A high-strength heat-insulating precast block for a lime rotary kiln and its preparation method

Abstract

The present invention belongs to the technical field of building materials, and particularly relates to a high-strength heat-insulating precast block for a lime rotary kiln and a preparation method thereof, including the following raw materials: 35-45 parts of α-aluminum oxide micropowder, 5-7 parts of mullite fiber, 4-10 parts of hollow ceramic microspheres, 12-15 parts of zirconium nitride powder, 6-8 parts of functional additives, and 8-12 parts of binder; it is prepared by the following method: S1. Mix the α-aluminum oxide micropowder, mullite fiber, hollow ceramic microspheres, zirconium nitride powder, functional additives and binder, and extrude to form a precast block blank; S2. Dry the precast block blank for 8-12 h, then sinter the dried blank, and finally cool it with the furnace to obtain the precast block. The prepared precast block for the lime rotary kiln has excellent compressive strength, flexural strength and heat-insulating performance, and can be widely used.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a high-strength heat-insulating precast block for a lime rotary kiln and a preparation method thereof. Background Art

[0002] The lime rotary kiln plays a key role in the lime production process, and the internal working conditions are extremely harsh. During the high-temperature calcination process, the temperature inside the kiln can usually reach above 1500 °C, and it also has to withstand the high-speed impact, abrasion of the materials, and strong corrosion of the alkaline steam. Although traditional lining materials, such as ordinary refractory bricks, can withstand a certain high temperature, they perform poorly in heat insulation, resulting in a large amount of heat energy loss, thereby increasing energy consumption; on the other hand, some materials with good heat insulation performance often have insufficient strength and are difficult to withstand the action of mechanical stress, are easily damaged, and cannot ensure the continuous and stable operation of the lime rotary kiln. Therefore, developing a precast block with both high strength and heat insulation performance is of great significance for improving the energy efficiency of the lime rotary kiln, reducing production costs, and extending the service life of the equipment. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the present invention provides a high-strength heat-insulating precast block for a lime rotary kiln and a preparation method thereof.

[0004] To solve the above problems, the technical solution adopted by the present invention is:

[0005] A high-strength heat-insulating precast block for a lime rotary kiln, comprising the following raw materials in parts by mass:

[0006] 35-45 parts of α-aluminum oxide fine powder, 5-7 parts of mullite fiber, 4-10 parts of hollow ceramic microspheres, 12-15 parts of zirconium nitride powder, 6-8 parts of functional additive, and 8-12 parts of binder.

[0007] Preferably, the functional additive is prepared by the following method:

[0008] A1. Add yttrium nitrate solution to zirconium solution, stir for 15-25 min, then add sodium hydroxide solution while stirring, heat and stir for 2-4 h, place at 60-80 °C for 3-4 h, filter, wash, dry, and calcine to obtain a composite fine powder;

[0009] A2. Disperse magnesium nitrate and aluminum sulfate in ethanol, stir for 12-20 min, add tartaric acid, stir for 3-6 h, then add the composite fine powder, stir for 35-45 min, let stand for 1-2 h, filter, dry, and calcine to obtain the functional additive.

[0010] Preferably, the calcination in step A1 is specifically as follows: control the heating rate at 6 - 8 °C / min, raise the temperature to 300 - 400 °C, and keep the temperature for 2 - 3 h; then control the heating rate at 3 - 4 °C / min, raise the temperature to 600 - 800 °C, keep the temperature for 3 - 4 h, and then cool down with the furnace.

[0011] Preferably, the mass ratio of the yttrium nitrate solution, zirconium solution, and sodium hydroxide solution in step A1 is 2 - 5:12 - 15:0.5 - 1, and the zirconium solution is prepared by mixing tetraethyl zirconate and acetone with a mass ratio of 8 - 12:50 - 60.

[0012] Preferably, the yttrium nitrate solution is an aqueous yttrium nitrate solution with a mass fraction of 10 - 15%.

[0013] Preferably, the sodium hydroxide solution is an aqueous sodium hydroxide solution with a mass fraction of 15 - 20%.

