What are the common faults of rotary kiln lime kiln
As an important equipment for lime production, the rotary kiln lime kiln is prone to various malfunctions due to the influence of various factors during long-term operation. These faults not only affect production efficiency and product quality, but may also lead to equipment damage and safety accidents. Therefore, understanding the common faults, causes, and solutions of rotary kiln lime kilns is of great significance for ensuring the smooth progress of production.
1、 Mechanical structural failure
（1） Deformation of kiln body
reason
Uneven thermal expansion: When the rotary kiln operates at high temperatures, the temperature of each part of the kiln body is not completely consistent. For example, there may be differences in temperature between the kiln head and tail, resulting in varying degrees of thermal expansion in different areas. If the structural design of the kiln body cannot adapt well to this thermal expansion difference, it is easy to cause deformation. In addition, uneven distribution of materials inside the kiln may also lead to local temperatures being too high or too low, thereby affecting the uniformity of thermal expansion of the kiln body.
Mechanical stress concentration: During the operation of the kiln body, certain mechanical stresses are generated on the kiln body due to the gravity, friction, and rotational inertia of the material. If there are weak links in the structure of the kiln body, such as welds, connections, etc., these areas are prone to stress concentration, which may accumulate over time and lead to deformation of the kiln body.
Improper installation and debugging: During the installation process of the rotary kiln, if the flatness of the foundation is insufficient, the installation position of the supporting wheel is inaccurate, or the concentricity of the kiln body is not adjusted properly, additional stress will be generated during the operation of the kiln body, which will cause deformation of the kiln body.
influence
Affects the movement of materials inside the kiln: Deformation of the kiln body can cause changes in the material channels inside the kiln, resulting in poor flow of materials inside the kiln, which may lead to material accumulation, blockage, and other situations, thereby affecting the quality and yield of lime calcination.
Damaged refractory materials: The deformed kiln will generate uneven compression and tensile forces on the internal refractory materials, which can easily lead to cracking and detachment of refractory materials, shorten their service life, and increase equipment maintenance costs.
Increasing equipment operating resistance: After the kiln body deforms, the frictional force during rotation will increase, requiring more energy to drive the kiln body to rotate. This not only increases the load on the motor, but may also cause overheating or even damage to the motor.
（2） Wheel failure
reason
Poor lubrication: The supporting wheel needs good lubrication to reduce wear while bearing the huge weight and rotational friction of the kiln body. If there is a malfunction in the lubrication system, such as damage to the lubrication pump, blockage of the oil pipe, or a decrease in the quality of the lubricating oil, it will lead to insufficient lubrication of the idler, thereby exacerbating the wear between the idler and the shaft neck.
Uneven stress: Factors such as deformation of the kiln body, uneven distribution of materials, or settlement of the support wheel installation foundation may cause uneven pressure on the support wheel. Excessive pressure on some supporting wheels can accelerate their wear rate, and even cause surface peeling, cracking, and other phenomena.
Fatigue damage: The idler wheel is constantly subjected to alternating stress during long-term continuous operation. If the material selection of the supporting wheel is improper or there are defects in the manufacturing process, its fatigue resistance performance will be poor, and it is easy to develop fatigue cracks and serious faults such as fracture after long-term operation.
influence
Causing kiln body vibration: After the supporting wheel wears or is damaged, its stability in supporting the kiln body will decrease, resulting in vibration of the kiln body during rotation. The vibration of the kiln body not only affects the normal operation of the equipment, but may also have adverse effects on surrounding buildings and equipment, and accelerate the damage of other components of the equipment.
Affects the concentricity of the kiln body: When the supporting wheel malfunctions, the rotational axis of the kiln body will shift, causing damage to the concentricity of the kiln body. This will further increase the friction and collision between the kiln body and other components, deteriorate the operation of the equipment, and may even cause the kiln body to malfunction.
（3） Transmission device malfunction
reason
Gear wear: During long-term operation, the gears in the transmission device will gradually wear due to the mutual meshing and friction between the tooth surfaces. If the material hardness of the gear is insufficient, the lubrication is poor, or the load is too high, the wear rate will accelerate. In addition, insufficient installation accuracy of gears can also lead to poor tooth contact and exacerbate wear.
Coupling damage: The coupling plays a role in transmitting torque between the motor, reducer, and kiln body. If the coupling is not properly aligned during installation or subjected to excessive impact loads during operation, such as the instantaneous impact force generated when materials get stuck in the kiln body, it is easy to cause damage to the elastic components of the coupling or loosening of the connecting parts.
