Preparation method of tubular gaseous membrane for wastewater treatment and denitrification process

Abstract

The invention discloses a preparation method of a tubular gaseous membrane for wastewater treatment and a denitrification process. The preparation method of the tubular gaseous membrane comprises the following steps: cutting a flat plate type denitrification membrane into strip ropes, and then sequentially winding, overlapping, bonding, tubulating and cutting the strip-rope-shaped flat plate type denitrification membrane to form the tubular gaseous membrane. The preparation method is based on an original flat plate type denitrification membrane and an optimized rolling processing technology, compared with a traditional gaseous membrane, the prepared tubular gaseous membrane has the advantages that the ammonia mass transfer efficiency is higher, the tubular gaseous membrane adopts a closed column type membrane structure, and the ammonia leakage rate can be obviously reduced, so that the wastewater denitrification efficiency is greatly improved. The tubular gaseous membrane preparation method and the denitrification process provided by the invention are wide in application range and high in denitrification efficiency, ammonia nitrogen resources can be recovered while ammonia nitrogen wastewater is treated, and the tubular gaseous membrane preparation method and the denitrification process have relatively good economic benefits and environmental benefits.

Description

Technical Field

[0001] The invention relates to a method for preparing a tubular gaseous membrane for wastewater treatment and a denitrification process, belonging to the technical field of wastewater denitrification treatment. Background Art

[0002] There are many application cases of physical denitrification technologies such as ammonia stripping (stripping), struvite and gas membrane for the recovery of ammonia nitrogen resources from wastewater. On the one hand, NH3-N can be separated and extracted from wastewater and converted into usable ammonium salt resources. On the other hand, the NH3-N content in wastewater can be reduced and the C / N ratio can be adjusted, which is more conducive to subsequent biological treatment. The ammonia stripping (stripping) method has a better effect on the removal of NH3-N from wastewater, but the gas-liquid ratio and energy consumption are relatively high, and the scaling problem on the inner wall of the ammonia stripping tower or stripping tower is more prominent; the advantages of the struvite method are that the reaction process is simple and rapid, the ammonia nitrogen removal effect is better, and the economic value of the struvite by-product is higher, but for wastewater lacking phosphorus and magnesium elements, a large amount of magnesium salts and phosphates need to be added, so the cost is relatively high.

[0003] The gas-permeable membrane (GPM) process uses a microporous hydrophobic membrane to separate the ammonia-nitrogen-containing feed liquid from the acidic absorption liquid and place them on both sides of the membrane, thereby increasing the pH of the feed liquid to allow ionic NH4 + It is converted into free gaseous NH3, and under the action of mass transfer driving force (mainly the NH3 partial pressure difference on both sides of the membrane), NH3 passes through the microporous membrane and is absorbed by the absorption liquid, and acid-base neutralization reaction occurs to form ammonium salt; compared with the ammonia stripping (stripping) method, the gaseous membrane method does not require a large amount of air or water vapor to strip out NH3, nor does it require the use of large-volume stripping towers and absorption tower equipment, and the denitrification cost is lower.

[0004] According to the form or arrangement of the membrane, the commonly used types of denitrification membrane assemblies are mainly: tubular membrane assemblies, hollow fiber membrane assemblies and flat membrane assemblies. Single or multiple assemblies can be assembled into membrane separation devices for use in factories and laboratories. The applicant's previously applied and authorized patent "A flat denitrification membrane for wastewater treatment and its preparation method" (ZL202010862209.4) has developed a flat denitrification membrane that solves the technical problem that the denitrification membrane assembly is prone to fouling. However, the existing denitrification membranes and membrane assemblies still have problems with low denitrification efficiency and ammonia leakage. Summary of the invention

[0005] The purpose of the present invention is to improve the denitrification efficiency of traditional denitrification membranes and their components and solve technical problems such as ammonia leakage. The present invention provides a method for preparing a tubular gas membrane for wastewater treatment and a denitrification process. Compared with traditional gas membranes, the tubular gas membrane prepared by the preparation method of the present invention has a higher ammonia mass transfer efficiency, and the tubular gas membrane adopts a closed columnar membrane structure, and the ammonia leakage rate can be significantly reduced, so the wastewater denitrification efficiency is greatly improved.

