Dry-pressing regenerated ceramic preparation method based on waste ceramic

Abstract

The invention provides a dry-pressing regenerated ceramic preparation method based on waste ceramic, which comprises the following steps: S1, raw material treatment: crushing ceramic waste into powder with the particle size of less than or equal to 35 microns, and screening into powder with coarse, medium and fine particle sizes; the powder is graded according to the particle size gradient, the coarse particles account for 40-60%, the medium particles account for 30-40%, and the fine particles account for 10-20%, so that the stacking density is improved; 12-15% of an inorganic binder and 1-3% of an organic binder are added, so that the strength of the green body is improved; s2, dry pressing molding: after uniformly mixing the mixture, controlling the water content of the mixture to be 4-6%; and carrying out dry pressing molding under the pressure of 50-100 MPa, wherein the pressure maintaining time is 10-30 seconds. According to the dry-pressing regenerated ceramic preparation method based on the waste ceramic, high-doping-amount (more than or equal to 70%) utilization of the waste ceramic is realized by optimizing the grain composition of the waste ceramic powder, a composite binder system and a low-temperature sintering process, and a regenerated ceramic product prepared by the method is high in strength, low in cost and suitable for the fields of decorative ceramics and cultural and creative ceramics.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material recycling, and more specifically, to a method for preparing recycled ceramic products using ceramic waste powder through a dry pressing molding process, which is suitable for recycling waste of daily-use ceramics, building ceramics and industrial ceramics. Background Art

[0002] The ceramic production process generates a large amount of waste, including defective products and scraps. Traditionally, these wastes are disposed of by landfill or stockpiling, resulting in significant resource waste and negative environmental impacts. Current waste recycling technologies rely heavily on slip casting, a process that is energy-intensive, complex for certain structurally complex products, and limited in its utilization by the plastic removal process.

[0003] In the dry pressing process, although this is a more environmentally friendly and efficient alternative, in actual application, due to problems such as unreasonable particle grading of waste porcelain powder, improper selection of binders and inaccurate matching of process parameters, the recycled green body has low strength, poor molding consistency and is prone to cracking after sintering. These problems limit the large-scale application of this technology.

[0004] The invention can solve the problems of low green body strength and poor sintering stability in dry pressing of waste porcelain powder. Summary of the Invention

[0005] The present invention aims to solve the technical problems raised by the above-mentioned background technology and provide a dry pressing method with high waste porcelain content (≥85%), low energy consumption and high strength, specifically a dry pressing method for preparing recycled ceramics based on ceramic waste porcelain.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a method for preparing recycled ceramics by dry pressing of ceramic waste, comprising the following steps: S1: Raw material processing: Ceramic waste is crushed into powder with a particle size of ≤35μm, and sieved into coarse, medium and fine powders; the powders are graded according to a particle size gradient, with coarse particles accounting for 40-60%, medium particles accounting for 30-40%, and fine particles accounting for 10-20% to improve the bulk density; 12-15% inorganic binder and 1-3% organic binder are added to improve the strength of the green body; S2: Dry pressing: After the mixture is evenly mixed, the moisture content of the mixture is controlled within the range of 4-6%. Dry pressing is performed under a pressure of 50-100 MPa with a holding time of 10-30 seconds. A bidirectional pressure mold is used to reduce density gradient and improve molding consistency. S3: Heating and sintering: Stepwise heating: gradually increase the temperature from room temperature to 300°C at a heating rate of 2°C / min, during which the binder is removed; continue to heat to 1100-1700°C and keep at this temperature for 1-3 hours to complete the sintering process and obtain recycled ceramic products.

[0007] A further preferred embodiment is that the inorganic binder is any one of bentonite, yew clay, black mud, or a mixture of more than one of them in any proportion, and the organic binder is polyvinyl alcohol.

[0008] A further preferred embodiment: the addition amount of the inorganic binder is 5-10%.

