Method for preparing high-performance porous ceramic material through high-value low-carbon recycling of oily solid waste pyrolysis ash

Abstract

The invention belongs to the field of oil-containing solid waste resource utilization and ceramic material preparation, and discloses a method for preparing a high-performance porous ceramic material through high-value low-carbon resource utilization of oil-containing solid waste pyrolysis ash, and the method comprises the following steps: S1, ash pretreatment: carrying out magnetic separation impurity removal, size grading and activation modification treatment on the oil-containing solid waste pyrolysis ash; s2, burdening and molding: mixing the pretreated ash with kaolin, a pore forming agent and a sintering aid according to a gradient ratio, and preparing a porous biscuit by adopting a dry pressing molding process; s3, optimizing a sintering process, and forming a porous ceramic matrix with a gradient pore channel structure through a staged temperature control sintering strategy; and S4, performance strengthening: carrying out surface modification treatment on the porous matrix by adopting a sol impregnation method. The porous ceramic material with high porosity and excellent mechanical strength is prepared through component reconstruction and structure regulation and control of the pyrolysis ash, the adsorption capacity of the porous ceramic material is improved by 40% or above compared with that of a traditional product, and effective combination of high-value utilization of hazardous waste resources and a low-carbon preparation technology is achieved.

Description

Technical Field

[0001] This invention relates to the field of resource utilization of oily solid waste and preparation of functional ceramic materials, specifically to a method for preparing high-performance porous ceramic materials from pyrolysis ash residue of oily solid waste with high value and low carbon content. This method is used to prepare high-performance porous ceramic materials through component reconstruction and structural regulation of pyrolysis ash residue, thereby achieving the synergistic treatment of harmlessness, high value and low carbon of oily solid waste. Background Technology

[0002] Oily solid waste (such as oil sludge and oil-based drill cuttings) still contains heavy metals, residual hydrocarbons, and inorganic mineral components (such as SiO2, Al2O3, and CaO) in its residual ash after pyrolysis. Direct landfilling can easily cause soil and groundwater pollution, while incineration poses a risk of dioxin formation. Existing resource utilization technologies are mostly focused on blending ash into building materials (such as brick making and roadbed materials) or co-processing in cement kilns, but these technologies suffer from low added value (product price < 500 yuan / ton), potential heavy metal leaching, and high carbon emission intensity (> 1.5 t CO2 / ton of product).

[0003] Porous ceramic materials are in high demand in industrial adsorption and catalytic support fields due to their high specific surface area, corrosion resistance, and designable pore structure. However, their traditional raw materials (such as kaolin and silicon carbide) rely on mineral mining and have high sintering energy consumption (≥1500℃). Studies have shown that the SiO2 / Al2O3 mass ratio (1.2-2.5) in oily solid waste pyrolysis ash is well-suited to porous ceramic matrices. However, residual oil (0.5-3wt%) and heavy metals (such as Cr and Ni) can disrupt the sintering density of ceramics, leading to porosity fluctuations (40-60%) and insufficient compressive strength (<15MPa).

[0004] In existing technologies, patent CN113003970A proposes "preparing ceramsite from oil sludge and ash," but its product porosity is only 45-50%, and the problem of heavy metal consolidation is not solved. The literature "Preparation of Porous Materials Based on Hazardous Waste Ash" uses an acid washing-high temperature melting method, which increases the Pb solidification rate to 90%, but increases energy consumption by 30%. In addition, CO2 generated by the decomposition of pore-forming agents (such as carbonates) in traditional processes is directly emitted, which contradicts the goal of low carbon emissions. Summary of the Invention

[0005] To address the problems mentioned in the background art, the present invention aims to provide a method for preparing high-performance porous ceramic materials from oily solid waste pyrolysis ash residue with high value and low carbon content. The prepared porous ceramic materials... With the characteristics of high ash content (60-75%), controllable pore structure (porosity > 65%), environmental safety (heavy metal leaching concentration < 1 mg / L) and low temperature sintering (≤ 1350℃), this method can promote the upgrading and transformation of hazardous waste disposal to functional material manufacturing.