[0006] In order to achieve the purpose of solving the above technical problems, the present invention adopts the following technical solutions:

[0007] In a first aspect of the present invention, a method for preparing a tubular gas membrane for wastewater treatment is provided, comprising: cutting a flat-plate denitrification membrane into strips, and then sequentially winding, laminating, bonding, pipe-making and cutting the strip-shaped flat-plate denitrification membrane to form a tubular tubular gas membrane;

[0008] The flat denitrification membrane comprises a non-woven fabric substrate layer and a gas permeation layer bonded together; the non-woven fabric substrate comprises 60-90wt% polypropylene fiber, 5-30wt% cellulose fiber and 5-15wt% carbon fiber; the gas permeation layer is an expanded polytetrafluoroethylene film.

[0009] Preferably, the quantitative range of the flat denitrification membrane is 50-100 g / m 2 , thickness is 100-250μm, air permeability is 0.05-1.5m / s, average pore size is 0.05-4.5μm, and contact angle is 110-140°.

[0010] Preferably, the width of the strip-shaped flat denitrification membrane after slitting is 10-20 mm.

[0011] Preferably, the winding diameter of the strip-shaped flat denitrification membrane is 5-10 mm, and during the winding process, the opposite sides of the denitrification membrane are overlapped, and the width of the overlapped area is set to 0.5-2 mm.

[0012] Preferably, the bonding is carried out using an ultrasonic assisted thermal curing bonding process, which specifically includes: uniformly coating the chemical adhesive on the overlapping area of ​​the opposite sides of the film during the winding process, and then performing ultrasonic assisted thermal curing treatment; the chemical adhesive is an aqueous dispersion of acrylonitrile multipolymer; the frequency of the ultrasound is 15-40kHz, and the temperature of the heating curing is 150-250°C.

[0013] Preferably, the pipe making comprises: cooling the tubular film formed by bonding, the cooling temperature is 5-20° C.; the inner diameter of the tubular film is 5-10 mm.

[0014] The second aspect of the present invention provides a tubular gas membrane prepared by the preparation method described in the first aspect of the present invention.

[0015] The third aspect of the present invention provides the use of the tubular gas membrane described in the second aspect of the present invention in the preparation of a tubular gas membrane module and in wastewater denitrification treatment.

[0016] A fourth aspect of the present invention provides a tubular gas membrane module, which comprises the tubular gas membrane described in the second aspect of the present invention.

[0017] Preferably, the preparation method of the tubular gas membrane assembly comprises: cutting the tubular gas membrane into suitable length dimensions and required filling quantity, then sequentially filling them into packaging tubes, and performing glue filling and curing treatment to prepare the tubular gas membrane assembly.

[0018] The fifth aspect of the present invention provides the use of the tubular gas membrane module described in the fourth aspect of the present invention in wastewater denitrification treatment.

[0019] The sixth aspect of the present invention provides a method for treating wastewater by denitrification using the tubular gas membrane assembly according to the fourth aspect of the present invention, comprising the following steps:

[0020] Step 1): adjusting the pH of the ammonia nitrogen wastewater to alkaline;

[0021] Step 2): After adjusting the temperature of the ammonia nitrogen wastewater, pump it into the tube side of the tubular gas membrane module and adjust the membrane surface flow rate;

[0022] Step 3): pumping the acid absorption liquid from the acid liquid tank into the shell side of the tubular gas membrane module, and then returning to the acid liquid tank to maintain a circulation state;

[0023] Step 4): Under the action of ammonia mass transfer inside the tubular gas membrane module, the ammonia nitrogen in the wastewater enters the acid absorption liquid in the form of NH3 molecules, and the discharge begins after the ammonia nitrogen in the wastewater is reduced to the discharge standard;

[0024] Step 5): the concentration of ammonium salt in the acid absorption solution gradually increases with the extension of the circulation operation time until the ammonium salt solution in the acid solution tank reaches a saturated state;

[0025] Step 6): Evaporating and crystallizing the saturated ammonium salt solution to obtain solid ammonium salt, thereby realizing ammonia nitrogen resource recovery.

[0026] Preferably, the concentration of the ammonia nitrogen wastewater in step 1) is 10-5000 mg / L, and the pH value of the ammonia nitrogen wastewater is adjusted to 10-12 by adding a combination of one or more of sodium hydroxide, calcium hydroxide and calcium oxide.

