A device and method for resourceful treatment of high-ammonia-nitrogen salt-containing wastewater

Abstract

This application relates to a resource-based treatment device and method for high-ammonia nitrogen saline wastewater. Along the material conveying direction, the resource-based treatment device includes a pretreatment unit, an evaporation and crystallization unit, and a recycled water purification unit connected in sequence. The pretreatment unit includes a heavy metal removal device, a suspended solids removal device, and an organic matter removal device connected in sequence. The evaporation and crystallization unit includes a first pH adjustment device, an MVR evaporation device, a flash crystallization device, and a mother liquor drying device connected in sequence. The recycled water purification unit includes a second pH adjustment device and a purification device connected in sequence. This application provides a short-process resource-based treatment device, which features simple process, wide water quality adaptability, good wastewater resource treatment effect, high value, stable and reliable operation, and low energy and material consumption. It is suitable for the effective treatment of high-ammonia nitrogen saline wastewater discharged during production processes and can simultaneously achieve efficient recovery and reuse of water and ammonia nitrogen resources.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and in particular to a resource-based treatment device and method for high ammonia nitrogen saline wastewater. Background Technology

[0002] High-ammonia nitrogen saline wastewater originates from various sources, including the production processes of fertilizers, pharmaceuticals, petrochemicals, coal chemicals, lithium batteries, and rare earth smelting. For example, fertilizer plants producing ammonium sulfate via neutralization (reaction of sulfuric acid and ammonia) generate high-concentration ammonium sulfate wastewater during crystallization, centrifugation, and washing processes. This wastewater contains ammonium sulfate, free ammonia, suspended solids, and trace amounts of heavy metals. In the petrochemical and coal chemical industries, high-concentration ammonium salt wastewater is generated during catalyst production (e.g., for heavy oil catalytic cracking and direct coal liquefaction). This wastewater contains ammonium sulfate, ammonium phosphate, or ammonium chloride. In the rare earth industry, acid roasting is commonly used to extract rare earth elements, generating large amounts of ammonium sulfate wastewater. Data shows that producing 1 ton of rare earth produces 12 tons of ammonium sulfate wastewater, with an ammonium sulfate concentration of 25-30 g / L, along with approximately 1 g / L of calcium ions and trace amounts of magnesium ions. In the lithium battery industry, the co-precipitation method for producing nickel-cobalt-manganese hydroxide ternary precursors generates high-salt, high-ammonia-nitrogen, heavy metal wastewater, with ammonia nitrogen content reaching over 10,000 mg / L. In the chemical and pharmaceutical industries, liquid ammonia is commonly used as a neutralizing and precipitating agent in sulfate systems, resulting in the discharge of saline wastewater containing ammonium sulfate while simultaneously obtaining the main target product.

[0003] According to the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918), for wastewater directly discharged into drinking water source protection areas, ammonia nitrogen should be controlled at ≤5 mg / L (daily average); for general water bodies, ammonia nitrogen should be controlled at ≤8 mg / L; and for key areas in the Yangtze / Yellow River basins, ammonia nitrogen should be ≤3 mg / L along the river. Additionally, according to industry-specific standards, such as coking wastewater (GB 16171) ammonia nitrogen control at ≤15 mg / L, with non-ionic ammonia ≤1 mg / L; electroplating wastewater (GB 21900) ammonia nitrogen control at ≤10 mg / L; and pharmaceutical industry (GB 21904) ammonia nitrogen ≤25 mg / L for fermentation-type pharmaceutical wastewater and ≤15 mg / L for chemical synthesis-type wastewater. The ammonia nitrogen concentration in ammonium sulfate wastewater generated by these industries far exceeds the discharge standards. Furthermore, wastewater typically contains other organic matter and possesses acidity, alkalinity, toxicity, and irritating odors. Direct discharge without treatment will cause serious environmental pollution and damage.

[0004] For the aforementioned high-ammonia-nitrogen saline wastewater, adopting a treatment approach that achieves compliant discharge is both difficult and uneconomical. On the one hand, with existing technologies, it is difficult to reduce the concentration of pollutants such as ammonia nitrogen to the permissible discharge limits; on the other hand, the water and ammonia nitrogen resources in the wastewater are not fully recovered and reused.

[0005] In summary, there is an urgent need for a treatment system and method that is simple in process, low in energy and material consumption, and can simultaneously achieve high-efficiency reuse of wastewater water and high-value utilization of ammonia nitrogen resources for the treatment of high-ammonia nitrogen wastewater. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a resource-based treatment device and method for high-ammonia nitrogen saline wastewater. The resource-based treatment device includes a pretreatment unit, an evaporation and crystallization unit, and a recycled water purification unit connected in sequence. This application provides a short-process resource-based treatment device, which features simple process, wide water quality adaptability, good wastewater resource treatment effect, high value, stable and reliable operation, and low energy and material consumption. It is suitable for the effective treatment of high-ammonia nitrogen saline wastewater discharged during the production process of industries such as fertilizer, pharmaceutical, petrochemical, coal chemical, lithium battery, and rare earth smelting, and can simultaneously achieve efficient recovery and reuse of water and ammonia nitrogen resources.

[0007] To achieve this objective, the following technical solution is adopted in this application: In a first aspect, this application provides a resource recovery treatment device for high ammonia nitrogen saline wastewater. Along the material conveying direction, the resource recovery treatment device includes a pretreatment unit, an evaporation and crystallization unit, and a recycled water purification unit connected in sequence. The pretreatment unit includes a heavy metal removal device, a suspended solids removal device, and an organic matter removal device connected in sequence. The evaporation crystallization unit includes a first pH adjustment device, an MVR evaporation device, a flash crystallization device, and a mother liquor drying device connected in sequence. The recycled water purification unit includes a second pH adjustment device and a purification device connected in sequence.

[0008] In this application, high-ammonia-nitrogen saline wastewater first enters a pretreatment unit, sequentially passing through a heavy metal removal device, a suspended solids removal device, and an organic matter removal device. Heavy metals, suspended solids, and organic matter in the wastewater are efficiently removed. The pretreated wastewater then enters an evaporation and crystallization unit. The distillate produced in the evaporation and crystallization unit enters a recycled water purification unit to obtain high-quality reclaimed water, and high-quality by-product salt is obtained in the evaporation and crystallization unit. This application effectively treats high-ammonia-nitrogen saline wastewater while achieving efficient recovery and utilization of water and ammonia nitrogen resources. The device provided in this application abandons the lengthy process route of conventional high-ammonia-nitrogen saline wastewater treatment, which involves first separating ammonia and then recovering it. Instead, it adopts a short-process technology route of direct evaporation and crystallization to recover ammonium sulfate by-product salt, effectively suppressing ammonia escape during the process and improving the efficiency and quality of wastewater resource treatment. The device has a simple process, stable and reliable operation, and low energy and material consumption.

