Membrane method concentrated desulfurization wastewater zero discharge system

Abstract

The utility model discloses a membrane method concentration desulfurization wastewater zero discharge system, and relates to the technical field of wastewater treatment. The device comprises a coagulating sedimentation system, an ultrafiltration system, brine concentration equipment, a full-automatic atomization system, a strong brine evaporator and an efficient purifier, the electrolysis flue gas purification exhaust pipe is connected with the strong brine evaporator, and the efficient purifier is connected with the electrolysis flue gas purification exhaust pipe. The waste heat of flue gas is used for providing heat for evaporation of atomized waste water, other heat sources do not need to be added, and energy consumption and cost are effectively reduced; the zero discharge of the wastewater is realized after the wastewater is treated by the device.

Description

Technical Field

[0001] The utility model relates to the technical field of wastewater treatment, and more specifically, it is a membrane-based concentrated desulfurization wastewater zero-discharge system. Background Art

[0002] During the production process of the electrolytic aluminum industry, a large amount of desulfurization wastewater is generated; with the increasingly strict environmental protection requirements and the growing preciousness of water resources, the effective treatment and zero-discharge of desulfurization wastewater in the electrolytic aluminum industry have become an urgent task.

[0003] The desulfurization wastewater in the electrolytic aluminum industry has complex components and great harmfulness, containing pollutants such as high-concentration suspended solids, heavy metal ions, chlorides, sulfates, and fluorides; traditional desulfurization wastewater treatment methods, such as chemical precipitation method, evaporation crystallization method, etc., have many limitations in treating such wastewater; the treatment effect of the chemical precipitation method is limited, and it is easy to generate a large amount of chemical sludge, increasing the subsequent treatment cost and difficulty; the evaporation crystallization method has too high energy consumption and high operating cost. And some physical filtration methods have poor removal effects on small molecule pollutants.

[0004] Due to the particularity of the desulfurization wastewater in the electrolytic aluminum industry, the treatment difficulty is extremely high; these pollutants not only have strict requirements on treatment equipment and processes, but if not treated properly, they will cause serious secondary pollution, posing a huge threat to the environment and the ecosystem; at the same time, in terms of resource recovery and utilization, traditional methods are difficult to effectively recover valuable substances in the wastewater, resulting in resource waste.

[0005] Therefore, in order to meet the development needs and environmental protection requirements of the electrolytic aluminum industry, it is necessary to develop a membrane-based concentrated desulfurization wastewater zero-discharge system that is efficient, economical and can achieve true zero-discharge. Summary of the Utility Model

[0006] At present, there are many technical problems in the treatment of desulfurization wastewater in the electrolytic aluminum industry and related fields; existing technologies often face the problem of too high energy consumption because additional heat sources are required during the wastewater concentration and evaporation crystallization processes, which greatly increases the treatment cost; at the same time, the coagulation and precipitation effect is not good, resulting in unsatisfactory removal rates of calcium hardness and silicon, and it is difficult to achieve effective recovery and utilization of resources; in addition, the effect of the ultrafiltration link is unstable, and it is unable to effectively remove fine particles, making it difficult to ensure the water quality entering the reverse osmosis and affecting the overall treatment effect; moreover, the membrane materials used have insufficient corrosion resistance and stability, making it difficult to adapt to complex and harsh water quality conditions, easily leading to problems such as low membrane separation efficiency and short service life; furthermore, the process parameters of membrane separation are not optimized enough to ensure the efficient and stable operation of the membrane separation process; in addition, the membrane has weak anti-pollution performance and large chemical irreversible resistance, and the membrane components need to be replaced frequently, increasing the operating cost.

[0007] These above-mentioned defects not only lead to unsatisfactory wastewater treatment effects, but also cause waste of resources and environmental pollution, and cannot achieve true zero discharge of wastewater.

[0008] The purpose of the present utility model is to overcome the deficiencies of the above-mentioned background technology, and provide a membrane method for concentrating desulfurized wastewater zero discharge system, to achieve efficient, energy-saving and environmental protection wastewater treatment, and to achieve the technical effects of resource recovery and zero discharge.

