A recovery and reprocessing process for waste brine generated in sodium dichloroisocyanurate production

Abstract

The application provides a waste brine recovery and reprocessing process generated in sodium dichloroisocyanurate production, and relates to the technical field of waste brine treatment. The waste brine recovery and reprocessing process has the following steps: step one, diluting the waste brine with a sodium chloride solution to obtain treated brine; step two, pumping the treated brine into a baffle tank, adding a sodium hypochlorite solution, a catalyst and an oxidation aid, then increasing the temperature and adjusting the pH value of the brine, and then entering a redox tank to continue the reaction for 6-8 hours; step three, adding a sodium sulfite solution into the redox tank, continuing the reaction for 30-60 minutes by blowing air, and then obtaining treated brine, and pumping the treated brine into a brine tank for storage. The catalyst is obtained by mixing ferric chloride and copper chloride; and the oxidation aid is a thiourea-silane composite modified montmorillonite. The treatment process has high deamination efficiency, fast reaction rate and low impurity content of the brine.

Description

Technical Field

[0001] This invention relates to the field of waste brine treatment technology, specifically to a process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate. Background Technology

[0002] Sodium dichloroisocyanurate, a highly effective disinfectant, is produced using cyanuric acid, caustic soda, and chlorine as main raw materials. The reaction generates sodium dichloroisocyanurate, but also produces a large amount of waste brine. This waste brine has distinct characteristics: on the one hand, it is rich in high-concentration sodium chloride, possessing extremely high salt resource recovery value; on the other hand, due to incomplete reactions or side reactions, the waste brine often contains residual cyanuric acid derivatives, nitrogenous organic impurities, free chlorine, and sulfate ions, becoming a core obstacle restricting its resource utilization.

[0003] Currently, the recycling and treatment of wastewater from sodium dichloroisocyanurate production mainly focuses on "denitrification and impurity removal - salt resource reuse". Existing processes have significant limitations in treating wastewater: the nitrogen-containing organic matter in the wastewater has a stable structure, making it difficult for conventional oxidation processes to completely decompose it; the reaction efficiency is low, and the high salt concentration in the wastewater inhibits the oxidation reaction kinetics; impurity accumulation is a prominent problem, as the excessive addition of sodium hypochlorite in existing processes leads to residual free chlorine, requiring large amounts of sodium sulfite for reduction, resulting in a high sulfate concentration in the brine. Existing technology with publication number CN102897948A discloses a clean treatment process for wastewater from chloroisocyanuric acid production, which involves a multi-step synergistic treatment process including alkali chlorination, acidification dechlorination, alkali reduction, melamine precipitation, activated carbon adsorption, and sodium hypochlorite oxidation. However, this process suffers from drawbacks such as complexity, low reaction efficiency, significant impurity accumulation, and insufficient stability. The prior art disclosed in CN114804533B discloses a method for efficient removal of ammonia nitrogen from wastewater and designs a "physical-chemical-biological" synergistic ammonia nitrogen removal process. However, the high salinity environment of dichloro brine inhibits biological activity, resulting in a slow reaction rate and excessive energy consumption in the actual application of the process, which is not suitable for industrial continuous production.

[0004] In summary, although the existing technical solutions have improved the waste brine recovery and reprocessing process to some extent, the following technical problems still exist: low ammonia removal efficiency, slow reaction rate, and high impurity content in the brine. Summary of the Invention

[0005] In order to solve the above-mentioned problems in the prior art, the present invention provides a waste brine recycling and reprocessing process generated in the production of sodium dichloroisocyanurate, and achieves the following objectives: to design a waste brine recycling and reprocessing process with high ammonia removal efficiency, fast reaction rate and low brine impurity content.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] This invention proposes a process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate, comprising the following steps:

[0008] Step 1: Dilute the waste brine with sodium chloride solution to obtain brine to be treated, with a concentration of 298-302 g / L. The concentration of the sodium chloride solution is 200-220 g / L.

[0009] Step 2: Pump the brine to be treated into a baffle tank. Add sodium hypochlorite solution, catalyst, and oxidizing agent to the baffle tank. The amount of sodium hypochlorite solution added is 0.015-0.02 kg / L, the amount of catalyst added is 0.2-0.4 g / L, and the amount of oxidizing agent added is 1.5-2 g / L. Then raise the temperature to 50-65℃ and add sodium hydroxide solution to adjust the pH of the brine to 10-11. After passing through the baffle tank, enter the redox tank and continue stirring at a stirring rate of 400-500 rpm for 6-8 hours. The sodium hypochlorite solution is a chlor-alkali product sodium hypochlorite solution with a content of 8-10%; the sodium hydroxide solution has a content of 38-40%.

