• Author / Uploaded
• joseph kafumbila

• Categories
• Solución
• Manganeso
• Equilibrio químico
• Hierro
• Solución acuosa

Citation preview

INDEPENDENT METALLURGIST

Design of wash stage in copper solvent extraction KAFUMBILA KASONTA JOSEPH

2020

Page 0

Design of wash stage in copper solvent extraction © Joseph Kafumbila [email protected]

Joseph Kafumbila

Page 1

1.

Introduction

Many copper SX-EW circuits experience high entrainment of aqueous in organic phase. Aqueous entrainment in organic phase results in the carry-over of unwanted ions into the electrowinning circuit. The elements like iron, chloride and manganese are controlling the electrolyte bleed in copper EW circuit. Ideally total iron is kept below 2 g/L, chloride below 35 ppm and manganese below 100 ppm (Hans Hein, 2005). In the case of iron, ferric reacts chemically with the organic phase. Ferrous and ferric are transferred into electrolyte by physical entrainment and in addition ferric is transferred from leach solution into electrolyte being chemically loaded in extraction stage and completely stripped in stripping stage. Aqueous entrainment in organic phase depends on the reagent type, the reagent concentration, the temperature, the viscosity, the phase continuity and mixer settler design (Hans Hein, 2005 and P. Cole et al, 2016). Ferric extraction on the organic phase depends on the pLS pH and the saturation of organic phase with copper (Hans Hein, 2005 and O. Tinkler et al, 2009). The originality of this paper is to simulate a block flow diagram of copper SXEW having a conventional configuration 2Ex2S by using Data from existing copper solvent extraction plants to visualize aqueous entrainment problem on SX-EW design. The simulation take account only the aqueous entrainment in organic phase. The simulation is done on the extreme cases: saturated organic phase with copper and the highest copper solvent extraction efficiency.

2.

Wash stage configuration

There are three configurations of wash stage in copper solvent extraction. In all configuration there is an aqueous coalescing tank separated to a surge loaded organic tank. In the first configuration that is usually used the wash stage comes after the surge organic tank (Figure 1). In this configuration the aqueous coalescing tank removes a big portion of aqueous entrainment before the wash stage. In the second configuration the wash stage comes after the first stage of extraction step (Figure 2). In the third configuration the wash stage is removed from the copper solvent extraction configuration and water is sprayed on the loaded organic in E1 organic weir (Figure 3). The third configuration is used when the chemical transfer of iron is negligible.

Joseph Kafumbila

Page 2

Figure 1: Wash stage comes after surge organic tank

Figure 2: Wash stage comes after extraction step

Joseph Kafumbila

Page 3

Figure 3: E1 configuration with wash stage in the organic weir

3.

Wash stage design criteria

In the first and second configurations wash stage needs addition mixer – settler having the same size than extraction and stripping mixers – settlers. The external O/A ratio varies from 40/1 to 80/1 in industrial practice. In practice the external O/A is around 50/1. The internal O/A ratio is 1.25 to avoid the formation of crud. The wash solution must have a pH less than 2 to avoid iron precipitation that can increase the formation of crud (Liu Jian she et al, 2002). In the conditions where the wash solution is acidified water; the increase of acid concentration in the wash solution is to strip iron in the loaded organic. In the same time copper is stripped from loaded organic also. In the conditions where the wash solution is a mixture of spent electrolyte and water; the decrease of ratio volume of water on volume of spent electrolyte increases the free acid in the wash solution for iron stripping. At certain level of copper in the wash solution copper can be extracted from the wash solution to the loaded organic. (Hans Hein, 2005).

4.

Wash stage equilibrium line

4.1. Wash stage equilibrium correlation The equilibrium correlation between copper concentration in organic phase, copper concentration in aqueous phase and acid concentration in aqueous phase of wash stage is the equilibrium correlation of extraction step. In the case where the extractant is Lix984N, Equation (1) gives the correlation between copper concentration Joseph Kafumbila

Page 4

in organic phase, copper concentration in aqueous phase and acid concentration in aqueous phase of wash stage (J. Kafumbila, 2017). Cueorg Cueaq

[Ace ]2

aq *[3.303∗V%−3.0842∗Cu e

2 org ]

=(-25.698*V%(−1.704) )*Cueorg +10.663*V%(−0.608)

(1)

Cueorg : The concentration of copper in organic phase at equilibrium (g/L). Cueaq : The concentration of copper in aqueous phase at equilibrium (g/L). e Acaq : The concentration of acid in aqueous phase at equilibrium (g/L). V%: The concentration of Lix984N in organic phase (%).

