Fly ash and leachate membrane concentrate co-processing resource system and method

Abstract

The present application relates to fly ash and leachate membrane concentrate collaborative processing resource system and method, belong to solid waste treatment and high concentration organic wastewater treatment technical field. The present application includes washing unit, the washing unit includes multistage water washing system, the water washing tank of the former stage water washing system is connected with the filtrate pool of the latter stage water washing system; the water washing tank of a non final stage water washing system is connected with the leachate treatment system; the filtrate pool of the first stage water washing system is provided with a sedimentation purification unit, and is connected with a filter press dewatering machine and an MVR evaporation crystallization system, the water production end of the MVR evaporation crystallization system is connected with a condensate tank, and the condensate tank is connected with the washing water tank of the last stage water washing system. The present application utilizes the alkaline environment of fly ash to make magnesium ions and heavy metal ions in membrane concentrate generate hydroxide precipitate, utilizes the activated carbon component in fly ash to adsorb organic matter in membrane concentrate, realizes the collaborative processing of fly ash dechlorination and membrane concentrate accommodation, and is low in cost and has no wastewater discharge.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and high-concentration organic wastewater treatment technology, and relates to a resource utilization system and method for the co-treatment of fly ash and leachate membrane concentrate. Background Technology

[0002] Municipal solid waste incineration power generation is the mainstream technology for municipal solid waste treatment, but the incineration fly ash and leachate membrane concentrate that are generated by it are two recognized challenges in disposal.

[0003] Incineration fly ash is classified as hazardous waste in the National Hazardous Waste List, with main hazards including: ① highly leaching toxic heavy metals (Pb, Zn, Cd, etc.); ② highly toxic persistent organic compounds (dioxins); ③ high content of soluble chloride salts (NaCl, KCl, CaCl2, etc., with content reaching 15%~30%). Chloride salts are a key obstacle restricting the resource utilization of fly ash (such as co-processing in cement kilns and utilization in building materials), and water washing and dechlorination are essential.

[0004] Landfill leachate membrane concentrate is the residual concentrated water after leachate has undergone deep membrane treatment such as nanofiltration and reverse osmosis. It is characterized by high salinity (TDS can reach 4%~6%), high COD (usually 1000~3000 mg / L), high hardness, and poor biodegradability. Conventional treatment technologies (evaporation, advanced oxidation) are extremely expensive, which is the "last mile" bottleneck for the full treatment of leachate.

[0005] Limitations of existing technology: (1) Current status of fly ash water washing dechlorination technology Currently, multi-stage countercurrent clean water washing process is widely used in industry. This process is mature and has high dechlorination efficiency, but it has the following drawbacks: First, it has a single function, only treating incineration fly ash; second, it generates high-salt washing wastewater, which usually requires the construction of a separate softening system and the addition of large amounts of sodium sulfate and sodium carbonate to remove calcium ions, etc., resulting in high investment and operating costs. (2) Current status of leachate membrane concentrate treatment technology Mainstream technologies include submerged combustion, advanced oxidation, and reflow incineration, all of which have problems such as high investment, high energy consumption, secondary pollution (incineration waste residue), and the resources in the concentrate are not effectively recovered.

