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

  • 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.


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.


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


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.


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.


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


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.


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%


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.


Figure 1 Mineralogical Composition as a function of the particle size


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


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


Pareto Chart


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.


ResponseSurface


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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