Wet desulphurization wastewater treatment system for waste incineration power plant

Abstract

The utility model discloses a wet desulphurization wastewater treatment system for a waste incineration power plant, which relates to the technical field of wastewater treatment and comprises a heat exchanger, a raw water regulating tank, a reaction tank, a sedimentation tank, an ultrafiltration system, a high-pressure membrane system, a reverse osmosis system and a recycled water tank which are connected in sequence, the sedimentation tank is also sequentially connected with a chemical softening sludge tank and a sludge treatment system; the high-pressure membrane system is connected with the concentrated water tank which is sequentially connected with the process water tank and the atomizer. The utility model provides a wet desulphurization wastewater treatment system for a waste incineration power plant, which is used for solving the problems that the pH value of a concentrated solution is low, more lime slurry needs to be input for pulping, and the production cost is low when the concentrated solution of the wastewater is conveyed into a lime slurry preparation system for pulping in the conventional wastewater treatment system. The technical problems of system failure, low recovery rate of the system and poor wastewater treatment effect due to the fact that the concentration of the lime slurry is increased and the pipeline is easily blocked are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of wastewater treatment, in particular to a wet desulfurization wastewater treatment system for a garbage incineration power plant. Background Art

[0002] At present, urban environmental infrastructure includes facilities for incineration of urban domestic waste, which is the basic guarantee for achieving waste reduction, resource utilization and harmless treatment. Flue gas is generated during the incineration of waste. If the flue gas is directly discharged into the air, it will cause pollution. Therefore, wet desulfurization technology is usually used to treat the flue gas, using about 30% liquid alkali (NaOH) to react with acidic gases such as SO2 and HCl in the flue gas to remove them.

[0003] However, wet desulfurization technology will eventually produce wastewater with high salinity and low acidity. The existing wastewater treatment system generally sends the concentrated liquid obtained after the wastewater is treated by the microfiltration system and the reverse osmosis system to the lime slurry preparation system for slurry preparation, and then sprays it back to the semi-dry reaction tower. However, the pH of the concentrated liquid is low, and more lime slurry is required for slurry preparation. The high concentration of lime slurry is easy to clog the pipeline and cause system failure. The recovery rate of the system is low, and the wastewater treatment effect is poor. Utility Model Content

[0004] The utility model provides a waste incineration power plant wet desulfurization wastewater treatment system, which is used to solve the technical problems that the existing wastewater treatment system sends the concentrated liquid of the wastewater to the lime slurry preparation system for slurrying, but the pH value of the concentrated liquid is low, and more lime slurry needs to be put into slurrying, the lime slurry concentration becomes high and it is easy to block the pipeline and cause system failure, the system recovery rate is low, and the wastewater treatment effect is not good.

[0005] The utility model provides a waste incineration power plant wet desulfurization wastewater treatment system, comprising: a heat exchanger, a raw water regulating tank, a reaction tank, a sedimentation tank, an ultrafiltration system, a high-pressure membrane system, a reverse osmosis system and a reuse water tank connected in sequence;

[0006] The sedimentation tank is also connected in sequence to the chemical softening sludge tank and the sludge treatment system;

[0007] The high-pressure membrane system is connected to a concentrated water tank, and the concentrated water tank is connected in turn to a process water tank and an atomizer.

[0008] Preferably, the concentrated water tank is connected to a fly ash solidification station.

[0009] Preferably, an activated carbon filter is connected between the sedimentation tank and the ultrafiltration system.

[0010] Preferably, a laminated filter is connected between the activated carbon filter and the ultrafiltration system.

[0011] Preferably, an intermediate water pool is connected between the activated carbon filter and the laminated filter, and the intermediate water pool is provided with a channel returning to the activated carbon filter.

[0012] Preferably, the ultrafiltration system comprises an ultrafiltration device and an ultrafiltration water production tank, and the reverse osmosis system is connected to the ultrafiltration water production tank.

[0013] Preferably, the reaction pool comprises a first reaction pool and a second reaction pool, and the second reaction pool is connected to an outlet of the first reaction pool.

[0014] Preferably, the reaction pool further comprises a third reaction pool, and the third reaction pool is connected to the outlet of the second reaction pool.

[0015] Preferably, the first reaction tank, the second reaction tank and the third reaction tank are connected to each other in a top-in and bottom-out manner.

[0016] Preferably, the ultrafiltration device is an external pressure PVDF ultrafiltration membrane.

