Optimization of a multi-parameter model for biomass pelletization to investigate temperature dependence and to facilitate fast testing of pelletization behavior

Pelletization of biomass residues increases the energy density, reduces storage and transportation costs and results in a homogeneous product with well-defined physical properties. However, raw materials for fuel pellet production consist of ligno-cellulosic biomass from various resources and are therefore different in their composition and structural properties. This has the consequence that different types of biomass require different processing conditions such as press channel length and moisture content. Nowadays the process optimization is mainly based on expensive and time consuming “trial and error” experiments and personal experience. However in recent years the utilization of single pellet press units for testing the biomass pelletizing properties has attracted more attention. The present study outlines an approach where single pellet press testing is combined with modeling to mimic the pelletizing behavior of new types of biomass in a large scale pellet mill. This enables a fast estimation of key process parameters such as optimal press channel length and moisture content. Secondly, the study addresses the question of the origin of the observed relationship between pelletizing pressure and temperature.