A method for the co-processing and resource utilization of waste from incineration power plants

Abstract

This invention proposes a method for the co-treatment and resource utilization of waste gas, wastewater, and solid waste generated during waste-to-energy incineration plants, belonging to the field of waste treatment and resource utilization technology. This invention utilizes leachate to wash away heavy metals and soluble chlorides from fly ash, employs an oxygen-free environment provided by flue gas, and performs low-temperature hot water hydrolysis on the fly ash to degrade dioxins in the fly ash and flue gas. The leachate is then used again for deep washing away residual heavy metals and soluble chlorides in the fly ash. CO2 from the flue gas is used for wet mineralization of the fly ash, allowing the CO2 to precipitate and separate heavy metals from the eluent. Membrane filtration and membrane evaporation technologies are used to recover KCl and NaCl from the concentrated eluent. This invention creatively solves the problems of high-salinity wastewater, solid waste resource utilization, and deep decarbonization of flue gas by co-treating and harmlessly utilizing the three wastes generated during the production process of waste-to-energy incineration plants: leachate, fly ash from municipal solid waste incineration, and flue gas.

Description

Technical Field

[0001] This invention belongs to the field of waste treatment and resource utilization technology, and particularly relates to a method for the co-processing and resource utilization of waste from incineration power plants. Background Technology

[0002] With the improvement of residents' living standards, the amount of municipal solid waste has increased rapidly. Due to its obvious advantages in volume reduction, stabilization and resource recovery, municipal solid waste incineration technology has been widely promoted in recent years. During the process of municipal solid waste incineration, power plants will generate solid, liquid and gaseous wastes such as leachate, fly ash and flue gas.

[0003] Landfill leachate contains high concentrations of ammonia nitrogen, COD, heavy metals, and organic matter. The chlorinated aromatic organics in the leachate are extremely difficult to biodegrade, and the high concentration of ammonia nitrogen further complicates matters. This results in low efficiency of conventional biological methods in destroying pollutants. While conventional physicochemical methods can effectively remove heavy metals from leachate, they are expensive and insufficient to simultaneously and effectively remove all organic matter in the leachate.

[0004] Municipal solid waste incineration fly ash refers to the fine particles emitted during waste incineration and collected by end-of-pipe dust collectors. It is rich in heavy metals and carcinogenic dioxins, exhibiting extremely high leaching toxicity. There are three main technical routes for the treatment and disposal of municipal solid waste incineration fly ash: solidification followed by hazardous waste landfilling, stabilization followed by sanitary landfilling, and resource utilization. Commonly used solidification and stabilization technologies include cement solidification, melt solidification, and chelation stabilization. After stabilization, the fly ash is disposed of in landfills. The entry cost for most hazardous waste treatment plants is over 1,000 yuan per ton of fly ash, and in some areas with scarce disposal sites, the cost can reach as high as 3,000 yuan per ton. Even after strict pretreatment before being disposed of in municipal solid waste landfills, the treatment cost is still as high as 500-1,000 yuan per ton, increasing the overall cost of municipal solid waste treatment by 80-300 yuan per ton. Therefore, developing fly ash resource utilization technologies and reducing fly ash landfill costs are currently a research hotspot and the mainstream development direction for incineration fly ash treatment and disposal technologies. Due to differences in production processes, grate furnace fly ash generally contains less than 2% SiO2 and Al2O3, and contains a large amount of soluble salts such as NaCl, KCl and CaClOH, which severely limits its value as an auxiliary cementitious material for traditional Portland cement and geopolymer cement.

[0005] Even after desulfurization and denitrification treatment, the flue gas produced by waste incineration often still contains excessive carbon dioxide. Direct release into the atmosphere will accelerate the greenhouse effect. How to make full use of the carbon dioxide in the flue gas is an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for the co-processing and resource utilization of three wastes from incineration power plants, thereby achieving the co-processing and resource utilization of leachate, fly ash, and flue gas generated during the incineration of municipal solid waste.

[0007] To achieve the above objectives, the present invention provides a method for the co-treatment and resource recovery of waste from incineration power plants, comprising the following steps:

[0008] S1. The fly ash from waste incineration and leachate are mixed and reacted through a three-stage countercurrent water washing device, and then solid-liquid separation is performed to obtain preliminary water-washed fly ash and water washing liquid;

[0009] S2. The preliminary water-washed fly ash obtained in step S1 is fed into a high-temperature and high-pressure reactor. Flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. After low-temperature hot hydrolysis reaction, centrifugation and solid-liquid separation are performed to obtain mineralized and detoxified fly ash, thus realizing resource utilization.

[0010] S3. The washing liquid obtained from solid-liquid separation in steps S1 and S2 is processed through a nanofiltration membrane to obtain a concentrated solution containing COD and heavy metals and a filtrate.