[0027] Preferably, in step 2), the temperature of the ammonia nitrogen wastewater is adjusted to 5-40° C., and the membrane surface flow rate is set to 1-100 m / min.

[0028] Preferably, the concentration of the acid absorption liquid in step 3) is 1-20 wt %, and the acid absorption liquid is a combination of one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The tubular gas membrane of the present invention has a double-layer structure of a porous support layer and a microporous hydrophobic layer, has good chemical resistance, and adopts an ultrasonic-assisted thermal curing bonding process. The overlapping area has high strength, good corrosion resistance and is not easy to fall off, which greatly improves the sealing performance and service life, and has the effect of long-term stable operation.

[0031] (2) The tubular gas membrane module of the present invention has a wide flow channel that is not easily clogged, and the wastewater pretreatment is simple, allowing wastewater with a high suspended matter content to enter the membrane module. The closed column membrane structure is used to avoid secondary pollution.

[0032] (3) The wastewater denitrification process of the present invention adopts cross-flow filtration. The higher cross-flow velocity can reduce the speed at which pollutants such as organic matter adhere to the membrane surface, reduce membrane pollution, and maintain a higher denitrification efficiency.

[0033] (4) The tubular gas membrane preparation method and denitrification process provided by the present invention have a wide range of applications and high denitrification efficiency. They can recover ammonia nitrogen resources while treating ammonia nitrogen wastewater, and have good economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the preparation process of the tubular gas membrane and its components of the present invention.

[0035] Figure 2 This is a physical picture of the tubular gas membrane assembly prepared in the present invention, wherein A is a top view and B is a side view.

[0036] Figure 3 This is a process flow chart of using the tubular gas membrane prepared in the present invention for denitrification treatment. DETAILED DESCRIPTION

[0037] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0038] The present invention provides a method for preparing a tubular gas membrane and a membrane assembly for wastewater treatment. The preparation process is as follows: Figure 1 As shown, the following steps are included:

[0039] Step 1: Cut the flat denitrification membrane into strips. The quantitative range of the flat denitrification membrane is 50-100g / m 2 , the thickness is set to 100-250μm, the air permeability is set to 0.05-1.5m / s, the average pore size is set to 0.05-4.5μm, the contact angle is set to 110-140°, and the width of the strip-shaped flat denitrification membrane is 10-20mm.

[0040] Step 2: Wind the above-mentioned strip-shaped flat denitrification membrane with a winding diameter of 5-10 mm. During the winding process, the width of the overlapping area of ​​the upper and lower layers of the denitrification membrane is controlled in the range of 0.5-2 mm.

[0041] Step 3: Use ultrasound-assisted thermal curing bonding process to evenly apply the chemical adhesive on the overlapping area of ​​the opposite sides of the film during the winding process, and then perform ultrasonic-assisted thermal curing treatment; the chemical adhesive is an aqueous dispersion of acrylonitrile multi-polymer; the frequency of the ultrasound is 15-40kHz, and the temperature of the heating curing is 150-250℃.

[0042] Step 4: Rapidly cool the tubular gas membrane formed by bonding during the tube making process to reduce the temperature of the membrane tube to room temperature, and the cooling temperature is controlled at 5-20° C. The inner diameter of the tubular gas membrane is in the range of 5-10 mm.

[0043] Step 5: The tubular gaseous membrane is cut and filled into a packaging tube, and then processed by glue filling and curing to form a tubular gaseous membrane assembly. Figure 1 shown.

[0044] In the preparation method of the present invention, after many attempts, it was found that the use of acrylonitrile multipolymer as an adhesive combined with an ultrasonic-assisted thermal curing bonding process can significantly improve the strength of the membrane stacking area, is not easy to fall off, and can operate stably for a long time in acid and alkali media, has good acid and alkali corrosion resistance and antioxidant properties, thereby significantly improving the service life of the membrane and its membrane components.

