A treatment method and device for synchronously resourceizing stainless steel pickling wastewater and waste gas

Abstract

The present invention discloses a treatment method and device for the synchronous resource utilization of stainless steel pickling wastewater and waste gas. The treatment method comprises the following steps: Step 1, wastewater pretreatment to obtain a first soluble salt solution; Step 2, waste gas pretreatment to obtain a second soluble salt solution; Step 3, mixing the first soluble salt solution and the second soluble salt solution to obtain high-salt wastewater, and introducing the high-salt solution into a bipolar membrane system for treatment to prepare a recovered alkali solution and a recovered acid solution. The recovered alkali solution is recycled in Step 1 and Step 2, and the recovered acid solution is used for the front-end stainless steel pickling process. The treatment method of the present invention can simultaneously treat wastewater and waste gas in the stainless steel cleaning process. The generated alkali can be used for the pretreatment of wastewater and waste gas and the electrode solution of the bipolar membrane, and the mixed acid can be used for the pre-treatment process of stainless steel in the early stage, realizing the simultaneous resource utilization treatment of wastewater and waste gas.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel cleaning waste treatment, and particularly to a treatment method and device for synchronously resourceifying stainless steel pickling wastewater and waste gas. Background Art

[0002] In order to achieve a smooth surface and corrosion resistance for stainless steel products, after first using sulfuric acid or a sulfuric acid - hydrofluoric acid mixed acid to clean and remove the black oxide scale, nitric acid is then used for a second cleaning to form an oxide film on the stainless steel surface and increase the surface smoothness. This processing process generates a large amount of cleaning wastewater. The cleaning wastewater contains nitric acid, sulfuric acid, hydrochloric acid, and hydrofluoric acid, and the main metal ions are iron, nickel, and chromium ions. At the same time, during the cleaning process, the reaction between the acid and surface oxides such as iron and the metal matrix is an exothermic reaction, forming local high - temperature areas on the metal surface. At high temperatures, a large amount of acid is volatilized to form acid mist, and the acid mist mainly consists of nitrogen oxides, hydrogen fluoride, sulfuric acid mist, and hydrogen chloride.

[0003] In the prior art, mainly the cleaning wastewater is treated while ignoring the waste gas. The continuous emission of these untreated waste gases causes environmental pollution. For example, in the prior art, patent CN218755115U discloses a stainless steel pickling waste liquid treatment device, and patent CN105776385B discloses a stainless steel waste liquid regeneration system based on spray roasting method and its control method. Therefore, how to synchronously resourceify the wastewater and waste gas in this process is a problem that needs to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a treatment method for synchronously resourceifying stainless steel pickling wastewater and waste gas in view of the ineffective treatment of waste gas during the stainless steel pickling process in the prior art.

[0005] Another object of the present invention is to provide a process device based on the above - mentioned treatment method.

[0006] The technical solution adopted to achieve the purpose of the present invention is as follows:

[0007] A treatment method for synchronously resourceifying stainless steel pickling wastewater and waste gas includes the following steps:

[0008] Step 1, wastewater pretreatment: Use an alkali solution to remove heavy metal ions from the wastewater to obtain a first soluble salt solution;

[0009] Step 2, waste gas pretreatment: Adopt the method of membrane absorption to absorb and treat the waste gas to be treated to obtain a second soluble salt solution;

[0010] Step 3: Mix the first soluble salt solution and the second soluble salt solution to obtain high-salt wastewater. The high-salt solution is fed into a bipolar membrane system for treatment to prepare a recovered alkali solution and a recovered acid solution. The recovered alkali solution is recycled in Steps 1 and 2, and the recovered acid solution is used for the front-end stainless steel pickling process.

[0011] In the above technical solution, the heavy metal ions are removed by the following method:

[0012] The wastewater is neutralized with an alkali, and at the same time, sufficient reaction is carried out through mechanical mixing. After adjusting the pH>7, filtration and precipitation are carried out to obtain the first soluble salt solution.

[0013] In the above technical solution, in Step 2, the waste gas is collected by induced air collection, and the waste gas capture rate is not less than 95%.

