Experimental and Simulation Investigation on Arching Behaviour of Two Biomass Materials from a Wedge Shape Hopper

The interest in solid biomass has been increasing over the last decades for their potential as renewable energy sources, to be used in thermochemical processes to produce energy or gaseous fuels or biochemical processes to produce liquid fuels like ethanol. Particle elasticity and particle fibrous shapes are the main characteristics of biomass and both may be a possible cause of deviation of the biomass behavior from the Coulomb model. One problem that happens during silo discharge is the formation of stable arches. This problem could be addressed through the knowledge of flow properties of bulk solids. However, common design methods for storage units to ensure flow, are based on Jenike analysis and have not yet been fully proven to work for biomass bulk solids. In particular Barletta et al. [1,2] measured the arching behavior of biomass materials in a wedge shape silo and compared the results with the method proposed by Jenike. In this research the critical outlet diameter that leads to arch free silo were experimentally measured for sawdusts and wood powders. These results were compared with the DEM simulation results and the model proposed by Jenike. Realistic mechanical properties of biomass plays a very important role in DEM simulation. In order to find the mechanical properties of the two biomasses, the approach used by [3] were followed to measure the modulus of elasticity. Furthermore, to measure the coefficients of static and rolling frictions as well as the coefficients of restitution between biomass particle materials and also biomass particles with silo wall, DEM simulation of the Schulze shear cell were conducted. These coefficients were changed to have the best fitting shear stress profile between simulations and shear tester results. After defining the material mechanical properties by the Schulze and the uniaxial tester, the discharging behavior of these two biomasses from a wedge shape silo were conducted by using EDEM software. Good agreement between experimental and simulation results of the critical opening diameter of arch free silo were observed. However, the critical opening diameter obtained by using the Jenike approach was higher than both simulation and experimental results. References [1] D. Barletta, M. Poletto, An assessment on silo design procedures for granular woody biomass, Chemical Eng. Transaction, 2013. doi:10.3303/CET1332369. [2] D. Barletta, R.J. Berry, S.H. Larsson, T.A. Lestander, M. Poletto, Alvaro Ramirez-Gomez, Assessment on bulk solids best practice techniques for flow characterization and storage/handling equipment design for biomass materials of different classes, Fuel Process. Technol, 2015. doi:10.1016/j.fuproc.2015.06.034. [3] M. Stasiak, M. Molenda, M. Bańda, E. Gondek, Mechanical properties of sawdust and woodchips, Fuel, 2015. doi:10.1016/j.fuel.2015.07.044.