[0045] The present invention also provides a method for treating wastewater denitrification using the above tubular gas membrane assembly, the process flow is as follows: Figure 2 As shown, it includes the following steps:

[0046] Step 1: Adjust the pH of the ammonia nitrogen wastewater to 10-12 and the temperature to 5-40°C, and pump it into the tube side of the tubular gas membrane module, with a membrane surface flow rate of 1-100m / min; pump the acid absorption liquid into the shell side of the gas membrane module, with the acid absorption liquid concentration of 1-20wt%, and then return it to the acid liquid tank to maintain the circulation state;

[0047] Step 2: Under the action of ammonia mass transfer inside the tubular gas membrane, the ammonia nitrogen in the wastewater enters the acid absorption liquid in the form of NH3 molecules, and the discharge begins after the ammonia nitrogen in the wastewater gradually decreases to the discharge standard;

[0048] Step 3: The concentration of ammonium salt in the acid absorption liquid gradually increases with the extension of the circulation operation time until the ammonium salt solution in the acid tank reaches a saturated state; the saturated ammonium salt solution is evaporated and crystallized to obtain solid ammonium salt, thereby realizing the recovery of ammonia nitrogen resources.

[0049] In Examples 1-5, the aqueous dispersion of the chemical adhesive acrylonitrile multipolymer is a LA133 brand product produced by Chengdu Yindile Power Technology Co., Ltd. The flat-plate denitrification membrane comes from the invention patent "A flat-plate denitrification membrane for wastewater treatment and its preparation method" (ZL202010862209.4) previously applied for and authorized by the applicant, and this application is incorporated herein by reference in its entirety. The flat-plate denitrification membrane comprises a non-woven fabric substrate layer and a gas permeation layer; the non-woven fabric substrate layer is bonded to the gas permeation layer as a whole; the non-woven fabric substrate comprises polypropylene fibers, cellulose fibers and carbon fibers; wherein the polypropylene fibers account for 60-90wt%, the cellulose fibers account for 5-30wt%, and the carbon fibers account for 5-15wt%, and the gas permeation layer is an expanded polytetrafluoroethylene film; the polypropylene fibers comprise one or both of single-component polypropylene fibers and two-component polyethylene / polypropylene fibers; the melting point of the single-component polypropylene fibers is 1 50-190℃; the bicomponent polyethylene / polypropylene fiber is a core-skin fiber, the melting point of the skin layer is 90-150℃, and the melting point of the fiber body is 150-190℃; the beating degree of the cellulose fiber is 30-60°SR; the cellulose fiber is bamboo pulp fiber and wood pulp fiber; the carbon fiber has a temperature resistance of more than 300℃; the air permeability of the expanded polytetrafluoroethylene film is 0.1-5m / s, the average pore size is 0.1-5μm, the porosity is 50-80%, and the contact angle is 110-140°; the preparation method comprises the following steps:

[0050] Step 1: using a wet papermaking process to paper a mixed fiber slurry consisting of polypropylene fiber, cellulose fiber and carbon fiber through a papermaking machine to form the non-woven fabric substrate; in the papermaking process parameters of the non-woven fabric substrate, the paper machine sizing concentration is set to 0.01-0.5wt%, the non-woven fabric substrate drying temperature is 90-120°C, and the soft calendering temperature is set to 100-130°C;

[0051] Step 2: The non-woven fabric substrate and the expanded polytetrafluoroethylene film are pre-laminated together;

[0052] Step 3: Place the fiber in a hot press for high-temperature hot pressing treatment. The hot pressing temperature is related to the melting point and hot pressing pressure of the selected polypropylene fiber. During the high-temperature hot pressing treatment, the hot pressing and laminating temperature of the denitrification film is 140-170°C, and the pressure range is set to 0.5-2.5MPa. The temperature required for the hot pressing and laminating process of the flat-type denitrification film and the temperature required for the drying and soft calendering process of the non-woven fabric substrate have a certain gradient relationship. The drying temperature of the non-woven fabric substrate is 90-120°C < the soft calendering temperature is 100-130°C < the hot pressing and laminating temperature of the denitrification film is 140-170°C.

[0053] Step 4: After hot pressing and lamination, the film is cooled to form a flat denitrification membrane; the weight of the formed flat denitrification membrane is 50-100g / m 2 , thickness is 100-250μm, air permeability is 0.05-1.5m / s, average pore size is 0.05-4.5μm, and contact angle is 110-140°.