[0009] It should be noted that, in this application, the total mass of the high ammonia nitrogen saline wastewater is 100%, the salt content of the high ammonia nitrogen saline wastewater is 2-6%, the content of ammonium ions in the high ammonia nitrogen saline wastewater is 0.5-1.6%, the content of sulfate ions is 1.3-4.3%, the proportion of impurity cations other than ammonium ions is less than 10%, and the proportion of impurity anions other than sulfate ions is less than 10%.

[0010] It should be noted that this application uses a flash crystallization device for processing under negative pressure and low temperature, instead of an MVR crystallization device. This can suppress ammonia escape during the crystallization process, improve the quality of the distillate, and reduce the impact of secondary steam mist entrainment on the stable operation of the compressor.

[0011] This application achieves zero wastewater discharge by transporting and disposing of sludge obtained from the suspended solids removal device and a small amount of miscellaneous salts obtained from the mother liquor drying device. The mother liquor drying device includes a vacuum drum dryer.

[0012] In some embodiments, the MVR evaporation apparatus includes a first concentrate outlet and a first distillate outlet; the first concentrate outlet is connected to the flash crystallization apparatus, and the first distillate outlet is connected to the second pH adjustment device.

[0013] In some embodiments, the flash crystallization apparatus includes a second concentrate outlet and a second distillate outlet; the second concentrate outlet is connected to the mother liquor drying apparatus, and the second distillate outlet is connected to the second pH adjustment apparatus.

[0014] In this application, the mother liquor drying device treats the second concentrate so that impurities such as organic matter, calcium sulfate salts, and inorganic salts other than ammonium sulfate accumulated in the crystallization unit are carried out of the system as mixed salts. This controls the concentration of impurities accumulated in the crystallization unit within a relatively small range, ensuring that the quality of the obtained ammonium sulfate by-product salt meets the requirements for reuse.

[0015] In some embodiments, the suspended solids removal device includes a sedimentation device, which includes a clear liquid outlet and a slurry outlet.

[0016] In some embodiments, the suspended solids removal device further includes a multi-media filter connected to the clear liquid outlet.

[0017] In some embodiments, the suspended solids removal device further includes a sludge thickening device and a filter press connected in sequence to the slurry outlet.

[0018] In some embodiments, the MVR evaporation apparatus includes a vertical tube falling film evaporator.

[0019] In this application, a demister is installed before the secondary steam outlet of the separation chamber in the vertical tube falling film evaporator, preventing the quality of the first distillate from deteriorating due to mist entrainment. The recovered first distillate enters the recovery water purification system.

[0020] In some embodiments, the flash crystallization apparatus includes a crystallization heater, an OSLO crystallizer, a circulating settling tank, and a crystallization circulation pump connected in a loop; wherein the circulating settling tank includes a top circulation pipe inlet, a circulation inner extension pipe, an upper discharge port, and a bottom circulation pipe outlet.

[0021] In this application, the circulating settling tank separates and discharges the small amount of calcium sulfate salt introduced from the MVR evaporation unit or the calcium sulfate generated during the crystallization process from the ammonium sulfate crystal solids, thereby effectively ensuring the purity of the produced ammonium sulfate by-product salt, meeting or exceeding the requirements of Type II of "Fertilizer Grade Ammonium Sulfate" (GB / T 535-2020), and can be sold as fertilizer to realize resource utilization.

[0022] In some embodiments, the impurity removal device includes a reverse osmosis membrane module.

[0023] It should be noted that this application returns the reverse osmosis concentrate obtained through the reverse osmosis membrane module to the organic matter removal device in the pretreatment unit in order to improve the recovery rate of ammonium sulfate in the resource recovery treatment device.

[0024] In this application, residual ammonia nitrogen, organic matter, and inorganic salts in the recovered first and second distillates are efficiently retained by a reverse osmosis membrane module. The final reclaimed water has an ammonia nitrogen concentration of less than 2 mg / L, a conductivity of less than 50 μS / cm, and a COD of less than 5 mg / L, meeting the requirements for high-quality reclaimed water reuse.

[0025] Secondly, this application provides a method for the resource-based treatment of high ammonia nitrogen saline wastewater, wherein the resource-based treatment method is carried out using the resource-based treatment device for high ammonia nitrogen saline wastewater described in the first aspect.

[0026] In some embodiments, the resource recovery method includes the following steps: (1) Pre-treat high ammonia nitrogen saline wastewater to obtain pre-treated wastewater; wherein the pre-treatment includes heavy metal removal treatment, suspended solids removal treatment and organic matter removal treatment performed sequentially; (2) The pretreated wastewater is subjected to evaporation, crystallization and recycling water purification in sequence to obtain by-product salt and reclaimed water.

[0027] This application first treats high-ammonia-nitrogen saline wastewater sequentially with heavy metal removal, suspended solids removal, and organic matter removal, achieving efficient removal of heavy metals, suspended solids, and organic matter from the wastewater. Then, the pretreated wastewater undergoes evaporation and crystallization treatments. The distillates produced during evaporation and crystallization enter a recycled water purification system to obtain high-quality reclaimed water, and byproduct salts are obtained during the crystallization process. This application effectively treats high-ammonia-nitrogen saline wastewater while achieving efficient recovery and utilization of water and ammonia-nitrogen resources.

[0028] In some embodiments, the heavy metal removal process includes precipitation treatment.

[0029] The heavy metal removal process must satisfy at least one of the following conditions: The pH value of the precipitation treatment is 7.5 to 8.5, for example, it can be 7.5, 7.7, 7.9, 8.1, 8.3 or 8.5, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] In some embodiments, the precipitant used in the precipitation treatment includes any one or a combination of at least two of sodium sulfide, sodium hydrosulfide, or trisodium trimercaptotriazine, wherein typical but non-limiting combinations include: a combination of sodium sulfide and sodium hydrosulfide, a combination of sodium sulfide and trisodium trimercaptotriazine, a combination of sodium hydrosulfide and trisodium trimercaptotriazine, a combination of sodium sulfide, sodium hydrosulfide, and trisodium trimercaptotriazine, preferably a combination of sodium sulfide and trisodium trimercaptotriazine.

[0031] The precipitant in this application can form stable, insoluble precipitates with various heavy metal ions in wastewater, such as nickel, cobalt, manganese, copper, mercury, or lead, under near-neutral pH conditions. The resulting precipitates are large particles with good settling properties, facilitating solid-liquid separation and effectively improving the removal efficiency of heavy metal ions. In contrast, using hydroxides as precipitants is less effective because in high-concentration ammonia nitrogen wastewater, heavy metal ions form stable complexes with ammonia. These complexes remain soluble under alkaline conditions, inhibiting the formation of heavy metal hydroxides. Furthermore, using hydroxides as precipitants results in a slightly alkaline feed solution, leading to significant ammonia escape and a risk of secondary pollution.

