Why Are Wood Pellet Mills So Different To Other Presses?

The equipment used to produce wood pellets is known by several names including a pellet mill, pellet machine and pellet press. The history of pellets predominately in the animal feed industry, and though the principle of an animal feed pellet mill and wood pellet mill are the same there are some significant differences in the raw material. These differences in the raw material means that the pellet mill also has to be modified. For example, with animal feed, the raw material is specifically grasses and low density materials. In essence it is much easier to compress low density materials into pellets. It requires less energy and puts less stress on the equipment. Temperature, a significant factor of pellet production is also different with higher density raw materials such as wood. A higher temperature has to be reached to melt the natural lignin within the wood fibre. On large scale production this often means the introduction of high temperature steam treatment conditioning prior to the pellet mill, to aid natural lignin melting.

Wood Pellet Making Machine Facts

In terms of the differences between a feed pellet mill and a wood pellet mill, one example of the difference is the speed at which the wood pellet mill operate. Due to the increased density of the wood, more power is required to compress the wood through the die. Therefore to increase power, the pellet mill is geared down lower to increase torque. However, the pellet mill is also geared lower to guarantee that the raw material spends longer in the die to reach the temperatures require to melt the natural lignin. Another key difference is the condition that the die needs to be in to process wood into pellets. The holes of the die template need to be smoother as there is increased resistance during wood pellet production. Without smooth die holes it is much harder to get the pellet mill up to efficient operating temperatures without causing the die to block. Gun drilling is normally used on the die templates to guarantee smooth hole finish.

Wood Pellet Production Processes

Other key factors of the wood pellet production process is the need for material drying. With wood pellet production particularly, the materials used have a very high moisture content of around 50%. Around 35% of this moisture needs to be removed before the material is suitable for pellet compression. To dry the raw, for cost and environmental reasons it makes sense to use the raw material as the fuel for the dryer. Particle size is also another important part of efficient pellet production. After a chipper for initial size reduction, a hammer mill is used to reduce to 5mm.

Wood Pellet Suppliers and Fuel Quality

Depending on the type of wood residue used, the grade and value of the wood pellets will change. To produce the highest grade pellet, the sawdust must be free from bark and produce an ash content below 1%. However, there is obviously large volumes of wood residue which can be used to produce wood pellets which will produce an ash content above this. For example tree surgeons generate large volumes of wood waste. Even though these pellets will produce a higher ash content, they are still a good quality pellet fuel. To learn more about the process of making pellets and the equipment used, please click the link below.

Wood Pellet Mills Guide

The Wood Pellet Production Guide © PelHeat Ltd - Why Are Wood Pellet Mills So Different To Other Presses?