An apparatus for electrochemically slow-releasing sulfate radicals in wastewater treatment

Abstract

The present invention relates to a device for electro-slowly releasing sulfate radicals in wastewater removal, which comprises a sulfate radical precipitation unit and a precipitation removal unit connected in sequence, and a sulfate radical detection unit arranged on the upstream pipeline communicating with the water inlet of the sulfate radical precipitation unit; the sulfate radical detection unit is used for detecting the concentration of sulfate ions contained in the raw water before entering the sulfate radical precipitation unit; the sulfate radical precipitation unit is used for releasing barium ions to the raw water according to the detected sulfate ion concentration, so that the barium ions react with the sulfate ions to generate barium sulfate, and the sulfate radical precipitation product water containing barium sulfate is obtained; the precipitation removal unit is used for removing the barium sulfate contained in the sulfate radical precipitation product water to obtain the precipitation removal product water. The present invention can accurately control the release rate of barium ions according to the concentration of sulfate radicals in the water body, and can recover the excessive barium ions in the water, overcoming the secondary pollution caused by the inability to accurately control the dosage of barium ions in the traditional precipitation method, and reducing the amount of sludge generated at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly to a device for electro-slowly releasing and removing sulfate radicals from wastewater. Background Art

[0002] The components of wastewater are usually complex, containing a large amount of sulfate radicals. These sulfate radicals are prone to form insoluble sulfate scale deposits such as calcium sulfate, barium sulfate, and strontium sulfate with cations such as calcium ions, barium ions, and strontium ions in the wastewater treatment process. The sulfate scale deposits are mostly white or yellowish-white, with a hard and dense texture. They usually form on the heated surface or heat transfer surface of the treatment equipment, especially in areas with higher temperatures and greater evaporation intensities. With the long-term use of the treatment equipment, these scale layers will gradually thicken. This scaling phenomenon will not only reduce the heat transfer efficiency of the equipment, but may also cause blockage, affecting the normal operation of the equipment. In severe cases, it may even cause under-scale corrosion, causing serious damage to the equipment.

[0003] Currently, common methods for removing sulfate radicals include ion exchange, membrane separation, biological methods, precipitation methods, etc. Each method has its own characteristics and is suitable for different water qualities and treatment requirements. Among them, the precipitation method is the most commonly used method for removing sulfate radicals. In this method, barium chloride is usually used as a precipitant, which is added to the wastewater to make barium ions combine with sulfate radicals to form insoluble barium sulfate precipitate, and then the barium sulfate precipitate is removed. The barium chloride precipitation method has a significant effect, but the addition amount of barium chloride is often difficult to control, and it cannot be adjusted according to the concentration of sulfate radicals in the water body. Therefore, it is easy to cause an excessive addition amount of barium ions, and the residual barium ions cause secondary pollution. And excessive barium ions will react with carbonate ions, phosphate ions, etc. in the water to form precipitates such as barium carbonate and barium phosphate, resulting in an increase in the amount of sludge and a higher treatment cost. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to overcome the defects or deficiencies of the prior art, and provide a device for electro-slowly releasing and removing sulfate radicals from wastewater, which can accurately control the release rate of barium ions according to the concentration of sulfate radicals in the water body, and can recover the excessive barium ions in the water, overcoming the defect that the residual barium ions cause secondary pollution due to the inability to accurately control the addition amount of barium ions in the traditional precipitation method, and at the same time reducing the amount of sludge generated.

[0005] An apparatus for electrochemically slow-releasing and removing sulfate ions from wastewater, comprising a sulfate ion precipitation unit and a precipitation removal unit connected in sequence, and a sulfate ion detection unit provided on an upstream pipeline communicating with the water inlet of the sulfate ion precipitation unit, wherein the sulfate ion detection unit is electrically connected to the sulfate ion precipitation unit; the sulfate ion detection unit is used for detecting the concentration of sulfate ions contained in the raw water before entering the sulfate ion precipitation unit; the sulfate ion precipitation unit is used for releasing barium ions into the raw water according to the detected sulfate ion concentration, so that the barium ions react with the sulfate ions to generate barium sulfate, and obtaining sulfate ion precipitation product water containing barium sulfate; the precipitation removal unit is used for removing the barium sulfate contained in the sulfate ion precipitation product water to obtain precipitation removal product water.

[0006] Compared with the prior art, the apparatus for electrochemically slow-releasing and removing sulfate ions from wastewater according to the present invention utilizes electrochemical means to precisely control the release rate of barium ions according to the detected sulfate ion concentration, so that the barium ions react with the sulfate ions in the water to generate barium sulfate precipitate, thereby removing the sulfate ions in the water and avoiding the accumulation and scaling of sulfate ions after forming sulfates.

[0007] In one embodiment, the sulfate ion precipitation unit includes a sulfate ion sedimentation tank, a water flow channel for the raw water to flow is formed in the sulfate ion sedimentation tank, and an electrode assembly is arranged in the water flow channel. A barium source substance is attached to the surface of the electrode assembly. When an electric current is applied to the electrode assembly, the barium source substance releases barium ions.

[0008] In one embodiment, the electrode assembly is integrally in a long strip shape, and the axial direction of the electrode assembly is perpendicular to the water flow direction in the sulfate ion sedimentation tank.

[0009] In one embodiment, the electrode assembly includes a first electrode and a second electrode with opposite polarities and not in contact with each other, and the barium source substance is attached to the surfaces of both the first electrode and the second electrode.

[0010] In one embodiment, the first electrode has a rod-shaped structure, and the second electrode is spirally wound around the outer peripheral side of the first electrode along the axial direction of the first electrode.

[0011] In one embodiment, the apparatus for electrochemically slow-releasing and removing sulfate ions from wastewater further includes a pH adjustment unit provided upstream of the sulfate ion detection unit; the pH adjustment unit is used for adding a pH adjustment agent to the raw water to adjust the pH value of the raw water to 7-9 to obtain pH-adjusted product water, and the pH-adjusted product water then enters the sulfate ion precipitation unit.

