A supergravity ammonia removal method for semiconductor high-concentration ammonia-containing wastewater
Patent Information
- Application Number
- CN202611225410.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-13
- Publication Date
- 2026-10-27
Smart Images
Figure CN122977620A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for removing ammonia from semiconductor wastewater with high concentrations of ammonia using ultragravity. Background Technology
[0002] Semiconductor manufacturing processes typically include silicon wafer cleaning, photolithography, etching, thin film deposition, diffusion, ion implantation, chemical mechanical polishing, and waste gas scrubbing. During these processes, ammonia-containing reagents such as ammonium fluoride, ammonia water, and ammonia gas are widely used, resulting in semiconductor ammonia-containing wastewater of varying concentrations and impurity types.
[0003] Existing semiconductor ammonia-containing wastewater is generally only roughly classified into two categories based on ammonia nitrogen concentration: high-ammonia nitrogen wastewater and low-ammonia nitrogen wastewater. High-concentration ammonia nitrogen wastewater treatment systems primarily treat high-ammonia, low-fluoride cleaning wastewater (this wastewater is generated during the silicon wafer cleaning process; its ammonia nitrogen mainly comes from ammonia water, with a high concentration, and also contains impurities such as hydrogen peroxide, dissolved silicon, particulate matter, and metal ions). The treatment process involves manganese sand filtration + two-stage air stripping + acid washing absorption. However, this process does not consider typical pollutants such as fluoride, dissolved silicon, and hydrogen peroxide in ammonia-containing wastewater, resulting in poor-quality ammonium sulfate (low purity) and a high amount of impurities in the effluent. This makes it impossible to achieve high-value resource recovery of ammonium sulfate and effective reuse of the deammonia-treated effluent. Furthermore, the gas-liquid interface mass transfer efficiency during ammonia nitrogen stripping is low, failing to achieve an ammonia nitrogen removal rate of over 99% under normal operating conditions. Summary of the Invention
[0004] Purpose of the invention: The purpose of this invention is to provide a method for removing ammonia from semiconductor high-concentration ammonia-containing wastewater by gravity. This method uses small-sized equipment, consumes low energy, has a short reaction time, and can achieve an ammonia nitrogen removal rate of over 99%. Furthermore, it can realize the recovery of high-purity ammonium sulfate and the effective reuse of the ammonia-removed effluent.
[0005] Technical solution: The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to the present invention includes the following steps:
[0006] (1) After being homogenized in the ammonia-containing wastewater equalization tank, the wastewater enters the manganese sand filter to remove hydrogen peroxide. The H2O2 in the effluent of the manganese sand filter is reduced to below 2 mg / L. Then the wastewater flows through the security filter and the precision filter in sequence to remove particulate matter, colloidal silica agglomerates and suspended solids in the wastewater before entering the pH equalization tank.
[0007] (2) Add 30% NaOH solution to the pH adjustment tank to adjust the pH of the wastewater to 10.5, and adjust the temperature of the wastewater to 45°C through a plate heat exchanger. The effluent from the pH adjustment tank enters the supergravity partitioned packed bed deammoniation reactor.
[0008] (3) The ammonia removal reactor with a supergravity partitioned packed bed is equipped with a partitioned packed bed; the partitioned packed bed is arranged radially as follows: an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone; among them, the radial thickness of the internal dispersion zone is 140 mm, and it uses large-pore PP structured packing with a porosity of 90%; the radial thickness of the central enhanced mass transfer zone is 240 mm, and it uses PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The external demisting and anti-entrainment zone has a radial thickness of 120mm and uses a wire mesh demister. Ammonia-containing wastewater enters the distributor through the central inlet pipe, is evenly sprayed into the internal dispersion zone through the distribution holes, and passes through the three packing zones sequentially from the inside to the outside under centrifugal force. The rotor (partitioned packing bed) operates at a speed of 1000r / min and has a treatment capacity of 10m³. 3 / h, gas-liquid ratio of 500:1, circulating gas volume of 5000m³ / h 3 / h;
[0009] (4) The ammonia-containing gas obtained after treatment by the high gravity partitioned packed bed deammoniation reactor enters the high gravity ammonia absorption reactor. The high gravity ammonia absorption reactor is equipped with a high gravity packed bed, which is made of PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The rotor (high-gravity packed bed) operates at a speed of 1000 r / min, and the sulfuric acid absorption liquid circulation rate is 10 m³ / min. 3 The gas-liquid ratio is 500:1; the pH of the sulfuric acid absorbent is maintained at 2.0~3.0 during the absorption process; after a period of reaction, when the mass fraction of ammonium sulfate in the absorbent in the acid storage tank reaches 20%~25%, a portion of the mother liquor (absorbent) is discharged to the ammonium sulfate resource utilization unit, with the discharge rate being 1%~3% of the absorbent circulation flow rate. Sulfuric acid is then added to the absorbent to continue the circulation and absorption; the ammonia concentration at the outlet of the gravity ammonia absorption reactor is below 5 mg / m³. 3 The deammoniation effluent obtained after treatment by the supergravity partitioned packed bed deammoniation reactor enters the subsequent reuse treatment unit.
[0010] In step (3), the supergravity partitioned packed bed ammonia removal reactor includes a reactor cavity I, which is equipped with a partitioned packed bed. The partitioned packed bed is arranged radially from the inside to the outside of the reactor cavity I as an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone. The reactor cavity I is also equipped with an ammonia-containing wastewater inlet, an ammonia removal outlet, a gas inlet, and a gas outlet. It also includes a motor I and a rotating shaft I connected to the motor I. The rotating shaft I is fixedly connected to the reactor cavity I through a sealed bearing. The rotating shaft I is fixedly connected to the partitioned packed bed. The ammonia-containing wastewater enters the distributor I through the central inlet pipe I and is evenly sprayed onto the internal dispersion zone. The wastewater is discharged onto the rotor (the partitioned packed bed serves as the distributor). Under the centrifugal force generated by the high-speed rotation of the rotor, the liquid flows from the inside to the outside through the three-zone packing. Air enters the zoned packing bed from the outside to the inside and comes into countercurrent contact with the liquid, causing free ammonia in the liquid phase to transfer to the gas phase. The internal dispersion zone is used to uniformly disperse the incoming water and pre-remove impurities such as particulate matter, colloidal silica, and metal hydroxides, reducing the risk of packing blockage caused by impurity deposition. The central enhanced mass transfer zone uses one of the following: metal wire mesh packing, plastic wire mesh packing, or ceramic structured packing, to form a liquid film, liquid filament, or liquid droplet with an extremely high specific surface area, realizing the main ammonia removal process. The external demisting and anti-entrainment zone is a wire mesh demister, used to remove entrained alkaline droplets, colloidal silica, particulate matter, metal impurities, etc.
