Ammonia nitrogen recovery system and method

Abstract

The invention provides an ammonia nitrogen recovery system and method. The system comprises an acid absorption unit, a reaction unit and an aeration unit, the reaction unit is provided with an expansion membrane tube assembly; a circulating pipeline for conveying acid absorption liquid is formed between the acid absorption unit and the expansion membrane tube assembly; and the aeration unit is used for aerating the expansion membrane tube assembly. The aeration mode is adopted to increase the pH value of the sewage, so that the concentration of free NH3 in the sewage is increased, the free NH3 is absorbed by the acid absorption liquid after entering the expansion membrane tube assembly, and the operation and subsequent treatment cost is greatly reduced compared with the mode of adjusting the pH by adopting an alkaline drug; the aeration mode is more convenient to control the pH value, NH3 overflow is avoided, molecular movement is accelerated, the NH3 transmembrane rate is increased, and the recovery efficiency is higher; concentration polarization can be reduced, so that membrane pollution is reduced; the adopted expansion membrane tube assembly is simple in structure and convenient to clean and replace, has higher tensile strength and temperature resistance range, and avoids the problems of blockage, breakage and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment and resource recovery, and in particular to an ammonia nitrogen recovery system and method. Background Art

[0002] Ammonia nitrogen is a valuable agricultural and chemical resource. In addition to natural nitrogen fixation, humans obtain ammonia nitrogen from nature mainly based on the Haber-Bosch process. This process uses atmospheric N2 as raw material and reacts N2 with H2 to produce NH3 under high temperature and high pressure under the catalysis of iron compounds. About 85% of the NH3 produced in this process is used as fertilizer for agricultural production, while 15% is used to make chemical products such as nylon and fiber plastics. In order to meet the growing demand for ammonia nitrogen, the global ammonia nitrogen production has reached 1.2×1011kg NH3-N / year. The energy consumption of the Haber-Bosch process to produce ammonia nitrogen is 12.1kWh / kg NH3-N. It is estimated that the greenhouse gas (GHGs) emissions released by the consumption of fossil energy in the production of NH3-N by the Haber-Bosch process account for 1-2% of the global GHGs emissions and consume about 50% of the global total hydrogen production. It can be seen that the demand for NH3-N and the energy intensity of its production process have forced people to seek economical, environmentally friendly and sustainable NH3-N regeneration methods.

[0003] The main technologies for recovering ammonia nitrogen from wastewater include: gas stripping (AS), ion exchange and adsorption (IE / AD), struvite precipitation (SP), reverse osmosis (RO) and gas permeable membrane (GPM). AS is usually carried out in a distillation tower and requires steam-assisted stripping of NH3. The energy consumption of AS may be very high because the gas phase must be pressurized to maintain the flow rate of the distillation tower, and a higher stripping temperature is required to maintain a good stripping effect. IE and AD are considered to be low-energy processes, but the non-selectivity of adsorption and resin materials poses a huge challenge to the recovery of higher purity ammonia nitrogen products. SP technology for recovering ammonia nitrogen is limited by PO4 in wastewater. 3- and Mg 2+ The concentration of struvite does not match, and generally requires additional precipitant to make the ratio of magnesium, nitrogen and phosphorus to Mg:N:P=1:1:1. In addition, the formation of struvite is also affected by Ca 2+ 、HCO3 - Interference of plasma. Reverse osmosis based on ultrafiltration requires pretreatment and high pressure to complete ammonia nitrogen recovery. Low pressure (<5bar) will cause serious membrane fouling in the porous membrane system. Hydrophobic GPM does not require pressurization. Driven by the ammonia nitrogen concentration gradient, it can spontaneously separate gaseous ammonia nitrogen from the feed solution into the acid absorption solution. Once entering the acid absorption solution, NH3 will combine with free protons to form non-volatile NH4 +, and converted into high-value nitrogen fertilizer. Based on 10 performance criteria including 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 and ranking of the above different ammonia nitrogen recovery methods showed that GPM is currently the best solution for ammonia nitrogen recovery.

