Method for recycling waste acid in steel cord electroplating process

Abstract

The invention provides a method for recycling waste acid in a steel cord electroplating process. The method comprises the following steps: collecting waste acid discharged by an electrolytic pickling tank; freezing crystallization treatment is performed at low temperature, ferrous sulfate is separated out through crystallization, and pretreated acid liquor is obtained after recovery; filtering the acid liquor to remove oil sludge impurities in the acid liquor, and storing at normal temperature; after secondary filtration of the acid liquor, part is pumped out and diluted with water, the concentration of iron ions and organic matter in the acid liquor is reduced, the acid concentration is controlled, and diluted acid liquor is obtained; concentrated sulfuric acid and diluted acid liquor are used for reconfiguration, and new dilute sulfuric acid is obtained; and dilute sulfuric acid is added into the electrolytic pickling tank for electrolytic pickling operation. According to the method, ferrous sulfate can be recycled from the waste acid, resource utilization of the waste acid is achieved, meanwhile, a dilute sulfuric acid preparation method is optimized, precipitates, impurities and acid liquor turbidity are reduced, the quality of prepared electrolytic pickling sulfuric acid is improved, the surface quality of a steel wire and the efficiency of an electrolytic polar plate and a heat exchanger are not affected, recycled waste acid is treated and utilized, and the economic benefit is increased. And emission and pollution are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel cord production, and in particular to a method for recycling waste acid from a steel cord electroplating process. Background Art

[0002] The electroplating process of steel cord is a key process to improve the quality of cord. Through the electroplating process, copper and zinc metal layers are plated on the surface of the cord to improve the corrosion resistance and subsequent processing performance, and to improve the bonding performance between the cord and rubber, and improve the mechanical properties of tires and other products. In the current electroplating process of steel cord, water cooling is carried out after the quenching process, and then electrolytic sulfuric acid washing is carried out, which has the problems of large consumption of new acid and large discharge of waste acid.

[0003] In the daily electroplating production process, the sulfuric acid concentration in the working tank is 320g / l. It is necessary to discharge and add a part of the acid every day to remove impurities such as iron ions (the pickling process removes the oxide skin on the surface of the cord), otherwise the steel wire cannot be cleaned. The added part of the acid needs to be additionally prepared. The normal operation is to prepare the new concentrated acid (98%) with water to a concentration of 400g / l for daily addition.

[0004] At present, the initial sulfuric acid recovery is about 3 cubic meters per day on average, and the concentration is 320g / l (directly mixed with concentrated acid). Consume about 5 tons of concentrated sulfuric acid (about 2.5 cubic meters) every day, need to make up about 12.5 tons of water to configure, configure to the interpolation acid supply workshop of concentration 400g / l to use, there will be acid solution turbidity phenomenon and more impurities, the reason is that, there will be a large amount of oxide skin on the steel wire surface, the electrolytic pickling process and the oxide skin reaction on the steel wire generate a large amount of ferrous sulfate, ferric sulfate, quenching liquid is organic matter, the water cooling after quenching can wash away most of to a certain extent, and a part also can enter pickling liquid, if it is not processed directly with new concentrated acid (98%) mixed configuration to 400g / l, when the two are mixed configuration, there will be acid solution turbidity phenomenon, the foreign matter content is high, resulting in poor workshop use effect, the electrolytic pickling plate is easily dirty after use, and the heat exchanger efficiency is easy to decline. Summary of the invention

[0005] The object of the present invention is to provide a method for recycling waste acid in a steel cord electroplating process. On the one hand, the waste acid discharged from an electrolytic pickling tank is collected and crystallized to obtain a pretreated acid solution. On the other hand, the pretreated acid solution is diluted and reconfigured to obtain a working concentration for the electrolytic pickling tank, thereby reducing and avoiding acid turbidity and crystallization problems and ensuring the quality of the pickling solution.

