high chloride in pls and their impact on copper solvent extraction
Post on 22-Jan-2018
271 Views
Preview:
TRANSCRIPT
High chloride in PLS and their impact on Copper solvent extractionCristobal del Río, Leonor Ardiles and Héctor Yañez, both BASF Chile S.A.
Agenda
• Introduction• Industrial SX experience with chloride in PLS• Experimental plan• Results and discussion• Conclusions and recommendations
Introduction• Due to water scarcity the use of seawater in Hydrometallurgical operations is
increasing• Also the lower copper grades and the complexity of coppers ores are pushing the
development of new leaching technologies. At present leach technologies usingchloride salt addition are increasing into the industry
• More process into the next future will have PLS with high Chloride• One of the challenges to the downstream process, solvent extraction and
electrowinning is related to the control of the chloride transfer from leachsolutions to electrowinning solutions (electrolyte)
• There are some experience into the industry about the control of the chloridetransfer to the electrolyte
• However the behavior of the solvent extraction chemical equilibrium has not beenintensively studied for mixed chloride and sulfate media.
• A laboratory study involving PLS with chloride and sulfate using BASF’s copperorganic extraction reagent was conducted and these results discussed
Copper OximesChemical behavior of Oximes in Sulphate Media (Source: Redbook BASF Mining Solutions)
Property Ketoxime Aldoxime Non-modified
blend Modified aldoxime
Extractive Strength Moderate Very strong Customized Customized
Stripping Very good Poor Customized Customized
Cu/Fe selectivity Excellent Excellent Excellent Excellent
Extraction kinetics Very good Very fast Fast Very fast
pH
Cu in
Org
anic
, gpl
Strong Moderate
Ald Ket/Ald Ket
RipiosAcido
Agua Evap Acido CátodosAgua Reposicion Agua Reposicion Aditivos
Mineral Purga Elec.
AditivosER Agua Lav W
PLS RF AguaRF E2 Acido
E-1 E-2 S-1 S-2 WOD S1 OC Lav
OC E1
Colescedores TK Org Carg
Purga Acuosoa circuito LX
Lixiviacion Electrobtencion
Process diagram with Chloride in PLS
Industrial SX with chloride in PLS
The use of wash stage, one or two, are the most common alternative to control of chloride transfer to the electrolyte
Operation [Cl-] PLS, g/L [Cl-] LE, ppm Configuration Coalescers, n° Wash stage, n° Reagent
A 80 20-50 SPT 1 1 LIX®9790N
B 80 20-50 SPT 1 1 LIX®9790N
C 10 50 Serie 0 0 LIX®984N
D 30 30-40 Serie 0 1 LIX®84I-C
E 50 10-30 Serie 0 2 LIX®9790N
F 90 20-45 Serie SX 1 /SP SX 2 0 2 LIX®84I-C / LIX®860N-C
G 30 20-30 Serie 0 1 LIX®84I-C
H 35-40 <20 Doble Serie // 0 2 LIX®984N
I 45-90 <25 Doble Serie // 0 2 LIX®84I-C / LIX®860N-C
J 5-7 30-40 Serie 0 1 LIX®84I-C / LIX®860N-C
Experimental planPregnant leach solutions (PLS) conditions
Solution PLS Cl- g/L SO42- g/L pH
PLS 1 A1 0 95 1,0 PLS 2 A2 0 95 1,5 PLS 3 B1 20 95 1,0 PLS 4 B2 20 95 1,5 PLS 5 C1 40 95 1,0 PLS 6 C2 40 95 1,5 PLS 7 D1 90 95 1,0 PLS 8 D2 90 95 1,5
PLS was prepared in the laboratory, with component concentrations (Al+3, Mg+2, Fe+3,Fe+2, Mn+2) adjusted to average conditions in Chilean operations (95 g SO4
-2/L).Chloride concentrations of 0, 20, 40 and 90 g/L were studied. Solutions were adjustedby NaCl addition. Other cations were added as sulfate salts. In addition, the pH wasadjusted to 1.5 and 1.0 by H2SO4 addition. Lean electrolyte: 35 g/L Cu and 180 g/L acidOrganic phase was prepared at 24% v/v with diluent and BASF extractants were basedon Ketoxime (LIX®84I) and Modified Aldoxime (LIX®684N-LV).
