A ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material and its preparation method

Abstract

This invention provides a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material and its preparation method. The aluminum-chromium slag produced by the aluminothermic smelting of metallic chromium is used as the main raw material. A certain amount of chromium trioxide, a small amount of MgO sintering aid, and ZrO2 reinforcing agent are added, and the mixture is then shaped and calcined to produce a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material. This material is mainly composed of Mg(Al,Cr)2O4 spinel, (Al,Cr)2O3 solid solution, and ZrO2. This composite refractory material exhibits excellent mechanical properties, good thermal stability, good slag erosion resistance, high strength, long service life, and high energy efficiency. This technical method can effectively improve the performance and slag erosion resistance of traditional chromium corundum refractories, and features a short process, low energy consumption, and simple production process.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials and relates to a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material. Background Technology

[0002] The molten reduction ironmaking process, due to its wide adaptability to raw materials, avoidance of coke use, low environmental pollution, and ease of establishing green plants, has long been considered the future direction of ironmaking. However, the oxy-fuel molten reduction process integrates the reduction and oxidation processes within a single reactor. The molten gasifier exhibits high oxidation levels, low slag basicity, high FeO content, violent molten pool fluctuations, severe gas flow erosion, and high furnace temperatures. This harsh high-temperature corrosive environment severely damages refractory materials. Simultaneously, the rapid molten reduction and gasification reactions result in high-FeO content foamy slag that significantly corrodes the refractory materials. The high-intensity stirring system within the hearth gives the melt strong fluidity, and the violent surface fluctuations further exacerbate the erosion and corrosion of the furnace lining. The HIsmelt equipment at the Kwinana plant in Australia selected Al2O3-Cr2O3 bricks with excellent slag resistance and suitability for use in oxidizing / reducing atmospheres, but its performance has been unsatisfactory. The reactor experiences severe corrosion annually, requiring partial lining replacement, and necessitates complete replacement of the entire reactor lining every two years. Therefore, there is an urgent need to develop high-temperature refractory materials that are strong, resistant to high temperatures, resistant to oxidation and erosion, have good thermal stability, and are highly resistant to slag erosion, suitable for use in the all-oxygen molten reduction ironmaking process. This is of great significance for promoting the development of low-carbon metallurgy and environmental protection. Summary of the Invention

[0003] The purpose of this invention is to provide a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material to overcome the problems of poor mechanical properties, poor slag erosion resistance, and short service life of chromium-containing refractories used in industrial kilns. A ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material is prepared using aluminum-chromium slag residue, which can significantly improve the density, mechanical properties, and slag erosion resistance of ordinary chromium-containing refractories.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material, wherein the mineral composition of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material consists of Mg(Al,Cr)2O4 spinel, (Al,Cr)2O3 solid solution and ZrO2, and the weight percentage range of its chemical composition is: Al2O3 32.4-35.1%, Cr2O3 48.6-52.7%, ZrO2 9-9.8%, MgO 2.5%-10%. Specifically, the weight percentage of its chemical composition can be 32.4%, 33.3%, 34.2% or 35.1% for Al2O3, 48.6%, 50%, 51.3% or 52.7% for Cr2O3, 9%, 9.3%, 9.5% or 9.8% for ZrO2, and 2.5%, 5%, 7.5% or 10% for MgO.

[0005] In the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory, the Mg(Al,Cr)2O4 spinel is distributed between the (Al,Cr)2O3 particles, which inhibits the growth of solid solution grains, reduces the porosity of the composite refractory, and effectively improves the mechanical properties of the composite material.

[0006] This invention also discloses a method for preparing a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material, the preparation method comprising the following steps:

[0007] S10: Add a certain percentage of chromium trioxide, a small amount of magnesium oxide, and a trace amount of zirconium dioxide to aluminum chromium slag for batching, mixing, and material forming.

[0008] Drying of S20:ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material.

[0009] Reaction sintering of S30:ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material.