[0009] A further preferred solution is that the moisture content of the mixture is controlled at 5%.

[0010] A further preferred embodiment is that the pressure in the dry pressing step is controlled between 70-90 MPa.

[0011] A further preferred solution is that the temperature range of the sintering stage is 1150-1200° C. and the temperature is kept at this temperature for 2 hours.

[0012] A further preferred solution is that the ceramic waste is defective products, scraps and discarded ceramic products in the ceramic production process.

[0013] A further preferred embodiment: the dry pressing process further comprises the following steps in sequence: material selection, inspection, washing, crushing, weight batching, fine grinding and ball milling, screening, iron removal, batching, uniform mixing, storage and aging, molding, glazing, firing, inspection and warehousing.

[0014] A further preferred solution is that in the crushing and screening steps of the waste porcelain powder, a ball mill or a jet mill is used for crushing, and a multi-stage vibrating screen is used for graded screening.

[0015] A further preferred solution is that the duration of the binder removal stage in the stepwise heating process is 1-2 hours. Beneficial effects

[0016] This dry-pressed recycled ceramic production method based on waste ceramics improves green body density and reduces sintering shrinkage by optimizing particle size distribution and designing the gradation of coarse, medium, and fine waste ceramic powders. A composite binder system, synergistically combining inorganic and organic binders, addresses the fragility of dry-pressed green bodies. A low-temperature sintering process, combined with adjustments to the waste ceramic powder composition (e.g., a high glass phase content), reduces the sintering temperature to below 1150°C, resulting in recycled ceramic products with high waste ceramic content, low energy consumption, and high strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic flow chart of the preparation method of the present invention.

[0018] Figure 2 This is a process flow chart of the waste porcelain dry pressing process of the present invention.

[0019] Figure 3 This is the particle size distribution diagram of the first powder provided by the present invention.

[0020] Figure 4 This is a detailed table of particle size distribution of the first powder provided by the present invention.

[0021] Figure 5 This is a particle size distribution diagram of the second powder provided by the present invention.

[0022] Figure 6 This is a detailed table of particle size distribution of the second powder provided by the present invention.

[0023] Figure 7 This is the particle size distribution diagram of the third powder provided by the present invention.

[0024] Figure 8 This is a detailed table of particle size distribution of the third powder provided by the present invention.

[0025] Figure 9 Schematic diagram of the sintering curve of the present invention.

[0026] Figure 10 This is a table showing the relationship between particle size distribution and green body density of the present invention. DETAILED DESCRIPTION

[0027] The following is a combination of the embodiments of the present invention Figures 1-10 , clearly and completely describe the technical solutions in the embodiments of the present invention.