[0014] In the above technical solution, the membrane absorption in Step 2 is carried out by the following method: The waste gas to be treated at a pressure of 0-150 kPa and the absorption liquid at a pressure of 0-150 kPa are subjected to membrane absorption treatment according to a gas-liquid flow ratio of 5:1 to 500:1.

[0015] In the above technical solution, the absorption liquid for the membrane absorption is NaOH, and the flow rate of the absorption liquid is 0.5-5 m 3 / h.

[0016] In the above technical solution, the current density of the bipolar membrane system is 200-900 A / m 2 , and the salt concentration of the high-salt wastewater is 10-15 wt%.

[0017] In the above technical solution, the solute of the electrode solution of the bipolar membrane system is NaOH, NaSO4 or NaCl, preferably NaOH, and the concentration of the electrode solution of the bipolar membrane system is 2-4 wt%.

[0018] In the above technical solution, the concentrations of the acid solution in the initial acid pool and the alkali solution in the initial alkali pool of the bipolar membrane system are both 0-0.1 mol / L. The concentration of hydroxide ions in the recovered alkali solution is 1.2-2.0 mol / L, and the concentration of hydrogen ions in the recovered acid solution is 1.0-1.5 mol / L.

[0019] On the other hand, the present invention provides a device for the above treatment method, including a wastewater treatment unit, a membrane absorption unit, and a bipolar membrane unit. The wastewater treatment unit includes a reaction tank, a sedimentation tank, and a sludge thickening tank connected by pipelines. The outlet pipelines of the sedimentation tank and the membrane absorption unit are connected to the inlet of the bipolar membrane device together. The alkali outlet of the bipolar membrane device is connected to the reaction tank and the membrane absorption unit respectively, and the sediment in the sedimentation tank enters the sludge thickening tank for treatment.

[0020] In the above technical solution, the membrane absorption unit includes a membrane absorption device, an absorption liquid storage tank, and a circulation pump. The liquid outlet of the absorption liquid storage tank is connected to the liquid inlet of the circulation pump. The liquid outlet of the circulation pump is connected to the lye inlet of the membrane absorption device. The liquid outlet of the membrane absorption device is connected to the circulating liquid inlet of the absorption liquid storage tank. The liquid outlet of the alkali tank of the bipolar membrane unit is connected to the alkali inlet of the absorption liquid storage tank;

[0021] The bipolar membrane unit includes a bipolar membrane device, a salt circulation module, an alkali circulation module, an acid circulation module, and a bipolar liquid circulation module;

[0022] The salt circulation module includes an intermediate water tank, a salt circulation pump, a salt heat exchanger, and a salt filter connected in sequence through pipelines. The liquid outlet of the salt filter is connected to the salt inlet of the bipolar membrane device. The salt outlet of the bipolar membrane device is connected to the liquid inlet of the intermediate water tank. The liquid outlets of the sedimentation tank and the circulating liquid storage tank are respectively connected to the liquid inlet of the intermediate water tank;

[0023] The alkali circulation module includes an alkali tank, an alkali circulation pump, an alkali heat exchanger, and an alkali filter connected in sequence through pipelines. The liquid outlet of the alkali filter is connected to the alkali inlet of the bipolar membrane device. The alkali outlet of the bipolar membrane device is connected to the liquid inlet of the alkali tank. The liquid outlet of the alkali tank is respectively connected to the alkali inlet of the absorption liquid storage tank and the alkali inlet of the reaction tank;

[0024] The acid circulation module includes an acid tank, an acid circulation pump, an acid heat exchanger, and an acid filter connected in sequence through pipelines. The liquid outlet of the acid filter is connected to the acid inlet of the bipolar membrane device. The acid outlet of the bipolar membrane device is connected to the liquid inlet of the acid tank;

[0025] The bipolar liquid circulation module is connected in sequence through pipelines with a bipolar liquid tank, a bipolar liquid circulation pump, a bipolar liquid heat exchanger, and a bipolar liquid filter. The liquid outlet of the bipolar liquid filter is connected to the bipolar liquid inlet of the bipolar membrane device. The bipolar liquid outlet of the bipolar membrane device is connected to the liquid inlet of the bipolar liquid tank.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The treatment method of the present invention can simultaneously treat wastewater and waste gas in the stainless steel cleaning process. The generated alkali can be used for the pretreatment of wastewater and waste gas and the bipolar liquid of the bipolar membrane. The mixed acid can be used in the preliminary stainless steel pretreatment process, realizing the simultaneous resource treatment of wastewater and waste gas.

