Lightweight periclase-spinel aggregate and preparation method thereof

Abstract

The invention particularly relates to a lightweight periclase-spinel aggregate and a preparation method thereof. According to the technical scheme, the preparation method comprises the following steps: taking 50.0-90.0 wt% of light calcined magnesia fine powder and 10.0-50.0 wt% of aluminum hydroxide fine powder as raw materials, adding 2.0-5.0 wt% of nickel oxide fine powder and 2.5-5.0 wt% of polyvinyl alcohol, uniformly stirring, carrying out mechanical pressing, and drying; and carrying out heat preservation for 1-3 hours at the temperature of 500-1000 DEG C, then carrying out heat preservation for 1-4 hours at the temperature of 1400-1600 DEG C, cooling, crushing, screening and packaging to obtain the lightweight periclase-spinel aggregate. According to the technical scheme, the particle size of the light calcined magnesia fine powder is smaller than 10 microns; the particle size of the aluminum hydroxide fine powder is 500-800 [mu] m; the particle size of the nickel oxide fine powder is smaller than 10 micrometers. The lightweight periclase-spinel aggregate prepared by the invention has the characteristics of high closed porosity, small pore size, high strength, excellent erosion resistance and low heat conductivity coefficient.

Description

Technical Field

[0001] The invention belongs to the technical field of periclase-spinel aggregates, and specifically relates to a lightweight periclase-spinel aggregate and a preparation method thereof. Background Art

[0002] Periclite-spinel refractories are widely used in steelmaking converters, electric furnaces, ladles and other metallurgical furnace linings due to their high melting point and excellent slag resistance. Existing periclase-spinel refractories are prepared from dense magnesia sand and spinel raw materials to ensure that they have excellent performance. However, the high thermal conductivity of dense magnesia sand and spinel causes a large amount of heat to dissipate from the metallurgical furnace lining, which is not conducive to energy conservation and emission reduction in high-temperature industries. For this reason, low thermal conductivity and high corrosion resistance have become the main development direction of periclase-spinel refractories.

[0003] The patented technology of "a sintered magnesia with a micro-nano composite pore structure and its preparation method" (CN108821750A) uses magnesium oxide micropowder and soluble magnesium solution as raw materials to produce lightweight magnesia with a micro-nano composite pore structure. However, the apparent porosity of the porous lightweight magnesia is too high, making it difficult for its strength and corrosion resistance to meet the use requirements.

[0004] The patented technology of "A microporous periclase-magnesium-aluminum-spinel refractory aggregate and its preparation method" (CN118125846A) uses magnesium hydroxide fine powder and different aluminum sources as raw materials to produce microporous periclase-magnesium-aluminum-spinel refractory aggregate with high strength, but the apparent porosity and thermal conductivity of the aggregate are still relatively high, and the corrosion resistance is difficult to meet the use requirements.

[0005] The patented technology of "in-situ decomposition preparation of lightweight periclase-magnesium-aluminum spinel composite materials" (CN103553672A) uses magnesium-aluminum hydrotalcite as the main raw material, polyvinyl alcohol or dextrin as a binder, and adopts the method of adding pore-forming agents to prepare lightweight periclase-spinel materials, but the material has a large pore size and poor anti-erosion and permeability properties.

[0006] "A lightweight periclase-magnesium-aluminum spinel ramming material and its preparation method" (CN108821750A) patented technology, which uses magnesite and Al-containing 3+ The porous periclase-magnesium-aluminum spinel aggregate was prepared by using the solution as raw material. However, due to the excessive spinel content and excessive reaction expansion of the aggregate, the pores existed in the form of large open pores, which significantly deteriorated the anti-corrosion performance of the aggregate. Summary of the invention

[0007] The present invention aims to overcome the defects of the prior art and aims to provide a lightweight periclase-spinel aggregate with high closed porosity, small pore size, high strength, excellent corrosion resistance and low thermal conductivity and a preparation method thereof.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is:

[0009] 50.0-90.0wt% of light-burned magnesium oxide fine powder and 10.0-50.0wt% of aluminum hydroxide fine powder are used as raw materials, and 2.0-5.0wt% of nickel oxide fine powder and 2.5-5.0wt% of polyvinyl alcohol are added to the raw materials, stirred evenly, pressed into shape by a machine, and dried; then kept warm at 500-1000°C for 1-3 hours, and then kept warm at 1400-1600°C for 1-4 hours, cooled, crushed, screened, and packaged to obtain lightweight periclase-spinel aggregate.