4.2. Resolution of equation The semi-empirical model of extraction step using Lix984N as extractant is given by the equation (1). Equation (2) gives the concentration of free acid at equilibrium. e i Acaq = Acaq + (Cuiaq - Cueaq ) * 1,54

(2)

Cuiaq : The concentration of copper in the wash solution (g/L). i “Acaq : The concentration of free acid in the wash solution (g/L). e The value of “Acaq ” in equation (1) is replaced by the equation (2), it appears equation (3). Cueorg Cueaq

(Aciaq +(Cuiaq −Cue )∗1.54) 2

aq *(3.3030∗ V%−3.0842∗ Cue

org

)2

=(-25.698*v%(−1.704) ) ∗ Cueor + 10.663* v%(−0.608)

(3)

After arrangement equation (3) becomes equation (4). Cueorg Cueaq

*

((Aciaq +1.54∗Cuiaq )−1.54∗Cueaq )) 2 (3.3030∗ V%−3.0842∗ Cueorg )2

=(-25.698 * v%(−1.704) ) ∗ Cueor+ 10.663 * v%(−0.608)

(4)

The new designations are introduced and equation (4) becomes equation (5).   Y

Y = Cueor X = Cueaq

(a+b∗X)2

* = e*Y +f X (c+d∗Y)2

(5)

Equations (6), (7), (8), (9), (10) and (11) give the values of a, b, c, d, e, and f. Joseph Kafumbila

Page 5

i a=Acaq + 1.54 * Cuiaq

(6)

b= −1.54

(7)

c= 3.303*V%

(8)

d= −3.0842

(9)

e= −25.698 * V%(−1.704)

(10)

f= 10.663 * V%(−0.608)

(11)

Equation (5) becomes equation (12) after placing “Y” on one side and “X” on other side. (a+b∗X)2

=

X

(e∗Y+f)∗(c+d∗Y)2 Y

(12)

The value of concentration of copper in the aqueous phase at equilibrium is known value. The unknown value is the concentration of copper in the organic phase at equilibrium. Equation (13) gives the value of constant “g”. g=

(a+b∗X)2 X

(13)

Equation (12) becomes equation (14) after introducing equation (13) where values of constants α, λ and ε are given by equations (15), (16) and (17) respectively. Y 3 + α*Y 2 +λ*Y +ε =0 α= λ=

2∗c∗d∗e+(d)2 ∗f (d)2 ∗e 2∗c∗d∗f + (c)2 ∗e − g (d)2 ∗e f∗(c)2

ε= (d)2 ∗e

(14) (15) (16) (17)

Equation (18) gives the value of variable “Y” as a function of variable “T”. α

Y=T-3

Joseph Kafumbila

(18) Page 6

Equation (14) becomes equation (19) after replacing the variable “Y” by equation (18). Equations (20) and (21) give the values of constants p and q. T 3 +p*T +q =0 p= λ q= ε -

(19)

(α)2

(20)

3 α∗λ 3

2

+ 27* (α)3

(21)

Equation (19) has a form of Cardan formula (three degree equation). The value of T is given by the equation (22). q

1

4

1

1

q

T= [− 2 − 2 ∗ ((q)2 + 27 ∗ (p)3 )(2) ](3) + [− 2 +

1

4

1

1

∗ ((q)2 + 27 ∗ (p)3 )(2) ](3) 2

(22)

4.3. Wash stage equilibrium lines 4.3.1. Equilibrium lines with wash solution containing only acid Figure (4) gives equilibrium lines of wash solutions containing 2, 10 and 20g/L of free acid respectively and the organic phase contains 20% of Lix984N.

Figure 4: Equilibrium lines of wash solution containing 2, 10 and 20 g/L of acid and 20% of Lix984N in organic phase Joseph Kafumbila

Page 7

4.3.2. Equilibrium lines with mixture spent electrolyte and water The organic phase contains 20% of Lix984N. The spent electrolyte contains 35 g/L of copper and 180 g/L of sulfuric acid.  Case 1 – wash solution is a mixture of 19 volume of water and one volume spent electrolyte. The wash solution contains 1.75 g/L of copper and 9 g/L of acid.  Case 2 – wash solution is a mixture of 11 volume of water and one volume spent electrolyte. The wash solution contains 2.92 g/L of copper and 15 g/L of acid.  Case 3 – wash solution is a mixture of 8 volume of water and one volume spent electrolyte. The wash solution contains 3.89 g/L of copper and 20 g/L of acid. Figure (5) gives equilibrium lines of mixtures having ratio of water volume on spent electrolyte volume about 19/1, 11/1 and 8/1 respectively and the organic phase contains 20% of Lix984N.

Figure 5: Mixtures having ratio of volume water on volume spent electrolyte about 19/1, 11/1 and 8/1 respectively and the organic phase contains 20% of Lix984N.

4.3.3. Observations Wash stage equilibrium lines developed using this model are similar to those developed by Hans Hein (Hans Hein, 2005). Applying Data from Figure (3) in Hans Hein

Joseph Kafumbila

Page 8

paper (Hans Hein, 2005) Figure (6) gives results. These results are close to Hans Hein simulation.

7,40

DATA Reagent: 20% Lix984N Spent Electr. (g/l Cu) : 36.00 (g/l H2SO4) : 180.00 Organic flow (m3/h) : 1000 Wash solution flow (m3/h):20 Spent electrolyte (m3/h) : 1 water (m3/h) : 19 O/A Ratio in W1 : 50/1 Loaded Organic (g/l Cu) : 7.28 Initial wash solution (g/l Cu): 1.8 (g/l H2SO4): 9.00 Mixing Efficiency in W1 : 95% Temperature : 25°C RESULTS Profile Or Aq Init. Conc. 7.2800 1.8000 Final Conc. 7.3001 0.7945

7,38

Wash stage Isotherm

7,36

O rganic phase: Cu (g/L)

7,34

Washed Loaded organic

7,32 7,30 7,28 7,26

Loaded organic Solution wash out

7,24

Solution wash in

Acid in W1 (g/l H2SO4): 10.5484

7,22 7,20 0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

Aqueous phase: Cu g/L

Figure 6: Simulation of wash stage with Data from Hans Hein paper Figure 3

5.

