Method and system for recycling ammonium fluoride wastewater

Abstract

The invention discloses a recovery treatment method of ammonium fluoride wastewater. The method comprises the following steps: firstly, separating ammonium ions from the ammonium fluoride wastewater in an ion exchange adsorption mode; and then, carrying out replacement reaction by utilizing a regeneration solution so as to transfer the ammonium ions into the regeneration solution. And then, controlling the pH value of the regeneration liquid subjected to the replacement reaction to be 10-11.5, so that the ammonium ions are converted into free ammonia. The pH-controlled regeneration liquid is then subjected to a stripping treatment to produce an ammonia-containing gas. And then, carrying out absorption treatment on the ammonia-containing gas to generate ammonia water. Therefore, the purposes of saving energy, reducing carbon and recycling waste can be achieved. The invention further discloses a recycling treatment system for the ammonium fluoride wastewater, which is used for implementing the steps.

Description

Technical Field

[0001] This invention relates to a wastewater treatment method and system, specifically to a method and system for the recovery and treatment of ammonium fluoride wastewater. Background Technology

[0002] Ammonium fluoride wastewater mainly originates from ammonium fluoride solutions used in industrial production processes, specifically in the semiconductor and electronics industries. In chip manufacturing, ammonium fluoride is used for etching and cleaning silicon wafers. This wastewater contains large amounts of fluoride and ammonium ions, and if discharged directly without treatment, it will have serious impacts on the environment and human health.

[0003] For ammonium fluoride wastewater, the commonly used treatment method is to first adjust the slightly acidic wastewater to alkaline, preheat it to 40-50°C using a heater, and then send it to a stripping tower for air stripping. The stripped free ammonia then enters an absorption tower with the air, where it is absorbed and captured using sulfuric acid. The resulting ammonium sulfate wastewater, once it reaches a fixed concentration range, is transported off-site by waste disposal companies for further treatment.

[0004] The above-mentioned treatment methods require large quantities of liquid alkali, sulfuric acid, heat sources, and electricity (for fans). Furthermore, the resulting ammonium sulfate waste liquid needs to be outsourced for treatment. Therefore, operating costs and indirect carbon emissions are often much higher than those of general wastewater treatment systems. In addition, in winter when ambient temperatures are low, the stripping and ammonia removal efficiency decreases significantly, often requiring additional heat sources to heat the wastewater to ensure that the residual ammonia nitrogen concentration in the treated water meets emission standards, further increasing operating costs. Therefore, the above-mentioned treatment methods are also susceptible to changes in ambient temperature. In summary, the above-mentioned treatment methods require large quantities of chemicals, consume high amounts of energy, have high waste treatment costs, and generate significant carbon emissions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for recycling and treating ammonium fluoride wastewater, in order to achieve the purpose of energy conservation, carbon reduction and resource recycling of waste, in order to overcome the shortcomings of the prior art.

[0006] To address the aforementioned technical problems, one of the technical solutions adopted by this invention is to provide a method for recycling and treating ammonium fluoride wastewater, comprising: separating ammonium ions from the ammonium fluoride wastewater by ion exchange adsorption; performing a displacement reaction using a regenerated liquid to transfer the ammonium ions into the regenerated liquid; controlling the pH value of the regenerated liquid after the displacement reaction at 10-11.5 to convert the ammonium ions into free ammonia; stripping the regenerated liquid with controlled pH value to generate ammonia-containing gas; and absorbing the ammonia-containing gas to generate ammonia water.

[0007] In an embodiment of the invention, the stripping process includes converting the free ammonia in the regenerated liquid with controlled pH into gaseous ammonia under the action of steam.

[0008] In an embodiment of the present invention, between the step of controlling the pH value of the regenerated liquid and the step of performing the stripping treatment, the method for recovering and treating ammonium fluoride wastewater further includes: heating the regenerated liquid with controlled pH value to increase the feed temperature of the stripping treatment.

[0009] In an embodiment of the present invention, the ammonium fluoride concentration in the ammonium fluoride wastewater is less than 0.05%, and the ammonia nitrogen concentration of the regenerated liquid after the displacement reaction is 10-12 times that of the ammonia nitrogen concentration in the ammonium fluoride wastewater.

