Ammonia nitrogen recovery system and method

Abstract

This invention provides an ammonia nitrogen recovery system and method. The system includes: an acid absorption unit, a reaction unit, and an aeration unit; the reaction unit has an expanded membrane assembly; a circulation pipeline for conveying acid absorbent is formed between the acid absorption unit and the expanded membrane assembly; the aeration unit is used to aerate the expanded membrane assembly. This invention uses aeration to increase the pH value of wastewater, thereby reducing the free NH4+ in the wastewater. 3 With increased concentration, the acid is absorbed by the acid absorbent after entering the expanded membrane assembly. Compared to using alkaline chemicals to adjust the pH, this significantly reduces operating and subsequent treatment costs. Furthermore, the aeration method makes pH control easier, preventing the generation of NH4+. 3 The spillover also accelerated molecular motion, causing NH4+ to... 3 The increased transmembrane rate results in higher recovery efficiency; it also reduces concentration polarization, thereby reducing membrane fouling; the expanded membrane tube assembly used has a simple structure that is easy to clean and replace, and has stronger tensile strength and temperature resistance range, avoiding problems such as clogging and breakage.

Description

An ammonia nitrogen recovery system and method Technical Field

[0001] This invention relates to the field of wastewater treatment and resource recovery technology, and in particular to an ammonia nitrogen recovery system and method. Background Technology

[0002] Ammonia nitrogen is a valuable agricultural and chemical resource. Besides natural nitrogen fixation, the primary method humans obtain ammonia nitrogen from nature is through the Haber-Bosch process. This process, under high temperature and pressure, uses atmospheric N2 as a raw material, reacting it with H2 to produce NH3 under the catalysis of iron compounds. Approximately 85% of the NH3 produced is used as fertilizer in agricultural production, while 15% is used to manufacture chemical products such as nylon and fiber plastics. To meet the ever-increasing demand for ammonia nitrogen, global ammonia nitrogen production has reached 1.2 × 10¹¹ kg NH3-N / year. The energy consumption for ammonia nitrogen production using the Haber-Bosch process is 12.1 kWh / kg NH3-N. It is estimated that the greenhouse gas (GHG) emissions from fossil fuel consumption during NH3-N production by the Haber-Bosch process account for 1-2% of global GHG emissions and consume approximately 50% of global hydrogen production. Therefore, the demand for NH3-N and the energy-intensive nature of its production process necessitate the search for economical, environmentally friendly, and sustainable NH3-N regeneration pathways.

[0003] The main technologies for ammonia nitrogen recovery from wastewater include: air stripping (AS), ion exchange and adsorption (IE / AD), struvite precipitation (SP), reverse osmosis (RO), and gas permeable membrane (GPM). AS is typically carried out in a distillation column, requiring steam-assisted stripping of NH3. AS can be energy-intensive because the gas phase must be pressurized to maintain the flow rate in the distillation column, and higher stripping temperatures are needed to maintain good stripping efficiency. IE and AD are considered low-energy processes, but the non-selectivity of adsorption and resin materials poses a significant challenge to recovering high-purity ammonia nitrogen products. SP technology for ammonia nitrogen recovery is limited by the presence of PO4 in wastewater. 3- and Mg 2+ If the concentrations are mismatched, an additional precipitant is generally needed to ensure that the molar ratio of magnesium, nitrogen, and phosphorus is Mg:N:P = 1:1:1. Furthermore, struvite formation is also affected by Ca... 2+ HCO3 - Interference from plasma. Reverse osmosis based on ultrafiltration requires pretreatment and high-pressure ammonia nitrogen recovery; low pressure (<5 bar) causes severe membrane fouling in porous membrane systems. Hydrophobic GPMs do not require pressurization and can spontaneously separate gaseous ammonia nitrogen from the feed solution into the acid absorption solution driven by the ammonia nitrogen concentration gradient. Once in the acid absorption solution, NH3 combines with free protons to form non-volatile NH4+. +It is then converted into high-value nitrogen fertilizer. Based on 10 performance criteria—recovery efficiency, pretreatment energy consumption, recovery energy consumption, alkalinity consumption, chemical cost, number of operation steps, effluent ammonia nitrogen content, recovered product purity, fertilizer price, and profit—a multi-standard Promethee analysis was conducted to rank the above-mentioned different ammonia nitrogen recovery methods. The results show that GPM is currently the best solution for ammonia nitrogen recovery.

