Permanent magnetic ferrite rotary kiln refractory brick protection method

Abstract

The invention relates to a method for protecting refractory bricks of a permanent magnetic ferrite rotary kiln, which comprises the following steps of: 1, preparing materials, namely determining the total amount according to the specification of the rotary kiln, preparing tap water according to the material amount of 60-85% by mass and the material amount of 80-87% by mass of iron oxide red, 12-18% by mass of strontium carbonate, 0.1-0.5% by mass of calcium carbonate and 0.2-2.0% by mass of kaolin, 2, mulling: putting the materials and water weighed according to the proportion into mulling equipment, and stirring until the material components are uniform and the viscosity meets the standard, and 3, coating: spraying the mulled viscous slurry onto the inner wall of the rotary kiln in a low-temperature section (the process temperature is about less than or equal to 500 DEG C) of the production process, coating at the kiln tail of 5 meters, and spraying the inner wall of the rotary kiln in a low-temperature section (the process temperature is about less than or equal to 500 DEG C); and 4, compacting: heating by adopting heating equipment or properly pulling a temperature zone to the tail of the kiln in the temperature rising process of the rotary kiln, keeping the speed of the kiln to be slow, and compacting and hardening. And step 5, detecting leakage, measuring the hardness of a compact layer until reaching a qualified standard area after completing high-temperature compaction, and if falling or relatively serious conditions exist, adjusting the formula, repeating the steps 2-4, improving the viscosity of the mulling coating material, and properly improving the percentage of kaolin. The method solves the problem that wet materials are infiltrated into the refractory bricks or infiltrated into gaps of the refractory bricks in wet permanent magnetic ferrite production. Corrosion of damp and hot water vapor to the refractory bricks and damage of the refractory bricks caused by rapid moisture gasification in the damp area when the temperature area in the kiln changes are avoided. And when the materials fall off, the materials are components in the permanent magnetic ferrite components, so that the fluctuation of the materials is reduced, and mass material quality accidents are avoided.

Description

Technical Field

[0001] The invention relates to a method for preparing refractory bricks, in particular to a method for protecting refractory bricks of a permanent magnet ferrite rotary kiln, and belongs to the technical field of permanent magnet ferrite magnetic powder production equipment. Background Art

[0002] Permanent ferrite pre-sintered powder is widely used in plastic magnets, toys, electro-acoustic equipment, office automation, auto parts, sensor materials, optoelectronic materials, pigments, catalysts and other fields. At present, permanent ferrite powder is mainly made by mixing, sintering and grinding red iron oxide and auxiliary materials such as barium carbonate, strontium carbonate and calcium carbonate.

[0003] The conventional process is: first wet-mix red iron oxide, barium carbonate, strontium carbonate and auxiliary materials, grind the mixed slurry into about 1-2um through a ball mill, with a water content of about 50%-60%, and pump the slurry into a rotary kiln through a mud pump or other equipment or dehydrate it to 30-40% through a dehydrator, and then pump it into the kiln through an injection pump, and the temperature is gradually heated from about 250°C to about 1300°C.

[0004] The disadvantages of the current wet ferrite pre-sintering rotary kiln are:

[0005] (1) Refractory materials are easy to fall off: Since the slurry or slag entering the kiln contains 30-60% water, the material will infiltrate the refractory material or the water will penetrate into the gaps of the refractory bricks after contacting the refractory bricks. During the heating process, the water changes from liquid to gas, generating continuous force, which makes the refractory bricks easy to lose strength. As the material continues to enter, the refractory bricks are easily corroded and fall off.

