To improve the purity of charcoal during carbonization, here are some methods you can take:

1. Choose high-quality raw materials: The purity of charcoal is directly affected by the raw materials. Choosing dry, pure wood as raw material is the first step to ensuring the purity of charcoal. Avoid wood that has impurities or chemical treatments.

2. Control carbonization conditions: Temperature, time and environmental conditions during the carbonization process will affect the purity of charcoal. Control the temperature and time during the carbonization process to ensure that the wood is fully carbonized without over-burning. In addition, ensure sufficient oxygen supply during the carbonization process to avoid incomplete combustion.

3. Optimize carbonization equipment: Using advanced carbonization equipment can improve the purity of charcoal. For example, a high temperature carbonization furnace or an inert atmosphere carbonization furnace can be used to provide higher temperatures and better control of the carbonization process.

4. Reduce impurities: During the carbonization process, pay attention to reducing the addition and production of impurities. Avoid using wood with chemical additives, as well as external sources of contamination during the carbonization process.

5. Post-carbonization treatment: Refining and processing after carbonization can further improve the purity of charcoal. For example, impurities and residues in charcoal can be removed through screening, washing, or specific chemical treatments.

Through the above methods, the purity of charcoal can be improved during the carbonization process and higher quality charcoal products can be obtained.