[0004] However, the traditional GPM process has the following problems:

[0005] (1) The non-pressurized hydrophobic GPM process is a shell-and-tube system, and membrane fouling is difficult to clean and restore;

[0006] (2) The most widely used traditional submersible GPM is a hollow fiber membrane with a diameter of less than 1 mm. However, due to the small diameter of the membrane, the inlet water pressure should not be too high, and it is prone to problems such as clogging and breakage.

[0007] (3) In the traditional GPM recovery process, the alkalinity needs to be adjusted by sodium hydroxide or lime to increase the concentration of free ammonia. The addition of a large amount of alkaline chemicals will increase the operating and subsequent treatment costs, and the pH adjustment is not easy to control. If the pH is adjusted too high, it will easily cause NH3 to overflow.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The purpose of this invention is to provide an ammonia nitrogen recovery system and method, which recovers ammonia nitrogen from wastewater based on an in-situ submerged expanded membrane tube assembly with aeration. This method can efficiently and with low energy consumption recover ammonia nitrogen from wastewater, overcoming the shortcomings of the prior art.

[0010] In a first aspect, the present invention provides an ammonia nitrogen recovery system, comprising: an acid absorption unit, a reaction unit, and an aeration unit; the reaction unit having an expanded membrane tube assembly; a circulation pipeline for conveying acid absorbent liquid being formed between the acid absorption unit and the expanded membrane tube assembly; and the aeration unit for aerating the expanded membrane tube assembly.

[0011] In this invention, the wastewater is ammonia nitrogen-containing wastewater, including but not limited to: biogas slurry, anaerobic digestion liquid, landfill leachate, and high ammonia nitrogen industrial wastewater.

[0012] In the aforementioned wastewater containing ammonia nitrogen, due to HCO3 - The content of [a substance] is relatively high, and during aeration, it releases CO2 and OH [electrolytes]. -The increased pH value of wastewater leads to an increase in the concentration of free NH3 in the wastewater. After entering the expanded membrane tube assembly, it is absorbed by the acid absorbent. Compared with the method of adjusting the pH with alkaline chemicals, this greatly reduces the operating and subsequent treatment costs. Aeration makes it easier to control the pH value and avoids NH3 overflow. Moreover, the aeration method accelerates molecular motion, which increases the transmembrane rate of NH3 and the recovery efficiency is higher. In addition, the aeration method can reduce concentration polarization, thereby reducing membrane fouling.

[0013] Preferably, the acid absorption unit includes an acid absorbent storage tank and a water pump; the acid absorbent storage tank, the water pump, and the expansion membrane assembly form a circulation pipeline for conveying the acid absorbent.

[0014] Preferably, the delivery rate of the acid absorption solution is 20-100 mL / min / cm. 2 (per cm) 2 The flow rate of the acid absorbent in the cross-sectional area of ​​the membrane tube is 20-100 mL / min, more preferably 60 mL / min / cm. 2 .

[0015] Preferably, the reaction unit and the absorption unit are temperature controlled by a water bath, which facilitates timely adjustment of the reaction system temperature.

[0016] Preferably, the acid absorbent storage tank is equipped with a pH controller to monitor for leaks in the acid absorbent and to determine the need for replenishment.

[0017] Preferably, the aeration unit includes an aerator and a releaser; the aerator is connected to the releaser, and the releaser is located below the expanded membrane tube assembly, releasing gas into the wastewater after aeration by the aerator.

