Stainless steel pickling wastewater treatment system and treatment method thereof

Abstract

This invention discloses a stainless steel pickling wastewater treatment system and its treatment method, including a mixed acid pickling wastewater treatment system and a sulfuric acid pickling wastewater treatment system. The mixed acid pickling wastewater treatment system and the sulfuric acid pickling wastewater treatment system are configured to treat wastewater separately. Wastewater from different steel grades is stored and treated in batches according to different categories, and the generated sludge is treated separately. By treating the mixed acid pickling wastewater and sulfuric acid pickling wastewater separately, the stainless steel pickling wastewater can be treated simultaneously or separately according to actual production conditions. This not only reduces environmental pollution but also enables wastewater resource utilization, solves the problem of stainless steel pickling wastewater recycling, and reduces the production costs of enterprises.

Description

[0001] The patent application is a divisional application of the Chinese patent application No. 201710152089.7, with the title of "Stainless Steel Pickling Wastewater Treatment System", and the filing date of March 15, 2017. TECHNICAL FIELD

[0002] The present application relates to the technical field of wastewater treatment, in particular to a stainless steel pickling wastewater treatment system and a treatment method thereof. BACKGROUND

[0003] Stainless steel is widely used due to its excellent corrosion resistance and good appearance. In the production process of stainless steel, the surface will often produce black oxide skin during annealing, normalizing, quenching, welding and other processing processes. The oxide skin not only affects the appearance quality of stainless steel, but also adversely affects the subsequent processing of the product, so it must be removed by pickling, polishing and other surface treatment methods before subsequent processing.

[0004] The surface of stainless steel will produce iron oxide skin, and the main components are FeO, Fe2O3, NiO, Cr2O3, Fe3O4, FeO·Cr2O3, Ni·Fe2O3, FeO·Cr2O3·Fe2O3 and other dense oxides. These oxides have strong adhesion, and in the treatment process of combined processes such as shot blasting, high-temperature alkali etching, molten salt electrolysis, mixed acid pickling, multi-stage rinsing, etc., neutral salt wastewater, acid-containing wastewater, fluorine-containing mixed acid wastewater and other pickling and rinsing wastewater will be inevitably discharged.

[0005] In the process of pickling stainless steel, generally first pre-pickling with sulfuric acid to remove the surface iron oxide skin, and then pickling with 90-160 g / L nitric acid and 50-60 g / L hydrofluoric acid mixed acid. Nitric acid with strong oxidizing property can oxidize metals and metal oxides to generate Cr 3+ , Fe 3+ and Ni 2+ , etc., and these metal ions (especially Cr 3+ , Ni 2+ and Fe 3+ , etc.) and nitric acid and hydrofluoric acid form stable compounds. In the multi-stage rinsing process, the above-mentioned acid and metal ions enter the rinsing water to form pickling wastewater.

[0006] For the treatment of such pickling wastewater, the most commonly used method is lime neutralization and single-step precipitation. The neutralization method is simple and easy to operate, but has problems of unstable and high fluoride ion concentration in the effluent, large amount of sludge, high treatment cost, etc.

[0007] In general, the sludge produced by the existing wastewater treatment facilities has a water content of about 50%, and after removing the water, the remaining 50% of solid materials contain about 65% of effective components and about 35% of waste solid materials. If these waste solid materials are recycled into the stainless steel production process, not only energy, raw materials, production line capacity, manpower, and production line output rate are wasted, but also the production process and product quality are adversely affected. SUMMARY

[0008] Therefore, the stainless steel pickling wastewater treatment system provided by the present application better overcomes the problems and defects of the prior art, and is safe and stable in operation, simple in operation, and convenient in management. By separately treating mixed acid pickling wastewater and sulfuric acid pickling wastewater, the treatment can be performed simultaneously or separately according to the actual production situation. Not only is the environmental pollution reduced, but also the wastewater is recycled, the stainless steel pickling wastewater recycling problem is solved, the effect of "comprehensive management" is achieved, and the production cost of the enterprise is reduced.

[0009] A stainless steel pickling wastewater treatment system, comprising a mixed acid pickling wastewater treatment system and a sulfuric acid pickling wastewater treatment system.

[0010] The mixed acid pickling wastewater treatment system comprises a first pH adjusting tank, a first concentration membrane device, a first collection tank, a defluorination reaction tank, and a resin adsorption purification system connected in sequence. The clean water outlet of the first concentration membrane device is connected with the first collection tank. The concentrated water outlet of the first concentration membrane device is further connected with a first sludge storage tank. The first sludge storage tank is connected with a first filter press. The sludge outlet of the first filter press is connected with a first calcining furnace. The defluorination reaction tank is further connected with a second sludge storage tank. The second sludge storage tank is connected with a second filter press. The sludge outlet of the second filter press is connected with a second calcining furnace.

