A multi-stage series cyanuric acid purification system and process

Abstract

The invention discloses a multi-stage series cyanuric acid purification system and process, comprising the following steps: crushing a crude cyanuric acid powder to obtain cyanuric acid powder; using a sulfuric acid solution with a mass percentage of 15%-25% to carry out a primary pickling of the cyanuric acid powder, the mass ratio of the cyanuric acid powder to the sulfuric acid solution is 1:2-3, the primary pickling temperature is 60-80 DEG C, and the time is 4-10min; using a 25%-35% sulfuric acid solution to carry out a secondary pickling of the cyanuric acid powder that has been pickled once, the mass ratio of the cyanuric acid powder to the 25%-35% sulfuric acid solution is 1:1-1.5, the secondary pickling temperature is 80-100 DEG C, and the time is 4-10min; after the secondary pickling is completed, washing with clean water to remove the acid on the surface of the cyanuric acid.

Description

Technical Field

[0001] The invention belongs to the technical field of cyanuric acid purification, and in particular relates to a multi-stage series cyanuric acid purification system and process. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] 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 a white crystal with a slightly bitter taste and is basically non-toxic. It is soluble in hot water and slightly soluble in cold water. Its aqueous solution is acidic and insoluble in cold organic solvents such as alcohol, ether, and benzene.

[0004] 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.

[0005] 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 a variety of parallel side reactions, reduces the selectivity of the target product, and has many product impurities, among which the main impurities are biuret, cyanuric acid monoamide, etc. According to reliable information, the content of cyanuric acid in the product of urea pyrolysis is only about 70%. Therefore, it is necessary to perform purification treatment to reach the national primary standard of 98.5%. However, the purity of existing cyanuric acid after purification is low, and the purification time is long and the energy consumption is high, which is difficult to meet the requirements in many aspects. Summary of the invention

[0006] In view of the deficiencies in the prior art, the object of the present invention is to provide a multi-stage series cyanuric acid purification system and process.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a multi-stage tandem cyanuric acid purification process, comprising the following steps:

[0009] The crude cyanuric acid powder is crushed to obtain cyanuric acid powder;

[0010] The cyanuric acid powder is pickled once with a sulfuric acid solution having a mass percentage of 15% to 25%, the mass ratio of the cyanuric acid powder to the sulfuric acid solution is 1:2-3, the temperature of the pickling is 60-80°C, and the time is 4-10 minutes;

[0011] The cyanuric acid powder that has been pickled once is pickled for a second time with a 25%-35% sulfuric acid solution, the mass ratio of the cyanuric acid powder to the 25%-35% sulfuric acid solution by mass is 1:1-1.5, the temperature of the second pickling is 80-100°C, and the time is 4-10 minutes;

[0012] After the secondary pickling is completed, clean water is used to wash to remove the acid on the surface of cyanuric acid.

[0013] The first pickling is to pickle at a lower speed and relatively low temperature. The main pickling target is impurities such as melamine outside the particle size. After testing, it was found that the temperature of the first pickling does not need to be too high.

[0014] The secondary pickling is carried out at a higher speed, because after the first pickling, the material is in a paste state, which is not conducive to the contact between the acid and cyanuric acid. At this time, stirring at a higher speed has a certain breaking / sticking effect, which has a better effect of breaking the stickiness and demulsification of the paste material, which is conducive to better contact between the acid and cyanuric acid. Under the action of higher temperature and higher concentration of sulfuric acid, a small amount of biuret is converted into cyanuric acid, so as to effectively improve the purity of cyanuric acid.

[0015] Cyanuric acid monoamide is easier to be washed off by pickling, while biuret requires a higher concentration of sulfuric acid to react. The acid solution after the secondary pickling can be used for the first pickling to achieve the recycling of the acid solution and save costs. If the primary pickling and the secondary pickling are carried out at the same time, after the cyanuric acid monoamide is pickled, the acid concentration is not enough to quickly react with the biuret therein, resulting in low purity of the material after pickling.

[0016] In some embodiments, the particle size of the crude cyanuric acid powder after crushing is less than 80 mesh. Cyanuric acid is usually produced by pyrolysis of urea, and the product after pyrolysis is often in large blocks. Crushing is to increase the contact area between cyanuric acid and pickling solution and improve the pickling effect.

[0017] In some embodiments, the mass percentage of sulfuric acid solution during the first pickling is 17%-22%.

[0018] Preferably, the temperature of the primary pickling is 65-75°C.

[0019] Preferably, during the first pickling, the mass ratio of cyanuric acid powder to sulfuric acid solution is 1:2.5-3.

[0020] In some embodiments, the mass percentage of the sulfuric acid solution during the secondary pickling is 25%-35%.

