Acid pickling wastewater zero discharge treatment system and method

Abstract

The present application relates to a kind of pickling wastewater zero discharge treatment system, including wastewater pretreatment unit, filter unit and first concentration reduction unit in turn, the water outlet pipe of the first concentration reduction unit is connected with post-processing mechanism, the concentrated water outlet pipe of the first concentration reduction unit is connected with evaporation concentration unit, the concentrated water outlet pipe of the evaporation concentration unit is connected to acid regeneration station.There is also provided a kind of pickling wastewater zero discharge treatment method accordingly.The pickling wastewater zero discharge treatment system and method provided by the present application, pickling wastewater is mainly treated in first concentration reduction unit, evaporation concentration unit and post-processing mechanism, and the consumption of reagent is small, and the sludge produced is also less, and a small amount of sludge can be sent to acid regeneration station for liquefaction combustion treatment, so it is not necessary to set up sludge treatment system, and investment cost and operating cost can be reduced.Pickling wastewater is concentrated and reduced by multiple stages, which can significantly reduce system operating cost.

Description

Technical Field

[0001] This invention belongs to the field of pickling wastewater treatment technology, specifically relating to a zero-discharge treatment system and method for pickling wastewater. Background Technology

[0002] Cold rolling is an important part of the steel industry. The pickling section of the cold rolling process pickles the surface of the strip steel. After pickling, it enters the rinsing wastewater section for rinsing to remove the acid remaining in the surface pickling process. The concentrated pickling wastewater generated during the pickling process and the dilute and concentrated pickling wastewater generated during the rinsing process need to be treated.

[0003] Mixed acid pickling wastewater contains large amounts of HF, HNO3, and metal ions (Me). Typically, the main components of dilute acid pickling wastewater are: HNO3: 3.0~7.1 g / L; HF: 1.0~9 g / L; Me: 1~5 g / L, while the main components of concentrated acid pickling wastewater are: HNO3: ~150 g / L; HF: ~50 g / L; Me: 40~150 g / L.

[0004] Hydrochloric acid pickling wastewater contains a large amount of HCl and metal ions (Me). Typically, the main components of dilute pickling wastewater are: HCl: 5.0~15.0 g / L; Me: 1~5 g / L, while the main components of concentrated pickling wastewater are: HCl: ~120 g / L; Me: 40~150 g / L.

[0005] A typical pickling wastewater treatment process is as follows: Figure 1 The dilute acid washing wastewater (hydrochloric acid or mixed acid) generated by the unit line is collected and enters the equalization tank. The concentrated acid washing wastewater (hydrochloric acid waste liquid or mixed acid waste liquid) enters the hydrochloric acid regeneration system and the mixed acid regeneration system. The water in the equalization tank enters the primary and secondary neutralization tanks where Ca(OH)2 is added to generate CaF2 and Me(OH)x to remove F from the waste liquid. - The sludge is reacted with metal ions (Me) and then enters a flocculation sedimentation tank to remove the precipitate. The supernatant from the sedimentation tank then enters a secondary pH adjustment tank to adjust the pH to neutral. Afterwards, methanol is added, and secondary biological denitrification is performed to reduce total nitrogen. Finally, the sludge enters a sedimentation tank for further settling, and the supernatant is discharged. The sludge is treated in a sludge thickening tank. Concentrated acid washing wastewater generated by the unit line is treated in an acid regeneration station, and the resulting regenerated acid is reused in the unit line. This process has the following problems:

[0006] 1) The treatment process consumes a large amount of chemicals, resulting in high costs;

[0007] 2) A large amount of sludge is generated after the treatment, which raises questions about the sludge and its subsequent treatment.

[0008] 3) The effluent is characterized by high hardness, high salinity, and high chlorine, making it unusable for reuse.