[0018] Preferably, a flow meter is installed on the pipe between the aerator and the releaser to adjust the aeration rate. The aeration rate of the aerator is preferably 50-400 mL / min / L (1L of liquid to be treated requires 50-400 mL of aeration volume per minute).

[0019] Preferably, the aerator is equipped with a timer switch on its air inlet pipe. The aeration time is controlled by the timer switch, preferably at intervals of 1-6 hours, such as: 1 hour aeration / 1 hour stop, 2 hours aeration / 2 hours stop, 4 hours aeration / 4 hours stop, 6 hours aeration / 6 hours stop, preferably 2 hours aeration / 2 hours stop.

[0020] Preferably, the material of the expanded membrane tube assembly includes: expanded polytetrafluoroethylene (ePTFE), polypropylene (PP), and polyvinylidene fluoride (PVDF). ) Any one of the following; more preferably ePTFE, which can make the membrane diameter from a few millimeters to tens of millimeters. Large-diameter membrane tubes have stronger tensile strength and temperature resistance range, avoiding problems such as blockage and breakage.

[0021] Specifically, the process of preparing the expanded membrane tube assembly is basically similar to that of the traditional shell-and-tube membrane contactor. Epoxy resin and curing agent are used to bond and fix the membrane to the water collection end. The difference is that the expanded membrane tube assembly of the present invention only retains the fixed water collection ends at both ends, while removing the middle shell, so that the membrane tube can be exposed and directly immersed in ammonia nitrogen-containing wastewater.

[0022] Preferably, the acid absorption solution includes any one of sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid, with a concentration range of 0.01-0.2M.

[0023] A second aspect of the present invention provides an ammonia nitrogen recovery method, employing the aforementioned ammonia nitrogen recovery system, comprising the following steps:

[0024] S1. The expansion membrane tube assembly of the reaction unit is immersed in the sewage, eliminating the need for the complex membrane assembly setup in shell-and-tube systems. The structure is simple and easy to clean and replace.

[0025] Specifically, the expansion membrane tube assembly of the reaction unit is submerged below the surface of the wastewater, and the release device is placed below the expansion membrane tube assembly.

[0026] S2. Aeration is carried out in the wastewater through the aeration unit to increase the concentration of free NH3 in the wastewater.

[0027] Specifically, aeration is achieved through an aerator, the aeration rate is adjusted by a flow meter, the aeration time is controlled by a timer switch, and the gas enters the wastewater through a release device, thereby increasing the concentration of free NH3 in the wastewater.

[0028] Preferably, the aeration rate of the aerator is 50-400 mL / min / L.

[0029] Preferably, the aeration time interval is 1-6 hours, for example: 1 hour aeration / 1 hour stop, 2 hours aeration / 2 hours stop, 4 hours aeration / 4 hours stop, 6 hours aeration / 6 hours stop, preferably 2 hours aeration / 2 hours stop.

[0030] S3. The acid absorbent is circulated between the acid absorption unit and the reaction unit through the expansion membrane tube assembly. Free NH3 in the wastewater enters the expansion membrane tube assembly and is absorbed by the acid absorbent.

[0031] Specifically, the acid absorbent in the acid absorbent storage tank is pumped into the expansion membrane tube assembly through a pipeline. The free NH3 in the wastewater enters the expansion membrane tube assembly, is absorbed by the acid absorbent, and then returns to the acid absorbent storage tank through the pipeline, thus circulating and transporting the solution.

[0032] Preferably, the acid absorption solution includes any one of sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid, with a concentration range of 0.01-0.2M.

[0033] Preferably, the delivery rate of the acid absorption solution is 20-100 mL / min / cm. 2 More preferably 60 mL / min / cm 2 .

[0034] Beneficial effects:

[0035] (1) The present invention uses aeration to increase the pH value of wastewater, thereby increasing the concentration of free NH3 in wastewater. After entering the expansion membrane tube assembly, it is absorbed by the acid absorption liquid. Compared with the method of adjusting pH with alkaline drugs, the operating and subsequent treatment costs are greatly reduced.