[0009] To achieve the above purpose, the technical solution of the present utility model is: a membrane method for concentrating desulfurized wastewater zero discharge system, characterized in that: it includes a coagulation sedimentation system, an ultrafiltration system connected to the coagulation sedimentation system, a brine concentration device connected to the ultrafiltration system, a full-automatic atomization system connected to the brine concentration device and compressed air, a concentrated brine evaporator connected to the full-automatic atomization system, and a high-efficiency purifier connected to the concentrated brine evaporator;

[0010] The electrolytic flue gas purification exhaust pipe is connected to the concentrated brine evaporator, and the high-efficiency purifier is connected to the electrolytic flue gas purification exhaust pipe.

[0011] In the above technical solution, a sand filtration system is provided between the coagulation sedimentation system and the ultrafiltration system.

[0012] In the above technical solution, the ultrafiltration system is connected to the brine concentration device through a first water storage tank.

[0013] In the above technical solution, the brine concentration device is connected to the full-automatic atomization system through a second water storage tank.

[0014] In the above technical solution, the brine concentration device is connected to the desulfurization process water tank.

[0015] In the above technical solution, the brine concentration device is connected to the desulfurization process water tank through a water pump.

[0016] In the above technical solution, the high-efficiency purifier is connected to the feed tank.

[0017] In the above technical solution, the high-efficiency purifier is connected to the electrolytic flue gas purification exhaust pipe through a booster fan.

[0018] In the above technical solution, the ultrafiltration system is a Dow column ultrafiltration membrane module; the brine concentration device is a RO reverse osmosis system; the full-automatic atomization system is a gas-liquid two-phase spray gun; the high-efficiency purifier is a bag filter.

[0019] Compared with the prior art, the present utility model has the following advantages:

[0020] 1) The concentrated liquid processed by the brine concentration equipment of the present utility model is atomized into fine droplets by using a fully automatic atomization system and cutting with compressed air in the concentrated brine evaporator. The atomized droplets quickly conduct heat transfer, mass transfer, and evaporation with the high-temperature flue gas. After complete evaporation, the crystalline salt formed and the water vapor are incorporated into the electrolytic flue gas purification exhaust pipe (the outlet flue gas temperature ≥ 180°C) between the air preheater and the low-temperature economizer together with the flue gas. The crystalline salt is captured and removed together with the fly ash in the dust collector, and the water vapor enters the desulfurization system and condenses into water under the action of spray cooling, indirectly supplementing the water used in the desulfurization system; a small amount of high-temperature flue gas in the electrolytic flue gas purification exhaust pipe is introduced into the concentrated brine evaporator, and the waste heat of the flue gas is used to provide heat for the evaporation of the atomized wastewater, without the need to add other heat sources, effectively reducing energy consumption and costs; after being processed by the present utility model, zero discharge of wastewater is achieved.

[0021] 2) After being processed by the present utility model, 80% of the fresh water can be recovered from the desulfurization wastewater, which is superior to the quality of industrial water in the factory area. The remaining concentrated liquid enters the electrolytic flue gas purification exhaust pipe for evaporation to achieve zero discharge; the utility model has the characteristics of treating waste with waste, recovering water resources, and not generating additional crystalline salt.

[0022] 3) The precipitates generated by coagulation and sedimentation in the coagulation and sedimentation system of the present utility model can be used as raw materials for making Mg(OH)2 and desulfurizing agent calcium carbonate respectively, realizing the recovery and reuse of resources.

[0023] 4) The ultrafiltration system of the present utility model can effectively remove fine particles in the wastewater, control SDI ≤ 5, ensure the water quality conditions entering the reverse osmosis, and improve the overall treatment effect.

[0024] 5) The membrane material used in the brine concentration equipment of the present utility model has been carefully selected and optimized, with good corrosion resistance and stability, and can adapt to complex and harsh water quality conditions; the present utility model optimizes the process parameters, conducts in-depth research and optimization on the process parameters of membrane separation, such as reasonably controlling the operating pressure, temperature, flow rate, etc., to ensure the efficient and stable operation of the membrane separation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of the present utility model.

[0026] Among them, 1 - coagulation and sedimentation system, 2 - ultrafiltration system, 21 - first storage tank, 3 - brine concentration equipment, 31 - second storage tank, 32 - desulfurization process water tank, 33 - water pump, 4 - fully automatic atomization system, 5 - concentrated brine evaporator, 6 - high-efficiency purifier, 61 - feed box, 62 - booster fan, 7 - electrolytic flue gas purification exhaust pipe, 8 - sand filtration system. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following will describe the implementation of the present utility model in detail with reference to the accompanying drawings. However, they do not constitute a limitation to the present utility model and are only for illustration purposes. Meanwhile, the advantages of the present utility model will become clearer and easier to understand through the description.