[0006] (3) Current status of co-washing technology for saline waste liquid Recent research has begun to explore the use of industrial saline wastewater to replace clean water for washing fly ash. For example, patent document CN118403878B discloses a "multi-stage countercurrent water washing method for incineration fly ash based on the equilibrium method to calculate the optimal liquid-solid ratio." This method can add saline wastewater for co-treatment to reduce water consumption. However, this patent has the following unresolved technical problems: First, it does not specify the exact source and nature of the saline wastewater, and in particular, it does not disclose its applicability to "landfill leachate membrane concentrate," a complex wastewater with high COD, high hardness, and heavy metal content. Secondly, the efficient purification process of the high-salt filtrate after washing was not disclosed; only the "wastewater treatment system" was mentioned in general terms, without achieving deep coupling with the evaporation and crystallization unit. Third, the simplified purification path that utilizes the alkalinity of fly ash itself to achieve the self-precipitation of magnesium and heavy metals has not been disclosed, and external reagents are still required. Fourth, the problem of full reuse and water balance of evaporative condensate within the system has not been solved, and there may still be a need for wastewater discharge. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a resource utilization system and method for the co-processing of fly ash and leachate membrane concentrate, so as to achieve the co-processing of fly ash dechlorination and membrane concentrate disposal.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A resource recovery system for the co-treatment of fly ash and leachate membrane concentrate includes a washing unit for multi-stage countercurrent washing of fly ash. The washing unit includes an n-stage water washing system, where n is a natural number not less than 2. The water washing tank of the previous stage water washing system is connected to the filtrate tank of the next stage water washing system. A water washing tank of a non-final stage water washing system is connected to a leachate treatment system to introduce leachate membrane concentrate into the water washing tank of the non-final stage water washing system. The filtrate tank of the first stage water washing system is equipped with a sedimentation and purification unit to add a calcium removal agent to the filtrate tank of the first stage water washing system. The filtrate tank of the first stage water washing system is connected to a filter press and a MVR evaporation and crystallization system. The product water end of the MVR evaporation and crystallization system is connected to a condensate tank, which is connected to the wash water tank of the last stage water washing system to use the condensate of the MVR evaporation and crystallization system as the washing medium of the last stage water washing system.

[0009] Optionally, the filtrate tank of the first-stage washing system is equipped with a degravation unit to control the heavy metal concentration by introducing sulfides into the filtrate tank of the first-stage washing system.

[0010] Optionally, the filtrate tank of the first-stage water washing system is equipped with an ozone oxidation unit to control the COD concentration through ozone aeration reaction.

[0011] Optionally, the condensate tank is connected to the leachate conditioning tank of the leachate treatment system to serve as dilution water for the leachate stock solution.

[0012] Optionally, the fly ash and leachate membrane concentrate co-treatment resource recovery system does not have a separate wastewater discharge outlet.

[0013] Optionally, n=3, the washing unit includes a first-stage washing system, a second-stage washing system, and a third-stage washing system arranged sequentially; the first-stage washing system includes a first-stage washing tank, a first-stage slurry pump, a first-stage dewatering machine, and a first-stage filtrate tank arranged sequentially; the second-stage washing system includes a second-stage washing tank, a second-stage slurry pump, a second-stage dewatering machine, and a second-stage filtrate tank arranged sequentially, with the wet sludge outlets of the second-stage washing tank and the first-stage dewatering machine connected; the third-stage washing system includes a third-stage washing tank, a third-stage slurry pump, a third-stage dewatering machine, and a third-stage filtrate tank arranged sequentially, with the third-stage washing tank and the second-stage filtrate tank connected to each other. The wet residue outlet of the dewatering machine is connected; the secondary washing tank is connected to the tertiary filtrate tank and the leachate treatment system to use the tertiary wash water and leachate membrane concentrate for the secondary washing medium; the primary washing tank is connected to the secondary filtrate tank to use the secondary wash water for the primary washing medium; the primary filtrate tank is equipped with a sedimentation and purification unit to add calcium removal agent to the primary filtrate tank; the primary filtrate tank is connected to a filter press and a MVR evaporation and crystallization system; the product water end of the MVR evaporation and crystallization system is connected to a condensate tank; the condensate tank is connected to the tertiary washing tank and the leachate conditioning tank of the leachate treatment system.

[0014] Optionally, n=4.

