Siliceous binding agent for Al2O3-SiO2 series cement-free castable and preparation method of siliceous binding agent

Abstract

The invention belongs to the technical field of unshaped refractory materials, and discloses a siliceous binding agent for an Al2O3-SiO2 series cement-free castable and a preparation method of the siliceous binding agent. The preparation method of the siliceous binding agent comprises the following steps: 1) adding water into mixed powder of silica powder, an aluminum sulfate-containing raw material and sericite powder, and carrying out ball milling to obtain ball-milled slurry; 2) placing the ball-milled slurry in a reaction kettle, pressurizing and heating for reaction to obtain mixed slurry; 3) sequentially adding boric acid, sodium tripolyphosphate and acrylamide into the mixed slurry, and stirring to obtain prefabricated slurry; and 4) drying the prefabricated slurry, crushing, and screening to obtain the siliceous binding agent for the Al2O3-SiO2 series cement-free castable. The preparation process is simple, production energy consumption and cost are low, pollution to the environment is avoided, and the Al2O3-SiO2 cement-free castable using the binding agent is good in fluidity, high in strength and excellent in burst resistance, thermal shock resistance and erosion resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of unshaped refractory materials, and particularly relates to a silica binder for Al 2 O 3 -SiO 2 series cement-free castables and a preparation method thereof. Background Art

[0002] Refractory castables are unshaped materials used at high temperatures and formed by casting. Their raw materials generally consist of aggregates, fine powders, and binders. The binder is an important component of refractory castables and has a significant impact on the construction performance (fluidity), drying performance (anti-explosion performance), and service performance (strength, corrosion resistance, and thermal shock resistance) of refractory castables. Calcium aluminate cement is currently the most widely used and largest-consumed binder in the field of refractory castables. Castables using it as a binder have advantages such as good fluidity and green strength. However, at high temperatures, CaO in the cement will react with other components in the castable to form low-melting phases such as anorthite, gehlenite, and tricalcium aluminate, reducing the high-temperature service performance (refractoriness, thermal shock resistance, corrosion resistance, and high-temperature strength) of the refractory castable. Moreover, if the operation is improper or the temperature control is not precise enough during the curing and dehydration processes of cement-bonded castables, spalling or even explosion is very likely to occur during the initial heating process. In addition, the Ca element introduced by the cement may also have a negative impact on the application scenario. For example, entering the refined molten steel does not meet the current requirements of the steel industry for improving cleanliness. Therefore, cement-free castables have become a research hotspot in recent years.

[0003] CN110668828A discloses a magnesia binder for cement-free castables and a preparation method thereof. The magnesia binder is obtained by high-temperature baking, grinding, and screening of magnesia raw materials containing crystal water. Using this magnesia binder can realize the production of cement-free castables. However, its preparation process requires high-temperature baking, resulting in high production costs. At the same time, since it is a magnesia binder, Al 2 O 3 、SiO 2 and MgO will form cordierite below 1400°C. Cordierite has poor high-temperature performance, affecting the service performance of the castable and cannot be used in Al 2 O 3 -SiO 2It is used in castables. CN113354401A discloses an ammonium ion-stabilized silica sol-bonded trough castable. Using ammonium ion-stabilized silica sol as a binder, compared with the existing sodium hydroxide-stabilized silica sol, it overcomes the disadvantage of sodium hydroxide as a stabilizer reducing the high-temperature performance of the castable. However, the liquid binder is not easy to transport and is prone to losing stability and precipitating silica under freezing conditions, reducing its binding performance. CN113943167A discloses an RH dipping tube castable and its preparation method, using hydrated alumina and phosphoric acid as binders to achieve the preparation of cement-free castables. However, the phosphoric acid-bonded castable will decompose and volatilize harmful gases (P 2 O 5 ) during use, which not only corrodes the equipment but also seriously pollutes the environment. At the same time, the castable with hydrated alumina as a binder has problems such as fast hydration, too short workable time, and low demolding strength. SUMMARY OF THE INVENTION

[0004] The technical problem to be solved by the present invention is to provide, in view of the deficiencies of the prior art, a silica-based binder for Al 2 O 3 -SiO 2 series cement-free castables and its preparation method, which has a simple preparation process, low production energy consumption and cost, and does not pollute the environment. The Al 2 O 3 -SiO 2 series cement-free castables using this binder have good fluidity and high strength (including after demolding, drying, medium-temperature firing, and high-temperature firing), and excellent anti-burst, anti-thermal shock, and anti-corrosion properties.

