Method for preparing foam ceramics from high-calcium and low-silicon municipal solid waste incineration fly ash

Abstract

The present invention belongs to the technical field of harmless and resourceful treatment of municipal solid waste incineration fly ash, and particularly relates to a method for preparing foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash. The method comprises the following steps: washing the high-calcium and low-silicon municipal solid waste incineration fly ash with water to reduce the chloride ion content; using the washed fly ash, kaolin, and quartz or waste glass powder as raw materials, silicon carbide as a foaming agent, and performing ball milling. After the ball milling is completed, drying and screening are carried out to prepare a mixture; pressing the mixture into tablets, and then sintering to obtain foam ceramics. The heavy metal ion leaching concentration of the foam ceramics prepared by this method meets the national standard requirements, and the flexural strength far exceeds the national standard requirements. It not only realizes waste utilization, provides a new way for the harmless treatment of municipal solid waste incineration fly ash, but also turns waste into treasure and broadens the resourceful application field of municipal solid waste incineration fly ash.

Description

Technical Field

[0001] The present invention belongs to the technical field of harmless and resource treatment of municipal solid waste incineration fly ash, and particularly relates to a method for preparing foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash. Background Art

[0002] With the continuous improvement of the material living standard of human beings, the scale of fly ash generated by municipal solid waste incineration has expanded rapidly. The current mainstream fly ash treatment method is to directly landfill the solidified or stabilized fly ash. This treatment method is simple and fast, but there is a problem of occupying land resources. At the same time, there are also small amounts of toxic substances such as dioxin and heavy metals in the fly ash, which may cause secondary pollution to the land. Therefore, it is urgent to research and develop green and environmentally friendly fly ash harmless treatment technologies.

[0003] Foam ceramics is a green and environmentally friendly ceramic material with high porosity, and has the characteristics of low bulk density, large specific surface area, strong sound insulation and heat insulation ability, low dielectric constant, etc. Its raw material components are mainly concentrated in the SiO2 - Al2O3 - RO - R2O system (RO is alkaline earth metal oxide, R2O is alkali metal oxide). The main components of fly ash are CaO, SiO2, and Al2O3, belonging to the CaO - SiO2 - Al2O3 system, and can be used as raw materials for producing foam ceramics. At present, although there are also methods for preparing foam ceramic materials using municipal solid waste incineration fly ash, the foam ceramic materials prepared by these methods generally have the problem of low strength. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash. The heavy metal ion leaching concentration of the foam ceramics prepared by the method of the present invention meets the national standard requirements, and the flexural strength far exceeds the national standard requirements.

[0005] The technical solution of the present invention:

[0006] A method for preparing foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash, comprising the following steps:

[0007] (1) Wash the high-calcium and low-silicon municipal solid waste incineration fly ash to reduce the chloride ion content; the high-calcium and low-silicon municipal solid waste incineration fly ash contains 30wt% - 45wt% of CaO and 15wt% - 25wt% of SiO2.

[0008] (2) Use the washed fly ash, kaolin, and quartz or waste glass powder as raw materials, and silicon carbide as a foaming agent, add them to a high-speed grinder for ball milling. After ball milling is completed, dry and screen to prepare a mixture.

[0009] (3) Weigh the required amount of the mixture for tabletting, place it on a corundum backing plate, and heat and sinter it in an electric resistance furnace according to the established firing system to obtain the foam ceramics. The mixture contains the following components: 40wt% - 60wt% of SiO2, 10wt% - 25wt% of Al2O3, 10wt% - 20wt% of CaO, and 0.2wt% - 1.0wt% of silicon carbide.

[0010] Preferably, the particle size of the raw materials does not exceed 100 mesh, the particle size of silicon carbide is ≤30μm. After ball-milling and drying the mixture, it is then sieved through a 100-mesh sieve.

[0011] Preferably, the high-calcium and low-silica municipal solid waste incineration fly ash is from Guangdong. The main chemical components of the Guangdong municipal solid waste incineration fly ash are as follows: the content of CaO is 30wt% - 35wt%, the content of SiO2 is 20wt% - 25wt%, the content of Al2O3 is 10wt% - 15wt%, the content of SO3 is 10wt% - 15wt%, the content of Fe2O3 is 5wt% - 10wt%, the content of MgO is 5wt% - 10wt%, the content of TiO2 is 1wt% - 2wt%, the content of K2O is 1wt% - 2wt%, the content of P2O5 is 0.5wt% - 1.5wt%, the content of MnO is 0.1wt% - 0.5wt%, and the balance is impurities, totaling 100%.

[0012] Preferably, the high-calcium and low-silica municipal solid waste incineration fly ash is from Guangxi. The main chemical components of the Guangxi municipal solid waste incineration fly ash are as follows: the content of CaO is 40wt% - 45wt%, the content of SiO2 is 15wt% - 20wt%, the content of SO3 is 10wt% - 15wt%, the content of Al2O3 is 5wt% - 10wt%, the content of MgO is 5wt% - 10wt%, the content of Fe2O3 is 1wt% - 5wt%, the content of TiO2 is 1wt% - 2wt%, the content of P2O5 is 1wt% - 2wt%, the content of K2O is 0.1wt% - 1wt%, the content of MnO is 0.1wt% - 0.5wt%, and the balance is impurities, totaling 100%.

[0013] Preferably, the kaolin is composed of the following components: the content of SiO2 is 55wt% - 60wt%, the content of Al2O3 is 40wt% - 45wt%, the content of Fe2O3 is 0.1wt% - 1wt%, the content of K2O is 0.1wt% - 1wt%, the content of TiO2 is 0.01wt% - 0.1wt%, the content of BaO is 0.01wt% - 0.1wt%, the content of MnO is 0.01wt% - 0.1wt%, the content of SO3 is 0.01wt% - 0.1wt%, and the balance is impurities, totaling 100%.

[0014] Preferably, the quartz consists of the following components: the content of SiO2 is 99.00 wt% - 99.80 wt%, the content of Al2O3 is 0.1 wt% - 1 wt%, the content of Fe2O3 is 0.01 wt% - 0.1 wt%, the content of CaO is 0.01 wt% - 0.1 wt%, the content of SO3 is 0.01 wt% - 0.1 wt%, with a total of 100%.

[0015] Preferably, the waste glass powder consists of the following components: the content of SiO2 is 90 wt% - 95 wt%, the content of Na2O is 5 wt% - 10 wt%, the content of Al2O3 is 1 wt% - 5 wt%, the content of CaO is 0.1 wt% - 0.5 wt%, the content of K2O is 0.1 wt% - 0.5 wt%, the content of P2O5 is 0.1 wt% - 0.5 wt%, the content of SO3 is 0.1 wt% - 0.5 wt%, the content of Fe2O3 is 0.01 wt% - 0.1 wt%, the content of TiO2 is 0.01 wt% - 0.1 wt%, and the balance is impurities, with a total of 100%.