[0028] 2. The treatment device of the present invention can achieve an exhaust gas treatment capacity of 100 t / a and a wastewater treatment capacity of 500 m 3 / d can meet the requirements of the existing stainless steel cleaning process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figure shows a schematic diagram of the treatment method for the synchronous resource utilization of stainless steel pickling wastewater and waste gas of the present invention.

[0030] Figure 2 The figure shows a schematic diagram of the setting of the membrane absorption unit.

[0031] Figure 3 The figure shows a schematic diagram of the setting of the bipolar membrane unit.

[0032] In the figure: 1 - membrane absorption device, 2 - absorption liquid circulation pump, 3 - absorption liquid storage tank, 4 - intermediate water tank, 5 - salt circulation pump, 6 - salt heat exchanger, 7 - salt filter, 8 - alkali tank, 9 - alkali circulation pump, 10 - alkali heat exchanger, 11 - alkali filter, 12 - acid tank, 13 - acid circulation pump, 14 - acid heat exchanger, 15 - acid filter, 16 - electrode solution tank, 17 - electrode solution circulation pump, 18 - electrode solution heat exchanger, 19 - electrode solution filter, 20 - bipolar membrane device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Embodiment 1

[0035] A treatment method for the synchronous resource utilization of stainless steel pickling wastewater and waste gas includes the following steps:

[0036] Step 1, wastewater pretreatment: The acidic cleaning wastewater undergoes a neutralization reaction with an alkali, and at the same time, a full reaction is carried out through mechanical mixing to remove heavy metal ions in the wastewater. After adjusting the pH > 7, filtration and precipitation are carried out to obtain a first soluble salt solution;

[0037] Step 2, waste gas pretreatment: Through induced air collection, the waste gas capture rate is not less than 95%. The membrane absorption method is adopted to absorb and treat the waste gas to be treated to obtain a second soluble salt solution;

[0038] Step 3, Mix the first soluble salt solution and the second soluble salt solution to obtain high-salt wastewater. The high-salt solution is introduced into a bipolar membrane system for treatment to prepare a recovered alkali solution and a recovered acid solution. The recovered alkali solution is recycled in Step 1 and Step 2, and the recovered acid solution is used for the front-end stainless steel cleaning process.

[0039] In step 2, the membrane absorption is carried out as follows: the waste gas to be treated at 0 - 150 kPa and the absorption liquid at 0 - 150 kPa are subjected to membrane absorption treatment according to a gas-liquid flow rate ratio of 5:1 to 500:1. The absorption liquid for the membrane absorption is NaOH, and the flow rate of the absorption liquid is 0.5 - 5 m 3 / h.

[0040] In step 3, the current density of the bipolar membrane system is 200 - 900 A / m 2 , and the salt concentration of the high-salt wastewater is 10 - 15 wt%. The solute of the bipolar membrane system's electrode solution is NaOH, NaSO4, or NaCl, preferably NaOH, and the concentration of the electrode solution is 2 - 4 wt%. The concentrations of the acid solution in the initial acid pool 12 and the alkali solution in the initial alkali pool 8 of the bipolar membrane system are both 0 - 0.1 mol / L, the concentration of hydroxide ions in the recovered alkali solution is 1.2 - 2.0 mol / L, and the concentration of hydrogen ions in the recovered acid solution is 1.0 - 1.5 mol / L.

[0041] Example 2

[0042] Based on the treatment method of Example 1, this example provides a process equipment, as Figure 1 shown, including a wastewater treatment unit, a membrane absorption unit, and a bipolar membrane unit. The wastewater treatment unit includes a reaction tank, a sedimentation tank, and a sludge thickening tank connected by pipelines. The sedimentation tank and the liquid outlet pipeline of the membrane absorption unit are connected together to the liquid inlet of the bipolar membrane device 20. The alkali outlet of the bipolar membrane device 20 is respectively connected to the reaction tank and the membrane absorption unit, and the sediment in the sedimentation tank enters the sludge thickening tank for treatment.

