A system for continuous production of cyanuric acid using urea solution and a method thereof

Abstract

The application discloses a system and method for continuously producing cyanuric acid by using urea solution. The system comprises two preheating tanks, a reaction crystallizer and a cooling tank, the upper part of the preheating tank is provided with a raw material and additive feeding pipeline, the preheating tank is connected with the reaction crystallizer, the lower part of the reaction crystallizer is connected with the cooling tank, and the cooling tank is connected with a slurry pump leading to a filtering and washing section. Firstly, urea solution and additives are added into the preheating tank to be mixed and preheated, the preheated mixed solution flows into the reaction crystallizer to be heated and reacted, cyanuric acid generated is settled in a crystal growing zone, and ammonia gas generated is discharged from a gas phase material outlet pipeline and led to an ammonia gas purification and recovery section; the obtained cyanuric acid slurry flows into the cooling tank, is cooled and cooled down, and then is sequentially subjected to centrifugal washing, filtering and drying to obtain cyanuric acid. The application can realize continuous production of cyanuric acid, and has the advantages of simple operation process, low equipment investment and high production efficiency.

Description

I. Technical Field:

[0001] This invention belongs to the field of organic chemical technology, specifically relating to a system and method for the continuous production of cyanuric acid using urea solution. II. Background Technology:

[0002] Cyanobacterial acid (CNA) has a triazine ring structure and can undergo addition reactions, N-halogenation reactions, condensation reactions, and ring-opening reactions. Hundreds of derivatives can be synthesized from CNA, primarily used in the chemical, pharmaceutical, and materials industries, with significant market demand for downstream products. Currently, the main industrialized CNA production process is the urea solid-phase pyrolysis method, which involves urea pyrolysis, acid boiling, washing, drying, and grinding. While this technology is mature, its high energy consumption and severe environmental pollution significantly limit its production efficiency and scale, and it does not meet the requirements of green and clean production.

[0003] Chinese patent CN 202010745901.9 discloses a method for preparing cyanuric acid. This patent discloses a method for synthesizing cyanuric acid by reacting a polyol reactive carrier with a urea intermediate, a dicarboxylate derivative, followed by pyrolysis of the latter. Because cyanuric acid is insoluble in this reaction system, it rapidly crystallizes and precipitates once formed, achieving rapid and high-purity synthesis from urea. However, this method is still an intermittent operation, resulting in high labor intensity and low production efficiency. III. Summary of the Invention:

[0004] The technical problem this invention aims to solve is: based on the current state of cyanuric acid preparation processes and the existing problems of non-continuous production, this invention provides a system and method for the continuous production of cyanuric acid using urea solution. Using this invention, continuous production of cyanuric acid can be achieved, with a simple operation process, low equipment investment, and high production efficiency.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a system for the continuous production of cyanuric acid using urea solution. The system includes two preheating tanks, a reaction crystallizer, and a cooling tank. The upper parts of the two preheating tanks are connected to raw material urea solution feed lines and auxiliary agent feed lines. The two preheating tanks are respectively connected to the reaction crystallizer via lower discharge lines and feed pumps. The upper part of the reaction crystallizer is connected to a feed line and a gaseous material outlet line. The upper gaseous material outlet line leads to an ammonia purification and recovery section. The lower slurry outlet of the reaction crystallizer is connected to the cooling tank via a star valve and a discharge line. The cooling tank leads to a filtration and washing section via a lower discharge line and a slurry pump.

[0007] According to the above-described system for the continuous production of cyanuric acid using urea solution, the two preheating tanks, the reaction crystallizer, and the cooling tank are all equipped with jackets to control their reaction temperature; the heating medium in the jackets of the preheating tank and the reaction crystallizer is heat transfer oil or medium-pressure steam, and the cooling medium in the jacket of the cooling tank is room temperature water.