[0006] (2) Pollution of ferrite materials: Since refractory bricks and refractory mud contain about 35%-70% alumina, as well as materials such as silicon dioxide and sodium silicate, when the materials fall off and enter the main product permanent ferrite material, it often leads to a decrease in magnetic properties, and sometimes even causes the main indicator of residual magnetism to drop by 10-15%, and the shrinkage ratio changes by 3%-5%, causing the processing dimensions of downstream customers to exceed the tolerance range, resulting in unqualified products and batch quality accidents. Therefore, a new solution is urgently needed to solve the above technical problems. Summary of the invention

[0007] The present invention is aimed at the technical problems existing in the prior art, and provides a method for protecting refractory bricks of a permanent magnet ferrite rotary kiln. In the scheme, iron oxide red, strontium carbonate, calcium carbonate, kaolin, etc. are mixed and kneaded according to a set ratio, and the kneaded viscous material is coated on the lining of the rotary kiln, air-dried with hot air ≤80°C, and then densified at a temperature of 1300-1400°C. The material ratio is adjusted according to the situation, and the process is repeated until the wet section of the rotary kiln involved in the production process has been coated and densified. The method solves the problem that wet materials infiltrate into refractory bricks or penetrate into the gaps of refractory bricks in the production of wet permanent magnet ferrites. It avoids the corrosion of refractory bricks by wet hot water steam, and the rapid gasification of moisture in the wet area when the temperature zone in the kiln changes, resulting in damage to the refractory bricks. And when the material falls off, since the material is a component of the permanent magnet ferrite, the material fluctuation is reduced, and a large number of material quality accidents are avoided.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows: a permanent ferrite rotary kiln refractory brick protection method, the method comprising the following steps:

[0009] Step 1: Ingredients: Determine the total amount according to the specifications of the rotary kiln, with the mass fraction being 80% to 87% iron oxide red, 12% to 18% strontium carbonate, 0.1% to 0.5% calcium carbonate, 0.2% to 2.0% kaolin, and 8% to 15% tap water by weight of solid materials.

[0010] Step 2: Mixing: Put the weighed materials and water in proportion into the mixing equipment and stir until the material components are uniform and the viscosity meets the standard.

[0011] Step 3: Coating: The mixed viscous slurry is sprayed onto the inner wall of the rotary kiln. The coating is carried out in the low temperature section of the production process (process temperature is about ≤500℃), generally within 0-5 meters from the kiln tail.

[0012] Step 4: Densification: Use heating equipment to heat or use a rotary kiln to heat up. Pull the temperature zone to the end of the kiln appropriately to keep the kiln speed slow for dense hardening.

[0013] Step 5: Check for leaks. After completing high-temperature densification, measure the hardness of the dense layer until it reaches the qualified standard area. If there is any shedding or serious situation, adjust the formula and repeat steps 2-4 to increase the viscosity of the mixed coating and appropriately increase the kaolin percentage.

[0014] Among them, step 1 ingredients: by consulting the equipment data, the rotary kiln is 30 meters long and 2 meters in diameter, and the total amount is determined according to the specifications of the rotary kiln. According to 84.5% iron oxide red, 14.8% strontium carbonate, 0.3% calcium carbonate, 0.4% kaolin, and 15% of the material amount of tap water.

[0015] Among them, step 2 mixing: the weighed materials and water according to the proportion are put into the mixing equipment, and a small magnetic powder slurry mixer is used to stir for 3.5 hours. The material components are uniform and have obvious viscosity.

[0016] Among them, step 3 coating: the mixed viscous slurry is sprayed onto the inner wall of the rotary kiln. Based on experience, 7 meters from the kiln tail to the kiln head are selected for coating. In order to reduce heating energy consumption, a double-layer coating is selected, the kiln speed is reduced to the lowest, the motor withstands 5Hz, 8 minutes and 20 seconds / revolution.

[0017] Among them, step 4 densification: the burner of the pre-firing kiln is used to adjust the flame length and maintain the temperature at 200-400℃.

[0018] Heat for 1 hour, keep at 700-900℃ for 2 hours, make the temperature of the kiln tail reach 1000-1100℃ and keep at this temperature for 2 hours. Among them, step 5: leak detection, after keeping at this temperature, check the inside of the kiln, the density ratio is about 99%, which is basically completed.

