A method for preparing a high refractory fly ash ceramsite

Abstract

The application provides a preparation method of high-fire-resistance fly ash ceramsite, which comprises the following steps: removing impurities, crushing and drying fly ash raw materials, testing components and performing component regulation, and then adding a binder to perform balling, aging and sintering. The method ensures a high fly ash proportion, promotes the formation of mullite, corundum and other crystalline phases in the interior of the ceramsite by adding skeleton components such as aluminum sources and silicon sources, reduces the addition of raw materials, and still has a part of aluminum-silicon intermediate phase products in the high-temperature reaction process. The aluminum-silicon eutectic material has a certain fire resistance, and can encapsulate low-melting-point impurities to form island-shaped distribution, avoids melting, and makes the ceramsite maintain a good appearance. The fly ash ceramsite developed in the application can be used at high temperature, has low thermal conductivity and high compressive strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of refractory materials, in particular to a preparation method of high refractory fly ash ceramsite. BACKGROUND

[0002] Fly ash is the main waste of thermal power plants, and the average fly ash output of coal in China is 26-30 kg / t. The fly ash output of each 10,000 kilowatt power plant is about 90-100 thousand tons. Its output is large, occupies a lot of land, and becomes dust, pollutes groundwater, and causes very serious environmental problems. In recent years, it is more and more widely used in the field of construction, such as building materials, roadbed materials, roadbed reinforcement materials, mud walls, cement slurry, cement fillers, fly ash ceramsite, etc., which plays a certain role in improving the environment.

[0003] Fly ash ceramsite is a kind of artificial light aggregate made of fly ash as the main raw material, mixed with a small amount of auxiliary raw materials (binder, fluxing agent, combustion improver, etc.) and sintered. It has the advantages of light weight, corrosion resistance, frost resistance, shock resistance and good insulation, and can be widely used in concrete components and building insulation materials, and can also be used in the fields of garden flowers, sewage treatment, etc. Although the preparation technology of ceramsite has gradually matured and the application field is continuously expanding, there are still some problems in industrial production, such as low refractoriness of ceramsite products, which cannot be applied to high temperature refractory field. This is because fly ash is an amorphous material, mainly composed of alumina, silica, iron oxide and calcium oxide, etc., with high impurity content, which is easy to melt into a glass state and bond with each other at high temperature, so untreated fly ash is less used in high temperature environment. The method of simply adding high melting point elements (such as alumina) to improve refractoriness cannot interact with the fly ash raw material itself, and the melting impurities will be out of the phenomenon, which requires a large amount of addition and high cost.

[0004] At present, there are few ceramsite products that can be applied in high temperature environment, and the existing technology has little reference for application in high temperature environment above 1300℃. Therefore, it is necessary to develop a high refractory fly ash ceramsite that can be applied above 1300℃. SUMMARY

[0005] Therefore, the present application aims to provide a preparation method of high refractory fly ash ceramsite to solve the above problems.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows:

[0007] A preparation method of high refractory fly ash ceramsite, the method comprising the following steps:

[0008] 1) removing impurities from fly ash, the composition of the fly ash after removing impurities includes 20%-45% of alumina, 25%-50% of silica, ≤23% of calcium oxide + magnesium oxide, ≤9% of iron oxide, and ≤2.5% of potassium and sodium;

[0009] 2) The fly ash after impurity removal is mixed with an aluminum source and a silicon source in a proportion to regulate the composition, and the mass percentage of each component after the component adjustment is: alumina: silica = 1.0-1.9; 1≤(iron oxide + aluminum oxide + titanium oxide) / silicon oxide≤1.75; 0.01≤(calcium oxide + magnesium oxide) / (aluminum oxide + silicon oxide)≤0.33;

[0010] 3) The fly ash after the component adjustment is added with a binder to form balls, aged, and sintered, and finally air-cooled to room temperature in the furnace to obtain high-refractory fly ash ceramsite.