[0017] The utility model provides a waste incineration power plant wet desulfurization wastewater treatment system, which has the following advantages:

[0018] It includes: a heat exchanger, a raw water regulating tank, a reaction tank, a sedimentation tank, an ultrafiltration system, a high-pressure membrane system, a reverse osmosis system and a recycled water tank which are connected in sequence; the sedimentation tank is also connected in sequence to a chemical softening sludge tank and a sludge treatment system; the high-pressure membrane system is connected to a concentrated water tank, and the concentrated water tank is connected in sequence to a process water tank and an atomizer.

[0019] The wet flue gas desulfurization wastewater is sequentially passed through a heat exchanger, a raw water regulating tank, a reaction tank and a sedimentation tank to obtain sludge and produced water; the sludge enters a chemical softening sludge tank and is mixed with the softened sludge, and then is dehydrated through a sludge treatment system to form a mud cake that is sent to a power plant for incineration; the produced water sequentially enters an ultrafiltration system, a high-pressure membrane system and a reverse osmosis system, where suspended solids and macromolecular organic matter are removed from the produced water and turbidity is reduced; the produced water is desalted in a high-pressure membrane system and a reverse osmosis system and then enters a reuse water tank for reuse in the power plant;

[0020] The concentrated liquid formed after the produced water passes through the high-pressure membrane system enters the concentrated water tank, then enters the process water tank for temporary storage, and is finally reused to the atomizer for atomization, achieving zero discharge of wastewater, better wastewater treatment effect, and improving the recovery rate of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 This is a schematic diagram of the structure of a wet desulfurization wastewater treatment system for a waste incineration power plant according to an embodiment of the utility model;

[0023] Figure 2 This is a schematic structural diagram of a wet desulfurization wastewater treatment system for a waste incineration power plant according to another embodiment of the utility model;

[0024] In the figure: 1. heat exchanger; 2. raw water regulating tank; 3. reaction tank; 31. first reaction tank; 32. second reaction tank; 33. third reaction tank; 4. sedimentation tank; 5. activated carbon filter; 6. intermediate water tank; 7. laminated filter; 8. ultrafiltration system; 81. ultrafiltration device; 82. ultrafiltration water production tank; 9. high-pressure membrane system; 10. reverse osmosis system; 11. recycled water tank; 12. chemical softening sludge tank; 13. sludge treatment system; 14. concentrated water tank; 15. process water tank; 16. atomizer; 17. fly ash solidification station; 18. high-pressure membrane water production tank. DETAILED DESCRIPTION

[0025] In order to make the purpose, features and advantages of the utility model more obvious and easy to understand, the technical solutions in the embodiments of the utility model are described clearly and completely. Obviously, the embodiments described below are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] It should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the utility model and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the embodiments of the utility model.

[0027] In addition, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0028] In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0029] In the description of the embodiments of the present utility model, it should be noted that, unless otherwise clearly specified and limited, 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 communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present utility model can be understood according to specific circumstances.

[0030] The mainstream flue gas purification system mainly adopts the double desulfurization and denitrification process, "SNCR denitrification (ammonia water) + rotary spray semi-dry method (calcium hydroxide) + dry injection system (calcium hydroxide) + activated carbon injection system + bag filter + wet scrubbing desulfurization (sodium hydroxide) + SCR denitrification" treatment process, and the pollutant concentration in the flue gas reaches the "Standard for Pollution Control of Municipal Waste Incineration" (GB18485-2014). Among them, wet desulfurization technology is the main process for more stringent emission of flue gas SO2 and HCl, using 30% liquid alkali (NaOH) to react with acidic gases such as SO2 and HCl in the flue gas to remove them.

[0031] Explanation of the English abbreviations in this article:

[0032] PVDF: Polyvinylidene fluoride.

[0033] The utility model provides a waste incineration power plant wet desulfurization wastewater treatment system, which is used to solve the technical problems that the existing wastewater treatment system sends the concentrated liquid of the wastewater to the lime slurry preparation system for slurrying, but the pH value of the concentrated liquid is low, and more lime slurry needs to be put into slurrying, the lime slurry concentration becomes high and it is easy to block the pipeline and cause system failure, the system recovery rate is low, and the wastewater treatment effect is not good.