[0028] Referring to the accompanying drawings, it can be seen that a membrane method for concentrating desulfurized wastewater zero-discharge system includes a coagulation sedimentation system 1, an ultrafiltration system 2 connected to the coagulation sedimentation system 1, a brine concentration device 3 connected to the ultrafiltration system 2, a full-automatic atomization system 4 connected to the brine concentration device 3 and compressed air, a concentrated brine evaporator 5 connected to the full-automatic atomization system 4, and a high-efficiency purifier 6 connected to the bottom of the concentrated brine evaporator 5;

[0029] The electrolytic flue gas purification exhaust pipe 7 after defluorination purification is connected to the top of the concentrated brine evaporator 5, and the high-efficiency purifier 6 is connected to the electrolytic flue gas purification exhaust pipe 7 after defluorination purification.

[0030] A sand filtration system 8 is provided between the coagulation sedimentation system 1 and the ultrafiltration system 2.

[0031] The ultrafiltration system 2 is connected to the concentrated brine evaporator 5 through a first water storage tank 21.

[0032] The brine concentration device 3 is connected to the full-automatic atomization system 4 through a second water storage tank 31.

[0033] The brine concentration device 3 is connected to a desulfurization process water tank 32.

[0034] The brine concentration device 3 is connected to the desulfurization process water tank 32 through a water pump 33.

[0035] The high-efficiency purifier 6 is connected to a feed box 61.

[0036] The high-efficiency purifier 6 is connected to the electrolytic flue gas purification exhaust pipe 7 through a booster fan 62.

[0037] The ultrafiltration system 2 is a Dow column ultrafiltration membrane module; the brine concentration device 3 is an RO reverse osmosis system; the full-automatic atomization system 4 is a gas-liquid two-phase spray gun; the high-efficiency purifier 6 is a bag filter.

[0038] In actual use, the present utility model first concentrates the wastewater generated by FGD. The concentrated wastewater uses the waste heat of the electrolytic flue gas itself for full evaporation and crystallization without using additional heat sources; the clear water generated by concentration is returned to the process production, the water vapor after evaporation is returned to the desulfurization system, and the crystalline salt is recovered using a bag filter; the main process route adopted by the present utility model is coagulation sedimentation + sand filtration + column ultrafiltration + brine concentration RO + bypass flue evaporation.

[0039] The coagulation and sedimentation system 1 of the present utility model adopts a step-by-step two-stage softening mode, which can significantly improve the removal rates of calcium hardness and silicon. The main precipitate in the first-step reaction is Mg(OH)2, which can be used as the raw material for producing Mg(OH)2. The main precipitate in the second-step reaction is CaCO3, which can be directly recycled in the factory for use as a desulfurizer.

[0040] The ultrafiltration system 2 of the present utility model adopts Dow column ultrafiltration membrane modules, and its operation mode is: run for 30 min - backwash for 2 min - run for 30 min - backwash for 2 min, and operate in a cycle; the filtration period is 30 min, the turbidity of the produced water is analyzed regularly, and the pressure difference on both sides of the membrane is recorded. The system removes fine particles in the wastewater, controls SDI ≤ 5, and ensures the water quality conditions for reverse osmosis of the brine concentration equipment 3.

[0041] To ensure that the ultrafiltration system 2 can stably control SDI ≤ 5 under various working conditions, a regular automatic backwashing method is adopted, and the backwashing frequency is once every 2 hours of operation, and each backwashing time is not less than 3 minutes. At the same time, on-line monitoring instruments are set to monitor the SDI value in real time. When the SDI value exceeds 5, the emergency plan is immediately started, the number and intensity of backwashing are increased, and the ultrafiltration membrane is chemically cleaned, and the chemical cleaning frequency does not exceed once every 30 days. If the SDI value cannot be controlled in time, it may lead to the deterioration of the water quality entering the brine concentration equipment 3, affect the operation efficiency and service life of the RO reverse osmosis system, and even may lead to the decline of the treatment effect of the whole system and fail to meet the requirement of zero discharge of wastewater. At this time, the wastewater entering the system should be immediately stopped, and the ultrafiltration system 2 should be comprehensively inspected and repaired to ensure that it resumes normal operation before restarting the system.