[0010] Step 3: After the stirring reaction is complete, add sodium sulfite solution to the redox tank at a concentration of 0.5-1.4 kg / L. Continue the reaction by purging with air for 30-60 minutes. After the reaction is complete, obtain treated brine, which is then pumped into a brine tank for storage. The sodium sulfite solution concentration is 10-12%.

[0011] The catalyst is a mixture of ferric chloride and copper chloride in a mass ratio of (0.5-0.8):1.

[0012] The oxidizing agent is thiourea-silane composite modified montmorillonite, which is obtained by modification with thiourea and 3-ureapropyltrimethoxysilane.

[0013] Further, the preparation steps of the thiourea-silane composite modified montmorillonite are as follows: montmorillonite is dispersed in an ethanol-water mixed solution, thiourea is added and stirred evenly, and then sodium hydroxide solution is added to adjust the pH value to 8-9; the temperature is raised to 60-65℃, the stirring rate is 300-400 rpm, and the reaction is carried out for 4-5 hours. After the reaction is completed, 3-ureapropyltrimethoxysilane is added, the temperature is raised to 80-90℃, and the reaction is carried out for 6-7 hours; after the reaction is completed, it is washed with deionized water until neutral, and then dried at 120-130℃ for 2-3 hours to obtain thiourea-silane composite modified montmorillonite.

[0014] Furthermore, the montmorillonite is a 100-300 mesh powder.

[0015] Furthermore, the ethanol-water mixed solution has an ethanol to water volume ratio of 3:1.

[0016] Furthermore, the thiourea is 5%-10% of the mass of montmorillonite.

[0017] Furthermore, the sodium hydroxide solution contains 10-20%.

[0018] Furthermore, the mass ratio of 3-ureapropyltrimethoxysilane to thiourea is (3-3.5):1.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The waste brine recovery and reprocessing process generated in the production of sodium dichloroisocyanurate of the present invention can efficiently remove nitrogen-containing compounds from the waste brine and significantly improve the deammoniation efficiency. The total ammonium content of the waste brine after oxidative deammoniation treatment is 1.09-1.54 ppm.

[0021] (2) The waste brine recovery and reprocessing process generated in the production of sodium dichloroisocyanurate of the present invention significantly improves the deammoniation reaction rate. During the oxidative deammoniation treatment of waste brine, the reaction rate constant k is 0.95-1.22 h. -1 .

[0022] (3) The waste brine recovery and reprocessing process generated in the production of sodium dichloroisocyanurate according to the present invention can significantly reduce the SO4 content in the treated brine. 2- The content of impurities, etc. After treatment, the waste brine contains SO4. 2- The content is 5.94-6.06 g / L. Attached Figure Description

[0023] Appendix Figure 1 This is a schematic diagram of a process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate according to the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] Example 1: A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate.

[0026] A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate includes the following steps:

[0027] Step 1: Dilute the waste brine with sodium chloride solution to obtain brine to be treated, with a concentration of 298-302 g / L. The concentration of the sodium chloride solution is 200 g / L. The waste brine is generated during the production of sodium dichloroisocyanurate.

[0028] Step 2: Pump the brine to be treated into a baffle tank. Add sodium hypochlorite solution, catalyst, and oxidizing agent to the baffle tank. The addition amount of sodium hypochlorite solution is 0.015 kg / L, the addition amount of catalyst is 0.2 g / L, and the addition amount of oxidizing agent is 1.5 g / L. Then raise the temperature to 50°C and add sodium hydroxide solution to adjust the pH of the brine to 10. After passing through the baffle tank, enter the redox tank for continued stirring and reaction at a stirring rate of 400 rpm for 8 hours. The sodium hypochlorite solution is: 8% sodium hypochlorite solution from chlor-alkali production; the sodium hydroxide solution has a content of 38%.

[0029] The catalyst is a mixture of ferric chloride and copper chloride in a mass ratio of 0.5:1.

