High brick breakage and cracking rate is one of the biggest profit killers for overseas brick factories. Many new brick plants suffer from 8%–20% brick loss rate due to improper drying and firing control, which directly raises production costs and cuts down net profit.
This professional guide shares practical, factory-tested methods to reduce brick breakage in drying and firing stages. All solutions fit fully automatic and semi-automatic tunnel kiln brick production lines
1. Main Causes of Brick Cracking and Breakage
Most brick defects happen in two critical stages: uneven drying shrinkage and excessive temperature difference during firing. Common reasons include unreasonable raw material moisture, wrong brick stacking method, rapid temperature rise, poor kiln airflow and immature aging process.
2. Reduce Breakage in the Drying Process (Key Pre-Firing Stage)
More than 60% of brick cracks are formed in the drying stage, not during firing. Controlling drying speed and uniformity is the most cost-effective way to lower brick scrap rate.
2.1 Control Raw Material Moisture and Aging Time
Unbalanced moisture inside brick blanks causes inconsistent shrinkage. For standard clay, shale and mixed raw materials, keep the forming moisture between 18%–24%. Extend material aging time to 24–48 hours to ensure even water distribution and plasticity stability.
Effect: Effectively eliminate irregular surface cracks and blank breakage before entering the dryer.
2.2 Adopt Gradient Slow Drying Mode
Many new factories make the mistake of fast high-temperature drying. Rapid surface water loss leads to surface hardening while the inner layer remains wet, causing burst cracks.
Set staged drying parameters: low temperature and high humidity at the initial stage, gradual temperature rise and dehumidification in the middle stage, and thorough drying in the final stage.
2.3 Standardize Automatic Brick Stacking Method
Disordered stacking blocks hot air circulation, resulting in partial under-drying and over-drying. Keep uniform gaps between brick layers to ensure 360° hot air flow. Avoid dense stacking at the edge of the drying car.
3. Reduce Brick Breakage in the Tunnel Kiln Firing Process
Firing breakage mainly comes from temperature shock, uneven kiln temperature and unreasonable fuel combustion. Stable temperature curve management can control the firing scrap rate below 3%.
3.1 Avoid Rapid Temperature Rising and Cooling
Brick blanks are fragile before sintering. Sharp temperature increase will produce huge internal thermal stress and cause layered cracking. Strictly follow the standard heating curve: slow heating, constant temperature sintering and slow cooling.
3.2 Balance Kiln Internal Airflow and Temperature
Local overheating or cold zones inside the tunnel kiln are common causes of deformed and broken bricks. Optimize the hot air circulation system and waste heat recovery system to ensure consistent temperature in all kiln zones.
3.3 Optimize Fuel Combustion Efficiency
Incomplete combustion leads to unstable fire power and temperature fluctuation. No matter using coal, natural gas or heavy oil, keep sufficient oxygen supply and uniform combustion to avoid local temperature deviation.
4. Raw Material Formula Optimization to Lower Breakage Rate
- Single pure clay material has large shrinkage coefficient after high-temperature firing. Proper material mixing can greatly improve brick stability.
- Mix 20%–40% shale into clay to reduce overall shrinkage rate
- Add 10%–30% coal gangue or fly ash to balance internal stress
- Remove large stone and hard impurities to prevent local stress concentration
5. Daily Operation Management Standards
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Regularly check dryer and tunnel kiln sealing to avoid cold air intrusion
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Keep stable production speed and avoid frequent line start-stop
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Train workers on standardized stacking and parameter adjustment
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Record daily breakage data to track abnormal fluctuations