[0011] S4. The concentrated liquid obtained in step S3 and the remaining flue gas in step S2 are fed into a high-pressure reactor. The metal in the concentrated liquid is removed by supercritical CO2 precipitation to form metal carbonate precipitate. The solid metal carbonate precipitate is separated by centrifugation and then landfilled. The COD-containing concentrated liquid is injected back into the waste incinerator and the decarbonized flue gas is discharged under reduced pressure.

[0012] S5. The filtrate obtained in step S3 is treated by reverse osmosis membrane to remove monovalent salts. The high-salt concentrate enters the high-pressure reverse osmosis and thermal evaporation process, and then industrial salt is obtained through concentration and crystallization. The resulting clear liquid or condensate is discharged in compliance with standards.

[0013] Furthermore, the solid-liquid ratio of the fly ash from waste incineration to the leachate described in S1 is 1:(2-10) kg / L.

[0014] Furthermore, the temperature of the mixing reaction described in S1 is 25–55°C, the rotation speed is 120–200 rpm, and the pH is 4–5.

[0015] Furthermore, one or more of salicylic acid, citric acid, and acetic acid are added to adjust the pH to 4-5.

[0016] Furthermore, the solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate described in S2 is 1:(2~10) kg / L.

[0017] Furthermore, the temperature of the low-temperature hot water hydrolysis reaction described in S2 is 300–400°C, and the reaction time is 2–5 hours.

[0018] Furthermore, the pressure of the high-pressure reactor described in S4 is 7.5–8.5 MPa, and the temperature is 31–35 °C.

[0019] Furthermore, the fly ash from waste incineration is a product collected by the flue gas purification system during the incineration process of municipal solid waste.

[0020] Furthermore, the leachate is an acidic liquid produced when municipal solid waste is piled up for 5 to 7 days before incineration.

[0021] Furthermore, the flue gas is the compliant flue gas emitted by the flue gas purification system during the incineration of municipal solid waste.

[0022] More specifically, a method for the co-treatment and resource recovery of waste from incineration power plants includes the following steps:

[0023] S1. The fly ash from waste incineration and leachate are passed through a three-stage countercurrent water washing device. The solid-liquid ratio of the fly ash to the leachate is 1:(2-10) kg / L. Under the conditions of 25-55℃ and 120-200 rpm, one or more of salicylic acid, citric acid and acetic acid are added to adjust the pH to 4-5. The heavy metals and soluble salts in the fly ash from waste incineration are separated through the leachate. After mixing and reacting for 30 min-1 h, solid-liquid separation is carried out to obtain preliminary washed fly ash and washing liquid.

[0024] S2. The preliminary water-washed fly ash obtained in step S1 is fed into a high-temperature and high-pressure reactor. Flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. The solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate is 1:(2~10)kg / L. The temperature is maintained at 300~400℃ using the residual heat of steam, and the reaction time is maintained at 2~5h. The dioxins in the flue gas and fly ash are degraded, and the CO2 in the flue gas is used to mineralize the fly ash. After the low-temperature hot hydrolysis reaction, centrifugation and solid-liquid separation are performed to obtain mineralized and detoxified fly ash and water washing liquid, which are then used together with the bottom ash to achieve resource utilization.

[0025] S3. The washing liquid obtained from solid-liquid separation in steps S1 and S2 is treated with nanofiltration membrane (nanofiltration NF) to remove COD, ammonia nitrogen and heavy metals (HMs) to obtain a concentrated solution containing COD and heavy metals and a filtrate.

[0026] S4. The concentrated liquid obtained in step S3 is passed into a high-pressure reactor. The pressure of the high-pressure reactor is 7.5–8.5 MPa, and the temperature is 31–35°C. The remaining flue gas from step S2 is also passed into the high-pressure reactor. Under these conditions, supercritical CO2 is formed. The CO2 in the flue gas reacts with the Pb in the concentrated liquid. 2+ Cd 2+ Cu 2+ Zn 2+ Cr 3+ Heavy metals and divalent Ca 2+Mg 2+ Ions form metal carbonate precipitates. These precipitates are then separated by centrifugation, and the solids are stabilized and landfilled. The resulting concentrated COD-containing liquid is injected back into the incinerator to adjust the furnace temperature, slow coking, and reduce NO content in the flue gas. x Content, decarbonized flue gas reduced pressure emission;

[0027] S5. The filtrate obtained in step S3 is treated with a reverse osmosis membrane (RO) to remove monovalent salts NaCl and KCl. The high-salt concentrate enters the high-pressure reverse osmosis DTRO / HPRO and thermal evaporation MVR processes, and then KCl and NaCl industrial salts are obtained through concentration and crystallization. The clear liquid or condensate obtained from the RO, DTRO / HPRO, MVR and concentration processes meets the discharge standards.

