A porous ceramic synthesized by sewage sludge and kaolin and its preparation method
By synthesizing high-strength porous ceramics from sewage sludge and kaolin, the problems of complex production and secondary pollution in sewage sludge treatment are solved, efficient resource utilization and performance improvement are achieved, and high-strength, low thermal conductivity porous ceramic materials are provided.
Patent Information
- Application Number
- CN202311144837.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-06
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2043-09-06
AI Technical Summary
Existing sewage sludge treatment methods have the problems of complex production processes, high costs, and easy secondary pollution. The sludge utilization rate is low, and it is difficult to achieve harmlessness and resource utilization.
Sewage sludge and kaolin are used to synthesize high-strength porous ceramics, which are mainly composed of mullite, sillimanite, hematite and quartz. High-strength porous ceramics are prepared through pretreatment, batching, mixing, molding and sintering, avoiding the addition of additional pore-forming agents and using low-melting-point quartz and aluminum iron phosphate to improve sintering performance.
It significantly improves the sintering performance and mechanical properties of porous ceramics, reduces production costs, realizes the harmlessness and resource utilization of sewage sludge, and provides a new type of lightweight thermal insulation material.
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Figure CN117185776B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of porous ceramics and relates to a high-strength porous ceramic synthesized by sewage sludge and kaolin and a preparation method thereof. Background Art
[0002] With the continuous acceleration of urban development and the gradual improvement of people's living standards, natural resources are becoming increasingly scarce, and human waste is accumulating, leading to extremely serious environmental problems. Among them, sewage sludge, as one of the most common and difficult-to-treat stubborn solid wastes, poses a significant burden on environmental protection. Undoubtedly, sewage sludge is extremely complex in composition. In addition to containing large amounts of water, it also contains many difficult-to-degrade toxic substances, such as heavy metals, organic matter, pathogenic microorganisms, parasitic eggs, colloids, and salts. Therefore, if not properly treated, it will cause serious environmental pollution. Currently, the mainstream methods for sewage sludge treatment remain landfill and incineration. Landfills not only occupy large amounts of land but are also prone to leakage, seriously contaminating soil and groundwater. Furthermore, sludge incineration has high investment costs and releases large amounts of toxic gases such as sulfur dioxide and dioxins, causing secondary pollution. These treatment methods still have some hidden dangers, resulting in low sewage sludge utilization rates and failure to achieve resource utilization and harmless treatment of sewage sludge. In recent years, significant progress has been made in the utilization of sewage sludge resources in agriculture, construction, industry, and the environment. Phosphate fertilizer was produced using Mg / Ca-modified biochar, and phosphorus was successfully extracted from incineration sludge, providing a new approach for the comprehensive utilization of sewage sludge. Furthermore, the conversion of sludge into environmental catalysts and microbial fuel cells also provides a new approach to stabilizing sludge. However, these methods have the problems of complex production processes, high production costs, and serious residue pollution generated during the production process. Therefore, it is urgent to develop a new type of sewage sludge material and a method for harmless and resource-based utilization of sludge. This is of great significance for promoting the comprehensive utilization of sewage sludge, improving environmental quality, and promoting the comprehensive green transformation of economic and social development. Summary of the Invention
[0003] The present invention aims to provide a porous ceramic synthesized from sewage sludge and kaolin, and a method for preparing the same. This method overcomes the complex production process, high production costs, and severe secondary pollution associated with conventional treatment methods. By using sewage sludge and kaolin together to produce a high-strength porous ceramic material, the material significantly improves the sintering properties of kaolin, as well as the mechanical and thermal insulation properties of the porous ceramic, achieving the harmless and efficient resource utilization of sewage sludge.
[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a high-strength porous ceramic synthesized by sewage sludge and kaolin, the high-strength porous ceramic is composed of mullite 3Al2O3·2SiO2, sillimanite Al2SiO5 and hematite Fe2O3 as well as quartz SiO2 and aluminum iron phosphate Al 0.67 Fe 0.33 PO4, the weight percentage of its main chemical components is as follows: Al2O330.79-38.1%, SiO2 47.82-52.5%, Fe2O3 3.53-7.23%, P2O5 4.28-10.31%, CaO 1.1-2.64%, MgO 0.5-1.21%. The low melting point quartz (SiO2) and aluminum iron phosphate (AlFePO4) in high strength porous ceramics are mainly composed of quartz and aluminum iron phosphate. 0.67 Fe 0.33 PO4) binder phase significantly improves the sintering performance and mechanical properties of porous ceramics.
[0005] The present invention also discloses a method for preparing high-strength porous ceramics synthesized by combining sewage sludge with kaolin, comprising the following steps: (1) pretreatment of sewage sludge; (2) adding a certain mass percentage of sewage sludge and a binder to industrial kaolin for batching, mixing, and material forming; and (3) drying and reaction sintering of the high-strength porous ceramics.
[0006] The pretreatment of the sewage sludge in step (1) is to dry the sewage sludge naturally at room temperature for 72 hours, then dry it in a belt dryer at a temperature of 120-150° C. for 12-18 hours. After drying, the dried sewage sludge is crushed to 5-8 mm using an impact crusher, and then crushed to 20-60 mesh using a thunder and wind mill.
[0007] The ingredients and mixing of the high-strength porous ceramic described in step (2) involve weighing kaolin, sewage sludge, and yellow dextrin in a certain proportion and mixing them uniformly using an automatic mixer. The weight percentage of kaolin is 48-72%, the weight percentage of sewage sludge is 20-50%, and the weight percentage of yellow dextrin is 2-8%. The high-strength porous ceramic is formed by using a refractory forming machine to prepare a porous ceramic green blank of the desired shape from the mixed materials.
[0008] The drying of the high-strength porous ceramics described in step (3) is to naturally dry the formed porous ceramic wet blank at room temperature for 48 hours, and then dry it with a belt dryer, the drying temperature is 300-450°C, and the drying time is 14-20 hours. After the mixing is completed, the dried porous ceramic green body is sent to a high-temperature tunnel kiln for high-temperature calcination, the calcination temperature is 1250-1400°C, and the calcination time is 12-18 hours. After the calcination is completed, the refractory material is cooled to room temperature by slow cooling in the furnace to obtain high-strength porous ceramics. The relevant properties of the high-strength porous ceramics can reach: the volume density of the high-strength porous ceramics is 1.53-2.02g / cm 3 The volume shrinkage is 12.17~20.34%, the porosity is 15.69~34.74%, the compressive strength is 35.05~90.46MPa, the flexural strength is 16.78~53.78MPa, the refractoriness is 1450~1600℃, the water absorption is 27.18~35.07%, and the thermal conductivity is 0.27~0.33W / m·K.
[0009] Compared with existing material technology methods, the present invention has the following advantages:
[0010] 1. The high-strength porous ceramic has the characteristics of high strength, low density, high porosity and low thermal conductivity. The volatilization and combustion of sewage sludge avoids the addition of additional pore-forming agents, and the combustion of sludge also provides part of the heat for the sintering of porous ceramics.
[0011] 2. The high strength porous ceramic material is mainly composed of mullite (3Al2O3·2SiO2), sillimanite (Al2SiO5) and hematite (Fe2O3) as well as a small amount of quartz (SiO2) and aluminum iron phosphate (Al 0.67 Fe 0.33 The formation of low-melting-point quartz and aluminum phosphate significantly improves the sintering performance and mechanical properties of porous ceramics.
[0012] 3. The method of the present invention significantly improves the sintering performance of kaolin, does not require additional pore-forming agents, reduces the sintering temperature and sintering cost, and has the characteristics of simple production process, short process, low energy consumption, high efficiency and cleanliness. The high-strength porous ceramic material prepared is a new type of lightweight thermal insulation material. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 Schematic diagram of the process flow of the method of the present invention;
[0014] Figure 2 This is the XRD pattern of high-strength porous ceramics.
[0015] Figure 3 SEM micrograph of high-strength porous ceramics.
[0016] Figure 4 Mechanical properties of high-strength porous ceramics. DETAILED DESCRIPTION
[0017] The following embodiments are used to illustrate the method of the present invention. It should be understood that these embodiments are only used to further illustrate the embodiments of the present invention, and are not used to limit the present invention.
[0018] Table 1 shows the ingredient scheme of high-strength porous ceramics.
[0019] Table 1
[0020] Sample number Kaolin (%) Sewage sludge (%) Yellow dextrin (%) S1 48 50 2 S2 56 40 4 S3 64 30 6 S4 72 20 8
[0021] See also Figure 1-Figure 4 :
[0022] Example 1: The weight percentage ratio of the basic raw materials for high-strength porous ceramics is: kaolin 48%, sewage sludge 50%, and yellow dextrin 2%. The kaolin particle size is 20-40 mesh, the sewage sludge particle size is 20-30 mesh, and the yellow dextrin particle size is 20-30 mesh. First, the sewage sludge is air-dried at room temperature for 72 hours and then dried in a belt dryer at 120°C for 12 hours. After drying, the dried sewage sludge is crushed to less than 6 mm using an impact crusher and then crushed to 20-30 mesh using a thunder wind mill. The basic raw materials are then mixed and formed into porous ceramic green sheets using a refractory forming machine. The formed porous ceramic green sheets are air-dried at room temperature for 96 hours and then dried in a 250°C kiln for 16 hours. After drying, the dried porous ceramic green sheets are sintered in a high-temperature tunnel kiln for reaction, with the final sintering temperature reaching 1250°C. The sintering schedule was: 500°C for 5 hours and 1250°C for 16 hours. After calcination, the refractory material was cooled to room temperature by slow cooling in the furnace to obtain a high-strength porous ceramic material, which was recorded as S1.
[0023] The chemical composition weight percentages of Al2O3, SiO2, Fe2O3, P2O5, CaO and MgO in the high-strength porous ceramic material are 30.79%, 47.82%, 7.23%, 10.31%, 2.64% and 1.12% respectively. The high-strength porous ceramic material is mainly composed of mullite (3Al2O3·2SiO2), sillimanite (Al2SiO5) and hematite (Fe2O3), as well as a small amount of quartz (SiO2) and aluminum iron phosphate (Al2SiO5). 0.67 Fe 0.33 (PO4). The volume density of this high-strength porous ceramic is 1.53g / cm 3The volume shrinkage is 12.17%, the porosity is 34.74%, the compressive strength is 35.05MPa, the flexural strength is 16.78MPa, the refractoriness is 1450℃, the water absorption is 35.07%, and the thermal conductivity is 0.27W / m·K.
[0024] Example 2: The weight percentage ratio of the basic raw materials for high-strength porous ceramics is: 56% kaolin, 40% sewage sludge, and 4% yellow dextrin. The kaolin particle size is 30-50 mesh, the sewage sludge particle size is 30-40 mesh, and the yellow dextrin particle size is 30-40 mesh. First, the sewage sludge is air-dried at room temperature for 72 hours and then dried in a belt dryer at 140°C for 10 hours. After drying, the dried sewage sludge is crushed to less than 5 mm using an impact crusher and then crushed to 30-40 mesh using a thunder wind mill. The basic raw materials are then mixed and formed into porous ceramic green sheets using a refractory forming machine. The formed porous ceramic green sheets are air-dried at room temperature for 96 hours and then dried in a 300°C kiln for 14 hours. After drying, the dried porous ceramic green sheets are sintered in a high-temperature tunnel kiln at a final sintering temperature of 1300°C. The sintering schedule was: 500°C for 5 hours and 1300°C for 14 hours. After calcination, the refractory material was cooled to room temperature by slow cooling in the furnace to obtain a high-strength porous ceramic material, which was recorded as S2.
[0025] The chemical composition weight percentages of Al2O3, SiO2, Fe2O3, P2O5, CaO and MgO in the high-strength porous ceramic material are 33.17%, 49.33%, 6.03%, 8.35%, 2.14% and 0.98% respectively. The high-strength porous ceramic material is mainly composed of mullite (3Al2O3·2SiO2), sillimanite (Al2SiO5) and hematite (Fe2O3), as well as a small amount of quartz (SiO2) and aluminum iron phosphate (Al2SiO5). 0.67 Fe 0.33 (PO4). The volume density of this high-strength porous ceramic is 1.86g / cm 3 The volume shrinkage is 17.84%, the porosity is 24.16%, the compressive strength is 50.68MPa, the flexural strength is 40.78MPa, the refractoriness is 1500℃, the water absorption is 32.66%; the thermal conductivity is 0.29W / m·K.
[0026] Example 3: The weight percentage ratio of the basic raw materials for high-strength porous ceramics is: 64% kaolin, 30% sewage sludge, and 6% yellow dextrin. The kaolin particle size is 40-60 mesh, the sewage sludge particle size is 40-50 mesh, and the yellow dextrin particle size is 40-50 mesh. First, the sewage sludge is air-dried at room temperature for 72 hours and then dried in a belt dryer at 160°C for 8 hours. After drying, the dried sewage sludge is crushed to less than 4 mm using an impact crusher and then crushed to 40-50 mesh using a thunder wind mill. The basic raw materials are then mixed and formed into porous ceramic green bodies using a refractory forming machine. The formed porous ceramic green bodies are air-dried at room temperature for 96 hours and then dried in a 350°C kiln for 12 hours. After drying, the dried porous ceramic green bodies are sintered in a high-temperature tunnel kiln for reaction, with the final sintering temperature reaching 1350°C. The sintering schedule was: 500°C for 5 hours and 1350°C for 12 hours. After calcination, the refractory material was cooled to room temperature by slow cooling in the furnace to obtain a high-strength porous ceramic material, which was designated as S3.
[0027] The weight percentages of the chemical components of Al2O3, SiO2, Fe2O3, P2O5, CaO, and MgO in the high-strength porous ceramic material are 35.6%, 50.89%, 4.8%, 6.34%, 1.63%, and 0.75%, respectively. The high-strength porous ceramic material is mainly composed of mullite (3Al2O3·2SiO2), sillimanite (Al2SiO5), hematite (Fe2O3), and a small amount of quartz (SiO2) and aluminum iron phosphate (Al2SiO5). 0.67 Fe 0.33 (PO4). The volume density of this high-strength porous ceramic is 1.92g / cm 3 The volume shrinkage is 19.15%, the porosity is 18.21%, the compressive strength is 90.46MPa, the flexural strength is 53.78MPa, the refractoriness is 1550℃, the water absorption is 30.24%, and the thermal conductivity is 0.31W / m·K.
[0028] Example 4: The weight percentage ratio of the basic raw materials for high-strength porous ceramics is: kaolin 72%, sewage sludge 20%, and yellow dextrin 8%. The kaolin particle size is 50-70 mesh, the sewage sludge particle size is 50-60 mesh, and the yellow dextrin particle size is 50-60 mesh. First, the sewage sludge is air-dried at room temperature for 72 hours and then dried in a belt dryer at 180°C for 6 hours. After drying, the dried sewage sludge is crushed to less than 3 mm using an impact crusher and then crushed to 50-60 mesh using a thunder wind mill. The basic raw materials are then mixed and formed into porous ceramic green sheets using a refractory forming machine. The formed porous ceramic green sheets are air-dried at room temperature for 96 hours and then dried in a 400°C kiln for 10 hours. After drying, the dried porous ceramic green sheets are sintered in a high-temperature tunnel kiln for reaction, with the final sintering temperature reaching 1400°C. The sintering schedule was: 500°C for 5 hours and 1400°C for 10 hours. After calcination, the refractory material was cooled to room temperature by slow cooling in the furnace to obtain a high-strength porous ceramic material, which was designated as S4.
