Device and method for refining ammonium fluoride by recovering ammonia-containing waste gas and fluorine-containing waste water through membrane method

Abstract

The invention relates to the technical field of resource recovery, in particular to a device and method for recovering ammonia-containing waste gas and fluorine-containing waste water to refine ammonium fluoride through a membrane method, and the device 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, 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; according to the method, silicon impurities can be effectively removed without introducing new chemical agents, and recycling of high-purity ammonium fluoride is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of resource recovery, and in particular to a device and method for refining ammonium fluoride by recovering ammonia-containing waste gas and fluorine-containing waste water through a membrane method. Background Art

[0002] Membrane Contactor is a device that uses membrane separation technology to achieve gas-liquid or liquid-liquid mass transfer. It can be used in gas absorption, gas release, liquid degassing, liquid extraction and other fields. Compared with traditional absorption towers, it not only has the advantages of large mass transfer area and no mist entrainment, liquid flooding, channeling, bubbling, etc., but also has the characteristics of low investment, low energy consumption, easy use and simple operation. In the photovoltaic and semiconductor industries, processes such as coating will produce ammonia-containing waste gas with different outputs and concentrations. Its main components are ammonia, silane and nitrogen. In the etching and texturing processes, a large amount of hydrofluoric acid waste liquid with different concentrations and impurities will be produced. Its main components are hydrofluoric acid, fluorosilicic acid and water. Therefore, it is very valuable to use membrane contactors to simultaneously treat such alkaline waste gas and acidic waste liquid to recycle fluorine and ammonia resources.

[0003] At present, when using membranes to absorb 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 precipitation, so that these silicon dioxides will adhere to the membrane surface and cause membrane blocking problems. However, if the silicon impurities are not removed, the quality of the ammonium fluoride product will be affected. If liquid ammonia or high-concentration ammonia water is purchased from outside, its proportion is very small, and transportation and storage are also very troublesome. How to effectively remove silicon impurities and improve product quality without introducing new chemical agents, and not affecting the performance of the membrane, is a major problem that needs to be solved at present. Therefore, a membrane method for recovering ammonia-containing waste gas and fluorine-containing waste water to purify ammonium fluoride is proposed, which can effectively remove silicon impurities without introducing new chemicals and realize the recovery and utilization of high-purity ammonium fluoride. Summary of the invention

[0004] In view of the problems in the prior art, the present invention provides a device and method for refining ammonium fluoride from ammonia-containing waste gas and fluorine-containing wastewater by membrane method, so as to effectively remove silicon impurities without introducing new chemical agents and realize the recovery and utilization of high-purity ammonium fluoride.

[0005] The technical solution adopted by the present invention to solve the technical problem is a device and method for refining ammonium fluoride by membrane recovery of ammonia-containing waste gas and fluorine-containing waste water, comprising a first membrane absorption device, a second membrane absorption device, a membrane desorption device, a silicon separation device, an ammonia-containing waste gas delivery pipe, a hydrofluoric acid waste liquid delivery pipe and a high-concentration waste acid delivery pipe;

[0006] The first membrane absorption device includes a first gas phase side and a first liquid phase side, and the gas outlet end of the ammonia waste gas delivery pipe is connected to the first gas phase side, and the liquid outlet end of the hydrofluoric acid waste liquid delivery pipe is connected to the first liquid phase side.

[0007] By adopting the above technical scheme, it is possible to control the pH value of the absorption liquid of the first membrane device by carrying out a staged reaction of fluorine and ammonia, so that the front-stage reaction is completed before the absorption liquid reaches the critical value for the precipitation of silicon dioxide, and then the high-concentration ammonia water and the absorption liquid are introduced into the silicon precipitation device to complete the back-stage reaction so that the silicon is removed outside the membrane, which not only avoids the problem of membrane blockage, but also realizes the recycling of high-purity ammonium fluoride. The second membrane absorption device and the membrane desorption device are used to extract and prepare high-concentration ammonia water from the waste gas to remove impurities, which not only does not introduce new chemical agents, but also avoids the risks of transportation and storage caused by purchasing liquid ammonia, truly realizing the purpose of "treating waste with waste" and having great environmental benefits.

