Thermal phosgene vaporization reactor and method for producing isocyanates

Abstract

The application relates to a thermal phosgene reactor and a preparation method of isocyanate, the thermal phosgene reactor comprising a reaction tower, a sieve plate and a pressurizing device, the sieve plate is installed in the reaction tower to divide the space in the tower into upper and lower parts, the sieve plate is located between a feeding port and a discharging port, the sieve plate comprises a plate body, the plate body is provided with through holes and flow channels, the through holes are arranged in a plurality of and penetrate the plate body in the up-down direction, the side wall of the through hole is provided with a gas outlet connected with the flow channel, and the plate body is provided with a gas inlet for allowing external airflow to enter the flow channel; the pressurizing device is arranged outside the reaction tower, and the exhaust port is communicated with the gas inlet of the sieve plate through the pressurizing device, so that the gas discharged at the exhaust port is pressurized and then introduced into the flow channel, the reaction of amine hydrochloride and unreacted free amine in the solid particle material with phosgene is accelerated, the generation of by-product urea is reduced, the product quality is improved, the probability of the occurrence of the plugging condition is reduced, and the operation stability of the device is enhanced.

Description

Technical Field

[0001] This application relates to the field of isocyanate preparation technology, and in particular to a thermophotogasification reactor and a method for preparing isocyanates. Background Technology

[0002] Currently, the mainstream industrial method for synthesizing isocyanates is the phosgene method. The liquid-phase phosgene method involves mixing the amine corresponding to the target product with an inert solvent and then reacting it with a phosgene solution to obtain a reaction solution containing isocyanate product, inert solvent, residual phosgene, and the reaction product hydrogen chloride. The reaction solution undergoes a post-treatment process to remove phosgene, hydrogen chloride, and solvent in sequence, ultimately yielding the isocyanate product.

[0003] The liquid-phase phosgenation reaction process is generally divided into a cold phosgenation stage and a hot phosgenation stage. In the cold reaction stage, the amine solution and the phosgene solution react to produce carbamoyl chloride and hydrogen chloride. The hydrogen chloride reacts with the unreacted amine to produce amine hydrochloride. In the hot reaction stage, the carbamoyl chloride is heated and decomposed into isocyanate and hydrogen chloride. The amine hydrochloride reacts with phosgene to produce isocyanate and hydrogen chloride.

[0004] Cold reaction stage:

[0005] RNH2 + COCl2 → RNHCOCl (carbamoyl chloride) + HCl;

[0006] RNH2 + HCl → RNH2·HCl (amine hydrochloride);

[0007] Thermal reaction stage:

[0008] RNHCOCl→RNCO+HCl;

[0009] RNH2·HCl+COCl2→RNCO+3HCl;

[0010] In the cold reaction stage, the reaction rate is relatively fast, and the carbamoyl chloride and amine hydrochloride produced by the reaction are both solid particles. Some amine hydrochloride and unreacted amines are trapped in the solid particles. In the hot reaction stage, if the amine hydrochloride and unreacted amines are not exposed in time and react quickly with phosgene, they will react with isocyanate to produce urea as a byproduct. Urea is a solid with extremely poor solubility. Its formation will not only block the reactor and downstream equipment, affecting the stable operation of the equipment, but also reduce the quality of the product and affect the application of subsequent products.

[0011] Side reactions:

[0012] RNH2·HCl + RNCO → RNHCONHR (urea) + HCl;

[0013] RNH2+RNCO→RNHCONHR (urea);

[0014] CN117619291A reports a thermophotogasification reactor, which includes a rectification section, a reaction section, and a stripping section. By optimizing the trays, the residence time of each reaction section on the trays is extended, making the thermophotogasification reaction more complete. However, it cannot reduce the side reaction of amine hydrochloride and unreacted amine reacting with isocyanate to form urea.

[0015] CN117466778B describes a staged process for the mixed feed stream obtained from a cold phosgene reaction. The lighter liquid stream (urea byproducts) is fed into a hot phosgene reaction tower, while the heavier liquid stream (carbamoyl chloride, amine hydrochloride, and their complexes) is fed into the middle section of the tower. This is intended to reduce the possibility of reactor clogging and scaling caused by light solid impurities. However, the cold reaction liquid contains relatively few urea byproducts, which are mainly formed during the hot reaction stage. Therefore, feeding carbamoyl chloride, amine hydrochloride, and their complexes into the middle section of the tower for reaction does not reduce the formation of urea byproducts.

[0016] CN101568519A uses a backmixed or non-backmixed reactor and a reactive distillation column as a thermal reactor. The backmixed reactor is, for example, a stirred vessel, a cascade of stirred vessels containing 2-4 stirred vessels, a circulating reactor, or a non-stirred vessel; the substantially non-backmixed reactor is, for example, a tubular reactor. When the cold reaction mixture enters the aforementioned thermal reactor, the amine hydrochloride and unreacted amine in the cold reaction mixture readily react with the isocyanate to form a significant amount of urea. Summary of the Invention

[0017] Therefore, it is necessary to provide a thermo-photogasification reactor and a method for preparing isocyanate to reduce the generation of urea, a byproduct, during the thermal reaction stage of isocyanate.

