Innocent treatment process for fly ash

Abstract

The invention belongs to the technical field of solid waste treatment, and discloses a fly ash innocent treatment process which comprises the following steps: pretreating fly ash, mixing fly ash slurry and a citric acid solution, adding CaO, fully grinding, feeding the ground material into drying equipment, drying and dehydrating, adding Ca (OH) 2, fully grinding, adding a curing agent, and uniformly stirring to obtain fly ash slurry; the stable harmless fly ash cured product is obtained. According to the method, dioxin and Cl in the municipal waste incineration fly ash are degraded through anhydrous citric acid under specific mechanical equipment, mutual impact and flowing are achieved along with high-speed irregular rotation of air under the action of mechanical energy, a mechanical disturbance effect and a chemical effect are formed, the effect of degrading and removing harmful toxicants in the fly ash is achieved, and the method is suitable for industrial production. Mechanical equipment is used for carrying out harmless treatment on the fly ash, and the equipment is simple, easy to operate, capable of achieving full automation and easy to maintain. The method has the advantages of high efficiency and short reaction time, and is free of sewage, smoke, dust, waste gas and carbon emission.

Description

Technical Field

[0001] The present application relates to the technical field of solid waste treatment, and more specifically, to a fly ash harmless treatment process. Background Art

[0002] With the widespread application of incineration technology in hazardous waste treatment, fly ash treatment in hazardous waste incineration plants will be a hot topic and a difficult problem in the current environmental field. This is because the fly ash output is large, and it contains a large amount of heavy metal elements, salts, and highly toxic dioxins and other pollutants, which are listed in the HW18 category of the National Hazardous Waste List. Therefore, fly ash must be disposed of in accordance with the standards for hazardous waste, and must be harmlessly disposed of before it can be used as a resource.

[0003] The output of fly ash is related to the type of garbage, incineration conditions, incinerator type and flue gas treatment process, and generally accounts for about 3% to 5% of the amount of garbage incinerated. Due to the continuous generation of urban garbage, domestic garbage incineration power plants maintain high-load operation all year round, increasing the emission and treatment needs of pollutants such as nitrogen oxides, dioxins, fly ash, and odorous gases. If they are not properly handled, it will bring environmental problems and social impacts; measures must be taken to promote the coordinated development of garbage incineration treatment capacity and incineration fly ash harmless disposal technology.

[0004] Municipal waste incineration fly ash is a highly alkaline fly ash with a Ph value of about 13, a surface area of ​​13.05㎡ / g, and a dioxin toxicity equivalent of 87-200 nanograms per kilogram. The Cl content in the fly ash reaches 20-40%.

[0005] At present, there is no effective technology to completely solve the problem of harmless treatment and resource recycling of garbage fly ash in various garbage incineration plants. Existing studies have shown that melting treatment can completely decompose dioxins in fly ash, and the low-boiling heavy metal elements and their compounds contained in the fly ash are volatilized and transferred to the air, while the remaining metals are transferred to glass slag. The high-temperature oxidizing atmosphere melting treatment is either to design special equipment or to use the pelletizing vertical furnace, sintering furnace, steelmaking converter, etc. in the ironmaking equipment. However, when the high-temperature oxidizing atmosphere melting treatment is used, when the melting temperature is above 800°C, the trivalent chromium in the heavy metals will be completely converted into hexavalent chromium, and hexavalent chromium is an ingested poison / inhaled extremely toxic substance. Skin contact may cause sensitivity, and it is more likely to cause hereditary gene defects. Inhalation may cause cancer and has a lasting danger to the environment. This is not allowed in domestic and foreign environmental protection standards. The use of high-temperature reducing atmosphere melting method can effectively avoid this problem, but the current high-temperature reducing atmosphere melting methods at home and abroad all use special high-temperature reducing atmosphere melting equipment, but the construction and operation costs of these equipment are extremely high, making it difficult to implement industrialization. Thereby limiting the harmless treatment of garbage fly ash.

