Effective Process Control to Avoid Clay Brick Collapse in Tunnel Kilns
Clay brick collapse is a common defective issue during tunnel kiln firing, which severely reduces finished product rate and affects continuous production. The occurrence of brick collapse is jointly caused by green brick quality, stacking method, preheating drying, firing temperature and tunnel kiln structure. Stable production relies on standardized full-process quality control, especially in the pre-kiln production stage.
1. Pre-kiln green brick quality control
Residual moisture is the core index affecting green brick strength. Clay bricks with moisture content higher than 6% cannot bear layered pressure, resulting in deformation and collapse inside the tunnel kiln. In terms of raw material processing, insufficient aging time (less than 3 days) and unreasonable particle gradation will cause loose green brick texture. For single-setting firing lines, manufacturers shall control forming moisture at 13%-15% and maintain extrusion pressure above 40kg/cm² to ensure qualified green brick hardness.
2. Standardized brick stacking procedures
Unstable and dense stacking is a man-made factor leading to stack tilting and poor internal ventilation. Uneven bottom force, mixed placement of wet bricks at the bottom, and overly compact gaps will trap internal moisture and soften lower bricks. Factories shall implement unified stacking standards: dry bricks at the bottom, damp bricks on the top, sparse middle and dense sides, and reserve 15-20mm ventilation gaps between brick bodies.
3. Drying and preheating zone moisture exhaust management
Most hidden dangers originate from improper preheating. Excessively high air supply temperature over 116°C and rapid temperature rise exceeding 6-8°C/h cause unbalanced internal and external dehydration. Insufficient exhaust air volume and poor kiln sealing lead to condensed moisture attaching to green bricks, resulting in overall softening and collapse.
4. Accurate temperature control in the firing zone
Over-firing and excessive internal combustion dosage push the kiln temperature beyond the sintering threshold. The bottom clay bricks lose structural rigidity and deform under pressure. Operators shall observe fire hole status; whitish and shaking brick stacks represent critical overheating risks.
5. Daily inspection of kiln body structure
Kiln arch settlement, protruding residual bricks at air outlets and inaccurate track installation cause unstable kiln car operation, triggering continuous brick collapse. Regular structural maintenance is indispensable for long-term stable firing.
In summary, standardized raw material treatment, green brick quality inspection and manual stacking operation solve most collapse risks. Cooperated with stable thermal system and equipment maintenance, manufacturers can effectively reduce defective clay bricks in tunnel kiln production.
