Apparatus and method for refining ammonium fluoride from ammonia-containing waste gas and fluorine-containing waste water by membrane process

Abstract

The application relates to the technical field of resource recycling, in particular to a device and a method for refining ammonium fluoride by recycling ammonia-containing waste gas and fluorine-containing waste water through a membrane method, which comprises a first membrane absorption device, a second membrane absorption device, a membrane desorption device, a silicon precipitation device, an ammonia-containing waste gas conveying pipe, a hydrofluoric acid waste liquid conveying pipe and a high-concentration waste acid conveying pipe; the first membrane absorption device comprises a first gas phase side and a first liquid phase side, and the gas outlet end of the ammonia-containing waste gas conveying pipe is connected with the first gas phase side, and the liquid outlet end of the hydrofluoric acid waste liquid conveying pipe is connected with the first liquid phase side; the silicon impurities can be effectively removed without introducing new chemical reagents, and recycling and utilization of high-purity ammonium fluoride are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resource recycling, in particular to a device and method for recovering ammonia-containing waste gas and fluorine-containing waste water to refine ammonium fluoride by membrane method. BACKGROUND

[0002] Membrane contactor is a kind of equipment that realizes gas-liquid or liquid-liquid mass transfer by using membrane separation technology, which can be applied to gas absorption, gas release, liquid degassing, liquid extraction and other fields. Compared with the traditional absorption tower, it not only has the advantages of large mass transfer area, no entrainment of mist, liquid overflow, channeling, bubbling and other advantages, but also has the characteristics of low investment, low energy consumption, convenient use and simple operation. In the process of coating in the photovoltaic and semiconductor industries, ammonia-containing waste gas with different production amounts and different concentrations will be produced, and the main components are ammonia, silane and nitrogen. In the etching and texturing processes, a large amount of hydrogen fluoride acid waste liquid with different concentrations and different impurities will be produced, and the main components are hydrofluoric acid, fluorosilicic acid and water. Therefore, it is very valuable to use membrane contactor to treat such alkaline waste gas and acidic waste liquid at the same time to realize the recycling of fluorine and ammonia resources.

[0003] At present, when using membrane absorption to treat ammonia-containing waste gas and hydrofluoric acid waste liquid, since the hydrofluoric acid waste liquid contains a large amount of silicon impurities, when the pH value of the absorption liquid is above 8-9, ammonia will react with fluorosilicic acid to gradually produce silicon dioxide precipitate, which will adhere to the surface of the membrane and cause membrane blockage. If the silicon impurities are not removed, the quality of ammonium fluoride products will be affected. If liquid ammonia or high-concentration ammonia water is purchased, the proportion of usage is very small, and transportation and storage are also very troublesome. How to effectively remove silicon impurities to improve product quality without introducing new chemical reagents, and how to maintain the performance of the membrane, are major problems to be solved at present. Therefore, a device and method for recovering ammonia-containing waste gas and fluorine-containing waste water to refine ammonium fluoride by membrane method are proposed, which can effectively remove silicon impurities without introducing new chemical reagents, and realize the recycling of high-purity ammonium fluoride. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a device and method for recovering ammonia-containing waste gas and fluorine-containing waste water to refine ammonium fluoride by membrane method, so as to effectively remove silicon impurities without introducing new chemical reagents, and realize the recycling of high-purity ammonium fluoride.

[0005] The technical solution adopted by the present application to solve the technical problems is a device and method for recovering ammonia-containing waste gas and fluorine-containing waste water to refine ammonium fluoride by membrane method, which comprises a first membrane absorption device, a second membrane absorption device, a membrane desorption device, a silicon precipitation device, an ammonia-containing waste gas conveying pipe, a hydrofluoric acid waste liquid conveying pipe and a high-concentration waste acid conveying pipe.

[0006] The first membrane absorption device comprises a first gas phase side and a first liquid phase side, and the gas outlet end of the ammonia-containing waste gas conveying pipe is communicated with the first gas phase side, and the liquid outlet end of the hydrofluoric acid waste liquid conveying pipe is communicated with the first liquid phase side.

