1985 Volume 11 Issue 3 Pages 331-336
In a screw press, solid-liquid mixture trapped in a worm channel passes through a gradually reduced flow-area, being dehydrated under variable pressure. The expression pressure in crease by use of a screw-type die is studied, and the effect on dehydration of the two separate driving systems of worm and die is shown.
The screw-type die consists of a constant pitch-constant depth screw and a fixed cylinder. The resistance against the flow of mixture is dependent on the thread depth, the axial length, and the difference in helical angles between worm and die. A high-pressure profile is produced inside the barrel when the screw-type die is used. Highly compressed cake is continuously discharged from the unit, though the die resistance is great. A further sharp increase in pressure profile can be caused by providing a driving system with different rotation for worm and die. It is shown that the improvement of performance is due to the great difference in the axial velocity components of the two separate rotations.