[0011] The sulfuric acid pickling wastewater treatment system comprises a second pH adjusting tank, a second concentration membrane device, and a second collection tank connected in sequence. The clean water outlet of the second concentration membrane device is connected with the second collection tank. The concentrated water outlet of the second concentration membrane device is connected with a third sludge storage tank. The third sludge storage tank is connected with a third filter press. The sludge outlet of the third filter press is connected with a third calcining furnace.

[0012] The resin adsorption purification system and the second collection tank are both connected with a clean water recycling treatment device.

[0013] Further, the mixed acid pickling wastewater treatment system further comprises a plurality of mixed acid pickling wastewater storage tanks, each of the mixed acid pickling wastewater storage tanks is in communication with the first pH adjusting tank through a first lifting pump, and a first electric control valve is arranged at the outlet of each of the mixed acid pickling wastewater storage tanks; the sulfuric acid pickling wastewater treatment system further comprises a plurality of sulfuric acid pickling wastewater storage tanks, each of the sulfuric acid pickling wastewater storage tanks is in communication with the second pH adjusting tank through a second lifting pump, and a second electric control valve is arranged at the outlet of each of the sulfuric acid pickling wastewater storage tanks.

[0014] Further, the outlet of the first filter press is in communication with the first pH adjusting tank, and the outlet of the third filter press is in communication with the second pH adjusting tank.

[0015] Further, a first sedimentation tank is arranged at the position where the first concentration membrane device is in communication with the first sludge storage tank, the sludge outlet of the first sedimentation tank is in communication with the first sludge storage tank, and the water outlet of the first sedimentation tank is in communication with the first collecting tank.

[0016] Further, a second sedimentation tank is arranged at the position where the second concentration membrane device is in communication with the first sludge storage tank, the sludge outlet of the second sedimentation tank is in communication with the third sludge storage tank, and the water outlet of the second sedimentation tank is in communication with the second collecting tank.

[0017] Further, a third sedimentation tank is arranged at the position where the defluorination reaction tank is in communication with the resin adsorption purification system, the water outlet of the third sedimentation tank is in communication with the resin adsorption purification system, and the sludge outlet of the third sedimentation tank is in communication with the second sludge storage tank.

[0018] Further, a membrane separation device is arranged at the position where the water outlet of the third sedimentation tank is in communication with the resin adsorption purification system, the water outlet of the membrane separation device is in communication with the resin adsorption purification system, and the sludge outlet of the membrane separation device is in communication with the second sludge storage tank.

[0019] Further, the water outlet of the second filter press is also in communication with the first collecting tank.

[0020] Further, the resin adsorption purification system comprises a plurality of resin adsorption purification devices.

[0021] Further, the resin adsorption purification system is in communication with the first collecting tank and the second collecting tank respectively.

[0022] Further, the mixed acid pickling wastewater and the sulfuric acid pickling wastewater are treated separately, different steel production wastewater is classified and stored through arranging a plurality of pickling wastewater storage tanks, and the produced sludge is also classified and treated, so that the content of the metal oxide obtained is similar to the content of the steel grade and is recovered respectively.

[0023] Compared with the prior art, the stainless steel pickling wastewater treatment system and the treatment method thereof have the following beneficial effects:

[0024] (1) The stainless steel pickling wastewater treatment system is used for treating stainless steel pickling wastewater, on the one hand, not only greatly reduces the sludge production amount and the sludge moisture content, but also changes the generated sludge into recyclable materials after calcination treatment, 100% of which is effective ingredients, and the waste material has zero invalid ingredients, 100% of which is recycled for use in the stainless steel production process, thereby effectively reducing the sludge treatment cost and load, and solving the problem of resource waste; on the other hand, by adding the resin adsorption purification system after adding the slaked lime to remove fluorine in the fluorine removal reaction tank, the fluorine ion concentration of the final effluent is greatly reduced by further adsorbing the fluorine ion through the resin, and in addition, the precipitate after the reaction of the fluorine removal reaction tank is recovered, pressure filtration and calcination treatment are performed to obtain high-purity CaF2(99% content), thereby changing waste into treasure, and avoiding the adverse effects on the stainless steel production process caused by inaccurate addition during subsequent mixed treatment and recovery.

