One dimensional simulation of extrusion channel of biomass pelleting machine

Abstract

This study was carried out to simulate the extrusion channel of a biomass pelleting machine. The numerical model developed by Nielsen was used. In order to obtain a simulation of the pelleting process, a number of assumptions for the material properties were made. These include Poisson’s ratio (υ = 0.02), Young modulus (E = 20) and Friction coefficient (μ = 0.4). Other variables (dimensions) used for the pelleting channel in the model are the active press length (l =70mm), diameter of pellets (50mm), inlet angle (30o) and chamfer depth (z = 2mm). MATLAB was used for the simulation analysis. Based on the sensitivity analysis, it was observed that the pressure increases at the inlet, which is mainly caused by the decreasing cross sectional area of the elements. The density also increases at the inlet, until it reaches its final value between the inlet and the cylindrical channel. An offset of the accumulated energy was observed at the start of pellet channel which is caused by the amount of energy used for compressing the pelleting material to the density. The peak pressure is found at the interface between the inlet section and the cylindrical channel. The maximum pressure in the die decreases when the inlet depth increases and also, the pressure gradients in the inlet increases, when the inlet angle increases. The highest pressure is 35MPa for compatibility of the pellets thereby increasing its durability.

Keywords: Pressure, Density, Energy consumption, Pelletizer