Process for fly ash innocuous treatment
By combining wet grinding and citric acid treatment with mechanical equipment, dioxins and heavy metals in fly ash are degraded to form stable, harmless fly ash solids. This solves the problem of high equipment cost in existing high-temperature melting methods and achieves efficient and low-cost harmless treatment of fly ash.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHUANGZHIXIN (SHANGHAI) ENVIRONMENTAL PROTECTION TECH CO LTD
- Filing Date
- 2025-02-12
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies are difficult to efficiently and economically treat dioxins and heavy metals in fly ash from waste incineration, and the high-temperature reducing atmosphere melting method has high equipment costs, making it difficult to industrialize.
Fly ash was ground to 2-5 μm using a wet grinding method. Citric acid solution was added, stirred, ground, and dried. CaO and Ca(OH)2 were added, and dioxins and heavy metals were degraded through mechanical disturbance and chemical reaction using mechanical equipment. Finally, a curing agent was added to form a stable and harmless solidified fly ash.
It achieves efficient and low-cost harmless treatment of fly ash. The equipment is simple and easy to operate, green and environmentally friendly, with no sewage, smoke, dust and exhaust gas emissions. It is suitable for automated production, with high processing efficiency and low power consumption.
Smart Images
Figure CN119870101B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of solid waste treatment technology, and more specifically, to a process for the harmless treatment of fly ash. Background Technology
[0002] With the widespread application of incineration technology in hazardous waste treatment, fly ash treatment from hazardous waste incineration plants has become a research hotspot and challenge in the environmental field. This is because fly ash is produced in large quantities and contains a large amount of heavy metals, salts, and highly toxic dioxins, classifying it as HW18 in the National Hazardous Waste List. Therefore, fly ash must be disposed of according to hazardous waste standards, and it must undergo harmless treatment before it can be utilized as a resource.
[0003] The production of fly ash is related to the type of waste, incineration conditions, incinerator type, and flue gas treatment process, generally accounting for about 3% to 5% of the total waste incineration. Due to the continuous generation of municipal solid waste, waste-to-energy incineration plants operate at high capacity year-round, increasing the emission and treatment needs of pollutants such as nitrogen oxides, dioxins, fly ash, and odorous gases. If not properly managed, this will lead to environmental problems and social impacts; therefore, measures must be taken to promote the coordinated development of waste incineration capacity and the harmless disposal technology of incineration fly ash.
[0004] Municipal solid waste incineration fly ash is a highly alkaline fly ash with a pH value of around 13, a surface area of 13.05 m² / g, and a dioxin toxicity equivalent of 87-200 nanograms per kilogram. The chloride (Cl) content in the fly ash reaches 20-40%.
[0005] Currently, no waste incineration plant has a completely effective technology to fully solve the problem of harmless treatment and resource recycling of fly ash. Existing research shows that melting treatment can completely decompose dioxins in fly ash, and low-boiling-point heavy metals and their compounds contained in fly ash volatilize and transfer to the air, while the remaining metals transfer to glass slag. High-temperature oxidizing atmosphere melting treatment requires either specially designed equipment or the use of pelletizing shaft furnaces, sintering furnaces, or steelmaking converters in ironmaking equipment. However, when using high-temperature oxidizing atmosphere melting treatment, at melting temperatures above 800℃, all trivalent chromium in heavy metals will be converted to hexavalent chromium. Hexavalent chromium is a poisonous substance that can be ingested / extremely toxic by inhalation. Skin contact may cause allergies and may even cause genetic defects. Inhalation may cause cancer and poses a persistent danger to the environment, which is not permitted under domestic and international environmental protection standards. High-temperature reducing atmosphere melting can effectively avoid this problem. However, current high-temperature reducing atmosphere melting methods both domestically and internationally use specialized high-temperature reducing atmosphere melting equipment, but the construction and operating costs of this equipment are extremely high, making industrial-scale implementation difficult. This limits the harmless treatment of fly ash from waste.
[0006] Patent CN106734099A discloses a process for high-temperature harmless treatment of waste incineration fly ash using secondary material composite technology, which includes the following steps: (1) using waste incineration fly ash as the core material, adding a reducing agent containing C, or further adding a chlorine absorbent containing CaO and / or additives, and forming a core under the action of a binder; the dry basis weight ratios of the waste incineration fly ash, reducing agent, chlorine absorbent, and additives are 50-80%, 10-30%, 0-6%, and 0-15%, respectively; (2) forming a chlorine absorbent layer on the outside of the core with the chlorine absorbent containing CaO under the action of a binder. The shielding layer forms a pellet, and the amount of chlorine absorbent accounts for 3-10% of the weight of the dry-based composite pellet; (3) the pellets made in step (2) and the shell material are coated with a shell on the outside of the pellet making equipment under the action of the adhesive to form a secondary material composite pellet; the shell material is made of non-toxic and harmless materials and other additives; (4) the secondary material composite pellets are finally put into the incineration device for incineration and high-temperature harmless treatment; the incineration device is a metallurgical sintering machine or a solid waste harmless incineration device; the moisture content of the core is controlled at 18-28%, the core diameter is 1-3 mm, the compressive strength is greater than 7 N / piece, and the drop strength is greater than 20 times / piece. Although this process effectively solves the above problems, it is necessary to add chlorine absorbent and C-containing reducing agent or fluxing additive before forming the core, and it is necessary to form pellets again after pre-coating. The process is relatively complicated and cumbersome, which is not conducive to saving time and space. The required equipment occupies a large area and is not suitable for construction in a waste incineration plant with a small open space. Summary of the Invention
[0007] To address the aforementioned problems, this application provides a process for the harmless treatment of fly ash.