[0043] The membrane absorption unit includes a membrane absorption device 1, an absorption liquid storage tank 3, and an absorption liquid circulation pump 2. The liquid outlet of the absorption liquid storage tank 3 is connected to the liquid inlet of the absorption liquid circulation pump 2. The liquid outlet of the absorption liquid circulation pump 2 is connected to the alkali liquid inlet of the membrane absorption device 1. The liquid outlet of the membrane absorption device 1 is connected to the circulating liquid inlet of the absorption liquid storage tank 3. The liquid outlet of the alkali pool 8 of the bipolar membrane unit is connected to the alkali inlet of the absorption liquid storage tank 3;

[0044] The bipolar membrane unit includes a bipolar membrane device 20, a salt circulation module, an alkali circulation module, an acid circulation module, and an electrode solution circulation module;

[0045] The salt circulation module includes an intermediate water tank 4, a salt circulation pump 5, a salt heat exchanger 6, and a salt filter 7 that are sequentially connected by pipelines. The liquid outlet of the salt filter 7 is connected to the salt inlet of the bipolar membrane device 20, and the salt outlet of the bipolar membrane device 20 is connected to the inlet of the intermediate water tank 4. The liquid outlets of the sedimentation tank and the circulating liquid storage tank are respectively connected to the inlet of the intermediate water tank 4. A salt flow controller is provided on the pipeline between the intermediate water tank 4 and the salt circulation pump 5;

[0046] The alkali circulation module includes an alkali tank 8, an alkali circulation pump 9, an alkali heat exchanger 10, and an alkali filter 11 that are sequentially connected by pipelines. The liquid outlet of the alkali filter 11 is connected to the alkali inlet of the bipolar membrane device 20, and the alkali outlet of the bipolar membrane device 20 is connected to the inlet of the alkali tank 8. The liquid outlet of the alkali tank 8 is respectively connected to the alkali inlet of the absorption liquid storage tank 3 and the alkali inlet of the reaction tank through a liquid storage tank flow controller and a reaction tank flow controller;

[0047] The acid circulation module includes an acid tank 12, an acid circulation pump 13, an acid heat exchanger 14, and an acid filter 15 that are sequentially connected by pipelines. The liquid outlet of the acid filter 15 is connected to the acid inlet of the bipolar membrane device 20, and the acid outlet of the bipolar membrane device 20 is connected to the inlet of the acid tank 12;

[0048] The electrode liquid circulation module is sequentially connected by pipelines to an electrode liquid tank 16, an electrode liquid circulation pump 17, an electrode liquid heat exchanger 18, and an electrode liquid filter 19. The liquid outlet of the electrode liquid filter 19 is connected to the electrode liquid inlet of the bipolar membrane device 20, and the electrode liquid outlet of the bipolar membrane device 20 is connected to the inlet of the electrode liquid tank 16.

[0049] Example 3

[0050] On the basis of Examples 1-2, this example takes the treatment of wastewater and waste gas from a stainless steel pickling enterprise as an example. The treatment volume of acidic cleaning wastewater is 400 m 3 / d, mainly containing Fe 3+ , Cr 3+ , Ni 2+ and fluorides, etc. The waste gas volume generated by acid mist is 80 t / a, mainly containing nitrogen oxides, fluorides, sulfuric acid mist, hydrochloric acid mist, etc.

[0051] Step 1, wastewater pretreatment: The acidic cleaning wastewater is adjusted in terms of water quality and quantity through a regulating tank and then enters the reaction tank. A pH meter is installed in the tank, and excessive NaOH is added for neutralization reaction. At the same time, sufficient reaction is carried out through mechanical mixing until the pH value reaches 8 - 10. After metal ions form precipitates such as Fe(OH)3, Cr(OH)3, and Ni(OH)2, they enter the sedimentation tank and then enter the sludge thickening tank in the form of heavy metal sludge. Conventional treatment is carried out through methods such as plate and frame pressure filtration and sludge drying. The obtained first soluble salt solution enters the intermediate water tank 4 for standby;

