The carbonization process of biomass carbonizing furnace is mainly divided into three stages, and the reaction characteristics and products of each stage are as follows:

1. Drying stage

-Temperature range: usually 100-200℃.

-Reaction process: The water (free water and partially bound water) in the biomass raw materials is heated and evaporated, and discharged out of the furnace.

-Product characteristics: there is almost no chemical change at this stage, mainly physical dehydration, the weight of raw materials is reduced, and the water content is reduced to below 10%, which is a preparation for subsequent pyrolysis.

1. Pyrolysis stage

-Temperature range: 200-600℃ (core reaction interval).

-Reaction process:

The macromolecular organics (such as cellulose, hemicellulose and lignin) in raw materials begin to decompose, and chemical reactions such as dehydration, decarboxylation and cracking occur.

Hemicellulose is decomposed first at 200-350℃ to produce CO, Co, HO and low molecular organic acids; Cellulose is decomposed at 300-400℃ to produce water vapor, CO, H and liquid tar; Lignin is decomposed at 350-500℃ to produce aromatic compounds and coke.

-Product characteristics:

Biomass carbon with high fixed carbon content (carbon content can reach 70%-90%) is generated, with hard texture, significantly enhanced adsorption capacity and chemical stability.

By-product gases are mainly CO and H, which can be used as fuel for heating in the furnace to realize energy cycle.

3. Carbonization stage (calcination stage)

-Temperature range: 600-800℃ (some equipment can be higher). -Reaction process:

Residual organic components are further decomposed, carbon chains are broken and rearranged, and hydrogen and oxygen elements are removed in the form of H, HO, CO, etc.

Biomass carbon tends to be graphitized, the arrangement of carbon atoms is more orderly, and the pore structure is further expanded and improved (such as micropore and mesopore development).

-Product characteristics: Biomass carbon with high fixed carbon content (carbon content can reach 70%-90%) is generated, with hard texture, significantly enhanced adsorption capacity and chemical stability. By-product gases are mainly CO and H, which can be used as fuel for heating in the furnace to realize energy cycle.

Three-stage summary: The drying stage is mainly physical dehydration, the pyrolysis stage is the core of organic matter decomposition, and the carbonization stage determines the final properties (such as carbon content and pore structure) of biomass carbon. By controlling the temperature and residence time in each stage, the quality of carbon can be adjusted to meet the needs of different fields such as agriculture, environmental protection and energy.