[0008] Specifically, the second membrane absorption device includes a second gas phase side and a second liquid phase side, and the liquid outlet end of the second membrane absorption device is connected to the membrane desorption device through a pipeline, the gas outlet end of the ammonia-containing waste gas delivery pipe is connected to the second gas phase side, and the liquid outlet end of the hydrofluoric acid waste liquid delivery pipe is connected to the second liquid phase side.

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

[0010] Specifically, the membrane desorption device includes a tube side and a shell side, and the liquid inlet end of the tube side is connected to 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 delivery pipe, a liquid alkali delivery pipe is provided on one side of the pure water delivery pipe, and the liquid outlet end of the liquid alkali delivery pipe is connected to the liquid outlet end of the second membrane absorption device.

[0011] By adopting the above technical scheme, high-concentration ammonium fluoride treated by the second membrane absorption device can be desorbed to prepare high-concentration ammonia water. Liquid alkali is added to the high-concentration ammonium fluoride solution to adjust the pH to 12, and then the solution is transported to the tube side of the membrane desorption device for cyclic desorption. Pure water is transported 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, so that the ionic NH4+ in the desorption liquid is converted into molecular volatile NH3↑ and passes through the tube side under pressure and is absorbed by the pure water on the shell side, thereby finally preparing high-concentration ammonia water.

[0012] Specifically, the silicon precipitation device includes a reaction sedimentation tank and a centrifugal filter, and the liquid outlets of the first membrane absorption device and the membrane desorption device are both connected to the reaction sedimentation tank, and the liquid outlet of the reaction sedimentation tank is connected to the centrifugal filter through a pipeline.

[0013] By adopting the above technical scheme, the crude ammonium fluoride solution prepared by the first membrane absorption device and the high-concentration ammonia water prepared by the membrane desorption device can be reacted to precipitate and filter silicon impurities in the solution to obtain a high-purity ammonium fluoride filtrate.

[0014] Specifically, the specific preparation method is as follows:

[0015] Step 1: Pass the ammonia-containing waste gas and the hydrofluoric acid waste liquid into the first gas phase side and the first liquid phase side of the first membrane absorption device through the ammonia-containing waste gas delivery pipe and the hydrofluoric acid waste liquid delivery pipe respectively, control the pH of the absorption liquid to be between 4.5-8.5 to start collecting the absorption liquid on the first liquid phase side, and the tail gas on the first gas phase side meets the emission standards;

[0016] Step 2: passing the ammonia-containing waste gas and the high-concentration waste acid into the second gas phase side and the second liquid phase side of the second membrane absorption device through the ammonia-containing waste gas delivery pipe and the high-concentration waste acid delivery pipe respectively, controlling the pH of the absorption liquid to be between 7-8.5 to start collecting the absorption liquid on the second liquid phase side, and the tail gas on the second gas phase side meets the emission standards;

[0017] Step 3: Add alkali solution into the absorption liquid obtained after the treatment in step 2 through the alkali liquid delivery pipe to adjust the pH to above 11;

[0018] Step 4: passing the solution obtained by the treatment in step 3 into the tube side / shell side of the membrane desorption device, and then passing pure water into the shell side / tube side of the membrane desorption device through the pure water delivery pipe to obtain desorption liquid and ammonia water;

[0019] Step 5: Add the absorption liquid obtained in step 1 and the ammonia water obtained in step 4 to a silicon precipitation device, control the pH of the reaction liquid to 8.5-13, and convert the fluorosilicic acid in the absorption liquid into silicon dioxide precipitate in the reaction precipitation tank. After separation by a centrifugal filter, filter residue and high-purity ammonium fluoride filtrate are obtained. The filter residue can be treated alone or refined into silicon dioxide.

[0020] By adopting the above technical solution, silicon impurities can be effectively removed without introducing new chemical agents, thereby realizing the recycling of high-purity ammonium fluoride.

