CN113480322A - Ceramsite prepared from high-alumina fly ash and preparation method thereof - Google Patents

Abstract

The invention discloses a ceramsite prepared by using high-alumina fly ash and a preparation method thereof, and solves the technical problem that no method for preparing high-strength ceramsite by using fly ash, calcium silicate slag and red mud is available in the prior art. The method comprises 70-80% of high-alumina fly ash, 5-15% of red mud and 5-15% of calcium silicon slag by mass percentage, wherein the granularity of the selected red mud is less than 150 mu m, the granularity of the selected calcium silicon slag is less than 150 mu m, and the oversize residue of the fly ash with the granularity of 45 mu m is less than 45%. The ceramsite product prepared by the method meets the index requirement of 900-grade ceramsite in GBT17431.1-2010 light aggregate and experimental method thereof, the strength is greatly improved, the water absorption is lower, the manufacturing process of the ceramsite is simple, the product strength is high, a large amount of solid wastes are used, the production cost is low, no secondary solid wastes are generated, and the method has important significance for relieving the stacking pressure of the fly ash in a power plant, improving the comprehensive utilization of the solid wastes and constructing an environment-friendly society.

Description

Ceramsite prepared from high-alumina fly ash and preparation method thereof

Technical Field

The invention relates to ceramsite and a preparation method thereof, in particular to ceramsite prepared by using high-alumina fly ash and a preparation method thereof.

Background

The ceramsite is artificial lightweight aggregate, has the characteristics of good heat insulation, low bulk density, good high temperature resistance and corrosion resistance, freezing resistance and the like, and is widely applied to the fields of building materials, water treatment, environment and the like. Clay and shale are mainly used for preparing the traditional ceramsite, but the two minerals belong to natural resources, and the environment is greatly damaged by mass mining. And the ceramsite prepared from the clay and the shale generally has lighter weight and lower strength.

The fly ash is a powdery substance formed by burning clay minerals in power plant coal dust in a boiler along with the coal dust, and decomposing, sintering, melting and cooling the clay minerals. About 5 hundred million tons of fly ash are generated in China every year, and the large stacking of the fly ash causes serious environmental problems.

The fly ash in inner Mongolia areas has the characteristics of high aluminum, high silicon and low iron, particularly in the middle and western areas of inner Mongolia, due to special geological background, the content of alumina in the fly ash in the areas is more than 35%, and the content of alumina in the fly ash in the areas can reach 50%, so that the fly ash belongs to high-alumina fly ash. The fly ash has low density, high alumina content, rich reserves and higher activity, and can be used for preparing high-strength ceramsite.

Generally, high-alumina fly ash with the alumina content of about 50 percent is often used for extracting alumina, the residual residue is called silico-calcium slag, the silico-calcium slag contains calcium oxide, sodium oxide and the like, and when the silico-calcium slag and the high-alumina fly ash are doped for firing ceramsite, the sintering temperature of the ceramsite is favorably reduced. In addition, red mud residues discharged by alumina extracted from bauxite are accumulated around the area, the red mud has high iron oxide content and certain cohesiveness, and can be used for granulating the high-alumina fly ash. How to better bond fly ash, calcium silicate slag and red mud into balls is an urgent problem to be solved when fly ash is used as a main raw material to produce high-strength ceramsite.

Disclosure of Invention

The invention aims to provide ceramsite prepared by using high-alumina fly ash and a preparation method thereof, and aims to solve the technical problem that no method for preparing high-strength ceramsite by using fly ash, calcium silicate slag and red mud is available in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme:

the invention provides a high-strength ceramsite prepared by using high-alumina fly ash, which is characterized in that: comprises 70-80% of high-alumina fly ash, 5-15% of red mud and 5-15% of calcium silicate slag according to mass percentage.

Further, the high-alumina fly ash comprises the following chemical components in percentage by mass: al (Al)₂O₃≥38：、SiO₂≥50％、Fe₂O₃More than or equal to 2 percent and CaO more than or equal to 2 percent.

