Gypsum composite crystal modifier, beta-semi-hydrated gypsum and preparation method of beta-semi-hydrated gypsum

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a gypsum composite crystal modifier, beta-semi-hydrated gypsum and a preparation method of the beta-semi-hydrated gypsum. In order to obtain the building gypsum with excellent comprehensive performance, the composite crystal modifier is added into calcium sulfate dihydrate slurry according to a certain mass percent, the composite crystal modifier comprises a component A and a component B, the component A is at least one of metal oxides or sulfates, the component B is at least one of C1-C10 unitary, binary and polybasic organic acids or carboxylates, and the component B is at least one of calcium sulfate dihydrate and calcium sulfate dihydrate. The method is used for preparing beta-semi-hydrated gypsum. According to the invention, the standard consistency water consumption of the gypsum can be reduced, the setting time is shortened, the strength of the gypsum is improved, and the building gypsum with stable properties and excellent comprehensive performance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a gypsum composite crystal-changing agent, beta-hemihydrate gypsum and a preparation method thereof. Background Art

[0002] Gypsum has been used as a building material for thousands of years. It has been increasingly valued for its excellent properties such as low carbon and environmental protection, and its product categories are becoming more and more complete. Gypsum is mainly divided into natural gypsum and industrial by-products. Common industrial by-product gypsum includes more than a dozen types such as desulfurized gypsum, phosphogypsum, titanium gypsum, citric acid gypsum, nickel gypsum, boric gypsum, and chromium gypsum. The output of desulfurized gypsum and phosphogypsum in my country accounts for more than 80% of the total amount of industrial by-product gypsum. As of 2020, the annual output of phosphogypsum is about 75 million tons, and the comprehensive utilization rate is about 35%; the annual output of desulfurized gypsum is about 120 million tons, and the comprehensive utilization rate can reach 80%. Since these wastes contain acidic and other harmful substances, they are mainly treated by stockpiling. However, the large amount of accumulated industrial by-products will have a huge negative impact on the land and the environment. The main component of industrial by-products is calcium sulfate dihydrate, which can be used to prepare building materials after being treated by various methods to achieve sustainable development of resources. Among the many treatment methods, building gypsum can be obtained by calcining at normal pressure. This method has the advantages of low preparation cost and simple process, but due to the presence of many impurities in industrial by-product gypsum, the added value of the prepared building materials is low. Therefore, it is particularly important to improve the performance of building materials.

[0003] Crystallization agents are often used to optimize high-strength gypsum, which has a similar crystal structure to building gypsum. Based on this revelation, it is likely that building gypsum with excellent performance can be prepared by introducing crystallization agents into industrial by-product gypsum and calcining it under normal pressure. Therefore, the use of additives in the roasting process to improve the quality of industrial by-product gypsum will greatly increase the added value of building gypsum and the utilization rate of industrial by-product gypsum, thereby achieving harmonious development between man and nature and protecting the natural environment. Summary of the invention

[0004] The present invention provides a gypsum composite crystal-changing agent for the above-mentioned problems, and uses the composite crystal-changing agent to prepare beta-hemihydrate gypsum, so as to improve the performance of building gypsum and increase its added value.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a gypsum composite crystal-changing agent, comprising component A and component B, wherein component A is at least one of a metal oxide or a sulfate, and component B is C1-C 10At least one of monobasic, dibasic and polybasic organic acids or carboxylates. The combination of component A and component B can achieve synergy, significantly reduce the standard consistency and setting time of building gypsum, and obtain β-hemihydrate gypsum with uniform particles, stable structure and excellent performance.

[0007] Furthermore, the component A is at least one of calcium oxide, aluminum sulfate, copper sulfate, magnesium sulfate, and potassium aluminum sulfate, and the component B is at least one of potassium sodium tartrate, magnesium acetate, disodium ethylenediaminetetraacetate, sodium citrate, succinic acid, and acetic acid. Component A is not limited to the listed inorganic substances or inorganic salts, and component B is not limited to the listed organic acids or organic acid salts.

[0008] In the gypsum composite crystal-changing agent of the present invention, component A and component B are independent of each other, dissolved in the slurry in sequence, and mixed with the gypsum slurry.

[0009] In a second aspect, the present invention provides a method for preparing β-hemihydrate gypsum, which is prepared by using the composite crystal-changing agent, comprising the following steps:

[0010] The gypsum composite crystal-changing agent is added to the desulfurized gypsum slurry, mixed evenly, and then dried. After the treatment, the gypsum is ground into powder, passed through a 0.2 mm standard sieve, and then calcined at normal pressure to obtain the β-hemihydrate gypsum.