[0034] See also Figure 1 , a waste incineration power plant wet desulfurization wastewater treatment system provided by an embodiment of the utility model comprises: a heat exchanger 1, a raw water regulating tank 2, a reaction tank 3, a sedimentation tank 4, an ultrafiltration system 8, a high-pressure membrane system 9, a reverse osmosis system 10 and a reuse water tank 11 connected in sequence;

[0035] The sedimentation tank 4 is also connected in sequence to the chemical softening sludge tank 12 and the sludge treatment system 13;

[0036] The high-pressure membrane system 9 is connected to the concentrated water tank 14 , and the concentrated water tank 14 is connected to the atomizer 16 .

[0037] It should be noted that the wet flue gas desulfurization wastewater is sequentially passed through the heat exchanger 1, the raw water regulating tank 2, the reaction tank 3 and the sedimentation tank 4 to obtain sludge and produced water; the sludge enters the chemical softening sludge tank 12 and is mixed with the softened sludge, and then passes through the sludge treatment system 13 for dehydration to form a mud cake and is sent to the power plant for incineration; the produced water sequentially enters the ultrafiltration system 8, the high-pressure membrane system 9 and the reverse osmosis system 10, and the produced water removes suspended solids and macromolecular organic matter in the water and reduces turbidity in the ultrafiltration system 8, and the produced water is desalted in the high-pressure membrane system 9 and the reverse osmosis system 10 and enters the reuse water tank 11 for reuse in the power plant;

[0038] The concentrated liquid formed after the produced water passes through the high-pressure membrane system 9 enters the concentrated water tank 14, and then enters the process water tank 15 of the flue gas purification system for temporary storage, and finally returns to the atomizer 16 for atomization, thereby achieving zero discharge of wastewater, having a better wastewater treatment effect, and improving the recovery rate of the system;

[0039] Due to the high temperature of flue gas, the temperature of the smoke washing wastewater generated during the wet desulfurization process is relatively high, at 60-70°C. Heat exchanger 1 is required to cool the wastewater to ensure that the temperature of the wastewater entering the system reaction is maintained below 40°C to ensure the normal operation of the subsequent system; the material of heat exchanger 1 is 316L, and the material of the pipe is rubber-lined / plastic-lined pipe;

[0040] The raw water regulating tank 2 plays a role in balancing water quality and water quantity. The raw water regulating tank 2 not only collects the raw water of tobacco washing wastewater, but also collects the flushing wastewater and chemical cleaning water generated during the operation of the system;

[0041] When the temperature of wet desulfurization wastewater has reached the appropriate temperature, it can also be directly transported to the raw water regulating tank 2 for treatment through the bypass;

[0042] The reaction tank 3 and the sedimentation tank 4 are used to remove suspended matter, silicate ions, etc. in the wastewater;

[0043] The prior art does not treat wastewater desalination thoroughly enough, and the concentration of chloride ions is high, which easily causes equipment corrosion and leakage. The utility model adopts a combination of a high-pressure membrane system 9 and a reverse osmosis system 10 to deeply remove the salt of the produced water and reduce the degree of equipment corrosion.

[0044] The high-pressure membrane of the high-pressure membrane system 9 is selected from 70 bar, 90 bar and 120 bar (1 bar = 1 kg force), and the 90 bar high-pressure membrane is preferred, which can balance the better desalination rate and pressure resistance;

[0045] The chemical softening sludge tank 12 is a component of the leachate treatment system of the power plant. The sludge produced by the sedimentation tank 4 is transported to the chemical softening sludge tank 12 for coordinated treatment, which can reduce the investment in sludge equipment.

[0046] The existing technology generally adopts a combined optimization process of "traditional chemical precipitation + tubular microfiltration + STRO + RO". The tubular microfiltration device used in the system requires a certain suspended matter and sludge concentration, which conflicts with the two-stage sedimentation tank set at the front end, resulting in the system being unable to operate stably. The system of the utility model can operate more stably.

[0047] See also Figure 2 In a more specific embodiment, a high-pressure membrane water production pool 18 is connected between the high-pressure membrane system 9 and the reverse osmosis system 10. The produced water after desalination treatment by the high-pressure membrane system 9 can be stored in the high-pressure membrane water production pool 18. The produced water is deeply desalinated in the reverse osmosis system 10 and is sent to the power plant for reuse only when it meets the circulating water reuse standard.

[0048] See also Figure 2 In a more specific embodiment, the concentrated water tank 14 is connected to the fly ash solidification station 17 .

[0049] It should be noted that the concentrated water tank 14 is connected to the fly ash solidification station 17, and a portion of the concentrated liquid in the concentrated water tank 14 can be transported to the fly ash solidification station 17 to be used as fly ash chelating water.

