Combined system and method for preparing cyanuric acid through urea pyrolysis and denitration

Abstract

The invention relates to the technical field of chemical engineering, and discloses a urea pyrolysis preparation cyanuric acid and denitration combined system and a method thereof. The system comprises a first reaction device, a flow dividing device, a product storage bin, a second reaction device and a denitration device, the first reaction device is used for adding a urea raw material through a urea inlet and carrying out a pyrolytic reaction, cyanuric acid enters an inner cavity of an inner cylinder from the bottom, and the second reaction device is used for carrying out denitration on the cyanuric acid. The material is lifted to the top through the spiral lifting structure and returns to the reaction chamber from the top, and an obtained mixed material is discharged through the overflow discharging opening, enters the flow dividing device and is separated into a gas phase and a solid phase under the action of gravity; the solid phase enters the product storage bin to be collected; the gas phase enters the second reaction device for a second pyrolytic reaction; and the denitration device is used for carrying out denitration reaction by taking the material flow treated by the second reaction device as a denitration agent. According to the invention, the purity of cyanuric acid is improved, and by-products are used for denitration.

Description

Technical Field

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

[0002] Cyanuric acid (chemical formula: C 3 H 3 N 3 O 3 ) is a white crystalline solid, odorless, slightly bitter, and hygroscopic. Cyanuric acid has a low solubility in water, but is soluble in hot water, hot alcohol, pyridine, concentrated hydrochloric acid and sulfuric acid, and insoluble in cold alcohol, ether, acetone, benzene and chloroform. Cyanuric acid is mainly used in industry to synthesize chlorinated derivatives, such as trichloroisocyanuric acid, sodium or potassium dichloroisocyanurate, which are widely used in the production of disinfectants, bleaches and water treatment agents. In addition, cyanuric acid is also used in synthetic resins, coatings, adhesives, pesticide herbicides, metal cyanide corrosion inhibitors, polymer material modifiers, etc. In organic synthesis, cyanuric acid is also an important chemical raw material. Cyanuric acid is also used as an ultraviolet absorber for plastic films, and as a non-protein nitrogen additive in animal feed, especially in ruminant feed, because they can be digested and utilized.

[0003] The urea pyrolysis method for producing cyanuric acid is currently the main method for industrial production of cyanuric acid, which has the advantages of simple operating conditions and low cost. The urea pyrolysis process can be carried out in different reaction media, including direct pyrolysis, molten salt pyrolysis and solvent pyrolysis. The direct pyrolysis method is a process of directly melting urea to synthesize cyanuric acid, while the solvent pyrolysis method is to pyrolyze and condense urea in an inert high-boiling point solvent, and the cyanuric acid generated by the pyrolysis crystallizes from the solvent to obtain a high-purity product. The currently commonly used tunnel kiln urea pyrolysis method has a large number of by-products due to the slow heating, and the cyanuric acid content is only about 70%, which requires further purification.

[0004] Therefore, there is an urgent need to develop a process flow that can improve product purity while solving the problem of excessive by-products and the problem of wall sticking caused by urea volatilization. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of low product purity, large amount of by-products and wall sticking caused by urea volatilization in the process of preparing cyanuric acid by urea pyrolysis in the prior art, and to provide a urea pyrolysis combined system for preparing cyanuric acid and denitrification and a method thereof. The technical scheme solves the problem of urea wall sticking caused by directly heating urea by using a mixing reactor, and through a diverter and a high-temperature reactor, while improving the product purity, all the by-products are converted into ammonia and isocyanic acid that can be used for denitrification, thereby increasing the proportion of ammonia in the by-products and further shortening the process flow.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a combined system for preparing cyanuric acid and denitrification by pyrolysis of urea, the system comprising a first reaction device, a diversion device, a product storage bin, a second reaction device and a denitrification device, wherein the first reaction device comprises 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 outlet is arranged on the other side opposite to the urea inlet, urea raw material is added through the urea inlet and a first pyrolysis reaction occurs in the reaction chamber to obtain cyanuric acid. 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, and the mixed material in the reaction chamber is discharged through the overflow outlet; the mixed material discharged through the overflow outlet enters the diversion device and is separated into a gas phase and a solid phase under the action of gravity; the solid phase enters the product storage bin for collection; the gas phase enters the second reaction device for a second pyrolysis reaction; the denitration device is used to use the logistics obtained by the second reaction device as a denitration agent for a denitration reaction.

