System and method for preparing cyanuric acid from urea

Abstract

The invention relates to the technical field of chemical engineering, and discloses a system and a method for preparing cyanuric acid from urea. The system comprises a reaction device, a filtering device and a product storage bin, the reaction device comprises an inner cylinder and an outer cylinder which are coaxially arranged, a reaction cavity is formed between the inner cylinder and the outer cylinder, a spiral lifting structure is arranged in the inner cylinder, one side of the outer cylinder is provided with a urea inlet, the other side of the outer cylinder is provided with an overflow discharge port, and the overflow discharge port is communicated with the inner cylinder. Urea raw materials are added through the urea inlet and are subjected to pyrolytic reaction, cyanuric acid enters an inner cavity of the inner cylinder from the bottom, is lifted to the top through the spiral lifting structure and returns to the reaction chamber from the top, and obtained mixed materials are discharged through the overflow discharging port and are separated into a gas phase and a solid phase under the action of gravity; the gas phase enters the filtering device for filtering treatment; the solid phase enters the product storage bin to be collected. The method improves the purity of cyanuric acid and the utilization rate of urea.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a system and a method for preparing cyanuric acid from urea. Background Art

[0002] Cyanuric acid, also known as tricyanic acid, has a chemical formula of C3H3N3O3. It has two isomers, namely keto and enol structures, and usually exists as a mixture of the two isomers. It is white crystal; it tastes slightly bitter, is basically non-toxic, is soluble in hot water, slightly soluble in cold water, and its aqueous solution is acidic. It is insoluble in cold organic solvents such as alcohol, ether, and benzene.

[0003] Cyanuric acid is a very important chemical synthetic raw material, mainly used to manufacture sodium dichloroisocyanurate, trichloroisocyanuric acid, tris(β-hydroxyethyl)isocyanurate, triallyl ester, cyanuric acid-formaldehyde resin, epoxy resin, antioxidant, coating, adhesive and medical halogen trihydroxyzine drugs. At present, there are more than 500 series of products developed using cyanuric acid at home and abroad, of which more than 200 are industrially commercialized. These products are fine chemical products with high added value, wide application, strong competitiveness and urgent market demand.

[0004] The existing methods for synthesizing cyanuric acid mainly include urea pyrolysis, phosgene and ammonia reaction synthesis, cyanate trimerization, hydrocyanic acid oxidation, cyanuric chloride hydrolysis, etc. The current mainstream process is urea pyrolysis, which has multiple parallel side reactions, reduced selectivity of the target product, and many product impurities, among which the main impurities are biuret and cyanuric acid monoamide. According to reliable information, the currently commonly used tunnel kiln urea pyrolysis method has a large number of by-products due to the slow heating, and the content of cyanuric acid is only about 70%. Further purification is required.

[0005] Therefore, there is an urgent need to develop a system and method for preparing cyanuric acid from urea to solve the problems of large footprint, high investment and urea sticking to the wall in the tunnel kiln used for conventional urea pyrolysis, reduce the generation of reaction by-products, improve the purity of the reaction products, and recover the volatilized urea and return it for reaction. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of large floor space, high investment, urea wall adhesion, low purity of reaction products and low urea utilization rate in the conventional tunnel kiln used for urea pyrolysis in the prior art, and to provide a system and method for preparing cyanuric acid from urea. The technical scheme solves the problem of urea wall adhesion caused by direct heating of urea by using a mixing reactor, and can also improve the heat exchange rate of the material in the reactor, accelerate the reaction speed, improve the reaction efficiency, reduce the reaction by-products, improve the purity of the reaction products, and filter out the volatilized urea through a filtering device and return it to the reactor for reaction.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a system for preparing cyanuric acid from urea, which system includes a reaction device, a filtering device and a product storage bin, wherein the reaction device includes an inner cylinder and an outer cylinder arranged coaxially, a reaction chamber is formed between the inner cylinder and the outer cylinder, a spiral lifting structure is arranged in the inner cylinder, a urea inlet is arranged on one side of the outer cylinder, and an overflow discharge port is arranged on the other side opposite to the urea inlet, a urea raw material is added through the urea inlet and a pyrolysis reaction occurs in the reaction chamber to obtain cyanuric acid and ammonia, the cyanuric acid in the reaction chamber enters the inner cavity of the inner cylinder from the bottom, is lifted to the top by the spiral lifting structure and returns to the reaction chamber from the top, the mixed material in the reaction chamber is discharged through the overflow discharge port, and is separated into a gas phase and a solid phase under the action of gravity; the gas phase enters the filtering device for filtering treatment; the solid phase enters the product storage bin for collection.

[0008] Preferably, in the reaction device, the inner cylinder and the spiral lifting structure are each connected to a transmission device for causing them to rotate.

[0009] Preferably, the inner cylinder and the spiral lifting structure rotate in opposite directions.

[0010] Preferably, the spiral lifting structure comprises a rotating shaft and spiral blades arranged around the outer circumference of the rotating shaft.

[0011] Preferably, a wall-scraping spiral streamer is provided on the inner side of the outer cylinder.

[0012] Preferably, the overflow discharge port is inclined downward by 45-60°.

[0013] Preferably, the ratio of the lower edge height of the urea inlet to the lower edge height of the overflow discharge port is (1.01-1.2):1.

