Research on Effect of Spruce Sawdust with Added Starch on Flowability and Pelletization of the Material

To verify the effect of added starch on flowability and pelletization of spruce sawdust, were prepared mixtures with addition of 0, 5, 10, 15 and 20% (w/w) starch. The measured basic mechanical-physical properties of the individual mixtures have shown that starch improves flowability of the mixture (growing value of the ffc parameter), reduces impact of friction forces on the contact stainless material (reduced wall friction), thus reducing energy demands of the process as regards flow of the mixture through the hopper of a pellet press. High-speed camera simulations, which evaluate the immediate speed of particles during discharge of the hopper, have proved that addition of a material with different distribution of size and shape of the particles (starch) has a favourable effect on the overall flowability of the mixture. When pelletizing a mixture with starch, which has a lower angle of internal friction, the pelletizing pressure in the die is slightly lower and the resulting pellets have a slightly lower density. This feature is compensated by prevailing positive effects of the added starch on the pelletization, where the resulting pellets have higher durability, higher hardness and moisture resistance.