[0011] Further, the specific steps of impurity removal are:

[0012] 1) The fly ash is screened to remove floating beads above 300 μm;

[0013] 2) The screened fly ash is calcined at high temperature to remove residual carbon;

[0014] 3) The calcined fly ash is ground, and the particle size after the grinding meets 1200 mesh, and the screening rate is ≤5%;

[0015] 4) The fly ash after the treatment in 3) is separated to remove magnetic minerals by a magnetic separator, and treated with 20% concentration hydrochloric acid to remove other impurities except aluminum-silicon phase.

[0016] Further, the screening in step 1) uses a 17-28K oscillation classification conveying device; and the calcination temperature in step 2) is 750-900℃, and the time is 1-5h.

[0017] Further, the specific steps of the balling are: the fly ash after the component adjustment is placed in a granulator, the inclination angle of the granulator is set to 30°-50°, the rotation speed is set to 10-60 rpm, the binder is uniformly dropped at a rate of 0.0001-10 L / s, and the ceramsite radius meets 1.5 mm≤R≤15 mm to discharge and age.

[0018] Further, the aging conditions are: temperature 18-30℃, humidity 35%-65%, wind speed 0.5-4 m / s, and aging≥8h.

[0019] Further, the specific steps of the calcination are: the ceramsite after the aging is heated from room temperature to 200℃ at a rate of 5-30℃ / min, 200℃ is kept for 15-30 min; then heated from 200℃ to 1400-1750℃ at a rate of 3-10℃ / min, the highest temperature is kept for 1-300 min; and then cooled to 900℃-1300℃ at a rate of 3-15℃ / min, and air-cooled to room temperature in the furnace to obtain high-refractory fly ash ceramsite.

[0020] Further, the fly ash accounts for 40-80 Wt.% of the total mass of the fly ash after the regulation.

[0021] Further, the aluminum source is one or more of alumina, aluminum hydroxide, aluminum silicate, bauxite, aluminum ash, kaolin, coal gangue, and bentonite.

[0022] Further, the silicon source is one or more of silicon oxide, quartz sand, and silicate.

[0023] Further, the binder is one or more of water, water glass, aluminum dihydrogen phosphate, silica sol, aluminum sol, and zirconium sol.

[0024] Compared with the prior art, the preparation method of the high-refractory fly ash ceramsite has the following advantages:

[0025] (1) The preparation method of the high-refractory fly ash ceramsite solves the problem that the existing fly ash ceramsite is difficult to use in a high-temperature environment. While ensuring a high fly ash ratio, the method promotes the formation of mullite, corundum, and other crystalline phases in the ceramsite by adding aluminum sources, silicon sources, and other skeleton components. The method reduces the amount of added raw materials, and there are still some aluminum-silicon intermediate phase products during the high-temperature reaction process. These aluminum-silicon eutectics have a certain refractoriness and can encapsulate low-melting-point impurities to form island-like distribution, avoiding melting and ensuring the ceramsite to maintain good morphology.

[0026] (2) The fly ash usage amount is large (40-80 Wt. %), which solves the environmental pollution and safety hazard problems caused by fly ash storage. The fly ash raw material is not finely treated, and has a high impurity content. The refractoriness of the fly ash is improved by adjusting the composition of the raw materials. The gas generated by the iron oxide in the ceramsite during sintering forms pores under the encapsulation of the molten liquid phase, thereby reducing the bulk density and thermal conductivity of the ceramsite.

[0027] (3) The method improves the refractoriness of the material by forming mullite, corundum, and other crystalline phases. However, the aluminum-silicon ratio is lower than that of traditional mullite materials. The aluminum-silicon eutectic is used to encapsulate impurities in the liquid phase, thereby meeting the demand while reducing the cost of raw materials. The method adds aluminum sources and silicon sources, and uses the liquid phase environment formed by the fly ash at high temperatures to react with the alumina and silicon oxide in the fly ash to generate mullite.

[0028] (4) The refractoriness of the ceramsite prepared by the method is improved by more than 30% compared with that of the traditional fly ash ceramsite. The load softening temperature is improved by more than 25%. The bulk density and thermal conductivity of the ceramsite product are also relatively low. DETAILED DESCRIPTION

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] The present application will be described in detail below with reference to the embodiments.