[0014] Preferably, the calcination in step A2 is specifically as follows: control the heating rate at 5 - 8 °C / min, raise the temperature to 600 - 800 °C, and keep the temperature for 1 - 2 h; then control the heating rate at 2 - 4 °C / min, raise the temperature to 1000 - 1200 °C, keep the temperature for 6 - 8 h, and then cool down with the furnace.

[0015] Preferably, the mass ratio of magnesium nitrate, aluminum sulfate, tartaric acid, and composite fine powder in step A2 is 2 - 3:3 - 6:0.5 - 0.8:12 - 16.

[0016] Preferably, the binder includes phosphate cement and ammonium pentaborate with a mass ratio of 4 - 6:1 - 2.

[0017] A preparation method of a high-strength heat-insulating precast block for a lime rotary kiln is obtained by the following method:

[0018] S1. By mass, mix α-aluminum oxide fine powder, mullite fiber, hollow ceramic microspheres, zirconium nitride powder, functional additives, and a binder, stir at 300 - 400 rpm for 20 - 30 min, and extrude to form a precast block blank.

[0019] S2. Place the precast block blank in an oven at 70 - 80 °C and dry for 8 - 12 h. Then sinter the dried blank. Raise the temperature to 700 - 800 °C at a rate of 4 - 6 °C / min and keep the temperature for 2 - 4 h; then raise the temperature to 1100 - 1200 °C at a rate of 8 - 12 °C / min and keep the temperature for 1 - 2 h; finally, raise the temperature to 1300 - 1450 °C at a rate of 2 - 4 °C / min and keep the temperature for 3 - 5 h, and finally cool down with the furnace to obtain the precast block.

[0020] In summary, the present invention has the following beneficial effects:

[0021] After mixing yttrium nitrate and zirconium solution with sodium hydroxide, a composite micropowder is prepared through a series of operations. Then, magnesium nitrate, aluminum sulfate, and tartaric acid are mixed and added to the composite micropowder, and calcined to obtain a functional additive. Yttrium ions can enter the lattice of the zirconium-based material during the calcination process, playing a role in stabilizing the lattice structure and improving the high-temperature stability of the material. The introduction of magnesium ions and aluminum ions, under the action of tartaric acid, forms a precursor with a specific structure. During the calcination process, high-temperature stable phases such as magnesium aluminate spinel are formed on the surface of the composite micropowder, which can provide excellent high-temperature performance and chemical stability for the preform, and improve the strength of the preform. Introducing yttrium first can make the surface of the composite micropowder have more suitable chemical activity, and promote the chemical bonding at the interface between the composite micropowder and magnesium aluminate spinel, making the functional additive form a more compact and synergistic overall structure. The yttrium-doped composite micropowder has advantages in toughness, activity, etc., while magnesium aluminate spinel performs well in high-temperature stability, hardness, and chemical resistance. After the two are combined, the functional additive can have a variety of excellent properties. During the sintering process, the presence of yttrium can reduce the sintering temperature, and the formation of magnesium aluminate spinel can play a role in skeleton support during the sintering process. The synergistic effect of the two can enable the preform to achieve densification sintering faster at a lower temperature, reducing energy consumption while improving the density and performance uniformity of the preform.

[0022] In the present invention, phosphate cement and ammonium pentaborate are mixed and then added to the preform as a binder. The chemical stability of ammonium pentaborate and the stability of phosphate cement in high-temperature and chemical environments complement each other, jointly improving the stability of the preform in complex chemical environments and high-temperature conditions. Both phosphate cement and ammonium pentaborate have certain high-temperature resistance properties. Through their interaction, a high-temperature stable structure is formed, enabling the preform to maintain good performance and structural integrity in a high-temperature environment. Specific Embodiments

[0023] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form.

[0024] α-aluminum oxide micropowder, purchased from Shanghai Liantian Materials Technology Co., Ltd., CAS No. 1344-28-1, analytical pure; mullite fiber, purchased from Zhengzhou Shengshi Jinding Thermal Insulation Refractory Materials Co., Ltd.; hollow ceramic microspheres, purchased from Lingshou County Shengfei Mineral Products Processing Factory, particle size 40 - 100 mesh, purity 99%; zirconium nitride powder, purchased from Hebei Guangtuo Welding Materials Co., Ltd., particle size: 1 - 30μm, purity 99.9%; phosphate cement, purchased from Beijing Wusheng Zhizao Construction Engineering Co., Ltd.; ammonium pentaborate, purchased from Jining Tangyi Chemical Co., Ltd.

