Treatment method of hot galvanizing cooling circulating water

Abstract

The invention discloses a treatment method of hot galvanizing cooling circulating water, and belongs to the technical field of water treatment. The treatment method comprises the following steps: adjusting the pH value of cooling circulating water to be alkalescent, adding a water treatment agent into a water system cooling tower, performing water circulation after the agent is added, and regularly monitoring water quality parameters and replacing the water treatment agent. The process is simple, the water quality of circulating water can be ensured, generation of carbonic acid scale and biological slime is reduced, corrosion loss of materials is reduced, and the service life of equipment and pipelines can be prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a method for treating hot-dip galvanizing cooling circulating water. Background Art

[0002] Galvanizing refers to a surface treatment technology that coats a layer of zinc on the surface of metals, alloys or other materials for aesthetic purposes and to prevent rust. Currently, the main method used for surface galvanizing of steel plates is hot-dip galvanizing. Hot-dip galvanizing (hot-dip galvanizing) is a surface treatment technology that forms a zinc-iron alloy coating by immersing steel products in molten zinc liquid. The corrosion resistance of hot-dip galvanizing is much higher than that of electroplating galvanizing. It is an effective way to prevent metal corrosion. The hot-dip galvanizing process is widely used in power facilities (such as transmission towers), traffic guardrails, building steel structures, automotive parts and other fields, especially in scenes that require long-term exposure to corrosive environments (such as marine engineering and chemical equipment).

[0003] The core process of hot-dip galvanizing includes degreasing, pickling, plating assistance, hot-dip galvanizing, cooling and passivation. Among them, the cooling process is the key step to cool the strip after plating. The cooling water in the water quenching tank needs to quickly reduce the strip temperature from about 170℃ to 40-45℃ to ensure the quality of the coating. However, the circulating water is prone to scaling, corrosion and biological slime during long-term operation. If not properly treated, it will inevitably cause a series of problems such as pipeline blockage, corrosion leakage, and greatly reduced heat transfer efficiency, affecting the normal operation of the entire system.

[0004] Chinese patent document CN112299612A discloses a method for treating industrial circulating water, including the following steps: Step 1: industrial circulating water is filtered through a filtering device for solid impurities and suspended matter; Step 2: filtered industrial circulating water is adsorbed and organic matter is removed through an adsorption device; Step 3: industrial circulating water enters a cooling device for cooling, and water is replenished in the cooling device at the same time; Step 4: enters a crystallization desalination device, and anions and cations in the water are precipitated in the form of crystallized salts; Step 5: enters a sterilization device, sterilizes and kills algae to obtain purified water. This invention requires multiple devices to process in sequence, with a complex process flow, high equipment investment and operating costs, and the operation of each device requires independent control and maintenance, which increases the complexity and maintenance difficulty of the system. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for treating hot-dip galvanizing cooling circulating water with a simple process, which can ensure the water quality of circulating water, reduce the generation of carbonate scale and biological slime, reduce the corrosion loss of materials, and extend the service life of equipment and pipelines.

[0006] To achieve the above object, the present invention provides a method for treating hot dip galvanizing cooling circulating water, comprising the following steps: Adjust the pH value of the cooling circulating water to a weak alkaline state, add water treatment chemicals to the cooling tower of the water system, circulate the water after adding the chemicals, monitor the water quality parameters regularly and replace the water treatment chemicals.

[0007] Preferably, the amount of the water treatment agent added is 5-10wt% of the mass of the cooling circulating water.

[0008] Preferably, the water treatment agent is a mixture of modified molecular sieve, dispersant and corrosion inhibitor in a mass ratio of 3-5:1-2:1-2.

[0009] Further preferably, the preparation method of the modified molecular sieve is as follows: The molecular sieve is added into a dilute acid aqueous solution for immersion to obtain a pretreated molecular sieve; the pretreated molecular sieve is then dispersed in anhydrous ethanol, chlorhexidine and epichlorohydrin are added, and the antibacterial molecular sieve is heated for reaction; the antibacterial molecular sieve is added into water, the pH value is adjusted to be weakly acidic, and then maleic anhydride is added, heated for reaction, and a solid product is obtained; the solid product and an initiator are added into toluene, 6-acrylamide-β-cyclodextrin is added, and the modified molecular sieve is heated for reaction.

[0010] Preferably, the molecular sieve is at least one of 3A zeolite molecular sieve, 4A zeolite molecular sieve, 5A zeolite molecular sieve, and 13X zeolite molecular sieve.

