A method for manufacturing refractory bricks for a permanent magnet ferrite rotary kiln

Abstract

This invention relates to a method for manufacturing refractory bricks in a rotary kiln for permanent magnet ferrite. The method includes the following steps: Step 1: a method for preparing a first component; Step 2: a method for preparing a second component; Step 3: a method for preparing a transition component; Step 4: molding and pressing the bricks; Step 5: heat treatment; Step 6: stacking; Step 7: densification firing. This method solves the problem in wet permanent magnet ferrite production where damp materials infiltrate into the refractory bricks or penetrate into the gaps between the refractory bricks. It avoids the corrosion of the refractory bricks by wet hot water steam, and the damage to the refractory bricks caused by rapid vaporization of moisture in damp areas when the temperature changes in the kiln. Furthermore, when material falls off, because the material is a component of the permanent magnet ferrite composition, it reduces material fluctuations and avoids large-scale material quality fluctuations or quality accidents.

Description

Technical Field

[0001] This invention relates to a method for preparing refractory bricks, specifically a method for manufacturing refractory bricks in a rotary kiln using permanent magnet ferrite, belonging to the technical field of permanent magnet ferrite magnetic powder production equipment. Background Technology

[0002] Pre-sintered permanent magnet ferrite powder is widely used in plastic magnets, toys, electroacoustic equipment, office automation, automotive components, sensing materials, optoelectronic materials, pigments, catalysts, and other fields. Currently, permanent magnet ferrite powder is mainly produced by mixing, sintering, and grinding with auxiliary materials such as iron oxide red and barium carbonate, strontium carbonate, and calcium carbonate.

[0003] The conventional process is as follows: First, iron oxide red, barium carbonate, strontium carbonate, and auxiliary materials are wet-mixed. The mixed slurry is then ground into a particle size of about 1-2 μm using a ball mill, with a water content of about 50%-60%. The slurry is then pumped into a rotary kiln using a mud pump or other equipment, or dehydrated to 30-40% using a dewatering machine, and then pumped into the kiln using an injection pump, with the temperature gradually heated from about 250℃ to about 1300℃.

[0004] The lining of the sintering rotary kiln is mainly composed of refractory bricks and insulating bricks. The layer in contact with the material is made of refractory bricks, which are mainly pressed from calcined hard clay, soft clay, water glass and other materials.

[0005] The current disadvantages of wet-process ferrite pre-fired rotary kiln refractory bricks are:

[0006] (1) Refractory material is prone to falling off: Since the material entering the kiln is a slurry or slag with a moisture content of 30-60%, the material will wet the refractory bricks or the water will penetrate into the gaps between the refractory bricks after contact with the material. During the heating process, the water changes from liquid to gas, generating continuous force, which makes the refractory bricks prone to weakening. As the material continues to enter, the refractory bricks are easily corroded and fall off.

[0007] (2) Contamination of ferrite materials: Because refractory bricks and refractory mortar contain about 35%-70% oxidation rate, as well as materials such as silicon dioxide and sodium silicate, when these materials fall into the main product permanent magnet ferrite materials, they often cause a decrease in magnetic properties. Sometimes, they can even cause a 10-15% decrease in the remanence of the main indicator, and a 3%-5% change in the shrinkage ratio. This causes the downstream customers' processing dimensions to exceed the tolerance range, resulting in unqualified products, batch quality fluctuations, or even quality accidents.

[0008] Therefore, it is necessary to design a manufacturing process for refractory bricks in rotary kilns for permanent magnet ferrite production, taking into account the wet process, functional properties of permanent magnet materials, and quality control requirements, so that the refractory bricks can be better adapted to the high-temperature and humid production process environment.

[0009] Currently published rotary kiln refractory bricks are mainly targeted at the cement and steel production fields. Rotary kiln refractory bricks include materials such as magnesia-chrome bricks, dolomite bricks, magnesia-zirconium bricks, magnesia-calcium-zirconium bricks, magnesia-iron spinel bricks, magnesia-alumina spinel bricks, and iron-alumina spinel bricks. This patent mainly addresses the characteristics and quality requirements of ferrite production processes, employing a binary formula of iron-strontium magnetite and high-alumina components. In the search, no literature or patents have been found that specifically address the refractory brick process design for ferrite product production processes and quality requirements. Summary of the Invention