[0007] By using the above technical scheme, the first membrane device can control the pH value of the absorption liquid by segmenting the reaction of fluorine and ammonia, so that the absorption liquid completes the front-stage reaction before reaching the critical value of silica precipitation, and then the high-concentration ammonia water and the absorption liquid are introduced into the silicon precipitation device to complete the rear-stage reaction to remove the silicon outside the membrane. Not only the problem of membrane blockage is avoided, but also the recycling of high-purity ammonium fluoride is realized. The second membrane absorption device and the membrane desorption device are used to extract and prepare high-concentration ammonia water from waste gas to remove impurities. Not only new chemical reagents are not introduced, but also the risks of transportation and storage of purchased liquid ammonia are avoided. The purpose of "waste treatment with waste" is truly realized, which has very good environmental benefits.

[0008] Specifically, the second membrane absorption device comprises a second gas phase side and a second liquid phase side, and the liquid outlet end of the second membrane absorption device is communicated with the membrane desorption device through a pipeline. The gas outlet end of the ammonia-containing waste gas conveying pipe is communicated with the second gas phase side, and the liquid outlet end of the hydrofluoric acid waste liquid conveying pipe is communicated with the second liquid phase side.

[0009] By using the above technical scheme, high-concentration ammonium salt can be prepared. The ammonia-containing waste gas is conveyed to the tube side of the second membrane absorption device, and the high-concentration waste acid is conveyed to the shell side of the second membrane absorption device. After the ammonia gas is absorbed by the waste acid, high-concentration ammonium fluoride is generated.

[0010] Specifically, the membrane desorption device comprises a tube side and a shell side. The liquid inlet end of the tube side is communicated with the liquid outlet end of the first membrane absorption device through a pipeline. The liquid inlet end of the shell side is provided with a pure water conveying pipe. One side of the pure water conveying pipe is provided with a liquid alkali conveying pipe. The liquid outlet end of the liquid alkali conveying pipe is communicated with the liquid outlet end of the second membrane absorption device.

[0011] By using the above technical scheme, high-concentration ammonia water can be prepared by desorbing the high-concentration ammonium fluoride treated by the second membrane absorption device. The high-concentration ammonium fluoride solution is added to the liquid alkali to adjust the pH to 12, and then is conveyed to the tube side of the membrane desorption device for cyclic desorption. The pure water is conveyed to the shell side of the membrane desorption device for cyclic absorption. By adjusting the operating pressure, the pressure on the desorption liquid side is greater than the pressure on the absorption liquid side, and a pressure difference is formed. The ionic NH4+ in the desorption liquid is converted into volatile NH3↑ in the molecular state, and is absorbed by the pure water in the shell side through the tube side under pressure. Finally, high-concentration ammonia water is prepared.

[0012] Specifically, the silicon precipitation device comprises a reaction precipitation tank and a centrifugal filter. The liquid outlet ends of the first membrane absorption device and the membrane desorption device are both communicated with the reaction precipitation tank. The liquid outlet end of the reaction precipitation tank is communicated with the centrifugal filter through a pipeline.

[0013] The crude ammonium fluoride solution prepared by the first membrane absorption device and the high-concentration ammonia water prepared by the membrane desorption device are reacted to precipitate and filter the silicon impurities in the solution, so that the high-purity ammonium fluoride filtrate is obtained.