[0009] Another typical zero-discharge treatment process for pickling wastewater is as follows: Figure 2 The concentrated acid washing wastewater generated by the unit line is roasted and reused in the acid regeneration station. The dilute acid washing wastewater enters the equalization tank. The water in the equalization tank enters the primary and secondary neutralization tanks where Ca(OH)2 is added to generate CaF2 and Me(OH)x to remove F from the wastewater. - The wastewater contains metal ions (Me) and then enters a flocculation sedimentation tank to remove the generated CaF2 and Me(OH)x precipitates. Afterwards, it passes through a multi-media filter and undergoes a two-stage biological denitrification process using methanol (optional; this step is omitted if the wastewater only contains hydrochloric acid pickling wastewater) to remove total nitrogen. Suspended solids and turbidity are further reduced through sedimentation and sand filtration. Finally, residual salts are removed through ultrafiltration, primary reverse osmosis, secondary reverse osmosis, and MVR evaporation concentration, achieving zero discharge of dilute pickling wastewater. The sludge generated during the process is treated in a sludge thickening tank. This process has the following problems:

[0010] 1) The treatment process consumes a large amount of chemicals, resulting in high costs;

[0011] 2) A large amount of sludge is generated after the treatment, which raises questions about the sludge and its subsequent treatment.

[0012] 3) The process flow is long, and ultrafiltration, reverse osmosis, and MVR evaporation and concentration require large investments, are difficult to operate, and have high operating costs;

[0013] 4) It produces a large amount of unusable miscellaneous salts. Summary of the Invention

[0014] This invention relates to a zero-discharge treatment system and method for pickling wastewater, which can at least solve some of the defects of the prior art.

[0015] This invention relates to a zero-discharge treatment system for pickling wastewater, comprising a wastewater pretreatment unit, a filtration unit, and a first concentration and reduction unit connected in sequence. The product water outlet pipe of the first concentration and reduction unit is connected to a post-treatment mechanism, and the concentrate outlet pipe of the first concentration and reduction unit is connected to an evaporation and concentration unit. The concentrate outlet pipe of the evaporation and concentration unit is connected to an acid regeneration station.

[0016] As one implementation method, an acid-locking tank is also arranged between the concentrated water outlet pipe of the first concentration and reduction unit and the evaporation and concentration unit, and the acid-locking tank is equipped with an acid-locking agent dosing unit.

[0017] As one embodiment, the post-treatment mechanism includes a second concentration and reduction unit, the product water outlet pipe of the second concentration and reduction unit is connected to the acid mixing unit of the pickling unit, and / or the product water outlet pipe of the second concentration and reduction unit is connected to a defluorination mechanism.

[0018] As one implementation method, when the product water outlet pipe of the second concentration and reduction unit is connected to the defluorination mechanism, the defluorination mechanism includes a neutralization tank, a carrier-induced crystallization tank, and a resin defluorination unit connected sequentially along the wastewater flow direction.

[0019] As one implementation method, the product water outlet pipe of the second concentration and reduction unit is connected to a reduced intermediate water tank, which is connected to the acid mixing unit through a first water supply pipe and to the defluorination mechanism through a second water supply pipe.

[0020] As one implementation method, the wastewater pretreatment unit has a sludge outlet pipe that is connected to an acid regeneration station.

[0021] This invention also relates to a method for zero-discharge treatment of pickling wastewater, comprising:

[0022] The pickling wastewater is pretreated and filtered sequentially.

[0023] The pickling wastewater after filtration is concentrated and reduced in volume once to obtain concentrated water and desalinated water.

[0024] The primary concentrate is evaporated and concentrated to obtain secondary concentrate, which is then sent to an acid regeneration station for acid regeneration.

[0025] The freshwater will be treated to render it harmless.

[0026] As one implementation method, before the primary concentrate is evaporated and concentrated, iron oxide powder is added to the primary concentrate to remove H₂. + .

[0027] As one implementation method, the post-treatment of the primary freshwater to render it harmless includes:

[0028] The primary freshwater is subjected to a secondary concentration and volume reduction process to obtain secondary freshwater.

[0029] Depending on the composition of the secondary desalination water, it can be used for acid preparation in pickling units or for defluorination treatment.

