Feeding small biomass particles at low rates

•Biomass particles (75–1000 μm) were fed at 9.0–66.5 mg min− 1.•Particle aggreation was found to influence feed rate stability.•Patterns in feed rate data were linked to changes in particle bed appearance.•Particle size affected feed rate but not feed rate stability.

Biomass particles (75–1000 μm) were fed at 9.0 –66.5 mg min− 1 (2.9–21.7 W) using a particle feeder that dispensed particles by gravity through an injection tube. Feed rate was controlled by altering the velocity of a pusher block. Particles were agitated using a vibration motor and fed onto a balance and mass readings were continuously logged. Factors impacting reproducibility and feed rate stability were investigated as well as the effects of particle size and of pusher block velocity. Statistical analysis was applied to investigate patterns in particle feed rate data. Particle aggregation was identified as a factor which influenced feed rate stability and thereby also influencing reproducibility. Feed rate correlated well with pusher block velocity (R2 = 0.99). Statistical analysis showed strong indications (P values < 0.01) of two patterns (clustering and trends) in the feed rate data which were attributed to changes in particle bed appearance with time. With all else being equal, particle size affected feed rate but not feed rate stability. A higher vibration amplitude was needed to agitate smaller particles. It was concluded that particle agitation control is a key to stable feeding of small biomass particles at low rates.

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