1 drying stage. The temperature at this stage is 120-150 degrees Celsius, and the pyrolysis rate is very slow. The main reason is that the moisture in the wood evaporates when it relies on externally supplied heat, and the chemical composition of the wood material hardly changes.

2 pre-carbonization stage. The temperature at this stage is 150-275 degrees Celsius, the pyrolysis reaction of wood materials is obvious, and the chemical composition of wood materials begins to change. The unstable combination components, such as semi-fibers, decompose to form carbon dioxide, carbon monoxide and a small amount of acetic acid.

3 carbonization stage. This temperature stage is 275-400 degrees Celsius. In this stage, the wood material is thermally decomposed rapidly, generating a large amount of decomposition products. The liquid product produced contains a large amount of acetic acid, alcohol and hibiscus oil, and the water content of the generated gas is gradually increased. The reduction, while methane, has been fading, and the gas is gradually getting more and more. This stage releases a large amount of heat of reaction, so it is also called the exothermic reaction stage.

4 calcination stage. The temperature rises to 450-500 degrees Celsius. At this stage, the charcoal is calcined by externally supplied heat, and the volatile matter remaining in the charcoal is discharged to increase the fixed carbon content of the charcoal. At this time, the liquid product is rarely formed.

5 carbonation stage. The temperature at this stage is 500-1200 degrees Celsius, and the key is this stage.