Waste incineration fly ash harmless treatment method and system based on low-temperature plasma

Abstract

The invention discloses a waste incineration fly ash innocent treatment method and system based on low-temperature plasma, and belongs to the technical field of dangerous solid waste treatment.The waste incineration fly ash innocent treatment method comprises the steps that fly ash and a silicon-aluminum-based conditioner are mixed and granulated and then placed in a low-temperature plasma reactor, and treatment is conducted with air as a discharge medium; high-energy electrons and active free radicals generated by plasmas are utilized to synchronously realize efficient decomposition and mineralization of dioxin organic pollutants in the fly ash and reduction and stable solidification of heavy metal ions; the treated tail gas containing the active substances is cyclically degraded through a cyclone separator, and solid products can be used as safe building material resources; according to the method, one-stop deep detoxification of two typical pollutants in the fly ash is realized, the treatment temperature is low, the energy consumption is low, secondary pollution is avoided, and an efficient solution is provided for safe treatment and value-added utilization of the waste incineration fly ash.

Description

Technical Field

[0001] This invention relates to the field of hazardous solid waste treatment and resource utilization technology, specifically to a method and system for the harmless treatment of fly ash from waste incineration based on low-temperature plasma. Background Technology

[0002] Fly ash from municipal solid waste incineration is fine particulate matter that accumulates pollutants (such as heavy metals and dioxins) during the incineration of municipal solid waste. It contains highly leaching toxic heavy metals (such as Pb, Cd, Cr, Zn, etc.) and highly toxic persistent organic pollutants (such as dioxins). If not properly disposed of, it will pose a serious and long-term potential risk to the ecological environment and human health.

[0003] Currently, industrial treatment technologies for fly ash mainly focus on stabilization / solidification and high-temperature conversion pathways, but significant technical bottlenecks remain. Cement-based solidification / stabilization technologies (such as CN101823762A and US20110085965A1) immobilize pollutants through physical encapsulation and partial chemical bonding, but their compatibilization effect is significant, long-term stability is greatly affected by environmental pH, and they are ineffective against dioxin-like organic pollutants. Chemical stabilization technologies (such as CN102380454B) use chelating agents and other chemical agents to form insoluble chelates with heavy metals. This method generally exhibits selectivity differences in complex systems where different types of heavy metals coexist, and it cannot fundamentally degrade organic pollutants. The cost of the agents and long-term stability are limiting factors. High-temperature melting / vitrification technology (such as JP 2000-254720A and WO2008020852A1) melts fly ash into a glassy substance at temperatures exceeding 1300°C, which can efficiently solidify heavy metals and decompose dioxins. However, this technology faces problems such as extremely high energy consumption, severe equipment corrosion, and the potential generation of secondary fly ash and volatile heavy metal emissions. Its economic efficiency and operational complexity limit its large-scale application.

[0004] Low-temperature plasma technology, as an emerging pollutant treatment technology, can generate high-density high-energy electrons, active free radicals, and excited-state particles under near-room to intermediate temperature conditions, providing a potential pathway for the simultaneous degradation of organic pollutants and passivation of heavy metals. On the one hand, the active particles generated by this technology can directly break down the molecular structure of organic pollutants such as dioxins in fly ash, ultimately mineralizing them completely into CO2, H2O, and small-molecule inorganic substances, eliminating their toxicity and environmental risks at the source. On the other hand, under specific catalytic conditions (such as silicon-aluminum based), the plasma process can achieve dual physicochemical locking and even deep stabilization of heavy metals. Currently, this technology has been explored in the purification of gaseous pollutants (such as CN105536532A) and wastewater treatment, but for complex solid hazardous wastes like fly ash, how to construct an efficient, uniform, and engineerable treatment process system remains a technical challenge in this field. Specifically, existing low-temperature plasma technology lacks methods for effectively pretreating fly ash materials to adapt to plasma reactors, as well as methods for optimizing the reaction atmosphere and energy transfer to simultaneously achieve deep stabilization of heavy metals and complete mineralization of dioxins, while ensuring the feasibility of resource utilization of the treated products. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method and system for harmless treatment of waste incineration fly ash based on low-temperature plasma, which has low energy consumption, thorough treatment, no secondary pollution, and can realize fly ash resource utilization, while simultaneously promoting the stabilization of heavy metals in fly ash and the efficient decomposition of dioxin-like organic pollutants.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for harmless treatment of fly ash from waste incineration based on low-temperature plasma includes the following steps: S1, mix and granulate the fly ash from waste incineration with a silicon-aluminum based conditioner to form homogeneous particles; S2, The homogeneous particles are placed in a low-temperature plasma reactor and subjected to low-temperature plasma treatment in a non-oxidizing atmosphere; S3 utilizes highly active particles generated by plasma to simultaneously decompose and mineralize dioxin-like pollutants and stabilize heavy metals in fly ash. S4 collects the processed solid products and uses a cyclone separator to recycle the exhaust gas.

