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Wood Pellet Plant Production Process Step Decomposition

Date: 07/10/2020 08:11:41 From: wood-pellet-plant.com Clicks:

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The wood pellet plant is large or small, and the output is more or less. But the production process of each wood pellet plant is the same. As a user, it is necessary to understand each section of the wood pellet production line in the early stage, understand the different production equipment that each section will require, and the characteristics and functions of each production machinery and equipment. A complete biomass wood pellet production line includes 8 processes. The following introduces the detailed information of the eight sections and the mechanical equipment used in the sections.

Flow chart of wood pellet production line
Flow chart of wood pellet production line

Chipping Section

The majority of the wood pellet manufacturers adopt all sized wooden raw materials, such as the logs, barks, saw dust, wood shavings, etc, which indicates that the size reduction process is not only a necessary step for wood pellet plants, but also extremely costly. The reasons can be seen as follow: firstly, the pellet mill can only process the raw materials with a diameter less than 5mm, obviously, the unprocessed raw materials are way too big to feed in the pellet mill directly. Secondly, for the upcoming drying process, the smaller particles means a shorter drying time and lower energy requirement, and the larger particles means a longer drying time and higher energy requirement. Therefore, the initial size reduction process can help reduce the energy consumption of the pellet plant, and enhance the serve life of the other machines in the pellet plant.

Disc Wood Chipper
Disc Wood Chipper

The equipment we use in the primary size reduction process is normally a wood chipper, also known as the wood crusher. The knives inside the wood chipper can shred the logs or barks into small particles with a diameter less than 50mm before they can go through the next step. Disc wood chipper can cut raw and small materials including logs, slab, veneer, bamboo, brushwood, corn stalk, cotton stalk, reed and other non wood fiber stalk, the length of chips can be adjusted in a certain range as needed.It is mainly made up of the base, feed port, cutterhead, casing, chipping blade and electronic control, the machine can adjust cutting blade as needed, produce different specifications and thickness of the chip.

For instance, be careful to avoid the foreign contaminants such like metal particles, small stone, sand, which may cause a mechanical failure or even a pellet plant safety incident.

Hammer Mill Section

During the grinding process, the machine we use is hammer mill. Compare with the wood chipper, the raw materials for hammer mill requires a diameter no more than 50mm, and the product it makes contains a diameter about 5mm, so that during the pelletizing procedure, the pellet mill only need to act as a molding machine not a grinding machine to enhance the serve life of the pellet mill and the lower the energy consumption. The price of a hammer mill is more expensive than the price of a wood chipper, but it maintenance costs is lower than the wood chipper.

Wood Pellet Mill
Wood Pellet Mill

Wood hammer mill is popular with many industries and we recommand it as well if you are considering biomass industry investment. Biomass fuel takes wood chips, wood sawdust, peanut stalks, corn straws and so on as materials and wood hammer mill can crush these materials into 3mm-5mm wood materials for pellet mill use.

Drying Section

After the hammer mill section process, the raw materials are moved to the next part, moisture reduction. Normally, the wooden raw materials has a moisture content no more than 50%, but the high quality wood pellet requires a moisture content about 8%-12%. The dryer is one of the most expensive machine in the wood pellet plant, by its obvious energy consumption. To reduce the capital input, we recommend the rotary drum dryer, which consist of a low price and simple operation procedures. In addition, the energy consumption reduction of the dryer can be realized by using the wood products in the wood pellet plant, therefore, connecting to the electric grid would not be necessary.

Due to its structure, the dryers can be divided into several types: the rotary drum dryer, suspension dryer, steam dryer, flash dryer, belt dryer, and etc. Different dryers have different features, for example, the rotary drum dryer get a competitive price, while the suspension dryer is expensive for its small footprint. The steam dryer is also very costly so only some real large- scale wood pellet plant will accept it. For flash dryer and belt dryer, the size of the raw materials must be controlled under 10mm, but the rotary drum dryer can manage a wider size range of the raw materials.

Initial Screening Section

For some pellet plants, the sieving procedure is not a necessary step, but in consideration of the pellet plant safety, it is a recommendable step.

