Improvements on a gravity-driven low-rate particle feeder.
A gravity-driven particle feeder has been modified to achieve sustained operation at steady rates. Particle reservoirs and rod for controlling the nozzle opening are completely redesigned. Particle attrition and rod wobbling are the two main contributors to the feed instabilities. They, in turn, are affected by the height of the particle bed, particle contact time with the moving rod, strength of the magnetic field, and the weight, shape, and position of the rod in the magnetic field. A secondary reservoir minimizes the residence time of particles in the main reservoir. Its shape, orientation, and connection with the main reservoir have profound influences on the feeding stabilities. Tests have been conducted with particles of different types, sizes, and feed rates; results showed good long-term and short-term stabilities.
Feeding small biomass particles at low rates
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.
Improvements on a particle feeder for experiments requiring low feed rates
The center piece of a particle feeder for steady feeding of fine particles at low rates has been modified by sweeping the particles upward into a concentric tube which also serves as the piston support. The new design has demonstrated superior short and long term stabilities of particle feeding rate; moreover, it has significantly extended the operating ranges of the carrier-gas flow rate, particle feeding rate, and particle size and type.