Effect of miscanthus addition and different grinding processes on the quality of wood pellets

In this study the mechanical properties of wood–miscanthus mixpellets for domestic use were investigated. The influences of a proportion of miscanthus of up to 0.20 kg kg−1 to the quality of wood pellets were tested. Furthermore binder addition (0.02 kg kg−1 of potato starch) and two different grinding processes (impact comminution under dry conditions and shearing comminution under wet conditions) were tested to improve the pellet quality. According to existing quality standards physical properties for the produced pellets have been determined to evaluate the quality. The results showed that for producing standardized pellets with miscanthus proportion the addition of a binder is necessary in the case of impact comminution. When using a shearing comminution for the raw material preparation no more binder addition is necessary to fulfil the quality criteria even with a miscanthus proportion of 0.20 kg kg−1. The shearing comminution leads to a highly fibrous material that can be more compacted in the press channels than normal shavings and furthermore these fibres have a high potential to create interlocking bonds. Another effect might be a successful mechano-chemical activation of binder substances like proteins in the raw materials through the wet preparation step.

► The influence of miscanthus addition and different grinding processes on the quality of wood pellets is investigated. ► Miscanthus addition weakens the pellet structure. ► Physico-mechanical quality can be improved by using shearing comminution instead of impact comminution.