[0010] The MgO content of the light-burned magnesia fine powder is greater than 99wt%; and the particle size of the light-burned magnesia fine powder is less than 10μm.

[0011] The Al(OH)3 content of the aluminum hydroxide fine powder is greater than 99wt%; the particle size of the aluminum hydroxide fine powder is 500-800μm.

[0012] The NiO content of the nickel oxide fine powder is greater than 98 wt %; and the particle size of the nickel oxide fine powder is less than 10 μm.

[0013] The pH value of the polyvinyl alcohol is 6-8.

[0014] The pressure of the machine compression molding is 10-20 MPa.

[0015] The drying temperature is 90-110° C., and the drying time is 6-10 hours.

[0016] Due to the adoption of the above technical solution, the present invention has the following positive effects compared with the prior art:

[0017] The lightweight periclase-spinel aggregate prepared by the present invention uses aluminum hydroxide with a particle size of 500-800 μm as a raw material, and the aluminum hydroxide can be decomposed in situ at 400-800° C. to form agglomerates containing a large number of micro-nano pores and Al2O3 microcrystals. At the same time, the lightly burned magnesium oxide fine powder used has a small particle size and high activity, can diffuse into the agglomerates and react with the Al2O3 microcrystals to form MgAl2O4 phases, forming a porous spinel core structure. The volume expansion accompanied by in-situ spinelization can hinder the merging, growth and discharge of pores in the agglomerates, so that the prepared lightweight periclase-spinel aggregate has small pore size and high closed porosity, giving the aggregate a low thermal conductivity and high slag erosion resistance.

[0018] The nickel oxide fine powder added in the present invention will be dissolved in the MgO lattice remaining after the spinel is formed under high temperature conditions, resulting in MgO lattice distortion and grain boundary diffusion, so that the pores in the MgO lattice cannot be removed in time and exist in the form of closed pores, further improving the closed porosity of the aggregate. At the same time, the MgO lattice distortion promotes material transfer, improves the neck bonding between the MgO matrix and the spinel core structure, and gives the lightweight periclase-spinel aggregate high strength and excellent thermal shock resistance. In addition, NiO reacts with the infiltrated slag to generate NiAl2O4 spinel, which increases the slag viscosity and effectively prevents further penetration and erosion of the slag. The prepared lightweight periclase-spinel aggregate has excellent corrosion resistance.

[0019] The lightweight periclase-spinel aggregate prepared by the present invention is tested to have the following characteristics: the apparent porosity is 1.0-4.0%; the closed porosity is 13.0-19.0%; the average pore size is 0.10-0.50 μm; the flexural strength is 130-180 MPa; the thermal conductivity is 1.5-4.5 W / (m·k) at 500° C.; and the thermal shock stability has a residual strength retention rate of 75-90% after one water cooling at 900° C.

[0020] Therefore, the lightweight periclase-spinel aggregate prepared by the present invention has the characteristics of high closed porosity, small pore size, high strength, excellent corrosion resistance and low thermal conductivity. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific embodiments, but is not intended to limit the scope of protection thereof:

[0022] A lightweight periclase-spinel aggregate and a preparation method thereof. The preparation method described in this specific embodiment is:

[0023] 50.0-90.0wt% of light-burned magnesium oxide fine powder and 10.0-50.0wt% of aluminum hydroxide fine powder are used as raw materials, and 2.0-5.0wt% of nickel oxide fine powder and 2.5-5.0wt% of polyvinyl alcohol are added to the raw materials, stirred evenly, pressed into shape by a machine, and dried; then kept warm at 500-1000°C for 1-3 hours, and then kept warm at 1400-1600°C for 1-4 hours, cooled, crushed, screened, and packaged to obtain lightweight periclase-spinel aggregate.

