PROCESSING OF CHAFFY GRASS SEEDS USING
AN AERODYNAMIC SEED CONDITIONER
Many useful grasses have light chaffy seeds which usually contain a high percentage of
inert material that causes difficulties in handling, processing, storage, testing and planting.
Specialised equipment is necessary to process chaffy grass seeds to a more uniform
product. Processing methods used for other seeds are not effective for chaffy grass seeds.
Various machines (hammer mill, cone thresher, belt thresher, de-bearder, filament
thresher) have been used in the past to process chaffy grass seeds, but most of these can
damage seeds and their capacity is also restricted. Compared to conventional seed
processing methods, the Woodward aerodynamic chaffy grass seed conditioner provides
better quality seed without causing significant physical damage. However, its processing
capacity is too low for commercial use. Non-continuous feeding and slow pre-cleaning
were the main reasons for the low capacity of the equipment.
Uniform delivery of chaffy seeds has always been a primary problem in seed processing
systems. A continuous feeding system and a higher capacity pre-cleaning device were
developed and attached to the Woodward aerodynamic chaffy seed conditioner. The
feeding system consists of a hopper and belt conveyor with plastic fingers mounted at an
angle of 30
0
to the belt surface. The pre-cleaning device has a rotating vertical screen on to
which seed is blown by air from a fan through a venturi.
An experiment was conducted to evaluate the performance of the feeding unit using
Queensland bluegrass (Dichanthium sericeum). Using this device, it was possible to
convey and meter seed up to 100 kg/h by increasing the belt pulley speed up to 1 m/s. This
is about three times the capacity of the original feeding system. Further increases in
capacity could be achieved by increasing the belt speed. The feed rate increased
proportionally (R
2
=0.9898) with the increase in conveyor belt speed indicating that the
device is metering seed uniformly.
Another experiment was carried out to test the effectiveness of the pre-cleaning unit. Feed
rate, speed of rotation of the vertical screen and rate of airflow from the fan were varied.
The seed cleaned using this device was manually separated into pure seed and
