Composite ceramsite based on waste incineration fly ash and preparation method thereof

Abstract

The invention discloses composite ceramsite based on waste incineration fly ash and a preparation method of the composite ceramsite, belongs to the field of recycling of solid wastes, and is used for solving at least one of the problems of high energy consumption, high cost and poor long-term stability of stable treatment of the waste incineration fly ash in the prior art. The composite ceramsite is of a three-layer structure and comprises an inner core, a middle-layer shell membrane and an outer-layer shell membrane, wherein the inner core is sequentially wrapped with the middle-layer shell membrane and the outer-layer shell membrane from inside to outside. The preparation method comprises the following steps: preparing a pellet from an inner core raw material, and drying and shaping the pellet to obtain an inner core; the inner core is placed in the middle-layer shell membrane slurry, the inner core wrapped with the middle-layer shell membrane slurry is dried and shaped, and a composite pellet is obtained; the composite pellets are placed in the outer layer shell membrane slurry, the composite pellets wrapped with the outer layer shell membrane slurry are dried and shaped, and composite ceramsite raw material pellets are obtained; and sintering the composite ceramsite raw material balls by adopting a two-stage sintering method, and cooling to obtain the composite ceramsite. The method can be used for preparing the composite ceramsite.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling, specifically relating to a composite ceramsite based on waste incineration fly ash and its preparation method, wherein composite ceramsite is prepared by using waste incineration fly ash as a base in conjunction with coal gangue and sludge. Background Technology

[0002] Currently, the technologies for stabilizing fly ash from waste incineration include cement solidification, alkali-activated solidification, high-temperature solidification, and chemical stabilization.

[0003] Cement solidification involves mixing fly ash with cement and water in a certain proportion. During the cement hydration process, the hydration products precipitate heavy metals as hydroxides or complexes in the cement hydration products through physical bonding, adsorption, and isomorphous displacement. However, the products have problems such as low strength and poor long-term stability.

[0004] Alkali-activated curing involves using high concentrations of alkali to further recombine and polymerize Si and Al leached from fly ash, forming hydrated calcium aluminosilicate (CASH) and hydrated sodium aluminosilicate (NASH) gels. The heavy metals are then cured through the gels. However, the high concentrations of alkali used in the curing process are highly corrosive and pollute the environment.

[0005] High-temperature solidification involves heating fly ash from waste incineration to 1100–1500°C to melt it, followed by water quenching to achieve extreme cooling. This solidification process forms a dense and uniform glassy body, which results in high energy consumption and high cost.

[0006] Chemical stabilization involves using inorganic stabilizers (such as NaOH, Na2S, phosphates, or silicates) and organic chelating agents (such as dithiocarbamate DTC, ethylenediaminetetraacetic acid EDTA and its sodium salt, 2,4,6-trithio-1,3,5-triazine trisodium salt TMT, etc.) to convert heavy metals in waste incineration fly ash into compounds with lower hazard levels. However, the products have poor long-term stability. Summary of the Invention

[0007] In view of the above analysis, the present invention aims to provide a composite ceramsite based on waste incineration fly ash and its preparation method, in order to solve at least one of the problems of high energy consumption, high cost and poor long-term stability in the stable disposal of waste incineration fly ash in the prior art.

[0008] The objective of this invention is mainly achieved through the following technical solutions.

[0009] In a first aspect, the present invention provides a composite ceramsite based on waste incineration fly ash. The composite ceramsite has a three-layer structure, including a core and a middle shell membrane and an outer shell membrane that are sequentially wrapped around the core from the inside out.

[0010] Furthermore, the pore diameters within the core, the middle shell, and the outer shell gradually decrease.

[0011] Furthermore, the porosity of the core, the middle shell, and the outer shell gradually decreases.

[0012] Secondly, the present invention also provides a method for preparing composite ceramsite based on waste incineration fly ash, characterized in that the preparation method for the above-mentioned composite ceramsite includes the following steps:

[0013] The kernel material is made into pellets, and the pellets are dried and shaped to obtain the kernel.

[0014] The core is placed in the middle shell membrane slurry, and the core coated with the middle shell membrane slurry is dried and shaped to obtain composite pellets;

[0015] The composite pellets are placed in the outer shell slurry, and the composite pellets coated with the outer shell slurry are dried and shaped to obtain composite ceramsite raw pellets.