[0030] As one implementation method, the defluoridation treatment of the secondary freshwater includes:

[0031] The secondary freshwater is neutralized to obtain neutralized permeable water;

[0032] The neutralized permeate is subjected to carrier-induced crystallization treatment to obtain crystallized permeate;

[0033] The crystallization product water was treated with a fluoride removal resin to obtain clean water that meets the standards.

[0034] The present invention has at least the following beneficial effects:

[0035] The pickling wastewater zero-discharge treatment system and method provided by this invention treats the pickling wastewater primarily in the first concentration and reduction unit, the evaporation and concentration unit, and the post-treatment mechanism. It consumes minimal reagents and produces relatively little sludge. A small amount of sludge can be sent to the acid regeneration station for liquefaction and combustion treatment, thus eliminating the need for a sludge treatment system and reducing investment and operating costs. The multi-stage concentration and reduction of pickling wastewater significantly reduces system operating costs.

[0036] The present invention further has the following beneficial effects:

[0037] In this invention, the concentrated water from the first concentration and reduction unit is acid-locked before evaporation and concentration treatment. This can prevent acid mist from overflowing and corroding the evaporation and concentration device, greatly extend the service life of the evaporation and concentration device, ensure the stability and reliability of system operation, and significantly improve the quality of the condensate produced by evaporation.

[0038] The present invention further has the following beneficial effects:

[0039] In this invention, a combination of neutralization and carrier-induced crystallization is used to treat the permeate from the second concentration and reduction unit, which effectively removes fluoride ions from the wastewater and improves the cleanliness of the effluent. Combined with a resin defluorination unit to further remove fluoride ions from the wastewater, compliant clean water can be obtained. The treatment process generates no sludge, further reducing system investment and operating costs. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 and Figure 2 Two typical pickling wastewater treatment flow diagrams are provided for the background technology.

[0042] Figure 3 A flowchart illustrating the zero-discharge treatment process for pickling wastewater provided in an embodiment of the present invention. Detailed Implementation

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] like Figure 3 This invention provides a zero-discharge treatment system for pickling wastewater, comprising a wastewater pretreatment unit, a filtration unit 2, and a first concentration and reduction unit 3 connected in sequence. The product water outlet pipe of the first concentration and reduction unit 3 is connected to a post-treatment mechanism, and the concentrate outlet pipe of the first concentration and reduction unit 3 is connected to an evaporation and concentration unit 42. The concentrate outlet pipe of the evaporation and concentration unit 42 is connected to an acid regeneration station 81.

[0046] In one embodiment, such as Figure 3 The wastewater pretreatment unit includes an equalization tank 11 and a pretreatment tank 12. The equalization tank 11 is equipped with an acid pickling wastewater supply pipe. The equalization tank 11 is connected to the pretreatment tank 12. The effluent from the equalization tank 11 enters the pretreatment tank 12 for pretreatment.

[0047] Optionally, in the pretreatment tank 12, the turbidity of the influent is reduced by adding an in-situ pH precipitant (acidic, pH 1-3). This method differs from the traditional method of adjusting the pH to neutral by adding neutralizing agents (lime, sodium hydroxide, etc.). It produces less sludge, and the sludge does not contain metal ions, mainly consisting of some suspended solids and turbidity. The dosage of the in-situ pH precipitant is in the range of 0.5-5 ppm.

[0048] Preferably, the precipitated sludge produced by the wastewater pretreatment unit is sent to the acid regeneration station 81 for sludge liquefaction and combustion. Accordingly, the wastewater pretreatment unit has a sludge outlet pipe connected to the acid regeneration station 81. This method can achieve effective sludge treatment without the need for a sludge treatment system, thereby reducing investment and operating costs.

[0049] The aforementioned filtration unit 2 can further reduce the turbidity of the incoming water to improve the subsequent treatment effect. For example, it can make the pickling wastewater meet the influent water quality requirements of the first concentration and reduction unit 3. The filtration unit 2 includes at least one set of filters. When there are multiple sets of filters, the filters are connected in series. In this embodiment, the filtration unit 2 includes a quartz sand filter and a security filter connected in series, wherein the quartz sand filter is connected to the wastewater pretreatment unit.