[0014] Preferably, the filtering device comprises a cavity, the cavity is filled with filtering filler, a filler inlet is arranged at the top of the cavity, a filler outlet is arranged at the bottom, a gas inlet is arranged at the upper part of the cavity, and a gas outlet is arranged at the lower part of the cavity, the gas phase separated from the mixed material enters the cavity through the gas inlet and is filtered in the presence of the filtering filler.

[0015] Preferably, the filter filler is zirconia balls and / or ceramic balls.

[0016] Preferably, the system further comprises a screening device. After the filtering device performs filtering treatment for a period of time, the filtering filler in the cavity is transported to the screening device through the filler outlet for screening, and the screened filtering filler is returned to the cavity of the filtering device through the filler inlet.

[0017] Preferably, the screening device is a drum screening machine.

[0018] Preferably, a material recycling pipeline is arranged between the screening device and the urea inlet, for returning the urea and cyanuric acid powder screened out by the screening device to the reaction device for reuse.

[0019] Preferably, the system further comprises a spray device, which is used for eluting the ammonia gas discharged from the gas outlet of the filtering device to obtain ammonia water.

[0020] A second aspect of the present invention provides a method for preparing cyanuric acid from urea, which is carried out in the above-mentioned system and comprises:

[0021] The reaction chamber of the reaction device is filled with cyanuric acid, and while the inner cylinder and the spiral lifting structure rotate simultaneously, urea raw material is added into the reaction chamber through the urea inlet for pyrolysis reaction; the mixed material in the reaction chamber is discharged through the overflow outlet, and separated into a gas phase and a solid phase under the action of gravity; the gas phase enters the filtering device for filtration treatment, and the ammonia gas obtained after filtration is eluted to obtain ammonia water, and the urea and cyanuric acid powders retained during the filtration treatment are separated and returned to the reaction chamber through the urea inlet for reuse.

[0022] Preferably, the ratio of the rotation speed of the inner drum to the rotation speed of the spiral lifting structure is 1:(5-15).

[0023] Preferably, the rotation speed of the spiral lifting structure is 80-120 r / min, and the rotation speed of the inner cylinder (12) is 10-15 r / min.

[0024] Preferably, the conditions of the pyrolysis reaction include: temperature of 270-300° C. and time of 10-15 h.

[0025] Preferably, during the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device (1) is maintained within the range of (10-12):1.

[0026] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0027] (1) The reaction device of the present invention adopts overflow discharge to ensure that there is enough cyanuric acid as filler in the reaction chamber, and there is no need to monitor the material level. Compared with the current conventional tunnel kiln production process, the investment cost is greatly reduced, the equipment volume is reduced, and the equipment footprint is reduced;

[0028] (2) Compared with the conventional tunnel kiln process, the purity of the product cyanuric acid is increased from about 70% to more than 89% through the system of the present invention. In addition, the system of the present invention has a high degree of automation, is easy to operate, reduces labor costs, reduces by-products in the product, improves the utilization rate of urea, and reduces the amount of acid required for the next step of impurity removal;

[0029] (3) In the system described in the present invention, the urea inlet is located at the material level. After the urea enters the reactor, it is quickly covered by the cyanuric acid falling from above. The generated ammonia gas carries the volatilized urea in the rising process. The volatilized urea is intercepted by the cyanuric acid powder, thereby reducing the amount of volatilized urea that needs to be processed later.

[0030] (4) The generated flue gas is filtered by a filtering device, which can effectively remove the gaseous urea generated during the thermal condensation of urea, and collect the urea to continue to participate in the reaction, thereby improving the utilization rate of urea;

[0031] (5) The system of the present invention can be used not only for the production of cyanuric acid, but also for the production of other substances that stick to the wall after heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process flow of the system for preparing cyanuric acid from urea according to the present invention;

[0033] Figure 2 It is a structural schematic diagram of the reaction device of the present invention;

[0034] Figure 3 It is a schematic structural diagram of the filtering device described in the present invention.

[0035] Description of Reference Numerals

[0036] 1. Reaction device; 11. Spiral lifting structure; 12. Inner cylinder; 13. Outer cylinder; 14. Urea inlet; 15. Overflow outlet; 16. Scraping spiral ribbon; 17. Transmission device; 18. Manhole; 19. Bracket; 2. Filter device; 21. Filler inlet; 22. Filler outlet; 23. Gas inlet; 24. Gas outlet; 25. Gate valve; 3. Product storage bin; 4. Spraying device; 5. Urea storage bin. DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0038] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0039] like Figure 1 As shown, the system for preparing cyanuric acid from urea of ​​the present invention comprises a reaction device 1, a filtering device 2 and a product storage bin 3, wherein, as Figure 2 As shown, the reaction device 1 includes an inner cylinder 12 and an outer cylinder 13 which are coaxially arranged, a reaction chamber is formed between the inner cylinder 12 and the outer cylinder 13, a spiral lifting structure 11 is arranged in the inner cylinder 12, a urea inlet 14 is arranged on one side of the outer cylinder 13, and an overflow outlet 15 is arranged on the other side opposite to the urea inlet 14, urea raw material is added through the urea inlet 14 and undergoes a pyrolysis reaction in the reaction chamber to obtain cyanuric acid and ammonia, the cyanuric acid in the reaction chamber enters the inner cavity of the inner cylinder 12 from the bottom, is lifted to the top by the spiral lifting structure 11 and returns to the reaction chamber from the top, the mixed material in the reaction chamber is discharged through the overflow outlet 15, and is separated into a gas phase and a solid phase under the action of gravity; the gas phase enters the filtering device 2 for filtering treatment; the solid phase enters the product storage bin 3 for collection.

