Phosphorus-containing wastewater treatment system

Abstract

The application relates to the technical field of wastewater purification, in particular to a phosphorus-containing wastewater treatment system. The system comprises a pre-purification unit, a deep purification unit, a membrane concentration unit and a multi-effect evaporation unit which are connected in sequence; the pre-purification unit is used for diluting and filtering impurities of the phosphorus-containing wastewater; the deep purification unit is used for receiving the wastewater treated by the pre-purification unit and filtering out multivalent metal cations, macromolecular substances and divalent salts in the wastewater; the membrane concentration unit is used for receiving the wastewater treated by the deep purification unit, evaporating water under low temperature in vacuum negative pressure and steam heating, and concentrating phosphoric acid; the multi-effect evaporation unit is used for receiving the phosphoric acid concentrated by the membrane concentration unit, further evaporating water under steam heating, further concentrating the phosphoric acid, and obtaining a phosphoric acid product which reaches the selling standard. The system has low operation energy consumption, can realize efficient recycling of the phosphorus-containing wastewater, reduces pollution to the environment, realizes the improvement of economic benefits through recycling of phosphorus resources.

Description

Technical Field

[0001] This application relates to the field of wastewater purification technology, specifically to a phosphorus-containing wastewater treatment system. Background Technology

[0002] Wastewater from cleaning components in the electronics industry mainly consists of phosphorus-containing wastewater and waste hydrochloric acid. Phosphorus-containing wastewater is a type of industrial wastewater that is difficult to treat. In traditional processes, it is usually discharged directly or after simple treatment before being released into the environment, leading to organic matter and heavy metal ion pollution of soil and water bodies, causing harm to the ecological environment. This treatment method lacks effective waste treatment and recycling measures, resulting in the pollution of the environment by phosphorus-containing wastewater.

[0003] Phosphorus-containing wastewater mainly originates from waste acid generated during the cleaning of electronic components in electronics companies. Although the concentration of phosphorus-containing wastewater meets the "Industrial Phosphoric Acid Standard" GB / T2091-2008, it still contains minute impurities such as inorganic particles, suspended solids, inorganic silicon, and colloids, as well as metal ions such as iron, aluminum, and zinc. Therefore, it does not meet the "Industrial Phosphoric Acid Standard" GB / T2091 and requires purification. Furthermore, because phosphoric acid is a moderately strong acid with certain corrosiveness, oxidizing properties, and high viscosity, high-concentration phosphorus-containing wastewater cannot be directly purified using nanofiltration membranes. It needs to be diluted first before purification, and finally concentrated to a phosphoric acid product that meets the standards.

[0004] Currently, the most common method for phosphoric acid treatment is acid concentration and purification. For example, Chinese patent application CN212246635U discloses a clean and efficient technology for the resource recovery of phosphorus-containing wastewater. While this reduces equipment investment and personnel costs, the recovery efficiency is low, and most recovery processes rely on chemical neutralization, which can impact the surrounding environment. Chinese patent application CN115636398A discloses a phosphorus-containing wastewater treatment process, which improves the recovery rate and efficiency, but requires significant equipment investment and does not provide information on whether the recovered phosphoric acid content meets standards or its intended use.

[0005] Therefore, there is a need for a phosphorus-containing wastewater treatment method that can more effectively recycle phosphorus-containing wastewater and has less environmental pollution. Summary of the Invention

[0006] In view of this, the present application provides a phosphorus-containing wastewater treatment system that can more effectively recycle phosphorus-containing wastewater, remove organic matter and heavy metal ions from the phosphorus-containing wastewater, reduce environmental pollution, and improve economic benefits through the recycling of phosphorus resources.

[0007] This application provides a phosphorus-containing wastewater treatment system, including a pre-purification unit, a deep purification unit, a membrane concentration unit, and a multi-effect evaporation unit;

[0008] The input end of the pre-purification unit is connected to pure water and phosphorus-containing wastewater, and the output end is sequentially connected to the deep purification unit, the membrane concentration unit and the multi-effect evaporation unit. The output end of the multi-effect evaporation unit outputs phosphoric acid products that meet the sales standards.

[0009] In one embodiment, the pre-purification unit includes a phosphoric acid dilution tank and a ceramic tubular membrane device;

[0010] The input end of the phosphoric acid dilution tank is connected to pure water and phosphorus-containing wastewater, and the output end is connected to the input end of the ceramic tube membrane device. The output end of the ceramic tube membrane device is connected to the input end of the deep purification unit.

