Waste mixed acid treatment device in stainless steel pickling process

Abstract

The utility model discloses a waste mixed acid treatment device in a stainless steel pickling process, which comprises a pretreatment unit, a first-stage membrane unit, a second-stage membrane unit and a third-stage membrane unit, and the pretreatment unit is used for receiving and precipitating solid impurities in waste mixed acid; the first-stage membrane unit is used for filtering suspended particles in the waste mixed acid; the second-stage membrane unit comprises a first circulating tank and a first nanofiltration membrane system, the first circulating tank is communicated with the first-stage membrane tank, and the first nanofiltration membrane system is communicated with the first circulating tank; the third-stage membrane unit comprises a second circulating tank and a second nanofiltration membrane system, the second circulating tank is communicated with a first produced water discharge branch of the second nanofiltration membrane system, and the second nanofiltration membrane system is communicated with the second circulating tank. Metal ions in the waste mixed acid are filtered through the two stages of nanofiltration membranes, the waste mixed acid does not need to be additionally subjected to dosing treatment, the problem that mud cakes are generated due to dosing is avoided, the filtered waste mixed acid can serve as regenerated acid to be recycled, and the technical effect of recycling treatment of the waste mixed acid is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of stainless steel pickling, in particular to a waste mixed acid treatment device in the stainless steel pickling process. Background Art

[0002] During the smelting, hot rolling and heat treatment process, a layer of black iron oxide scale is easily formed on the surface of stainless steel. In order to obtain the ideal surface finish and brightness of stainless steel and extend its service life, it must be surface treated before drawing, passivation, electroplating and other processes. Pickling is an effective method to remove the scale. In order to ensure the dephosphorization effect of pickling, mixed acid is usually used for continuous pickling, such as 8%-20% HNO3 and 1%-5% HF.

[0003] As the pickling process progresses, metal oxides continue to dissolve and enter the pickling solution. The hydrogen ions in the original pickling solution are gradually replaced by metal salts, the acid concentration gradually decreases, and the metal salt concentration increases accordingly. As a result, the speed at which the pickling solution dissolves oxides gradually slows down, and it is necessary to continuously discharge the waste liquid and replenish new pickling liquid. This used waste liquid with poor pickling effect becomes waste mixed acid. Stainless steel pickling wastewater has the characteristics of high acidity (4-7 mol·L-1), strong toxicity (containing toxic pollutants such as nickel, chromium, and fluorine), large output (about 1.15m3·t-1), and difficulty in treatment (the use of conventional neutralization and precipitation technology not only consumes a large amount of reagents but also produces a large amount of hazardous waste, and the treatment and disposal costs are high), etc., which poses a huge threat to the environment and human health.

[0004] The treatment of a large amount of waste mixed acid generated during the production of stainless steel has always been a difficult problem for steel companies. As people's environmental awareness increases, they gradually realize that waste mixed acid has a huge potential for pollution to the environment, especially to soil and groundwater.

[0005] At present, the main research directions for treating waste mixed acid in the stainless steel pickling process at home and abroad include neutralization precipitation, evaporation, spray pyrolysis, electrolysis, solvent extraction, activated carbon adsorption, and ion exchange resin. Taking the most common neutralization precipitation method as an example, it is necessary to add a neutralizing agent to adjust the pH value first, which will produce a large amount of heavy metal sludge. The disposal cost of the sludge is high. There are a lot of salts and NO3- in the water after neutralization, which requires further desalination treatment; the acid, water, Fe, Cr, Ni, Cu and other metals in the waste liquid cannot be used, resulting in great waste. Therefore, it is necessary to design an easy-to-use device for treating waste mixed acid in the stainless steel pickling process. Utility Model Content

[0006] The embodiment of the present application provides a waste mixed acid treatment device in the stainless steel pickling process, which is used to solve the problem that the existing waste mixed acid needs to add reagents, produces mud cakes or produces waste liquid that is difficult to recycle.