[0050] In one embodiment, the first concentration and reduction unit 3 employs an electrochemical concentration method, which can achieve a better concentration and reduction effect. Optionally, the first concentration and reduction unit 3 uses a carbon-based ruthenium-iridium anode, a stainless steel mesh cathode, a current density of 15-30 A / m², and a distance of 2-10 mm between the anode and cathode.

[0051] In one embodiment, such as Figure 3 A lock-in tank 41 is also arranged between the concentrate outlet pipe of the first concentration and reduction unit 3 and the evaporation and concentration unit 42. The lock-in tank 41 is equipped with a lock-in agent dosing unit. The lock-in tank 41 is mainly used to remove H from the concentrate. + Among them, the acid-locking agent includes, but is not limited to, iron oxide powder. This allows the use of high-quality iron oxide powder obtained from acid regeneration station 81 (accounting for 10-20% of the iron oxide powder production of acid regeneration station 81), which not only reduces the system production cost but also achieves a very good acid-locking effect. Of course, externally purchased iron oxide powder, chromium oxide, scrap iron, etc. are also suitable as the above-mentioned acid-locking agents.

[0052] Among them, it can be calculated according to formula Q _Fe =k×[H + The amount of iron oxide powder added is calculated as ]×V, where k ranges from 0.8 to 1.2, and V is the volume of concentrated water.

[0053] Based on the above scheme, by setting up an acid lock tank 41 to lock the concentrated water with acid, it is possible to prevent acid mist from overflowing and causing corrosion to the evaporation and concentration device, which can greatly extend the service life of the evaporation and concentration device, ensure the stability and reliability of system operation, and significantly improve the quality of the condensate produced by evaporation.

[0054] In the aforementioned acid-locking tank 41, it is preferable to raise the pH of the concentrated water to 4.0-4.5 to ensure the acid-locking effect. In this way, the corrosion rate of the evaporation and concentration device can be ≤0.05mm / year, and the conductivity of the condensate produced after evaporation after acid-locking is low (can be reduced to about 500μs / cm).

[0055] The aforementioned evaporation and concentration unit 42 is used to further concentrate the concentrated water from the first concentration and reduction unit 3, reduce the amount of water to be treated, lower operating costs, and increase the concentration of the concentrated water to meet the acid inlet concentration requirements of the acid regeneration station 81 (generally, the total Me is controlled at 40~150g / L).

[0056] In one embodiment, such as Figure 3 The post-treatment mechanism includes a second concentration and reduction unit 5, the product water outlet pipe of the second concentration and reduction unit 5 is connected to the acid mixing unit 82 of the pickling unit, and / or the product water outlet pipe of the second concentration and reduction unit 5 is connected to a defluorination mechanism.

[0057] In one embodiment, the second concentration and reduction unit 5 employs an electrochemical concentration method, which can achieve a better concentration and reduction effect. Optionally, the second concentration and reduction unit 5 uses a carbon-based ruthenium-iridium anode, a stainless steel mesh cathode, a current density of 10~20 A / m², and a distance of 1~5 mm between the anode and cathode.

[0058] The system can select whether to connect the outlet pipe of the second concentration and reduction unit 5 to the acid mixing unit 82 of the pickling unit or to the defluorination mechanism, depending on the composition of the produced water. For example, when the system is treating hydrochloric acid pickling wastewater, the produced water of the second concentration and reduction unit 5 can be directly reused, that is, sent to the acid mixing unit 82 of the pickling unit for acid mixing; when the system is treating mixed acid pickling wastewater, the produced water of the second concentration and reduction unit 5 can enter the defluorination mechanism for further treatment.

[0059] Understandably, when the product water outlet pipe of the second concentration and reduction unit 5 is connected to both the acid mixing unit 82 and the defluorination mechanism, the production flexibility and reliability of the system can be improved accordingly. For example, the product water outlet pipe is connected to the first water supply pipe and the second water supply pipe. The first water supply pipe is connected to the acid mixing unit 82, and the second water supply pipe is connected to the defluorination mechanism. Control valves can be installed on the first water supply pipe and the second water supply pipe respectively to control the wastewater flow direction and flow rate.