[0011] In step (4), the supergravity ammonia absorption reactor includes a reactor cavity II, which is equipped with a supergravity packing bed. The reactor cavity II is also equipped with an absorbent inlet, an absorbent outlet, an ammonia-containing waste gas inlet, and a tail gas outlet. It also includes a motor II and a rotating shaft II that is connected to the motor II for transmission. The rotating shaft II is fixedly connected to the reactor cavity II through a sealed bearing. The rotating shaft II is fixedly connected to the supergravity packing bed. The sulfuric acid absorbent enters the distributor through a circulation pump and forms a liquid film, liquid filaments, and liquid droplets with extremely high specific surface area under the action of centrifugal force generated by the high-speed rotation of the rotor (the supergravity packing bed is the rotor). The ammonia-containing gas enters the supergravity packing bed from the outside to the inside and fully countercurrently contacts the sulfuric acid in the supergravity field. The ammonia is rapidly absorbed and reacts with the sulfuric acid to generate ammonium sulfate mother liquor. The sulfuric acid absorbent is industrial-grade sulfuric acid or waste sulfuric acid from a semiconductor plant. The reactor tail gas outlet may also be equipped with a demister, which is one of a wire mesh demister, a baffle demister, or a cyclone demister. The demister is used to collect acid mist and ammonium sulfate droplets, and the collected liquid is returned to the mother liquor circulation tank. This invention determines the concentration of ammonium sulfate in the absorbent by density, conductivity, or refractive index. When the mass fraction of ammonium sulfate in the absorbent in the acid storage tank reaches 20%~25%, a portion of the mother liquor is discharged to the ammonium sulfate resource utilization unit. The discharge amount is 1%~3% of the absorbent circulation flow rate. Sulfuric acid is then added to the absorbent to continue the circulation and absorption.
[0012] This invention utilizes high-speed rotation to generate an ultra-strong centrifugal force field (100~1000g, where g is the acceleration due to gravity), significantly increasing the gas-liquid contact area and mass transfer efficiency (more than 10 times that of traditional ammonia stripping towers). Under the same processing load and effect, it has a smaller volume (the packing height in the reactor is less than 1 / 10 of the packing height in traditional ammonia stripping towers, which require high packing heights to achieve high ammonia removal efficiency). The equipment footprint is reduced, and the system's resistance to load fluctuations is improved (when influent flow rate, ammonia nitrogen concentration, pH, temperature, etc., fluctuations occur, traditional ammonia stripping towers, due to their high gas-liquid contact area and mass transfer efficiency, are less efficient). With relatively fixed mass transfer areas, packing height, and gas-liquid ratio, the effluent ammonia nitrogen level tends to rise when water quality fluctuates. This invention's supergravity reactor features stronger gas-liquid mass transfer and faster operating speed. When influent water quality fluctuates, the system can utilize existing mass transfer margins to maintain high ammonia removal efficiency. Simultaneously, the internal dispersion zone within the partitioned packing bed buffers particulate matter and colloidal silica impacts, the middle enhanced mass transfer zone ensures ammonia mass transfer efficiency, and the outer demisting and anti-entrainment zone reduces the impact of gas entrainment on the subsequent acid absorption system, thereby improving the system's adaptability to fluctuations in ammonia-containing wastewater quality and load shocks. Furthermore... The partitioned packing bed used in this invention is divided into three zones radially from the inside to the outside along the rotation axis: an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone. This not only effectively reduces the risk of packing blockage caused by impurities in wastewater, but also reduces the pollution of ammonium sulfate mother liquor quality caused by gas phase entrainment. This invention employs a dual-hypergravity reactor coupling process to treat ammonia-containing wastewater. The front end uses a hypergravity partitioned packing bed ammonia removal reactor to rapidly transfer ammonium ions in the wastewater to the gas phase, while the rear end uses a hypergravity ammonia absorption reactor to rapidly absorb ammonia and convert it into ammonium sulfate mother liquor. This effectively avoids... It eliminates the risk of ammonia escape caused by the mismatch in mass transfer efficiency between the front and rear ends. Moreover, the dual-gravity system is more compact and has a lower height (under the same processing load and effect, the packing height is only 1 / 10 of the packing height of the traditional ammonia stripping tower), which can significantly shorten the conversion path of ammonia-containing gas, reduce the residence time of ammonia-containing gas in the system, and make it easier to control the tail gas to meet standards (the gas transport path is shorter, NH3 does not need to rely on the long gas-liquid contact path in the high tower, but is quickly captured and absorbed in a shorter process, reducing the risk of ammonia-containing gas entrainment and leakage in pipelines and towers, and improving the acid absorption response speed).
[0013] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: On the one hand, the equipment used in the method of the present invention is small in size, has low operating energy consumption, short reaction time, and the ammonia nitrogen removal rate can reach more than 99%; on the other hand, it can realize the recovery of high-purity ammonium sulfate and the effective reuse of deammoniation effluent. Attached Figure Description
[0014] Figure 1 This is a flowchart of the denitrification method of the present invention;
[0015] Figure 2 This is a schematic diagram of the structural principle of a high-gravity partitioned packed bed ammonia removal reactor.