[0012] In one embodiment, the device for electrochemically slow-releasing and removing sulfate radicals from wastewater further includes a secondary sulfate radical precipitation unit and a secondary precipitation removal unit that are connected in sequence, and a secondary sulfate radical detection unit disposed on the pipeline between the water outlet of the precipitation removal unit and the water inlet of the secondary sulfate radical precipitation unit; the secondary sulfate radical detection unit is used to detect the concentration of sulfate ions contained in the precipitation removal product water before entering the secondary sulfate radical precipitation unit; the secondary sulfate radical precipitation unit is used to release barium ions into the precipitation removal product water according to the detected concentration of sulfate ions, so that the barium ions react with the sulfate ions remaining in the water to generate barium sulfate, obtaining secondary sulfate radical removal product water containing barium sulfate; the secondary precipitation removal unit is used to remove the barium sulfate contained in the secondary sulfate radical removal product water, obtaining secondary precipitation removal product water.

[0013] In one embodiment, the secondary sulfate radical precipitation unit includes a secondary sulfate radical sedimentation tank, a water flow channel for the precipitation removal product water to flow is formed in the secondary sulfate radical sedimentation tank, a secondary electrode assembly is disposed in the water flow channel, and a barium source substance is attached to the surface of the secondary electrode assembly. When an electric current is applied to the secondary electrode assembly, the barium source substance releases barium ions.

[0014] In one embodiment, the structure of the secondary electrode assembly is the same as that of the electrode assembly, and the arrangement mode of the secondary electrode assembly in the secondary sulfate radical sedimentation tank is the same as the arrangement mode of the electrode assembly in the sulfate radical sedimentation tank.

[0015] In one embodiment, the device for electrochemically slow-releasing and removing sulfate radicals from wastewater further includes a secondary pH adjustment unit disposed upstream of the secondary sulfate radical detection unit. The secondary pH adjustment unit is used to add a secondary pH adjustment agent to the precipitation removal product water to adjust the pH value of the precipitation removal product water to 7-9, obtaining secondary pH adjustment product water, and the secondary pH adjustment product water then enters the secondary sulfate radical precipitation unit.

[0016] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of Embodiment 1 of the device for electrochemically slow-releasing and removing sulfate radicals from wastewater according to the present invention;

[0018] Figure 2 It is a schematic structural diagram of the electrode assembly in Embodiment 1 of the device for electrochemically slow-releasing and removing sulfate radicals from wastewater according to the present invention;

[0019] Figure 3 It is a schematic structural diagram of the sedimentation tank in Embodiment 1 of the device for electrochemically slow-releasing and removing sulfate radicals from wastewater according to the present invention;

[0020] Figure 4 This is a schematic structural diagram of Embodiment 2 of the device for electrochemically slow-releasing and removing sulfate radicals from wastewater according to the present invention;

[0021] Figure 5 This is a schematic structural diagram of Embodiment 3 of the device for electrochemically slow-releasing and removing sulfate radicals from wastewater according to the present invention;

[0022] Figure 6 This is a schematic structural diagram of Embodiment 4 of the device for electrochemically slow-releasing and removing sulfate radicals from wastewater according to the present invention;

[0023] Reference numerals:

[0024] 100, sulfate radical precipitation unit; 1000, sulfate radical sedimentation tank; 1002, partition board; 1004, electrode assembly; 1004a, first electrode of the electrode assembly; 1004b, second electrode of the electrode assembly; 102, precipitation removal unit; 1020, coagulation tank; 1022, flocculation tank; 1024, precipitation removal tank; 1026, barium hydroxide collection tank; 1028, water storage tank; 104, sulfate radical detection unit; 106, pH adjustment unit; 1060, pH adjustment tank; 1062, acid-base liquid dosing device;

[0025] 200, secondary sulfate radical precipitation unit; 2000, secondary sulfate radical sedimentation tank; 2002, secondary partition board; 2004, secondary electrode assembly; 202, secondary precipitation removal unit; 2020, secondary coagulation tank; 2022, secondary flocculation tank; 2024, secondary precipitation removal tank; 2026, secondary barium hydroxide collection tank; 204, secondary sulfate radical detection unit; 206, secondary pH adjustment unit; 2060, secondary pH adjustment tank; 2062, secondary acid-base liquid dosing device;

[0026] 304, tertiary sulfate radical detection unit;

[0027] 40, tail gas treatment unit. Detailed implementation manners

[0028] Traditionally, the precipitation method is mostly used to remove sulfate ions from wastewater. In this method, barium chloride is quantitatively added to the raw water through valve control. Barium ions will react with sulfate ions in the raw water to form water-insoluble barium sulfate precipitates, and then the barium sulfate precipitates are removed. However, due to the relatively low opening and closing accuracy of existing valves (such as electronically controlled flow valves), it is often difficult to accurately control the dosing amount by the method of dosing liquid through valves, which is likely to cause an excessive amount of barium ions, and the residual barium ions cause secondary pollution.

[0029] Based on this, the present invention adopts an electrochemically controlled method. According to the detected concentration of sulfate ions in the raw water, a current is passed through the electrode assembly attached with a barium source substance to slowly release barium ions into the raw water, so that the barium ions react with the sulfate ions in the water to form water-insoluble barium sulfate precipitates, and then the barium sulfate precipitates are removed to prevent the sulfate ions from forming water-insoluble scale with metal ions in the water. During this process, the slow release rate of barium ions is controlled by the current. By adjusting the magnitude of the current, the release of barium ions can be precisely controlled, avoiding barium ion residues caused by excessive addition of barium ions, thereby causing secondary pollution. Further, the present invention uses barium hydroxide as the barium source substance attached to the surface of the electrode assembly. By utilizing the characteristic that barium hydroxide has a relatively low solubility in water, the stability of barium hydroxide on the electrode assembly can be maintained, and instantaneous release of excessive barium ions after passing a current through the electrode assembly can be avoided. At the same time, the unreacted barium ions in the water can react with the hydroxide ions in the water to regenerate barium hydroxide and deposit on the surface of the electrode assembly, realizing the dynamic balance of the decomposition and formation of barium hydroxide. In this way, the service time of the electrode assembly can be extended, and there is no need to frequently replace the electrode assembly.

