The fact that you can reuse the leftover wood to create wood pellets is one good reason for the increase in popularity of these pellets. So, how are wood pellets made? If you are interested to know the solution to this question, you will find this guide useful.
What are wood pellets?
Wood pellets are made of compressed biomass. It can be any type of biomass. It can be forest slash, tree branches, furniture manufacturing wood waste, etc. It is used for power generation, cooking, and commercial purposes. So, they are often referred to as fuel pellets.
How are wood pellets made?
There are multiple processes involved in the manufacturing of wood pellets. All these processes are listed below.
1. Processing Raw Materials
You can use different types of raw materials to manufacture wood pellets. But there will be slight variation in the manufacturing process with the change in the raw material type.
1.1 Chipper machine
If the size of the raw material is large, you need to break it into smaller pieces. You can use the chipper machine to break large chunks of wood into smaller wood chips for processing. You will need this machine only if you deal with large blocks of wood as the raw material.
You don’t need this machine if your raw material is in the form of wood chips.
1.2 Hammer mill
All wood pellet manufacturing plants will have a hammer mill in the manufacturing line. The hammer mill is responsible for converting the non-uniform wood chips and sawdust into sawdust of smaller sizes. It helps to provide a uniform smaller size to all the raw materials. If you are getting sawdust or wood chips as the raw material, then this machine will be the first equipment in your wood pellet production line.
1.3 Dryer machine
If your raw material is freshly cut material, you need to process it with the dryer machine. The fresh-cut raw material will have high moisture content. The moisture content in the final wood pellet needs to be ideally under 10 percent. Only then, it will burn efficiently with less smoke.
So, you must remove the excess moisture and bring the moisture level to a consistently lower value. The dryer machine will help to remove the excess moisture.
If you depend on the sun for drying the sawdust, it will take a lot of time. Also, you will not be able to get the exact moisture level across all the particles. This variation can affect the pelleting process. So, it is not an economically viable solution when you have to manufacture a large quantity of wood pellets.
2. Pelleting process
After drying, the uniform-sized sawdust will go through the pellet machine to create the wood pellets. The pellet maker comes with dies of particular sizes. The sawdust is made to pass through these dies at high pressure.
There are three types of machines for manufacturing pellets. They are horizontal ring die pellet machine, flat die pellet machine, and hybrid ones. The hybrid pellet maker can provide the benefits of both the flat and horizontal ring pellet making machines.
This process results in a heat buildup in the sawdust particles. It will help to produce natural lignin from the sawdust. This lignin act as the binding material for the sawdust particles.
You can control the different parameters and properties of the wood pellet in the pellet machine It includes length, diameter, durability, and density. You need to set proper values for these parameters in the pellet maker to ensure high-quality wood pellets as the output.
3. Cooling process
The pellets that come out of the pellet maker machines will be very hot. The temperature on the pellets will be around 200 degrees Celsius. These wood pellets will be in a soft state at this temperature. So, proper cooling is required to harden the pellets.
You need to use the pellet cooler machine to cool the hot pellets. The pellets will be at room temperature after this process. Once the cooling process is complete, these pellets are stored in large silos. Now, the manufacturing process is complete.
4. Packing process
Now comes the final step. It is the packaging process. The wood pellets stored in the large silos need to be transferred to multiple plastic bags for distribution. You need to use a proper pellet packing machine for packaging. It will allow you to pack the pellets in bags of different sizes.
What are the challenges in the wood pellet manufacturing process?
You will have to face many challenging situations if your business deal with the manufacturing of wood pellets. We will look at some common challenges faced in this manufacturing process.
1. Raw material quality
One important factor that affect the quality of the wood pellets is the quality of the raw material. You may not be able to get the same quality raw material every time. Sometimes, the density of the wood will be low, whereas high at other times. Therefore, you need to ensure the machine you use to manufacture wood pellets can handle both low and high-density materials.
2. Raw material particle size
The size of the raw material particles can affect the quality of the pellets. Once the raw material is processed using the hammer mill, all the particles need to be of the same size. If there are large variations in particle size, it will affect the quality of the wood pellets.
3. Quality of the processing machines
Multiple machines are used in the production line to manufacture wooden pellets. You need to ensure that all these machines are of very good quality. The machine must be capable of delivering consistent results all the time with minimum maintenance.
4. Rotational speed of die & roller
You need to set the rotation speed for the die and the roller. This speed will depend on the raw material type. The material that requires less time to compress should be rotated at a faster rate. The pellet maker machine’s specification will decide the rotation speed range you can set in the machine.