[0025] (2) Further, the stainless steel pickling wastewater treatment system separates the mixed acid pickling wastewater and the sulfuric acid pickling wastewater for treatment, and by arranging a plurality of pickling wastewater storage tanks, the production wastewater of different steel types is stored and treated in batches, so that the generated sludge is also treated in batches, and the content of the metal oxide obtained finally is similar to that of the steel type, which can be recycled and used as raw materials in the production process of the corresponding steel type, without causing any adverse effects on the product quality, thereby effectively solving the problem of the influence of product quality caused by the mixed wastewater discharge and mixed treatment; at the same time, the additional chemical reaction Ca(OH)2+H2SO4=CaSO4↓+2H2O in the mixed discharge and mixed treatment process is also avoided, thereby greatly reducing the addition amount of the slaked lime, avoiding the generation of CaSO4 precipitate, and further reducing the sludge amount.

[0026] (3) Further, the stainless steel pickling wastewater treatment system recycles the filtrate filtered by the first pressure filter to the first pH adjusting tank, recycles the filtrate filtered by the second pressure filter to the first collecting tank, and recycles the filtrate filtered by the third pressure filter to the second pH adjusting tank, thereby realizing the secondary recycling and utilization of the filtrate, and reducing pollution.

[0027] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be considered as a limitation to the scope. Other related drawings can also be obtained by those of ordinary skill in the art without any creative effort, on the premise of not paying any creative effort.

[0029] Figure 1 The figure is a structural schematic diagram of the stainless steel pickling wastewater treatment system of the present application.

[0030] Explanation of figure numbers:

[0031] 101 mixed acid pickling wastewater storage tank

[0032] 1011 first electric control valve

[0033] 102 first lifting pump

[0034] 103 first pH adjusting tank

[0035] 104 first concentration membrane device

[0036] 105 first sedimentation tank

[0037] 106 first collection tank

[0038] 107 defluorination reaction tank

[0039] 108 third sedimentation tank

[0040] 109 membrane separation device

[0041] 110 resin adsorption purification system

[0042] 111 first sludge storage tank

[0043] 112 first filter press

[0044] 113 first calcination furnace

[0045] 114 second sludge storage tank

[0046] 115 second filter press

[0047] 116 second calcination furnace

[0048] 201 sulfuric acid pickling wastewater storage tank

[0049] 2011 second electric control valve

[0050] 202 second lifting pump

[0051] 203 second pH adjusting tank

[0052] 204 second concentration membrane device

[0053] 205 second sedimentation tank

[0054] 206 second collection tank

[0055] 207 third sludge storage tank

[0056] 208 third filter press

[0057] 209 third calcination furnace

[0058] 300 clean water recovery treatment device DETAILED DESCRIPTION

[0059] For the purpose of facilitating the understanding of the present application, a stainless steel pickling wastewater treatment system will be described more fully below with reference to the accompanying drawings. The preferred embodiments of the stainless steel pickling wastewater treatment system are illustrated in the drawings. However, the stainless steel pickling wastewater treatment system can be realized in many different forms and should not be limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the stainless steel pickling wastewater treatment system to those skilled in the art.

[0060] In the description of the present application, it needs to be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0061] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0062] In the description of the present application, unless otherwise specified and limited, it is necessary to explain that the terms "mounting", "connection", "communication" should be understood in a broad sense, for example, it can be mechanical communication or electrical communication, it can be the communication inside two elements, it can be direct connection or indirect connection through intermediate medium, and the specific meaning of the above terms can be understood by those skilled in the art according to the specific circumstances.

[0063] Referring to Figure 1 The present application provides a stainless steel pickling wastewater treatment system, comprising a mixed acid pickling wastewater treatment system and a sulfuric acid pickling wastewater treatment system.

[0064] The mixed acid pickling wastewater treatment system comprises a first pH adjusting tank 103, a first concentration membrane device 104, a first collecting tank 106, a defluorination reaction tank 107 and a resin adsorption purification system 110 connected in sequence. The clean water outlet of the first concentration membrane device 104 is communicated with the first collecting tank 106, and the concentrated water outlet of the first concentration membrane device 104 is further communicated with a first sludge storage tank 111. The first sludge storage tank 111 is communicated with a first filter press 112, the sludge outlet of the first filter press 112 is communicated with a first calcining furnace 113, the defluorination reaction tank 107 is further communicated with a second sludge storage tank 114, the second sludge storage tank 114 is communicated with a second filter press 115, and the sludge outlet of the second filter press 115 is communicated with a second calcining furnace 116.