[0006] To achieve the above objectives, the present invention provides the following technical approach: a method for preparing high-performance porous ceramic materials from oily solid waste pyrolysis ash residue with high value and low carbon content, comprising the following steps: S1. Ash and Slag Pretreatment: Oily solid waste is kept at 550℃ in air for 2 hours to obtain pyrolysis ash and slag. The pyrolysis ash and slag is then separated by a permanent magnet drum separator to remove metal impurities (iron content ≤0.5%), followed by coarse crushing to below 5mm by a jaw crusher, and then fine grinding to D50=20-50μm by a ball mill. The ground ash and slag are mixed with 3% by mass of silane coupling agent and stirred at 60℃ for 30min for surface activation. Finally, the ash and slag are soaked in 5% by mass of dilute hydrochloric acid for 2 hours to remove residual oil and calcium and magnesium impurities (residual oil content <0.3%), and then dried to obtain pretreated ash and slag. In step S1, pretreatment of the ash can adjust the particle size and uniformity of the ash, which facilitates subsequent molding.

[0007] S2. Batching and Molding: Pretreated ash (60-75wt%), kaolin (15-25wt%), starch pore-forming agent (10-15wt%), and borax sintering aid (3-5wt%) are mixed according to the mass percentage. After dry mixing in a planetary ball mill for 2 hours, a 5% mass fraction polyvinyl alcohol (PVA) solution is sprayed to granulate the mixture. The mixture is then molded under a pressure of 30MPa (holding pressure for 120s) to prepare a green blank with a diameter of 50mm and a thickness of 10mm. In step S2, more than 60% by mass of ash is used as the main material, realizing the high-value utilization of solid waste; through pore-forming agent and molding pressure, the final pore structure of the material can be pre-designed to meet specific functional requirements such as loading and adsorption.

[0008] S3. Sintering process optimization: The green body is heated to 600℃ at 5℃ / min and held for 1h to remove the pore-forming agent. The temperature is then increased to 1100℃ at 3℃ / min to form a skeleton structure. Subsequently, the temperature is increased to 1350℃ at 2℃ / min and held for 2h to achieve mullite crystal phase growth. Finally, the furnace is cooled by gradient cooling and then air-cooled to obtain a porous ceramic matrix with gradient channels. In step S3, the sintering process optimization aims to address: completely removing the pore-forming agent and preventing cracking and deformation of the green body; constructing a stable framework and maintaining the expected porosity; promoting the growth of high-strength crystalline phases and inhibiting excessive densification or abnormal grain growth. Firstly, the pore-forming agent removal stage requires slow heating to allow organic matter such as starch to completely decompose without damaging the green body structure. A heating rate of 5℃ / min ensures sufficient decomposition of the pore-forming agent while avoiding excessive thermal stress that could damage the green body structure. A slower heating rate of 3℃ / min is used from 600℃ to 1100℃ because the ceramic particles begin initial sintering and require sufficient time to rearrange themselves and form a preliminary pore network structure. Finally, a heating rate of 2℃ / min is used to reach 1350℃ to drive the growth of the mullite crystalline phase, reducing the temperature difference between the inside and outside of the green body and preventing thermal stress cracking to strengthen the structure.

[0009] S4. Performance Enhancement: The substrate is immersed in a 20% SiO2-Al2O3 composite sol and vacuum-assisted infiltration is carried out for 30 min. The temperature is then increased to 1250℃ at a heating rate of 10℃ / min and held for 1 h to form a nano-modification layer. Subsequently, a 150-250 nm thick TiO2 photocatalytic coating is sprayed on and dried and cured at 80℃ to obtain a high-performance porous ceramic material.

[0010] In step S4, the porous ceramic matrix is ​​enhanced to strengthen the ceramic framework and endow it with the ability to photocatalytically degrade pollutants. Through vacuum impregnation and secondary sintering of the SiO2-Al2O3 composite sol, nanoparticles fill the micro-defects within the matrix, forming a reinforcing layer on the framework surface. This significantly improves the material's mechanical strength, thermal stability, and corrosion resistance, while optimizing the pore structure. The subsequent application of a TiO2 photocatalytic coating further endows the robust matrix with the ability to photocatalytically degrade organic pollutants.

[0011] Preferably, in step S1, the SiO2 / Al2O3 mass ratio of the pretreated ash is 1.2-2.5, and the total heavy metal content is ≤3wt%.