[0016] Preferably, using Guangdong fly ash or Guangxi fly ash, kaolin, and quartz or waste glass powder as raw materials, and silicon carbide as the foaming agent, high-strength foam ceramics are prepared. Using a microcomputer-controlled electronic universal testing machine, referring to [national standard] GBT6569-2006 "Test Method for Flexural Strength of Fine Ceramics" and [national standard] JCT647-2005 "Foam Ceramic Thermal Insulation Products", the specimen size is 3*4*40 mm, the loading speed is 0.5 mm / min, the span is 30 mm, and its flexural strength is tested and compared; the Archimedes drainage method is used to test its various physical properties; the flame atomic absorption spectrophotometer method is used, referring to [national standard] HJ1222-2021 "Solid Waste - Determination of Moisture and Dry Matter Content - Gravimetric Method" and HJT766-2015 "Solid Waste - Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method", to test its heavy metal leaching concentration.

[0017] Preferably, in step (1), for fly ash pretreatment, the liquid-solid ratio of deionized water to fly ash is 2.5:1, magnetic stirring is carried out for 30 - 60 min, and the washed fly ash is dried at 105°C for 12 h.

[0018] Preferably, in step (2), the washed Guangdong fly ash or Guangxi fly ash, kaolin, and quartz or waste glass powder are mixed in a ratio of 2:2:1, the foaming agent silicon carbide is added, and ball milling is carried out in a high-speed grinder for 8 h (the ball-to-material-water ratio is 2:1:0.8). The ball-milled mixture is dried at 105°C for 12 h and sieved through a 100-mesh sieve. The particle size of the raw materials does not exceed 100 mesh, and the particle size of silicon carbide is ≤30 μm.

[0019] Preferably, in step (3), after pressing the mixture into tablets, sintering of the foam ceramics is carried out according to the established firing system (① Using Guangdong fly ash as raw material: heating from room temperature to 1230 °C - 1250 °C at a heating rate of 2 °C / min - 4 °C / min, holding for 20 min - 60 min, and then cooling; ② Using Guangxi fly ash as raw material: heating from room temperature to 1145 °C - 1155 °C at a heating rate of 2 °C / min - 4 °C / min, holding for 20 min - 60 min, and then cooling).

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention first pre-treats the high-calcium and low-silicon domestic waste incineration fly ash, reduces its chloride ion content through the water washing process, and then mixes and formulates the high-calcium and low-silicon domestic waste incineration fly ash, kaolin, and quartz or waste glass powder to make the effective components in the mixture match the effective components of the foam ceramics. Silicon carbide is used as the foaming agent, and the mixture is ball-milled. The mixture contains the following components: 40wt% - 60wt% of SiO2, 10wt% - 25wt% of Al2O3, 10wt% - 20wt% of CaO, and 0.2wt% - 1.0wt% of silicon carbide. Finally, the foam ceramics are obtained by high-temperature sintering according to the established firing system. During the firing process, the fixation of heavy metal ions is achieved, the leaching concentration of heavy metal ions is reduced, and at the same time, the material has a pore structure and the strength is improved. The leaching concentration of heavy metal ions in the prepared foam ceramic material meets the national standard requirements, and the flexural strength far exceeds the national standard requirements. It can be used for sound insulation, heat insulation, structural construction, etc. It not only realizes waste utilization, provides a new way for the harmless treatment of domestic waste incineration fly ash, but also turns waste into treasure and broadens the application of domestic waste incineration fly ash. Description of the Drawings

[0022] Figure 1 XRD patterns and physical diagrams of Guangdong fly ash, Guangxi fly ash, kaolin, quartz, and waste glass powder in Example 1 and Example 10; (a1) Guangdong fly ash; (a2) Guangxi fly ash; (b) kaolin; (c1) quartz; (c2) waste glass powder.

[0023] Figure 2 XRD patterns and physical diagrams of the mixture and foam ceramics in Example 1 and Example 10, where (d1) mixture containing Guangdong fly ash; (d2) mixture containing Guangxi fly ash; (e1) foam ceramic containing Guangdong fly ash; (e2) foam ceramic containing Guangxi fly ash.

[0024] Figure 3 SEM diagrams and pore size distribution diagrams of different regions of the foam ceramic containing Guangdong fly ash in Example 1, where (a), (b), (c), and (d) are SEM diagrams of different positions respectively, and (e) is the pore size distribution diagram.

[0025] Figure 4 SEM images and pore size distribution diagrams of different regions of the foam ceramics containing Guangxi fly ash in Example 10: Among them, (a), (b), (c), and (d) are SEM images at different positions, and (e) is the pore size distribution diagram.

[0026] Figure 5 Among them, (a) is the SEM image of the foam ceramics containing Guangdong fly ash in Example 1, (b) is the EDS spectrum of the foam ceramics containing Guangdong fly ash in Example 1, and (c) is the distribution diagram of each element in (a).

[0027] Figure 6 Among them, (a) is the EDS spectrum of the foam ceramics containing Guangxi fly ash in Example 10, (b) is the EDS spectrum of the foam ceramics containing Guangxi fly ash in Example 10, and (c) is the distribution diagram of each element in (a).

[0028] Figure 7 Among them, (a) is the physical diagram of the foam glass in Comparative Example 1, and (b) is the physical diagram of the cross-section of the foam glass in Comparative Example 1.

[0029] Figure 8 Among them, (a) is the physical object of the foam ceramics with insufficient sintering in Comparative Example 2 Figure 1 , (b) is the physical object of the foam ceramics with insufficient sintering in Comparative Example 2 Figure 2 .

[0030] Figure 9 Among them, (a) is the physical object of the glass ceramics in Comparative Example 3 Figure 1 , (b) is the physical object of the glass ceramics in Comparative Example 3 Figure 2 .

[0031] Figure 10 Among them, (a) is the physical diagram of the foam ceramics in Comparative Example 4, and (b) is the physical diagram of the cross-section of the foam ceramics in Comparative Example 4. Detailed implementation manners

[0032] In order to enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and the accompanying drawings. However, the described embodiments are not intended to limit the present invention. In the following embodiments, the experimental methods and detection methods are all conventional methods unless otherwise specified; the reagents and materials can all be purchased on the market unless otherwise specified.

[0033] After detection, the specific components of the municipal solid waste incineration fly ash from Guangdong used in the following examples are as follows: the content of CaO is 33.04 wt%, the content of SiO2 is 23.72 wt%, the content of SO3 is 12.57 wt%, the content of Al2O3 is 12.34 wt%, the content of Fe2O3 is 7.51 wt%, the content of MgO is 5.86 wt%, the content of TiO2 is 1.66 wt%, the content of K2O is 1.19 wt%, the content of P2O5 is 0.98 wt%, the content of MnO is 0.19 wt%, and the balance is impurities, totaling 100%.