[0036] (2) The aeration method of this invention makes it easier to control the pH value and avoid NH3 overflow. In addition, the aeration method accelerates molecular motion, increases the transmembrane rate of NH3, and improves the recovery efficiency.

[0037] (3) The aeration method used in this invention can reduce concentration polarization, thereby reducing membrane fouling and extending service life;

[0038] (4) The present invention uses the method of directly immersing the expansion membrane tube assembly in the sewage, which does not require the complex membrane assembly setup in the shell-and-tube system. The structure is simple and easy to clean and replace.

[0039] (5) The expansion membrane tube assembly used in this invention can make the membrane diameter from a few millimeters to tens of millimeters. Large-diameter membrane tubes have stronger tensile strength and temperature resistance range than traditional fiber membrane filaments, avoiding problems such as blockage and breakage, extending service life and reducing costs. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 is a schematic diagram of the system structure for recovering ammonia nitrogen from wastewater provided by the present invention.

[0042] Explanation of reference numerals in the attached diagram: 1. Acid absorption liquid storage tank; 2. pH controller; 3. Water pump; 4. Expanded membrane tube assembly; 5. Release device; 6. Aerator; 7. Flow meter; 8. Timer switch. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] Example 1

[0047] As shown in Figure 1, this embodiment provides an ammonia nitrogen recovery system, including: an acid absorption unit, a reaction unit, and an aeration unit; the reaction unit has an expansion membrane tube assembly 4, which is immersed in wastewater; a circulation pipeline for conveying acid absorption liquid is formed between the acid absorption unit and the expansion membrane tube assembly 4; the aeration unit is used to aerate the expansion membrane tube assembly 4.

[0048] In this embodiment, the wastewater is biogas slurry.

[0049] In this embodiment, the acid absorption unit includes: an acid absorption liquid storage tank 1 and a water pump 3; the acid absorption liquid storage tank 1, the water pump 3 and the expansion membrane tube assembly 4 are connected by a pipeline to form a circulation pipeline for conveying the acid absorption liquid.

[0050] Specifically, the outlet of the acid absorbent storage tank 1 is connected to the water pump 3 via a first hose, the water pump 3 is connected to the inlet of the expansion membrane assembly 4 via a second hose, and the outlet of the expansion membrane assembly 4 is connected to the inlet of the acid absorbent storage tank 1 via a third hose.

[0051] In this embodiment, both the acid absorption unit and the reaction unit are temperature-controlled by a water bath.

[0052] In this embodiment, the acid absorbent storage tank 1 stores acid absorbent and is equipped with a pH controller 2, which can monitor whether there is any leakage of acid absorbent and the need to replenish acid absorbent.

[0053] In this embodiment, the acid absorption solution is sulfuric acid with a concentration of 0.05M, and the delivery rate is 60mL / min / cm. 2 .

[0054] In this embodiment, the aeration unit includes an aerator 6 and a releaser 5. The aerator 6 is connected to the releaser 5, which is located in the sewage and below the expansion membrane tube assembly 4. After aeration by the aerator 6, the releaser 5 releases gas into the sewage.

[0055] In this embodiment, a flow meter 7 is installed on the pipe between the aerator 6 and the release device 5 to control the aeration rate of the aerator 6 to be 100 mL / min / L.

[0056] In this embodiment, a timer switch 8 is connected to the air inlet pipe of the aerator 6, and the aeration time is controlled by the timer switch 8 to aerate for 2 hours and stop for 2 hours.

[0057] In this embodiment, the material of the expansion membrane tube assembly 4 is ePTFE.

[0058] This embodiment also provides an ammonia nitrogen recovery method, which uses the ammonia nitrogen recovery system of this embodiment and includes the following steps:

[0059] S1. Immerse the expansion membrane tube assembly 4 of the reaction unit below the sewage surface and place the release device 5 below the expansion membrane tube assembly 4.

