Acid pickling wastewater resource treatment system
By combining concentration reduction and defluorination processes to treat pickling wastewater, the problems of high reagent consumption, excessive sludge, and high cost in existing technologies have been solved. This approach enables the resource-based treatment and reuse of pickling wastewater, reducing system costs and sludge generation.
Patent Information
- Application Number
- CN202522015871.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2035-09-19
AI Technical Summary
Existing pickling wastewater treatment processes suffer from problems such as high reagent consumption, high cost, large sludge production, long process flow, large investment, high operation difficulty, and inability to reuse effluent.
Acid washing wastewater is treated by concentration reduction and defluorination. The treatment combines neutralization, carrier-induced crystallization and resin defluorination units. Fluoride ions are removed through an electrochemical concentration reduction device and a high-temperature sintered modified ceramic carrier, achieving resource recovery.
It achieves resource-based treatment of pickling wastewater, reduces system investment and operating costs, reduces sludge production, obtains compliant clean water for reuse, requires low equipment investment, and has high operational stability.
Smart Images
Figure CN224677934U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of cold rolling production technology, specifically relating to a pickling wastewater resource utilization system. 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 the issue of 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 the issue of 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. Utility Model Content
[0014] This utility model relates to a resource-based treatment system for pickling wastewater, which can at least solve some of the defects of the prior art.
[0015] This utility model relates to a pickling wastewater resource utilization treatment system, including a wastewater pretreatment unit, a filtration unit, a concentration and reduction mechanism, and a defluorination mechanism connected sequentially along the wastewater flow direction. The defluorination mechanism includes a neutralization tank, a carrier-induced crystallization tank, and a resin defluorination unit connected sequentially along the wastewater flow direction. The neutralization tank is equipped with a calcium salt dosing unit.
[0016] As one implementation method, a reduced-volume intermediate water tank is provided between the concentration and reduction mechanism and the neutralization tank. The reduced-volume intermediate water tank is connected to the acid mixing unit of the pickling unit through a first water supply pipe and to the neutralization tank through a second water supply pipe.
[0017] As one embodiment, the concentration and reduction mechanism includes a first concentration and reduction unit and a second concentration and reduction unit. The first concentration and reduction unit is connected to the filtration unit, the product water outlet pipe of the first concentration and reduction unit is connected to the second concentration and reduction unit, and the product water outlet pipe of the second concentration and reduction unit is connected to the neutralization tank.
[0018] As one implementation method, the first concentration and reduction unit employs an electrochemical concentration and reduction device.
[0019] As one implementation method, the first concentration and reduction unit 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 the cathode.
[0020] As one implementation method, the second concentration and reduction unit employs an electrochemical concentration and reduction device.
[0021] As one implementation method, the second concentration and reduction unit uses a carbon-based ruthenium-iridium anode, a stainless steel mesh cathode, a current density of 10~20A / m², and a distance of 1~5mm between the anode and the cathode.
[0022] As one implementation method, an intermediate water tank before reduction is provided between the filtration unit and the first concentration and reduction unit, and the concentrate outlet pipe of the second concentration and reduction unit is connected to the intermediate water tank before reduction.
[0023] As one embodiment, the wastewater pretreatment unit includes an equalization tank and a pretreatment tank connected in sequence. The equalization tank is equipped with an acid washing wastewater supply pipe, and the pretreatment tank is equipped with an in-situ pH precipitant dosing unit.
[0024] As one implementation method, the wastewater pretreatment unit has a sludge outlet pipe that is connected to an acid regeneration station.
[0025] This utility model has at least the following beneficial effects:
[0026] This invention employs a concentration-reduction + defluorination method to treat pickling wastewater, simultaneously meeting the treatment requirements for both hydrochloric acid and mixed acid pickling wastewater. A combination of neutralization and carrier-induced crystallization is used to treat the permeate from the second concentration-reduction unit, effectively removing fluoride ions and improving effluent cleanliness. Further removal of fluoride ions from the wastewater using a resin defluorination unit yields compliant clean water. The obtained CaF2 particles can be recycled, realizing the resource-based treatment of pickling wastewater. The equipment investment is relatively small, and the treatment process generates little to no sludge, effectively reducing system investment and operating costs. Attached Figure Description
[0027] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0028] Figure 1 and Figure 2 Two typical pickling wastewater treatment flow diagrams are provided for the background technology.
[0029] Figure 3 A flowchart illustrating the zero-discharge treatment process for pickling wastewater provided in this embodiment of the utility model. Detailed Implementation
[0030] The technical solutions in the embodiments of this utility model are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0031] Example 1
[0032] like Figure 3 This utility model provides a pickling wastewater resource utilization system, which includes a wastewater pretreatment unit, a filtration unit 2, a concentration and reduction mechanism, and a defluorination mechanism connected in sequence.
[0033] Preferably, 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.
[0034] Optionally, the neutralization tank 61 is used for adding calcium salts, and is accordingly equipped with a calcium salt addition unit, preferably using Ca(OH)2, which can react with F ions in the wastewater to generate CaF2. The effluent from the neutralization tank 61 enters the carrier-induced crystallization tank 62, where the generated CaF2 can be removed by carrier-induced crystallization. The combination of neutralization and carrier-induced crystallization can effectively remove fluoride ions from the wastewater, improving the effluent cleanliness. Combined with the resin defluorination unit 63 for further removal of fluoride ions, compliant clean water can be obtained, including but not limited to industrial water reuse.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] In one embodiment, such as Figure 3 The concentration and reduction mechanism includes a first concentration and reduction unit 3 and a second concentration and reduction unit 5. The first concentration and reduction unit 3 is connected to the filter unit 2. The water outlet pipe of the first concentration and reduction unit 3 is connected to the second concentration and reduction unit 5. The water outlet pipe of the second concentration and reduction unit 5 is connected to the defluorination mechanism.