[0016] Composite ceramsite raw material balls are sintered using a two-stage sintering method, and then cooled to obtain composite ceramsite.

[0017] Furthermore, the drying and setting temperature is 100℃~110℃, and the drying and setting time is 1.5h~2.5h.

[0018] Furthermore, the particle size of the composite ceramsite raw material balls is 8mm to 10mm.

[0019] Furthermore, the two-stage sintering method includes the following steps:

[0020] The composite ceramsite raw material balls are heated and kept at a constant temperature for preheating;

[0021] The preheated composite ceramsite raw material balls are heated and kept at a constant temperature for sintering.

[0022] Furthermore, the heating rates for both preheating and sintering are 8℃ / min to 12℃ / min.

[0023] Furthermore, the preheating temperature is 350℃~550℃, and the preheating and holding time is 10min~50min.

[0024] Furthermore, the sintering temperature is 1075℃~1175℃, and the sintering holding time is 5min~45min.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] A) The method for preparing composite ceramsite based on waste incineration fly ash provided by the present invention uses waste incineration fly ash, coal gangue and sludge to synergistically prepare three-layer composite ceramsite. This method not only enables diversified and efficient utilization of waste incineration fly ash, coal gangue and sludge, but also produces composite ceramsite products with light spacing and high strength.

[0027] B) The method for preparing composite ceramsite based on waste incineration fly ash provided by this invention uses a core of sludge powder and waste incineration fly ash powder. Since sludge contains organic matter (e.g., carbon) and waste incineration fly ash contains iron oxide, calcium oxide, sodium oxide, silicon oxide and aluminum oxide, alkali metal oxides such as calcium oxide and sodium oxide also act as fluxes to reduce the firing temperature of composite ceramsite. Silicon oxide and aluminum oxide, as ceramic aids, provide a dense ceramic skeleton through crystal phase transformation. Carbon and iron oxide will generate gas through reduction reaction during the subsequent high-temperature sintering process. At the same time, the low-temperature combustion gas of organic matter will also be adhered to the composite ceramsite embryo, initially forming a porous structure. Therefore, using this structure as the core can ensure the rich pores inside the composite ceramsite.

[0028] C) The method for preparing composite ceramsite based on waste incineration fly ash provided by this invention has a porous core structure, which means poor strength. To improve the strength, it is necessary to increase the content of SiO2 and Al2O3 in the raw materials. Therefore, the middle shell membrane is made of waste incineration fly ash combined with sludge and coal gangue. Coal gangue is a solid waste generated during coal mining and coal preparation. Its chemical composition contains SiO2 and Al2O3, which can supplement the ceramic skeleton of the middle shell membrane and make up for the insufficient strength caused by the porosity. At the same time, the rich iron oxide and organic matter in waste incineration fly ash and sludge will also form some small and dense pores in the middle shell membrane, which can ensure the continuity between the three layers.

[0029] D) The method for preparing composite ceramsite based on waste incineration fly ash provided by the present invention uses pure coal gangue as raw material for the outermost layer (i.e., outer membrane shell) of the composite ceramsite, forming a glass-like shell, which can further improve the structural strength of the composite ceramsite.

[0030] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0031] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0032] Figure 1 A schematic diagram of the structure of composite ceramsite based on waste incineration fly ash provided by the present invention;

[0033] Figure 2 This is a comparison chart of the 1-hour water absorption rate and compressive strength of Examples 1-3 and Comparative Example 1;

[0034] Figure 3 This is a comparison chart of the chloride salt content in the fly ash of incinerated waste obtained in step A of Examples 1-3 and Comparative Example 1;

[0035] Figure 4 This is a performance comparison chart of the kernels in Examples 1-3, 2-1, and 2-4;

[0036] Figure 5 This is a performance comparison chart of the composite pellets from Examples 2-1, 2-2, and 2-3;

[0037] Figure 6 This is a comparison chart of the compressive strength and 1-hour water absorption rate of the core, composite pellets and composite ceramsite in Example 2-2;

[0038] Figure 7 This is a comparison chart of the performance parameters of the composite ceramsite in Examples 1-3 and Examples 3-1 to 3-4;

[0039] Figure 8 This is a comparison chart of the performance parameters of the composite ceramsite in Examples 1-3, 3-5 to 3-8;

[0040] Figure 9 This is a comparison chart of the performance parameters of the composite ceramsite in Examples 1-3, 3-9 to 3-12;

[0041] Figure 10 The graph shows a comparison of the performance parameters of the composite ceramsite in Examples 1-3, 3-13 to 3-16.

