Wedge-Shaped Hopper Design for Milled Woody Biomass Flow

Abstract

The bioenergy industry has been challenged by unstable flow and transport of milled biomass in material handling operations. Handling issues such as hopper clogging and auger jamming are attributed to knowledge gaps between existing handling units designed for bulk solids and their suitability for milled biomass with high compressibility. This work investigates various flow behaviors of granular woody biomass in wedge-shaped hoppers. Hopper flow physical experiments and numerical simulations are conducted to study the influence of the critical material attributes and critical processing parameters on the flow pattern, arching, and throughput. The results show that (1) the preferred flow pattern, mass flow, can be achieved by controlling the material's internal friction angle, hopper inclination, and hopper wall friction; (2) hopper arching, governed by the competing gravity-driven force against flow resistance from material internal friction and material− wall friction, can be controlled by the hopper wall friction angle and the inclination angle; and (3) flow throughput can be accurately estimated from our empirical equation with inputs of hopper outlet geometry and particle-scale to bulk-scale material attributes. This study elucidates woody biomass flow physics and provides guidance for industrial equipment design.

Effects of the Moisture Content on the Flow Behavior of Milled Woody Biomass

“…A quasi-3D model, i.e., a 2D plane-strain slice of the wedge-shaped hopper, was developed and presented in Figure a. The numerical model is the same as the one developed in the previous work , except for the boundary conditions on hopper walls. In this study, the no-slip boundary was implemented on both hopper walls by directly fixing all six degrees of freedom of boundary nodes.…”

“…In this study, the no-slip boundary was implemented on both hopper walls by directly fixing all six degrees of freedom of boundary nodes. Given the magnitude of the hopper wall friction has trivial influences on the flow rate, , this Eulerian boundary condition will not undermine the prediction accuracy of the hopper flow rate. In addition, no Eulerian–Lagrangian contacts can boost the computational efficiency.…”

“…Among various constitutive models simulating the flow behavior of milled biomass, the Gudehus–Bauer (G–B) hypoplastic model , has been implemented and utilized to explore the physics of biomass granular flow with success. ,,, Therefore, the G–B model is also used in this study to simulate biomass flow behavior with various moisture contents. The G–B hypoplastic model describes the Jaumann stress rate σ ̊ as a function of the current state (i.e., stress σ and void ratio e ) for a given strain rate bold-italicγ̇ .…”

“…Thus, it is necessary to apply the recently developed numerical framework based on the Gudehus–Bauer (G–B) hypoplastic model, which can describe the flow behavior of woody biomass materials, to investigate the influences of the moisture content during feedstock handling. The G–B hypoplastic model incorporates the critical state theory, density dependency, and nonlinear elasticity, which are critical for accurately predicting flow features of milled biomass. , …”

Promoting Pellet Feed Flow in a Screw Feeder with an Agitator

“…The silo was primarily optimized in three aspects. First, by adjusting the silo inclination angle − and optimizing the wall curve, the structure and shape of the silo were optimized, which could successfully alter the particle flow state and improve the mass flow rate and discharge stability. For example, in contrast to a cone hopper, the mass flow rate of a hyperbolic hopper is greater. , Second, either ventilation or vibration of the silo, the discharge performance was enhanced.…”