[0019] Compared with the prior art, the present invention has the following advantages: 1. The water in the slag and slurry is out of contact with the refractory bricks: due to the high temperature, the coating forms a dense hexagonal crystal structure with ceramic properties, which is not easily penetrated and infiltrated by water. In this way, when the permanent magnet ferrite magnetic powder production process is in progress, the wet material moves from the tail of the kiln to the head of the kiln on the dense layer with dense ceramic properties. During the movement, the temperature gradually increases from room temperature to about 500°C, and it is separated from the dense layer formed by this patent. The water has changed from liquid to gas and is drawn away by the induced draft fan. The corrosion and wear of refractory bricks by water and high-temperature steam are avoided; 2. The maintenance frequency of refractory bricks is reduced: due to the solid-phase reaction in the coating during the high-temperature densification process, the refractory bricks themselves are reinforced, thereby greatly reducing the falling of brick heads at the tail of the kiln, reducing the frequency of stopping the kiln for maintenance, and reducing the production and quality losses caused by starting and stopping;

[0020] 3. Reduce impurities in permanent magnet ferrite products. Since the method of the present invention reduces the shedding of refractory bricks, it reduces the entry of alumina, silicon oxide and other substances into permanent magnet products, reduces product fluctuations, and overcomes the problem of unqualified product quality caused by the large amount of refractory bricks falling off. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the integrated process of the present invention. DETAILED DESCRIPTION

[0022] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0023] Embodiment 1:

[0024] In this embodiment, a wet process permanent ferrite rotary kiln in Anhui Province is used, and the slurry entering the kiln has a moisture content of about 55%. The method of the present invention is used for protection, and the specific process is as follows:

[0025] (1) Ingredients: By consulting the equipment data, the rotary kiln is 30 meters long and 2 meters in diameter. The total amount is determined according to the specifications of the rotary kiln, which is 84.5% red iron ore, 14.8% strontium carbonate, 0.3% calcium carbonate, and 0.4% kaolin. Tap water is added according to 13% of the material volume.

[0026] (2) Mixing: The weighed materials and water are placed in a mixing device according to the proportion. A small magnetic powder slurry mixer (general equipment in the magnetic material industry) is used to stir for 3.5 hours. The material components are uniform and have obvious viscosity.

[0027] (3) Coating: The mixed viscous slurry is sprayed onto the inner wall of the rotary kiln. Based on experience, a coating distance of 7 meters is selected from the kiln tail to the kiln head. In order to reduce heating energy consumption, a double-layer coating is selected. The kiln speed is set to the lowest, and the motor withstands 5Hz, about 8 minutes and 20 seconds per revolution.

[0028] (4) Density: The pre-firing kiln's own burner is used to adjust the flame length, and the temperature at 200-400℃ is maintained for 1 hour, and 700-900℃ is maintained for 2 hours, so that the temperature at the tail of the kiln reaches 1000-1100℃ and is maintained for 2 hours.

[0029] (5) Check for leaks: After insulation, check the inside of the kiln and the density ratio is about 99%, which is basically completed.

[0030] Before the protection scheme of the present invention was implemented, refractory bricks would fall off each time the kiln was started and stopped, and the residual magnetism of the product would decrease and the coercive force would increase. After the scheme of the present invention was implemented, the kiln did not fall off bricks in 10 months after production, and the performance was stable.

[0031] Embodiment 2:

[0032] This embodiment is a wet process permanent magnet ferrite rotary kiln in Zhejiang. Before entering the kiln, the slag is made by a dehydrator, and the moisture content is about 35%. The method of the present invention is used for protection, and the specific process is as follows:

[0033] (1) Ingredients: By consulting the equipment data, the rotary kiln is 36 meters long and 2.2 meters in diameter. The total amount is determined according to the specifications of the rotary kiln, which is 85.0% red iron ore, 13.5% strontium carbonate, 0.1% calcium carbonate, and 1.4% kaolin. Tap water is added according to 15% of the material volume.

[0034] (2) Mixing: The weighed materials and water are placed in a mixing device according to the proportion, and a stirring kettle (general equipment in the magnetic material industry) is used for stirring for 2.0 hours. The material components are uniform, the color is consistent, and there is obvious viscosity.