[0012] Preferably, in step S1, the CaO content in the acid-washed ash is ≤1.5wt%.

[0013] Preferably, in step S2, the particle size of the starch pore-forming agent is 80-150 μm, and the amount of borax added is preferably 4 wt%.

[0014] Preferably, in step S3, the heat preservation time during the high-temperature crystallization stage is positively correlated with the amount of ash and slag added. When the proportion of ash and slag is ≥70wt%, the heat preservation time is extended to 2.5h.

[0015] Preferably, in step S4, the Al / Si molar ratio of the SiO2-Al2O3 composite sol is 0.3-0.6, the TiO2 photocatalytic coating is prepared by the sol-gel method, the bonding strength between the coating and the substrate after curing is ≥15MPa, and the photocatalytic efficiency of the TiO2 coating is ≥80% (based on the degradation rate of methylene blue over 4 hours).

[0016] Preferably, in step S3, the gradient cooling process is as follows: the temperature is reduced from 1350℃ to 800℃ at a rate of 5℃ / min, followed by air cooling, with a total cooling time of ≥4h.

[0017] Preferably, in step S4, the porous ceramic material has a porosity of 65-72%, a compressive strength ≥25MPa, a photocatalytic efficiency ≥80%, an adsorption capacity >300mg / g, and a heavy metal leaching concentration <1mg / L (tested according to GB5085.3-2007 standard).

[0018] Preferably, in step S4, the vacuum degree of sol impregnation is -0.08 to -0.1 MPa, and the weight gain of the blank after impregnation is 8-12%.

[0019] The key steps of this invention are as follows: S1: Ash pretreatment, which solves the problem of ash containing metals, residual oil, impurities, etc., affecting sintering stability, and obtains raw materials with uniform particle size and low impurity content to ensure the stability and controllability of subsequent formulations and sintering processes. S2: Batching and molding, which solves the problem of difficulty in simultaneously ensuring molding performance, pore structure, and strength when the ash content is high (>60%), by adding pore-forming agents and pressure molding to meet the functional requirements of pore structure. S3: Sintering process optimization, which solves the problem of simultaneously completing organic matter decomposition, framework construction, and high-strength crystal phase growth at a lower temperature, achieving the effect of low-temperature and high-efficiency sintering and obtaining gradient channels and a high-strength framework structure. S4: Performance enhancement, which solves the problem that traditional porous ceramics only have physical adsorption functions and limited added value, and obtains composite materials with both excellent mechanical properties and photocatalytic degradation functions, realizing "waste treatment with waste".

[0020] Compared with the prior art, the beneficial effects of the present invention are: This invention uses oily solid waste pyrolysis ash as a raw material for preparing porous ceramics, with the ash content exceeding 70%. As an industrial waste, the ash is far less expensive than traditional ceramic raw materials (such as kaolin and clay). High-proportion use significantly reduces material production costs. Through component reconstruction and surface modification, the material is endowed with adsorption-catalysis dual functions. The synergistic effect of pore-forming agent decomposition and liquid-phase sintering forms a three-tiered gradient structure of micropores, mesopores, and macropores. (See details...) Figure 3 It has stable porosity and high adsorption volume, which effectively increases the added value of traditional ceramsite products and meets the needs of high-value resource utilization of oily solid waste.

[0021] 2. This invention reduces the sintering temperature of porous ceramics to 1350℃, thus reducing energy consumption. The pore-forming agent decomposes CO2, achieving in-situ fixation through sol impregnation. After sol impregnation, the porous ceramic matrix's large internal surface area and abundant nanopores provide a vast number of reaction sites for CO2 gas. Furthermore, the active nanostructures formed during drying and sintering can chemically react with CO2, converting it into stable carbonate minerals that are permanently "locked" inside the ceramic framework. This reduces carbon emission intensity, and the triple barrier of acid washing, silane modification, and sol coating controls the leaching concentration of heavy metals, achieving the low-carbon and harmless utilization of oily solid waste. Attached Figure Description

[0022] Figure 1 This is a process flow diagram for preparing high-performance porous ceramic materials from oily solid waste pyrolysis ash residue according to the present invention.