[0052] Step 2, waste gas pretreatment: For the acid mist generated during pickling, the waste gas is collected by means of induced air collection. The air collection hood is required to surround and be as close as possible to the pollution source and be consistent with the movement direction of the polluted air flow. The waste gas capture rate is 97%. The waste gas collected from each production line is stored in the waste gas tank for standby. First, start the absorption liquid pump to introduce the absorption liquid to the membrane absorption device 1. The absorption liquid is a 10wt% sodium hydroxide solution, and the absorption liquid flow rate is 3m 3 / h, and the pressure is 25 kPa; Secondly, introduce the waste gas in the waste gas tank to the alkaline liquid membrane absorption device 1 for treatment at a flow rate of 120m 3 / h and a pressure of 15 kPa. After the waste gas is absorbed by the alkaline liquid, it can be directly discharged up to the standard. The obtained second soluble salt solution enters the intermediate water tank 4 for standby;

[0053] Step 3, introduce the high-salt wastewater in the intermediate water tank 4 into the bipolar membrane system, control the current density to be 600 A / m 2 , use NaOH as the electrode solution, and the electrode solution concentration is 4wt%. Real-time test the conductivity of the wastewater solution until the conductivity drops to 1 mS / cm and then stop the treatment. Use the acid-base titration method to test the acid-base concentration after treatment. The generated alkali concentration after treatment is 1.8 mol / L, and the mixed acid concentration is 1.3 mol / L. The generated alkali can be used for the pretreatment of wastewater and waste gas and the electrode solution of the bipolar membrane, and the mixed acid can be used for the pretreatment process of stainless steel in the early stage, realizing the simultaneous resource treatment of wastewater and waste gas.

[0054] Example 4

[0055] This example takes the treatment of wastewater and waste gas from a certain stainless steel pickling enterprise as an example. The treatment volume of acidic cleaning wastewater is 100m 3 / d, mainly containing Fe 3+ , Cr 3+ , Ni 2+ and fluorides, etc. The waste gas volume generated by the acid mist is 10 t / a, mainly containing nitrogen oxides, fluorides, sulfuric acid mist, hydrochloric acid mist, etc.

[0056] Step 1, wastewater pretreatment: The acidic cleaning wastewater is adjusted in terms of water quality and quantity in an adjustment tank and then enters a reaction tank. A pH meter is installed in the tank, and excessive NaOH is added for neutralization reaction. Meanwhile, sufficient reaction is carried out through mechanical mixing until the pH value reaches 9 - 11. After metal ions form precipitates such as Fe(OH)3, Cr(OH)3, and Ni(OH)2, they enter a sedimentation tank and then enter a sludge thickening tank in the form of heavy metal sludge, and are conventionally treated through methods such as plate and frame pressure filtration and sludge drying. The obtained first soluble salt solution enters an intermediate water tank 4 for standby;

[0057] Step 2, waste gas pretreatment: For the acid mist generated during pickling, the waste gas is collected by the method of induced air collection. The air collecting hood is required to surround and be as close as possible to the pollution source and be consistent with the movement direction of the polluted air flow. The waste gas capture rate is 99%. The waste gas collected from each production line is stored in a waste gas tank for standby. First, start the absorption liquid pump to introduce the absorption liquid to an alkali liquid membrane absorption device 1. The absorption liquid is a sodium hydroxide solution with a concentration of 8wt%, the flow rate of the absorption liquid is 1m 3 / h, and the pressure is 18kPa; secondly, introduce the waste gas in the waste gas tank to the alkali liquid membrane absorption device 1 for treatment at a flow rate of 50m 3 / h and a pressure of 12kPa. After the waste gas is absorbed by the alkali liquid, it can be directly discharged up to the standard, and the obtained second soluble salt solution enters the intermediate water tank 4 for standby;

[0058] Step 3, introduce the high-salt wastewater in the intermediate water tank 4 into a bipolar membrane system, control the current density at 500A / m 2 , use NaOH as the electrode solution, the concentration of the electrode solution is 2wt%, the initial concentrations in the acid-base tank 8 are 0.02mol / L and 0.03mol / L respectively, and the conductivity of the wastewater solution is measured in real time until the conductivity drops to 1mS / cm and then the treatment is stopped. The acid-base concentration after treatment is measured by acid-base titration. The concentration of the generated alkali is 1.4mol / L, and the concentration of the mixed acid is 1.1mol / L. The generated alkali can be used for the pretreatment of wastewater and waste gas and the electrode solution of the bipolar membrane, and the mixed acid can be used for the pretreatment process of stainless steel in the early stage, realizing the simultaneous resource treatment of wastewater and waste gas.