[0042] As an efficient separation technology, the core of membrane separation technology lies in utilizing the selective permeability of the membrane to achieve precise separation and concentration of different components in wastewater under the action of specific driving forces. In this utility model, the membrane materials used in the brine concentration device 3 have been carefully selected and optimized, possessing good corrosion resistance and stability, and being able to adapt to the complex and harsh water quality conditions of desulfurized wastewater in the electrolytic aluminum industry. Specifically, these membrane materials have specific pore sizes and surface chemical properties, which can effectively block macromolecular pollutants, suspended solids, heavy metal ions, and various dissolved organic substances in the wastewater, while allowing water molecules and some small harmless substances to pass through. To achieve the best treatment effect, in this utility model, in-depth research and optimization have also been carried out on the process parameters of membrane separation. For example, parameters such as operating pressure, temperature, and flow rate are reasonably controlled to ensure the efficient and stable operation of the membrane separation process. In addition, a multi-stage membrane combination method is adopted to gradually increase the concentration multiple of the wastewater. First, larger particles and suspended solids in the wastewater are removed through the primary ultrafiltration membrane, and then the wastewater is further concentrated through the intermediate RO reverse osmosis membrane to increase the concentration of pollutants. Finally, the advanced special membrane is used for in-depth treatment of the wastewater to minimize the volume of wastewater. In each stage of membrane combination, appropriate membrane materials and operating parameters are selected according to the characteristics and treatment requirements of the wastewater. In the stage of the intermediate RO reverse osmosis membrane, membrane materials with high salt rejection rate and high water flux are selected, and the designed salt rejection rate is not less than 98%, and the water production recovery rate is not less than 80%. Through this multi-stage membrane combination method, extremely favorable conditions are created for subsequent treatment and resource recovery, greatly improving the treatment efficiency and resource recovery utilization rate of the entire system.

[0043] During the membrane separation process, through various action mechanisms such as physical sieving, electrostatic repulsion, and adsorption, efficient removal and concentration of harmful substances in desulfurized wastewater are achieved. At the same time, special coatings or modification technologies on the membrane surface are used to enhance the anti-fouling performance of the membrane, extend the service life of the membrane, and reduce the operating cost.

[0044] Setting aeration and backwashing can achieve more stable water production; and its chemical irreversible resistance is small, and membrane fouling can be significantly controlled through chemical cleaning, extending the service life of the membrane.

[0045] Embodiment

[0046] The method of the present invention first pre-treats the desulfurized wastewater to remove large particulate impurities and some easily precipitable substances, so as to reduce the pollution load on the membrane. Then, the pre-treated wastewater enters the brine concentration device 3, and under the action of each stage of membrane modules, the separation and concentration of harmful substances are achieved. The concentrated wastewater can be further processed through processes such as evaporation crystallization and drying to convert the salts and pollutants therein into solid substances for proper disposal, while the clear water passing through the membrane can be recycled for the production process to achieve the recycling of water resources. The utility model is closely integrated with the electrolytic production, uses the waste heat of the flue gas system itself to evaporate and crystallize the wastewater, realizes the true zero discharge of the desulfurized wastewater, and at the same time, the water in the wastewater completely returns to the desulfurization system. Whether analyzed from the aspect of technological advancement or energy conservation and consumption reduction, the utility model is an excellent solution for solving the desulfurized wastewater of electrolytic flue gas wet desulfurization, and has great technological foresight.

[0047] In the treatment of desulfurized wastewater in a large electrolytic aluminum plant, the desulfurized wastewater is introduced into the coagulation and precipitation system 1 of the utility model. In the first step of the reaction, precipitates mainly composed of Mg(OH)2 are generated, and these precipitates are collected and prepared for the production of Mg(OH)2 products. In the second step of the reaction, precipitates mainly composed of CaCO3 are generated, and they are directly recycled to the desulfurization process in the factory and act as desulfurizing agents. Subsequently, the wastewater passes through the sand filtration system 8 to remove larger impurities and then enters the ultrafiltration system 2. In this link, the Dow column ultrafiltration membrane module operates in a cycle of running for 30 minutes and backwashing for 2 minutes, effectively removing the fine particles in the wastewater and stably controlling the SDI below 5. After that, the treated wastewater enters the brine concentration device 3 for RO reverse osmosis concentration. The concentrated wastewater uses a gas-liquid two-phase spray gun to be cut and atomized into fine droplets by compressed air in the concentrated brine evaporator 5. At this time, a small amount of high-temperature flue gas in the power plant flue is introduced, and its waste heat is used to provide heat for the evaporation of the atomized wastewater. The atomized droplets quickly conduct heat and mass transfer and evaporation with the high-temperature flue gas, and the crystalline salts formed after complete evaporation are captured and removed together with the fly ash in the bag filter. The generated water vapor enters the desulfurization system and condenses into water under the action of spray cooling, indirectly supplementing the water used in the desulfurization system.

