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How does bulk powder flow testing sit alongside other physical characterization techniques such as particle sizing?
Particle size is just one of many variables that impact bulk powder flow. Examples of others that are particularly relevant to biomass handling include particle shape, surface roughness, bulk density and moisture content. It’s quite easy to see the impact of these variables in practice and their effects are widely recognized. For example, bulk solids can be transformed from free-flowing to a solid-like mass by moisture ingress, and more regular-shaped particles tend to be associated with better flowability than elongated analogues with the propensity to mechanically interlock during transfer. When a biomass feedstock doesn’t behave as required, the default may be to investigate whether changing particle size will improve things and to what extent, not least because particle size is relatively easy to measure. But as the preceding observations make Bulk powder flow testers can quantify biomass feedstock flow properties, yielding data that can help improve clear, this approach is fundamentally flawed. flowability and productivity. It involves measuring just one of many influential variables as a proxy for the behavior of interest. Measuring bulk powder flow properties is more productive because it directly quantifies the behavior of interest. Such measurements support systematic investigation of the factors that can be manipulated to improve flowability and promote more robust optimization of the feedstock. For example, BY JAMIE CLAYTON longer drying times may be a far more benefihandling rates, making it a major cause of cial strategy than particle size reduction, but What is the relevance inefficiency in biomass handling facilities. there is no scope to compare these options of bulk powder flow testing Bulk powder flow testing can quantify the with particle size measurement alone. for biomass? Converting biomass into usable prod- flow properties of biomass feedstocks, prouct involves steps such as storage, chute viding insights that can help processors to What are the options transfer, conveying, mixing and feeding/ improve flowability and work more produc- when it comes to discharge into a mill or grinder, for ex- tively. The inherent variability of biomass measuring powder flow? ample. Effective bulk solids handling is and the impact of moisture are undoubtedEngineers and scientists have been detherefore essential, with poor flowabil- ly complicating factors in biomass handling, vising techniques for measuring the flowability routinely highlighted as a primary cause but there is considerable scope to gain valu- ity of bulk solids for decades, so there are of operational problems. Poor flowability able information that can have a direct im- plenty of commercial options to consider. causes unplanned shutdowns and can limit pact on processing efficiency. The lowest cost, such as angle of repose,
Q&A: Biomass and Bulk Powder Flow Testing
CONTRIBUTION: The claims and statements made in this article belong exclusively to the author(s) and do not necessarily reflect the views of Pellet Mill Magazine or its advertisers. All questions pertaining to this article should be directed to the author(s). 24 PELLET MILL MAGAZINE | ISSUE 2 2022