[0034] The municipal solid waste incineration fly ash from Guangxi contains the following components: the content of CaO is 44.24 wt%, the content of SiO2 is 16.92 wt%, the content of SO3 is 13.67 wt%, the content of MgO is 8.59 wt%, the content of Al2O3 is 7.26 wt%, the content of Fe2O3 is 4.18 wt%, the content of TiO2 is 1.33 wt%, the content of P2O5 is 1.18 wt%, the content of K2O is 0.77 wt%, the content of MnO is 0.18 wt%, and the balance is impurities, totaling 100%.

[0035] Kaolin contains the following components: the content of SiO2 is 57.50 wt%, the content of Al2O3 is 40.97 wt%, the content of Fe2O3 is 0.71 wt%, the content of K2O is 0.60 wt%, the content of SO3 is 0.06 wt%, the content of BaO is 0.05 wt%, the content of TiO2 is 0.04 wt%, the content of MnO is 0.03 wt%, the content of CuO is 0.02 wt%, and the content of Zr2O is 0.02 wt%.

[0036] Quartz contains the following components: the content of SiO2 is 99.24 wt%, the content of Al2O3 is 0.72 wt%, the content of SO3 is 0.02 wt%, the content of Fe2O3 is 0.01 wt%, and the content of CaO is 0.01 wt%.

[0037] The waste glass powder contains the following components: the content of SiO2 is 90.90 wt%, the content of Na2O is 5.40 wt%, the content of Al2O3 is 2.71 wt%, the content of CaO is 0.24 wt%, the content of SO3 is 0.20 wt%, the content of P2O5 is 0.17 wt%, the content of Zr2O is 0.13 wt%, the content of K2O is 0.10 wt%, the content of Fe2O3 is 0.08 wt%, the content of CuO is 0.04 wt%, and the content of TiO2 is 0.03 wt%.

[0038] Foamed ceramics are a kind of green and environmentally friendly ceramic materials with high porosity. Their raw material components mainly focus on the SiO2-Al2O3-RO-R2O system (RO is alkaline earth metal oxide, and R2O is alkali metal oxide); while the main components of fly ash are CaO, SiO2, and Al2O3, belonging to the CaO-SiO2-Al2O3 system, which can be used as raw materials for producing foamed ceramics. Among them, SiO2 plays a role in the skeleton. Too much will lead to an increase in the sintering temperature, and its content needs to be moderate, controlled at 40wt% - 60wt%; Al2O3 has the function of enhancing mechanical strength and stabilizing the bubble structure. Too high will lead to an increase in the softening temperature of the raw materials, and its content is controlled at 10wt% - 25wt%; CaO can improve the material properties and is a sintering aid, but excessive amount is not conducive to the formation of pores, and its content is controlled at 10wt% - 20wt%; SiC - foaming agent, and its content is controlled at 0.2wt% - 1wt%.

[0039] The following is a specific description of the content of the present invention through the following examples and comparative examples.

[0040] Example 1

[0041] In this example, a method for preparing high-strength foamed ceramics based on high-calcium and low-silicon domestic waste incineration fly ash includes the following steps:

[0042] (1) First, pre-treat the fly ash from domestic waste incineration in Guangdong. Through the water washing process, reduce its chloride ion content. Experimentally weigh 100g of dry fly ash from domestic waste incineration and add 250ml of deionized water to a 500ml beaker (liquid-solid ratio is 2.5:1), add a magnetic rotor, stir magnetically for 30min, use a "qualitative filter paper + sand core filtration device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear, and then dry and weigh (dry at 105°C for 12h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: the chloride ion content in the fly ash after water washing is lower than 0.1%).

[0043] (2) Then mix the washed Guangdong fly ash, kaolin, and quartz in a ratio of 2:2:1, and add an appropriate amount of foaming agent silicon carbide to form a mixture; in the mixture, the content of SiO2 is 51.81 wt%, the content of Al2O3 is 21.25 wt%, the content of CaO is 13.09 wt%, the content of SO3 is 5.01 wt%, the content of Fe2O3 is 3.26 wt%, the content of MgO is 2.32 wt%, the content of SiC is 1 wt%, the content of K2O is 0.71 wt%, the content of TiO2 is 0.67 wt%, the content of P2O5 is 0.39 wt%, the content of MnO is 0.08 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (the ball-to-material-to-water ratio is 2:1:0.8), after ball milling is completed, dry at 105 °C for 12 h, and pass through a 100-mesh sieve.

[0044] (3) Finally, weigh the required amount of the mixture for tabletting (from 10 Mpa until the pressure no longer decreases), place it on a corundum backing plate, and sinter it in an electric resistance furnace according to the established firing system (heat from room temperature to 1230 °C at a heating rate of 3 °C / min, hold for 40 min, and then cool down) to obtain a foam ceramic product.

[0045] Refer to [national standard] GBT6569-2006 "Test Method for Flexural Strength of Fine Ceramics" and [national standard] JCT647-2005 "Foam Ceramic Thermal Insulation Products", use a microcomputer-controlled electronic universal testing machine, the specimen size is 3*4*40 mm, the loading speed is 0.5 mm / min, and the span is 30 mm, to test and compare its flexural strength.

[0046] Refer to [national standard] GBT1966-1996 "Test Methods for Apparent Porosity and Bulk Density of Porous Ceramics", [national standard] HJ1222-2021 "Solid Waste - Determination of Moisture and Dry Matter Content - Gravimetric Method", and HJT766-2015 "Solid Waste - Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method", use the Archimedes drainage method to test its various physical properties and use the flame atomic absorption spectrophotometer method to test its heavy metal leaching concentration. The results are shown in Table 1:

[0047] Table 1 Physical Properties, Flexural Strength, and Heavy Metal Ion Leaching Concentration of Foam Ceramics

[0048]

[0049] Example 2

[0050] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon domestic waste incineration fly ash includes the following steps:

[0051] (1) First, pre-treat the municipal solid waste incineration (MSWI) fly ash from Guangdong. Through the water washing process, reduce its chloride ion content. In the experiment, weigh 100 g of dry MSWI fly ash and add 250 ml of deionized water into a 500 ml beaker (liquid-solid ratio is 2.5:1). Add a magnetic rotor and stir magnetically for 30 min. Use a combination of "qualitative filter paper + sintered filter funnel + vacuum pump" for solid-liquid separation. Then add deionized water for suction filtration until the filtrate is clear. Then dry and weigh it (dry at 105 °C for 12 h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: the chloride ion content in the fly ash after water washing is less than 0.1%).