[0060] Optionally, such as Figure 3 The product water outlet pipe of the second concentration and reduction unit 5 is connected to a reduced-volume intermediate water tank 72. The reduced-volume intermediate water tank 72 is connected to the acid mixing unit 82 through a first water supply pipe and to the defluorination mechanism through a second water supply pipe. The reduced-volume intermediate water tank 72 can buffer wastewater, coordinate the production pace of upstream and downstream processes, and facilitate reliable control of the wastewater flow direction.

[0061] like Figure 3 The condensate produced by the evaporation and concentration unit 42 can be sent to the reduced-volume intermediate water tank 72. That is, the condensate pipe of the evaporation and concentration unit 42 is connected to the reduced-volume intermediate water tank 72, which is green and economical and reduces environmental pollution.

[0062] In one embodiment, the concentrated water produced by the second concentration and reduction unit 5 can be returned to the first concentration and reduction unit 3 for recycling, further ensuring zero wastewater discharge from the system. Optionally, as... Figure 3 An intermediate water tank 71 before reduction is provided between the filtration unit 2 and the first concentration and reduction unit 3, and the concentrate outlet pipe of the second concentration and reduction unit 5 is connected to the intermediate water tank 71 before reduction.

[0063] In this embodiment, the recovery rates of both the first concentration and reduction unit 3 and the second concentration and reduction unit 5 are 70% to 85%.

[0064] In one embodiment, such as Figure 3 The aforementioned defluorination mechanism includes a neutralization tank 61, a carrier-induced crystallization tank 62, and a resin defluorination unit 63, which are connected sequentially along the wastewater flow direction.

[0065] Optionally, Ca(OH)₂ is added to the neutralization tank 61, which can react with F ions in the wastewater to form CaF₂. The effluent from the neutralization tank 61 enters the carrier-induced crystallization tank 62, where the generated CaF₂ is removed by carrier-induced crystallization. This combination of neutralization and carrier-induced crystallization effectively removes fluoride ions from the wastewater, improving effluent cleanliness. Combined with the resin defluorination unit 63 for further fluoride removal, compliant clean water can be obtained, including but not limited to industrial water reuse.

[0066] Preferably, the carrier-induced crystallization uses high-temperature (above 1200℃) sintered modified ceramic particles as the crystallization core, and the particle size of the high-temperature sintered modified ceramic particles is in the range of 0.3~0.4mm; furthermore, in the carrier-induced crystallization tank 62, the upward flow velocity is controlled at 5~15m / h, the pH is controlled at 5.8~6.2, and the Ca / F molar ratio is controlled at 1.05~1.21, so that CaF2 grows and separates on the surface of the sintered modified ceramic particle carrier to form CaF2 particles. While efficiently removing fluoride, the obtained CaF2 particles can be utilized as resources, realizing the resource-based treatment of pickling wastewater.

[0067] Example 2

[0068] like Figure 3 This invention provides a method for zero-discharge treatment of pickling wastewater, comprising:

[0069] The pickling wastewater is pretreated and filtered sequentially.

[0070] The pickling wastewater after filtration is concentrated and reduced in volume once to obtain concentrated water and desalinated water.

[0071] The primary concentrate is evaporated and concentrated to obtain secondary concentrate, which is then sent to acid regeneration station 81 for acid regeneration.

[0072] The freshwater will be treated to render it harmless.

[0073] The zero-discharge treatment method for pickling wastewater in this embodiment can be implemented based on the zero-discharge treatment system for pickling wastewater in Embodiment 1 above.

[0074] The pickling wastewater treatment method described in Example 1 is also applicable to this example, for example:

[0075] (1) Before the primary concentrate is evaporated and concentrated, iron oxide powder is added to the primary concentrate to remove H. + The relevant acid-locking methods can be found in the content of Example 1, and will not be repeated here.