[0042] Figure label:

[0043] 1-Core; 2-Middle membrane shell; 3-Outer membrane shell. Detailed Implementation

[0044] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0045] In a first aspect, the present invention provides a method for preparing composite ceramsite based on waste incineration fly ash, comprising the following steps:

[0046] Step 1: Mix the incineration fly ash powder and sludge powder evenly, then add water to obtain the core material. The incineration fly ash powder accounts for 35% to 40% by mass percentage, and the sludge powder accounts for 60% to 70%. For example, the mass percentages of incineration fly ash powder and sludge powder are 30%:70%, 35%:65%, or 40%:60%, respectively. The mass percentage of water in the core material is 28% to 32% (for example, 30%).

[0047] After uniformly mixing waste incineration fly ash powder, sludge powder, and coal gangue powder, water is added to obtain the intermediate shell membrane slurry. The waste incineration fly ash powder accounts for 20% to 40% by mass, the sludge powder accounts for 25% to 35%, and the coal gangue powder accounts for 35% to 45%. For example, the mass percentages of waste incineration fly ash powder, sludge powder, and coal gangue powder are 40%:25%:35%, 30%:30%:40%, or 20%:35%:45%, respectively. The mass percentage of water in the intermediate shell membrane slurry is 30% to 38% (e.g., 35 wt%).

[0048] Water is added to coal gangue powder to obtain an outer shell membrane slurry, wherein the mass percentage of water in the outer shell membrane slurry is 30% to 38% (e.g., 35 wt%).

[0049] Step 2: Form the kernel material into pellets with a particle size of 5 mm to 6 mm, and place the pellets in a drying oven at 100°C to 110°C (e.g., 105°C) for 1.5 h to 2.5 h (e.g., 2 h) to obtain the kernel;

[0050] Step 3: Place the core in the middle shell membrane slurry, and place the core coated with the middle shell membrane slurry in a drying oven at 100℃~110℃ (e.g., 105℃) for 1.5h~2.5h (e.g., 2h) to obtain composite pellets;

[0051] Step 4: Place the composite pellets in the outer shell slurry, and place the composite pellets coated with the outer shell slurry in a drying oven at 100℃~110℃ (e.g., 105℃) for 1.5h~2.5h (e.g., 2h) to obtain composite ceramsite raw pellets with a particle size of 8mm~10mm.

[0052] Step 5: Place the composite ceramsite raw pellets in a muffle furnace and fire them using a two-stage sintering method. After naturally cooling to room temperature, the composite ceramsite is obtained.

[0053] Compared with the prior art, the method for preparing composite ceramsite based on waste incineration fly ash provided by the present invention uses waste incineration fly ash, coal gangue and sludge to synergistically prepare a three-layer composite ceramsite. This method not only enables diversified and efficient utilization of waste incineration fly ash, coal gangue and sludge, but also produces composite ceramsite products with high strength and light spacing.

[0054] Specifically, on the one hand, in the above-mentioned composite ceramsite, the core is made of a mixture of sludge powder and waste incineration fly ash powder. Since sludge contains organic matter (e.g., carbon) and waste incineration fly ash contains iron oxide, calcium oxide, sodium oxide, silicon oxide and aluminum oxide, etc. Alkali metal oxides such as calcium oxide and sodium oxide will also act as fluxes to reduce the firing temperature of composite ceramsite. Silicon oxide and aluminum oxide, as ceramic aids, provide a dense ceramic skeleton through crystal phase transformation. Carbon and iron oxide will generate gas through reduction reaction during the subsequent high-temperature sintering process. At the same time, the low-temperature combustion gas of organic matter will also be adhered to the composite ceramsite body, initially forming a porous structure. Therefore, using this structure as the core can ensure the rich pores inside the composite ceramsite.