[0028] This invention utilizes leachate to wash away heavy metals and soluble chlorides in fly ash. It also employs an oxygen-free environment provided by flue gas and low-temperature hot water hydrolysis to degrade dioxins in both the fly ash and flue gas. The leachate is then used again for deep washing away residual heavy metals and soluble chlorides in the fly ash, and CO2 from the flue gas is used for wet mineralization of the fly ash. Thirdly, CO2 from the flue gas is used to precipitate and separate heavy metals from the eluent, and membrane filtration and evaporation technologies are used to recover KCl and NaCl from the concentrated eluent. The final fly ash contains a total dioxin residue that meets the requirements of HJ 1134; the heavy metal leaching concentration meets the national standard GB 8978, allowing for resource utilization by mixing with bottom ash; the leachate is discharged in compliance with standards, and the concentrated leachate is re-injected into the furnace; and the CO2 volume fraction in the flue gas is reduced to below 2%.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] (1) This invention provides a synergistic solution for the harmless treatment and resource utilization of leachate, fly ash from municipal solid waste incineration, and flue gas generated during the production process of waste-to-energy plants. It creatively solves the problems of high-salt wastewater, solid waste resource utilization, and deep decarbonization of flue gas.

[0031] The method of this invention utilizes the weak acidity of a portion of the landfill leachate to perform a three-stage countercurrent water washing process on municipal solid waste incineration fly ash to remove more than 90% of the soluble salts and heavy metals. Then, the remaining leachate, washed fly ash, and flue gas are subjected to a low-temperature hot water hydrolysis process to further remove soluble salts and heavy metals from the fly ash and degrade dioxins in the fly ash and flue gas. Part of the CO2 in the flue gas is used to form mineralized detoxified fly ash, so that the total dioxin residue in the final fly ash meets the requirements of HJ 1134; the heavy metal leaching concentration meets the national standard GB 8978, and it can be mixed into the bottom ash for resource utilization.

[0032] The washing liquid produced by the three-stage countercurrent washing and low-temperature hot water hydrolysis process of this invention is rich in COD, ammonia nitrogen, and sodium. + K + Cl - Characterized by high levels of heavy metal ions and CO2 in flue gas, nanofiltration was used to separate a clear solution containing monovalent salts and a concentrated solution containing high COD and heavy metals. Furthermore, a supercritical CO2 reactor was used to promote the formation of supercritical CO2 in the flue gas, significantly increasing its solubility in the concentrated solution to over 30,000 ppm, thereby promoting the separation of heavy metals and calcium from the concentrated solution. 2+ Mg 2+ Ions produce carbonate precipitates, separating COD and ammonia nitrogen concentrate, which is then injected back into the incinerator furnace to adjust the furnace temperature, slow down coking, and reduce NO in the flue gas. x The content of carbon dioxide is reduced, and the flue gas is discharged under reduced pressure. The reduced amount of carbonate precipitate is stabilized and solidified before being landfilled. After supercritical CO2 deep decarbonization, the CO2 volume fraction of the flue gas is reduced to below 2%. The monovalent salt clear liquid after nanofiltration is further processed through reverse osmosis, high-pressure reverse osmosis, thermal evaporation and concentration processes to obtain separated and crystallized salts NaCl and KCl. The clear liquid is discharged or used as makeup water for a three-stage countercurrent water washing process and a high-temperature hot water hydrolysis process.

[0033] (2) The resource utilization method of the present invention does not require chemical consumption, which reduces the procurement costs of chelating agents for fly ash treatment and flocculants for leachate treatment in municipal solid waste incineration plants. It utilizes the heat energy of boiler flue gas and the electricity generated by incineration power generation, which is clean and environmentally friendly. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 This is a flowchart of the method for the co-treatment and resource utilization of waste from incineration power plants according to the present invention;

[0036] Figure 2 XRD mineral composition maps of the original fly ash, the mineralized and detoxified fly ash in Example 1 and Comparative Example 1. Detailed Implementation

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0039] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0040] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0041] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0042] This invention provides a method for the co-treatment and resource recovery of waste from incineration power plants (see flowchart). Figure 1 This includes the following steps:

[0043] S1. The fly ash from waste incineration and leachate are passed through a three-stage countercurrent water washing device. The heavy metals and soluble salts in the fly ash from waste incineration are separated by leachate. After mixing and reacting, solid-liquid separation is carried out to obtain preliminary washed fly ash and washing liquid.

[0044] S2. The preliminary water-washed fly ash obtained in step S1 is fed into a high-temperature and high-pressure reactor. Flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor to degrade dioxins in the flue gas and fly ash. The CO2 in the flue gas is used to mineralize the fly ash. After low-temperature hot hydrolysis reaction, centrifugation and solid-liquid separation are performed to obtain mineralized and detoxified fly ash, which is then used together with the bottom ash for resource utilization.

[0045] S3. The washing liquid obtained from solid-liquid separation in steps S1 and S2 is treated with nanofiltration membrane (nanofiltration NF) to remove COD, ammonia nitrogen and heavy metals (HMs) to obtain a concentrated solution containing COD and heavy metals and a filtrate.

