Lignin Pellets for Advanced Thermochemical Process—From a Single Pellet System to a Laboratory-Scale Pellet Mill

Abstract

Lignin pellets were produced using a single pellet system as well as a laboratory-scale pellet mill. The feedstock used in this work was lignin isolated from poplar wood (Populus tremuloides) using a direct saccharification process. An investigation was performed on the influence of the initial moisture content on the dimensions, impact and water resistance, fines content, mechanical durability, calorific value, and ash content, and, finally, the ultimate analysis was performed. These properties were then compared to pellets made from softwood bark using the same pelletization unit. Lignin pellets were then manufactured using four different types of additives (corn oil, citric acid, glycerol, and d-xylose) and ultimately, they were stored in two different conditions prior being tested. In general, manufacturing pellets that were entirely made of lignin generated samples with an overall higher hydrophobicity and higher calorific value. However, the ash and sulfur content of the lignin pellets (1.58% and 0.32% in scenario 2, respectively) were slightly higher than the expected CANplus certification values for Grade A pellets of ≤0.7%, and ≤0.04%, respectively. This study intends to show that lignin could be used to produce this new kind of pellets, pending that the initial material has a low ash and moisture content.