Treatment method of municipal solid waste incineration fly ash

Abstract

The invention provides a treatment method of municipal solid waste incineration fly ash, which belongs to the technical field of solid waste treatment and specifically comprises the following steps: infiltrating the municipal solid waste incineration fly ash by using animal fat to obtain primarily detoxified fly ash and poison-containing fat A; mixing the primarily detoxified fly ash with hot water, fully vibrating, and performing centrifugal separation to obtain low-toxicity fly ash and poison-containing fat B; the low-toxicity fly ash is used as a raw material of a cement material, and toxic fat A and toxic fat B are used as raw materials of an incineration power plant. According to the method, the content of toxic substances in the fly ash can be greatly reduced, the residual amount of fat in the fly ash is reduced, and the content of the toxic substances in the fly ash obtained after treatment conforms to relevant index regulations; the cost is low, the operation is simple, the toxic substance reduction effect is obvious, and the thought is provided for solving the leakage risk of the toxic substances of the traditional fly ash cement solidified body.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste treatment, and in particular relates to a method for treating fly ash from the incineration of urban solid waste. Background Art

[0002] With the development of economy, the annual output of urban solid waste is also increasing year by year, and has reached or exceeded 10 7 Tons / year level. Incineration is a common method for treating municipal solid waste. This method has the advantages of reducing the mass and volume of municipal solid waste and releasing energy to generate electricity. It is gradually replacing landfill as the preferred method for treating municipal solid waste. However, the incineration of municipal solid waste will produce two main by-products, namely municipal solid waste incineration fly ash and municipal solid waste incineration bottom ash. The mass of these two by-products is between 1:4-1:5. Municipal solid waste incineration bottom ash is relatively low in toxicity and can be directly landfilled or directly utilized. However, municipal solid waste incineration fly ash contains more heavy metals, dioxins and other toxic substances than bottom ash. Therefore, municipal solid waste incineration fly ash is identified as a hazardous solid waste that needs to be strictly controlled, and further treatment is required to reduce its potential harm to the environment so that it can meet relevant needs.

[0003] At present, the most common method of treating fly ash from municipal solid waste is to landfill after cement solidification. However, this method cannot remove toxic substances, but encapsulates them in the solidified body. Untreated fly ash-based cement solidified bodies have poor impermeability. Under water penetration, toxic substances will leach out with water and pollute groundwater and soil. Untreated fly ash-based cement solidified bodies have poor durability. As the cement solidified bodies age, toxic substances will eventually leak into the environment.

[0004] Therefore, there is an urgent need for a method for detoxifying and resource-utilizing urban solid waste fly ash. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for treating fly ash from the incineration of urban solid waste, which can solidify toxic substances, reduce the risk of leakage of toxic substances, and is low-cost and simple to operate.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a method for treating fly ash from the incineration of urban solid waste, comprising the following steps: S1. The fly ash from municipal solid waste incineration is filtered using animal fat to obtain the initial detoxified fly ash and toxic fat A; S2. The primary detoxified fly ash is mixed with hot water and then fully vibrated and centrifuged to obtain low-toxic fly ash and toxic fat B; S3. Use low-toxic fly ash as raw material for cement, and use toxic fat A and toxic fat B as raw materials for incineration power plants.

[0007] Preferably, the mass ratio of animal fat to municipal solid waste incineration fly ash in S1 is 3-8:1.

[0008] Preferably, the diafiltration in S1 uses a 100-mesh filter; the diafiltration times are 1-4 times.

[0009] Preferably, the animal fat in S1 is one of animal body fat, animal visceral fat, animal milk fat and fish oil.

[0010] Preferably, the mass ratio of the primary detoxified fly ash to the hot water in S2 is 1:1-4; and the temperature of the hot water is 60°C.

[0011] Preferably, the vibration frequency in S2 is 50 Hz to 60 Hz, and the vibration time is 3 minutes; Preferably, the rotation speed of the centrifuge in S2 is 4000 r / min, and the centrifugation time is 15-30 minutes.

[0012] The present invention provides a method for preparing a cement solidified body, comprising the following steps: The low-toxic fly ash obtained in the above step S2 is fully mixed with cement and then shaped. After demolding the next day, the solidified body is placed in a sodium hydroxide solution for curing to obtain a cement solidified body.

[0013] Preferably, the mass ratio of fly ash to cement is 1-4:6-9, and the water-cement ratio is 0.4; and the cement is 42.5R cement.

[0014] Preferably, the concentration of the sodium hydroxide solution is 1 mol / L and the temperature is 60°C.

[0015] Contains at least the following beneficial technical effects: 1) The method obtained by the present invention can significantly reduce the content of toxic substances in fly ash and reduce the residual fat in fly ash. The content of toxic substances in the fly ash obtained after treatment complies with the provisions of the "Technical Specifications for Pollution Control of Fly Ash from Incineration of Municipal Waste" (HJ 1134-2020).