[0010] This invention addresses the technical problems existing in the prior art by providing a method for manufacturing refractory bricks in a rotary kiln for permanent magnet ferrite. In this method, iron oxide red, strontium carbonate, calcium carbonate, kaolin, and other materials are mixed and kneaded in a predetermined ratio to produce refractory bricks. This method solves the problem of damp materials seeping into the refractory bricks or penetrating into the gaps between the refractory bricks during wet-process permanent magnet ferrite production. It avoids the corrosion of the refractory bricks by wet hot water steam and the damage to the refractory bricks caused by rapid vaporization of moisture in damp areas when the kiln temperature changes. Furthermore, when material falls off, because the material is a component of the permanent magnet ferrite, material fluctuations are reduced, avoiding large-scale material quality fluctuations or quality accidents.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows: a method for manufacturing refractory bricks in a permanent magnet ferrite rotary kiln, the method comprising the following steps:

[0012] Step 1: Preparation method of the first component: Determine the total amount according to the specifications of the rotary kiln. The mass fraction is as follows: iron oxide red 70%–87%, strontium carbonate 5%–25%, calcium carbonate 0.1%–0.5%, chromium oxide 0.1%–1.5%, and water 5–13%. Mix in a mixer for 30–60 minutes.

[0013] Step 2: Preparation method of the second component: 45%–65% alumina, 35%–52% clay, and 3%–5% water are mixed in a mixer for 30–60 minutes.

[0014] Step 3: Preparation of the transition component: Mix the first component and the second component at a ratio of 1:2 to 3, and knead in a mixer for 30 minutes.

[0015] Step 4: Molding and Pressing Bricks: Fill the molding mold of the refractory brick press with materials in a volume percentage ratio of 1:1.5:3, and press them under double-sided pressure at 2.5-2.8 MPa. The side corresponding to the first component material is the inner side, marked with an "I" in the mold imprint; the side corresponding to the second component material is the outer side, marked with an "O" in the mold imprint. The inner and outer sides are stacked separately.

[0016] Step 5: Heat treatment. In the heat treatment furnace, the material is sequentially held at 130℃, 200℃, 500℃, and 700℃ to ensure thorough and even water removal and hardening, preparing it for high-temperature firing.

[0017] Step 6: Stacking: The heat-treated brick blanks are stacked in preparation for firing.

[0018] Step 7: Dense Firing of Refractory Brick Blanks. The first stage of sintering is carried out in a tunnel kiln at a temperature between 1250-1350℃. During this stage, the first component region of the refractory brick develops an iron-strontium hexagonal magnetoplumble structure. The temperature is then raised to approximately 1350-1500℃ for the second stage of sintering, resulting in a common high-alumina spinel refractory structure.

[0019] Compared with existing technologies, this invention has the following advantages: 1. Resistance to chloride ion corrosion: Iron oxide red is a common raw material in the ferrite wet process. Since iron oxide red comes from the Lushner process, it contains about 0.1% to 0.2% chloride ions, and in severe cases, it can reach about 4%. The refractory bricks involved in this patent have better resistance to chloride ions than conventional refractory bricks. 2. Protection against water vapor expansion damage: In the first component area, due to the high temperature, the coating material forms a dense hexagonal crystal structure with ceramic properties. During the production process of permanent magnet ferrite powder, the wet material moves from the kiln tail to the kiln head on the dense ceramic layer, and the temperature gradually increases from room temperature to about 500°C. As it leaves the dense layer formed by this patent, the water changes from liquid to gas and is drawn away by the induced draft fan. The refractory bricks are not easily penetrated or wetted by water, avoiding damage to the strength of the refractory bricks when soaked in water. 3. Significantly reduces the destructive stress caused by water vaporization inside the refractory brick. This patent allows the refractory brick to fuse well with the materials used in production, essentially filling the gaps where water enters the refractory brick, preventing the formation of high-temperature steam inside the brick, and greatly reducing corrosion and damage to the refractory brick; 4. Minimal contamination of ferrite magnetic powder products. The first component area of ​​the refractory brick has the same structural elements as the permanent magnet ferrite, with overlapping proportions. Even if some material falls off and enters the material, the impact on the performance of the main product is relatively small, overcoming the risk of large-scale non-compliance of magnetic powder caused by material detachment from conventional high-alumina bricks. Attached Figure Description

[0020] Figure 1 Schematic diagram of the manufacturing process of the first component.

