In the refractory industry, kilns often face various technical issues during operation, which can affect production efficiency, product quality, and equipment life. The following is a classification and specific manifestations of common kiln problems, analyzed based on industry practices and technical analysis:
1. Refractory Damage
➤ Kiln Lining Brick Debris and Wear: Red areas appear on the kiln shell surface (red kiln), refractory brick fractures, or castable material falls off.
Causes:
Insufficient refractory brick strength or poor construction quality (such as missing anchors or excessive brick joints);
Thermal stress leading to material spalling (such as excessive temperature fluctuations or excessive kiln speeds);
Chemical attack (such as penetration of alkali metal oxides and corrosion by low-melting-point substances).
Solutions:
Select high-thermal shock-resistant materials (such as andalusite bricks and corundum-mullite composite bricks);
Optimize construction techniques, increase anchors, and strictly control brick joints.
➤ Localized Melting Corrosion and Ring Coking: Pit-shaped melting corrosion or ring coking appears on the refractory surface in the firing zone.
Causes:
Abnormal flame shape (e.g., ball-shaped flames with localized overheating);
Incompletely burned coal cores adhering to the material surface.
Solutions:
Adjust burner position and flame shape to ensure uniform calcination;
Use corrosion-resistant materials (e.g., magnesia-alumina spinel castable).
II. Abnormal Temperature Control
➤ Fluctuating circulating gas temperature: Unstable kiln temperature leads to overburning or underburning of lime.
Causes:
Fluctuating coal gas calorific value or varying driving air pressure;
Uneven discharge rate affects heat balance.
Solutions:
Install an automatic control system to stabilize coal gas flow;
Optimize discharge rate to match heat load.
➤ Excessive kiln top temperature (abnormal flue gas temperature): Excessive exhaust gas temperature, material adhesion or nodules.
Causes:
Heat exchanger blockage or expansion joint leakage;
Uncontrolled exhaust gas ratio leading to heat accumulation.
Solutions:
Regularly clean the heat exchanger and install an automatic dust removal device;
Adjust the kiln negative pressure and exhaust gas ratio.
III. Structural and Process Defects
➤ Kiln Deformation and Red Kiln: The kiln shell becomes partially red or even warped (temperature > 650°C).
Causes:
Refractory bricks lack effective kiln lining protection and are directly exposed to high-temperature flames;
Excessive coal loading leads to localized overburning.
Solutions:
Strengthen kiln lining maintenance and control kiln temperature uniformity;
Use alkali-resistant bricks or nano-enhanced castables to improve corrosion resistance.
➤ Ringing and Material Blockage: Ring-shaped nodules form inside the kiln, obstructing the flow of material and gas.
Causes:
Limestone contains high levels of impurities (including low-melting-point substances);
Poor kiln air permeability and uneven heat distribution.
Solutions:
Use online ash cleaning equipment (such as multi-frequency concentrated speed ash cleaning technology);
Optimize raw material particle size and screening processes.
IV. Equipment and System Failures
➤ Combustion System Abnormalities: Flame instability, gas leakage, or incomplete combustion.
Causes:
Gas filter blockage or calorimeter malfunction;
Burner misalignment causes misaligned flames.
Solutions:
Regularly clean equipment and pre-treat coal gas (e.g., water washing and dehydration);
Strengthen burner maintenance and flame monitoring.
➤ Decreased heat exchanger efficiency: Flue gas heat transfer efficiency decreases, increasing energy consumption.
Causes:
Dust or scale accumulation on heat exchange tubes;
Leakage in the lower expansion joint, introducing cold air.
Solutions:
Improve the expansion joint structure and add automatic dust removal;
Regularly purge the heat exchanger.
V. Process Operation Errors
➤ Improper ignition and heating: Refractory bricks crack or kiln lining peels off.
Causes:
Excessive heating rate (failure to follow the heating curve);
Poor kiln humidity control leading to cracking.
Solutions:
Slowly increase the temperature (recommended 24-48 hours) and monitor the kiln outlet temperature;
Strictly control the moisture content of the bricks entering the kiln (<6%).
➤ Poor fuel and raw material management: Fluctuating fuel calorific value and excessive raw material impurities.
Causes:
Large coal particle size or high moisture content leads to unstable combustion;
Uneven limestone particle size affects temperature distribution.
Solutions:
Optimize fuel pretreatment (e.g., particle size screening and moisture control);
Strengthen raw material quality testing and screening.
VI. New Technology Application and Improvement Directions
Material Upgrade: Use nano-enhanced castables and high-thermal-shock-resistant corundum bricks to extend refractory life (up to 4 years or more).
Intelligent Monitoring: Embedded temperature sensors monitor kiln lining status in real time and predict damage risks.
Process Optimization: Reduce localized overheating and ringing by adjusting flame shape and pulverized coal injection rate.
The above issues require targeted solutions tailored to the specific kiln type (e.g., rotary kiln, sleeve kiln, tunnel kiln) and operating conditions. Regular maintenance, strict operating procedures, and technological innovation are key to ensuring stable kiln operation.