[0016] 2) The treated fly ash of the present invention is mixed with cement to form a cement solidification body, which can solidify toxic substances and reduce the risk of toxic substance leakage. Hot sodium hydroxide solution curing can stimulate active substances such as CaO, Al2O3 and other substances in municipal solid waste fly ash to react, and the reaction products make the internal structure of cement solidification more compact, effectively improve the anti-seepage performance, and further reduce the risk of toxic substance leakage.

[0017] 3) The method provided by the present invention has the characteristics of low cost, simple operation, and significant effect of reducing toxic substances, and provides a solution to the risk of leakage of toxic substances in traditional fly ash cement solidification bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a simplified diagram of the process. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0020] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0021] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the main idea or essential features of the present invention. Therefore, from all points of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0022] In addition, it should be understood that although this specification is described according to the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. These other implementation modes are also covered within the protection scope of the present invention.

[0023] It should also be understood that the specific embodiments described above are only used to explain the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention / invention.

[0024] The parameters of the untreated fly ash and the pig fat used in the following examples are shown in Tables 1 and 2.

[0025] Table 1 Chemical composition of fly ash (wt%) Table 2 Related parameters of pig fat Example 1 This embodiment provides a method for treating fly ash from the incineration of municipal solid waste, comprising the following steps: S1. The municipal solid waste incineration fly ash is filtered repeatedly in a 100-mesh filter screen using pig fat 1-4 times to allow the toxic substances in the municipal solid waste incineration fly ash to enter the animal fat to obtain the initial detoxified fly ash and toxic fat A; wherein the mass ratio of animal fat to municipal solid waste incineration fly ash is 8:1; S2. The primary detoxified fly ash was mixed with hot water at 60°C in a mass ratio of 1:4 and vibrated at 60Hz for 3 minutes, and then centrifuged at a centrifuge speed of 4000 r / min for 30 minutes to obtain low-toxic fly ash and toxic fat B; toxic fat B is the residual animal fat in the primary detoxified fly ash recovered by hot water washing; S3. Use low-toxic fly ash as raw material for cement, and use toxic fat A and toxic fat B as raw materials for incineration power plants.

[0026] S4. Preparation of cement solidified body: The obtained low-toxic fly ash was fully mixed with 42.5R cement in a mass ratio of 1:9 and shaped. After demolding the next day, the solidified body was placed in a 1 mol / L sodium hydroxide solution at a temperature of 60°C for curing to obtain a cement solidified body.

[0027] The cement solidified body after curing in step 5 was subjected to a compressive test, and the compressive strength was measured to be 32.8±2.26MPa, which meets the compressive strength required for landfill; After the sample was solidified for 210 days, the sample leaching solution was prepared according to the "Toxicity Leaching Method for Solidified Waste - Acetate Buffer Method" (HJ / T300-2007) and the heavy metal concentration in the buffer was tested, as shown in Table 3. The limit values ​​in Table 3 are the landfill limit values ​​specified in the "Pollutant Control Standard for Municipal Waste Landfill" (GB 16889-2008). The test results show that the common heavy metals in fly ash can meet the leaching requirements.

[0028] Table 3 Heavy metal leaching from fat-treated fly ash after cement solidification According to the "Determination of Dioxins in Solid Waste by Isotope Dilution High Resolution Gas Chromatography-High Resolution Mass Spectrometry" (HJ77.3-2008), the dioxin content of the solidified body was measured to be 2.1 ng TEQ / kg and the fat content was 0.92% after cement solidification. After being solidified by cement, the groundwater leaching was simulated for 210 days, and the mass ratio of water to solid was 20:1. Thereafter, the fat content in the cement solidified body was measured to be 0.85%. Based on the fact that dioxins are soluble in fat but not in water, the calculated leaked dioxins are as low as 0.00007 ngTEQ / kg, and the solidification effect is obvious.

[0029] Example 2 This embodiment provides a method for treating fly ash from the incineration of municipal solid waste, comprising the following steps: S1. The municipal solid waste incineration fly ash is filtered repeatedly in a 100-mesh filter screen using pig fat 1-4 times to allow the toxic substances in the municipal solid waste incineration fly ash to enter the animal fat to obtain the initial detoxified fly ash and toxic fat A; wherein the mass ratio of animal fat to municipal solid waste incineration fly ash is 3:1; S2. The primary detoxified fly ash was mixed with hot water at 60°C in a mass ratio of 1:1 and vibrated at 50Hz for 3 minutes, and then centrifuged at a centrifuge speed of 4000 r / min for 15 minutes to obtain low-toxic fly ash and toxic fat B; toxic fat B is the residual animal fat in the primary detoxified fly ash recovered by hot water washing; S3. Use low-toxic fly ash as raw material for cement, and use toxic fat A and toxic fat B as raw materials for incineration power plants.

[0030] S4. Preparation of cement solidified body: The obtained low-toxic fly ash was fully mixed with 42.5R cement in a mass ratio of 2:3 and shaped. After demolding the next day, the solidified body was placed in a 1 mol / L sodium hydroxide solution at a temperature of 60°C for curing to obtain a cement solidified body.

