Method for on-line repair of refractory in a rotary kiln

Abstract

The application discloses a rotary kiln refractory on-line repairing method, which can realize full-process mechanized operation and out-kiln operation, reduces labor intensity of workers, improves essential safety degree of operation, reduces artificial cost and safety protection cost, adopts self-reaction of materials such as aluminum sulfate, potassium sulfate, quartz and bentonite to repair the rotary kiln refractory, does not need to prepare refractory bricks or blocks, and has low overall material cost; the rotary kiln refractory repairing time is effectively reduced, the rotary kiln operation rate is improved; the refractory thickness can be supplemented at any time, long-time thin refractory operation of the traditional rotary kiln is avoided, the heat preservation capacity and thermal efficiency in the production process of the rotary kiln are improved, and the overall economy of the rotary kiln production is improved.

Description

Technical Field

[0001] This invention belongs to the fields of building materials, metallurgy, chemical industry and equipment systems, and relates to an online repair method for rotary kiln refractory materials. Background Technology

[0002] Rotary kilns are a common industrial equipment used in cement and building material production, ferrous metal magnetization roasting, direct metal reduction, and related material drying and heating. This equipment has advantages such as fast heat transfer speed and large scale potential, occupying a huge market space and having great potential for future industrialization.

[0003] Mullite or a mixture with mullite as the main crystalline phase and anorthite as the bonding phase has advantages such as high refractoriness, strong flexural and compressive strength, good thermal shock stability, and abundant resources. Therefore, it is often used in the production of rotary kiln refractory materials to protect the rotary kiln lining and improve the thermal efficiency of the rotary kiln.

[0004] Due to the periodic temperature changes of hot airflow and materials, the scouring and abrasion caused by high-temperature materials, and the extrusion and mechanical forces caused by the tilt and rotation of the rotary kiln, the consumption rate of refractory materials in rotary kilns is relatively fast. The replacement cycle of refractory materials in cement and metallurgical rotary kilns is generally 1 to 2 years. Moreover, due to the limitations of current technology, all refractory material replacements are carried out by rebuilding or pouring, which generally takes 30 to 50 days. Limited by the existing refractory material repair methods, all rotary kilns suffer from problems such as short operation cycles, high repair costs, long periods of operation with defects, and low thermal efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide an online repair method for rotary kiln refractory materials to solve the problems of short operation cycle, high repair cost, long operation time with defects, and low thermal efficiency in the existing reconstruction or pouring modes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for online repair of refractory materials in rotary kilns includes the following steps:

[0008] 1) Mix aluminum sulfate, potassium sulfate, quartz, and bentonite in a mass ratio of 100:(180~220):(12~16):(2~6), and grind the mixture to -1mm.

[0009] 2) Add water accounting for 15%~20% of the total weight of the mixture to the mixture, granulate it using a pelletizer and then dry it to form granules with a particle size diameter of -50mm, a moisture content of 5%~8%, and a strength of over 200N.

[0010] 3) Wash the river sand to remove impurities and then dry it, ensuring that its particle size is 0.2~0.5mm and its moisture content is less than 8%;

[0011] 4) Ensure that the rotary kiln operates at a speed of 1~3Hz under no-load, and that the kiln tail induced draft system, dust removal system and desulfurization system are operating normally. Through the combustion method of the rotary kiln head burner, the temperature of the section of the rotary kiln to be repaired and the area to the kiln head reaches 1100~1300℃, so as to remove the low melting point impurities adhering to the refractory material of the section to be repaired.

[0012] 5) Control the rotary kiln to run at a speed of 1~3Hz under no-load. Inject the granules obtained in step 2) into the rotary kiln through the air pressure injection system at the kiln head. Visually observe that the landing point is concentrated between the kiln tail and the section to be repaired. The granules gradually roll to the depression of the section to be repaired and gradually heat up to become a liquid phase with higher viscosity. The substances that generate the liquid phase begin to react from the inside to the surface, and after generating mullite with a higher melting point, they gradually solidify into solid phase refractory material.

[0013] 6) Continue to operate the rotary kiln at a speed of 1~3Hz, and maintain the temperature of the section to be repaired at 700~1100℃. The subsequent granules will continuously roll to the depression of the section to be repaired, and will be continuously bonded, liquefied, reacted and solidified. Stop spraying when the depression of the section to be repaired is consistent with the height of the surrounding kiln wall.