[0016] Figure 3 This is a top view of the partitioned packed bed in a high-gravity partitioned packed bed ammonia removal reactor;
[0017] Figure 4 This is a schematic diagram of the structural principle of a supergravity ammonia absorption reactor. Detailed Implementation
[0018] like Figures 1-4 As shown, the system corresponding to the method of the present invention includes a homogenization conditioning tank, a manganese sand filter, a security filter, a precision filter, a pH conditioning tank, a high-gravity partitioned packed bed deammoniation reactor, and a high-gravity ammonia absorption reactor.
[0019] The supergravity partitioned packed bed ammonia removal reactor includes a reactor cavity I1, within which a partitioned packed bed 2 is provided. The partitioned packed bed, arranged radially from the inside to the outside of the reactor cavity I, consists of an internal dispersion zone 11, a central enhanced mass transfer zone 12, and an external demisting and anti-entrainment zone 13. The reactor cavity I1 also includes an ammonia-containing wastewater inlet 3, a deammoniation outlet 10, a gas inlet 8, and a gas outlet 9. The supergravity partitioned packed bed ammonia removal reactor also includes a motor I4 and a rotating shaft I5 connected to the motor I4. The rotating shaft I5 is fixedly and sealed to the reactor cavity I1 via a sealed bearing. The rotating shaft I4 is fixedly connected to the partitioned packed bed 2, and a sealing sleeve can be fitted over the rotating shaft I4. Ammonia-containing wastewater enters the distributor I7 through the central inlet pipe I6 (which is fixedly connected to the reactor and connected to the ammonia-containing wastewater inlet 3) and is evenly sprayed onto the internal dispersion zone 11. Under the centrifugal force generated by the high-speed rotation of the rotor, the wastewater passes through the three-zone packing in sequence from the inside to the outside. Air enters the partitioned packing bed 2 from the outside to the inside and comes into countercurrent contact with the liquid, causing the free ammonia in the liquid phase to transfer to the gas phase.
[0020] The supergravity ammonia absorption reactor includes a reactor cavity II14, which contains a supergravity packing bed 15. The reactor cavity II14 also has an absorbent inlet 18, an absorbent outlet 19, an ammonia-containing waste gas inlet 16, and a tail gas outlet 17. The supergravity ammonia absorption reactor also includes a motor II20 and a rotating shaft II21 that is connected to the motor II20 for transmission. The rotating shaft II21 is fixedly and sealed to the reactor cavity II14 through a sealed bearing. The rotating shaft II21 is fixedly connected to the supergravity packing bed 15. A sealing sleeve can be fitted over the rotating shaft II21. Sulfuric acid absorbent is pumped by circulation pump 24 and enters distributor II22 via central inlet pipe II23 (central inlet pipe II23 is fixedly connected to the reactor and communicates with absorbent inlet 18). Under the centrifugal force generated by the high-speed rotation of the rotor (the supergravity packing bed is used as the rotor), liquid film, liquid filaments, and droplets with extremely high specific surface area are formed. Ammonia-containing gas enters the supergravity packing bed 15 from the outside to the inside, and comes into full countercurrent contact with sulfuric acid in the supergravity field. The ammonia gas is rapidly absorbed and reacts with sulfuric acid to generate ammonium sulfate mother liquor. This invention uses density, conductivity, or refractive index to determine the concentration of ammonium sulfate in the absorbent in acid storage tank 25. When the mass fraction of ammonium sulfate in the absorbent in acid storage tank 25 reaches 20%~25%, part of the mother liquor (absorbent) is discharged to the ammonium sulfate resource utilization unit. The discharge amount is 1%~3% of the absorbent circulation flow rate. Sulfuric acid is then added to acid storage tank 25 to continue the circulation and absorption.
[0021] Example 1
[0022] High-ammonia, low-fluoride cleaning wastewater from a semiconductor factory: 10m³ 3 / h, pH 9.5, average ammonia nitrogen concentration of 1800 mg / L, fluoride ion concentration of 25 mg / L, H2O2 concentration of 100 mg / L, SiO2 concentration of 20 mg / L, total metal ion concentration of Cu, Ni, Fe and other metals of approximately 0.5 mg / L, turbidity of 8 NTU.
[0023] The method of the present invention for treating the above-mentioned ammonia-containing wastewater includes the following steps:
[0024] (1) The wastewater first undergoes water quality and quantity equalization treatment in an ammonia-containing wastewater equalization tank, and then enters a manganese sand filter to remove hydrogen peroxide. The H2O2 in the effluent from the manganese sand filter is reduced to below 2 mg / L. Subsequently, the ammonia-containing wastewater enters a security filter and a precision filter in sequence to remove particulate matter, colloidal silica agglomerates, suspended solids and other easily clogged substances in the ammonia-containing wastewater before entering the pH equalization tank.
[0025] (2) Add 30% NaOH by mass to the pH adjustment tank to adjust the pH of the wastewater to 10.5, and adjust the wastewater temperature to 45℃ through a plate heat exchanger. The effluent enters the super gravity partitioned packed bed deammoniation reactor.
[0026] (3) The ammonia removal reactor with a supergravity partitioned packed bed is equipped with a partitioned packed bed; the partitioned packed bed is arranged radially as follows: an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone; among them, the internal dispersion zone (radius of 140 mm) has a radial thickness of 140 mm and uses large-pore PP structured packing with a porosity of 90%; the central enhanced mass transfer zone has a radial thickness of 240 mm and uses PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The radial thickness of the external demisting and anti-entrainment zone is 120mm. The material used for demisting and anti-entrainment is the same as that of the wire mesh demister, i.e., the wire mesh is woven from a large number of metal / plastic filaments into a multi-layered interwoven mesh pad. The axial height of the zoned packing bed (rotor - cylindrical) is 500mm. Ammonia-containing wastewater enters the distributor I through the central inlet pipe I, and is evenly sprayed into the internal dispersion zone through the distribution holes. Under the action of centrifugal force, it passes through the three packing zones sequentially from the inside to the outside. The rotor operating speed is 1000r / min, the gas-liquid ratio is 500:1 (the flow ratio of gas (air) to liquid (ammonia-containing wastewater), and the circulating gas volume is 5000m³. 3 / h, at a water treatment capacity of 10m³ 3 Under the condition of / h, the hydraulic retention time of wastewater through the partitioned packed bed is about 15~20s. Under the above short contact time, the ammonia nitrogen in the effluent drops to 16mg / L, and the ammonia nitrogen removal rate is 99.1%. The deammoniated effluent obtained after treatment by the high gravity partitioned packed bed ammonia removal reactor enters the subsequent reuse treatment unit. In contrast, the traditional ammonia stripping tower (the axial height of the packing in the ammonia stripping tower (5m) is 10 times the axial height of the packing in the high gravity partitioned packed bed ammonia removal reactor) requires 1~2 hours to achieve an ammonia nitrogen removal rate of about 95%.