[0030] The following will describe the solution of the present invention in detail with reference to the accompanying drawings.

[0031] Example 1

[0032] Figure 1 Shows the specific structure of the device for electrochemically slow-releasing and removing sulfate in wastewater of the present invention, which is applicable to wastewater with a relatively low chloride ion concentration. As Figure 1 shown, the device for electrochemically slow-releasing and removing sulfate in wastewater of the present invention includes a sulfate precipitation unit 100 and a precipitation removal unit 102 that are connected in sequence, and a sulfate detection unit 104 that is disposed on the upstream pipeline of the sulfate precipitation unit 100 and is electrically connected thereto.

[0033] Specifically, the sulfate precipitation unit 100 includes a sulfate sedimentation tank 1000, and the sulfate sedimentation tank 1000 has an inlet and an outlet. A plurality of parallel partition plates 1002 are arranged inside the sulfate sedimentation tank 1000, and these partition plates 1002 divide the sulfate sedimentation tank 1000 into multiple cavities, and these cavities are connected end to end to form a water flow channel for the raw water to flow through. By arranging the partition plates 1002, the residence time of the raw water in the sulfate sedimentation tank 1000 can be extended. Of course, the partition plates 1002 can also not be provided, but this will shorten the residence time of the raw water in the sulfate sedimentation tank 1000. A plurality of electrode assemblies 1004 are provided in the water flow channel, as Figure 2As shown, the single electrode assembly 1004 is overall in a long strip shape, and it includes a first electrode 1004a and a second electrode 1004b with opposite polarities and not in contact with each other. The first electrode 1004a has a rod-like structure, and the second electrode 1004b spirally surrounds the outer peripheral side of the first electrode 1004a along the axial direction of the first electrode 1004a. Such a structural design can reduce the floor space of the electrode and is convenient for installation. In this embodiment, the first electrode 1004a is the anode and is connected to the positive pole of the external power supply, and the second electrode 1004b is the cathode and is connected to the negative pole of the external power supply. Among them, a layer of barium source material is attached to the surfaces of the first electrode 1004a and the second electrode 1004b. Multiple electrode assemblies 1004 are arranged in a matrix, and there is a gap between adjacent electrode assemblies 1004 on the same cross-section of the water flow channel for raw water to pass through. The axial direction of the electrode assembly 1004 can be parallel to the water flow direction in the sulfate sedimentation tank 1000 or can intersect with the water flow direction, but it is preferably as Figure 1 shown, the axial direction of the electrode assembly 1004 is perpendicular to the water flow direction. In this way, a flow resistance can be formed for the water flow. With the structural settings of the first electrode 1004a and the second electrode 1004b in the electrode assembly 1004, the reaction time between sulfate in the water and barium ions released into the water by the electrode assembly 1004 can be prolonged. The number of electrode assemblies 1004 can be determined according to actual needs and is not uniquely limited here.

[0034] The first electrode 1004a and the second electrode 1004b are respectively connected to the anode and cathode of the power supply. When an electric current is passed through the electrode assembly 1004, the first electrode 1004a undergoes an oxidation reaction:

[0035]

[0036] The barium source material on the surface will be ionized into barium ions and hydroxide ions and released into the water.

[0037] The consumption of hydroxide ions in the water causes the barium hydroxide on the surface of the first electrode 1004a to dissolve, releasing barium ions and hydroxide ions into the water:

[0038]

[0039] Meanwhile, the second electrode 1004b undergoes a reduction reaction to generate hydroxide ions:

[0040]

[0041] The generated hydroxide ions recombine with barium ions to form barium hydroxide and precipitate and adhere to the surface of the second electrode 1004b:

[0042]

[0043] The sedimentation removal unit 102 comprises a coagulation tank 1020, a flocculation tank 1022, and a barium ion regeneration tank 1024, which are interconnected in sequence. The coagulation tank 1020 is connected to the outlet of the sulfate precipitation tank 1000. Specifically, the coagulation tank 1020 is equipped with a coagulant doser (not shown) for adding a flocculant, specifically PAC (polyaluminum chloride). Upon addition of PAC, PAC undergoes hydrolysis in water to form aluminum hydroxide colloids. The aluminum hydroxide colloids can also connect colloidal particles and suspended matter in the water through adsorption and bridging, forming larger flocs. The flocculation tank 1022 is equipped with a flocculant doser (not shown) for adding a flocculant, specifically PAM (polyacrylamide), a high molecular weight polymer with numerous reactive groups on its molecular chains that can adsorb colloidal particles and suspended matter in the water. Through the stretching and entanglement of molecular chains, PAM can form bridges between particles, connecting the particles to form larger flocs containing barium sulfate precipitates.