Simulation copper solvent extraction circuit

5.1. Equilibrium correlations The equilibrium correlation between copper concentration in organic phase, copper concentration in aqueous phase and acid concentration in aqueous phase of extraction step is given by Equation (1). The equilibrium correlation between copper concentration in organic phase, copper concentration in aqueous phase and acid concentration in aqueous phase of stripping step is given by Equation (23) (J. Kafumbila, 2017). Cueorg Cueaq

*

[Aceaq ]2 [3.3030∗ V%−3.0842∗ Cueorg ]2

=(5.11*10(−3) *V% - 0.194)∗ Cueor + 12.81 * v%(−0.901)

(23)

The resolution of Equation (23) follows the same model explained in chapter (4.2).

Joseph Kafumbila

Page 9

5.2. Copper solvent extraction without wash stage 5.2.1. Data Figure (7) gives the block diagram of copper SX-EW circuit without wash stage. This flow diagram shows only the aqueous entrainment in organic phase. The description of flows is the following:

Figure 7: Block diagram of copper solvent extraction circuit without wash stage          

PLS: Pregnant leach solution E1: Stage 1 of extraction step E2: Stage 2 of extraction step Raf E1: Raffinate from E1 Raf E2: Raffinate from E1 LO E1: Loaded organic from E1 ELO E1: Entrainment aqueous in LO E1 LO E2: Loaded organic from E2 ELO E2: Entrainment aqueous in LO E1 CO: Aqueous coalescing tank

Joseph Kafumbila

Page 10

             

LO CO: Loaded organic from CO ELO CO: Entrainment aqueous in LO CO DS CO: Discharged solution from CO S1: Stage 1 of stripping step S2: Stage 2 of stripping step SO S1: Stripped organic from S1 ESO S1: Entrainment aqueous in SO S1 SO: Stripped organic from S2 ESO: Entrainment aqueous in SO SP: Spent electrolyte AD S2: Advance electrolyte from S2 AD S1: Advance electrolyte from S1 CuEW: Copper electrowinning circuit CuEWB: Copper electrowinning circuit bleed

The design criteria are the following: -

-

Extraction step o Number of stages: 2 o Phase continuity: Organic continuous o PLS flow rate: 1000 m3/h o PLS - Copper: 8.04 g/L o PLS - acid: 2 g/L o PLS - iron: 0.8 g/L o PLS - manganese: 2.75 g/L o O/A internal: 1.25 o O/A external: 1.25 o Mixing efficiency E1: 95% o Mixing efficiency E2: 97% o Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry) Stripping step o Number of stages: 2 o Phase continuity: Organic continuous o Spent electrolyte - Copper: 35 g/L o Spent electrolyte - acid: 180 g/L o Spent electrolyte - iron: 2g/L o Stripped organic from S1 - Iron: 1ppm o Advance electrolyte copper: 50 g/L o Mixing efficiency S1: 98% o Mixing efficiency S2: 95%

Joseph Kafumbila

Page 11

-

o Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry) Aqueous coalescing tank o Aqueous entrainment recovery: 65% (P. Cole et al, 2016) Copper tank house o Spent electrolyte – Iron: 2g/L

There are two cases:  The first case – the organic phase is saturated with copper – the ratio of loaded organic on maximum load organic (LO/ML) is equal to 80%. In this condition the ratio of Cu on ferric (Cu/Fe) in LO E1 is around 1000 (O. Tinkler et al, 2009).  The second case – the organic phase is unsaturated with copper – the highest value of extraction efficiency. For this configuration (2Ex2S) the stripping efficiency must be equal to 60% (J. Kafumbila, 2017). In this condition the ratio of Cu on ferric (Cu/Fe) in LO E1 is around 500 (assumed). It has been observed that Ferric concentration in the loaded organic increases with decreasing PLS pH (Hans Hein, 2005) and increases with decreasing LO/ML (O. Tinkler et al, 2009). Ferric concentration in loaded organic is around 10 ppm with concentration of Lix984N in organic phase about 20% and iron concentration in PLS about 1.16 g/L at pH range of 1.5 – 1.8. Copper loading has priority over ferric loading. Almost in all SX plants it is observed, that iron loaded in organic phase exceeds iron loaded in E1 organic phase. Ferric concentration in the organic phase depends on the concentration of ferric in solution, saturation of organic phase by copper and the acid concentration in solution. In this simulation it assumes that ferric is loaded in organic in E1 and is stripped in S1 because the equilibrium correlations of ferric is not yet established. Ferric concentration in the stripped organic is 1ppm (Hans Hein, 2005).

5.2.2. Simulation results The procedure of simulation of copper solvent extraction configurations using the equilibrium correlations is explained in paper (J. Kafumbila, 2017).