[0054] Example 1

[0055] A tubular gas membrane and its components, the preparation process is as follows: a quantitative 50g / m 2 , thickness of 100μm, air permeability of 0.05m / s, average pore size of 0.05μm, contact angle of 110°, flat denitrification membrane cut into 10mm rope strips, winding them, winding diameter of 5mm, two opposite sides are double-layered, upper and lower layer overlap width of 0.5mm, chemical adhesive acrylonitrile multi-polymer water dispersion is evenly coated on the overlapped area, and then ultrasonic ultrasonic assisted heating curing treatment is carried out, the ultrasonic frequency is 15kHz, the curing temperature is 150℃, and then cooled at 20℃ to obtain a gaseous membrane tube with an inner diameter of 5mm. The membrane tube is cut and filled into the pipe, and after treatment such as glue filling and curing, it is formed. Tubular gas membrane components.

[0056] The process of using the above-mentioned tubular gas membrane assembly to denitrify wastewater is as follows: denitrify landfill leachate with an ammonia nitrogen concentration of 10 mg / L, add sodium hydroxide to adjust the pH of the inlet water to 10, adjust the temperature to 5°C, pump the above-mentioned landfill leachate into the tube side of the tubular gas membrane assembly at a membrane surface flow rate of 1 m / min, and pump 1wt% sulfuric acid solution into the shell side of the tubular gas membrane assembly, and then return to the acid tank to maintain a circulation state; the ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the sulfuric acid solution, and the ammonium sulfate concentration in the acid tank gradually increases; the final wastewater denitrification efficiency is 82.9%, and the ammonium sulfate in the acid tank is evaporated and crystallized to obtain solid ammonium sulfate, whose N content is 20.5wt%.

[0057] Example 2

[0058] A tubular gas membrane and its components, the preparation process is as follows: a quantitative 100g / m 2 , thickness is 250μm, air permeability is 1.5m / s, average pore size is 4.5μm, contact angle is 140°, flat denitrification membrane is cut into 20mm strips, and wound, winding diameter is 10mm, two opposite sides are double-layered, upper and lower layer overlap width is 2mm, chemical adhesive acrylonitrile multi-polymer water dispersion is evenly coated on the overlapped area, and then ultrasonic ultrasonic assisted heating curing treatment is performed, ultrasonic frequency is 20kHz, curing temperature is 250℃, and then cooled at 20℃ to obtain a gaseous membrane tube with an inner diameter of 10mm. The membrane tube is cut and filled into the pipe, and after glue filling and curing, it is formed. Tubular gas membrane components.

[0059] The process of using the above-mentioned tubular gas membrane assembly to denitrify wastewater is as follows: denitrify restaurant biogas slurry with an ammonia nitrogen concentration of 5000 mg / L, add calcium hydroxide to adjust the pH of the inlet water to 12, adjust the temperature to 40°C, pump the above-mentioned restaurant biogas slurry into the tube side of the tubular gas membrane assembly at a membrane surface flow rate of 100 m / min, and pump 20wt% nitric acid solution into the shell side of the tubular gas membrane assembly, and then return to the acid tank to maintain a circulation state; the ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the nitric acid solution, and the ammonium nitrate concentration in the acid tank gradually increases; the final wastewater denitrification efficiency is 88.3%, and the ammonium nitrate in the acid tank is evaporated and crystallized to obtain solid ammonium nitrate, and its N content is 32.4wt%.

[0060] Example 3

[0061] A tubular gas membrane and its components, the preparation process is as follows: a quantitative 80g / m 2 , thickness of 140μm, air permeability of 0.08m / s, average pore size of 0.3μm, contact angle of 120°, flat denitrification membrane cut into 12.5mm strips, winding them, winding diameter of 7mm, two opposite sides are double-layered, upper and lower layer overlap width of 0.8mm, chemical adhesive acrylonitrile multi-polymer water dispersion is evenly coated on the overlapped area, and then ultrasonic ultrasonic assisted heating curing treatment is carried out, the ultrasonic frequency is 25kHz, the curing temperature is 170℃, and then cooled at 10℃ to obtain a gaseous membrane tube with an inner diameter of 7mm. The membrane tube is cut and filled into the pipe, and after treatment such as glue filling and curing, it is formed. Tubular gas membrane components.

