With the rising cost of traditional fuels (and the need to find alternatives to fossil fuels), biomass energy is increasing in popularity across the world. The wood pellet machine is one technology for converting biomass into more efficient alternative fuels for heating, etc.
What exactly is the wood pellet machine and how does it work? This article will provide answers to these questions and more.
What is a pellet machine?
A pellet machine, which is also called a pellet mill, is a machine that is used to make pellets (a small rounded compressed mass of something).
The pellet machine was invented in the early 1900s. However, the first pellet machines were feed pellet machines. They were developed to compress animal feeds into pellet form, allowing for the production of feeds with different blends of nutrients, and making rationing and transportation of feeds easier.
Then in the 1970s, people started to experiment with producing wood pellets for fuel, giving birth to the wood pellet machines. Today, the majority of the pellet machines in the market are wood pellet machines designed to use biomass to make fuel pellets (specifically wood pellets).
Wood pellets
Wood pellets are compressed biomass wastes that can be used as alternatives to fossil fuels for heating and cooking. The wood pellet machines make pellets using different kinds of biomass wastes, including wood shavings, sawdust, twigs, hays, straws, corn stalks, peanut shells, leaves, coffee husks, spent coffee grounds, etc.
You feed the biomass material into the pellet making machine, and after processing the material, the wood pellets come out as small compressed biomass cylinders (about 6 – 8 mm wide and 40mm long).
Is a wood pellet machine really necessary?
A wood pellet machine is essential because it increases the burning value of biomass and generally makes biomass more efficient in energy production.
It is true that biomass from plants can be used as alternative fuel without processing them into wood pellets. However, unprocessed natural biomass is not very efficient in energy production because they have low density. The density of herbaceous biomass is 80 – 150 kg/ m3, while that of woody biomass is 150 – 200 kg/m3.
Interestingly, pelletizing biomass increases the density of biomass to increase its combustion efficiency and make them more efficient as an alternative fuel.
Wood pellets have a bulk density of 700 – 750 kg/m3. So, a wood pellet machine makes herbaceous biomass 6x more efficient in energy production and makes woody biomass 4x more efficient.
How does a pellet machine work?
The operation of a pellet machine is fairly simple. The major parts of a pellet machine are:
- Feeder/ feed hopper
- Pressure roller
- Die
- Knife/ slicer
- Discharge unit
- Electrical cabinet and motor (or a diesel engine)
- Underframe
Main parts of a wood pellet machine
The biomass material is fed into the pellet machine through the wide opening of the feeder at the top of the machine. The materials enter the upper box body of the machine, where they fall onto the thick perforated die, spreading over it.
When you start the machine, a rotating mechanism (making use of an electric motor, transmission shaft, and gearbox) provides a motive force that rotates the pressure roller against the die. The rotating roller crushes the biomass material against the die, thereby pressing the material into the die holes (the small holes on the die).
The biomass material is forced through the die holes, compressing the materials in the process. The high pressure and friction heat up the raw materials as they are molded into the holes, causing them to fuse together. Thus, the materials come out of the other side of the holes as solid cylindrical masses.
A knife under the die cuts the extruding condensed biomass cylinders into certain lengths to form pellets. The cut pellets fall onto a tray and come out of the machine through the discharge outlet.
The diameter of the wood pellets is equal to the inner diameter of the perforated holes of the die. Also, the position of the slicer/ knife under the die determines the length of the wood pellets.
What are the types of pellet machines?
Pellet making machines are classified into two, according to their mechanical working principles. The two types of wood pellet machines are: flat die pellet making machines and ring die pellet making machines.
1. Flat die pellet machine
The flat die pellet-making machine was the first to be created. As the name suggests, the perforated die is a thick flat plate. Also, the raw materials drop into the pelletizing chamber by their own weight.
Working principle of a flat die pellet maker (Source: medium)
The flat die pellet machines can be categorized into two:
- The rotating roller pellet machine. In the rotating roller pellet makers, the die is stationary, while the roller rotates to compress the raw material into the holes of the stationary die.
- The rotating die pellet machine. In the rotating die pellet makers, the roller is stationary while the perforated die rotates under it. As the die rotates, the roller grinds the biomass material into the die holes.
Flat die pellet machines are generally small-scale machines with a production capacity of 50 – 400 kg/ h. They are the choice pellet making machines of small-scale pellet makers like households, schools, etc.
2. Ring die pellet machine
The ring die pellet machines were developed a few decades after the flat die pellet makers. The distinguishing feature is that the perforated die is a ring, with two or more rollers inside. The rollers grind the raw material against the inside wall of the ring to force the material through the die holes.
Working principle of a ring die pellet machine (source: medium)
There are two types of ring die pellet machines depending on how the dies are placed.
- Horizontal ring die pellet machines. These are ring die pellet machines where the ring die is vertical. This means the raw material cannot fall directly into the pelletizing chamber but has to be carried in via a forced feeder.
- Vertical ring die pellet machines. These are ring die machines where the ring die is horizontal. So, the raw material you feed into the machine will fall directly into the pelletizing chamber.
The ring die pellet machines are best suited for large-scale pellet production. Their production capacity is between 0.8 – 2 tons/ h. So, if you’re looking to start a pellet business, you should go for a ring die pellet maker.
How much does a pellet machine cost?
The price of a pellet machine varies widely depending on the type and model of the machine and the retailer. However, prices typically range between $4,000 and $48,000.
The more the production capacity of a pellet machine, the more it costs. Thus, flat die pellet machines are generally cheaper than the ring die types.
You’ll find pellet machine for sale costing as follows:
| Production Capacity | Price Range |
| 300 – 500 kg/h | $4,000 – $8,000 |
| 500 – 1,000 kg/h | $7,000 – $14,000 |
| 1,000 – 1,500 kg/h | $15,000 – $25,000 |
| 1,500 – 2,000 kg/h | $23,000 – $30,000 |
| 2,000 – 2,500 kg/h | $33,000 – $42,000 |
| 2,500 – 3,500 kg/h | $42,000 – $50,000 |
Final Thoughts
A pellet machine helps you convert biomass into wood pellets that can be used as alternatives to fossil fuels for heating and cooking. Using a rotating mechanism, the pellet making machine uses a roller to press biomass material into the holes of a die plate. The materials exit the die holes as solid cylinders and are cut into pellets.
Wood pellets are cheaper and more renewable alternatives to fossil fuels. To produce fuel pellets for household or office use, go for a flat die pellet machine as it is suitable for small-scale pellet production. To enter the wood pellets business and produce these fuel pellets for sale, go for a ring die pellet machine which is suitable for large-scale pellet production.