[0021] Preferably, the mass percentage of sulfuric acid solution during the secondary pickling is 27%-32%.

[0022] In some embodiments, the stirring speed during the first pickling is 90-110 r / min; the stirring speed during the second pickling is 140-160 r / min.

[0023] In some embodiments, when using clean water for cleaning, an acid-resistant filter cloth is laid on the conveyor belt, cyanuric acid is spread on the conveyor belt, and the cyanuric acid is sprayed and cleaned with clean water.

[0024] In a second aspect, the present invention provides a multi-stage series cyanuric acid purification system, comprising a primary pickling tank, a secondary pickling tank and a washing tank, wherein the bottom of the primary pickling tank is connected to the top of the secondary pickling tank through a pipeline, and the bottom of the secondary pickling tank is connected to the washing tank;

[0025] A conveyor belt is provided in the washing tank, and a strong acid-resistant filter cloth is laid on the conveyor belt;

[0026] There is a set distance between the conveyor belt and the bottom of the washing tank;

[0027] A spray layer is installed on the top of the conveyor belt.

[0028] There is no solid-liquid separation device between the primary pickling tank and the secondary pickling tank. After pickling, the pickling liquid and the material all enter the secondary pickling tank through the pipeline. A strong acid-resistant filter cloth is installed between the secondary pickling tank and the washing tank. The filter cloth can achieve the purpose of solid-liquid separation, and a spray is installed above the filter cloth to wash away the residual pickling liquid.

[0029] In some embodiments, the spray layer covers the entire length of the conveyor belt.

[0030] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0031] The content of cyanuric acid in the product of urea thermal decomposition is only about 70%, which needs to be purified. The current purification process has high energy consumption, which increases the production cost of cyanuric acid. The present invention proposes a multi-stage series cyanuric acid purification process, which can increase the purity of cyanuric acid from 72% to more than 99%. The whole process has a high degree of automation, is easy to operate, and the product meets the national quality requirements of superior products.

[0032] This process does not generate any wastewater or waste, and is green and environmentally friendly.

[0033] This process proposes an efficient multi-stage pickling process. The acid concentration, stirring speed and temperature of each stage of pickling are different, which greatly shortens the pickling time, improves the production capacity under the same scale, and reduces energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0035] Figure 1 is a pickling process flow chart of an embodiment of the present invention;

[0036] Figure 2 This is the arrangement of the strong acid resistant filter cloth in the embodiment of the present invention;

[0037] Figure 3 It is a comparison diagram before and after pickling of an embodiment of the present invention.

[0038] In the figure, A: primary pickling tank; B: secondary pickling tank; C: washing tank: ①: crude powder inlet; ②: pickling liquid inlet; ③: agitator; ④: connecting pipe between primary pickling tank and secondary pickling tank; ⑤: secondary tank outlet; ⑥: strong acid resistant filter cloth; ⑦: spray layer; ⑧: washing liquid outlet; ⑨: vent valve; ⑩ washed material. DETAILED DESCRIPTION

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] The present invention will be further described below in conjunction with the embodiments.

[0041] Example 1

[0042] After being crushed, the crude cyanuric acid powder enters the primary pickling tank A through the crude powder inlet ①, and the prepared pickling liquid (the ratio and addition ratio of the pickling liquid are introduced below) enters through the pickling liquid inlet ②. The residence time of the mixture in the primary pickling tank A is 5 minutes, and the residence time is controlled by controlling the addition amount. The stirring rate in the primary pickling tank A is 100r / min. The primary pickling tank A and the secondary pickling tank B are connected by pipeline ④ and enter the secondary pickling tank B. The residence time of the mixture in the secondary pickling tank B is also 5 minutes, and the stirring rate is 150r / min.

[0043] After the mixed material is washed twice, it falls into the strong acid resistant filter cloth ⑥ in the washing tank C (the arrangement of the strong acid resistant filter cloth is as follows Figure 2As shown in the figure, as the conveyor belt rotates forward, the material enters the process water spray, and the residual acid is washed into the water tank, and the remaining solid falls into the drying container. The compound in the water tank is mainly ammonium sulfate, which can be discharged and crystallized and sold as agricultural fertilizer.

[0044] The primary washing tank uses a 20% sulfuric acid solution, the mass ratio of crude cyanuric acid: sulfuric acid solution is 1:2.7, the reaction temperature is 70°C, the rotation speed is 100r / min, and the residence time is 5min; the concentration of sulfuric acid solution in the secondary tank is 30%, the crude cyanuric acid: sulfuric acid solution = 1: 1.5, the reaction temperature is 90°C, the rotation speed is 150r / min, and the residence time is 5min.