[0014] Specifically, the method is as follows:

[0015] Step one: the ammonia-containing waste gas and the hydrofluoric acid waste liquid are respectively introduced into the first gas phase side and the first liquid phase side of the first membrane absorption device through the ammonia-containing waste gas conveying pipe and the hydrofluoric acid waste liquid conveying pipe, the pH of the absorption liquid is controlled to be between 4.5 and 8.5, the absorption liquid on the first liquid phase side is collected, and the tail gas on the first gas phase side is discharged up to the standard;

[0016] Step two: the ammonia-containing waste gas and the high-concentration waste acid are respectively introduced into the second gas phase side and the second liquid phase side of the second membrane absorption device through the ammonia-containing waste gas conveying pipe and the high-concentration waste acid conveying pipe, the pH of the absorption liquid is controlled to be between 7 and 8.5, the absorption liquid on the second liquid phase side is collected, and the tail gas on the second gas phase side is discharged up to the standard;

[0017] Step three: the absorption liquid obtained after the treatment in step two is added with lye through the lye conveying pipe to adjust the pH to be above 11;

[0018] Step four: the solution obtained after the treatment in step three is introduced into the tube side of the membrane desorption device, and pure water is introduced into the shell side of the membrane desorption device through the pure water conveying pipe, so that the desorption liquid and ammonia water are obtained;

[0019] Step five: the absorption liquid obtained in step one and the ammonia water obtained in step four are added into the silicon precipitation device, the pH of the reaction liquid is controlled to be between 8.5 and 13, the fluosilicic acid in the absorption liquid is changed into silicon dioxide precipitate in the reaction precipitation tank, and the filter residue and the high-purity ammonium fluoride filtrate are obtained after separation by the centrifugal filter, and the filter residue can be treated alone or refined into silicon dioxide.

[0020] By adopting the above technical scheme, the silicon impurities can be effectively removed without introducing new chemical reagents, and the recycling of high-purity ammonium fluoride is realized.

[0021] The pH of the absorption liquid in step one is controlled to be between 7 and 8, so that the hydrofluoric acid reaction is complete, and the silicon dioxide is prevented from being precipitated too early to cause membrane blockage.

[0022] The pressure on the desorption liquid side in step four is always greater than the pressure on the absorption liquid side;

[0023] The pH of the reaction liquid in step five is controlled to be between 9 and 12, so that all the fluosilicic acid impurities in the reaction liquid are reacted to form silicon dioxide and are precipitated, and the purity of the ammonium fluoride is improved.

[0024] The beneficial effects of the present application are as follows:

[0025] The device and method for refining ammonium fluoride from ammonia-containing waste gas and fluorine-containing waste water by membrane method, by carrying out segmented reaction on fluorine and ammonia, controlling the pH value of the absorption liquid of the first membrane device, making the absorption liquid complete the front-stage reaction before the critical value of silica precipitation, then introducing the high-concentration ammonia water and the absorption liquid into the silica precipitation device to complete the rear-stage reaction to remove silica outside the membrane, not only avoids the problem of membrane blockage, but also realizes the recycling of high-purity ammonium fluoride, and the second membrane absorption device and the membrane desorption device are used to extract and prepare high-concentration ammonia water from waste gas to remove impurities, which not only does not introduce new chemical reagents, but also avoids the transportation, storage and other risks brought by outsourcing liquid ammonia, truly realizes the purpose of "waste treatment", and has very high economic value and environmental protection benefits. BRIEF DESCRIPTION OF DRAWINGS

[0026] The application will be further described below in combination with the drawings and examples.

[0027] Figure 1 It is a structural schematic diagram of Example 1 of the application.

[0028] Figure 2 It is a structural schematic diagram of the first membrane absorption device of the application.

[0029] Figure 3 It is a structural schematic diagram of the second membrane absorption device of the application.

[0030] Figure 4 It is a structural schematic diagram of the membrane desorption device of the application.

[0031] Figure 5 It is a structural schematic diagram of the silica precipitation device of the application.

[0032] Figure 6 It is a structural schematic diagram of Example 2 of the application.

