Ceramic mold gypsum taking industrial byproduct semi-hydrated gypsum as base material and preparation method of ceramic mold gypsum

Abstract

The invention discloses ceramic mold gypsum with industrial byproduct semi-hydrated gypsum as a base material and a preparation method thereof.The ceramic mold gypsum is prepared from, by mass, 75%-85% of alpha-semi-hydrated gypsum and 15%-25% of power plant fire coal waste, the alpha-semi-hydrated gypsum is prepared from the industrial byproduct semi-hydrated gypsum, and the technical parameters of the alpha-semi-hydrated gypsum are as follows: the standard thickness is 40%-45%, the initial setting time is 16-22 minutes, and the wet fracture resistance is 6.0-6.5 Mpa in two hours. Alpha-semi-hydrated gypsum prepared from industrial by-product gypsum is taken as a basis, power plant fire coal waste in a specific proportion is doped, the two materials are uniformly mixed, water is added, the ceramic mold gypsum (powder) is obtained, the strength requirement and the water absorption requirement of the ceramic mold gypsum are met, and compared with natural gypsum ceramic mold (powder), the ceramic mold gypsum has obvious cost advantage and environmental protection advantage.

Description

Technical Field

[0001] This invention relates to a ceramic mold plaster for making ceramic molds, and more particularly to a ceramic mold plaster for rolling molds of ceramic products made from α-hemihydrate gypsum produced as an industrial by-product gypsum, and its preparation method. Background Technology

[0002] The fineness of hemihydrate gypsum powder has a significant and complex impact on the water absorption rate of ceramic molds. The core issue is that fineness determines the degree of hydration, crystal structure, and final pore structure (pore size, distribution, and connectivity) of the gypsum slurry. For example, finer particles result in a larger specific surface area. At the same water-to-slurry ratio, finer gypsum powder has a larger contact area with water, leading to a faster and more complete hydration reaction (CaSO4·½H2O + 1.5H2O → CaSO4·2H2O). A more complete hydration reaction typically means the formation of more and denser acicular crystal networks in dihydrate gypsum, theoretically reducing the total pore volume and potentially lowering the water absorption rate. Therefore, a suitable fineness range for the gypsum powder used in ceramic molds is fundamental to obtaining molds with ideal water absorption rates.

[0003] Currently, ceramic mold plaster in my country is made from hemihydrate plaster (mainly α-type hemihydrate plaster) produced from natural gypsum. The fineness range of the ceramic mold plaster is artificially controlled, and the standard is the "sieve residue (%)" specified in the "Gypsum Powder for Ceramic Molds (QB / T 1639-2014)". The fineness standard range for ceramic mold plaster is: 0% sieve residue for 0.15mm aperture and less than 1% sieve residue for 0.09mm aperture. In contrast, the Japanese Industrial Standard "Gypsum for Ceramic Molds (JISR9111-2009)" specifies a fineness standard range of 0% sieve residue for 0.425mm aperture and less than 7% sieve residue for 0.15mm aperture.

[0004] Alpha-type hemihydrate gypsum can also be produced using industrial by-product gypsum, which is beneficial to the consumption of industrial solid waste and environmental protection. In addition, industrial by-product gypsum has extremely low cost, while natural gypsum requires mining and resource tax payment, and its distribution is extremely uneven and mining is restricted. Therefore, the cost of using industrial by-product gypsum to produce ceramic molding gypsum will be much lower than that of natural gypsum.

[0005] However, the particle size of industrial by-product gypsum is generally below 0.15 mm, and the resulting α-type hemihydrate gypsum has an even smaller particle size and lower fineness. For example, the α-type hemihydrate gypsum produced using desulfurized gypsum has a particle size below 0.05 mm, and 85% of the α-type hemihydrate gypsum has a particle size below 0.01 mm. When used in ceramic molding gypsum, this will severely affect its water absorption rate. Therefore, it is necessary to adjust its pore structure and water absorption performance through material modification. Summary of the Invention

[0006] The purpose of this invention is to provide a ceramic mold plaster based on industrial by-product hemihydrate gypsum and its preparation method. Based on α-hemihydrate gypsum prepared from industrial by-product gypsum, a specific proportion of power plant coal combustion waste is added to prepare a ceramic mold plaster that meets both strength requirements and has a suitable water absorption rate.

[0007] To achieve the above objectives, according to one aspect of the present invention, a ceramic molding gypsum based on industrial by-product hemihydrate gypsum is provided, comprising, by weight percentage, 75-85% α-hemihydrate gypsum and 15-25% power plant coal combustion waste, wherein the α-hemihydrate gypsum is prepared from industrial by-product hemihydrate gypsum, and its technical parameters are: standard consistency 40%-45%, initial setting time 16-22 minutes, and wet flexural strength of 6.0-6.5 MPa after two hours.