[0032] In some embodiments, the mass ratio of sodium sulfide to trisodium trimercaptotriazine in the precipitant is (2~4):1, for example, it can be 2:1, 2.4:1, 2.8:1, 3.2:1, 3.6:1 or 4:1, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] The precipitant in this application can effectively remove heavy metals from high ammonia nitrogen saline wastewater. When the precipitant is a combination of sodium sulfide and trithiotriazine trisodium salt, and the mass ratio of sodium sulfide to trithiotriazine trisodium salt is (2~4):1, it has better removal efficiency and economy compared to adding a single precipitant or other combinations of precipitants. This is because, compared to a single precipitant or other combinations of precipitants, sodium sulfide and trithiotriazine trisodium salt have a synergistic effect. Sodium sulfide can quickly and effectively remove ionic heavy metals, removing 80~90% of conventional free heavy metals in a short time. At the same time, in saline wastewater with high salinity and high ammonium concentration, trithiotriazine trisodium salt can effectively break stable complex bonds and capture complex residual heavy metals that sodium sulfide cannot precipitate. Furthermore, the chelated flocs generated by the reaction of trithiotriazine trisodium salt have a good bridging effect, which can make ultrafine sulfides agglomerate. Combined with suitable coagulants and flocculants, large and dense flocs are generated, which settle quickly. If only trisodium trimercaptotriazine is added throughout the entire process, the chemical consumption cost is extremely high; if only sodium sulfide is added throughout the entire process, the content of residual heavy metals in the complexation is high, and the sludge in the subsequent sedimentation tank is easily flowed out with the effluent, resulting in serious waste of chemicals and a large amount of residual sulfur. 2- Furthermore, when the mass ratio of sodium sulfide to trisodium trimercaptotriazine is (2~4):1, the synergistic effect and economy of sodium sulfide and trisodium trimercaptotriazine can be fully utilized, avoiding the performance or economic decline caused by excessive use of a single precipitant. However, a single precipitant or a combination of other precipitants cannot simultaneously optimize the heavy metal removal efficiency and reagent dosage cost.

[0034] In some embodiments, the coagulant used in the suspended solids removal treatment includes any one or a combination of at least two of polyaluminum chloride, polyaluminum sulfate, or polyferric sulfate, wherein typical but non-limiting combinations include: a combination of polyaluminum chloride and polyaluminum sulfate, a combination of polyaluminum chloride and polyferric sulfate, a combination of polyaluminum sulfate and polyferric sulfate, and a combination of polyaluminum chloride, polyaluminum sulfate, and polyferric sulfate.

[0035] In some embodiments, the flocculants used in the suspended solids removal treatment include anionic polyacrylamide and / or nonionic polyacrylamide.

[0036] In some embodiments, the mass ratio of coagulant to flocculant in the suspended solids removal treatment is (40~60):1, for example, it can be 40:1, 45:1, 50:1, 55:1 or 60:1, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] In this application, the addition of coagulants and flocculants during the suspended solids removal process causes the suspended solids in the wastewater (including the suspended solids originally present in the wastewater and the insoluble precipitates generated during heavy metal removal) to rapidly settle in the sedimentation device. The resulting supernatant is then further treated by a multi-media filter to reduce the suspended solids content in the wastewater. The lower slurry is then further concentrated by a sludge thickening device, and finally forms sludge under the action of a plate and frame filter press, which is then transported off-site for disposal. In addition, the coagulation and sedimentation process provides preliminary removal of organic matter from the wastewater.

[0038] In some embodiments, the organic matter removal treatment includes ozone catalytic oxidation treatment.

[0039] This application utilizes ozone catalytic oxidation to achieve highly efficient removal of toxic, harmful, and recalcitrant organic matter from wastewater that was not removed during suspended solids removal. For high-ammonia nitrogen and saline wastewater, conventional organic matter removal technologies such as biochemical processes cannot achieve deep removal of organic matter. Furthermore, activated carbon adsorption can be added after ozone catalytic oxidation to further adsorb and remove organic matter that was not fully mineralized by ozone catalytic oxidation and has been degraded from large molecules into smaller molecules. This results in a lower concentration of residual organic matter in the wastewater, providing favorable conditions for the stable operation of the subsequent evaporation and crystallization system and the recovery of high-quality by-product salts.

[0040] In some embodiments, the heavy metal content in the pretreated wastewater is ≤1 mg / L, for example, it can be 0.2 mg / L, 0.4 mg / L, 0.6 mg / L, 0.8 mg / L or 1 mg / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] In some embodiments, the suspended solids content in the pretreated wastewater is ≤5 mg / L, for example, it can be 1 mg / L, 2 mg / L, 3 mg / L, 4 mg / L or 5 mg / L, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0042] In some embodiments, the organic matter content in the pretreated wastewater is ≤30mg / L, for example, it can be 10mg / L, 15mg / L, 20mg / L, 25mg / L or 30mg / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] In some embodiments, the resource recovery method further includes performing a first pH adjustment treatment on the pretreated wastewater before evaporation treatment.

[0044] Wherein, the first pH adjustment treatment satisfies at least one of the following conditions: The pH adjuster used in the first pH adjustment treatment includes concentrated sulfuric acid; wherein the mass fraction of the concentrated sulfuric acid used in the first pH adjustment treatment is 70~98%, for example, it can be 70%, 77%, 84%, 91% or 98%, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0045] In some embodiments, the pH value of the pretreated wastewater after the first pH adjustment treatment is 3 to 5, for example, it can be 3, 3.5, 4, 4.5 or 5, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0046] The application adjusts the pH of the wastewater to a slightly acidic level before evaporation treatment for the following reasons: (1) It eliminates alkalinity in the wastewater, which helps prevent scaling in the subsequent evaporation and crystallization equipment; (2) Under slightly acidic conditions, the escape of ammonia from the secondary steam generated by the subsequent evaporation and crystallization equipment is effectively suppressed, and the ammonia nitrogen content of the recovered distillate is significantly reduced, thereby improving the quality of the reclaimed water. At the same time, the application uses concentrated sulfuric acid for pH adjustment, which will not introduce more impurity anions into the system, thus affecting the effect of resource recovery of by-product salts.

