Process and apparatus for the separation of foreign matter from a liquid by flotation

A process for the separation of foreign matter from a liquid, which process comprises the steps of:

• (a) passing a stream of liquid contaminated with particles of foreign matter and in which gas is dissolved through a variable orifice nozzle and then causing the stream of liquid to mix with a stream of induced gas which is the same as the gas which is dissolved in the liquid, thereby to provide a mult-phase flow;
• (b) causing said multi-phase flow to be subjected to turbulence and shearing thereby to produce a well dispersed bubbly liquid stream;
• (c) causing said bubbly liquid steam to pass into a vessel which contains said liquid contaminated with particles of foreign matter, said liquid in the vessel having a free surface, and said liquid stream being introduced below said free surface of the liquid in the vessel;
• and
• (d) allowing the bubbles of gas in said liquid to rise to said free surface of said liquid, whereby the particles of foreign matter contaminating the liquid are caused to float to said free surface by their surface adhesion to said bubbles of gas.