[0007] Preferably, a wall-scraping spiral streamer is provided on the inner side of the outer cylinder.

[0008] Preferably, the overflow discharge port is inclined downward by 45-60°.

[0009] 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.

[0010] Preferably, in the first reaction device, the inner cylinder and the spiral lifting structure are each connected to a transmission device for causing them to rotate.

[0011] Preferably, the inner cylinder and the spiral lifting structure rotate in opposite directions.

[0012] Preferably, the spiral lifting structure comprises a rotating shaft and spiral blades arranged around the outer circumference of the rotating shaft.

[0013] Preferably, the diversion device comprises a V-shaped chamber, a material inlet and a gas phase outlet are arranged at the upper portion of the chamber, and the material inlet and the gas phase outlet are respectively located on both sides of the V-shaped chamber, and a solid phase outlet is arranged at the bottom of the chamber.

[0014] Preferably, the inner cavity of the second reaction device has multiple partitions, which divide the inner cavity into a number of reaction channels connected in series, so that the material entering the inner cavity can flow around up and down in sequence, and a reaction channel inlet is provided on one side of the upper part of the inner cavity, and a reaction channel outlet is provided on the lower part of the other side opposite to the reaction channel inlet.

[0015] The second aspect of the present invention provides a combined method for preparing cyanuric acid and denitrification by thermal decomposition of urea, which is carried out in the above-mentioned system and comprises:

[0016] Cyanuric acid is filled in the reaction chamber of the first reaction device, and while the inner cylinder and the spiral lifting structure are rotating simultaneously, urea raw material is added into the reaction chamber through the urea inlet to carry out a first pyrolysis reaction; the mixed material in the reaction chamber is discharged through the overflow outlet, and is separated into a gas phase and a solid phase by gravity through a diverter device; the solid phase enters the product storage bin for collection; the gas phase enters the second reaction device for a second pyrolysis reaction, and the logistics obtained by the treatment of the second reaction device is passed into the denitrification device as a denitrification agent for a denitrification reaction.

[0017] Preferably, the ratio of the rotation speed of the inner drum to the rotation speed of the spiral lifting structure is 1:(5-15).

[0018] Preferably, the rotation speed of the spiral lifting structure is 80-120 r / min, and the rotation speed of the inner drum is 10-15 r / min.

[0019] Preferably, the conditions of the first pyrolysis reaction include: temperature of 270-300°C and time of 10-15h.

[0020] Preferably, the conditions of the second pyrolysis reaction include: temperature of 450-550° C. and time of 1-2 min.

[0021] Preferably, during the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first reaction device is maintained in the range of (10-12):1.

[0022] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0023] (1) The urea pyrolysis system for preparing cyanuric acid and denitrification of the present invention adopts an overflow method to discharge the material, thereby ensuring that there is sufficient cyanuric acid in the reaction chamber as a filler, 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;

[0024] (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 urea pyrolysis to cyanuric acid and denitrification combined system of the present invention. In addition, the urea pyrolysis to cyanuric acid and denitrification combined 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;

[0025] (3) According to the combined system for preparing cyanuric acid and denitrification by urea pyrolysis of the present invention, the urea inlet is located at the material level. After the urea enters the first reaction device, it is quickly covered by the cyanuric acid falling from above. The generated ammonia gas carries the volatilized urea in the rising process, and the volatilized urea is intercepted by the cyanuric acid powder, thereby reducing the amount of volatilized urea that needs to be processed later;

[0026] (4) The combined system for preparing cyanuric acid and denitrification by pyrolysis of urea according to the present invention uses a second reaction device to treat volatilized urea and cyanuric acid which is difficult to replenish at high temperature, and directly pyrolyzes them at high temperature into ammonia and isocyanic acid, which are introduced into the denitrification system as denitrification agents, thereby increasing the proportion of ammonia in the by-products and solving the problem of wall sticking caused by urea volatilization;

[0027] (5) The combined system for producing cyanuric acid by pyrolysis of urea and denitrification of the present invention uses a diversion device to facilitate the precipitation of powdered cyanuric acid in the reaction product, and a small amount of fine dust particles are discharged with the gas phase and enter the second reaction device for pyrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process flow of the combined system for producing cyanuric acid by pyrolysis of urea and denitrification according to the present invention;

[0029] Figure 2 It is a structural schematic diagram of the first reaction device of the present invention;

[0030] Figure 3 is a schematic structural diagram of the flow diversion device of the present invention;

[0031] Figure 4 It is a schematic structural diagram of the second reaction device described in the present invention.