[0055] On the other hand, the porous structure of the core means poor strength. To improve the strength, the content of SiO2 and Al2O3 in the raw materials needs to be increased. Therefore, the middle shell membrane is made of a mixture of waste incineration fly ash, sludge and coal gangue. Coal gangue is a solid waste generated during coal mining and coal preparation. Its chemical composition contains SiO2 and Al2O3, which can supplement the ceramic skeleton of the middle shell membrane and make up for the lack of strength caused by the porosity. At the same time, the rich iron oxide and organic matter in waste incineration fly ash and sludge will also form some small and dense pores in the middle shell membrane, which can ensure the continuity between the three layers.

[0056] On the other hand, the outermost layer (i.e., the outer membrane shell) of the composite ceramsite is made of pure coal gangue as raw material, forming a glass-like shell, which can further improve the structural strength of the composite ceramsite.

[0057] In order to obtain the above-mentioned raw material powder, the following steps are included before step 1:

[0058] Waste incineration fly ash powder, sludge powder, and coal gangue powder were prepared separately.

[0059] Specifically, the preparation method of waste incineration fly ash powder includes the following steps:

[0060] The fly ash from waste incineration is washed with water at a solid-liquid ratio of 6 to 9:1, a temperature of 50°C to 70°C, and a washing time of 40 to 60 minutes to remove soluble chloride salts from the fly ash.

[0061] The mixture after washing with water is subjected to solid-liquid separation to obtain a solid phase and a liquid phase;

[0062] The solid phase is dried in a drying oven at 100°C to 110°C (e.g., 105°C) for 18 to 30 hours (e.g., 24 hours).

[0063] The dried solid phase is crushed into powder and passed through a 100-mesh sieve to obtain waste incineration fly ash powder.

[0064] It should be noted that since incineration fly ash contains soluble chloride salts, direct use will not only affect the performance of composite sintered ceramic particles, but will also promote the low-temperature resynthesis of dioxins during the sintering cooling process by providing a chlorine source. Therefore, water washing of incineration fly ash during the preparation of incineration fly ash powder can remove most of the soluble chloride salts, which can not only further improve the overall performance of composite ceramic particles, but also avoid the generation of dioxins. In addition, water washing can also improve the compressive strength of composite ceramic particles.

[0065] The preparation method of the above-mentioned sludge powder includes the following steps:

[0066] The sludge was dried in a drying oven at 100°C to 110°C (e.g., 105°C) for 18 to 30 hours (e.g., 24 hours).

[0067] The dried sludge was crushed into powder and passed through a 100-mesh sieve to obtain sludge powder.

[0068] The preparation method of the above-mentioned coal gangue powder includes the following steps:

[0069] The coal gangue is crushed into powder and passed through a 100-mesh sieve to obtain coal gangue powder.

[0070] To ensure the stability of the three-layer structure and the overall performance of the composite ceramsite, step 5 above, the two-stage sintering method, includes the following steps:

[0071] Step 51: Preheat the composite ceramsite raw material balls by heating them to 350℃~550℃ at a heating rate of 8℃ / min~12℃ / min and holding them at that temperature for 10min~50min.

[0072] Step 52: Sinter the preheated composite ceramsite raw material balls at a heating rate of 8℃ / min~12℃ / min to 1075℃~1175℃ for 5min~45min.

[0073] In this way, by adopting the above two-stage sintering method and limiting the preheating and sintering process parameters within the above range, it is possible to ensure the full sintering of the composite ceramsite raw pellets and form a three-layer composite ceramsite structure.

[0074] Secondly, the present invention also provides a composite ceramsite based on waste incineration fly ash, which is prepared by the method for preparing composite ceramsite based on waste incineration fly ash provided in the first aspect.

[0075] Specifically, the composite ceramsite has a three-layer structure, see [link to documentation]. Figure 1 It includes the kernel 1 and the middle shell 2 and the outer shell 3 that wrap around the kernel from the inside out.

[0076] Among them, the pores of the core 1 are large and scattered, the pores of the middle shell 2 are small and dense, and the outer shell 3 is almost poreless. That is to say, the pore size and porosity of the pores in the core 1, the middle shell 2 and the outer shell 3 gradually decrease.