[0033] In the figure: 1, first membrane absorption device; 101, first gas phase side; 102, first liquid phase side; 2, second membrane absorption device; 201, second gas phase side; 202, second liquid phase side; 3, membrane desorption device; 301, tube side; 302, shell side; 303, pure water conveying pipe; 304, liquid alkali conveying pipe; 4, silica precipitation device; 401, reaction and precipitation tank; 402, centrifugal filter; 5, ammonia-containing waste gas conveying pipe; 6, hydrofluoric acid waste liquid conveying pipe; 7, high-concentration waste acid conveying pipe. DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, purposes and effects realized by the application easy to understand, the application will be further described below in combination with specific embodiments. Example 1

[0035] Firstly, the ammonia-containing waste gas (ammonia concentration of 1.2%) is transported to the tube side of the first membrane absorption device 1 through the ammonia-containing waste gas conveying pipe 5, and the hydrofluoric acid waste liquid (pH of 2.1, hydrofluoric acid content of 6%) is transported to the shell side of the first membrane absorption device 1 through the hydrofluoric acid waste liquid conveying pipe 6. Since the gas-liquid contact surface of the membrane absorption device is a hydrophobic selective permeation membrane material, the gas can permeate the membrane from the tube side to the shell side of the first liquid phase side 102, and the liquid cannot permeate the membrane from the shell side to the first gas phase side 101 of the tube side. When the gas enters the shell side of the first liquid phase side 102, the ammonia is rapidly absorbed by the hydrofluoric acid to generate ammonium fluoride, and the remaining gas such as nitrogen is discharged up to the standard because it is not absorbed by the shell side liquid (chemical reaction equation: NH3+HF→NH4F).

[0036] The membrane desorption device 3 is used to desorb the high-concentration ammonium fluoride treated by the second membrane absorption device 2 to prepare high-concentration ammonia water (the high-concentration waste acid is a concentrated fluorine waste acid with a hydrofluoric acid content of 23.5% generated by the BSG process). Specifically, the high-concentration ammonium fluoride solution is added to the liquid alkali through the liquid alkali conveying pipe 304 to adjust the pH to 12, and then is transported to the tube side 301 of the membrane desorption device 3 for cyclic desorption. Pure water is transported to the shell side 302 of the membrane desorption device 3 for cyclic absorption. By adjusting the operating pressure, the pressure on the desorption liquid side is greater than the pressure on the absorption liquid side, and a pressure difference is formed, so that the ion state NH4+ in the desorption liquid is converted into the molecular state volatile NH3↑, and is absorbed by the pure water in the shell side under pressure by permeating the tube side. Finally, high-concentration ammonia water is prepared (tube side chemical reaction equation: NH4++OH-→NH3↑+H2O, shell side chemical reaction equation: NH3+H2O→NH3·H2O).

[0037] The silicon precipitation device 4 is composed of a reaction precipitation tank 401 and a centrifugal filter 402, which is used to react the crude ammonium fluoride solution prepared by the first membrane absorption device 1 and the high-concentration ammonia water prepared by the membrane desorption device 3, precipitate and filter the silicon impurities in the solution, so as to obtain high-purity ammonium fluoride filtrate (chemical reaction equation: H2SiF6+6NH3+2H2O→SiO2↓+6NH4F). Example 2

[0038] Firstly, the ammonia-containing waste gas (ammonia concentration of 1.2%) is transported to the tube side of the first membrane absorption device 1 through the ammonia-containing waste gas conveying pipe 5, and the hydrofluoric acid waste liquid (pH of 2.1, hydrofluoric acid content of 6%) is transported to the shell side of the first membrane absorption device 1 through the hydrofluoric acid waste liquid conveying pipe 6. Since the gas-liquid contact surface of the membrane absorption device is a hydrophobic selective permeation membrane material, the gas can permeate the membrane from the tube side to the shell side of the first liquid phase side 102, and the liquid cannot permeate the membrane from the shell side to the first gas phase side 101 of the tube side. When the gas enters the shell side of the first liquid phase side 102, the ammonia is rapidly absorbed by the hydrofluoric acid to generate ammonium fluoride, and the remaining gas such as nitrogen is discharged up to the standard because it is not absorbed by the shell side liquid (chemical reaction equation: NH3+HF→NH4F).