[0044] The raw water after coagulation and flocculation treatment flows to the sedimentation removal tank 1024, such as Figure 3 As shown, the sedimentation removal tank 1024 includes at least two chambers, namely a first chamber and a second chamber. A filter is provided in the first chamber, through which the flocculated water containing flocs is subjected to solid-liquid separation in the first chamber to obtain sedimentation removal water and a precipitate containing barium sulfate. The precipitate is then passed through the outlet of the sedimentation removal tank 1024 to the downstream treatment process. For the precipitate retained in the sedimentation removal tank 1024, after the wastewater treatment is completed, carbon materials such as coke or graphene are added to the first chamber, causing the barium sulfate and carbon materials to react under high temperature conditions to produce barium sulfide and carbon monoxide:

[0045]

[0046] The carbon monoxide is discharged through the exhaust port of the first cavity, and the barium sulfide enters the second cavity. The second cavity is connected to the water storage tank 1028. Water is added to the second cavity through the water storage tank 1028, and the barium sulfide undergoes a hydrolysis reaction to generate barium hydroxide and hydrogen sulfide:

[0047]

[0048] The generated barium hydroxide is collected in the barium hydroxide collection tank 1026 and can be reused for the barium source material attached to the surface of the electrode assembly 1004. At the same time, the carbon monoxide generated is collected by the tail gas treatment unit 40 which is respectively connected to the first cavity and the second cavity. The tail gas treatment unit 40 uses the method of torch combustion to fully burn the collected carbon monoxide and hydrogen sulfide into carbon dioxide and sulfur dioxide, and absorbs them with 5% alkali solution. The solution obtained after absorption can be used as the addition of the hard removal agent in the pretreatment process.

[0049] The sulfate radical precipitation unit 100 is specifically a sulfate radical ion concentration detection sensor, which is used to detect the sulfate radical ion concentration in the raw water before entering the sulfate radical precipitation unit 100, and then feedback the detected sulfate radical ion concentration information to the sulfate radical precipitation unit 100. The controller (not shown in the figure) of the sulfate radical precipitation unit 100 then adjusts the magnitude of the current applied to the electrode assembly 1004 according to the sulfate radical ion concentration, so as to adjust the speed of releasing barium ions. The greater the current, the greater the amount of barium ions released; the smaller the current, the smaller the amount of barium ions released, realizing the accuracy of barium ion release. In addition to controlling the release speed of barium ions by the magnitude of the current, the controller can also control the release speed of barium ions by controlling the number of the energized electrode assemblies 1004. The more the number of the energized electrode assemblies 1004, the greater the amount of barium ions released; the fewer the number of the energized electrode assemblies 1004, the smaller the amount of barium ions released. Since it is a prior art for the controller to control the energization of the electrode assembly 1004 according to the feedback signal, it will not be elaborated here.

[0050] When the device for electro-slow-release removal of sulfate radicals in wastewater of this embodiment works, first, the sulfate concentration in the incoming raw water is detected by the sulfate detection unit 104 and fed back to the sulfate radical precipitation unit 100. After the raw water enters the sulfate radical sedimentation tank 1000 of the sulfate radical precipitation unit 100, a current is applied to the electrode assembly 1004 according to the sulfate radical ion concentration detected by the sulfate detection unit 104. After applying the current, the barium hydroxide attached to the surface of the first electrode 1004a ionizes, releasing barium ions and hydroxide ions. The barium ions react with the sulfate radical ions in the raw water to form water-insoluble barium sulfate precipitates. The barium sulfate is separated by precipitation in the precipitation removal unit 102, and the produced water after precipitation removal enters the next-stage treatment process.

[0051] Thus, according to the concentration of sulfate ions detected in the water body, the above device for electrochemically slow-releasing and removing sulfate in wastewater passes an electric current through the electrode assembly 1004 attached with barium hydroxide, so that its first electrode 1004a slowly releases barium ions into the water body to precipitate the sulfate ions in the water, so as to prevent the sulfates generated by the sulfate ions in the water from gradually accumulating and adhering to the equipment or pipelines during the treatment process and then forming scale. During this process, the slow-release rate of barium ions is controlled by the electric current. By adjusting the magnitude of the electric current, the release of barium ions can be precisely controlled, thus avoiding secondary pollution caused by the residual barium ions due to excessive addition of barium ions.

[0052] Compared with the traditional precipitation method that usually uses barium chloride as the precipitant for precipitating sulfate ions, the solubility of barium hydroxide in water (about 5.6 g / 100 g of water, 20 °C) is much lower than that of barium chloride (35.8 g / 100 g of water, 20 °C). Therefore, using barium hydroxide as the barium source substance attached to the first electrode 1004a and the second electrode 1004b of the electrode assembly 1004 can avoid the instantaneous release of excessive barium ions when the raw water flows through the electrode assembly 1004a, which is beneficial to achieving precise control of the release amount of barium ions. Moreover, the hydroxide ions released by the electrolysis of barium hydroxide can adjust the pH of the water body and inhibit the reduction of sulfate to hydrogen chloride. If barium chloride is used as the barium source substance and attached to the surfaces of the first electrode 1004a and the second electrode 1004b, chlorine gas and hypochlorous acid will be generated after the first electrode 1004a is energized. For the generated chlorine gas, additional treatment is required, which will undoubtedly increase the complexity of the water body components and the treatment cost.

[0053] In addition, by using barium hydroxide as the barium source material, the reattachment of barium ions in water to the first electrode 1004a can be promoted through the polarity reversal between the first electrode 1004a and the second electrode 1004b, and barium hydroxide is generated by reacting with hydroxide ions. Specifically, the polarity of the first electrode 1004a and the second electrode 1004b is reversed by reversing the direction of the current output by the power supply, that is, the first electrode 1004a changes from the anode to the cathode, and the second electrode 1004b changes from the cathode to the anode. After the polarity of the first electrode 1004a and the second electrode 1004b is reversed, the second electrode 1004b will undergo an oxidation reaction, continuously releasing barium ions and hydroxide ions into the water body. The barium ions continue to react with sulfate ions in the water to precipitate the sulfate ions. The first electrode 1004a, which originally released barium ions, becomes the cathode, and a reduction reaction occurs on the surface of the first electrode 1004a, promoting the generation of hydroxide ions. The barium ions that did not participate in the formation of barium sulfate will react with these hydroxide ions on the first electrode 1004a to generate barium hydroxide, which is deposited on the surface of the first electrode 1004a, restoring the barium hydroxide on the surface of the first electrode 1004a to a certain extent. Thus, through the in-situ regeneration of barium hydroxide, the residual barium ions in the water can be recovered. Thus, through the periodic polarity switching between the first electrode and the second electrode, a dynamic balance between the decomposition and generation of barium hydroxide is achieved, enabling the electrode assembly 1004 to be continuously used for a long period of time without the need to frequently disassemble and replace the electrode assembly 1004.

