Ammonia-nitrogen-containing wastewater treatment device adopting double-membrane method

Abstract

The utility model relates to a double-membrane ammonia-nitrogen-containing wastewater treatment device, and belongs to the technical field of water treatment. Comprising a wastewater container used for adjusting the pH value of desulfurization wastewater; the alkali liquor tank is used for adding alkali liquor into the wastewater container; the concentration device is connected to the wastewater container and is used for concentrating the wastewater; the degassing membrane assembly comprises a porous polymer membrane and is used for enabling ammonia gas in the wastewater to penetrate through a membrane layer and be absorbed by the acid absorption liquid on the other side; the degassing membrane assembly is also connected with an absorption liquid pipeline for feeding an acid absorption liquid; and the bipolar membrane electrodialysis device is connected to one side of the absorption liquid of the degassing membrane assembly and is used for performing bipolar membrane electrodialysis treatment on the absorption liquid which absorbs the ammonia gas.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of double-membrane ammonia-nitrogen-containing wastewater treatment device, belong to water treatment technical field. BACKGROUND

[0002] Desulfurization wastewater is generated in the desulfurization process of power plants, mainly because limestone-gypsum wet flue gas desulfurization technology is widely used in domestic and foreign thermal power plants. Although this technology has high desulfurization efficiency, it inevitably generates desulfurization wastewater in the process. Desulfurization wastewater is generally acidic (pH 4-6) and contains a large amount of suspended solids, ammonia-nitrogen and heavy metal pollutants, as well as Ca 2+ , Mg 2+ , F - , SO4 2- , Cl - , S 2- , etc. There are two main sources of ammonia-nitrogen in desulfurization wastewater: denitration system: during the denitration process, if too much ammonia gas is injected, not all of the ammonia gas can participate in the denitration reaction, and the escaped ammonia enters the desulfurization absorption tower with the flue gas and is washed, eventually entering the desulfurization wastewater, resulting in an increase in ammonia-nitrogen content. Process water use: the desulfurization system process water has gradually used wastewater with high ammonia-nitrogen content such as municipal reclaimed water, circulating water sewage, etc., which also increases the ammonia-nitrogen content in desulfurization wastewater. These wastewaters contain high concentrations of ammonia-nitrogen, and direct discharge will cause serious pollution to the environment, especially to the water ecosystem. Ammonia-nitrogen is one of the main causes of water eutrophication, it promotes the excessive growth of algae, consumes dissolved oxygen in water, causes aquatic organisms to die from lack of oxygen, and disrupts the ecological balance of water bodies.

[0003] Currently, the main methods for treating ammonia-nitrogen in desulfurization wastewater are biological and physicochemical methods: stripping or distillation process: this method has the problem of poor economic efficiency in removing ammonia-nitrogen. Adsorption method has problems such as large amount of adsorbent and frequent regeneration. Biological method needs to supplement a large amount of alkalinity and carbon source, and the high salt content of desulfurization wastewater inhibits the activity and reproduction of microorganisms, making operation and maintenance difficult, and the effluent easily exceeds the standard. The breakpoint chlorination method adds excessive chlorine or sodium hypochlorite to oxidize ammonia-nitrogen in wastewater into nitrogen gas. The treatment efficiency can reach 90%-100%, but the operation cost is high, and the by-products chloramine and chlorinated organic compounds will cause secondary pollution. SUMMARY

[0004] The utility model relates to a kind of degassing membrane and the process combination of bipolar membrane, the treatment process of ammonia-nitrogen-containing alkaline wastewater.The process first introduces ammonia-nitrogen-containing alkaline wastewater into degassing membrane system, and ammonia gas is separated from wastewater by the selective permeability of degassing membrane.Ammonia gas is collected and transferred into bipolar membrane system by sulfuric acid absorption after permeating membrane.In bipolar membrane system, ammonia gas reacts with water to generate ammonia water and hydrogen ion.Ammonia water can be recycled as product, while hydrogen ion participates in acid-base cycle to react with alkaline substances in wastewater to generate water and salt.Through this way, not only the effective removal of ammonia-nitrogen is realized, but also the recycling of acid-base is realized, greatly reducing the operating cost and environmental impact of wastewater treatment.In addition, the process also has the advantages of simple operation, small floor area, easy maintenance, etc., suitable for application in various scale wastewater treatment occasions.In summary, the ammonia-nitrogen-containing wastewater double-membrane treatment process provides an efficient, environmentally friendly and economic solution for wastewater treatment, with broad market application prospects.