[0028] See also Figure 1-10 In an embodiment of the present invention, a method for preparing dry-pressed recycled ceramics based on ceramic waste includes the following steps: S1: Raw material processing: Ceramic waste is crushed into powder with a particle size of ≤35μm, and then sieved into coarse, medium, and fine powders; the powders are graded according to a particle size gradient, with coarse particles accounting for 40-60%, medium particles accounting for 30-40%, and fine particles accounting for 10-20% to improve the bulk density; 12-15% inorganic binder and 1-3% organic binder are added to improve the strength of the green body; particle size grading optimization: Through the grading design of coarse, medium, and fine waste ceramic powders, the green body density is improved and sintering shrinkage is reduced; composite binder system: The synergistic effect of inorganic and organic binders solves the problem of fragile dry-pressed green bodies; The proportion of waste porcelain powder is: coarse particles (9.8-35μm) 50%, medium particles (4-9.8μm) 30%, fine particles (<4μm) 20%; Additives: bentonite 8% (plasticizing effect), PVA 2% (improving bonding and strength); S2: Dry pressing: After the mixture is evenly mixed, the moisture content of the mixture is controlled within the range of 4-6%. By controlling the moisture content of the mixture, the powder is ensured to have appropriate fluidity during the pressing process, which facilitates filling the mold and forming a uniform green body. Dry pressing is performed under a pressure of 50-100 MPa, with a holding time of 10-30 seconds. Dry pressing is performed under high pressure to ensure that the powder particles are closely arranged to form a green body with a certain strength. A bidirectional pressure mold is used to reduce the density gradient and improve the molding consistency. Dry pressing parameters: pressure 80MPa, holding pressure 20 seconds, moisture content 5%; Dry pressing is to make up for the improvement of process flow and work efficiency of some products. For example, thick-walled products are more suitable for dry pressing. It is fast and efficient, eliminating the long plastic discharge process. Energy consumption and efficiency are significantly improved, saving 10%-15% of energy consumption. S3: Heating and sintering: Stepwise heating: gradually heating from room temperature to 300°C at a heating rate of 2°C / min. During this stage, the binder is removed and heated at a lower heating rate (2°C / min) in the low temperature section (such as 300°C) to ensure that the organic binder is fully decomposed and discharged to avoid bubbles or cracks during high-temperature sintering. Continue heating to 1100-1700°C and keep at this temperature for 1-3 hours to complete the sintering process to obtain recycled ceramic products. Sintering is carried out in the high temperature section (1100-1700°C). At this time, the diffusion and bonding between particles are accelerated to form a dense ceramic structure. By controlling the sintering time and temperature, the product can achieve the required physical and chemical properties. Low-temperature sintering process: by adjusting the composition of waste porcelain powder (such as high glass phase content), the sintering temperature is reduced to below 1150°C. like Figure 9 , sintering temperature and time: 300℃ debinding for 1 hour, 1250℃ sintering for 2 hours; Sintering results: finished product compressive strength 65MPa, water absorption 0.3%; Through the process of the above embodiment, the utilization rate of waste porcelain reaches 70-90%, and the cost is reduced by more than 30%; the flexural strength of the green body is ≥8MPa, the water absorption rate of the sintered product is ≤0.5%, and the compressive strength is ≥60MPa; The remaining embodiments can also verify the effect on performance by adjusting the gradation of waste porcelain powder or the ratio of binder.

[0029] In an embodiment of the present invention, the inorganic binder is any one of bentonite, yew clay, black mud, or a mixture of more than one of them in any proportion. These materials have good plasticity and bonding strength, can enhance the strength of the green body during the pressing process, and promote the bonding between particles during the sintering process. The organic binder is polyvinyl alcohol (PVA). PVA, an organic binder, can provide a temporary bonding effect to help maintain the shape of the green body until the sintering process is completed.

[0030] In the embodiment of the present invention, the addition amount of the inorganic binder is 5-10%.

[0031] In the embodiment of the present invention, the moisture content of the mixture is controlled at 5% to ensure optimal molding conditions and subsequent sintering quality.

[0032] In an embodiment of the present invention, the pressure in the dry pressing step is controlled between 70-90 MPa to obtain the best forming effect.

[0033] In the embodiment of the present invention, the temperature range of the sintering stage is 1150-1200° C., and the temperature is kept at this temperature for 2 hours to ensure that the ceramic product has good mechanical properties.

[0034] In the embodiment of the present invention, the ceramic waste is defective products, scraps and discarded ceramic products in the ceramic production process.

[0035] In an embodiment of the present invention, the dry pressing molding process further includes the following steps in sequence: material selection, inspection, washing, crushing, weight batching, fine crushing and ball milling, screening, iron removal, batching, uniform mixing, storage and aging, molding, glazing, firing, inspection and warehousing.

[0036] In an embodiment of the present invention, in the crushing and screening steps of the waste porcelain powder, a ball mill or a jet mill is used for crushing, and a multi-stage vibrating screen is used for graded screening. Through mechanical crushing and screening, the waste porcelain is crushed into powders of different particle sizes. A reasonable particle size distribution helps to improve the density and uniformity of the green body, thereby enhancing the mechanical properties of the final product.