[0024] The MgO content of the light-burned magnesia fine powder is greater than 99 wt %.

[0025] The Al(OH)3 content of the aluminum hydroxide fine powder is greater than 99 wt%.

[0026] The NiO content of the nickel oxide fine powder is greater than 98 wt %.

[0027] The pH value of the polyvinyl alcohol is 6-8.

[0028] The pressure of the machine compression molding is 10-20 MPa.

[0029] The drying temperature is 90-110° C., and the drying time is 6-10 hours.

[0030] In this specific implementation mode:

[0031] The particle size of the light-burned magnesium oxide fine powder is less than 10 μm;

[0032] The particle size of the aluminum hydroxide fine powder is 500 to 800 μm;

[0033] The particle size of the nickel oxide fine powder is less than 10 μm.

[0034] This will not be described in detail in the embodiments.

[0035] Example 1

[0036] A lightweight periclase-spinel aggregate and a preparation method thereof. The preparation method described in this embodiment is:

[0037] 50.0wt% of light-burned magnesium oxide fine powder and 50.0wt% of aluminum hydroxide fine powder are used as raw materials, and 2.0% of nickel oxide fine powder and 2.5wt% of polyvinyl alcohol are added to the raw materials, stirred evenly, pressed into shape, and dried; then kept warm at 500°C for 1 hour, and then kept warm at 1400°C for 1 hour, cooled, crushed, sieved, and packaged to obtain lightweight periclase-spinel aggregate.

[0038] The light-burned magnesia fine powder has a MgO content of 99.2 wt %.

[0039] The Al(OH)3 content of the aluminum hydroxide fine powder is 99.6 wt%.

[0040] The NiO content of the nickel oxide fine powder is 98.4 wt %.

[0041] The pH value of the polyvinyl alcohol is 6.

[0042] The pressure of the machine compression molding is 10 MPa.

[0043] The drying temperature is 90° C. and the drying time is 6 hours.

[0044] The lightweight periclase-spinel aggregate prepared in this embodiment was tested: the apparent porosity was 4.0%; the closed porosity was 19.0%; the average pore size was 0.39 μm; the flexural strength was 130 MPa; the thermal conductivity was 1.5 W / (m·k) at 500°C; the thermal shock stability was 75% after one water cooling at 900°C.

[0045] Example 2

[0046] A lightweight periclase-spinel aggregate and a preparation method thereof. The preparation method described in this embodiment is:

[0047] 90.0wt% of light-burned magnesium oxide fine powder and 10.0wt% of aluminum hydroxide fine powder are used as raw materials, and 5.0wt% of nickel oxide fine powder and 5.0wt% of polyvinyl alcohol are added as raw materials, stirred evenly, pressed into shape, and dried; then kept warm at 1000°C for 3 hours, and then kept warm at 1540°C for 4 hours, cooled, crushed, sieved, and packaged to obtain lightweight periclase-spinel aggregate.

[0048] The light-burned magnesia fine powder has a MgO content of 99.4 wt %.

[0049] The Al(OH)3 content of the aluminum hydroxide fine powder is 99.4 wt%.

[0050] The NiO content of the nickel oxide fine powder is 98.6 wt %.

[0051] The pH value of the polyvinyl alcohol is 7.

[0052] The pressure of the machine compression molding is 13 MPa.

[0053] The drying temperature is 100° C. and the drying time is 7 hours.

[0054] The lightweight periclase-spinel aggregate prepared in this embodiment was tested: the apparent porosity was 3.1%; the closed porosity was 13.0%; the average pore size was 0.10 μm; the flexural strength was 180 MPa; the thermal conductivity was 4.5 W / (m·k) at 500°C; the thermal shock stability was 85% after one water cooling at 900°C.

[0055] Example 3

[0056] A lightweight periclase-spinel aggregate and a preparation method thereof. The preparation method described in this embodiment is:

[0057] 80.0wt% of light-burned magnesium oxide fine powder and 20.0wt% of aluminum hydroxide fine powder are used as raw materials, and 3.0wt% of nickel oxide fine powder and 4.0wt% of polyvinyl alcohol are added to the raw materials, stirred evenly, pressed into shape, and dried; then kept warm at 800°C for 2 hours, and then kept warm at 1600°C for 3 hours, cooled, crushed, sieved, and packaged to obtain lightweight periclase-spinel aggregate.