[0032] Description of Reference Numerals

[0033] 1. First reaction device; 11. Spiral lifting structure; 12. Inner cylinder; 13. Outer cylinder; 14. Urea inlet; 15. Overflow outlet; 16. Wall scraping spiral streamer; 17. Transmission device; 18. Manhole; 19. Bracket; 2. Diverter device; 21. Material inlet; 22. Gas phase outlet; 23. Solid phase outlet; 3. Product storage bin; 4. Second reaction device; 41. Reaction channel inlet; 42. Reaction channel outlet; 5. Denitrification device; 6. Urea storage bin. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] 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.

[0036] like Figure 1 As shown, the urea pyrolysis system for preparing cyanuric acid and denitrification of the present invention comprises a first reaction device 1, a diversion device 2, a product storage bin 3, a second reaction device 4 and a denitrification device 5, wherein Figure 2 As shown, the first reaction device 1 comprises an inner cylinder 12 and an outer cylinder 13 which are coaxially arranged, wherein a reaction chamber is formed between the inner cylinder 12 and the outer cylinder 13, wherein 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, wherein urea raw material is added through the urea inlet 14 and undergoes a first pyrolysis reaction in the reaction chamber to obtain cyanuric acid and ammonia, and the cyanuric acid in the reaction chamber enters the inner cylinder 12 from the bottom. The inner cavity is lifted to the top by the spiral lifting structure 11 and returned to the reaction chamber from the top, and the mixed material in the reaction chamber is discharged through the overflow outlet 15; the mixed material discharged through the overflow outlet 15 enters the diversion device 2 and is separated into a gas phase and a solid phase under the action of gravity; the solid phase enters the product storage bin 3 for collection; the gas phase enters the second reaction device 4 for a second pyrolysis reaction; the denitration device 5 is used to use the logistics obtained by the second reaction device 4 as a denitration agent for a denitration reaction.

[0037] According to the combined system for preparing cyanuric acid and denitrification by pyrolysis of urea of ​​the present invention, the material is discharged by overflow, which reduces the investment cost, reduces the equipment volume, and reduces the equipment footprint; moreover, the combined system for preparing cyanuric acid and denitrification by pyrolysis of 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 required for the next step of impurity removal; the use of a diversion device is conducive to the precipitation of powdered cyanuric acid in the reaction product, and a small part of fine particle dust is discharged with the gas phase and enters the second reaction device for pyrolysis, and the second reaction device is used to treat the volatilized urea and the cyanuric acid that is difficult to replenish at high temperature, directly pyrolyze them at high temperature into ammonia and isocyanic acid, and introduce them into the denitrification system as a denitrification agent, while improving the purity of the product, all the by-products are converted into ammonia and isocyanic acid that can be used for denitrification, the proportion of ammonia in the by-products is increased, and the problem of wall adhesion caused by urea volatilization is solved.

[0038] In the combined system for producing cyanuric acid and denitrification by urea pyrolysis of the present invention, in order to prevent cyanuric acid from sticking to the wall, a wall scraping spiral streamer 16 is preferably provided on the inner side of the outer cylinder 13. The rotation of the wall scraping spiral streamer 16 can be driven by the rotation of the inner cylinder 12.

[0039] In the urea pyrolysis system for preparing cyanuric acid and denitrification of the present invention, in order to facilitate the generated cyanuric acid and ammonia to flow out in an overflow manner, the overflow discharge port 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 discharge port 15 and the urea inlet 14 are preferably symmetrically arranged along the center line of the first reaction device 1.

[0040] In the combined system of urea pyrolysis to produce cyanuric acid and denitrification 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 first 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.

[0041] In the combined system for preparing cyanuric acid and denitrification by urea pyrolysis of the present invention, in order to prevent cyanuric acid from sticking to the wall, in the first 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 combined system for producing cyanuric acid and denitrification by urea pyrolysis of the present invention, the first 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 first reaction device 1. The first 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 first reaction device 1. In a preferred embodiment, the first reaction device 1 includes two brackets 19, which are symmetrically arranged along the center line of the first reaction device 1.