[0018] This application provides a thermophotogasification reactor, including a reaction tower, a sieve plate, and a pressurizing device. The reaction tower has a feed inlet at its bottom and an exhaust port and a discharge port located above the feed inlet. The sieve plate is installed inside the reaction tower to divide the internal space vertically. The sieve plate is located between the feed inlet and the discharge port. The sieve plate includes a plate body with through holes and flow channels. Multiple through holes extend through the plate body vertically. The sidewalls of the through holes have exhaust ports that communicate with the flow channels. The plate body has an inlet for external airflow to enter the flow channels. The pressurizing device is located outside the reaction tower. The exhaust port is connected to the inlet of the sieve plate through the pressurizing device, so that the gas discharged at the exhaust port is pressurized and then enters the flow channels.

[0019] In one embodiment, a cutter is installed at the through hole to cut solid particles passing through the through hole.

[0020] In one embodiment, the cutting element is disposed within the through hole, and the cutting element includes a plurality of cutting plates distributed circumferentially around the through hole, with the thickness direction of the cutting plates along the circumferential direction of the through hole.

[0021] In one embodiment, a plurality of sieve plates are provided and the plurality of sieve plates are arranged at intervals along the height direction of the reaction tower.

[0022] In one embodiment, the pressurizing device is connected to the air inlet of each of the screen plates by a connecting pipe, and each connecting pipe is provided with a second valve to adjust the flow rate of the corresponding connecting pipe.

[0023] In one embodiment, each of the through holes is provided with a plurality of air outlets at regular intervals along the circumferential direction, and the plurality of air outlets of each through hole are evenly distributed.

[0024] In one embodiment, the air inlet is located on the side wall of the plate.

[0025] In one embodiment, multiple feed inlets are provided, and the multiple feed inlets are angled toward each other toward the interior of the reaction tower.

[0026] This application also provides a method for preparing isocyanate, which utilizes the above-mentioned thermophotochemical reactor to prepare isocyanate, and the preparation method includes the following steps:

[0027] The cold light vaporization reaction liquid is fed into the reaction tower through the feed port. The reaction temperature in the reaction tower is 80℃~150℃ and the reaction pressure is 0.15MPa~0.5MPa. The reaction gas is discharged through the gas outlet and then pressurized by the pressurizing device before flowing into the gas inlet.

[0028] The reaction gas pressurized by the booster device accounts for 20% to 60% of the total gas emitted from the exhaust port, and the pressure of the reaction gas after being pressurized by the booster device is 0.5 MPa to 3 MPa.

[0029] In one embodiment, when multiple sieve plates are arranged at intervals along the height of the reaction tower, the air intake at the inlet of the nth sieve plate arranged from bottom to top satisfies the following:

[0030] ;

[0031] in:

[0032] n is the sequence number of the sieve plates from bottom to top;

[0033] X n The proportion of the gas intake at the inlet of the nth sieve plate to the total gas output from the exhaust port of the reaction tower.

[0034] m is the total number of sieve plates;

[0035] T n The reaction temperature is located at the position of the nth sieve plate;

[0036] e is the natural constant, taken as 2.71828;

[0037] Σ is the summation symbol, representing the summation of the numerator terms for all sieve plates from k=1 to k=m.

[0038] Compared with the prior art, the thermo-phosgene reactor and isocyanate preparation method provided in this application have at least the following advantages: through holes are opened in the sieve plate inside the reaction tower so that the material can pass through the sieve plate from bottom to top. The gas containing phosgene discharged from the top of the reaction tower is pressurized by the pressurizing device and then enters the through holes through the air inlet and flow channel, thereby impacting the material flowing through the through holes, accelerating the reaction of amine hydrochloride and unreacted free amine in the solid particulate material with phosgene, reducing the generation of by-product urea, improving product quality, reducing the probability of blockage, and enhancing the stability of the device operation. Attached Figure Description

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

[0040] Figure 1 This is a schematic diagram of the structure of a thermophotogasification reactor according to an embodiment of this application;

[0041] Figure 2 This is a perspective view of a sieve plate according to an embodiment of this application;

[0042] Figure 3 This is a partially enlarged schematic diagram of the through hole in an embodiment of this application;

[0043] Figure 4 This is an axial schematic diagram of eight embodiments of the cutting plate at the through hole in this application;

[0044] Figure 5 This is a schematic diagram of the connection between the connecting pipe and the reaction tower and sieve plate;

[0045] Figure 6 This is a schematic diagram of the structure of a thermophotogasification reactor according to another embodiment of this application.