[0004] However, there are the following problems in the traditional GPM process:

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

[0006] (2) The most widely studied and applied submerged GPM is a hollow fiber membrane with a diameter of less than 1 mm. However, due to the small diameter of the membrane, the water inlet pressure should not be too large, and it is easy to cause problems such as blockage 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 operation and subsequent treatment costs, and the pH adjustment is difficult to control. Once the pH is adjusted too high, it is easy to cause NH3 overflow.

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

[0009] The object of the present invention is to provide an ammonia nitrogen recovery system and method, which can recover ammonia nitrogen in sewage with high efficiency and low energy consumption based on an aerated in-situ submerged expansion membrane tube assembly, thus overcoming the shortcomings of the prior art.

[0010] According to a first aspect of the present invention, an ammonia nitrogen recovery system is provided, comprising: an acid absorption unit, a reaction unit and an aeration unit; the reaction unit comprises an expansion membrane tube assembly; a circulation pipeline for conveying acid absorption liquid is formed between the acid absorption unit and the expansion membrane tube assembly; and the aeration unit is used for aerating the expansion membrane tube assembly.

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

[0012] In the above-mentioned ammonia nitrogen-containing wastewater, due to HCO3 - The content is high, and when aerated, CO2 and OH are released. -, the pH value of the sewage increases, thereby increasing the concentration of free NH3 in the sewage, which is absorbed by the acid absorption liquid after entering the expansion membrane tube assembly. Compared with the method of adjusting the pH with alkaline drugs, the operation and subsequent treatment costs are greatly reduced; the aeration method is more convenient to control the pH value and avoid NH3 overflow; and the aeration method accelerates the molecular movement to increase the NH3 transmembrane rate and higher the recovery efficiency; in addition, the aeration method can reduce concentration polarization and thus reduce membrane pollution.

[0013] Preferably, the acid absorption unit comprises: an acid absorption liquid storage tank and a water pump; a circulation pipeline for conveying the acid absorption liquid is formed between the acid absorption liquid storage tank, the water pump and the expansion membrane tube assembly.

[0014] Preferably, the delivery rate of the acid absorption liquid is 20-100 mL / min / cm 2 (per cm 2 The flow rate of the acid absorption liquid per 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, so as to adjust the temperature of the reaction system in a timely manner.

[0016] Preferably, a pH controller is provided in the acid absorption liquid storage tank for monitoring whether the acid absorption liquid has leakage and the need to replenish the acid absorption liquid.

[0017] Preferably, the aeration unit comprises: an aerator and a releaser; the aerator is connected to the releaser, and the releaser is located below the expansion membrane tube assembly, and releases gas into the sewage after aeration by the aerator.

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

[0019] Preferably, a timer switch is connected to the air inlet pipe of the aerator, and the aeration time is controlled by the timer switch, preferably at intervals of 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.

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

[0021] Specifically, the preparation process of the expansion membrane tube assembly is basically similar to that of the traditional shell and tube membrane contactor, and the membrane is bonded and fixed to the water collection end using epoxy resin and curing agent. The difference is that the expansion membrane tube assembly of the present invention only retains the fixed water collection ends at both ends, and removes the middle outer shell, so that the membrane tube can be exposed to the outside and directly immersed in the ammonia nitrogen-containing wastewater.

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

[0023] A second aspect of the present invention provides an ammonia nitrogen recovery method, using the above-mentioned ammonia nitrogen recovery system, comprising the following steps:

[0024] S1. Immerse the expansion membrane tube assembly of the reaction unit in sewage, which does not require the complex membrane assembly setting in the shell and tube system. The structure is simple and easy to clean and replace.

[0025] Specifically, the expansion membrane tube assembly of the reaction unit is immersed below the sewage liquid surface, and the releaser is placed below the expansion membrane tube assembly.

[0026] S2. Aerate the sewage through an aeration unit to increase the concentration of free NH3 in the sewage.

[0027] Specifically, aeration is performed through an aerator, a flow meter adjusts the aeration rate, a timer switch controls the aeration time, and the gas enters the sewage through a releaser, thereby increasing the concentration of free NH3 in the sewage.