[0008] According to the above-described system for the continuous production of cyanuric acid using urea solution, the urea solution feed pipeline, the auxiliary agent feed pipeline, and the preheating tank discharge pipeline are all equipped with external heating devices.

[0009] According to the above-described system for the continuous production of cyanuric acid using urea solution, flow regulating valves are installed on the urea solution feed line, the additive feed line, and the preheating tank discharge line.

[0010] According to the above-described system for the continuous production of cyanuric acid using urea solution, the feed pump is a high-temperature diaphragm pump.

[0011] In addition, a method for continuous production of cyanuric acid using the above system is provided, the production method comprising the following steps:

[0012] a. The urea solution and the additives are added to the preheating tank separately through the urea solution feed pipeline and the additive feed pipeline for mixing and preheating. The preheating temperature of the liquid in the preheating tank is 130-150℃.

[0013] b. The preheated mixture is continuously fed into the reaction crystallizer for reaction. The temperature of the liquid in the reaction crystallizer is 230-240℃ and the residence time of the liquid is 30-80min. The cyanuric acid generated by the reaction settles into the crystal growth zone of the reaction crystallizer. The gaseous material mainly composed of ammonia generated during the reaction is discharged from the gaseous material outlet pipeline of the reaction crystallizer and leads to the ammonia purification and recovery section.

[0014] c. The cyanuric acid slurry obtained in step b flows into a cooling tank and is cooled in the cooling tank to reduce the temperature of the cyanuric acid slurry to 60-100℃.

[0015] d. After cooling in step c, the cyanuric acid slurry is centrifuged, washed with room temperature water, and filtered in sequence. The resulting filter cake is dried to obtain cyanuric acid. The centrifuged mother liquor and washing liquid are mixed and distilled. The auxiliaries obtained after distilling off the water are recycled.

[0016] According to the above-described continuous production method for cyanuric acid, in step a, before preheating, the temperature of the urea solution is 130–140°C and the temperature of the additive is 80–100°C; the additive is at least one selected from 2-methyl-1,3-propanediol, 1,5-pentanediol, 2,3-dimethyl-1,4-butanediol, glycerol, polyethylene glycol 800, and polypropylene glycol 600; the mass ratio of the urea solution to the additive is 1:2–3.

[0017] The stirring speed of the preheating tank is 50-100 r / min.

[0018] According to the above-mentioned method for continuous production of cyanuric acid, during the continuous flow of the mixed liquid into the reaction crystallizer in step b, the flow rate needs to stabilize the liquid level in the reaction crystallizer and the residence time of the liquid in the reactor should be 30-80 minutes.

[0019] According to the above-mentioned method for continuous production of cyanuric acid, the reaction crystallizer in step b is equipped with a stirring paddle, which is located in the middle of the inner sleeve and rotates at a speed of 200-400 r / min.

[0020] According to the above-described continuous production method for cyanuric acid, the cooling medium used in step c of the cooling tank is room temperature water.

[0021] The technical solution of this invention employs two preheating tanks, which alternately supply the reaction crystallizer with liquid to maintain its continuous operation. The liquid level in the reaction crystallizer is flush with the upper edge of the inner sleeve, and the liquid level is maintained stable by adjusting the feed and discharge flow rates.

[0022] The positive and beneficial effects of this invention are as follows:

[0023] 1. The continuous production process of cyanuric acid of the present invention can realize the continuous production of cyanuric acid. The process is simple, the equipment investment is small, and the production efficiency is high.

[0024] 2. The additives, ammonia, and water used in the production process of this invention can all be recycled and reused, resulting in less waste discharge and benefiting environmental protection.

[0025] 3. In the production process of this invention, cyanuric acid is rapidly precipitated from the reaction solution in crystal form, with few byproducts and a product purity of over 98.5% (the product purity is determined according to the HG / T4818-2015 method).