[0043] In the combined system for urea pyrolysis to produce cyanuric acid and denitrification of the present invention, if Figure 3 As shown, the diverter device 2 may include a V-shaped chamber, the upper portion of the chamber may be provided with a material inlet 21 and a gas phase outlet 22, and the material inlet 21 and the gas phase outlet 22 may be located at both sides of the V-shaped chamber, respectively, and the bottom of the chamber may be provided with a solid phase outlet 23. The V-shaped chamber is conducive to solid phase deposition, and a small portion of fine dust particles are discharged from the gas phase outlet 22 along with the gas phase and enter the second reaction device 4. In the V-shaped chamber, most of the powder in the mixed material discharged through the overflow outlet 15 falls to the solid phase outlet 23 under the action of gravity and is discharged by the valve at the bottom.

[0044] In the combined system of urea pyrolysis to produce cyanuric acid and denitrification of the present invention, the inner cavity of the second reaction device 4 may have a plurality of partitions, and the plurality of partitions may divide the inner cavity into a plurality of reaction channels connected in series, so that the material entering the inner cavity can flow around in sequence up and down, and a reaction channel inlet 41 may be provided on one side of the upper part of the inner cavity, and a reaction channel outlet 42 may be provided on the lower part of the other side opposite to the reaction channel inlet 41. The number of the partitions may be 5-11, and specifically may be 5, 6, 7, 8, 9, 10 or 11. The ratio of the length of the partition to the height of the inner cavity is (0.7-0.9):1.

[0045] In a specific embodiment, Figure 4 As shown, the inner cavity of the second reaction device 4 has 7 partitions, and the 7 partitions divide the inner cavity into 8 reaction channels connected in series, so that the materials entering the inner cavity can flow around in sequence up and down, wherein a reaction channel inlet 41 is provided on one side of the upper part of the inner cavity, and a reaction channel outlet 42 is provided on the lower part of the other side opposite to the reaction channel inlet 41, wherein, from the reaction channel inlet 41 to the reaction channel outlet 42, the partitions are respectively the first partition, the second partition, the third partition, the fourth partition, the fifth partition, the sixth partition and the seventh partition, the first partition, the third partition, the fifth partition and the seventh partition are connected to the top plate of the inner cavity and extend downward, and the second partition, the fourth partition and the sixth partition are connected to the bottom of the inner cavity and extend upward. The ratio of the length of the partition to the height of the inner cavity is (0.7-0.9):1. The spacing of the reaction channels is equal.

[0046] In the combined system of urea pyrolysis to produce cyanuric acid and denitrification of the present invention, the denitrification device 5 may be a conventional denitrification device in the art. Specifically, the denitrification device 5 may include a delivery pipeline and a denitrification flue. The delivery pipeline may also be provided with a heating device. The delivery pipeline may be used to deliver the denitrification agent obtained by the second reaction device 4 to the denitrification flue and decompose the unreacted cyanuric acid into isocyanic acid. The denitrification flue may be used to perform a denitrification reaction under the action of the denitrification agent.

[0047] In the combined system for preparing cyanuric acid and denitrification by urea pyrolysis of the present invention, the system may further include a urea storage bin 6, which is used to store urea, and the urea in the urea storage bin 6 enters the first reaction device 1. The urea in the urea storage bin 6 may enter the first reaction device 1 through a screw feeder.