[0047] In some embodiments, the evaporation process yields a first distillate and a first concentrate; the mass concentration of the first concentrate obtained by the evaporation process is 30-45%, for example, it can be 30%, 32%, 35%, 40% or 45%, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0048] In some embodiments, the salt used in the evaporation process includes calcium sulfate; the amount of calcium sulfate added in the evaporation process is 3 to 5 wt% of the pretreated wastewater, for example, it can be 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt% or 5 wt%, but it is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0049] This application employs a salt-based anti-scaling technology in the evaporation process, significantly reducing the risk of scaling in the evaporation equipment and extending stable operation and cleaning cycles. Furthermore, due to the use of this technology, no calcium removal chemicals are needed during wastewater pretreatment, greatly reducing chemical dosage costs. Within the permissible range of influent calcium hardness (≤2500mg / L), the newly generated calcium sulfate can serve as the salt within the system, eliminating the need for continuous external salt addition and maintaining a salt concentration of 3-5wt% within the evaporator. Simultaneously, the wastewater pH is controlled at 3-5 during the evaporation process, effectively reducing the ammonia nitrogen content of the recovered first distillate to less than 50mg / L while preventing excessively low pH levels that could exacerbate corrosion of equipment materials, thus requiring higher material grades and increasing equipment investment. The coupled use of MVR technology fully utilizes the latent heat energy of secondary steam, reducing energy consumption during the evaporation process compared to multi-effect evaporation technology, while also reducing the equipment footprint. Maintaining a feed concentration of 30%-45% within the evaporator contributes to the stable and economical operation of the unit.

[0050] In some embodiments, the temperature of the evaporation process is 102~106°C, for example, 102°C, 103°C, 104°C, 105°C or 106°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0051] In some embodiments, the crystallization process yields a second concentrate and a second distillate; the mass concentration of the second concentrate obtained by the crystallization process is ≥45%, for example, it may be 48.0%, 48.5%, 49.0%, 49.5% or 50.0%, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0052] In some embodiments, the temperature of the crystallization process is 70~80°C, for example, 70°C, 72°C, 75°C, 78°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0053] In some embodiments, the pressure of the crystallization process is 0.02 to 0.04 MPa, for example, 0.02 MPa, 0.025 MPa, 0.03 MPa, 0.035 MPa or 0.04 MPa, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0054] This application controls the pressure within the crystallizer at 0.02 MPa to 0.04 MPa, the pH of the feed solution at 3 to 5, and the temperature at 70 to 80°C during the crystallization process. This suppresses ammonia escape during crystallization, reducing the ammonia nitrogen content in the recovered second distillate to less than 50 mg / L. Simultaneously, the pH is prevented from being too low, which would affect the normal growth of ammonium sulfate crystals and reduce the occurrence of small needle-like crystals. The feed solution concentration within the crystallizer reaches supersaturation, thereby precipitating solid ammonium sulfate crystals. The solid crystal content in the feed solution is controlled at 25% to 30%, which is beneficial for stable salt production from the system.

[0055] In some embodiments, the by-product salt includes ammonium sulfate.

[0056] In some embodiments, the resource recovery method further includes drying the second concentrate to obtain mixed salts; the drying process includes vacuum drying.

[0057] The mother liquor drying treatment shall at least satisfy one of the following conditions: The pressure of the vacuum drying process is 0.02~0.03MPa, for example, it can be 0.02MPa, 0.022MPa, 0.025MPa, 0.028MPa or 0.03MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0058] In some embodiments, the temperature of the vacuum drying process is 60~70°C, for example, 60°C, 62°C, 65°C, 68°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0059] In some embodiments, the moisture content of the mixed salt is <5%, for example, it may be 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0060] In some embodiments, the recycled water purification treatment includes a second pH adjustment treatment and a reverse osmosis membrane treatment performed sequentially.

[0061] The second pH adjustment treatment must satisfy at least one of the following conditions: The first distillate and the second distillate are subjected to the second pH adjustment treatment; the temperature of the first distillate and the second distillate are each independently 20~30℃, for example, 20℃, 22℃, 25℃, 28℃ or 30℃, but not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0062] It should be noted that the first distillate is obtained by cooling the secondary steam generated by the MVR evaporator after passing through the evaporation heating chamber and the preheater; the second distillate is obtained by cooling the secondary steam generated by the flash crystallization device after passing through the crystallization condenser and the preheater.

[0063] In some embodiments, the pH adjuster used in the second pH adjustment treatment includes concentrated sulfuric acid; the mass fraction of the concentrated sulfuric acid used in the second pH adjustment treatment is 70-98%, for example, it can be 70%, 77%, 84%, 91% or 98%, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0064] In some embodiments, the pH value of the wastewater after the second pH adjustment treatment is 5 to 6, for example, it can be 5, 5.2, 5.5, 5.7 or 6, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0065] This application adjusts the pH of the recovered first and second distillates to 5-6, so that most of the residual ammonia nitrogen is converted into ammonium ions, which is beneficial for removal in subsequent units.

[0066] In some embodiments, the resource recovery method includes the following steps: (1) The high ammonia nitrogen saline wastewater is subjected to precipitation treatment with a pH value of 7.5~8.5 to remove heavy metals from the high ammonia nitrogen saline wastewater, and the wastewater after heavy metal removal is obtained; the precipitant used in the precipitation treatment includes any one or a combination of at least two of sodium sulfide, sodium hydrosulfide or trisodium trimercaptotriazine. (2) The wastewater after heavy metal removal, coagulant and flocculant are mixed to remove suspended solids in the wastewater to obtain wastewater after suspended solids removal; wherein the mass ratio of coagulant and flocculant is (40~60):1; (3) The wastewater after the removal of suspended solids is subjected to ozone catalytic oxidation treatment to remove organic matter in the wastewater and obtain pretreated wastewater, wherein the heavy metal content in the pretreated wastewater is ≤1mg / L, the suspended solids content is ≤5mg / L, and the organic matter content is ≤30mg / L; (4) The pretreated wastewater is subjected to a first pH adjustment treatment with a target pH value of 3 to 5, an evaporation treatment at a temperature of 102 to 106°C, a crystallization treatment at a temperature of 70 to 80°C and a pressure of 0.02 to 0.04 MPa, and a recycled water purification treatment in sequence to obtain ammonium sulfate by-product salt and reclaimed water; wherein, the recycled water purification treatment includes a second pH adjustment treatment with a target pH value of 5 to 6 and a reverse osmosis membrane treatment in sequence; The pH adjuster used in the first pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 70-98%; The evaporation process yields a first distillate and a first concentrate with a mass concentration of 30-45%; calcium sulfate is added during the evaporation process at a mass of 3-5 wt% of the pretreated wastewater. The crystallization process yields a second distillate and a second concentrate with a mass concentration ≥45%; the resource recovery method further includes drying the second concentrate to obtain miscellaneous salts with a water content <5%. The first distillate and the second distillate are subjected to the second pH adjustment treatment. The pH adjuster used in the second pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 70-98%.