[0040] According to the system for preparing cyanuric acid from urea of ​​the present invention, the material is discharged in an overflow manner, which reduces the investment cost, reduces the equipment volume, and reduces the equipment floor space; the system for preparing cyanuric acid from urea of ​​the present invention has a high degree of automation, is easy to operate, reduces labor costs, and improves the purity of the product cyanuric acid from about 70% to more than 89%, reduces the by-products in the product, and reduces the amount of acid solution required for the next step of impurity removal; the generated flue gas is filtered by the filtering device, which can effectively remove the gaseous urea generated during the thermal condensation of urea, and the urea is collected to continue to participate in the reaction, thereby improving the utilization rate of urea; after the urea enters the reaction device, it is quickly covered by the cyanuric acid falling from above, so as to prevent the urea from adhering to the wall.

[0041] In the system for producing cyanuric acid from urea of ​​the present invention, in order to prevent cyanuric acid from sticking to the wall, in the reaction device 1, the inner cylinder 12 and the spiral lifting structure 11 are each preferably connected to a transmission device 17 for rotating them. In a more preferred case, the inner cylinder 12 and the spiral lifting structure 11 rotate in opposite directions. The spiral lifting structure 11 may include a rotating shaft and spiral blades arranged around the outer circumference of the rotating shaft. The transmission device 17 may include a motor and a reducer. In some embodiments, under the action of the transmission device 17, the inner cylinder 12 and the spiral lifting structure 11 rotate simultaneously, and the inner cylinder 12 and the spiral lifting structure 11 rotate in opposite directions.

[0042] In the system for producing cyanuric acid from urea of ​​the present invention, in order to prevent cyanuric acid from sticking to the wall, a wall scraping spiral ribbon 16 is preferably provided on the inner side of the outer cylinder 13. The rotation of the wall scraping spiral ribbon 16 can be driven by the rotation of the inner cylinder 12.

[0043] In the system for preparing cyanuric acid from urea of ​​the present invention, in order to facilitate the generated cyanuric acid and ammonia to flow out in an overflow manner, the overflow outlet 15 is preferably tilted downward by 45-60°, and the specific downward tilt angle can be 45°, 48°, 50°, 53°, 55°, 58° or 60°. In order to fully pyrolyze the urea entering from the urea inlet 14, the overflow outlet 15 and the urea inlet 14 are preferably symmetrically arranged along the center line of the reaction device 1.

[0044] In the system for preparing cyanuric acid from urea of ​​the present invention, the ratio of the lower edge height of the urea inlet 14 to the lower edge height of the overflow outlet 15 can be (1.01-1.2):1, preferably (1.1-1.2):1, and specifically for example can be 1.01:1, 1.05:1, 1.1:1, 1.15:1 or 1.2:1. The lower edge height is the distance from the lower edge to the bottom of the reaction device. In order to prevent urea from sticking to the wall after urea enters the reaction device, the ratio of the lower edge height of the urea inlet 14 to the height of the reaction device 1 is preferably (0.7-0.9):1, more preferably (0.75-0.85):1, and specifically for example can be 0.7:1, 0.75:1, 0.78:1, 0.8:1, 0.83:1, 0.85:1 or 0.9:1.

[0045] In the system for producing cyanuric acid from urea of ​​the present invention, the reaction device 1 may further include a manhole 18, which is disposed on the outside of the outer cylinder 13 and is used for inspecting the reaction device 1. The reaction device 1 may further include a bracket 19, which is disposed on the outside of the outer cylinder 13 and is used for fixing the reaction device 1. In a preferred embodiment, the reaction device 1 includes two brackets 19, which are symmetrically arranged along the center line of the reaction device 1.

[0046] In the system for preparing cyanuric acid from urea of ​​the present invention, if Figure 3 As shown, the filter device 2 may include a cavity, the cavity may be filled with a filter filler, the top of the cavity may be provided with a filler inlet 21, the bottom may be provided with a filler outlet 22, the upper part of the cavity may be provided with a gas inlet 23, the lower part of the cavity may be provided with a gas outlet 24, and the gas phase separated from the mixed material may enter the cavity through the gas inlet 23 and be filtered in the presence of the filter filler. In order to improve the utilization rate of urea, the filter filler is preferably a zirconia ball and / or a ceramic ball. The filter filler is heat-exchanged with the gas phase to reduce the temperature of the gas phase, and the gaseous urea contained in the gas phase becomes liquid or solid and sticks to the filter filler, thereby achieving the purpose of separation from ammonia. The filter device 2 may also include a gate valve 25.

[0047] In the system for preparing cyanuric acid from urea of ​​the present invention, in order to improve the utilization rate of urea, the system preferably further includes a screening device, and after the filtering device 2 performs filtering treatment for a period of time, the filtering filler in the cavity is transported to the screening device through the filler outlet 22 for screening, and the screened filtering filler is returned to the cavity of the filtering device 2 through the filler inlet 21. The screening device can be a drum screening machine.