[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, circulating the acid absorption liquid between the expansion membrane tube assembly of the acid absorption unit and the reaction unit, and the free NH3 in the sewage enters the expansion membrane tube assembly and is absorbed by the acid absorption liquid.

[0031] Specifically, the acid absorption liquid in the acid absorption liquid storage tank enters the expansion membrane tube assembly through the pipeline under the action of the water pump, and the free NH3 in the sewage enters the expansion membrane tube assembly, is absorbed by the acid absorption liquid, and then returns to the acid absorption liquid storage tank through the pipeline, and the circulation is repeated.

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

[0033] Preferably, the delivery rate of the acid absorption liquid 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 sewage, thereby increasing the concentration of free NH3 in the sewage, which is absorbed by the acid absorption liquid after entering the expansion membrane tube assembly. Compared with the method of adjusting the pH by alkaline chemicals, the operation and subsequent treatment costs are greatly reduced;

[0036] (2) The present invention adopts aeration to more easily control the pH value, avoid NH3 overflow, and adopt aeration to accelerate molecular movement to increase the NH3 transmembrane rate, resulting in higher recovery efficiency;

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

[0038] (4) The present invention directly immerses the expansion membrane tube assembly in sewage, which does not require the complex membrane assembly arrangement in the shell and tube system, and has a simple structure and is easy to clean and replace;

[0039] (5) The expansion membrane tube assembly used in the present invention can make the diameter of the membrane range from a few millimeters to tens of millimeters. The large-diameter membrane tube has 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0042] Explanation of the reference numerals: 1. Acid absorption liquid storage tank; 2. pH controller; 3. Water pump; 4. Expansion membrane tube assembly; 5. Releaser; 6. Aerator; 7. Flow meter; 8. Timing switch. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0045] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Example 1

[0047] like Figure 1 As shown, 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 sewage; 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 sewage is biogas slurry.

[0049] In this embodiment, the acid absorption unit comprises: 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 pipelines to form a circulation pipeline for conveying the acid absorption liquid.

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

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

[0052] In this embodiment, the acid absorption liquid storage tank 1 stores the acid absorption liquid, and is provided with a pH controller 2 to monitor whether the acid absorption liquid has leakage and the need to replenish the acid absorption liquid.

[0053] In this embodiment, the acid absorption liquid is sulfuric acid with a concentration of 0.05M and a delivery rate of 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, and the releaser 5 is located in the sewage and below the expansion membrane tube assembly 4, and releases gas into the sewage after aeration by the aerator 6.

[0055] In this embodiment, a flow meter 7 is provided on the pipeline between the aerator 6 and the releaser 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 timer switch 8 is used to control the aeration time to be 2 hours of aeration / 2 hours of stop.

[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, including the following steps:

[0059] S1, immerse the expansion membrane tube assembly 4 of the reaction unit below the sewage liquid surface, and place the releaser 5 below the expansion membrane tube assembly 4;

[0060] S2, aeration is performed through the aerator 6, the flow meter 7 adjusts the aeration rate, the timer switch 8 controls the aeration time, and the gas enters the sewage through the releaser 5, so that the concentration of free NH3 in the sewage increases;

[0061] S3. The acid absorption liquid in the acid absorption liquid storage tank 1 enters the expansion membrane tube assembly 4 through the pipeline under the action of the water pump 3. The free NH3 in the sewage enters the expansion membrane tube assembly 4, is absorbed by the acid absorption liquid, and then returns to the acid absorption liquid storage tank 1 through the pipeline, and the circulation is repeated.

[0062] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 99%.

[0063] Example 2

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

[0065] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 96%.

[0066] Example 3

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

[0068] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 99%.

[0069] Example 4

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

[0071] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 97%.

[0072] Example 5

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

[0074] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 94%.

[0075] Example 6

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

[0077] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 91%.

[0078] Example 7

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

[0080] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 99%.

[0081] Example 8

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

[0083] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 97%.

[0084] Example 9

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

[0086] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 95%.

[0087] Example 10

[0088] This embodiment is basically the same as the embodiment 1, except that: in this embodiment, the aeration time is controlled by the timer switch 8 to aerate for 1 hour and stop for 1 hour.