[0011] Preferably, the mass ratio of the pretreated molecular sieve, chlorhexidine and epichlorohydrin is 5-10:2-4:3-5.

[0012] Preferably, the mass ratio of the antibacterial molecular sieve to maleic anhydride is 4-8:2-5.

[0013] Preferably, the mass ratio of the solid product, the initiator, and 6-acrylamide-β-cyclodextrin is 3-5:0.5-1:2-3.

[0014] The water treatment agent of the present invention is a mixture of modified molecular sieve, dispersant and corrosion inhibitor; the dispersant can prevent the deposition of suspended matter and dirt, improve the distribution uniformity of the water treatment agent, prevent the deposition of scaling metal ions and improve the fluidity of cooling circulating water, and by improving the molecular sieve, the water treatment agent can significantly improve the scaling metal ion Ca 2+ Mg 2 +It can adsorb calcium and magnesium ions in the water to prevent scale from forming; it can effectively kill microorganisms and algae in the cooling circulating water. The amino, amide and cyclodextrin cavities on the modified molecular sieve have strong adsorption, which can adsorb the killed microorganisms and prevent the killed microorganisms from aggregating to form a large amount of biological sludge deposited on the equipment surface, which is beneficial to improving the water quality of the cooling circulating water; the corrosion inhibitor can form a protective film on the surface of the metal equipment to prevent the corrosive medium from directly contacting the surface of the metal equipment, achieving a good corrosion inhibition effect, which is beneficial to prolonging the service life of the equipment and pipelines.

[0015] More preferably, the dispersant is one of sodium dodecyl sulfate and sodium lignin sulfonate.

[0016] Further preferably, the corrosion inhibitor is a mixture of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid; the mass ratio of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid is 1:2-3:1.2-1.5.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for treating hot-dip galvanizing cooling circulating water, which can ensure the water quality of circulating water, reduce the generation of carbonate scale and biological slime, reduce the corrosion loss of materials, and extend the service life of equipment and pipelines; (2) The preparation of the modified molecular sieve of the present invention is first to activate it with acid solution, which can improve its reaction site and adsorption performance, and then the antibacterial agent chlorhexidine is grafted on the surface of the molecular sieve through the action of epichlorohydrin, which not only gives the molecular sieve antibacterial properties, but also introduces a large number of active amino groups. Then, part of the amino groups on the chlorhexidine react with maleic anhydride to obtain a solid product with carbon-carbon double bonds. Finally, the carbon-carbon double bonds on the solid product react with 6-acrylamide-β-cyclodextrin to obtain a water treatment agent. Compared with molecular sieves, chlorhexidine The modified molecular sieve of the present invention significantly improves the stability and adsorption capacity of the water treatment agent by physical mixing of biguanidine and 6-acrylamide-β-cyclodextrin, significantly enhances the adsorption performance and dispersion performance of the molecular sieve, makes the water treatment agent more evenly distributed in the cooling circulating water system, and has a higher agent utilization rate; at the same time, the modified molecular sieve has stronger chemical stability, can maintain good performance under complex working conditions such as high temperature and high flow rate, avoids agent failure or separation, and prevents the deposition of suspended matter and dirt through the synergistic effect of the dispersant, so as to keep the cooling circulating water system clean and efficient; (3) The corrosion inhibitor of the present invention does not contain phosphorus and will not cause eutrophication of water bodies due to phosphorus discharge; methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid have a relatively good synergistic effect. Toluenetriazole and 2-thiopheneboric acid can form coordination bonds with the metal surface, adsorb on the metal surface, and work together with the passivation film type corrosion inhibitor sodium molybdate to form a continuous and dense protective film, which prevents corrosive media from directly contacting the surface of metal equipment and achieves a good corrosion inhibition effect. DETAILED DESCRIPTION

[0018] To avoid redundancy, the items used in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0019] The sources of some raw materials used in the present invention are as follows: Molecular sieve, 13X zeolite molecular sieve, bulk density 0.67 g / mL, purchased from Pingxiang Global New Material Technology Co., Ltd.

[0020] Example 1

[0021] A method for treating hot-dip galvanizing cooling circulating water comprises the following steps: Adjust the pH value of the cooling circulating water to 8, add water treatment agents to the water system, the amount of water treatment agents added is 8wt% of the mass of the cooling circulating water, and circulate the water after dosing. The cycle time is 48h. Monitor water quality parameters regularly and replace water treatment agents.

[0022] The water treatment agent is a mixture of modified molecular sieve, sodium dodecyl sulfate and corrosion inhibitor in a mass ratio of 4:1.5:1.2.