[0048] The utility model has successfully increased the removal rate of harmful substances in the wastewater to over 95% by precisely regulating the membrane separation parameters and optimizing the process flow. The volume of the concentrated wastewater has been reduced by 80%, greatly reducing the difficulty and cost of subsequent treatment. At the same time, the recovered clear water has good quality and fully meets the requirements of production reuse, realizing the maximum utilization of resources.

[0049] The concentrated wastewater is sent to the brine evaporator 5 for drying and solidification to achieve zero discharge of wastewater. To address the corrosion problem of equipment caused by the possible acidic gases in the flue gas, the components in the system that come into contact with the flue gas, such as the brine evaporator 5, are made of materials with a corrosion resistance level not lower than C3, ensuring that during long-term operation, the corrosion rate of the equipment does not exceed 0.1 mm per year. At the same time, the equipment is regularly inspected, and when the corrosion thickness reaches 20% of the original equipment thickness, maintenance or replacement is carried out in a timely manner.

[0050] Using the present utility model to treat desulfurized wastewater not only meets the environmental protection requirement of zero discharge but also reduces the treatment cost by 30% through optimizing the membrane material and process, bringing significant economic and environmental benefits to the enterprise.

[0051] Other parts not described belong to the prior art.

Claims

1. A membrane-based concentrated desulfurized wastewater zero-discharge system, characterized in that: It includes a coagulation sedimentation system (1), an ultrafiltration system (2) connected to the coagulation sedimentation system (1), a brine concentration device (3) connected to the ultrafiltration system (2), a full-automatic atomization system (4) connected to the brine concentration device (3) and compressed air, a concentrated brine evaporator (5) connected to the full-automatic atomization system (4), and a high-efficiency purifier (6) connected to the concentrated brine evaporator (5); An electrolytic flue gas purification exhaust pipe (7) is connected to the concentrated brine evaporator (5), and the high-efficiency purifier (6) is connected to the electrolytic flue gas purification exhaust pipe (7).

2. The membrane method for concentrating and zero-discharging desulfurized wastewater system according to claim 1, wherein: A sand filtration system (8) is arranged between the coagulation sedimentation system (1) and the ultrafiltration system (2).

3. The membrane method for concentrating desulfurized wastewater zero-discharge system according to claim 2, wherein: The ultrafiltration system (2) is connected to the brine concentration device (3) through a first water storage tank (21).

4. The membrane-based concentrated desulfurized wastewater zero-discharge system according to claim 3, wherein: The brine concentration device (3) is connected to the full-automatic atomization system (4) through a second water storage tank (31).

5. The zero-discharge system for membrane method concentrated desulfurized wastewater according to claim 4, characterized in that: The brine concentration device (3) is connected to a desulfurization process water tank (32).

6. The zero-discharge system for membrane method concentrated desulfurization wastewater according to claim 5, characterized in that: The brine concentration device (3) is connected to the desulfurization process water tank (32) through a water pump (33).

7. A membrane-based concentrated desulfurized wastewater zero-discharge system according to claim 6, characterized in that: The high-efficiency purifier (6) is connected to a feed box (61).

8. The membrane method for concentrating desulfurized wastewater zero - discharge system according to claim 7, characterized in that: The high-efficiency purifier (6) is connected to the electrolytic flue gas purification exhaust pipe (7) through a booster fan (62).

9. The membrane-based concentrated zero-discharge system for desulfurized wastewater according to claim 1, wherein: The ultrafiltration system (2) is a Dow column ultrafiltration membrane module; the brine concentration device (3) is an RO reverse osmosis system; the full-automatic atomization system (4) is a gas-liquid two-phase spray gun; the high-efficiency purifier (6) is a bag filter.

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