[0005] Technical scheme is:

[0006] A kind of double-membrane ammonia-nitrogen-containing wastewater treatment device, comprising:

[0007] Wastewater container is used to adjust pH treatment to desulfurization wastewater;

[0008] Lye tank is used to add lye to wastewater container;

[0009] Concentration device is connected to wastewater container, for wastewater concentration;

[0010] Degassing membrane assembly, including porous polymer membrane, for ammonia gas in wastewater to permeate membrane layer and be absorbed by acid absorption liquid on the other side;Degassing membrane assembly is also connected with absorption liquid pipeline for supplying into acid absorption liquid;

[0011] Bipolar membrane electrodialysis device is connected to the absorption liquid side of degassing membrane assembly, for ammonia gas absorbed absorption liquid to carry out bipolar membrane electrodialysis treatment.

[0012] The pore size of the porous polymer membrane ranges from 20 to 500 nm.

[0013] The material of the porous polymer membrane is polytetrafluoroethylene, polydimethylsiloxane, polysulfone or polyolefin.

[0014] The concentration device is an evaporator.

[0015] The ammonia-removing wastewater side of degassing membrane assembly is connected with ammonia-removing liquid container.

[0016] Bipolar membrane electrodialysis device is also connected with acid liquid container and lye tank, respectively for receiving obtained acid and base.

[0017] The acid container is connected to the absorption liquid pipeline and is used to apply the obtained acid to the absorption liquid.

[0018] The beneficial effects of this utility model are:

[0019] Degassing membrane technology is a highly efficient separation method that relies on the selective permeability of the membrane to effectively separate ammonia gas from the liquid phase in ammonia nitrogen wastewater. Thanks to this membrane characteristic, ammonia gas permeates through the membrane and is separated, while water and other substances that cannot permeate are retained. The ammonia gas that permeates through the membrane can then be collected for further treatment. This method not only efficiently removes ammonia nitrogen but also achieves ammonia resource recovery, offering both environmental and economic benefits. To further improve treatment efficiency and reduce operating costs, a combination of degassing membrane technology and bipolar membrane technology has been proposed. This integrated process achieves acid and alkali recycling while treating wastewater, further reducing wastewater treatment costs and emissions.

[0020] The process of this invention has high efficiency, and the ammonia nitrogen removal rate can reach more than 95%.

[0021] The operating cost of this invention is relatively low. The degassing membrane process can effectively remove ammonia nitrogen from wastewater, and the bipolar membrane enables the reuse of sulfuric acid. The dual-membrane process can effectively reduce the amount of sulfuric acid added in the process and generate ammonium salts that can be reused in the production process. Attached Figure Description

[0022] Figure 1 : Flowchart of this process;

[0023] Figure 2 Schematic diagram of bipolar film process;

[0024] Figure 3 : A diagram of the device in this patent.

[0025] 1. Alkali tank; 2. Wastewater container; 3. Concentration device; 4. Degassing membrane assembly; 5. Absorbent liquid pipeline; 6. Bipolar membrane electrodialysis device; 7. Ammonia removal waste liquid container; 8. Acid container; 9. Alkali container. Detailed Implementation

[0026] The ammonia nitrogen wastewater treatment system is designed to treat desulfurization wastewater discharged during power plant production. This water sample has a complex composition, fluctuates significantly in quality, and exhibits high ammonia nitrogen concentration and hardness. The water quality parameters are as follows: pH: 6.2–9.3; COD: 6–257 mg / L; ammonia nitrogen: 1.2–129.5 mg / L; suspended solids: 17–285 mg / L; conductivity: 13582–34052 μS / cm; hardness: 140–345 mmol / L; chloride ions: 4140–15341 mg / L.

[0027] likeFigure 3 As shown, the processing device includes:

[0028] Wastewater container 2 is used to adjust the pH of desulfurization wastewater;

[0029] Alkali tank 1 is used to add alkali solution to wastewater container 2;

[0030] Concentration device 3 is connected to wastewater container 2 and is used to concentrate wastewater.