[0011] The phosphoric acid dilution tank is used to dilute the phosphorus-containing wastewater with the pure water;

[0012] The ceramic tube membrane device is used to filter impurities from the phosphoric acid dilution tank diluted phosphoric acid wastewater. The impurities include at least one of insoluble particles, colloids, and inorganic silicon.

[0013] In one embodiment, the ceramic membrane used in the ceramic tubular membrane device is an acid-resistant special inorganic tubular membrane, and the ceramic tubular membrane device separates substances through its own porous inorganic medium and the sieving effect of the attached membrane layer.

[0014] In one embodiment, the deep purification unit includes a nanofiltration membrane device, which includes a first nanofiltration membrane device section, a second nanofiltration membrane device section, and a nanofiltration membrane device permeate tank.

[0015] The input end of the first stage of the nanofiltration membrane device is connected to the output end of the pre-purification unit. The concentrated liquid output end of the first stage of the nanofiltration membrane device is connected to the input end of the second stage of the nanofiltration membrane device. The permeate output ends of the first stage and the second stage of the nanofiltration membrane device are connected to the input end of the permeate tank of the nanofiltration membrane device. The output end of the permeate tank of the nanofiltration membrane device is connected to the input end of the membrane concentration unit.

[0016] In one embodiment, the membrane concentration unit includes an MD membrane evaporation device and a first-concentration phosphoric acid recovery tank;

[0017] The input end of the MD membrane evaporation device is connected to the output end of the deep purification unit, the output end of the MD membrane evaporation device is connected to the input end of the first concentration phosphoric acid recovery tank, and the output end of the first concentration phosphoric acid recovery tank is connected to the input end of the multi-effect evaporation unit.

[0018] The MD membrane evaporation device is used to evaporate the water in the phosphoric acid from the deep purification unit under vacuum negative pressure and steam heating, so that the phosphoric acid is concentrated to a first concentration;

[0019] The first concentration phosphoric acid recovery tank is used to collect phosphoric acid solutions of the first concentration.

[0020] In one embodiment, the multi-effect evaporation unit includes a multi-effect evaporation device, which includes a recovered acid evaporation chamber, a recovered acid cooler, a recovered acid condensate preheater, a recovered acid heater, a vacuum device, a concentrated phosphoric acid pump, and a phosphoric acid product tank.

[0021] The output end of the multi-effect evaporator is connected to a second concentration phosphoric acid recovery tank, which outputs phosphoric acid products that meet the sale standards.

[0022] In one embodiment, the cold-side inlet of the recovered acid cooler is connected to the first concentration of phosphoric acid output from the membrane concentration unit, the cold-side outlet is connected to the feed end of the multi-effect evaporation unit, the hot-side inlet is connected to the second concentration of phosphoric acid output from the multi-effect evaporation unit, and the hot-side outlet is connected to the second concentration of phosphoric acid recovery tank.

[0023] The recovered acid cooler is used to use the first concentration of phosphoric acid output from the membrane concentration unit as a cooling medium to exchange heat and cool the second concentration of phosphoric acid output from the multi-effect evaporation unit.

[0024] In one embodiment, it also includes a concentrate tank and a neutralization reactor;

[0025] The concentrated liquid produced by the deep purification unit and the membrane concentration unit is output to the concentrate tank. The sewage discharge end of the concentrate tank is connected to the neutralization reactor, and the purification output end of the concentrate tank is connected to the circulating wastewater input end of the pre-purification unit.

[0026] The concentrate tank is used to separate high concentrations of suspended solids and high cations in the concentrate and output them to the neutralization reactor, and to output the concentrate after separating high concentrations of suspended solids and high cations to the pre-purification unit.

[0027] The neutralization reactor is used to neutralize wastewater containing high concentrations of suspended solids and high cations by using lime slurry, and to generate calcium phosphate precipitate. The calcium phosphate precipitate and supernatant generated by the neutralization reactor are output to the incineration unit for incineration.

[0028] In one embodiment, it further includes a steam condensate tank, an evaporative condensate tank, and an RO phosphorus removal device;

[0029] The steam condensate output terminals of the membrane concentration unit and the multi-effect evaporation unit are connected to the input terminals of the steam condensate tank, and the output terminal of the steam condensate tank is connected to the pure water input pipe of the pre-purification unit.

[0030] The membrane concentration unit and the evaporation condensate output end are connected to the input end of the evaporation condensate tank. The output end of the evaporation condensate tank is connected to the pure water input pipe of the pre-purification unit and / or to the inlet end of the RO phosphorus removal device. The concentrated water output end of the RO phosphorus removal device is connected to the filtrate tank of the ceramic tube membrane device of the deep purification unit.

