Coal briquette is made by the coal briquette machine which uses coal dust or coal fine as the raw material. Sometimes we add other materials like the binder or something to make the briquette as most of the coal fine is hard to form together only by briquette machine.

The following are the coal powder requirements for making coal balls, covering core indicators such as composition, physical properties and process adaptability to ensure the production of high-quality and high-combustion-efficiency coal balls:

Physical property requirements

1. Particle size distribution

• Optimal particle size: 80%~90% of the particles should pass through 80~200 mesh sieves (0.075~0.18mm).
• Function:
  • High proportion of fine powder → Close contact between particles and high molding strength.
  • Too many coarse particles → Coal balls are prone to cracking and falling off.

2. Fluidity

• Appropriate fluidity is required to ensure uniform filling of the mold in the molding machine (such as a roller press).

Process adaptability requirements

1. Binder process (binder needs to be added)

Coal powder requirements:

• The ash content can be slightly higher (≤20%), but it needs to be compatible with the binder (such as starch, bentonite).
• The particle size can be relaxed to 60~150 mesh (0.1~0.25mm).

2. Binder-free process (high-pressure direct molding)

Coal powder requirements:

• Low ash content (≤10%): Too high ash content will hinder the natural bonding of particles.
• High volatile matter (20%~28%): Enhance the bonding of coal powder itself.
• Ultrafine powder ratio: at least 30% pass 200 mesh sieve (≤0.075mm).

Special scenario adjustment suggestions

1. Biomass mixed briquettes

If biomass such as straw and sawdust is added:

• The coal powder particle size needs to be finer (90% pass 100 mesh sieve) to ensure uniform mixing with biomass.
• The sulfur content needs to be further reduced (≤0.8%) to avoid the production of corrosive gases during mixed combustion.

2. Industrial fuel briquettes

• High calorific value requirements: coal powder with fixed carbon ≥60% and volatile matter ≤25% is preferred.

3. Barbecue/household smokeless briquettes

• Use low-sulfur (≤0.5%) and low-ash (≤8%) coal powder, and mix with charcoal powder to improve combustion cleanliness.

Pretreatment steps

• 1. Crushing and screening: crush the raw coal to the target particle size and remove impurities (stones, metals).
• 2. Drying: control the moisture to 8%~12% (natural drying or dryer).
• 3. Homogeneous mixing: if binders or biomass are added, use a mixer to mix thoroughly.

Common problems and solutions

High-quality coal powder is the basis for producing high-performance coal balls. Parameters need to be adjusted according to the process type (with or without binder), application (industrial/household) and environmental protection requirements. It is recommended to conduct a small test to determine the formula before large-scale production.