Standard parameters of performanceThe standard parameters to be analyzed are Extraction and Strip isotherms, whichgive us the metallurgical performance approach and the Extraction kinetic tests tohave an approach to the industrial mixing efficiency expected. Isotherms andkinetics tests were determined for each PLS solution contacted with the organicsolution prepared at 24% v/v, LIX®84I or LIX®684N-LV. All tests were determinedaccording to the BASF standard procedures.
Chemical characterization of PLS
For samples containing the same acid content, higher chloride concentration leadsto a lower pH. The equilibrium of the sulfate/bisulfate/sulfuric acid is altered by theaddition of chloride.
Ion Unit Value
Cu2+ g/L 4.5
SO42- g/L 95
Cl- g/L 0; 20; 40; 90 Fe T g/L 2.0 Fe2+ g/L 0.4
Fe3+ g/L 1.6
Mn2+ g/L 2.0
Al3+ g/L 6.1
Mg2+ g/L 11.2
Ni+ g/L 0 – 58 pH 1.0; 1.5
Extraction Isotherms
Copper load in organic PLS pH 1.0 Copper load in organic PLS pH 1.5
LIX®84I LIX®684N-LV
LIX®84I LIX®684N-LV
90 g/L Cl- 9.5 11.4 90 g/L Cl- 11.2 13.2 0 g/L Cl- 7.1 9.5 0 g/L Cl- 10.6 12.6
Diff. 2.4 1.9 Diff. 0,6 0.6 % increase 34 20 % increase 6 5
Mechanism proposed
• Extraction
*More favorable with low pH (4)
• Extraction increase: Equilibrium changes, K1 Products consumption Secondary reactions
𝐶𝐶𝐶𝐶𝐶𝐶𝑙𝑙+ + 2𝐻𝐻𝐻𝐻 ↔ 𝐶𝐶𝐶𝐶𝐻𝐻2 + 2𝐻𝐻+ + 𝐶𝐶𝑙𝑙−∗ 𝐾𝐾1
(1) HSC Chemistry 6.0, ©Outokompu Research 1974 – 2006(4) Szymanowski, J. Journal of R. & N. C. 208 (1996) p 183-194
0 10 20 30 40 50 60 70 80 900
0.005
0.01
0.015
0.02
0.025
0.03
0.035
[Cl-] gL-1[H
Cl (a
)] mol
L-1
pH 1.00pH 1.50pH 2.00
𝐻𝐻+ + 𝐶𝐶𝑙𝑙− ↔ 𝐻𝐻𝐶𝐶𝑙𝑙(𝑎𝑎𝑎𝑎)
∆𝐺𝐺𝑅𝑅(25°𝐶𝐶) = 0.968 𝑘𝑘𝑘𝑘𝑘𝑘𝑙𝑙 (1)
𝐾𝐾𝑒𝑒𝑎𝑎(25°𝐶𝐶) = 1.952 × 10−1 (1)
PRODUCTS
Stripping isotherms (Cu: g/L)
O/A ratio
LIX84I LIX684N-LV aq org aq org
1/10 37 0,45 37 2,09 1/4 38 0,49 38 2,23 1/3 39 0,50 39 2,34 1/1 47 0,66 46 2,80 3/2 52 0,88 51 3,31 5/2 58 1,13 58 3,98
LE: Cu 35 g/L, acid 180 g/L
Stripping stage have the usual behaviorKetoximes allow lower cooper in unloaded organic than modified aldoxime
Extraction kinetics
ion kinetic tests were performed at pH 1.5 and 1.0, with PLS having 0 and 90 g/L ofchloride concentration. Isotherm Graphs are illustrated in Figure 3. PLS withoutChloride content resulted in good extractions kinetics, considering the mixing time isindustrial operations is 150-180 seconds. When the PLS has high chlorideconcentration (90 g/L) the resulting kinetics show a relevant improvement, with theresults similar for both reagents, Ketoxime or Modified Aldoxime.