[0025] Example 1

[0026] A high-strength heat-insulating precast block for a lime rotary kiln, comprising raw materials in the following parts by mass:

[0027] 35 parts of α-aluminum oxide fine powder, 5 parts of mullite fiber, 4 parts of hollow ceramic microspheres, 12 parts of zirconium nitride powder, 6 parts of functional additive, and 8 parts of binder.

[0028] Among them, the functional additive is prepared by the following method:

[0029] A1. Add yttrium nitrate solution to zirconium solution, stir at 100 rpm for 15 min, then add sodium hydroxide solution while stirring, stir at 40 °C and 100 rpm for 2 h, place at 60 °C for 3 h, filter, wash 3 times with deionized water, dry at 70 °C for 6 h, calcine, control the heating rate at 6 °C / min, rise to 300 °C, and keep warm for 2 h; control the heating rate at 3 °C / min, rise to 600 °C, keep warm for 3 h, and cool with the furnace to obtain composite fine powder; among them, the mass ratio of yttrium nitrate solution, zirconium solution and sodium hydroxide solution is 2:12:0.5, the zirconium solution is prepared by mixing tetraethyl zirconate and acetone with a mass ratio of 8:50, the yttrium nitrate solution is a 10% aqueous solution of yttrium nitrate, and the sodium hydroxide solution is a 15% aqueous solution of sodium hydroxide;

[0030] A2. Disperse magnesium nitrate and aluminum sulfate in ethanol, stir at 100 rpm for 12 min, add tartaric acid, stir at 100 rpm for 3 h, then add the composite fine powder, stir at 40 °C and 100 rpm for 35 min, let stand for 1 h, filter, dry at 60 °C for 4 h, calcine, control the heating rate at 5 °C / min, rise to 600 °C, and keep warm for 1 h; control the heating rate at 2 °C / min, rise to 1000 °C, keep warm for 6 h, and cool with the furnace to obtain the functional additive; among them, the mass ratio of magnesium nitrate, aluminum sulfate, tartaric acid and the composite fine powder is 2:3:0.5:12.

[0031] Among them, the binder includes phosphate cement and ammonium pentaborate with a mass ratio of 4:1.

[0032] A preparation method of a high-strength heat-insulating precast block for a lime rotary kiln is obtained by the following method:

[0033] S1. According to the parts by mass, mix α-aluminum oxide fine powder, mullite fiber, hollow ceramic microspheres, zirconium nitride powder, functional additive and binder, stir at 300 rpm for 20 min, and extrude and mold to obtain a precast block blank;

[0034] S2. Place the precast blank at 70°C for drying for 8 h, then sinter the dried blank. Heat it up to 700°C at a rate of 4°C / min and hold for 2 h; heat it up to 1100°C at a rate of 8°C / min and hold for 1 h. Finally, heat it up to 1300°C at a rate of 2°C / min and hold for 3 h. Finally, cool it in the furnace to obtain the precast block.

[0035] Example 2

[0036] A high-strength heat-insulating precast block for a lime rotary kiln comprises raw materials in the following mass parts:

[0037] 45 parts of α-aluminum oxide fine powder, 7 parts of mullite fiber, 10 parts of hollow ceramic microspheres, 15 parts of zirconium nitride powder, 8 parts of functional additive, and 12 parts of binder.

