After the hammermill
attained its full speed, at no-load conditions, the feed
hopper was opened to feed the entire material charge into
the grinding chamber. After 5 min of grinding, the
hammermill was stopped, and the output (mass passed
through the screen) and unground (mass retained above the
screen) portions were weighed for mass balance
determination. The grinding time of 5 min was chosen by
grinding the above-mentioned quantity of samples for 1 to
7 min (results not shown).