[0005] To solve the technical problems proposed by the present invention, the present invention provides a preparation method of a silica-based binder for Al 2 O 3 -SiO 2 series cement-free castables, including the following steps:

[0006] 1) Add water to the mixed powder of silica powder, aluminum sulfate-containing raw material, and sericite powder and perform ball milling to obtain a ball-milled slurry;

[0007] 2) Place the ball-milled slurry in a reaction kettle, pressurize and heat it for reaction to obtain a mixed slurry;

[0008] 3) Add boric acid, sodium tripolyphosphate, and acrylamide to the mixed slurry in sequence and stir to obtain a prefabricated slurry;

[0009] 4) Dry, crush, and screen the prefabricated slurry to obtain a silica-based binder for Al 2 O 3 -SiO 2 series cement-free castables.

[0010] In the above scheme, the SiO 2 Content ≥95.1wt%, particle size ≤0.4μm.

[0011] In the above scheme, the Al of the aluminum sulfate-containing raw material 2 (SO 4 ) 3 Content ≥50wt%, particle size ≤0.088mm.

[0012] In the above scheme, the aluminum sulfate-containing raw material is one or more of aluminum sulfate fine powder and aluminum sulfate hydrate fine powder.

[0013] Preferably, the aluminum sulfate-containing raw material is a mixture of aluminum sulfate fine powder and aluminum sulfate hydrate fine powder, wherein the mass proportion of aluminum sulfate fine powder is 30-40%, and the mass proportion of aluminum sulfate hydrate fine powder is 60-70%.

[0014] In the above scheme, the Al content of the sericite powder is 2 O 3 Content ≥ 10.0wt%, SiO 2 Content ≥80.0wt%, K 2 O+Na 2 O content ≤2.0wt%, particle size ≤100μm.

[0015] In the above scheme, the H of the boric acid 3 BO 3 Content ≥99.5wt%, particle size ≤0.1mm.

[0016] In the above scheme, the Na of the sodium tripolyphosphate is 5 P 3 O 10 Content ≥95.0wt%, particle size ≤0.1mm.

[0017] In the above scheme, the purity of the acrylamide is ≥99% and the particle size is ≤100 μm.

[0018] In the above scheme, the mass percentage content of each raw material in the mixed powder is: 87-92% silicon powder, 5-10% aluminum sulfate-containing raw material, and 2-6% sericite powder.

[0019] In the above scheme, the amount of water added is 90-150% of the mass of the mixed powder.

[0020] In the above scheme, the ball milling speed is 200-300 r / min, and the ball milling time is 60-180 min.

[0021] In the above solution, the reaction pressure in step 2) is 1 - 2 MPa, the reaction temperature is 150 - 200 °C, and the reaction time is 24 - 36 h.

[0022] In the above solution, the mass ratio of the mixed slurry, boric acid, sodium tripolyphosphate, and acrylamide is 100:(1 - 2):(1 - 4):(2 - 5).

[0023] In the above solution, the drying temperature for drying is 110 - 120 °C, and the drying time is 24 - 36 h.

[0024] The present invention also provides a silica binder for Al 2 O 3 -SiO 2 series non-cement castables, which is prepared by the above method.

[0025] In the above solution, the particle size of the silica binder is ≤ 0.1 mm.

[0026] In the above solution, when the silica binder is used, its mass proportion in the dry materials (excluding externally added water reducing agent and water) of the Al 2 O 3 -SiO 2 series non-cement castables is 5 - 10%.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1) During the preparation process of the silica binder of the present invention, silica fume, aluminum sulfate-containing raw material, and sericite powder are placed in a reaction kettle for pressurized heating. Under this reaction condition, the silica fume reacts with the aluminum sulfate-containing raw material, so that the negative charges on the surface of the silica fume and Al 3+ form a bridge connection (gel bonding). This structure can bond with the alumina in the Al 2 O 3 -SiO 2 series castables at room temperature, enabling the castable to have good demolding and drying strength, and the mullitization reaction can occur below 1200 °C, making the castable have high medium-temperature strength; controlling the conditions of heating and pressurization is the key. If the heating temperature and pressure are too low, the reaction cannot proceed. If the heating temperature and pressure are too high, the formed bridge connection and chemical bonds will break, and no binding effect can be achieved; sericite can complete cleavage under this reaction condition to generate a thinner layered structure, which is beneficial to improving the fluidity of the castable.