[0048] In some embodiments, Figure 1 As shown, the urea pyrolysis system for preparing cyanuric acid and denitrification of the present invention comprises a first reaction device 1, a diversion device 2, a product storage bin 3, a second reaction device 4, a denitrification device 5 and a urea storage bin 6, wherein Figure 2As shown, the first 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 45-60 degrees, and the lower edge height of the urea inlet 14 is the same as that of the overflow discharge port 15. The ratio of the lower edge height of the urea inlet 14 to the height of the first reaction device 1 is (1.01-1.2):1, the ratio of the lower edge height of the urea inlet 14 to the height of the first reaction device 1 is (0.7-0.9):1, the urea raw material is added through the urea inlet 14 and undergoes a thermal decomposition 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, and the mixed material in the reaction chamber is discharged through the overflow discharge port 15; the first 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 for repairing the first reaction device 1; the bracket 19 is used to fix the first reaction device 1; the mixed material discharged through the overflow discharge port 15 enters the diversion device 2 and is separated into a gas phase and a solid phase under the action of gravity, such as Figure 3 As shown, the flow dividing device 2 comprises a V-shaped chamber, a material inlet 21 and a gas phase outlet 22 are arranged at the upper part of the chamber, and the material inlet 21 and the gas phase outlet 22 are respectively located at the two sides of the V-shaped chamber, and a solid phase outlet 23 is arranged at the bottom of the chamber; the solid phase enters the product storage bin 3 for collection; the gas phase enters the second reaction device 4 for the second pyrolysis reaction, as shown in FIG. Figure 4As shown, the inner cavity of the second reaction device 4 has 5-11 partitions, and the plurality of partitions divide the inner cavity into a plurality of reaction channels connected in series, so that the material entering the inner cavity can flow around in sequence from top to bottom, and a reaction channel inlet 41 is provided on one side of the upper part of the inner cavity, and a reaction channel outlet 42 is provided on the lower part of the other side opposite to the reaction channel inlet 41, and the ratio of the length of the partition to the height of the inner cavity is (0.7-0.9):1; the denitration device 5 is used to use the logistics obtained by the treatment of the second reaction device 4 as a denitration agent for denitration reaction; the urea storage bin 6 is used to store urea, and the urea in the urea storage bin 6 enters the first reaction device 1. The urea in the urea storage bin 6 enters the first reaction device 1 through a screw feeder.

[0049] The present invention also provides a combined method for preparing cyanuric acid and denitrification by thermal decomposition of urea, which is carried out in the above-mentioned system and comprises:

[0050] Cyanuric acid is filled in the reaction chamber of the first 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 carry out a first 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 by gravity through the diverter device 2; the solid phase enters the product storage bin 3 for collection; the gas phase enters the second reaction device 4 for a second pyrolysis reaction, and the logistics obtained by the treatment of the second reaction device 4 is passed into the denitrification device 5 as a denitrification agent for a denitrification reaction.

[0051] 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 used for denitration, and the purity of the product cyanuric acid is increased from about 70% to more than 89%.

[0052] 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.

[0053] 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.

[0054] In the method of the present invention, the conditions of the first pyrolysis reaction include: the temperature can be 270-300°C, preferably 270-290°C, and specifically can be 270°C, 275°C, 280°C, 285°C, 290°C, 295°C or 300°C; the time can be 10-15h, preferably 10-12h, and specifically can be 10h, 11h, 12h, 13h, 14h or 15h. In the first reaction device 1, the heating method can be electric heating or hot flue gas heating.

[0055] In the method of the present invention, the method may further include: passing urea in the urea storage bin 6 into the first reaction device 1 through a screw feeder. In order to improve the purity of the product cyanuric acid, during the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first 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.

[0056] In the method of the present invention, the conditions of the second pyrolysis reaction include: the temperature can be 450-550°C, preferably 480-520°C, specifically for example 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C or 550°C; the time can be 1-2 minutes, preferably 1-1.5 minutes. In the second reaction device 4, the heating method can be electric heating or flue gas heating.

[0057] In the method of the present invention, in the second reaction device 4, the second pyrolysis reaction may include the following reaction:

[0058] 3CO(NH 2 ) 2 →3NH3 +C 3 H 3 O 3 N 3

[0059] C 3 H 3 O 3 N 3 →3HCNO.

[0060] In the method of the present invention, in the denitration device 5, the conditions of the denitration reaction include: the temperature can be 450-550°C, preferably 500°C; the time can be 1-2 minutes, preferably 1-1.5 minutes. The denitration reaction may include the following reactions:

[0061] 4NH 3 +4NO+O 2 →4N 2 +6H 2 O

[0062] 4HCNO+6NO→5N 2 +2H 2 O+4CO 2 .

[0063] In some embodiments, the combined method of urea pyrolysis to produce cyanuric acid and denitrification according to the present invention is carried out in the above-mentioned system, and the method comprises:

[0064] The reaction chamber of the first reaction device 1 is filled with cyanuric acid, and the urea raw material is added into the reaction chamber through the urea inlet 14 under the condition that 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, and the first pyrolysis reaction is carried out for 10-15 hours at a temperature of 270-300° C. During the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first reaction device 1 is maintained at (10-12). : 1; 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 through the diverter device 2; the solid phase enters the product storage bin 3 for collection; the gas phase enters the second reaction device 4 for a second pyrolysis reaction at a temperature of 450-550°C for 1-2min, and the logistics obtained by the treatment of the second reaction device 4 is passed into the denitrification device 5 as a denitrification agent for a denitrification reaction at a temperature of 300-500°C for 1-2h.

