Comminution of Dry Lignocellulosic Biomass, a Review: Part I. From Fundamental Mechanisms to Milling Behaviour

Abstract

The comminution of lignocellulosic biomass is a key operation for many applications as bio-based materials, bio-energy or green chemistry. The grinder used can have a significant impact on the properties of the ground powders, of those of the end-products and on the energy consumption. Since several years, the milling of lignocellulosic biomass has been the subject of numerous studies most often focused on specific materials and/or applications but there is still a lack of generic knowledge about the relation between the histological structure of the raw materials, the milling technologies and the physical and chemical properties of the powders. This review aims to point out the main process parameters and plant raw material properties that influence the milling operation and their consequences on the properties of ground powders and on the energy consumption during the comminution.

Keywords: energy consumption; grinding; grinding law; mechanical stresses; plant materials.

Figure 1

Main mechanical properties for different biomasses: (a) longitudinal Young’s modulus and (b) tensile strength according to [37,42].

Figure 2

The metric and histological scales of a plant material in relation to the different milling steps.

Figure 3

The main mechanical stresses in a grinder: (a) impact, (b) compression, (c) shear, and (d) friction and the particles that can be expected in case of comminution of an homogeneous materials according to Kaya et al. [45].

Figure 4

The different loading modes applied at the micro-scale leading to the failure of the materials according to Karinkanta [44].

Figure 5

Intercellular failure (a) and Intracellular failure (b) observed during the milling of cork with impact and shear as main mechanical stresses, respectively [50]. (Tissue scale).