[0006] According to a first aspect of the present invention, a method for recycling waste acid in a steel cord electroplating process is provided, comprising the following steps:

[0007] Step 1, collecting waste acid discharged from the electrolytic pickling tank;

[0008] Step 2, performing freeze crystallization treatment on the collected waste acid at low temperature, so that ferrous sulfate is crystallized from the waste acid, recovering the ferrous sulfate and obtaining a first pretreated acid solution;

[0009] Step 3, filtering the first pretreated acid solution to remove sludge impurities therein to obtain a second pretreated acid solution;

[0010] Step 4, collecting the second pretreated acid solution for storage at room temperature;

[0011] Step 5: After filtering the second pretreated acid solution, the extracted part is diluted with water to reduce the concentration of iron ions and organic matter in the acid solution, and the acid concentration is controlled to obtain a diluted acid solution with a concentration of 110 g / ml;

[0012] Step 6: re-configure new 98% concentrated sulfuric acid and dilute acid solution in the configuration tank to obtain new dilute sulfuric acid with a concentration of 400 g / ml;

[0013] Step 7: Add the newly configured dilute sulfuric acid with a concentration of 400 g / ml into the electrolytic pickling tank to perform the electrolytic pickling process operation.

[0014] As an optional embodiment, in step 2, the collected waste acid is subjected to freeze crystallization treatment at low temperature so that ferrous sulfate is crystallized from the waste acid, and the ferrous sulfate is recovered to obtain a first pretreated acid solution, comprising:

[0015] The collected waste acid is transported to a crystallization kettle equipped with a jacket cooling device through an acid-resistant pump;

[0016] Chilled brine is passed through the jacket to gradually reduce the temperature of the spent acid;

[0017] Start the agitator in the crystallization kettle and control the stirring speed at 30-50 rpm to evenly reduce the solution temperature. During the cooling process, monitor the solution temperature and the crystallization of ferrous sulfate in real time. When the temperature drops to -5°C to -8°C, ferrous sulfate begins to crystallize.

[0018] Continue stirring and maintain this temperature for 1-2 hours to ensure sufficient crystallization;

[0019] After the crystallization is completed, stop stirring and cooling, and let it stand for 30-60 minutes to allow the crystals to settle at the bottom of the crystallization kettle;

[0020] The mixed solution after crystallization is discharged to obtain the first pretreated acid solution.

[0021] As an optional embodiment, in step 3, the first pretreated acid solution is sent to a filter through a pipeline, and under pressure, the waste liquid passes through a polypropylene filter cloth, and the sludge is retained on the polypropylene filter cloth for collection.

[0022] As an optional embodiment, in step 5, a secondary filtration is first performed with a filtration accuracy of 20-30 microns to remove tiny impurities.

[0023] As an optional embodiment, in step 5, the acid solution after secondary filtration is transported to a dilution tank using a metering pump, and deionized water is added according to a calculated ratio for dilution; during the water addition process, the solution in the dilution tank is stirred to ensure uniform mixing.

[0024] As an optional embodiment, in step 5, during the dilution process with water, an acidity meter is used to monitor the acid concentration in real time.

[0025] As an optional embodiment, in step 5, the concentration of the diluted acid solution is controlled to be 110 g / ml.

[0026] As an optional embodiment, in step 6, the concentration of the dilute sulfuric acid having the working concentration for electrolytic pickling is obtained by reconfiguration, and its concentration is controlled to be 400 g / ml.

[0027] As an optional embodiment, in step 6, first, the amount of 98% concentrated sulfuric acid and diluted acid solution is calculated according to the concentration and volume of the required dilute sulfuric acid; then the measured diluted acid solution is transported to the preparation tank through a pipeline, and concentrated sulfuric acid is slowly added under stirring; the addition of concentrated sulfuric acid is precisely controlled by a corrosion-resistant metering device to prevent local overheating and acid splashing due to too rapid acid addition.

[0028] As an optional embodiment, in step 6, during the addition of concentrated sulfuric acid, a cooling coil is used to cool the solution in the preparation tank to control the solution temperature to be lower than 50°C.