[0015] A method for the co-processing and resource utilization of fly ash and leachate membrane concentrate, based on the aforementioned co-processing and resource utilization system for fly ash and leachate membrane concentrate, includes the following steps: S1. Multi-stage washing and dechlorination: Multi-stage countercurrent washing is performed on fly ash from municipal solid waste incineration. The first stage non-final stage washing uses landfill leachate membrane concentrate as the washing medium. The alkaline environment of the fly ash itself causes magnesium ions and heavy metal ions in the membrane concentrate to form hydroxide precipitates. The activated carbon components in the fly ash adsorb organic matter in the membrane concentrate, thereby achieving synergistic removal of fly ash dechlorination and membrane concentrate pollutants. S2. Calcium removal: Sodium carbonate is added to the filtrate tank of the first-stage water washing system to remove calcium ions, and then the precipitate is filtered out. The filtrate after filtration is refined brine. S3. Evaporation and Crystallization: The refined brine is evaporated and crystallized to separate and recover sodium chloride and / or potassium chloride resources, and evaporation condensate is generated; S4. Closed-loop reuse of condensate: The evaporated condensate is preferentially reused as the final washing water in step S1, and the remaining surplus condensate is returned to the landfill leachate equalization tank to achieve zero wastewater discharge from the system.

[0016] Optionally, in step S1, the multi-stage countercurrent washing is a three-stage countercurrent washing, specifically including: First-stage washing: Using the secondary wash water generated from the second-stage washing as a medium, the incineration raw ash is washed to obtain first-stage dechlorinated fly ash and first-stage wash water; Second-stage washing: Using the mixture of tertiary wash water from the third-stage washing and landfill leachate membrane concentrate as a medium, the primary dechlorination fly ash from the first stage is washed to obtain secondary dechlorination fly ash and secondary wash water; Third-stage washing: Using evaporated condensate as a medium, the secondary dechlorinated fly ash produced in the second stage is washed to obtain the dechlorinated fly ash product and the third-stage wash water.

[0017] Optionally, in the second-stage washing, the volume ratio of the tertiary wash water to the landfill leachate membrane concentrate is 1:0.5 to 2; the liquid-solid ratio of the first-stage washing to the second-stage washing is 2 to 4:1, and the washing time is 10 to 30 minutes.

[0018] Optionally, in step S1, the water quality characteristics of the landfill leachate membrane concentrate are: COD ≥ 1000 mg / L, Mg²⁺ ≥ 1000 mg / L. + ≥500 mg / L, Pb≥10 μg / L, SO4² - ≥10000 mg / L.

[0019] Optionally, in step S2, the amount of sodium carbonate added is 1.05 to 1.2 times the theoretical calcium molar ratio, and the reaction time is 20 to 40 min; the resulting calcium carbonate precipitate is directly recycled as a by-product after pressure filtration and dehydration.

[0020] Optionally, after step S2, a deep degravation step is also included: adding an organic sulfide or sodium sulfide to the filtrate after calcium ion removal, reacting for 15 to 30 minutes, so that the concentration of heavy metal ions is lower than 0.1 mg / L.

[0021] Optionally, after step S2, an ozone oxidation step is also included: ozone is introduced into the filtrate after calcium ion removal for 10-20 min to aerate and react, and the residual COD is controlled to be below 50 mg / L.

[0022] Optionally, the multi-stage countercurrent washing can be adjusted to 2-4 stages based on the fly ash chlorine content and the membrane concentrate volume. The multi-stage countercurrent washing can be adjusted to 2-4 stages based on the fly ash chlorine content, the membrane concentrate volume, and the dechlorination requirements. The higher the fly ash chlorine content or the higher the dechlorination requirements, the more washing stages are required. When the fly ash chlorine content is low, the dechlorination requirements are low, and the membrane concentrate volume is sufficient, fewer washing stages are selected.

[0023] The beneficial effects of this invention are as follows: 1. Zero water consumption, full utilization of membrane concentrate, zero cost of membrane concentrate disposal, achieving "waste treatment with waste".