[0011] Furthermore, the desulfurized gypsum slurry is a mixed slurry of desulfurized gypsum (the main component is calcium sulfate dihydrate) and water, and its solid-liquid ratio is 1:1 to 1.5 g / mL.

[0012] Furthermore, in the composite crystal-changing agent, in component A, the metal oxide accounts for 0.2% to 0.6% of the mass of the desulfurized gypsum, the sulfate accounts for 0.03% to 0.6% of the mass of the desulfurized gypsum; and component B accounts for 0.03% to 0.2% of the mass of the desulfurized gypsum.

[0013] Furthermore, the drying process is carried out at a temperature of 45±5° C. and for a period of 1 to 2 days.

[0014] Furthermore, the temperature of the atmospheric pressure calcination is 165-190° C., and the time is 1.5-2.5 hours.

[0015] Furthermore, the method also includes room temperature aging treatment, which is carried out after normal pressure calcination, and is specifically divided into indoor aging and sealed aging. The ambient temperature of the aging treatment is 18-28°C, the ambient humidity is 40-70%, the indoor aging time is 1-2 days, and the sealed aging time is 2-5 days.

[0016] In a third aspect, the present invention also provides β-hemihydrate gypsum obtained by the preparation method.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The present invention provides a new composite crystal-changing agent, which is evenly mixed with desulfurized gypsum and then calcined to obtain β-hemihydrate gypsum. The composite crystal-changing agent helps to obtain β-hemihydrate gypsum with high strength, low standard consistency water consumption, short setting time, stable structure and uniform particles. In the prior art, desulfurized gypsum is usually subjected to a hydrothermal method to obtain α-hemihydrate gypsum, and the morphology is mostly needle-shaped, rod-shaped, or columnar crystals.

[0019] The present invention utilizes a composite crystal-changing agent to prepare β-hemihydrate gypsum with excellent performance. For example, its 2h flexural strength is greater than 3.0MPa, its 2h compressive strength is greater than 6.0MPa, its absolute dry flexural strength is greater than 5.0MPa, and its absolute dry compressive strength is greater than 12MPa, which belongs to 3.0 or 4.0 grade building gypsum.

[0020] In addition, the method of the present invention has simple process, convenient operation and short reaction time, and is very suitable for industrialization. DETAILED DESCRIPTION

[0021] The specific implementation scheme of the method for preparing β-hemihydrate gypsum according to the present invention is described in detail below.

[0022] The standard consistency water consumption and setting time of β-hemihydrate gypsum shall refer to GB / T 17669.4 "Determination of physical properties of building gypsum paste", and the flexural strength and compressive strength shall be determined in accordance with GB / T 9776-2022 "Building Gypsum" standard.

[0023] Example 1

[0024] Preparation method:

[0025] The desulfurized gypsum is mixed with water at a solid-liquid ratio of 1:1.3 (g / mL), and then 0.5% of calcium oxide and 0.1% of magnesium acetate relative to the mass of the desulfurized gypsum are added, and stirred for 10 minutes; then, it is placed in an oven at 45°C for drying for 48 hours, and then, it is ground into powder and passed through a 0.2mm standard sieve; it is placed in an oven and calcined at 170°C for 2 hours, and then taken out, and aged indoors for 1 day under the conditions of an ambient temperature of 18-28°C and an ambient humidity of 40-70%, and aged in a sealed state for 3 days to obtain β-hemihydrate gypsum.

[0026] Example 2

[0027] Preparation method:

[0028] Mix the desulfurized gypsum with water at a solid-liquid ratio of 1:1.4 (g / mL), then add 0.03% potassium sodium tartrate, 0.3% aluminum sulfate and 0.3% calcium oxide relative to the mass of the desulfurized gypsum, and stir for 10 minutes; then put it into an oven at 50°C and dry it for 24 hours, then grind it into powder and pass it through a 0.2mm standard sieve; put the gypsum powder into an oven and calcine it at 170°C for 2 hours, then take it out, and age it indoors for 1.5 days under the conditions of an ambient temperature of 18-28°C and an ambient humidity of 40-70%, and age it in a sealed state for 2 days to obtain β-hemihydrate gypsum.