[0021] Figure 2 Schematic diagram of the manufacturing process of the second component.

[0022] Figure 3 Schematic diagram of the transition component manufacturing process.

[0023] Figure 4 Schematic diagram of the refractory brick manufacturing process. Detailed Implementation

[0024] To enhance understanding of the present invention, the embodiments will be described in detail below with reference to the accompanying drawings.

[0025] Example 1: This example describes the production of kiln bricks for permanent magnet ferrite rotary kilns. The raw materials are iron oxide, strontium carbonate, oxidizing agent, clay, and water. The production process using the method of this invention is as follows:

[0026] (1) Preparation of the first component: See process details. Figure 1 Raw material testing, weighing, mixing, and preparation are as follows: Iron oxide red 83.5%, strontium carbonate 14.5%, calcium carbonate 0.1%, chromium oxide 0.1%, plus 11.0% water by weight of the solid materials. Mix in a mixer for 40 minutes and set aside.

[0027] (2) The second component is prepared; see the detailed process below. Figure 2 Raw material testing, jaw crushing, roller crushing, Raymond milling, weighing and batching, mixing, and preparation.

[0028] Ingredients weighing: 55% alumina, 45% clay, plus 5% water by weight of solid materials, mix in a mixer for 30 minutes and set aside;

[0029] (3) Preparation of transition components: See process details. Figure 3 Weigh and mix the ingredients, then set aside.

[0030] Mix the first and second components in a 1:2 ratio and knead in a mixer for 30 minutes. Set aside.

[0031] (4) Molding and pressing bricks: See process details. Figure 4 ,

[0032] The material is filled into the molding die of the refractory brick press in a volume percentage ratio of 1:1.5:3.

[0033] Under 2.5 MPa, double-sided pressure molding is performed. The side corresponding to the first component material is the inner side, and the mold imprint is "I". The corresponding part of the second component material is the outer side, and the mold imprint is "O". The materials are arranged according to the inner and outer sides.

[0034] (5) Heat treatment:

[0035] In the heat treatment furnace, the process involves sequentially holding the water at 130°C for 3 hours, at 200°C for 2 hours, at 500°C for 2 hours, and at 700°C for 2 hours to ensure even water flow and hardening, thus preparing the furnace for high-temperature firing.

[0036] (6) Palletizing:

[0037] After heat treatment, the brick blanks are stacked to prepare for firing.

[0038] (7) Dense firing

[0039] In a tunnel kiln, the temperature of the refractory brick blanks is gradually increased to 1280-1300℃ and held for 3 hours for the first stage of firing; then the temperature is gradually increased to 1360-138℃ and held for 1 hour for the second stage of sintering.

[0040] This invention produces refractory bricks specifically for wet-process ferrite rotary kilns, which are then laid into the kiln body with the "I" side pointing towards the center and the "O" side pointing towards the kiln shell. During production, when the slurry enters the kiln, high-temperature steam forms on the kiln bricks. At this time, the slurry or dewatered slag fills the gaps, generating a magnetolite structure similar to the material of the bricks on the "I" side. This repairs the kiln bricks, making the refractory bricks more durable. Simultaneously, it avoids introducing undesirable elements such as aluminum and silicon into the kiln brick material, thus preventing fluctuations in the magnetic properties of the product.

[0041] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

[0042] Example 2: This example describes the production of kiln bricks for permanent magnet ferrite rotary kilns. The raw materials include iron oxide, strontium carbonate, oxidizing agent, clay, and water. The production process using the method of this invention is as follows:

[0043] (8) Preparation of the first component: See process details. Figure 1 Raw material testing, weighing, mixing, and preparation are as follows: Iron oxide red 76.2%, strontium carbonate 23.5%, calcium carbonate 0.2%, chromium oxide 0.1%, with an additional 11.0% water. Mix in a mixer for 50 minutes and set aside.

[0044] (9) The second component is prepared; see the detailed process below. Figure 2 Raw material testing, jaw crushing, roller crushing, Raymond milling, weighing and batching, mixing, and preparation.

[0045] Ingredients weighing: 60% alumina, 40% clay, and 5% water. Mix in a mixer for 30 minutes and set aside.

[0046] (10) Preparation of transition components: See process details. Figure 3 Weigh and mix the ingredients, then set aside.

