How Is Wood Charcoal Manufactured?

The process of charcoal production essentially involves the pyrolysis and carbonization of wood. Wood or other biomass materials undergo high-temperature treatment within a carbonization furnace. This effectively removes moisture, volatile substances, and combustible gases from the wood. The end result is a solid carbonised product—charcoal. Today, we shall provide a detailed explanation of the principles and procedures involved in charcoal production.
 

Principles of Charcoal Production

Dehydration Stage

During the preheating phase, free water and bound water within the wood commence gradual evaporation. As temperatures progressively rise above 1000°C, this dehydration stage is completed.

Pyrolysis Stage

With continued temperature increase, furnace temperatures exceed 100°C. At this point, the wood has completed dehydration.

Carbonization Stage

When temperatures exceed 400°C, macromolecular compounds within the wood—including cellulose, hemicellulose, and lignin—decompose into smaller molecular gases (combustible gases, carbon monoxide, carbon dioxide, etc.), tar, and other liquid by-products.

Cooling Stage

To enhance charcoal quality and stability, the material undergoes prolonged calcination at high temperatures. It is then gradually cooled to prevent internal stress and crack formation.

Steps in Charcoal Production

Material Selection and Preparation

Prioritise dense, high-oil-content woods such as hardwoods (oak, birch, maple, etc.). Cut timber into appropriately sized blocks and strips to facilitate subsequent pyrolysis and carbonization.

Drying Treatment

Dry timber to low moisture content either naturally or using drying equipment. This reduces energy consumption and duration during subsequent pyrolysis.

Pyrolysis and Carbonization

Wood must be stacked in alternating layers within the carbonization furnace, maintaining uniform spacing. Reserve central voids to facilitate airflow, avoiding overcrowding or loose packing that impairs carbonization efficiency. Within the sealed furnace environment, the wood undergoes pyrolysis and carbonization stages to ultimately form charcoal.

Discharge and Cooling

Once the furnace temperature has dropped to a safe level, the horizontal carbonization furnace door is opened to remove the finished charcoal. This is then cooled either naturally or through forced ventilation.

Screening and Grading: Charcoal is screened and graded according to wood dimensions, density, and quality to meet diverse application requirements.

Precautions for Charcoal Production

• Throughout the process, ensure adequate ventilation to prevent oxygen-deficient combustion and the accumulation of harmful gases.
• The design and construction of the carbonization furnace must prioritise operational safety and production efficiency to ensure smooth charcoal production.
• Multiple factors must be considered during charcoal production to avoid compromising quality. Key considerations include: raw material type, pyrolysis conditions, carbonization duration, carbonization temperature, and cooling method. Process parameters require continuous optimisation and adjustment during trial production runs.

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