[0089] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 96%, and the ammonia nitrogen recovery efficiency reached more than 94%.

[0090] Embodiment 11

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

[0092] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding 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, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 95%, and the ammonia nitrogen recovery efficiency reached more than 92%.

[0096] Embodiment 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, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 99%, and the ammonia nitrogen recovery efficiency reached more than 93%.

[0099] Embodiment 14

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

[0101] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 99%, and the ammonia nitrogen recovery efficiency reached more than 94%.

[0102] Embodiment 15

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

[0104] In this embodiment, the sewage was placed in a plexiglass reactor with an effective volume of 1 L 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 liquid in this embodiment is 0.01M.

[0107] In this embodiment, the sewage was placed in a 1L organic glass reactor for testing. After the reaction was completed, without adding alkalinity, the ammonia nitrogen removal efficiency reached more than 89%, and the ammonia nitrogen recovery efficiency reached more than 88%.

[0108] Embodiment 17

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

[0110] In this embodiment, the sewage was placed in a plexiglass reactor with an effective volume of 1 L 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, the present invention adopts aeration to increase the pH value of sewage, thereby increasing the concentration of free NH3 in sewage, which is absorbed by the acid absorption liquid after entering the expansion membrane tube assembly. Compared with the method of adjusting the pH by alkaline drugs, the operation and subsequent treatment costs are greatly reduced; the aeration method is more convenient to control the pH value, avoiding NH3 overflow, and the aeration method is used to accelerate molecular movement to increase the NH3 transmembrane rate, and the recovery efficiency is higher; the aeration method can reduce concentration polarization, thereby reducing membrane pollution and extending the service life; the present invention directly immerses the expansion membrane tube assembly in sewage, and does not require the complex membrane assembly setting in the shell and tube system. The structure is simple and easy to clean and replace; the expansion membrane tube assembly used in the present invention can make the membrane diameter a few millimeters to tens of millimeters. The large-diameter membrane tube has stronger tensile strength and temperature resistance range than traditional fiber membrane filaments, avoiding problems such as blockage and breakage, extending the 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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. An ammonia nitrogen recovery system, characterized in that: include: An acid absorption unit, a reaction unit and an aeration unit; the reaction unit has an expansion membrane tube assembly; a circulation pipeline for conveying acid absorption liquid is formed between the acid absorption unit and the expansion membrane tube assembly; the aeration unit is used for aerating the expansion membrane tube assembly.

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

3. The ammonia nitrogen recovery system according to claim 2, characterized in that: A pH controller is arranged in the acid absorption liquid storage tank.

4. The ammonia nitrogen recovery system according to claim 1, characterized in that: The aeration unit comprises: an aerator and a releaser; the aerator is connected to the releaser, and the releaser is located below the expansion membrane tube assembly, and releases gas into the sewage after aeration by the aerator.

5. The ammonia nitrogen recovery system according to claim 4, characterized in that: A flow meter is arranged on the pipeline between the aerator and the releaser.

6. The ammonia nitrogen recovery system according to claim 4, characterized in that: A timing switch is connected to the air inlet pipeline of the aerator.

7. The ammonia nitrogen recovery system according to claim 4, characterized in that: The aeration rate of the aerator is 50-400 mL / min / L.

8. The ammonia nitrogen recovery system according to claim 1, characterized in that: The material of the expansion membrane tube assembly includes any one of expanded polytetrafluoroethylene, polypropylene and polyvinylidene fluoride.

9. The ammonia nitrogen recovery system according to claim 1, characterized in that: The acid absorbing liquid includes any one of sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid.

10. A method for recovering ammonia nitrogen, characterized in that: The ammonia nitrogen recovery system according to any one of claims 1 to 9 comprises the following steps: S1. Immerse the expansion membrane tube assembly of the reaction unit in sewage; S2, aerating the sewage through an aeration unit to increase the concentration of free NH3 in the sewage; S3. The acid absorption liquid is circulated and transported between the expansion membrane tube assembly of the acid absorption unit and the reaction unit, and the free NH3 in the sewage enters the expansion membrane tube assembly and is absorbed by the acid absorption liquid.

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