[0007] The silica-aluminum based conditioning agent mentioned in step S1 is one or more of metakaolin, silica fume, and bentonite, and the amount added is 5%-15% of the fly ash mass; the particle size of the resulting particles is 10-50μm.

[0008] In step S2, the non-oxidizing atmosphere is air; the low-temperature plasma is generated by DC corona discharge, the plasma power density is 1-3 W / cm³, the processing time is 10-30 minutes, and the temperature of the reaction zone is controlled at 80℃.

[0009] The stabilization of heavy metals in step S3 includes reduction, encapsulation by a glassy phase, or embedding in a newly formed aluminosilicate mineral lattice.

[0010] The solid product processed in step S4 is utilized as artificial aggregate or building material admixture.

[0011] A waste incineration fly ash harmless treatment system based on low-temperature plasma includes: Pretreatment unit: includes a mixing and granulating machine 1, used for mixing and granulating fly ash to promote its transport and reaction; Feeding and distributing unit: including hopper 2 and feeder 3 for conveying pretreated fly ash particles to plasma reactor; Core reaction unit: includes plasma reactor 4, used to generate plasma and treat fly ash; Atmosphere control system: The centrifugal fan 5 provides power for fly ash and precisely controls the processing atmosphere within the plasma reactor 4; Plasma power supply and matching network: Provides DC high voltage power supply 6, and is equipped with frequency converter voltage regulation network to control the voltage output 5kV-35kV; The recycling unit includes a cyclone separator 7, which is used to separate the gas and solids of the fly ash after plasma treatment. The treated fly ash is discharged and collected through the solid outlet 9. The gas contains some oxidizing gas and active free radicals, and then enters the plasma reactor again through the tail gas outlet 8 for reaction. Product collection and cooling unit: including product collection bin 10, after which the treated fly ash is cooled and utilized as a resource.

[0012] The plasma reactor 4 is a corona discharge reactor.

[0013] The plasma reactor 4 is equipped with a cage-shaped coaxial cylindrical electrode, and the electrode surface is covered with an alumina ceramic dielectric layer 13; the outer wall of the reactor is equipped with a heating and insulation device.

[0014] Compared with the prior art, the present invention has the following significant advantages: 1. Highly efficient detoxification and simultaneous treatment: The high-energy electrons and active free radicals generated by low-temperature plasma can simultaneously attack heavy metals and dioxins, achieving a "one-stop" solution for heavy metal stabilization and organic pollutant decomposition. The dioxin decomposition rate can reach over 99%, and the heavy metal leaching concentration is far below the limit of the "Pollution Control Standard for Municipal Solid Waste Landfills".

[0015] 2. Low temperature and energy saving, avoiding sintering: The core reaction temperature is significantly lower than that of the high temperature melting method, reducing energy consumption by 70%-80%, and avoiding problems such as fly ash melting and kiln formation caused by high temperature and secondary fly ash generation.

[0016] 3. No secondary pollution: The process is carried out in a fully enclosed system and under a high-voltage electric field, which effectively inhibits the resynthesis of dioxins; the exhaust gas is recycled and there are no harmful gas emissions.

[0017] 4. Resource recovery: The treated fly ash particles have stable physical and chemical properties, and the heavy metals are firmly solidified. They can be directly used as safe and environmentally friendly building materials, realizing the value-added transformation of hazardous waste, which is in line with the concept of circular economy.

[0018] 5. Strong system adaptability: The process parameters are adjustable and can adapt to the fly ash treatment needs of different sources and compositions. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the method and system of an embodiment of the present invention.

[0020] Figure 2 The diagram shows the structure of the low-temperature plasma discharge reactor in this embodiment of the invention, where (a) is a top view, (b) is a cross-sectional view, and (c) is an overall structural diagram.