[0065] The sulfuric acid pickling wastewater treatment system comprises a second pH adjusting tank 203, a second concentration membrane device 204 and a second collecting tank 206 connected in sequence. The clean water outlet of the second concentration membrane device 204 is communicated with the second collecting tank 206, and the concentrated water outlet of the second concentration membrane device 204 is communicated with a third sludge storage tank 207, the third sludge storage tank 207 is communicated with a third filter press 208, and the sludge outlet of the third filter press 208 is communicated with a third calcining furnace 209.

[0066] The resin adsorption purification system 110 and the second collecting tank 206 are both communicated with a clean water recovery treatment device 300.

[0067] From the above description, the present application provides a stainless steel pickling wastewater treatment system which is integrated and modularized, and the whole system is automatically operated, safe and stable in operation, simple in operation and convenient in management. The mixed acid pickling wastewater and the sulfuric acid pickling wastewater are treated separately, so that they can be treated simultaneously or individually according to the actual production situation. Not only the environmental pollution is reduced, but also the wastewater is recycled, the problem of recycling of stainless steel pickling wastewater is solved, the effect of "comprehensive management" is realized, and the production cost of enterprises is reduced.

[0068] The first concentration membrane device 104 and the second concentration membrane device 204 can be listed as high-pressure reverse osmosis spiral membrane or high-pressure reverse osmosis disc membrane or vibration membrane or positive osmosis membrane. The first concentration membrane device 104 and the second concentration membrane device 204 can also be listed as nanofiltration membrane, ultrafiltration membrane, microfiltration membrane or general filter element, etc. In the concentration membrane device, the hydroxide precipitated particles in the concentrated water are further concentrated, gathered, thickened and increased by membrane separation, forming clear and turbid separation.

[0069] The fluoride removal reaction tank 107 reacts with the fluoride ions in the acid pickling wastewater by adding lime to generate CaF2 precipitate.

[0070] Further, the mixed acid pickling wastewater treatment system further comprises a plurality of mixed acid pickling wastewater storage tanks 101, each of the mixed acid pickling wastewater storage tanks 101 is communicated with the first pH adjusting tank 103 through a first lifting pump 102, and a first electric control valve 1011 is arranged at the outlet of each of the mixed acid pickling wastewater storage tanks 101; the sulfuric acid pickling wastewater treatment system further comprises a plurality of sulfuric acid pickling wastewater storage tanks 201, each of the sulfuric acid pickling wastewater storage tanks 201 is communicated with the second pH adjusting tank 203 through a second lifting pump 202, and a second electric control valve 2011 is arranged at the outlet of each of the sulfuric acid pickling wastewater storage tanks 201.

[0071] The term "several" can be understood as two, three, four or six, etc. The several mixed acid pickling wastewater storage tanks 101 or the several sulfuric acid pickling wastewater storage tanks 201 can be arranged in parallel discharge mode. For example, the stainless steel produced by the enterprise is divided into 200 series, 300 series and 400 series steel grades, and the wastewater produced by the three different steel grades is divided into A200 sulfuric acid pickling wastewater, A300 sulfuric acid pickling wastewater, A400 sulfuric acid pickling wastewater, B200 mixed acid pickling wastewater, B300 mixed acid pickling wastewater and B400 mixed acid pickling wastewater. Therefore, before the acid wastewater is treated, the pickling wastewater of different steel grades is classified and stored, that is, it includes B200 mixed acid pickling wastewater storage tank, B300 mixed acid pickling wastewater storage tank and B400 mixed acid pickling wastewater storage tank, and A200 sulfuric acid pickling wastewater storage tank, A300 sulfuric acid pickling wastewater storage tank and A400 sulfuric acid pickling wastewater storage tank. The application classifies and stores the pickling wastewater of different steel grades, controls the discharge of each pickling wastewater storage tank through the electric control valve, and processes the wastewater in batches, so that the subsequent sludge can also be classified and calcined. The content of the metal oxide obtained finally is similar to the content of the steel grade, which can be recycled and used as raw material in the production process of the corresponding steel grade, without causing any adverse effects on the product quality, effectively solving the problem of product quality affected by the subsequent sludge recycling caused by mixed wastewater discharge and mixed treatment. At the same time, the chemical reaction Ca(OH)2+H2SO4=CaSO4↓+2H2O caused by mixed discharge and mixed treatment is also avoided, so the amount of added lime Ca(OH)2 is greatly reduced, the generation of CaSO4 precipitate is avoided, and the amount of sludge generated is further reduced.

[0072] Preferably, in the embodiment of the application, the water outlet of the first filter press 112 is communicated with the first pH adjusting tank 103; and the water outlet of the third filter press 208 is communicated with the second pH adjusting tank 203.