[0026] 4. In the continuous production process of this invention, the mixing and preheating not only maintains the temperature stability in the reaction crystallizer, but also improves thermal efficiency and reduces energy consumption through segmented heating. IV. Description of the attached drawings:

[0027] Figure 1 This invention presents a schematic diagram of a system for the continuous production of cyanuric acid using urea solution.

[0028] Figure 1 In the diagram, 1 is preheating tank A, 2 is preheating tank B, 3 is reaction crystallizer, 4 is cooling tank, 5 is feed pump A, 6 is feed pump B, 7 is slurry pump, and 8 is star valve. V. Detailed Implementation Methods:

[0029] The present invention will be further illustrated below with reference to the embodiments, but this does not limit the scope of protection of the technical solution of the present invention.

[0030] Example 1:

[0031] See appendix Figure 1 This invention discloses a system for the continuous production of cyanuric acid using urea solution, comprising a preheating tank A1, a preheating tank B2, a reaction crystallizer 3, and a cooling tank 4. Both preheating tanks A1 and B2 are connected to a raw material urea solution feed line and an auxiliary agent feed line at their upper parts. Preheating tanks A1 and B2 are connected to the reaction crystallizer 3 via a lower discharge line and a feed pump (feed pump A or feed pump B). The reaction crystallizer 3 is connected to a feed line and a gaseous material outlet line at its upper part. The upper gaseous material outlet line leads to an ammonia purification and recovery section. The slurry outlet at the lower part of the reaction crystallizer 3 is connected to the cooling tank 4 via a star valve 8 and a discharge line. The cooling tank 4 leads to a filtration and washing section via a lower discharge line and a slurry pump 7. The feed pump is a high-temperature diaphragm pump.

[0032] The preheating tank A1, preheating tank B2, reaction crystallizer 3, and cooling tank 4 are all equipped with jackets to control their reaction temperature. The heating medium in the jackets of preheating tank A1, preheating tank B2, and reaction crystallizer 3 is medium-pressure steam, and the cooling medium in the jacket of cooling tank 4 is room temperature water. The urea solution inlet pipeline, the auxiliary agent inlet pipeline, and the discharge pipelines of the two preheating tanks are all equipped with heating devices. Flow regulating valves are installed on the urea solution inlet pipeline, the auxiliary agent inlet pipeline, and the discharge pipelines of the two preheating tanks.

[0033] Example 2:

[0034] The present invention utilizes the system described in Example 1 for the continuous production of cyanuric acid, the detailed steps of which are as follows:

[0035] a. Through the urea solution feed line and the auxiliary agent feed line, urea solution at 135°C and compounded auxiliary agent at 90°C (according to the mass ratio of 2-methyl-1,3-propanediol: 2,3-dimethyl-1,4-butanediol: polyethylene glycol 800 = 2:2:1) are added to preheating tank A and preheating tank B at a mass ratio of 1:2.5 and mixed and heated to 150°C at a stirring speed of 70 r / min.

[0036] b. The preheated mixture is continuously pumped into the reaction crystallizer via a high-temperature diaphragm pump until the liquid level is flush with the upper edge of the inner sleeve. Then, heating is turned on until the temperature of the reaction liquid in the reaction crystallizer reaches 230°C for reaction. The stirring speed of the agitator in the reaction crystallizer is 200 r / min. The ammonia gas generated during the reaction is discharged from the gas phase material outlet pipeline of the reaction crystallizer and leads to the ammonia purification and recovery section. Melamine crystals are generated and settle into the crystal growth zone below the reaction crystallizer. After 30 minutes, the bottom star valve and the feed high-temperature diaphragm pump are opened, and the feed and discharge flow rates are adjusted so that the residence time of the reaction liquid in the reaction crystallizer is 40 minutes. The two preheating tanks, A and B, are used alternately to maintain the continuous and stable operation of the reaction crystallizer.

[0037] c. The cyanuric acid slurry obtained in step b flows into a cooling tank and is cooled in the cooling tank to reduce the temperature of the cyanuric acid slurry to below 100°C.