[0023] The preparation method of the modified molecular sieve is as follows: 100g of 13X zeolite molecular sieve was added to 500mL of 30wt% dilute sulfuric acid aqueous solution for immersion for 4h, filtered, solids were collected, washed and dried to obtain a pretreated molecular sieve; then 70g of the pretreated molecular sieve was dispersed in 300mL of anhydrous ethanol, 30g of chlorhexidine and 40g of epichlorohydrin were added, heated at 60°C for reaction for 2h, filtered, solids were collected, washed and dried to obtain an antibacterial molecular sieve; 60g of the antibacterial molecular sieve was added to 300mL of water, the pH value was adjusted to 6, and then 35.8g of maleic anhydride was added, heated at 50°C for reaction for 3h, filtered, solids were collected, washed and dried to obtain a solid product; 40.3g of the solid product and 8g of ammonium persulfate were added to 200mL of toluene, 25.6g of 6-acrylamide-β-cyclodextrin was added, heated at 80°C for reaction for 5h, cooled, filtered, solids were collected, washed and dried to obtain a modified molecular sieve.

[0024] The corrosion inhibitor is a mixture of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid in a mass ratio of 1:2.5:1.3.

[0025] Example 2

[0026] A method for treating hot-dip galvanizing cooling circulating water comprises the following steps: Adjust the pH value of the cooling circulating water to 7.5, add water treatment agents to the water system, the amount of water treatment agents added is 5wt% of the mass of the cooling circulating water, and circulate the water after dosing for 48 hours. Monitor water quality parameters regularly and replace water treatment agents.

[0027] The water treatment agent is a mixture of modified molecular sieve, sodium dodecyl sulfate and corrosion inhibitor in a mass ratio of 3:1:1.

[0028] The preparation method of the modified molecular sieve is as follows: 100g of 13X zeolite molecular sieve was added to 500mL of 30wt% dilute sulfuric acid aqueous solution for immersion for 4h, filtered, solids were collected, washed and dried to obtain a pretreated molecular sieve; then 98g of the pretreated molecular sieve was dispersed in 300mL of anhydrous ethanol, 40g of chlorhexidine and 50g of epichlorohydrin were added, heated at 60°C for reaction for 2h, filtered, solids were collected, washed and dried to obtain an antibacterial molecular sieve; 41g of the antibacterial molecular sieve was added to 300mL of water, the pH value was adjusted to 6, and then 20.3g of maleic anhydride was added, heated at 50°C for reaction for 3h, filtered, solids were collected, washed and dried to obtain a solid product; 30g of the solid product and 5g of ammonium persulfate were added to 200mL of toluene, 25.6g of 6-acrylamide-β-cyclodextrin was added, heated at 80°C for reaction for 5h, cooled, filtered, solids were collected, washed and dried to obtain a modified molecular sieve.

[0029] The corrosion inhibitor is a mixture of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid in a mass ratio of 1:2:1.2.

[0030] Example 3

[0031] A method for treating hot-dip galvanizing cooling circulating water comprises the following steps: Adjust the pH value of the cooling circulating water to 8, add water treatment agents to the water system, the amount of water treatment agents added is 10wt% of the mass of the cooling circulating water, and circulate the water after dosing. The cycle time is 48h. Monitor water quality parameters regularly and replace water treatment agents.

[0032] The water treatment agent is a mixture of modified molecular sieve, dispersant and corrosion inhibitor in a mass ratio of 5:2:2.

[0033] The preparation method of the modified molecular sieve is as follows: 100g of 13X zeolite molecular sieve was added to 500mL of 30wt% dilute sulfuric acid aqueous solution for immersion for 4h, filtered, solids were collected, washed and dried to obtain a pretreated molecular sieve; then 98g of the pretreated molecular sieve was dispersed in 300mL of anhydrous ethanol, 40g of chlorhexidine and 50g of epichlorohydrin were added, heated at 60°C for reaction for 2h, filtered, solids were collected, washed and dried to obtain an antibacterial molecular sieve; 80g of the antibacterial molecular sieve was added to 300mL of water, the pH value was adjusted to 6, and then 50g of maleic anhydride was added, heated at 50°C for reaction for 3h, filtered, solids were collected, washed and dried to obtain a solid product; 50g of the solid product and 10g of ammonium persulfate were added to 200mL of toluene, 30g of 6-acrylamide-β-cyclodextrin was added, heated at 80°C for reaction for 5h, cooled, filtered, solids were collected, washed and dried to obtain a modified molecular sieve.