[0007] The embodiment of the present application provides a waste mixed acid treatment device in a stainless steel pickling process, comprising: a pretreatment unit, a primary membrane unit, a secondary membrane unit, and a tertiary membrane unit;

[0008] The pre-processing unit comprises:

[0009] A sedimentation tank, used to receive and precipitate solid impurities in the waste mixed acid;

[0010] A first sewage discharge device, connected to the sedimentation tank, for discharging impurities;

[0011] The primary membrane unit comprises:

[0012] A primary membrane tank connected to the sedimentation tank and used to remove suspended particles in the waste mixed acid;

[0013] A second sewage discharge device, connected to the primary membrane pool, for discharging impurities;

[0014] The secondary membrane unit comprises:

[0015] A first circulation tank is connected to the primary membrane pool;

[0016] A first nanofiltration membrane system is connected to the first circulation tank, and the first nanofiltration membrane system includes: a first produced water discharge branch;

[0017] The three-stage membrane unit comprises:

[0018] A second circulation tank is connected to the first produced water discharge branch;

[0019] The second nanofiltration membrane system is connected to the second circulation tank, and the second nanofiltration membrane system includes: a second produced water discharge branch, and the second produced water discharge branch is used to discharge the regenerated acid.

[0020] The beneficial effect of the above embodiment is that the metal ions in the waste mixed acid are filtered through the two-stage nanofiltration membrane, and there is no need to additionally treat the waste mixed acid with drugs, thereby avoiding the problem of mud cake produced by adding drugs. The filtered waste mixed acid can be reused as regenerated acid, thereby achieving the technical effect of resource treatment of waste mixed acid.

[0021] Based on the above embodiments, the embodiments of the present application may also be improved as follows:

[0022] In one embodiment of the present application: the first sewage discharge device includes: a first mud pump, the first mud pump connects the sedimentation tank with the filter press; the second sewage discharge device includes: a second mud pump, the second mud pump connects the primary membrane tank with the filter press, and the discharge port of the filter press is connected with the primary membrane tank. The beneficial effect of this step: the solid impurities are compressed by the filter press, and the filtrate is returned to the primary membrane unit, thereby improving the recovery rate of the waste liquid.

[0023] In one embodiment of the present application: the primary membrane unit further comprises: an aeration pipe, the aeration pipe is connected to the primary membrane pool, and the aeration pipe is used to aerate and flush the filter membrane in the primary membrane pool. The beneficial effect of this step: flushing the filter membrane through the aeration pipe prevents the filter membrane from being blocked.

[0024] In one embodiment of the present application, it further comprises: a cooling unit, which is connected to the first circulation tank and is used to cool the waste mixed acid in the first circulation tank. The beneficial effect of this step is to prevent the rise of the feed liquid temperature from affecting the stability of the nanofiltration membrane.

[0025] In one embodiment of the present application: the secondary membrane unit further comprises: a first liquid level gauge, a first lifting pump, a first pressure sensor assembly, a first filter, and a first high-pressure pump, wherein the first liquid level gauge is installed in the first circulation tank, the first circulation tank is connected to the first nanofiltration membrane system through the first lifting pump, the first filter, and the first high-pressure pump, and the first pressure sensor assembly is connected to the pipeline of the secondary membrane unit. The beneficial effects of this step are: the action of the first lifting pump is controlled by the first liquid level gauge, and whether the first filter and the first nanofiltration membrane system are blocked is determined by the first pressure sensor assembly, and low-pressure protection and high-pressure protection are performed on the first high-pressure pump at the same time.

[0026] In one embodiment of the present application: the three-stage membrane unit also includes: a second liquid level gauge, a second lifting pump, a second pressure sensor assembly, a second filter, and a second high-pressure pump. The second liquid level gauge is installed in the second circulation tank. The second circulation tank is connected to the second nanofiltration membrane system through the second lifting pump, the second filter, and the second high-pressure pump. The second pressure sensor assembly is connected to the pipeline of the three-stage membrane unit. The beneficial effects of this step are: the action of the second lifting pump is controlled by the second liquid level gauge, and the second filter and the second nanofiltration membrane system are judged by the second pressure sensor assembly whether they are blocked, and the second high-pressure pump is protected by low pressure and high pressure.

