI vapor stream.

8. The method according to claim 6, characterized in that In the separated high-temperature TDI vapor stream (3) obtained in step a, the content of tar powder is not more than 0.05 wt % and the content of halogen group-containing compounds is not more than 2.0 wt %, based on the total weight of the separated high-temperature TDI vapor stream.

9. The method according to claim 6, characterized in that In step a, the flow rate of the high-temperature TDI vapor flow passing through the maximum inner diameter region of the novel gas chamber is no more than 30 m / s.

10. The method according to claim 6, characterized in that In step a, the flow rate of the high-temperature TDI vapor flow passing through the maximum inner diameter region of the novel gas chamber is no more than 5 m / s.

11. The method according to claim 6, characterized in that The mass flow ratio of the separated high-temperature TDI vapor flow to the circulating liquid flow (7) transported by the return pipe is 1:20-1:

500.

12. The method according to claim 6, characterized in that The mass flow ratio of the separated high-temperature TDI vapor flow to the circulating liquid flow (7) transported by the return pipe is 1:100-1:

150.

13. The method according to any one of claims 6 to 12, characterized in that In step a, the drying process conditions include: temperature of 150-350°C; pressure of 0.1-90 mbar; and / or In the novel gas chamber of step a, the separation process conditions include: temperature of 150-350°C; pressure of 0.1-90 mbar; and / or In the gas phase delivery pipe of step b, the internal temperature is 140-340° C.; the internal pressure is 0.1-90 mbar; and / or In step b, the bottom temperature of the spray tower is 30-100° C.; the top pressure is 0.1-90 mbar.

14. The method according to claim 13, characterized in that In the gas phase delivery pipe of step b, the internal temperature is 180-280° C. and the internal pressure is 5-15 mbar.

15. The method according to claim 13, characterized in that In step b, the bottom temperature of the spray tower is 30-100° C.; the top pressure is 5-10 mbar.

16. The method according to any one of claims 6 to 12, 14 and 15, characterized in that: In step c, in the TDI product material flow (2), based on the total weight of the TDI product material flow, the content of tar powder is not more than 0.5 wt%; and the content of halogen group-containing compounds is not more than 0.2 wt%.

17. The method according to claim 16, characterized in that In step c, in the TDI product material flow (2), based on the total weight of the TDI product material flow, the content of tar powder is not more than 0.05 wt%; and the content of halogen group-containing compounds is not more than 0.02 wt%.

18. The method according to any one of claims 6 to 12, 14, 15 and 17, characterized in that: In the TDI distillation residue to be treated, based on the total weight of the TDI distillation residue, the content of the halogen group compound is no more than 30wt%; the content of the carbodiimide group compound is 20-70wt%; and the balance is TDI.

19. The method according to claim 18, characterized in that In the TDI distillation residue to be treated, based on the total weight of the TDI distillation residue, the content of the halogen group compound is no more than 5wt%; the content of the carbodiimide group compound is 45-60wt%; and the balance is TDI.

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