[0038] d. After cooling in step c, the cyanuric acid slurry is pumped into a centrifuge for separation, washed with room temperature water, and then dried to obtain the product cyanuric acid (yield of 86.7% and purity of 98.85%). The auxiliary agent obtained after evaporating the water from the centrifugal washing liquid is recycled.

[0039] Example 3:

[0040] The present invention utilizes the system described in Example 1 for the continuous production of cyanuric acid, the detailed steps of which are as follows:

[0041] a. Through the urea solution feed line and the auxiliary agent feed line, urea solution at 130°C and glycerol at 100°C are added to preheating tank A and preheating tank B at a mass ratio of 1:3 for preheating. The mixture is heated to 135°C with stirring at a speed of 50r / min.

[0042] b. The preheated mixture is continuously pumped into the reaction crystallizer via a high-temperature diaphragm pump until the liquid level is flush with the upper edge of the inner sleeve. Then, heating is turned on until the temperature of the reaction liquid in the reaction crystallizer reaches 240°C for reaction. The stirring speed of the agitator in the reaction crystallizer is 300 r / min. The ammonia gas generated during the reaction is discharged from the gas phase material outlet pipeline of the reaction crystallizer and leads to the ammonia purification and recovery section. Melamine crystals are generated and settle into the crystal growth zone below the reaction crystallizer. After 30 minutes, the bottom star valve and the feed high-temperature diaphragm pump are opened, and the feed and discharge flow rates are adjusted so that the residence time of the reaction liquid in the reaction crystallizer is 60 minutes. The two preheating tanks, A and B, are used alternately to maintain the continuous and stable operation of the reaction crystallizer.

[0043] c. The cyanuric acid slurry obtained in step b flows into a cooling tank and is cooled in the cooling tank to reduce the temperature of the cyanuric acid slurry to below 80°C.

[0044] d. After cooling in step c, the cyanuric acid slurry is pumped into a centrifuge for separation, washed with room temperature water, and then dried to obtain the product cyanuric acid (yield of 89.2% and purity of 99.34%). The auxiliary agent obtained after evaporating the centrifugal washing liquid is recycled.

[0045] Example 4:

[0046] The present invention utilizes the system described in Example 1 for the continuous production of cyanuric acid, the detailed steps of which are as follows:

[0047] a. Through the urea solution feed pipeline and the auxiliary agent feed pipeline, urea solution at 140°C and compounded auxiliary agent at 80°C (according to the mass ratio of 1,5-pentanediol:polypropylene glycol 600 = 3:2) are added to preheating tank A and preheating tank B at a mass ratio of 1:2 and mixed and heated to 140°C at a stirring speed of 100r / min.

[0048] b. The preheated mixture is continuously pumped into the reaction crystallizer via a high-temperature diaphragm pump until the liquid level is flush with the upper edge of the inner sleeve. Then, heating is turned on until the temperature of the reaction liquid in the reaction crystallizer reaches 235°C for reaction. The stirring speed of the agitator in the reaction crystallizer is 350 r / min. The ammonia gas generated during the reaction is discharged from the gas phase material outlet pipeline of the reaction crystallizer and leads to the ammonia purification and recovery section. Melamine crystals are generated and settle into the crystal growth zone below the reaction crystallizer. After 30 minutes, the bottom star valve and the feed high-temperature diaphragm pump are opened, and the feed and discharge flow rates are adjusted so that the residence time of the reaction liquid in the reaction crystallizer is 80 minutes. The two preheating tanks, A and B, are used alternately to maintain the continuous and stable operation of the reaction crystallizer.

[0049] c. The cyanuric acid slurry obtained in step b flows into a cooling tank and is cooled in the cooling tank to reduce the temperature of the cyanuric acid slurry to below 60°C.

