Biomass feeding problems greatly hinder the industrialization of entrained-flow gasification systems for production of 2 nd generation biofuels. Appropriate DEM modelling could allow engineers to design solutions that overcome these flow problems. This work shows the application of a DEM calibration framework to produce a realistic, calibrated and efficient material model for lignocellulosic biomass. A coarse (500-710 µm) and a fine (200-315 µm) sieving cuts of milled poplar were used in this study. The elongated shape and the cohesive behavior were respectively simulated using a coarse-grained multisphere approach and a cohesive SJKR contact model. Measurements of three physical responses (angle-of-repose, bulk density, a retainment ratio) allowed calibration of the sliding (µ s) and rolling friction (µ r) coefficients and the cohesion energy density (CED). Using a statistical analysis, the most influential calibration parameters for each bulk response were identified. A Non-Dominated Sorting Genetic Algorithm was used to solve the calibration multi-objective optimization problem. Several sets of optimal solutions reproduced accurately the three physical responses and the experimental shear responses were closely reproduced by simulations for the population of coarse particles. The DEM calibration framework studied here aims to produce material models useful for assessing flow behavior and equipment interaction for biomass particles.

Flowability characterization of milled lignocellulosic biomass is essential for developing viable conveying, storing and handling solutions for gasification processes. This study investigated the effect of torrefaction on particles size and shape obtained after grinding and on flow properties of pulverized wood.Spruce and poplar samples with six torrefaction intensities were knife-milled to obtain biomass powders.Particles size and shape distribution were assessed using a morphological particle size analyser and flowability parameters were determined with a ring shear tester. A more intense treatment produces finer, rounder and more regular particles. Simultaneously, a gradual shifting was observed from a cohesive behaviour for native biomass to a nearly free flowing behaviour for the most intensively treated samples. The trends in flowability cannot be explained by the size reduction nor the increase of distribution width. Instead, the explanation lies in the reduction of shape factor and the sharpness of particle surfaces for treated samples. However, all observations are consistent with the loss of resilience of treated wood. From our results, it is clear that torrefaction, in addition to its interest on reduction of energy consumption of grinding, should also be considered as a pre-treatment step allowing to modify the flow behaviour of biomass powders.