[0006] Patent CN106734099A discloses a process for high-temperature harmless disposal of waste incineration fly ash using secondary material composite technology, which includes the following steps: (1) waste incineration fly ash is used as a core material, a reducing agent containing a C raw material is added, or a chlorine absorbent and / or additive containing CaO is further added, and a core is made under the action of an adhesive; the dry weight ratio of the waste incineration fly ash, the reducing agent, the chlorine absorbent, and the additive is 50-80%, 10-30%, 0-6%, and 0-15% respectively; (2) the core and the chlorine absorbent containing CaO are mixed, and a layer of chlorine absorbent is formed on the outside of the core under the action of an adhesive. shielding layer, forming pellets, the amount of chlorine absorbent accounts for 3-10% of the weight of the dry composite ball; (3) the pellets prepared in step (2) and the shell material are wrapped with a shell on the outside under the action of an adhesive through a ball making device to form a secondary material composite pellet; the shell material uses non-toxic and harmless materials and other additives; (4) the secondary material composite pellets are finally incinerated in an incineration device for high-temperature harmless disposal; the incineration device uses a metallurgical sintering machine or a solid waste harmless incineration device; the moisture content of the ball core is controlled to be 18-28%, the diameter of the ball core is 1-3 mm, the compressive strength is greater than 7N / piece, and the drop strength is greater than 20 times / piece. Although this process effectively solves the above problems, it is necessary to add a chlorine absorbent and a C-containing reducing agent or a melting additive before forming the ball core, and it is necessary to form a ball 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 area. Summary of the invention

[0007] In order to solve the above problems, the present application provides a fly ash harmless treatment process.

[0008] The present application provides a fly ash harmless treatment process using the following technical solutions:

[0009] A fly ash harmless treatment process, the process comprising the following steps:

[0010] S1, pre-treating the fly ash, screening to remove large particles, adding the fly ash to a first grinding device, using water as a medium, and grinding the fly ash by wet grinding to an average particle size of 2 to 5 μm to obtain a fly ash slurry with a water content of 20% to 30%;

[0011] S2, dissolving anhydrous citric acid in deionized water to prepare a citric acid aqueous solution with a concentration of 30-45%;

[0012] S3, mixing the fly ash slurry and the citric acid solution, placing them in a stirring tank for sufficient stirring to obtain a mixed slurry, wherein the weight ratio of the fly ash slurry to the citric acid solution is 1:1.5-2;

[0013] S4, the fully stirred material is sent to the second grinding device, CaO is added for full grinding, and O3 gas is introduced during grinding;

[0014] S5, sending the ground material to a drying device for drying and dehydration to obtain a solid fly ash slag with a moisture content of ≤3.5%;

[0015] S6, placing the solid fly ash residue into a third grinding device, adding Ca(OH)2 for full grinding, and obtaining fly ash microparticles with a particle size of ≤0.8 μm;

[0016] S7. Adding a curing agent to the fly ash microparticles to obtain a stable harmless fly ash solidified material.

[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 the CaO added in S4 to the fully stirred material is 3% to 8%.

[0020] Furthermore, O3 gas is introduced twice during the drying and dehydration process in S5.

[0021] Furthermore, the weight ratio of Ca(OH)2 added to the S6 to the solid fly ash 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 piled up, or can be utilized as a building material for resource utilization.

[0024] In summary, the present application includes at least one of the following beneficial technical effects:

[0025] (1) The present invention utilizes anhydrous citric acid to degrade dioxins and Cl in fly ash from municipal waste incineration in a specific mechanical device. Under the action of mechanical energy, the materials impact and flow with each other with the irregular rotation of air at high speed, forming a mechanical disturbance effect and a chemical effect, so that the materials and fly ash impact repeatedly at high speed, and anions and cations are leached out. At the same time, oxygen atoms continuously attack C bonds, and physical and chemical reactions occur at the same time, achieving the effect of degrading and removing harmful and toxic substances in fly ash;

[0026] (2) The present invention uses mechanical equipment to harmlessly treat fly ash. The equipment is simple and easy to operate, fully automated, and easy to repair and maintain. It has the advantages of high efficiency and short reaction time, no sewage, no smoke, no dust, no exhaust gas, and no carbon emissions. The materials are all from production and life, which is green, environmentally friendly and safe. The power required to process one ton per hour is 330KW, and the power consumption is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the process flow of this application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application; obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application without making creative work are within the scope of protection of the present application.

[0029] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0030] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "set / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0031] Embodiment 1:

[0032] The present application is further described in detail below in conjunction with the accompanying drawings.

[0033] The present application discloses a fly ash harmless treatment process, which comprises the following steps:

[0034] S1, pre-treating the fly ash, screening to remove large particles, adding the fly ash to a first grinding device, using water as a medium, and grinding the fly ash by wet grinding to an average particle size of 2 to 5 μm to obtain a fly ash slurry with a water content of 20% to 30%;

[0035] S2, dissolving anhydrous citric acid in deionized water to prepare a citric acid aqueous solution with a concentration of 30-45%;

[0036] S3, mixing the fly ash slurry and the citric acid solution, placing them in a stirring tank for sufficient stirring to obtain a mixed slurry, wherein the weight ratio of the fly ash slurry to the citric acid solution is 1:1.5-2;

[0037] S4, the fully stirred material is sent to the second grinding device, CaO is added for full grinding, and O3 gas is introduced during grinding;

[0038] S5, sending the ground material to a drying device for drying and dehydration to obtain a solid fly ash slag with a moisture content of ≤3.5%;

[0039] S6, placing the solid fly ash slag into a third grinding device, adding Ca(OH)2 for full grinding, and obtaining fly ash microparticles with a particle size of ≤0.8 μm;

[0040] S7. Adding a curing agent to the fly ash microparticles to obtain a stable harmless fly ash solidified material.