[0031] In one embodiment, the system further includes a waste gas absorption tower, to which the acidic waste gas generated by the pre-purification unit, the deep purification unit, the membrane concentration unit, and the multi-effect evaporation unit is input. The output end of the waste gas absorption tower is used to connect to a waste gas incineration device.

[0032] The phosphorus-containing wastewater treatment system provided in this application includes a pre-purification unit, a deep purification unit, a membrane concentration unit, and a multi-effect evaporation unit connected in sequence. The pre-purification unit is used to dilute and filter impurities from the phosphorus-containing wastewater. The deep purification unit is used to receive the wastewater treated by the pre-purification unit and filter out multivalent metal cations, macromolecules, and divalent salts from the wastewater. The membrane concentration unit is used to receive the wastewater treated by the deep purification unit and evaporate water at low temperature under vacuum negative pressure and steam heating to concentrate phosphoric acid. The multi-effect evaporation unit is used to receive the phosphoric acid concentrated by the membrane concentration unit and further evaporate water under steam heating to further concentrate the phosphoric acid to obtain a phosphoric acid product with a concentration that meets the sales standard. The pre-purification unit is responsible for initial concentration adjustment and removal of coarse impurities, creating conditions for subsequent precision processing. The deep purification unit specifically removes key impurities such as metal ions, macromolecules, and salts to improve the purity of phosphoric acid. The membrane concentration unit utilizes the characteristics of vacuum and low-temperature evaporation to achieve initial concentration of phosphoric acid with low energy consumption. The multi-effect evaporation unit provides powerful evaporation capacity to ensure that the final product meets the required high concentration standard. This structured treatment pathway forms the technological foundation for achieving efficient, stable, and controllable phosphoric acid recovery and concentration. It maximizes heat energy recovery and, compared to conventional evaporation technologies, has lower operating energy consumption. It offers advantages in environmental protection, resource recovery, and economic benefits, enabling the efficient recycling of phosphorus-containing wastewater, reducing environmental pollution, and improving economic efficiency through phosphorus resource recovery. Furthermore, the phosphorus-containing wastewater recovery process does not involve chemical reactions, making it safer and more efficient. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a connection of a phosphorus-containing wastewater treatment system provided in an embodiment of this application. Detailed Implementation

[0035] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0036] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0037] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0038] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0040] like Figure 1 As shown in the figure, the phosphorus-containing wastewater treatment system provided in this application includes a pre-purification unit 1, a deep purification unit 2, a membrane concentration unit 3, and a multi-effect evaporation unit 4 connected in sequence.

[0041] Pre-purification unit 1 is used to dilute phosphorus-containing wastewater and filter impurities.

[0042] The deep purification unit 2 is used to receive the wastewater treated by the pre-purification unit 1 and filter out multivalent metal cations, macromolecules and divalent salts in the wastewater;

[0043] The membrane concentration unit 3 is used to receive the wastewater treated by the deep purification unit 2, and evaporate the water at low temperature under vacuum negative pressure and steam heating to concentrate the phosphoric acid.

[0044] The multi-effect evaporation unit 4 is used to receive phosphoric acid concentrated by the membrane concentration unit 3, and further evaporate the water under steam heating to further concentrate the phosphoric acid and obtain a phosphoric acid product with a concentration that meets the sales standard.

[0045] This application's embodiments decompose the complex phosphorus-containing wastewater treatment process into four logical stages: pretreatment, deep purification, preliminary concentration, and final refining. The pre-purification unit is responsible for initial concentration adjustment and removal of coarse impurities, creating conditions for subsequent precision treatment; the deep purification unit specifically removes key impurities such as metal ions, macromolecules, and salts, improving phosphoric acid purity; the membrane concentration unit utilizes the characteristics of vacuum and low-temperature evaporation to achieve preliminary concentration of phosphoric acid with low energy consumption; and the multi-effect evaporation unit provides powerful evaporation capacity, ensuring that the final product meets the required high concentration standards. This structured treatment path is the technological foundation for achieving efficient, stable, and controllable phosphoric acid recovery and concentration. It can maximize the recovery of heat energy and has lower operating energy consumption compared to conventional evaporation technologies. It has advantages in environmental protection, resource recovery, and economic benefits, enabling efficient recycling of phosphorus-containing wastewater, reducing environmental pollution, and improving economic benefits through phosphorus resource recovery. Furthermore, the phosphorus-containing wastewater recovery process does not involve chemical reactions, making it safer and more efficient.