[0054] The following provides a preparation method for the first electrode 1004a and the second electrode 1004b with a barium hydroxide layer attached, including the following steps:

[0055] S1: Prepare the substrate;

[0056] Specifically, pure titanium (Ti) or a titanium alloy is selected as the substrate for the first electrode 1004a and the second electrode 1004b of the electrode assembly 1004, and the first electrode 1004a is made into a sheet-like shape and the second electrode 1004b is made into a filamentous shape. Among them, the thickness of the first electrode 1004a is 3 mm, and the diameter of the second electrode 1004b is 3 mm.

[0057] S2: Perform microporization treatment on the surface of the substrate;

[0058] Specifically, it includes the following steps:

[0059] S21: Cleaning and degreasing: Use acetone or ethanol to clean the titanium surface to remove grease and dirt. Then perform ultrasonic cleaning in deionized water;

[0060] S22: Pickling: Immerse the titanium substrate in a mixed solution of 5% HF and 10% to remove the oxide layer and generate a uniform rough or microporous surface, with a treatment time of 10 minutes;

[0061] S23: Immediately after pickling, thoroughly rinse the titanium surface with deionized water, and then dry it in an oven at a low temperature (about 60 °C) to prevent further oxidation.

[0062] S3: Form a barium source material layer on the substrate surface;

[0063] Specifically, it includes the following steps:

[0064] S31: Prepare the barium source material layer: Mix barium hydroxide with a small amount of binder (aluminum oxide powder), and control the binder ratio at about 2%. Among them, the binder can increase the adhesion of the coating and improve the stability of the electrode assembly 1004.

[0065] S32: Mixing: Uniformly mix barium hydroxide and the binder to form a viscous suspension or paste to ensure uniform distribution of components during uniform coating.

[0066] S33: Coating: Uniformly coat the barium hydroxide mixture on the microporous surface of the titanium substrate by brushing, spraying or dipping. The coating thickness does not exceed 3 mm to ensure a sufficient amount of material and prevent peeling caused by an overly thick coating.

[0067] S4: Coating curing;

[0068] Specifically, it includes the following steps:

[0069] S41: Drying: After coating, place the electrode assembly 1004 at room temperature to dry and evaporate the surface moisture to avoid excessive shrinkage of the coating during high-temperature treatment;

[0070] S42: Sintering: Put the dried electrode assembly 1004 into an oven and gradually heat it to 200 °C for sintering treatment (about 2 hours). Sintering can enhance the adhesion of the coating, firmly combine the binder with barium hydroxide, and prevent peeling during use;

[0071] S43: Cooling: After sintering, let the electrode assembly 1004 cool slowly to room temperature to avoid cracks or coating damage caused by rapid cooling.

[0072] Example 2

[0073] Figure 4 Shows the specific structure of the device for electrochemically slow-releasing sulfate in wastewater in Example 2 of the present invention. As Figure 4As shown in the figure, the structure of the device for electro-slow-release removal of sulfate in wastewater in Embodiment 2 of the present invention is substantially the same as that in Embodiment 1, and the only difference is that: the device for electro-slow-release removal of sulfate in wastewater in this embodiment further includes a pH adjustment unit 106 provided upstream of the sulfate precipitation unit 100, and the sulfate precipitation unit 100 is located on the pipeline connecting the pH adjustment unit 106 and the sulfate precipitation unit 100.

[0074] Specifically, the pH adjustment unit 106 includes a pH adjustment tank 1060 and an acid-base solution dosing device 1062 provided on the pH adjustment tank 1060. When the device for electro-slow-release removal of sulfate in wastewater works, the raw water first enters the pH adjustment tank 1060 of the pH adjustment unit 106, and an acid solution or an alkali solution is added to the raw water through the acid-base solution dosing device 1062 to adjust the pH value of the water body to 7-9, and then the raw water is introduced into the sulfate precipitation tank 1000 of the sulfate precipitation unit 100. In this embodiment, the acid solution is concentrated sulfuric acid and the alkali solution is sodium hydroxide.

[0075] Under acidic conditions, barium hydroxide attached to the surface of the electrode assembly 1004 will react with hydrogen ions in the water, accelerating the dissolution of barium hydroxide, resulting in too fast release of barium ions, which is not conducive to controlling the release rate of barium ions and is likely to cause the problem of excessive barium ions. Under neutral or slightly alkaline conditions with a pH of 7-9, the solubility of barium hydroxide is relatively low, so that it remains stable on the surface of the electrode assembly 1004, avoiding direct dissolution of barium hydroxide in the solution, which is conducive to improving the accuracy of the release rate of barium ions and realizing the slow release of barium ions. Under the condition of a pH of 7-9, barium ions can form insoluble barium sulfate precipitate with sulfate, realizing efficient removal of sulfate and reducing the corrosion risk of the electrode material. In addition, the relatively high concentration of hydroxide ions contained in the slightly alkaline aqueous solution is also conducive to combining with barium ions to regenerate barium hydroxide at the cathode.

[0076] Embodiment 3

[0077] Figure 5 Shows the specific structure of the device for electro-slow-release removal of sulfate in wastewater in Embodiment 3 of the present invention. As Figure 5 shown, the structure of the device for electro-slow-release removal of sulfate in wastewater in Embodiment 3 of the present invention is substantially the same as that in Embodiment 2, and the only difference is that: the device for electro-slow-release removal of sulfate in wastewater in this embodiment further includes a secondary sulfate precipitation unit 200 and a secondary precipitation removal unit 202 which are provided downstream of the sulfate precipitation unit 100 and are connected in sequence, and a secondary sulfate detection unit 204 which is provided on the pipeline between the precipitation removal unit 102 and the secondary sulfate precipitation unit 200.