[0046] Reference numerals: 10. Sieve plate; 11. Plate body; 12. Through hole; 13. Cutting component; 14. Cutting plate; 15. Flow channel; 16. Gas outlet; 17. Gas inlet; 18. Reaction tower; 19. Feed inlet; 20. Exhaust outlet; 21. Discharge outlet; 22. Pressurization device; 23. Pressure sensor; 24. Temperature sensor; 25. Dynamic mixer; 26. First feed pipe; 27. Second feed pipe; 28. First valve; 29. ​​Second valve; 30. Connecting pipe; 31. Through cavity. Detailed Implementation

[0047] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0048] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," "side," "top," "bottom," and similar expressions used in this application's specification are merely for describing various exemplary structural parts and elements of this application. However, their use herein is for illustrative purposes only and is determined based on the exemplary orientations shown in the accompanying drawings, and does not represent the only possible implementation. Since the embodiments disclosed in this application can be arranged in different orientations, these terms indicating orientation are for illustrative purposes only and should not be considered as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0051] It should be noted that "axial arrangement" means that the overall arrangement direction is along the axial direction, including but not limited to axial extension, and may be at an angle to the axial direction.

[0052] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0053] See Figures 1 to 6 This application provides a thermo-photovaporization reactor for the thermal reaction stage of isocyanates. Specifically, as follows... Figure 1 As shown, the thermophotogasification reactor includes a reaction tower 18, a sieve plate 10, and a pressurizing device 22. The bottom of the reaction tower 18 has a feed inlet 19, and an exhaust port 20 and a discharge port 21 are located above the feed inlet 19. The sieve plate 10 is installed inside the reaction tower 18 to divide the internal space vertically. The sieve plate 10 is located between the feed inlet 19 and the discharge port 21; specifically, the sidewall of the sieve plate 10 is fixedly connected to the inner wall of the reaction tower 18. The sieve plate 10 includes a plate body 11 and a flow channel 15. Multiple through holes 12 are provided and penetrate the plate body 11 vertically. The sidewall of the through holes 12 has an exhaust port 16 communicating with the flow channel 15. The plate body 11 has an inlet 17 for external airflow to enter the flow channel 15. The pressurizing device 22 is located on the outside of the reaction tower 18. The exhaust port 20 is connected to the air inlet 17 of the sieve plate 10 through the pressurizing device 22, so that the gas discharged at the exhaust port 20 is pressurized and then enters the flow channel 15.

[0054] In this way, the phosgene-containing gas emitted from exhaust port 20 is pressurized by pressurization device 22, and the high-pressure gas is introduced into flow channel 15, eventually flowing from exhaust port 16 into through hole 12, impacting the material flowing in through hole 12. Under the action of airflow, the solid particles passing through through hole 12 can be impacted and dispersed. More specifically, in the thermal reaction stage of isocyanate preparation, the airflow introduced from exhaust port 16 can more easily expose the free amines in the solid particles, thereby accelerating the reaction of amine hydrochloride and unreacted free amines in the solid particle material with phosgene, reducing the reaction of amine hydrochloride and free amines with a large amount of isocyanate in the later stage of the reaction to form the byproduct urea, improving the product yield and quality of isocyanate, reducing the probability of blockage, and enhancing the operational stability of the device.

[0055] The booster can be any existing booster, and this application does not impose any restrictions.

[0056] Please continue reading Figure 1 In the reaction tower 18, gas-liquid separation is performed at the top inner side. The liquid phase is discharged from the outlet 21 and then processed to obtain isocyanate products; the gas phase (including phosgene and hydrogen chloride gas) is discharged from the exhaust port 20. In this embodiment, a pressurizing device 22 is provided on the outside of the reaction tower 18. The exhaust port 20 is connected to the air inlet 17 of the sieve plate 10 through the pressurizing device 22. After the gas phase is pressurized by the pressurizing device 22, the pressure reaches 0.5MPa~3MPa. Then, the gas phase is introduced into the through hole 12 from the air inlet 17 and the flow channel 15 to impact and disperse the solid particles in the through hole 12. That is, the pressure of the gas phase introduced into the through hole 12 through the air inlet 17 and the flow channel 15 can reach 0.5MPa~3MPa.

[0057] It is worth mentioning that the high-pressure gas introduced into the through-hole 12 contains phosgene, which can increase the amount of phosgene at the through-hole 12 and improve the reaction effect of amine hydrochloride and free amine exposed inside the solid particles with phosgene. In addition, the gas introduced into the through-hole 12 after being pressurized by the pressurization device 22 comes from the gas discharged from the reaction tower 18, which also plays a role in circulation and energy saving.

[0058] Please see Figure 2 , Figure 3 as well as Figure 4 In some embodiments of this application, a cutting element 13 is installed at the through hole 12 to cut solid particles passing through the through hole 12. During the process of the solid particles passing through the through hole 12, that is, during the process of the solid particles moving from one side of the plate 11 to the other side, the solid particles are cut by the cutting element 13 and their interior is exposed, so as to accelerate the process of the reactants inside the solid particles participating in the chemical reaction.