[0058] The light-burned magnesia fine powder has a MgO content of 99.6 wt %.

[0059] The Al(OH)3 content of the aluminum hydroxide fine powder is 99.2 wt%.

[0060] The NiO content of the nickel oxide fine powder is 98.7 wt %.

[0061] The pH value of the polyvinyl alcohol is 8.

[0062] The pressure of the machine compression molding is 15 MPa.

[0063] The drying temperature is 110° C. and the drying time is 8 hours.

[0064] The lightweight periclase-spinel aggregate prepared in this embodiment was tested: the apparent porosity was 1.0%; the closed porosity was 14.9%; the average pore size was 0.50 μm; the flexural strength was 155 MPa; the thermal conductivity was 3.0 W / (m·k) at 500°C; the thermal shock stability was 90% after one water cooling at 900°C.

[0065] Example 4

[0066] A lightweight periclase-spinel aggregate and a preparation method thereof. The preparation method described in this embodiment is:

[0067] 70.0wt% of light-burned magnesium oxide fine powder and 30.0wt% of aluminum hydroxide fine powder are used as raw materials, and 3.5wt% of nickel oxide fine powder and 4.5wt% of polyvinyl alcohol are added to the raw materials, stirred evenly, pressed into shape, and dried; then kept warm at 700°C for 3 hours, and then kept warm at 1570°C for 2 hours, cooled, crushed, sieved, and packaged to obtain lightweight periclase-spinel aggregate.

[0068] The light-burned magnesia fine powder has a MgO content of 99.7 wt %.

[0069] The Al(OH)3 content of the aluminum hydroxide fine powder is 99.3 wt%.

[0070] The NiO content of the nickel oxide fine powder is 99.1 wt %.

[0071] The pH value of the polyvinyl alcohol is 6.5.

[0072] The pressure of the machine compression molding is 18 MPa.

[0073] The drying temperature is 100° C. and the drying time is 9 hours.

[0074] The lightweight periclase-spinel aggregate prepared in this embodiment was tested: the apparent porosity was 1.9%; the closed porosity was 17.2%; the average pore size was 0.21 μm; the flexural strength was 140 MPa; the thermal conductivity was 2.5 W / (m·k) at 500°C; the thermal shock stability was 82% after one water cooling at 900°C.

[0075] Example 5

[0076] A lightweight periclase-spinel aggregate and a preparation method thereof. The preparation method described in this embodiment is:

[0077] 60.0wt% of light-burned magnesium oxide fine powder and 40.0wt% of aluminum hydroxide fine powder are used as raw materials, and 4wt% of nickel oxide fine powder and 3wt% of polyvinyl alcohol are added to the raw materials, stirred evenly, pressed into shape, and dried; then kept warm at 600°C for 2 hours, and then kept warm at 1500°C for 3 hours, cooled, crushed, sieved, and packaged to obtain lightweight periclase-spinel aggregate.

[0078] The light-burned magnesia fine powder has a MgO content of 99.4 wt %.

[0079] The Al(OH)3 content of the aluminum hydroxide fine powder is 99.2 wt%.

[0080] The NiO content of the nickel oxide fine powder is 98.3 wt %.

[0081] The pH value of the polyvinyl alcohol is 7.5.

[0082] The pressure of the machine compression molding is 20MPa.

[0083] The drying temperature is 90° C. and the drying time is 10 hours.

[0084] The lightweight periclase-spinel aggregate prepared in this embodiment was tested: the apparent porosity was 2.8%; the closed porosity was 16.1%; the average pore size was 0.28 μm; the flexural strength was 175 MPa; the thermal conductivity was 3.5 W / (m·k) at 500°C; the thermal shock stability was 86% after one water cooling at 900°C.

