I. Raw Material Selection
The main raw materials for calcined alumina are bauxite and chalk. Bauxite is an aluminum-containing quartz stone commonly found in rocks in tropical and subtropical regions. Chalk is a sedimentary rock composed of a mixture of marl, clay, and quartz, and is widely distributed on the Earth's surface.
II. Preparation Process
During the production of calcined alumina, the raw materials undergo multiple processing steps. The specific processes are as follows:
1. Ore Crushing: The raw materials are crushed to facilitate subsequent processing.
2. Washing: The crushed raw materials are washed to remove impurities and harmful substances.
3. Screening: The washed raw materials are screened to remove uneven particles.
4. Blending: The screened raw materials are mixed in specific proportions to prepare a suitable batch.
5. Grinding: The batch is ground to facilitate the subsequent calcination process.
III. Calcination Process
After the above preparation process, the raw materials undergo calcination. Calcination involves heating the powdered raw materials at high temperatures, causing a series of chemical reactions to occur, ultimately producing alumina. The calcination process includes the following steps:
1. Heating: The raw materials are placed in a calciner and heated. The heating temperature is typically between 1200°C and 1600°C.
2. Soaking: The raw materials are maintained at a constant temperature for soaking to ensure sufficient reaction.
3. Pyrolysis: During the soaking process, organic matter in the raw materials gradually decomposes, producing gases such as CO and CO₂.
4. Oxidation: Gases such as CO and CO₂ react with the aluminum ore in the raw materials to produce alumina.
5. Cooling: The calcined alumina is cooled to room temperature.
In summary, the calcined alumina process includes raw material selection, preparation, and calcination. In actual production, parameters at each step must be strictly controlled to ensure product quality.