[0041] Using multi-stage concentration and volume reduction to treat pickling wastewater can significantly reduce system operating costs.
[0042] Preferably, the first concentration and reduction unit 3 adopts an electrochemical concentration method, which can achieve a better concentration and reduction effect. Optionally, the first concentration and reduction unit 3 adopts 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 the cathode.
[0043] Preferably, the second concentration and reduction unit 5 adopts an electrochemical concentration method, which can achieve a better concentration and reduction effect. Optionally, the second concentration and reduction unit 5 adopts a carbon-based ruthenium-iridium anode, a stainless steel mesh cathode, a current density of 10~20A / m², and a distance of 1~5mm between the anode and the cathode.
[0044] In one embodiment, such as Figure 3 The concentrated water outlet pipe of the first concentration and reduction unit 3 is connected to an evaporation and concentration unit 42, and the concentrated water outlet pipe of the evaporation and concentration unit 42 is connected to an acid regeneration station 81. The 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, reduce 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).
[0045] Preferably, 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.
[0046] 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.
[0047] 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.
[0048] 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).
[0049] In this embodiment, a concentration-reduction + defluorination method is used to treat pickling wastewater, which can simultaneously meet the treatment requirements of hydrochloric acid pickling wastewater and mixed acid pickling wastewater. Specifically, based on the composition of the product water from the second concentration-reduction unit 5, the product water can be either sent to the acid mixing unit 82 of the pickling unit for reuse, or sent to the defluorination mechanism for further treatment. For example, when the system is treating hydrochloric acid pickling wastewater, the product water from the second concentration-reduction unit 5 can be directly reused, i.e., sent to the acid mixing unit 82 of the pickling unit for acid mixing; when the system is treating mixed acid pickling wastewater, the product water from the second concentration-reduction unit 5 can enter the defluorination mechanism for further treatment. Accordingly, the product water outlet pipe of the second concentration-reduction unit 5 can be connected to a first water supply pipe and a 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 and second water supply pipes respectively to control the wastewater flow direction and flow rate.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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%.
[0054] Example 2
[0055] This embodiment provides a treatment process for pickling wastewater, which is a specific embodiment of the pickling wastewater resource utilization treatment system in Embodiment 1 above.
[0056] The system processes mixed acid pickling wastewater, and the water quality indicators are shown in the table below:
[0057]
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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 inventor 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.
[0062] 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.
[0063] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. A pickling wastewater resource utilization treatment system, characterized in that: The system includes a wastewater pretreatment unit, a filtration unit, a concentration and reduction mechanism, and a defluorination mechanism connected sequentially along the wastewater flow direction. The defluorination mechanism includes a neutralization tank, a carrier-induced crystallization tank, and a resin defluorination unit connected sequentially along the wastewater flow direction. The neutralization tank is equipped with a calcium salt dosing unit.
2. The pickling wastewater resource utilization treatment system as described in claim 1, characterized in that: An intermediate water tank for volume reduction is provided between the concentration and reduction mechanism and the neutralization tank. The intermediate water tank for volume reduction is connected to the acid mixing unit of the pickling unit through a first water supply pipe and to the neutralization tank through a second water supply pipe.
3. The pickling wastewater resource utilization treatment system as described in claim 1, characterized in that: The concentration and reduction mechanism includes a first concentration and reduction unit and a second concentration and reduction unit. The first concentration and reduction unit is connected to the filtration unit. The product water outlet pipe of the first concentration and reduction unit is connected to the second concentration and reduction unit. The product water outlet pipe of the second concentration and reduction unit is connected to the neutralization tank.
4. The pickling wastewater resource utilization treatment system as described in claim 3, characterized in that: The first concentration and reduction unit uses an electrochemical concentration and reduction device.
5. The pickling wastewater resource utilization treatment system as described in claim 4, characterized in that: The first concentration and reduction unit uses a carbon-based ruthenium-iridium anode and a stainless steel mesh cathode. The current density is 15-30 A / m², and the distance between the anode and the cathode is 2-10 mm.
6. The pickling wastewater resource utilization treatment system as described in claim 3, characterized in that: The second concentration and reduction unit employs an electrochemical concentration and reduction device.
7. The pickling wastewater resource utilization treatment system as described in claim 6, characterized in that: The second concentration and reduction unit uses a carbon-based ruthenium-iridium anode and a stainless steel mesh cathode. The current density is 10~20A / m², and the distance between the anode and the cathode is 1~5mm.
8. The pickling wastewater resource utilization treatment system as described in claim 3, characterized in that: An intermediate water tank before reduction is provided between the filtration unit and the first concentration and reduction unit, and the concentrate outlet pipe of the second concentration and reduction unit is connected to the intermediate water tank before reduction.
9. The pickling wastewater resource utilization treatment system as described in claim 1, characterized in that: The wastewater pretreatment unit includes an equalization tank and a pretreatment tank connected in sequence. The equalization tank is equipped with an acid washing wastewater supply pipe, and the pretreatment tank is equipped with an in-situ pH precipitant dosing unit.
10. The pickling wastewater resource utilization treatment system as described in claim 9, characterized in that: The wastewater pretreatment unit has a sludge outlet pipe, which is connected to an acid regeneration station.