When it comes to particle size reduction, we always have it attached to the hammer mill in wood pellet making plant. Wood hammer mill is generally employed in size reduction process and provides the pellet press with suitable sized particles. The main job for hammer mill is making right particle size. If the particle size gets fairly small, you may find that the pellet mill struggles to compress this material through the die holes. Because the roller and die can not easily touch such small particle size of materials which may be possible to directly discharge from the die holes. Therefore more attention should paid on the particle size reduction in wood crushing process. There are many factors affect the crushing size of particles. Now let’s have a better understanding of factors that affect particle size.
In wood crushing process of hammer mill, the particle size is determined by a combination of screen size, rotor speed, the size & number of hammers, hammer blows, collision with the walls of the grinding chamber, and particle on particle impact. The major factor that affects particle size is screen which accounts for 70% of what determines the finished particle size, and the rotor speed is also an important factor.
Actually we are all clear that final size is mainly controlled by the use of screens on the bottom of the machine. In the hammer mill there are flailing hammers spinning very fast and close to a perforated screen. Any material that enters the grinding chamber must be reduced to a size below the diameter of the screen holes to pass through the screen that covers the mill's discharge opening. You can control size reduction through inserting a screen with different sized holes. So you can choose the right screen hole size based on the size of pellets you would like.
When the hammer mill rotor spins, the hammers flail out and impact the material with great severity causing it to break down. As a result, the higher the rotor speed, the greater the number of hammer mill blows, and thus a finer end product. Conversely, if tap the same material with the same hammer at slow rotor speed, it is hard to grind the material into particles. Therefore controlling the rotor speed can get your ideal particle size.