[0078] Specifically, having the same structure as the sulfate precipitation unit 100, the secondary sulfate precipitation unit 200 includes a secondary sulfate sedimentation tank 2000. A plurality of secondary partition plates 2002 arranged in parallel with each other in the secondary sulfate sedimentation tank 2000 and the side walls of the secondary sulfate sedimentation tank 1000 form a water flow channel for the flow of the water after precipitation removal. A plurality of secondary electrode assemblies 2004 with barium hydroxide attached to their surfaces are provided in the water flow channel. The distribution method and working principle of the secondary electrode assemblies 2004 in the secondary sulfate sedimentation tank 2000 are the same as those of the electrode assemblies 1004 in the sulfate sedimentation tank 1000, and will not be elaborated here.

[0079] Similar to the structure of the precipitation removal unit 102, the secondary precipitation removal unit 202 includes a secondary coagulation tank 2020, a secondary flocculation tank 2022, and a secondary precipitation removal tank 2024 that are connected in sequence. The water inlet of the secondary coagulation tank 2020 is connected to the water outlet of the secondary sulfate sedimentation tank 2000. Specifically, a secondary coagulant feeder (not shown in the figure) is provided in the secondary coagulation tank 2020 for adding a coagulant to the secondary coagulation tank 2020. A secondary flocculant feeder (not shown in the figure) is provided in the secondary flocculation tank 2022 for adding a flocculant to the secondary flocculation tank 2022. The coagulant is PAC, and the flocculant is PAM. The water after flocculation treatment flows to the secondary precipitation removal tank 2024. The structures and working principles of the secondary coagulation tank 2020, the secondary flocculation tank 2022, and the secondary precipitation removal tank 2024 are the same as those of the coagulation tank 1020, the flocculation tank 1022, and the precipitation removal tank 1024, and will not be elaborated here. The secondary precipitation removal water flowing out of the secondary precipitation removal tank 2024 flows to the next-stage treatment process for subsequent treatment; while the barium hydroxide obtained after chemical reaction treatment of the precipitate filtered by the secondary precipitation removal tank 2024 is recycled to the secondary barium hydroxide collection tank 2026 and can be reused as the barium source material attached to the surface of the secondary electrode assemblies 2004.

[0080] When the device for electrically slow-releasing and removing sulfate in wastewater of this embodiment works, first, the sulfate in the raw water is subjected to the first treatment by the sulfate precipitation unit 100 and the precipitation removal unit 102, and then the secondary sulfate detection unit 204 detects the concentration of sulfate ions contained in the water after precipitation removal obtained after the treatment. If the concentration does not meet the standard, the secondary sulfate precipitation unit 200 and the secondary precipitation removal unit 202 are used to perform the second treatment on the water after precipitation removal to further remove the sulfate in the water.

[0081] Thus, through the sulfate precipitation unit 100 and the precipitation removal unit 102, as well as the secondary sulfate precipitation unit 200 and the secondary precipitation removal unit 202, the raw water is treated in two stages to ensure that the concentration of sulfate ions in the raw water can be reduced to below 100 mg / L (below this concentration, sulfates are not likely to scale).

[0082] Furthermore, a tertiary sulfate detection unit 304 is provided on the pipeline between the secondary sulfate precipitation unit 200 and the secondary precipitation removal unit 202, which is used to detect the concentration of sulfate ions in the secondary precipitation removal product water obtained after being treated by the secondary sulfate precipitation unit 200. After ensuring that the concentration of sulfate ions is below 100 mg / L, the next process treatment is carried out.

[0083] Example 4

[0084] Figure 6 Shows the specific structure of the device for electrochemically slow-releasing sulfate in wastewater in Example 4 of the present invention. As Figure 6 shown, the structure of the device for electrochemically slow-releasing sulfate in wastewater in Example 4 of the present invention is substantially the same as that in Example 3, and the only difference is that: the device for electrochemically slow-releasing sulfate in wastewater in this embodiment further includes a secondary pH adjustment unit 206 provided upstream of the secondary sulfate precipitation unit 200, and the water inlet of the secondary pH adjustment unit 206 is communicated with the water outlet of the precipitation removal unit 102.

[0085] Having the same structure as the pH adjustment unit 106, the secondary pH adjustment unit 206 includes a secondary pH adjustment tank 2060 and a secondary acid-base solution dosing device 2062 provided on the secondary pH adjustment tank 2060. The precipitation removal product water obtained after the primary treatment first enters the secondary pH adjustment tank 2060 of the secondary pH adjustment unit 206, and an acid solution or an alkali solution is added to the raw water through the secondary acid-base solution dosing device 2062 to make the pH value of the water body reach 7 - 9. In this embodiment, the acid solution is concentrated sulfuric acid and the alkali solution is sodium hydroxide. The precipitation removal product water after pH adjustment is then introduced into the sulfate precipitation tank 2000 of the secondary sulfate precipitation unit 200.

[0086] Thus, through the setting of the secondary pH adjustment unit 206, the precipitation removal product water entering the secondary sulfate precipitation unit 200 is made neutral or slightly alkaline, so as to improve the accuracy of controlling the barium ion release rate in the secondary sulfate precipitation unit 200, realize the slow release of barium ions, avoid the excessive release of barium ions resulting in secondary pollution, and at the same time is beneficial to the in-situ growth of barium hydroxide on its cathode when the polarity of the secondary electrode assembly 2004 is reversed.