[0050] See also Figure 2 In a more specific embodiment, an activated carbon filter 5 is connected between the sedimentation tank 4 and the ultrafiltration system 8 .

[0051] It should be noted that an activated carbon filter 5 is connected between the sedimentation tank 4 and the ultrafiltration system 8. The activated carbon filter 6 adsorbs and removes hydrophobic organic matter, oxidizing substances and suspended solids in the system that have a greater impact on the membrane equipment, thereby ensuring the normal operation of the subsequent membrane system.

[0052] See also Figure 2 In a more specific embodiment, a laminated filter 7 is connected between the activated carbon filter 5 and the ultrafiltration system 8 .

[0053] It should be noted that the laminated filter 7 is used as a pre-treatment for the ultrafiltration system 8 to ensure that the turbidity and suspended solids of the ultrafiltration influent meet the standards;

[0054] The laminated filter is preferably made of all-plastic material to prevent chloride ions from corroding the inside of the laminated filter 7 .

[0055] See also Figure 2 In a more specific embodiment, an intermediate water pool 6 is connected between the activated carbon filter 5 and the laminated filter 7 , and the intermediate water pool 6 is provided with a channel returning to the activated carbon filter 5 .

[0056] It should be noted that the intermediate water tank 6 stores the produced water filtered by the activated carbon filter 5 , and the produced water can further flow into the laminated filter 7 for treatment, or can be used as a backwash water source for the activated carbon filter 5 through the channel returning to the activated carbon filter 5 .

[0057] See also Figure 2 In a more specific embodiment, the ultrafiltration system 8 includes an ultrafiltration device 81 and an ultrafiltration water production tank 82 , and the reverse osmosis system 9 is connected to the ultrafiltration water production tank 82 .

[0058] It should be noted that the produced water is first filtered by the ultrafiltration device 81 of the ultrafiltration system 8 and stored in the ultrafiltration produced water tank 82. The reverse osmosis system 10 will produce some concentrated liquid, which will be returned to the ultrafiltration produced water tank 82 for use. The concentrated water is connected and the produced water is reused to form a cycle, thereby improving the recovery rate of the system.

[0059] See also Figure 2 In a more specific embodiment, the reaction tank 3 includes a first reaction tank 31 and a second reaction tank 32 , and the second reaction tank 32 is connected to the outlet of the first reaction tank 31 .

[0060] It should be noted that, since the tobacco washing wastewater is acidic, it is necessary to add liquid alkali (30% NaOH) or calcium hydroxide in the first reaction tank 31 to adjust the pH value of the wastewater to 9-11 to ensure that impurities are removed under the required pH value environment;

[0061] Polyaluminium chloride or ferrous sulfate is added into the second reaction tank 32, so that after passing through the first reaction tank, it can undergo flocculation reaction with the wastewater through the second reaction tank 32 to remove suspended solids in the water.

[0062] See also Figure 2 In a more specific embodiment, the reaction tank 3 also includes a third reaction tank 33 , and the third reaction tank 33 is connected to the outlet of the second reaction tank 32 .

[0063] It should be noted that the reaction pool 3 is a vertical cuboid, which is isolated to form a first reaction pool 31, a second reaction pool 32 and a third reaction pool 33 connected in series, the first reaction pool 31 is connected to the second reaction pool 32, and the second reaction pool 32 is connected to the third reaction pool 33. The third reaction pool 33 temporarily buffers the wastewater passing through the second reaction pool 32, which is conducive to the full mixing reaction of the wastewater and the reagent.

[0064] The third reaction tank 33 is added with sodium carbonate to reduce the hardness of the wastewater (remove calcium and magnesium ions), while the addition of magnesium oxide is used to remove silicate ions in the wastewater. According to the water quality characteristics of the desulfurization wastewater, chemical pretreatment agent recommendations are provided.

[0065] In a more specific embodiment, the first reaction tank 31, the second reaction tank 32 and the third reaction tank 33 are connected to each other in a top-in and bottom-out manner.

[0066] It should be noted that the first reaction tank 31, the second reaction tank 32 and the third reaction tank 33 are connected to each other in a top-in and bottom-out manner, so that the wastewater flows up and down in the reaction tank, which can extend the reaction time of the agent and the wastewater, make the agent fully contact with the wastewater, and improve the effect of removing impurities such as suspended matter.

[0067] In a more specific embodiment, the ultrafiltration device 81 is an external pressure PVDF ultrafiltration membrane.