[0039] The second membrane absorption device 2 is used for preparing high-concentration ammonia water, specifically, the ammonia-containing waste gas is transported to the tube side of the second membrane absorption device 2 through the ammonia-containing waste gas conveying pipe 5, and pure water is transported to the shell side of the second membrane absorption device 2, ammonia gas is absorbed by the pure water circulation to generate high-concentration ammonia water, and the remaining tail gas is connected to the first membrane absorption device 1 to continue to absorb the ammonia-containing waste gas that is not completely absorbed to reach the discharge standard; (chemical reaction equation: NH3+H2O→NH3.H2O).

[0040] The silicon precipitation device 4 is composed of a reaction precipitation tank 401 and a centrifugal filter 402, which is used for reacting the crude ammonium fluoride solution prepared by the first membrane absorption device 1 and the high-concentration ammonia water prepared by the second membrane absorption device 2 to precipitate and filter the silicon impurities in the solution, so as to obtain high-purity ammonium fluoride filtrate (chemical reaction equation: H2SiF6+6NH3+2H2O→SiO2↓+6NH4F).

[0041] In use, first, the ammonia-containing waste gas and the hydrofluoric acid waste liquid are respectively introduced into the first gas phase side 101 and the first liquid phase side 102 of the first membrane absorption device 1 through the ammonia-containing waste gas conveying pipe 5 and the hydrofluoric acid waste liquid conveying pipe 6, the pH of the absorption liquid is controlled to be between 4.5-8.5, the absorption liquid of the first liquid phase side 102 is collected, and the tail gas of the first gas phase side 101 is discharged to reach the standard, then the ammonia-containing waste gas and the high-concentration waste acid are respectively introduced into the second gas phase side 201 and the second liquid phase side 202 of the second membrane absorption device 2 through the ammonia-containing waste gas conveying pipe 5 and the high-concentration waste acid conveying pipe 7, the pH of the absorption liquid is controlled to be between 7-8.5, the absorption liquid of the second liquid phase side 202 is collected, and the tail gas of the second gas phase side 201 is discharged to reach the standard.

[0042] Then, the absorption liquid obtained after the treatment of the second membrane absorption device 2 is added with lye through the lye conveying pipe 304 to adjust the pH to be above 11, and then the obtained solution is introduced into the tube side 301 of the membrane desorption device 3, and pure water is introduced into the shell side 302 of the membrane desorption device 3 through the pure water conveying pipe 303 to obtain desorption liquid and ammonia water.

[0043] Finally, the absorption liquid obtained by the first membrane absorption device 1 and the ammonia water obtained by the membrane desorption device 3 are added to the silicon precipitation device 4, the pH of the reaction liquid is controlled at 8.5-13, the fluosilicic acid in the absorption liquid is changed into silicon dioxide precipitate in the reaction precipitation tank 401, and after separation by the centrifugal filter 402, the filter residue and high-purity ammonium fluoride filtrate are obtained, the filter residue can be treated alone or refined silicon dioxide, so that the fluorine ammonia is reacted in stages, the pH of the absorption liquid of the first membrane device is controlled, the front-stage reaction of the absorption liquid is completed before the critical value of the absorption liquid to the silicon dioxide precipitation, then the high-concentration ammonia water and the absorption liquid are introduced into the silicon precipitation device to complete the rear-stage reaction, so that the silicon is removed outside the membrane, not only avoiding the problem of membrane blockage, but also realizing the recycling of high-purity ammonium fluoride, and using the second membrane absorption device and the membrane desorption device to extract high-concentration ammonia water from the waste gas to remove impurities, not only without introducing new chemical reagents, but also avoiding the transportation, storage and other risks brought by the purchased liquid ammonia, truly realizing the purpose of "waste treatment with waste", and having very high economic value and environmental protection benefits.