[0014] 7) After the repair is completed, the excess liquid phase is discharged with the rotation of the rotary kiln. The river sand obtained in step 3) is added from the feed end of the rotary kiln tail. The rotation speed of the rotary kiln is increased to 5~8Hz. The river sand will wash away the residual liquid phase and the loosely bonded solid phase in the repair area of ​​the rotary kiln. The material formed after washing is discharged from the kiln head of the rotary kiln and recycled as river sand.

[0015] Under the action of the induced draft system, the dust generated in the above process enters the dust removal system and desulfurization system from the kiln tail, and is discharged in compliance with standards after dust removal and desulfurization.

[0016] The repair principle of this invention is as follows:

[0017] When the temperature of the granules in the rotary kiln reaches 770℃, the aluminum sulfate in the granules begins to decompose, generating solid alumina with high surface activity and gaseous sulfur trioxide (see Formula 1). The sulfur trioxide escapes to the outside of the material layer and, under the action of the induced draft fan, passes through the dust removal system and is finally fixed in the desulfurization system.

[0018] Al2(SO4)3→Al2O3+3SO3(1)

[0019] When the temperature of the granules in the rotary kiln reaches 1067℃, the potassium sulfate in the granules reaches its melting point and melts; the silica in the quartz and bentonite begins to dissolve in the potassium sulfate solution, and reacts with the solid active alumina in liquid form to generate solid active mullite (see Formula 2). The newly formed solid active mullite is released into the original refractory surface in the potassium sulfate solution, combines with the mullite crystals in the original refractory, and gradually grows, which macroscopically manifests as an increase in the size of the refractory material.

[0020] 3Al2O3+2SiO2→3Al2O3·2SiO2 (2)

[0021] As the reaction proceeds, the proportions of aluminum sulfate, quartz, and bentonite in the liquid phase decrease significantly, and the main component in the liquid phase changes to potassium sulfate, which is eventually discharged from the rotary kiln head. After being discharged from the rotary kiln head, it is cooled into a solid phase by ambient air, and then recycled as potassium sulfate after crushing and fine grinding.

[0022] Compared with traditional rotary kiln refractory reconstruction or casting methods, the present invention has the following advantages:

[0023] (1) Reduce the labor intensity of workers

[0024] This invention enables fully mechanized operations, eliminating the need for personnel to dismantle and transport old refractory materials, transport new refractory materials, weld anchors, and perform masonry work, thus significantly reducing the labor intensity of workers.

[0025] (2) Improve the inherent safety of the operation

[0026] This invention enables full-process external kiln operations without requiring personnel to enter the rotary kiln, and also avoids the safety hazards associated with the unconventional operation of traditional rotary kiln refractory repair.

[0027] (3) Improve the economic efficiency of rotary kiln equipment

[0028] This invention enables fully mechanized operation and off-kiln work, reducing labor intensity and improving inherent safety while lowering labor and safety costs. It utilizes the self-reaction of materials such as aluminum sulfate, potassium sulfate, quartz, and bentonite for rotary kiln refractory repair, eliminating the need for refractory bricks or blocks and resulting in lower overall material costs. It effectively reduces rotary kiln refractory repair time and increases rotary kiln operating rate. Furthermore, it allows for on-the-fly refractory replenishment, avoiding prolonged thin-refractory operation in traditional rotary kilns, improving insulation and thermal efficiency during production, and enhancing the overall economic efficiency of rotary kiln production. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0030] The present invention will be further explained and described below with reference to specific embodiments. Example

[0031] 1) The rotary kiln using the process of this invention has a total length of 48m, an internal diameter of 2.2m, a refractory material thickness of 200mm, and the location of the breakage is 8~17m from the kiln head. The refractory material is corundum mullite castable with an Al2O3 content of 71.42%.

[0032] 2) Mix aluminum sulfate, potassium sulfate, quartz, and bentonite in a mass ratio of 100:200:14:3, and grind the mixture to -1mm.

[0033] 3) Add water accounting for 18% of the total weight of the mixture to the mixture, granulate it using a pelletizer, and dry it to form granules with a particle size diameter of -50mm, a moisture content of 6%, and an average strength of 270N.