[0034] The corrosion inhibitor is a mixture of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid in a mass ratio of 1:3:1.5.

[0035] Comparative Example 1 A method for treating hot-dip galvanizing cooling circulating water is similar to Example 1, except that 6-acrylamide-β-cyclodextrin is not added to the modified molecular sieve in the water treatment agent, and specifically comprises the following steps: Adjust the pH value of the cooling circulating water to 8, add water treatment agents to the water system, the amount of water treatment agents added is 8wt% of the mass of the cooling circulating water, and circulate the water after dosing. The cycle time is 48h. Monitor water quality parameters regularly and replace water treatment agents.

[0036] The water treatment agent is a mixture of modified molecular sieve, sodium dodecyl sulfate and corrosion inhibitor in a mass ratio of 4:1.5:1.2.

[0037] The preparation method of the modified molecular sieve is as follows: 100g of 13X zeolite molecular sieve was added to 500mL of 30wt% dilute sulfuric acid aqueous solution and immersed for 4h, filtered, solids were collected, washed and dried to obtain a pretreated molecular sieve; then 70g of the pretreated molecular sieve was dispersed in 300mL of anhydrous ethanol, 30g of chlorhexidine and 40g of epichlorohydrin were added, heated at 60°C for reaction for 2h, filtered, solids were collected, washed and dried to obtain an antibacterial molecular sieve; 60g of the antibacterial molecular sieve was added to 300mL of water, the pH value was adjusted to 6, and then 35.8g of maleic anhydride was added, heated at 50°C for reaction for 3h, filtered, solids were collected, washed and dried to obtain a solid product, i.e., a modified molecular sieve.

[0038] The corrosion inhibitor is a mixture of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid in a mass ratio of 1:2.5:1.3.

[0039] Comparative Example 2 A method for treating hot-dip galvanizing cooling circulating water is similar to Example 1, except that the molecular sieve in the water treatment agent is not modified, and specifically comprises the following steps: Adjust the pH value of the cooling circulating water to 8, add water treatment agents to the water system, the amount of water treatment agents added is 8wt% of the mass of the cooling circulating water, and circulate the water after dosing. The cycle time is 48h. Monitor water quality parameters regularly and replace water treatment agents.

[0040] The water treatment agent is a mixture of 13X zeolite molecular sieve, sodium dodecyl sulfate and corrosion inhibitor in a mass ratio of 4:1.5:1.2.

[0041] The corrosion inhibitor is a mixture of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid in a mass ratio of 1:2.5:1.3.

[0042] Comparative Example 3 A method for treating hot-dip galvanizing cooling circulating water is similar to Example 1, except that 2-thiophene boric acid is not added to the sustained-release agent in the water treatment agent, and specifically comprises the following steps: Adjust the pH value of the cooling circulating water to 8, add water treatment agents to the water system, the amount of water treatment agents added is 8wt% of the mass of the cooling circulating water, and circulate the water after dosing. The cycle time is 48h. Monitor water quality parameters regularly and replace water treatment agents.

[0043] The water treatment agent is a mixture of modified molecular sieve, sodium dodecyl sulfate and corrosion inhibitor in a mass ratio of 4:1.5:1.2.

[0044] The preparation method of the modified molecular sieve is as follows: 100g of 13X zeolite molecular sieve was added to 500mL of 30wt% dilute sulfuric acid aqueous solution for immersion for 4h, filtered, solids were collected, washed and dried to obtain a pretreated molecular sieve; then 70g of the pretreated molecular sieve was dispersed in 300mL of anhydrous ethanol, 30g of chlorhexidine and 40g of epichlorohydrin were added, heated at 60°C for reaction for 2h, filtered, solids were collected, washed and dried to obtain an antibacterial molecular sieve; 60g of the antibacterial molecular sieve was added to 300mL of water, the pH value was adjusted to 6, and then 35.8g of maleic anhydride was added, heated at 50°C for reaction for 3h, filtered, solids were collected, washed and dried to obtain a solid product; 40.3g of the solid product and 8g of ammonium persulfate were added to 200mL of toluene, 25.6g of 6-acrylamide-β-cyclodextrin was added, heated at 80°C for reaction for 5h, cooled, filtered, solids were collected, washed and dried to obtain a modified molecular sieve.

[0045] The corrosion inhibitor is a mixture of methylbenzotriazole and sodium molybdate in a mass ratio of 2.3:2.5.