[0060] S2. Aeration is carried out by aerator 6, flow meter 7 adjusts the aeration rate, timer switch 8 controls the aeration time, and gas enters the sewage through release device 5, thereby increasing the concentration of free NH3 in the sewage.

[0061] S3. The acid absorbent in the acid absorbent storage tank 1 is pumped by the water pump 3 and enters the expansion membrane tube assembly 4 through the pipeline. The free NH3 in the sewage enters the expansion membrane tube assembly 4 and is absorbed by the acid absorbent. Then it returns to the acid absorbent storage tank 1 through the pipeline, and so on.

[0062] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 99% without the addition of alkalinity.

[0063] Example 2

[0064] This embodiment is basically the same as embodiment 1, except that the wastewater in this embodiment is anaerobic digestion liquid of kitchen waste.

[0065] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 96% without the addition of alkalinity.

[0066] Example 3

[0067] This embodiment is basically the same as embodiment 1, except that the wastewater in this embodiment is landfill leachate.

[0068] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 99% without the addition of alkalinity.

[0069] Example 4

[0070] This embodiment is basically the same as Embodiment 1, except that the wastewater in this embodiment is high ammonia nitrogen industrial wastewater.

[0071] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 97% without the addition of alkalinity.

[0072] Example 5

[0073] This embodiment is basically the same as embodiment 1, except that the material of the expansion membrane tube assembly 4 in this embodiment is PP.

[0074] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 94% without the addition of alkalinity.

[0075] Example 6

[0076] This embodiment is basically the same as embodiment 1, except that the material of the expansion membrane tube assembly 4 in this embodiment is PVDF.

[0077] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached more than 91% without the addition of alkalinity.

[0078] Example 7

[0079] This embodiment is basically the same as Embodiment 1, except that the acid absorption solution in this embodiment is hydrochloric acid.

[0080] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 99% without the addition of alkalinity.

[0081] Example 8

[0082] This embodiment is basically the same as Embodiment 1, except that the acid absorption solution in this embodiment is phosphoric acid.

[0083] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 97% without the addition of alkalinity.

[0084] Example 9

[0085] This embodiment is basically the same as Embodiment 1, except that the acid absorption solution in this embodiment is nitric acid.

[0086] In this embodiment, wastewater was placed in an plexiglass reactor with an effective volume of 1L for testing. After the reaction was completed, the ammonia nitrogen removal efficiency reached over 95% without the addition of alkalinity.

[0087] Example 10

[0088] This embodiment is basically the same as embodiment 1, except that: in this embodiment, the aeration time is controlled by timer switch 8, which is 1 hour of aeration and 1 hour of stopping.

[0089] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 96%, and the ammonia nitrogen recovery efficiency reached more than 94%.

[0090] Example 11

[0091] This embodiment is basically the same as embodiment 1, except that: in this embodiment, the aeration time is controlled by a timer switch 8, which controls the aeration time to 6 hours for aeration and 6 hours for stopping.

[0092] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 93%, and the ammonia nitrogen recovery efficiency reached more than 92%.

[0093] Example 12

[0094] This embodiment is basically the same as embodiment 1, except that the aeration rate of the aerator 6 in this embodiment is 50 mL / min / L.

[0095] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 95%, and the ammonia nitrogen recovery efficiency reached more than 92%.

[0096] Example 13

[0097] This embodiment is basically the same as embodiment 1, except that the aeration rate of the aerator 6 in this embodiment is 400 mL / min / L.

[0098] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 99%, and the ammonia nitrogen recovery efficiency reached more than 93%.

[0099] Example 14

[0100] This embodiment is basically the same as Embodiment 1, except that the delivery rate of the acid absorption solution in this embodiment is 20 mL / min / cm. 2 .

[0101] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 99%, and the ammonia nitrogen recovery efficiency reached more than 94%.

[0102] Example 15

[0103] This embodiment is basically the same as Embodiment 1, except that the delivery rate of the acid absorption solution in this embodiment is 100 mL / min / cm. 2 .

