Test Plan for Evaluating Hammer and Fixed Cutter Grinders Using Multiple Varieties and Moistures of Biomass Feedstock

Abstract

Biomass preprocessing is a critical operation in the preparation of feedstock for the front-end of a cellulosic ethanol biorefinery. Its purpose is to chop, grind, or otherwise format the biomass material into a suitable feedstock for optimum conversion to ethanol and other bioproducts. Without this operation, the natural size, bulk density, and flowability characteristics of harvested biomass would decrease the capacities and efficiencies of feedstock assembly unit operations and biorefinery conversion processes to the degree that programmatic cost targets could not be met. The preprocessing unit operation produces a bulk flowable material that 1) improves handling and conveying efficiencies throughout the feedstock assembly system and biorefinery 2) increases biomass surface areas for improved pretreatment efficiencies, 3) reduces particle sizes for improved feedstock uniformity and density, and 4) fractionates structural components for improved compositional quality. The Idaho National Laboratory (INL) is tasked with defining the overall efficiency/effectiveness of current commercial hammer and fixed cutter grinding systems and other connecting systems such as harvest and collection, storage, transportation, and handling for a wide variety of feedstock types used in bioethanol or syngas production. This test plan details tasks and activities for two separate full-scale grinding tests: Material Characterization Test and Machine Characterization Test. For the Material Characterization Test, a small amount (~5-7 tons each) of several feedstock varieties will be ground. This test will define the fractionation characteristics of the grinder that affect the bulk density, particle size distribution, and quality of the size reduced biomass resulting from different separation screen sizes. A specific screen size will be selected based on the characteristics of the ground material. The Machine Characterization Test will then use this selected screen to grind several 30-ton batches of different feedstock varieties and moistures. This test will focus on identifying the performance parameters of the grinding system specific to the feed, fractionation, and screen separation components and their affect on machine capacity and efficiency.