Feeder trials

The three systems considered were:

· auger screw feeder; an Ajax Standard Massflow Mark Il;
· vibratory feeder; a Triton type TR1S electromagnetic vibrating feeder/ hopper unit; and
· turntable feeder; NRI design.

The auger screw feeder is driven by a variable speed motor connected to a controller and adjustable by the operator. The hopper capacity is approximately 0.14 m3. The auger screw fed sawdust. groundnut shells. coir dust and rice husks well. However, sawdust at moisture contents above 12%, woodchips, groundnut shells and coir dust tended to form stable bridges in the conical shaped hopper and the hopper throat thus restricting flow. A stirrer was fitted to agitate the material in the hopper but gave limited success.

The vibratory feeder table, with a 0.3 m3-capacity vibrating hopper, successfully fed sawdust at all moisture contents, rice husks, groundnut shells and coir dust. Some feeding difficulties occurred when the feedstocks contained a large proportion of fibres or larger particles - these tended to block the feed outlet between the hopper and vibrating table. A similar problem occurred with large woodchips and woodshavings.

The turntable system described in the section on the feeder unit was considered to give the best results with feedstocks containing larger particles. However, feedstocks containing any appreciable amount of fibre tended to restrict the flow of material between the hopper and the turntable.