[0030] The oxidizing agent is thiourea-silane composite modified montmorillonite;

[0031] The preparation steps of the thiourea-silane composite modified montmorillonite are as follows: montmorillonite is dispersed in an ethanol-water mixed solution, thiourea is added and stirred until homogeneous (thiourea accounts for 5% of the mass of montmorillonite), and sodium hydroxide solution is added to adjust the pH to 8; the temperature is raised to 60℃, the stirring speed is 300 rpm, and the reaction is carried out for 5 hours. After the reaction, 3-ureapropyltrimethoxysilane is added, with a mass ratio of 3-ureapropyltrimethoxysilane to thiourea of ​​3:1, and the temperature is raised to 80℃, and the reaction is carried out for 7 hours. After the reaction, the mixture is washed with deionized water until neutral, and then dried at 120℃ for 3 hours to obtain the thiourea-silane composite modified montmorillonite. The ethanol-water mixed solution has an ethanol to water volume ratio of 3:1; the sodium hydroxide solution content is 10%; and the montmorillonite is a 100-300 mesh powder.

[0032] Step 3: After the stirring reaction is complete, add sodium sulfite solution to the redox tank at a concentration of 0.5 kg / L. Continue the reaction by purging with air for 30 minutes. After the reaction is complete, the treated brine is obtained and pumped into a brine tank for storage. The sodium sulfite solution has a concentration of 10%.

[0033] Example 2: A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate.

[0034] A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate includes the following steps:

[0035] Step 1: Dilute the waste brine with sodium chloride solution to obtain brine to be treated, with a concentration of 298-302 g / L. The concentration of the sodium chloride solution is 210 g / L. The waste brine is generated during the production of sodium dichloroisocyanurate.

[0036] Step 2: Pump the brine to be treated into a baffle tank. Add sodium hypochlorite solution, catalyst, and oxidizing agent to the baffle tank. The addition amount of sodium hypochlorite solution is 0.02 kg / L, the addition amount of catalyst is 0.3 g / L, and the addition amount of oxidizing agent is 2 g / L. Then raise the temperature to 60℃ and add sodium hydroxide solution to adjust the pH of the brine to 11. After passing through the baffle tank, enter the redox tank for continued stirring and reaction at a stirring rate of 500 rpm for 8 hours. The sodium hypochlorite solution consists of 8% sodium hypochlorite solution from chlor-alkali production and 40% sodium hydroxide solution.

[0037] The catalyst is a mixture of ferric chloride and copper chloride in a mass ratio of 0.7:1.

[0038] The oxidizing agent is thiourea-silane composite modified montmorillonite. The preparation steps of the thiourea-silane composite modified montmorillonite are as follows: montmorillonite is dispersed in an ethanol-water mixed solution, thiourea is added and stirred until homogeneous (thiourea is 5% of the mass of montmorillonite), and sodium hydroxide solution is added to adjust the pH to 8; the temperature is raised to 60℃, the stirring speed is 400 rpm, and the reaction is carried out for 5 hours. After the reaction, 3-ureapropyltrimethoxysilane is added (the mass ratio of 3-ureapropyltrimethoxysilane to thiourea is 3:1), the temperature is raised to 80℃, and the reaction is carried out for 7 hours. After the reaction, the mixture is washed with deionized water until neutral, and then dried at 120℃ for 3 hours to obtain thiourea-silane composite modified montmorillonite. The ethanol-water mixed solution has an ethanol to water volume ratio of 3:1; the sodium hydroxide solution content is 20%; and the montmorillonite is a 100-300 mesh powder.

[0039] Step 3: After the stirring reaction is complete, add sodium sulfite solution to the redox tank at a concentration of 1.0 kg / L. Continue the reaction by purging with air for 60 minutes. After the reaction is complete, the treated brine is obtained and pumped into a brine tank for storage. The sodium sulfite solution has a concentration of 10%.

[0040] Example 3: A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate.

[0041] A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate includes the following steps:

[0042] Step 1: Dilute the waste brine with sodium chloride solution to obtain brine to be treated, with a concentration of 298-302 g / L. The concentration of the sodium chloride solution is 220 g / L. The waste brine is generated during the production of sodium dichloroisocyanurate.

[0043] Step 2: Pump the brine to be treated into a baffle tank. Add sodium hypochlorite solution, catalyst, and oxidizing agent to the baffle tank. The addition amount of sodium hypochlorite solution is 0.02 kg / L, the addition amount of catalyst is 0.4 g / L, and the addition amount of oxidizing agent is 2 g / L. Then raise the temperature to 65℃ and add sodium hydroxide solution to adjust the pH of the brine to 11. After passing through the baffle tank, enter the redox tank and continue stirring at a stirring rate of 500 rpm for 6 hours. The sodium hypochlorite solution consists of 10% sodium hypochlorite solution from chlor-alkali production and 40% sodium hydroxide solution.