[0047] Mix the first and second components in a 1:2 ratio and knead in a mixer for 30 minutes. Set aside.

[0048] (11) Molding and pressing bricks: See process details. Figure 4 ,

[0049] The material is filled into the molding die of the refractory brick press in a volume percentage ratio of 1:2:3.5.

[0050] Under 2.5 MPa, double-sided pressure molding is performed. The side corresponding to the first component material is the inner side, and the mold imprint is "I". The corresponding part of the second component material is the outer side, and the mold imprint is "O". The materials are arranged according to the inner and outer sides.

[0051] (12) Heat treatment:

[0052] In the heat treatment furnace, the process involves sequentially holding the water at 130°C for 3 hours, at 200°C for 1 hour, at 500°C for 1 hour, and at 700°C for 2 hours to ensure even water flow and hardening, thus preparing the furnace for high-temperature firing.

[0053] (13) Palletizing:

[0054] After heat treatment, the brick blanks are stacked to prepare for firing.

[0055] (14) Dense firing

[0056] In a tunnel kiln, the temperature of the refractory brick blanks is gradually increased to 1280℃ and held for 3 hours for the first stage of firing; then the temperature is gradually increased to 1350℃ and held for 1.5 hours for the second stage of sintering.

[0057] This invention produces refractory bricks specifically for wet-process ferrite rotary kilns, which are then laid into the kiln body with the "I" side pointing towards the center and the "O" side pointing towards the kiln shell. During production, when the slurry enters the kiln, high-temperature steam forms on the kiln bricks. At this time, the slurry or dewatered slag fills the gaps, generating a magnetolite structure similar to the material of the bricks on the "I" side. This repairs the kiln bricks, making the refractory bricks more durable. Simultaneously, it avoids introducing undesirable elements such as aluminum and silicon into the kiln brick material, thus preventing fluctuations in the magnetic properties of the product.

[0058] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for manufacturing refractory bricks for a permanent magnet ferrite rotary kiln, characterized in that, The method includes the following steps: Step 1: Method for preparing the first component Step 2: Method for preparing the second component Step 3: Method for preparing the transition component. Step 4: Molding and pressing bricks. Step 5: Heat treatment, Step 6: Palletizing Step 7: Dense firing; Step 1: Preparation method of the first component: Determine the total amount according to the specifications of the rotary kiln, and the mass fraction is 70%~84% iron oxide red, 5%~14.5% strontium carbonate, 0.1%~0.5% calcium carbonate, 0.1%~1.3% chromium oxide, and add 5-13% water by weight of solid materials. Mix in a mixer for 30~60 minutes. Step 2: Preparation method of the second component: 42%~65% alumina, 35%~58% clay, and 3%~5% water by weight of solid materials. Mix in a mixer for 30~60 minutes. Step 3: Preparation method of transition component: Mix the first component and the second component at a ratio of 1:2 to 3, and knead in a mixer for 30 minutes. Step 4: Molding and pressing bricks: Fill the molding mold of the refractory brick press with materials in a volume percentage ratio of 1:1.5:3, and press them on both sides at 2.5~2.8MPa. The side corresponding to the first component material is the inner side, and the mold mark is "I". The part corresponding to the second component material is the outer side, and the mold mark is "O". The inner and outer sides are stacked separately.

2. The method for manufacturing refractory bricks in a permanent magnet ferrite rotary kiln according to claim 1, characterized in that, Step 5: Heat treatment. In the heat treatment furnace, the water is held at 130℃, 200℃, 500℃ and 700℃ in sequence to fully and evenly promote water flow and hardening, preparing for high-temperature firing.

3. The method for manufacturing refractory bricks in a permanent magnet ferrite rotary kiln according to claim 1, characterized in that, Step 6: Stacking: The heat-treated brick blanks are stacked to prepare for firing.

4. The method for manufacturing refractory bricks in a rotary kiln with permanent magnet ferrite according to claim 1, characterized in that, Step 7: Dense firing. The refractory brick blanks are placed in a tunnel kiln at a temperature between 1250-1350℃ for the first stage. At this time, the first component region of the refractory brick produces an iron-strontium hexagonal magnetic leadstone structure. The temperature is then raised to 1350-1500℃ for the second stage of sintering, producing a common high-alumina spinel refractory structure.

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