The large-scale separation of fluids from fibrous pulps

Most of the free fluid can generally be expressed from fibrous pulps in a few seconds at 50 lb/in2 if the layer of pulp is kept thinner than 1 in. after it has been pressed, and if the fluid is allowed to run away freely. The need for this time and the frictional properties of many pulps are serious obstacles to the design of any strictly continuous press. Roller presses do not allow enough time, screw expellers create too much friction, continuous centrifuges and some other arrangements are intricate and vulnerable.

An intermittent but automatic press which avoids these defects is described. In this the material on a perforated conveyor is pressed by a ram and then moved forward as the ram lifts. One such machine has already been made. An outline is given of the principles on which an improved design will depend.