1. P. Crane, M. Urbani, K. Dudley, A. Horner and M. Virnig
Solvent Extraction (SX) reagent selection for high temperature, high acid, high chloride and high Cu concentration leach solution at Port Pirie and its impact on electrowinning By
P. Crane, M. Urbani, K. Dudley, A. Horner and M. Virnig

2. Nyrstar Port Pirie Smelter
Courtesy Google
Port Pirie
Broken Hill
Rich lead deposit
Nyrstar Port Pirie Smelter
The smelter is situated 230km north of Adelaide in South Australia on the Spencer Gulf.

3. The smelter was built on a natural harbour allowing ease of product export

4. Background
History: The smelter has been processing lead concentrates since 1889, after the ore field in Broken Hill was discovered.
Much expansion occurred during the 1950s and 1960s.
Zinc production commenced in 1967
Copper production commenced in 1984
Production Capacity: Lead – 235,000 Tonnes
Zinc – 45,000 Tonnes
Silver – 11.5 million troy ounces (357 Tonnes)
Gold - 16,000 million troy ounces (497 kilos)
Sulphuric Acid – 80,000 Tonnes
Copper – 4,500 Tonnes

5. Copper plant Feedstock mainly sourced from lead concentrates

6. NPPS Copper Process
Copper is recovered from the lead furnace in the form of a matte, which is treated in the copper plant
The Copper recovery process employs a unique mixed chloride-sulphate leach technology (formerly known as the BHAS process) developed by BHAS engineers.
This aggressive chloride-assisted leach is followed by conventional Cu SX / EW processes operated under fairly harsh conditions.

7. Basic NPPS Copper Plant Circuit Process description
Matte from CDF
Leach (primary and secondary)
Solvent Extraction
Residue/
Neutralisation
Milling
Residue back to Sinter Plant
Electrowinning

8. Ball Mill and Feed Hopper

9. Grinding
A conventional ball mill in closed circuit with a spiral classifier, treating 12,000 tpa matte.
Product goes to Primary Leach after thickening and storage.
To leach

10. Overall leach chemistry (effect of chloride not shown)
Cu2S + PbS + H2SO4 + 4H+ + 3/2 O2  PbSO4 + 2Cu2+ + 2S + 3H2O
Black Acid
Primary
Leach Thickener
Underflow
Secondary
To Neutralisation then Sinter Plant
PLS
Underflow
PLS to Clarifier

11. Leach Reactors

12. 2nd Stage Leach and washing
Thickener U/F from 1st stage leach at 35-40% solids is pumped to a one-stage repulp reactor.
Salt, white acid and Oxygen added.
4-5 hrs residence time.
2nd stage leach discharge washed with raffinate in a repulp mixer.
Polysil added in repulp mixer for silica control, and Magnafloc added to Repulp Thickener as a settling aid.
Repulp slurry is thickened; solids are sent to neutralisation and return to the sinter plant, whilst liquids go to 1st stage leach.

13. Salt addition to repulp reactor
NaCl prevents precipitation of CuS from Cu+ and S0.

14. Preg Clarifier
Leach Thickener

15. Copper SX Conventional 2E x 1W x 2S circuit.
Washing
Stripping
Pregnant
Leach Solution
Raffinate
Extraction
Spent
Electrolyte
Advance
Wash Water
Cu2+
Impurities E1 E2 S2 S1
aqueous
organic
Pregnant Leach Solution (PLS) containing approx. 40 g/L Cu, 20 g/L acid and 20 g/L Cl- at >40 deg C.

16. SX Mixer-settlers, S1 and S2

17. Electrowinning
Two stage cascade systems in series with 15 cells per unit.
Each cell has capacity for 40 stainless steel or titanium cathodes and 41 antimonial lead anodes
Cathodes and anodes are connected to two 10,000A rectifiers.
Spent Electrolyte
to S2 after cooling
Advance Electrolyte

18. Cell house

19. Process Difficulties
The use of the highly effective chloride – sulphate leach process results in several challenges for the operation of the Cu SX-EW plant, namely it:
Produces a hot PLS, high in acid, chloride and copper content;
Requires effective silica control and solids liquid separation;
Requires a high SX extractant concentration and high O/A ratios;
Requires careful monitoring of organic health and regular, effective, organic treatment.