[0027] In one of the embodiments of the present application: the secondary membrane unit also includes: a first concentrated water reflux branch, connecting the concentrated water outlet of the first nanofiltration membrane system with the first circulation tank; a first concentrated water quick discharge branch, connecting the concentrated water outlet of the first nanofiltration membrane system with the first circulation tank; a first concentrated water external discharge branch, connecting the concentrated water outlet of the first nanofiltration membrane system with the mixed acid regeneration system. The beneficial effects of this step: the recovery rate of the waste mixed acid is improved through the first concentrated water reflux branch, the system's quick discharge pressure is released through the first concentrated water quick discharge branch, the concentrated water is sent out for harmless treatment through the first concentrated water external discharge branch, the produced water is sent to the tertiary membrane system for further filtration through the first produced water external discharge branch, and the waste mixed acid is further filtered, thereby realizing the recycling of the waste mixed acid.

[0028] In one embodiment of the present application: the three-stage membrane unit also includes: a second brine reflux branch, connecting the brine outlet of the second nanofiltration membrane system with the second circulation tank; a second brine quick discharge branch, connecting the brine outlet of the second nanofiltration membrane system with the second circulation tank; a second brine external discharge branch, connecting the brine outlet of the second nanofiltration membrane system with the first circulation tank. The beneficial effects of this step: the recovery rate of the waste mixed acid is improved through the second brine reflux branch, the system is quickly depressurized through the second brine quick discharge branch, and the brine is sent back to the secondary membrane system for further filtration through the second brine external discharge branch, thereby improving the recovery rate of the waste mixed acid, and the recycling of the regenerated acid is achieved through the second produced water external discharge branch. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation of the utility model or the technical solution in the prior art, the following is a brief introduction to the drawings required for the specific implementation or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0030] Figure 1 It is a structural schematic diagram of a waste mixed acid treatment device in the stainless steel pickling process;

[0031] Figure 2 It is a structural schematic diagram of a pre-processing unit;

[0032] Figure 3 It is the structural schematic diagram of the primary membrane unit;

[0033] Figure 4 It is the structural schematic diagram of the secondary membrane unit;

[0034] Figure 5 It is a schematic diagram of the structure of the three-stage membrane unit;

[0035] Figure 6 It is a structural schematic diagram of the cooling unit.

[0036] Among them, 1 pretreatment unit, 101 sedimentation tank, 102 first sewage discharge device, 103 water inlet electromagnetic flow meter;

[0037] 2 primary membrane unit, 201 primary membrane tank, 202 second sewage discharge device, 203 filter membrane, 204 aeration pipe, 205 membrane tank liquid level gauge, 206 suction pump;

[0038] 3 secondary membrane unit, 301 first circulation tank, 302 first nanofiltration membrane system, 303 first produced water discharge branch, 304 first liquid level meter, 305 first lift pump, 306 first filter, 307 first high-pressure pump, 308 first pressure sensor a, 309 first pressure sensor b, 310 first pressure sensor c, 311 first pressure sensor d, 312 first concentrated water reflux branch, 313 first concentrated water fast discharge branch, 314 first concentrated water discharge branch, 315 first stop valve, 316 first rotor flowmeter, 317 first concentrated water electromagnetic flowmeter, 318 first electric valve;

[0039] 4 tertiary membrane unit, 401 second circulation tank, 402 second nanofiltration membrane system, 403 second produced water discharge branch, 404 second liquid level meter, 405 second lift pump, 406 second filter, 407 second high-pressure pump, 408 second concentrated water reflux branch, 409 second concentrated water fast discharge branch, 410 second concentrated water discharge branch, 411 second stop valve, 412 second produced water electromagnetic flowmeter, 413 second rotor flowmeter, 414 second electric valve;