[0044] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A membrane-based apparatus for recovering ammonia-containing waste gas and refining ammonium fluoride from fluoride-containing wastewater, characterized in that, It includes a first membrane absorption device (1), a second membrane absorption device (2), a membrane desorption device (3), a silicon precipitation device (4), an ammonia-containing waste gas conveying pipe (5), a hydrofluoric acid waste liquid conveying pipe (6), and a high-concentration waste acid conveying pipe (7). The first membrane absorption device (1) includes a first gas phase side (101) and a first liquid phase side (102), and the outlet end of the ammonia-containing waste gas conveying pipe (5) is connected to the first gas phase side (101), and the outlet end of the hydrofluoric acid waste liquid conveying pipe (6) is connected to the first liquid phase side (102). The second membrane absorption device (2) includes a second gas phase side (201) and a second liquid phase side (202), and the outlet end of the second membrane absorption device (2) is connected to the membrane desorption device (3) through a pipe. The outlet end of the ammonia-containing waste gas conveying pipe (5) is connected to the second gas phase side (201), and the outlet end of the hydrofluoric acid waste liquid conveying pipe (6) is connected to the second liquid phase side (202). The membrane desorption device (3) includes a tube side (301). The shell side (302) and the inlet end of the tube side (301) are connected to the outlet end of the first membrane absorption device (1) through a pipe. The inlet end of the shell side (302) is provided with a pure water delivery pipe (303). A liquid alkali delivery pipe (304) is provided on one side of the pure water delivery pipe (303). The outlet end of the liquid alkali delivery pipe (304) is connected to the outlet end of the second membrane absorption device (2). The silicon precipitation device (4) includes a reaction precipitation tank (401) and a centrifugal filter (402). The outlet ends of the first membrane absorption device (1) and the membrane desorption device (3) are both connected to the reaction precipitation tank (401). The outlet end of the reaction precipitation tank (401) is connected to the centrifugal filter (402) through a pipe.

2. A method for recovering ammonia-containing waste gas and refining ammonium fluoride from fluoride-containing wastewater using a membrane process, comprising the apparatus for recovering ammonia-containing waste gas and refining ammonium fluoride from fluoride-containing wastewater as described in claim 1, characterized in that, The specific method is as follows: Step 1: Ammonia-containing waste gas and hydrofluoric acid waste liquid are respectively introduced into the first gas phase side (101) and the first liquid phase side (102) of the first membrane absorption device (1) through the ammonia-containing waste gas conveying pipe (5) and the hydrofluoric acid waste liquid conveying pipe (6). The pH of the absorbent is controlled between 4.5 and 8.5 to start collecting the absorbent from the first liquid phase side (102). The tail gas from the first gas phase side (101) is discharged in compliance with the standard. Step 2: Ammonia-containing waste gas and high-concentration waste acid are respectively introduced into the second gas phase side (201) and the second liquid phase side (202) of the second membrane absorption device (2) through the ammonia-containing waste gas conveying pipe (5) and the high-concentration waste acid conveying pipe (7). The pH of the absorbent is controlled between 7 and 8.5 to start collecting the absorbent from the second liquid phase side (202). The tail gas from the second gas phase side (201) is discharged in compliance with the standard. Step 3: Add the absorbent obtained after step 2 to the alkali solution through the alkali delivery tube (304) and adjust the pH to above 11; Step 4: Pass the solution obtained after step 3 into the tube side (301) of the membrane desorption device (3), and then pass pure water into the shell side (302) of the membrane desorption device (3) through the pure water delivery pipe (303) to obtain desorption liquid and ammonia water; Step 5: Add the absorbent obtained in Step 1 and the ammonia obtained in Step 4 to the silicon precipitation device (4), control the pH of the reaction solution to 8.5-13, and convert the fluorosilicic acid in the absorbent into silicon dioxide precipitate in the reaction precipitation tank (401). After separation by centrifugal filter (402), filter residue and high-purity ammonium fluoride filtrate are obtained. The filter residue can be processed separately or refined into silicon dioxide.

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