Device for removing sulfate radicals in wastewater through electric slow release

Abstract

The invention relates to a device for removing sulfate radicals in wastewater through electric slow release. The device comprises a sulfate radical precipitation unit and a precipitate removal unit which are communicated in sequence, and a sulfate radical detection unit arranged on an upstream pipeline communicated with a water inlet of the sulfate radical precipitation unit, the sulfate radical detection unit is used for detecting the concentration of sulfate radical ions contained in the raw water before the raw water enters the sulfate radical precipitation unit; the sulfate radical 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 sulfate radical precipitation produced water containing the barium sulfate is obtained; and the precipitate removal unit is used for removing barium sulfate contained in the sulfate radical precipitate produced water to obtain precipitate-removed produced water. According to the method, the release speed of barium ions can be accurately controlled according to the concentration of sulfate radicals in the water body, excessive barium ions in the water can be recycled, secondary pollution caused by the fact that the adding amount of the barium ions cannot be accurately controlled in a traditional precipitation method is overcome, and meanwhile the amount of generated sludge is reduced.

Description

Technical Field

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

[0002] The components of wastewater are usually complex, containing a large amount of sulfate ions. These sulfate ions are likely 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 sulfate removal 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 ions 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. 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-slow-release removal of 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 sulfate in wastewater, comprising a sulfate precipitation unit and a precipitation removal unit connected in sequence, and a sulfate detection unit disposed on an upstream pipeline communicating with an inlet of the sulfate precipitation unit, wherein the sulfate detection unit is electrically connected to the sulfate precipitation unit; the sulfate detection unit is configured to detect the concentration of sulfate ions contained in raw water before entering the sulfate precipitation unit; the sulfate precipitation unit is configured to release barium ions into 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, thereby obtaining sulfate precipitation product water containing barium sulfate; and the precipitation removal unit is configured to remove the barium sulfate contained in the sulfate precipitation product water to obtain precipitation removal product water.

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

[0007] In one embodiment, the sulfate precipitation unit includes a sulfate precipitation tank, a water flow channel for the raw water to flow is formed in the sulfate precipitation tank, and an electrode assembly is disposed 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 precipitation 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 spirally surrounds 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 sulfate in wastewater further includes a pH adjustment unit disposed upstream of the sulfate detection unit; the pH adjustment unit is configured 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 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 a 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, 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, and 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 chemical 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. Description of the Drawings

[0017] Figure 1 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; Figure 2 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; Figure 3 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; Figure 4 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; Figure 5 Schematic structural diagram of Embodiment 3 of the device for electrochemically slow-releasing and removing sulfate radical in wastewater according to the present invention; Figure 6 Schematic structural diagram of Embodiment 4 of the device for electrochemically slow-releasing and removing sulfate radical in wastewater according to the present invention; Reference numerals: 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; 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; 304, tertiary sulfate radical detection unit; 40, tail gas treatment unit. Detailed implementation manners

[0018] Traditionally, the precipitation method is mostly used to remove sulfate ions in 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.

[0019] Based on this, the present invention adopts an electrochemically controlled method. According to the detected concentration of sulfate ions in the raw water, an electric 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 avoid the formation of water-insoluble scale substances by the reaction of sulfate ions with metal ions in the water. 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, avoiding the residual barium ions caused by excessive addition of barium ions, thus causing secondary pollution. Further, the present invention uses barium hydroxide as the barium source substance attached to the surface of the electrode assembly. 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 the instantaneous release of excessive barium ions after passing an electric 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.

[0020] The following further elaborates on the solution of the present invention with reference to the accompanying drawings.

[0021] Example 1 Figure 1 The specific structure of the device for electrochemically slow-releasing and removing sulfate in wastewater according to the present invention is shown, 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 according to 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.

[0022] 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. 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 non-contact. The first electrode 1004a is in 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 an anode and is connected to the positive pole of an external power source, and the second electrode 1004b is a cathode and is connected to the negative pole of the external power source. Among them, a layer of barium source substance 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 intersect with the water flow direction, but it is preferably as Figure 1 shown that 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. Combining with the structural settings of the first electrode 1004a and the second electrode 1004b in the electrode assembly 1004, the reaction time of sulfate in water with 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.