[0067] This application has at least the following beneficial effects: In this application, high-ammonia-nitrogen saline wastewater first enters a pretreatment unit, enabling efficient removal of heavy metals, suspended solids, and organic matter. The pretreated wastewater then enters an evaporation and crystallization unit. The distillate produced in the evaporation and crystallization unit enters a recycled water purification system to obtain high-quality reclaimed water, and high-quality by-product salts are obtained in the evaporation and crystallization unit. This application effectively treats high-ammonia-nitrogen saline wastewater while achieving efficient recovery and utilization of water and ammonia-nitrogen resources. Specifically, the wastewater recovery rate can reach over 98.6%, and the reclaimed water has an ammonia-nitrogen concentration of less than 2 mg / L, a conductivity of less than 25 μS / cm, and a COD of less than 4.5 mg / L, meeting the influent requirements of desalination plants. The ammonium sulfate by-product salt recovery rate can reach over 89.8%, and the quality of the recovered ammonium sulfate by-product salt meets or exceeds the requirements of Type II in the "Fertilizer Grade Ammonium Sulfate" (GB / T 535-2020), making it suitable for export as agricultural nitrogen fertilizer. Attached Figure Description

[0068] Figure 1 This is the resource utilization treatment device for high ammonia nitrogen saline wastewater provided in Embodiment 1 of this application.

[0069] Figure 2 This is a schematic diagram of the main structure of the flash crystallization apparatus provided in Embodiment 1 of this application.

[0070] Figure 3 This is a schematic diagram of the structure of the circulating settling tank provided in Embodiment 1 of this application.

[0071] The system comprises: 1-Pretreatment unit; 11-Heavy metal removal device; 12-Suspended solids removal device; 13-Organic matter removal device; 2-Evaporation and crystallization unit; 21-First pH adjustment device; 22-MVR evaporation device; 23-Flash crystallization device; 231-OSLO crystallizer; 232-Circulating settling tank; 2321-Top circulation pipe inlet; 2322-Circulating inner extension pipe; 2323-Bottom circulation pipe outlet; 2324-Upper discharge port; 233-Crystallization circulation pump; 234-Crystallization heater; 24-Mother liquor drying device; 3-Recycled water purification unit; 31-Second pH adjustment device; 32-Impurity removal device. Detailed Implementation

[0072] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments. However, the examples below are merely simplified examples of this application and do not represent or limit the scope of protection of this application. The scope of protection of this application shall be determined by the claims.

[0073] Currently, high-ammonia-nitrogen saline wastewater is typically treated using a stripping process. The basic principle is to adjust the wastewater pH to alkaline, using air or steam as the carrier gas. The ammonia is separated from the wastewater by utilizing the pressure difference between the equilibrium partial pressure of ammonia in the wastewater and the partial pressure of ammonia in the carrier gas, simultaneously recovering ammonia water or ammonium sulfate solution for subsequent resource recovery and reuse. This process only recovers ammonia nitrogen from the wastewater; the remaining saline wastewater requires further treatment, typically employing a zero-discharge wastewater treatment process with resource recovery of sodium sulfate.

[0074] The above-mentioned overall treatment process has the following problems: 1) The process of adjusting the pH of wastewater requires a large amount of alkali solution, increasing the material consumption during operation; 2) The generation and operation of the carrier gas in the wastewater deammoniation process requires a large amount of heat and electricity, increasing the energy consumption during operation; 3) During the wastewater deammoniation process, due to the presence of hardness ions in the wastewater, scaling will occur in the stripping tower or steam stripping tower, affecting the deammoniation efficiency and even the normal operation of the equipment; 4) The wastewater after deammoniation treatment is still saline wastewater, which needs to undergo a series of processes including pretreatment, evaporation crystallization, and zero discharge before the resource recovery of sodium sulfate. The overall process flow is long and complex, and the operation and control are difficult; 5) The ammonia nitrogen in the wastewater is recovered in the form of ammonia water or ammonium sulfate solution, but it still needs to be further treated (such as concentrating the ammonia water to more than 20% and evaporating and crystallizing the ammonium sulfate solution to produce solid ammonium sulfate) before it can be effectively utilized in the future. The process flow is relatively long; 6) The sodium ions introduced by adding alkali solution are finally recovered as sodium sulfate, and their resource utilization value is generally not high.

[0075] This application provides a resource-based treatment device for high-ammonia nitrogen saline wastewater. The device comprises a pretreatment unit, an evaporation and crystallization unit, and a recycled water purification unit connected in sequence. The high-ammonia nitrogen saline wastewater first enters the pretreatment unit, where it passes sequentially through a heavy metal removal device, a suspended solids removal device, and an organic matter removal device. Heavy metals, suspended solids, and organic matter in the wastewater are efficiently removed. The pretreated wastewater then enters the evaporation and crystallization unit. The distillate produced in the evaporation and crystallization unit enters the recycled water purification unit to obtain high-quality reclaimed water. High-quality by-product salt is also obtained in the evaporation and crystallization unit. This application effectively treats high-ammonia nitrogen saline wastewater while achieving efficient recovery and utilization of water and ammonia nitrogen resources.

[0076] The high-ammonia nitrogen salinity wastewater used in the following examples is wastewater discharged from the production of a coal chemical catalyst, with a discharge volume of 10~12m³. 3 The concentration is as follows: pH 6-8, salt content 40000-50000 mg / L, suspended solids 100-150 mg / L, COD 400-500 mg / L, calcium hardness 800-1000 mg / L, ammonia nitrogen 8500-10000 mg / L, chloride ion content 50-100 mg / L, sodium ion content 300-500 mg / L, and also contains small amounts of heavy metals such as cobalt and molybdenum, with a total content of less than 50 mg / L. The above limitations are merely for illustrative purposes and are not intended to further limit the scope of this application.

[0077] Example 1 This embodiment provides a resource-based treatment device for high ammonia nitrogen saline wastewater, such as... Figure 1 As shown, along the material conveying direction, the resource recovery processing device includes a pretreatment unit 1, an evaporation and crystallization unit 2, and a recycled water purification unit 3 connected in sequence; The pretreatment unit 1 includes a heavy metal removal device 11, a suspended solids removal device 12, and an organic matter removal device 13 connected in sequence. The evaporation crystallization unit 2 includes a first pH value adjustment device 21, an MVR evaporation device 22, a flash crystallization device 23, and a mother liquor drying device 24 connected in sequence. The recycled water purification unit 3 includes a second pH value adjustment device 31 and a dirt removal device 32 connected in sequence. The MVR evaporation device 22 includes a first concentrated liquid outlet and a first distillate outlet; the first concentrated liquid outlet is connected to the flash crystallization device 23, and the first distillate outlet is connected to the second pH adjustment device 31. The flash crystallization device 23 includes a second concentrated liquid outlet and a second distillate outlet; the second concentrated liquid outlet is connected to the mother liquor drying device 24, and the second distillate outlet is connected to the second pH adjustment device 31. The suspended solids removal device 12 includes a sedimentation device; the sedimentation device includes a clear liquid outlet and a slurry outlet; the suspended solids removal device 12 also includes a multi-media filter connected to the clear liquid outlet; the suspended solids removal device 12 also includes a sludge thickening device and a filter press connected in sequence to the slurry outlet. The MVR evaporation unit 22 includes a vertical tube falling film evaporator; like Figure 2 As shown, the flash crystallization device 23 includes a crystallization heater 234, an OSLO crystallizer 231, a circulating settling tank 232, and a crystallization circulation pump 233, all connected in a circulating manner; Figure 3 As shown, the circulating settling tank 232 includes a top circulating pipe inlet 2321, a circulating inner extension pipe 2322, an upper discharge port 2324, and a bottom circulating pipe outlet 2323; The impurity removal device 32 includes a reverse osmosis membrane module.