[0008] The fly ash harmless treatment process provided in this application adopts the following technical solution:
[0009] A process for harmless treatment of fly ash, the process comprising the following steps:
[0010] S1. The fly ash is pretreated by sieving to remove large particles and added to the first grinding device. Water is used as the medium to grind the fly ash to an average particle size of 2-5 μm using wet grinding method, so as to obtain a fly ash slurry with a water content of 20%-30%.
[0011] S2. Dissolve anhydrous citric acid in deionized water to prepare a citric acid aqueous solution with a concentration of 30-45%.
[0012] S3. Mix fly ash slurry and citric acid solution, place them in a mixing tank and stir thoroughly to obtain a mixed slurry. The weight ratio of fly ash slurry to citric acid solution is 1:1.5 to 2.
[0013] S4. The fully stirred material is fed into the second grinding device, CaO is added and it is fully ground, and O3 gas is introduced during the grinding process.
[0014] S5. The ground material is sent to a drying equipment for drying and dehydration to obtain solid fly ash residue with a moisture content of ≤3.5%.
[0015] S6. Place the solid fly ash residue into the third grinding device, add Ca(OH)2 and grind it thoroughly to obtain fly ash micro particles with a particle size ≤0.8μm;
[0016] S7. Add a curing agent to the fly ash microparticles to obtain a stable and harmless fly ash solidified product.
[0017] Furthermore, the stirring speed in S3 is 300-500 rp / min and the time is 0.5-3 h.
[0018] Furthermore, the grinding speed in S4 is 1000-1200 rp / min, and the grinding time is 2-4 h.
[0019] Furthermore, the weight ratio of CaO added in S4 to the fully stirred material is 3% to 8%.
[0020] Furthermore, O3 gas is introduced a second time during the drying and dehydration process in S5.
[0021] Furthermore, the weight ratio of Ca(OH)2 and solid fly ash residue added in S6 is 6% to 10%.
[0022] Furthermore, the curing agent in S7 is cement, gypsum, bentonite, and quartz sand.
[0023] Furthermore, the harmless fly ash solidified material can be landfilled or stockpiled, or it can be used as a building material for resource utilization.
[0024] In summary, this application includes at least one of the following beneficial technical effects:
[0025] (1) This invention utilizes anhydrous citric acid to degrade dioxins and Cl in municipal solid waste incineration fly ash using specific mechanical equipment. Under the action of mechanical energy, the material rotates and impacts each other at high speed with the air, forming a mechanical disturbance effect and a chemical effect. This causes the material to repeatedly impact the fly ash at high speed, and leach out anions and cations. At the same time, oxygen atoms continuously attack C bonds, and physical and chemical reactions occur simultaneously, achieving the effect of degrading and removing harmful and toxic substances from fly ash.
[0026] (2) This invention utilizes mechanical equipment to treat fly ash in a harmless manner. The equipment is simple to operate, fully automated, and easy to maintain. It has the advantages of high efficiency and short reaction time, and produces no wastewater, smoke, dust, waste gas, or carbon emissions. The materials are all derived from production and daily life, making it green, environmentally friendly, and safe. The power required to process one ton per hour is 330KW, which is relatively low. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the process flow of this application. Detailed Implementation
[0028] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0029] In the description of this application, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0030] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0031] Example 1:
[0032] The present application will be further described in detail below with reference to the accompanying drawings.
[0033] This application discloses a process for the harmless treatment of fly ash, the process including the following steps:
[0034] S1. The fly ash is pretreated by sieving to remove large particles and added to the first grinding device. Water is used as the medium to grind the fly ash to an average particle size of 2-5 μm using wet grinding method, so as to obtain a fly ash slurry with a water content of 20%-30%.
[0035] S2. Dissolve anhydrous citric acid in deionized water to prepare a citric acid aqueous solution with a concentration of 30-45%.
[0036] S3. Mix fly ash slurry and citric acid solution, place them in a mixing tank and stir thoroughly to obtain a mixed slurry. The weight ratio of fly ash slurry to citric acid solution is 1:1.5 to 2.
[0037] S4. The fully stirred material is fed into the second grinding device, CaO is added and it is fully ground, and O3 gas is introduced during the grinding process.
[0038] S5. The ground material is sent to a drying equipment for drying and dehydration to obtain solid fly ash residue with a moisture content of ≤3.5%.
[0039] S6. The solid fly ash residue is placed in the third grinding device, and Ca(OH)2 is added for thorough grinding to obtain fly ash microparticles with a particle size ≤0.8μm;
[0040] S7. Add a curing agent to the fly ash microparticles to obtain a stable and harmless fly ash solidified product.