[0024] 2. Utilizing the inherent properties of fly ash and leachate membrane concentrate to remove pollutants and reduce treatment costs is reflected in: • Magnesium self-precipitation: Mg²⁺ in the washing solution +The magnesium concentration decreased from 812 mg / L to 1.2 mg / L, with a removal rate >99.9%, requiring no magnesium removal agents. • Heavy metal self-precipitation: Pb² + Once the hydroxide precipitates, there is no need to add alkali to adjust the pH. • Complete COD adsorption: The COD of the membrane concentrate is 1240 mg / L, and the COD of the filtrate after washing is below the detection limit (<10 mg / L), so there is no need to set up an advanced oxidation unit; • Calcium sulfate precipitation: SO4 in membrane concentrate 2- It can precipitate some of the calcium ions in fly ash, reducing the amount of sodium carbonate used in subsequent processes.

[0025] 3. Significantly improved economic efficiency of evaporation crystallization: The introduction of membrane concentrate can increase the TDS concentration of the washing liquid, reduce evaporation energy consumption, and the produced sodium and potassium salts can be utilized as resources.

[0026] 4. System water balance closed loop, zero wastewater discharge: Condensate is preferentially reused for washing, and surplus condensate is returned to the leachate equalization tank and incorporated into the plant's leachate treatment system. There is no independent process wastewater discharge outlet, achieving near-zero discharge.

[0027] 5. Strong compatibility and easy engineering: It can be modified on the basis of existing fly ash washing lines without demolition and reconstruction; the number of multi-stage washing stages is adjustable (two-stage / three-stage / four-stage) to adapt to different ash qualities; the membrane concentrate has a wide range of applications (suitable for STRO / DTRO / NF concentrates).

[0028] 6. The system is highly robust and capable of handling raw material fluctuations: In case of insufficient activated carbon in fly ash or abnormally high COD in concentrated liquid, the backup ozone oxidation unit can be started to ensure that the COD of the effluent meets the standards; for fly ash with high heavy metal content, the deep heavy metal removal unit (addition of TMT-15) can be started to achieve deep removal of heavy metals and ensure the quality of crystallized salt.

[0029] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the fly ash and leachate membrane concentrate co-processing resource recovery system of the present invention. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0033] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0034] Please see Figure 1 This invention provides a synergistic treatment system and method that is extremely simple in process, low in cost, has no wastewater discharge, and simultaneously realizes fly ash dechlorination and membrane concentrate disposal, in order to replace the existing separate treatment mode of fly ash washing and membrane concentrate evaporation, and achieve near-zero emission and resource utilization of hazardous waste in incineration plants.

[0035] 1. Overall Technical Concept The core concept of this invention is to use leachate membrane concentrate as the main washing medium for fly ash washing. By utilizing the high alkalinity of fly ash and the activated carbon components, the spontaneous precipitation of magnesium and heavy metals and the complete adsorption of COD in the membrane concentrate are simultaneously achieved during the washing process. After washing, only one stage of settling and one stage of sodium carbonate calcium removal are required to obtain refined brine that meets the requirements for evaporation and crystallization feed water. The evaporation condensate is preferentially reused for washing, and the surplus is returned to the leachate conditioning tank, forming a closed loop for the entire plant's water system.

[0036] 2. Complete process flow This invention adopts a technical route of three-stage washing + centralized purification of primary wash water + evaporation crystallization + closed-loop reuse of condensate, and the specific steps are as follows: Step 1: Three-stage washing and dechlorination • Third-stage washing: Using evaporated condensate (clean water) as the medium, the fly ash after secondary dechlorination is washed for 10-30 minutes with a liquid-to-solid ratio of 1-2:1, producing tertiary wash water and dechlorinated fly ash (chlorine content ≤1.0%).

[0037] • Second-stage washing: The tertiary wash water produced in the third stage is mixed with the leachate membrane concentrate (from the plant's leachate treatment system) at a volume ratio of 1:0.5 to 2 as the washing medium to wash the fly ash after the first-stage dechlorination. The washing time is 10 to 30 minutes, and the liquid-solid ratio is 2 to 4:1 (when the tertiary wash water and leachate membrane concentrate are mixed at a 1:1 ratio), producing secondary wash water.