[0046] In one embodiment, the pre-purification unit 1 includes a phosphoric acid dilution tank 101 and a ceramic tubular membrane device 102;

[0047] The input end of the phosphoric acid dilution tank 101 is connected to pure water and phosphorus-containing wastewater, and the output end is connected to the input end of the ceramic tube membrane device 102. The output end of the ceramic tube membrane device 102 is connected to the input end of the deep purification unit 2.

[0048] Phosphoric acid dilution tank 101 is used to dilute phosphorus-containing wastewater with pure water;

[0049] The ceramic tube membrane device 102 is used to filter impurities from the phosphorus-containing wastewater diluted by the phosphoric acid dilution tank 101. The impurities include at least one of insoluble particles, colloids, and inorganic silicon.

[0050] In the application, phosphorus-containing wastewater is pumped into the phosphoric acid dilution tank, where pure water or evaporated condensate (preferred) is added to dilute the phosphoric acid concentration to about 15%. The dilute phosphoric acid is then pumped into the ceramic membrane device of the phosphoric acid pre-purification unit to remove insoluble particles, colloids, inorganic silicon and other impurities in the waste acid. The filtrate is then fed into the filtrate tank of the ceramic tube membrane device.

[0051] In this embodiment, the phosphoric acid dilution tank precisely controls the phosphoric acid concentration to a level suitable for subsequent membrane treatment by adding pure water. This avoids potential clogging or membrane damage caused by high-concentration phosphoric acid directly entering the membrane system. The ceramic tube membrane device utilizes its physical filtration mechanism to effectively intercept insoluble particles, colloids, and inorganic silicon and other solid impurities in the wastewater. This combination ensures that the feed solution entering the deep purification unit meets the requirements in terms of concentration and cleanliness, reducing the burden on subsequent precision membrane treatment and extending its service life.

[0052] In one embodiment, the ceramic membrane used in the ceramic tubular membrane device 102 is an acid-resistant special inorganic tubular membrane. The ceramic tubular membrane device 102 separates substances through its own porous inorganic medium and the sieving effect of the attached membrane layer.

[0053] In application, the ceramic membrane device of the phosphoric acid pre-purification unit uses an acid-resistant special inorganic tubular membrane. This type of membrane is an inorganic membrane with special selective separation function. It adopts a dynamic "cross-flow filtration" method that is completely different from traditional filtration methods such as "full flow filtration" and "filter cake filtration". It achieves material separation through the sieving effect of its own porous inorganic medium and the attached membrane layer.

[0054] This application employs an acid-resistant special inorganic tubular membrane material, enabling it to operate stably for extended periods in highly acidic and potentially corrosive environments such as phosphorus-containing wastewater. The membrane's porous inorganic media and surface layer separate substances through a sieving effect; this is a purely physical process requiring no additional chemical reagents, thus avoiding secondary pollution. Furthermore, the separation mechanism is clear and reliable, and maintenance is relatively simple. Compared to dead-end filtration (full-flow filtration / cake filtration), cross-flow filtration (dynamic filtration) effectively mitigates membrane fouling and maintains a higher membrane flux.

[0055] In one embodiment, the deep purification unit 2 includes a nanofiltration membrane device, which includes a nanofiltration membrane device section 201, a nanofiltration membrane device section 202, and a nanofiltration membrane device permeate tank 203.

[0056] The input end of the first stage 201 of the nanofiltration membrane device is connected to the output end of the pre-purification unit 1. The concentrated liquid output end of the first stage 201 of the nanofiltration membrane device is connected to the input end of the second stage 202 of the nanofiltration membrane device. The permeate output ends of the first stage 201 and the second stage 202 of the nanofiltration membrane device are connected to the input end of the permeate tank 203 of the nanofiltration membrane device. The output end of the permeate tank of the membrane device is connected to the input end of the membrane concentration unit 3.

[0057] In the application, the phosphoric acid treated by the pre-purification unit is pressurized by the nanofiltration feed pump and enters the first stage of the nanofiltration membrane equipment in the deep purification unit of phosphoric acid. Under pressure, the nanofiltration membrane will trap impurities such as metal ions, phosphates, and organosilicon in the dilute phosphoric acid. The permeate from the first stage of the nanofiltration membrane equipment enters the permeate tank of the nanofiltration membrane equipment. The resulting concentrated liquid enters the second stage of the nanofiltration membrane equipment for further concentration and separation of impurities. The permeate also enters the permeate tank of the nanofiltration membrane equipment.