[0027] (4) The ammonia-containing waste gas generated by the high-gravity partitioned packed bed ammonia removal reactor enters the high-gravity ammonia absorption reactor. The high-gravity ammonia absorption reactor is equipped with a high-gravity packed bed. The axial height of the high-gravity packed bed (rotor) is 500 mm, and the outer diameter is 600 mm. The high-gravity packed bed uses PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The rotor operates at a speed of 1000 r / min, and the sulfuric acid absorption liquid circulation rate is 10 m³ / min. 3 The flow rate is 500:1 (gas (ammonia-containing waste gas) to liquid (absorbent)); the pH of the absorbent is controlled at 2.0~3.0 during acid absorption, and the ammonia concentration at the outlet of the supergravity ammonia absorption reactor is less than 5 mg / m³. 3 After 3-4 hours of reaction, when the mass fraction of ammonium sulfate in the absorbent in the acid storage tank reaches 20%-25%, part of the absorbent is discharged into the subsequent ammonium sulfate resource utilization unit, and sulfuric acid is added to the remaining absorbent to continue the circulation (the discharge volume is 3% of the absorbent circulation flow rate), while ensuring that the pH of the absorbent is 2-3.
[0028] The ammonium sulfate-containing absorbent solution (ammonium sulfate mass fraction of 20%) after the reaction in Example 1 was first passed through a 5μm precision filter to remove suspended solids, and then entered a reaction tank for silicon removal, fluorine removal, and metal removal. MgCl2 (Mg...) was then added to the tank. 2+ The dosage was 80 mg / L, with 500 mg / L PAC and 2 mg / L PAM added, the pH controlled at 5.5-6.5, and the reaction time 25 min. The effluent after precipitation was further treated with selective chelating resin to remove metal impurities, followed by ultrafiltration. The purified liquid had a fluoride ion concentration of 1 mg / L, a SiO2 concentration of 5 mg / L, a total metal concentration below 0.5 mg / L, and a turbidity of 0.8 NTU. The purified liquid was then introduced into an evaporation, concentration, and crystallization system, concentrated to an ammonium sulfate mass fraction of 38%-42%, and then introduced into a cooling crystallizer. The crystallization temperature was reduced from 55℃ to 25℃, and the crystallization time was 3 h. The wet ammonium sulfate crystals were obtained by centrifugation, dried at 80℃ for 60 min. The resulting ammonium sulfate crystals had a total nitrogen mass fraction of 21.0%, a moisture content below 1.0%, a free acid content below 0.2%, and a water-insoluble matter content below 0.1%. The crystals were white or off-white in appearance, and the purity of the ammonium sulfate crystals was above 99%.
[0029] Comparative Example 1
[0030] The only difference between Comparative Example 1 and Example 1 is that in step (4), the rotor speed of the supergravity ammonia absorption reactor is 0 r / min; the rest is the same as in Example 1.
[0031] High-ammonia, low-fluoride cleaning wastewater from a semiconductor factory: 10m³ 3 / h, pH 9.5, average ammonia nitrogen concentration of 1800 mg / L, fluoride ion concentration of 25 mg / L, H2O2 concentration of 100 mg / L, SiO2 concentration of 20 mg / L, total metal ion concentration of Cu, Ni, Fe and other metals of approximately 0.5 mg / L, turbidity of 8 NTU.
[0032] The specific steps for treating the above-mentioned ammonia-containing wastewater include:
[0033] (1) The wastewater first undergoes water quality and quantity equalization treatment in an ammonia-containing wastewater equalization tank, and then enters a manganese sand filter to remove hydrogen peroxide. The H2O2 in the effluent from the manganese sand filter is reduced to below 2 mg / L. Subsequently, the ammonia-containing wastewater enters a security filter and a precision filter in sequence to remove particulate matter, colloidal silica agglomerates, suspended solids and other easily clogged substances in the ammonia-containing wastewater before entering the pH equalization tank.
[0034] (2) Add 30% NaOH by mass to the pH adjustment tank to adjust the pH of the wastewater to 10.5, and adjust the wastewater temperature to 45℃ through a plate heat exchanger. The effluent enters the super gravity partitioned packed bed deammoniation reactor.
[0035] (3) The ammonia removal reactor with a supergravity partitioned packed bed is equipped with a partitioned packed bed; the partitioned packed bed is arranged radially as follows: an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone; among them, the radial thickness of the internal dispersion zone is 140 mm, and it uses large-pore PP structured packing with a porosity of 90%; the radial thickness of the central enhanced mass transfer zone is 240 mm, and it uses PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The radial thickness of the external demisting and anti-entrainment zone is 120mm. The material used for demisting and anti-entrainment is the same as that of the wire mesh demister, i.e., the wire mesh is woven from a large number of metal / plastic filaments into a multi-layered interwoven mesh pad. The axial height of the zoned packing bed (rotor) is 500mm. Ammonia-containing wastewater enters the distributor I through the central inlet pipe I, is evenly sprayed into the internal dispersion zone through the distribution holes, and passes through the three packing zones sequentially from the inside to the outside under the action of centrifugal force. The rotor operates at a speed of 1000r / min and has a processing capacity of 10m³. 3 / h, gas-liquid ratio 500:1, circulating gas volume 5000m³ / h 3 / h;
[0036] (4) The ammonia-containing waste gas generated by the high-gravity partitioned packed bed deammoniation reactor enters the high-gravity ammonia absorption reactor. The high-gravity ammonia absorption reactor is equipped with a high-gravity packed bed. The axial height of the high-gravity packed bed (rotor-cylindrical) is 500 mm, and the outer diameter is 600 mm. The high-gravity packed bed uses PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The rotor operating speed is 0 r / min, and the sulfuric acid absorption liquid circulation rate is 10 m³ / min. 3 / h, gas-liquid ratio is 500:1; pH of absorbent is controlled at 2.0~3.0 during acid absorption; under the same operating cycle as in Example 1 (after 3~4h of reaction), the mass fraction of ammonium sulfate in absorbent is only 12~16%.