[0062] The process of using the above-mentioned tubular gas membrane assembly to denitrify wastewater is as follows: metallurgical wastewater with an ammonia nitrogen concentration of 1000 mg / L is denitrified, calcium oxide is added to adjust the pH of the inlet water to 10.7, the temperature is adjusted to 20°C, the above-mentioned metallurgical wastewater is pumped into the tube side of the tubular gas membrane assembly at a membrane surface flow rate of 30 m / min, and a 5wt% phosphoric acid solution is pumped into the shell side of the tubular gas membrane assembly, and then returned to the acid tank to maintain a circulation state; the ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the phosphoric acid solution, and the ammonium phosphate concentration in the acid tank gradually increases; the final wastewater denitrification efficiency is 87.1%, and the ammonium phosphate in the acid tank is evaporated and crystallized to obtain solid ammonium phosphate, whose N content is 25.8wt%.

[0063] Example 4

[0064] A tubular gas membrane and its components, the preparation process is as follows: a quantitative 85g / m 2 , thickness is 200μm, air permeability is 1.0m / s, average pore size is 2.5μm, contact angle is 125°, flat denitrification membrane is cut into 16.5mm strips, and wound, winding diameter is 8mm, two opposite sides are double-layered, upper and lower layer overlap width is 1.2mm, chemical adhesive acrylonitrile multi-polymer water dispersion is evenly coated on the overlapped area, and then ultrasonic ultrasonic assisted heating curing treatment is performed, ultrasonic frequency is 30kHz, curing temperature is 200℃, and then cooled at 15℃ to obtain a gaseous membrane tube with an inner diameter of 8mm. The membrane tube is cut and filled into the pipe, and after glue filling and curing, it is formed. Tubular gas membrane components.

[0065] The process of using the above-mentioned tubular gas membrane assembly for denitrification of wastewater is as follows: denitrification of photovoltaic wastewater with an ammonia nitrogen concentration of 2800 mg / L is carried out, sodium hydroxide is added to adjust the pH of the inlet water to 11, the temperature is adjusted to 30°C, the above-mentioned photovoltaic wastewater is pumped into the tube side of the tubular gas membrane assembly at a membrane surface flow rate of 70 m / min, and a 10wt% hydrochloric acid solution is pumped into the shell side of the tubular gas membrane assembly, and then returned to the acid tank to maintain a circulation state; the ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the hydrochloric acid solution, and the ammonium chloride concentration in the acid tank gradually increases; the final wastewater denitrification efficiency is 85.4%, and the ammonium chloride in the acid tank is evaporated and crystallized to obtain solid ammonium chloride, and its N content is 21.8wt%.

[0066] Example 5

[0067] A tubular gas membrane and its components, the preparation process is as follows: a quantitative 90g / m 2, thickness is 200μm, air permeability is 1.2m / s, average pore size is 3.2μm, contact angle is 128°, flat denitrification membrane is cut into 18mm strips, and wound, winding diameter is 8mm, two opposite sides are double-layered, upper and lower layer overlap width is 1.5mm, chemical adhesive acrylonitrile multi-polymer water dispersion is evenly coated on the overlapped area, and then ultrasonic ultrasonic assisted heating curing treatment is performed, ultrasonic frequency is 40kHz, curing temperature is 220℃, and then cooled at 15℃ to obtain a gaseous membrane tube with an inner diameter of 8mm. The membrane tube is cut and filled into the pipe, and after treatment such as glue filling and curing, it is formed. Tubular gas membrane components.

[0068] The process of using the above-mentioned tubular gas membrane assembly to denitrify wastewater is as follows: denitrify the landfill leachate with an ammonia nitrogen concentration of 3500 mg / L, add sodium hydroxide to adjust the pH of the inlet water to 11, adjust the temperature to 35°C, pump the above-mentioned landfill leachate into the tube side of the tubular gas membrane assembly at a membrane surface flow rate of 85m / min, and pump a 17.5wt% sulfuric acid solution into the shell side of the tubular gas membrane assembly, and then return to the acid tank to maintain a circulation state; the ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the sulfuric acid solution, and the ammonium sulfate concentration in the acid tank gradually increases; the final wastewater denitrification efficiency is 90.3%, and the ammonium sulfate in the acid tank is evaporated and crystallized to obtain solid ammonium sulfate, and its N content is 20.8wt%

[0069] The above description is only a preferred embodiment of the present invention and is not any formal or substantial limitation of the present invention. It should be pointed out that a person skilled in the art can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a tubular gas membrane for wastewater treatment, characterized in that: include: The flat-plate denitrification membrane is cut into strips, and then the strip-shaped flat-plate denitrification membrane is successively wound, stacked, bonded, pipe-formed and cut to form a tubular gas membrane; The flat denitrification membrane comprises a non-woven fabric substrate layer and a gas permeation layer bonded together; the non-woven fabric substrate comprises 60-90wt% polypropylene fiber, 5-30wt% cellulose fiber and 5-15wt% carbon fiber; the gas permeation layer is an expanded polytetrafluoroethylene film.