[0046] S4. The concentrated liquid obtained in step S3 is passed into a high-pressure reactor, and the remaining flue gas from step S2 is also passed into the high-pressure reactor. Under these conditions, supercritical CO2 is formed, and the CO2 in the flue gas reacts with the Pb in the concentrated liquid. 2+ Cd 2+ Cu 2+ Zn 2+ Cr 3+ Heavy metals and divalent Ca 2+ Mg 2+ Ions form metal carbonate precipitates. These precipitates are then separated by centrifugation, and the solids are stabilized and landfilled. The resulting concentrated COD-containing liquid is injected back into the incinerator to adjust the furnace temperature, slow coking, and reduce NO content in the flue gas. x Content, decarbonized flue gas reduced pressure emission;

[0047] S5. The filtrate obtained in step S3 is treated by reverse osmosis membrane (RO) to remove monovalent salts NaCl and KCl. The high-salt concentrate enters the high-pressure reverse osmosis DTRO / HPRO and thermal evaporation MVR process, and then KCl and NaCl industrial salts are obtained through concentration and crystallization. The clear liquid or condensate obtained from RO, DTRO / HPRO, MVR and concentration processes meets the discharge standards.

[0048] In this embodiment of the invention, the solid-liquid ratio of the fly ash from waste incineration to the leachate in S1 is 1:(2-10) kg / L.

[0049] In this embodiment of the invention, the temperature of the mixing reaction in S1 is 25-55°C, the rotation speed is 120-200 rpm, and the pH is 4-5.

[0050] In this embodiment of the invention, one or more of salicylic acid, citric acid and acetic acid are added to adjust the pH to 4-5.

[0051] In this embodiment of the invention, the solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate in S2 is 1:(2~10)kg / L.

[0052] In this embodiment of the invention, the temperature of the low-temperature hot water hydrolysis degradation reaction in S2 is 300-400°C, and the reaction time is 2-5 hours.

[0053] In this embodiment of the invention, the pressure of the high-pressure reactor in S4 is 7.5-8.5 MPa, and the temperature is 31-35°C.

[0054] In this embodiment of the invention, the fly ash from waste incineration is a product collected by the flue gas purification system during the incineration of municipal solid waste.

[0055] In this embodiment of the invention, the landfill leachate is an acidic liquid produced when municipal solid waste is piled up for 5 to 7 days before incineration.

[0056] In this embodiment of the invention, the flue gas is the compliant flue gas emitted by the flue gas purification system during the incineration of municipal solid waste.

[0057] In the embodiments of the present invention, the three-stage countercurrent water washing device, high-temperature and high-pressure reactor, reverse osmosis (RO) process, nanofiltration (NF) treatment process, high-pressure reverse osmosis (DTRO / HPRO) and thermal evaporation (MVR) process used are all conventional technical devices and means in the field.

[0058] In this embodiment of the invention, the fly ash, leachate, and flue gas used in the waste incineration process specifically come from a waste-to-energy plant in Wuhan, and the technology employed is a grate furnace process. The content of characteristic pollutants in the fly ash, leachate, and flue gas is shown in Table 1.

[0059] Table 1. Content of characteristic pollutants from waste gas, wastewater, and solid waste in waste-to-energy plants

[0060]

[0061] The technical solution of the present invention will be further illustrated by the following embodiments.

[0062] Example 1

[0063] A method for the co-treatment and resource recovery of waste from incineration power plants includes the following steps:

[0064] S1. The fly ash from waste incineration and leachate are passed through a three-stage countercurrent water washing device (using the three-stage countercurrent water washing device for fly ash treatment disclosed in CN114798681A). The solid-liquid ratio of the fly ash from waste incineration and leachate is 1:8 (kg / L). Under the conditions of 35℃ and 180 rpm, salicylic acid is added to adjust the pH to 4. Heavy metals and soluble salts in the fly ash from waste incineration are separated by leachate. After mixing and reacting for 50 min, solid-liquid separation is performed to obtain preliminary washed fly ash and washing liquid.

[0065] S2. The preliminary water-washed fly ash obtained in step S1 is fed into a high-temperature and high-pressure reactor. Flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. The solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate is 1:8 (kg / L). The temperature is maintained at 380℃ using the residual heat of steam, and the reaction time is maintained at 3h. The dioxins in the flue gas and fly ash are degraded, and the fly ash is mineralized using CO2 in the flue gas. After low-temperature hot hydrolysis reaction, centrifugation and solid-liquid separation are performed to obtain mineralized and detoxified fly ash, which is then used together with the bottom ash for resource utilization.

[0066] S3. The washing liquid obtained from solid-liquid separation in steps S1 and S2 is treated with nanofiltration membrane (nanofiltration NF) to remove COD, ammonia nitrogen and heavy metals (HMs) to obtain a concentrated solution containing COD and heavy metals and a filtrate.