[0046] Performance Testing Scale inhibition performance test: Refer to GB / T 16632-2019 "Determination of scale inhibition performance of water treatment agents - calcium carbonate deposition method" to prepare water for scale inhibition static experiment. The test objects are the water treatment agents of Examples 1-3 and Comparative Examples 1-2. In the calcium carbonate scale inhibition experiment, the calcium ion concentration is 689 mg / L, the bicarbonate ion concentration is 1036 mg / L, and the water treatment agent concentration is 10 mg / L; the test temperature is 80°C, and after maintaining for 12 hours, the scale inhibition rate is determined; the test results are shown in Table 1: Table 1 Scale inhibition performance test results

[0047] Biological sludge stripping performance: Take several 250mL conical flasks, add 50mL biological sludge and 50mL distilled water respectively, and ensure that the concentration of the added biological sludge is consistent. After shaking, add the water treatment agents prepared in Examples 1-3 and Comparative Examples 1-2 respectively, and the concentration of the water treatment agents after addition is 10mg / L respectively, and shake well immediately, then place on a rotator and rotate at a speed of 150r / min for 24h, first filter with filter paper, and then filter with a 0.2μm microporous filter membrane, and determine the concentration of polysaccharides and proteins in the filtrate. The higher the concentration of polysaccharides and proteins in the filtrate, the better the stripping performance of the water treatment agent on the biological sludge; the test results are shown in Table 2: Table 2 Test results of biological sludge stripping performance of water treatment agents

[0048] Corrosion inhibition performance test: 1 g of Example 1 and Comparative Example 3 were added into 100 mL of a neutral corrosive medium containing a Si-Mn steel test piece, and the corrosion inhibition rate was tested after soaking at room temperature for 24 hours. The test results are shown in Table 3: Table 3 Corrosion inhibition performance test results

[0049] It can be seen from the experimental results in Table 1, Table 2 and Table 3 that the water treatment agent of the present invention has good scale inhibition and biological sludge stripping performance, and can adsorb scale-forming metal ions Ca 2+ Mg 2+ It also reduces the adhesion of sludge on the equipment surface and has good corrosion inhibition performance.

[0050] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A method for treating hot-dip galvanizing cooling circulating water, characterized in that: The steps include: Adjust the pH value of the cooling circulating water to a weak alkaline state, add water treatment chemicals to the cooling tower of the water system, circulate the water after adding the chemicals, monitor the water quality parameters regularly and replace the water treatment chemicals.

2. The processing method according to claim 1, characterized in that: The amount of the water treatment agent added is 5-10wt% of the mass of the cooling circulating water.

3. The processing method according to claim 1 or 2, characterized in that: The water treatment agent is a mixture of modified molecular sieve, dispersant and corrosion inhibitor in a mass ratio of 3-5:1-2:1-2.

4. The processing method according to claim 3, characterized in that: The preparation method of the modified molecular sieve is as follows: The molecular sieve is added into a dilute acid aqueous solution for immersion to obtain a pretreated molecular sieve; the pretreated molecular sieve is then dispersed in anhydrous ethanol, chlorhexidine and epichlorohydrin are added, and the antibacterial molecular sieve is heated for reaction to obtain the antibacterial molecular sieve; the antibacterial molecular sieve is added into water, the pH value is adjusted to be weakly acidic, and then maleic anhydride is added, and the reaction is heated to obtain a solid product; the solid product and an initiator are added into toluene, and 6-acrylamide-β-cyclodextrin is added, and the reaction is heated to obtain the modified molecular sieve.

5. The processing method according to claim 4, characterized in that: The molecular sieve is at least one of 3A zeolite molecular sieve, 4A zeolite molecular sieve, 5A zeolite molecular sieve and 13X zeolite molecular sieve.

6. The processing method according to claim 4, characterized in that: The mass ratio of the pretreated molecular sieve, chlorhexidine and epichlorohydrin is 5-10:2-4:3-5.

7. The processing method according to claim 4, characterized in that: The mass ratio of the antibacterial molecular sieve to maleic anhydride is 4-8:2-5.

8. The processing method according to claim 4, characterized in that: The mass ratio of the solid product, the initiator and 6-acrylamide-β-cyclodextrin is 3-5:0.5-1:2-3.

9. The processing method according to claim 3, characterized in that: The dispersant is one of sodium lauryl sulfate and sodium lignin sulfonate.

10. The processing method according to claim 3, characterized in that: The corrosion inhibitor is a mixture of methylbenzotriazole, sodium molybdate and 2-thiopheneboric acid.

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