[0038] • First-stage washing: Using the secondary wash water produced in the second stage as the washing medium, the incinerator ash is washed under the same conditions as above, producing primary wash water (high-salt concentrate, pH 11-12) and primary dechlorinated fly ash (entering the secondary washing stage). The synergistic effect occurring during the secondary and primary washing processes includes: Mg²⁺ in the membrane concentrate... + Under strongly alkaline conditions, Mg(OH)₂ precipitate is formed, and a large amount of SO₄²⁻ is present in the membrane concentrate. 2- With Ca² in fly ash + Precipitation occurs, reducing the Ca²⁺ content in subsequent treatments. + Concentration of Pb² in fly ash + Zn² + Cu² + Heavy metal ions are converted into hydroxide precipitates, and activated carbon in fly ash and COD in membrane concentrate are completely adsorbed.

[0039] Step 2: Deep calcium removal with sodium carbonate The supernatant from step 1 contains a high concentration of calcium ions (10,000–20,000 mg / L). Sodium carbonate solution is added (the dosage is 1.05–1.2 times the theoretical molar ratio), and the reaction time is 20–40 min, resulting in the formation of CaCO3 precipitate. The precipitate is dehydrated by plate and frame filtration, and the filter cake (high-purity calcium carbonate) can be sold as a fly ash carbonizing agent, desulfurizing agent, or building material raw material.

[0040] Step 3: Evaporation and crystallization of refined brine The filtrate from step 2 is a low-hardness, low-COD, high-concentration sodium chloride / potassium chloride brine, which enters the MVR evaporation crystallization system to recover sodium chloride and potassium chloride. The evaporation condensate enters the condensate tank.

[0041] Step 4: Condensate Reuse and Water Balance The evaporation condensate (COD < 10 mg / L, NH3-N < 5 mg / L, TDS < 50 mg / L) is preferentially supplied to the third-stage washing in step 1. Because the membrane concentrate is continuously introduced into the system, the condensate production exceeds the water required for the third-stage washing. All surplus condensate is recycled to the leachate equalization tank as dilution water for the leachate concentrate and is then incorporated into the plant's leachate treatment system for unified disposal. The system does not have a separate wastewater discharge outlet.

[0042] Alternative steps: Furthermore, when treating fly ash with high levels of heavy metals or requiring extremely high purity of crystalline salts, a deep heavy metal removal unit can be added after deep calcium removal. Organic sulfides (TMT-15) or sodium sulfide can be added, and the reaction time can be 15-30 minutes to ensure that the heavy metal concentration in the effluent is below 0.1 mg / L. Furthermore, when treating high COD membrane concentrate or low activated carbon fly ash, an ozone oxidation unit is added after sodium carbonate decalcification (or after the degravation unit if one is available). The residual COD is controlled below 50 mg / L through ozone aeration reaction for 10-20 minutes.

[0043] 3 Other preferred process modes This invention is not limited to three-stage washing. Depending on factors such as fly ash chlorine content, membrane concentrate production, and dechlorination requirements, two-stage or four-stage washing can also be used. As long as the principles of "using clean water (evaporated condensate) in the final stage" and "introducing the membrane concentrate in a non-final stage" are met, it falls within the scope of this invention. Two-stage washing is suitable for applications where the initial fly ash chlorine content is ≤10%, or the required chlorine content after dechlorination is ≤2%, or the membrane concentrate production is sufficient. Four-stage washing is suitable for applications where the initial fly ash chlorine content is >20%, or the required chlorine content after dechlorination is ≤0.5%, or where further reduction in washing water consumption is desired. The media distribution logic for two-stage and four-stage washing is the same as for three-stage washing, i.e., evaporated condensate is used in the final stage, the membrane concentrate is introduced in a non-final stage, and the first-stage wash water enters the purification system.

[0044] This invention uses leachate membrane concentrate as the main washing medium: Unlike the broad description of "usable saline wastewater" in existing technologies, this invention explicitly specifies the washing medium as landfill leachate membrane concentrate, based on its measured water quality characteristics (COD ≥ 1000 mg / L, Mg²⁺ ≥ 1000 mg / L, Mg²⁺ ≥ 1000 mg / L). + ≥500 mg / L, Pb≥10 μg / L, SO4 2- A synergistic processing pathway was designed for (≥10000mg / L, etc.).