[0077] Compared with the prior art, the beneficial effects of the composite ceramsite based on waste incineration fly ash provided by the present invention are basically the same as the beneficial effects of the preparation method of composite ceramsite based on waste incineration fly ash provided in the first aspect, and will not be elaborated here.

[0078] Example 1

[0079] This embodiment provides a method for preparing composite ceramsite based on waste incineration fly ash, including the following steps:

[0080] Step A: Wash the fly ash from waste incineration with water, and perform solid-liquid separation on the mixture after washing to obtain a solid phase and a liquid phase. Place the solid phase in a drying oven at 105℃ and dry it for 24 hours. Crush the dried solid phase into powder and pass it through a 100-mesh sieve to obtain waste incineration fly ash powder.

[0081] The sludge was dried in a drying oven at 105℃ for 24 hours. The dried sludge was then crushed into powder and passed through a 100-mesh sieve to obtain sludge powder.

[0082] The coal gangue is crushed into powder and passed through a 100-mesh sieve to obtain coal gangue powder.

[0083] Step B: Mix 30% of the waste incineration fly ash powder and 70% of the sludge powder evenly, then add 30% water to obtain the core raw material;

[0084] Mix 30% of waste incineration fly ash powder, 30% of sludge powder and 40% of coal gangue powder evenly, then add 30% water to obtain the middle shell membrane slurry.

[0085] Adding 30% water to coal gangue powder yields an outer shell slurry.

[0086] Step C: The kernel material is made into pellets with a particle size of 5mm to 6mm, and the pellets are placed in a drying oven at 105℃ for 2 hours to set, thus obtaining the kernel;

[0087] Step D: Place the core in the middle shell membrane slurry, and place the core coated with the middle shell membrane slurry in a drying oven at 105°C for 2 hours to set, thereby obtaining composite pellets;

[0088] Step E: Place the composite pellets in the outer shell slurry, and place the composite pellets coated with the outer shell slurry in a drying oven at 105℃ for 2 hours to fix them, thereby obtaining composite ceramsite raw pellets with a particle size of 8mm.

[0089] Step F: Preheat the composite ceramsite raw material balls to 400℃ at a heating rate of 10℃ / min and hold for 20 minutes;

[0090] Step G: The preheated composite ceramsite raw material balls are heated to 1150℃ at a heating rate of 10℃ / min and sintered for 35 minutes. After naturally cooling to room temperature, the composite ceramsite is obtained.

[0091] The water washing parameters for Examples 1-1 to 1-5 are shown in Table 1.

[0092] Table 1. Washing parameters for Examples 1-1 to 1-5

[0093] Liquid-to-solid ratio Water washing temperature / ℃ Washing time / min Chloride content / % Example 1-1 6：1 50 40 7.12 Examples 1-2 9：1 50 40 6.89 Examples 1-3 6：1 50 40 7.12 Examples 1-4 6：1 70 40 7.04 Examples 1-5 6：1 50 60 7.86

[0094] Comparative Example 1

[0095] Comparative Example 1 and Example 1 follow essentially the same steps, with the only difference being:

[0096] In step A, the fly ash from waste incineration was not washed with water during the preparation of the waste incineration fly ash powder.

[0097] According to the national standard GB-T 17431.1-2010 "Lightweight aggregates and their test methods - Part 1: Lightweight aggregates", the water absorption rate and compressive strength of Example 1 and Comparative Example 1 were determined after 1 hour.

[0098] Figure 2 This is a comparison chart of the 1-hour water absorption rate and compressive strength of Examples 1-3 and Comparative Example 1. Figure 3 This is a comparison chart of the chloride salt content in the fly ash of incinerated waste obtained in step A of Examples 1-3 and Comparative Example 1.

[0099] from Figure 2 It can be seen that the composite ceramsite prepared in Examples 1-3 has significantly better 1-hour water absorption rate and compressive strength than the composite ceramsite prepared in Comparative Example 1. Figure 3 It can be seen that the water washing process can significantly reduce soluble chloride salts in waste incineration fly ash.