[0023] Figure 2 The N2 adsorption-desorption isotherms are those of the ceramic materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 of this invention.

[0024] Figure 3 The image shows the pore size distribution of the ceramic materials prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1 This invention provides a method for preparing high-performance porous ceramic materials from oily solid waste pyrolysis ash residue with high value and low carbon content. The oily solid waste pyrolysis ash residue mainly includes the components shown in Table 1 below: Table 1. Composition of Pyrolysis Ash Residue from Oily Solid Waste Example 1 A method for preparing high-performance porous ceramic materials from oily solid waste pyrolysis ash residue with high value and low carbon content includes the following steps: S1: Ash and Slag Pretreatment Oily solid waste pyrolysis ash residue (SiO2 / Al2O3=1.8, total heavy metals 2.8wt%) was sorted by permanent magnet drum (iron content reduced to 0.4%), jaw crushed to particle size ≤5mm and then ball-milled to D50=30μm; 3% by mass of silane coupling agent was added and stirred at 60℃ for 30min, then soaked in 5% by mass of dilute hydrochloric acid for 2h (oil residue 0.25%), and dried to obtain pretreated ash residue; S2: Ingredient Preparation and Molding Pretreated ash (70wt%), kaolin (17wt%), starch pore-forming agent (100μm particle size, 10wt%) and borax (3wt%) were mixed by mass percentage, dry-mixed by planetary ball milling for 2 hours, and then sprayed with 5% PVA solution by mass fraction for granulation. The mixture was then molded at 30MPa (holding pressure for 120s) to obtain a green blank with a diameter of 50mm and a thickness of 10mm. S3: Sintering process optimization The pore-forming agent was removed by heating to 600℃ at 5℃ / min and holding for 1 hour. The temperature was then increased to 1100℃ at 3℃ / min to form a framework structure. Subsequently, the temperature was increased to 1350℃ at 2℃ / min and held for 2.5 hours to achieve mullite crystal phase growth. The temperature was then reduced to 800℃ at 5℃ / min and air-cooled. The total cooling time was ≥4 hours. S4: Performance Enhancement The substrate was immersed in a 20% SiO2-Al2O3 composite sol (Al / Si=0.4) for vacuum permeation for 30 min, heated to 1250℃ at a heating rate of 10℃ / min and held for 1 h, then a 200nm TiO2 coating was sprayed on, and dried and cured at 80℃ to obtain a high-performance porous ceramic material.

[0027] Example 2 A method for preparing high-performance porous ceramic materials from oily solid waste pyrolysis ash residue with high value and low carbon content includes the following steps: S1: Ash and Slag Pretreatment Oily solid waste pyrolysis ash residue (SiO2 / Al2O3=2.2, total heavy metals 2.1wt%) was sorted by permanent magnet drum (iron content reduced to 0.4%), jaw crushed to particle size ≤4mm, and then ball-milled to D50=40μm; 3% by mass of silane coupling agent was added and stirred at 60℃ for 30min, then soaked in 5% by mass of dilute hydrochloric acid for 2h (oil residue 0.2%), and dried to obtain pretreated ash residue; S2: Ingredient Preparation and Molding Pretreated ash (65wt%), kaolin (22wt%), starch pore-forming agent (120μm particle size, 12wt%), and borax (3.5wt%) were mixed by mass percentage, dry-mixed by planetary ball milling for 2 hours, and then sprayed with 5% PVA solution by mass fraction for granulation. The mixture was then molded at 30MPa (holding pressure for 120s) to obtain a green blank with a diameter of 50mm and a thickness of 10mm. S3: Sintering process optimization The pore-forming agent was removed by heating to 600℃ at 5℃ / min and holding for 1 hour. The temperature was then increased to 1100℃ at 3℃ / min to form a framework structure. Subsequently, the temperature was increased to 1350℃ at 2℃ / min and held for 2 hours to achieve mullite crystal phase growth. The temperature was then reduced to 800℃ at 5℃ / min and air-cooled. The total cooling time was ≥4 hours. S4: Performance Enhancement The substrate was immersed in a 20% SiO2-Al2O3 composite sol (Al / Si=0.5) for vacuum permeation for 30 min, heated to 1250℃ at a heating rate of 10℃ / min and held for 1 h, then sprayed with an 180nm TiO2 coating and dried and cured at 80℃ to obtain a high-performance porous ceramic material.