[0045] This invention utilizes the self-alkalinity of fly ash to achieve zero-chemical precipitation of magnesium and heavy metals: the wash water pH is as high as 11-12, eliminating the need for any pH adjusters, thus allowing Mg²⁺ to precipitate. + Heavy metal ions such as Pb, Zn, and Cu form hydroxide precipitates.

[0046] This invention utilizes the activated carbon component in fly ash to achieve complete COD adsorption: the measured COD of the membrane concentrate was 1240 mg / L, and the COD of the filtrate after primary washing was below the detection limit (<10 mg / L), proving that the activated carbon in fly ash itself has a strong adsorption capacity for organic matter in the leachate concentrate, without the need to set up any advanced oxidation unit or biochemical treatment unit.

[0047] This invention achieves full reuse of condensate and system water balance: evaporation condensate is preferentially reused for washing, and the surplus is returned to the leachate equalization tank, where it is mixed with the original leachate solution and then enters the plant's leachate treatment system, realizing a closed-loop system for the incineration plant's water system with no process wastewater discharge.

[0048] This invention uses leachate membrane concentrate as the washing medium, incineration fly ash as the adsorption / precipitation carrier, and evaporation crystallization as the salt recovery method to achieve synergistic treatment of fly ash dechlorination and membrane concentrate disposal, solving the following technical problems: 1. High consumption of clean water for fly ash washing and high wastewater treatment costs; 2. High treatment costs and difficulties in resource utilization of leachate membrane concentrate; 3. Existing salt-containing wastewater washing technologies do not specifically address the high COD, high hardness, and heavy metal problems of membrane concentrate, as well as the complex purification process and high reagent consumption of washing liquid; 4. The system water balance cannot be closed-loop, and there is still wastewater discharge.

[0049] Example 1 A resource recovery system for the co-processing of fly ash and leachate membrane concentrate (three-stage water washing mode), using actual materials from a certain plant as an example: The water quality of the leachate STRO concentrate is shown in Table 1.

[0050] Table 1: Main Water Quality Indicators of Leachate STRO Concentrate

[0051] Three-stage washing: Third stage: condensate water washes the secondary ash, liquid-to-solid ratio 1.5:1, 30 min, filter press to obtain filter residue (chlorine <1%), and third-stage wash water.

[0052] Secondary: The tertiary wash water + membrane concentrate (3:2) is used to wash the primary ash to obtain secondary wash water.

[0053] First-level wash: The raw ash is washed with second-level wash water at a liquid-to-solid ratio of 2.5:1 to obtain first-level wash water (pH 11.7, COD not detected, Mg 1.2mg / L).

[0054] Calcium removal: Add Na2CO3 (1.1 equivalents) to the wash water, react for 30 min, and filter under pressure. The calcium content of the filtrate is ≤30 mg / L.

[0055] Heavy metal removal: After treatment with TMT-15, the heavy metal concentration in the clarified liquid is ≤0.1mg / L.

[0056] Evaporation and crystallization: The refined brine was evaporated via MVR to obtain sodium chloride and potassium chloride. The COD of the condensate was <10 mg / L.

[0057] Reuse: Condensate is preferentially supplied to the third-stage washing, and the surplus is returned to the leachate equalization tank.

[0058] Example 2 A resource recovery system for the co-treatment of fly ash and leachate membrane concentrate (two-stage washing mode) can be used for fly ash with low chlorine content (<12%) or low membrane concentrate production, as detailed below: • Second stage: Evaporation and condensation water are used to wash the first-stage dechlorinated ash, producing second-stage wash water and finished fly ash; • First stage: The secondary wash water is mixed with the membrane concentrate to wash the raw ash, producing the primary wash water (subsequent purification is the same as in Example 1).

