Wood Charcoal Production Equipment

I. What raw materials are suitable for making machine-made charcoal?

The raw material sources for machine-made charcoal are extremely diverse. Any biomass material possessing a certain fibrous structure and capable of bonding can be utilized. The core requirements are: appropriate moisture content and the ability to soften and bond under high temperature and pressure.

Hard Materials (Produce hard charcoal with high heat output):

Bamboo: Bamboo offcuts, bamboo shavings. Bamboo charcoal produced from these has extremely high density and exceptionally long burn times.

Fruit Shells/Pits: Coconut shells, olive pits, palm shells, walnut shells. Among the highest-grade materials, these yield charcoal with immense heat output after carbonization and are commonly used for barbecuing.

Hardwood waste: Sawdust, wood shavings, shredded branches.

Soft raw materials (yield slightly looser charcoal with high flammability):

Straw/stalk materials: Corn stalks, cotton stalks, bean stalks, rice husks.

Softwoods: Pine sawdust, fir sawdust (oil-rich, also easy to form).

Industrial waste: Sugarcane bagasse, peanut shells, coffee husks, mushroom spawn waste.

II. Complete Production Process (Four Core Stages)

Mechanical charcoal production primarily consists of four stages: crushing, drying, briquetting (forming), and carbonization.

Stage 1: Raw Material Crushing

Purpose: To reduce large raw material chunks into fine particles for efficient drying and compression molding.

Process:

Raw materials (e.g., branches, large wood pieces) are fed into a wood crusher.

If sawdust or fine particles are used, they proceed directly to the screening stage.

Particle Size Requirements: Typically, crushed particles should measure between 3mm and 8mm. Larger particles may not soften sufficiently during briquetting, leading to“exploding briquettes”(cracking). Conversely, excessively fine particles (like dust) impair internal air permeability within the formed briquettes.

Characteristics: This stage fundamentally determines the ease of subsequent briquetting.

Stage 2: Drying (Critical Process)

Purpose: Remove excess moisture from raw materials. This is pivotal for the success of mechanized charcoal production.

Background: Whether sawdust or straw, natural moisture content often ranges from 30% to 50%.

Process:

Wet crushed material enters the drum dryer via conveyor.

Heat source (typically hot air generated by burning wood waste, coal, or biomass pellets) enters the drum and mixes with the wet material.

Moisture rapidly evaporates as the drum rotates and tumbles the material.

Moisture Requirement: The moisture content of the dried raw material must be controlled between 8%-12%.

Practical Insight: Excessively dry material (below 4%) fails to plasticize under high pressure and tends to disintegrate; excessively wet material (above 15%) generates excessive steam pressure during briquetting, causing explosions or machine jams.

Stage Three: Briquetting (Core Process)

Objective: Compress loose powder into high-density“fuel briquettes”(commonly known as semi-finished briquettes) under high temperature and pressure.

Principle: Exploits lignin’s property of softening and developing adhesive properties at high temperatures (approx. 260°C-300°C).

Process:

Dried material enters a screw extruder (most commonly a screw conveyor).

The mechanical screw rod generates extreme pressure (up to 500-800 kg/cm²) while friction creates high temperatures.

The material becomes plastic within the barrel and is continuously extruded through the die at the outlet.

The extruded rods emerge at high temperatures (approximately 200-300°C) and require cooling to harden.

The resulting product is called a semi-finished rod (eco-rod, biomass fuel rod). At this stage, it is already a high-density fuel suitable for direct combustion in boilers.

Characteristics: This process consumes significant electricity and causes substantial mechanical wear (especially on the screw rod). Finished rods typically feature a central borehole (for ventilation and to reduce expansion stress).

Stage Four: Carbonization (Transformation Phase)

Purpose: Pyrolyze semi-finished rods (brown) into black charcoal under high temperatures in an oxygen-deprived (or limited oxygen) environment.

Process: Currently, two mainstream methods exist:

1. Earthen Kiln/Brick Kiln Carbonization (Traditional):

Prepared semi-finished briquettes are stacked inside a sealed kiln.

After ignition, heat generated from partially burning briquettes raises the kiln temperature (approximately 400°C-600°C), promoting carbonization of the remaining briquettes.

The entire process requires manual monitoring of smoke color and heat intensity to control air intake. The kiln is finally sealed for cooling.

*Advantages: Low investment. Disadvantages: Long cycle (7-10 days), significant smoke pollution, unstable quality.*

2. Pyrolysis-type Carbonization Furnace (Modern/Eco-friendly):

Semi-finished rods are hoisted or stacked into a sealed carbonization chamber (typically a vertical or horizontal retort kiln).

Process: Carbonization occurs in four stages: drying, pre-carbonization, carbonization, and cooling.

External heating (or combustion of combustible gases generated internally) raises the chamber temperature to the set point (around 600°C).

Under oxygen-free or oxygen-deficient conditions, volatile components (wood tar, wood vinegar, combustible gases) in the raw material decompose and escape.

These escaping combustible gases can be recovered and piped back to the combustion chamber as a heat source, achieving self-sufficiency.

After carbonization, the material is cooled via water or air cooling before discharge.

Advantages: High automation, short production cycle (only a few hours), chemical recovery (wood tar/wood vinegar), and environmental compliance.

III. Summary of Process Features

Waste-to-Wealth: Transforms difficult-to-process agricultural and forestry waste (e.g., sawdust, rice husks, straw) into high-value industrial/civilian fuel.

High Density & Calorific Value: Mechanically produced charcoal typically boasts 2-3 times the density of raw charcoal, with a calorific value reaching 7000-8000 kcal/kg. Its burn time is 3-5 times longer than conventional charcoal.

Clean & Eco-Friendly: Mechanically produced charcoal burns smoke-free, odorless, and without sparks or crackling (due to high-pressure restructuring and uniform structure). Modern continuous carbonization processes also eliminate smoke emissions associated with traditional charcoal production.

Uniform shape: Products feature regular square or hexagonal prisms, facilitating packaging, transportation, and usage.

Through these steps, discarded wood shavings and straw are transformed into uniformly sized charcoal blocks sold in stores for barbecuing or heating.