[0029] In combination with the method for recycling waste acid from the steel cord electroplating process of the above embodiment, the waste acid is directly recycled and configured with the prior art, that is, the waste acid is not diluted and used directly, and is configured with new concentrated acid (98%) to 400g / l. When the two are mixed and configured, the acid solution will become turbid and ferrous sulfate will precipitate. This is because concentrated sulfuric acid has extremely strong water absorption, which instantly absorbs the bound water of ferrous sulfate, resulting in a decrease in the saturation of ferrous sulfate, crystallization and precipitation, and turbid acid solution.

[0030] The method for recycling waste acid from the steel cord electroplating process of the present invention can, on the one hand, effectively recover ferrous sulfate from the waste acid through low-temperature freezing crystallization treatment, thereby realizing resource utilization of the waste acid and improving the resource utilization rate of the entire steel cord production process; on the other hand, the waste acid after crystallization is diluted after impurities are removed, and after further controlling and reducing the concentration of residual iron ions and organic matter therein, it is configured with new sulfuric acid (98% concentration), and the dilute sulfuric acid that meets the working concentration of electrolytic pickling is obtained through an optimized configuration method, thereby reducing precipitates, impurities, and acid turbidity, improving the quality of the newly configured electrolytic pickling sulfuric acid, reducing electrolytic precipitates, and meeting the requirements of not affecting the surface quality of the steel wire, the efficiency of the electrolytic plate and the heat exchanger, and reprocessing and utilizing the recovered waste acid to reduce emissions and pollution.

[0031] By utilizing the steel cord electroplating process waste acid recovery and utilization method of the present invention, the amount of recovered acid can be stabilized at 5 cubic meters per day, thereby improving the recovery and utilization rate of the waste acid and reducing the consumption of new concentrated sulfuric acid (98%).

[0032] It should be understood that all combinations of the aforementioned concepts and the additional concepts described in more detail below can be considered as part of the inventive subject matter of the present disclosure as long as such concepts are not mutually inconsistent. In addition, all combinations of the claimed subject matter are considered as part of the inventive subject matter of the present disclosure.

[0033] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are not intended to be drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in each figure may be represented by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings.

[0035] Figure 1 The present invention is a schematic flow chart of a method for recycling waste acid from a steel cord electroplating process according to an embodiment of the present invention.

[0036] Figure 2 yes Figure 1 Embodiment A process flow chart of a method for recycling waste acid in a steel cord electroplating process. DETAILED DESCRIPTION

[0037] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0038] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed by the present invention are not limited to any implementation. In addition, some aspects disclosed by the present invention can be used alone or in any appropriate combination with other aspects disclosed by the present invention.

[0039] {Example 1}

[0040] Combination Figure 1 , 2 As shown, the method for recycling waste acid in the steel cord electroplating process according to an embodiment of the present invention is applicable to the steel cord electroplating process, realizes the recycling of waste acid, improves the utilization rate of waste acid and reconfigures the quality of the pickling solution for electrolytic pickling by recycling waste acid, and reduces impurities and precipitates.

[0041] In the electroplating process, electrolytic pickling is the key process. The surface of the steel wire is pickled with acid such as sulfuric acid to remove impurities such as oxide scale, so as to improve the functionality of the steel wire and enhance the bonding strength between the electroplated coating and the substrate (such as pre-copper plating, copper plating, zinc plating, etc.).

[0042] However, as described in the background art, in the traditional method, waste acid is directly reconfigured with new concentrated sulfuric acid to obtain a working concentration, and the configured acid solution contains many impurities and precipitates and has poor quality.

[0043] To this end, the embodiment of the present invention proposes a method for recycling waste acid from a steel cord electroplating process, combining Figure 2 As shown, the method includes the following steps: step 1, collecting waste acid discharged from the electrolytic pickling tank; step 2, performing freeze crystallization treatment on the collected waste acid at low temperature, so that ferrous sulfate is crystallized from the waste acid, recovering ferrous sulfate and obtaining a first pretreated acid solution; step 3, filtering the first pretreated acid solution, removing sludge impurities therein, and obtaining a second pretreated acid solution; step 4, collecting the second pretreated acid solution for room temperature storage; step 5, after filtering the second pretreated acid solution, extracting a portion for dilution with water to reduce the concentration of iron ions and organic matter in the acid solution, and controlling the acid concentration to obtain a diluted acid solution with a concentration of 110g / ml; step 6, using new 98% concentrated sulfuric acid and the diluted acid solution to reconfigure in a configuration tank to obtain new dilute sulfuric acid with a concentration of 400g / ml; step 7, adding the newly configured dilute sulfuric acid with a concentration of 400g / ml to the electrolytic pickling tank to perform an electrolytic pickling process operation.