[0059] In the thermal reaction production process of isocyanate, the isocyanate content increases as the reaction proceeds. If the interior of the solid particles is not exposed in time, the amine hydrochloride and free amine inside the solid particles can easily react with the large amount of isocyanate present in the later stages of the reaction to generate the byproduct urea. This not only reduces the yield and quality of isocyanate, but also easily causes equipment blockage due to the byproduct urea. In order to reduce the reaction between amine hydrochloride and free amine and isocyanate, the aforementioned sieve plate 10 is used to cut the solid particles in the thermal reaction stage, further exposing the amine hydrochloride and free amine encapsulated inside the solid particles. This allows the amine hydrochloride and free amine inside the solid particles to react quickly with the phosgene solution, thereby further reducing the occurrence of side reactions, reducing the formation of solid byproduct urea, improving the yield and quality of isocyanate products, reducing the probability of blockage, and enhancing the operational stability of the equipment.

[0060] In some preferred embodiments of this application, the opening ratio of the through holes 12 on the plate 11 is 30% to 70%, for example, the opening ratio of the through holes 12 on the plate 11 is 30%, 40%, 50%, 60%, 70%, or any value between 30% and 70%. It is understood that if the opening ratio of the through holes 12 on the plate 11 is too small, the sieve plate 10 will have an excessively large obstructive effect on the material, affecting the normal production process; if the opening ratio of the through holes 12 on the plate 11 is too large, the sieve plate 10 will have a smaller cutting effect on the solid particles in the material, and will not be able to achieve the effect of exposing the amine hydrochloride and free amine inside the solid particles to react rapidly with the phosgene solution.

[0061] Please continue reading Figure 2 and Figure 3 In some embodiments of this application, the cutting element 13 is disposed within the through hole 12. The cutting element 13 includes a plurality of cutting plates 14, which are distributed circumferentially around the through hole 12, and the thickness direction of the cutting plates 14 is along the circumferential direction of the through hole 12. In this way, as solid particles pass through the through hole 12, the arrangement of the plurality of cutting plates 14 can cut as many solid particles as possible through the through hole 12, thereby exposing as many amine hydrochloride and free amine coated within the solid particles as possible for reaction.

[0062] Preferably, the number of cutting plates 14 is 2 to 15. It is understood that the more cutting plates 14 there are, the denser their distribution, resulting in a higher cutting rate for solid particles. This ensures that all solid particles passing through the through-holes 12 are cut. However, this will affect the flow rate of material through the through-holes 12. The cutting rate refers to the percentage of solid particles that are cut out of the total number of solid particles passing through the through-holes 12. A higher cutting rate results in fewer subsequent side reactions and higher yield and quality of the target product (such as isocyanate). The flow rate of material through the through-holes 12 refers to the amount of material passing through the through-holes 12 within a certain time. A higher flow rate results in higher production capacity. In this embodiment, the number of cutting plates 14 can be 2, 3, 4, or any other number between 2 and 15, balancing the cutting rate of solid particles and the flow rate of material through the through-holes 12, thus balancing product yield, quality, and production capacity.

[0063] In addition, the radial cross-sectional shape of the cutting plate 14 can be a straight line, a curve, etc., that is, the entire cutting plate 14 can be a straight plate, a curved plate, etc.

[0064] See Figure 4 For example, in embodiments a to d, the cutting plate 14 is a straight plate, and in embodiments e to h, the cutting plate 14 is a curved plate. In embodiments a and e, two cutting plates 14 are used, with the width of the two cutting plates 14 along the radial direction of the through hole 12 being the same as the radius of the through hole 12, and the included angle between the two cutting plates 14 along the circumference of the through hole 12 being 180°. The two cutting plates 14 divide the through hole 12 into two passage cavities 31 for fixing particles. In embodiments b and f, three cutting plates 14 are used, with the width of the three cutting plates 14 along the radial direction of the through hole 12 being the same as the radius of the through hole 12, and the included angle between two adjacent cutting plates 14 along the circumference of the through hole 12 being 120°. The three cutting plates 14 divide the through hole 12 into three passage cavities 31 for fixing particles. In embodiments c and g, four cutting plates 14 are used, with the width of the four cutting plates 14 along the radial direction of the through hole 12 being the same as the radius of the through hole 12, and the included angle between two adjacent cutting plates 14 along the circumference of the through hole 12 being 90°. The four cutting plates 14 divide the through hole 12 into four passage cavities 31 for fixing particles. Figure 1 and Figure 2 The sieve plate 10 shown has four cutting plates 14 in the through holes 12. In embodiments d and h, eight cutting plates 14 are provided. The width of the eight cutting plates 14 along the radial direction of the through holes 12 is the same as the radius of the through holes 12, and the included angle between two adjacent cutting plates 14 along the circumference of the through holes 12 is 45°. The eight cutting plates 14 divide the through holes 12 into eight passage cavities 31 for fixing particles.

[0065] Of course, the specific form, quantity, and included angle of the cutting plate 14 can be determined based on actual needs, and this application does not impose any restrictions.

