by Wensheng Zhang, Fuping Hao, Yoko Pranolo, Chu Yong Cheng, and Dave Robinson Presented by Wensheng Zhang 8 July 2011

Transcription

1 A study of copper extraction kinetics with LIX 984N using a Lewis cell by Wensheng Zhang, Fuping Hao, Yoko Pranolo, Chu Yong Cheng, and Dave Robinson Presented by Wensheng Zhang 8 July 2011

2 Content of presentation 1. Introduction SXT2 an Industry Sponsored Project Review of techniques for kinetics study Development of an improved Lewis cell 2. A kinetic study on Cu solvent extraction 3. Conclusions

3 CSIRO SXT2 Project; Improved Performance by Reduction of Entrainment Operational impact; Understanding of flow field, drop size and entrainment loss Improved mixer design for optimum drop size generation Improved settler design for improved coalescence Physical modelling; Development of velocity and interface probes On-site measuring flow pattern and drop size CFD modelling; Drop size distribution, flow pattern and residence time distributions Changes in mass transfer and kinetics Changes in design and operational parameters CFD models for drop size and mass transfer in mixers Mass transfer and entrainment; Developing measurement techniques Establishing rate equation and mechanism Incorporation in CFD models

4 Solvent extraction kinetics principles Extraction regimes; Diffusion regime Kinetic regime Mixed regime Reaction locations; In the bulk phases - homogeneous At interface heterogeneous Key parameters; Stirring speed Interfacial area Temperature Species concentrations

5 Techniques 1 Highly stirred tank Features; One phase dispersed in the other Similar to practical SX conditions Reactor readily available Easy to operate A/O O/A Disadvantages; Hydrodynamic complex Difficult to control interfacial area Uncertainty in the derived extraction regimes Not suitable for fast kinetics A/O/A O/A/O

6 Techniques 2 Moving drops Features; Good control of drop size Known interfacial area Simple set-up and operation Falling drop Rising drop

7 Techniques 2 Moving drops Disadvantages; Complex and variable hydrodynamics Difficult to determine the degree of turbulence Uncertainty in extraction regimes Not suitable for very fast or slow kinetics

8 Techniques 3 Lewis cell Features; Constant interfacial area Hydrodynamics well controlled Hydrodynamic calibration feasible Disadvantages; Difficult to maintain stable interface under turbulent flows Lewis cell by Lewis 1954

9 CSIRO Lewis cell features and performance Design features: Curved horizontal baffles Centred vertical baffles Cylindrical grid Two shafts separate controls 45 pitched blade turbines Water jacket for temperature control Auto ph control Continuous on-line analysis Clear body for visual observations Determination of EX regimes; Maintaining constant interfacial area in a wide range of turbulent flows Extraction locations; Able to vary interfacial areas Separate phase stirring speeds

10 CSIRO Lewis cell set-up for kinetic study Lewis Cell On-line UV-Vis analyser Water bath

11 Experimental for Cu kinetic study Typical aqueous feed solution 2 g/l Cu as sulphate Typical organic solution 10% (v/v) LIX 984N (LIX LIX 84 at 1:1, supplied by BASF/Cognis) In Shellsol D70 Typical test conditions 30 C ph rpm in both phases Analysis Organic phase continuously measured by an on-line UV-Vis analyser ICP for off-line calibration

12 Cu extraction (mg/l) Effect of stirring speed rpm 50 rpm 60 rpm 180 rpm 200 rpm 220 rpm 240 rpm 260 rpm 280 rpm Linear function of Cu extraction with time Initial rate determined by the slop values Time (min) At 20 C and ph 1.8 with 10% LIX 984N in Shellsol D70

13 Cu extraction rate (mg/l/min) Extraction regimes 4.0 Lower speeds Zone A Zone A Diffusion regime Zone B Kinetic regime Laminar or less turbulent Constant interfacial area 2.5 Re: 8,000-15,000 Diffusion regime C 30 C Higher speeds Zone B 1.5 Turbulent flow 1.0 Constant interfacial area 0.5 Kinetic regime Stirring speed (rpm) Zone C - even higher speed Disturbance of interface Varying interfacial area ph 1.8 with 10% LIX 984N in Shellsol D70