[0031] Example 1

[0032] A method for preparing a high refractory fly ash ceramsite includes the following steps:

[0033] 1) Take fly ash and sieve it through a 17K shock classification conveyor, remove floating beads above 300 μm, and then sieve the remaining fly ash at 800°C for 5 hours, air cool to 25°C, and then grind it using a high-energy jet mill. Take the 1200 mesh undersize material. Then, use a magnetic separator to remove magnetic minerals from the treated fly ash, and then treat it with 20% concentration hydrochloric acid to remove other impurities except for aluminum and silicon phases. Finally, take 1000g of the treated fly ash.

[0034] 2) The composition of the fly ash after removing impurities is 26% aluminum oxide, 45% silicon oxide, 11% calcium oxide, 3% magnesium oxide, 6.05% iron oxide, and 1.25% potassium and sodium.

[0035] 3) Add 750g of alpha-aluminum oxide (2N, i.e. 99% purity) and 250g of quartz sand (2N) to the fly ash after removing impurities, and mix them in a three-dimensional powder mixer for 0.5 hours.

[0036] 4) Put the mixed powder into a granulator, set the disc inclination to 35°, and set the rotation speed to 20 rpm. Uniformly drop 500g of neutral water at a rate of 0.3L / s. When most of the ceramsite is discharged with a size of about R=10mm.

[0037] 5) Age the ceramsite at a temperature of 25°C, a humidity of 45%, and a wind speed of 3m / s for 17 hours.

[0038] 6) After aging, put the ceramsite into a muffle furnace, increase the temperature to 200°C at a rate of 10°C / min, keep the temperature at 200°C for 30 minutes, then increase the temperature to 1700°C at a rate of 5°C / min, keep the temperature at 1700°C for 200 minutes, and then decrease the temperature to 1000°C at a rate of 10°C / min to obtain the high refractory fly ash ceramsite.

[0039] Test the performance as shown in Table 1.

[0040] Example 2

[0041] A method for preparing a high refractory fly ash ceramsite includes the following steps:

[0042] 1) Take fly ash and sieve it through a 17K shock classification conveyor, remove floating beads above 300 μm, and then sieve the remaining fly ash at 800°C for 5 hours, air cool to 25°C, and then grind it using a high-energy jet mill. Take the 1200 mesh undersize material. Then, use a magnetic separator to remove magnetic minerals from the treated fly ash, and then treat it with 20% concentration hydrochloric acid to remove other impurities except for aluminum and silicon phases. Finally, take 1000g of the treated fly ash.

[0043] 2) the composition of the fly ash after impurity removal is 21.2% aluminum oxide, 41.68% silicon oxide, 9.68% calcium oxide, 1.7% magnesium oxide, 6.06% iron oxide, and 0.005% potassium and sodium;

[0044] 3) after impurity removal, 1200g of aluminum ash (aluminum oxide > 88%) and 300g of quartz sand (2N) are added to the fly ash and mixed in a three-dimensional powder mixer for 0.5h;

[0045] 4) the mixed powder is loaded into a granulator, the disc surface is inclined at 35°, the rotation speed is set to 20rpm, and 500g of zirconium sol (0.06%) is uniformly dripped at a rate of 1.2L / s; after most of the ceramsite R = 10mm or so is discharged;

[0046] 5) aging for 17h at a temperature of 25℃, humidity of 45%, and wind speed of 3m / s;

[0047] 6) after aging, the ceramsite is loaded into a muffle furnace, the temperature is raised to 200℃ at a rate of 10℃ / min, kept at 200℃ for 30min, then raised to 1650℃ at a rate of 5℃ / min, kept at 1650℃ for 180min, and then reduced to 1000℃ at a rate of 10℃ / min to obtain high refractory fly ash ceramsite.

[0048] Test performance is shown in Table 1.