[0059] This model requires lower equipment investment and is suitable for small and medium-sized incineration plants.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A resource recovery system for the co-treatment of fly ash and leachate membrane concentrate, comprising a washing unit for multi-stage countercurrent washing of fly ash, the washing unit including an n-stage water washing system, where n is a natural number not less than 2, and the water washing tank of the previous stage water washing system being connected to the filtrate tank of the next stage water washing system; characterized in that: A non-final stage water washing system has its washing tank connected to a leachate treatment system to introduce leachate membrane concentrate into the washing tank of the non-final stage water washing system. The filtrate tank of the first stage water washing system is equipped with a sedimentation and purification unit to add calcium removal agent to the filtrate tank of the first stage water washing system. The filtrate tank of the first stage water washing system is connected to a filter press and a MVR evaporation and crystallization system. The product water end of the MVR evaporation and crystallization system is connected to a condensate tank, which is connected to the washing tank of the final stage water washing system to use the condensate of the MVR evaporation and crystallization system as the washing medium of the final stage water washing system.

2. The fly ash and leachate membrane concentrate co-treatment resource utilization system according to claim 1, characterized in that: The filtrate tank of the first-stage washing system is equipped with a weight removal unit to control the heavy metal concentration by introducing sulfides into the filtrate tank of the first-stage washing system.

3. The fly ash and leachate membrane concentrate co-treatment resource recovery system according to claim 1, characterized in that: The filtrate tank of the first-stage water washing system is equipped with an ozone oxidation unit to control the COD concentration through ozone aeration reaction.

4. The fly ash and leachate membrane concentrate co-processing resource recovery system according to claim 1, characterized in that: The condensate tank is connected to the leachate equalization tank of the leachate treatment system to serve as dilution water for the leachate stock solution.

5. The fly ash and leachate membrane concentrate co-processing resource recovery system according to claim 1, characterized in that: The fly ash and leachate membrane concentrate co-processing resource recovery system does not have a separate wastewater discharge outlet.

6. The fly ash and leachate membrane concentrate co-processing resource recovery system according to claim 1, characterized in that: n=3, the washing unit includes a first-stage washing system, a second-stage washing system, and a third-stage washing system arranged sequentially; the first-stage washing system includes a first-stage washing tank, a first-stage slurry pump, a first-stage dewatering machine, and a first-stage filtrate tank arranged sequentially; the second-stage washing system includes a second-stage washing tank, a second-stage slurry pump, a second-stage dewatering machine, and a second-stage filtrate tank arranged sequentially, with the wet sludge outlets of the second-stage washing tank and the first-stage dewatering machine connected; the third-stage washing system includes a third-stage washing tank, a third-stage slurry pump, a third-stage dewatering machine, and a third-stage filtrate tank arranged sequentially, with the third-stage washing tank and the second-stage dewatering machine connected sequentially. The wet sludge outlet is connected; the secondary washing tank is connected to the tertiary filtrate tank and the leachate treatment system to use the tertiary washing water and leachate membrane concentrate for the secondary washing medium; the primary washing tank is connected to the secondary filtrate tank to use the secondary washing water for the primary washing medium; the primary filtrate tank is equipped with a sedimentation and purification unit to add calcium removal agent to the primary filtrate tank; the primary filtrate tank is connected to a filter press and a MVR evaporation crystallization system; the product water end of the MVR evaporation crystallization system is connected to a condensate tank; the condensate tank is connected to the tertiary washing tank and the leachate conditioning tank of the leachate treatment system.

7. The fly ash and leachate membrane concentrate co-treatment resource recovery system according to claim 1, characterized in that: The filtrate tank of the first-stage water washing system is equipped with a weight removal unit and an ozone oxidation unit arranged upstream and downstream.