[0100] Example 2

[0101] This embodiment provides a method for preparing composite ceramsite based on waste incineration fly ash, including the following steps:

[0102] Step A: Wash the waste incineration fly ash with water at a solid-liquid ratio of 6:1, a washing temperature of 50℃, and a washing time of 40 minutes. Separate the solid and liquid phases after washing. Place the solid phase in a drying oven at 105℃ and dry it for 24 hours. Crush the dried solid phase into powder and pass it through a 100-mesh sieve to obtain waste incineration fly ash powder.

[0103] The sludge was dried in a drying oven at 105℃ for 24 hours. The dried sludge was then crushed into powder and passed through a 100-mesh sieve to obtain sludge powder.

[0104] The coal gangue is crushed into powder and passed through a 100-mesh sieve to obtain coal gangue powder.

[0105] Step B: Mix the fly ash powder from waste incineration with the sludge powder evenly, then add water to obtain the core raw material;

[0106] After mixing the fly ash powder from waste incineration, sludge powder, and coal gangue powder evenly, water is added to obtain the middle shell membrane slurry.

[0107] Water is added to coal gangue powder to obtain an outer shell slurry;

[0108] Step C: The kernel material is made into pellets with a particle size of 5mm to 6mm, and the pellets are placed in a drying oven at 105℃ for 2 hours to set, thus obtaining the kernel;

[0109] Step D: Place the core in the middle shell membrane slurry, and place the core coated with the middle shell membrane slurry in a drying oven at 105°C for 2 hours to set, thereby obtaining composite pellets;

[0110] Step E: Place the composite pellets in the outer shell slurry, and place the composite pellets coated with the outer shell slurry in a drying oven at 105℃ for 2 hours to fix them, thereby obtaining composite ceramsite raw pellets with a particle size of 8mm.

[0111] Step F: Preheat the composite ceramsite raw material balls to 400℃ at a heating rate of 10℃ / min and hold for 20 minutes;

[0112] Step G: The preheated composite ceramsite raw material balls are heated to 1150℃ at a heating rate of 10℃ / min and sintered for 35 minutes. After naturally cooling to room temperature, the composite ceramsite is obtained.

[0113] The composition of the three-layer raw materials in Examples 2-1 to 2-4 is shown in Table 2.

[0114] Table 2. Composition of the three-layer raw materials in Examples 2-1 to 2-4

[0115]

[0116] According to the national standard GB-T 17431.1-2010 "Lightweight aggregates and their test methods - Part 1: Lightweight aggregates", the bulk density, volume density, 1-hour water absorption rate and compressive strength of the cores of Examples 1-3, 2-1 and 2-4, the composite pellets of Examples 2-1, 2-2 and 2-3, and the composite ceramsite of Example 2-2 were determined, as shown in Table 3.

[0117] Table 3. Bulk density, volume density, 1-hour water absorption rate, and compressive strength data for Example 2.

[0118]

[0119]

[0120] Figure 4 This is a performance comparison chart of the kernels for Examples 1-3, 2-1, and 2-4. Figure 5 This is a performance comparison chart of the composite pellets from Examples 2-1, 2-2, and 2-3. Figure 6 This is a comparison chart of the compressive strength and 1-hour water absorption rate of the core, composite pellets and composite ceramsite in Example 2-2.

[0121] contrast Figure 4 and Figure 5 It can be seen that the core has the lowest bulk density and compressive strength as well as the highest water absorption rate, indicating that the organic matter in the sludge is fully combusted, resulting in a lighter porous structure in the core. Compared with the core, the composite pellets obtained after sintering the middle shell slurry significantly improve the compressive strength and reduce the water absorption rate. This indicates that the ceramic aid components SiO2 and Al2O3 in the coal gangue provide a dense ceramic skeleton for the composite pellets through crystal phase transformation during the sintering process, forming a dense intermediate shell on the surface of the core, reducing the water absorption rate and improving the compressive strength.

[0122] from Figure 6 It can be seen that the compressive strength of the three-layer composite ceramsite is significantly improved due to the coating of pure coal gangue slurry on the outer layer. At the same time, the water absorption rate in 1 hour is also greatly reduced, indicating that the multi-layer composite ceramsite has both low water absorption and high strength.

