Apparatus for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles

A microbubble froth flotation column apparatus for the separation of one constituent from another constituent in a mixture of fine particles of said constituents where one or more of said constituents at the time is hydrophobic and the other constituents at the time are non-hydrophobic comprising:

• a generally tubular flotation column having a top portion, a bottom portion, and a portion between said top portion and said bottom portion;
• a microbubble generator means with no moving parts for generating microbubbles where most of the bubbles leaving the microbubble generator are below 400 microns in an aqueous solution having frothing characteristics;
• a conduit for feeding said microbubble aqueous mixture to the bottom portion of said flotation column;
• a froth launder communicating with the top portion of the column for containing froth, said froth having an upper surface;
• a mineral pulp feed means for feeding mineral pulp into said flotation column above said bottom portion but below said top portion;
• a wash water feed for distributing wash water at a multiplicity of points in the froth below or just above the upper surface of said froth to wash entrained particles from the froth;
• a froth removal means communicating with said froth launder;
• a discharge means located in the bottom portion of said column through which the non-hydrophobic constituents are removed;
• said microbubble generator comprises:
• an elongated conduit having an entrance end and an exit end for conducting an aqueous solution containing a frothing agent;
• an elongated flow direction changer arrangement located in said conduit and extending along the length thereof, said direction changer arrangement having a multiplicity of surfaces adapted to rapidly change the direction of flow of said aqueous solution;
• a source of gas and means to aerate said aqueous solution with said gas;
• a source of said aqueous solution containing a frothing agent connected to said entrance end of said elongated conduit;
• and
• a pressurizing arrangement for applying sufficient pressure to said aqueous solution to propel it through said conduit over said flow changer arrangement at a velocity sufficient to break bubbles of gas in said aqueous solution into microbubbles;
• said elongated conduit is a cylindrical tube;
• said flow direction changer is a series of elements;
• said elements each being a substantially uniformly thick sheet-like member twisted about a longitudinal axis and having a leading relatively straight edge on one side and a trailing relatively straight edge on an opposite side twisted through a substantial arc relative to said leading straight edge;
• and
• said elements adjacent in said series being oriented at substantially right angles with opposite twist to one another whereby a stream of said aqueous solution containing bubbles is first divided by said leading edge of a first element and twisted one direction until it leaves said trailing edge of said first element and then is again divided by said leading edge of a second adjacent element and twisted in an opposite direction with such dividing and reverse twisting repeating itself until the last of said elements is traversed.