[0040] 5 cooling unit, 501 heat exchanger, 502 heat exchange circulation pump. DETAILED DESCRIPTION

[0041] In this application, unless otherwise clearly specified and limited, the terms in this application should be understood in a broad sense, such as connection can be fixed connection, detachable connection or integration, direct connection, or indirect connection through an intermediate medium; if it involves the electrical field, it can also be electrical connection or communication signal connection, etc. For ordinary technicians in this field, the specific meanings of different terms in this utility model can be understood according to specific circumstances, and the scope of the specific meaning should be limited to realizing the functions of this application.

[0042] like Figure 1-6As shown, a treatment device for waste mixed acid of stainless steel pickling includes: a pretreatment unit 1, a primary membrane unit 2, a secondary membrane unit 3, and a tertiary membrane unit 4. The pretreatment unit 1 includes: a sedimentation tank 101, a first sewage discharge device 102, the sedimentation tank 101 is used to receive and precipitate solid impurities in the waste mixed acid, the first sewage discharge device 102 is connected to the sedimentation tank 101, and is used to discharge impurities; the primary membrane unit 2 includes: a primary membrane pool 201, a second sewage discharge device 202, the primary membrane pool 201 is connected to the sedimentation tank 101, and is used to pass the suspended particles in the waste mixed acid, the second sewage discharge device 202 is connected to the primary membrane pool 201, and is used to discharge impurities; the secondary membrane unit 3 includes: a first circulation tank 301, a first nanofiltration membrane system 3 02, the first circulation tank 301 is connected to the primary membrane pool 201, the first nanofiltration membrane system 302 is connected to the first circulation tank 301, the first nanofiltration membrane system 302 includes: a first produced water discharge branch 303; the tertiary membrane unit 4 includes: a second circulation tank 401, a second nanofiltration membrane system 402, the second circulation tank 401 is connected to the first produced water discharge branch 303, the second nanofiltration membrane system 402 is connected to the second circulation tank 401, the second nanofiltration membrane system 402 includes: a second produced water discharge branch 403, and the second produced water discharge branch 403 is used to discharge the regenerated acid.

[0043] Specifically, Figure 2 As shown, the sedimentation tank 101 is equipped with an inlet electromagnetic flowmeter 103, and the inlet electromagnetic flowmeter 103 is used to measure the total inlet water volume.

[0044] Specifically, Figure 2 , 3 As shown, the first sewage discharge device 102 includes: a first sludge pump, which connects the sedimentation tank 101 with the filter press; the second sewage discharge device 202 includes: a second sludge pump, which connects the primary membrane tank 201 with the filter press, and the discharge port of the filter press is connected to the primary membrane tank 201. The first sludge pump and the second sludge pump are used to regularly extract impurities from the bottom of the tank and transport them to the filter press for filtration, recover the filter residue, and return the filtrate to the primary membrane tank 201. The solid impurities are compressed by the filter press, and the filtrate is returned to the primary membrane unit 2, so as to improve the recovery rate of the waste liquid.

[0045] Specifically, Figure 3 As shown, a filter membrane 203 is disposed in the primary membrane pool 201. In this embodiment, the filter membrane 203 adopts an acid-resistant MBR membrane component, but is not limited to the acid-resistant MBR membrane component. Tubular microfiltration membranes, tubular ultrafiltration membranes, etc. can also be used. The MBR membrane component is connected to the primary membrane pool 201 through a UPVC bracket.

[0046] Specifically, Figure 3As shown, the primary membrane unit 2 further includes: an aeration pipe 204, the aeration pipe 204 is connected to the primary membrane pool 201, one end of the aeration pipe 204 is communicated with the inner side of the MBR membrane assembly, the aeration pipe 204 is externally connected to an aeration device, and the aeration pipe 204 is used to aerate and flush the filter membrane 203 in the primary membrane pool 201. Compressed air is introduced into the aeration pipe 204 to form stirring, and at the same time, the surface of the MBR membrane assembly is flushed to prevent mud residue from accumulating on the membrane surface and clogging the membrane.