[0038] Among them, the functional additive is prepared by the following method:

[0039] A1. Add yttrium nitrate solution to zirconium solution, stir at 200 rpm for 25 min, then add sodium hydroxide solution while stirring, stir at 60°C and 150 rpm for 4 h, place at 80°C for 4 h, filter, wash with deionized water 5 times, dry at 80°C for 8 h, calcine, control the heating rate at 8°C / min, rise to 400°C, and hold for 3 h; control the heating rate at 4°C / min, heat up to 800°C, and hold for 4 h, then cool in the furnace to obtain the composite fine powder; among them, the mass ratio of yttrium nitrate solution, zirconium solution, and sodium hydroxide solution is 5:15:1. The zirconium solution is prepared by mixing tetraethyl zirconate and acetone with a mass ratio of 12:60. The yttrium nitrate solution is a 15% aqueous solution of yttrium nitrate, and the sodium hydroxide solution is a 20% aqueous solution of sodium hydroxide;

[0040] A2. Disperse magnesium nitrate and aluminum sulfate in ethanol, stir at 150 rpm for 20 min, add tartaric acid, stir at 150 rpm for 6 h, then add the composite fine powder, stir at 50°C and 150 rpm for 45 min, stand for 2 h, filter, dry at 80°C for 6 h, calcine, control the heating rate at 8°C / min, rise to 800°C, and hold for 2 h; control the heating rate at 4°C / min, heat up to 1200°C, and hold for 8 h, then cool in the furnace to obtain the functional additive; among them, the mass ratio of magnesium nitrate, aluminum sulfate, tartaric acid, and the composite fine powder is 3:6:0.8:16.

[0041] Among them, the binder includes phosphate cement and ammonium pentaborate with a mass ratio of 6:2.

[0042] A preparation method of a high-strength heat-insulating precast block for a lime rotary kiln is obtained by the following method:

[0043] S1. Mix α-aluminum oxide micropowder, mullite fiber, hollow ceramic microspheres, zirconium nitride powder, functional additive and binder by mass parts, stir at 400 rpm for 30 min, and extrude to form a precast block blank;

[0044] S2. Place the precast block blank at 80 °C for drying for 12 h, then sinter the dried blank. Heat it up to 800 °C at a rate of 6 °C / min and hold for 4 h; heat it up to 1200 °C at a rate of 12 °C / min and hold for 2 h, and finally heat it up to 1450 °C at a rate of 4 °C / min and hold for 5 h, and finally cool it with the furnace to obtain a precast block.

[0045] Example 3

[0046] A high-strength heat-insulating precast block for a lime rotary kiln, comprising raw materials in the following mass parts:

[0047] 40 parts of α-aluminum oxide micropowder, 6 parts of mullite fiber, 7 parts of hollow ceramic microspheres, 14 parts of zirconium nitride powder, 7 parts of functional additive, 10 parts of binder.

[0048] Among them, the functional additive is prepared by the following method:

[0049] A1. Add yttrium nitrate solution to zirconium solution, stir at 150 rpm for 20 min, then add sodium hydroxide solution while stirring, stir at 50 °C and 130 rpm for 3 h, place at 70 °C for 3.5 h, filter, wash 4 times with deionized water, dry at 75 °C for 7 h, calcine, control the heating rate at 7 °C / min, rise to 350 °C, and hold for 2.5 h; control the heating rate at 4 °C / min, rise to 700 °C, and hold for 3.5 h, and cool with the furnace to obtain a composite micropowder; among them, the mass ratio of yttrium nitrate solution, zirconium solution and sodium hydroxide solution is 4:13:0.8, the zirconium solution is prepared by mixing tetraethyl zirconate and acetone with a mass ratio of 10:55, the yttrium nitrate solution is a 13% aqueous solution of yttrium nitrate, and the sodium hydroxide solution is an 18% aqueous solution of sodium hydroxide;

[0050] A2. Disperse magnesium nitrate and aluminum sulfate in ethanol, stir at 130 rpm for 16 min, add tartaric acid, stir at 130 rpm for 5 h, then add the composite micropowder, stir at 45 °C and 130 rpm for 40 min, let stand for 1.5 h, filter, dry at 70 °C for 5 h, calcine, control the heating rate at 7 °C / min, rise to 700 °C, and hold for 1.5 h; control the heating rate at 3 °C / min, rise to 1100 °C, and hold for 7 h, and cool with the furnace to obtain the functional additive; among them, the mass ratio of magnesium nitrate, aluminum sulfate, tartaric acid and the composite micropowder is 2.5:5:0.7:14.

