Pellet production requires optimization of many parameters, including the proper selection of matrix parameters to ensure high efficiency and quality of the final product. How to produce pellets is the most frequently asked question. Here is a detailed description of the pellet production process and the impact of matrix parameters on this process:
How does the pellet production process work?
1. Preparing sawdust for granulation
Collection and preliminary preparation of raw material: Raw material such as wood, straw, sawdust or other biomasses is collected and prepared by cutting to appropriate sizes.
Drying: The raw material must be dried to the optimum moisture content (usually 10-15%) for the pelleting process to be effective.
2. Grinding of sawdust and raw materials on a hammer mill
The raw material is ground into fine particles in hammer mills or other grinding devices to obtain a uniform fraction.
3. Mixing in the granulator conditioner
The ground raw material is mixed with steam or other additives to increase its temperature and moisture, which facilitates pellet formation.
4. Pelleting = granulation
The raw material is fed into the pelletizer where it is pushed through a die using rollers. The die shapes the raw material into cylindrical pellets.
Cooling: Freshly produced pellets are hot and must be cooled to achieve the proper hardness and stability.
5. Packing pellets in big bags and 15 kg bags
Once cooled, the pellets are sieved to remove dust and unsuitable pieces and then packed in bags or other packaging.
How to produce pellets: Matrix parameters and their impact on pellet production
1. What is the popular diameter of the die holes?
Smaller holes (e.g. 6 mm) are used to produce fine pellets that are suitable for animal feed or finely structured biomass.
Larger holes (e.g. 8-10 mm) are used for fuel pellets from forest or agricultural biomass, where larger diameters are required, e.g. in industrial incinerators.
2. Thickness of the matrix for pelleting machines and granulators
Thicker dies allow the raw material to stay in the die longer, which increases pellet compression and density. They are ideal for harder raw materials such as wood.
Thinner dies can be used for softer raw materials that do not require intensive compression, as well as for hardwood sawdust.
3. Shape and profile of holes in flat and ring dies
Conical holes facilitate feedstock flow and reduce the risk of die blockage, which is beneficial for feedstocks with varying particle sizes.
Cylindrical holes ensure uniform compression and are used when consistent pellet quality is required.
4. Matrix material and processing
Stainless steel is often used for its corrosion resistance and long service life. It is used for vacuum hardened ring dies.
Tool steel or dies with protective coatings are used in the production of pellets from highly abrasive raw materials. Used for flat, through-hardened dies.
5. Hole arrangement and their number in flat and ring dies
The density of the holes affects production efficiency: more holes increase the efficiency but require more power to push the raw material through the die.
The optimal hole arrangement allows for efficient use of energy and ensures even loading of the matrix.
Optimization of matrix parameters for sawdust, feed and other raw materials
Wood: Thicker dies with larger holes (8-10 mm) are recommended to obtain high density fuel pellets.
Straw: Requires dies with medium holes (6-8 mm) and a conical profile to facilitate flow and prevent blockages.
Animal feed: Small holes (4-6 mm) and thin dies are optimal to obtain uniform, small diameter pellets.
Fertilizers and other minerals: Matrices with special protective coatings and carefully selected hole patterns to minimize wear and corrosion.
Selecting the appropriate matrix parameters for a specific raw material is crucial for achieving high pellet efficiency and quality, as well as for optimizing production costs and the service life of the pelleting machine.
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