[0058] This application embodiment uses a nanofiltration membrane device as the main processing unit. Under pressure, it selectively removes small molecule impurities such as polyvalent metal ions, phosphates, and organosilicones. Most of the purified permeate enters the next unit. The concentrated liquid produced in the first stage (rich in removed impurities) is not directly discharged but enters the second-stage nanofiltration for further concentration and separation. This two-stage series design maximizes the recovery rate of phosphate (because the permeate produced in the second stage is also collected and reused), while concentrating impurities to a smaller volume for easier subsequent disposal, significantly improving the system's resource utilization efficiency and impurity removal efficiency.

[0059] In one embodiment, the membrane concentration unit 3 includes an MD membrane evaporation device 301 and a first concentration phosphoric acid recovery tank 302;

[0060] The input end of the MD membrane evaporation device 301 is connected to the output end of the deep purification unit 2, the output end of the MD membrane evaporation device 301 is connected to the input end of the first concentration phosphoric acid recovery tank 302, and the output end of the first concentration phosphoric acid recovery tank 302 is connected to the input end of the multi-effect evaporation unit 4.

[0061] The MD membrane evaporation device 301 is used to evaporate the water in the phosphoric acid from the deep purification unit 2 under vacuum negative pressure and steam heating, so that the phosphoric acid is concentrated to a first concentration;

[0062] The first concentration phosphoric acid recovery tank 302 is used to collect phosphoric acid solutions of the first concentration.

[0063] In the application, the deeply purified phosphoric acid is pumped to the feed solution tank of the MD membrane evaporation equipment in the membrane concentration unit. Under the action of a vacuum pump, the MD membrane evaporation equipment creates negative pressure, drawing the phosphoric acid from the feed solution tank into the MD membrane evaporation equipment. Under steam heating, the water in the phosphoric acid vaporizes into water vapor at low temperature. Driven by the steam pressure difference across the evaporation membrane, the water vapor continuously permeates through the evaporation membrane, concentrating the phosphoric acid to a concentration of over 50%, and then entering the first concentration phosphoric acid recovery tank 302, i.e., the 50% phosphoric acid recovery tank. The evaporation condensate and steam condensate generated during the phosphoric acid evaporation process are collected by the evaporation condensate tank and steam condensate tank, respectively. The evaporation condensate is preferentially returned to the phosphoric acid dilution tank for use as phosphoric acid dilution water, while the steam condensate is returned to the phosphoric acid dilution tank as makeup water to further dilute the phosphoric acid. When there is a surplus of evaporation condensate and steam condensate used as phosphoric acid dilution water, the surplus evaporation condensate enters the evaporation condensate RO phosphorus removal equipment for treatment, the RO permeate is used as circulating water makeup water, and the RO concentrate is returned to the filtrate tank of the ceramic tube membrane equipment; the surplus steam condensate is returned to the plant's pure water main pipe.

[0064] This application employs membrane distillation technology, which is particularly suitable for processing heat-sensitive, highly corrosive, and concentrated solutions such as phosphoric acid. Under vacuum negative pressure, the boiling point of water decreases, and combined with a lower heating steam temperature, low-temperature evaporation and concentration of phosphoric acid is achieved. This significantly reduces energy consumption and the risk of thermal decomposition of phosphoric acid. The MD membrane evaporation equipment concentrates phosphoric acid to over 50% (first concentration), creating favorable conditions for subsequent multi-effect evaporation units to process higher concentrations of phosphoric acid. The first concentration phosphoric acid recovery tank provides a stable buffer and storage.

[0065] In one embodiment, the multi-effect evaporation unit 4 includes a multi-effect evaporation device 401, which includes a recovered acid evaporation chamber, a recovered acid cooler, a recovered acid condensate preheater, a recovered acid heater, a vacuum device, a concentrated phosphoric acid pump, and a phosphoric acid product tank.

[0066] The output end of the multi-effect evaporator 401 is connected to the second concentration phosphoric acid recovery tank 5, and the second concentration phosphoric acid recovery tank 5 outputs phosphoric acid products that meet the sales standards.

[0067] In application, 50% phosphoric acid is pumped into the multi-effect evaporation unit. Under the heating effect of steam, the water in the phosphoric acid is continuously evaporated, and the phosphoric acid is further concentrated to obtain a phosphoric acid product with a concentration of over 75%, which then enters the second concentration phosphoric acid recovery tank, namely the 75% phosphoric acid recovery tank.

[0068] The recovered acid evaporation chamber in this embodiment is the main site for water evaporation; the recovered acid heater provides the heat required for evaporation (primary steam as the heat source); the recovered acid condensate preheater uses the latent heat of secondary steam to preheat the feed and recover heat energy; the recovered acid cooler is responsible for cooling the final product. A vacuum system maintains the low-pressure environment required for evaporation. This integrated equipment combination is key to the efficient operation of multi-effect evaporators, and by utilizing steam heat energy in stages (such as using secondary steam generated from primary steam for preheating), the overall thermal efficiency can be effectively improved. The concentrated phosphoric acid pump and phosphoric acid product tank ensure the smooth transport and storage of the concentrated product.