[0066] Please see Figure 1 In some preferred embodiments of this application, multiple sieve plates 10 are provided and the multiple sieve plates 10 are arranged at intervals along the height direction of the reaction tower 18. By providing multiple layers of sieve plates 10, multiple impact and cutting positions are formed in the height direction of the reaction tower 18, which improves the impact effect and cutting rate on solid particles, so that the amine hydrochloride and free amine coated in the solid particles can be exposed as much as possible to react with the phosgene solution, and the occurrence of side reactions is reduced.

[0067] Preferably, the number of sieve plates 10 is set to 3 to 15. That is, the number of sieve plates 10 can be any number from 3 to 15, which can be selected according to actual production needs, and this application does not impose any restrictions.

[0068] In some embodiments of this application, the pressurizing device 22 is connected to the air inlet 17 of each sieve plate 10 via a connecting pipe 30, and each connecting pipe 30 is equipped with a second valve 29 to adjust the flow rate of the corresponding connecting pipe 30. It is understood that, due to the different installation positions of each sieve plate 10, the time points of the thermal reaction stages of different sieve plates 10 are also different, and the particle size of the solid particles passing through the through holes 12 of each sieve plate 10 is also different, so the flow rate of the gas used for impact can also be varied accordingly.

[0069] During the thermal reaction stage of isocyanate, as the reaction proceeds, the particle size of the solid particles gradually decreases, thus reducing the need for high-pressure gas flow. Therefore, the higher the sieve plate 10 is located, the smaller the gas flow rate entering its inlet 17. In this embodiment, the high-pressure gas flow rate entering each sieve plate 10 is adjusted by regulating the opening degree of each second valve 29.

[0070] See Figure 3 In some embodiments of this application, each through hole 12 is provided with a plurality of air outlets 16 at regular intervals along the circumference, and the plurality of air outlets 16 in each through hole 12 are evenly distributed. Preferably, the number of air outlets 16 provided on the sidewall of each through hole 12 is 3 to 20, and the opening ratio of the air outlets 16 relative to the sidewall of the through hole 12 is 20% to 50%, so that airflow can enter from multiple parts of the sidewall of the through hole 12, thereby enhancing the impact and dispersion effect on solid particles. It should be noted that the cutting plate 14 should be arranged in a way that avoids blocking the air outlets 16 as much as possible.

[0071] In some embodiments of this application, the air inlet 17 is located on the side wall of the plate 11. Thus, the connecting pipe 30, which connects to the air inlet 17 and is used to transport airflow, can be connected to the side wall of the plate 11 to meet some practical installation requirements. The number of air inlets 17 can be one or multiple. See also... Figures 1 to 3 In this embodiment, only one air inlet 17 is provided to reduce the number of connecting pipes 30 connected to the air inlet 17.

[0072] It is also worth mentioning that, see Figure 5 Since the air inlet 17 is located on the side wall of the plate 11, the connecting pipe 30 used to connect the booster device 22 and the air inlet 17 is also connected to the side wall of the plate 11. Since the side wall of the plate 11 is connected to the inner wall of the reaction tower 18, the connecting pipe 30 can be connected to the air inlet 17 after passing through the reaction tower 18, thus avoiding the connecting pipe 30 from extending into the internal space of the reaction tower 18 and interfering with the thermal reaction.

[0073] Combination Figure 1 and Figure 6 In some embodiments of this application, multiple feed inlets 19 are provided, and the directions of the multiple feed inlets 19 toward the interior of the reaction tower 18 are at angles to each other. Specifically, with multiple feed inlets 19, the material that has undergone the cold reaction stage will have multiple source paths when it is introduced into the reaction tower 18. By setting the multiple feed inlets 19 at angles toward the interior of the reaction tower 18, the materials introduced from the multiple source paths form a convection pattern, and convective mixing occurs at the bottom of the reaction tower 18, improving the uniformity of the material entering from the bottom of the reaction tower 18.

[0074] For example, see Figure 6 As shown, the reaction tower 18 has three feed inlets 19 at its bottom, meaning there are three material supply paths at the bottom of the reaction tower 18. Each material supply path includes a dynamic mixer 25 for the cold reaction stage. Each dynamic mixer 25 is independently connected to a first feed pipe 26 and a second feed pipe 27 for conveying phosgene solution and amine solution, respectively. It is understood that the concentrations of the phosgene solution and amine solution input into each dynamic mixer 25 are not necessarily identical, and the material concentrations after the reaction in each dynamic mixer 25 will also differ. Therefore, in this embodiment, the three feed inlets 19 are oriented at angles to each other, ensuring that the materials input into the reaction tower 18 from the three material supply paths are mixed uniformly at the bottom of the reaction tower 18, thus ensuring uniform reaction during the hot reaction stage.

[0075] Preferably, the number of feed inlets 19 at the bottom of the reaction tower 18 is 1 to 5. The specific number can be selected based on actual production needs, and this application does not impose any restrictions.