[0076] (2) The post-treatment of the primary freshwater to render it harmless includes:

[0077] The primary freshwater is subjected to a secondary concentration and volume reduction process to obtain secondary freshwater.

[0078] Depending on the composition of the secondary desalination water, it can be used for acid preparation in pickling units or for defluorination treatment.

[0079] Optionally, the defluoridation treatment of the secondary freshwater includes:

[0080] The secondary freshwater is neutralized to obtain neutralized permeable water;

[0081] The neutralized permeate is subjected to carrier-induced crystallization treatment to obtain crystallized permeate;

[0082] The crystallization product water was treated with a fluoride removal resin to obtain clean water that meets the standards.

[0083] The relevant defluorination process can be found in the relevant content of Example 1, and will not be repeated here.

[0084] Example 3

[0085] This embodiment provides a treatment process for pickling wastewater, which is a specific embodiment of the zero-discharge treatment system for pickling wastewater in Embodiment 1 above / the zero-discharge treatment method for pickling wastewater in Embodiment 2 above.

[0086] The system processes mixed acid pickling wastewater, and the water quality indicators are shown in the table below:

[0087]

[0088] like Figure 3 After collection, the dilute acid washing wastewater enters the equalization tank 11 for homogenization. The effluent from the equalization tank 11 enters the pretreatment tank 12, where an in-situ pH precipitant is added to reduce the turbidity of the influent. After sedimentation, the effluent enters the quartz sand filter and the security filter to remove suspended solids and turbidity from the influent. The effluent then enters the intermediate water tank 71 before the reduction.

[0089] The water in intermediate pool 71 before volume reduction undergoes a first concentration and volume reduction unit 3 (primary electrochemical concentration treatment unit) to remove 70% of its ions (F). - NO3 - H +At this point, the conductivity of the effluent is approximately 2000-3000 μS / cm, F - ≤240mg / L, NO3 - ≤150mg / L, the effluent from the first concentration and reduction unit 3 further enters the second concentration and reduction unit 5 (secondary electrochemical concentration treatment unit); the conductivity of the effluent from the second concentration and reduction unit 5 is ≤1000μs / cm, F - ≤60mg / L, NO3 - ≤45mg / L.

[0090] The effluent from the second concentration and reduction unit 5 enters the intermediate water tank 72 after reduction. The effluent from the intermediate water tank 72 is further treated in the neutralization tank 61, where Ca(OH)2 is added to generate CaF2. The effluent from the neutralization tank 61 then enters the carrier-induced crystallization tank 62, where the generated CaF2 is removed by carrier-induced crystallization. Finally, the defluorination resin in the resin defluorination unit 63 further removes F from the incoming water. - F in the treated water - ≤1mg / L is considered high-quality industrial water and can be reused.

[0091] The conductivity of the concentrate in the first concentration and reduction unit 3 is approximately 40,000-50,000 μS / cm, and the volume is approximately 6 m³. 3 / h (adjustable) The concentrate contains a large amount of H + By adding iron oxide powder, the H in the concentrated water is reduced. + Remove to prevent H from being produced during the evaporation and concentration stage. + Overflow causes corrosion to the evaporation and concentration equipment, with a corrosion rate ≤0.05mm / year. The concentrated water then enters evaporation and concentration unit 42 for further concentration, yielding condensate (with a conductivity of approximately 500μs / cm) and the concentrated water. (During the pilot-scale test, the inventors discovered that without acid locking, i.e., without adding iron oxide powder to remove H+ from the concentrated water...) + The corrosion rate of the evaporation equipment is approximately 0.5 mm / year, and the conductivity of the condensate is around 3000~4000 μS / cm.