2. The preparation method according to claim 1, characterized in that The quantitative range of the flat denitrification membrane is 50-100g / m 2 , thickness is 100-250μm, air permeability is 0.05-1.5m / s, average pore size is 0.05-4.5μm, and contact angle is 110-140°.

3. The preparation method according to claim 1, characterized in that: The width of the strip-shaped flat denitrification membrane after cutting is 10-20 mm.

4. The preparation method according to claim 1, characterized in that: The winding diameter of the strip-shaped flat denitrification membrane is 5-10 mm. During the winding process, the opposite sides of the denitrification membrane are overlapped, and the width of the overlapped area is set to 0.5-2 mm.

5. The preparation method according to claim 1, characterized in that: The bonding adopts an ultrasonic assisted thermal curing bonding process, which specifically includes: uniformly coating the chemical adhesive on the overlapping area of ​​the opposite sides of the film during the winding process, and then performing ultrasonic assisted thermal curing treatment; the chemical adhesive is an aqueous dispersion of acrylonitrile multi-polymer; the frequency of the ultrasound is 15-40kHz, and the temperature of the heating curing is 150-250°C.

6. The preparation method according to claim 1, characterized in that: The pipe making comprises: cooling the tubular film formed by bonding, wherein the cooling temperature is 5-20° C.; and the inner diameter of the tubular film is 5-10 mm.

7. The tubular gas membrane prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the tubular gas membrane according to claim 7 in the preparation of tubular gas membrane modules and in wastewater denitrification treatment.

9. A tubular gas membrane module, characterized in that: Comprising the tubular gas membrane as claimed in claim 7.

10. The tubular gas membrane module according to claim 8, characterized in that: The preparation method of the tubular gas membrane assembly comprises: cutting the tubular gas membrane into a suitable length and a required filling quantity, then filling it into a packaging tube in sequence, and performing glue filling and curing treatment to prepare the tubular gas membrane assembly.

11. Use of the tubular gas membrane module according to claim 9 in wastewater denitrification treatment.

12. A method for treating wastewater denitrification using the tubular gas membrane module according to claim 9, characterized in that: The following steps are involved: Step 1): adjusting the pH of the ammonia nitrogen wastewater to alkaline; Step 2): After adjusting the temperature of the ammonia nitrogen wastewater, pump it into the tube side of the tubular gas membrane module and adjust the membrane surface flow rate; Step 3): pumping the acid absorption liquid from the acid liquid tank into the shell side of the tubular gas membrane module, and then returning to the acid liquid tank to maintain a circulation state; Step 4): Under the action of ammonia mass transfer inside the tubular gas membrane module, the ammonia nitrogen in the wastewater enters the acid absorption liquid in the form of NH3 molecules, and the discharge begins after the ammonia nitrogen in the wastewater is reduced to the discharge standard; Step 5): the concentration of ammonium salt in the acid absorption solution gradually increases with the extension of the circulation operation time until the ammonium salt solution in the acid solution tank reaches a saturated state; Step 6): Evaporating and crystallizing the saturated ammonium salt solution to obtain solid ammonium salt, thereby realizing ammonia nitrogen resource recovery.

13. The method according to claim 12, characterized in that The concentration of the ammonia nitrogen wastewater in step 1) is 10-5000 mg / L, and the pH value of the ammonia nitrogen wastewater is adjusted to 10-12 by adding one or more combinations of sodium hydroxide, calcium hydroxide and calcium oxide.

14. The method according to claim 12, characterized in that In the step 2), the temperature of the ammonia nitrogen wastewater is adjusted to 5-40° C., and the membrane surface flow rate is set to 1-100 m / min.

15. The method according to claim 12, characterized in that The concentration of the acid absorption liquid in step 3) is 1-20 wt %, and the acid absorption liquid is a combination of one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

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