[0076] This application also provides a method for preparing isocyanate, using a thermophotovoltaic reactor as described in any of the above embodiments. Specifically, the preparation method includes the following steps:

[0077] The cold photochemical vaporization reaction liquid is fed into the reaction tower 18 through the feed port 19. The reaction temperature in the reaction tower 18 is 80℃~150℃ and the reaction pressure is 0.15MPa~0.5MPa. The reaction gas is discharged through the outlet 16 and then pressurized by the booster device 22. After being pressurized by the booster device 22, it flows into the inlet 17. The reaction gas pressurized by the booster device 22 accounts for 20%~60% of the total gas discharged through the exhaust port 20. The pressure of the reaction gas after being pressurized by the booster device 22 is 0.5MPa~3MPa.

[0078] Understandably, in order to facilitate the monitoring of the reaction temperature and reaction pressure inside the reaction tower 18, pressure sensor 23 and temperature sensor 24 can be set to monitor the reaction temperature and reaction pressure inside the reaction tower 18 in real time, so that operators can observe and adjust the pressure and temperature inside the tower.

[0079] In addition, the pressurized reaction gas by the booster device 22 accounts for 20% to 60% of the total gas emitted from the exhaust port 20, and the remaining part is discharged to the outside and can be used for other processes or recycled. This application does not impose any restrictions.

[0080] Furthermore, when multiple sieve plates 10 are provided and the multiple sieve plates 10 are arranged at intervals along the height direction of the reaction tower 18, the air intake at the air inlet 17 of the nth sieve plate 10 arranged from bottom to top satisfies:

[0081] ;

[0082] in:

[0083] n is the sequence number of the sieve plate 10 from bottom to top;

[0084] X n The proportion of the air intake at the inlet 17 of the nth sieve plate 10 to the total amount of gas discharged from the exhaust port 20 of the reaction tower 18;

[0085] m represents the total number of sieve plates (10).

[0086] T n The reaction temperature is located at the position of the nth sieve plate 10;

[0087] e is the natural constant, taken as 2.71828;

[0088] Σ is the summation symbol, representing the summation of the numerator terms of all sieve plates 10 from k=1 to k=m.

[0089] In addition, combined Figure 4 and Figure 6 To facilitate control of the air intake from the air inlet 17 of each screen plate 10, a first valve 28 is connected between the booster device 22 and the exhaust port 20. The first valve 28 controls the overall flow of the pipeline between the exhaust port 20 and the air inlet 17. A second valve 29 is provided on the connecting pipe 30 connecting the booster device 22 and the air inlet 17 of each screen plate 10 to facilitate the control of the flow and flow of each connecting pipe 30.

[0090] When the gas discharged from the exhaust port 20 flows back to the inlet gas on each sieve plate 10 and satisfies the above relationship, the generation of urea, a byproduct, in the internal thermal reaction stage of the reaction tower 18 is less and the effect is better. The urea content in the liquid phase discharged from the outlet 21 is less than 0.1%. The determination method of urea compounds can be determined by conventional liquid chromatography, which will not be elaborated in this application.

[0091] Isocyanates are prepared by reacting raw amines with phosgene. The raw amines include methylene diphenyl diamine (mMDA), polymethylene polyphenyl polyamine (pMDA), a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA), 2,4-toluenediamine (TDA-100), a mixture of 2,4-toluenediamine and 2,6-toluenediamine (TDA-80 or TDA-65), m-phenylenediamine (XDA) and its isomers, and p-phenylenediamine (PPD). A) and its isomers, tetramethylxylenediamine (TMXDA), 1,3-dimethylaminocyclohexane (H6XDA), 2,6-dimethylamine, 1,5-naphthyldiamine (1,5-NDA), 1,4-diaminobutane, 1,5-diaminopentane (PDA), 1,6-diaminohexane (HDA), 4,4'-dicyclohexylmethanediamine (H12MDA), 2,4'-dicyclohexylmethanediamine, 1,8-diaminooctane, 1,9-diaminononane, 1,10- Diaminodecane, 2,2-dimethyl-1,5-diaminopentane, 2-methyl-1,5-pentanediamine (MPDA), 2,4,4 (or 2,2,4)-trimethyl-1,6-diaminohexane (TMDA), 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 2,4- or 2,6-diamino-1-methylcyclohexane (H6-TDA), 1-amino-1-methyl-4(3)-amino Methylcyclohexane (AMCA), 1,3 (and / or 1,4)-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornene (NBDA), triaminocyclohexane, tri(aminomethyl)cyclohexane, triamino-methylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, 1,6,11-undecanetriamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, 1,3,5-tri(aminomethyl)cyclohexane.

[0092] Example 1:

[0093] MDI (an isocyanate product) is prepared using a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA) as raw materials.

[0094] First, a chlorobenzene solution containing 50% phosgene and a chlorobenzene solution containing 35% MDA are subjected to a cold reaction in a dynamic mixer 25 with a phosgene-amine ratio of 5:1 and a reaction temperature of 60°C to obtain a cold phosgene reaction liquid.