[0052] (2) Then mix the water-washed MSWI fly ash from Guangdong, kaolin, and quartz in a ratio of 2:2:1, and add an appropriate amount of foaming agent silicon carbide to form a mixture. In the mixture, the content of SiO2 is 51.81 wt%, the content of Al2O3 is 21.25 wt%, the content of CaO is 13.09 wt%, the content of SO3 is 5.01 wt%, the content of Fe2O3 is 3.26 wt%, the content of MgO is 2.32 wt%, the content of SiC is 1 wt%, the content of K2O is 0.71 wt%, the content of TiO2 is 0.67 wt%, the content of P2O5 is 0.39 wt%, the content of MnO is 0.08 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (ball-to-material-to-water ratio is 2:1:0.8). After ball milling, dry at 105 °C for 12 h and pass through a 100-mesh sieve.

[0053] (3) Finally, weigh the required amount of the mixed material for tablet pressing (from 10 Mpa until the pressure no longer decreases), place it on a corundum backing plate, and sinter it in an electric resistance furnace according to the established firing system (heat from room temperature to 1230 °C, heating rate is 2 °C / min, hold for 20 min, and then cool down) to obtain a foam ceramic product.

[0054] Refer to [national standard] GBT6569-2006 "Test Method for Flexural Strength of Fine Ceramics" and [national standard] JCT647-2005 "Foam Ceramic Thermal Insulation Products". Use a microcomputer-controlled electronic universal testing machine. The specimen size is 3*4*40 mm, the loading speed is 0.5 mm / min, and the span is 30 mm. Test and compare its flexural strength.

[0055] Refer to [national standard] GBT1966-1996 "Test Method for Apparent Porosity and Bulk Density of Porous Ceramics", and use the Archimedes drainage method to test its various physical properties. The results are shown in Table 2:

[0056] Table 2 Physical Properties and Flexural Strength of Foam Ceramics

[0057]

[0058] Example 3

[0059] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0060] Except for the firing regime in step (3) (heating from room temperature to 1250 °C at a heating rate of 3 °C / min, holding for 60 min, and then cooling), the other steps are the same as those in Example 2. The results are shown in Table 3:

[0061] Table 3 Physical properties and flexural strength of foam ceramics

[0062]

[0063] Example 4

[0064] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0065] (1) First, pretreat the Guangdong waste incineration fly ash. By means of a water washing process, reduce its chloride ion content. Experimentally weigh 100 g of dry waste incineration fly ash and 250 ml of deionized water and add them to a 500 ml beaker (liquid-solid ratio is 2.5:1). Add a magnetic rotor and stir magnetically for 30 min. Use a "qualitative filter paper + sintered filter device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear, and then perform drying and weighing (drying at 105 °C for 12 h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: chloride ion content in the fly ash after water washing is less than 0.1%).

[0066] (2) Then mix the water-washed Guangdong fly ash, kaolin, and quartz in a ratio of 2:2:1, and add an appropriate amount of foaming agent silicon carbide to form a mixture; in the mixture, the content of SiO2 is 52.07 wt%, the content of Al2O3 is 21.36 wt%, the content of CaO is 13.15 wt%, the content of SO3 is 5.03 wt%, the content of Fe2O3 is 3.27 wt%, the content of MgO is 2.33 wt%, the content of K2O is 0.71 wt%, the content of TiO2 is 0.68 wt%, the content of SiC is 0.5 wt%, the content of P2O5 is 0.39 wt%, the content of MnO is 0.08 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (ball-to-material-water ratio is 2:1:0.8). After ball milling is completed, dry at 105 °C for 12 h and pass through a 100-mesh sieve.

[0067] (3) Finally, weigh the required amount of the mixed material and press it into tablets (from 10 Mpa until the pressure no longer decreases). Place it on a corundum backing plate and sinter it in an electric resistance furnace according to the established firing system (heating from room temperature to 1240 °C at a heating rate of 4 °C / min, holding for 40 min, and then cooling down) to obtain the foam ceramic product.

[0068] The detection method is the same as that in Example 2, and the results are shown in Table 4:

[0069] Table 4 Physical properties and flexural strength of foam ceramics

[0070]

[0071] Example 5

[0072] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0073] Except for (3) the firing system (heating from room temperature to 1240 °C at a heating rate of 2 °C / min, holding for 60 min, and then cooling down), the remaining steps are the same as those in Example 4, and the results are shown in Table 5:

[0074] Table 5 Physical properties and flexural strength of foam ceramics

[0075]

[0076] Example 6

[0077] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0078] Except for (3) the firing system (heating from room temperature to 1250 °C at a heating rate of 4 °C / min, holding for 20 min, and then cooling down), the remaining steps are the same as those in Example 4, and the results are shown in Table 6:

[0079] Table 6 Physical properties and flexural strength of foam ceramics

[0080]

[0081] Example 7

[0082] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0083] (1) First, pre-treat the municipal solid waste incineration (MSWI) fly ash from Guangdong. Through the water washing process, reduce its chloride ion content. In the experiment, weigh 100 g of dry MSWI fly ash and add 250 ml of deionized water into a 500 ml beaker (liquid-solid ratio is 2.5:1), add a magnetic rotor, and stir magnetically for 30 min. Use a "qualitative filter paper + sintered filter funnel + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear. Then, conduct drying and weighing (dry at 105 °C for 12 h), and use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: the chloride ion content in the fly ash after water washing is lower than 0.1%).

[0084] (2) Then, mix the water-washed MSWI fly ash from Guangdong, kaolin, and quartz in a ratio of 2:2:1, and add an appropriate amount of foaming agent silicon carbide to form a mixture. In the mixture, the content of SiO2 is 52.23 wt%, the content of Al2O3 is 21.42 wt%, the content of CaO is 13.19 wt%, the content of SO3 is 5.05 wt%, the content of Fe2O3 is 3.28 wt%, the content of MgO is 2.34 wt%, the content of K2O is 0.71 wt%, the content of TiO2 is 0.68 wt%, the content of P2O5 is 0.39 wt%, the content of SiC is 0.2 wt%, the content of MnO is 0.08 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (ball-to-material-to-water ratio is 2:1:0.8). After ball milling, dry at 105 °C for 12 h and pass through a 100-mesh sieve.

[0085] (3) Finally, weigh the required amount of the mixed material for tabletting (from 10 Mpa until the pressure no longer decreases), place it on a corundum backing plate, and sinter in an electric resistance furnace according to the established firing system (heat from room temperature to 1230 °C, heating rate is 4 °C / min, hold for 60 min, and then cool down) to obtain a foam ceramic product.