[0078] Example 2 This embodiment provides a resource-based treatment device for high ammonia nitrogen saline wastewater. The only difference from Embodiment 1 is that, except that the evaporation and crystallization unit does not include a mother liquor drying device, everything else is the same as in Embodiment 1.

[0079] Example 3 This embodiment provides a resource-based treatment device for high ammonia nitrogen saline wastewater. The only difference from Embodiment 1 is that, except that the evaporation and crystallization unit does not include a circulating settling tank, everything else is the same as in Embodiment 1.

[0080] Example 4 This embodiment provides a resource recovery treatment device for high ammonia nitrogen saline wastewater. The only difference between this embodiment and Embodiment 1 is that the resource recovery treatment device does not include a pretreatment unit; otherwise, they are the same as in Embodiment 1.

[0081] Example 5 This embodiment provides a resource-based treatment device for high ammonia nitrogen saline wastewater. The only difference from Embodiment 1 is that, except that the pretreatment unit includes a suspended solids removal device, a heavy metal removal device, and an organic matter removal device connected in sequence, the rest are the same as in Embodiment 1.

[0082] Example 6 This embodiment provides a resource-based treatment device for high ammonia nitrogen saline wastewater. The only difference from Embodiment 1 is that, except that the pretreatment unit includes an organic matter removal device, a suspended solids removal device, and a heavy metal removal device connected in sequence, the rest are the same as in Embodiment 1.

[0083] Application Example 1 This application example provides a resource recovery method for treating high-ammonia nitrogen saline wastewater. This application example uses the resource recovery treatment apparatus provided in Example 1. The resource recovery method includes the following steps: (1) The high ammonia nitrogen saline wastewater is subjected to precipitation treatment with a pH value of 8 to remove heavy metals from the high ammonia nitrogen saline wastewater, and the wastewater after heavy metal removal is obtained; the precipitant used in the precipitation treatment is sodium sulfide and trithiotriazine trisodium salt with a mass ratio of 3:1; the amount of precipitant added is 3 times the heavy metal content in the wastewater; (2) Add polyaluminum sulfate coagulant and anionic polyacrylamide flocculant (brand name FP3530S) in a mass ratio of 50:1 to the wastewater after heavy metal removal, wherein the coagulant dosage is 120ppm (i.e., 120g of polyaluminum sulfate per ton of water) to remove suspended solids in the wastewater and obtain wastewater after removing suspended solids. (3) The wastewater after the removal of suspended solids is subjected to ozone catalytic oxidation treatment to remove organic matter in the wastewater, and pretreated wastewater is obtained. The pretreated wastewater contains 0.2 mg / L of heavy metals, 1 mg / L of suspended solids, and 10 mg / L of organic matter. (4) The pretreated wastewater is subjected to a first pH adjustment treatment with a target pH of 4, an evaporation treatment at a temperature of 105°C, a crystallization treatment at a temperature of 75°C and a pressure of 0.03 MPa, and a recycled water purification treatment in sequence to obtain ammonium sulfate by-product salt and reclaimed water; wherein, the recycled water purification treatment includes a second pH adjustment treatment with a target pH of 5.5 and a reverse osmosis membrane treatment in sequence. The pH adjuster used in the first pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 98%; The evaporation process yields a first distillate and a first concentrate with a mass concentration of 40%; calcium sulfate is added during the evaporation process at a mass of 4 wt% of the pretreated wastewater. The crystallization process yields a second concentrate and a second distillate with a mass concentration of 49.0%; the resource recovery method further includes drying the second concentrate to obtain mixed salts. The first and second distillates, both at a temperature of 25°C, were subjected to the second pH adjustment treatment. The pH adjuster used in the second pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 98%.

[0084] Application Example 2 This application example provides a resource recovery method for treating high-ammonia nitrogen saline wastewater. This application example uses the resource recovery treatment apparatus provided in Example 1. The resource recovery method includes the following steps: (1) The high ammonia nitrogen saline wastewater is subjected to precipitation treatment with a pH value of 8.5 to remove heavy metals from the high ammonia nitrogen saline wastewater, and the wastewater after heavy metal removal is obtained; the precipitant used in the precipitation treatment is sodium sulfide and trithiotriazine trisodium salt with a mass ratio of 2:1; the amount of precipitant added is 2.5 times the heavy metal content in the wastewater; (2) Add polyaluminum sulfate coagulant and anionic polyacrylamide flocculant (brand name FP3530S) in a mass ratio of 45:1 to the wastewater after heavy metal removal, wherein the coagulant dosage is 100ppm (i.e., 100g of polyaluminum sulfate per ton of water) to remove suspended solids in the wastewater and obtain wastewater after removing suspended solids. (3) The wastewater after the removal of suspended solids is subjected to ozone catalytic oxidation treatment to remove organic matter in the wastewater, and pretreated wastewater is obtained. The pretreated wastewater contains 0.5 mg / L of heavy metals, 2 mg / L of suspended solids, and 15 mg / L of organic matter. (4) The pretreated wastewater is subjected to a first pH adjustment treatment with a target pH value of 3, an evaporation treatment at a temperature of 106°C, a crystallization treatment at a temperature of 70°C and a pressure of 0.02 MPa, and a recycled water purification treatment in sequence to obtain ammonium sulfate by-product salt and reclaimed water; wherein, the recycled water purification treatment includes a second pH adjustment treatment with a target pH value of 5 and a reverse osmosis membrane treatment in sequence. The pH adjuster used in the first pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 70%; The evaporation process yields a first steam and a first concentrated liquid with a mass concentration of 35%; calcium sulfate is added during the evaporation process at a mass of 3 wt% of the pretreated wastewater. The crystallization process yields a second concentrate and a second distillate with a mass concentration of 48.5%; the resource recovery method further includes drying the second concentrate to obtain mixed salts. The first and second distillates, both at a temperature of 30°C, were subjected to the second pH adjustment treatment. The pH adjuster used in the second pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 70%.