[0021] The pH of the absorption liquid in step 1 is controlled at 7-8, which can not only make the hydrofluoric acid react completely, but also prevent the premature precipitation of silicon dioxide and cause membrane blockage;

[0022] The pressure on the desorption liquid side in step 4 is always greater than the pressure on the absorption liquid side;

[0023] The pH of the reaction solution in step 5 is controlled at 9-12, so that all the fluorosilicic acid impurities in the reaction solution are reacted into silicon dioxide and precipitated, thereby improving the purity of ammonium fluoride.

[0024] Beneficial effects of the present invention:

[0025] The present invention discloses a device and method for refining ammonium fluoride by membrane method for recovering ammonia-containing waste gas and fluorine-containing waste water. The method comprises the following steps: performing a staged reaction of fluorine and ammonia, controlling the pH value of the absorption liquid of the first membrane device, completing the front-stage reaction of the absorption liquid before the critical value of silicon dioxide precipitation, and then introducing high-concentration ammonia water and the absorption liquid into a silicon precipitation device to complete the back-stage reaction so that silicon is removed outside the membrane. This not only avoids the problem of membrane blockage, but also realizes the recovery and utilization of high-purity ammonium fluoride. The second membrane absorption device and the membrane desorption device are used to extract and prepare high-concentration ammonia water from the waste gas to remove impurities. This not only does not introduce new chemical agents, but also avoids the risks of transportation and storage caused by purchasing liquid ammonia. This truly realizes the purpose of "treating waste with waste" and has great economic value and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0027] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0028] Figure 2 It is a schematic structural diagram of the first membrane absorption device of the present invention;

[0029] Figure 3 It is a schematic structural diagram of the second membrane absorption device of the present invention;

[0030] Figure 4 It is a schematic structural diagram of the membrane desorption device of the present invention;

[0031] Figure 5 It is a schematic structural diagram of the silicon precipitation device of the present invention;

[0032] Figure 6 This is a schematic structural diagram of Embodiment 2 of the present invention;

[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 delivery pipe; 304. liquid alkali delivery pipe; 4. siliconization device; 401. reaction precipitation tank; 402. centrifugal filter; 5. ammonia-containing waste gas delivery pipe; 6. hydrofluoric acid waste liquid delivery pipe; 7. high-concentration waste acid delivery pipe. DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0035] Embodiment 1:

[0036] First, 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 transport 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 transport pipe 6. Since the gas-liquid contact surface of the membrane absorption device is a hydrophobic selective permeable membrane material, the gas can pass through the membrane from the tube side to enter the first liquid phase side 102 of the shell side, while the liquid cannot pass through the membrane from the shell side to enter the first gas phase side 101 of the tube side. When the gas enters the shell side liquid phase side 102, the ammonia is quickly absorbed by the hydrofluoric acid to generate ammonium fluoride, while the remaining gas nitrogen, etc., is not absorbed by the shell side liquid and is discharged in compliance with the standards (chemical reaction equation: NH3+HF→NH4F);

[0037] 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 the concentrated fluorine waste acid with a hydrofluoric acid content of 23.5% produced by the BSG process). Specifically, the high-concentration ammonium fluoride solution is added with liquid caustic soda through the liquid caustic soda delivery pipe 304 to adjust the pH to 12, and then is transported to the membrane desorption device 3 tube side 301 for cyclic desorption, and the pure water is transported to the membrane desorption device 3 shell side 302 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 ionic NH4+ in the desorption liquid is converted into molecular volatile NH3↑ and passes through the tube side under pressure and is absorbed by the pure water in the shell side, and finally prepares high-concentration ammonia water (tube side chemical reaction equation: NH4++OH-→NH3↑+H2O, shell side chemical reaction equation: NH3+H2O→NH3.H2O);

[0038] The silicon precipitation device 4 is composed of a reaction sedimentation tank 401 and a centrifugal filter 402, and is used to react the crude ammonium fluoride solution prepared by the first membrane absorption device 1 with the high-concentration ammonia water prepared by the membrane desorption device 3, precipitate and filter silicon impurities in the solution, so as to obtain a high-purity ammonium fluoride filtrate (chemical reaction equation: H2SiF6+6NH3+2H2O→SiO2↓+6NH4F).

