Role of Hornification of Cellulose Rich Biomass for Pellet Production

Abstract

Hornification of cellulose-rich materials, particularly wood pulps, occurs when chemical bonds form between cellulose surfaces, along with intermolecular forces created during dewatering and drying, preventing the material from reswelling in water to its original structure. Hornification of pulps results in a reduced ability to form effective fiber networks and therefore weaker paper products. The objective of this work was to investigate the role of hornification in pelletized cellulosic biomass and materials in general to provide more information than can be obtained by measuring standard wet state properties, such as water retention. Pellets were produced from chemical pulps with different degrees of hornification, as indicated by the water retention value (WRV), and their mechanical performance was evaluated. The chemical pulps served as a model material for investigating hornification. Pulps with higher hornification produced pellets with inferior mechanical properties, which has not been shown before by such a test. This effect is attributed to increased fiber stiffness and reduced surface flexibility, which limits fiber-fiber bonding. In addition, high drying temperatures prior to pelletizing, and thus higher hornification, will increase compression energy and friction in the pelletizing process. A novel connection was observed between WRV and mechanical performance, highlighting the impact of hornification on the surface interactions of cellulose-based materials.