8. A method for the co-processing and resource utilization of fly ash and leachate membrane concentrate, based on the co-processing and resource utilization system for fly ash and leachate membrane concentrate according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Multi-stage washing and dechlorination: Multi-stage countercurrent washing is performed on fly ash from municipal solid waste incineration. The first stage non-final stage washing uses landfill leachate membrane concentrate as the washing medium. The alkaline environment of the fly ash itself causes magnesium ions and heavy metal ions in the membrane concentrate to form hydroxide precipitates. The activated carbon components in the fly ash adsorb organic matter in the membrane concentrate, thereby achieving synergistic removal of fly ash dechlorination and membrane concentrate pollutants. S2. Calcium removal: Sodium carbonate is added to the filtrate tank of the first-stage water washing system to remove calcium ions, and then the precipitate is filtered out. The filtrate after filtration is refined brine. S3. Evaporation and Crystallization: The refined brine is evaporated and crystallized to separate and recover sodium chloride and / or potassium chloride resources, and evaporation condensate is generated; S4. Closed-loop reuse of condensate: The evaporated condensate is preferentially reused as the final washing water in step S1, and the remaining surplus condensate is returned to the landfill leachate equalization tank to achieve zero wastewater discharge from the system.

9. The method for co-processing and resource utilization of fly ash and leachate membrane concentrate according to claim 8, characterized in that: In step S1, the multi-stage countercurrent washing is a three-stage countercurrent washing, specifically including: First-stage washing: Using the secondary wash water generated from the second-stage washing as a medium, the incineration raw ash is washed to obtain first-stage dechlorinated fly ash and first-stage wash water; Second-stage washing: Using the mixture of tertiary wash water from the third-stage washing and landfill leachate membrane concentrate as a medium, the primary dechlorination fly ash from the first stage is washed to obtain secondary dechlorination fly ash and secondary wash water; Third-stage washing: Using evaporated condensate as a medium, the secondary dechlorinated fly ash produced in the second stage is washed to obtain the dechlorinated fly ash product and the third-stage wash water.

10. The method for co-processing and resource utilization of fly ash and leachate membrane concentrate according to claim 9, characterized in that: In the second stage of washing, the volume ratio of the tertiary wash water to the landfill leachate membrane concentrate is 1:0.5 to 2; the liquid-solid ratio of the first and second stages of washing is 2 to 4:1, and the washing time is 10 to 30 minutes.

11. The method for co-processing and resource utilization of fly ash and leachate membrane concentrate according to claim 8, characterized in that: In step S1, the water quality characteristics of the landfill leachate membrane concentrate are: COD ≥ 1000 mg / L, Mg²⁺ ≥ 1000 mg / L. + ≥500 mg / L, Pb≥10μg / L, SO4² - ≥10000 mg / L.

12. The method for co-processing and resource utilization of fly ash and leachate membrane concentrate according to claim 8, characterized in that: In step S2, the amount of sodium carbonate added is 1.05 to 1.2 times the theoretical calcium molar ratio, and the reaction time is 20 to 40 min; the resulting calcium carbonate precipitate is dehydrated by pressure filtration and then recycled as a by-product.

13. The method for co-processing and resource utilization of fly ash and leachate membrane concentrate according to claim 8, characterized in that: After step S2, a deep degravation step is also included: adding organic sulfides or sodium sulfide to the filtrate after calcium ion removal, reacting for 15-30 min, so that the concentration of heavy metal ions is lower than 0.1 mg / L.

14. The method for co-processing and resource utilization of fly ash and leachate membrane concentrate according to claim 8, characterized in that: The process after step S2 also includes an ozone oxidation step: ozone is introduced into the filtrate after calcium ion removal and the reaction is carried out for 10 to 20 minutes to control the residual COD to below 50 mg / L.

15. The method for co-processing and resource utilization of fly ash and leachate membrane concentrate according to claim 8, characterized in that: Multi-stage countercurrent washing is adjusted to 2 to 4 stages based on fly ash chlorine content, membrane concentrate volume, and dechlorination requirements. The higher the fly ash chlorine content or the higher the dechlorination requirements, the more washing stages are needed. When the fly ash chlorine content is low, the dechlorination requirements are low, and the membrane concentrate volume is sufficient, fewer washing stages are selected.

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