[0010] In step S10, the batching and mixing of the composite refractory material refers to mixing and homogenizing aluminum-chromium slag, chromium trioxide, dolomite, and zirconium dioxide in a certain proportion. Specifically, the weight percentages of the aluminum-chromium slag are 40–44.89%, chromium trioxide is 40–45.11%, zirconium dioxide is 10%, and magnesium oxide is 2.5–10%. The forming of the composite high-temperature refractory material involves using a refractory forming machine to prepare a wet composite refractory blank of the desired shape. In specific implementations, the weight percentages of the aluminum-chromium slag can be 40%, 41.23%, 42.50%, or 43.72%, the weight percentages of the chromium trioxide can be 40%, 41.27%, 42.50%, or 43.78%, and the weight percentages of the magnesium oxide can be 2.5%, 5%, 7.5%, or 10%.

[0011] The drying of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material in step S20 involves naturally drying the molded composite refractory wet blank at room temperature for 48 hours, and then drying it with a belt dryer at a temperature of 300-500℃ for 8-20 hours.

[0012] The reaction sintering of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material described in step S30 involves feeding the dried composite refractory wet blank into a high-temperature tunnel kiln for high-temperature calcination at 1500–1600°C for 4–6 hours. After calcination, the refractory is cooled to room temperature by slow cooling within the furnace, thus obtaining the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material of this invention.

[0013] The ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material exhibits the following properties: relative density of 86.95–93.40%, volume shrinkage of 5.85–12.52%, porosity of 3.75–7.42%, hardness of 10.5–14.2 GPa, compressive strength of 163.7–275.4 MPa, flexural strength of 55.8–80.5 MPa, refractoriness of 1760–1800℃, and thermal stability (1100℃ – number of water cooling cycles) of 9–12.

[0014] Compared with existing material technology methods, the present invention has the following advantages:

[0015] 1. The ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material has the characteristics of high density, good mechanical properties and thermal shock resistance, good slag erosion resistance, high strength, long service life and high energy efficiency.

[0016] 2. This ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material is mainly composed of Mg(Al,Cr)2O4 spinel, (Al,Cr)2O3 solid solution, and ZrO2. The Mg(Al,Cr)2O4 spinel formed by the reaction is distributed between the (Al,Cr)2O3 particles, inhibiting the growth of solid solution grains and reducing the porosity of the composite refractory material.

[0017] 3. This technical method significantly improves the mechanical properties and slag erosion resistance of traditional aluminochromium refractories. It features a short process, low energy consumption, and simple production process. The prepared ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractories are a new type of high-temperature erosion-resistant refractories. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow of the method of the present invention;

[0019] Figure 2 The XRD pattern of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material.

[0020] Figure 3 SEM micrograph of ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material.

[0021] Figure 4 The mechanical properties of ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory are described.

[0022] Figure 5 Macroscopic photograph of ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material after being eroded by high-temperature slag. Detailed Implementation

[0023] The following embodiments illustrate the method of the present invention. It should be understood that these embodiments are merely for further illustrating the implementation of the present invention and are not intended to limit the present invention.

[0024] Tables 1 and 2 show the chemical composition of aluminum-chromium slag raw materials and the batching scheme of composite refractory materials, respectively.

[0025] Table 1 Chemical composition of aluminum-chromium slag

[0026] Aluminum chromium slag <![CDATA[Al2O3]]> <![CDATA[Cr2O3]]> MgO <![CDATA[SiO2]]> CaO Mass percentage (%) 84.5 14.2 0.14 0.11 1.05

[0027] Table 2. Batching scheme for ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material

[0028]

[0029]