[0008] In a preferred embodiment, the composition of the power plant coal-fired waste is 40%–55% SiO2, 20%–30% Al2O3, with the remainder being impurities.

[0009] In a preferred embodiment, the impurities include Fe2O3, CaO, MgO, and carbon particles present in normal amounts.

[0010] In a preferred embodiment, the loss on ignition of the power plant's coal-fired waste is ≤8.0%.

[0011] In a preferred embodiment, the Fe2O3 content in the power plant coal-fired waste is ≤8.0%.

[0012] In a preferred embodiment, the content of spongy vitreous in the coal-fired power plant waste is 75% to 80%.

[0013] In a preferred embodiment, the content of glass microspheres in the coal-fired power plant waste is ≤10%.

[0014] According to another aspect of the present invention, a method for preparing ceramic molding plaster using industrial by-product hemihydrate gypsum as a base material is provided, comprising the steps of: Step 1: Based on the different water absorption and strength requirements of ceramic molds, set different proportions of α-hemihydrate gypsum and power plant coal waste in the preparation materials; Step 2: Mix the ingredients thoroughly. Step 3: Add water according to the standard consistency of ceramic plaster and stir well before pouring into a ceramic mold.

[0015] This invention proposes a method using α-type hemihydrate gypsum produced from industrial by-product gypsum as the base material, and adding materials extracted from waste generated during the coal combustion process of coal-fired power plants in a proportion not exceeding 25% to increase the water absorption rate. The two materials are mixed evenly and water is added to obtain ceramic mold gypsum (powder), which meets the strength and water absorption requirements of ceramic mold gypsum. Compared with natural gypsum ceramic mold (powder), it has significant cost and environmental advantages. Detailed Implementation

[0016] This invention provides a ceramic molding gypsum based on industrial by-product hemihydrate gypsum, comprising, by weight percentage, 75-85% α-hemihydrate gypsum and 15-25% power plant coal-fired waste. The α-hemihydrate gypsum is prepared from industrial by-product hemihydrate gypsum and conforms to the requirements of JC / T2038-2010, with the following technical parameters: standard consistency 40%-45%, initial setting time 16-22 minutes, and wet flexural strength of 6.0-6.5 MPa after two hours.

[0017] The term "standard consistency" refers to the water addition ratio at the maximum flow diameter of a standard gypsum slurry.

[0018] The composition of the coal-fired waste from the power plant is 40%–55% SiO2, 20%–30% Al2O3, with the remainder being impurities.

[0019] Impurities include Fe2O3, CaO, MgO, and carbon particles, which are present in normal amounts. Calcium oxide and magnesium oxide have no effect on water absorption, so they do not require specific testing. The Fe2O3 content is ≤8.0%, and the loss on ignition (carbon particles) is ≤8.0%.

[0020] The majority of coal-fired waste from power plants is in the form of sponge-like glass, with some glass microspheres and carbon particles. The content of sponge-like glass is 75% to 80%. The sponge-like glass is mostly porous and honeycomb-like, with a large specific surface area and strong water storage capacity. The content of glass microspheres is ≤10%.

[0021] Because ceramic products vary in size and thickness, the rolling molds used for them may differ. Some require a slightly higher water absorption rate (for thicker ceramic products), which results in a slight decrease in strength; others require a lower water absorption rate, allowing for a slightly higher strength. Therefore, determining which formulation of industrial by-product gypsum and coal-fired power plant solid waste used to produce ceramic mold gypsum is more suitable depends on actual production needs within a certain range.

[0022] Another typical embodiment of the present invention provides a method for preparing ceramic molding plaster using industrial by-product hemihydrate gypsum as a base material, comprising the steps of: Step 1: Based on the different water absorption and strength requirements of ceramic molds, set different proportions of α-hemihydrate gypsum and power plant coal waste in the preparation materials; Step 2: Mix the ingredients thoroughly. Step 3: Add water according to the standard consistency of ceramic plaster and stir well before pouring into a ceramic mold.

[0023] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments are for explaining the implementation of the present invention and do not exceed the scope of the subject matter of the present invention. The scope of protection of the present invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art. Example 1

[0024] In this embodiment, the technical parameters of α-hemihydrate gypsum are: standard consistency 41%, initial setting time 15 minutes, final setting time 22 minutes, and wet flexural strength of 6.2 MPa after two hours. The technical parameters of the power plant coal-fired waste are: 0.045 mm sieve residue 16.9%, loss on ignition (carbon particles) 6.6%, spongy glass content 78%, and glass microsphere content 9%. The composition of the power plant coal-fired waste is: silicon dioxide 48.5%, aluminum oxide 26.8%, ferric oxide 6.3%, carbon particles 6.6%, with the remainder being impurities.