[0086] The detection method is the same as that in Example 2, and the results are shown in Table 7:

[0087] Table 7 Physical properties and flexural strength of foam ceramics

[0088]

[0089] Example 8

[0090] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0091] Except for the firing regime in step (3) (heating from room temperature to 1240 °C at a heating rate of 3 °C / min, holding for 20 min, and then cooling), the other steps are the same as in Example 7. The results are shown in Table 8:

[0092] Table 8 Physical properties and flexural strength of the foam ceramics

[0093]

[0094] Example 9

[0095] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0096] Except for the firing regime in step (3) (heating from room temperature to 1250 °C at a heating rate of 2 °C / min, holding for 40 min, and then cooling), the other steps are the same as in Example 7. The results are shown in Table 9:

[0097] Table 9 Physical properties and flexural strength of the foam ceramics

[0098]

[0099] Example 10

[0100] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0101] (1) First, pre-treat the Guangxi waste incineration fly ash. Through the water washing process, reduce its chloride ion content. Experimentally weigh 100 g of dry waste incineration fly ash and 250 ml of deionized water and add them to a 500 ml beaker (liquid-solid ratio of 2.5:1). Add a magnetic rotor and stir magnetically for 30 min. Use a "qualitative filter paper + sintered filter device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear, and then dry and weigh (dry at 105 °C for 12 h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: the chloride ion content in the fly ash after water washing is less than 0.1%).

[0102] (2) Then mix the washed Guangxi fly ash, kaolin, and waste glass powder in a ratio of 2:2:1, and add an appropriate amount of foaming agent silicon carbide to form a mixture. In the mixture, the content of SiO2 is 47.47 wt%, the content of Al2O3 is 19.43 wt%, the content of CaO is 17.57 wt%, the content of SO3 is 5.48 wt%, the content of MgO is 3.40 wt%, the content of Fe2O3 is 1.95 wt%, the content of Na2O is 1.07 wt%, the content of SiC is 1 wt%, the content of K2O is 0.56 wt%, the content of TiO2 is 0.55 wt%, the content of P2O5 is 0.50 wt%, the content of MnO is 0.08 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (the ratio of balls to materials to water is 2:1:0.8). After ball milling is completed, dry at 105 °C for 12 h and pass through a 100-mesh sieve.

[0103] (3) Finally, weigh the required amount of the mixed material for tabletting (from 10 Mpa until the pressure no longer decreases), put it into a corundum crucible, and sinter it in an electric resistance furnace according to the established firing system (heating from room temperature to 1145 °C at a heating rate of 3 °C / min, holding for 60 min, and then cooling) to obtain a foam ceramic product;

[0104] Refer to [National Standard] GBT6569-2006 "Test Method for Flexural Strength of Fine Ceramics" and [National Standard] JCT647-2005 "Foam Ceramic Thermal Insulation Products". Use a microcomputer-controlled electronic universal testing machine with a specimen size of 3*4*40 mm, a loading speed of 0.5 mm / min, and a span of 30 mm to test and compare its flexural strength.

[0105] Refer to [National Standard] GBT1966-1996 "Test Methods for Apparent Porosity and Bulk Density of Porous Ceramics", [National Standard] HJ1222-2021 "Solid Waste - Determination of Moisture and Dry Matter Content - Gravimetric Method", and HJT766-2015 "Solid Waste - Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method". Use the Archimedes drainage method to test its various physical properties and use the flame atomic absorption spectrophotometer method to test its heavy metal leaching concentration. The results are shown in Table 10:

[0106] Table 10 Physical Properties, Flexural Strength, and Heavy Metal Ion Leaching Concentration of Foam Ceramics

[0107]

[0108] Example 11

[0109] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon domestic waste incineration fly ash includes the following steps:

[0110] (1) First, pre-treat the municipal solid waste incineration fly ash. Through the water washing process, reduce its chloride ion content. Experimentally, weigh 100 g of dry municipal solid waste incineration fly ash and add 250 ml of deionized water into a 500 ml beaker (liquid-solid ratio is 2.5:1). Add a magnetic rotor and stir magnetically for 30 min. Use a "qualitative filter paper + sintered filter plate device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear. Then dry and weigh it (dry at 105 °C for 12 h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: chloride ion content in the fly ash after water washing is lower than 0.1%).

[0111] (2) Then mix the water-washed Guangxi fly ash, kaolin, and waste glass powder in a ratio of 2:2:1, and add an appropriate amount of foaming agent silicon carbide to form a mixture. In the mixture, the content of SiO2 is 47.47 wt%, the content of Al2O3 is 19.43 wt%, the content of CaO is 17.57 wt%, the content of SO3 is 5.48 wt%, the content of MgO is 3.40 wt%, the content of Fe2O3 is 1.95 wt%, the content of Na2O is 1.07 wt%, the content of SiC is 1 wt%, the content of K2O is 0.56 wt%, the content of TiO2 is 0.55 wt%, the content of P2O5 is 0.50 wt%, the content of MnO is 0.08 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (ball-material-water ratio is 2:1:0.8). After ball milling, dry at 105 °C for 12 h and pass through a 100-mesh sieve.

[0112] (3) Finally, weigh the required amount of the mixture for tabletting (from 10 Mpa until the pressure no longer decreases), put it into a corundum crucible, and sinter it in an electric resistance furnace according to the established firing system (heat from room temperature to 1145 °C, heating rate is 2 °C / min, hold for 20 min, and then cool down) to obtain a foam ceramic product.

[0113] Refer to [national standard] GBT6569-2006 "Test Method for Flexural Strength of Fine Ceramics" and [national standard] JCT647-2005 "Foam Ceramic Thermal Insulation Products". Use a microcomputer-controlled electronic universal testing machine. The specimen size is 3*4*40 mm, the loading speed is 0.5 mm / min, and the span is 30 mm. Test and compare its flexural strength.

[0114] Refer to [national standard] GBT1966-1996 "Test Method for Apparent Porosity and Bulk Density of Porous Ceramics", and use the Archimedes drainage method to test its various physical properties. The results are shown in Table 11:[[]]END]]

[0115] Table 11 Physical Properties, Flexural Strength, and Heavy Metal Ion Leaching Concentration of Foam Ceramics

[0116]

[0117] Example 12

[0118] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0119] Except for the firing regime in step (3) (heating from room temperature to 1145 °C at a heating rate of 4 °C / min, holding for 40 min, and then cooling), the remaining steps are the same as those in Example 11. The results are shown in Table 12:

[0120] Table 12 Physical properties, flexural strength, and heavy metal ion leaching concentrations of the foam ceramics

[0121]

[0122] Example 13

[0123] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0124] Except for the firing regime in step (3) (heating from room temperature to 1150 °C at a heating rate of 4 °C / min, holding for 20 min, and then cooling), the remaining steps are the same as those in Example 11. The results are shown in Table 13:

[0125] Table 13 Physical properties, flexural strength, and heavy metal ion leaching concentrations of the foam ceramics

[0126]

[0127] Example 14

[0128] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0129] Except for the firing regime in step (3) (heating from room temperature to 1150 °C at a heating rate of 3 °C / min, holding for 40 min, and then cooling), the remaining steps are the same as those in Example 11. The results are shown in Table 14:

[0130] Table 14 Physical properties, flexural strength, and heavy metal ion leaching concentrations of the foam ceramics

[0131]

[0132] Example 15

[0133] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0134] Except for the firing regime in step (3) (heating from room temperature to 1150 °C at a heating rate of 2 °C / min, holding for 60 min, and then cooling), the other steps are the same as those in Example 11. The results are shown in Table 15:

[0135] Table 15 Physical properties, flexural strength, and heavy metal ion leaching concentration of the foam ceramics

[0136]

[0137] Example 16

[0138] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silica municipal solid waste incineration fly ash includes the following steps:

[0139] Except for the firing regime in step (3) (heating from room temperature to 1155 °C at a heating rate of 3 °C / min, holding for 20 min, and then cooling), the other steps are the same as those in Example 11. The results are shown in Table 16:

[0140] Table 16 Physical properties, flexural strength, and heavy metal ion leaching concentration of the foam ceramics

[0141]

[0142] Example 17

[0143] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silica municipal solid waste incineration fly ash includes the following steps:

[0144] Except for the firing regime in step (3) (heating from room temperature to 1155 °C at a heating rate of 2 °C / min, holding for 40 min, and then cooling), the other steps are the same as those in Example 11. The results are shown in Table 17:

[0145] Table 17 Physical properties, flexural strength, and heavy metal ion leaching concentration of the foam ceramics

[0146]

[0147] Example 18

[0148] In this example, a method for preparing high-strength foam ceramics based on high-calcium and low-silica municipal solid waste incineration fly ash includes the following steps:

[0149] Except for the firing regime in step (3) (heating from room temperature to 1155 °C at a heating rate of 4 °C / min, holding for 60 min, and then cooling), the other steps are the same as those in Example 11. The results are shown in Table 18:

[0150] Table 18 Physical properties, flexural strength and heavy metal ion leaching concentration of foam ceramics

[0151]

[0152] Structural and property descriptions of the samples prepared in the above typical implementation process:

[0153] Figure 1 XRD patterns and physical pictures of Guangdong fly ash, Guangxi fly ash, kaolin, quartz, and waste glass powder in Example 1 and Example 10: (a1) Guangdong fly ash; (a2) Guangxi fly ash; (b) kaolin; (c1) quartz; (c2) waste glass powder; Figure 2 XRD patterns and physical pictures of the mixed materials and foam ceramics in Example 1 and Example 10, where (d1) mixed material containing Guangdong fly ash; (d2) mixed material containing Guangxi fly ash; (e1) foam ceramic containing Guangdong fly ash; (e2) foam ceramic containing Guangxi fly ash. From Figure 1 and Figure 2 It can be seen from the XRD images that the components of fly ash and the mixed materials are relatively complex, kaolin, quartz, and waste glass powder are relatively pure, and the main crystal phases in the foam ceramics are anorthite and calcium silicate.

[0154] Figure 3 SEM images and pore size distribution diagrams of different regions of the foam ceramic containing Guangdong fly ash in Example 1, where (a), (b), (c), and (d) are SEM images at different positions respectively, and (e) is the pore size distribution diagram. It can be seen that the pores are evenly distributed, mostly single pores, and there are very few connected pores. The pore size is mainly distributed at 284 μm.

[0155] Figure 4 SEM images and pore size distribution diagrams of different regions of the foam ceramic containing Guangxi fly ash in Example 10: where (a), (b), (c), and (d) are SEM images at different positions respectively, and (e) is the pore size distribution diagram. It can be seen that the pores are evenly distributed, mostly single pores, and there are very few connected pores. The pore size is mainly distributed at 192 μm.

[0156] Figure 5 In (a) is the SEM image of the foam ceramic containing Guangdong fly ash in Example 1, (b) is the EDS spectrum of the foam ceramic containing Guangdong fly ash in Example 1, and (c) is the distribution diagram of each element in (a). It can be seen from the figure the EDS spectra corresponding to the four elements O, Si, Al, and Ca, and the distribution of the four elements is relatively uniform.

[0157] Figure 6Figure (a) is the EDS spectrum of the foam ceramic containing Guangxi fly ash in Example 10, figure (b) is the EDS spectrum of the foam ceramic containing Guangxi fly ash in Example 10, and figure (c) is the distribution map of each element in (a). It can be seen from the figure that the EDS spectra corresponding to the four elements of O, Si, Al, and Ca, and the distribution of the four elements is relatively uniform.

[0158] The implementation results show that for the foam ceramic prepared by the method of the present invention, the leaching concentration of heavy metal ions meets the national standard requirements, and the flexural strength far exceeds the national standard requirements. It not only realizes waste utilization, provides a new way for the harmless treatment of municipal solid waste incineration fly ash, but also turns waste into treasure and broadens the resource application field of municipal solid waste incineration fly ash.

[0159] Comparative Example 1

[0160] In this comparative example, the method for preparing foam ceramic based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0161] (1) First, pretreat the Guangxi waste incineration fly ash. Through the water washing process, reduce its chloride ion content. Experimentally weigh 100 g of dry waste incineration fly ash and 250 ml of deionized water and add them to a 500 ml beaker (liquid-solid ratio is 2.5:1). Add a magnetic rotor and stir magnetically for 30 min. Use a "qualitative filter paper + sintered filter device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear, and then dry and weigh (dry at 105 °C for 12 h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: the chloride ion content in the fly ash after water washing is less than 0.1%).

[0162] (2) Then mix the water-washed Guangxi fly ash, kaolin, and waste glass powder in a ratio of 5:4:11, and add an appropriate amount of foaming agent silicon carbide to form a mixture; in the mixture, the content of SiO2 is 65.07 wt%, the content of Al2O3 is 11.38 wt%, the content of CaO is 11.08 wt%, the content of SO3 is 3.51 wt%, the content of Na2O is 2.94 wt%, the content of Mg is 2.13 wt%, the content of Fe2O3 is 1.22 wt%, the content of SiC is 1 wt%, the content of P2O5 is 0.38 wt%, the content of K2O is 0.36 wt%, the content of TiO2 is 0.35 wt%, the content of MnO is 0.05 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (ball-material-water ratio is 2:1:0.8). After ball milling, dry at 105 °C for 12 h and pass through a 100-mesh sieve.

[0163] (3) Finally, weigh the required amount of the mixed material and press it into tablets (from 10 Mpa until the pressure no longer decreases). Place it on a corundum backing plate and sinter it in an electric resistance furnace according to the established firing system (heating from room temperature to 1145 °C at a heating rate of 3 °C / min, holding for 60 min, and then cooling down) to obtain a foam ceramic product.