[0010] To address the aforementioned technical problems, another technical solution adopted by the present invention is to provide a system for the recovery and treatment of ammonium fluoride wastewater, comprising an ion exchange device, a liquid supply device, an adjustment tank, a stripping device, and an absorption device. The ion exchange device is configured to separate ammonium ions from the ammonium fluoride wastewater through ion exchange adsorption. The liquid supply device is connected to the ion exchange device and is configured to supply a regenerated liquid to the ion exchange device for a displacement reaction, thereby transferring the ammonium ions into the regenerated liquid. The adjustment tank is connected to the ion exchange device and is configured to control the pH value of the regenerated liquid after the displacement reaction at 10-11.5, so that the ammonium ions are converted into free ammonia. The stripping device is connected to the adjustment tank and is configured to strip the pH-controlled regenerated liquid to generate ammonia-containing gas. The absorption device is connected to the stripping device and is configured to absorb the ammonia-containing gas to produce ammonia water.

[0011] In an embodiment of the present invention, the ion exchange device includes a strong acid type ion exchange resin for ion exchange adsorption of ammonium ions in the ammonium fluoride wastewater.

[0012] In an embodiment of the present invention, the liquid supply device includes a mixer for mixing a regenerator with water to form the regenerated liquid, wherein the regenerator is sodium hydroxide.

[0013] In an embodiment of the present invention, the stripping device is an ammonia stripping tower, which converts the free ammonia in the regenerated liquid with controlled pH value into gaseous ammonia under the action of steam.

[0014] In an embodiment of the present invention, the ammonium fluoride wastewater recycling system further includes a regenerated liquid collection tank, and the adjustment tank is connected to the ion exchange device through the regenerated liquid collection tank.

[0015] In an embodiment of the present invention, the ammonium fluoride wastewater recovery and treatment system further includes a heater. The heater is disposed between the adjusting tank and the stripping device to heat the regenerated liquid with controlled pH value, thereby increasing the feed temperature of the stripping process.

[0016] In an embodiment of the present invention, the ammonium fluoride wastewater recovery and treatment system further includes a heat exchanger. The heat exchanger is disposed between the adjusting tank and the heater, and is connected to the stripping device to recover the waste heat of the wastewater from the stripping device and transfer it to the regenerated liquid with controlled pH value.

[0017] In summary, the ammonium fluoride wastewater recovery and treatment method and system provided by this invention, by "separating ammonium ions from ammonium fluoride wastewater through ion exchange adsorption", "using a regenerated liquid for a displacement reaction to transfer the adsorbed ammonium ions to the regenerated liquid", "controlling the pH value of the regenerated liquid after the displacement reaction at 10-11.5 so that the ammonium ions in the regenerated liquid are converted into free ammonia", "stripping the regenerated liquid with controlled pH value to generate ammonia-containing gas", and "absorbing the ammonia-containing gas to generate ammonia water", can convert low-concentration ammonium fluoride wastewater into industrial-grade ammonia water, while reducing energy consumption and the amount of chemicals used, and avoiding pollution of the recovered ammonia water by fluoride ions.

[0018] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of one embodiment of the ammonium fluoride wastewater recovery and treatment system of the present invention.

[0020] Figure 2 This is another implementation diagram of the ammonium fluoride wastewater recovery and treatment system of the present invention.

[0021] Figure 3 This is another implementation architecture diagram of the ammonium fluoride wastewater recovery and treatment system of the present invention.

[0022] Figure 4 This is a flowchart of the ammonium fluoride wastewater recovery and treatment system of the present invention. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the "Method and System for Recycling and Treating Ammonium Fluoride Wastewater" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention. Furthermore, the accompanying drawings of this invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention.

[0024] Unless otherwise defined, the terms used herein have the same meaning as commonly understood by those skilled in the art. The operations or instruments involved in the various embodiments are, unless otherwise specified, conventional operations or instruments in the art.

[0025] The inventive concept of this invention is to first separate ammonium ions from low-concentration ammonium fluoride wastewater using ion exchange, and then introduce the resulting fluoride-containing wastewater into a separate treatment system; next, the ammonium ions are transferred to the regeneration liquid by displacement, which can concentrate the low-concentration ammonia nitrogen contained in the wastewater; then, through pH control, air stripping, absorption and other operations, industrial-grade ammonia water is finally produced, achieving the purpose of energy saving, carbon reduction and waste resource recycling.

[0026] First Embodiment

[0027] See Figure 1 As shown, the first embodiment of the present invention provides a recycling and treatment system Z for ammonium fluoride wastewater that fully embodies the above-described inventive concept. It mainly includes a liquid supply device 1, an ion exchange device 2, an adjustment tank 3, a stripping device 4, and an absorption device 5. The liquid supply device 1 is connected to the ion exchange device 2, and the ion exchange device 2 and the adjustment tank 3 operate in conjunction, meaning that the operation of the ion exchange device 2 and the operation of the adjustment tank 3 are interconnected and causally related. Furthermore, the adjustment tank 3 is connected to the stripping device 4, and the stripping device 4 is connected to the absorption device 5.