[0067] S4. The concentrated liquid obtained in step S3 is passed into a high-pressure reactor. The pressure of the high-pressure reactor is 8 MPa and the temperature is 32°C. The remaining flue gas from step S2 is also passed into the high-pressure reactor. Under these conditions, supercritical CO2 is formed. The CO2 in the flue gas reacts with the Pb in the concentrated liquid. 2+ Cd 2+ Cu 2+ Zn 2+ Cr 3+ Heavy metals and divalent Ca 2+ Mg 2+ Ions form metal carbonate precipitates. These precipitates are then separated by centrifugation, and the solids are stabilized and landfilled. The resulting concentrated COD-containing liquid is injected back into the incinerator to adjust the furnace temperature, slow coking, and reduce NO content in the flue gas. x Content, decarbonized flue gas reduced pressure emission;

[0068] S5. The filtrate obtained in step S3 is treated by reverse osmosis membrane (RO) to remove monovalent salts NaCl and KCl. The high-salt concentrate enters the high-pressure reverse osmosis DTRO / HPRO and thermal evaporation MVR process, and then KCl and NaCl industrial salts are obtained through concentration and crystallization. The clear liquid or condensate obtained from RO, DTRO / HPRO, MVR and concentration processes meets the discharge standards.

[0069] The determination results showed that the total dioxin residue in the mineralized and detoxified fly ash obtained in step S2 was 0.028 μg TEQ / kg, and the leaching concentrations of heavy metals Pb, Cd, Cu, Zn, and Cr were 0.07 mg / L, 0.08 mg / L, 0.01 mg / L, 0.1 mg / L, and 0.02 mg / L, respectively. The soluble chlorine content was 0.8%, meeting the pollution control requirements for fly ash treatment and disposal in the Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial) (HJ 1134—2020). The CO2 volume fraction in the decarbonized flue gas in step S4 was 1.5%, and the CO2 removal rate reached 91%. The COD and NH3 content in the clear liquid or condensate in step S5 were... 4- The concentrations of -N, turbidity, chloride ions, total Pb, total Cd, total Cu, total Zn, and total Cr were 44 mg / L, 0.8 mg / L, 4.7 NTU, 55 mg / L, 0.58 mg / L, 0.05 mg / L, 0.32 mg / L, 1.13 mg / L, and 0.61 mg / L, respectively, all of which were lower than the allowable discharge concentrations of the Integrated Wastewater Discharge Standard (GB 8978-1996).

[0070] Example 2

[0071] A method for the co-treatment and resource recovery of waste from incineration power plants includes the following steps:

[0072] S1. The fly ash from waste incineration and leachate are passed through a three-stage countercurrent water washing device. The solid-liquid ratio of the fly ash to the leachate is 1:2 (kg / L). At 25℃ and 200 rpm, citric acid is added to adjust the pH to 4. Heavy metals and soluble salts in the fly ash from waste incineration are separated by leachate. After mixing and reacting for 1 hour, solid-liquid separation is performed to obtain preliminary washed fly ash and washing liquid.

[0073] S2. The preliminary water-washed fly ash obtained in step S1 is fed into a high-temperature and high-pressure reactor. Flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. The solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate is 1:2 (kg / L). The temperature is maintained at 400℃ using the residual heat of steam, and the reaction time is maintained at 2h. The dioxins in the flue gas and fly ash are degraded, and the fly ash is mineralized using CO2 in the flue gas. After the low-temperature hot water hydrolysis degradation reaction, centrifugation and solid-liquid separation are performed to obtain mineralized and detoxified fly ash, which is then used together with the bottom ash to achieve resource utilization.

[0074] S3. The washing liquid obtained from solid-liquid separation in steps S1 and S2 is treated with nanofiltration membrane (nanofiltration NF) to remove COD, ammonia nitrogen and heavy metals (HMs) to obtain a concentrated solution containing COD and heavy metals and a filtrate.

[0075] S4. The concentrated liquid obtained in step S3 is passed into a high-pressure reactor at a pressure of 8.5 MPa and a temperature of 31°C. The remaining flue gas from step S2 is also passed into the high-pressure reactor. Under these conditions, supercritical CO2 is formed. The CO2 in the flue gas reacts with the Pb in the concentrated liquid. 2+ Cd 2+ Cu 2+ Zn 2+ Cr 3+ Heavy metals and divalent Ca 2+ Mg 2+ Ions form metal carbonate precipitates. These precipitates are then separated by centrifugation, and the solids are stabilized and landfilled. The resulting concentrated COD-containing liquid is injected back into the incinerator to adjust the furnace temperature, slow coking, and reduce NO content in the flue gas. x Content, decarbonized flue gas reduced pressure emission;

[0076] S5. The filtrate obtained in step S3 is treated by reverse osmosis membrane (RO) to remove monovalent salts NaCl and KCl. The high-salt concentrate enters the high-pressure reverse osmosis DTRO / HPRO and thermal evaporation MVR process, and then KCl and NaCl industrial salts are obtained through concentration and crystallization. The clear liquid or condensate obtained from RO, DTRO / HPRO, MVR and concentration processes meets the discharge standards.