[0073] Preferably, in the embodiment of the application, a first sedimentation tank 105 is arranged at the communication position of the first concentration membrane device 104 and the first sludge storage tank 111; the sludge outlet of the first sedimentation tank 105 is communicated with the first sludge storage tank 111, and the water outlet of the first sedimentation tank 105 is communicated with the first collection tank 106.

[0074] Preferably, in the embodiment of the application, a second sedimentation tank 205 is arranged at the communication position of the second concentration membrane device 204 and the third sludge storage tank 207; the sludge outlet of the second sedimentation tank 205 is communicated with the third sludge storage tank 207, and the water outlet of the second sedimentation tank 205 is communicated with the second collection tank 206.

[0075] Preferably, in this embodiment of the invention, a third sedimentation tank 108 is provided at the connection between the defluorination reaction tank 107 and the resin adsorption purification system 110. The outlet of the third sedimentation tank 108 is connected to the resin adsorption purification system 110, and the sludge outlet of the third sedimentation tank 108 is connected to the second sludge storage tank 114.

[0076] Preferably, in this embodiment of the invention, a membrane separation device 109 is provided at the connection between the third sedimentation tank 108 and the resin adsorption purification system 110, the outlet of the membrane separation device 109 is connected to the resin adsorption purification system 110, and the sludge outlet of the membrane separation device 109 is connected to the second sludge storage tank 114.

[0077] The membrane separation device 109 can be, for example, a reverse osmosis membrane, a microfiltration membrane, or an ultrafiltration membrane. Because the membrane pore size is very small, it can trap fine particles and other pollutants in the wastewater, further performing solid-liquid separation and wastewater purification. The solid matter obtained from membrane separation is transported from the sludge outlet of the membrane separation device 109 to the second sludge storage tank 114, while the purified water after membrane separation is directly discharged from the effluent outlet of the membrane separation device 109 to the next stage of processing. This achieves [the desired effect].

[0078] Preferably, in this embodiment of the invention, the outlet of the second filter press 115 is also connected to the first collection tank 106.

[0079] Preferably, in this embodiment of the invention, the resin adsorption purification system 110 includes a plurality of resin adsorption purification devices.

[0080] The resin adsorption purification system 110 utilizes the highly efficient and specific selective adsorption performance of defluorination resins (such as strongly basic anion exchange resins and chelating resins) for fluoride ions, thereby removing fluoride ions from the water. - With OH on the resin - An exchange occurs, F - Adsorbed by resin, OH - The wastewater is exchanged into the water, and through the exchange process, the effluent F is further reduced. - The purpose of the concentration is to meet higher and stricter standards for the recycling of pickling wastewater.

[0081] Preferably, in this embodiment of the invention, the resin adsorption purification system 110 is connected to the first collection tank 106 and the second collection tank 206 respectively.

[0082] like Figure 1 As shown, the process flow of the stainless steel pickling wastewater treatment system is as follows:

[0083] The mixed acid pickling wastewater in the pickling wastewater storage tank 101 is pumped into the first pH adjusting tank 103 by the first pump 102, and the pH value of the mixed acid pickling wastewater is adjusted to 10.5-11 by adding alkali (such as sodium hydroxide, etc.), and reacts with heavy metal ions (Cr 3+ , Fe 3+ and Ni 2+ , etc.) in the wastewater to form hydroxide precipitate; the pickling wastewater after pH adjustment is passed through the first concentration membrane device 104, so that the hydroxide precipitate particles are concentrated, gathered, thickened and increased, and clear and turbid separation is formed, and the supernatant obtained is directly discharged into the first collection tank 106, and the concentrated water enters the first sedimentation tank 105 for sedimentation to achieve solid-liquid separation, the supernatant in the first sedimentation tank 105 is discharged into the first collection tank 106, and the hydroxide sediment in the lower part is discharged into the first sludge storage tank 111, and when the amount of sludge in the first sludge storage tank 111 reaches a certain amount, it is pumped to the first filter press 112 by a sludge pump (not shown in the figure) for pressure filtration, and the mud cake produced is sent to the first calcining furnace 113 for high-temperature calcination to obtain metal oxide, and the filtrate is recovered to the first pH adjusting tank 103 for secondary treatment. The waste liquid in the first collection tank 106 is continuously lifted to the defluorination reaction tank 107, and after the pH is adjusted to about 8.0, calcium hydroxide Ca(OH)2 is added to react with fluoride ions in the wastewater to form CaF2 precipitate, which is then subjected to solid-liquid separation in the third sedimentation tank 108, and the precipitate in the sedimentation tank is discharged into the second sludge storage tank 114, and is pumped to the second filter press 115 by a sludge pump (not shown in the figure) for pressure filtration, and the mud cake produced is automatically sent to the second calcining furnace 116 for high-temperature calcination or is placed and then intermittently calcined to obtain high-purity CaF2 powder, and the filtrate is recovered to the first collection tank 106 for secondary treatment; the supernatant in the sedimentation tank is subjected to solid-liquid separation again by the membrane separation device 109. The filtrate separated by the membrane separation device 109 is discharged into the second sludge storage tank 114, and the filtrate is subjected to ion adsorption exchange in the resin adsorption purification system 110, and the purified water discharged from the resin adsorption purification system 110 is discharged into the second collection tank 206, and the generated resin regeneration wastewater is recovered to the first collection tank 106 for secondary treatment.