[0048] In the system for preparing cyanuric acid from urea of ​​the present invention, in order to improve the utilization rate of urea, a material recycling pipeline is preferably arranged between the screening device and the urea inlet 14, for returning the urea and cyanuric acid powder screened out by the screening device to the reaction device 1 for reuse.

[0049] In the system for preparing cyanuric acid from urea of ​​the present invention, the system may further include a spray device 4, and the spray device 4 is used to rinse the ammonia gas discharged from the gas outlet 24 of the filter device 2 to obtain ammonia water.

[0050] In the system for preparing cyanuric acid from urea of ​​the present invention, the system may further include a urea storage bin 5, which is used to store urea, and the urea in the urea storage bin 5 enters the reaction device 1. The urea in the urea storage bin 5 may enter the reaction device 1 through a screw feeder.

[0051] In some embodiments, Figure 1 As shown, the system for preparing cyanuric acid from urea of ​​the present invention comprises a reaction device 1, a filtering device 2, a product storage bin 3, a spraying device 4 and a urea storage bin 5, wherein Figure 2As shown, the reaction device 1 includes an inner cylinder 12 and an outer cylinder 13 arranged coaxially, a reaction chamber is formed between the inner cylinder 12 and the outer cylinder 13, a spiral lifting structure 11 is arranged in the inner cylinder 12, and the inner cylinder 12 and the spiral lifting structure 11 are respectively connected with a transmission device 17 for rotating them, and the rotation directions of the inner cylinder 12 and the spiral lifting structure 11 are opposite, the spiral lifting structure 11 includes a rotating shaft and a spiral blade arranged around the outer circumference of the rotating shaft, and the transmission device 17 includes a motor and a reducer; a wall-scraping spiral streamer 16 is arranged on the inner side of the outer cylinder 13, and the rotation of the wall-scraping spiral streamer 16 is driven by the rotation of the inner cylinder 12, a urea inlet 14 is arranged on one side of the outer cylinder 13, and an overflow discharge port 15 is arranged on the other side opposite to the urea inlet 14, and the overflow discharge port 15 is inclined downward by 45-60 degrees, and the lower edge height of the urea inlet 14 is 1.5-2.0 degrees ... The ratio of the lower edge height of the outflow port 15 is (1.01-1.2):1, the ratio of the lower edge height of the urea inlet 14 to the height of the reaction device 1 is (0.7-0.9):1, the urea raw material is added through the urea inlet 14 and undergoes a pyrolysis reaction in the reaction chamber to obtain cyanuric acid and ammonia, the cyanuric acid in the reaction chamber enters the inner cavity of the inner cylinder 12 from the bottom, is lifted to the top by the spiral lifting structure 11 and returns to the reaction chamber from the top, the mixed material in the reaction chamber is discharged through the overflow outlet 15, and is separated into a gas phase and a solid phase under the action of gravity; the reaction device 1 also includes a manhole 18 and a bracket 19, the manhole 18 and the bracket 19 are respectively arranged on the outside of the outer cylinder 13, the manhole 18 is used to inspect the reaction device 1; the bracket 19 is used to fix the reaction device 1; the gas phase enters the filtering device 2 for filtering treatment, such as Figure 3As shown, the filtering device 2 includes a cavity, the cavity is filled with filtering fillers, the top of the cavity is provided with a filler inlet 21, the bottom is provided with a filler outlet 22, the upper part of the cavity is provided with a gas inlet 23, the lower part of the cavity is provided with a gas outlet 24, the gas phase separated from the mixed material enters the cavity through the gas inlet 23 and is filtered in the presence of the filtering fillers; the filtering device 2 also includes a gate valve 25; the filtering device 2 also includes a drum screening machine, after the filtering device 2 performs filtering treatment for a period of time, the filtering fillers in the cavity are transported to the The urea is screened in the drum screening machine, and the screened filter filler is returned to the cavity of the filter device 2 through the filler inlet 21; a material recycling pipeline is arranged between the drum screening machine and the urea inlet 14, which is used to return the urea and cyanuric acid powder screened in the drum screening machine to the reaction device 1 for reuse; the solid phase enters the product storage bin 3 for collection; the spray device 4 is used to leach the ammonia gas discharged from the gas outlet 24 of the filter device 2 to obtain ammonia water; the urea storage bin 5 is used to store urea, and the urea in the urea storage bin 5 enters the reaction device 1 through a screw feeder.

[0052] The present invention also provides a method for preparing cyanuric acid from urea, which is carried out in the above-mentioned system and comprises:

[0053] The reaction chamber of the reaction device 1 is filled with cyanuric acid, and while the inner cylinder 12 and the spiral lifting structure 11 are rotating simultaneously, urea raw material is added into the reaction chamber through the urea inlet 14 for pyrolysis reaction; the mixed material in the reaction chamber is discharged through the overflow outlet 15, and is separated into a gas phase and a solid phase under the action of gravity; the gas phase enters the filtering device 2 for filtration treatment, and the ammonia gas obtained after filtration is eluted to obtain ammonia water, and the urea and cyanuric acid powders retained during the filtration treatment are separated and returned to the reaction chamber through the urea inlet 14 for reuse.