[0035] (3) Coating: The mixed viscous slurry is sprayed onto the inner wall of the rotary kiln. Based on experience, a coating distance of 9 meters is selected from the kiln tail to the kiln head. In order to reduce heating energy consumption, a double-layer coating is selected and the kiln speed is set to the lowest, about 7 minutes per revolution.

[0036] (4) Density: The pre-firing kiln’s own burner is used to adjust the flame length, and the temperature at 150-250℃ is maintained for 3 hours, and 700-850℃ is maintained for 2 hours, so that the temperature at the tail of the kiln reaches 1000-1250℃ and is maintained for 4 hours.

[0037] (5) Check for leaks: After insulation, check the inside of the kiln to ensure it is dense and complete.

[0038] Before the protection scheme of the present invention was implemented, refractory bricks occasionally fell off. Through the implementation of the scheme of the present invention, the kiln was used for 6 months after production without any brick falling and the product performance was normal.

[0039] It should be noted that the above embodiments are not intended to limit the protection scope of the present invention, and equivalent changes or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A permanent magnet ferrite rotary kiln refractory brick protection method, characterized in that: The method The following steps are involved: The following steps are involved: Step 1: Ingredients: Determine the total amount according to the specifications of the rotary kiln, with a mass fraction of 80% to 87% iron oxide red, 12% to 18% strontium carbonate, 0.1% to 0.5% calcium carbonate, 0.2% to 2.0% kaolin, and 8% to 15% tap water according to the weight of solid materials. Step 2: Mixing: Put the weighed materials and water in proportion into the mixing equipment and stir until the material components are uniform and the viscosity meets the standard. Step 3: Coating: The mixed viscous slurry is sprayed onto the inner wall of the rotary kiln. The coating is carried out in the low temperature section of the production process (process temperature is about ≤500℃), 5 meters from the kiln tail. Step 4: Densification: Use heating equipment to heat or use a rotary kiln to heat up. Appropriately pull the temperature zone to the end of the kiln, keep the kiln speed slow, and harden the densification. Step 5: Check for leaks. After completing high-temperature densification, measure the hardness of the dense layer until it reaches the qualified standard area. If there is any shedding or serious situation, adjust the formula and repeat steps 2-4 to increase the viscosity of the mixed coating and appropriately increase the kaolin percentage.

2. The method for protecting refractory bricks of a permanent magnet ferrite rotary kiln according to claim 1, characterized in that: Step 1 Batching: By consulting the equipment data, the rotary kiln is 30 meters long and 2 meters in diameter. The total amount is determined according to the specifications of the rotary kiln, according to 84.5% red iron ore, 14.8% strontium carbonate, 0.3% calcium carbonate, 0.4% kaolin, and 65% of the material amount of tap water.

3. The method for protecting refractory bricks of a permanent magnet ferrite rotary kiln according to claim 1, characterized in that: Step 2: Mixing: The weighed materials and water according to the proportion are put into the mixing equipment, and a small magnetic powder slurry mixer is used to stir for 3.5 hours. The material components are uniform and have obvious viscosity.

4. The method for protecting refractory bricks of a permanent magnet ferrite rotary kiln according to claim 1, characterized in that: Step 3: Coating: Spray the mixed viscous slurry onto the inner wall of the rotary kiln. Based on experience, a coating distance of 7 meters is selected from the kiln tail to the kiln head. In order to reduce heating energy consumption, a double-layer coating was selected, the kiln speed was set to the lowest, and the motor tolerance was 5Hz, 8 minutes and 20 seconds per revolution.

5. The method for protecting refractory bricks of permanent magnet ferrite rotary kiln according to claim 1, characterized in that: Step 4: Densification: The pre-firing kiln’s own burner is used to adjust the flame length and keep the temperature at 200-400℃ for 1 hour. Keep at 700-900℃ for 2 hours, so that the temperature at the tail of the kiln reaches 1000-1100℃ and keep it for 2 hours.

6. The method for protecting refractory bricks of a permanent magnet ferrite rotary kiln according to claim 1, characterized in that: Step 5: Check for leaks. After insulation, check the inside of the kiln. The density ratio is about 99%, which is basically completed.

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