[0059] Example 5

[0060] On the basis of Examples 1 - 2, this example takes the treatment of wastewater and waste gas from a certain stainless steel pickling enterprise as an example. The treatment volume of acidic cleaning wastewater is 300m 3 / d, mainly containing Fe 3+ , Cr 3+ , Ni 2+ and fluorides, etc. The waste gas volume generated by acid mist is 70t / a, mainly containing nitrogen oxides, fluorides, sulfuric acid mist, hydrochloric acid mist, etc.

[0061] Step 1, wastewater pretreatment: The acidic cleaning wastewater is adjusted in terms of water quality and quantity through an adjustment tank and then enters the reaction tank. A pH meter is installed in the tank, and excessive NaOH is added for neutralization reaction. Meanwhile, sufficient reaction is carried out through mechanical mixing until the pH value reaches 8 - 9. After metal ions form precipitates such as Fe(OH)3, Cr(OH)3, and Ni(OH)2, they enter the sedimentation tank and then enter the sludge thickening tank in the form of heavy metal sludge, and are conventionally treated through methods such as plate and frame pressure filtration and sludge drying. The obtained first soluble salt solution enters the intermediate water tank 4 for standby;

[0062] Step 2, waste gas pretreatment: For the acid mist generated during pickling, the waste gas is collected by the method of induced air collection. The air collection hood is required to surround and be as close as possible to the pollution source and be consistent with the movement direction of the polluted air flow. The waste gas capture rate is 98%. The waste gas collected from each production line is stored in the waste gas tank for standby. First, start the absorption liquid pump to introduce the absorption liquid to the alkaline liquid membrane absorption device 1. The absorption liquid is a 12wt% sodium hydroxide solution, and the flow rate of the absorption liquid is 0.8m 3 / h, and the pressure is 20 kPa; Secondly, introduce the waste gas in the waste gas tank to the alkaline liquid membrane absorption device 1 for treatment at a flow rate of 80m 3 / h and a pressure of 15 kPa. After the waste gas is absorbed by the alkaline liquid, it can be directly discharged up to the standard, and the obtained second soluble salt solution enters the intermediate water tank 4 for standby;

[0063] Step 3, introduce the high-salt wastewater in the intermediate water tank 4 into the bipolar membrane system, control the current density to be 800 A / m 2 , use NaOH as the electrode solution, the concentration of the electrode solution is 3wt%, the concentrations in the initial acid-base tank 8 are both 0.05 mol / L, and the conductivity of the wastewater solution is measured in real time until the conductivity drops to 1 mS / cm and then the treatment is stopped. The acid-base concentration after treatment is measured by the acid-base titration method. The concentration of the generated alkali is 1.8 mol / L, and the concentration of the mixed acid is 1.4 mol / L. The generated alkali can be used for the pretreatment of wastewater and waste gas and the electrode solution of the bipolar membrane, and the mixed acid can be used for the pretreatment process of stainless steel in the early stage, realizing the simultaneous resource treatment of wastewater and waste gas.

[0064] The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A treatment method for synchronous resource utilization of stainless steel pickling wastewater and waste gas, characterized in that, It includes the following steps: Step 1, wastewater pretreatment: Use an alkaline solution to remove heavy metal ions from the wastewater to obtain a first soluble salt solution; Step 2, waste gas pretreatment: Adopt the method of membrane absorption to absorb and treat the waste gas to be treated to obtain a second soluble salt solution; Step 3, Mix the first soluble salt solution and the second soluble salt solution to obtain high-salt wastewater. The high-salt solution is introduced into a bipolar membrane system for treatment to prepare a recovered alkaline solution and a recovered acid solution. The recovered alkaline solution is recycled in Step 1 and Step 2, and the recovered acid solution is used for the front-end stainless steel pickling process.

2. The processing method according to claim 1, wherein The heavy metal ions are removed by the following method: The wastewater is neutralized with an alkali, and at the same time, sufficient reaction is carried out through mechanical mixing. After adjusting the pH>7, filtration and precipitation are carried out to obtain the first soluble salt solution.