[0077] The determination results showed that the total dioxin residue in the mineralized and detoxified fly ash obtained in step S2 was 0.011 μg TEQ / kg, and the leaching concentrations of heavy metals Pb, Cd, Cu, Zn, and Cr were 0.23 mg / L, 0.1 mg / L, 0.04 mg / L, 0.22 mg / L, and 0.10 mg / L, respectively. The soluble chlorine content was 1.37%, meeting the pollution control requirements for fly ash treatment and disposal in the Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial) (HJ 1134—2020). The CO2 volume fraction in the decarbonized flue gas in step S4 was 1.2%, and the CO2 removal rate reached 93%. The COD and NH3 content in the clear liquid or condensate in step S5 were... 4- The concentrations of -N, turbidity, chloride ions, total Pb, total Cd, total Cu, total Zn, and total Cr were 46 mg / L, 0.9 mg / L, 4.9 NTU, 51 mg / L, 0.40 mg / L, 0.07 mg / L, 0.32 mg / L, 0.58 mg / L, and 0.38 mg / L, respectively, all of which were lower than the allowable discharge concentrations of the Integrated Wastewater Discharge Standard (GB 8978-1996).

[0078] Example 3

[0079] A method for the co-treatment and resource recovery of waste from incineration power plants includes the following steps:

[0080] S1. The fly ash from waste incineration and leachate are passed through a three-stage countercurrent water washing device. The solid-liquid ratio of the fly ash to the leachate is 1:10 (kg / L). At 55℃ and 120 rpm, acetic acid is added to adjust the pH to 5. Heavy metals and soluble salts in the fly ash from waste incineration are separated by leachate. After mixing and reacting for 30 minutes, solid-liquid separation is performed to obtain preliminary washed fly ash and washing liquid.

[0081] S2. The preliminary water-washed fly ash obtained in step S1 is fed into a high-temperature and high-pressure reactor. Flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. The solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate is 1:10 (kg / L). The temperature is maintained at 300℃ using the residual heat of steam, and the reaction time is maintained at 5h. The dioxins in the flue gas and fly ash are degraded, and the fly ash is mineralized using CO2 in the flue gas. After the low-temperature hot water hydrolysis degradation reaction, centrifugation and solid-liquid separation are performed to obtain mineralized and detoxified fly ash, which is then used together with the bottom ash to achieve resource utilization.

[0082] S3. The washing liquid obtained from solid-liquid separation in steps S1 and S2 is treated with nanofiltration membrane (nanofiltration NF) to remove COD, ammonia nitrogen and heavy metals (HMs) to obtain a concentrated solution containing COD and heavy metals and a filtrate.

[0083] S4. The concentrated liquid obtained in step S3 is passed into a high-pressure reactor at a pressure of 7.5 MPa and a temperature of 35°C. The remaining flue gas from step S2 is also passed into the high-pressure reactor. Under these conditions, supercritical CO2 is formed. The CO2 in the flue gas reacts with the Pb in the concentrated liquid. 2+ Cd 2+ Cu 2+ Zn 2+ Cr 3+ Heavy metals and divalent Ca 2+ Mg 2+ Ions form metal carbonate precipitates. These precipitates are then separated by centrifugation, and the solids are stabilized and landfilled. The resulting concentrated COD-containing liquid is injected back into the incinerator to adjust the furnace temperature, slow coking, and reduce NO content in the flue gas. x Content, decarbonized flue gas reduced pressure emission;

[0084] S5. The filtrate obtained in step S3 is treated by reverse osmosis membrane (RO) to remove monovalent salts NaCl and KCl. The high-salt concentrate enters the high-pressure reverse osmosis DTRO / HPRO and thermal evaporation MVR process, and then KCl and NaCl industrial salts are obtained through concentration and crystallization. The clear liquid or condensate obtained from RO, DTRO / HPRO, MVR and concentration processes meets the discharge standards.

[0085] The determination showed that the total dioxin residue in the mineralized and detoxified fly ash obtained in step S2 was 0.048 μg TEQ / kg, and the leaching concentrations of heavy metals Pb, Cd, Cu, Zn, and Cr were not detected, 0.02 mg / L, not detected, 0.18 mg / L, and 0.03 mg / L, respectively. The soluble chlorine content was 0.5%, meeting the pollution control requirements for fly ash treatment and disposal in the Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial) (HJ 1134—2020). The CO2 volume fraction in the decarbonized flue gas in step S4 was 1.8%, and the CO2 removal rate reached 89%. The COD and NH3 content in the clear liquid or condensate in step S5 were... 4- The concentrations of -N, turbidity, chloride ions, total Pb, total Cd, total Cu, total Zn, and total Cr were 44 mg / L, 0.8 mg / L, 4.4 NTU, 66 mg / L, 0.37 mg / L, 0.03 mg / L, 0.10 mg / L, 0.42 mg / L, and 0.53 mg / L, respectively, all of which were lower than the allowable discharge concentrations of the Integrated Wastewater Discharge Standard (GB 8978-1996).

