The key process of forming fired bricks is roasting, which aims to transform various loose mineral mixtures into hard and stable products. It is mainly divided into four stages: preheating, baking, insulation, and cooling, known as the "four zones". The main content includes:
1. Pre tropical
The stage of preheating the preheated bricks from room temperature to 120 ℃ is the low-temperature preheating stage, during which the main purpose is to eliminate residual moisture in the bricks - natural water. Due to the evaporation of water inside the steel billet, it can only be discharged from its tiny pores. If the temperature rises too quickly, the water vapor will rapidly increase and cannot be squeezed out, so the steel billet will have to burst. Therefore. The heating rate limit for this stage is 25-35 ℃/h.
2. Baking tape
The roasting zone usually refers to the part from the beginning to the end of coal injection. It should only be regarded as a row of fire eyes where the temperature above and below the chimney reaches the ignition point, and fine coal can burn in all parts of the chimney. Otherwise, it is not allowed to accept grilled tapes.
3. Insulation tape
About 10-15 rows of heat barriers start from the fireproof holes where coal is stopped. Their function is to make the physical and chemical reactions during the roasting process more complete, thereby fully burning and reducing the pores in the brick body, giving it good sound, color, and sufficient strength. Avoid rapid cooling to prevent hair like cracks or explosions on the brick surface caused by uneven shrinkage due to rapid cooling. Especially during the stage when the temperature drops from 600 ℃ to 550 ℃, free silica undergoes crystal transformation, particle volume shrinks, and is more prone to cracking. Hollow bricks have large blocks, thin walls, and are very fragile, so caution is more important.
4. Cooling belt
The part from the end of the insulation belt to the kiln outlet is called the cooling belt. The purpose is to ensure product quality while facilitating exit operations. The shorter the cooling zone, the lower the intake resistance, and it is also more conducive to roasting.
When firing fired bricks, attention should be paid to controlling the temperature. The part from the end of the insulation belt to the kiln outlet is called the cooling belt. The purpose is to facilitate the exit operation. On the premise of ensuring product quality, the shorter the cooling belt, the lower the intake resistance, and the more conducive it is to ignition.