[0095] Then, the cold photochemical vaporization reaction liquid enters the bottom of the reaction tower 18, where the reaction pressure is 0.2 MPa. The reaction liquid passes through six sieve plates 10 from bottom to top. Each sieve plate 10 has one air inlet 17 on its side wall, and the opening rate of the through holes 12 is 50%. The cutting plate 14 installed within the through holes 12 is in the form of Example c. There are ten air outlets 16 on the inner wall of the through holes 12, with an opening rate of 30% relative to the inner wall of the through holes 12. The temperature of each sieve plate 10 from bottom to top is 90℃, 100℃, 110℃, 120℃, 125℃, and 130℃. The gas pressurized by the pressurization device 22 accounts for 40% of the gas discharged at the exhaust port 20, and the pressure of the gas after pressurization by the pressurization device 22 is 1 MPa. According to the calculation formula, the proportions of the pressurized gas introduced into each sieve plate 10 from bottom to top to the total amount emitted from the exhaust port 20 are 25.7%, 21.0%, 17.1%, 14.0%, 12.0%, and 10.3%, respectively.

[0096] The thermal photogasification reaction liquid is discharged from the outlet 21. The liquid phase is sampled and tested, and the urea content in the liquid phase is 0.039%.

[0097] Example 2:

[0098] Toluene diisocyanate (TDI) was prepared using toluene diamine (TDA) as a raw material.

[0099] First, a chlorobenzene solution containing 60% phosgene and a chlorobenzene solution containing 30% TDA were subjected to a cold reaction in three dynamic mixers 25, with a phosgene-amine ratio of 6:1 and a reaction temperature of 70°C, to obtain a cold phosgene reaction liquid.

[0100] Then, the cold photochemical vaporization reaction liquid convects into the bottom of the reaction tower 18. The reaction pressure inside the tower is 0.3 MPa. The reaction liquid passes through eight sieve plates 10 from bottom to top. There are two air inlets 17 on the side walls of each sieve plate 10, and the opening rate of the through holes 12 on the sieve plate 10 is 40%. The cutting plate 14 installed inside the through hole 12 is in the form of embodiment f. There are six air outlets 16 on the inner wall of the through hole 12, and the opening rate of the air outlets 16 relative to the inner wall of the through hole 12 is 25%. The temperature of each sieve plate 10 from bottom to top is 80℃, 90℃, 100℃, 110℃, 120℃, 125℃, 130℃, and 135℃. The gas pressurized by the pressurization device 22 accounts for 35% of the gas discharged at the exhaust port 20, and the pressure of the gas after pressurization by the pressurization device 22 is 1.2 MPa. According to the calculation formula, the proportions of the pressurized gas introduced into each sieve plate 10 from bottom to top to the total amount emitted from the exhaust port 20 are 22.4%, 18.3%, 14.9%, 12.2%, 10.0%, 8.5%, 7.3%, and 6.3%, respectively.

[0101] The thermal photogasification reaction liquid is discharged from the outlet 21. The liquid phase is sampled and tested, and the urea content in the liquid phase is 0.045%.

[0102] Comparative Example 1:

[0103] MDI products are prepared using a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA) as raw materials.

[0104] First, a chlorobenzene solution containing 50% phosgene and a chlorobenzene solution containing 35% MDA are subjected to a cold reaction in a dynamic mixer 25 with a phosgene-amine ratio of 5:1 and a reaction temperature of 60°C to obtain a cold phosgene reaction liquid.

[0105] Then, the cold light vaporization reaction liquid enters the bottom of the reaction tower 18. The reaction pressure inside the tower is 0.2 MPa. The reaction liquid passes through each level of sieve plate 10 from bottom to top, with a total of six sieve plates 10. There is one air inlet 17 on the side wall of each sieve plate 10, and the opening rate of the through holes 12 on the sieve plate 10 is 50%. The cutting plate 14 set in the through hole 12 is in the form of embodiment c. There are ten air outlets 16 on the inner wall of the through hole 12, and the opening rate of the air outlets 16 relative to the inner wall of the through hole 12 is 30%. The temperature of each layer of sieve plate 10 from bottom to top is 90℃, 100℃, 110℃, 120℃, 125℃, and 135℃. The gas pressurized by the pressurizing device 22 accounts for 40% of the gas discharged at the exhaust port 20. The pressure of the gas after pressurization by the pressurizing device 22 is 1 MPa. The amount of pressurized gas introduced into each sieve plate 10 is evenly distributed.

[0106] The thermal photogasification reaction liquid is discharged from the outlet 21. The liquid phase is sampled and tested, and the urea content in the liquid phase is 0.18%.

[0107] Comparative Example 2:

[0108] MDI products are prepared using a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA) as raw materials.

[0109] First, a chlorobenzene solution containing 50% phosgene and a chlorobenzene solution containing 35% MDA are subjected to a cold reaction in a dynamic mixer 25 with a phosgene-amine ratio of 5:1 and a reaction temperature of 60°C to obtain a cold phosgene reaction liquid.