5.2.2.1. Saturated organic phase Tables 1A, 1B, 1C, 1D and 2 give the mass balance of copper solvent extraction circuit working with saturated organic phase. Joseph Kafumbila

Page 12

Table 1A: Mass balance of Cu-SX circuit – Saturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

PLS Raf E1 Raf E2 LO E1 ELO E1 1000 1002.63 1001.63 1250.00 2.5 8.04 2.588 0.403 8.772 2.588 0.80 0.790 0.793 0.009 0.790 2.75 2.750 2.744 2.750 2.0 10.424 14.335 10.424 8040.0 2591.8 403.2 10965.2 6.47 800.0 791.6 794.6 10.97 1.98 2750.0 27454.5 2748.8 6.87 2000.0 10440.7 14358.4 10.42

Table 1B: Mass balance of Cu-SX circuit – Saturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

LO E2 ELO E2 SO ESO SP 1250.0 2.5 1250.0 2.5 514.54 4.414 0.403 2.590 37.328 35.000 0.001 0.793 0.001 2.000 2.000 2.744 0.462 0.462 14.335 176.41 180.00 5518.2 1.01 3237.3 93.32 18008.8 1.25 1.98 1.25 5.00 1029.1 6.86 1.16 237.9 35.84 441.03 92616.5

Table 1C: Mass balance of Cu-SX circuit – Saturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

AD S2 AD S1 SO S1 ESO S1 LO CO m3/h 514.54 512.91 1250.0 2.5 1250.0 g/L 37.328 50.00 3.523 50.000 8.77 g/L 2.000 2.017 0.001 2.017 0.009 g/L 0.462 0.466 0.466 g/L 176.41 156.58 156.58 Kg/h 19206.6 25645.6 4403.5 125.0 10965.2 Kg/h 1029.1 1034.5 1.25 5.04 10.97 Kg/h 238.0 239.2 1.17 Kg/h 90771.1 80309.3 391.44

Joseph Kafumbila

Page 13

Table 1D: Mass balance of Cu-SX circuit – Saturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

ELO DS CO CuEWB CO m3/h 0.88 1.63 2.70 g/L 2.588 2.588 35.000 0.790 0.790 2.000 2.750 2.750 0.462 g/L 10.424 10.424 180.00 Kg/h 2.26 4.20 94.61 0.69 1.28 5.41 2.41 4.47 1.25 Kg/h 9.12 16.94 486.58

Table 2: Additional results of mass balance of cu-SX circuit – saturated organic phase Description Extractant percentage in organic phase Extraction efficiency Net transfer Stripping O/A Stripping efficiency Spent electrolyte Fe/Mn Copper production Copper recycle from CuEWB/Copper production

19.89 94.98 0.311 2.43 70.48 4.32 7.54 1.25

% % g/l/V% % t/h %

Figures (8), (9) and (10) gives mass flow percentage of copper, iron and manganese by taking the mass flow of elements in the PLS as 100%. The designation of flows is on Figure (7).

Joseph Kafumbila

Page 14

Figure 8: Copper mass flow percentage – copper mass flow in PLS 100%

Figure 9: Iron mass flow percentage – iron mass flow in PLS 100% Joseph Kafumbila

Page 15

Figure 10: Manganese mass flow percentage – Manganese mass flow in PLS 100%

5.2.2.2. Unsaturated organic phase Tables 3A, 3B, 3C, 3D and 4 give the mass balance of copper solvent extraction circuit working with saturated organic phase. Table 3A: Mass balance of Cu-SX circuit – unsaturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

Joseph Kafumbila

PLS Raf E1 Raf E2 LO E1 ELO E1 1000 1001.63 1001.63 1250.00 2.5 8.04 1.171 0.193 10.588 1.171 0.80 0.775 0.778 0.021 0.775 2.75 2.75 2.744 2.75 2.0 12.646 14.698 12.646 8040.0 1172.9 193.4 13235.2 2.93 800.0 776.1 779.1 26.47 1.94 2750.0 2745.5 2748.1 6.87 2000.0 12666.6 14722.3 12.65

Page 16

Table 3B: Mass balance of Cu-SX circuit – unsaturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

LO E2 ELO E2 SO ESO SP 1250.00 2.5 1250.00 2.5 528.52 5.095 0.193 4.235 38.225 35.000 0.001 0.778 0.001 2.000 2.000 2.744 0.186 0.186 14.698 175.032 180.00 6368.7 0.48 5294.1 95.56 18498.3 1.25 1.94 1.25 5.00 1057.1 6.86 0.46 98.21 36.75 437.58 95134.2

Table 3C: Mass balance of Cu-SX circuit – unsaturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

AD S2 AD S1 SO S1 ESO S1 LO CO 528.52 526.90 1250.00 2.5 1250.00 38.225 50.000 5.575 50.000 10.590 2.000 2.046 0.001 2.046 0.021 0.186 0.190 0.190 175.03 156.66 156.66 20203.0 26344.9 6969.3 125.0 13235.2 1057.2 1077.9 1.25 5.11 26.47 98.2 100.2 0.48 92508.4 82544.7 391.65

Table 3D: Mass balance of Cu-SX circuit – unsaturated organic phase Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

