BROGIM®: A new three-phase mixing system testwork and scale-up

Abstract

BROGIM® is a mixing concept for bioleach tanks that provides high oxygen transfer performances, by means of an air dispersing flat blade turbine at the bottom, and mixing, with low power-consuming propellers at the upper part of the rotating shaft. Oxygen transfer performances of this system have been firstly determined in a small-scale testwork in an 850-l tank. A pilot-scale study in a 65-m3 tank enabled to define rules for the scaling-up procedure. The paper describes the philosophy for the scale-up of the mixing system installed in industrial tanks of up to 1250 m3 operating volume. At industrial scale, it has been shown that the BROGIM® system exhibits little power differences between gassed and ungassed conditions, for air flowrates up to 24,000 Nm3 h− 1 comparatively to what was found at smaller scales. The agitator is able to run with or without air with no need for oversizing the power of the electrical driving motor. A procedure for oxygen transfer coefficient (kla) determination in real conditions has been tested. It is essentially based on gas balance measurement for establishing the oxygen uptake rate and dissolved oxygen measurement at different levels in the tank.