[0054] According to the method of the present invention, urea and cyanuric acid can be prevented from adhering to the wall, by-products in the product are reduced, the utilization rate of urea is improved, and the purity of the product cyanuric acid is increased from about 70% to more than 89%.

[0055] In the method described in the present invention, in order to prevent cyanuric acid from sticking to the wall, the ratio of the rotation speed of the inner drum 12 to the rotation speed of the spiral lifting structure 11 is preferably 1:(5-15), more preferably 1:(6-12), for example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15.

[0056] In the method of the present invention, the rotation speed of the spiral lifting structure 11 can be 80-120r / min, preferably 90-110r / min, and specifically can be 80r / min, 85r / min, 90r / min, 95r / min, 100r / min, 105r / min, 110r / min, 115r / min or 120r / min. The rotation speed of the inner cylinder 12 can be 10-15r / min, preferably 11-14r / min, and specifically can be 10r / min, 11r / min, 12r / min, 13r / min, 14r / min or 15r / min. The rotation of the wall scraping spiral ribbon 16 is driven by the rotation of the inner cylinder 12, and the rotation speed of the wall scraping spiral ribbon 16 is the same as the rotation speed of the inner cylinder 12.

[0057] In the method of the present invention, the conditions of the pyrolysis reaction include: the temperature can be 270-300°C, preferably 270-290°C, specifically for example 270°C, 275°C, 280°C, 285°C, 290°C, 295°C or 300°C; the time can be 10-15h, preferably 10-12h, specifically for example 10h, 11h, 12h, 13h, 14h or 15h. In the reaction device 1, the heating method can be electric heating or hot flue gas heating.

[0058] In the method of the present invention, the method may further include: passing urea in the urea storage bin 5 into the reaction device 1 through a screw feeder. In order to improve the purity of the product cyanuric acid, during the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device 1 is preferably maintained in the range of (10-12):1, and specifically may be 10:1, 10.5:1, 11:1, 11.5:1 or 12:1.

[0059] In the method described in the present invention, in the filtering device 2, the specific process of the filtering may include: the gas phase exchanges heat with the filtering filler, the gaseous urea contained in the gas phase becomes liquid or solid and sticks to the filtering filler, the cyanuric acid powder contained in the gas phase can stick to the filtering filler, and the ammonia contained in the gas phase is separated therefrom.

[0060] In the method of the present invention, the method may further include: after the filtering device 2 performs filtering treatment for a period of time, the filtering filler in the cavity is transported to the screening device through the filler outlet 22 for screening, the filtered filler after screening is returned to the cavity of the filtering device 2 through the filler inlet 21, and the urea and cyanuric acid powder screened in the screening device are returned to the reaction device 1 for reuse. The particle size of the filtering filler can be 0.5cm-1.5cm, preferably 1cm-1.5cm. In the screening device, the particle size of the screening can be 0.5cm-1cm, preferably 0.5cm-0.8cm.

[0061] In the method of the present invention, the rinsing can be performed by the spraying device 4. The concentration of the ammonia water can be 15-25wt%, preferably 18-22wt%.

[0062] In some embodiments, the method for preparing cyanuric acid from urea of ​​the present invention is carried out in the above-mentioned system, and the method comprises the following steps:

[0063] (1) Cyanuric acid is filled in the reaction chamber of the reaction device 1, and urea raw material is added into the reaction chamber through the urea inlet 14 while the inner cylinder 12 rotates at a speed of 10-15 r / min and the spiral lifting structure 11 rotates at a speed of 80-120 r / min. The urea raw material is subjected to a pyrolysis reaction for 10-15 hours at a temperature of 270-300° C. During the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device 1 is maintained within the range of (10-12):1; the mixed material in the reaction chamber is discharged through the overflow outlet 15 and separated into a gas phase and a solid phase under the action of gravity;

[0064] (2) The gas phase enters the filtering device 2 for filtering treatment, the gas phase exchanges heat with the filtering filler, the gaseous urea contained in the gas phase becomes liquid or solid and adheres to the filtering filler, the cyanuric acid powder contained in the gas phase adheres to the filtering filler, and the ammonia contained in the gas phase is separated therefrom; after the filtering device 2 performs filtering treatment for a period of time, the filtering filler in the cavity is transported to the screening device through the filler outlet 22 for screening, the screened filtering filler is returned to the cavity of the filtering device 2 through the filler inlet 21, and the urea and cyanuric acid powder screened in the screening device are returned to the reaction chamber in the reaction device 1 through the urea inlet 14 for reuse;

[0065] (3) The ammonia gas obtained after filtration is passed into the spray device 4 for elution to obtain ammonia water with a concentration of 15-25wt%, and the solid phase is passed into the product storage bin 3 for collection.