[0123] Example 3

[0124] This embodiment provides a method for preparing composite ceramsite based on waste incineration fly ash, including the following steps:

[0125] Step A: Wash the fly ash from waste incineration with water, and perform solid-liquid separation on the mixture after washing to obtain a solid phase and a liquid phase. Place the solid phase in a drying oven at 110℃ and dry it for 30 hours. Crush the dried solid phase into powder and pass it through a 100-mesh sieve to obtain fly ash powder from waste incineration.

[0126] The sludge was dried in a drying oven at 110℃ for 30 hours. The dried sludge was then crushed into powder and passed through a 100-mesh sieve to obtain sludge powder.

[0127] The coal gangue is crushed into powder and passed through a 100-mesh sieve to obtain coal gangue powder.

[0128] Step B: Mix 30% of the waste incineration fly ash powder and 70% of the sludge powder evenly, then add 30% water to obtain the core raw material;

[0129] Mix 30% of waste incineration fly ash powder, 30% of sludge powder and 40% of coal gangue powder evenly, then add 30% water to obtain the middle shell membrane slurry.

[0130] Adding 30% water to coal gangue powder yields an outer shell slurry.

[0131] Step C: The kernel material is made into pellets with a particle size of 5mm to 6mm, and the pellets are placed in a drying oven at 110℃ for 2.5h to set, thus obtaining the kernel;

[0132] Step D: Place the core in the middle shell membrane slurry, and place the core coated with the middle shell membrane slurry in a drying oven at 110°C for 2.5 hours to set, thereby obtaining composite pellets;

[0133] Step E: Place the composite pellets in the outer shell slurry, and place the composite pellets coated with the outer shell slurry in a drying oven at 110℃ for 2.5 hours to set, thereby obtaining composite ceramsite raw pellets with a particle size of 8mm.

[0134] Step F: Preheat the composite ceramsite raw material balls by heating and maintaining the temperature;

[0135] Step G: The preheated composite ceramsite raw material balls are heated to sinter and then naturally cooled to room temperature to obtain composite ceramsite.

[0136] The sintering process parameters and composite ceramsite performance parameters of Examples 1-3, 3-1 to 3-16 are shown in Table 4.

[0137] Table 4. Sintering process and composite ceramsite performance parameters for Examples 1-3 and 3-1 to 3-16

[0138]

[0139] Figure 7 This is a comparison chart of the performance parameters of the composite ceramsite in Examples 1-3 and Examples 3-1 to 3-4. Figure 7 It can be seen that the compressive strength first increases and then decreases with increasing sintering temperature. Conversely, the 1-hour water absorption rate first decreases and then increases with increasing sintering temperature, reaching its extreme value at 1150℃. At this point, the compressive strength reaches 31.84 MPa, and the 1-hour water absorption rate is 0.95%. This is attributed to the fact that sintering temperature directly affects the formation of the liquid phase within the composite ceramic aggregate system. As the sintering temperature increases, the various components within the composite ceramic aggregate system react fully. The closer to the optimal sintering temperature of 1150℃, the more crystalline phases (such as mullite, anorthite, and sodium feldspar) are generated that contribute to the increase in the compressive strength of the composite ceramic aggregate. When the sintering temperature is 1175℃, the composite ceramic aggregate exhibits severe overheating and mutual adhesion. This indicates that at this temperature, many mineral phases within the composite ceramic aggregate have reached their melting points, leading to a large amount of molten glass phase flowing through the interior of the composite ceramic aggregate, opening up the internal pores and correspondingly explaining the increase in water absorption rate. Therefore, a suitable preheating temperature helps more hydrous mineral phases in the composite ceramsite system to remove adsorbed water and structural water, avoiding cracking of the composite ceramsite during subsequent heating. It also facilitates the decomposition of organic matter and carbon to produce gas, which will be adhered to the composite ceramsite embryo and is crucial for the initial formation of internal pores.