[0037] Under the above conditions, since the packing bed in the absorption reactor does not rotate, the acid absorbent mainly passes through the static packing layer by ordinary spraying and gravity flow. The effective contact area and mass transfer rate between ammonia-containing gas and sulfuric acid absorbent are lower than in Example 1. The ammonia nitrogen concentration in the effluent of the supergravity partitioned packed bed reactor is approximately 75 mg / L, with an ammonia nitrogen removal rate of 95.8%. The ammonia concentration at the outlet of the supergravity ammonia absorption reactor reaches 200-250 mg / m³. 3 It is significantly higher than that of Example 1, which is less than 5 mg / m³. 3The ammonia concentration in the exhaust gas cannot consistently meet the requirements for deep exhaust gas control.
[0038] Comparative Example 1 used the same method as Example 1 to treat the ammonium sulfate-containing absorbent. The resulting ammonium sulfate crystals had a total nitrogen mass fraction of 19.2-19.5%, water content of less than 1.5%, free acid content of less than 0.3%, water-insoluble matter content of less than 0.2%, and appeared as white or off-white crystals. The purity of the ammonium sulfate was approximately 90.5%-92%.
[0039] Compared with Example 1, Comparative Example 1 shows that under the same operating conditions of the deammoniation reactor, if the rotor of the supergravity ammonia absorption reactor does not rotate, an effective supergravity gas-liquid enhanced mass transfer process cannot be formed at the acid absorption end, resulting in an increase in effluent ammonia nitrogen concentration, an increase in tail gas ammonia concentration, a decrease in ammonium sulfate mother liquor concentration, and a decrease in resource utilization efficiency.
[0040] Comparative Example 2
[0041] The only difference between Comparative Example 2 and Example 1 is that in step (3), the reactor operating speed is 3000 r / min, the gas-liquid ratio is 1000:1, and the circulating gas volume is 10000 m³ / min. 3 / h; the rest is the same as in Example 1. Under the above operating conditions, the ammonia nitrogen concentration in the deammoniation effluent is 12 mg / L, and the ammonia nitrogen removal rate is 99.3%. Compared with the effluent ammonia nitrogen of 16 mg / L and the ammonia nitrogen removal rate of 99.1% in Example 1, the ammonia nitrogen in the deammoniation effluent of Comparative Example 2 is only slightly lower, and the improvement in removal rate is limited.
[0042] Due to excessively high rotor speed and gas-liquid ratio, the liquid is over-atomized within the packed bed, significantly increasing the gas phase velocity. This leads to a higher load on the external demisting and anti-entrainment zone, resulting in increased alkaline droplets, colloidal particles, and metallic impurities entrained in the gas phase. Simultaneously, the gas flow rate entering the high-gravity ammonia absorption reactor reaches 10,000 m³ / s. 3 / h, while the sulfuric acid absorption liquid circulation rate is 10m³. 3 With an increase in gas-liquid load at the acid absorption end, the stability of tail gas ammonia concentration control decreases, and the concentration rises to 20-30 mg / m³. 3 Higher than 5 mg / m³ in Example 1 3 ammonia concentration in exhaust gas;
[0043] Within the same operating cycle as in Example 1, the ammonium sulfate mother liquor obtained in Comparative Example 2 had a mass fraction of 16%~20%. This mother liquor was subjected to precision filtration, silicon removal, fluoride removal, metal removal, ultrafiltration, evaporation concentration, cooling crystallization, centrifugation, and drying in the same manner as in Example 1. The resulting ammonium sulfate crystals had a total nitrogen mass fraction of 20.5%, moisture content below 1.2%, free acid content below 0.3%, and water-insoluble matter content below 0.2%. They appeared as white or off-white crystals, with an ammonium sulfate purity of approximately 96.7%, lower than the approximately 99.0% purity of ammonium sulfate in Example 1.
[0044] Comparative Example 2 shows that, in the process of deammoniation in a supergravity partitioned packed bed, although excessively high rotor speed and excessively large gas-liquid ratio can improve the ammonia nitrogen removal rate to a certain extent, the improvement is limited; at the same time, it will significantly increase mist entrainment, downstream acid absorption load and increase reaction energy consumption, and reduce the quality of ammonium sulfate mother liquor.
[0045] Comparative Example 3
[0046] The only difference between Comparative Example 3 and Example 1 is that in step (3), the operating speed of the ultragravity partitioned packed bed deammoniation reactor is 300 r / min; all other conditions are the same as in Example 1.
[0047] Under the above conditions, due to the reduced rotor speed, the centrifugal acceleration formed within the packing bed decreases, the degree of liquid dispersion weakens, and the effective gas-liquid contact area decreases. During continuous operation, the ammonia nitrogen concentration in the deammoniation effluent increases to 165 mg / L, with an ammonia nitrogen removal rate of 90.8%.
[0048] Because the amount of ammonia released into the gas phase at the deammoniation end is reduced, the mass fraction of ammonium sulfate mother liquor obtained at the acid absorption end is 10-15% within the same operating cycle. After the same crystallization treatment, the total nitrogen mass fraction of the obtained ammonium sulfate crystals is 20.2%, and the purity of ammonium sulfate is about 95.3%.