[0021] In the diagram: 1 is the mixing granulator, 2 is the silo, 3 is the feeder, 4 is the plasma reactor, 5 is the centrifugal fan, 6 is the DC high voltage power supply, 7 is the cyclone separator, 8 is the exhaust gas outlet, 9 is the solid outlet, 10 is the product collection bin, 11 is the high voltage electrode, 12 is the grounding electrode, and 13 is the dielectric layer. Detailed Implementation

[0022] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0023] Example 1, referring to Figure 1 A waste incineration fly ash harmless treatment system based on low-temperature plasma constructs a highly efficient, controllable, and uniformly processed closed-loop plasma reaction environment, integrating complete pretreatment and post-treatment units to form a safe, closed-loop industrial processing flow, including: Pretreatment unit: includes a mixing granulator 1, used for conditioning and forming fly ash; Feeding and distributing unit: The unit uses hopper 2 for storage and feeder 3, which is either a screw feeder or a vibrating distributor to ensure that fly ash particles are evenly distributed in the plasma reactor. Core reaction unit: includes plasma reactor 4, which is preferably a corona discharge reactor; see reference Figure 2The plasma reactor 4 is equipped with a cage-type multi-stage discharge structure, in which the high-voltage electrode 11 is connected to a DC high-voltage power supply 6, and the grounding electrode 12 is connected to a 50cm grounding wire. The surface of the high-voltage electrode 11 is coated with a wear-resistant dielectric layer 13 (such as alumina ceramic). The outer wall of the reactor is equipped with a heat preservation and heating device to help control the temperature of the reaction zone below 80℃. Atmosphere control system: The centrifugal fan 5 provides power for fly ash and precisely controls the processing atmosphere within the plasma reactor 4; Plasma power supply and matching network: Provides DC high voltage power supply 6, and is equipped with frequency converter voltage regulation network to control the voltage output 5kV-35kV; The recycling unit includes a cyclone separator 7, which is used to separate the gas and solids of the fly ash after plasma treatment. The treated fly ash is discharged and collected through the solid outlet 9. The gas contains some oxidizing gas (mainly O3) and active free radicals, and then enters the plasma reactor 4 again through the tail gas outlet 8 for reaction. Product collection and cooling unit: including product collection bin 10, after which the treated fly ash is cooled and utilized as a resource.

[0024] A method for the harmless treatment of fly ash from waste incineration based on low-temperature plasma utilizes the synergistic effect of non-equilibrium low-temperature plasma and process conditions to achieve simultaneous, efficient, and thorough removal and stabilization of heavy metals and organic pollutants, including the following steps: S1 Fly Ash Pretreatment and Conditioning: Waste incineration fly ash is uniformly mixed with a silica-alumina based conditioner and water, and granulated into homogeneous particles of 10-50 μm; the silica-alumina based conditioner is selected from one or more of metakaolin, silica fume, and bentonite, and the addition amount is 5%-15% of the fly ash mass; S2 Low-Temperature Plasma Treatment: Pretreated and conditioned fly ash particles are driven into the low-temperature plasma reactor by air and treated in a non-equilibrium low-temperature plasma environment. The treatment atmosphere is air, the plasma power density is 1-3W / cm³, and the treatment time is 10-30 minutes. S3 Stabilization and Activation: After low-temperature plasma treatment, fly ash particles are bombarded by active particles and subjected to heat treatment, resulting in the breakdown and deconstruction of dioxin-like molecules by high-energy electrons and free radicals, ultimately mineralizing into CO2, H2O and small molecule inorganic substances; heavy metal compounds are encapsulated by high-energy electrons or enter the silicon-aluminum network structure formed by the conditioning agent through ion intercalation, forming a chemically stable mineral phase with a low leaching rate; S4 exhaust gas recycling and product collection: The exhaust gas generated during the stabilization and activation process contains O3 and active free radicals, which are recycled into the plasma reactor for secondary utilization to degrade dioxins; the degraded fly ash particles are cooled and then used as artificial aggregates or building material admixtures for resource utilization.

[0025] In this embodiment, fly ash from a municipal solid waste incineration plant (original Pb leaching concentration 8.5 mg / L, Cd leaching concentration 2.1 mg / L, dioxin toxicity equivalent concentration 12.2 μg TEQ / kg) was taken; 10% metakaolin and 12% water were added, and the mixture was added to a mixing granulator 1 for uniform extrusion and granulation into particles with a diameter of approximately 10-50 μm; a centrifugal fan 5 was turned on to use air as the carrier gas, with a flow rate controlled at 40 L / min; a DC high-voltage power supply 6 was started to apply an AC current of 16 kV to generate uniform low-temperature plasma; the temperature of the reaction zone was maintained at approximately 80°C, and the treatment time was 30 minutes; the fly ash particles were uniformly fed into the plasma reactor 4 at a rate of 8 kg / min by controlling the hopper 2 and the feeder 3; after treatment, samples were taken for testing. The results showed that the dioxin toxicity equivalent concentration in the fly ash particles decreased to below 50 ng TEQ / kg, and the decomposition rate was >99.99%. According to the "Solid Waste Leaching Toxicity Leaching Method - Acetic Acid Buffer Solution Method", the Pb leaching concentration was reduced to below 0.1 mg / L and the Cd leaching concentration was reduced to below 0.05 mg / L, both meeting the standards for safe landfilling and even resource utilization. The treated particles have a compressive strength of over 15 MPa and can be used as lightweight aggregate.