[0049] Example 3

[0050] A method for preparing high refractory fly ash ceramsite includes the following steps:

[0051] 1) fly ash is screened through a 17K shock classification conveyor, and floating beads above 300μm are removed; the remaining screened fly ash is discharged after high-temperature calcination at 800℃ for 5h, air-cooled to 25℃, and ground by a high-energy jet mill; 1200 mesh undersize material is taken after grinding; then the treated fly ash is separated by a magnetic separator to remove magnetic minerals, treated with 20% hydrochloric acid to remove other impurities except aluminum and silicon phases, and 1000g is taken;

[0052] 2) the composition of the fly ash after impurity removal is 21.2% aluminum oxide, 41.68% silicon oxide, 9.68% calcium oxide, 1.7% magnesium oxide, 6.06% iron oxide, and 0.005% potassium and sodium;

[0053] 3) after impurity removal, 1100g of bauxite (aluminum oxide > 85%) and 500g of quartz sand (2N) are added to the fly ash and mixed in a three-dimensional powder mixer for 0.5h;

[0054] 4) the mixed powder is loaded into a granulator, the disc surface is inclined at 35°, the rotation speed is set to 20rpm, and 600g of neutral aluminum sol (10%) is uniformly dripped at a rate of 3.5L / s; after most of the ceramsite R = 10mm or so is discharged;

[0055] 5) Ageing at temperature 25°C, humidity 45%, wind speed 3m / s for 17h;

[0056] 6) After ageing, the ceramsite is loaded into a muffle furnace, heated to 200°C at 10°C / min, kept at 200°C for 30min, then heated to 1600°C at 5°C / min, kept at 1600°C for 150min, and then cooled to 1000°C at 10°C / min to obtain high refractory fly ash ceramsite.

[0057] The test performance is shown in Table 1.

[0058] Comparative Example 1 (aluminum-silicon ratio not in the set range: aluminum-silicon ratio is 0.8)

[0059] The difference from Example 1 is that after impurity removal, 300g of α-alumina (2N) and 250g of quartz sand (2N) are added to the fly ash.

[0060] It is found that the ceramsite melts and liquefies at high temperature, cannot maintain the shape of the ceramsite, and melts on the bottom of the crucible and cannot be taken out. It cannot be tested.

[0061] Comparative Example 2 (aluminum-silicon ratio not in the set range: aluminum-silicon ratio is 2.3)

[0062] The difference from Example 1 is that after impurity removal, 1350g of α-alumina (2N) and 250g of quartz sand (2N) are added to the fly ash.

[0063] It is found that the ceramsite melts and liquefies at high temperature, cannot maintain the shape of the ceramsite, and melts on the bottom of the crucible and cannot be taken out. It cannot be tested.

[0064] Comparative Example 3 (no fly ash impurity control)

[0065] The difference from Example 1 is that no fly ash impurity control is performed.

[0066] 1) Take fly ash, grade by 17K oscillation, remove floating beads above 300 microns, and take the remaining fly ash after screening to 800°C high temperature calcination for 5h, then air cool to 25°C, and grind by high-energy jet mill, take 1200 mesh undersize 1000g after grinding;

[0067] 2) The composition of fly ash without impurity removal process such as acid dissolution is 26% of alumina, 45% of silica, 22% of calcium oxide, 2.3% of magnesium oxide, 5.03% of iron oxide, and 1.06% of potassium and sodium;

[0068] 3) After impurity removal, 750g of α-alumina (2N) and 250g of quartz sand (2N) are added to the fly ash and mixed in a three-dimensional powder mixer for 0.5h;

[0069] 4) Put the mixed powder into a granulator, tilt the disc surface at 35°, set the rotation speed at 20 rpm, and drop neutral water 500 g evenly; when most of the ceramsite R=10 mm or so is discharged;

[0070] 5) Temperature 25℃, humidity 45%, air speed 3 m / s, and age for 17 h;

[0071] 6) Put the aged ceramsite into a muffle furnace, increase the temperature to 200℃ at 10℃ / min, keep the temperature at 200℃ for 30 min, then increase the temperature to 1700℃ at 5℃ / min, keep the temperature at 1700℃ for 200 min, and then decrease the temperature to 1000℃ at 10℃ / min.

[0072] The ceramsite melts and liquefies at high temperature, and cannot keep the shape of the ceramsite, melts in the bottom of the crucible and cannot be taken out. It cannot be tested.