[0049] Comparative Example 3 illustrates that the supergravity partitioned packed bed deammoniation reactor needs to maintain an appropriate rotation speed. When the rotation speed is too low, an effective supergravity enhanced mass transfer state cannot be formed, resulting in a decrease in ammonia nitrogen removal rate and ammonium sulfate mother liquor generation efficiency.
[0050] Comparative Example 4
[0051] The only difference between Comparative Example 4 and Example 1 is that in step (3), the gas-liquid ratio of the ultragravity partitioned packed bed deammoniation reactor is 100:1, and the circulating gas volume is 1000 m³ / s. 3 / h; all other conditions are the same as in Example 1.
[0052] Under the above conditions, due to the reduced gas-liquid ratio, the ammonia-carrying capacity of the gas phase decreases for the same water volume, and the driving force for mass transfer from the liquid phase to the gas phase weakens. During continuous operation, the ammonia nitrogen concentration in the deammoniation effluent is 240 mg / L, and the ammonia nitrogen removal rate is approximately 86.7%.
[0053] Within the same operating cycle, the mass fraction of ammonium sulfate mother liquor obtained in Comparative Example 4 was about 8-12%, which was significantly lower than that in Example 1. After the same crystallization treatment, the total nitrogen mass fraction of the obtained ammonium sulfate crystals was 20%, and the purity of ammonium sulfate was about 94.3%.
[0054] Comparative Example 4 shows that a low gas-liquid ratio restricts the mass transfer process of ammonia from the liquid phase to the gas phase, resulting in a significant decrease in deammoniation efficiency. At the same time, due to insufficient ammonia entering the acid absorption end, the concentration of ammonium sulfate mother liquor increases and the resource utilization efficiency decreases.
[0055] Comparative Example 5
[0056] The only difference between Comparative Example 5 and Example 1 is that in step (4), the pH of the absorption solution is controlled at 5.0~6.0 during the acid absorption process; the other conditions are the same as those in Example 1.
[0057] Under the above conditions, due to the increase in pH of the acid absorbent, the reaction efficiency between ammonia and the acid absorbent decreases, the fixation capacity of NH3 at the acid absorbent end weakens, and the NH3 that is not fully absorbed returns to the supergravity partitioned packed bed deammoniation reactor, resulting in a decrease in deammoniation efficiency.
[0058] During continuous operation, the ammonia nitrogen concentration in the effluent from the ammonia removal process increased to 90 mg / L, with an ammonia nitrogen removal rate of 95%; the NH3 concentration at the outlet of the supergravity ammonia absorption reactor was 150~180 mg / m³. 3 Higher than 5 mg / m³ in Example 1 3 The concentration of NH3 in the exhaust gas.
[0059] Within the same operating cycle, the mass fraction of the ammonium sulfate mother liquor obtained in Comparative Example 5 was 14%–18%. After the same crystallization treatment, the total nitrogen mass fraction of the obtained ammonium sulfate crystals was 20.6%, and the purity of the ammonium sulfate was approximately 97.2%.
[0060] Comparative Example 5 shows that an excessively high pH in the acid absorbent reduces the ammonia absorption rate, leading to an increase in the NH3 concentration in the tail gas and further weakening the front-end ammonia removal effect.
[0061] Comparative Example 6
[0062] The only difference between Comparative Example 6 and Example 1 is that the ammonium sulfate mother liquor after the reaction in Example 1 is not subjected to 5μm precision filtration, silicon removal, fluoride removal, metal removal and ultrafiltration purification treatment, but is directly introduced into the evaporation concentration and crystallization system; all other conditions are the same as in Example 1.
[0063] Under the above conditions, the ammonia nitrogen concentration in the effluent from the ammonia removal process remains at 16 mg / L, the ammonia nitrogen removal rate is 99.1%, and the NH3 concentration at the outlet of the supergravity ammonia absorption reactor is below 5 mg / m³. 3 However, because the ammonium sulfate mother liquor was not purified and pretreated, the colloidal silicon, fluoride ions, metal ions and suspended particles carried in the mother liquor were enriched during the concentration process and entered the ammonium sulfate crystallization system, affecting the purity and appearance of the crystals.
[0064] After direct evaporation, concentration, crystallization, and centrifugation, the obtained ammonium sulfate crystals have a total nitrogen content of 20.2% to 20.5%, a water content of 1.0% to 1.8%, a free acid content of 0.2% to 0.5%, and a water-insoluble content of 0.5% to 1.0%. They appear as off-white to yellow crystals, and the purity of the ammonium sulfate is approximately 94.3% to 96.7%, which is lower than the approximately 99.0% purity of the ammonium sulfate in Example 1.
[0065] Comparative Example 6 illustrates that the filtration, silicon removal, fluoride removal, metal removal, and ultrafiltration purification steps before the ammonium sulfate mother liquor is recycled play an important role in improving the purity of ammonium sulfate crystals and enhancing the product appearance.
[0066] Example 2
[0067] The ammonia-removed effluent from the supergravity partitioned packed bed deammoniation reactor in Example 1 was neutralized with CO2 to adjust the pH to 7.0-7.5, and then treated by a precision filter. The effluent from the filter had an ammonia nitrogen concentration of 4.5 mg / L, a turbidity of 5 NTU, a COD of 25 mg / L, a BOD5 of 8 mg / L, a TDS of 850 mg / L, a color of 5 degrees, and no detected anionic surfactants. Therefore, this effluent can be used as tertiary recycled water for internal reuse in wastewater treatment plants, floor washing, low-requirement washing water, and partial cooling tower makeup water.
[0068] Example 3
[0069] High ammonia nitrogen cleaning wastewater from a semiconductor factory: 8m³ 3 / h, pH 7.8, average ammonia nitrogen concentration 1000mg / L, fluoride ion concentration 10mg / L, H2O2 concentration 20mg / L, SiO2 concentration 5mg / L, total metal ion concentration of Cu, Ni, Fe, etc. approximately 0.5mg / L, turbidity 10NTU.