[0034] 4) Wash the river sand to remove impurities and then dry it to a moisture content of 6% and a sand particle size of 0.2~0.5mm;

[0035] 5) Control the rotary kiln to run at 1Hz under no-load, and ensure that the kiln tail induced draft system, dust removal system and desulfurization system are running normally. Through the combustion method of the rotary kiln head burner, the temperature of the section to be repaired and the area to the kiln head of the rotary kiln reaches 1100~1300℃. After 5 hours, the low melting point impurities adhering to the refractory material of the section to be repaired will be completely removed.

[0036] 6) Control the rotary kiln to run at 1Hz under no-load. Inject the granules obtained in step 2) into the rotary kiln through the air pressure injection system at the kiln head. Visually observe that the landing point is concentrated between the kiln tail and the section to be repaired. The granules gradually roll to the depression of the section to be repaired and gradually heat up to become a liquid phase with higher viscosity. The substances that generate the liquid phase start to react from the inside to the surface, and after generating mullite refractory with a higher melting point, they gradually solidify into a solid phase.

[0037] 7) Continue to operate the rotary kiln at a speed of 1Hz, and maintain the temperature of the section to be repaired at 1000~1100℃. The subsequent granules will continuously roll to the depression of the section to be repaired, and will be continuously bonded, liquefied, reacted and solidified. Stop spraying when the depression of the section to be repaired is consistent with the height of the surrounding kiln wall. A total of 1.8 tons of granules will be sprayed.

[0038] 8) After the repair is completed, stop the combustion and heating of the rotary kiln head burner, add the river sand obtained in step 3) from the feed end of the rotary kiln tail, increase the rotary kiln speed to 8Hz, and the river sand will wash away the residual liquid phase and loosely bonded solid phase in the repair area of ​​the rotary kiln. The material formed after washing is discharged from the rotary kiln head and recycled as river sand.

[0039] 9) After the overall work is completed, the rotary kiln head burner is used to provide heat and raise the temperature of the section of the rotary kiln to be repaired to 1000~1100℃. At this time, a handheld thermometer is used to measure the temperature of the outer wall of the section of the rotary kiln to be repaired. The temperature is 190~230℃, which is not significantly different from the temperature of the surrounding area, indicating that the refractory repair work has achieved the expected results.

Claims

1. A method for online repair of refractory materials in rotary kilns, characterized in that, Includes the following steps: 1) Mix aluminum sulfate, potassium sulfate, quartz, and bentonite in a mass ratio of 100:(180~220):(12~16):(2~6), and grind the mixture to -1mm. 2) Add water accounting for 15%~20% of the total weight of the mixture to the mixture, granulate it using a pelletizer and then dry it to form granules with a particle size diameter of -50mm, a moisture content of 5%~8%, and a strength of over 200N. 3) Wash the river sand to remove impurities and then dry it, ensuring that its particle size is 0.2~0.5mm and its moisture content is less than 8%; 4) Ensure that the rotary kiln operates at a speed of 1~3Hz under no-load, and that the kiln tail induced draft system, dust removal system and desulfurization system are operating normally. Through the combustion method of the rotary kiln head burner, the temperature of the section of the rotary kiln to be repaired and the area to the kiln head reaches 1100~1300℃, so as to remove the low melting point impurities adhering to the refractory material of the section to be repaired. 5) Control the rotary kiln to run at a speed of 1~3Hz under no-load. Inject the granules obtained in step 2) into the rotary kiln through the air pressure injection system at the kiln head. Visually observe that the landing point is concentrated between the kiln tail and the section to be repaired. The granules gradually roll to the depression of the section to be repaired and gradually heat up to become liquid. The liquid phase material starts to react from the inside to the surface, and after forming mullite, it gradually solidifies into solid phase refractory. 6) Continue to operate the rotary kiln at a speed of 1~3Hz, and maintain the temperature of the section to be repaired at 700~1100℃. The subsequent granules will continuously roll to the depression of the section to be repaired, and will be continuously bonded, liquefied, reacted and solidified. Stop spraying when the depression of the section to be repaired is consistent with the height of the surrounding kiln wall. 7) After the repair is completed, the excess liquid phase is discharged with the rotation of the rotary kiln. The river sand obtained in step 3) is added from the feed end of the rotary kiln tail. The rotation speed of the rotary kiln is increased to 5~8Hz. The river sand will wash away the residual liquid phase and the loosely bonded solid phase in the repair area of ​​the rotary kiln. The material formed after washing is discharged from the kiln head of the rotary kiln and recycled as river sand.

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