[0086] Comparative Example 1

[0087] Same as Example 1, except that in S2, the preliminary water-washed fly ash obtained in step S1 is introduced into a high-temperature and high-pressure reactor, and flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. The solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate is 1:1 (kg / L). The temperature is maintained at 380°C using residual steam heat, and the reaction time is maintained at 3 hours.

[0088] The determination showed that the total dioxin residue in the mineralized and detoxified fly ash obtained in step S2 was 0.07 μg TEQ / kg, and the leaching concentrations of heavy metals Pb, Cd, Cu, Zn, and Cr were 0.79 mg / L, 1.17 mg / L, 0.47 mg / L, 13.4 mg / L, and 2.37 mg / L, respectively. The soluble chlorine content was 11.3%. The leaching concentrations of Cd, Zn, and Cr, as well as the soluble chlorine content, exceeded the pollution control requirements for the treatment and disposal of fly ash from municipal solid waste incineration in the Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial) (HJ 1134—2020).

[0089] Comparative Example 2

[0090] Same as Example 1, except that in S2, the preliminary water-washed fly ash obtained in step S1 is introduced into a high-temperature and high-pressure reactor, and flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. The solid-liquid ratio of the preliminary water-washed fly ash to the landfill leachate is 1:8 (kg / L). The temperature is maintained at 200°C using the residual heat of steam, and the reaction time is maintained at 3 hours to degrade dioxins in the flue gas and fly ash. The CO2 in the flue gas is used to mineralize the fly ash. After low-temperature hot hydrolysis reaction, centrifugation and solid-liquid separation are performed to obtain mineralized and detoxified fly ash, which is then used together with the bottom ash for resource utilization.

[0091] The determination showed that the total dioxin residue in the mineralized and detoxified fly ash obtained in step S2 was 14.21 μg TEQ / kg, and the leaching concentrations of heavy metals Pb, Cd, Cu, Zn, and Cr were 0.08 mg / L, 0.08 mg / L, not detected, 0.13 mg / L, and 0.04 mg / L, respectively. The soluble chlorine content was 0.8%. The dioxin content exceeded the pollution control requirements for the treatment and disposal of fly ash from municipal solid waste incineration in the Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial) (HJ 1134—2020).

[0092] Comparative Example 3

[0093] Same as Example 1, except that in S4, the concentrated liquid obtained in step S3 is passed into a high-pressure reactor at a pressure of 5 MPa and a temperature of 32°C. The remaining flue gas from step S2 is also passed into the high-pressure reactor to form supercritical CO2 under these conditions. The CO2 in the flue gas reacts with the Pb in the concentrated liquid. 2+ Cd 2+ Cu 2+ Zn 2+Cr 3+ Heavy metals and divalent Ca 2+ Mg 2+ Ions form metal carbonate precipitates. These precipitates are then separated by centrifugation, and the solids are stabilized and landfilled. The resulting concentrated COD-containing liquid is injected back into the incinerator to adjust the furnace temperature, slow coking, and reduce NO content in the flue gas. x Content, decarbonized flue gas pressure reduction emission.

[0094] The CO2 volume fraction in the decarbonized flue gas of S4 was measured to be 14.5%, and the CO2 removal rate was 13%.

[0095] Comparative Example 4

[0096] Same as Example 1, except that in S4, the concentrated liquid obtained in step S3 is passed into a high-pressure reactor at a pressure of 8 MPa and a temperature of 25°C. The remaining flue gas from step S2 is also passed into the high-pressure reactor to form supercritical CO2 under these conditions. The CO2 in the flue gas reacts with the Pb in the concentrated liquid. 2+ Cd 2+ Cu 2+ Zn 2+ Cr 3+ Heavy metals and divalent Ca 2+ Mg 2+ Ions form metal carbonate precipitates. These precipitates are then separated by centrifugation, and the solids are stabilized and landfilled. The resulting concentrated COD-containing liquid is injected back into the incinerator to adjust the furnace temperature, slow coking, and reduce NO content in the flue gas. x Content, decarbonized flue gas pressure reduction emission.

[0097] The CO2 volume fraction in the decarbonized flue gas of S4 was measured to be 15.2%, and the CO2 removal rate was 9%.

[0098] The concentration results of characteristic pollutants in solid, liquid, and gaseous products in the examples and comparative examples are detailed in Table 2.

[0099] Table 2. Concentrations of characteristic pollutants in solid-liquid-gas products in the examples and comparative examples.

[0100]

[0101]

[0102] It can be seen that, compared with Example 1, Comparative Example 1 shows that the concentration of some heavy metals in the mineralized detoxified fly ash exceeds the standard, and the soluble chlorine content does not meet the requirements for fly ash resource utilization. This is because the solid-liquid ratio of the initial water-washed fly ash to the landfill leachate used was 1:1 (kg / L), which results in low leaching efficiency of the leachate for heavy metals and soluble chlorides in the fly ash. The XRD mineral composition maps of the original fly ash, the mineralized detoxified fly ash in Example 1, and Comparative Example 1 are shown below. Figure 2 ,from Figure 2 The XRD mineral analysis of the demineralized fly ash also shows that the fly ash in the comparative example still contains some sodium chloride and potassium chloride, while the demineralized fly ash in Example 1 only contains obvious calcium carbonate, quartz, calcium sulfate and amorphous aluminosilicates.