Joseph Kafumbila

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

ELO CO DS CO CuEWB 0.88 1.63 10.45 1.171 1.171 35.000 0.775 0.775 2.000 2.75 2.75 0.186 12.646 12.646 180.00 1.02 1.90 365.71 0.68 1.26 20.90 2.41 4.47 1.94 11.07 20.55 1880.81

Page 17

Table 4: Additional results of mass balance of cu-SX circuit – unsaturated organic phase Description Extractant percentage in organic phase Extraction efficiency LO/ML Net transfer Stripping O/A Spent electrolyte Fe/Mn Copper production Copper recycle from CuEWB/Copper production

30.50 97.59 60.45 0.208 2.37 10.76 7.48 4.89

% % % g/l/V% t/h %

Figures (11), (12) and (13) gives mass flow percentage of copper, iron and manganese by taking the mass flow of elements in the PLS as 100%. The designation of flows is on Figure (7).

Figure 11: Copper mass flow percentage – copper mass flow in PLS 100%

Joseph Kafumbila

Page 18

Figure 12: Iron mass flow percentage – iron mass flow in PLS 100%

Figure 13: Manganese mass flow percentage – Manganese mass flow in PLS 100%

Joseph Kafumbila

Page 19

5.2.2.3. Observations  The concentration of Lix984N is 19.39% for saturated organic phase with copper and 30.50% for unsaturated organic phase with copper.  LO/ML is 80% for saturated organic phase with copper and 60.45% for unsaturated organic phase with copper.  93.8% of copper from PLS are platted as cathode for saturated organic phase with copper and 93.05% are platted as cathode for unsaturated organic phase with copper.  5.02% are exited from the SX-EW circuit in the raffinate for saturated organic phase with copper and 2.41% are exited from the SX-EW circuit in the raffinate for unsaturated organic phase with copper.  1.18% is exited from the SX-EW circuit in the EW bleed for saturated organic phase with copper and 4.55% are exited from the SX-EW circuit in the EW bleed for unsaturated organic phase with copper.  Stripping efficiency is 70.4% for saturated organic phase with copper and is 60% for unsaturated organic phase with copper.  Cu/Fe ratio transferred in EW is 1412.53 for saturated organic phase with copper and is 375.47 for unsaturated organic phase with copper.  Fe/Mn ratio transferred in EW is 4.32 for saturated organic phase with copper and is 10.76 for unsaturated organic phase with copper. The configuration with saturated organic phase need wash stage to wash manganese only. The wash stage is placed after Aqueous coalescing tank and wash solution is acidified water. Wash stage works as a dilution process and the dilution process works well when the ratio Water/solution is high. Copper electrowinning bleed can be recycled directly to copper extraction step to recover the copper. The configuration with unsaturated organic phase need wash stage to partial stripped ferric on the loaded organic. The preferential place of wash stage is before aqueous coalescing tank and the wash solution is a mixture of water and all copper electrowinning bleed. The aqueous coalescing tank works as an aqueous cleaner.

Joseph Kafumbila

Page 20

5.3. Copper solvent extraction with wash stage 5.3.1. Saturated organic phase 5.3.1.1. Data Figure (14) gives the block diagram of copper SX-EW circuit with wash stage and saturated organic phase with copper. This flow diagram shows only the aqueous entrainment in organic phase. The description of flows is the following:

Figure 14: Block diagram of copper SX-EW circuit with wash stage and saturated organic with copper       

PLS: Pregnant leach solution F E1: Feed solution to E1 E1: Stage 1 of extraction step E2: Stage 2 of extraction step Raf E1: Raffinate from E1 Raf E2: Raffinate from E1 LO E1: Loaded organic from E1

Joseph Kafumbila

Page 21

                     

ELO E1: Entrainment aqueous in LO E1 LO E2: Loaded organic from E2 ELO E2: Entrainment aqueous in LO E1 CO: Aqueous coalescing tank LO CO: Loaded organic from CO ELO CO: Entrainment aqueous in LO CO DS CO: Discharged solution from CO WS: wash solution SAW: solution after wash WLO: washed loaded organic EWLO: Entrainment aqueous in washed loaded organic S1: Stage 1 of stripping step S2: Stage 2 of stripping step SO S1: Stripped organic from S1 ESO S1: Entrainment aqueous in SO S1 SO: Stripped organic from S2 ESO: Entrainment aqueous in SO SP: Spent electrolyte AD S2: Advance electrolyte from S2 AD S1: Advance electrolyte from S1 CuEW: Copper electrowinning circuit CuEWB: Copper electrowinning circuit bleed

The design criteria are the following: -

-

Extraction step o Number of stages: 2 o Phase continuity: Organic continuous o PLS flow rate: 1000 m3/h o PLS - Copper: 8.04 g/L o PLS - acid: 2 g/L o PLS - iron: 0.8 g/L o PLS - manganese: 2.75 g/L o O/A internal: 1.25 o O/A external: 1.25 o Mixing efficiency E1: 95% o Mixing efficiency E2: 97% o Cu/Fe in loaded organic E1: 1000 o Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry) o LO/ML: 80% Stripping step