[0069] In one embodiment, the cold-side inlet of the acid recovery cooler is connected to the first concentration of phosphoric acid output from the membrane concentration unit 3, the cold-side outlet is connected to the feed end of the multi-effect evaporation unit 4, the hot-side inlet is connected to the second concentration of phosphoric acid output from the multi-effect evaporation unit 4, and the hot-side outlet is connected to the second concentration of phosphoric acid recovery tank 5.

[0070] The acid recovery cooler is used to use the first concentration of phosphoric acid output from the membrane concentration unit 3 as a cooling medium to exchange heat and cool the second concentration of phosphoric acid output from the multi-effect evaporation unit 4.

[0071] In the application, within the multi-effect evaporation unit: A recovered acid cooler utilizes the ambient temperature 50% phosphoric acid from the multi-effect evaporation unit's feed as a cooling medium to exchange heat and cool the 75% phosphoric acid output from the multi-effect evaporation unit. Simultaneously, the 50% feed phosphoric acid is also preheated. A recovered acid condensate preheater and a recovered acid heater are also included. Primary steam from the main steam pipe circulates through the recovered acid heater to heat and evaporate the phosphoric acid in the recovered acid evaporation chamber. Secondary steam exiting the recovered acid heater preheats the 50% feed phosphoric acid a second time before entering the recovered acid evaporation chamber. The condensate from the secondary steam goes to the steam condensate tank. Except for the primary steam, the system's internal heat is fully recycled, maximizing heat energy recovery.

[0072] The acid recovery cooler in this embodiment is designed as a heat exchanger, cleverly utilizing the relatively low-temperature first-concentration phosphoric acid (e.g., 50% phosphoric acid) just emerging from the membrane concentration unit as a cooling medium to cool the high-temperature second-concentration phosphoric acid (e.g., 75% phosphoric acid) finally produced by the multi-effect evaporation unit. This process achieves dual technical benefits: on the one hand, it efficiently cools the final product to a temperature suitable for storage or transportation; on the other hand, during the cooling process, the heat released by the product phosphoric acid is used to preheat the feed phosphoric acid that is about to enter the evaporation process, thereby significantly reducing the amount of fresh steam required to heat the feed, demonstrating significant energy-saving and consumption-reducing effects.

[0073] In one embodiment, it also includes a concentrate tank 9 and a neutralization reactor 10;

[0074] The concentrated liquid produced by the deep purification unit 2 and the membrane concentration unit 3 is output to the concentrate tank 9. The sewage discharge end of the concentrate tank 9 is connected to the neutralization reactor 10, and the purification output end of the concentrate tank 9 is connected to the circulating wastewater input end of the pre-purification unit 1.

[0075] The concentrate tank 9 is used to separate high concentrations of suspended solids and high cations in the concentrate and output them to the neutralization reactor 10, and to output the concentrate after separating high concentrations of suspended solids and high cations to the pre-purification unit 1;

[0076] Neutralization reactor 10 is used to neutralize waste liquid containing high concentrations of suspended solids and high cations by lime slurry, and to generate calcium phosphate precipitate. The calcium phosphate precipitate and supernatant generated by neutralization reactor 10 are output to the incineration unit for incineration.

[0077] This embodiment of the application utilizes a concentrate tank to separate the concentrate from the deep purification and membrane concentration units: most of the concentrate with relatively low impurity concentrations can be returned to the front end of the pre-purification unit for recycling and concentration, which improves the overall recovery rate of valuable phosphate components; for the small amount of waste concentrate that cannot be recycled and contains high concentrations of suspended solids and metal cations, chemical neutralization is carried out in the neutralization reactor 10 using lime slurry. The neutralization reaction generates a stable calcium phosphate precipitate, solidifying the harmful substances, and finally, the precipitate and supernatant are sent together for incineration for complete and harmless disposal. This staged treatment strategy maximizes resources and minimizes waste, reducing the environmental impact of the system operation.

[0078] In one embodiment, it also includes a steam condensate tank 6, an evaporative condensate tank 7, and an RO phosphorus removal tower 8;

[0079] The steam condensate output terminals of membrane concentration unit 3 and multi-effect evaporation unit 4 are connected to the input terminals of steam condensate tank 6, and the output terminal of steam condensate tank 6 is connected to the pure water input pipe of pre-purification unit 1.