[0029] 2) During the preparation process of the silica binder of the present invention, boric acid, sodium tripolyphosphate, and acrylamide are introduced. On the one hand, boric acid and sodium tripolyphosphate can improve the pH value of the solution, enabling acrylamide to play a more sufficient dispersing role. Acrylamide can reduce the agglomeration of silica fume, and it can also act as a bridging agent, exerting a good adsorption and traction effect on the aggregates and fine powders in the castable, improving the connection tightness of each component in the castable, and achieving an improvement in the thermal shock resistance and erosion resistance of the castable, making the anti-burst performance better. On the other hand, boric acid and sodium tripolyphosphate can improve the negative charge effect carried on the surface of silica fume, reduce its agglomeration, and thus improve the fluidity of the castable. In addition, boric acid can generate aluminum borate whiskers at about 1000 °C, playing a role in strengthening and toughening, improving the strength and thermal shock resistance of the castable. Compared with the castable directly adding aluminum borate whiskers, it not only reduces the raw material cost but also enhances the internal bonding strength of the castable.

[0030] 3) Among the main raw materials of the silica binder of the present invention, aluminum sulfate raw material, acrylamide, boric acid, and sodium tripolyphosphate can carry crystal water and interact with each other to stabilize the crystal water, enabling the castable to slowly dehydrate during the drying, baking, or first use process, and being less likely to undergo peeling, cracking, and bursting phenomena, significantly improving the anti-burst performance of the castable.

[0031] 4) The silica binder of the present invention has a wide range of applications and can be used in aluminous, corundum, mullite, bauxite-based, etc. Al 2 O 3 -SiO 2 series castables. The Al 2 O 3 -SiO 2 series castables using this binder have good fluidity, can significantly reduce the water addition amount of the castable, have no Ca element introduced, can achieve an improvement in the cleanliness of the Al 2 O 3 -SiO 2 series castables, do not generate low melting point phases at high temperatures, have little pollution to molten steel while improving various properties such as the high-temperature performance of the castable, and meet the usage requirements of the cement-free castable for clean steel smelting, having significant advantages in the applications in this field. Detailed Embodiments

[0032] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments only.

[0033] In the following embodiments, the SiO 2 content of the silica fume used is 96.3 wt%, and the particle size is 0.1 - 0.2 μm; the Al 2 (SO 4 ) 3The content is 65.8 wt%, the particle size is ≤ 0.067 mm, and it is composed of 30% by mass of fine aluminum sulfate powder and 70% by mass of fine aluminum sulfate hydrate powder; the Al of sericite powder 2 O 3 content is 13.1 wt%, the SiO 2 content is 85.4 wt%, the K 2 O + Na 2 O content is 1.2 wt%, the particle size is ≤ 84 μm; the H of boric acid 3 BO 3 content is 99.8 wt%, the particle size is ≤ 0.082 mm; the Na of sodium tripolyphosphate 5 P 3 O 10 content is 96.5 wt%, the particle size is ≤ 0.076 mm; acrylamide is of analytical purity, the purity is ≥ 99%, and the particle size is ≤ 74 μm.

[0034] Example 1

[0035] An Al 2 O 3 -SiO 2 system silica binder for non-cement castables, and its preparation method is as follows:

[0036] 1) To a mixed powder composed of 87% by mass of silica fume, 10% of aluminum sulfate-containing raw material, and 3% of sericite powder, add 110% of the mass of the mixed powder of water, and carry out ball milling. The ball milling speed is 200 rpm, and the ball milling time is 80 min to obtain a ball mill slurry;

[0037] 2) Place the ball mill slurry in a reaction kettle, pressurize to 1.85 MPa, heat to 180 °C, and keep reacting for 24 h to obtain a mixed slurry;

[0038] 3) To the mixed slurry, add boric acid, sodium tripolyphosphate, and acrylamide in sequence. The mass ratio of the mixed slurry, boric acid, sodium tripolyphosphate, and acrylamide is 100:1:3:4. After adding each one and stirring evenly, then add the next one. After all are added and stirred evenly, a prefabricated slurry is obtained;

[0039] 4) Dry the prefabricated slurry, the drying temperature is 110 °C, the drying time is 24 h, then crush and screen to obtain an Al with a particle size ≤ 0.08 mm 2 O 3 -SiO 2 system silica binder for non-cement castables.