Joseph Kafumbila

Page 22

Number of stages: 2 Phase continuity: Organic continuous Spent electrolyte - Copper: 35 g/L Spent electrolyte - acid: 180 g/L Spent electrolyte - iron: 2g/L Stripped organic from S1 - Iron: 1ppm Advance electrolyte copper: 50 g/L Mixing efficiency S1: 98% Mixing efficiency S2: 95% Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry) Aqueous coalescing tank o Aqueous entrainment recovery: 65% (P. Cole et al, 2016) Wash stage o Number of stages: one o O/A: 40 o Phase continuity: Organic continuous o Wash solution - acid: 2 g/L o Iron stripping efficiency: 0% (assumed) o Mixing efficiency W: 95% o Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry) Copper tank house o Spent electrolyte – Iron: 2g/L o o o o o o o o o o

-

-

5.3.1.2. Simulation results Tables 5A, 5B, 5C, 5D, 5E and 6 give the mass balance of copper SX-EW circuit working with saturated organic phase and wash stage. Table 5A: Mass balance of Cu-SX circuit – Saturated organic phase and wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

Joseph Kafumbila

PLS FE1 Raf E1 Raf E2 LO E1 1000 1032.94 1034.62 1034.62 1291.17 8.04 7.865 2.610 0.420 8.576 0.80 0.780 0.770 0.773 0.009 2.75 2.665 2.665 2.658 2.0 2.409 10.528 14.447 8040.0 8124.3 2700.3 434.6 11073.3 800.0 805.3 796.8 800.00 11.07 2750.0 2752.3 2756.8 2750.00 2000.0 2488.3 10892.7 14946.87

Page 23

Table 5B: Mass balance of Cu-SX circuit – Saturated organic phase and wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

ELO E1 LO E2 ELO E2 SO ESO 2.58 1291.17 2.58 1291.17 2.58 2.610 4.376 0.420 2.548 37.375 0.770 0.001 0.773 0.001 2.000 2.665 2.658 0.038 10.528 14.447 176.34 6.74 5650.69 1.08 3289.6 96.51 1.99 1.29 2.00 1.29 5.16 6.88 6.86 0.10 10.53 37.31 455.4

Table 5C: Mass balance of Cu-SX circuit – Saturated organic phase with wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

SP AD S2 AD S1 SO S1 ESO S1 512.47 512.47 512.47 1291.17 2.58 35.000 37.375 50.000 3.465 50.000 2.000 2.000 2.009 0.001 2.009 0.038 0.038 0.038 0.038 180.00 176.34 155.78 155.78 17936.6 19153.5 25623.8 4473.9 129.12 1025.0 1025.0 1029.6 1.29 5.19 19.53 19.53 19.62 0.10 92245.5 90368.6 79835.1 402.3

Table 5D: Mass balance of Cu-SX circuit – Saturated organic phase with wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

Joseph Kafumbila

LO CO ELO CO DS CO WS m3/h 1291.17 0.90 1.68 32.28 g/L 8.580 2.610 2.610 g/L 0.009 0.770 0.770 g/L 2.665 2.665 g/L 10.528 10.528 2.000 Kg/h 11073.3 2.36 4.38 Kg/h 11.07 0.70 1.29 Kg/h 2.41 4.47 Kg/h 9.52 17.67 64.56

SAW 30.60 0.082 0.021 0.073 2.216 2.5 0.64 2.22 67.81

Page 24

Table 5E: Mass balance of Cu-SX circuit – Saturated organic phase with wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

WLO EWLO CuEWB 1291.17 2.58 2.34 8.576 0.082 35.000 0.009 0.021 2.000 0.073 0.038 2.216 180.00 11073.0 0.21 81.75 11.07 0.05 4.67 0.19 0.09 5.72 420.44

Table 6: Additional results of mass balance of cu-SX circuit – saturated organic phase Description Extractant percentage in organic phase Extraction efficiency Net transfer Stripping O/A Stripping efficiency Spent electrolyte Fe/Mn Copper production Copper recycle from CuEWB/Copper production Wash stage - Organic stripping efficiency

19.50 94.59 0.309 2.52 70.29 52.48 7.61 1.07 0.003

% % g/l/V% % t/h % %

Figures (15), (16) and (17) gives mass flow percentage of copper, iron and manganese by taking the mass flow of elements in the PLS as 100%. The designation of flows is on Figure (14).

Joseph Kafumbila

Page 25

Figure 15: Copper mass flow percentage – Copper mass flow in PLS 100%

Figure 16: Iron mass flow percentage – Iron mass flow in PLS 100%

Joseph Kafumbila

Page 26

Figure 17: Manganese mass flow percentage – Manganese mass flow in PLS 100%

5.3.2. Unsaturated organic phase 5.3.2.1. Data Figure (18) gives the block diagram of copper SX-EW circuit with wash stage and saturated organic phase with copper. This flow diagram shows only the aqueous entrainment in organic phase. The description of flows is the following:           

PLS: Pregnant leach solution F E1: Feed solution to E1 E1: Stage 1 of extraction step E2: Stage 2 of extraction step Raf E1: Raffinate from E1 Raf E2: Raffinate from E1 LO E1: Loaded organic from E1 ELO E1: Entrainment aqueous in LO E1 LO E2: Loaded organic from E2 ELO E2: Entrainment aqueous in LO E1 CO: Aqueous coalescing tank