[0045] Example 2

[0046] The first washing tank uses a 20% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 70°C, the rotation speed is 100r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 30%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 90°C, the rotation speed is 150r / min, and the residence time is 5min.

[0047] Example 3

[0048] The first washing tank uses a 20% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 70°C, the rotation speed is 150r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 30%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 90°C, the rotation speed is 100r / min, and the residence time is 5min.

[0049] Example 4

[0050] The first washing tank uses a 30% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 70°C, the rotation speed is 100r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 20%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 90°C, the rotation speed is 150r / min, and the residence time is 5min.

[0051] Example 5

[0052] The first washing tank uses a 30% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 90°C, the rotation speed is 150r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 20%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 70°C, the rotation speed is 100r / min, and the residence time is 5min.

[0053] Example 6

[0054] The first washing tank uses a 30% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 90°C, the rotation speed is 100r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 20%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 70°C, the rotation speed is 150r / min, and the residence time is 5min.

[0055] Example 7

[0056] The first washing tank uses a 15% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 40°C, the rotation speed is 80r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 25%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 60°C, the rotation speed is 120r / min, and the residence time is 5min.

[0057] Example 8

[0058] The first washing tank uses a 25% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 60°C, the rotation speed is 120r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 15%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 40°C, the rotation speed is 80r / min, and the residence time is 5min.

[0059] Example 9

[0060] The first washing tank uses a 20% sulfuric acid solution, with the crude cyanuric acid: sulfuric acid solution = 1:2.7, the reaction temperature is 70°C, the rotation speed is 100r / min, and the residence time is 5min; the sulfuric acid solution concentration in the secondary tank is 25%, with the crude cyanuric acid: sulfuric acid solution = 1:1.5, the reaction temperature is 90°C, the rotation speed is 150r / min, and the residence time is 5min.

[0061] The purity of cyanuric acid after pickling in each embodiment is shown in Table 1.

[0062] Table 1

[0063]

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-stage series cyanuric acid purification process, characterized in that: The steps include: The crude cyanuric acid powder is crushed to obtain cyanuric acid powder; The cyanuric acid powder is pickled once with a sulfuric acid solution having a mass percentage of 15%-25%, the mass ratio of the cyanuric acid powder to the sulfuric acid solution is 1:2-3, the temperature of the pickling is 60-80°C, the time is 4-10min; the stirring speed during the pickling is 90-110 r / min; The cyanuric acid powder that has been pickled once is pickled for a second time with a sulfuric acid solution with a mass percentage of 25%-35%, the mass ratio of the cyanuric acid powder to the sulfuric acid solution with a mass percentage of 25%-35% is 1:1-1.5, the temperature of the second pickling is 80-100°C, the time is 4-10min; the stirring speed during the second pickling is 140-160 r / min; After the secondary pickling is completed, clean water is used to wash to remove the acid on the surface of cyanuric acid.

2. The multi-stage tandem cyanuric acid purification process according to claim 1, characterized in that: The particle size of the crude cyanuric acid powder after crushing is less than 80 mesh.

3. The multi-stage tandem cyanuric acid purification process according to claim 1, characterized in that: The mass percentage of sulfuric acid solution during the primary pickling is 17%-22%; the temperature of the primary pickling is 65-75°C.

4. The multi-stage tandem cyanuric acid purification process according to claim 3, characterized in that: During the first pickling, the mass ratio of cyanuric acid powder to sulfuric acid solution is 1:2.5-3.

5. The multi-stage tandem cyanuric acid purification process according to claim 1, characterized in that: The mass percentage of sulfuric acid solution during secondary pickling is 25%-35%.

6. The multi-stage tandem cyanuric acid purification process according to claim 5, characterized in that: The mass percentage of sulfuric acid solution during secondary pickling is 27%-32%.

7. The multi-stage tandem cyanuric acid purification process according to claim 1, characterized in that: When using clean water for cleaning, an acid-resistant filter cloth is laid on the conveyor belt, cyanuric acid is spread on the conveyor belt, and the cyanuric acid is sprayed and cleaned with clean water.

8. A multi-stage tandem cyanuric acid purification system using the multi-stage tandem cyanuric acid purification process according to any one of claims 1 to 7, characterized in that: It includes a primary pickling tank, a secondary pickling tank and a washing tank, the bottom of the primary pickling tank is connected to the top of the secondary pickling tank through a pipeline, and the bottom of the secondary pickling tank is connected to the washing tank; A conveyor belt is provided in the washing tank, and a strong acid-resistant filter cloth is laid on the conveyor belt; There is a set distance between the conveyor belt and the bottom of the washing tank; A spray layer is installed on the top of the conveyor belt.

9. The multi-stage series cyanuric acid purification system according to claim 8, characterized in that: The spray layer covers the entire length direction of the conveyor belt.

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