[0070] The method of the present invention for treating the above-mentioned ammonia-containing wastewater includes the following steps:
[0071] (1) The wastewater first undergoes water quality and quantity equalization treatment in an ammonia-containing wastewater equalization tank, and then enters a manganese sand filter to remove hydrogen peroxide. The H2O2 in the effluent from the manganese sand tower is reduced to below 1 mg / L. Subsequently, the wastewater enters a security filter and a precision filter in sequence to remove particulate matter, colloidal silica agglomerates, suspended solids and other easily clogged substances before entering a pH equalization tank.
[0072] (2) Add 30% NaOH to the pH adjustment tank to adjust the pH to 10.5, and adjust the wastewater temperature to 45℃ through a plate heat exchanger. The effluent enters the super gravity partitioned packed bed deammoniation reactor.
[0073] (3) The ammonia removal reactor with a supergravity partitioned packed bed is equipped with a partitioned packed bed; the partitioned packed bed is arranged radially as follows: an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone; among them, the radial thickness of the internal dispersion zone is 140 mm, and it uses large-pore PP structured packing with a porosity of 90%; the radial thickness of the central enhanced mass transfer zone is 240 mm, and it uses PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The radial thickness of the external demisting and anti-entrainment zone is 120mm. The material used for demisting and anti-entrainment is the same as that of the wire mesh demister, i.e., the wire mesh is woven from a large number of metal / plastic filaments into a multi-layered interwoven mesh pad. The axial height of the zoned packing bed (rotor) is 500mm. Ammonia-containing wastewater enters the distributor through the central inlet pipe, is evenly sprayed into the internal dispersion zone through the distribution holes, and passes through the three packing zones sequentially from the inside to the outside under the action of centrifugal force. The rotor operating speed is 1000r / min, the gas-liquid ratio is 600:1 (gas to liquid flow ratio), and the circulating gas volume is 4800m³. 3 / h, at a water treatment capacity of 10m³ 3 Under the condition of / h, the hydraulic retention time of wastewater through the partitioned packing bed is about 15~20s. Under the above short contact time, the average effluent ammonia nitrogen concentration is 8mg / L, and the ammonia nitrogen removal rate is 99.2%.
[0074] (4) The ammonia-containing waste gas generated by the high-gravity partitioned packed bed ammonia removal reactor enters the high-gravity ammonia absorption reactor. The high-gravity ammonia absorption reactor is equipped with a high-gravity packed bed. The axial height of the high-gravity packed bed (rotor) is 500 mm, and the outer diameter is 600 mm. The high-gravity packed bed uses PVDF wire mesh packing with a specific surface area of 500 m². 2 / m 3 The rotor operates at a speed of 1000 r / min, and the sulfuric acid absorption liquid circulation rate is 8 m³. 3 The gas-liquid ratio is 600:1; the pH of the absorbent is controlled at 2.0~3.0 during acid absorption, and the ammonia concentration in the tail gas is below 5mg / m³. 3 .
[0075] Example 4
[0076] The ammonia-removed effluent from the supergravity partitioned packed bed deammoniation reactor in Example 2 is first neutralized with CO2 to adjust the pH to 7.0-7.5, then treated by a precision filter, with an effluent turbidity of 1 NTU; subsequently, it enters a silicon removal, fluoride removal, and metal removal reaction tank, where MgCl2 (Mg... 2+ The dosage was 80 mg / L, with the addition of 500 mg / L PAC and 2 mg / L PAM. The reaction pH was controlled at 9.5–10.0, and the reaction time was 25 min. After sedimentation, the effluent was further treated with selective chelating resin to remove metal impurities, followed by ultrafiltration and reverse osmosis. The RO recovery rate was 80%, and the operating pressure was 1.0–1.2 MPa. After RO treatment, the average conductivity of the effluent was 50 μS / cm, ammonia nitrogen was 1 mg / L, SiO2 concentration decreased to 0.8 mg / L, TOC reached 0.8 mg / L, total hardness was 2.5 mg / L, and F... - The concentration reaches 0.6 mg / L, the turbidity is 0.4 NTU, and the total metal ion concentrations such as Cu, Ni, and Fe are reduced to 0.02 mg / L. This effluent can be used as secondary recycled water for high-quality plant reuse, makeup water for pure water stations, and process auxiliary water.
[0077] Example 5
[0078] Example 5, based on Example 4, further prepares RO permeate into primary recycled water and performs quality control and concentration crystallization on ammonium sulfate mother liquor.
[0079] (1) The RO permeate volume obtained in Example 4 was 6.4 m³. 3 / h, the average conductivity of the effluent is 50 μS / cm, ammonia nitrogen is 1 mg / L, SiO2 concentration is 0.8 mg / L, TOC is 0.8 mg / L, total hardness is 2.5 mg / L, F - The concentration is 0.6 mg / L, the turbidity is 0.4 NTU, and the total metal ion concentration (Cu, Ni, Fe, etc.) is 0.02 mg / L. The RO permeate first enters a decarbonator to remove dissolved CO2, and then enters the EDI system. The EDI system has a recovery rate of 90%, an operating current of 4-6 A, and an operating voltage of 180-250 V.
[0080] (2) The EDI permeate further enters the terminal polishing unit. The terminal polishing unit includes a UV oxidizer, a polishing mixed bed, and a 0.05 μm terminal filter. The UV oxidizer wavelength is 185 nm / 254 nm, the resin layer height of the polishing mixed bed is 1.2 m, and the operating flow rate is 20 m / h. After terminal polishing, the resistivity of the effluent is 15 MΩ·cm, ammonia nitrogen is 0.05 mg / L, SiO2 is 8 μg / L, TOC is 10 μg / L, and F... -The concentration of particulate matter was 0.05 mg / L, and the total metal ion concentration was 0.001 mg / L. This effluent was used as high-end recycled water and entered the front-end makeup water tank of the ultrapure water system.