After the initial size reduction process, the raw materials stay in a small particle appearance. Hence, it may easily mixed in some unpurified particles such like stone, metal pieces, which will cause the mechanical failure or even start a fire during the following steps. The machine to manage the initial sieving process would be a magnetic separator, which is an optional part for our customers.

Granulation Section

The core machine for a pellet plant is the plant mill, which used to form the raw materials into wood pellet. Actually, there are several factors that determined the choice of pellet mills for the pellet plant. Such as: the type of raw materials , the pellet plant capacity, the wood pellet quality requirement, the pellet diameter and length.

Typically, two types of pellet mills are in consideration, the flat die pellet mill and the ring die pellet mill. Both of the two types of pellet mills remain a simple working principle: the prepared raw materials will be fed into the pellet mill, and straightly go in the chamber. In it, the rollers will continually push a strong pressure to the raw materials, which will generate a higher temperature of the materials and the lignin in the wooden materials will be a natural glue for the materials. In the same time, the raw materials will try to find a way out, which is the holes on the die. So the rollers press the raw materials and force them to go through the holes in a cylinder shape. Outside the holes, there is a knife that used to cut the wood pellet into a required length. Last step, the well made wood pellet will be distributed from the discharge hole.

Wood Pellet Mill
Wood Pellet Mill

The most simple way to choose pellet mills for your pellet plant is to find out the capacity you need. For a household application, the flat die pellet mill is our recommendation , which has a suitable capacity, a competitive price and a small footprint. But for large scale business, the ring die pellet mill is definitely the perfect choice for you, as it maintain a large capacity and an automated procedure.

Cooling Section

As we have mentioned before, the pelletizing procedure will generate a higher temperature and moisture of the wood pellet, which makes the pellet very easy to deformed when it leaves the pellet mill. In that case, after the pelletizing process, the wood pellet will be send to a cooler immediately. A cooler is used to reduce the temperature and moisture of the wood pellet and after that you can expect a dry pellet with a proper rigidity.

The working principle of SKLN Cooler

The wet and hot pellet, pressed by pellet machine, through the inlet of rotate airlock feeder into cooler machine. When the pellet materials are cumulate and touch on door, switch on motor and discharging works. The motor goes reciprocating motion with reducer and eccentric mechanism, and the pellet are discharged from the gap of discharging frame and fixed frame, when discharge door closed, no discharging. When feeding is more than discharging, the motor and discharging stop running, and feeding is going. Like this, fan is always working. Because raw materials is flowing from up to down, while wind is from down to up, which pellets touch with fan to cool, so it is called counter-flow cooler machine.

SKLN Cooler
SKLN Cooler

Final Screening Section

After the cooling process, the main process of making wood pellet is finished. But for some commercial requirement, there might need another step, the final sieving.

During the pelletizing and cooling process, the fines is a unavoidable by-product. When you shipped the wood pellet to your customers, or wholesalers, there will be a limit of fine content. So before the storage, the finial sieving is a optional choice for wood pellet manufacturers. The different screening degrees depend on the different market conditions and specifications.

Packing Section

The packaging section is the last section of the entire pellet production line. Because the pellets need to be packaged and stored after cooling, the packaging machine is not opened here.The automatic feed pellet weighing and packing machine is suitable for large and medium sized feed pellet production plants. It is always applied to a automatic weighing and packing system combined with the transport mechanism and the sewing machine. The automatic weighing and packing machine can pack wood pellets, feed pellets, fertilizer granules and other particle material and powder material with good fluidity. With an excellent performance, it has been adopted by a great many large feed pellet production factories.

The above is the Wood pellet plant production process step decomposition introduced to you. If you are going to build a wood pellet production line or other biomass pellet production line, please contact us. From free design in the early stage to commissioning and testing in the later stage, Richi Machinery will serve you wholeheartedly!

The above is the article for you: Wood Pellet Plant Production Process Step Decomposition. If you are interested in our products or project solutions, please contact us. We will give you the best product quality and the best price. Email: sales@cnrichi.cn

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