20. Cognis Involvement
Cognis visited Port Pirie in mid 2003 to view the plant operation and offer technical assistance. Main observations:
Operating with high concentration of Acorga® M5640 (C9 aldoxime with TXIB modifier) and high O/A ratio.
No phase separation under Organic Continuous conditions  Forced Aqueous Continuous operation.
Evidence of silica-based crud.
Re-oximation stage due to high reagent degradation rate.
Viscous organic with dark colouration after strong acid strip.
High entrainment and resultant high Cl transfer to electrolyte (consistently >200 ppm Cl in electrolyte)  titanium plates.
Poor atmospheric environment in EW (low levels Cl2 gas).

21. Cognis Involvement, cont.
In August 2003, a sample of Port Pirie plant organic was analysed in Cognis’ Tucson laboratory. The main findings were:
Extremely poor OC phase break >15 minutes at 25C
Slow stripping kinetics – 62% after 30 sec (typically 95%)
High nitro-C9 aldoxime level (16.2 % of total oxime)
Excessive levels of hydrolysis product (aldehyde)
High TXIB : C9 aldoxime ratio (0.38 compared to 0.28 in Acorga M5640)
Presence of 2-cyano-4-nonylphenol and 5-nonylsalicylamide
The organic did not respond to clay treatment

22. Stripping tests indicated the scale of the problem
33%(v/v) LIX® 674N-LV in SX 12 after a few load strip cycles then completely stripped.
Note the clarity.
Stripping tests indicated the scale of the problem

23. 33%(v/v) LIX® 674N-LV in SX 12 after a few load strip cycles then completely stripped.
Red colour warning signs of nitration
Port Pirie plant sample completely stripped – 4 contacts with 250 g/L acid, O/A 2:1.

24. Nitration of oximes Requires acid, nitrate and high ORP
Catalysed by presence of modifiers (Virnig, et. al. Copper2003)

25. Effect of modifiers on oxime degradation in presence of nitrate
Stripped organic phases of all modified reagents: LIX 622N, M5640 and LIX 84-I + TDA; were red in colour

26. Cognis Manufactured Oximes
INCREASING REAGENT STABILITY
C9 Aldoxime
C12 Aldoxime
C9 Ketoxime
Acorga M5640 (incl. TXIB modifier) LIX 984
© Copyright, Cognis Corporation, 2005

27. Cognis recommendations
Convert reagent to a more stable non-modified reagent type to:
Reduce rate of nitration
Reduce rate of degradation
Reduce viscosity of organic phase
Cease re-oximation of the organic, since:
Re-oximated organics demonstrate poor physical performance
Re-oximated organics are typically difficult to clean up
Hydroxylamine may have been at least a partial source of the nitrogen oxide species
Recommendations were all intended to improve the physical state and the performance of the organic phase.

28. Port Pirie accepted the Cognis offer.
LIX 984 was selected because:
50/50 blend of LIX 84-I (ketoxime) and LIX 860-I (C12 aldoxime), both of which are more stable than the C9 aldoxime present in Acorga M5640.
LIX 984 contains no modifier  Modifiers promote nitration.
LIX 984 showed good chemical performance in initial screening tests.

29. Pre-LIX reagent addition plant profile (April 2004)
Cu Mass balance OK
High oxime concentration (43%(v/v))
Low Cu net transfer (0.14 g/L Cu / % oxime)
Low % Cu max load
Laboratory PDT’s – aqueous continuous seconds, organic continuous - no separation after 15 minutes
Again clay treatment had no effect, organic not filterable
Extremely high viscosity (26.5 cSt compared to 3.9 cSt for fresh LIX reagent at 43%(v/v)

30. Acorga addition stopped in April 2004 and LIX addition commenced.
Regular plant monitoring involved:
Chemical composition –C9 and C12 aldoxime, ketoxime, TXIB, hydrolysis and nitration products
Chemical performance – Cu recovery, % Cu ML, Cu net transfer (g/L Cu / % oxime), extraction and stripping kinetics
Physical performance – Plant PDTs, mixer continuity, temp, laboratory PDTs, Effect of clay treatment, viscosity
Monitoring the Cl- concentration in the electrolyte