[0103] Compared with Example 1, Comparative Example 2 showed a higher level of dioxin residue in the detoxified fly ash, which was far higher than the requirements for fly ash resource utilization. This was because when using the low-temperature hot water decomposition process, the temperature was maintained at 200°C using waste steam heat, which was lower than the temperature requirement for supercritical water reaction, resulting in a sharp decrease in dioxin degradation efficiency.

[0104] Compared with Example 1, Comparative Example 3 showed a higher CO2 volume fraction in the decarbonized flue gas in S4. This was because the concentrated liquid obtained in S3 was fed into a high-pressure reactor. The pressure of the high-pressure reactor was 5 MPa, which was lower than the critical pressure of supercritical carbon dioxide. This reduced the diffusion and solubility of CO2 in water, thereby decreasing the ability of alkaline earth metals Ca, Mg and heavy metals in fly ash to capture CO2.

[0105] Compared with Example 1, Comparative Example 4 showed a higher CO2 volume fraction in the decarbonized flue gas in S4. This was because the concentrated liquid obtained in S3 was fed into a high-pressure reactor at a temperature of 25°C, lower than the critical temperature of supercritical carbon dioxide. This reduced the diffusion and solubility of CO2 in water, decreasing the capture capacity of alkaline earth metals (Ca), Mg, and heavy metals in the fly ash for CO2. In summary, the total dioxin residue in the fly ash obtained in the embodiments of this invention meets the requirements of HJ 1134; the heavy metal leaching concentration meets the national standard GB 8978, allowing for resource utilization by mixing with bottom ash; the leachate meets discharge standards, and the concentrated liquid is reinjected into the furnace; the CO2 volume fraction in the flue gas is reduced to below 2%. Furthermore, the treatment process requires no chemical consumption, reducing the procurement costs of chelating agents for fly ash treatment and flocculants for leachate treatment in municipal solid waste incineration plants. It utilizes the boiler's flue gas heat and the electricity generated from incineration power generation, making it clean and environmentally friendly.

[0106] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for the co-treatment and resource utilization of waste from incineration power plants, characterized in that, Includes the following steps: S1. The fly ash from waste incineration and leachate are mixed and reacted through a three-stage countercurrent water washing device, and then solid-liquid separation is performed to obtain preliminary water-washed fly ash and water washing liquid; S2. The preliminary water-washed fly ash obtained in step S1 is fed into a high-temperature and high-pressure reactor. Flue gas and landfill leachate are introduced into the high-temperature and high-pressure reactor. After low-temperature hot hydrolysis reaction, centrifugation and solid-liquid separation are performed to obtain mineralized detoxified fly ash and water-washing liquid, thereby realizing resource utilization. S3. The washing liquid obtained from solid-liquid separation in steps S1 and S2 is processed through a nanofiltration membrane to obtain a concentrated solution containing COD and heavy metals and a filtrate. S4. The concentrated liquid obtained in step S3 and the remaining flue gas in step S2 are fed into a high-pressure reactor. The metal in the concentrated liquid is removed by supercritical CO2 precipitation to form metal carbonate precipitate. The solid metal carbonate precipitate is separated by centrifugation and then landfilled. The COD-containing concentrated liquid is injected back into the waste incinerator and the decarbonized flue gas is discharged under reduced pressure. S5. The filtrate obtained in step S3 is treated by reverse osmosis membrane to remove monovalent salts. The high-salt concentrate enters the high-pressure reverse osmosis and thermal evaporation process, and then is concentrated and crystallized to obtain industrial salt. The resulting clear liquid or condensed clear liquid meets the discharge standards. The solid-liquid ratio of the preliminary washed fly ash to the landfill leachate described in S2 is 1:(2~10)kg / L; The temperature of the low-temperature hot water hydrolysis reaction described in S2 is 300-400℃, and the reaction time is 2-5h; The pressure of the high-pressure reactor described in S4 is 7.5–8.5 MPa, and the temperature is 31–35 °C.

2. The method for co-processing and resource utilization of waste from incineration power plants according to claim 1, characterized in that, The solid-liquid ratio of the fly ash from waste incineration to the leachate described in S1 is 1:(2~10) kg / L.

3. The method for co-processing and resource utilization of waste from incineration power plants according to claim 1, characterized in that, The mixing reaction described in S1 is carried out at a temperature of 25–55°C, a rotation speed of 120–200 rpm, and a pH of 4–5.

4. The method for co-processing and resource utilization of waste from incineration power plants according to claim 3, characterized in that, Add one or more of salicylic acid, citric acid, and acetic acid to adjust the pH to 4-5.

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