[0047] Specifically, Figure 3 As shown, the first-level membrane pool 201 is equipped with a membrane pool level meter 205 for measuring the liquid level in the first-level membrane pool 201 . The water production end of the MBR membrane assembly is connected to a suction pump 206 through a pipeline. A pressure sensor is installed at the inlet of the suction pump 206 . The membrane pool level meter 205 controls the start and stop of the suction pump 206 .

[0048] Specifically, Figure 6 As shown, the treatment device for waste mixed acid from stainless steel pickling further includes: a cooling unit 5 , which is connected to the first circulation tank 301 and is used to cool the waste mixed acid in the first circulation tank 301 .

[0049] Specifically, during the operation of the system, due to the continuous increase in acid concentration, under high-pressure operation, the temperature of the feed liquid in the first circulation tank 301 will continue to accumulate and rise. When the temperature is higher than a certain range (40°C), it will affect the treatment effect and life of the nanofiltration membrane. Therefore, a cooling unit 5 is provided to cool the feed liquid.

[0050] Specifically, Figure 6 As shown, the cooling unit 5 is configured with a heat exchanger 501 and a heat exchange circulation pump 502. The heat exchanger 501 adopts a graphite shell and tube heat exchanger 501. The heat exchange circulation pump 502 connects the heat exchanger 501 with the first circulation tank 301. The heat exchanger 501 is connected to the cooling tower through a cooling water circulation pump, and the refrigerant is circulated between the heat exchangers 501 in the cooling tower through the cooling water circulation pump.

[0051] Specifically, Figure 4As shown, the secondary membrane unit 3 further includes: a first liquid level gauge 304, a first lifting pump 305, a first pressure sensor assembly, a first filter 306, and a first high-pressure pump 307. The first liquid level gauge 304 is installed in the first circulation tank 301. The first circulation tank 301 is connected to the first nanofiltration membrane system 302 through the first lifting pump 305, the first filter 306, and the first high-pressure pump 307. The first pressure sensor assembly is connected to the pipeline of the secondary membrane unit 3. The start and stop of the first lifting pump 305 is controlled by the first liquid level gauge 304. The first liquid level gauge 304 also controls the action of the suction pump 206 together with the membrane pool liquid level gauge 205, that is, the suction pump 206 can only be started when the set conditions of the first liquid level gauge 304 and the membrane pool liquid level gauge 205 are met. The first pressure sensor assembly is used to determine whether the first filter 306 and the first nanofiltration membrane system 302 are blocked, and the first high-pressure pump 307 is protected by low pressure and high pressure.

[0052] Specifically, Figure 4 As shown, the first pressure sensor assembly includes: a first pressure sensor a308, a first pressure sensor b309, a first pressure sensor c310, and a first pressure sensor d311. The first pressure sensor a308 is located at the liquid inlet of the first filter 306, the first pressure sensor b309 is located between the liquid outlet of the first filter 306 and the liquid inlet of the first high-pressure pump 307, the first pressure sensor c310 is located between the liquid outlet of the first high-pressure pump 307 and the liquid inlet of the first nanofiltration membrane system 302, and the first pressure sensor d311 is located at the concentrated water outlet of the first nanofiltration membrane system 302.

[0053] Specifically, Figure 4 As shown, the first high-pressure pump 307 adopts a high-pressure plunger pump. The first high-pressure pump 307 needs to meet the conditions of the first pressure sensor b309 and the first pressure sensor c310 when it is started; the first pressure sensor a308 and the first pressure sensor b309 monitor the changes in the inlet and outlet pressures of the first filter 306, and judge the fouling condition of the first filter 306 so as to replace the filter element in time; at the same time, the first pressure sensor b309 serves as a low-pressure protection for the first high-pressure pump 307, and the pressure of the first pressure sensor b309 needs to reach a certain range to allow the first high-pressure pump 307 to start; the first pressure sensor c310 and the first pressure sensor d311 monitor the inlet and outlet pressures of the first membrane system, and judge the fouling condition of the membrane so as to find problems in time and clean or replace it in time; at the same time, the first pressure sensor c310 serves as a high-pressure protection for the first high-pressure pump 307, and the first high-pressure pump 307 stops when the pressure of the first pressure sensor d311 is higher than the set range.