[0040] Example 2

[0041] An Al 2 O 3 -SiO2 It is a silica binder for non-cement castables, and its preparation method is as follows:

[0042] 1) Add water with a mass percentage of 100% of the mixed powder to the mixed powder composed of 89% of silica fume, 8% of raw materials containing aluminum sulfate, and 3% of sericite powder by mass percentage, and carry out ball milling. The ball milling speed is 260 rpm, and the ball milling time is 150 min to obtain a ball-milled slurry;

[0043] 2) Place the ball-milled slurry in a reaction kettle, pressurize it to 1.94 MPa, heat it to 160 °C, and keep it for 36 h for reaction to obtain a mixed slurry;

[0044] 3) Add boric acid, sodium tripolyphosphate, and acrylamide to the mixed slurry in sequence. The mass ratio of the mixed slurry, boric acid, sodium tripolyphosphate, and acrylamide is 100:2:3:2. After adding each one and stirring evenly, then add the next one. After all are added and stirred evenly, a prefabricated slurry is obtained;

[0045] 4) Dry the prefabricated slurry. The drying temperature is 120 °C, and the drying time is 36 h. Then crush and screen it to obtain Al with a particle size ≤ 0.07 mm 2 O 3 -SiO 2 It is a silica binder for non-cement castables.

[0046] Example 3

[0047] An Al 2 O 3 -SiO 2 It is a silica binder for non-cement castables, and its preparation method is as follows:

[0048] 1) Add water with a mass percentage of 150% of the mixed powder to the mixed powder composed of 87% of silica fume, 7% of raw materials containing aluminum sulfate, and 6% of sericite powder by mass percentage, and carry out ball milling. The ball milling speed is 300 rpm, and the ball milling time is 180 min to obtain a ball-milled slurry;

[0049] 2) Place the ball-milled slurry in a reaction kettle, pressurize it to 1.76 MPa, heat it to 190 °C, and keep it for 30 h for reaction to obtain a mixed slurry;

[0050] 3) Add boric acid, sodium tripolyphosphate, and acrylamide to the mixed slurry in sequence. The mass ratio of the mixed slurry, boric acid, sodium tripolyphosphate, and acrylamide is 100:2:4:3. After adding each one and stirring evenly, then add the next one. After all are added and stirred evenly, a prefabricated slurry is obtained;

[0051] 4) Dry the prefabricated slurry. The drying temperature is 120 °C, and the drying time is 36 h. Then crush and screen it to obtain Al with a particle size ≤ 0.07 mm2 O 3 -SiO 2 It is a silica binder for non-cement castables.

[0052] Comparative Example 1

[0053] The binder in Comparative Example 1 is CA71 calcium aluminate cement.

[0054] Comparative Example 2

[0055] The difference between Comparative Example 2 and Example 1 is only that: Step 2) is not carried out.

[0056] Comparative Example 3

[0057] The difference between Comparative Example 3 and Example 1 is only that: the reaction pressure in Step 2) is 2.1 MPa, the reaction temperature is 220 °C, and the reaction time is 38 h.

[0058] Comparative Example 4

[0059] The difference between Comparative Example 4 and Example 1 is only that: Step 3) is not carried out, that is, boric acid, sodium tripolyphosphate and acrylamide are not added, and in Step 4), the mixed slurry is directly dried, crushed and screened to obtain the binder.

[0060] Comparative Example 5

[0061] The difference between Comparative Example 5 and Example 1 is only that: in Step 1), the mass percentage content of silica fume is increased to 95%, and the mass percentage contents of the raw material containing aluminum sulfate and sericite powder are respectively reduced to 4% and 1%.

[0062] Apply the binders of each example and each comparative example to Al 2 O 3 -SiO 2 castable, and the specific formula is: tabular corundum with a particle size of 0 - 5 mm is 68 wt%, tabular corundum fine powder of 200 mesh is 17 wt%, reactive alumina fine powder with a particle size ≤ 0.088 mm is 10 wt%, binder is 5 wt%, polycarboxylic acid-based water reducer is added externally at 0.3 wt%, and water is added externally at 3.5 wt%; the specific preparation method is: stir and mix the raw materials other than water evenly, and finally add water and stir evenly to obtain Al 2 O 3 -SiO 2 castable.