[0085] Compared with the prior art, this specific implementation has the following positive effects:

[0086] The lightweight periclase-spinel aggregate prepared in this specific embodiment uses aluminum hydroxide with a particle size of 500-800 μm as a raw material, and the aluminum hydroxide can be decomposed in situ at 400-800°C to form agglomerates containing a large number of micro-nano pores and Al2O3 microcrystals. At the same time, the lightly burned magnesium oxide fine powder used has a small particle size and high activity, can diffuse into the agglomerate and react with the Al2O3 microcrystals to form a MgAl2O4 phase, forming a porous spinel core structure. The volume expansion associated with in-situ spinelization can hinder the merging, growth and discharge of pores in the agglomerate, so that the prepared lightweight periclase-spinel aggregate has small pore size and high closed porosity, giving the aggregate a low thermal conductivity and high resistance to slag erosion.

[0087] The nickel oxide fine powder added in this specific embodiment will be dissolved in the MgO lattice remaining after the spinel is formed under high temperature conditions, resulting in MgO lattice distortion and grain boundary diffusion, so that the pores in the MgO lattice cannot be eliminated in time and exist in the form of closed pores, further increasing the closed porosity of the aggregate. At the same time, the MgO lattice distortion promotes material transfer, improves the neck bonding between the MgO matrix and the spinel core structure, and gives the lightweight periclase-spinel aggregate high strength and excellent thermal shock resistance. In addition, NiO reacts with the infiltrated slag to generate NiAl2O4 spinel, which increases the viscosity of the slag and effectively prevents further penetration and erosion of the slag. The prepared lightweight periclase-spinel aggregate has excellent corrosion resistance.

[0088] The lightweight periclase-spinel aggregate prepared in this specific embodiment has been tested: the apparent porosity is 1.0-4.0%; the closed porosity is 13.0-19.0%; the average pore size is 0.10-0.50 μm; the flexural strength is 130-180 MPa; the thermal conductivity is 1.5-4.5 W / (m·k) at 500°C; the thermal shock stability is 75-90% of the residual strength retention rate after one water cooling at 900°C.

[0089] Therefore, the lightweight periclase-spinel aggregate prepared in this specific embodiment has the characteristics of high closed porosity, small pore size, high strength, excellent corrosion resistance and low thermal conductivity.

Claims

1. A method for preparing a lightweight periclase-spinel aggregate, characterized in that: 50.0-90.0wt% of light-burned magnesium oxide fine powder and 10.0-50.0wt% of aluminum hydroxide fine powder are used as raw materials, and 2.0-5.0wt% of nickel oxide fine powder and 2.5-5.0wt% of polyvinyl alcohol are added to the raw materials, stirred evenly, pressed into shape by a machine, and dried; then kept warm at 500-1000°C for 1-3 hours, and then kept warm at 1400-1600°C for 1-4 hours, cooled, crushed, screened, and packaged to obtain lightweight periclase-spinel aggregate.

2. The method for preparing lightweight periclase-spinel aggregate according to claim 1, characterized in that The MgO content of the light-burned magnesia fine powder is greater than 99wt%; and the particle size of the light-burned magnesia fine powder is less than 10μm.

3. The method for preparing lightweight periclase-spinel aggregate according to claim 1, characterized in that The Al(OH)3 content of the aluminum hydroxide fine powder is greater than 99wt%; the particle size of the aluminum hydroxide fine powder is 500-800μm.

4. The method for preparing lightweight periclase-spinel aggregate according to claim 1, characterized in that The NiO content of the nickel oxide fine powder is greater than 98 wt %; and the particle size of the nickel oxide fine powder is less than 10 μm.

5. The method for preparing lightweight periclase-spinel aggregate according to claim 1, characterized in that The pH value of the polyvinyl alcohol is 6-8.

6. The method for preparing lightweight periclase-spinel aggregate according to claim 1, characterized in that The pressure of the machine compression molding is 10-20 MPa.

7. The method for preparing lightweight periclase-spinel aggregate according to claim 1, characterized in that The drying temperature is 90-110° C., and the drying time is 6-10 hours.

8. A lightweight periclase-spinel aggregate, characterized in that The lightweight periclase-spinel aggregate is a lightweight periclase-spinel aggregate prepared by the method for preparing a lightweight periclase-spinel aggregate according to any one of claims 1 to 7.