3. The processing method according to claim 1, wherein In Step 2, the waste gas is collected by induced air collection, and the waste gas capture rate is not less than 95%.

4. The processing method according to claim 1, wherein, In Step 2, the membrane absorption is carried out by the following method: The waste gas to be treated with a pressure of 0-150 kPa and the absorbent liquid with a pressure of 0-150 kPa are subjected to membrane absorption treatment according to a gas-liquid flow ratio of 5:1 to 500:

1.

5. The processing method according to claim 1, characterized in that The absorbent solution for membrane absorption is NaOH, and the flow rate of the absorbent solution is 0.5 - 5 m 3 / h.

6. The processing method according to claim 1, characterized in that, The current density of the bipolar membrane system is 200 - 900 A / m 2 , and the salt concentration of the high-salt wastewater is 10 - 15 wt%.

7. The processing method according to claim 1, wherein The solute of the electrode solution of the bipolar membrane system is NaOH, NaSO4 or NaCl, and the concentration of the electrode solution of the bipolar membrane system is 2-4 wt%.

8. The processing method according to claim 1, wherein, The concentrations of the acid solution in the initial acid pool and the alkali solution in the initial alkali pool of the bipolar membrane system are both 0-0.1 mol / L. The concentration of hydroxide ions in the recovered alkaline solution is 1.2-2.0 mol / L, and the concentration of hydrogen ions in the recovered acid solution is 1.0-1.5 mol / L.

9. An apparatus for the processing method according to any one of claims 1-8, characterized in that, It includes a wastewater treatment unit, a membrane absorption unit and a bipolar membrane unit. The wastewater treatment unit includes a reaction tank, a sedimentation tank and a sludge thickening tank connected by pipelines. The outlet pipelines of the sedimentation tank and the membrane absorption unit are connected to the inlet of the bipolar membrane device together. The alkali outlet of the bipolar membrane device is respectively connected to the reaction tank and the membrane absorption unit, and the sediment in the sedimentation tank enters the sludge thickening tank for treatment.

10. The device according to claim 9, characterized in that, The membrane absorption unit includes a membrane absorption device, an absorbent liquid storage tank and a circulation pump. The outlet of the absorbent liquid storage tank is connected to the inlet of the circulation pump. The outlet of the circulation pump is connected to the alkali liquid inlet of the membrane absorption device. The outlet of the membrane absorption device is connected to the circulating liquid inlet of the absorbent liquid storage tank. The outlet of the alkali pool of the bipolar membrane unit is connected to the alkali inlet of the absorbent liquid storage tank; The bipolar membrane unit includes a bipolar membrane device, a salt circulation module, an alkali circulation module, an acid circulation module and an electrode solution circulation module; The salt circulation module includes an intermediate water tank, a salt circulation pump, a salt heat exchanger and a salt filter connected in sequence by pipelines. The outlet of the salt filter is connected to the salt inlet of the bipolar membrane device. The salt outlet of the bipolar membrane device is connected to the inlet of the intermediate water tank. The outlet of the sedimentation tank and the outlet of the circulating liquid storage tank are respectively connected to the inlet of the intermediate water tank; The alkali circulation module includes an alkali tank, an alkali circulation pump, an alkali heat exchanger, and an alkali filter connected in sequence through pipelines. The liquid outlet of the alkali filter is connected to the alkali inlet of the bipolar membrane device, the alkali outlet of the bipolar membrane device is connected to the inlet of the alkali tank, and the liquid outlet of the alkali tank is respectively connected to the alkali inlet of the absorption liquid storage tank and the alkali inlet of the reaction tank; The acid circulation module includes an acid tank, an acid circulation pump, an acid heat exchanger, and an acid filter connected in sequence through pipelines. The liquid outlet of the acid filter is connected to the acid inlet of the bipolar membrane device, and the acid outlet of the bipolar membrane device is connected to the inlet of the acid tank; The electrode liquid circulation module is connected in sequence through pipelines to an electrode liquid tank, an electrode liquid circulation pump, an electrode liquid heat exchanger, and an electrode liquid filter. The liquid outlet of the electrode liquid filter is connected to the electrode liquid inlet of the bipolar membrane device, and the electrode liquid outlet of the bipolar membrane device is connected to the inlet of the electrode liquid tank.

Images