[0037] In the embodiment of the present invention, the duration of the binder removal stage in the step-by-step heating process is 1-2 hours to ensure that the binder is completely discharged.

[0038] Working principle: Collect defective products, scraps and discarded ceramic products generated during the ceramic production process, use a ball mill or air flow mill to crush the waste porcelain into powder with a particle size of ≤35μm, and use a multi-stage vibrating screen to grade and screen the crushed powder into coarse particles (9.8-35μm), medium particles (4-9.8μm) and fine particles (<4μm); grade the powder into coarse, medium and fine particle sizes according to a specific ratio, with coarse particles accounting for 40-60%, medium particles accounting for 30-40% and fine particles accounting for 10-20% to optimize the bulk density; add 12-15% inorganic binder (such as bentonite, zuoyuntu, black mud) and 1-3% organic binder (such as polyethylene) The waste porcelain powder that has been graded and treated with additives is mixed evenly, and the moisture content of the mixture is controlled within the range of 4-6%; dry pressing is carried out under a pressure of 50-100MPa, with a holding time of 10-30 seconds, and a bidirectional pressure mold is used to reduce the density gradient and improve the molding consistency; the temperature is gradually increased from room temperature to 300℃ at a heating rate of 2℃ / min, and the binder is removed at this stage; the temperature is continued to be increased to 1100-1700℃ and kept at this temperature for 1-3 hours to complete the sintering process; after sintering, it is gradually cooled to room temperature and the finished product is inspected to ensure that its compressive strength is ≥60MPa and its water absorption rate is ≤0.5%.

Claims

1. A method for preparing recycled ceramics by dry pressing of waste ceramics, characterized by: The following steps are involved: S1: Raw material processing: Ceramic waste is crushed into powder with a particle size of ≤35μm, and sieved into coarse, medium and fine powders; the powders are graded according to a particle size gradient, with coarse particles accounting for 40-60%, medium particles accounting for 30-40%, and fine particles accounting for 10-20% to improve the bulk density; 12-15% inorganic binder and 1-3% organic binder are added to improve the strength of the green body; S2: Dry pressing: After the mixture is evenly mixed, the moisture content of the mixture is controlled within the range of 4-6%. Dry pressing is performed under a pressure of 50-100 MPa with a holding time of 10-30 seconds. A bidirectional pressure mold is used to reduce density gradient and improve molding consistency. S3: Heating and sintering: Stepwise heating: gradually increase the temperature from room temperature to 300°C at a heating rate of 2°C / min, during which the binder is removed; continue to heat to 1100-1700°C and keep at this temperature for 1-3 hours to complete the sintering process and obtain recycled ceramic products.

2. The method for preparing recycled ceramics by dry pressing of waste ceramics according to claim 1, characterized in that: The inorganic binder is any one of bentonite, yew clay, and black mud, or a mixture of more than one of them in any proportion, and the organic binder is polyvinyl alcohol.

3. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: The addition amount of the inorganic binder is 5-10%.

4. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: The moisture content of the mixture is controlled at 5%.

5. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: The pressure in the dry pressing step is controlled between 70-90 MPa.

6. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: The temperature range of the sintering stage is 1150-1200° C. and is maintained at this temperature for 2 hours.

7. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: The ceramic waste materials are defective products, scraps and discarded ceramic products in the ceramic production process.

8. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: The dry pressing molding process also includes the following steps in sequence: material selection, inspection, water washing, crushing, weight batching, fine crushing and ball milling, screening, iron removal, batching, uniform mixing, storage and aging, molding, glazing, firing, inspection and warehousing.

9. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: In the crushing and screening steps of the waste porcelain powder, a ball mill or a jet mill is used for crushing, and a multi-stage vibrating screen is used for classification and screening.

10. The method for preparing recycled ceramics by dry pressing based on ceramic waste according to claim 1, characterized in that: The duration of the binder removal stage in the step-by-step heating process is 1-2 hours.

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