[0030] Example 1: The weight percentage of the basic raw materials for ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory is as follows: 43.72% aluminum chromium slag, 43.78% chromium trioxide, 10% zirconium dioxide, and 2.5% magnesium oxide. The particle size of the aluminum chromium slag is 2-4 mm, the Cr2O3 particle size is 30-50 mesh, the zirconium dioxide particle size is 30-50 mesh, and the magnesium oxide particle size is 30-50 mesh. After mixing the basic raw materials, a composite refractory wet blank is prepared using a refractory forming machine. The formed composite refractory wet blank is then naturally dried at room temperature for 48 hours, followed by drying in a 300℃ drying kiln for 20 hours. After drying, the dried composite refractory wet blank is fed into a high-temperature tunnel kiln for reaction sintering. The final sintering temperature is 1600℃, and the sintering time is 4 hours. The sintering process was as follows: holding at 500℃ for 5 hours, holding at 1000℃ for 3 hours, and holding at 1600℃ for 4 hours. After calcination, the refractory was cooled to room temperature by slow cooling in the furnace, yielding a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory, denoted as S1. Its SEM micrograph is shown below. Figure 3 (a).

[0031] The weight percentages of Al2O3, Cr2O3, ZrO2, and MgO in the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory are 35.1%, 52.7%, 9.8%, and 2.5%, respectively. The mineral composition of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory mainly consists of Mg(Al,Cr)2O4 spinel, (Al,Cr)2O3 solid solution, and ZrO2. Its XRD pattern can be found in [reference needed]. Figure 2 -S1. The ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material has a relative density of 86.95%, a volume shrinkage rate of 5.85%, a porosity of 7.42%, a hardness of 10.5 GPa, a compressive strength of 163.7 MPa, a flexural strength of 55.8 MPa, a refractoriness of 1800℃, and a thermal stability (1100℃ - water cooling cycles) of 12. Its mechanical properties are described in [reference needed]. Figure 4 -S1. Furthermore, this ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material also exhibits excellent resistance to slag erosion. Even after prolonged high-temperature erosion, it retains its complete refractory morphology without dissolution. See the macroscopic morphology photographs after erosion. Figure 5 -S1.

[0032] Example 2: The weight percentage of the basic raw materials for the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory is as follows: 42.50% aluminum chromium slag, 42.50% chromium trioxide, 10% zirconium dioxide, and 5% magnesium oxide. The particle size of the aluminum chromium slag is 1-3 mm, the Cr2O3 particle size is 40-60 mesh, the zirconium dioxide particle size is 40-60 mesh, and the magnesium oxide particle size is 40-60 mesh. After mixing the basic raw materials, a composite refractory wet blank is prepared using a refractory forming machine. The formed composite refractory wet blank is then naturally dried at room temperature for 48 hours, followed by drying in a 350℃ drying kiln for 16 hours. After drying, the dried composite refractory green blank is fed into a high-temperature tunnel kiln for reaction sintering. The final sintering temperature is 1575℃, and the sintering time is 5 hours. The sintering process was as follows: holding at 500℃ for 5 hours, holding at 1000℃ for 3 hours, and holding at 1575℃ for 5 hours. After calcination, the refractory was cooled to room temperature by slow cooling in the furnace, yielding a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory, denoted as S2. Its SEM micrograph is shown below. Figure 3 (b)

[0033] The weight percentages of Al2O3, Cr2O3, ZrO2, and MgO in the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory are 34.2%, 51.3%, 9.5%, and 5%, respectively. The mineral composition of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory mainly consists of Mg(Al,Cr)2O4 spinel, (Al,Cr)2O3 solid solution, and ZrO2. Its XRD pattern can be found in [reference needed]. Figure 2 -S2. The ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material has a relative density of 90.05%, a volume shrinkage rate of 9.65%, a porosity of 6.21%, a hardness of 12.6 GPa, a compressive strength of 184.5 MPa, a flexural strength of 65.7 MPa, a refractoriness of 1785℃, and a thermal stability (1100℃ - water cooling cycles) of 11 times. Its mechanical properties are described in [reference needed]. Figure 4 -S2. Furthermore, this ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material also exhibits excellent resistance to slag erosion. Even after prolonged high-temperature erosion, it retains its complete refractory morphology without dissolution. See the macroscopic morphology photographs after erosion. Figure 5 -S2.