[0044] As an optional embodiment, in step 1, a special collection pipe made of an acid-resistant material (such as polyvinyl chloride or fiberglass) is used to connect the acid discharge port of the electrolytic pickling tank to an acid-resistant collection container such as a storage tank to collect waste acid discharged from the electrolytic pickling tank.

[0045] During the electrolytic pickling process, the rust (mainly iron oxide, etc.) on the surface of the steel cord reacts chemically with sulfuric acid to generate iron-containing compounds such as iron sulfate and dissolve in the acid solution. As the reaction proceeds, the acid solution is gradually consumed and impurities increase, forming waste acid. The acid outlet of the pickling tank is connected to the collection container through a pipeline, and the waste acid is transferred by gravity or the suction effect of a pump.

[0046] During the collection process, a liquid level sensor (preferably a non-contact sensor) is used to monitor the waste acid liquid level in the storage tank. When the liquid level reaches a set height (such as 90%), the collection is automatically stopped.

[0047] Combination Figure 2 As shown, in step 2, the collected waste acid is subjected to low-temperature freezing crystallization treatment. Specifically, the collected waste acid can be transported to a crystallization kettle with a jacket cooling device through an acid-resistant pump. A frozen brine (such as calcium chloride brine, the temperature of which drops to about -15°C) is passed into the jacket to gradually reduce the temperature of the waste acid. The agitator in the crystallization kettle is started, and the stirring speed is controlled at 30-50 rpm to uniformly reduce the solution temperature.

[0048] During the cooling process, the solution temperature and the crystallization of ferrous sulfate are monitored in real time. When the temperature drops to -5°C to -8°C, ferrous sulfate begins to crystallize. Continue stirring and maintain this temperature for 1-2 hours to ensure sufficient crystallization. After the crystallization is completed, stop stirring and cooling, and let it stand for 30-60 minutes to allow the crystals to settle at the bottom of the crystallization kettle.

[0049] The solubility of ferrous sulfate in water decreases significantly as the temperature decreases. When the temperature of the waste acid decreases, the solution reaches a supersaturated state, and ferrous sulfate crystals will precipitate from the solution. According to the solubility curve of ferrous sulfate, its solubility drops significantly under low temperature (-5°C to -8°C), which is conducive to the crystallization process. Therefore, ferrous sulfate is separated from the waste acid through low-temperature crystallization, and the ferrous sulfate in the waste acid is recovered and collected for reuse.

[0050] It should be understood that ferrous sulfate can be applied to other industrial fields or sold as a chemical raw material, which improves resource utilization while reducing the impurity content in the waste acid, and obtains a relatively pure first pre-treated acid solution, which is convenient for subsequent further processing. After recovery, ferrous sulfate also needs to be washed, dried, and stored in a sealed manner.

[0051] As an optional embodiment, in step 3, the first pretreated acid solution is further filtered to remove the sludge in the waste acid to obtain the second pretreated acid solution.

[0052] Specifically, the oil sludge is intercepted by the filter medium. The first pre-treated acid solution is sent to the filter (such as a plate and frame filter) through a pipeline. Under the action of pressure, the waste liquid passes through the polypropylene filter cloth, and the oil sludge is intercepted on the polypropylene filter cloth for collection. When the oil sludge on the filter cloth accumulates to a certain extent and the filtration speed decreases significantly, the filtration is stopped, the filter cloth is taken out for cleaning or replacement, and the oil sludge is collected.