[0066] In other embodiments, the method for preparing cyanuric acid from urea of ​​the present invention is carried out in the above-mentioned system, and the method comprises:

[0067] (1) Cyanuric acid is filled in the reaction chamber of the reaction device 1, and the inner cylinder 12 rotates at a speed of 11-14 r / min and the spiral lifting structure 11 rotates at a speed of 90-110 r / min, and the speed of the scraping spiral streamer 16 is the same as the speed of the inner cylinder 12. The urea raw material in the urea storage bin 5 is fed into the reaction chamber through the screw feeder and the urea inlet 14 at a temperature of 270-290° C. for pyrolysis reaction for 10-12 hours. During the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device 1 is maintained in the range of (10-12): 1; the mixed material in the reaction chamber is discharged through the overflow outlet 15 and separated into a gas phase and a solid phase under the action of gravity;

[0068] (2) The gas phase enters the filtering device 2 for filtering treatment, the gas phase exchanges heat with the filtering filler, the gaseous urea contained in the gas phase becomes liquid or solid and adheres to the filtering filler, the cyanuric acid powder contained in the gas phase adheres to the filtering filler, and the ammonia contained in the gas phase is separated therefrom; after the filtering device 2 performs filtering treatment for a period of time, the filtering filler in the cavity is transported to the screening device through the filler outlet 22 for screening, the screened filtering filler is returned to the cavity of the filtering device 2 through the filler inlet 21, and the urea and cyanuric acid powder screened in the screening device are returned to the reaction chamber in the reaction device 1 through the urea inlet 14 for reuse;

[0069] (3) The ammonia gas obtained after filtration is passed into the spray device 4 for elution to obtain ammonia water with a concentration of 18-22 wt%, and the solid phase is passed into the product storage bin 3 for collection.

[0070] The system and method for preparing cyanuric acid from urea of ​​the present invention are further described below by way of examples. The examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0071] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0072] The process of preparing cyanuric acid from urea in the following examples is Figure 1 The system shown in FIG. 1 is implemented in the system shown in FIG. 1 , specifically, the system includes a reaction device 1, a filtering device 2, a product storage bin 3, a spraying device 4 and a urea storage bin 5, wherein Figure 2 As shown, the reaction device 1 includes an inner cylinder 12 and an outer cylinder 13 arranged coaxially, a reaction chamber is formed between the inner cylinder 12 and the outer cylinder 13, a spiral lifting structure 11 is arranged in the inner cylinder 12, and the inner cylinder 12 and the spiral lifting structure 11 are respectively connected with a transmission device 17 for rotating them, and the rotation directions of the inner cylinder 12 and the spiral lifting structure 11 are opposite, the spiral lifting structure 11 includes a rotating shaft and spiral blades arranged around the outer circumference of the rotating shaft, and the transmission device 17 includes a motor and a reducer; a wall-scraping spiral streamer 16 is arranged on the inner side of the outer cylinder 13, and the rotation of the wall-scraping spiral streamer 16 is driven by the rotation of the inner cylinder 12, a urea inlet 14 is arranged on one side of the outer cylinder 13, and an overflow discharge port 15 is arranged on the other side opposite to the urea inlet 14, and the overflow discharge port 15 is inclined downward by 50°, and the lower edge height of the urea inlet 14 is 1.5° to the overflow discharge port 15. The ratio of the lower edge height of the inner cylinder 15 to the lower edge height of the reaction device 1 is 1.1:1, and the ratio of the lower edge height of the urea inlet 14 to the height of the reaction device 1 is 0.8:1. The urea raw material is added through the urea inlet 14 and undergoes a pyrolysis reaction in the reaction chamber to obtain cyanuric acid and ammonia. The cyanuric acid in the reaction chamber enters the inner cavity of the inner cylinder 12 from the bottom, is lifted to the top by the spiral lifting structure 11, and returns to the reaction chamber from the top. The mixed material in the reaction chamber is discharged through the overflow outlet 15 and is separated into a gas phase and a solid phase under the action of gravity; the reaction device 1 also includes a manhole 18 and a bracket 19, the manhole 18 and the bracket 19 are respectively arranged on the outside of the outer cylinder 13, and the manhole 18 is used to inspect the reaction device 1; the heating method of the reaction device 1 is electric heating; the bracket 19 is used to fix the reaction device 1; the gas phase enters the filtering device 2 for filtering treatment, such as Figure 3As shown, the filtering device 2 includes a cavity, the cavity is filled with a filtering filler, the filtering filler is a zirconia ball, the particle size of the zirconia ball is 1 cm, the top of the cavity is provided with a filler inlet 21, the bottom is provided with a filler outlet 22, the upper part of the cavity is provided with a gas inlet 23, the lower part of the cavity is provided with a gas outlet 24, the gas phase separated from the mixed material enters the cavity through the gas inlet 23 and is filtered in the presence of the filtering filler; the filtering device 2 also includes a gate valve 25; the filtering device 2 also includes a drum screening machine, after the filtering device 2 performs filtering treatment for a period of time, the filtering filler in the cavity is output through the filler outlet 22 The urea is sent to the drum screening machine for screening, and the screened particle size is 0.5cm-0.8cm. The screened filter filler is returned to the cavity of the filter device 2 through the filler inlet 21; a material recycling pipeline is arranged between the drum screening machine and the urea inlet 14, which is used to return the urea and cyanuric acid powder screened out of the drum screening machine to the reaction device 1 for reuse; the solid phase enters the product storage bin 3 for collection; the spray device 4 is used to leach the ammonia gas discharged from the gas outlet 24 of the filter device 2 to obtain ammonia water; the urea storage bin 5 is used to store urea, and the urea in the urea storage bin 5 enters the reaction device 1 through a screw feeder.