[0028] Example 3 A method for preparing high-performance porous ceramic materials from oily solid waste pyrolysis ash residue with high value and low carbon content includes the following steps: S1: Ash and Slag Pretreatment Oily solid waste pyrolysis ash residue (SiO2 / Al2O3=1.3, total heavy metals 3.0wt%) was sorted by permanent magnet drum (iron content reduced to 0.4%), jaw crushed to particle size ≤3mm and then ball-milled to D50=20μm; 3% by mass of silane coupling agent was added and stirred at 60℃ for 30min, then soaked in 5% by mass of dilute hydrochloric acid for 2h (oil residue 0.15%), and dried to obtain pretreated ash residue; S2: Ingredient Preparation and Molding Pretreated ash (75wt%), kaolin (15wt%), starch pore-forming agent (80μm particle size, 10wt%) and borax (5wt%) were mixed by mass percentage, and then dry-mixed by planetary ball milling for 2 hours. After spraying with 5% PVA solution by mass fraction, the mixture was granulated and molded at 30MPa (holding pressure for 120s) to obtain a green blank with a diameter of 50mm and a thickness of 10mm. S3: Sintering process optimization The pore-forming agent was removed by heating to 600℃ at 5℃ / min and holding for 1 hour. The temperature was then increased to 1100℃ at 3℃ / min to form a framework structure. Subsequently, the temperature was increased to 1350℃ at 2℃ / min and held for 2.5 hours to achieve mullite crystal phase growth. The temperature was then reduced to 800℃ at 5℃ / min and air-cooled. The total cooling time was ≥4 hours. S4: Performance Enhancement The substrate was immersed in a 20% SiO2-Al2O3 composite sol (Al / Si=0.6) for vacuum permeation for 30 min, heated to 1250℃ at a heating rate of 10℃ / min and held for 1 h, then a 250 nm TiO2 coating was sprayed on, and dried and cured at 80℃ to obtain a high-performance porous ceramic material.

[0029] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that step S1 was omitted, the silane coupling agent modification and acid washing steps were omitted, and unactivated ash residue (iron content 1.8%, oil residue 1.2%) was used directly. The remaining steps are exactly the same as in Example 1.

[0030] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that step S3 was cooled down. The sintering temperature of step S3 was reduced to 1250°C, and no mullite crystal phase was formed. The remaining steps were exactly the same as those in Example 1.

[0031] Comparative Example 3 Comparative Example 3 differs from Example 1 in that step S1 was omitted, thus eliminating the sol impregnation and TiO2 coating in S4, retaining only the substrate, while the remaining steps are exactly the same as in Example 1.

[0032] The porous ceramics prepared in the above six examples were cured at 30℃ for 10 days. The porosity (%), compressive strength (MPa), heavy metal leaching (mg / L), adsorption capacity (mg / g), and photocatalytic efficiency (%) of the porous ceramics prepared in the six examples were measured. Porosity was measured using the Archimedes water displacement method (boiling method); compressive strength was measured using a universal testing machine; heavy metal leaching was measured using acid leaching-atomic absorption spectrometry; adsorption capacity was measured using a static adsorption experiment (using methylene blue solution as a model pollutant); and photocatalytic efficiency was measured using the methylene blue degradation method. The test results are shown in Table 2 below. Table 2. Test results of porosity, compressive strength, heavy metal leaching, adsorption capacity, and photocatalytic efficiency for each embodiment. As can be seen from Table 2, compared with Examples 1, 2 and 3, the porous ceramic materials prepared by Comparative Examples 1 and 2 showed a significant decrease in porosity, compressive strength and photocatalytic efficiency when ash activation modification or sintering process optimization was lacking.