[0065] The following examples further illustrate the combined system and method for preparing cyanuric acid and denitrification by urea thermal decomposition of the present invention. The examples are implemented on the premise of 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.

[0066] 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.

[0067] In the following examples, the process of urea pyrolysis to produce cyanuric acid and denitration is combined in Figure 1 The system shown in the figure is implemented, specifically, the system includes a first reaction device 1, a diversion device 2, a product storage bin 3, a second reaction device 4, a denitrification device 5 and a urea storage bin 6, wherein, as Figure 2 As shown, the first 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, the inner cylinder 12 and the spiral lifting structure 11 have opposite rotation directions, 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, the overflow discharge port 15 is inclined downward by 50 degrees, and the lower edge height of the urea inlet 14 is 1.5 degrees to the overflow discharge port 15, and ... The ratio of the lower edge height of the discharge port 15 is 1.1:1, and the ratio of the lower edge height of the urea inlet 14 to the height of the first 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 discharge port 15; the first 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 first reaction device 1; the bracket 19 is used to fix the first reaction device 1; the mixed material discharged through the overflow discharge port 15 enters the diversion device 2 and is separated into a gas phase and a solid phase under the action of gravity, such as Figure 3As shown, the flow dividing device 2 comprises a V-shaped chamber, a material inlet 21 and a gas phase outlet 22 are arranged at the upper part of the chamber, and the material inlet 21 and the gas phase outlet 22 are respectively located at the two sides of the V-shaped chamber, and a solid phase outlet 23 is arranged at the bottom of the chamber; the solid phase enters the product storage bin 3 for collection; the gas phase enters the second reaction device 4 for the second pyrolysis reaction, as shown in FIG. Figure 4 As shown, the inner cavity of the second reaction device 4 has 7 partitions, and the 7 partitions divide the inner cavity into 8 reaction channels connected in series, so that the material entering the inner cavity can flow around in sequence up and down, and a reaction channel inlet 41 is provided on one side of the upper part of the inner cavity, and a reaction channel outlet 42 is provided on the lower part of the other side opposite to the reaction channel inlet 41. From the direction from the reaction channel inlet 41 to the reaction channel outlet 42, the partitions are respectively the first partition, the second partition, the third partition, the fourth partition, the fifth partition, the sixth partition and the seventh partition. The first partition, the third partition, the fifth partition and the seventh partition are connected to the top plate of the inner cavity and extend downward, and the second partition, the fourth partition and the sixth partition are connected to the bottom of the inner cavity and extend upward. The length of the partition is The ratio of the height of each to the inner cavity is 0.8:1, and the spacing between the 8 reaction channels is equal; the denitrification device 5 is used to use the logistics obtained by the treatment of the second reaction device 4 as a denitrification agent for denitrification reaction; the denitrification device 5 includes a conveying pipeline and a denitrification flue, and the conveying pipeline is also provided with a heating device. The conveying pipeline is used to convey the denitrification agent obtained by the treatment of the second reaction device 4 to the denitrification flue and decompose the unreacted cyanuric acid into isocyanic acid; the denitrification flue is used to carry out a denitrification reaction under the action of the denitrification agent; the urea storage bin 6 is used to store urea, and the urea in the urea storage bin 6 enters the first reaction device 1, and the urea in the urea storage bin 6 enters the first reaction device 1 through a screw feeder; in the first reaction device 1 and the second reaction device 4, the heating method is electric heating.

[0068] Example 1

[0069] The reaction chamber of the first reaction device 1 is filled with cyanuric acid, and the urea raw material in the urea storage bin 6 is fed into the reaction chamber through the screw feeder and the urea inlet 14 at a temperature of 280° C. while the inner cylinder 12 and the scraping spiral ribbon 16 rotate at a speed of 12 r / min and the spiral lifting structure 11 rotates at a speed of 100 r / min. The first pyrolysis reaction is carried out for 11 hours at a temperature of 280° C. During the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first reaction device 1 is maintained at a ratio of 11:1; the mixture in the reaction chamber The material is discharged through the overflow outlet 15 and enters the diverter 2 through the material inlet 21, and is separated into a gas phase and a solid phase under the action of gravity; the solid phase is discharged through the solid phase outlet 23 and enters the product storage bin 3 for collection; the gas phase is discharged through the gas phase outlet 22 and enters the second reaction device 4 through the reaction channel inlet 41 to perform a second pyrolysis reaction at a temperature of 500°C for 1 minute, and the logistics obtained by the treatment of the second reaction device 4 is discharged through the reaction channel outlet 42 and passed into the denitrification device 5 as a denitrification agent to perform a denitrification reaction at a temperature of 300°C for 1 minute. The purity of the cyanuric acid collected in the product storage bin 3, the concentration of ammonia in the denitrification agent, and the denitrification efficiency in the denitrification device 5 are measured and shown in Table 1.