[0054] Specifically, Figure 5As shown, the tertiary membrane unit 4 further includes: a second liquid level gauge 404, a second lifting pump 405, a second pressure sensor assembly, a second filter 406, and a second high-pressure pump 407. The second liquid level gauge 404 is installed in the second circulation tank 401. The second circulation tank 401 is connected to the second nanofiltration membrane system 402 through the second lifting pump 405, the second filter 406, and the second high-pressure pump 407. The second pressure sensor assembly is connected to the pipeline of the tertiary membrane unit 4. The action of the second lifting pump 405 is controlled by the second liquid level gauge 404, and whether the second filter 406 and the second nanofiltration membrane system 402 are blocked is determined by the second pressure sensor assembly, and the second high-pressure pump 407 is protected by low pressure and high pressure.

[0055] Specifically, Figure 5 As shown, the arrangement of the second pressure sensor assembly in the tertiary membrane unit 4 is the same as the arrangement of the first pressure sensor assembly in the secondary membrane unit 3, and the functions are also the same.

[0056] Specifically, Figure 4 As shown, the secondary membrane unit 3 further includes: a first concentrated water return branch 312, a first concentrated water quick discharge branch 313, and a first concentrated water external discharge branch 314. The first concentrated water return branch 312 connects the concentrated water outlet of the first nanofiltration membrane system 302 with the first circulation tank 301, and the first concentrated water quick discharge branch 313 connects the concentrated water outlet of the first nanofiltration membrane system 302 with the first circulation tank 301, and connects the concentrated water outlet of the first nanofiltration membrane system 302 with the mixed acid regeneration system. The recovery rate of the regenerated acid is improved through the first concentrated water return branch 312, and the system is quickly discharged and depressurized through the first concentrated water quick discharge branch 313. The concentrated water is sent to the mixed acid regeneration system for treatment through the first concentrated water external discharge branch 314, and the mixed acid regeneration system adopts an APU treatment system.

[0057] Specifically, Figure 4 As shown, the first concentrated water return branch 312 and the first concentrated water discharge branch 314 adjust the system pressure through the first stop valve 315 to control the operating pressure of the first nanofiltration membrane system 302. The first concentrated water return branch 312 and the first concentrated water discharge branch 314 are both equipped with a first rotor flowmeter 316. The first concentrated water discharge branch 314 is equipped with a first concentrated water electromagnetic flowmeter 317 for counting the concentrated water discharge volume. The first concentrated water quick discharge branch 313 is controlled to start and stop by the first electric valve 318. The first electric valve 318 is opened and closed at a fixed time. When the first electric valve 318 is opened, the system quickly discharges the pressure. At the same time, the first high-pressure pump 307 is reduced in frequency to achieve the purpose of regularly flushing the nanofiltration membrane, prevent the accumulation of metal ions on the membrane surface to form fouling, and ensure the membrane water production.

[0058] Specifically, Figure 5As shown, the three-stage membrane unit 4 also includes: a second concentrated water return branch 408, a second concentrated water quick discharge branch 409, and a second concentrated water external discharge branch 410. The second concentrated water return branch 408 connects the concentrated water outlet of the second nanofiltration membrane system 402 with the second circulation tank 401, the second concentrated water quick discharge branch 409 connects the concentrated water outlet of the second nanofiltration membrane system 402 with the second circulation tank 401, and the second concentrated water external discharge branch 410 connects the concentrated water outlet of the second nanofiltration membrane system 402 with the first circulation tank 301. The second concentrated water return branch 408 improves the recovery rate of the regenerated acid, the second concentrated water quick discharge branch 409 realizes the quick discharge pressure relief of the system, and the concentrated water is circulated into the first circulation tank 301 through the second concentrated water external discharge branch 410, thereby improving the recovery rate of the regenerated acid.