[0051] Among them, the binder includes phosphate cement and ammonium pentaborate with a mass ratio of 5:1.5.

[0052] A preparation method of a high-strength heat-insulating precast block for a lime rotary kiln is obtained by the following method:

[0053] S1. By mass, mix α-aluminum oxide micropowder, mullite fiber, hollow ceramic microspheres, zirconium nitride powder, functional additive and binder, stir at 350 rpm for 25 min, and extrude to form a precast block blank.

[0054] S2. Place the precast block blank in an oven at 75 °C and dry for 10 h. Then sinter the dried blank. Heat it up to 750 °C at a rate of 5 °C / min and hold for 3 h; heat it up to 1150 °C at a rate of 10 °C / min and hold for 1.5 h. Finally, heat it up to 1400 °C at a rate of 3 °C / min and hold for 4 h, and then cool it down with the furnace to obtain the precast block.

[0055] Comparative Example 1

[0056] Comparative Example 1 is the same as Example 1, the only difference being that the preparation method of the functional additive is different, specifically as follows:

[0057] The functional additive is obtained by the following method:

[0058] Add yttrium nitrate solution to zirconium solution, stir at 100 rpm for 15 min, then add sodium hydroxide solution while stirring, stir at 40 °C and 100 rpm for 2 h, place at 60 °C for 3 h, filter, wash with deionized water 3 times, dry at 70 °C for 6 h, calcine, control the heating rate to be 6 °C / min, rise to 300 °C, and hold for 2 h; control the heating rate to be 3 °C / min, heat up to 600 °C, hold for 3 h, and cool with the furnace to obtain the functional additive; among them, the mass ratio of yttrium nitrate solution, zirconium solution and sodium hydroxide solution is 2:12:0.5, the zirconium solution is prepared by mixing tetraethyl zirconate and acetone with a mass ratio of 8:50, the yttrium nitrate solution is a 10% aqueous solution of yttrium nitrate, and the sodium hydroxide solution is a 15% aqueous solution of sodium hydroxide.

[0059] Comparative Example 2

[0060] Comparative Example 2 is the same as Example 1, the only difference being that the preparation method of the functional additive is different, specifically as follows:

[0061] The functional additive is obtained by the following method:

[0062] Disperse magnesium nitrate and aluminum sulfate in ethanol, stir at 150 rpm for 20 min, add tartaric acid, stir at 150 rpm for 6 h, then add zirconium solution, stir at 50 °C and 150 rpm for 45 min, let stand for 2 h, filter, dry at 80 °C for 6 h, calcine, control the heating rate at 8 °C / min, raise the temperature to 800 °C, hold for 2 h; control the heating rate at 4 °C / min, raise the temperature to 1200 °C, hold for 8 h, and cool with the furnace to obtain the functional additive; among them, the mass ratio of magnesium nitrate, aluminum sulfate, tartaric acid and zirconium solution is 3:6:0.8:16, and the zirconium solution is prepared by mixing tetraethyl zirconate and acetone with a mass ratio of 12:60.

[0063] Comparative Example 3

[0064] Comparative Example 3 is the same as Example 1, the only difference is that the binder is phosphate cement.

[0065] Comparative Example 4

[0066] Comparative Example 4 is the same as Example 1, the only difference is that the binder is ammonium pentaborate.

[0067] Performance Test

[0068] Carry out the following performance tests on the high-strength heat-insulating precast blocks for lime rotary kilns of Examples 1-3 and Comparative Examples 1-4:

[0069] Compressive strength: Test according to the national standard GB / T 5072-2008;

[0070] Flexural strength: Test according to GB / T3001-2007;

[0071] High-temperature flexural strength: According to GB / T3002-2004, keep the precast block at 1500 °C for 2 h, and then test its high-temperature flexural strength;

[0072] Thermal conductivity: Test according to GB / T 36133-2018;

[0073] Table 1 Performance test results of the precast blocks of Examples 1-3 and Comparative Examples 1-4

[0074]

[0075] It can be seen from the test results in Table 1 that the precast blocks for lime rotary kilns prepared by the present invention show excellent compressive and flexural properties, and still have a certain flexural property after high-temperature treatment. At the same time, the precast block has a low thermal conductivity, indicating that it has good heat-insulating properties. In summary, the precast block can be used as a refractory material with excellent performance.