Further, the red mud comprises the following chemical components in percentage by mass: 20-25% of Al₂O₃、15-25％SiO₂、18-25％Fe₂O₃、1-4％Na₂O and 4-6% CaO; the red mud is residue left after alumina is extracted by a bauxite Bayer process, and the ignition loss is 15-20%.

Further, the calcium silicate slag comprises the following chemical components in percentage by mass: 2.5-6% Al₂O₃、20-30％SiO₂、1-5％Fe₂O₃、2-10％Na₂O and 45-60% CaO; the calcium silicate slag is the residue left after alumina is extracted by the fly ash soda lime sintering method, and the loss on ignition is 5-15%.

Furthermore, the granularity of the red mud is less than 150 μm, the granularity of the silico-calcium slag is less than 150 μm, and the granularity of the fly ash requires that the 45 μm screen residue is less than 45%.

The invention provides a preparation method for firing high-strength ceramsite according to claims 1-5 by using high-alumina fly ash, which is characterized by comprising the following steps:

s1, preprocessing, namely processing red mud and calcium silicate slag to reduce the water content to be 5% or below; grinding and sieving the red mud and the calcium silicate slag respectively;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at high temperature, heating the raw material balls from room temperature to 500 ℃, preserving heat for 10-30min, then gradually heating the raw material balls to 1150-plus-material 1280 ℃, preserving heat for 5-30min, wherein the total sintering time is 1-4h, and slowly cooling the fired ceramsite to room temperature to obtain a finished product.

Further, the time for raising the temperature from room temperature to 500 ℃ and then raising the temperature to 1150-1280 ℃ in the step S4 are both 30-60 min.

Further, the method comprises the following steps:

s1, preprocessing, namely processing red mud and calcium silicate slag to reduce the water content to be 5% or below; grinding and sieving the red mud and the calcium silicate slag respectively;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at a high temperature, heating the raw material balls from room temperature to 500 ℃, heating the raw material balls for 60min, keeping the temperature for 30min, heating the raw material balls from 500 ℃ to 800 ℃, finally heating the raw material balls from 800 ℃ to 1230 ℃, heating the raw material balls for 60min, keeping the temperature for 30min, and slowly cooling the fired ceramsite to the room temperature to obtain a finished product.

Further, the method comprises the following steps:

s1, preprocessing, namely processing red mud and calcium silicate slag to reduce the water content to be 5% or below; grinding and sieving the red mud and the calcium silicate slag respectively;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at a high temperature, heating the raw material balls from room temperature to 500 ℃, preserving heat for 20min, then heating the raw material balls from 500 ℃ to 800 ℃, finally heating the raw material balls from 800 ℃ to 1200 ℃, heating the raw material balls for 60min, preserving heat for 20min, and slowly cooling the fired ceramsite to room temperature to obtain a finished product.

Based on the technical scheme, the embodiment of the invention can at least produce the following technical effects:

(1) the invention provides a ceramsite prepared by using high-alumina fly ash and a preparation method thereof, wherein the high-alumina fly ash is selected as a main raw material, the advantage of high alumina content is fully utilized to prepare high-strength ceramsite with good quality, the prepared high-strength ceramsite is tested according to related evaluation indexes of light aggregate in GBT17431.1-2010 (light aggregate and experimental method thereof), the strength of the prepared high-strength ceramsite reaches 12-20MP, and the water absorption rate is less than 6%.

(2) According to the ceramsite prepared by using the high-alumina fly ash and the preparation method thereof, provided by the invention, the calcium silicate slag and the red mud are used as auxiliary materials, the fluxing action of iron oxide and sodium oxide in the calcium silicate slag and the red mud auxiliary materials is fully utilized, and the sintering temperature of the high-strength ceramsite is reduced. Meanwhile, the strength of the raw material balls can be effectively improved in the process of granulating and manufacturing the ceramsite raw material balls by utilizing the good plasticity of the calcium silicon slag and the red mud auxiliary materials.