[0085] Application Example 3 This application example provides a resource recovery method for treating high-ammonia nitrogen saline wastewater. This application example uses the resource recovery treatment apparatus provided in Example 1. The resource recovery method includes the following steps: (1) The precipitant used in the precipitation treatment of high ammonia nitrogen saline wastewater at pH 7.5 was sodium sulfide and trisodium trimercaptotriazine in a mass ratio of 4:1; the amount of precipitant added was twice the amount of heavy metals in the wastewater. (2) Add polyaluminum sulfate coagulant and anionic polyacrylamide flocculant (brand name FP3530S) in a mass ratio of 40:1 to the wastewater after heavy metal removal, wherein the coagulant dosage is 80ppm (i.e., 80g of polyaluminum sulfate per ton of water) to remove suspended solids in the wastewater and obtain wastewater after removing suspended solids. (3) The wastewater after the removal of suspended solids is subjected to ozone catalytic oxidation treatment to remove organic matter in the wastewater, and pretreated wastewater is obtained. The pretreated wastewater contains 0.8 mg / L of heavy metals, 4 mg / L of suspended solids, and 20 mg / L of organic matter. (4) The pretreated wastewater is subjected to a first pH adjustment treatment with a target pH value of 5, an evaporation treatment at a temperature of 104°C, a crystallization treatment at a temperature of 80°C and a pressure of 0.04 MPa, and a recycled water purification treatment in sequence to obtain ammonium sulfate by-product salt and reclaimed water; wherein, the recycled water purification treatment includes a second pH adjustment treatment with a target pH value of 6 and a reverse osmosis membrane treatment in sequence. The pH adjuster used in the first pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 93%; The evaporation process yields a first distillate and a first concentrate with a mass concentration of 45%; calcium sulfate is added during the evaporation process at a mass of 5 wt% of the pretreated wastewater. The crystallization process yields a second concentrate and a second distillate with a mass concentration of 49.5%; the resource recovery method further includes drying the second concentrate to obtain mixed salts. The first and second distillates, both at a temperature of 20°C, were subjected to the second pH adjustment treatment. The pH adjuster used in the second pH adjustment treatment is concentrated sulfuric acid with a mass fraction of 93%.

[0086] Application Example 4 This application example provides a resource recovery method for treating high ammonia nitrogen saline wastewater. The only difference between this application example and application example 1 is that, except that the resource recovery method is carried out using the apparatus provided in example 2, all other aspects are the same as in application example 1.

[0087] Application Example 5 This application example provides a resource recovery method for high ammonia nitrogen saline wastewater. The only difference between this application example and application example 1 is that the resource recovery method is carried out using the apparatus provided in example 3, while the rest is the same as application example 1.

[0088] Application Example 6 This application example provides a resource-based treatment method for high ammonia nitrogen saline wastewater. The only difference between this method and Application Example 1 is that, except that the sodium ion content in the high ammonia nitrogen saline wastewater is 2000 mg / L, everything else is the same as in Application Example 1.

[0089] Application Example 7 This application example provides a resource-based treatment method for high ammonia nitrogen saline wastewater. The only difference between this method and Application Example 1 is that, except that the chloride ion content in the high ammonia nitrogen saline wastewater is 2000 mg / L, everything else is the same as in Application Example 1.

[0090] Application Example 8 This application example provides a resource-based treatment method for high ammonia nitrogen saline wastewater. The only difference between this method and application example 1 is that the resource-based treatment method is carried out using the apparatus provided in example 4, that is, the resource-based treatment method does not include steps (1), (2), and (3). All other aspects are the same as in application example 1.

[0091] Application Example 9 This application example provides a resource-based treatment method for high ammonia nitrogen saline wastewater. The only difference between this method and application example 1 is that the resource-based treatment method is carried out using the apparatus provided in example 5, that is, the resource-based treatment method includes steps (2), (1), (3), and (4) performed sequentially. All other steps are the same as in application example 1.

[0092] Application Example 10 This comparative application example provides a resource recovery method for high ammonia nitrogen saline wastewater. The only difference between this method and application example 1 is that the resource recovery method is carried out using the apparatus provided in example 6, that is, the resource recovery method includes steps (3), (2), (1) and (4) performed in sequence. All other steps are the same as in application example 1.

[0093] Using formula Calculate the reclaimed water recovery rate using the formula. The recovery rate of ammonium sulfate by-product salts was calculated. The ammonia nitrogen concentration in the reclaimed water was detected by Nessler's reagent spectrophotometry (HJ 535-2009). The conductivity of the reclaimed water was tested by a conductivity meter. The nitrogen content in ammonium sulfate was tested by an automatic analyzer (GB / T 22923-2008). The chemical oxygen demand (COD) in the reclaimed water was detected by the potassium dichromate method (GB / T 22597-2014). The test results are shown in Table 1.

[0094] Table 1 The test results show that: (1) As can be seen from Application Examples 1 to 3, this application can effectively treat high ammonia nitrogen saline wastewater after treatment by the pretreatment unit, evaporation crystallization unit and recycled water purification unit, and simultaneously achieve efficient recovery and reuse of water and ammonia nitrogen resources. The wastewater recovery rate can reach more than 98.6%, and the ammonia nitrogen concentration of the reclaimed water is less than 2 mg / L, the conductivity is less than 25 μS / cm, and the COD is less than 4.5 mg / L; meeting the influent requirements of the desalination station; the recovery rate of ammonium sulfate by-product salt can reach more than 89.8%, and the quality of the recovered ammonium sulfate by-product salt meets the requirements of Type II or above in "Fertilizer Grade Ammonium Sulfate" (GB / T 535-2020).

[0095] (2) As can be seen from Application Example 1 and Application Example 4, the mother liquor drying device in the evaporation crystallization unit of this application plays an important role in improving the quality of the recycled water and by-product salt, and is indispensable. When the mother liquor drying device is missing in the resource treatment device, the recovery rate of reclaimed water and the recovery rate of ammonium sulfate by-product salt are reduced.

[0096] (3) As can be seen from Application Example 1 and Application Example 5, the circulating settling tank in the evaporation crystallization unit of this application plays an important role in improving the quality of by-product salt and is indispensable. When the circulating settling tank is missing in the resource treatment device, the quality of the recovered ammonium sulfate by-product salt is significantly reduced and cannot meet the requirements of Type II or above.

[0097] (4) As can be seen from Application Example 1 and Application Example 6-7, the resource recovery treatment device of this application is suitable for treating high ammonia nitrogen salinity wastewater with impurity cations other than ammonium ions accounting for less than 10% and impurity anions other than sulfate ions accounting for less than 10%. If the impurity cations or impurity anions in the wastewater are too high, the quality and recovery rate of the by-product ammonium sulfate will be greatly reduced.

[0098] (5) As can be seen from Application Example 1 and Application Examples 8-10, whether or not a pretreatment unit is set up in this application, and the connection sequence of the heavy metal removal device, suspended solids removal device and organic matter removal device in the pretreatment unit, plays an important role in improving the quality of recycled water and by-product salt, and cannot be omitted or arbitrarily combined.