[0039] Embodiment 2:

[0040] First, the ammonia-containing waste gas (ammonia concentration is 10%) is transported to the tube side of the first membrane absorption device 1 through the ammonia-containing waste gas transport pipe 5, and the fluoric acid waste liquid (hydrofluoric acid waste liquid pH is 2.1, and the hydrofluoric acid content is 6%) is transported to the shell side of the first membrane absorption device 1 through the hydrofluoric acid waste liquid transport pipe 6. Since the gas-liquid contact surface of the membrane absorption device is a hydrophobic selective permeable membrane material, the gas can pass through the membrane from the tube side to the liquid side of the shell side, while the liquid cannot pass through the membrane from the shell side to the gas side of the tube side. When the gas enters the liquid side of the shell side, the ammonia is quickly absorbed by the hydrofluoric acid to generate ammonium fluoride, and the remaining gas nitrogen, etc., is not absorbed by the shell side liquid and is discharged in compliance with the standards (chemical reaction equation: NH3+HF→NH4F);

[0041] The second membrane absorption device 2 is used to prepare 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 transport pipe 5, and the pure water is transported to the shell side of the second membrane absorption device 2. The ammonia gas is circulated and absorbed by the pure water 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 has not been completely absorbed until it meets the emission standards; (chemical reaction equation: NH3+H2O→NH3.H2O);

[0042] The silicon precipitation device 4 is composed of a reaction sedimentation tank 401 and a centrifugal filter 402, and is used to react the crude ammonium fluoride solution prepared by the first membrane absorption device 1 with the high-concentration ammonia water prepared by the second membrane absorption device 2, precipitate and filter silicon impurities in the solution, so as to obtain a high-purity ammonium fluoride filtrate (chemical reaction equation: H2SiF6+6NH3+2H2O→SiO2↓+6NH4F).

[0043] When the present invention is used, firstly, 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 delivery pipe 5 and the hydrofluoric acid waste liquid delivery pipe 6, and the pH of the absorption liquid is controlled to be between 4.5-8.5 to start collecting the absorption liquid of the first liquid phase side 102, and the tail gas of the first gas phase side 101 meets the discharge standard, and 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 delivery pipe 5 and the high-concentration waste acid delivery pipe 7, and the pH of the absorption liquid is controlled to be between 7-8.5 to start collecting the absorption liquid of the second liquid phase side 202, and the tail gas of the second gas phase side 201 meets the discharge standard;

[0044] Then, the absorption liquid obtained after the treatment of the second membrane absorption device 2 is added with alkali liquid through the liquid alkali delivery pipe 304 to adjust the pH to above 11, and then the obtained solution is passed into the tube side 301 / shell side 302 of the membrane desorption device 3, and then the pure water is passed into the shell side 302 / tube side 301 of the membrane desorption device 3 through the pure water delivery pipe 303 to obtain the desorption liquid and ammonia water;

[0045] 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, and the pH value of the reaction liquid is controlled to be 8.5-13. The fluorosilicic acid in the absorption liquid is converted into silicon dioxide precipitation in the reaction precipitation tank 401. After separation by the centrifugal filter 402, the filter residue and the high-purity ammonium fluoride filtrate are obtained. The filter residue can be treated separately or refined into silicon dioxide, so that the pH value of the absorption liquid of the first membrane device can be controlled by performing a staged reaction of fluorine and ammonia, so that the absorption liquid can complete the front-stage reaction before the critical value of silicon dioxide 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 so that silicon is removed outside the membrane, which not only avoids the problem of membrane clogging, but also realizes the recycling of high-purity ammonium fluoride. The second membrane absorption device and the membrane desorption device are used to extract and prepare high-concentration ammonia water from the waste gas to remove impurities, not only without introducing new chemical agents, but also avoiding the risks of transportation and storage caused by purchasing liquid ammonia, and truly realizing the purpose of "treating waste with waste", which is of great economic value and environmental benefits. 。

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A device and method for refining ammonium fluoride by membrane recovery of ammonia-containing waste gas and fluorine-containing waste water, characterized in that: It comprises 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 delivery pipe (5), a hydrofluoric acid waste liquid delivery pipe (6) and a high-concentration waste acid delivery pipe (7); The first membrane absorption device (1) comprises a first gas phase side (101) and a first liquid phase side (102), and the gas outlet end of the ammonia waste gas delivery pipe (5) is connected to the first gas phase side (101), and the liquid outlet end of the hydrofluoric acid waste liquid delivery pipe (6) is connected to the first liquid phase side (102).