[0031] The compressive strength of the cement solidified body after curing was tested to be 4.77±0.71 MPa, which meets the compressive strength required for landfill. After the sample was solidified for 210 days, the sample leaching solution was prepared according to the "Toxicity Leaching Method for Solidified Waste - Acetate Buffer Method" (HJ / T300-2007) and the heavy metal concentration in the buffer was tested, as shown in Table 4. The limit values ​​in Table 4 are the landfill limit values ​​specified in the "Pollutant Control Standard for Municipal Waste Landfill" (GB 16889-2008). The test results show that the common heavy metals in fly ash can meet the leaching requirements.

[0032] Table 4 Heavy metal leaching from fat-treated fly ash after cement solidification According to the "Determination of Dioxins in Solid Waste by Isotope Dilution High Resolution Gas Chromatography-High Resolution Mass Spectrometry" (HJ77.3-2008), the dioxin content of the solidified body was measured to be 7.14 ng TEQ / kg and the fat content was 5.63% after cement solidification. After being solidified by cement, the groundwater leaching was simulated for 210 days, and the mass ratio of water to solid was 20:1. Thereafter, the fat content in the cement solidified body was measured to be 5.26%. Based on the fact that dioxins are soluble in fat but not in water, the calculated leaked dioxins are as low as 0.00132 ngTEQ / kg, and the dioxin solidification effect is obvious.

[0033] From the above, it can be seen that the leaching concentration of heavy metals in the fly ash cement solidified body obtained after treatment meets the landfill limit value specified in the "Standard for Pollutant Control of Municipal Waste Landfill" (GB 16889-2008), and the dioxin toxicity equivalent is less than 20ng TEQ / kg, which is less than 50ngTEQ / kg specified in the "Technical Specification for Pollution Control of Municipal Waste Incineration Fly Ash" (HJ 1134-2020). The method described in the present invention realizes the separation and solidification of toxic substances in fly ash from municipal solid waste incineration, and effectively reduces the content of toxic substances including heavy metals and dioxins in the fly ash cement solidified body. The method uses pig fat as a dioxin separation agent, which effectively reduces the toxic equivalent of dioxins in the original municipal solid waste incineration fly ash, reduces the toxicity of fly ash, and uses pig fat as a separation agent and cement as a curing agent, which is inexpensive. In addition, the pig fat used for leaching dioxins can be used as a fuel for incineration, and compared with traditional leaching agents, a zero waste liquid flow containing dioxins is achieved. Therefore, the method provided by the present invention has the characteristics of low cost, simple operation, and significant effect in reducing the content of toxic substances such as heavy metals and dioxins. It not only provides a solution to the potential risk of toxic substance leakage in traditional cement solidified fly ash treatment methods, but also provides an environmental basis for the initial resource utilization of cement solidified bodies.

[0034] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for treating fly ash from incineration of municipal solid waste, characterized in that: The following steps are involved: S1. The fly ash from the incineration of municipal solid waste is filtered using animal fat to obtain the initial detoxified fly ash and toxic fat A; S2. The primary detoxified fly ash is mixed with hot water and then fully vibrated and centrifuged to obtain low-toxic fly ash and toxic fat B; S3. Use low-toxic fly ash as raw material for cement, and use toxic fat A and toxic fat B as raw materials for incineration power plants.

2. The processing method according to claim 1, characterized in that: The mass ratio of animal fat to municipal solid waste incineration fly ash in S1 is 3-8:

1.

3. The processing method according to claim 1, characterized in that: In the S1, a 100-mesh filter is used for diafiltration; the diafiltration times are 1-4 times.

4. The processing method according to claim 1, characterized in that: The animal fat in S1 is one of animal body fat, animal visceral fat, animal milk fat and fish oil.

5. The processing method according to claim 1, characterized in that: The mass ratio of the primary detoxified fly ash to the hot water in S2 is 1:1-4; the temperature of the hot water is 60°C.

6. The processing method according to claim 1, characterized in that: The vibration frequency in S2 is 50 Hz to 60 Hz, and the vibration time is 3 minutes.

7. The processing method according to claim 1, characterized in that: The rotation speed of the centrifuge in S2 is 4000 r / min, and the centrifugation time is 15-30 minutes.

8. A method for preparing a cement solidified body, characterized in that: The following steps are involved: The low-toxic fly ash obtained in step S2 of claim 1 is fully mixed with cement and then shaped. After demolding the solidified body the next day, the solidified body is placed in a sodium hydroxide solution for curing to obtain a cement solidified body.

9. The preparation method according to claim 8, characterized in that: The mass ratio of fly ash to cement is 1-4:6-9, and the water-cement ratio is 0.4; the cement is 42.5R cement.

10. The preparation method according to claim 8, characterized in that: The concentration of the sodium hydroxide solution is 1 mol / L and the temperature is 60°C.

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