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Experimental Design to evaluate a reagent system for a nickel ore flotation

Experimental Design to evaluate a reagent system for a nickel ore flotation. Authors. Jean Louzada; Ronald Hacha ; Marisa Monte and Mônica Cassola (a) CETEM – Centre for Mineral Technology, Rio de Janeiro, Brazil (b) Clariant S.A, São Paulo, Brazil. MOTIVATION.

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Experimental Design to evaluate a reagent system for a nickel ore flotation

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  1. Experimental Design to evaluate a reagent system for a nickel ore flotation

  2. Authors • Jean Louzada; Ronald Hacha; Marisa Monte and Mônica Cassola • (a) CETEM – Centre for Mineral Technology, Rio de Janeiro, Brazil • (b) Clariant S.A, São Paulo, Brazil

  3. MOTIVATION • The optimization of flotation conditions is a complex task because many process variables can affect flotation responses. • It is not uncommon for multiple interactions to occur between independent variables; • The identification of these interactions play an important role in advancing our understanding of the chemistry of such system in plant operations.

  4. OBJECTIVES • To employ a factorial design to investigate the effect of chemical variables on the flotation performance of dithiophosphates for a nickel ore; • To optimize these variables for maximum nickel recovery and grade.

  5. EXPERIMENTAL • REAGENTS • Ethyl secbutil sodium dithiophosphates (Hostaflot E501) and sodium dialkyldithiophosphate (Hostaflot M92) were supplied by Clariant; • Polypropylene glycol methyl ether (CH3(OC3H6)n-OH and other consisting of a mixture of aliphatic alcohols, ethers and esters. The two frothers were supplied by Clariant . • The activator and the depressant used were copper sulfate and carboxymethyl cellulose, respectively

  6. EXPERIMENTAL • A nickel ore sample from Minas Gerais, Brasil, was completely characterized for mineralogical and chemical compositions: • Mineralogical composition, associations and liberation were measured in a FEI Quanta 400 SEM with the Mineral Liberation Analyzer (MLA) software. • Chemical analysis were carried out in a PanAnalytical Epsilon 3 X-ray Fluorescence machine.

  7. EXPERIMENTAL • Factorial Design; • Only factors which influenced in the recovery of nickel by flotation will be presented here. • The factorial design was implemented with two levels and six factors resulting in thirty two experiments. • The Statistics software was used for the regression analysis, statistical and optimization calculations.

  8. Table 1. Factorsandlevelsapplied in 26-1 fractionalfactorial design. Flotanol(low: 20; high: 40); Montanol (low: 20; high: 80).

  9. Experimental • FlotationTests • The samples were ground in a rod mill, to which were added the dispersant and the activator at pH 6.0. • Immediately after grinding, the material was deslimed and, subsequently, the sample was transferred to a cell with two liters. • The pulp was kept under stirring at 1400 rpm and the pH was adjusted to 9.5 with a solution of NaOH 10% (p/v). • pH adjustment was immediately followed by depressant addition, carboxymethyl cellulose, and conditioning for 4 minutes. • Afterwards, the collector was added and conditioned for 30 seconds. • Finally, the frother was added to the system and conditioned for 1 minute. • The pH was kept at about 9.5 during the conditioning with all reagents. The flotation time was 4 min.

  10. Experimental • Curve Fitting and Statistical Analysis • The important response variable chosen in this study was nickel recovery • The statistical significance of effects and interactions between processes and the response variable was determined using the F-test. • Probability (P) values larger than 0.05 were indicative of a measured effect being statistically significant at a confidence level  95%

  11. RESULTS AND DISCUSSION Mineralogical characterization • These studies showed that the major minerals are talc, hornblende, ilmenite, pyrite and pyrrhotite. • The results revealed that talc is not the predominant magnesium carrier mineral • Hornblende is present and predominates over talc in all ranges of particle size.

  12. Figure 1 Mineralogical Composition as a function of the particle size

  13. Figure 2 Minerals associated to pentlandite in the particle size range between 210 and 38 μm.

  14. Figure 3 - Synthesis of the results obtained for theoretical recovery and grades of pentlandite in the concentrate at different size ranges.

  15. Pareto Chart

  16. AnalysisofVariance These variables and their interactions presented higher probabilities: • B: Concentration of collector ; • D: Concentration of frother • BD: interactions between them • In other cases, the null hypothesis is rejected because the estimated values of p-levels (Test P) are smaller than 0.05, i.e., the effects have a probability smaller than 5% so they represent only of noise.

  17. ResponseSurface

  18. CONCLUSIONS • The results of these studies showed that the main factors that influence more significantly the nickel recovery are the collectors and frothers concentrations. • The differences between the collectors are the alkyl chains do not influence the recovery.

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