[0034] Example 3: The weight percentage of the basic raw materials for ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory is as follows: 41.23% aluminum chromium slag, 41.27% chromium trioxide, 10% zirconium dioxide, and 7.5% magnesium oxide. The particle size of the aluminum chromium slag is 0.5–2 mm, the particle size of Cr2O3 is 50–70 mesh, the particle size of zirconium dioxide is 50–70 mesh, and the particle size of magnesium oxide is 50–70 mesh. After mixing the basic raw materials, a composite refractory wet blank is prepared using a refractory forming machine. The formed composite refractory wet blank is then naturally dried at room temperature for 48 hours, followed by drying in a 400℃ drying kiln for 12 hours. After drying, the dried composite refractory green blank is fed into a high-temperature tunnel kiln for reaction sintering. The final sintering temperature is 1550℃, and the sintering time is 6 hours. The sintering process was as follows: holding at 500℃ for 5 hours, holding at 1000℃ for 3 hours, and holding at 1550℃ for 6 hours. After calcination, the refractory was cooled to room temperature by slow cooling in the furnace, yielding a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory, designated S3. Its SEM micrograph is shown below. Figure 3 (c)

[0035] The weight percentages of Al2O3, Cr2O3, ZrO2, and MgO in the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory are 33.3%, 50%, 9.3%, and 7.5%, respectively. The mineral composition of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory mainly consists of Mg(Al,Cr)2O4 spinel, (Al,Cr)2O3 solid solution, and ZrO2. Its XRD pattern can be found in [reference needed]. Figure 2 -S3. The ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material has a relative density of 92.11%, a volume shrinkage rate of 10.07%, a porosity of 4.45%, a hardness of 13.7 GPa, a compressive strength of 232.6 MPa, a flexural strength of 72.3 MPa, a refractoriness of 1770℃, and a thermal stability (1100℃ - water cooling cycles) of 10 times. Its mechanical properties are described in [reference needed]. Figure 4 -S3. Furthermore, this ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material also exhibits excellent resistance to slag erosion. Even after prolonged high-temperature erosion, it retains its complete refractory morphology without dissolution. See the macroscopic morphology photographs after erosion. Figure 5 -S3.

[0036] Example 4: The weight percentage of the basic raw materials for ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory is as follows: 40% aluminum chromium slag, 40% chromium trioxide, 10% zirconium dioxide, and 10% magnesium oxide. The particle size of the aluminum chromium slag is 0.2–1.5 mm, the particle size of Cr2O3 is 60–80 mesh, the particle size of zirconium dioxide is 60–80 mesh, and the particle size of magnesium oxide is 60–80 mesh. After mixing the basic raw materials, a composite refractory wet blank is prepared using a refractory forming machine. The formed composite refractory wet blank is then naturally dried at room temperature for 48 hours, followed by drying in a 500℃ drying kiln for 8 hours. After drying, the dried composite refractory green blank is fed into a high-temperature tunnel kiln for reaction sintering. The final sintering temperature is 1525℃, and the sintering time is 7 hours. The sintering process was as follows: holding at 500℃ for 5 hours, holding at 1000℃ for 3 hours, and holding at 1525℃ for 7 hours. After calcination, the refractory was cooled to room temperature by slow cooling in the furnace, yielding a ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory, designated S4. Its SEM micrograph is shown below. Figure 3 (d)

[0037] The weight percentages of Al2O3, Cr2O3, ZrO2, and MgO in the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory are 32.4%, 48.6%, 9%, and 10%, respectively. The mineral composition of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory mainly consists of Mg(Al,Cr)2O4 spinel, (Al,Cr)2O3 solid solution, and ZrO2. Its XRD pattern can be found in [reference needed]. Figure 2 -S4. The ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material has a relative density of 93.40%, a volume shrinkage rate of 12.52%, a porosity of 3.75%, a hardness of 14.2 GPa, a compressive strength of 275.4 MPa, a flexural strength of 80.5 MPa, a refractoriness of 1760℃, and a thermal stability (1100℃ - water cooling cycles) of 9 times. Its mechanical properties are described in [reference needed]. Figure 4 -S4. Furthermore, this ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory material also exhibits excellent resistance to slag erosion. Even after prolonged high-temperature erosion, it retains its complete refractory morphology without dissolution. See the macroscopic morphology photographs after erosion. Figure 5 -S4.