[0033] First, sintering effectively increases the compressive strength of porous ceramics, and the effect is quite significant. This is because during the process, MgO and Al2O3 components in the pyrolysis ash begin to react to form spinel (MgAl2O4); SiO2 reacts with some Al2O3 to form the precursor of mullite (3Al2O3·2SiO2), and may also be accompanied by the formation of enstatite (MgSiO3). As the sintering continues, the above unstable intermediate phases further react with the remaining SiO2 to form μ-cordierite (a metastable high-temperature cordierite with disordered structure). As the temperature rises, μ-cordierite gradually transforms into stable α-cordierite (Indian stone, with an ordered structure) with a low coefficient of thermal expansion. With the gradual growth of the crystal phases, the porous ceramic structure framework tends to stabilize, and the compressive strength also increases accordingly.

[0034] Secondly, due to the high-temperature decomposition characteristics of pore-forming agents, the thermal decomposition of starch pore-forming agents during sintering mainly occurs in the temperature range of 300°C to 600°C. Within this range, starch undergoes combustion or pyrolysis, leaving pores in the ceramic body, thereby increasing the porosity of the porous ceramic material.

[0035] Finally, the significant decrease in photocatalytic efficiency in the absence of sol impregnation and TiO2 coating is primarily due to the lack of a stable chemical interface and synergistic structure constructed through activation modification. Specifically, the directly sprayed TiO2 coating exhibits only weak physical adsorption with the original porous ceramic substrate, lacking the robust chemical bonds (such as Ti-O-Si bonds) provided by the SiO2-Al2O3 nano-modification layer. This results in high defect density and high resistance at the interface. This unstable interface becomes a rapid recombination center for photogenerated electron-hole pairs, causing most photogenerated carriers to be deactivated before participating in the catalytic reaction. Simultaneously, the rough, defective surface of the original substrate cannot provide a uniformly loaded nanoscale platform for TiO2, leading to uneven coating distribution, easy pore blockage, severely hindering the transmission and diffusion of pollutant molecules and light, and significantly reducing effective catalytic reaction sites. Furthermore, the missing nano-modification layer also loses its surface adsorption function, failing to achieve the synergistic effect of "first adsorption and enrichment, then in-situ catalysis." This results in the TiO2 coating only passively contacting low-concentration pollutants, leading to slow reaction kinetics. Therefore, the decrease in efficiency is essentially the result of the combined effects of three major mechanisms: intensified interfacial charge recombination, hindered mass transport, and the lack of adsorption-catalysis synergy.

[0036] Among them, Comparative Example 1 suffered a 17% decrease in porosity and a photocatalytic efficiency of less than 20% due to residual oil and metallic impurities. Comparative Example 2 experienced a 13% decrease in compressive strength and a significant deterioration in structural stability due to insufficient sintering. Although Comparative Example 3 had a porosity comparable to Example 1, its photocatalytic efficiency decreased by 57% due to the lack of sol impregnation and TiO2 coating, severely limiting its functional performance. This demonstrates that the complete process technology of ash pretreatment-component optimization-sintering control-surface modification of the present invention plays a decisive role in improving the structural strength, porosity control, and functional performance of porous ceramics based on oily solid waste pyrolysis ash, and is a core guarantee for achieving high-value and low-carbon resource utilization.

[0037] like Figure 2 As shown, the adsorption isotherms of the synthesized material exhibit typical Type I characteristics. The adsorption amount increases slowly when the relative pressure P / P < 0.6, and then shows an exponential steep increase when P / P0 ≥ 0.8. This two-stage adsorption behavior reveals the hierarchical pore structure of the material, where mesopores (2-50 nm) serve as the main adsorption channels, while macropores (> 50 nm) function as mass transfer channels. Notably, a significant hysteresis loop exists between the adsorption and desorption curves, and its morphology conforms to the criteria for an H3-type hysteresis loop, indicating the presence of a non-uniform pore structure formed by particle stacking within the synthesized material.

[0038] like Figure 3 As shown, the pore size distribution data calculated using the BJH model indicates that the pore sizes of oil-containing solid waste pyrolysis ash and synthetic ceramic materials are mainly distributed around 24 nm and 28 nm, respectively, ranging from 2 to 50 nm, indicating the presence of mesopores in both materials. Mesopores constitute the majority, macropores are the minor pore size, and a small amount of micropores are also present. Macropores (>50 nm) account for 25.6%, mesopores (2-50 nm) account for 68.7%, and micropores (<2 nm) account for 5.7%.