[0028] In this invention, ion exchange device 2 is configured to separate ammonium ions from ammonium fluoride wastewater by ion exchange adsorption; liquid supply device 1 is configured to supply a regenerated liquid to ion exchange device 2 for a displacement reaction, thereby transferring ammonium ions into the regenerated liquid; adjustment tank 3 is configured to control the pH value of the regenerated liquid after the displacement reaction at 10-11.5, so that ammonium ions are converted into free ammonia; stripping device 4 is configured to strip the regenerated liquid with controlled pH value to generate ammonia-containing gas; absorption device 5 is configured to absorb the ammonia-containing gas to generate ammonia water.

[0029] The ion exchange device 2 may contain an ion exchange resin, such as, but not limited to, a strong acid type ion exchange resin, to adsorb ammonium ions in wastewater at room temperature. The ion exchange device 2 may be a resin tower, but is not limited to this. Furthermore, the ion exchange device 2 can receive ammonium fluoride wastewater (such as low-concentration ammonium fluoride wastewater) to be treated via a wastewater pipeline L1. The wastewater pipeline L1 can be connected to a pump P, which propels the wastewater through the wastewater pipeline L1 into the ion exchange device 2 to contact the ion exchange resin, allowing the exchangeable ions in the resin to exchange with the ammonium ions in the water. Therefore, the ion exchange device 2 can rapidly reduce the ammonia nitrogen concentration in the wastewater to less than 30 mg / L.

[0030] The liquid supply device 1 may include a mixer 11 to mix a regenerant with water to form a regenerant of appropriate concentration. The regenerant may contain sodium ions, which can displace ammonium ions adsorbed on the ion exchange resin, causing the ammonium ions to desorb from the resin and release into the liquid, thereby achieving resin regeneration and reuse. For example, the regenerant may be an aqueous sodium hydroxide solution, i.e., the regenerant is sodium hydroxide, but it is not limited thereto. Furthermore, the liquid supply device 1 may supply the regenerant to the ion exchange device 2 via a dosing line L2 to contact the ion exchange resin for a displacement reaction; the dosing line L2 may be connected between the liquid supply device 1 and the ion exchange device 2. Therefore, the ammonia nitrogen in the wastewater can be significantly concentrated for subsequent reprocessing into ammonia water. In some embodiments, the ammonium fluoride concentration in the ammonium fluoride wastewater to be treated is less than 0.05%, and the ammonia nitrogen concentration of the regenerant after the displacement reaction is 10-12 times that of the ammonium fluoride wastewater.

[0031] In practical applications, when the ion exchange resin reaches a state of near-saturation or saturation, it can be determined by detecting the ammonia nitrogen concentration in the wastewater of the ion exchange device 2. The water in the ion exchange device 2 can be drained first, and then the regenerated liquid can be supplied to the ion exchange device 2 by the liquid supply device 1 to perform resin regeneration.

[0032] The pH of the regenerated solution in the conditioning tank 3 can be adjusted to the range of 10-11.5 by adding reagents, ensuring that almost all ammonium ions are converted into free ammonia that can be stripped to the gas phase; the reagents can be alkaline agents (such as sodium hydroxide) or acidic agents (such as sulfuric acid). In addition, a water quality detector 31 (such as a pH meter) can be installed in the conditioning tank 3 to detect the pH value of the regenerated solution, and the detection results can be used as a basis for adjusting the amount of reagent added.

[0033] The ammonium fluoride wastewater recovery and treatment system Z of the present invention may further include a regenerated liquid collection tank 6 connected to the ion exchange device 2. Therefore, the regenerated liquid, enriched with ammonia nitrogen after the displacement reaction, can first be sent to the regenerated liquid collection tank 6, awaiting pH adjustment in the subsequent adjustment tank 3. Furthermore, the ammonia nitrogen-rich regenerated liquid can flow from the regenerated liquid collection tank 6 through a liquid pipeline L3 into the adjustment tank 3; the liquid pipeline L3 can be connected between the adjustment tank 3 and the regenerated liquid collection tank 6. Alternatively, the ammonia nitrogen-rich regenerated liquid can be removed from the regenerated liquid collection tank 6 and transferred to the adjustment tank 3.