[0023] The first electrode 1004a and the second electrode 1004b are respectively connected to the anode and cathode of the power source. When an electric current is passed through the electrode assembly 1004, the first electrode 1004a undergoes an oxidation reaction:

[0024] The barium source substance on the surface will be ionized into barium ions and hydroxide ions and released into the water.

[0025] 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:

[0026] Meanwhile, the second electrode 1004b undergoes a reduction reaction to generate hydroxide ions:

[0027] The generated hydroxide ions recombine with barium ions to form barium hydroxide and precipitate and adhere to the surface of the second electrode 1004b:

[0028] The precipitation removal unit 102 includes a coagulation tank 1020, a flocculation tank 1022, and a barium ion regeneration tank 1024 that are connected in sequence. The coagulation tank 1020 is connected to the outlet of the sulfate precipitator 1000. Specifically, the coagulation tank 1020 is equipped with a coagulant feeder (not shown in the figure) for adding a flocculant to the coagulation tank 1020. The coagulant is specifically PAC. By adding the coagulant PAC (poly aluminum chloride), PAC will undergo a hydrolysis reaction in water to generate aluminum hydroxide colloid. The aluminum hydroxide colloid can also connect the colloid particles and suspended substances in water together through adsorption bridging to form larger flocs. The flocculation tank 1022 is equipped with a flocculant feeder (not shown in the figure) for adding a flocculant to the flocculation tank 1022. The flocculant is specifically PAM (polyacrylamide). By adding the flocculant PAM, PAM is a high molecular polymer with many active groups on its molecular chain, which can adsorb the colloid particles and suspended substances in water. Through the stretching and entanglement of the molecular chain, PAM can form a bridge between the particles, causing the particles to connect with each other to form larger flocs containing barium sulfate precipitate.

[0029] The raw water after coagulation and flocculation treatment flows to the precipitation removal tank 1024. As Figure 3 shown, the precipitation removal tank 1024 includes at least two cavities, divided into a first cavity and a second cavity. A filter is provided in the first cavity. The floc-containing flocculation produced water is subjected to solid-liquid separation in the first cavity through the filter to obtain precipitation removal produced water and a precipitation product containing barium sulfate. The precipitation removal produced water flows to the next-stage treatment process through the outlet of the precipitation removal tank 1024. For the precipitation product intercepted in the precipitation removal tank 1024, after the wastewater treatment is completed, carbon substances such as coke or graphene are added to the first cavity, so that barium sulfate reacts with the carbon substance under high-temperature conditions to generate barium sulfide and carbon monoxide:

[0030] Among them, carbon monoxide is discharged through the exhaust port of the first cavity, and barium sulfide enters the second cavity. The second cavity is connected to a water storage tank 1028. Water is added to the second cavity through the water storage tank 1028, and barium sulfide undergoes a hydrolysis reaction to generate barium hydroxide and hydrogen sulfide:

[0031] The generated barium hydroxide is collected into the barium hydroxide collection tank 1026 and can be reused as the barium source substance attached to the surface of the electrode assembly 1004. At the same time, the carbon monoxide generated is collected through the tail gas treatment unit 40 that 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 hardening removal agent in the pretreatment process.

[0032] 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. Then, the detected sulfate radical ion concentration information is fed back to the sulfate radical precipitation unit 100. The controller (not shown in the figure) of the sulfate radical precipitation unit 100 adjusts the magnitude of the current applied to the electrode assembly 1004 according to the sulfate radical ion concentration, so as to adjust the rate of barium ion release. The greater the current, the greater the amount of barium ion release; the smaller the current, the smaller the amount of barium ion release, thus achieving the accuracy of barium ion release. In addition to controlling the release rate of barium ions by the magnitude of the current, the controller can also control the release rate of barium ions by controlling the number of energized electrode assemblies 1004. The more the number of energized electrode assemblies 1004, the greater the amount of barium ion release; the fewer the number of energized electrode assemblies 1004, the smaller the amount of barium ion release. Since it is a prior art that the controller controls the energization of the electrode assembly 1004 according to the feedback signal, it will not be elaborated here.