[0063] Use the slump method to measure the flow value and pourable time of the castable. The prepared Al 2 O 3 -SiO 2The castable is cast in a mold, demolded after being placed at a temperature of 25°C and a humidity of 35% for 24 hours, and then baked. The maximum baking temperature is 450°C. After the baking is completed, the temperature is raised to 1200°C and 1550°C to prepare samples for testing strength, and the samples prepared at 1550°C are subjected to thermal shock resistance tests.

[0064] Table 1 Performance test results

[0065]

[0066] The above embodiments are merely examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here, and the obvious changes or modifications thus extended are still within the protection scope of the present invention.

Claims

1. A method for preparing a siliceous binder for an Al2O3-SiO2 cement-free castable, characterized in that: The following steps are involved: 1) adding water to a mixed powder of silicon micropowder, aluminum sulfate-containing raw material and sericite powder for ball milling to obtain a ball milling slurry; 2) placing the ball mill slurry in a reaction kettle and heating it under pressure to react to obtain a mixed slurry; 3) adding boric acid, sodium tripolyphosphate and acrylamide to the mixed slurry in sequence and stirring to obtain a prefabricated slurry; 4) The prefabricated slurry is dried, crushed and sieved to obtain a siliceous binder for Al2O3-SiO2 based cement-free castable.

2. The method for preparing a siliceous binder for an Al2O3-SiO2-based cement-free castable according to claim 1, characterized in that: The mass percentage content of each raw material in the mixed powder is: 87-92% silicon micropowder, 5-10% aluminum sulfate-containing raw material, and 2-6% sericite powder.

3. The method for preparing a siliceous binder for an Al2O3-SiO2 cement-free castable according to claim 1, characterized in that: The reaction pressure in step 2) is 1-2 MPa, the reaction temperature is 150-200° C., and the reaction time is 24-36 h.

4. The method for preparing a siliceous binder for an Al2O3-SiO2-based cement-free castable according to claim 1, characterized in that: The mass ratio of the mixed slurry, boric acid, sodium tripolyphosphate and acrylamide is 100:(1-2):(1-4):(2-5).

5. The method for preparing a siliceous binder for an Al2O3-SiO2 cement-free castable according to claim 1, characterized in that: The amount of water added is 90-150% of the mass of the mixed powder; the ball milling speed is 200-300 r / min, and the ball milling time is 60-180 min.

6. The method for preparing a siliceous binder for an Al2O3-SiO2 cement-free castable according to claim 1, characterized in that: The SiO2 content of the silicon micropowder is ≥95.1wt%, and the particle size is ≤0.4μm; the Al2(SO4)3 content of the aluminum sulfate-containing raw material is ≥50wt%, and the particle size is ≤0.088mm, and the aluminum sulfate-containing raw material is one or more of aluminum sulfate fine powder and aluminum sulfate hydrate fine powder; the Al2O3 content of the sericite powder is ≥10.0wt%, the SiO2 content is ≥80.0wt%, the K2O+Na2O content is ≤2.0wt%, and the particle size is ≤100μm.

7. The method for preparing a siliceous binder for an Al2O3-SiO2 cement-free castable according to claim 1, characterized in that: The aluminum sulfate-containing raw material is a mixture of aluminum sulfate fine powder and aluminum sulfate hydrate fine powder, wherein the weight proportion of aluminum sulfate fine powder is 30-40%, and the weight proportion of aluminum sulfate hydrate fine powder is 60-70%.

8. The method for preparing a siliceous binder for Al2O3-SiO2 cement-free castable according to claim 1, characterized in that: The boric acid has a H3BO3 content of ≥99.5wt% and a particle size of ≤0.1mm; the sodium tripolyphosphate has a Na5P3O 10 The content is ≥95.0wt%, and the particle size is ≤0.1mm; the purity of the acrylamide is ≥99%, and the particle size is ≤100μm.

9. A siliceous binder for Al2O3-SiO2 based cement-free castable prepared by the method according to any one of claims 1 to 8.

10. The siliceous binder for Al2O3-SiO2 based cement-free castable according to claim 9, characterized in that: The particle size of the siliceous binder is ≤0.1 mm; when the siliceous binder is used, its mass proportion in the dry material of the Al2O3-SiO2 cement-free castable is 5-10%.

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