[0073] Example 1

[0074] (1) Cyanuric acid is filled in the reaction chamber of the reaction device 1, the inner cylinder 12 and the scraping spiral ribbon 16 are rotated at a speed of 12 r / min and the spiral lifting structure 11 is rotated at a speed of 100 r / min, and the urea raw material in the urea storage bin 5 is fed into the reaction chamber through the screw feeder and the urea inlet 14 at a temperature of 280° C. for pyrolysis reaction for 11 hours. During the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device 1 is maintained at a ratio of 11:1; the mixed material in the reaction chamber is discharged through the overflow outlet 15 and separated into a gas phase and a solid phase under the action of gravity;

[0075] (2) The gas phase enters the filter device 2 for filtering treatment, the gas phase exchanges heat with the filter filler, the gaseous urea contained in the gas phase becomes liquid or solid and sticks to the filter filler, the cyanuric acid powder contained in the gas phase sticks to the filter filler, and the ammonia contained in the gas phase is separated therefrom; after the filter device 2 performs filtering treatment for a period of time, the filter filler in the cavity is transported to the drum screening machine through the filler outlet 22 for screening, the screened filter filler is returned to the cavity of the filter device 2 through the filler inlet 21, and the urea and cyanuric acid powder screened in the drum screening machine are returned to the reaction chamber in the reaction device 1 through the urea inlet 14 for reuse;

[0076] (3) The ammonia gas obtained after filtration is passed into the spray device 4 for elution to obtain ammonia water with a concentration of 20 wt%, and the solid phase is passed into the product storage bin 3 for collection. The purity of the cyanuric acid collected in the product storage bin 3 and the loss rate of urea are measured and recorded in Table 1.

[0077] Example 2

[0078] (1) Cyanuric acid is filled in the reaction chamber of the reaction device 1, the inner cylinder 12 and the scraping spiral ribbon 16 are rotated at a speed of 10 r / min and the spiral lifting structure 11 is rotated at a speed of 80 r / min, and the urea raw material in the urea storage bin 5 is fed into the reaction chamber through the screw feeder and the urea inlet 14 at a temperature of 270° C. for pyrolysis reaction for 10 hours. During the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device 1 is maintained at a ratio of 10:1; the mixed material in the reaction chamber is discharged through the overflow outlet 15 and separated into a gas phase and a solid phase under the action of gravity;

[0079] (2) The gas phase enters the filter device 2 for filtering treatment, the gas phase exchanges heat with the filter filler, the gaseous urea contained in the gas phase becomes liquid or solid and sticks to the filter filler, the cyanuric acid powder contained in the gas phase sticks to the filter filler, and the ammonia contained in the gas phase is separated therefrom; after the filter device 2 performs filtering treatment for a period of time, the filter filler in the cavity is transported to the drum screening machine through the filler outlet 22 for screening, the screened filter filler is returned to the cavity of the filter device 2 through the filler inlet 21, and the urea and cyanuric acid powder screened in the drum screening machine are returned to the reaction chamber in the reaction device 1 through the urea inlet 14 for reuse;

[0080] (3) The ammonia gas obtained after filtration is passed into the spray device 4 for elution to obtain ammonia water with a concentration of 15 wt%, and the solid phase is passed into the product storage bin 3 for collection. The purity of the cyanuric acid collected in the product storage bin 3 and the loss rate of urea are measured and recorded in Table 1.

[0081] Example 3

[0082] (1) Cyanuric acid is filled in the reaction chamber of the reaction device 1, the inner cylinder 12 and the scraping spiral ribbon 16 are rotated at a speed of 15 r / min and the spiral lifting structure 11 is rotated at a speed of 120 r / min, and the urea raw material in the urea storage bin 5 is fed into the reaction chamber through the screw feeder and the urea inlet 14 at a temperature of 300° C. for pyrolysis reaction for 15 hours. During the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device 1 is maintained at a ratio of 12:1; the mixed material in the reaction chamber is discharged through the overflow outlet 15 and separated into a gas phase and a solid phase under the action of gravity;

[0083] (2) The gas phase enters the filter device 2 for filtering treatment, the gas phase exchanges heat with the filter filler, the gaseous urea contained in the gas phase becomes liquid or solid and sticks to the filter filler, the cyanuric acid powder contained in the gas phase sticks to the filter filler, and the ammonia contained in the gas phase is separated therefrom; after the filter device 2 performs filtering treatment for a period of time, the filter filler in the cavity is transported to the drum screening machine through the filler outlet 22 for screening, the screened filter filler is returned to the cavity of the filter device 2 through the filler inlet 21, and the urea and cyanuric acid powder screened in the drum screening machine are returned to the reaction chamber in the reaction device 1 through the urea inlet 14 for reuse;

[0084] (3) The ammonia gas obtained after filtration is passed into the spray device 4 for elution to obtain ammonia water with a concentration of 25 wt%, and the solid phase is passed into the product storage bin 3 for collection. The purity of the cyanuric acid collected in the product storage bin 3 and the loss rate of urea are measured and recorded in Table 1.

[0085] Comparative Example 1

[0086] The method of Example 1 was followed, except that the reaction device 1 was replaced with a tunnel kiln reactor. The results are shown in Table 1.

[0087] Test Case

[0088] The purity of cyanuric acid prepared according to the method described in Examples 1-3 and Comparative Example 1 was tested, and the test method was referred to HG / T4818-2015 "Cyanuric Acid Industry Standard"; the calculation formula for the urea loss rate was: (total mass of urea-mass of recovered cyanuric acid / (87 / 129)) / total mass of urea.