[0059] Specifically, Figure 5 As shown, the second concentrated water return branch 408 and the second concentrated water discharge branch 410 adjust the system pressure through the second stop valve 411 to control the operating pressure of the second nanofiltration membrane system 402. The second produced water discharge branch 403 is also equipped with a second produced water electromagnetic flowmeter 412 for counting the discharged water production. The second concentrated water return branch 408 and the second concentrated water discharge branch 410 are both equipped with a second rotor flowmeter 413. The second concentrated water quick discharge branch 409 is controlled to start and stop by the second electric valve 414. The second electric valve 414 is opened and closed at a fixed time. When the second electric valve 414 is opened, the system quickly discharges the pressure. At the same time, the second high-pressure pump 407 is reduced in frequency to achieve the purpose of regularly flushing the nanofiltration membrane, prevent the accumulation of metal ions on the membrane surface to form fouling, and ensure the membrane water production.

[0060] The working process of the treatment device for the waste mixed acid from stainless steel pickling is as follows:

[0061] The waste mixed acid discharged from the workshop enters the sedimentation tank 101, where it stays for a certain period of time. Impurities and large particles of oxide scale in the waste mixed acid are precipitated to the bottom of the tank and are pumped to the filter press by the first mud pump for filtration. The filter residue is collected and recovered, and the filtrate enters the primary membrane system; the supernatant in the sedimentation tank 101 flows into the primary membrane system by gravity. In the primary membrane system, the waste mixed acid is filtered through the MBR membrane assembly to produce water to the secondary membrane system through the action of the suction pump 206, and the insoluble matter such as SS in the waste mixed acid is retained in the primary membrane tank 201. After a certain period of time, it is pumped to the filter press by the second mud pump for filtration treatment; the waste mixed acid in the first circulation tank 301 is transported to the first large flow filter by the first lifting pump 305 for precision filtration again After filtering (filtration pore size 5um), the material enters the first high-pressure pump 307, and after being pressurized by the first high-pressure pump 307, it enters the first nanofiltration membrane system 302; after passing through the nanofiltration membrane, the produced water (clean water) enters the second circulation tank 401, and part of the concentrated water returns to the first circulation tank 301, and part is discharged and collected; the material in the second circulation tank 401 is transported by the second booster pump 405 into the second filter 406 for further precision filtration (filtration pore size 5um), and after being pressurized by the second high-pressure pump 407, it enters the second nanofiltration membrane system 402, and after nanofiltration, the produced water is measured by the second produced water electromagnetic flowmeter 412 and then collected for reuse, and the concentrated water enters the second circulation tank 401 for circulation after distribution, and part is discharged back to the first circulation tank 301.

[0062] This solution is to use physical processes to concentrate the waste mixed acid and filter it using the characteristics of various membranes. The metal ions are enriched and concentrated, the free acid in the waste mixed acid is selectively permeated, and the resources in the waste mixed acid are recovered. No reagents are added during the treatment process, and no secondary sludge is generated. The treatment process is purely physical and does not cause the volume of the material to expand. The treatment device can be used as a supporting device for the APU system. The device has low operating costs, simple operation, high degree of automation, small footprint, high metal ion removal rate, and high acid recovery rate.

[0063] The above are only embodiments of the utility model. The common sense such as the known specific structures and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field are aware of all the common technical knowledge in the technical field to which the utility model belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement the scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for the ordinary technicians in the relevant field to implement this application. It should be pointed out that for the technicians in this field, without departing from the structure of the utility model, several deformations and improvements can be made, which should also be regarded as the protection scope of the utility model, and these will not affect the effect of the implementation of the utility model and the practicality of the patent.