[0068] It should be noted that the ultrafiltration device 81 of the ultrafiltration system 8 adopts an external pressure PVDF ultrafiltration membrane and adopts dead-end filtration, which can reduce the generation of concentrated water.

[0069] An embodiment of the utility model provides a method for using a wet desulfurization wastewater treatment system for a waste incineration power plant, comprising:

[0070] The wet desulfurization wastewater is sequentially passed through the heat exchanger 1 and the raw water regulating tank 2 to adjust the water temperature to a preset threshold range, and then sequentially passed through the reaction tank 3 and the sedimentation tank 4 to remove suspended solids and silicate ions in the water to obtain sludge and produced water;

[0071] The sludge enters the chemical softening sludge tank 12 and is mixed with the softened sludge, and then passes through the sludge treatment system 13 for dehydration to form a mud cake that is sent to the power plant for incineration;

[0072] The produced water enters the ultrafiltration system 8, the high-pressure membrane system 9 and the reverse osmosis system 10 in sequence. The produced water removes suspended solids and macromolecular organic matter in the water and reduces turbidity in the ultrafiltration system 8. The produced water enters the reuse water pool 11 after being desalted in the high-pressure membrane system 9 and the reverse osmosis system 10.

[0073] The water produced by the high-pressure membrane system 9 forms a concentrated liquid, which enters the concentrated water tank 14 and then enters the process water tank 15 for temporary storage, and then is reused in the atomizer 16 for atomization.

[0074] It should be noted that the preset threshold range for water temperature is 60-70°C;

[0075] Hydrochloric acid is added to the pipeline before the produced water enters the high-pressure membrane system 9. The mixture of hydrochloric acid and produced water can reduce the pH value of the produced water, thereby preventing the concentrated water side from scaling on the equipment of the high-pressure membrane system 9 after the produced water enters the high-pressure membrane system 9;

[0076] The sludge in the sedimentation tank 4 is transported to the chemical softening sludge tank 12 of the leachate treatment system through a sludge transport pump, and is mixed together with the softened sludge produced by the reduction treatment device of the leachate treatment system;

[0077] The sludge treatment system 13 includes a centrifugal dehydrator, which is used to centrifugally dehydrate the mixed sludge to form a mud cake and send it to the power plant for incineration. The remaining clear liquid is transported to the leachate treatment system for "secondary nitrification / denitrification + ultrafiltration + nanofiltration + reverse osmosis" process treatment, clear liquid reuse or concentrated water return to the power plant furnace.

[0078] The above is a detailed introduction to a wet desulfurization wastewater treatment system for a waste incineration power plant provided by the utility model. For a general technician in this field, according to the idea of ​​the embodiment of the utility model, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the utility model.

Claims

1. A waste incineration power plant wet desulfurization wastewater treatment system, characterized in that: include: The heat exchanger, raw water regulating tank, reaction tank, sedimentation tank, ultrafiltration system, high pressure membrane system, reverse osmosis system and recycled water tank are connected in sequence; The sedimentation tank is also connected in sequence to the chemical softening sludge tank and the sludge treatment system; The high-pressure membrane system is connected to a concentrated water tank, and the concentrated water tank is connected in turn to a process water tank and an atomizer.

2. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 1 is characterized in that: The concentrated water tank is connected to the fly ash solidification station.

3. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 1 is characterized in that: An activated carbon filter is connected between the sedimentation tank and the ultrafiltration system.

4. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 3 is characterized in that: A laminated filter is connected between the activated carbon filter and the ultrafiltration system.

5. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 4 is characterized in that: An intermediate water pool is connected between the activated carbon filter and the laminated filter, and the intermediate water pool is provided with a channel returning to the activated carbon filter.

6. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 1 is characterized in that: The ultrafiltration system comprises an ultrafiltration device and an ultrafiltration water production tank, and the reverse osmosis system is connected to the ultrafiltration water production tank.

7. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 1 is characterized in that: The reaction pool includes a first reaction pool and a second reaction pool, and the second reaction pool is connected to the outlet of the first reaction pool.

8. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 7 is characterized in that: The reaction pool further includes a third reaction pool, and the third reaction pool is connected to the outlet of the second reaction pool.

9. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 8, characterized in that: The first reaction tank, the second reaction tank and the third reaction tank are connected to each other in a top-in and bottom-out manner.

10. The wet desulfurization wastewater treatment system for a waste incineration power plant according to claim 6, characterized in that: The ultrafiltration device is an external pressure PVDF ultrafiltration membrane.

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