[0050] d. After cooling in step c, the cyanuric acid slurry is pumped into a centrifuge for separation, washed with room temperature water, and then dried to obtain the product cyanuric acid (yield of 91.06% and purity of 99.57%). The auxiliary agent obtained after evaporating the water from the centrifugal washing liquid is recycled.

[0051] Example 5:

[0052] The present invention utilizes the system described in Example 1 for the continuous production of cyanuric acid, the detailed steps of which are as follows:

[0053] a. Through the urea solution feed line and the auxiliary agent feed line, urea solution at 135°C and compounded auxiliary agent at 85°C (2-methyl-1,3-propanediol: 2,3-dimethyl-1,4-butanediol = 1:1 by mass) are added to preheating tank A and preheating tank B at a mass ratio of 1:2.5 for preheating. The mixture is heated to 130°C by stirring at a speed of 85 r / min.

[0054] b. The preheated mixture is continuously pumped into the reaction crystallizer via a high-temperature diaphragm pump until the liquid level is flush with the upper edge of the inner sleeve. Then, heating is turned on until the temperature of the reaction liquid in the reaction crystallizer reaches 235°C for reaction. The stirring speed of the agitator in the reaction crystallizer is 200 r / min. The ammonia gas generated during the reaction is discharged from the gas phase material outlet pipeline of the reaction crystallizer and leads to the ammonia purification and recovery section. Melamine crystals are generated and settle into the crystal growth zone below the reaction crystallizer. After 30 minutes, the bottom star valve and the feed high-temperature diaphragm pump are opened, and the feed and discharge flow rates are adjusted to ensure that the reaction liquid stays in the reaction crystallizer for 30 minutes. The two preheating tanks, A and B, are used alternately to maintain the continuous and stable operation of the reaction crystallizer.

[0055] c. The cyanuric acid slurry obtained in step b flows into a cooling tank and is cooled in the cooling tank to reduce the temperature of the cyanuric acid slurry to below 80°C.

[0056] d. After cooling in step c, the cyanuric acid slurry is pumped into a centrifuge for separation, washed with room temperature water, and then dried to obtain the product cyanuric acid (yield of 90.35% and purity of 98.92%). The auxiliary agent obtained after evaporating the water from the centrifugal washing liquid is recycled.

[0057] Example 6:

[0058] The present invention utilizes the system described in Example 1 for the continuous production of cyanuric acid, the detailed steps of which are as follows:

[0059] a. Through the urea solution feed line and the auxiliary agent feed line, urea solution at 140°C and auxiliary agent polyethylene glycol 800 at 95°C are added to preheating tank A and preheating tank B at a mass ratio of 1:3 for preheating. They are mixed and heated to 145°C at a stirring speed of 75r / min.

[0060] b. The preheated mixture is continuously pumped into the reaction crystallizer via a high-temperature diaphragm pump until the liquid level is flush with the upper edge of the inner sleeve. Then, heating is turned on until the temperature of the reaction liquid in the reaction crystallizer reaches 240°C for reaction. The stirring speed of the agitator in the reaction crystallizer is 400 r / min. The ammonia gas generated during the reaction is discharged from the gas phase material outlet pipeline of the reaction crystallizer and leads to the ammonia purification and recovery section. Melamine crystals are generated and settle into the crystal growth zone below the reaction crystallizer. After 30 minutes, the bottom star valve and the feed high-temperature diaphragm pump are opened, and the feed and discharge flow rates are adjusted so that the residence time of the reaction liquid in the reaction crystallizer is 50 minutes. The two preheating tanks, A and B, are used alternately to maintain the continuous and stable operation of the reaction crystallizer.

[0061] c. The cyanuric acid slurry obtained in step b flows into a cooling tank and is cooled in the cooling tank to reduce the temperature of the cyanuric acid slurry to below 70°C.

[0062] d. After cooling in step c, the cyanuric acid slurry is pumped into a centrifuge for separation, washed with room temperature water, and then dried to obtain the product cyanuric acid (yield of 92.47% and purity of 99.16%). The auxiliary agent obtained after evaporating the water from the centrifugal washing liquid is recycled.