[0087] The device for electrochemically slow-releasing and removing sulfate radicals from wastewater in any of the above embodiments can be applied to the front end of a wastewater treatment system. By using the device for electrochemically slow-releasing and removing sulfate radicals from wastewater, the sulfate radical ions contained in the raw wastewater are removed, and their concentration is reduced to 100 mg / L. Then, the next-stage treatment process is carried out to avoid the continuous accumulation and scaling of sulfates during the treatment process, which may affect the operation of equipment or even damage the equipment.

[0088] Effect verification

[0089] The same batch of oilfield produced water was treated (pilot-scale amplification) respectively by the device for electrochemically slow-releasing and removing sulfate radicals from wastewater in Example 2 of the present invention and the device for electrochemically slow-releasing and removing sulfate radicals from wastewater using the precipitation method (hereinafter referred to as "comparative example"), and then the effects of removing sulfates from water by the two were compared. Compared with Example 2 of the present invention, the differences in the comparative example are as follows: Figure 4 On the basis of Example 2 of the present invention as shown, the sulfate radical sedimentation tank provided with an electrode assembly in Example 2 was replaced with a sulfate radical sedimentation tank connected to a barium source material dosing device in the comparative example. The barium source material dosing device in the comparative example includes a storage tank for storing the barium source material and a flow control valve provided on the pipeline between the outlet of the storage tank and the sulfate radical sedimentation tank. The flow control valve is purchased from the market and is provided on the pipeline between the outlet of the storage tank and the sulfate radical sedimentation tank to control the addition amount of the barium source material added to the sulfate radical sedimentation tank. The specific barium source material used is barium chloride. The comparative example controls the opening degree of the flow control valve according to the detected sulfate radical ion concentration in the raw water to add barium chloride to the sulfate radical sedimentation tank. The structural settings of other functional units in the comparative example are the same as those in Example 2.

[0090] Then, the device for electrochemically slow-releasing and removing sulfate radicals from wastewater in Example 2 and the device for electrochemically slow-releasing and removing sulfate radicals from wastewater in the comparative example were used to treat the raw oilfield produced water shown in Table 1 for 30 minutes respectively. The results before and after the treatment are compared as shown in Table 2:

[0091] Table 1

[0092]

[0093] Table 2

[0094]

[0095] * The sludge volume refers to the amount of the sediment product obtained after solid-liquid separation in the sedimentation and removal tank.

[0096] As can be seen from Table 2, through Example 2 of the present invention, the barium ion concentration in water can be reduced to 20 mg / L within a short time (30 min), which is much lower than the sulfate ion concentration of 500 mg / L in the water after treatment in the comparative example; and the concentration of residual barium ions after treatment in Example 2 of the present invention is lower than that of the residual barium ions in the comparative example. It can be seen that the removal effect of sulfate ions in the raw water in Example 2 of the present invention is better than that in the comparative example, and the residual amount of barium ions after treatment in Example 2 of the present invention is also lower than that in the comparative example. From the speculation based on the observation of the experimental process, the reason for the above difference between the two is as follows: The opening degree accuracy of the flow control valves sold on the market is relatively low, and it is impossible to finely adjust the added barium chloride according to the concentration of sulfate ions, so it is easy to add an excessive amount, resulting in too much barium ions in the water. However, as can be seen from Table 2, although a large amount of barium ions remain in the water after treatment in the comparative example, these barium ions fail to fully combine with sulfate ions in the water to form barium sulfate ions, resulting in a relatively high residual amount of sulfate ions in the treated produced water. This is because: The chemical composition of the raw water of oilfield produced water is relatively complex (including various inorganic ions such as carbonate ions and phosphate ions, as well as organic ligands), and the barium chloride directly added in the comparative example reacts with the complex components of the raw water through the following mechanisms: (1) Competitive coordination effect: Anions such as carbonate ions (<ID= ), phosphate ions (<ID= ), etc. in the oilfield produced water, which have strong coordination abilities, can form soluble complexes (such as <ID= )) with metal ions or produce steric hindrance effects, significantly delaying the precipitation reaction rate of barium ions and sulfate ions; (2) Ion strength effect: The ion atmosphere effect generated in a high-salinity environment (<ID= ) will greatly reduce the activity coefficients of barium and sulfate ions, making it difficult to reach the critical supersaturation under conventional mixing conditions; (3) Mass transfer limitation: In the traditional dosing method, barium ions are diffusely distributed, and the average diffusion distance from sulfate ions > 500 μm, while the turbulent diffusion time constant (<ID= , <ID= ) shows that it takes a relatively long time (up to dozens of minutes) to complete effective mass transfer. The occurrence of the above mechanisms results in poor removal effect of sulfate ions in the comparative example in a short time. In Example 2 of the present invention, a microreaction environment (effective action radius < 50 μm) is formed near the electrode assembly 1004 after passing an electric current through the electrode assembly 1004. The following mechanisms occur in this microreaction environment: (1) Electromigration enrichment: Under the action of an electric current, the migration rate of barium ions is increased to 10³ times that of traditional diffusion, and the local concentration can reach 10² times that of the bulk solution; (2) Double-layer compression: The Stern layer potential at the electrode interface makes <ID= The surface charge density is reduced by 40%, significantly decreasing the absolute value of the Zeta potential (from -35 mV to -12 mV), effectively overcoming the colloidal stability; (3) Micro-region isolation: The concentration of the organic ligand in the reaction micro-region decays by more than 90%, eliminating its inhibitory effect on the growth of precipitation crystal nuclei. The occurrence of the above mechanisms is beneficial to improving the reaction efficiency of barium ions and sulfate ions in Example 2, so that sulfate ions can be rapidly consumed in a short time, effectively reducing the concentration of sulfate ions in the produced water after precipitation removal.

[0097] In addition, since the amount of barium chloride added cannot be precisely controlled in the comparative example, barium ions in the comparative example will react with other anions (such as carbonate ions, phosphate ions, etc.) contained in the water in addition to reacting with sulfate ions, generating barium carbonate, barium phosphate precipitates, etc., resulting in a higher sludge volume than that obtained after treatment in Example 2 of the present invention. The increase in sludge volume will undoubtedly increase the treatment cost.

