Company Blog 2025-09-10

What Are The Stages Of Charcoal Formation?

2025-09-10

Back to Article
List

Charcoal is formed by heating wood to high temperatures in an oxygen-deprived environment. This entire process is termed carbonization. The core stages of charcoal formation comprise: raw material selection and screening, drying treatment, pyrolytic carbonization, and cooling. Charcoal production methods can be categorised into three primary types: traditional kiln firing, carbonization furnace firing, and simplified smouldering furnace firing.

Raw Material Selection and Pre-treatment

Select hardwoods (oak, birch, beech, etc.) or fruitwoods (apple, peach, pear, jujube) as raw materials. These woods possess a hard texture, high calorific value, and prolonged burning duration.
Cut the timber into 30-50cm lengths. Bark may be retained or removed to prevent compromising charcoal quality.

Drying and Dehydration Stage

To reduce production costs, wood may be sun-dried for 1-2 days or dried using a kiln. Moisture content must be reduced below 12% to prevent cracking during carbonization.

Pyrolysis Carbonization Stage

Modern Kiln Method

Mechanically load wood into a compact configuration.
Employ multi-stage temperature control. Preheat at 150°C → Pyrolysis at 300°C → Calcination at 500°C.
Collect by-products such as combustible gases and wood tar.

Traditional Kiln-Firing Method

Stack wood conically with a top ignition port and eight bottom ventilation holes.
After igniting the top, regulate oxygen levels via bottom vents. Immediately seal the kiln once flames descend to the base.
Under airtight conditions, sustain combustion for 8–12 hours.

Cooling Process

Typically employs natural cooling for 12–24 hours (kiln-fired method) or utilises water-cooling systems for rapid temperature reduction.
Charcoal undergoes re-screening and packaging. High-purity charcoal requires acid washing to remove ash residues.