[0033] When the device for electrochemically slow-releasing and removing sulfate radicals from wastewater in this embodiment works, first, the sulfate radical detection unit 104 detects the sulfate concentration in the incoming raw water and feeds it 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 radical detection unit 104. After the current is applied, 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.

[0034] In this way, the above device for electrochemically slow-releasing and removing sulfate radicals from wastewater applies a current to the electrode assembly 1004 attached with barium hydroxide according to the detected sulfate radical ion concentration in the water body, so that its first electrode 1004a slowly releases barium ions into the water body to precipitate the sulfate radical ions in the water, so as to prevent sulfates formed by sulfate radical 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 current. By adjusting the magnitude of the current, the release of barium ions can be accurately controlled, and secondary pollution caused by barium ion residue due to excessive addition of barium ions can be avoided.

[0035] Compared with the traditional precipitation method which usually uses barium chloride as the precipitating agent 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 material 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 barium ion release amount. 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 ions to generate hydrogen chloride. If barium chloride is used as the barium source material 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.

[0036] In addition, by using barium hydroxide as the barium source material, the barium ions in the water can be promoted to reattach to the first electrode 1004a and react with hydroxide ions to form barium hydroxide through the polarity reversal between the first electrode 1004a and the second electrode 1004b. Specifically: by reversing the direction of the current output by the power supply to reverse the polarities of the first electrode 1004a and the second electrode 1004b, 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 polarities of the first electrode 1004a and the second electrode 1004b are 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 the sulfate ions in the water to precipitate the sulfate ions. And the first electrode 1004a that 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 at the first electrode 1004a to form barium hydroxide, which is deposited on the surface of the first electrode 1004a, so that the barium hydroxide on the surface of the first electrode 1004a is restored to a certain extent. In this way, through the in-situ regeneration of barium hydroxide, the residual barium ions in the water can be recovered. In this way, through the periodic polarity switching between the first electrode and the second electrode, the dynamic balance of the decomposition and generation of barium hydroxide is achieved, so that the electrode assembly 1004 can be continuously used for a long time without frequently disassembling and replacing the electrode assembly 1004.

[0037] The following provides a preparation method for the first electrode 1004a and the second electrode 1004b attached with a barium hydroxide layer, including the following steps: S1: Prepare the substrate; Specifically, pure titanium (Ti) or a titanium alloy is selected as the base material of the first electrode 1004a and the second electrode 1004b of the electrode assembly 1004, and the first electrode 1004a in the form of a sheet and the second electrode 1004b in the form of a filament are fabricated. Among them, the thickness of the first electrode 1004a is 3 mm, and the diameter of the second electrode 1004b is 3 mm.

[0038] S2: Microporize the surface of the base material; Specifically, it includes the following steps: S21: Cleaning and degreasing: Clean the titanium surface with acetone or ethanol to remove grease and dirt. Then ultrasonically clean in deionized water; S22: Pickling: Immerse the titanium base material 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; 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.

[0039] S3: Form a barium source material layer on the surface of the base material; Specifically, it includes the following steps: 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.

[0040] S32: Mixing: Uniformly mix barium hydroxide and the binder to form a viscous suspension or paste, ensuring consistent composition distribution during uniform coating.

[0041] S33: Coating: Uniformly coat the barium hydroxide mixture on the microporous surface of the titanium base material by brushing, spraying or dipping. The thickness of the coating does not exceed 3 mm to ensure sufficient material quantity while preventing peeling caused by excessive coating thickness.

[0042] S4: Cure the coating; Specifically, it includes the following steps: S41: Drying: After coating, place the electrode assembly 1004 at room temperature to dry, allowing the surface moisture to evaporate and avoiding excessive shrinkage of the coating during high-temperature treatment; 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 bond the binder and barium hydroxide, and prevent peeling during use; S43: Cooling: After sintering is completed, slowly cool the electrode assembly 1004 to room temperature to avoid cracks or coating damage caused by rapid cooling.

