The Flat Plate Die Pellet Mill and the Ring Die Type Pellet Mill – The Two Main Types of Pellet Machines

A pellet machine, or pellet mill as it’s most commonly known, is quite possibly the most important piece of equipment that you’ll need if you’re going to make wood pellets. The pellet mills sole task is to transform your biomass or wood waste into fully formed and utilizable pellets. Doesn’t sound so difficult does it? Well, it may sound easy, but the devil’s in the details as they say. Even though the concept of making pellets, aka pelletization, is simple to grasp, taming the process of making wood pellets is not so straightforward. Between understanding the idiosyncrasies of the pellet mill and the subtleties of using different wood and biomass materials to make pellets, initially learning how to make wood pellets can have a very steep learning curve.

The simple fact is that the pellet mill does one thing: It forms pellets. What makes pelletization tricky is the many variables associated with the different types of biomass or wood raw materials used to produce pellets. When most people start out, they mistakenly blame their pellet mill rather than fully understanding that the raw materials they are using are the reason for their problems. I can’t stress enough how useful you’ll find this guide on how to make pellets. With that said, lets take a closer look at the pellet mills themselves.

First of all, there are two basic types of pellet mills. The ring die type, and the flat plate die type. As their names imply, the differences between the two machines are the type of die that’s used to form the pellets. These pellet mills also employ some type of gear reduction system that’s used to drive the rollers that in turn feed the material through the dies.

Ring die type pellet machines are a little different than their flat plate die siblings. The die is in the form of a ring, and the rollers force the materials through the die from the inside of the ring to the outside. Ring die type pellet mills are normally used in commercial production environments, and as such their prices and outputs are significantly higher. If you’re interested in making wood pellets to sell commercially, this is the type of pellet mill that you’d typically use.

Here’s a good video demonstration of the flow through a large commercial ring die type pellet machine:

The flat plate die pellet mill uses a flat plate die. This die is a thick flat “plate” made of metal with holes drilled through it. On top of this die ride the rollers. Raw material is dropped down onto the die, and the rollers turn and force or push the materials in an extrusion process through the flat plate die. When they exit the flat plate die, they’re in the form of a pellet. These pellet machines are much simpler in construction than the ring die type pellet machines, and are much less expensive. They’re also the type of pellet mill that most homeowners use when they’re making their own wood or biomass pellets.

Here’s a great example of what the rollers and dies look like and how easy it is to change them out:

Flat plate pellet machines can either be powered by an engine (gas, diesel, lp), an electric motor, or a powered take off (p.t.o) unit on a tractor. If you’re going to go with an electric motor powered unit, make sure you have enough power capacity where you’ll be using it. Also, make sure you factor in the costs of upgrading your electrical system, or the costs associated with wiring it into your electrical system. Even though this is a one time cost, it will still affect your return on investment.

A few other caveats you should pay attention to before you buy. Don’t forget that pellet mills are high wear equipment. The dies and rollers will need to be replaced on occasion. Just how often will depend on the production rate and the type of raw material or feedstock that you will be using to make pellets. And unless you’re buying a larger commercial unit, most of the smaller less expensive units are made in china, therefore parts are more difficult to source.

This is becoming less of a problem though due to the rise in popularity of small pellet mills and the fact that many people are selling replacement parts that are locally manufactured. Most any machine shop can easily manufacture whatever part you need, although it may be somewhat expensive if you’re buying parts one piece at a time.

Another thing to keep in mind is their energy usage. Pelletization is a rather energy intensive operation, and as such requires a fair amount of energy input. Be careful to factor in these power costs as this will directly influence the total cost of your homemade pellets.

And last of all, remember that practice makes perfect. Making pellets isn’t a plug and play process. There is a definite learning curve that will need to be surmounted. This will be especially true if you’re planning on using biomass waste, as it seems to be more difficult to pelletize than wood waste material. Note though that it’s more difficult, not impossible.

Make Wood Pellets

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