[0089] Table 1

[0090] serial number Purity of cyanuric acid (%) Urea loss rate (%) Example 1 93.56 2.8 Example 2 93.48 3.1 Example 3 93.88 2.7 Comparative Example 1 69.60 9.6

[0091] It can be seen from the results in Table 1 that the embodiment of the system for preparing cyanuric acid from urea according to the present invention improves the purity of cyanuric acid, reduces the generation of by-products, and reduces the loss rate of urea.

[0092] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A system for preparing cyanuric acid from urea, characterized in that: The system comprises a reaction device (1), a filtering device (2) and a product storage bin (3). The reaction device (1) comprises an inner cylinder (12) and an outer cylinder (13) which are coaxially arranged, a reaction chamber is formed between the inner cylinder (12) and the outer cylinder (13), a spiral lifting structure (11) is arranged in the inner cylinder (12), a urea inlet (14) is arranged on one side of the outer cylinder (13), and an overflow discharge port (15) is arranged on the other side opposite to the urea inlet (14), urea raw material is added through the urea inlet (14) and undergoes a pyrolysis reaction in the reaction chamber to obtain cyanuric acid and ammonia, the cyanuric acid in the reaction chamber enters the inner cavity of the inner cylinder (12) from the bottom, is lifted to the top by the spiral lifting structure (11), and returns to the reaction chamber from the top, the mixed material in the reaction chamber is discharged through the overflow discharge port (15), and is separated into a gas phase and a solid phase under the action of gravity; The gas phase enters the filtering device (2) for filtering; The solid phase enters the product storage bin (3) for collection.

2. The system according to claim 1, characterized in that In the reaction device (1), the inner cylinder (12) and the spiral lifting structure (11) are each connected to a transmission device (17) for causing them to rotate; Preferably, the inner cylinder (12) and the spiral lifting structure (11) rotate in opposite directions; Preferably, the spiral lifting structure (11) comprises a rotating shaft and spiral blades arranged around the outer circumference of the rotating shaft.

3. The system according to claim 1 or 2, characterized in that: A wall-scraping spiral ribbon (16) is arranged on the inner side of the outer cylinder (13).

4. The system according to any one of claims 1 to 3, characterized in that: The overflow discharge port (15) is inclined downward by 45-60 degrees.

5. The system according to claim 1 or 4, characterized in that: The ratio of the lower edge height of the urea inlet (14) to the lower edge height of the overflow outlet (15) is (1.01-1.2):

1.

6. The system according to any one of claims 1 to 5, characterized in that: The filtering device (2) comprises a cavity, the cavity is filled with filtering filler, the top of the cavity is provided with a filler inlet (21), the bottom is provided with a filler outlet (22), the upper part of the cavity is provided with a gas inlet (23), the lower part of the cavity is provided with a gas outlet (24), the gas phase separated from the mixed material enters the cavity through the gas inlet (23) and is filtered in the presence of the filtering filler; Preferably, the filter filler is zirconia balls and / or ceramic balls.

7. The system according to claim 6, characterized in that The system further comprises a screening device, wherein after the filtering device (2) performs filtering treatment for a period of time, the filtering filler in the cavity is transported to the screening device through the filler outlet (22) for screening, and the screened filtering filler is returned to the cavity of the filtering device (2) through the filler inlet (21); Preferably, the screening device is a drum screening machine.

8. The system according to claim 7, characterized in that A material recycling pipeline is arranged between the screening device and the urea inlet (14) for returning the urea and cyanuric acid powder screened out by the screening device to the reaction device (1) for reuse.

9. The system according to any one of claims 6 to 8, characterized in that: The system further comprises a spray device (4), wherein the spray device (4) is used to rinse the ammonia gas discharged from the gas outlet (24) of the filtering device (2) to obtain ammonia water.

10. A method for preparing cyanuric acid from urea, characterized in that: The method is carried out in a system as described in any one of claims 1 to 9, and the method comprises: Cyanuric acid is filled in the reaction chamber of the reaction device (1), and while the inner cylinder (12) and the spiral lifting structure (11) are rotating simultaneously, urea raw material is added into the reaction chamber through the urea inlet (14) to perform a pyrolysis reaction; The mixed material in the reaction chamber is discharged through the overflow outlet (15) and separated into a gas phase and a solid phase under the action of gravity; The gas phase enters the filtering device (2) for filtering treatment, the ammonia gas obtained after filtering is eluted to obtain ammonia water, and the urea and cyanuric acid powders retained during the filtering treatment are separated and returned to the reaction chamber through the urea inlet (14) for reuse.

11. The method according to claim 10, characterized in that The ratio of the rotation speed of the inner cylinder (12) to the rotation speed of the spiral lifting structure (11) is 1:(5-15); Preferably, the rotation speed of the spiral lifting structure (11) is 80-120 r / min, and the rotation speed of the inner cylinder (12) is 10-15 r / min.

12. The method according to claim 10 or 11, characterized in that: The conditions of the pyrolysis reaction include: temperature of 270-300° C. and time of 10-15 h.

13. The method according to any one of claims 10 to 12, characterized in that: During the pyrolysis reaction, the mass ratio of cyanuric acid to urea in the reaction device (1) is maintained within the range of (10-12):1.

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