2. The device and method for refining ammonium fluoride by membrane recovery of ammonia-containing waste gas and fluorine-containing waste water according to claim 1, characterized in that: The second membrane absorption device (2) comprises a second gas phase side (201) and a second liquid phase side (202), and the liquid outlet end of the second membrane absorption device (2) is connected to the membrane desorption device (3) through a pipeline, the gas outlet end of the ammonia-containing waste gas delivery pipe (5) is connected to the second gas phase side (201), and the liquid outlet end of the hydrofluoric acid waste liquid delivery pipe (6) is connected to the second liquid phase side (202).

3. The device and method for refining ammonium fluoride by membrane recovery of ammonia-containing waste gas and fluorine-containing waste water according to claim 2, characterized in that: The membrane desorption device (3) comprises a tube side (301) and a shell side (302), and the liquid inlet end of the tube side (301) is connected to the liquid outlet end of the first membrane absorption device (1) through a pipeline, and the liquid inlet end of the shell side (302) is provided with a pure water delivery pipe (303), and a liquid alkali delivery pipe (304) is provided on one side of the pure water delivery pipe (303), and the liquid outlet end of the liquid alkali delivery pipe (304) is connected to the liquid outlet end of the second membrane absorption device (2).

4. The device and method for refining ammonium fluoride by membrane recovery of ammonia-containing waste gas and fluorine-containing waste water according to claim 3, characterized in that: The silicon precipitation device (4) comprises a reaction sedimentation tank (401) and a centrifugal filter (402), and the liquid outlet ends of the first membrane absorption device (1) and the membrane desorption device (3) are both connected to the reaction sedimentation tank (401), and the liquid outlet end of the reaction sedimentation tank (401) is connected to the centrifugal filter (402) through a pipeline.

5. The device and method for refining ammonium fluoride by membrane recovery of ammonia-containing waste gas and fluorine-containing waste water according to claims 1-4, characterized in that: The specific preparation method is as follows: Step 1: passing ammonia-containing waste gas and hydrofluoric acid waste liquid 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 delivery pipe (5) and the hydrofluoric acid waste liquid delivery pipe (6), respectively, controlling the pH of the absorption liquid to be between 4.5 and 8.5 to start collecting the absorption liquid on the first liquid phase side (102), and the tail gas on the first gas phase side (101) meets the emission standards; Step 2: passing the ammonia-containing waste gas and the high-concentration waste acid 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 delivery pipe (5) and the high-concentration waste acid delivery pipe (7), respectively, controlling the pH of the absorption liquid to be between 7 and 8.5 to start collecting the absorption liquid on the second liquid phase side (202), and the tail gas on the second gas phase side (201) meets the emission standards; Step 3: adding alkali solution into the absorption liquid obtained after the treatment in step 2 through the alkali liquid delivery pipe (304) to adjust the pH to above 11; Step 4: passing the solution obtained by the treatment in step 3 into the tube side (301) / shell side (302) of the membrane desorption device (3), and then passing pure water into the shell side (302) / tube side (301) of the membrane desorption device (3) through the pure water delivery pipe (303) to obtain a desorption liquid and aqueous ammonia; Step 5: Add the absorption liquid obtained in step 1 and the ammonia water obtained in step 4 to the silicon precipitation device (4), control the pH of the reaction liquid to be 8.5-13, and convert the fluorosilicic acid in the absorption liquid into silicon dioxide precipitate in the reaction precipitation tank (401). After separation by a centrifugal filter (402), filter residue and high-purity ammonium fluoride filtrate are obtained. The filter residue can be treated alone or refined into silicon dioxide.

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