[0025] Using the above-mentioned α-hemihydrate gypsum and power plant coal waste as preparation materials, they are mixed evenly at a mass ratio of 85:15, and water is added at the target standard thickness of 43%. After stirring evenly, the mixture is poured into a ceramic mold.

[0026] The ceramic mold obtained in this embodiment has a standard viscosity of 43%, an initial setting time of 16 minutes, a final setting time of 23 minutes, and a wet flexural strength of 4.95 MPa after two hours.

[0027] The dry weight of the ceramic mold test block was 376.6 grams. After soaking in water for two hours, the wet weight of the test block was 451.7 grams. The water absorption rate was calculated as (wet weight of test block - dry weight of test block) / dry weight of test block = 19.94%. Example 2

[0028] In this embodiment, the technical parameters of α-hemihydrate gypsum are: standard consistency 41%, initial setting time 15 minutes, final setting time 22 minutes, and wet flexural strength of 6.2 MPa after two hours. The technical parameters of the power plant coal-fired waste are: 0.045 mm sieve residue 16.9%, loss on ignition (carbon particles) 6.6%, spongy glass content 78%, and glass microsphere content 9%. The composition of the power plant coal-fired waste is: silicon dioxide 48.5%, aluminum oxide 26.8%, ferric oxide 6.3%, carbon particles 6.6%, with the remainder being impurities.

[0029] Using the above-mentioned α-hemihydrate gypsum and coal waste as preparation materials, they are mixed evenly at a mass ratio of 80:20, and water is added at the target standard thickness of 44%. After stirring evenly, the mixture is poured into a ceramic mold.

[0030] The ceramic mold obtained in this embodiment has a standard viscosity of 44%, an initial setting time of 16.5 minutes, a final setting time of 23 minutes, and a wet flexural strength of 4.72 MPa after two hours.

[0031] The dry weight of the ceramic mold test block was 365.0 g, and the wet weight of the test block after soaking in water for two hours was 443.8 g; the water absorption rate = (wet weight of test block - dry weight of test block) / dry weight of test block = 21.6%. Example 3

[0032] In this embodiment, the technical parameters of α-hemihydrate gypsum are: standard consistency 41%, initial setting time 15 minutes, final setting time 22 minutes, and wet flexural strength of 6.2 MPa after two hours. The technical parameters of power plant coal-fired waste are: 0.045 mm sieve residue 16.9%, loss on ignition (carbon particles) 6.6%, spongy glass content 78%, and glass microsphere content 9%. The composition of power plant coal-fired waste is: silicon dioxide 48.5%, aluminum oxide 26.8%, ferric oxide 6.3%, carbon particles 6.6%, with the remainder being impurities.

[0033] Using the above-mentioned α-hemihydrate gypsum and coal waste as preparation materials, they are mixed evenly at a mass ratio of 75:25, and water is added at the target standard thickness of 45.5%. After stirring evenly, the mixture is poured into a ceramic mold.

[0034] The ceramic mold obtained in this embodiment has a standard viscosity of 45.5%, an initial setting time of 17 minutes, a final setting time of 24 minutes, and a wet flexural strength of 4.01 MPa after two hours.

[0035] The dry weight of the ceramic mold test block was 354.6 grams, and the wet weight of the test block was 438.0 grams after soaking in water for two hours; the water absorption rate = (wet weight of test block - dry weight of test block) / dry weight of test block = 23.5%. Example 4

[0036] In this embodiment, the technical parameters of α-hemihydrate gypsum are: standard consistency 40%, initial setting time 16 minutes, final setting time 21 minutes, and wet flexural strength of 6.5 MPa after two hours. The technical parameters of power plant coal-fired waste are: 0.045mm sieve residue = 16.9%, loss on ignition (carbon particles) 3.5%, spongy glass content 75%, and glass microsphere content 8.5%. The composition of power plant coal-fired waste is: silicon dioxide 55%, aluminum oxide 30%, ferric oxide 3.8%, carbon particles 3.5%, with the remainder being impurities.

[0037] Using the above-mentioned α-hemihydrate gypsum and coal waste as preparation materials, they are mixed evenly at a mass ratio of 78:22, and water is added at the target standard thickness of 43.5%. After stirring evenly, the mixture is poured into a ceramic mold.