[0043] Example 2 Figure 4 The specific structure of the device for electrochemically slow-release removing sulfate radical in wastewater according to Example 2 of the present invention is shown. As Figure 4 shown, the structure of the device for electrochemically slow-release removing sulfate radical in wastewater according to Example 2 of the present invention is substantially the same as that of Example 1, and the difference is only that: the device for electrochemically slow-release removing sulfate radical in wastewater of this embodiment further includes a pH adjustment unit 106 provided upstream of the sulfate radical precipitation unit 100, and the sulfate radical precipitation unit 100 is located on the pipeline connecting the pH adjustment unit 106 and the sulfate radical precipitation unit 100.

[0044] 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 electrochemically slow-release removing sulfate radical in wastewater works, the raw water first enters the pH adjustment tank 1060 of the pH adjustment unit 106, and acid solution or alkali solution is dosed into 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 radical sedimentation tank 1000 of the sulfate radical precipitation unit 100. In this embodiment, the acid solution is concentrated sulfuric acid and the alkali solution is sodium hydroxide.

[0045] 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 radicals, realizing efficient removal of sulfate radicals and reducing the corrosion risk of the electrode material at the same time. In addition, the higher 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.

[0046] Example 3 Figure 5 The specific structure of the device for electrochemically slow-release removing sulfate radical in wastewater according to Example 3 of the present invention is shown. As Figure 5As shown in the figure, the structure of the device for electrochemically slow-releasing and removing sulfate radicals from wastewater in Embodiment 3 of the present invention is substantially the same as that in Embodiment 2, and the difference lies only in that: the device for electrochemically slow-releasing and removing sulfate radicals from wastewater in this embodiment further includes a secondary sulfate radical precipitation unit 200 and a secondary precipitation removal unit 202 that are arranged downstream of the sulfate radical precipitation unit 100 and are connected in sequence, and a secondary sulfate radical detection unit 204 arranged on the pipeline between the precipitation removal unit 102 and the secondary sulfate radical precipitation unit 200.

[0047] Specifically, having the same structure as the sulfate radical precipitation unit 100, the secondary sulfate radical precipitation unit 200 includes a secondary sulfate radical sedimentation tank 2000. A plurality of secondary partitions 2002 arranged in parallel in the secondary sulfate radical sedimentation tank 2000 and the side wall of the secondary sulfate radical sedimentation tank 1000 form a water flow channel for the flow of the water produced by precipitation removal. A plurality of secondary electrode assemblies 2004 with barium hydroxide attached to their surfaces are arranged in the water flow channel. The distribution manner and working principle of the secondary electrode assemblies 2004 in the secondary sulfate radical sedimentation tank 2000 are the same as those of the electrode assemblies 1004 in the sulfate radical sedimentation tank 1000, and will not be elaborated here.

[0048] 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 radical sedimentation tank 2000. Specifically, the secondary coagulation tank 2020 is provided with a secondary coagulant feeder (not shown in the figure) for adding a coagulant to the secondary coagulation tank 2020. The secondary flocculation tank 2022 is provided with a secondary flocculant feeder (not shown in the figure) for adding a flocculant to the secondary flocculation tank 2022. The coagulant is PAC, and the flocculant is PAM. The water produced 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 produced flowing out of the secondary precipitation removal tank 2024 flows to the downstream 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.

[0049] When the device for electrochemically slow-releasing and removing sulfate ions from wastewater in this embodiment is in operation, the sulfate ions in the raw water are first treated for the first time by the sulfate precipitation unit 100 and the precipitation removal unit 102. Then, the secondary sulfate detection unit 204 detects the concentration of sulfate ions contained in the water produced by the precipitation removal after 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 a second treatment on the water produced by the precipitation removal to further remove the sulfate ions in the water.

[0050] In this way, 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).

[0051] Further, 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 water produced by the secondary precipitation removal 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.

[0052] Embodiment 4 Figure 6 The specific structure of the device for electrochemically slow-releasing and removing sulfate ions from wastewater in Embodiment 4 of the present invention is shown. As Figure 6 shown, the structure of the device for electrochemically slow-releasing and removing sulfate ions from wastewater in Embodiment 4 of the present invention is substantially the same as that of Embodiment 3, and the only difference is that: the device for electrochemically slow-releasing and removing sulfate ions from 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.

[0053] The same as the structure of 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 water produced by the precipitation removal 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 water produced by the precipitation removal after pH adjustment is then introduced into the sulfate precipitation tank 2000 of the secondary sulfate precipitation unit 200.