[0070] Example 2

[0071] The reaction chamber of the first reaction device 1 is filled with cyanuric acid, and the urea raw material in the urea storage bin 6 is fed into the reaction chamber through the screw feeder and the urea inlet 14 while 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 80 r / min. The first pyrolysis reaction is carried out for 10 hours at a temperature of 270° C. During the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first reaction device 1 is maintained at a ratio of 10:1; the mixed material in the reaction chamber The product is discharged through the overflow outlet 15 and enters the diverter 2 through the material inlet 21, and is separated into a gas phase and a solid phase under the action of gravity; the solid phase is discharged through the solid phase outlet 23 and enters the product storage bin 3 for collection; the gas phase is discharged through the gas phase outlet 22 and enters the second reaction device 4 through the reaction channel inlet 41 to perform a second pyrolysis reaction at a temperature of 450°C for 2 minutes, and the logistics obtained by the treatment of the second reaction device 4 is discharged through the reaction channel outlet 42 and passed into the denitrification device 5 as a denitrification agent to perform a denitrification reaction at a temperature of 300°C for 1 minute. The purity of the cyanuric acid collected in the product storage bin 3, the concentration of ammonia in the denitrification agent, and the denitrification efficiency in the denitrification device 5 are measured and shown in Table 1.

[0072] Example 3

[0073] The reaction chamber of the first reaction device 1 is filled with cyanuric acid, and the urea raw material in the urea storage bin 6 is fed into the reaction chamber through the urea inlet 14 at a temperature of 300° C. while 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 120 r / min. The first pyrolysis reaction is carried out for 15 hours at a temperature of 300° C. During the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first reaction device 1 is maintained at a ratio of 12:1; the mixture in the reaction chamber The material is discharged through the overflow outlet 15 and enters the diverter 2 through the material inlet 21, and is separated into a gas phase and a solid phase under the action of gravity; the solid phase is discharged through the solid phase outlet 23 and enters the product storage bin 3 for collection; the gas phase is discharged through the gas phase outlet 22 and enters the second reaction device 4 through the reaction channel inlet 41 to perform a second pyrolysis reaction at a temperature of 550°C for 2 minutes, and the logistics obtained by the treatment of the second reaction device 4 is discharged through the reaction channel outlet 42 and passed into the denitrification device 5 as a denitrification agent to perform a denitrification reaction at a temperature of 400°C for 1 minute. The purity of cyanuric acid collected in the product storage bin 3, the concentration of ammonia in the denitrification agent, and the denitrification efficiency in the denitrification device 5 are measured and shown in Table 1.

[0074] Comparative Example 1

[0075] The method of Example 1 was followed, except that the first reaction device 1 was replaced with a tunnel kiln reactor. The results are shown in Table 1.

[0076] Comparative Example 2

[0077] The method of Example 1 is implemented, except that the diverting device 2 and the second reaction device 4 are not introduced. Specifically, cyanuric acid is filled in the reaction chamber of the first reaction device 1, and the urea raw material in the urea storage bin 6 is fed into the reaction chamber through the screw feeder and the urea inlet 14 while the inner cylinder 12 and the scraping spiral ribbon 16 rotate at a speed of 12 r / min and the spiral lifting structure 11 rotates at a speed of 100 r / min. The first pyrolysis reaction is carried out for 11 hours at a temperature of 280°C. During the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first 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; the solid phase enters the product storage bin 3 for collection; the gas phase is passed into the denitrification device 5 as a denitrification agent to carry out a denitrification reaction at a temperature of 300°C for 1 minute. The purity of the cyanuric acid collected in the product storage bin 3, the concentration of ammonia in the denitrification agent and the denitrification efficiency in the denitrification device 5 are measured and are shown in Table 1.

