Pelletizer and granulator - similarities and differences

Searching the Internet for information about biomass fuels, and in particular the equipment facilities needed to start producing them, you will undoubtedly come across two recurring terms: pelletizer and granulator. In some cases they will be used interchangeably - to describe one piece of equipment, while in other contexts they will refer to different types of machinery. Sometimes you will even encounter them in the form of the two-word cluster "pelletizer/granulator."

It's not hard to get lost in this convoluted terminology.

So what is the difference between a pelletizer and a granulator? What are their applications? Let's check it out.

Pelletizer and granulator - presses for pressing pellets

Both a pelletizer and a granulator are so-called biomass pellet presses.

This type of equipment is used to process biomass, or natural waste, into uniformly sized pellets of uniform consistency.

The operation of a pellet press is based on the interaction of several mechanisms. These are:

The drive motor
The motor provides the energy for the operation of the pellet press, most often in electric versions, although there are also combustion models.

Grinder
The shredder grinds the raw material into small pieces thanks to rapidly rotating blades, preparing it for further processing.

REMEMBER: The shredder grinds the input biomass accurately, but before feeding the raw material into the press, it should already be pre-chopped, for example, with a chipper. The fraction of the input raw material should not be larger than the diameter of the die openings.

Rollers or rollers
Rotating rollers move the biomass through the die, shaping it into pellets and ensuring the right density of pellets. Depending on the mechanism that drives the rotation of the rollers, there are single-axis models with two, three or four runners. The higher the number of runners, the higher the efficiency of the machine.

Matrix
The matrix is a metal plate with holes through which the biomass is pressed, forming pellets of a certain diameter. It is this element that is responsible for the final shape of the granules.

IMPORTANT: The type of matrix is the element that distinguishes pellet presses from granulators. Read more.

Pelletizer and pellet press - differences

Now that we have established that a pelletizer and a granulator are devices with an identical operating principle, what makes us divide them into two, separate categories?

The main differences are:

- Application

Pelletizers are machines for producing high-quality biomass fuel - pellets.

Most often, wood-based material such as wood chips, wood chips or wood pulp is used to make pellets.

By definition, a granulator is an agricultural equipment used to process agro material to produce granulated feed for livestock. Due to this function, a granulator is mainly designed to process animal edible raw material such as grain husks. That is why it is sometimes called a "feed pelletizer." Granulators in agriculture can also be used to produce granulated fertilizer.

It is worth noting that the raw material processed by granulators is, as a rule, softer, and due to the application, pellets from the granulator may have a lower quality (homogeneity, density) than a specialized fuel such as pellets - the product of a pelletizer.

Consequently, granulators designed only for processing agro material (i.e., those models that do not function as both machines) may be less accurate and robust.

This is because the margin of error for feed or fertilizer production is greater.

- Die thickness

The most important design difference between the types of biomass presses discussed is the thickness of the die. The general rule of thumb for selecting the thickness of the die for the type of biomass being processed is that the softer the raw material, the thicker the die. It follows that a pelletizer should be equipped with a THICKER die than a feed pelletizer, since wood-based material is characterized by greater hardness than agro material.

While this rule may seem illogical at first, it has a functional rationale. This is because harder material has a greater tendency to form blockages in the die. With thicker dies, wood chips could accumulate in deep holes and inhibit the extrusion process. Softer material has less tendency to dam die perforations.

Consequently, feed extrusion dies are thicker than those dedicated to wood chip pelleting.

For example, for spelt husk it is 50 mm thick, for straw it is 45 mm thick, for pine chips the recommended die thickness is about 33 mm.

For harder woods, the appropriate die thickness is proportionally smaller.

IMPORTANT: In many models of pellet presses, the die is a replaceable component. Some manufacturers consult the thickness of the installed die with the buyer before selling the pelletizing press. Hence the functioning of multifunctional pelletizers on the market.

Every pelletizer is a granulator - not every granulator is a pelletizer

On the Internet, it is not difficult to come across pelletizers/granulators that combine the functions of both devices. In our offer, too, most pellet machines can serve as granulators for feed or fertilizer (such as this model). From a practical point of view, this is the best solution, because by designing a device intended for more technically demanding pellet production, you meet, so to speak, in passing the requirements of pressing agro - pellets.

Pelleting machines, designed for the production of fuel from different types of wood, by definition have the possibility of changing the die. In most cases, nothing prevents replacing it with one that will allow the formation of feed or fertilizer pellets.

To summarize this convoluted regularity: every type of pellet is a pellet. However, as we have already established, there are many types of pellets and definitely not every pellet is a pellet. It follows directly that, EVERY pelletizer is a type of pelletizer and can successfully function as a feed pelletizer, but NOT EVERY feed pelletizer (for technical reasons) is also a pelletizer.

In short:

A pelletizer is the most versatile device in the category of biomass pelletizing presses and can serve a variety of purposes, both industrial and agricultural.