[0054] 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 the secondary sulfate precipitation unit 200 in controlling the release rate of barium ions, realize the slow release of barium ions, avoid the excessive release of barium ions and cause secondary pollution, and at the same time be beneficial to the in-situ growth of barium hydroxide on the cathode of the secondary electrode assembly 2004 during the polarity inversion.

[0055] The device for electrochemically slow-releasing and removing sulfate in wastewater according to any of the above embodiments can be applied to the front end of a wastewater treatment system. The sulfate ions contained in the raw wastewater are removed by the device for electrochemically slow-releasing and removing sulfate in wastewater, so that the concentration is reduced to 100 mg / L, and then the next-stage treatment process is carried out to avoid the continuous accumulation and scaling of sulfates during the treatment process, which affects the operation of the equipment and even damages the equipment.

[0056] Effect verification The device for electrochemically slow-releasing and removing sulfate in wastewater of Example 2 of the present invention and the device for electrochemically slow-releasing and removing sulfate in wastewater using the precipitation method (hereinafter referred to as "comparative example") were respectively used to treat the same batch of oilfield produced water (pilot-scale amplification), and then the effects of removing sulfates in the water by the two were compared. The difference between the comparative example and Example 2 of the present invention is that: on the basis of Example 2 shown in Figure 4 In the present invention, the sulfate precipitation tank provided with the electrode assembly in Example 2 was replaced with a sulfate precipitation tank connected to the barium source substance feeder in the comparative example. The barium source substance feeder of the comparative example includes a storage tank for storing the barium source substance and a flow control valve provided on the pipeline between the outlet of the storage tank and the sulfate precipitation tank. The flow control valve is purchased on the market and is provided on the pipeline between the outlet of the storage tank and the sulfate precipitation tank to control the addition amount of the barium source substance added to the sulfate precipitation tank. The specific barium source substance used is barium chloride. The comparative example controls the opening degree of the flow control valve according to the detected sulfate ion concentration in the raw water to add barium chloride to the sulfate precipitation tank. The structural settings of other functional units in the comparative example are the same as those in Example 2.

[0057] Then, the device for electrochemically slow-releasing and removing sulfate in wastewater of Example 2 and the device for electrochemically slow-releasing and removing sulfate in wastewater of the comparative example were respectively used to treat the raw oilfield produced water shown in Table 1 for 30 minutes, and the results before and after the treatment are compared as shown in Table 2: Table 1

[0058] Table 2

[0059] * The sludge volume refers to the amount of the precipitation product obtained after solid-liquid separation in the precipitation removal tank.

[0060] As can be seen from Table 2, through Example 2 of the present invention, the concentration of barium ions in water can be reduced to 20 mg / L within a short time (30 min), which is much lower than the concentration of sulfate ions of 500 mg / L in the water treated by the comparative example; and the concentration of residual barium ions after being treated by 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 by Example 2 of the present invention is better than that of the comparative example, and the residual amount of barium ions after being treated by Example 2 of the present invention is also lower than that of 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 and closing 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 being treated by the comparative example, these barium ions fail to fully combine with the 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 the 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 ( ), phosphate ions ( ), etc. in the oilfield produced water, which have strong coordination abilities, can form soluble complexes (such as ), or produce steric hindrance effects with metal ions, significantly delaying the precipitation reaction rate of barium ions and sulfate ions; (2) Ionic strength effect: The ionic atmosphere effect generated by the high salinity environment ( ) 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 ( , ) shows that it takes a relatively long time (up to dozens of minutes) to complete effective mass transfer. The occurrence of the above mechanisms leads to poor removal effect of sulfate ions in a short time in the comparative example. And in Example 2 of the present invention, a micro-reaction 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 micro-reaction environment: (1) Electromigration enrichment: Under the action of the 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 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 treated water of the precipitation.

[0061] In addition, since the amount of barium chloride added in the comparative example cannot be precisely controlled, 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.

[0062] 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 ions react with sulfate ions in the water to form barium sulfate precipitates to remove sulfate ions from the water, avoiding 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 utilizing the characteristic that barium hydroxide has a low solubility 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 precision 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 continuously used without frequent replacement of the electrode assembly.