[0084] The pickling wastewater in the sulfuric acid pickling wastewater storage tank 201 is pumped into the second pH adjusting tank 203 by the second pump 202, and the pH value of the mixed acid pickling wastewater is adjusted to 10.5-11 by adding alkali (such as sodium hydroxide, etc.), and reacts with heavy metal ions (Cr 3+ , Fe 3+ and Ni 2+The hydroxide precipitate is formed by the reaction of the mixed acid and the sulfuric acid; the acid washing wastewater after pH adjustment is treated by the second concentration membrane device 204, and the supernatant is directly discharged into the second collecting tank 206, and the concentrated water is discharged into the second precipitation tank 205 to achieve solid-liquid separation; the supernatant in the second precipitation tank 205 is discharged into the second collecting tank 206, and the hydroxide precipitate at the bottom is discharged into the third sludge tank 207; when the amount of sludge in the third sludge tank 207 reaches a set amount, the sludge is pumped by a sludge pump (not shown in the figure) to the third filter press 208 for pressure filtration, and the generated mud cake is automatically sent into the third calcining furnace 209 for high-temperature calcination or is placed for intermittent calcination treatment to obtain metal oxide, and the filtrate is recovered to the second pH adjusting tank 203 for secondary treatment. The clean water collected in the second collecting tank 206 is discharged into the clean water recovery treatment device 300.

[0085] In summary, the stainless steel pickling wastewater treatment system of the present application has the following beneficial effects:

[0086] (1) In the process of treating stainless steel pickling wastewater by the stainless steel pickling wastewater treatment system of the present application, on the one hand, the amount of sludge generated and the moisture content of the sludge are greatly reduced, and the generated sludge is changed into recyclable material after calcination treatment, with 100% effective components and 0% waste material, which is 100% recycled for use in the production process of stainless steel, effectively reducing the sludge treatment cost and load, and solving the problem of resource waste; on the other hand, by adding a resin adsorption purification system after adding lime to remove fluorine in the defluorination reaction tank, the concentration of fluorine ions in the final effluent is greatly reduced by further adsorbing fluorine ions by the resin, and in addition, the precipitate after the reaction in the defluorination reaction tank is recovered, pressure filtered and calcined to obtain high-purity CaF2 (99% content), thereby changing waste into treasure and avoiding the adverse effects on the production process of stainless steel due to inaccurate addition during subsequent mixed treatment and recovery.

[0087] (2) Further, the stainless steel pickling wastewater treatment system of the present application separately treats mixed acid pickling wastewater and sulfuric acid pickling wastewater, and by providing a plurality of pickling wastewater storage tanks, the production wastewater of different steel types is stored and treated in batches, and the generated sludge is also treated in batches, so that the content of the components in the obtained metal oxide is similar to that of the steel type, which can be recycled and used as raw material in the production process of the corresponding steel type without causing any adverse effects on the product quality, effectively solving the problem of the influence of product quality caused by mixed wastewater discharge and mixed treatment; at the same time, the additional chemical reaction Ca(OH)2+H2SO4=CaSO4↓+2H2O is also avoided in the process of mixed discharge and mixed treatment, thereby greatly reducing the amount of added lime Ca(OH)2, avoiding the generation of CaSO4 precipitate, and further reducing the amount of sludge generated.

[0088] (3), further, the stainless steel pickling wastewater treatment system of the present application realizes the secondary recovery treatment and utilization of the filtrate by recycling the filtrate after being pressed by the first filter press to the first pH adjusting tank, recycling the filtrate after being pressed by the second filter press to the first collecting tank, recycling the filtrate after being pressed by the third filter press to the second pH adjusting tank, and reduces pollution.

