Wendel Rodrigues - Academia.edu (original) (raw)

Papers by Wendel Rodrigues

Research paper thumbnail of Reverse iron ore flotation by collectors in aqueous nanoemulsion

Research paper thumbnail of Process for removing uranium from copper concentrate via magnetic separation

Research paper thumbnail of The role of hydrodynamics in coarse apatite flotation

Research paper thumbnail of Mecanismo de flotação de partículas grossas em células mecânicas: influência das variáveis hidrodinâmicas e suas implicações cinéticas

Coarse particles badly float mostly because the bubble-particle aggregates are not strong enough ... more Coarse particles badly float mostly because the bubble-particle 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 average≅248 µm) 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 bubble-particle 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.

Research paper thumbnail of Importância da hidrodinâmica na cinética de flotação de partículas grossas

Rem: Revista Escola de Minas, 2010

Os processos básicos que governam a recuperação de partículas em uma célula de flotação compreend... more Os processos básicos que governam a recuperação de partículas em uma célula de flotação compreendem os consecutivos subprocessos de colisão, adesão e estabilidade do agregado partícula/bolha. Entre eles, a colisão é controlada pelo ambiente hidrodinâmico na célula de flotação, enquanto que a adesão é dominada pelo comportamento físico-químico da interface entre partícula e bolha. Por sua vez, a eficiência da estabilidade depende, tanto dos eventos hidrodinâmicos, como dos físico-químicos. A recuperação de partículas grossas de apatita (densidade 3,08 g/cm³) e esferas de vidro (densidade 2,48 g/cm³) foi medida através de ensaios de microflotação e flotação em escala de bancada, variando-se diferentes parâmetros hidrodinâmicos na célula, como rotação e geometria do impelidor e números adimensionais (Reynolds & Froude). Os resultados indicam que velocidades apropriadas do impelidor produziram níveis de turbulência capazes de manter as partículas em completa suspensão, otimizando, assim...

Research paper thumbnail of Hydrodynamic dimensionless parameters and their influence on flotation performance of coarse particles

Minerals Engineering, 2001

The upper particle size limit of mineral floatability is a parameter of great importance in the f... more The upper particle size limit of mineral floatability is a parameter of great importance in the flotation process and the sharp decrease of flotation response when particle size approaches such a limit is a very well known phenomenon. The aim of this research was to find the most suitable hydrodynamic conditions to float coarse particles in microflotation tests. To reach such a target, the influence of some hydrodynamic parameters (Reynolds Number-Re, Froude Number-Fr, Weber Number-We and Power Number-Po) on microflotation response of coarse glass spheres (0.417-0.589mm, 0.208-0.295mm) and quartz particles (0.208-0.295mm) was studied in the presence of the collector ether amine acetate (75 mg/dm 3) at pH=lO. Maximum flotation response (almost 100%) was observed at 3,000<Re<8,000; O.l<Fr<l.O; lO<We0.54. For either more quiescent (Re<3,000; Fr<0.1 and We<lO) or more turbulent (Re>8,000; Fr> l.0; We> lO0 and Po<0.52) hydrodynamic conditions, flotation recovery decreased steadily. Under more quiescent hydrodynamic conditions, the lower recovery was due to the fact that the impeller was not capable of keeping particles in suspension properly whereas under more turbulent conditions the disruption of particle/bubble aggregates was intensively observed.

Research paper thumbnail of Reverse iron ore flotation by collectors in aqueous nanoemulsion

Research paper thumbnail of Process for removing uranium from copper concentrate via magnetic separation

Research paper thumbnail of The role of hydrodynamics in coarse apatite flotation

Research paper thumbnail of Mecanismo de flotação de partículas grossas em células mecânicas: influência das variáveis hidrodinâmicas e suas implicações cinéticas

Coarse particles badly float mostly because the bubble-particle aggregates are not strong enough ... more Coarse particles badly float mostly because the bubble-particle 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 average≅248 µm) 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 bubble-particle 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.

Research paper thumbnail of Importância da hidrodinâmica na cinética de flotação de partículas grossas

Rem: Revista Escola de Minas, 2010

Os processos básicos que governam a recuperação de partículas em uma célula de flotação compreend... more Os processos básicos que governam a recuperação de partículas em uma célula de flotação compreendem os consecutivos subprocessos de colisão, adesão e estabilidade do agregado partícula/bolha. Entre eles, a colisão é controlada pelo ambiente hidrodinâmico na célula de flotação, enquanto que a adesão é dominada pelo comportamento físico-químico da interface entre partícula e bolha. Por sua vez, a eficiência da estabilidade depende, tanto dos eventos hidrodinâmicos, como dos físico-químicos. A recuperação de partículas grossas de apatita (densidade 3,08 g/cm³) e esferas de vidro (densidade 2,48 g/cm³) foi medida através de ensaios de microflotação e flotação em escala de bancada, variando-se diferentes parâmetros hidrodinâmicos na célula, como rotação e geometria do impelidor e números adimensionais (Reynolds & Froude). Os resultados indicam que velocidades apropriadas do impelidor produziram níveis de turbulência capazes de manter as partículas em completa suspensão, otimizando, assim...

Research paper thumbnail of Hydrodynamic dimensionless parameters and their influence on flotation performance of coarse particles

Minerals Engineering, 2001

The upper particle size limit of mineral floatability is a parameter of great importance in the f... more The upper particle size limit of mineral floatability is a parameter of great importance in the flotation process and the sharp decrease of flotation response when particle size approaches such a limit is a very well known phenomenon. The aim of this research was to find the most suitable hydrodynamic conditions to float coarse particles in microflotation tests. To reach such a target, the influence of some hydrodynamic parameters (Reynolds Number-Re, Froude Number-Fr, Weber Number-We and Power Number-Po) on microflotation response of coarse glass spheres (0.417-0.589mm, 0.208-0.295mm) and quartz particles (0.208-0.295mm) was studied in the presence of the collector ether amine acetate (75 mg/dm 3) at pH=lO. Maximum flotation response (almost 100%) was observed at 3,000<Re<8,000; O.l<Fr<l.O; lO<We0.54. For either more quiescent (Re<3,000; Fr<0.1 and We<lO) or more turbulent (Re>8,000; Fr> l.0; We> lO0 and Po<0.52) hydrodynamic conditions, flotation recovery decreased steadily. Under more quiescent hydrodynamic conditions, the lower recovery was due to the fact that the impeller was not capable of keeping particles in suspension properly whereas under more turbulent conditions the disruption of particle/bubble aggregates was intensively observed.