[0029] Example 3

[0030] Preparation method:

[0031] The desulfurized gypsum is mixed with water at a solid-liquid ratio of 1:1.5 (g / mL), and then 0.05% copper sulfate and 0.1% succinic acid relative to the mass of the desulfurized gypsum are added and stirred for 10 minutes; then the mixture is placed in an oven at 50°C and dried for 24 hours, and then ground into powder and passed through a 0.2mm standard sieve; the gypsum powder is placed in an oven and calcined at 170°C for 2 hours, and then taken out and aged indoors for 2 days and sealed for 4 days under the conditions of an ambient temperature of 18-28°C and an ambient humidity of 40-70%, thereby obtaining β-hemihydrate gypsum.

[0032] Comparative Example 1

[0033] Mix desulfurized gypsum with water at a solid-liquid ratio of 1:1.5 (g / mL), and stir for 10 minutes; then put it into an oven at 50°C and dry it for 24 hours, then grind it into powder and pass it through a 0.2mm standard sieve; put the gypsum powder into an oven and calcine it at 170°C for 2 hours, then take it out, and age it indoors for 1 day under the conditions of an ambient temperature of 18-28°C and an ambient humidity of 40-70%, and age it in a sealed state for 3 days to obtain β-hemihydrate gypsum.

[0034] The performance test table of Examples 1 to 3 and Comparative Example 1 is shown in Table 1:

[0035] Table 1 Performance values ​​of the embodiments

[0036]

[0037] It can be seen from the test results in Table 1 that the early strength of Example 3 is the best, and the late strength of Example 1 is the best. The initial setting time of the building gypsum obtained in Examples 1 to 3 of the present invention is ≥3min, the final setting time is ≤30min, the 2h flexural strength is ≥3.0MPa, the 2h compressive strength is ≥6.0MPa, the absolute dry flexural strength is ≥5.0MPa, and the absolute dry compressive strength is ≥12.0MPa. The building gypsum obtained in Examples 1 to 2 belongs to Grade 3.0, and the building gypsum obtained in Example 3 belongs to Grade 4.0, all of which show higher strength and improve the performance of the building gypsum.

[0038] The above shows and describes the main features and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0039] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A gypsum composite crystal-changing agent, characterized in that: The invention comprises component A and component B, wherein component A is at least one of metal oxides or sulfates, and component B is C1-C 10 At least one of monobasic, dibasic and polybasic organic acids or carboxylates.

2. A gypsum composite crystal-changing agent according to claim 1, characterized in that: The component A is at least one of calcium oxide, aluminum sulfate, copper sulfate, magnesium sulfate, and potassium aluminum sulfate, and the component B is at least one of potassium sodium tartrate, magnesium acetate, disodium ethylenediaminetetraacetate, sodium citrate, succinic acid, and acetic acid.

3. A method for preparing β-hemihydrate gypsum, characterized in that: The following steps are involved: The gypsum composite crystal-changing agent according to any one of claims 1 to 2 is added to the desulfurized gypsum slurry, mixed evenly, and then dried. After the treatment, the gypsum is ground into powder, passed through a 0.2 mm standard sieve, and then calcined at normal pressure to obtain the β-hemihydrate gypsum.

4. The method for preparing β-hemihydrate gypsum according to claim 3, characterized in that: The desulfurized gypsum slurry is a mixed slurry of desulfurized gypsum and water, and its solid-liquid ratio is 1:1-1.5 g / mL.

5. The method for preparing β-hemihydrate gypsum according to claim 4, characterized in that: In the composite crystal-changing agent, in component A, metal oxide accounts for 0.2% to 0.6% of the mass of desulfurized gypsum, sulfate accounts for 0.03% to 0.6% of the mass of desulfurized gypsum; component B accounts for 0.03% to 0.2% of the mass of desulfurized gypsum.

6. The method for preparing β-hemihydrate gypsum according to claim 3, characterized in that: The temperature of the drying treatment is 45±5° C. and the time is 1 to 2 days.

7. The method for preparing β-hemihydrate gypsum according to claim 3, characterized in that: The temperature of the atmospheric pressure calcination is 165-190° C., and the time is 1.5-2.5 hours.

8. The method for preparing β-hemihydrate gypsum according to claim 3, characterized in that: The method also includes room temperature aging treatment, which is carried out after normal pressure calcination, and is specifically divided into indoor aging and sealed aging. The ambient temperature of the aging treatment is 18-28°C, the ambient humidity is 40-70%, the indoor aging time is 1-2 days, and the sealed aging time is 2-5 days.

9. β-hemihydrate gypsum obtained by the preparation method according to any one of claims 3 to 8.

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