[0080] The membrane concentration unit 3 and the evaporation condensate output end are connected to the input end of the evaporation condensate tank 7. The output end of the evaporation condensate tank 7 is connected to the pure water input pipe of the pre-purification unit 1 and / or to the inlet end of the RO phosphorus removal tower 8. The concentrated water output end of the RO phosphorus removal tower 8 is connected to the filtrate tank of the ceramic tube membrane device 102 of the deep purification unit 2.

[0081] This application embodiment constructs a closed-loop system for water resource recycling within the system. The membrane concentration unit (MD) and multi-effect evaporation unit generate two types of condensate during operation: steam condensate (obtained by condensing heated steam, which is relatively pure) and evaporation condensate (obtained by evaporating feed liquid). These two types of condensate are collected separately and preferentially reused as dilution water in the phosphoric acid dilution tank of the pre-purification unit, directly saving fresh water consumption. When there is excess evaporation condensate or when water quality requirements are more stringent, it undergoes advanced treatment through a reverse osmosis (RO) phosphorus removal unit: RO permeate can be used as makeup water for a high-quality circulating cooling water system; RO concentrate, still containing a certain amount of phosphorus, is returned to the ceramic tube membrane filtrate tank at the front end of the system for reprocessing. This design maximizes the recycling of water generated within the system, reducing the overall system's clean water supply and wastewater discharge.

[0082] In one embodiment, the system also includes an exhaust gas absorption tower 11. Acidic exhaust gases generated by the pre-purification unit 1, the deep purification unit 2, the membrane concentration unit 3, and the multi-effect evaporation unit 4 are input into the exhaust gas absorption tower 11. The output end of the exhaust gas absorption tower 11 is used to connect to an exhaust gas incineration device.

[0083] In the embodiments of this application, the pre-purification, deep purification, membrane concentration, and multi-effect evaporation units may release waste gas containing acidic components (such as phosphoric acid mist) when treating acidic wastewater. By installing a waste gas absorption tower, these dispersed acidic waste gases are collected and introduced into the tower. Inside the tower, the waste gas fully contacts and reacts with an alkaline absorbent liquid (such as alkali solution), neutralizing and removing the acidic substances. The pre-treated and purified waste gas is then sent to a waste gas incineration unit for high-temperature incineration, achieving final harmless emission or utilization as combustion air. This measure effectively prevents the direct emission of acidic gases from polluting the atmospheric environment and ensures the environmental friendliness of the treatment process.

[0084] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A phosphorus-containing wastewater treatment system, characterized in that, It includes a pre-purification unit (1), a deep purification unit (2), a membrane concentration unit (3), and a multi-effect evaporation unit (4). The input end of the pre-purification unit (1) is connected to pure water and phosphorus-containing wastewater, and the output end is connected to the deep purification unit (2), the membrane concentration unit (3) and the multi-effect evaporation unit (4) in sequence. The output end of the multi-effect evaporation unit (4) outputs phosphoric acid products that meet the sales standards.

2. The phosphorus-containing wastewater treatment system as described in claim 1, characterized in that, The pre-purification unit (1) includes a phosphoric acid dilution tank (101) and a ceramic tubular membrane device (102). The input end of the phosphoric acid dilution tank (101) is connected to pure water and phosphorus-containing wastewater, and the output end is connected to the input end of the ceramic tube membrane device (102). The output end of the ceramic tube membrane device (102) is connected to the input end of the deep purification unit (2). The phosphoric acid dilution tank (101) is used to dilute the phosphorus-containing wastewater with the pure water; The ceramic tube membrane device (102) is used to filter impurities from the phosphoric acid dilution tank (101) containing phosphorus wastewater, the impurities including at least one of insoluble particles, colloids and inorganic silicon.

3. The phosphorus-containing wastewater treatment system as described in claim 2, characterized in that, The ceramic tubular membrane device (102) uses an acid-resistant special inorganic tubular membrane. The ceramic tubular membrane device (102) separates substances through its own porous inorganic medium and the sieving effect of the attached membrane layer.

4. The phosphorus-containing wastewater treatment system as described in claim 1, characterized in that, The deep purification unit (2) includes a nanofiltration membrane device, which includes a first nanofiltration membrane device (201), a second nanofiltration membrane device (202), and a nanofiltration membrane device permeate tank (203). The input end of the first stage (201) of the nanofiltration membrane device is connected to the output end of the pre-purification unit (1). The concentrated liquid output end of the first stage (201) of the nanofiltration membrane device is connected to the input end of the second stage (202) of the nanofiltration membrane device. The permeate output ends of the first stage (201) and the second stage (202) of the nanofiltration membrane device are connected to the input end of the permeate tank (203) of the nanofiltration membrane device. The output end of the permeate tank (203) of the nanofiltration membrane device is connected to the input end of the membrane concentration unit (3).