[0092] The concentration of the concentrated water after evaporation and concentration (total Me controlled at 40~150g / L) meets the influent conditions for acid regeneration. It is treated simultaneously with the concentrated acid washing wastewater generated by the unit line, and then roasted in the acid regeneration station (81) to obtain regenerated acid and high-quality iron oxide powder. The iron oxide powder can be used for acid lock-in treatment, and excess high-quality iron oxide powder can be sold as finished products. The regenerated acid is recycled back to the unit line.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A zero-discharge treatment system for pickling wastewater, characterized in that: The system includes a wastewater pretreatment unit, a filtration unit, and a first concentration and reduction unit connected in sequence. The product water outlet pipe of the first concentration and reduction unit is connected to a post-treatment mechanism, and the concentrate outlet pipe of the first concentration and reduction unit is connected to an evaporation and concentration unit. The concentrate outlet pipe of the evaporation and concentration unit is connected to an acid regeneration station. The evaporation and concentration unit is used to further concentrate the concentrate from the first concentration and reduction unit. The total me of the concentrate after evaporation and concentration is controlled at 40~150g / L, which can meet the influent conditions for acid regeneration. It is treated simultaneously with the concentrated acid washing wastewater generated by the unit line, and regenerated acid and iron oxide powder are obtained through roasting treatment in the acid regeneration station. A lock-in tank is also arranged between the concentrate outlet pipe of the first concentration and reduction unit and the evaporation and concentration unit. The lock-in tank is equipped with a lock-in agent dosing unit, which is used to add iron oxide powder from the acid regeneration station to the lock-in tank to remove H from the concentrate. + This raises the pH of the concentrate to 4.0-4.

5.

2. The pickling wastewater zero-discharge treatment system as described in claim 1, characterized in that: The post-treatment mechanism includes a second concentration and reduction unit, the product water outlet pipe of the second concentration and reduction unit is connected to the acid mixing unit of the pickling unit, and / or the product water outlet pipe of the second concentration and reduction unit is connected to a defluorination mechanism.

3. The pickling wastewater zero-discharge treatment system as described in claim 2, characterized in that: When the product water outlet pipe of the second concentration and reduction unit is connected to the defluorination mechanism, the defluorination mechanism includes a neutralization tank, a carrier-induced crystallization tank, and a resin defluorination unit connected sequentially along the wastewater flow direction.

4. The pickling wastewater zero-discharge treatment system as described in claim 2, characterized in that: The product water outlet pipe of the second concentration and reduction unit is connected to the intermediate water tank after reduction. The intermediate water tank after reduction is connected to the acid mixing unit through the first water supply pipe and to the defluorination mechanism through the second water supply pipe.

5. The pickling wastewater zero-discharge treatment system as described in claim 1, characterized in that: The wastewater pretreatment unit has a sludge outlet pipe, which is connected to an acid regeneration station.

6. A method for zero-discharge treatment of pickling wastewater, characterized in that, include: The pickling wastewater is pretreated and filtered sequentially. The pickling wastewater after filtration is concentrated and reduced in volume once to obtain concentrated water and desalinated water. The primary concentrate is evaporated and concentrated to obtain secondary concentrate. The total Me of the secondary concentrate is controlled at 40~150g / L, which can meet the influent conditions for acid regeneration. It is treated simultaneously with the concentrated acid washing wastewater generated by the unit line and obtained by roasting in the acid regeneration station to obtain regenerated acid and iron oxide powder. The primary freshwater is then treated to render it harmless. Before the primary concentrate is evaporated and concentrated, iron oxide powder from the acid regeneration station is added to the primary concentrate to remove H2. + This raises the pH of the concentrate to 4.0-4.

5.

7. The zero-discharge treatment method for pickling wastewater as described in claim 6, characterized in that, The post-treatment of the primary freshwater to render it harmless includes: The primary freshwater is then subjected to a secondary concentration and volume reduction process to obtain secondary freshwater. Depending on the composition of the secondary desalination water, it can be used for acid preparation in pickling units or for defluorination treatment.

8. The zero-discharge treatment method for pickling wastewater as described in claim 7, characterized in that, The defluoridation treatment of the secondary freshwater includes: The secondary freshwater is neutralized to obtain neutralized permeable water; The neutralized permeate is subjected to carrier-induced crystallization treatment to obtain crystallized permeate; The crystallization product water was treated with a fluoride removal resin to obtain clean water that meets the standards.

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