Gearbox malfunction: The internal components of the gearbox are numerous, such as gears, bearings, shafts, etc. Common causes of malfunctions include lubricant contamination, overload operation, and manufacturing defects in components. For example, impurities mixed in lubricating oil can lead to increased wear of gears and bearings; Long term overload operation can cause excessive stress on gears and shafts, leading to fatigue damage.
influence
Reduced transmission efficiency: Gear wear and gearbox failure can both lead to a decrease in the transmission efficiency of the transmission device, requiring the motor to output more power to maintain the normal operation of the kiln body, thereby increasing energy consumption. At the same time, the decrease in transmission efficiency will also make the rotational speed of the kiln unstable, affecting the quality of lime calcination.
Equipment shutdown: When there is a serious malfunction in the transmission device, such as gear breakage, coupling damage, or severe damage to internal components of the reducer, it can cause power transmission to be interrupted, forcing the rotary kiln to shut down, affecting the continuity of production, and causing significant economic losses to the enterprise.
2、 Refractory material failure
（1） Refractory bricks falling off
reason
Masonry quality issues: During the masonry process of refractory bricks, if the construction personnel do not operate in a standardized manner, such as uneven size of mortar joints, incomplete mortar, or insufficient compression force between bricks during masonry, it will affect the overall stability of refractory bricks. During the operation of the rotary kiln, due to the vibration and temperature changes of the kiln body, these quality defects may cause the refractory bricks to loosen and eventually fall off.
Thermal stress failure: During the opening and stopping of the rotary kiln, the temperature inside the kiln changes dramatically. Refractory bricks generate significant thermal stress due to their different coefficients of thermal expansion from the steel structure of the kiln body. If the thermal stress exceeds the bearing limit of the refractory brick, it will cause cracking and subsequent detachment of the refractory brick. In addition, frequent fluctuations in temperature inside the kiln can also exacerbate the thermal stress damage of refractory bricks.
Mechanical impact: During the movement of materials in the kiln, there may be a certain degree of mechanical impact on refractory bricks, especially when there are large hard objects in the materials or abnormal vibrations in the kiln body, the impact force will increase. Long term mechanical impact may cause damage to the surface of refractory bricks, gradually loosening and falling off.
influence
Shortening the service life of the kiln body: The detachment of refractory bricks will directly expose the steel structure of the kiln body to high temperature environment. High temperature will reduce the strength of the steel structure, cause deformation or even damage, thereby shortening the overall service life of the kiln body.
Impact on production safety: Fallen refractory bricks may block the ventilation ducts and material channels inside the kiln, causing abnormal pressure rise inside the kiln and increasing the risk of safety accidents. Meanwhile, the fallen refractory bricks may also cause harm to the equipment and operators inside the kiln.
Increased production costs: Frequent detachment of refractory bricks requires frequent maintenance and replacement, which not only increases the procurement cost of refractory materials, but also leads to increased equipment downtime, reduced production efficiency, and thus increases the overall production cost of the enterprise.
（2） Corrosion of refractory materials
reason
Chemical erosion: The materials inside the lime kiln undergo a series of chemical reactions at high temperatures, producing corrosive gases and substances such as alkaline oxides. These substances will undergo chemical reactions with refractory materials, gradually eroding the structure of refractory materials. In addition, impurities in fuel may also produce harmful gases during combustion, which can corrode refractory materials.
High temperature erosion: In the high-temperature environment of a rotary kiln, some materials may melt and adhere to the surface of refractory materials. Over time, these melted materials will penetrate into the interior of refractory materials, change their organizational structure, and lead to a decrease in the performance of refractory materials, resulting in erosion.
Airflow erosion: The high-temperature airflow and material particles in the kiln will cause erosion on the surface of refractory materials during the flow process. Especially when the wind speed inside the kiln is high or the material particles are hard, the scouring force will increase, accelerating the wear and erosion of refractory materials.
influence
Reduce the thermal insulation performance of refractory materials: After erosion, the thickness of refractory materials will decrease and the structure will become loose, which will lead to a decrease in their thermal insulation performance. The heat loss of the kiln body increases, and in order to maintain the temperature inside the kiln, more fuel needs to be consumed, thereby increasing energy costs.
Affects the thermal system inside the kiln: The erosion of refractory materials will change the heat distribution inside the kiln, making the temperature field inside the kiln uneven. This will affect the calcination quality of lime, leading to unstable product quality, and also affect the normal operation of the kiln body, increasing the probability of equipment failure.
