Procedure and apparatus of the concentration of hydrophobic materials

A procedure for the concentration by flotation of hydrophobic materials from a pulp of hydrophobic and hydrophilic materials contained in an aqueous medium by the addition of a gas, wherein the concentration is achieved in two devices, a first and a second device, operating in series, the gas and pulp are supplied continuously to the first device consisting of a gas-pulp mixer containing solid mixing objects with a density lower than that of the pulp and with discrete freedom to move inside said gas-pulp mixer as the pulp and gas pass through interstices generating a plurality of bubbles which come in contact with the hydrophobic materials which adhere to the surface of the bubbles thereby forming a pulp-bubble mixture;

• the
• pulp-bubble mixture leaves the gas-pulp mixer by an inclined bottom end of the gas-pulp mixer, through discharge slots having a width lesser than the diameter of the solid mixing objects which prevents the mixing objects outflow;
• the discharged pulp-bubble mixture, from the gas-pulp mixer is fed to the second device, forming a froth phase in the second device, which consists of a froth separating tank, with a surface area permitting the obtention of a descending speed in a range between 0.3 and 1.5 centimeters per second and a volume permitting a residence time for the pulp in a range of 20 to 60 seconds, having at the froth separating tank's upper end overflow edges and froth collecting troughs, with an inclined bottom of greater than 20 degrees inclination, and, at a lower end thereof, having discharge orifices with valves for controlling flow rates of tailings.