[0073] Table 1: Performance data table

[0074]

[0075]

[0076] It can be found from Table 1 that the ceramsite prepared by the embodiment of the present application has a balling rate of more than 95%, high cylinder compressive strength, load softening temperature, and refractoriness, and also reduces the bulk density of the ceramsite.

[0077] Comparative Examples 1 and 2 do not meet the preparation conditions in terms of the silicon-aluminum ratio, and cannot obtain the formed ceramsite; and moreover, without impurity control of the fly ash, the formed ceramsite cannot be obtained.

[0078] The above only describes the preferred embodiments of the present application, and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing high-refractory fly ash ceramsite, characterized in that: The method includes the following steps: 1) Remove impurities from the fly ash. The composition of the fly ash after impurity removal includes 20%~45% aluminum oxide, 25%~50% silicon oxide, ≤23% calcium oxide + magnesium oxide, ≤9% iron oxide, and ≤2.5% potassium and sodium. The specific steps for removing impurities are as follows: 1-1) Screen the fly ash to remove cenospheres larger than 300μm; 1-2) The sieved fly ash is then roasted at high temperature to remove residual carbon; 1-3) Grind the calcined fly ash until the particle size meets 1200 mesh and the sieve residue rate is ≤5%; 1-4) The fly ash treated in 1-3) is separated by a magnetic separator to remove magnetic minerals, and then treated with 20% hydrochloric acid to remove impurities other than the aluminum-silicon phase; 2) After impurity removal, the fly ash is mixed with aluminum and silicon sources in proportion to adjust the composition. The mass ratio of each component after adjustment is: aluminum oxide: silicon oxide = 1.0-1.9; 1≤(iron oxide + aluminum oxide + titanium oxide) / silicon oxide≤1.75; 0.01≤(calcium oxide + magnesium oxide) / (alumina + silicon oxide)≤0.33; 3) The fly ash with adjusted composition is added to a binder for pelletizing, aging, and sintering, and finally air-cooled to room temperature in the furnace to obtain high-refractory fly ash ceramsite. The specific steps for pelletizing are as follows: After adjusting the composition, the fly ash body is placed in a pelletizer, the tilt angle of the pelletizer is set to 30°-50°, the rotation speed is set to 10-60 rpm, the binder is uniformly dripped in at a rate of 0.0001-10 L / s, and the radius of the ceramsite meets the requirement of 1.5 mm ≤ R ≤ 15 mm for discharge aging; The aging conditions are: temperature 18-30℃, humidity 35%-65%, wind speed 0.5-4m / s, aging time ≥8h; The specific steps of calcination are as follows: after aging, the ceramsite is heated from room temperature to 200℃ at a rate of 5-30℃ / min, and held at 200℃ for 15-30min; then the temperature is increased from 200℃ to 1400-1750℃ at a rate of 3-10℃ / min, and held at the highest temperature for 1-300min; then the temperature is decreased to 900℃-1300℃ at a rate of 3-15℃ / min, and then air-cooled with the furnace to room temperature to obtain high refractoriness fly ash ceramsite.

2. The method for preparing high-refractory fly ash ceramsite according to claim 1, characterized in that: Step 1-1) Screening is performed using a 17-28K vibrating grading conveyor; Step 1-2) The roasting temperature is 750-900℃ and the time is 1-5h.

3. The method for preparing high-refractory fly ash ceramsite according to claim 1, characterized in that: Fly ash accounts for 40-80 wt.% of the total mass of the powder after regulation.

4. The method for preparing high-refractory fly ash ceramsite according to claim 1, characterized in that: The aluminum source is one or more of the following: alumina, aluminum hydroxide, aluminum silicate, bauxite, aluminum ash, kaolin, coal gangue, and bentonite.

5. The method for preparing high-refractory fly ash ceramsite according to claim 1, characterized in that: The silicon source is one or more of silicon oxide, quartz sand, and silicates.

6. The method for preparing high-refractory fly ash ceramsite according to claim 1, characterized in that: The binder is one or more of the following: water, water glass, aluminum dihydrogen phosphate, silica sol, aluminum sol, and zirconium sol.

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