[0089] Although the above more uses the terms of structure, for example, "pickling wastewater storage tank", "defluorination reaction tank", "resin adsorption purification system" and so on, but does not exclude the possibility of using other terms. Use these terms is only for more convenient description and explanation of the essence of the present application; they are interpreted as any kind of additional limitation is contrary to the spirit of the present application.

[0090] The above, only for the specific embodiments of the present application, but the scope of protection of the present application is not limited to this, any skilled in the art of the technical personnel in the technical range disclosed by the present application, can easily think of changes or replacement, should be covered in the scope of protection of the present application.

Claims

1. A stainless steel pickling wastewater treatment system, characterized in that, The system includes a mixed acid pickling wastewater treatment system and a sulfuric acid pickling wastewater treatment system, which are configured to treat wastewater separately. Wastewater from different steel grades is stored and treated in batches according to their classification, and the resulting sludge is treated separately. The mixed acid pickling wastewater treatment system includes a first pH adjustment tank, a first thickening membrane device, a first collection tank, a defluorination reaction tank, and a resin adsorption purification system connected in sequence. The sulfuric acid pickling wastewater treatment system includes a second pH adjustment tank, a second thickening membrane device, and a second collection tank connected in sequence. The mixed acid pickling wastewater treatment system includes several mixed acid pickling wastewater storage tanks. Each of the mixed acid pickling wastewater storage tanks is connected to the first pH adjustment tank through a first booster pump. Each of the mixed acid pickling wastewater storage tanks is equipped with a first electrically controlled valve at its outlet.

2. The stainless steel pickling wastewater treatment system according to claim 1, characterized in that, The clear water outlet of the first thickening membrane device is connected to the first collection tank, and the concentrated water outlet of the first thickening membrane device is also connected to the first sludge storage tank. The first sludge storage tank is connected to the first filter press, and the sludge outlet of the first filter press is connected to the first calcining furnace. The defluorination reaction tank is also connected to the second sludge storage tank, and the second sludge storage tank is connected to the second filter press. The sludge outlet of the second filter press is connected to the second calcining furnace.

3. The stainless steel pickling wastewater treatment system according to claim 1, characterized in that, The clear water outlet of the second thickening membrane device is connected to the second collection tank, the concentrated water outlet of the second thickening membrane device is connected to the third sludge storage tank, the third sludge storage tank is connected to the third filter press, and the sludge outlet of the third filter press is connected to the third calcining furnace; the resin adsorption purification system and the second collection tank are both connected to the clear water recovery and treatment device.

4. The stainless steel pickling wastewater treatment system according to claim 1, characterized in that, The sulfuric acid pickling wastewater treatment system includes several sulfuric acid pickling wastewater storage tanks. These tanks are connected to the second pH adjustment tank via a second booster pump. Each of the sulfuric acid pickling wastewater storage tanks is equipped with a second electrically controlled valve at its outlet.

5. The stainless steel pickling wastewater treatment system according to claim 2, characterized in that, The outlet of the first filter press is connected to the first pH adjustment tank, and the outlet of the second filter press is also connected to the first collection tank.

6. The stainless steel pickling wastewater treatment system according to claim 3, characterized in that, The outlet of the third filter press is connected to the second pH adjustment tank.

7. The stainless steel pickling wastewater treatment system according to claim 2, characterized in that, A first sedimentation tank is provided at the connection between the first thickening membrane device and the first sludge storage tank; the sludge outlet of the first sedimentation tank is connected to the first sludge storage tank, and the water outlet of the first sedimentation tank is connected to the first collection tank.

8. The stainless steel pickling wastewater treatment system according to claim 3, characterized in that, A second sedimentation tank is provided at the connection between the second thickening membrane device and the third sludge storage tank; the sludge outlet of the second sedimentation tank is connected to the third sludge storage tank, and the water outlet of the second sedimentation tank is connected to the second collection tank.

9. The stainless steel pickling wastewater treatment system according to claim 2, characterized in that, A third sedimentation tank is provided at the connection between the defluorination reaction tank and the resin adsorption purification system. The outlet of the third sedimentation tank is connected to the resin adsorption purification system, and the sludge outlet of the third sedimentation tank is connected to the second sludge storage tank.

10. The stainless steel pickling wastewater treatment system according to claim 9, characterized in that, A membrane separation device is installed at the connection between the outlet of the third sedimentation tank and the resin adsorption purification system; the outlet of the membrane separation device is connected to the resin adsorption purification system, and the sludge outlet of the membrane separation device is connected to the second sludge storage tank.

