Device and method for separating the solid fraction from the liquid fraction of a slurry

A method of separating slurry into a solid fraction and the liquid fraction comprising the steps of:

• a) conveying a slurry into a container;
• b) introducing gas into the container to increase the internal pressure thereof;
• c) filtering the slurry and contemporaneously, executing at least once a cycle composed of the steps of:
• c1) allowing partial clarification of the slurry in the container to obtain a clarified fraction and a thickened slurry fraction;
• c2) withdrawing at least a portion of the clarified fraction in the container, the withdrawal occurring at varying levels over time.

An apparatus for separating a slurry into a solid fraction from and a liquid fraction, comprising:

• a) a container which defines a chamber for containing the slurry, the chamber having a top and a bottom;
• b) a filter medium located on the bottom of the chamber for retaining the solid fraction of the slurry;
• c) a slurry inflow conduit for flowing the slurry into the chamber;
• d) an outflow conduit for outflowing of liquid filtered through the filter medium;
• e) a gas inflow conduit for increasing pressure in the chamber;
• f) a conduit for inflow of washing liquids into the container;
• g) a shaft installed in the container, the shah supporting a plurality of blades;
• the shaft being adapted to rotate about a substantially and/or generally vertical axis of rotation (X),
• g1) the shaft being adapted to rotate in both directions about the axis of rotation (X),
• g2) the distance of the blades from the filter medium being adjustable,
• g3) the blades being so conformed as to be able to scrape the solid fraction of the slurry deposited on the filter medium, when the shaft rotates in a first direction of rotation, the blades being adapted to press the solid fraction deposited on the filter medium when the shaft rotates in a second direction of rotation, opposite the first direction of rotation;
• j) a lateral access port, for controlled removal of the solid fraction retained by the filter medium;
• k) a tube introduced into the tank to an adjustable draft, and disposed to avoid interference with the blades, for controllably withdrawing clarified liquid from the container at a level dependent on the draft to which the tube is introduced.