[0044] The catalyst is a mixture of ferric chloride and copper chloride in a mass ratio of 0.8:1.

[0045] The oxidizing agent is thiourea-silane composite modified montmorillonite. The preparation steps of the thiourea-silane composite modified montmorillonite are as follows: montmorillonite is dispersed in an ethanol-water mixed solution, thiourea is added and stirred until homogeneous (thiourea accounts for 10% of the mass of montmorillonite), and sodium hydroxide solution is added to adjust the pH to 9; the temperature is raised to 65℃, the stirring speed is 400 rpm, and the reaction is carried out for 4 hours. After the reaction, 3-ureapropyltrimethoxysilane is added (the mass ratio of 3-ureapropyltrimethoxysilane to thiourea is 3.5:1), the temperature is raised to 90℃, and the reaction is carried out for 6 hours. After the reaction, the mixture is washed with deionized water until neutral, and then dried at 130℃ for 2 hours to obtain thiourea-silane composite modified montmorillonite. The ethanol-water mixed solution has an ethanol to water volume ratio of 3:1; the sodium hydroxide solution content is 20%; and the montmorillonite is a 100-300 mesh powder.

[0046] Step 3: After the stirring reaction is complete, add sodium sulfite solution to the redox tank at a concentration of 1.4 kg / L. Continue the reaction by purging with air for 60 minutes. After the reaction is complete, the treated brine is obtained and pumped into a brine tank for storage. The sodium sulfite solution has a concentration of 12%.

[0047] Comparative Example 1

[0048] A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate includes the following steps:

[0049] Step 1: This step is the same as "Step 1" in Example 2.

[0050] Step 2: Pump the brine to be treated into a baffled tank, add sodium hypochlorite solution and catalyst to the baffled tank. The amount of sodium hypochlorite solution added is 0.02 kg / L, and the amount of catalyst added is 0.3 g / L. Then, heat to 60℃, add sodium hydroxide solution to adjust the pH of the brine to 11. After passing through the baffled tank, enter the redox tank for continued stirring and reaction at a stirring rate of 500 rpm for 8 hours. The sodium hypochlorite solution is a chlor-alkali product sodium hypochlorite solution with a content of 8%; the sodium hydroxide solution has a content of 40%; the catalyst is a mixture of ferric chloride and copper chloride in a mass ratio of 0.7:1.

[0051] Step 3: This step is the same as "Step 3" in Example 2.

[0052] Comparative Example 2

[0053] A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate includes the following steps:

[0054] Step 1: This step is the same as "Step 1" in Example 2.

[0055] Step 2: Pump the brine to be treated into a baffle tank, and add sodium hypochlorite solution and an oxidizing agent to the baffle tank. The amount of sodium hypochlorite solution added is 0.02 kg / L, and the amount of oxidizing agent added is 2 g / L. Then, heat to 60°C, add sodium hydroxide solution to adjust the pH of the brine to 11, and then transfer it to a redox tank for further stirring at a stirring rate of 500 rpm for 8 hours. The sodium hypochlorite solution is composed of 8% sodium hypochlorite solution from chlor-alkali production, and the sodium hydroxide solution has a content of 40%.

[0056] The oxidizing agent is thiourea-silane composite modified montmorillonite, which is obtained by modifying montmorillonite with thiourea and 3-ureapropyltrimethoxysilane; the preparation steps of the oxidizing agent are the same as those of the oxidizing agent in Example 2.

[0057] Step 3: This step is the same as "Step 3" in Example 2. Example 4

[0058] (a) The waste brine was treated using the methods of Examples 1-3 and Comparative Examples 1-2 respectively; the total ammonium content (ppm) of the waste brine before and after treatment was measured. The specific test results are shown in Table 1.

[0059] Table 1

[0060]

[0061] As shown in Table 1, the total ammonium content of the waste brine after oxidation and deammoniation treatment in Examples 1-3 was 1.09-1.54 ppm, which proves that the waste brine recovery and reprocessing process generated in the production of sodium dichloroisocyanurate of the present invention can efficiently remove nitrogen-containing compounds from the waste brine and significantly improve the deammoniation efficiency.