[0031] The degassing membrane assembly 4 includes a porous polymer membrane for allowing ammonia gas in the wastewater to permeate through the membrane and be absorbed by the acid absorbent on the other side; the degassing membrane assembly 4 is also connected to an absorbent pipeline 5 for supplying the acid absorbent.

[0032] The bipolar membrane electrodialysis device 6 is connected to the absorbent side of the degassing membrane assembly 4 and is used to perform bipolar membrane electrodialysis treatment on the absorbent that has absorbed ammonia.

[0033] The pore size range of the porous polymer membrane is 20-500 nm.

[0034] The porous polymer membrane is made of polytetrafluoroethylene, polydimethylsiloxane, polysulfone, or polyolefin materials.

[0035] The concentration device 3 is an evaporator.

[0036] The deammonia wastewater side of the degassing membrane module 4 is connected to the deammonia waste liquid container 7.

[0037] The bipolar membrane electrodialysis device 6 is also connected to an acid container 8 and an alkali container 9, which are used to receive the obtained acid and alkali, respectively.

[0038] In a preferred embodiment of an ammonia nitrogen wastewater treatment system, the system includes an alkali addition pH adjustment tank and a degassing membrane unit.

[0039] The pH adjustment tank for adding alkali is connected to the inlet of ammonia nitrogen wastewater.

[0040] The wastewater inlet of the degassing membrane unit is connected to the alkali addition pH adjustment tank to receive ammonia nitrogen wastewater; the absorbent inlets of the degassing membrane units are all connected to the acid absorbent pipeline to receive the acid absorbent. The degassing membrane unit uses hollow fiber membranes to remove ammonia gas from the ammonia nitrogen wastewater, and the removed ammonia gas is absorbed by the acid absorbent. The ammonium salt outlet of the degassing membrane unit is connected to the ammonium salt production pipeline to produce ammonium salt; the product water outlet of the degassing membrane unit is connected to the ammonia nitrogen removal water pipeline to produce ammonia nitrogen removal water.

[0041] The hollow fiber membrane in the degassing membrane unit is a PTFE membrane, which has the characteristics of corrosion resistance, acid and alkali resistance, strong hydrophobicity, antifouling and high strength. It has a good ammonia removal effect, can be connected in series in multiple stages, and the ammonia nitrogen in the effluent is controllable. It can be customized according to the ammonia nitrogen concentration of the effluent to meet the needs.

[0042] The ammonia nitrogen wastewater inlet and the alkali pH adjustment tank are connected sequentially from front to back by a collection tank and an activated carbon filter.

[0043] In this embodiment, the alkali added to the alkali pH adjustment tank is liquid alkali; the acid absorbent is sulfuric acid.

[0044] High-concentration ammonia nitrogen wastewater is collected in a closed alkali-addition pH adjustment tank. Liquid alkali is added to the wastewater to adjust the pH to 11.8. The wastewater is then pumped to the degassing membrane unit using a lift pump. Sulfuric acid enters the degassing membrane unit via the acid absorbent pipeline. During treatment, 98% sulfuric acid and ammonia nitrogen wastewater flow concurrently in the degassing membrane unit, with the wastewater flowing in the shell side and the sulfuric acid flowing in the tube side. The hollow fiber membrane in the degassing membrane unit removes ammonia from the wastewater at an operating temperature of 298K and an operating pressure of 5-10 bar. The ammonia then enters the sulfuric acid solution and is absorbed, producing ammonium sulfate. The deammonia-free water is discharged through the product outlet of the degassing membrane unit. During treatment, the ammonia nitrogen wastewater passes through the hollow fiber membrane of the membrane contact unit only once, while the acid absorbent is recycled. The ammonia nitrogen wastewater flow rate is 1-1.5 m / s. 3 / h, sulfuric acid flow rate 0.5-1L / min.