[0026] Example 2: This example describes a waste incineration fly ash harmless treatment system based on low-temperature plasma, which is the same as Example 1. The difference in the method for harmless treatment of waste incineration fly ash based on low-temperature plasma is that the silica-alumina based conditioning agent in step S1 is silica fume, and the amount added is 5% of the fly ash mass; the plasma power density in step S2 is 1 W / cm³, and the treatment time is 30 minutes. The effect of this example is similar to that of Example 1.

[0027] Example 3: This example describes a waste incineration fly ash harmless treatment system based on low-temperature plasma, which is the same as that in Example 1. The difference in the method for harmless treatment of waste incineration fly ash based on low-temperature plasma is that the silicon-aluminum based conditioning agent in step S1 is bentonite, and the amount added is 15% of the fly ash mass; the plasma power density in step S2 is 3W / cm³, and the treatment time is 10 minutes. The effect of this example is similar to that of Example 1.

Claims

1. A method for non-hazardous treatment of waste incineration fly ash based on low-temperature plasma, characterized in that, The method comprises the following steps: S1. mixing and granulating the waste incineration fly ash with a silicon-aluminum-based conditioning agent to form homogeneous particles; S2. placing the homogeneous particles in a low-temperature plasma reactor for low-temperature plasma treatment in a non-oxidizing atmosphere; S3. using the high-activity particles generated by the plasma to simultaneously achieve the decomposition and mineralization of dioxin pollutants and the stabilization of heavy metals in the fly ash; S4. collecting the treated solid product and recycling the tail gas by using a cyclone separator.

2. The method of claim 1, wherein: The silicon-aluminum-based conditioning agent in step S1 is one or more of metakaolin, silica fume and bentonite, and the addition amount is 5%-15% of the mass of the fly ash; the particle size of the granules is 10-50 μm.

3. The method of claim 1, wherein: In step S2, the non-oxidizing atmosphere is air; the low-temperature plasma is generated by direct-current corona discharge, the plasma power density is 1-3 W / cm³, the treatment time is 10-30 minutes, and the reaction zone temperature is controlled at 80°C.

4. The method of claim 1, wherein: In step S3, the stabilization of the heavy metals includes being reduced, being wrapped by a glass phase or being embedded in the crystal lattice of newly generated silicate minerals.

5. The method of claim 1, wherein: In step S4, the treated solid product is used as artificial aggregate or building material admixture for resource utilization.

6. A low temperature plasma based waste incineration fly ash decontamination system for implementing the method of any one of claims 1-5, characterized in that, It comprises: a pretreatment unit comprising a mixing and granulating machine (1) for mixing and granulating the fly ash to facilitate its transportation and reaction; a feeding and distribution unit comprising a silo (2) and a feeder (3) for conveying the pretreated fly ash particles to the plasma reactor; a core reaction unit comprising a plasma reactor 4, which is a corona discharge reactor, for generating plasma and treating the fly ash; an atmosphere control system for providing fly ash power by using a centrifugal fan (5) and accurately controlling the treatment atmosphere in the plasma reactor (4); a plasma power supply and matching network for providing a direct-current high-voltage power supply (6) and being equipped with a variable-frequency voltage regulation network to control the voltage output of 5kV-35kV; a circulating treatment unit comprising a cyclone separator (7) for gas-solid separation of the fly ash after plasma treatment, the treated fly ash is discharged from the solid outlet (9) for collection, and the gas containing part of the oxidizing gas and active free radicals is introduced into the plasma reactor again through the tail gas outlet (8) for reaction; a product collection and cooling unit comprising a product collection silo (10) for resource utilization of the treated fly ash after self-cooling.

7. The system of claim 6, wherein: The plasma reactor (4) is a corona discharge reactor.

8. The system of claim 6, wherein: The plasma reactor (4) is provided with a squirrel-cage type coaxial cylindrical electrode, and the surface of the electrode is covered with an alumina ceramic dielectric layer (13); the outer wall of the reactor is provided with a heating and heat preservation device.

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