[0164] Compared with Example 10, only the formulation ratio of the raw materials is changed, and the SiO2 content exceeds the control range of 40 wt% - 60 wt%. The foam glass is as Figure 7 shown. Figure 7 In it, (a) is a physical picture of the foam glass of Comparative Example 1, and (b) is a cross-sectional physical picture of the foam glass of Comparative Example 1.

[0165] It can be Figure 7 seen that the SiO2 content in the formulated raw materials should be controlled within 40 wt% - 60 wt%. Beyond this range, it is impossible to sinter and obtain a foam ceramic within the determined firing system range. This is because the increase in the SiO2 content will lead to an increase in the sintering temperature, and preparing a foam ceramic product requires consuming more energy, which is not conducive to energy conservation and emission reduction. At the same time, the fly ash utilization rate of this ratio formulation is relatively low, and the waste utilization effect is average.

[0166] Comparative Example 2

[0167] In this comparative example, a method for preparing a foam ceramic based on high-calcium and low-silicon domestic waste incineration fly ash includes the following steps:

[0168] (1) First, pretreat the Guangxi waste incineration fly ash. Through the water washing process, reduce its chloride ion content. Experimentally weigh 100 g of dry waste incineration fly ash and 250 ml of deionized water and add them to a 500 ml beaker (liquid-solid ratio is 2.5:1). Add a magnetic rotor and stir magnetically for 30 min. Use a "qualitative filter paper + sand core filtration device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear, and then dry and weigh it (dry at 105 °C for 12 h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the chloride ion removal effect (ideal effect: the chloride ion content in the fly ash after water washing is lower than 0.1%).

[0169] (2) Then mix the washed Guangxi fly ash, kaolin, and waste glass powder in a ratio of 3:6:1, and add an appropriate amount of foaming agent silicon carbide to form a mixture. In the mixture, the content of SiO2 is 48.18 wt%, the content of Al2O3 is 26.76 wt%, the content of CaO is 13.16 wt%, the content of SO3 is 4.12 wt%, the content of MgO is 2.55 wt%, the content of Fe2O3 is 1.67 wt%, the content of SiC is 1 wt%, the content of K2O is 0.59 wt%, the content of Na2O is 0.53 wt%, the content of TiO2 is 0.42 wt%, the content of P2O5 is 0.37 wt%, the content of MnO is 0.06 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (the ratio of balls to materials to water is 2:1:0.8). After ball milling, dry at 105 °C for 12 h and screen through a 100-mesh sieve.

[0170] (3) Finally, weigh the required amount of the mixed material for tableting (from 10 Mpa until the pressure no longer decreases), place it on a corundum backing plate, and sinter it in a resistance furnace according to the established firing system (heating from room temperature to 1145 °C at a heating rate of 3 °C / min, holding for 60 min, and then cooling) to obtain a foam ceramic product.

[0171] Compared with Example 10, only the formulation ratio of the raw materials is changed, and the content of Al2O3 exceeds the control range of 10 wt% - 20 wt%. The insufficiently sintered foam ceramics are as Figure 8 shown. Figure 8 In Figure 1 , (a) is the physical object of the insufficiently sintered foam ceramic of Comparative Example 2 Figure 2 .

[0172] It can be seen from Figure 8 that the content of Al2O3 in the formulated raw materials should be controlled within 10 wt% - 25 wt%. Beyond this range, within the determined firing system range, foam ceramics cannot be sintered. This is because the increase in the content of Al2O3 will cause the softening temperature of the specimen to rise, resulting in an increase in the sintering temperature. Preparing foam ceramic products requires consuming more energy, which is not conducive to energy conservation and emission reduction. At the same time, the utilization rate of fly ash in this ratio formulation is relatively low, and the waste utilization effect is average.

[0173] Comparative Example 3

[0174] In this comparative example, the method for preparing foam ceramics based on high-calcium and low-silicon domestic waste incineration fly ash includes the following steps:

[0175] (1) First, pre-treat the municipal solid waste incineration fly ash in Guangxi. Through the water washing process, reduce its chloride ion content. In the experiment, weigh 100 g of dry municipal solid waste incineration fly ash and add 250 ml of deionized water into a 500 ml beaker (liquid-solid ratio is 2.5:1). Add a magnetic rotor and stir magnetically for 30 min. Use a "qualitative filter paper + sintered filter plate device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear. Then, dry and weigh (dry at 105 °C for 12 h). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: the chloride ion content in the fly ash after water washing is lower than 0.1%).

[0176] (2) Then, mix the water-washed fly ash in Guangxi, kaolin, and waste glass powder in a ratio of 11:4:5, and add an appropriate amount of foaming agent silicon carbide to form a mixture. In the mixture, the content of SiO2 is 43.10 wt%, the content of CaO is 24.15 wt%, the content of Al2O3 is 12.73 wt%, the content of SO3 is 7.51 wt%, the content of MgO is 4.68 wt%, the content of Fe2O3 is 2.44 wt%, the content of Na2O is 1.34 wt%, the content of SiC is 1 wt%, the content of TiO2 is 0.74 wt%, the content of P2O5 is 0.68 wt%, the content of K2O is 0.56 wt%, the content of MnO is 0.10 wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 h (ball-to-material-to-water ratio is 2:1:0.8). After ball milling, dry at 105 °C for 12 h and pass through a 100-mesh sieve.

[0177] (3) Finally, weigh the required amount of the mixed material for tabletting (from 10 Mpa until the pressure no longer decreases), place it on a corundum backing plate, and sinter it in an electric resistance furnace according to the established firing system (heat from room temperature to 1145 °C at a heating rate of 3 °C / min, hold for 60 min, and then cool down) to obtain a foam ceramic product.

[0178] Compared with Example 10, only the formulation ratio of the raw materials is changed, and the CaO content exceeds the controlled range of 10 wt% - 20 wt%. The glass ceramics are as Figure 9 shown. Figure 9 In Figure 1 , (a) is the glass ceramic in Comparative Example 3 Figure 2 .

[0179] From Figure 9It is known that the content of CaO in the formula raw materials should be controlled within 10wt% - 20wt%. Beyond this range, within the determined firing regime, it is impossible to sinter and obtain foamed ceramics. This is because CaO can act as a sintering aid, and if the content is too high, it will significantly reduce the sintering temperature, causing the foaming agent SiC to be difficult to function effectively.

[0180] Comparative Example 4

[0181] In this comparative example, a method for preparing foamed ceramics based on high-calcium and low-silicon municipal solid waste incineration fly ash includes the following steps:

[0182] (1) First, pretreat the Guangxi waste incineration fly ash. Through the water washing process, reduce its chloride ion content. Experimentally, weigh 100g of dry waste incineration fly ash and add 250ml of deionized water to a 500ml beaker (liquid-solid ratio is 2.5:1). Add a magnetic rotor and stir magnetically for 30 minutes. Use a "qualitative filter paper + sintered filter device + vacuum pump" for solid-liquid separation, then add deionized water for suction filtration until the filtrate is clear, and then dry and weigh (dry at 105°C for 12 hours). Use EDX to detect the content of each element in the fly ash before and after water washing to verify the removal effect of chloride ions (ideal effect: the chloride ion content in the fly ash after water washing is less than 0.1%).