[0062] (II) In Examples 1-3 and Comparative Examples 1-2, after the deamination reaction began, 10 mL of reaction solution was taken at 0 h, 1 h, 2 h, 4 h, 6 h, and 8 h, respectively. Excess sodium sulfite was immediately added, and the total ammonium concentration in the solution was determined by ion chromatography. For each set of data, the first-order reaction kinetic equation ln(C) was applied. t A linear fit is performed on / C0)=-kt, and the reaction rate constant k(h) is calculated from the slope of the fitted line. -1 The specific test results are shown in Table 2.

[0063] Table 2

[0064]

[0065] As shown in Table 2, the reaction rate constant k in the wastewater oxidation and deammoniation treatment process of Examples 1-3 is 0.95-1.22 h. -1 Compared with the comparative example, the improvement is significant, proving that the waste brine recovery and reprocessing process generated in the production of sodium dichloroisocyanurate of the present invention can significantly improve the deammoniation reaction rate.

[0066] (III) SO4 after treatment of waste brine from Examples 1-3 and Comparative Examples 1-2 2- The content of [specific component] was determined. Specific test results are shown in Table 3.

[0067] Table 3

[0068]

[0069] As shown in Table 3, after the waste brine in Examples 1-3 was treated, SO4 levels decreased. 2- The content was 5.94-6.06 g / L. Compared to the comparative examples, all showed a significant reduction, proving that the waste brine recovery and reprocessing process for sodium dichloroisocyanurate production of this invention can not only efficiently remove ammonia nitrogen, but also significantly reduce the SO4 content in the treated brine. 2- The content of impurities, etc.

[0070] Obviously, there are many other possible implementation methods under the concept of this invention. It should be stated here that any changes made under the inventive concept of this invention will fall within the protection scope of this invention.

Claims

1. A process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate, characterized in that: Includes the following steps: Step 1: Dilute the waste brine with sodium chloride solution to obtain the brine to be treated; Step 2: Pump the brine to be treated into the baffle tank, add sodium hypochlorite solution, catalyst, and oxidizing agent to the baffle tank; then heat to 50-65℃ and adjust the pH value of the brine; after passing through the baffle tank, enter the redox tank and continue stirring and reacting for 6-8 hours. Step 3: After the stirring reaction is complete, add sodium sulfite solution to the redox tank and continue the reaction for 30-60 minutes by purging with air. After the reaction is complete, the treated brine is obtained and pumped into the brine tank for storage. The catalyst is obtained by mixing ferric chloride and copper chloride, with a mass ratio of ferric chloride to copper chloride of (0.5-0.8):1; The oxidizing agent is thiourea-silane composite modified montmorillonite. The preparation steps of the thiourea-silane composite modified montmorillonite are as follows: montmorillonite is dispersed in an ethanol-water mixed solution, thiourea is added and stirred evenly, and then sodium hydroxide solution is added to adjust the pH of the solution to 8-9; the temperature is raised to 60-65℃ and the reaction is stirred for 4-5 hours; after the reaction is completed, 3-ureapropyltrimethoxysilane is added, the temperature is raised to 80-90℃ and the reaction is carried out for 6-7 hours; after the reaction is completed, the thiourea-silane composite modified montmorillonite is obtained by washing and drying.

2. The waste brine recovery and reprocessing process generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: The concentration of the brine to be treated is 298-302 g / L.

3. The process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: The sodium hypochlorite solution is a sodium hypochlorite solution produced by chlor-alkali production, with a content of 8-10%, and the amount of sodium hypochlorite solution added is 0.015-0.02 kg / L.

4. The waste brine recovery and reprocessing process generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: The catalyst is added at a rate of 0.2-0.4 g / L.

5. The waste brine recovery and reprocessing process generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: The amount of the oxidizing agent added is 1.5-2 g / L.

6. The process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: Adjusting the pH of the saline solution: Add sodium hydroxide solution to adjust the pH of the saline solution to 10-11.

7. The process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: The sodium sulfite solution has a content of 10-12%, and the amount of sodium sulfite solution added is 0.5-1.4 kg / L.

8. The process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: The thiourea is 5%-10% of the mass of montmorillonite.

9. The process for recovering and reprocessing waste brine generated during the production of sodium dichloroisocyanurate according to claim 1, characterized in that: The mass ratio of 3-ureapropyltrimethoxysilane to thiourea is (3-3.5):1.

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