[0076] This specific embodiment is only an interpretation of the present invention and is not a limitation thereof. After reading this specification, those skilled in the art may make modifications to this embodiment that do not contribute creatively, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A high-strength heat-insulating precast block for a lime rotary kiln, characterized in that, It includes raw materials in the following parts by mass: 35 - 45 parts of α-aluminum oxide fine powder, 5 - 7 parts of mullite fiber, 4 - 10 parts of hollow ceramic microspheres, 12 - 15 parts of zirconium nitride powder, 6 - 8 parts of functional additive, 8 - 12 parts of binder; The functional additive is prepared by the following method: A1. Add yttrium nitrate solution into zirconium solution, stir for 15 - 25 min, then add sodium hydroxide solution while stirring, heat and stir for 2 - 4 h, place at 60 - 80 °C for 3 - 4 h, filter, wash, dry, calcine to obtain composite fine powder; A2. Disperse magnesium nitrate and aluminum sulfate in ethanol, stir for 12 - 20 min, add tartaric acid, stir for 3 - 6 h, then add the composite fine powder, stir for 35 - 45 min, let stand for 1 - 2 h, filter, dry, calcine to obtain the functional additive.

2. The high-strength heat-insulating prefabricated block for a lime rotary kiln according to claim 1, wherein The calcination in step A1 is specifically as follows: Control the heating rate to be 6 - 8 °C / min, raise the temperature to 300 - 400 °C, keep the temperature for 2 - 3 h; Control the heating rate to be 3 - 4 °C / min, raise the temperature to 600 - 800 °C, keep the temperature for 3 - 4 h, and cool with the furnace.

3. The high-strength heat-insulating precast block for a lime rotary kiln according to claim 1, characterized in that, In step A1, the mass ratio of yttrium nitrate solution, zirconium solution and sodium hydroxide solution is 2 - 5:12 - 15:0.5 - 1, and the zirconium solution is prepared by mixing tetraethyl zirconate and acetone in a mass ratio of 8 - 12:50 - 60.

4. The high-strength heat-insulating precast block for a lime rotary kiln according to claim 1, characterized in that, The calcination in step A2 is specifically as follows: Control the heating rate to be 5 - 8 °C / min, raise the temperature to 600 - 800 °C, keep the temperature for 1 - 2 h; Control the heating rate to be 2 - 4 °C / min, raise the temperature to 1000 - 1200 °C, keep the temperature for 6 - 8 h, and cool with the furnace.

5. The high-strength heat-insulating precast block for a lime rotary kiln according to claim 1, characterized in that, In step A2, the mass ratio of magnesium nitrate, aluminum sulfate, tartaric acid and composite fine powder is 2 - 3:3 - 6:0.5 - 0.8:12 - 16.

6. The high-strength heat-insulating prefabricated block for a lime rotary kiln according to claim 1, characterized in that, The binder includes phosphate cement and ammonium pentaborate in a mass ratio of 4 - 6:1 - 2.

7. A preparation method of a high-strength heat-insulating precast block for a lime rotary kiln according to any one of claims 1-6, characterized in that, It is prepared by the following method: S1. According to the parts by mass, mix α-aluminum oxide fine powder, mullite fiber, hollow ceramic microspheres, zirconium nitride powder, functional additive and binder, stir at 300 - 400 rpm for 20 - 30 min, and extrude and mold to obtain a precast block blank; S2. Place the precast block blank at 70 - 80 °C and dry for 8 - 12 h, then sinter the dried blank, raise the temperature to 700 - 800 °C at 4 - 6 °C / min, and keep the temperature for 2 - 4 h; Raise the temperature to 1100 - 1200 °C at 8 - 12 °C / min, keep the temperature for 1 - 2 h, and finally raise the temperature to 1300 - 1450 °C at 2 - 4 °C / min, keep the temperature for 3 - 5 h, and finally cool with the furnace to obtain the precast block.

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