[0140] Figure 9 This is a comparison chart of the performance parameters of the composite ceramsite in Examples 1-3, 3-9 to 3-12. Figure 9 It can be seen that the changes in the 1-hour water absorption rate and compressive strength of the composite ceramsite are similar to the effects of sintering temperature on the composite ceramsite. It is noteworthy that when the preheating temperature is 350℃, the compressive strength of the composite ceramsite is significantly worse than the other groups. This may be due to the incomplete removal of the crystal water of the mineral phase within the composite ceramsite system caused by the excessively low preheating temperature. Furthermore, when the preheating temperature is 550℃, the 1-hour water absorption rate of the composite ceramsite is higher than the other groups. This may be due to the excessively high preheating temperature leading to an increase in reducing components within the system, generating more gas during sintering, and increasing the porosity inside the composite ceramsite. At this temperature, the bulk density of the composite ceramsite is 846.90 kg / m³. 3 Therefore, higher preheating temperatures may be more suitable for producing ultra-lightweight composite ceramic aggregates.

[0141] Figure 8 This is a comparison chart of the performance parameters of the composite ceramsite in Examples 1-3, 3-5 to 3-8. Figure 8It can be seen that the variation trend of the composite ceramsite is similar to that of the sintering temperature and preheating temperature. It is worth noting that, unlike other parameters, the extension of sintering time caused fluctuations in both bulk density and volume density. At the optimal sintering time of 25 min, the bulk density of the composite ceramsite was 822.19 kg / m³. 3 Its bulk density is 1975.20 kg / m³. 3 All of them are lighter than the other groups. This is attributed to the appropriate sintering time, which allows the gases generated by the reaction inside the composite ceramic particles to be tightly wrapped inside the composite ceramic particles by the glaze layer, resulting in increased porosity and thus lower density of the composite ceramic particles.

[0142] Figure 10 This is a comparison chart of the performance parameters of the composite ceramsite in Examples 1-3, 3-13 to 3-16. Figure 10 It can be seen that when the preheating time is 30 min, the composite ceramsite has the lowest 1-hour water absorption rate (0.73%), the highest compressive strength (41.76 MPa), and the highest bulk density (862.78 kg / m³). 3 Its bulk density is 2034.42 kg / m³. 3 .

[0143] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite ceramsite based on waste incineration fly ash, characterized in that, The composite ceramic particles have a three-layer structure, including a core and a middle shell and an outer shell that are sequentially attached to the core from the inside out.

2. The composite ceramsite based on waste incineration fly ash according to claim 1, characterized in that, The pore diameters in the core, the middle shell, and the outer shell gradually decrease.

3. The composite ceramsite based on waste incineration fly ash according to claim 1, characterized in that, The porosity of the core, the middle shell, and the outer shell gradually decreases.

4. A method for preparing composite ceramsite based on waste incineration fly ash, characterized in that, The method for preparing the composite ceramsite as described in any one of claims 1 to 3 comprises the following steps: The kernel material is made into pellets, and the pellets are dried and shaped to obtain the kernel. The core is placed in the middle shell membrane slurry, and the core coated with the middle shell membrane slurry is dried and shaped to obtain composite pellets; The composite pellets are placed in the outer shell slurry, and the composite pellets coated with the outer shell slurry are dried and shaped to obtain composite ceramsite raw pellets. Composite ceramsite raw material balls are sintered using a two-stage sintering method, and then cooled to obtain composite ceramsite.

5. The method for preparing composite ceramsite based on waste incineration fly ash according to claim 4, characterized in that, The drying and setting temperature is 100℃~110℃, and the drying and setting time is 1.5h~2.5h.

6. The method for preparing composite ceramsite based on waste incineration fly ash according to claim 4, characterized in that, The particle size of the composite ceramsite raw material balls is 8mm to 10mm.

7. The method for preparing composite ceramsite based on waste incineration fly ash according to any one of claims 4 to 6, characterized in that, The two-stage sintering method includes the following steps: The composite ceramsite raw material balls are heated and kept at a constant temperature for preheating; The preheated composite ceramsite raw material balls are heated and kept at a constant temperature for sintering.

8. The method for preparing composite ceramsite based on waste incineration fly ash according to claim 7, characterized in that, The heating rates for both preheating and sintering are 8°C / min to 12°C / min.

9. The method for preparing composite ceramsite based on waste incineration fly ash according to claim 7, characterized in that, The preheating temperature is 350℃~550℃, and the preheating holding time is 10min~50min.

10. The method for preparing composite ceramsite based on waste incineration fly ash according to claim 7, characterized in that, The sintering temperature is 1075℃~1175℃, and the sintering holding time is 5min~45min.

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