[Cl-] in PLS and TSF• O Continuity (pH 1.00; 23°C)
LIX® 84I 0 gL-1 Cl- LIX® 84I 90 gL-1 Cl-
TSF registered 10x
0 900
10
20
30
40
50
60
70
80
90
100
Cl- gL-1
Tiem
po, s
TSF C.O. LIX 84I pH 1.00 95 gL-1 SO42-
84
57
0 900
10
20
30
40
50
60
70
80
90
100
Cl- gL-1
Tiem
po, s
TSF C.O. LIX 684NLV pH 1.00 95 gL-1 SO42-
71
51
Iron transfer and washing stage• Organic iron behavior (20 gL-1 H2SO4)
OC OW1 OW20
1
2
3
4
5
6
7
8
9
10Variación FeT en orgánico sin Cl-
Etapa
FeT,
ppm
LIX 84ILIX 684NLV
OC OW1 OW20
1
2
3
4
5
6
7
8
9
10Variación FeT en orgánico con Cl-
Etapa
FeT,
ppm
LIX 84ILIX 684NLV
Chloride concentration in PLS: 0 gpl Chloride concentration in PLS: 90 gpl
Circuit evaluationPLS, g/L Conc. LE, g/L Conc. Stream Flow, m3/h SE, %
Cu+2 4.4 Cu+2 35 PLS 1000 E1 90
SO4-2 95 Acid 180 LE 230 E2 90
Cl- 0-90 Organic 1200 S 95 pH 1 O/A ratio 1.2
PLS: Pregnant leach solution, LE: Lean Electrolyte and SE: Stage Efficiency To evaluate the metallurgical performance, a 2E1S configuration was evaluated using the BASFISOCAL™ software to model the isothermsprepared previously. PLS with pH 1.0 having 0 or90 g/L of chloride concentration was modeled forKetoxime (LIX®84I) or Modified aldoxime(LIX®684N-LV) reagents. Principal parametersevaluated are; copper recovery, Max. copper load(ML), Cu in organic unloaded (UO) and Cu inorganic loaded (LO).
Copper behavior in organic circuit
Copper transfer increase when the chloride concentration in PLS is high
Copper extraction in 2E 1S circuit (%)Copper extraction in 2E 1S circuit (%)
Cl- g/L LIX®84I LIX®684N-LV
0 76.8 79.4 90 88.5 87.2
Diff. +11.7 +7.8
Conclusions and Recommendations(1/2)• For South America, hydrometallurgical operations are expected to increase
the use of seawater and/or the addition of chloride salts to the leachingprocess to improve the leaching performance of refractory and/orsecondary sulfides ores. Therefore, in South America, a 30% or 40% increaseof the hydrometallurgical operations in the next future will have highchloride concentration in their PLS (higher than 25 g/L).
• For these plants, PLS will have a low pH, with values between 1.0 to 1.5.This is a challenge to solvent extraction in terms of copper transfer. Whilethe higher chloride concentration in PLS means lower pH, it improves thechemical behavior of the oximes in extraction stages, having a positiveeffect on copper loaded in organic and in the extraction kinetics.
Conclusions and Recommendations (2/2)• Ketoximes (LIX®84I) have more improvement than Modified Aldoxime
(LIX®684N-LV). For a PLS with 4.4 g Cu/L and pH 1.0, the maximumcopper load increase is 34% for Ketoximes, while in the case of the ModifiedAldoxime the increase is 20%.
• Due to the better stripping performance of Ketoxime over ModifiedAldoxime in a conventional circuit with configuration 2E 1S with PLS at pH1.0, the Ketoxime (LIX®84I) performs slightly better than the ModifiedAldoxime (LIX®684N-LV) in terms of copper transfer.
• For a PLS having higher chloride concentration and low pH, the reagentsbased on Ketoxime are excellent alternatives in terms of copper transfer andphysical behavior. A positive physical behavior is reported in actualoperations due to the low viscosity of the reagent based on ketoximewithout equilibrium modifiers.
Oilfield and Mining Solutions
INTERNAL
top related