1. Drying stage
When the temperature is below 150-200 ℃, the water evaporates and the main components of wood remain unchanged.
2. Pre carbonization stage
At 200-275 ℃, wood begins to decompose, and unstable parts such as hemicellulose decompose first to produce CO and a small amount of acetic acid.
3. Carbonization stage
In the exothermic decomposition reaction stage at 275-400 ℃, the decomposition is intense, cellulose is decomposed first and then lignin, a large amount of acetic acid, tar, methanol and wood gas are produced, and a large amount of wood vinegar and wood gas are produced at 275-300 ℃; 300-400 ℃ wood vinegar gradually decreases, and a large amount of wood gas is discharged. At 400 ℃ or 450 ℃, the carbonization has actually ended.
4. Calcination stage
Above 400 ℃ or 450 ℃, the residual volatile in charcoal should be volatilized by external heat.