[0104] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 99%, and the ammonia nitrogen recovery efficiency reached more than 96%.

[0105] Example 16

[0106] This embodiment is basically the same as Embodiment 1, except that the concentration of the acid absorption solution in this embodiment is 0.01M.

[0107] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 89%, and the ammonia nitrogen recovery efficiency reached more than 88%.

[0108] Example 17

[0109] This embodiment is basically the same as Embodiment 1, except that the concentration of the acid absorption solution in this embodiment is 0.2M.

[0110] In this embodiment, wastewater was placed in an organic glass reactor with an effective volume of 1L for testing. After the reaction was completed, without the addition of alkalinity, the ammonia nitrogen removal efficiency reached more than 99%, and the ammonia nitrogen recovery efficiency reached more than 97%.

[0111] In summary, this invention increases the pH value of wastewater through aeration, thereby increasing the concentration of free NH3 in the wastewater. Upon entering the expanded membrane tube assembly, it is absorbed by the acid absorbent. Compared to adjusting the pH with alkaline chemicals, this significantly reduces operating and subsequent treatment costs. Aeration also facilitates pH control, preventing NH3 overflow. Furthermore, aeration accelerates molecular motion, increasing the NH3 transmembrane rate and improving recovery efficiency. Aeration reduces concentration polarization, thus reducing membrane fouling and extending service life. This invention directly immerses the expanded membrane tube assembly in the wastewater, eliminating the need for complex membrane assembly setups in shell-and-tube systems, resulting in a simple structure that is easy to clean and replace. The expanded membrane tube assembly used in this invention allows for membrane diameters ranging from a few millimeters to tens of millimeters. Larger diameter membrane tubes offer greater tensile strength and temperature resistance than traditional fiber membranes, preventing clogging and breakage, extending service life, and reducing costs.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering ammonia nitrogen, characterized in that, The process includes the following steps: S1, immersing the expanded membrane tube assembly of the reaction unit in wastewater; S2, aerating the wastewater through an aeration unit to increase the concentration of free NH3 in the wastewater; S3, circulating the acid absorbent between the acid absorption unit and the expanded membrane tube assembly of the reaction unit, allowing free NH3 in the wastewater to enter the expanded membrane tube assembly and be absorbed by the acid absorbent; the ammonia nitrogen recovery system used in the ammonia nitrogen recovery method includes: an acid absorption unit, a reaction unit, and an aeration unit; the reaction unit has an expanded membrane tube assembly; a circulation pipeline for transporting the acid absorbent is formed between the acid absorption unit and the expanded membrane tube assembly; the aeration unit is used to aerate the expanded membrane tube assembly. The membrane tube assembly is used for aeration; the expanded membrane tube assembly is made of expanded polytetrafluoroethylene; the process of preparing the expanded membrane tube assembly involves bonding and fixing the membrane to the water collection end using epoxy resin and a curing agent, leaving only the two fixed water collection ends exposed, allowing the membrane tube to be directly immersed in the ammonia-nitrogen-containing wastewater; the aeration unit includes an aerator and a release device; the aerator is connected to the release device, which is located below the expanded membrane tube assembly, and releases gas into the wastewater after aeration by the aerator; a timer switch is connected to the air inlet pipe of the aerator, controlling the aeration time at intervals of 1-6 hours; the aeration rate of the aerator is 50-400 mL / min / L; the acid absorption solution includes any one of sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid, with a concentration range of 0.01-0.2M.

2. The ammonia nitrogen recovery method according to claim 1, characterized in that, The acid absorption unit includes an acid absorbent storage tank and a water pump; a circulation pipeline for conveying the acid absorbent is formed between the acid absorbent storage tank, the water pump and the expansion membrane tube assembly.

3. The ammonia nitrogen recovery method according to claim 2, characterized in that, The acid absorption liquid storage tank is equipped with a pH controller.

4. The ammonia nitrogen recovery method according to claim 1, characterized in that, A flow meter is installed on the pipe between the aerator and the releaser.

Images