Everything You Need to Know About Pellet Mills – Operation and Use

Pellet is a fuel material that in recent years has risen to a leading position among ecological fuels. Its growing popularity is driven by both economic and environmental factors. Compared to fossil fuels such as hard coal or heating gas, pellet is a more balanced fuel material with low environmental impact, both at the production and combustion stages. 

In times of constant turbulence on fossil fuel markets, easy-to-produce and easy-to-transport pellet can also prove to be a guarantee of energy stability, especially for farms producing their own biofuel. The simplicity of the pellet production process is also one of its undeniable advantages. 

The tool necessary for pellet production is in fact only one simple machine, thanks to which wooden chips, shavings, sawdust and other natural waste can be transformed into energy-rich granules.

This machine is a pellet mill (or if you prefer – pellet machine). Let us take a closer look at it.

What Is a Pellet Mill? – Basics

Pellet mills are machines designed to press biomass into pellet granules. These devices come in various sizes and configurations and may differ in operating speed, level of automation, or power supply method. However, their operation is always based on the same principle – biomass is fed into the device, and during the pelletizing process it is ground, subjected to temperature and pressure, and then extruded. 

As a result, we obtain cylindrical granules of compressed biomass with high density and low moisture content – that is, pellet. 

How Does a Pellet Mill Work? Pellet Mill Construction

A pellet mill contains several key mechanisms enabling efficient biomass processing:

Drive Motor 

It supplies energy for the operation of the entire machine, driving other components. 

The most popular type is electrically powered pellet mills. Combustion models are also available – powered by a gasoline or diesel engine.

Crusher 

The crusher contains blades or mills that rotate at high speed.

These elements break the raw material into smaller pieces, cutting it to the appropriate size. 

In this way, the material introduced into the machine is first thoroughly ground. Some pellet mill models are additionally equipped with a particle size control system in the form of a sieve or perforated sheet. This type of protection captures oversized biomass particles that could reduce pellet quality.

Thanks to the initial mechanical processing of the raw material, further processes are possible.

NOTE: a pellet mill does not function as a wood chipper, and the biomass fed into the machine should be pre-crushed. The loose fraction of the raw material should not be larger than the die holes.

Rollers

The rotating roller mechanism causes the biomass to move inside the pellet mill. The rotating rollers move over the die, pressing sawdust into the holes and thus giving it the characteristic pellet shape. Friction of the pellet mill rollers generates high temperature (up to 135 degrees Celsius), which increases the plasticity of the processed biomass. The pressure force of the rollers is also responsible for the “compression” of the heated biomass, resulting in the high density of the finished pellet. 

Pellet Mill Die

The die is a flat metal plate with round holes several millimeters in diameter (most commonly between 6 and 10 mm). 

Its thickness depends on the type of processed raw material.

The general rule for selecting the appropriate die states that the harder the material fed into the pellet mill, the thinner the die should be. 

For pine shavings, for example, it is 33 mm.

This is the component that gives the final shape and size to the granules. 

The roller mechanism presses the heated biomass of appropriate consistency through the perforations of the die. In this way, pellet particles are formed.

IMPORTANT: thanks to the lignin contained in wood (a natural substance with adhesive properties), there is no need to use an external binder in the biomass granulation process. 

As a result, the finished pellet contains no added external chemicals.

Discharge Chute

The finished pellet falls out of the machine through a chute, most often in the form of a metal trough.

After extrusion, the granules accumulate in a container placed under the chute, where they must cool down to room temperature. Special coolers equipped with fans are sometimes used for this purpose. To transport the finished pellet, a screw conveyor can be used, facilitating continuous fuel production.

The cooled granules are ready for use. 

Is Operating a Pellet Mill Difficult?

The competitiveness of pellet lies, among other things, in the simplicity of its production. After the initial calibration of the pellet production device, its operation is simple and does not require the constant presence of a specialist. The operation of a pellet mill can also be easily automated using screw conveyor systems feeding biomass and transporting finished pellet to a designated storage area. 

The wide range of models in different sizes and capacities means that a pellet mill can be used both for local fuel production for personal use and for automated, large-scale commercial production.

Pellet mills, like all mechanical devices, require periodic maintenance such as lubricating mechanisms and removing contaminants from inside the machine. However, these are not complicated operations and their level of complexity does not exceed that of maintaining a gasoline lawn mower or a hay shredder.

Pellet Mill – Efficiency

The efficiency of a pellet mill depends on the size and power of the particular model. Small, mobile pellet mills such as pelletnik 150 achieve a capacity of 50–100 kilograms of granulate per hour. Large pellet production lines can produce about one ton of pellet per hour.

In the case of the largest industrial pellet mills, capacity may reach up to ten tons per hour.

Pellet Mill – For Whom?

A pellet mill is a universal device that can be used both in specialized wood processing plants and in farms or smaller workshops. To successfully produce pellet, one condition must be met – constant access to biomass. Farms generating large amounts of bio-waste or sawmills producing significant quantities of wood residues can successfully achieve energy independence thanks to a pellet mill. Turning waste into fuel is an ecological and cost-effective solution. 

However, it is worth making sure that the type of biomass available is suitable for pellet production. Otherwise, one may opt for less demanding briquette production.

More on this topic can be found here: Briquetter vs Pellet Mill

What Can Be Pelletized?

The best base materials for processing with a pellet mill are:

Wood, wood shavings, wood dust, chips, bark, brushwood, hay, straw, seed husks, leaves, sunflower waste.

Why Is It Worth Using a Pellet Mill?

Using a pellet mill guarantees a high level of energy independence. Own fuel allows users to become resistant to market price fluctuations or long and uncertain supply chains. By producing our own fuel, we also gain control over the entire production process and certainty regarding fuel quality. This may prove important for maintaining the good condition of your heating system. 

Pellet production is also an alternative form of waste management. Many materials forming the basis for biofuel production must be disposed of in one way or another anyway, so using their energy potential in the pelletizing process prevents waste of resources.

In the long term, a one-time expense may prove to be a profitable investment. A pellet mill simply pays off.