[0053] Furthermore, the filtered acid solution is collected to obtain the second pretreated acid solution, which is stored at room temperature and sent to an acid-resistant storage tank for storage, which should be placed in a cool, well-ventilated area with anti-leakage measures.

[0054] In a further embodiment, in step 5, after filtering the second pretreated acid solution, the extracted portion is diluted with water to reduce the concentration of iron ions and organic matter in the acid solution, and the acid concentration is controlled to obtain a diluted acid solution with a concentration of 110 g / ml.

[0055] In this step, when the waste acid is actually used to reconfigure the new electrolytic pickling pickling solution, the waste liquid stored at room temperature is still filtered again to remove impurities such as tiny particles and precipitation. For example, secondary filtration is performed through a polypropylene filter with a filtration accuracy of 20-30 microns to remove tiny impurities.

[0056] Then use a metering pump to transport the filtered acid solution to the dilution tank, and add deionized water to dilute it according to the calculated ratio. Determine the amount of water to be added based on the iron ion and organic concentration of the initial acid solution and the target diluted acid solution concentration (110g / ml). For example, if the initial acid solution has an iron ion concentration and an organic concentration, calculate the amount of water to be added per liter of acid solution. During the water addition process, stir the solution in the dilution tank to ensure uniform mixing. Use an acidity meter to monitor the acid concentration in real time, and stop adding water when the concentration approaches 110g / ml.

[0057] In an embodiment of the present invention, water is added to dilute the acid solution to reduce its concentration, and the concentration of solutes such as iron ions and organic matter is further reduced accordingly, thereby avoiding problems such as poor pickling effect or precipitation caused by excessively high iron ion concentration during subsequent reconfiguration and use; reducing the concentration of organic matter to reduce its interference with the electrolytic pickling process. By controlling the amount of water added, the concentration of the acid solution and the concentration of impurities therein are accurately adjusted, and the concentration of the acid solution is adjusted to a suitable value (110g / ml) to prepare for the next step of mixing with concentrated sulfuric acid to reconfigure dilute sulfuric acid.

[0058] Furthermore, in step 6, the diluted acid solution and new sulfuric acid (concentration 98%) are used to reconfigure dilute sulfuric acid to obtain dilute sulfuric acid of electrolytic pickling working concentration.

[0059] According to the concentration (400g / ml) and volume of the required new dilute sulfuric acid, calculate the amount of 98% concentrated sulfuric acid and diluted acid solution. For example, suppose that a volume of V liters of new dilute sulfuric acid is required, the density of concentrated sulfuric acid is ρ1 (about 1.84g / ml), and the density of diluted acid solution is ρ2 (about 1.05g / ml), then the volume of concentrated sulfuric acid V1 = (400V-110V) / (1.84×98%) liters, and the volume of diluted acid solution V2 = V-V1 liters.

[0060] First, the measured diluted acid solution is transported to the configuration tank through a pipeline, and then concentrated sulfuric acid is slowly added under stirring (stirring speed 30-40 rpm). The addition of concentrated sulfuric acid should be accurately controlled by a corrosion-resistant metering device (such as a glass rotor flowmeter) to prevent local overheating and acid splashing due to too fast acid addition. During the addition process, the solution in the configuration tank is cooled by a cooling coil (cooling water is passed through the coil) to control the solution temperature below 50°C.

[0061] Therefore, the remaining sulfuric acid components in the diluted waste acid and the newly added concentrated sulfuric acid are used to reconfigure dilute sulfuric acid with a concentration that meets the requirements of the electrolytic pickling process, thereby realizing the recycling of sulfuric acid resources in the waste acid, reducing the purchase and use of new acid, reducing production costs, and increasing the utilization of waste acid. At the same time, it is ensured that the reconfigured dilute sulfuric acid can meet the process performance requirements of steel cord electroplating pickling.

[0062] Finally, in step 7, the prepared new dilute sulfuric acid is added to the electrolytic pickling tank to electrolytically pickle the steel wire.