Joseph Kafumbila

Page 27

Figure 18: Block diagram of copper SX-EW circuit with wash stage and unsaturated organic with copper                 

LO CO: Loaded organic from CO ELO CO: Entrainment aqueous in LO CO DS CO: Discharged solution from CO WS: wash solution SAW: solution after wash WLO: washed loaded organic EWLO: Entrainment aqueous in washed loaded organic S1: Stage 1 of stripping step S2: Stage 2 of stripping step SO S1: Stripped organic from S1 ESO S1: Entrainment aqueous in SO S1 SO: Stripped organic from S2 ESO: Entrainment aqueous in SO SP: Spent electrolyte AD S2: Advance electrolyte from S2 AD S1: Advance electrolyte from S1 CuEW: Copper electrowinning circuit

Joseph Kafumbila

Page 28

 CuEWB: Copper electrowinning circuit bleed The design criteria are the following: -

-

-

Extraction step o Number of stages: 2 o Phase continuity: Organic continuous o PLS flow rate: 1000 m3/h o PLS - Copper: 8.04 g/L o PLS - acid: 2 g/L o PLS - iron: 0.8 g/L o PLS - manganese: 2.75 g/L o O/A internal: 1.25 o O/A external: 1.25 o Mixing efficiency E1: 95% o Mixing efficiency E2: 97% o Cu/Fe in loaded organic E1: 500 o Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry) Stripping step o Number of stages: 2 o Phase continuity: Organic continuous o Spent electrolyte - Copper: 35 g/L o Spent electrolyte - acid: 180 g/L o Spent electrolyte - iron: 2g/L o Stripped organic from S1 - Iron: 1ppm o Advance electrolyte copper: 50 g/L o Mixing efficiency S1: 98% o Mixing efficiency S2: 95% o Stripping efficiency: 60% o Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry) Aqueous coalescing tank o Aqueous entrainment recovery: 65% (P. Cole et al, 2016) Wash stage o Number of stages: one o O/A: 40 o Phase continuity: Organic continuous o Wash solution: mixture of water and spent electrolyte o Iron stripping efficiency: 50% (Hans Hein, 2005) o Mixing efficiency W: 95% o Aqueous entrainment in organic: 2000 ppm (250-2500 ppm industry)

Joseph Kafumbila

Page 29

-

Copper tank house o Spent electrolyte – Iron: 2g/L

5.3.2.2. Simulation results Tables 7A, 7B, 7C, 7D, 5E and 8 give the mass balance of copper SX-EW circuit working with unsaturated organic phase and wash stage. Table 7A: Mass balance of Cu-SX circuit – unsaturated organic phase and wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

PLS FE1 Raf E1 Raf E2 LO E1 1000 1032.26 1033.94 1033.94 1290.32 8.04 7.858 1.188 0.202 10.336 0.80 0.795 0.771 0.774 0.021 2.75 2.670 2.666 2.660 2.0 2.662 13.020 15.083 8040.0 8111.6 1228.1 209.2 13336.1 800.0 821.1 796.8 800.0 26.67 2750.0 2756.5 2756.8 2750.0 2000.0 2748.2 13561.6 15594.7

Table 7B: Mass balance of Cu-SX circuit – unsaturated organic phase and wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

ELO E1 LO E2 ELO E2 SO ESO m3/h 2.58 1290.32 2.58 1290.32 2.58 g/L 1.188 5.000 0.202 4.134 38.204 g/L 0.771 0.001 0.774 0.001 2.000 g/L 2.666 2.660 0.029 g/L 13.020 15.083 175.06 Kg/h 3.07 6451.5 0.52 5334.5 98.59 Kg/h 1.99 1.29 2.00 1.29 5.16 Kg/h 6.88 6.86 0.07 Kg/h 13.02 38.92 451.78

Joseph Kafumbila

Page 30

Table 7C: Mass balance of Cu-SX circuit – unsaturated organic phase with wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

SP AD S2 AD S1 SO S1 ESO S1 536.37 536.37 534.69 1290.32 2.58 35.000 38.204 50.000 5.443 50.000 2.000 2.000 2.020 0.001 2.020 0.029 0.029 0.029 0.029 180.00 175.06 156.61 156.61 18772.9 20491.5 26734.6 7022.6 129.03 1072.7 1072.8 1080.2 1.29 5.21 15.38 15.38 15.49 0.07 96546.5 93899.2 83737.7 404.15

Table 7D: Mass balance of Cu-SX circuit – unsaturated organic phase with wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

m3/h g/L g/L g/L g/L Kg/h Kg/h Kg/h Kg/h

Water 28.52

WS SAW WLO EWLO 32.26 32.26 1290.32 2.58 4.055 2.219 10.379 2.219 0.232 0.654 0.001 0.654 0.003 0.201 0.201 20.856 23.194 2.194 130.82 71.58 13392.7 5.73 7.48 21.11 13.34 1.69 0.11 6.47 0.52 672.79 748.18 59.85