[0098] Compared with the prior art, the device for electrochemically releasing and removing sulfate ions from wastewater in the present invention adopts an electrochemically controlled method. According to the detected sulfate ion concentration, the release rate of barium ions is precisely controlled by electrochemistry, so that barium sulfate precipitates are formed by reacting with sulfate ions in the water to remove sulfate ions from the water and avoid the accumulation and scaling of sulfates; in addition, by using barium hydroxide as the barium source substance attached to the surface of the electrode assembly, and taking advantage of the low solubility of barium hydroxide in water, the stability of barium hydroxide on the electrode assembly is maintained, avoiding a large amount of barium ions being released into the water in a short time, which is beneficial to improving the controllability and accuracy of barium ion release. At the same time, the unreacted barium ions in the water react with hydroxide ions in the water to regenerate barium hydroxide in situ, enabling the electrode assembly to be used continuously without frequent replacement of the electrode assembly.

[0099] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present application. The singular forms "a", "the" and "said" used in the embodiments of the present application and the claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that unless otherwise specified, "a plurality" means two or more; the terms "first", "second", "third", etc. are only used for distinction and not for describing a specific order or sequence, nor can they be understood as indicating or implying relative importance. The term "and / or" used herein means and includes any or all possible combinations of one or more of the associated listed items. When the above description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present application, for those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0100] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. An apparatus for electrochemically slow-releasing and removing sulfate radicals from wastewater, characterized in that: it includes a sulfate radical precipitation unit and a precipitation removal unit that are connected in sequence, and a sulfate radical detection unit arranged on the upstream pipeline communicating with the water inlet of the sulfate radical precipitation unit, wherein the sulfate radical detection unit is electrically connected to the sulfate radical precipitation unit; the sulfate radical detection unit is used to detect the concentration of sulfate ions contained in the raw water before entering the sulfate radical precipitation unit; the sulfate radical precipitation unit is used to release barium ions to the raw water according to the detected concentration of sulfate ions, so that the barium ions react with the sulfate ions to generate barium sulfate, and obtain sulfate radical precipitation product water containing barium sulfate. The sulfate radical precipitation unit includes a sulfate radical sedimentation tank, and a water flow channel for the raw water to flow is formed in the sulfate radical sedimentation tank. An electrode assembly is arranged in the water flow channel, and a barium source substance is attached to the surface of the electrode assembly. When an electric current is applied to the electrode assembly, the barium source substance releases barium ions; the electrode assembly is integrally in a long strip shape, the axial direction of the electrode assembly is perpendicular to the water flow direction in the sulfate radical sedimentation tank, the electrode assembly includes a first electrode and a second electrode with opposite polarities and not in contact with each other, and the barium source substance is attached to the surfaces of both the first electrode and the second electrode. The first electrode is in a rod-shaped structure, and the second electrode is spirally wound around the outer peripheral side of the first electrode along the axial direction of the first electrode. The barium source substance is barium hydroxide; the precipitation removal unit is used to remove the barium sulfate contained in the sulfate radical precipitation product water to obtain precipitation removal product water.

2. The apparatus for electrochemically slow-releasing and removing sulfate radicals from wastewater according to claim 1, characterized in that: it further includes a pH adjustment unit arranged upstream of the sulfate radical detection unit; the pH adjustment unit is used to add a pH adjustment agent to the raw water to adjust the pH value of the raw water to 7-9 to obtain pH-adjusted product water, and the pH-adjusted product water then enters the sulfate radical precipitation unit.

3. The apparatus for electrochemically slow-releasing and removing sulfate radicals from wastewater according to claim 1 or 2, characterized in that: it further includes a secondary sulfate radical precipitation unit and a secondary precipitation removal unit that are connected in sequence, and a secondary sulfate radical detection unit arranged on the pipeline between the water outlet of the precipitation removal unit and the water inlet of the secondary sulfate radical precipitation unit; the secondary sulfate radical detection unit is used to detect the concentration of sulfate ions contained in the precipitation removal product water before entering the secondary sulfate radical precipitation unit; the secondary sulfate radical precipitation unit is used to release barium ions to the precipitation removal product water according to the detected concentration of sulfate ions, so that the barium ions react with the sulfate ions remaining in the water to generate barium sulfate, and obtain secondary sulfate radical removal product water containing barium sulfate; the secondary precipitation removal unit is used to remove the barium sulfate contained in the secondary sulfate radical removal product water to obtain secondary precipitation removal product water.

4. The apparatus for electrochemically slow-releasing and removing sulfate radicals from wastewater according to claim 3, characterized in that: The secondary sulfate radical precipitation unit includes a secondary sulfate radical sedimentation tank, in which a water flow channel for the flow of the water produced by precipitation removal is formed. A secondary electrode assembly is arranged in the water flow channel, and a barium source substance is attached to the surface of the secondary electrode assembly. When an electric current is applied to the secondary electrode assembly, the barium source substance releases barium ions.

5. The device for electrochemically slow-releasing and removing sulfate radicals in wastewater according to claim 4, wherein: The structure of the secondary electrode assembly is the same as that of the electrode assembly, and the arrangement mode of the secondary electrode assembly in the secondary sulfate radical sedimentation tank is the same as that of the electrode assembly in the sulfate radical sedimentation tank.

6. The device for electrochemically slow-releasing and removing sulfate radicals in wastewater according to claim 3, wherein: It further includes a secondary pH adjustment unit arranged upstream of the secondary sulfate radical detection unit. The secondary pH adjustment unit is used to add a secondary pH adjustment agent to the water produced by precipitation removal to adjust the pH value of the water produced by precipitation removal to 7-9, so as to obtain secondary pH-adjusted water, and the secondary pH-adjusted water then enters the secondary sulfate radical precipitation unit.

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