[0110] Then, the cold light vaporization reaction liquid enters the bottom of the reaction tower 18. The reaction pressure inside the tower is 0.2 MPa. The reaction liquid passes through each level of sieve plate 10 from bottom to top. There are a total of six sieve plates 10. The opening rate of the through holes 12 on the sieve plate 10 is 50%. The temperature of each layer of sieve plate 10 from bottom to top is 90℃, 100℃, 110℃, 120℃, 125℃ and 135℃.

[0111] The thermal photogasification reaction liquid is discharged from the outlet 21. The liquid phase is sampled and tested, and the urea content in the liquid phase is 0.62%.

[0112] Compared with Comparative Example 1, in Example 1, the proportion of pressurized gas introduced into each sieve plate 10 from bottom to top to the total amount emitted from exhaust port 20 was calculated according to the above formula, and was 25.7%, 21.0%, 17.1%, 14.0%, 12.0%, and 10.3%, respectively, thereby significantly reducing the urea content in the liquid phase discharged from the discharge port 21.

[0113] Compared with Comparative Example 2, in Example 1, a cutting plate 14 is provided at the through hole 12 of the sieve plate 10, and pressurized gas is introduced into each sieve plate 10 through the pressurizing device 22. The amount of gas introduced into each sieve plate 10 is calculated by the above formula, thereby significantly reducing the urea content in the liquid phase discharged from the discharge port 21.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the patent protection scope of this application should be determined by the appended claims.

Claims

1. A thermophotogasification reactor, characterized in that, include: The reaction tower has a feed inlet at the bottom and an exhaust outlet and a discharge outlet located above the feed inlet. A sieve plate, installed inside the reaction tower to vertically divide the tower space, is located between the feed inlet and the discharge outlet. The sieve plate includes a plate body with through holes and flow channels. Multiple through holes extend through the plate body vertically. The sidewalls of the through holes have air outlets communicating with the flow channels. The plate body also has air inlets for external airflow to enter the flow channels. A pressurizing device is provided on the outside of the reaction tower. The exhaust port is connected to the air inlet of the sieve plate through the pressurizing device, so that the gas discharged at the exhaust port is pressurized and then enters the flow channel.

2. The thermophotogasification reactor according to claim 1, characterized in that, A cutting tool for cutting solid particles that pass through the through hole is installed at the through hole.

3. The thermophotogasification reactor according to claim 2, characterized in that, The cutting element is disposed in the through hole, and the cutting element includes multiple cutting plates, which are distributed around the circumference of the through hole, and the thickness direction of the cutting plates is along the circumference of the through hole.

4. The thermophotogasification reactor according to claim 1, characterized in that, Multiple sieve plates are provided and are spaced apart along the height direction of the reaction tower.

5. The thermophotogasification reactor according to claim 4, characterized in that, Each of the pressurizing devices is connected to an air inlet of each of the screen plates by a connecting pipe, and each connecting pipe is equipped with a second valve to adjust the flow rate of the corresponding connecting pipe.

6. The thermophotogasification reactor according to claim 1, characterized in that, Each of the through holes is provided with a plurality of air outlets at intervals along the circumference, and the plurality of air outlets of each through hole are evenly distributed.

7. The thermophotogasification reactor according to claim 1, characterized in that, The air inlet is located on the side wall of the plate.

8. The thermophotogasification reactor according to claim 1, characterized in that, The feed inlets are provided in multiple ways, and the directions of the multiple feed inlets toward the interior of the reaction tower are at angles to each other.

9. A method for preparing an isocyanate, characterized in that, Isocyanates are prepared using the thermophotogasification reactor according to any one of claims 1 to 8, the preparation method comprising the following steps: The cold light vaporization reaction liquid is fed into the reaction tower through the feed port. The reaction temperature in the reaction tower is 80℃~150℃ and the reaction pressure is 0.15MPa~0.5MPa. The reaction gas is discharged through the gas outlet and then pressurized by the pressurizing device before flowing into the gas inlet. The reaction gas pressurized by the booster device accounts for 20% to 60% of the total gas emitted from the exhaust port, and the pressure of the reaction gas after being pressurized by the booster device is 0.5 MPa to 3 MPa.

10. The method for preparing isocyanate according to claim 9, characterized in that, When multiple sieve plates are installed and arranged at intervals along the height of the reaction tower, the air intake at the inlet of the nth sieve plate from bottom to top satisfies the following: ； in: n is the sequence number of the sieve plates from bottom to top; X n The proportion of the gas intake at the inlet of the nth sieve plate to the total gas output from the exhaust port of the reaction tower. m is the total number of sieve plates; T n The reaction temperature is located at the position of the nth sieve plate; e is the natural constant, taken as 2.71828; Σ is the summation symbol, representing the summation of the numerator terms for all sieve plates from k=1 to k=m.

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