Claims

1. A method for continuous production of cyanuric acid using urea solution, characterized in that, The method includes the following steps: a. The urea solution and the additives are added to the preheating tank separately through the urea solution feed pipeline and the additive feed pipeline for mixing and preheating. The preheating temperature of the liquid in the preheating tank is 130-150℃. Before preheating, the urea solution temperature is 130–140°C and the additive temperature is 80–100°C; the additive is at least one selected from 2-methyl-1,3-propanediol, 1,5-pentanediol, 2,3-dimethyl-1,4-butanediol, glycerol, polyethylene glycol 800, and polypropylene glycol 600; the mass ratio of the urea solution to the additive is 1:2–3; the stirring speed of the preheating tank is 50–100 r / min. b. The preheated mixture is continuously fed into the reaction crystallizer for reaction. The temperature of the liquid in the reaction crystallizer is 230-240℃ and the residence time of the liquid is 30-80min. The cyanuric acid generated by the reaction settles into the crystal growth zone of the reaction crystallizer. The gaseous material mainly composed of ammonia generated during the reaction is discharged from the gaseous material outlet pipeline of the reaction crystallizer and leads to the ammonia purification and recovery section. During the continuous flow of the mixture into the reaction crystallizer, the inflow rate needs to stabilize the liquid level in the reaction crystallizer and the residence time of the liquid in the reactor should be 30-80 minutes. The reaction crystallizer is equipped with a stirring paddle, which is located in the middle of the inner sleeve and rotates at a speed of 200-400 r / min. c. The cyanuric acid slurry obtained in step b flows into a cooling tank and is cooled in the cooling tank to reduce the temperature of the cyanuric acid slurry to 60-100℃. d. After cooling in step c, the cyanuric acid slurry is centrifuged, washed with room temperature water, and filtered in sequence. The resulting filter cake is dried to obtain cyanuric acid. The centrifuged mother liquor and washing liquid are mixed and distilled. The auxiliaries obtained after distilling off the water are recycled.

2. The method for continuous production of cyanuric acid using urea solution according to claim 1, characterized in that: The cooling medium used in the cooling tank described in step c is room temperature water.

3. A system for continuous production of cyanuric acid using the method described in claim 1 or 2, characterized in that, The system includes two preheating tanks, a reaction crystallizer, and a cooling tank. The upper parts of the two preheating tanks are connected to raw material urea solution feed lines and auxiliary agent feed lines. The two preheating tanks are connected to the reaction crystallizer via lower discharge lines and feed pumps, respectively. The upper part of the reaction crystallizer is connected to a feed line and a gaseous material outlet line. The upper gaseous material outlet line leads to the ammonia purification and recovery section. The lower slurry outlet of the reaction crystallizer is connected to the cooling tank via a star valve and a discharge line. The cooling tank leads to the filtration and washing section via a lower discharge line and a slurry pump.

4. The system for continuous production of cyanuric acid according to claim 3, characterized in that: The two preheating tanks, the reaction crystallizer, and the cooling tank are all equipped with jackets to control their reaction temperature; the heating medium in the jackets of the preheating tank and the reaction crystallizer is heat transfer oil or medium-pressure steam, and the cooling medium in the jacket of the cooling tank is room temperature water.

5. The system for continuous production of cyanuric acid according to claim 3, characterized in that: The urea solution inlet pipeline, the additive inlet pipeline, and the preheating tank outlet pipeline are all equipped with external heating devices.

6. The system for continuous production of cyanuric acid according to claim 3, characterized in that: Flow regulating valves are installed on the urea solution inlet pipeline, the additive inlet pipeline, and the preheating tank outlet pipeline.

7. The system for continuous production of cyanuric acid according to claim 3, characterized in that: The feed pump is a high-temperature diaphragm pump.

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