[0183] (2) Then mix the water-washed Guangxi fly ash, kaolin, and waste glass powder in a ratio of 2:2:1, and add an appropriate amount of the foaming agent silicon carbide to form a mixture. In the mixture, the content of SiO2 is 46.99wt%, the content of Al2O3 is 19.43wt%, the content of CaO is 17.39wt%, the content of SO3 is 5.42wt%, the content of MgO is 3.37wt%, the content of Fe2O3 is 1.93wt%, the content of SiC is 2wt%, the content of Na2O is 1.06wt%, the content of K2O is 0.56wt%, the content of TiO2 is 0.54wt%, the content of P2O5 is 0.50wt%, the content of MnO is 0.08wt%, and the balance is impurities, totaling 100%; ball mill in a high-speed grinder for 8 hours (ball-material-water ratio is 2:1:0.8). After ball milling is completed, dry at 105°C for 12 hours and pass through a 100-mesh sieve.

[0184] (3) Finally, weigh the required amount of the mixed material for tabletting (from 10 Mpa until the pressure no longer decreases), place it on a corundum backing plate, and sinter in an electric resistance furnace according to the established firing regime (heat up from room temperature to 1145°C at a heating rate of 3°C / min, hold for 60 minutes, and then cool down) to obtain the foamed ceramic product.

[0185] Compared with Example 10, only the content of the foaming agent is increased to 2wt%, exceeding the content control range of SiC of 0.2wt% - 1wt%. The foamed ceramics are as followsFigure 10 As shown Figure 10 In (a) is the physical diagram of the foam ceramic of Comparative Example 4, and (b) is the cross-sectional physical diagram of the foam ceramic of Comparative Example 4.

[0186] It can be seen from Figure 10 that: the content of the foaming agent SiC in the formula raw materials should be controlled at 0.2wt~1wt%. Exceeding this range, the foaming effect of the foam ceramic is extremely poor. This is because the excessive aggregation of the foaming agent content leads to the appearance of a large number of large pores, making it difficult to carry out processing and performance testing and unable to be applied to production practice.

[0187] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing foam ceramics from municipal solid waste incineration fly ash with high calcium and low silicon content, characterized in that It includes the following steps: Wash the high-calcium and low-silicon municipal solid waste incineration fly ash to reduce the chloride ion content; the high-calcium and low-silicon municipal solid waste incineration fly ash contains 30 wt% - 45 wt% of CaO and 15 wt% - 25 wt% of SiO2; Using the washed fly ash, kaolin, quartz or waste glass powder as raw materials, silicon carbide as the foaming agent, mix and ball-mill. After ball-milling is completed, dry and screen to prepare a mixture; Press the mixture into tablets and then sinter to obtain a porous ceramic; The mixture contains the following components: 40 wt% - 60 wt% of SiO2, 19.43 wt% - 21.42 wt% of Al2O3, 10 wt% - 20 wt% of CaO, 0.2 wt% - 1.0 wt% of silicon carbide; The sintering procedure is: heat from room temperature to 1230 °C - 1250 °C at a heating rate of 2 °C / min - 4 °C / min, hold for 20 min - 60 min, and then cool down.

2. The method according to claim 1, characterized in that The municipal solid waste incineration fly ash consists of the following components Composition: CaO: 30 wt% - 35 wt%, SiO2: 20 wt% - 25 wt%, Al2O3: 10 wt% - 15 wt%, SO3: 10 wt% - 15 wt%, Fe2O3: 5 wt% - 10 wt%, MgO: 5 wt% - 10 wt%, TiO2: 1 wt% - 2 wt%, K2O: 1 wt% - 2 wt%, P2O5: 0.5 wt% - 1.5 wt%, MnO: 0.1 wt% - 0.5 wt%, and the balance is impurities, totaling 100%.

3. The method according to claim 1, characterized in that The municipal solid waste incineration fly ash consists of the following components: CaO: 40 wt% - 45 wt%, SiO2: 15 wt% - 20 wt%, SO3: 10 wt% - 15 wt%, Al2O3: 5 wt% - 10 wt%, MgO: 5 wt% - 10 wt%, Fe2O3: 1 wt% - 5 wt%, TiO2: 1 wt% - 2 wt%, P2O5: 1 wt% - 2 wt%, K2O: 0.1 wt% - 1 wt%, MnO: 0.1 wt% - 0.5 wt%, and the balance is impurities, totaling 100%.

4. The method according to claim 3, wherein The sintering procedure is: heat from room temperature to 1145 °C - 1155 °C at a heating rate of 2 °C / min - 4 °C / min, hold for 20 min - 60 min, and then cool down.

5. The method according to claim 1, wherein The kaolin consists of the following components: SiO2: 55 wt% - 60 wt%, Al2O3: 40 wt% - 45 wt%, Fe2O3: 0.1 wt% - 1 wt%, K2O: 0.1 wt% - 1 wt%, TiO2: 0.01 wt% - 0.1 wt%, BaO: 0.01 wt% - 0.1 wt%, MnO: 0.01 wt% - 0.1 wt%, SO3: 0.01 wt% - 0.1 wt%, the balance being impurities, totaling 100%.

6. The method according to claim 1, wherein Quartz consists of the following components: SiO2: 99.00 wt% - 99.80 wt%, Al2O3: 0.1 wt% - 1 wt%, Fe2O3: 0.01 wt% - 0.1 wt%, CaO: 0.01 wt% - 0.1 wt%, SO3: 0.01 wt% - 0.1 wt%, totaling 100%.

7. The method according to claim 1, characterized in that Waste glass powder consists of the following components: SiO2: 90 wt% - 95 wt%, Na2O: 5 wt% - 10 wt%, Al2O3: 1 wt% - 5 wt%, CaO: 0.1 wt% - 0.5 wt%, K2O: 0.1 wt% - 0.5 wt%, P2O5: 0.1 wt% - 0.5 wt%, SO3: 0.1 wt% - 0.5 wt%, Fe2O3: 0.01 wt% - 0.1 wt%, TiO2: 0.01 wt% - 0.1 wt%, the balance being impurities, totaling 100%.

8. The method according to claim 1, wherein The mass ratio of the washed fly ash, kaolin, quartz or waste glass powder is 2:2:

1.

9. The method according to claim 1, wherein The particle size of the raw materials does not exceed 100 mesh, the particle size of silicon carbide ≤ 30 μm, the mixture is ball-milled and then dried, and then passed through a 100-mesh sieve.

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