[0034] The stripping unit 4 extracts free ammonia from the regenerated liquid to the gas phase via gas-liquid contact, generating an ammonia-containing gas that is output from the top of the unit. The stripping unit 4 can be an ammonia stripping tower, but is not limited to this. Furthermore, the conditioning tank 3 can feed the ammonia-nitrogen-rich regenerated liquid to the stripping unit 4 via a liquid pipeline L4; the liquid pipeline L4 can be connected between the conditioning tank 3 and the stripping unit 4. Additionally, a suitable amount of saturated steam (steam pressure 1–2 kg / cm³) can be introduced from the bottom of the stripping unit 4. 2 The regenerated liquid flows from top to bottom in the device and comes into countercurrent contact with the rising water vapor, causing the free ammonia in the liquid phase to transfer to the gas phase.

[0035] See Figure 2 and Figure 3 As shown, the ammonium fluoride wastewater recovery and treatment system Z of the present invention may further include a heater 7 disposed between the adjusting tank 3 and the stripping unit 4 to heat the ammonia-nitrogen-rich regenerated liquid, thereby increasing the feed temperature of the stripping unit 4. The heater 7 may be a direct-heating electric heater or an indirect-heating heat medium heat exchanger, but is not limited thereto. In some embodiments, the temperature difference between the heated regenerated liquid and the temperature at the top of the stripping unit 4 (e.g., the temperature at the top of the ammonia stripping tower) may be in the range of 90°C to 95°C. Optionally, the ammonium fluoride wastewater recovery and treatment system Z of the present invention may further include a heat exchanger 8 disposed between the adjusting tank 3 and the heater 7, and the heat exchanger 8 is connected to the stripping unit 4 to recover the waste heat from the drainage of the stripping unit 4 and transfer it to the regenerated liquid. Therefore, the energy consumption of the heater 7 can be significantly reduced.

[0036] Absorption unit 5 can absorb gaseous ammonia with water (i.e., water as the absorbent) to form ammonia water. Absorption unit 5 can be an absorption tower, but is not limited to this. Furthermore, absorption unit 5 can receive ammonia-containing gas discharged from the top of stripping unit 4 through gas pipeline L5, and use spray absorption to directly contact water with the ammonia-containing gas to absorb and capture gaseous ammonia.

[0037] Second Embodiment

[0038] See Figure 4As shown, the second embodiment of the present invention provides a method for recycling and treating ammonium fluoride wastewater, which can be implemented by the ammonium fluoride wastewater recycling and treatment system provided in the first embodiment. The method for recycling and treating ammonium fluoride wastewater of the present invention includes at least the following steps: Step S100, separating ammonium ions from the ammonium fluoride wastewater by ion exchange adsorption; Step S102, performing a displacement reaction using a regenerated liquid to transfer the adsorbed ammonium ions to the regenerated liquid; Step S104, controlling the pH value of the regenerated liquid after the displacement reaction at 10-11.5 to convert the ammonium ions in the regenerated liquid into free ammonia; Step S106, stripping the pH-controlled regenerated liquid to generate ammonia-containing gas; and Step S108, absorbing the ammonia-containing gas to generate ammonia water.

[0039] In step S100, an ion exchange resin (such as a strong acid type ion exchange resin) can be used to adsorb ammonium ions in the wastewater at room temperature, so that the ammonium ions in the wastewater are adsorbed onto the ion exchange resin.

[0040] In step S102, the regenerated solution may contain sodium ions, which can displace the ammonium ions adsorbed on the ion exchange resin, causing the ammonium ions to desorb from the resin and release into the liquid, thereby achieving resin regeneration and reuse. For example, the regenerated solution is an aqueous solution of sodium hydroxide, that is, the regenerator is sodium hydroxide, but it is not limited to this.

[0041] In step S104, the pH of the regenerated solution can be adjusted to the range of 10-11.5 by adding a reagent to ensure that almost all ammonium ions are converted into free ammonia that can be stripped to the gas phase; the reagent can be an alkaline agent (such as sodium hydroxide) or an acidic agent (such as sulfuric acid).

[0042] In step S106, the stripping process includes converting free ammonia in the pH-controlled regenerated liquid into gaseous ammonia under the action of water vapor; during the process, the regenerated liquid flows from top to bottom and comes into countercurrent contact with the rising water vapor, causing the free ammonia in the liquid phase to transfer to the gas phase.

[0043] In step S108, gaseous ammonia can be absorbed by water (i.e., water is used as an absorbent). For example, water can be directly contacted with ammonia-containing gas and the gaseous ammonia can be absorbed and captured by spray absorption to form ammonia water. In this embodiment, before performing step S108, the regenerated liquid with controlled pH value can be heated to increase the feed temperature of the stripping treatment.