[0029] The weight percentages of the chemical components of Al2O3, SiO2, Fe2O3, P2O5, CaO, and MgO in the high-strength porous ceramic material are 38.1%, 52.5%, 3.53%, 4.28%, 1.1%, and 0.5%, respectively. The high-strength porous ceramic material is mainly composed of mullite (3Al2O3·2SiO2), sillimanite (Al2SiO5), hematite (Fe2O3), and a small amount of quartz (SiO2) and aluminum iron phosphate (Al2SiO5). 0.67 Fe 0.33 (PO4). The volume density of this high-strength porous ceramic is 2.02g / cm 3 The volume shrinkage is 20.34%, the porosity is 15.69%, the compressive strength is 86.47MPa, the flexural strength is 50.65MPa, the refractoriness is 1600℃, the water absorption is 27.18%, and the thermal conductivity is 0.33W / m·K.
[0030] Figure 2 The XRD pattern of high-strength porous ceramics is shown in Figure 2. It can be seen that high-strength porous ceramic materials are mainly composed of mullite (3Al2O3·2SiO2), sillimanite (Al2SiO5) and hematite (Fe2O3) as well as a small amount of quartz (SiO2) and aluminum iron phosphate (Al2SiO5). 0.67 Fe 0.33 (PO4) composition, the formation of mullite and sillimanite can significantly improve the refractoriness of high-strength porous ceramics, while the formation of a small amount of quartz and aluminum iron phosphate can effectively bond the high-melting point mullite and sillimanite phases, significantly improving the sintering performance and mechanical properties of porous ceramics. Figure 3This is an SEM micrograph of a high-strength porous ceramic. It can be seen that high-strength porous ceramic materials have a very dense skeleton and a complex porous structure. Increasing the sintering temperature significantly increases the pore size and reduces the pore number. The complex pore structure and high porosity give the porous ceramic a low thermal conductivity and excellent thermal insulation properties. Figure 4 The mechanical properties of high-strength porous ceramics. It can be seen that the porous ceramics have low bulk density, high sintering shrinkage, compressive strength and flexural strength, which shows that the porous ceramics synthesized by sewage sludge and kaolin have good sintering properties and excellent mechanical properties. Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should all be included in the scope of the claims of the present invention.
Claims
1. A high-strength porous ceramic synthesized from sewage sludge and kaolin, characterized by: The high-strength porous ceramic is composed of mullite 3Al2O3·2SiO2, sillimanite Al2SiO5, hematite Fe2O3, quartz SiO2 and aluminum iron phosphate Al 0.67 Fe 0.33 PO4, and the weight percentage range of its chemical composition is: Al2O330.79~38.1%, SiO247.82~52.5%, Fe2O33.53~7.23%, P2O54.28~10.31%, CaO 1.1~2.64%, and MgO 0.5~1.12%.
2. The high-strength porous ceramic synthesized from sewage sludge and kaolin according to claim 1, characterized in that: The volume density of the high-strength porous ceramic is 1.53 to 2.02 g / cm 3 The volume shrinkage is 12.17-20.34%, and the porosity is 15.69-34.74%.
3. The high-strength porous ceramic synthesized from sewage sludge and kaolin according to claim 1, characterized in that: The high-strength porous ceramic has a compressive strength of 35.05 to 90.46 MPa, a flexural strength of 16.78 to 53.78 MPa, a refractoriness of 1450 to 1600°C, a water absorption rate of 27.18 to 35.07%, and a thermal conductivity of 0.27 to 0.33 W·m -1 ·K -1 .
4. A method for preparing high-strength porous ceramics synthesized from sewage sludge and kaolin, characterized by: The high-strength porous ceramic as claimed in any one of claims 1 to 3, wherein the preparation method comprises the following steps: S10: pretreatment of sewage sludge, drying and crushing the sewage sludge into 20-60 mesh; S20: adding sewage sludge and a binder to industrial kaolin to prepare a porous ceramic green body, wherein the mass percentage of each raw material is as follows: kaolin 48-72%, sewage sludge 20-50%, and yellow dextrin 2-8%; S30: Drying the porous ceramic wet body prepared in S20 to obtain a porous ceramic green body, and sending the porous ceramic green body into a high-temperature tunnel kiln for high-temperature calcination, wherein the drying temperature is 300-500° C., the drying time is 14-20 hours, the calcination temperature is 1250-1400° C., and the calcination time is 12-18 hours.