[0041] Preferably, the stirring speed in step S3 is 300-500 rp / min and the stirring time is 0.5-3 h.
[0042] Preferably, the grinding speed in S4 is 1000-1200 rp / min, and the grinding time is 2-4 h.
[0043] Preferably, the weight ratio of CaO added in step S4 to the fully stirred material is 3% to 8%.
[0044] Preferably, O3 gas is introduced a second time during the drying and dehydration process in step S5.
[0045] Preferably, the weight ratio of Ca(OH)2 to solid fly ash residue added in S6 is 6% to 10%.
[0046] Preferably, the curing agent in S7 is cement, gypsum, bentonite, and quartz sand.
[0047] Preferably, the harmless fly ash solidified material can be landfilled or stockpiled, or it can be used as a building material for resource utilization.
[0048] The implementation principle of the fly ash harmless treatment process in this application embodiment is as follows: This invention utilizes anhydrous citric acid in specific mechanical equipment to degrade dioxins and Cl in municipal solid waste incineration fly ash. Citric acid is an organic acid, colorless crystals that often contain one molecule of water of crystallization, and is derived from microbial fermentation extraction. Citric acid, under acidic conditions, can promote the dissolution of heavy metals in fly ash. For example, citric acid can react with lead (Pb). 2 +), cadmium (Cd 2 Citric acid reacts with metal ions such as copper (Cu2+) to form soluble citrates (e.g., lead citrate, cadmium citrate). As a ligand, citric acid can encapsulate metal ions through complexation, reducing their free ion concentration and thus decreasing the bioavailability and toxicity of the metal. For example, citric acid can form stable complexes with metal ions, making them less prone to migration and diffusion. Under the synergistic effect of mechanical energy and organic acids, physical and chemical reactions occur, effectively removing Cl from fly ash. The strong mechanical disturbance generated by the stirring and grinding equipment ensures thorough mixing of fly ash and citric acid, resulting in repeated collisions and impacts, and the generation of free radicals. Therefore, under the influence of high-speed mechanical impact and high-speed air rotation and impact, the material, under the action of mechanical energy, rotates and impacts irregularly with the air at high speed, creating mechanical disturbance and chemical effects. This causes the material to repeatedly impact the fly ash at high speed, leaching anions and cations, while oxygen atoms continuously attack C bonds, resulting in physical and chemical reactions that degrade and remove harmful and toxic substances from the fly ash.
[0049] This invention utilizes mechanical equipment for the harmless treatment of fly ash. The equipment is simple to operate, fully automated, and easy to maintain. It boasts advantages such as high efficiency and short reaction time, producing no wastewater, smoke, dust, waste gas, or carbon emissions. The materials are all derived from production and daily life, making it green, environmentally friendly, and safe. The power required to process one ton per hour is 330KW, resulting in low electricity consumption.
[0050] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A process for harmless treatment of fly ash, characterized in that, The process includes the following steps: S1. The fly ash is pretreated by sieving to remove large particles and added to the first grinding device. Water is used as the medium to grind the fly ash to an average particle size of 2-5 μm using wet grinding method, so as to obtain a fly ash slurry with a water content of 20%-30%. S2. Dissolve anhydrous citric acid in deionized water to prepare a citric acid aqueous solution with a concentration of 30-45%. S3. Mix fly ash slurry and citric acid solution, place them in a mixing tank and stir thoroughly to obtain a mixed slurry. The weight ratio of fly ash slurry to citric acid solution is 1:1.5 to 2. S4. The fully stirred material is fed into the second grinding device, CaO is added and it is fully ground, and O3 gas is introduced during the grinding process. S5. The ground material is sent to a drying equipment for drying and dehydration to obtain solid fly ash residue with a moisture content of ≤3.5%. S6. The solid fly ash residue is placed in the third grinding device, and Ca(OH)2 is added for thorough grinding to obtain fly ash microparticles with a particle size ≤0.8μm; S7. Add a curing agent to the fly ash microparticles to obtain a stable and harmless fly ash solidified product.
2. The fly ash harmless treatment process according to claim 1, characterized in that: The stirring speed in S3 is 300-500 rp / min and the stirring time is 0.5-3 h.
3. The fly ash harmless treatment process according to claim 1, characterized in that: The grinding speed in S4 is 1000-1200 rp / min, and the grinding time is 2-4 h.
4. The fly ash harmless treatment process according to claim 1, characterized in that: The weight ratio of CaO added in S4 to the fully stirred material is 3% to 8%.
5. The fly ash harmless treatment process according to claim 1, characterized in that: O3 gas is introduced a second time during the drying and dehydration process in S5.
6. The fly ash harmless treatment process according to claim 1, characterized in that: The weight ratio of Ca(OH)2 and solid fly ash residue added in S6 is 6% to 10%.
7. The fly ash harmless treatment process according to claim 1, characterized in that: The curing agent in S7 is cement, gypsum, bentonite, and quartz sand.
8. The fly ash harmless treatment process according to claim 1, characterized in that: The solidified, harmless fly ash can be landfilled or stockpiled, or it can be used as a building material for resource utilization.