Claims

1. A device for treating waste mixed acid in the process of stainless steel pickling, characterized in that: include: Pretreatment unit, primary membrane unit, secondary membrane unit, tertiary membrane unit; The pre-processing unit comprises: A sedimentation tank, used to receive and precipitate solid impurities in the waste mixed acid; A first sewage discharge device, connected to the sedimentation tank, for discharging impurities; The primary membrane unit comprises: A primary membrane tank connected to the sedimentation tank and used to remove suspended particles in the waste mixed acid; A second sewage discharge device, connected to the primary membrane pool, for discharging impurities; The secondary membrane unit comprises: A first circulation tank is connected to the primary membrane pool; A first nanofiltration membrane system is connected to the first circulation tank, and the first nanofiltration membrane system includes: a first produced water discharge branch; The three-stage membrane unit comprises: A second circulation tank is connected to the first produced water discharge branch; The second nanofiltration membrane system is connected to the second circulation tank, and the second nanofiltration membrane system includes: a second produced water discharge branch, and the second produced water discharge branch is used to discharge the regenerated acid.

2. The device for treating waste mixed acid in the stainless steel pickling process according to claim 1, characterized in that: The first sewage discharge device comprises: a first sludge pump, the first sludge pump connects the sedimentation tank with the filter press; The second sewage discharge device includes: a second sludge pump, the second sludge pump connects the primary membrane pool with the above-mentioned filter press, and the discharge port of the filter press is connected with the primary membrane pool.

3. The device for treating waste mixed acid in the stainless steel pickling process according to claim 1, characterized in that: The primary membrane unit further comprises: an aeration pipe, which is connected to the primary membrane pool and is used for aeration and flushing of the filter membrane in the primary membrane pool.

4. The device for treating waste mixed acid in the stainless steel pickling process according to claim 1, characterized in that: Also includes: A cooling unit is connected to the first circulation tank and is used to cool the waste mixed acid in the first circulation tank.

5. The device for treating waste mixed acid in the stainless steel pickling process according to claim 1, characterized in that: The secondary membrane unit also includes: a first liquid level gauge, a first lifting pump, a first pressure sensor assembly, a first filter, and a first high-pressure pump. The first liquid level gauge is installed in the first circulation tank. The first circulation tank is connected to the first nanofiltration membrane system through the first lifting pump, the first filter, and the first high-pressure pump. The first pressure sensor assembly is connected to the pipeline of the secondary membrane unit.

6. The device for treating waste mixed acid in the stainless steel pickling process according to claim 1, characterized in that: The three-stage membrane unit also includes: a second liquid level gauge, a second lifting pump, a second pressure sensor assembly, a second filter, and a second high-pressure pump. The second liquid level gauge is installed in the second circulation tank. The second circulation tank is connected to the second nanofiltration membrane system through the second lifting pump, the second filter, and the second high-pressure pump. The second pressure sensor assembly is connected to the pipeline of the three-stage membrane unit.

7. The device for treating waste mixed acid in the stainless steel pickling process according to claim 1, characterized in that: The secondary membrane unit also includes: a first concentrated water reflux branch, connecting the concentrated water outlet of the first nanofiltration membrane system with the first circulation tank; A first concentrated water quick discharge branch, connecting the concentrated water outlet of the first nanofiltration membrane system with the first circulation tank; The first concentrated water discharge branch connects the concentrated water outlet of the first nanofiltration membrane system to the mixed acid regeneration system.

8. The device for treating waste mixed acid in the stainless steel pickling process according to claim 7, characterized in that: The three-stage membrane unit also includes: A second concentrated water reflux branch, connecting the concentrated water outlet of the second nanofiltration membrane system with the second circulation tank; A second concentrated water quick discharge branch connects the concentrated water outlet of the second nanofiltration membrane system with the second circulation tank; The second concentrated water discharge branch connects the concentrated water outlet of the second nanofiltration membrane system with the first circulation tank.

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