3、 Production process malfunction
（1） Material looping
reason
Unreasonable material composition: If the content of low melting point substances in the material is too high, such as impurities such as potassium, sodium, chlorine, etc., these substances will melt and form viscous substances at high temperatures, which are easy to bond to the kiln wall and gradually form rings. In addition, the particle size distribution of the material is uneven, and when there is too much fine powder, it is easy for the fine powder to adhere to the kiln wall under the influence of the airflow inside the kiln, which is also a factor in forming a ring.
Improper operating parameters: Operating parameters such as temperature, wind speed, and material residence time inside the kiln have a significant impact on the formation of material loops. If the temperature inside the kiln is too high or the local temperature is too high, it will cause the material to melt prematurely and form a ring; When the wind speed is too low, the suspension state of the material in the kiln is poor, and it is easy to deposit on the kiln wall; However, if the material stays for too long, it will increase the chance of bonding inside the kiln.
Insufficient fuel combustion: When fuel combustion is insufficient, a large amount of unburned substances and reducing gases will be produced. These substances will undergo complex chemical reactions with the components in the material, promoting the bonding and ring formation of the material.
influence
Reduce production efficiency: Material looping will reduce the effective volume inside the kiln, decrease the throughput of materials, and thus affect the production of lime. At the same time, in order to deal with the problem of ring formation, frequent shutdowns are required for cleaning, which will greatly reduce the operating rate of the equipment and further affect production efficiency.
Impact on product quality: Ring formation can lead to uneven heat distribution inside the kiln, causing excessive calcination of some materials and insufficient calcination of others, thereby affecting the quality stability of lime products and reducing indicators such as product activity.
Increasing equipment load: After the material is looped, the rotational resistance of the kiln body will increase, and the motor will need to consume more energy to drive the kiln body to rotate. This not only increases energy consumption, but may also cause damage to the motor and transmission device.
（2） Unstable calcination temperature
reason
Fuel supply system failure: The fuel delivery pipeline may be blocked, such as coal powder clumping in the coal powder pipeline or impurities blocking in the gas pipeline, resulting in poor fuel supply and unstable heat input into the kiln. Errors in fuel metering equipment may also cause fluctuations in fuel supply, thereby affecting the calcination temperature. In addition, the unstable quality of fuel, such as changes in calorific value, can also alter the combustion efficiency and cause temperature fluctuations.
Ventilation system issues: Fan malfunctions, blocked air ducts, or improper adjustment of air dampers can all affect the ventilation volume inside the kiln. Insufficient ventilation can lead to incomplete fuel combustion, insufficient heat generation, and a decrease in temperature; However, excessive ventilation will carry away too much heat, making it difficult for the temperature inside the kiln to rise.
Poor sealing of the kiln body: If there are problems with the sealing of the kiln head, kiln tail, and other parts of the rotary kiln, it can lead to the intake of cold air from the outside or the leakage of hot air inside the kiln. The inhalation of cold air will lower the temperature inside the kiln, while the leakage of hot air will increase heat loss and affect temperature stability.
influence
Product quality fluctuation: Unstable calcination temperature can cause uneven calcination of lime, resulting in significant fluctuations in product quality. Possible occurrence of partial lime burning with low activity; However, if some lime is burnt too much, its hardness will increase and its activity will also decrease. This will affect the competitiveness of the product in the market and reduce the economic benefits of the enterprise.
Energy waste: In order to maintain the temperature inside the kiln within a certain range, it is necessary to increase the supply of fuel when the temperature decreases, and then reduce the supply of fuel when the temperature increases. This frequent adjustment can lead to energy waste. Meanwhile, unstable temperature can also affect combustion efficiency and further increase energy consumption.
Shortened equipment lifespan: Frequent temperature fluctuations can subject the kiln body and refractory materials to significant thermal stress, accelerating their damage and aging. For example, the thermal expansion and contraction of the kiln body can cause problems such as weld cracking and steel structure deformation. Refractory materials are also more prone to cracking and detachment due to repeated thermal stress, thereby shortening the service life of the equipment.
The rotary kiln lime kiln is prone to various malfunctions during operation, involving multiple aspects such as mechanical structure, refractory materials, and production processes. The causes of these faults are complex and may be interrelated. In order to ensure the normal operation of the rotary kiln lime kiln, improve production efficiency and product quality, and extend the service life of equipment, enterprises need to strengthen the daily maintenance and management of equipment, regularly inspect and repair equipment, optimize production process parameters, and improve the technical level and sense of responsibility of operators. At the same time, in the design, selection, and installation process of equipment, various factors should be fully considered, and reliable equipment and materials should be selected to ensure the overall performance and stability of the equipment. Only in this way can we effectively reduce the occurrence of faults, achieve safe, efficient, and stable operation of rotary kiln lime kilns, and create greater economic and social benefits for enterprises.