11. The stainless steel pickling wastewater treatment system according to claim 10, characterized in that, The solids obtained from membrane separation are transported from the sludge outlet of the membrane separation device to the second sludge storage tank, while the clean water after membrane separation is discharged directly from the outlet of the membrane separation device to the next process.

12. The stainless steel pickling wastewater treatment system according to claim 1, characterized in that, The resin adsorption purification system is connected to the first collection tank and the second collection tank respectively.

13. The processing method of the processing system according to any one of claims 1-12, characterized in that, The mixed acid pickling wastewater and the sulfuric acid pickling wastewater are treated separately. By setting up several pickling wastewater storage tanks, the production wastewater of different steel grades is classified, stored, and treated in batches. The sludge produced is also classified and treated. The final metal oxides have a composition content similar to that of the steel grade and are recycled separately.

14. The processing method of the processing system according to claim 13, characterized in that, The stainless steel pickling wastewater treatment system recovers the filtrate after filtration by the first filter press to the first pH adjustment tank, the filtrate after filtration by the second filter press to the first collection tank, and the filtrate after filtration by the third filter press to the second pH adjustment tank.

15. The processing method of the processing system according to claim 13, characterized in that, The acid pickling wastewater in the mixed acid pickling wastewater storage tank is pumped into the first pH adjustment tank. The pH value of the mixed acid pickling wastewater is adjusted to 10.5-11 by adding alkaline solution, which reacts with the heavy metal ions in the wastewater to form hydroxide precipitates.

16. The processing method of the processing system according to claim 15, characterized in that, The pH-adjusted pickling wastewater passes through a first thickening membrane device, causing the hydroxide precipitate particles to concentrate, aggregate, and increase in size, resulting in a clear-turbidity separation. The supernatant is directly discharged into a first collection tank, while the concentrated water enters a first sedimentation tank for sedimentation to achieve solid-liquid separation. The supernatant in the first sedimentation tank is discharged into the first collection tank, and the hydroxide sediment is discharged into a first sludge storage tank. When the amount of sludge in the first sludge storage tank reaches a set amount, it is pumped to a first filter press for filtration. The resulting sludge cake is sent to a first calcining furnace for high-temperature calcination to obtain metal oxides. The filtrate is recycled to a first pH adjustment tank for further secondary treatment.

17. The processing method of the processing system according to claim 16, characterized in that, The waste liquid in the first collection tank is further pumped to the defluorination reaction tank. After adjusting the pH to 8.0, quicklime is added to react with the fluoride ions in the wastewater to form CaF2 precipitate. Then, solid-liquid separation is performed in the third sedimentation tank. The precipitate in the sedimentation tank enters the second sludge storage tank and is pumped to the second filter press for filtration. The resulting sludge cake is automatically sent to the second calcining furnace for direct high-temperature calcination or intermittent calcination after being placed to obtain high-purity CaF2 powder. The filtrate is recycled to the first collection tank for secondary treatment.

18. The processing method of the processing system according to claim 17, characterized in that, The supernatant in the sedimentation tank undergoes solid-liquid separation again via a membrane separation device. The filtered material separated by the membrane separation device is discharged into the second sludge storage tank, while the filtrate enters the resin adsorption purification system for ion adsorption exchange. The purified water from the resin adsorption purification system is discharged into the second collection tank, while the resin regeneration wastewater generated is recycled to the first collection tank for further secondary treatment.

19. The processing method of the processing system according to claim 13, characterized in that, The acid pickling wastewater in the sulfuric acid pickling wastewater storage tank is pumped into the second pH adjustment tank by the second lift pump. The pH value of the mixed acid pickling wastewater is adjusted to 10.5-11 by adding alkali solution, which reacts with the heavy metal ions in the wastewater to form hydroxide precipitates. After the pH adjustment, the acid pickling wastewater is treated by the second thickening membrane device. The supernatant is directly discharged into the second collection tank, while the concentrated water enters the second sedimentation tank for sedimentation to achieve solid-liquid separation. The supernatant in the second sedimentation tank is discharged into the second collection tank, and the hydroxide sediment at the bottom is discharged into the third sludge storage tank. When the amount of sludge in the third sludge storage tank reaches the set amount, it is pumped to the third filter press for filtration. The resulting sludge cake is sent to the third calcination furnace for direct high-temperature calcination or intermittent calcination after being placed to obtain metal oxides. The filtrate is recycled to the second pH adjustment tank for secondary treatment, and the clear water collected in the second collection tank is discharged into the clear water recovery and treatment device.

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