Wood Pellet Production Facts and Details

The production of wood pellet fuel is an area of growing interest, however there is little quality information available on how the process actually works. At first the pellet production process may appear basic and even simple. The fact is this couldn't be further from the truth, by the fact that to produce quality pellets from any raw material requires the raw material to have specific qualities and the right equipment. In a sentence, pellet production is the compression of a loose material into a compressed pellet form with a uniform size, shape and density. However to achieve a pellet of suitable quality will require a deeper understanding of the process of what the raw material requires to produce a quality pellet. Firstly one of the key criteria for wood pellet production, or any pellet pellet production is the removal of moisture from the raw material. There are two reasons for this, firstly as a fuel, moisture reduces combustion efficiency, heat generation and increases ash content. Secondly it is not possible to compress moisture, therefore for the pellet to hold its shape, a low moisture content is vital. However a certain percentage of moisture is required for the pellet to form. The percentage of moisture required depends on each raw material and equipment used. For example if steam conditioning is used in the production process, a raw material moisture content as low as 10% can be used. However steam conditioning is generally only used on a large scale due to the expensive and risk control required. Therefore where steam conditioning is not used, a raw material closer to 15% is required. Too much or too little moisture can effect wear of the rollers and die and also the energy consumption of the pellet mill. Therefore is is generally recommend to experiment with the moisture content of the raw material to achieve best pellet quality and lowest energy usage.

Biomass and Wood Pellet Manufacturing

Pellet production can be carried out on either a small or large scale. However as with steam conditioning, the equipment and processes used does vary. In terms of drying equipment, there are preferences for small and large scale production based on available space, cost, and process control. For small scale production, pipe flash dryers are commonly used as they are fairly basic, and the cost to manufacturer are fairly low. Pipe dryers however are not ideally suited to dry raw materials with a high moisture content around 50%, for example virgin wood. The raw material may require several passes to remove sufficient moisture. For large scale wood pellet production rotary dryers are used, these are larger and more expensive, however the drying time can be controlled to dry in a single pass. 

There are also differences in the types of pellet mill used in small and large scale production. The most basic design of pellet mill is the flat die pellet mill. This design is commonly used for small scale production, due to lower production costs and cheaper consumables. For large scale production ring die pellet mills are more commonly used as they are generally regarded as being more energy efficient. All pellet mill designs share similar principles of operation. These include a roller and die configuration. The design of the pellet mill may either have the die or roller shell rotating, the rotation speed required changes.

PelHeat Wood Pellet Production Guide

At PelHeat we have many years of experience in pellet production, and we provide a pellet production consultation service. The PelHeat guide download will show you how to make wood and other fuel pellets.

 The Wood Pellet Production Guide © PelHeat Ltd - Wood Pellet Production