Mechanisms of coarse particle flotation in mechanical cell: influence of the hydrodynamic parameters and kinetics involvement.

Author(s)

Wendel Johnson Rodrigues

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2010-08-26

Examining board members

Laurindo de Salles Leal Filho; Eldon Azevedo Masini; Song Won Park; Antônio Eduardo Clark Peres; Roberto Mattioli Silva

• Advisor: Laurindo de Salles Leal Filho

Abstract

Coarse particles badly float mostly because the bubbleparticle aggregates are not strong enough to prevent the particle detachment from the bubble surface caused by the particle weight and turbulence eddies during the rise of the aggregates in the pulp phase to the froth phase and then to the froth launder. The aim this work was to determine effects and degrees of significance of hydrodynamic variables on coarse particle flotation and their kinetic implications. The tests were carried out in flotation cells with mechanical stirring system and each experimental condition was related to group of hydrodynamic variables: hydrodynamic dimensionless numbers, impeller geometries, minimum impeller rotational speed, energy dissipation rate and detachment energy. The influence of hydrodynamic parameters on flotation of the apatite and glass spheres (diameter average248 micrometers) was determined in the presence of sodium oleate and etheramine acetate at pH 10. For more quiescent hydrodynamic conditions, recovery of coarse particles decreased due to a lack in particle suspension, on the other hand, in the most severe hydrodynamic conditions the recovery was almost nil because the bubbleparticle aggregates detachment. Flotation kinetics of apatite was studied in laboratory scale under strong hydrodynamic conditions, the results indicated that coarse particles of apatite float at a lower rate than finer particles and the flotation kinetics of coarse particles did not fit to first order model. Those results evidenced that coarse particles demand a suitable hydrodynamic environment to float efficiently. (AU)