[0044] Beneficial effects of the embodiments

[0045] The ammonium fluoride wastewater recovery and treatment method and system provided by this invention, by "separating ammonium ions from ammonium fluoride wastewater through ion exchange adsorption", "using a regenerated liquid for a displacement reaction to transfer the adsorbed ammonium ions to the regenerated liquid", "controlling the pH value of the regenerated liquid after the displacement reaction at 10-11.5 so that the ammonium ions in the regenerated liquid are converted into free ammonia", "stripping the regenerated liquid with controlled pH value to generate ammonia-containing gas", and "absorbing the ammonia-containing gas to generate ammonia water", can convert low-concentration ammonium fluoride wastewater into industrial-grade ammonia water, while reducing energy consumption and chemical usage, and avoiding pollution of the recovered ammonia water by fluoride ions.

[0046] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of protection of the claims of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included within the scope of protection of the claims of the present invention.

Claims

1. A method for recovering and treating ammonium fluoride wastewater, characterized in that, The methods for recycling and treating this ammonium fluoride wastewater include: Ammonium ions were separated from ammonium fluoride wastewater by ion exchange adsorption. A displacement reaction is performed using a regenerated solution to transfer the ammonium ions into the regenerated solution; The pH of the regenerated solution after the displacement reaction is controlled at 10-11.5 so that the ammonium ions are converted into free ammonia; The regenerated liquid, with its pH controlled, is stripped to produce ammonia-containing gas; and The ammonia-containing gas is absorbed to produce ammonia water.

2. The method for recovering and treating ammonium fluoride wastewater according to claim 1, characterized in that, The stripping process involves converting free ammonia in the pH-controlled regenerated solution into gaseous ammonia under the action of steam.

3. The method for recovering and treating ammonium fluoride wastewater according to claim 2, characterized in that, Between the step of controlling the pH value of the regenerated liquid and the step of performing the stripping treatment, the method for recovering and treating ammonium fluoride wastewater further includes: heating the regenerated liquid with controlled pH value to increase the feed temperature of the stripping treatment.

4. The method for recovering and treating ammonium fluoride wastewater according to claim 1, characterized in that, The ammonium fluoride concentration in the ammonium fluoride wastewater is less than 0.05%, and the ammonia nitrogen concentration in the regenerated liquid after the replacement reaction is 10-12 times that of the ammonium fluoride wastewater.

5. A system for recovering and treating ammonium fluoride wastewater, characterized in that, The ammonium fluoride wastewater recovery and treatment system includes: An ion exchange device configured to separate ammonium ions from ammonium fluoride wastewater by ion exchange adsorption. A liquid supply device is connected to the ion exchange device. The liquid supply device is configured to supply a regenerated liquid to the ion exchange device for a displacement reaction, thereby transferring the ammonium ions into the regenerated liquid. An adjustment tank is connected to the ion exchange device. The adjustment tank is configured to control the pH value of the regenerated solution after the displacement reaction at 10-11.5 so that the ammonium ions are converted into free ammonia. A stripping unit, connected to the conditioning tank, is configured to strip the pH-controlled regenerated liquid to generate ammonia-containing gas; and An absorption device is connected to the stripping device and is configured to absorb and treat the ammonia-containing gas to produce ammonia water.

6. The ammonium fluoride wastewater recovery and treatment system according to claim 5, characterized in that, The ion exchange device includes a strong acid type ion exchange resin for ion exchange adsorption of ammonium ions in the ammonium fluoride wastewater.

7. The ammonium fluoride wastewater recovery and treatment system according to claim 5, characterized in that, The liquid supply device includes a mixer to mix a regenerant with water to form the regenerant solution, wherein the regenerant is sodium hydroxide.

8. The ammonium fluoride wastewater recovery and treatment system according to claim 5, characterized in that, The stripping unit is an ammonia stripping tower, which converts the free ammonia in the regenerated liquid with controlled pH into gaseous ammonia under the action of steam.

9. The ammonium fluoride wastewater recovery and treatment system according to claim 5, characterized in that, The ammonium fluoride wastewater recycling system further includes a regenerated liquid collection tank, and the adjustment tank is connected to the ion exchange device through the regenerated liquid collection tank.

10. The ammonium fluoride wastewater recovery and treatment system according to claim 5, characterized in that, The ammonium fluoride wastewater recovery and treatment system further includes a heater, which is located between the conditioning tank and the stripping device, to heat the regenerated liquid with controlled pH value, thereby increasing the feed temperature of the stripping process.

11. The ammonium fluoride wastewater recovery and treatment system according to claim 10, characterized in that, The ammonium fluoride wastewater recovery and treatment system further includes a heat exchanger located between the adjustment tank and the heater, and the heat exchanger is connected to the stripping device to recover the waste heat from the wastewater of the stripping device and transfer it to the regenerated liquid with controlled pH value.

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