[0081] Comparative Example 7: Existing conventional two-stage air stripping + acid washing and absorption process
[0082] The high-ammonia, low-fluoride mixed cleaning wastewater with the same water quality as in Example 1 was treated using conventional processes. High-ammonia, low-fluoride cleaning wastewater from a semiconductor factory: 10m³ 3 / h, pH 9.5, average ammonia nitrogen concentration of 1800 mg / L, fluoride ion concentration of 25 mg / L, H2O2 concentration of 100 mg / L, SiO2 concentration of 20 mg / L, total metal ion concentration of Cu, Ni, Fe and other metals of approximately 0.5 mg / L, turbidity of 8 NTU.
[0083] (1) After the wastewater is adjusted to pH 11.5, it enters the secondary stripping tower. The stripping tower has a diameter of 1.5m, an axial height of 5m for the packing, a gas-liquid ratio of 2000:1, and an operating temperature of 45℃. The ammonia nitrogen in the effluent is reduced to 85mg / L, and the ammonia nitrogen removal rate is 95.28%.
[0084] (2) The stripping tail gas enters the acid washing tower, which has a diameter of 1.5m and a packing height of 3.5m; ammonia is absorbed by dilute sulfuric acid, and the ammonia concentration at the outlet is 26mg / m³. 3 The ammonium sulfate content in the acid absorption solution is about 20%, the turbidity is 10 NTU, the SiO2 concentration is 15 mg / L, and the fluoride ion concentration is 24 mg / L. Therefore, the ammonium sulfate mother liquor needs further treatment.
Claims
1. A method for removing ammonia from semiconductor high-concentration ammonia-containing wastewater using centrifugal force, characterized in that, Includes the following steps: (1) After being homogenized in the homogenization and equalization tank, the ammonia-containing wastewater flows through the manganese sand filter, the security filter and the precision filter in sequence before entering the pH equalization tank; (2) Adjust the pH of the ammonia-containing wastewater to 10~10.5 in the pH adjustment tank and adjust the wastewater temperature to not less than 45℃. The effluent from the pH adjustment tank enters the supergravity partitioned packed bed deammoniation reactor. (3) The ammonia removal reactor with partitioned packing bed under high gravity is equipped with partitioned packing bed; The partitioned packing bed is radially arranged with an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone. Ammonia-containing wastewater is uniformly sprayed into the internal dispersion zone of the packing bed by a distributor and passes through the three packing zones sequentially from the inside to the outside under centrifugal force. The rotation speed of the partitioned packing bed is 1000~1500 r / min, and the treatment capacity is 8~10 m³ / min. 3 / h, gas-liquid ratio of 500~600:1; the deammoniation effluent obtained after treatment by the supergravity zoned packed bed deammoniation reactor enters the subsequent reuse treatment unit; (4) The ammonia-containing gas obtained after treatment by the high gravity partitioned packed bed deammoniation reactor enters the high gravity ammonia absorption reactor. The high gravity ammonia absorption reactor is equipped with a high gravity packed bed with a rotation speed of 1000~1500 r / min and a sulfuric acid absorption liquid circulation rate of 8~10 m³ / min. 3 The gas-liquid ratio is 500~600:1 per hour; the pH of the sulfuric acid absorption solution is maintained at 2.0~3.0 during the absorption process.
2. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 1, characterized in that: In step (3), the supergravity partitioned packed bed deammoniation reactor includes a reactor cavity I, which is equipped with a partitioned packed bed. The partitioned packed bed is arranged radially from the inside to the outside as an internal dispersion zone, a central enhanced mass transfer zone, and an external demisting and anti-entrainment zone. The reactor cavity I is also equipped with an ammonia-containing wastewater inlet, a deammoniation outlet, a gas inlet, and a gas outlet. It also includes a motor I and a rotating shaft I that is connected to the motor I for transmission. The rotating shaft I is fixedly connected to the reactor cavity I through a sealed bearing, and the rotating shaft I is fixedly connected to the partitioned packed bed.
3. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 2, characterized in that: The internal dispersion zone uses large-pore PP structured packing with a porosity of not less than 90%; the central enhanced mass transfer zone uses one of the following: metal wire mesh packing, plastic wire mesh packing, or ceramic structured packing, with a specific surface area of not less than 500 m². 2 / m 3 The external defogging and anti-entrapment zone is a wire mesh demister.
4. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 3, characterized in that: The radial thickness of the internal dispersion zone is 130~140mm; the radial thickness of the central enhanced mass transfer zone is 240~260mm; and the radial thickness of the external defogging and anti-entrapment zone is 120~130mm.
5. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 1, characterized in that: In step (4), the concentration of ammonium sulfate in the absorbent is determined by density, conductivity or refractive index. When the mass fraction of ammonium sulfate in the absorbent in the acid storage tank reaches 20% to 25%, part of the absorbent is discharged to the ammonium sulfate resource utilization unit.
6. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 5, characterized in that: The amount of absorbent discharged is 1% to 3% of the absorbent circulation flow rate. Sulfuric acid is continuously added to the absorbent to continue the circulation and absorption.
7. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 1, characterized in that: In step (4), the supergravity ammonia absorption reactor includes a reactor cavity II, which is equipped with a supergravity packing bed. The reactor cavity II is also equipped with an absorbent inlet, an absorbent outlet, an ammonia-containing waste gas inlet, and a tail gas outlet. It also includes a motor II and a rotating shaft II that is connected to the motor II for transmission. The rotating shaft II is fixedly connected to the reactor cavity II through a sealed bearing. The rotating shaft II is fixedly connected to the supergravity packing bed.
8. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 7, characterized in that: The ultragravity packing bed uses one of the following: metal wire mesh packing, plastic wire mesh packing, or ceramic structured packing, with a specific surface area of not less than 500 m². 2 / m 3 .
9. The method for removing ammonia from high-concentration ammonia-containing semiconductor wastewater by gravity according to claim 7, characterized in that: The reactor exhaust outlet is also equipped with a demister, which is one of a wire mesh demister, a baffle demister, or a cyclone demister.