5. The phosphorus-containing wastewater treatment system as described in claim 1, characterized in that, The membrane concentration unit (3) includes an MD membrane evaporation device (301) and a first concentration phosphoric acid recovery tank (302). The input end of the MD membrane evaporation device (301) is connected to the output end of the deep purification unit (2), the output end of the MD membrane evaporation device (301) is connected to the input end of the first concentration phosphoric acid recovery tank (302), and the output end of the first concentration phosphoric acid recovery tank (302) is connected to the input end of the multi-effect evaporation unit (4). The MD membrane evaporation device (301) is used to evaporate the water in the phosphoric acid from the deep purification unit (2) under vacuum negative pressure and steam heating, so that the phosphoric acid is concentrated to a first concentration; The first concentration phosphoric acid recovery tank (302) is used to collect phosphoric acid solution of the first concentration.

6. The phosphorus-containing wastewater treatment system as described in claim 1, characterized in that, The multi-effect evaporation unit (4) includes a multi-effect evaporation device (401), which includes a recovered acid evaporation chamber, a recovered acid cooler, a recovered acid condensate preheater, a recovered acid heater, a vacuum device, a concentrated phosphoric acid pump, and a phosphoric acid product tank. The output end of the multi-effect evaporator (401) is connected to the second concentration phosphoric acid recovery tank (5), which outputs phosphoric acid products that meet the sales standards.

7. The phosphorus-containing wastewater treatment system as described in claim 6, characterized in that, The cold-side inlet of the acid recovery cooler is connected to the first concentration of phosphoric acid output from the membrane concentration unit (3), the cold-side outlet is connected to the feed end of the multi-effect evaporation unit (4), the hot-side inlet is connected to the second concentration of phosphoric acid output from the multi-effect evaporation unit (4), and the hot-side outlet is connected to the second concentration of phosphoric acid recovery tank (5). The recovered acid cooler is used to use the first concentration of phosphoric acid output from the membrane concentration unit (3) as a cooling medium to exchange heat and cool the second concentration of phosphoric acid output from the multi-effect evaporation unit (4).

8. The phosphorus-containing wastewater treatment system as described in claim 1, characterized in that, It also includes a concentrate tank (9) and a neutralization reactor (10); The concentrated liquid produced by the deep purification unit (2) and the membrane concentration unit (3) is output to the concentrate tank (9). The sewage discharge end of the concentrate tank (9) is connected to the neutralization reactor (10). The purification output end of the concentrate tank (9) is connected to the circulating wastewater input end of the pre-purification unit (1). The concentrate tank (9) is used to separate high concentrations of suspended solids and high cations in the concentrate and output them to the neutralization reactor (10), and to output the concentrate after separating high concentrations of suspended solids and high cations to the pre-purification unit (1). The neutralization reactor (10) is used to neutralize waste liquid containing high concentration of suspended solids and high cations by lime milk and generate calcium phosphate precipitate. The calcium phosphate precipitate and supernatant generated by the neutralization reactor (10) are output to the incineration device for incineration.

9. The phosphorus-containing wastewater treatment system as described in claim 1, characterized in that, It also includes a steam condensate tank (6), an evaporation condensate tank (7), and an RO phosphorus removal tower (8); The steam condensate output terminals of the membrane concentration unit (3) and the multi-effect evaporation unit (4) are connected to the input terminal of the steam condensate tank (6), and the output terminal of the steam condensate tank (6) is connected to the pure water input pipe of the pre-purification unit (1). The membrane concentration unit (3) and the evaporation condensate output end are connected to the input end of the evaporation condensate tank (7). The output end of the evaporation condensate tank (7) is connected to the pure water input pipe of the pre-purification unit (1) and / or connected to the inlet end of the RO phosphorus removal device tower (8). The concentrated water output end of the RO phosphorus removal device tower (8) is connected to the filtrate tank of the ceramic tube membrane device (102) of the deep purification unit (2).

10. The phosphorus-containing wastewater treatment system as described in claim 1, characterized in that, It also includes a waste gas absorption tower (11), and the acidic waste gas generated by the pre-purification unit (1), the deep purification unit (2), the membrane concentration unit (3) and the multi-effect evaporation unit (4) is input to the waste gas absorption tower (11). The output end of the waste gas absorption tower (11) is used to connect to the waste gas incineration device.

Images