• Diameter: 6 – 8 cm
  • Moisture: 10% max
  • Ash: < 2%
  • Bulk density: > 730 kg/m3
  • Calorific value: >4.500 cal/kg
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1. Overview

Wood pellet is a solid fuel that is produced by crushing and densifying waste timber like sawdust, forestry residues, industrial byproducts like old paper and forestry wastes. The length is 1-2 cm and the diameter is generally 6, 8, 10, or 12mm. It is possible to produce 25mm wood pellet at maximum.

Characteristic of wood pellet is very easy to manage compared to other biomass fuel. As the shape and hydrous rate are stable, wood pellet is suitable to use in automatic combustion installation and it can remarkably save time and labor for both of electric power generation boiler and pellet stove for house. It is possible to transport long distance because wood pellet has high energy density and much energy can be transported at once. Also wood pellet which is heattreated, can be stored in long term with less risk for molding.

Dried timber 1ton can generate energy equivalent to electric power 1,000 kWh or heat 4,500kWh. Energy ratio for pelletizing in comparison with wood pellet product’s is as follows:

  • To pelletize dried materials needs energy equivalent to 8-13% of energy contained in wood pellet product
  • To pelletize materials (sawdust) after drying needs energy equivalent to 10-25% of energy contained in wood pellet product.
  • Whole process of pelletization of wood chip (including drying and crush) needs energy equivalent to 18-35% of energy contained in wood pellet product

2. How are Pellet made?

Pellet Mill Process

Truckloads of raw materials are brought to pellet mills every day and can arrive in many different forms. Some of the raw material may be sawdust, wood chips, lumber mill scrap, and even full trees unsuitable for lumber. The raw materials may be green, or freshly cut, may be partial dry or even kiln dried. By processing these raw material all in the same way, the end product has consistent moisture content, heat value, ash content, and burn characteristics. It is very important that all pellet manufacturers produce pellet to the same standard so that pellet appliances burn and heat consistently. Here are some of the processes:

Chippers & Hammer Mills

Some pellet plants start their process by putting large pieces of wood through a chipping machine for processing. These are only necessary for mills that accept this non-uniform feed stock. There are many different configurations to pellet manufacturing plants depending on their raw material source. While they all don’t have chippers, almost all of them have a hammer mill at the beginning of their milling process. These machines take sawdust and wood chips and break them down into a consistent smaller size, making drying and pressing through the pellet die quick and consistent.


If a pellet mill uses fresh cut raw material, material exposed to the weather or high humidity, or a mix of raw materials that may contain moisture, they have to dry the sawdust to a consistent moisture level. Large dryer drums may use natural gas, propane, sawdust burners, or other fuels to heat the drum, driving off the extra moisture.

The Pellet Mill

After drying, the sawdust is pressed through dies at high pressure. This process causes the sawdust to heat up and release natural lignins in the wood that bind the sawdust together. The mill also determines the density of the pellet, the diameter, the durability, and the length. All of these characteristics are very important for consistent pellet appliance operation.

Cooling and Storage

The pellets come out of the mill between 200 and 250 degrees and soft. A cooling tower is used to bring the temperature down and harden the pellets. After cooling, they are usually stored in a large silo to await bagging or bulk distribution.

Bagging or Bulk

According requirements

3. Specifications:

  • Diameter: 6 – 8 cm
  • Moisture: 10% max
  • Ash: < 2%
  • Bulk density: > 730 kg/m3
  • Calorific value: >4.500 cal/kg

4. The photograhps

viên nén mùn cưa - wood pellets

viên nén mùn cưa - wood pellets




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