[0038] Figure 3The image shows a SEM micrograph of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory. It can be seen that the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory has a very dense microstructure, with micropores only 2-5 μm in size. Increasing the MgO content significantly reduces the number and size of pores in the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory, effectively improving the density of the composite refractory. Figure 4 The mechanical properties of ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory are shown. It can be seen that with the increase of MgO content, the hardness, compressive strength, flexural strength, and thermal shock resistance loss rate of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory are significantly improved, effectively enhancing the mechanical properties of the composite refractory. This is mainly attributed to the formation and increased density of Mg(Al,Cr)2O4. Figure 5 This is a macroscopic photograph of the ZrO2-(Al,Cr)2O3-Mg(Al,Cr)2O4 composite refractory after being eroded by high-temperature slag. It can be seen that the refractory retains its complete morphology even after prolonged high-temperature erosion; only slag penetration occurred, without erosion or dissolution. The composite refractory exhibits excellent resistance to slag erosion.

Claims

1. A ZrO2-(Al, Cr)2O3-Mg(Al, Cr)2O4 composite refractory material, characterized in that: The mineral composition of the ZrO2-(Al,Cr)2O3-Mg(Al, Cr)2O4 composite refractory material consists of Mg(Al, Cr)2O4 spinel, (Al, Cr)2O3 solid solution, and ZrO2. The weight percentages of its chemical composition range as follows: Al2O3 32.4–35.1%, Cr2O3 48.6–52.7%, ZrO2 9–9.8%, and MgO 2.5%–10%. The preparation method of the ZrO2-(Al, Cr)2O3-Mg(Al, Cr)2O4 composite refractory material includes the following steps: S10: A certain mass percentage of chromium trioxide, a small amount of magnesium oxide, and a trace amount of zirconium dioxide are added to aluminum-chromium slag for batching. After the basic raw materials are mixed evenly, a composite refractory wet blank is prepared using a refractory forming machine. The weight percentage range of each component is as follows: 40-43.72% aluminum-chromium slag, 40-43.78% chromium trioxide, 10% zirconium dioxide, and 2.5-10% magnesium oxide. S20: The composite refractory green blank is naturally dried at room temperature for 48 hours, and then dried in a belt dryer at a temperature of 300-500℃ for 10-20 hours to obtain the composite refractory green blank. S30: The composite refractory green billet is fed into a high-temperature tunnel kiln for high-temperature calcination at a temperature of 1500-1600℃ for 4-6 hours. After calcination, the refractory is cooled to room temperature by slow cooling in the furnace to obtain ZrO2-(Al,Cr)2O3-Mg(Al, Cr)2O4 composite refractory material.

2. The ZrO2-(Al, Cr)2O3-Mg(Al, Cr)2O4 composite refractory material as described in claim 1, characterized in that: The ZrO2-(Al, Cr)2O3-Mg(Al, Cr)2O4 composite refractory material has a relative density of 86.95-93.40%, a volume shrinkage rate of 5.85-12.52%, and a porosity of 3.75-7.42%.

3. The ZrO2-(Al, Cr)2O3-Mg(Al, Cr)2O4 composite refractory material as described in claim 1, characterized in that: The ZrO2-(Al, Cr)2O3-Mg(Al, Cr)2O4 composite refractory material has a hardness of 10.5–14.2 GPa, a compressive strength of 163.7–275.4 MPa, a flexural strength of 55.8–80.5 MPa, a refractoriness of 1760–1800℃, and a thermal stability test at 1100℃ followed by water cooling of 9–12 cycles.

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