31. Conversion rate tracked by decline in TXIB content

32. Net Transfer (g/L Cu/vol%)
Plant chemical performance
Parameter
Survey Date
May-04
Nov-04
Jan-05
Jun-05
Nov - 06
Apr - 07
Oct - 07
Sept - 08
PLS Cu(g/L)
41.0
45.8
44.6
42.3
45.0
51.9
32.0
45.2
Raffinate Cu(g/L)
12.9
15.4
13.9
15.0
15.5
14.8
8.1
10.9
Cu recovery (%)
68.5
66.4
68.8
64.5
65.6
70.7
65.5
75.8
Reagent Conc. (vol%)
34.0
30.0
25.8
32.6
33.5
33.3
Net Transfer (g/L Cu/vol%)
0.150
0.220
0.234
0.255
0.229
0.273
0.174
0.211
% max load
59.0
83.9
81.5
88.2
74.6

33. Net Transfer (g/L Cu/vol%)
Plant chemical performance
Parameter
Survey Date
May-04
Nov-04
Jan-05
Jun-05
Nov - 06
Apr - 07
Oct - 07
Sept - 08
PLS Cu(g/L)
41.0
45.8
44.6
42.3
45.0
51.9
32.0
45.2
Raffinate Cu(g/L)
12.9
15.4
13.9
15.0
15.5
14.8
8.1
10.9
Cu recovery (%)
68.5
66.4
68.8
64.5
65.6
70.7
65.5
75.8
Reagent Conc. (vol%)
34.0
30.0
25.8
32.6
33.5
33.3
Net Transfer (g/L Cu/vol%)
0.150
0.220
0.234
0.255
0.229
0.273
0.174
0.211
% max load
59.0
83.9
81.5
88.2
74.6

34. Net Transfer (g/L Cu/vol%)
Plant chemical performance
Parameter
Survey Date
May-04
Nov-04
Jan-05
Jun-05
Nov - 06
Apr - 07
Oct - 07
Sept - 08
PLS Cu(g/L)
41.0
45.8
44.6
42.3
45.0
51.9
32.0
45.2
Raffinate Cu(g/L)
12.9
15.4
13.9
15.0
15.5
14.8
8.1
10.9
Cu recovery (%)
68.5
66.4
68.8
64.5
65.6
70.7
65.5
75.8
Reagent Conc. (vol%)
34.0
30.0
25.8
32.6
33.5
33.3
Net Transfer (g/L Cu/vol%)
0.150
0.220
0.234
0.255
0.229
0.273
0.174
0.211
% max load
59.0
83.9
81.5
88.2
74.6

35. Laboratory extraction and stripping kinetics
Aug 03
Jul 05
Mar 06
Jun 06
Dec 06
Feb 07
Sept 08
30 sec -
86 %
90 %
96 %
92%
30 sec
62 %
71 %
78 %
92 %
97%

36. Plant physical performance
Laboratory PD tests using plant organic and plant PLS.
Date
PDT (seconds) OC AC
Apr 2004
No break
126
Jan 2005
130
July 2005
110
October 2005
>600 90
March 2006 72
June 2006
600
100
December 2006 93
February 2007
474
109
April 2007
114
201
Oct 2007 49 26
Feb 2009 30

37. PD time before and after clay treatment.
Extraction (OC) sec
Strip (AC) (sec)
Pre CT
Post CT
April 04
No break -
March 06
920 22 72 20
June 06
627
100
Viscosity of the plant organic
Apr 04
Sep 04
Jan 05
Jul 05
Oct 05
Mar 06
Jun 06
Dec 06
Feb 07
May 08
Sept 08
25oC (cSt)
26.48
19.43
15.06
15.13
13.15
13.90
12.20
9.50
8.93
7.72
6.66

38. Chloride in electrolyte (and PLS)

39. EW Chloride vs TXIB in organic

40. Conclusions
The conversion of Acorga modified reagent to the more stable LIX non-modified reagent resulted in:
reduction in reagent concentration to <35vol% (now at 30%).
improvement in extraction and strip kinetics.
higher net transfer (>0.2gplCu/vol%).
very significant improvement in phase separation behaviour.
organic phase viscosity reduced by 75%.
very significant decrease in chloride transfer to EW.
reduction in electrolyte chloride level by ~90%.
much easier plant operation.

41. Acknowledgements
Nyrstar Port Pirie
Cognis
Co-authors and investigators: Kym Dudley, Mark Urbani, Dr Michael Virnig and Anissa Horner

42. Questions?