(3) According to the ceramsite prepared by using the high-alumina fly ash and the preparation method thereof, the using amount of the high-alumina fly ash reaches 70% -80%, so that the treatment cost of the fly ash is reduced, the problem of stockpiling of the fly ash is solved, and a new idea is provided for treating and utilizing the fly ash. Meanwhile, the silico-calcium slag and the red mud in the ingredients belong to solid wastes. The method improves the environmental benefit in the preparation process of the high-strength ceramsite besides the high-strength ceramsite serving as a target product. While producing high-strength ceramsite, the solid waste is consumed, and the environmental benefit is remarkable.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

Example 1

1.1 starting materials

The high-strength ceramsite prepared in the embodiment 1 comprises the following raw materials in percentage by mass: 80% of fly ash, 12% of red mud and 8% of calcium silicate slag.

The red mud is residue left after alumina is extracted by a bauxite Bayer process, and the ignition loss is 15-20%; the calcium silicate slag is the residue left after alumina is extracted by a fly ash soda lime sintering method, and the loss on ignition is 5-15%; the granularity of the red mud is less than 150 mu m, the granularity of the selected calcium silicate slag is less than 150 mu m, and the granularity of the fly ash requires that the 45 mu m sieve residue is less than 45 percent.

The mass percentages of the chemical components of the selected high-alumina fly ash, red mud and calcium silicate slag are shown in table 1.

Table 1 mass percent of each chemical component of raw materials

1.2 preparation method

S1, preprocessing, namely drying red mud and calcium silicate slag to reduce the water content to 5% or below; grinding the red mud and the calcium silicate slag by a ball mill respectively, and sieving the ground red mud and the ground calcium silicate slag by a 100-mesh sieve;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at a high temperature, raising the temperature from room temperature to 500 ℃, and keeping the temperature for 20 min; then heating from 500 ℃ to 800 ℃ for 20 min; and finally, raising the temperature from 800 ℃ to 1220 ℃, keeping the temperature for 60min, preserving the temperature for 20min, and naturally cooling to room temperature to obtain the TL1 sample of the example 1.

1.3 ceramsite hardness detection

According to the relevant evaluation indexes of the lightweight aggregate in GBT17431.1-2010, namely the lightweight aggregate and the experimental method thereof, the prepared sample TL1 of the example is respectively tested for volume weight, water absorption of 1h, cylinder pressure strength, loss on ignition and apparent density, and the specific indexes are shown in Table 2.

TABLE 2 Haydite Performance index

In conclusion, the invention uses a large amount of high-alumina fly ash, the prepared ceramsite has low water absorption, greatly improved strength and 12-20Mp cylinder pressure strength, and in addition, the invention also fully utilizes the pore-forming of the red mud and the calcium silicate slag, reduces the sintering temperature and the bonding property, so that the process is simple and easy to implement. The invention fully utilizes the advantages of regional resources, uses solid wastes in the formula, does not destroy the natural environment, does not generate secondary solid waste pollution in the solid waste disposal process, and has great environmental significance.

The index of the high-strength ceramsite is higher than the index requirement of corresponding size-fraction ceramsite in GBT17431.1-2010 (lightweight aggregate and experimental method thereof), the bulk density is 800-.

Example 2

2.1 starting materials

The high-strength ceramsite prepared in the embodiment 2 comprises the following raw materials in percentage by mass: 79% of fly ash, 11% of red mud and 10% of calcium silicate slag.

The red mud is residue left after alumina is extracted by a bauxite Bayer process, and the ignition loss is 15-20%; the calcium silicate slag is the residue left after alumina is extracted by a fly ash soda lime sintering method, and the loss on ignition is 5-15%; the granularity of the red mud is less than 150 mu m, the granularity of the selected calcium silicate slag is less than 150 mu m, and the granularity of the fly ash requires that the 45 mu m sieve residue is less than 45 percent.

The mass percentages of the chemical components of the selected high-alumina fly ash, red mud and calcium silicate slag raw materials are shown in table 3.

TABLE 3 mass percents of the chemical components of the raw materials

2.2 preparation method

S1, preprocessing, namely drying red mud and calcium silicate slag to reduce the water content to 5% or below; grinding the red mud and the calcium silicate slag by a ball mill respectively, and sieving the ground red mud and the ground calcium silicate slag by a 100-mesh sieve;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at a high temperature, raising the temperature from room temperature to 500 ℃, and keeping the temperature for 20 min; then heating from 500 ℃ to 800 ℃ for 15 min; and finally, raising the temperature from 800 ℃ to 1240 ℃, raising the temperature for 50min, preserving the temperature for 18min, and naturally cooling to room temperature to obtain the TL2 sample of the example 2.

2.3 ceramsite hardness detection

According to the relevant evaluation indexes of the lightweight aggregate in GBT17431.1-2010, namely the lightweight aggregate and the experimental method thereof, the prepared sample TL2 of the example is respectively tested for volume weight, water absorption of 1h, cylinder pressure strength, loss on ignition and apparent density, and the specific indexes are shown in Table 4.

TABLE 4 Haydite Performance index

Example 3

2.1 starting materials

The high-strength ceramsite prepared in the embodiment 2 comprises the following raw materials in percentage by mass: 75% of fly ash, 14% of red mud and 11% of calcium silicate slag.

The red mud is residue left after alumina is extracted by a bauxite Bayer process, and the ignition loss is 15-20%; the calcium silicate slag is the residue left after alumina is extracted by a fly ash soda lime sintering method, and the loss on ignition is 5-15%; the granularity of the red mud is less than 150 mu m, the granularity of the selected calcium silicate slag is less than 150 mu m, and the granularity of the fly ash requires that the 45 mu m sieve residue is less than 45 percent.

The mass percentages of the chemical components of the selected high-alumina fly ash, red mud and calcium silicate slag raw materials are shown in table 5.

TABLE 5 mass percents of the chemical components of the raw materials

3.2 preparation method

S1, preprocessing, namely drying red mud and calcium silicate slag to reduce the water content to 5% or below; grinding the red mud and the calcium silicate slag by a ball mill respectively, and sieving the ground red mud and the ground calcium silicate slag by a 100-mesh sieve;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at a high temperature, raising the temperature from room temperature to 500 ℃, and keeping the temperature for 20 min; then heating from 500 ℃ to 800 ℃ for 15 min; finally, the temperature is raised from 800 ℃ to 1240 ℃ for 50min, the temperature is kept for 18min, and the TL3 sample of the example 3 is obtained after natural cooling to the room temperature.

3.3 ceramsite hardness detection

The prepared sample TL3 of the example was tested for volume weight, water absorption of 1h, cylinder pressure strength, loss on ignition and apparent density according to the relevant evaluation indexes of lightweight aggregates in GBT17431.1-2010, lightweight aggregates and their test methods.

In conclusion, the invention uses a large amount of high-alumina fly ash, the prepared ceramsite has low water absorption, greatly improved strength and 12-20Mp cylinder pressure strength, and in addition, the invention also fully utilizes the pore-forming of the red mud and the calcium silicate slag, reduces the sintering temperature and the bonding property, so that the process is simple and easy to implement. The invention fully utilizes the advantages of regional resources, uses solid wastes in the formula, does not destroy the natural environment, does not generate secondary solid waste pollution in the solid waste disposal process, and has great environmental significance.

The index of the high-strength ceramsite is higher than the index requirement of corresponding size-fraction ceramsite in GBT17431.1-2010 (lightweight aggregate and experimental method thereof), the bulk density is 800-.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (9)

1. A high-strength ceramsite prepared from high-alumina fly ash is characterized in that: comprises 70-80% of high-alumina fly ash, 5-15% of red mud and 5-15% of calcium silicate slag according to mass percentage.

2. The high-strength ceramsite prepared from high-alumina fly ash according to claim 1 is characterized by comprising the following chemical components in percentage by mass: al (Al)₂O₃≥38：、SiO₂≥50%、Fe₂O₃More than or equal to 2 percent and CaO more than or equal to 2 percent.

3. The high-strength ceramsite prepared from high-alumina fly ash according to claim 1, wherein the red mud comprises the following chemical components in percentage by mass: 20-25% of Al₂O₃、15-25%SiO₂、18-25%Fe₂O₃、1-4%Na₂O and 4-6% CaO; the red mud is residue left after alumina is extracted by a bauxite Bayer process, and the ignition loss is 15-20%.

4. The high-strength ceramsite prepared from high-alumina fly ash according to claim 1 is characterized in that the calcium silicate slag comprises the following chemical components in percentage by mass: 2.5-6% Al₂O₃、20-30%SiO₂、1-5%Fe₂O₃、2-10%Na₂O and 45-60% CaO; the calcium silicate slag is the residue left after alumina is extracted by the fly ash soda lime sintering method, and the loss on ignition is 5-15%.

5. The high-strength ceramsite prepared from high-alumina fly ash according to claim 1, is characterized in that: the selected red mud granularity is less than 150 mu m, the selected calcium silicon slag granularity is less than 150 mu m, and the fly ash granularity requires that the 45 mu m screen allowance is less than 45%.

6. The preparation method for firing the high-strength ceramsite of claims 1-5 by using the high-alumina fly ash is characterized by comprising the following steps of:

s1, preprocessing, namely processing red mud and calcium silicate slag to reduce the water content to be 5% or below; grinding and sieving the red mud and the calcium silicate slag respectively;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at high temperature, heating the raw material balls from room temperature to 500 ℃, preserving heat for 10-30min, then gradually heating the raw material balls to 1150-plus-material 1280 ℃, preserving heat for 5-30min, wherein the total sintering time is 1-4h, and slowly cooling the fired ceramsite to room temperature to obtain a finished product.

7. The preparation method for firing the high-strength ceramsite by using the high-alumina fly ash as claimed in claim 6, is characterized in that: the time for raising the temperature from room temperature to 500 ℃ and raising the temperature to 1150-1280 ℃ in the step S4 are both 30-60 min.

8. The preparation method for firing the high-strength ceramsite by using the high-alumina fly ash as claimed in claim 6 is characterized by comprising the following steps:

s1, preprocessing, namely processing red mud and calcium silicate slag to reduce the water content to be 5% or below; grinding and sieving the red mud and the calcium silicate slag respectively;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at a high temperature, heating the raw material balls from room temperature to 500 ℃, heating the raw material balls for 60min, keeping the temperature for 30min, heating the raw material balls from 500 ℃ to 800 ℃, finally heating the raw material balls from 800 ℃ to 1230 ℃, heating the raw material balls for 60min, keeping the temperature for 30min, and slowly cooling the fired ceramsite to the room temperature to obtain a finished product.

9. The preparation method for firing the high-strength ceramsite by using the high-alumina fly ash as claimed in claim 6 is characterized by comprising the following steps:

s1, preprocessing, namely processing red mud and calcium silicate slag to reduce the water content to be 5% or below; grinding and sieving the red mud and the calcium silicate slag respectively;

s2, mixing, namely mixing the red mud and the calcium silicate slag which are ground and sieved in the step S1 with the fly ash according to a ratio, and putting the mixed raw materials into a mixer to be uniformly mixed;

s3, preparing balls, namely adding the mixed raw materials into a disc granulator for water spraying granulation to prepare raw material balls with the diameter of 5-20mm, and controlling the water content of the raw material balls to be 10-18%;

s4, firing, namely firing the raw material balls at a high temperature, heating the raw material balls from room temperature to 500 ℃, preserving heat for 20min, then heating the raw material balls from 500 ℃ to 800 ℃, finally heating the raw material balls from 800 ℃ to 1200 ℃, heating the raw material balls for 60min, preserving heat for 20min, and slowly cooling the fired ceramsite to room temperature to obtain a finished product.