[0078] Test Case

[0079] The purity of cyanuric acid prepared according to the method described in Examples 1-3 and Comparative Examples 1 and 2 was tested, and the test method was referred to HG / T4818-2015 "Cyanuric Acid Industry Standard". The concentration of ammonia in the denitrification agent prepared according to the method described in Examples 1-3 and Comparative Examples 1 and 2 was tested using an ammonia meter. The denitration efficiency in the denitration device 5 described in Examples 1-3 and Comparative Examples 1 and 2 was tested using a nitrogen oxide meter.

[0080] Table 1

[0081] serial number Purity of cyanuric acid (%) Ammonia concentration (wt%) Denitrification efficiency (%) Example 1 93.56 35.8 93.25 Example 2 93.48 36.3 93.14 Example 3 93.88 36.0 94.28 Comparative Example 1 70.60 25.3 82.35 Comparative Example 2 92.85 26.9 81.86

[0082] It can be seen from the results in Table 1 that the use of the embodiment of the combined system for preparing cyanuric acid and denitrification by urea pyrolysis and the method thereof of the present invention improves the purity of cyanuric acid, and improves the concentration of ammonia in the denitrification agent and the denitrification efficiency.

[0083] 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 combined system for preparing cyanuric acid by pyrolysis of urea and denitrification, characterized in that: The system comprises a first reaction device (1), a flow dividing device (2), a product storage bin (3), a second reaction device (4) and a denitration device (5). The first 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 a first 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 (12) from the bottom, is lifted to the top by the spiral lifting structure (11), and returns to the reaction chamber from the top, and the mixed material in the reaction chamber is discharged through the overflow discharge port (15); The mixed material discharged through the overflow outlet (15) enters the flow dividing device (2) and is separated into a gas phase and a solid phase under the action of gravity; The solid phase enters the product storage bin (3) for collection; The gas phase enters the second reaction device (4) to undergo a second pyrolysis reaction; The denitration device (5) is used to use the logistics obtained by the treatment of the second reaction device (4) as a denitration agent to carry out a denitration reaction.

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

3. The system according to claim 1 or 2, characterized in that: The overflow discharge port (15) is inclined downward by 45-60 degrees.

4. The system according to claim 1 or 3, 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.

5. The system according to any one of claims 1 to 4, characterized in that: In the first 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.

6. The system according to any one of claims 1 to 5, characterized in that: The flow dividing device (2) comprises a V-shaped chamber, a material inlet (21) and a gas phase outlet (22) are arranged at the top of the chamber, and the material inlet (21) and the gas phase outlet (22) are respectively located on both sides of the V-shaped chamber, and a solid phase outlet (23) is arranged at the bottom of the chamber.

7. The system according to any one of claims 1 to 6, characterized in that: The inner cavity of the second reaction device (4) has a plurality of partitions, and the plurality of partitions divide the inner cavity into a plurality of reaction channels connected in series, so that the material entering the inner cavity can flow around in sequence up and down. A reaction channel inlet (41) is provided on one side of the upper part of the inner cavity, and a reaction channel outlet (42) is provided on the lower part of the other side opposite to the reaction channel inlet (41).

8. A combined method for preparing cyanuric acid and denitrification by pyrolysis of urea, characterized in that: The method is carried out in a system as described in any one of claims 1 to 7, and the method comprises: Filling cyanuric acid in the reaction chamber of the first reaction device (1), and adding urea raw material into the reaction chamber through the urea inlet (14) to carry out a first pyrolysis reaction while the inner cylinder (12) and the spiral lifting structure (11) rotate simultaneously; 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 through the diversion device (2); The solid phase enters the product storage bin (3) for collection; The gas phase enters the second reaction device (4) to perform a second pyrolysis reaction, and the logistics obtained by the treatment of the second reaction device (4) is passed into the denitrification device (5) as a denitrification agent to perform a denitrification reaction.

9. The method according to claim 8, 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.

10. The method according to claim 8 or 9, characterized in that: The conditions of the first pyrolysis reaction include: temperature of 270-300° C. and time of 10-15 h.

11. The method according to any one of claims 8 to 10, characterized in that: The conditions of the second pyrolysis reaction include: temperature of 450-550° C. and time of 1-2 min.

12. The method according to any one of claims 8 to 11, characterized in that: During the first pyrolysis reaction, the mass ratio of cyanuric acid to urea in the first reaction device (1) is maintained in the range of (10-12):1.

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