[0063] 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 stated, "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.

[0064] 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. A device for removing sulfate from wastewater by electric slow release, characterized in that: It comprises a sulfate precipitation unit and a precipitation removal unit which are connected in sequence, and a sulfate detection unit which is arranged on an upstream pipeline which is connected to a water inlet of the sulfate precipitation unit, wherein the sulfate detection unit is electrically connected to the sulfate precipitation unit; The sulfate detection unit is used to detect the sulfate ion concentration contained in the raw water before entering the sulfate precipitation unit; The sulfate precipitation unit is used to release barium ions into the raw water according to the sulfate ion concentration detected, so that the barium ions react with the sulfate ions to generate barium sulfate, thereby obtaining sulfate precipitation water containing barium sulfate; The precipitation removal unit is used to remove the barium sulfate contained in the sulfate precipitation produced water to obtain precipitation removal produced water.

2. The device for removing sulfate from wastewater by electric slow release according to claim 1, characterized in that: The sulfate precipitation unit includes a sulfate precipitation tank, in which a water flow channel for the raw water to flow is formed. An electrode assembly is arranged in the water flow channel. A barium source material is attached to the surface of the electrode assembly. When current is passed through the electrode assembly, the barium source material releases barium ions.

3. The device for removing sulfate from wastewater by electric slow release according to claim 2, characterized in that: The electrode assembly is in an elongated strip shape as a whole, and the axial direction of the electrode assembly is perpendicular to the water flow direction in the sulfate precipitation tank.

4. The device for removing sulfate from wastewater by electric slow release according to claim 2, characterized in that: The electrode assembly comprises a first electrode and a second electrode which have opposite polarities and are not in contact with each other, and the barium source material is attached to the surfaces of both the first electrode and the second electrode.

5. The device for removing sulfate from wastewater by electric slow release according to claim 4, characterized in that: The first electrode is in a rod-shaped structure, and the second electrode is spirally wound around the outer periphery of the first electrode along the axial direction of the first electrode.

6. The device for removing sulfate from wastewater by electric slow release according to claim 1, characterized in that: Also included is a pH adjustment unit disposed upstream of the sulfate 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 produced water, and the pH-adjusted produced water then enters the sulfate precipitation unit.

7. The device for removing sulfate from wastewater by electric slow release according to any one of claims 1 to 6, characterized in that: It also includes a secondary sulfate precipitation unit and a secondary precipitation removal unit connected in sequence, and a secondary sulfate detection unit arranged on a pipeline between a water outlet of the precipitation removal unit and a water inlet of the secondary sulfate precipitation unit; The secondary sulfate detection unit is used to detect the sulfate ion concentration contained in the precipitation removal produced water before entering the secondary sulfate precipitation unit; The secondary sulfate precipitation unit is used to release barium ions into the precipitation removal produced water according to the sulfate ion concentration obtained by detection, so that the barium ions react with the sulfate ions remaining in the water to generate barium sulfate, thereby obtaining secondary sulfate removal produced water containing barium sulfate; The secondary precipitation removal unit is used to remove the barium sulfate contained in the secondary sulfate removal produced water to obtain secondary precipitation removal produced water.

8. The device for removing sulfate from wastewater by electric slow release according to claim 7, characterized in that: The secondary sulfate precipitation unit includes a secondary sulfate precipitation tank, in which a water flow channel is formed for the precipitation removal produced water to flow, and a secondary electrode assembly is arranged in the water flow channel. A barium source material is attached to the surface of the secondary electrode assembly. When current is passed through the secondary electrode assembly, the barium source material releases barium ions.

9. The device for removing sulfate from wastewater by electric slow release according to claim 8, characterized in that: The structure of the secondary electrode assembly is the same as the structure of the electrode assembly, and the arrangement of the secondary electrode assembly in the secondary sulfate precipitation tank is the same as the arrangement of the electrode assembly in the sulfate precipitation tank.

10. The device for removing sulfate from wastewater by electric slow release according to claim 7, characterized in that: It also includes a secondary pH adjustment unit arranged upstream of the secondary sulfate detection unit, and 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 to obtain secondary pH adjusted product water, and the secondary pH adjusted product water then enters the secondary sulfate precipitation unit.

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