[0039] The porous ceramics prepared in this invention form a three-level gradient structure of micropores-mesopores-macropores, with stable porosity and high adsorption volume, effectively increasing the added value compared to traditional ceramsite products and meeting the requirements for high-value resource utilization of oily solid waste.

[0040] The above description is merely a specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any transformations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing high-performance porous ceramic materials from high-value, low-carbon resource utilization of oily solid waste pyrolysis ash residue, characterized in that, Includes the following steps: S1. Ash and slag pretreatment: Pyrolysis ash and slag are obtained after treating oily solid waste. Metal impurities are removed from the pyrolysis ash and slag, and then it is coarsely crushed and finely ground. The finely ground ash and slag are mixed with silane coupling agent for surface activation. Finally, the residual oil and calcium and magnesium impurities are removed by soaking in dilute hydrochloric acid, and the ash and slag are dried to obtain pretreated ash and slag. S2. Batching and Molding: Mix the pretreated ash, kaolin, pore-forming agent and sintering aid in proportion and dry mix them, then spray with polyvinyl alcohol solution to granulate; mold the mixture into a green body. S3. Sintering process optimization: The green body is heated to remove the pore-forming agent, then heated to form a skeleton structure, then heated again to achieve mullite crystal phase growth, and finally cooled by gradient cooling and air cooling to obtain a porous ceramic matrix with gradient channels. S4. Performance Enhancement: The matrix is ​​immersed in SiO2-Al2O3 composite sol, vacuum-assisted infiltration is performed, and a nano-modification layer is formed by secondary sintering; then TiO2 photocatalytic coating is sprayed, dried and cured to obtain high-performance porous ceramic material.

2. The method according to claim 1, characterized in that, In step S1, the SiO2 / Al2O3 mass ratio of the pretreated ash is 1.2-2.5, and the total heavy metal content is ≤3wt%; it is coarsely crushed to below 5mm and then finely ground to D50=20-50μm; the surface activation conditions are: stirring at 60℃ for 30min.

3. The method according to claim 1, characterized in that, In step S1, the CaO content in the acid-washed ash is ≤1.5wt%.

4. The method according to claim 1, characterized in that, In step S2, the pretreated ash, kaolin, pore-forming agent and sintering aid are in the following mass percentages: (60-75) wt%, (15-25) wt%, (10-15) wt%, (3-5) wt%; the pore-forming agent is starch and the sintering aid is borax; the particle size of the starch is 80-150 μm and the preferred amount of borax added is 4 wt%.

5. The method according to claim 1, characterized in that, In step S3, the temperature is increased to 600℃ at 5℃ / min and held for 1 hour to remove the pore-forming agent. The temperature is then increased to 1100℃ at 3℃ / min from 600℃ to form a framework structure. Subsequently, the temperature is increased to 1350℃ at 2℃ / min from 1100℃ and held for 2 hours to achieve mullite crystal phase growth. Finally, the temperature is gradually cooled from 1350℃ to 800℃ at 5℃ / min and then air-cooled, with a total cooling time of ≥4 hours.

6. The method according to claim 5, characterized in that, In step S3, the heat preservation time during the high-temperature crystallization stage is positively correlated with the amount of ash and slag added. When the proportion of ash and slag is ≥70wt%, the heat preservation time is extended to 2.5h.

7. The method according to claim 1, characterized in that, In step S4, the Al / Si molar ratio of the SiO2-Al2O3 composite sol is 0.3-0.

6.

8. The method according to claim 1, characterized in that, In step S4, vacuum-assisted infiltration is performed for 30 minutes, and the secondary sintering conditions are: heating to 1250°C at a heating rate of 10°C / min and holding for 1 hour to form a nano-modified layer.

9. The method according to claim 1, characterized in that, In step S4, the TiO2 photocatalytic coating is sprayed using the sol-gel method, with a spraying thickness of 150-250 nm. After curing, the bonding strength between the coating and the substrate is ≥15 MPa, and the photocatalytic efficiency of the TiO2 coating is ≥80%.

10. The method according to claim 1, characterized in that, In step S4, the vacuum degree of sol impregnation is -0.08 to -0.1 MPa, and the weight gain of the blank after impregnation is 8-12%.

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