[0063] In this way, the recycled dilute sulfuric acid is re-involved in the pickling process of steel cord electroplating, forming a closed loop for waste acid recycling. This not only ensures the pickling quality during the steel cord production process, but also realizes the recycling of resources, improving the environmental protection and economy of the entire electroplating process.

[0064] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A method for recycling waste acid from a steel cord electroplating process, characterized in that: The following steps are involved: Step 1, collecting waste acid discharged from the electrolytic pickling tank; Step 2, performing freeze crystallization treatment on the collected waste acid at low temperature, so that ferrous sulfate is crystallized from the waste acid, recovering the ferrous sulfate and obtaining a first pretreated acid solution; Step 3, filtering the first pretreated acid solution to remove sludge impurities therein to obtain a second pretreated acid solution; Step 4, collecting the second pretreated acid solution for storage at room temperature; Step 5: After filtering the second pretreated acid solution, the extracted part is diluted with water to reduce the concentration of iron ions and organic matter in the acid solution, and the acid concentration is controlled to obtain a diluted acid solution with a concentration of 110 g / ml; Step 6: re-configure new 98% concentrated sulfuric acid and dilute acid solution in the configuration tank to obtain new dilute sulfuric acid with a concentration of 400 g / ml; Step 7: Add the newly configured dilute sulfuric acid with a concentration of 400 g / ml into the electrolytic pickling tank to perform the electrolytic pickling process operation.

2. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In the step 2, the collected waste acid is subjected to freeze crystallization treatment at low temperature, so that ferrous sulfate is crystallized from the waste acid, and the ferrous sulfate is recovered to obtain a first pretreated acid solution, comprising: The collected waste acid is transported to a crystallization kettle equipped with a jacket cooling device through an acid-resistant pump; Chilled brine is passed through the jacket to gradually reduce the temperature of the spent acid; Start the agitator in the crystallization kettle and control the stirring speed at 30-50 rpm to evenly reduce the solution temperature. During the cooling process, monitor the solution temperature and the crystallization of ferrous sulfate in real time. When the temperature drops to -5°C to -8°C, ferrous sulfate begins to crystallize. Continue stirring and maintain this temperature for 1-2 hours to ensure sufficient crystallization; After the crystallization is completed, stop stirring and cooling, and let it stand for 30-60 minutes to allow the crystals to settle at the bottom of the crystallization kettle; The mixed solution after crystallization is discharged to obtain the first pretreated acid solution.

3. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In step 3, the first pretreated acid solution is sent to the filter through a pipeline. Under the action of pressure, the waste liquid passes through the polypropylene filter cloth, and the sludge is intercepted on the polypropylene filter cloth for collection.

4. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In step 5, a secondary filtration is first performed with a filtration accuracy of 20-30 microns to remove tiny impurities.

5. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In step 5, the acid solution after secondary filtration is transported to a dilution tank using a metering pump, and deionized water is added to dilute it according to a calculated ratio; during the water addition process, the solution in the dilution tank is stirred to ensure uniform mixing.

6. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In step 5, during the dilution process of adding water, an acid meter is used to monitor the acid concentration in real time.

7. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In step 5, the concentration of the diluted acid solution is controlled to be 110 g / ml.

8. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In step 6, the concentration of the dilute sulfuric acid having the working concentration for electrolytic pickling is obtained by reconfiguration, and its concentration is controlled to be 400 g / ml.

9. The method for recycling waste acid from steel cord electroplating process according to claim 1, characterized in that: In step 6, firstly, the amount of 98% concentrated sulfuric acid and diluted acid solution is calculated according to the concentration and volume of the required dilute sulfuric acid; then the measured diluted acid solution is transported to the preparation tank through a pipeline, and concentrated sulfuric acid is slowly added under stirring; the addition of concentrated sulfuric acid is precisely controlled by a corrosion-resistant metering device to prevent local overheating and acid splashing caused by too fast acid addition.

10. The method for recycling waste acid from steel cord electroplating process according to claim 9, characterized in that: In step 6, during the addition of concentrated sulfuric acid, the solution in the preparation tank is cooled by a cooling coil to control the solution temperature to be lower than 50°C.

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