[0038] The ceramic mold obtained in this embodiment has a standard viscosity of 43.5%, an initial setting time of 17 minutes, a final setting time of 23 minutes, and a wet flexural strength of 4.78 MPa after two hours.

[0039] The dry weight of the ceramic mold test block was 361.2 grams, and the wet weight of the test block was 440.1 grams after soaking in water for two hours; the water absorption rate = (wet weight of test block - dry weight of test block) / dry weight of test block = 21.84%. Example 5

[0040] In this embodiment, the technical parameters of α-hemihydrate gypsum are: standard consistency 45%, initial setting time 22 minutes, final setting time 26 minutes, and wet flexural strength of 6.0 MPa after two hours. The technical parameters of power plant coal-fired waste are: 0.045mm sieve residue = 16.9%, loss on ignition (carbon particles) 8.0%, spongy glass content 80%, and glass microsphere content 9.5%. The composition of power plant coal-fired waste is: silicon dioxide 40%, aluminum oxide 20%, ferric oxide 6.6%, carbon particles 8.0%, with the remainder being impurities.

[0041] Using the above-mentioned α-hemihydrate gypsum and coal waste as preparation materials, they are mixed evenly at a mass ratio of 83:17, and water is added at the target standard thickness of 46%. After stirring evenly, the mixture is poured into a ceramic mold.

[0042] The ceramic mold obtained in this embodiment has a standard viscosity of 46%, an initial setting time of 20 minutes, a final setting time of 26 minutes, and a wet flexural strength of 4.15 MPa after two hours.

[0043] The dry weight of the ceramic mold was 352.3 grams, and the wet weight of the test block was 436.2 grams after soaking in water for two hours; the water absorption rate = (wet weight of test block - dry weight of test block) / dry weight of test block = 23.8%.

[0044] Comparative Example 1: Ceramic mold plaster produced from natural gypsum The technical parameters of this natural gypsum are: standard consistency 50.5%, initial setting time 19 minutes, and wet flexural strength 4.85 MPa after two hours.

[0045] The dry weight of the mold block was 355.6 grams, and the wet weight of the block after soaking in water for two hours was 436.3 grams; the water absorption rate = (wet weight of the block - dry weight of the block) / dry weight of the block = 22.7%.

[0046] Compared with natural gypsum ceramic molds (powder), the various indicators of this invention are similar, but its cost advantage and green advantage are obvious.

[0047] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A ceramic molding plaster using industrial by-product hemihydrate gypsum as a base material, characterized in that: By mass percentage, it comprises 75-85% α-hemihydrate gypsum and 15-25% coal-fired waste from power plants. The α-hemihydrate gypsum is prepared from industrial by-product hemihydrate gypsum, and its technical parameters are: standard consistency 40%-45%, initial setting time 16-22 minutes, and wet flexural strength of 6.0-6.5 MPa after two hours.

2. The ceramic molding plaster based on industrial by-product hemihydrate gypsum as described in claim 1, characterized in that: The composition of the coal-fired waste from the power plant is 40%–55% SiO2, 20%–30% Al2O3, with the remainder being impurities.

3. The ceramic molding plaster based on industrial by-product hemihydrate gypsum as described in claim 2, characterized in that: The impurities include Fe2O3, CaO, MgO, and carbon particles, which are present in normal amounts.

4. The ceramic molding plaster based on industrial by-product hemihydrate gypsum as described in claim 2, characterized in that: The loss on ignition of the coal-fired waste from the power plant is ≤8.0%.

5. The ceramic molding plaster based on industrial by-product hemihydrate gypsum as described in claim 2, characterized in that: The Fe2O3 content in the coal-fired waste from the power plant is ≤8.0%.

6. The ceramic molding plaster based on industrial by-product hemihydrate gypsum as described in claim 1 or 2, characterized in that: The content of spongy vitreous matter in the coal-fired waste from the power plant is 75% to 80%.

7. The ceramic molding plaster based on industrial by-product hemihydrate gypsum as described in claim 6, characterized in that: The content of glass microspheres in the coal-fired waste from the power plant is ≤10%.

8. The method for preparing ceramic molding plaster using industrial by-product hemihydrate gypsum as a base material as described in any one of claims 1-7, characterized in that: Including the following steps: Step 1: Based on the different water absorption and strength requirements of ceramic molds, set different proportions of α-hemihydrate gypsum and power plant coal waste in the preparation materials; Step 2: Mix the ingredients thoroughly. Step 3: Add water according to the standard consistency of ceramic plaster and stir well before pouring into a ceramic mold.