[0099] In summary, in this application, high-ammonia-nitrogen saline wastewater first enters a pretreatment unit, enabling efficient removal of heavy metals, suspended solids, and organic matter. The pretreated wastewater then enters an evaporation and crystallization unit. The distillate produced in the evaporation and crystallization unit enters a recycled water purification system, resulting in high-quality reclaimed water that meets the influent requirements of the desalination plant. High-quality by-product salts are also obtained in the evaporation and crystallization unit. The quality of the ammonium sulfate by-product salts meets or exceeds the requirements of Type II in the "Fertilizer Grade Ammonium Sulfate" standard (GB / T 535-2020), and can be sold as agricultural nitrogen fertilizer. This application effectively treats high-ammonia-nitrogen saline wastewater while achieving efficient recovery and utilization of water and ammonia nitrogen resources.

[0100] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A resource-based treatment device for high-ammonia nitrogen saline wastewater, characterized in that, Along the material conveying direction, the resource recovery processing device includes a pretreatment unit, an evaporation and crystallization unit, and a recycled water purification unit connected in sequence; The pretreatment unit includes a heavy metal removal device, a suspended solids removal device, and an organic matter removal device connected in sequence. The evaporation crystallization unit includes a first pH adjustment device, an MVR evaporation device, a flash crystallization device, and a mother liquor drying device connected in sequence. The recycled water purification unit includes a second pH adjustment device and a purification device connected in sequence.

2. The resource recovery processing apparatus according to claim 1, characterized in that, The MVR evaporation device includes a first concentrate outlet and a first distillate outlet; the first concentrate outlet is connected to the flash crystallization device, and the first distillate outlet is connected to the second pH adjustment device. And / or, the flash crystallization apparatus includes a second concentrate outlet and a second distillate outlet; the second concentrate outlet is connected to the mother liquor drying apparatus, and the second distillate outlet is connected to the second pH adjustment apparatus.

3. The resource recovery processing apparatus according to claim 1 or 2, characterized in that, The suspended solids removal device includes a sedimentation device; the sedimentation device includes a clear liquid outlet and a slurry outlet; And / or, the suspended solids removal device further includes a multi-media filter connected to the clear liquid outlet; And / or, the suspended solids removal device further includes a sludge thickening device and a filter press device connected in sequence to the slurry outlet.

4. The resource recovery processing apparatus according to any one of claims 1-3, characterized in that, The MVR evaporation device includes a vertical tube falling film evaporator; And / or, the flash crystallization device includes a crystallization heater, an OSLO crystallizer, a circulating settling tank, and a crystallization circulating pump connected in a cycle; wherein, the circulating settling tank includes a top circulating pipe inlet, a circulating inner pipe, an upper discharge port, and a bottom circulating pipe outlet; And / or, the impurity removal device includes a reverse osmosis membrane assembly.

5. A method for the resource-based treatment of high-ammonia nitrogen saline wastewater, characterized in that, The resource recovery treatment method is carried out using the resource recovery treatment device for high ammonia nitrogen saline wastewater as described in any one of claims 1-4.

6. The resource recovery method according to claim 5, characterized in that, The resource recovery method includes the following steps: (1) Pre-treat high ammonia nitrogen saline wastewater to obtain pre-treated wastewater; wherein the pre-treatment includes heavy metal removal treatment, suspended solids removal treatment and organic matter removal treatment performed sequentially; (2) The pretreated wastewater is subjected to evaporation, crystallization and recycling water purification in sequence to obtain by-product salt and reclaimed water.

7. The resource recovery method according to claim 6, characterized in that, The heavy metal removal process includes precipitation treatment; The heavy metal removal process must satisfy at least one of the following conditions: The pH value of the precipitation treatment is 7.5~8.5; And / or, the precipitant used in the precipitation treatment includes any one or a combination of at least two of sodium sulfide, sodium hydrosulfide, or trisodium trimercaptotriazine; preferably a combination of sodium sulfide and trisodium trimercaptotriazine. And / or, the mass ratio of sodium sulfide to trisodium trimercaptotriazine in the precipitant is (2~4):

1.

8. The resource recovery method according to claim 6 or 7, characterized in that, The coagulant used in the suspended solids removal treatment includes any one or at least a combination of two of polyaluminum chloride, polyaluminum sulfate, or polyferric sulfate. And / or, the flocculants used in the suspended solids removal treatment include anionic polyacrylamide and / or nonionic polyacrylamide; And / or, the mass ratio of coagulant to flocculant in the suspended solids removal treatment is (40~60):

1.

9. The resource recovery method according to any one of claims 6-8, characterized in that, The organic matter removal treatment includes ozone catalytic oxidation treatment; And / or, the heavy metal content in the pretreated wastewater is ≤1 mg / L; And / or, the suspended solids content in the pretreated wastewater is ≤5 mg / L; And / or, the organic matter content in the pretreated wastewater is ≤30mg / L.

10. The resource recovery method according to any one of claims 6-9, characterized in that, The resource recovery method further includes performing a first pH adjustment treatment on the pretreated wastewater before evaporation treatment; Wherein, the first pH adjustment treatment satisfies at least one of the following conditions: The pH adjuster used in the first pH adjustment treatment includes concentrated sulfuric acid; wherein the mass fraction of the concentrated sulfuric acid used in the first pH adjustment treatment is 70-98%. And / or, the pH value of the pretreated wastewater after the first pH adjustment treatment is 3~5.

11. The resource recovery method according to any one of claims 6-10, characterized in that, The evaporation process yields a first distillate and a first concentrate; the mass concentration of the first concentrate obtained by the evaporation process is 30-45%. And / or, the salt used in the evaporation process includes calcium sulfate; the amount of calcium sulfate added in the evaporation process is 3-5 wt% of the pretreated wastewater; And / or, the temperature of the evaporation treatment is 102~106℃.

12. The resource recovery method according to claim 11, characterized in that, The crystallization process yields a second concentrate and a second distillate; the mass concentration of the second concentrate obtained from the crystallization process is ≥45%. And / or, the temperature of the crystallization treatment is 70~80℃; And / or, the pressure of the crystallization treatment is 0.02~0.04 MPa; And / or, the by-product salt includes ammonium sulfate; And / or, the resource recovery method further includes drying the second concentrate to obtain mixed salts; the drying process includes vacuum drying. The mother liquor drying treatment shall at least satisfy one of the following conditions: The pressure of the vacuum drying process is 0.02~0.03 MPa; And / or, the temperature of the vacuum drying treatment is 60~70℃; And / or, the moisture content of the mixed salt is <5%.

13. The resource recovery method according to claim 12, characterized in that, The recycled water purification treatment includes a second pH adjustment treatment and a reverse osmosis membrane treatment performed sequentially. The second pH adjustment treatment must satisfy at least one of the following conditions: The first distillate and the second distillate are subjected to the second pH adjustment treatment; the temperature of the first distillate and the second distillate are each independently set to 20~30℃; And / or, the pH adjuster used in the second pH adjustment treatment includes concentrated sulfuric acid; the mass fraction of the concentrated sulfuric acid used in the second pH adjustment treatment is 70-98%; And / or, the pH value of the wastewater after the second pH adjustment treatment is 5~6.

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