[0045] The principle of the above ammonia nitrogen removal process is as follows: ammonium ions and free ammonia (NH3) in water exist in an equilibrium state as shown in formula (1). The proportion of free ammonia in water increases with the increase of pH. When pH>11, more than 90% of the ammonia nitrogen in the water exists in the form of free ammonia. The ammonia gas in the ammonia nitrogen wastewater is degassed using the degassing membrane (hollow fiber membrane) of the degassing membrane group. The ammonia gas that permeates through the hollow fiber membrane reacts directly with the sulfuric acid circulating in the degassing membrane group to generate ammonium sulfate, as shown in formula (2).

[0046]

[0047] After treatment by this system, the ammonia nitrogen concentration in the deammonia nitrogen-removed water produced by the degassing membrane unit is less than 50 ppm. In this embodiment, under the action of a DC electric field, the bipolar membrane stack can dissociate water on both sides of the membrane to obtain H+ and OH- respectively; utilizing this characteristic, the bipolar membrane electrodialysis system, which combines the bipolar membrane with other anion and cation exchange membranes, can convert the salt in the ammonium sulfate solution into the corresponding acid and base without introducing new components, with a current density of 30 mA / cm². 2The ammonium sulfate solution produced during the degassing membrane process is sent to the bipolar membrane electrodialysis raw water tank, where it is processed by a bipolar membrane electrodialysis device to obtain three solutions. The solutions consist of approximately 6% sulfuric acid, 1.7% ammonia-containing sodium hydroxide, and approximately 1% sodium-containing ammonium sulfate solution remaining in the raw water tank. The 1% sodium sulfate solution needs to be concentrated to approximately 4% using an electrodialysis concentration system. The acid and alkali solutions produced by the bipolar membrane system are transferred to the recovery tank and raw water tank of the ammonia removal membrane system, respectively. The alkali solution is pumped from the raw water tank into a heat exchanger, where it exchanges heat with the cold water in the plate heat exchanger to cool down. It then passes sequentially through the fiber membrane and membrane core of the ammonia removal membrane assembly via the tube side and returns to the raw water tank. During its return flow, the fiber membrane exchanges its residual heat with the acid solution. The sulfuric acid absorbent in the absorption tank is pumped through the ammonia removal membrane assembly in a counter-current manner with the alkali solution via the tube side, and then circulates back to the absorption tank. This repeated circulation reduces the ammonia content in the alkali solution to below 0.1%, and the ammonium sulfate content in the recovery tank reaches above 6%.

Claims

1. A dual-membrane wastewater treatment device for ammonia nitrogen, characterized in that, include: Wastewater container (2) is used to adjust the pH of desulfurization wastewater; Alkali tank (1), used to add alkali solution to wastewater container (2); A concentration device (3) is connected to a wastewater container (2) and is used to concentrate wastewater; The degassing membrane assembly (4) includes a porous polymer membrane for allowing ammonia in the wastewater to permeate through the membrane and be absorbed by the acid absorbent on the other side; the degassing membrane assembly (4) is also connected to an absorbent pipeline (5) for supplying the acid absorbent. The bipolar membrane electrodialysis device (6) is connected to the absorbent side of the degassing membrane assembly (4) and is used to perform bipolar membrane electrodialysis treatment on the absorbent that has absorbed ammonia.

2. The dual-membrane ammonia nitrogen-containing wastewater treatment device according to claim 1, characterized in that, The pore size range of the porous polymer membrane is 20-500 nm.

3. The dual-membrane ammonia nitrogen-containing wastewater treatment device according to claim 1, characterized in that, The porous polymer membrane is made of polytetrafluoroethylene, polydimethylsiloxane, polysulfone, or polyolefin materials.

4. The dual-membrane ammonia nitrogen-containing wastewater treatment device according to claim 1, characterized in that, The concentration device (3) is an evaporator.

5. The dual-membrane ammonia nitrogen-containing wastewater treatment device according to claim 1, characterized in that, The deammonia wastewater side of the degassing membrane module (4) is connected to a deammonia waste liquid container (7).

6. The dual-membrane ammonia nitrogen-containing wastewater treatment device according to claim 1, characterized in that, Bipolar membrane electrodialysis device ( 6 ) It is also connected to an acid container (8) and an alkali container (9), which are used to receive the obtained acid and alkali respectively.

7. The dual-membrane ammonia nitrogen-containing wastewater treatment device according to claim 1, characterized in that, The acid container (8) is connected to the absorption liquid pipeline (5).

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