Optimizing hammer mill performance through screen selection and hammer design

Background: Mechanical preprocessing, which includes particle-size reduction and mechanical separation, is one of the primary operations in the feedstock supply system for a lignocellulosic biorefinery. It is the means by which raw biomass from the field or forest is mechanically transformed into an on-spec feedstock with characteristics better suited for the fuel conversion process. Results: This work provides a general overview of the objectives and methodologies of mechanical preprocessing and then presents experimental results illustrating improved size reduction via optimization of hammer mill configuration, improved size reduction via pneumatic-assisted hammer milling and improved control of particle size and particle-size distribution through proper selection of grinder process parameters. Conclusion: Optimal grinder configuration for maximal process throughput and efficiency is strongly dependent on feedstock type and properties, such as moisture content. Tests conducted using a HG200 hammer grinder indicate that tip speed, screen size and optimizing hammer geometry can increase grinder throughput as much as 400%.