[0041] Preferably, the stirring speed in S3 is 300-500 rp / min and the 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 S4 to the fully stirred material is 3% to 8%.

[0044] Preferably, O3 gas is introduced twice during the drying and dehydration process in S5.

[0045] Preferably, the weight ratio of Ca(OH)2 added to the S6 to the solid fly ash slag 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 piled up, or can be utilized as a building material for resource utilization.

[0048] The implementation principle of the fly ash harmless treatment process of the present application embodiment is as follows: the present invention uses anhydrous citric acid to degrade dioxins and Cl in the fly ash of municipal waste incineration in a specific mechanical device. Citric acid is an organic acid, and its colorless crystals often contain 1 molecule of crystal water, which is derived from microbial fermentation extraction. Citric acid can promote the dissolution of heavy metals in fly ash under acidic conditions. For example, citric acid can react with lead (Pb 2 +), cadmium (Cd 2 +), copper (Cu2+) and other metal ions to form soluble citrates (such as lead citrate, cadmium citrate, etc.). Citric acid, as a ligand, can encapsulate metal ions together through complexation, reduce their free ion concentration, and thus reduce the bioavailability and toxicity of metals. For example, citric acid can form stable complexes with metal ions, making it difficult for these metal ions to migrate and diffuse. Under the synergistic effect of mechanical energy and organic acids, physical and chemical reactions occur, thereby effectively removing Cl from fly ash. Under the action of the mechanical energy of the stirring equipment and the grinding equipment, strong mechanical disturbances are generated, so that the fly ash and citric acid are fully mixed, repeatedly collide and impact with each other, and free radicals are generated at the same time. Therefore, under the high-speed impact of the machine and the high-speed rotation flow and impact of the air, the materials, under the action of mechanical energy, impact and flow with each other with the high-speed irregular rotation of the air, forming a mechanical disturbance effect and a chemical effect, so that the materials and fly ash repeatedly impact at high speed, and leaching anions and cations, while oxygen atoms continuously attack C bonds, and physical and chemical reactions occur at the same time, achieving the effect of degradation and removal of harmful and toxic substances in fly ash.

[0049] The present invention uses mechanical equipment to harmlessly treat fly ash. The equipment is simple and easy to operate, fully automated, and easy to maintain. It has the advantages of high efficiency and short reaction time, no sewage, no smoke, no dust, no exhaust gas, and no carbon emissions. The materials are all from production and life, which is green, environmentally friendly and safe. The power required to process one ton per hour is 330KW, and the power consumption is relatively low.

[0050] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A fly ash harmless treatment process, characterized in that: The process comprises the following steps: S1, pre-treating the fly ash, screening to remove large particles, adding the fly ash to a first grinding device, using water as a medium, and grinding the fly ash by wet grinding to an average particle size of 2 to 5 μm to obtain a fly ash slurry with a water content of 20% to 30%; S2, dissolving anhydrous citric acid in deionized water to prepare a citric acid aqueous solution with a concentration of 30-45%; S3, mixing the fly ash slurry and the citric acid solution, placing them in a stirring tank for sufficient stirring to obtain a mixed slurry, wherein the weight ratio of the fly ash slurry to the citric acid solution is 1:1.5-2; S4, the fully stirred material is sent to the second grinding device, CaO is added for full grinding, and O3 gas is introduced during grinding; S5, sending the ground material to a drying device for drying and dehydration to obtain a solid fly ash slag with a moisture content of ≤3.5%; S6, placing the solid fly ash slag into a third grinding device, adding Ca(OH)2 for full grinding, and obtaining fly ash microparticles with a particle size of ≤0.8 μm; S7. Adding a curing agent to the fly ash microparticles to obtain a stable harmless fly ash solidified material.

2. A fly ash harmless treatment process according to claim 1, characterized in that: The stirring speed in S3 is 300-500 rp / min and the 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: In the drying and dehydration process in S5, O3 gas is introduced twice.

6. The fly ash harmless treatment process according to claim 1, characterized in that: The weight ratio of Ca(OH)2 added to the S6 to the solid fly ash slag 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 harmless fly ash solidified material can be landfilled or piled up, and can also be utilized as a building material for resource utilization.

Images