The fundamental reason for adopting differentiated hot air temperature in fired brick drying lies in the varying drying sensitivity of raw materials. The drying sensitivity coefficient is positively correlated with the plasticity index of brick raw materials. Raw materials with high plasticity index have strong drying sensitivity, slow internal water migration, and high risk of drying cracks, which require lower hot air temperature and longer drying time; low-sensitivity raw materials can adapt to high-temperature rapid drying.
This raw material characteristic directly guides the hierarchical setting of drying chamber hot air temperature. Low-sensitivity raw materials with a coefficient less than 1 have uniform water evaporation and extremely low cracking risk, so the hot air temperature can be raised to 120℃-125℃. This high-temperature drying mode only requires a drying cycle of 12-20 hours, achieving the highest production efficiency while ensuring drying quality.
For medium-sensitivity raw materials with a drying sensitivity coefficient of 1 to 2, temperature setting must be strictly classified by brick type. Solid bricks with dense internal structure have high water resistance, suitable for 100℃-120℃ hot air drying; hollow bricks with porous structure are prone to stress concentration, so the temperature needs to be reduced to 80℃-100℃ to ensure gradual and balanced dehydration. Correspondingly, the drying time of such raw materials is extended to 20-32 hours with the change of temperature parameters.
In industrial production, blind high-temperature drying for high-sensitivity raw materials (coefficient > 2) is prohibited. Such raw materials have severe unbalanced internal and external water loss, and can only adopt low-temperature slow drying with extended drying time up to 32-48 hours. Unreasonable temperature matching will directly lead to a surge in defective bricks and waste production energy consumption.
Scientific temperature differentiation also matches fixed energy consumption standards for brick drying. Evaporating 1kg of green brick water consumes 1300kcal of heat (equivalent to 0.186kg standard coal), and requires 33m³ of 30℃ hot air to take away water vapor. Reasonable temperature adjustment based on raw material sensitivity can avoid excessive heat waste caused by blind high temperature and incomplete dehydration caused by low temperature, realizing energy-saving and efficient drying.
In addition, the green brick forming moisture will affect the temperature adaptation effect. Properly reducing forming moisture (2 percentage points for lean raw materials, 4-6 percentage points for fat raw materials) can double green brick strength, reduce drying shrinkage, and make the raw materials more adaptable to differentiated hot air temperature drying, further reducing the risk of quality defects.