Table 7E: Mass balance of Cu-SX circuit – unsaturated organic phase with wash stage Description Volume Cu Fe Mn Acid Cu Fe Mn Acid

Joseph Kafumbila

LO CO ELO CO DS CO CuEWB m3/h 1290.32 0.90 1.68 3.74 g/L 10.38 2.219 2.219 35.000 g/L 0.001 0.654 0.654 2.000 g/L 0.201 0.201 0.029 g/L 23.194 23.194 180.00 Kg/h 13392.7 2.00 3.72 130.82 Kg/h 13.34 0.59 1.10 7.48 Kg/h 0.18 0.34 0.11 Kg/h 20.95 38.91 672.79

Page 31

Table 8: Additional results of mass balance of cu-SX circuit – unsaturated organic phase Description Extractant percentage in organic phase Extraction efficiency Net transfer LO/ML Stripping O/A Spent electrolyte Fe/Mn Copper production Copper recycle from CuEWB/Copper production Wash stage – extraction efficiency from solution

30.02 97.40 0.207 60.13 2.41 69.75 7.83 1.67 45.28

% % g/l/V% % t/h % %

Figures (19), (20) and (21) gives mass flow percentage of copper, iron and manganese by taking the mass flow of elements in the PLS as 100%. The designation of flows is on Figure (18).

Figure 19: Copper mass flow percentage – Copper mass flow in PLS 100%

Joseph Kafumbila

Page 32

Figure 20: Iron mass flow percentage – Iron mass flow in PLS 100%

Figure 21: Manganese mass flow percentage – Manganese mass flow in PLS 100% Joseph Kafumbila

Page 33

5.3.3. Observations  The concentration of Lix984N is 19.50% for saturated organic phase with copper and 30.02% for unsaturated organic phase with copper.  LO/ML is 80% for saturated organic phase with copper and 60.13% for unsaturated organic phase with copper.  94.59% of copper from PLS are platted as cathode for saturated organic phase with copper and 97.4% are platted as cathode for unsaturated organic phase with copper.  5.41% are exited from the SX-EW circuit in the raffinate for saturated organic phase with copper and 2.60% are exited from the SX-EW circuit in the raffinate for unsaturated organic phase with copper.  Stripping efficiency is 70.29% for saturated organic phase with copper and is 60% for unsaturated organic phase with copper.  Cu/Fe ratio transferred in EW is 1645.53 for saturated organic phase with copper and is 1065.05 for unsaturated organic phase with copper.  Fe/Mn ratio transferred in EW is 52.48 for saturated organic phase with copper and is 69.75 for unsaturated organic phase with copper. For this case, chapters (5.3.1.) and (5.3.2.) give the configuration of the extreme cases. In the case with saturated organic with copper the solvent extraction efficiency is low. Copper loss in the water balance bleed of the copper circuit is high. In the case with unsaturated organic with copper the percentage of extractant in the organic phase is high. The cost of organic loss in organic entrainment in aqueous phase is high. Most of the time designers take the flow diagram of saturated organic phase with copper and increase the extractant percentage in the organic phase at 25%. In this case, copper loss in the water balance bleed and the cost of organic phase entrainment in aqueous phase decrease. The optimum flow diagram is the flow diagram with saturated organic phase with copper and the copper in the water balance bleed can be recovered by addition a third stage of solvent extraction on the water balance bleed (D.R. Shaw et al, 2004) or by introducing the split circuit (G.M. Miller, 2005). Depending on the level of manganese in the PLS, wash stage placed after organic surge tank can be removed in the circuit and loaded organic phase can be sprayed with water in organic weir of E1 stage. For the low concentration of copper in the PLS, it is important to find the copper SX configuration that can facilitated to reach the saturation of organic phase with copper and can give high copper solvent extraction efficiency.

Joseph Kafumbila

Page 34

6.

References

Liu Jian she et al, Mechanism of crud formation in copper solvent extraction, J. CENT. SOUTH UNIV. TECHNOL., Vol. 9, No. 3, 2002. Hans Hein, Importance of a wash stage in copper solvent extraction, Hydrocopper 2005. J. Kafumbila, Design and optimization of copper solvent extraction configurations, Researchgate, 2017. https://www.researchgate.net/publication/321849653_Design_and_optimization_of_co pper_solvent_extraction_configurations P. Cole et al, Understanding aqueous in organic entrainment in copper solvent extraction, SAIMM, Vol. 116, 2016. O. Tinkler et al, The Acorga OPT series: Comparative studies against aldoxime: Ketoxime reagents, SAIMM, 2009. D.R. Shaw and D.B. Dreisinger, The commercialization of the FENIX iron control system for purifying copper electrowinning electrolytes, the journal of the minerals, metals and materials society, July 2004. G.M. Miller and A. Nisbett, Decreasing operating costs and soluble loss in copper hydrometallurgy with use of innovative solvent extraction circuits, First extractive metallurgy operations conference, Brisbane, 2005.

It has now been a good four years since we published technical reports on the design and optimization of copper hydrometallurgical plants. If these technical reports have brought you a little more in your work we are happy. If for this service your heart urges you to offer us a small tip, you can do so using our PayPal account (Joseph Kafumbila).

Joseph Kafumbila

Page 35