14 Cu extraction rate (mg/l/min) Cu extraction rate (mg/l/min/cm 2 ) Effect of interfacial area 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0,2 0,1 Rate proportional to interfacial area (A) Constant R/A ratio Interfacial reactions 0,5 0, Interfacial area (cm 2 ) 0 30 C, ph 1.8 with 10% LIX 984N in Shellsol D70

15 Log(rate) Log (rate) Ln (rate) Log (rate) Effect of temperature and chemical species 2 1,0 1,5 1 0, C, Ea = 25 kj/mol Arrhenius type plot 0,5 0,0-0,5 ph y = -0,9169x - 1,2687 R² = 0,9668-0,5-1 -1,5 0,8 0,6 0,4 0, C, Ea = 67 kj/mol 3,00 3,10 3,20 3,30 3,40 3,50 3, K/T y = 0,9863x + 2,2663 R² = 0,9823-1,0-1,5 0,5-0,5-2,5-2 -1,5-1 -0,5 0 Log[H + ] 0 y = 1,095x - 0,4774 R² = 0, ,2-0,4-0, g/l Cu -3-2,5-2 -1,5-1 Log[Cu 2+ ] (M) % (v/v) LIX 984-1,5-2 -1,50-1,00-0,50 0,00 0,50 1,00 1,50 Log[LIX 984N]

16 Empirical rate equation Empirical rate equation R k exp 2 [Cu ][HL] 0.9 [H ] 1.1 o Condition range ph , [Cu 2+ ]: g/l, LIX 984N: 0.1-5% (v/v) ( M) Temperature: 30 C

17 Proposed reaction mechanism Dimerisation 2HL o = HL 2o (fast) (1) Equilibrium HL o = HL ad = HL int-aq (fast) (2) Complexation of 1 st ligand at the interface Cu 2+ + (HL) ad (CuL + ) ad + H + (fast) (3) Complexation of 2 nd ligand at the interfacial Aq side (CuL + ) ad + (HL) int-aq (CuL 2 ) ad + H + (slow) (4) Adsorption-desorption of interfacial complex (CuL 2 ) ad = (CuL 2 ) o (fast) (5)

18 Derived rate equations Derived rate equation R k [Cu 2 ][HL] [H ] o [HL] ad Applying Langmuir isotherms for adsorption [HL] ad = 1 [HL] o [HL] o / / Where and are Langmuir constants

19 Derived rate equations For saturation where 1 << [HL] Then [HL] ad = α Then the derived rate equation becomes R k 2 2 [Cu ][HL] [H ] o In a good agreement with the empirical rate equation R k exp 2 [Cu ][HL] 0.9 [H ] 1.1 o

20 Conclusions Excellent performance of the Lewis cell Obtained constant interface area under turbulent flows Demonstrated by the study on Cu SX kinetics with LIX 984N Measurement of Cu SX kinetics using the Lewis cell Determined Cu extraction regimes Proposed Cu extraction mechanism and rate limiting step Established empirical and derived rate equations Good agreement between the empirical and the derived

21 Lewis cell capability going forward Industrial sponsors and reagent suppliers interest for employing the Lewis cell for kinetic studies Kinetic characterisation of new SX reagents Performance comparison with existing reagents Mechanistic studies Systematic kinetic studies on real SX operation systems Different extractants and their ratios Types of modifier Types of diluent Effect of degradation products Changes in aqueous feed (impurities etc)

22 CSIRO upgraded Lewis cell features Features Original model Upgraded model Volume Larger smaller Interfacial area Variable Variable V Org /V aq ratio Fixed 1:1 Variable Water jacket Ring seal Built-in Motors Overlay on top Side arrangements Driven mechanism Direct engagement Belts Operating Easy Easier Locating Need for adjustment Auto locating

23 Acknowledgement The financial support of sponsors are greatly appreciated Anglo American BHP Billiton FLSmidth Freeport McMoRan Minara Newmont QNI Umicore CSIRO MDU Research Flagship Funding from CSIRO Minerals Down Under National Flagship Parker CRC for Integrated Hydrometallurgy Solutions MERIWA

24 National Research Flagship Minerals Down Under Parker Centre/CSIRO Process Science and Engineering Dr Wensheng Zhang Research Team Leader Phone: wensheng.zhang@csiro.au Web: National Research Flagship Minerals Down Under Parker Centre/CSIRO Process Science and Engineering Dr Dave Robinson Research Program Leader Phone: david.robinson@csiro.au Web: Thank you Thank you Contact Us Phone: or enquiries@csiro.au Web: