Cobalt Nickel and Copper Recovery With Resin-In-pulp

7/22/2019 Cobalt Nickel and Copper Recovery With Resin-In-pulp

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COBALT, NICKEL AND COPPER RECOVERY WITH RESIN-IN-PULP

by

J.P, Wyethe, M.H. Kotze, I.P. Greagerand A.C. Swarts

Mintek Anglovaal Mining

Private Bag X3015 PO Box 62379

Randburg Marshalltown

South Africa South Africa

2125 2107

Resin-in-pulp (RIP) technology was developed for the recovery of valuable metals from

high volumes of low grade pulps, as is the case with gold processing. More recently, the

application of this technology has been evaluated for the recovery of soluble losses of

valuable metals from solid residues in base metal plants. For this type of application, theRIP process will improve overall plant recoveries, especially where solid-liquid separation

proves difficult as a result of poor filterability or settling characteristics of the solids. An

added benefit of the RIP process is a reduction in the environmental impact of the solid

residues contaminated with entrained base metals from the plant.

Mintek investigated the metallurgical and economic feasibility of using RIP technology for

the recovery of soluble cobalt, nickel and copper from thickener underflows on behalf of

Anglovaal Mining. Laboratory and mini-plant investigations included the recovery ofcopper with RIP, followed by simultaneous nickel and cobalt recovery using a second RIP

circuit. Recovery of copper, nickel and cobalt in a single RIP circuit was also investigated.


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Cobalt, Nickel and Copper recovery with RIP

1

1. INTRODUCTION

The development of the resin-in-pulp (RIP) process at Mintek was initially targeted at the

recovery of metals from large volumes of low-grade leach pulps, as is the case in the gold

processing industry. Minteks RIP expertise culminated in the development of a resin-in-

pulp process, MINRIPTM, for the recovery of gold from leached slurries. Mintek has

subsequently evaluated the applicability of this technology for the in-pulp extraction of

copper, zinc, nickel, cobalt, vanadium, manganese and cyanide [1,2,3].

The main application of the RIP process in the base metal industry will be the scavenging

of soluble metals from leach residues, precipitation residues and other solid wastes that

have poor filterability or settling characteristics. However, this technology can also be

applied to the recovery of metals from the leach slurries when low-grade materials are

treated. The major advantages of the resin-in-pulp process are as follows:

It is effective for the recovery of soluble metals from pulps. The fact that the process

operates in a pulp medium means that the upstream solid-liquid requirements may be

reduced or possibly eliminated. In addition, it may be possible to significantly reduce

wash water requirements associated with conventional solid-liquid separation steps.

The RIP process may be able to achieve lower discharge metal concentrations than

those possible with the more conventional filtration or solid-liquid separation systems,hence reducing the potential for problems associated with the disposal of wastes

containing soluble metals.

The overall metal recoveries on the plant can be improved.

Co-precipitated and adsorbed metal species can generally be recovered with the RIP

process, which will further improve the overall metal recovery.

Anglovaal Mining commissioned Mintek to evaluate the feasibility of a RIP process for the

recovery of soluble cobalt, nickel and copper from a thickener underflow. This paper

outlines the process development, from the batch laboratory testwork to the continuous

mini-plant campaign. Based on these results, full-scale plants were sized and preliminary

techno-economic studies were conducted on three flowsheet options.

2. PROCESS DESCRIPTION

A RIP plant could either be operated in a carousel counter-current mode where resin

handling can be limited and the resin inventory is accurately controlled in each stage, or in

a continuous counter-current mode. Although inventory control may prove more difficult

during continuous operation, a substantial capital expenditure (CAPEX) saving is possible.


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For the recovery of base metals with RIP, typical upgrading ratios vary between 10 and 50,

in comparison with 1000 or more for gold as applied in the CIS and MinRIP. Hence, in

order to achieve barren specifications on a base metal plant, resin inventory control across

the adsorption train will be critical. Consequently, a carousel mode of operation was

chosen for the mini-plant evaluation for the recovery of cobalt, nickel and copper from the

Anglovaal Mining slurries. A schematic layout of the proposed process is given in Figure

1.

FEED SLURRY

REPULP TANK

ADSORPTION

ELUTION

RESIN-PULP SEPARATION

WASH

ELUANT

WATER

RECYCLETO PRIMARYRECOVERY

CIRCUIT

BARREN PULP

STAGE 1 PULPRECYCLED ATTRANSFER

DENOTES RESIN FLOW

DENOTES PULP/SOLUTION FLOW

Figure 1 : Schematic representation of the carousel resin-in-pulp circuit

During the adsorption stage, the feed pulp is contacted with resin in a multi-stage, counter-

current plant. After the resin has been passed counter-currently through the adsorption

plant, the resin will be loaded predominantly with the valuable metals together with lower

concentrations of other metals. The barren pulp from the last stage could be discarded to

the slimes dam, after a pH adjustment, or alternatively the barren pulp could be thickened,

and the thickener overflow could be returned to the plant for use as process water.

The loaded resin exiting the adsorption circuit is separated from the pulp by means of a

linear belt, sieve bend or vibrating screen, and the pulp is returned to the repulp tank. The

loaded resin is then rinsed with water to remove any particulates, after which the resin is

transferred into an elution column. During elution, the metals are stripped from the resin

with sulphuric acid (this could be fresh acid or any acid-bearing stream), producing aconcentrated metal sulphate eluate. Excess acid and entrained eluate solution are

washed from the resin bed with water, and the eluate, and possibly the wash water, are


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returned to the relevant unit operation in the primary process flowsheet. The eluted,

washed resin is returned to the adsorption circuit during the next transfer.

Elution and washing of resin in a fixed bed are established operations, therefore the mini-

plant investigation focused on the adsorption circuit.

3. LABORATORY TEST WORK

During the laboratory test work a suitable resin was selected, the optimum operating pH

determined and adsorption equilibrium isotherms established.

3.1 RESIN SELECTION

The selection of the best resin and associated operating strategy for a specific application

depends primarily on the feed solution composition. For the Anglovaal Mining application,

Co, Ni and Cu had to be recovered from a pulp containing Ni, Co, Cu, Ca, Mg, Al, Fe, Zn

and Mn. The resin that was selected for this investigation was a commercially available

chelating resin. The final resin choice was based on techno-economic comparisons of

potential commercial resins. The resin selectivity order is given below:

Fe3+> Cu2+> Ni2+> Co2+> Fe2+> Ca2+> Mg2+

The selectivity order indicates that copper, nickel and cobalt load in preference to ferrous,

calcium and magnesium present in the feed, but ferric loads preferentially to all these

metals. Therefore, iron removal will be required prior to RIP, where this resin is employed.

3.2 EFFECT OF pH

The effect of pH on copper loading onto the resin, as shown in Figure 2, was established

using synthetic copper sulphate solution. The pH profile indicates that, at equilibrium pH

values above 2.5, the resin was fully loaded with copper.

0

20

40

60

80

100

1.0 1.5 2.0 2.5 3.0 3.5 4.0

Solution pH

Culoading,g/l

Figure 2 : Effect of pH on copper loading.


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The effect of equilibrium pH on nickel and cobalt loading from the Anglovaal feed solution,

after iron removal, is shown in Figure 3.

0

20

40

60

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

Solution pH

Niloading,g/l

0

1

2

3

Coloading,g/l

Nickel Cobalt

Figure 3 : Effect of pH on nickel and cobalt loading.

The nickel and cobalt pH profiles were very similar and indicated that both metals

extracted efficiently at pH values higher than 4.5. However, an increase in solution pH

beyond 3, could result in precipitation of copper present in solution. Therefore, the

optimum pH conditions for cobalt and nickel extraction could probably not be used for

copper. For this reason, different process options had to be considered for the recovery of

copper, nickel and cobalt by means of RIP.

3.3 ION EXCHANGE EQUILIBRIUM ISOTHERMS

Ion exchange equilibrium isotherms were established by batch contact of Anglovaal pulp,

after iron removal, with resin at controlled pH. The copper isotherm was determined at pH

2.7 and the nickel and cobalt isotherms at pH 5. Laboratory data and Langmuir isotherm

model fits are shown in Figures 4, 5 and 6 for copper, nickel and cobalt respectively. (Y =

resin loading, g/l; X = solution concentration, mg/l)


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5

0

1530

45

60

75

0 200 400 600 800

Solution concentration, mg/l

Resinloading,g/l

Equilibrium data Langmuir model

Figure 4 : Ion exchange equilibrium isotherm for copper loading.

0

20

40

60

0 1000 2000 3000 4000


Resinloading,g/l


Figure 5 : Ion exchange equilibrium isotherm for nickel loading

0

1

2

3

0 50 100 150 200 250


Resinloading,g/l


Figure 6 : Ion exchange equilibrium isotherm for cobalt loading

A drop in nickel and cobalt loadings at the higher solution concentrations, where high

solution-to-resin ratios were used, were caused by greater competition from copper forwhich the resin has a higher affinity.

Y=1.3X/(1+0.02X)

Y=5.1X/(1+0.11X)

Y=1.6X/(1+0.71X)


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3.4 Process options

Three different process options were evaluated during the mini-plant campaign in order to

determine the most cost-effective option for the recovery of copper, cobalt and nickel from

the Anglovaal Mining slurry. Potential flowsheets for these options are shown in Figure 7.

LEACH

Fe

PRECIPITATION

L/S

Cu

RIP

Ni & Co

RIP

EXISTING

PROCESS

REPULP

OPTION 1

THICKENER

EXISTING

PROCESS

LEACH

Fe

PRECIPITATION

L/S

Cu

RIP

Ni & Co

RIP

REPULP

OPTION 2

THICKENER

LEACH

Fe & PARTIAL Cu

PRECIPITATION

L/S

Ni, Co & Cu

RIP

EXISTING

PROCESS

REPULP

OPTION 3

THICKENER

Figure 7 : Process options evaluated during RIP mini-plant campaign

The leach liquor composition (all three options) is shown in Table 1.

Table 1 : Metal concentration in g/l in leach solution

Ni Co Cu Ca Mg Al Fe Zn Mn

42 2 8 0.6 4 0.3 28 0.1 0.4

Because of the selectivity order of the resin, it was necessary to conduct iron removal,prior to RIP, in order to reduce the degree of iron co-loading on the resin (as shown for

each option in Figure 7). This is critical in order to limit the CAPEX and operating

expenditure (OPEX) associated with the co-loading of iron. Iron removal for this study was

done in batch. However, the iron removal step will have to be optimised for the full-scale

application to minimise base metal losses.

Since ion exchange resins have a limited capacity for metal loading, the thickened leach

pulp, containing 42 g/l nickel, was unsuitable for nickel RIP. However, the much lower

copper concentration of 8g/l could be considered for direct RIP (Option 1 Figure 7). After


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solid-liquid separation of the high-grade solution from the pulp, the underflow would have a

manageable nickel concentration for nickel and cobalt RIP as a result of dilution during

washing of the solids. The final concentration will depend on the efficiency of washing on

the belt filter. For Process Option 2, different nickel concentrations (3.9 and 1.7 g/l) were

tested. The corresponding copper concentrations for Option 2 are of the order of 0.8 and

0.35 g/l. The feasibility of simultaneous recovery of copper, nickel and cobalt (Process

Option 3) was tested at a nickel concentration of 3.9 g/l.

4. CONTINUOUS MINI-PLANT CAMPAIGN

The mini-plant consisted of a four-stage cascade of contactors, each with an active volume

of 960mL. The resin-pulp mixing in each stage was achieved with mechanical overhead

stirrers. Resin was retained in the contactor by means of a 200 m peripheral screen, and

pulp gravitated through the screens from one stage to the next. During adsorption, the pH

was controlled at the desired set point in each stage. Lime slurry, limestone slurry or any

other alkali may be used for pH control.

In order to minimise the CAPEX associated with the adsorption circuit, pulp and resin

residence times are minimised, whilst resin loading is maximised to limit the OPEX of the

operation. For a carousel operation, physical constraints often restrict the design, e.g. the

time required to drain the first adsorption stage and separate the loaded resin from thepulp.

4.1 COPPER MINI-PLANT CAMPAIGN

The parameters investigated during the copper mini-plant campaign included:

feed concentration [Figure 7, Option 1 and Option 2];

pulp residence time [Figure 7, Option 2];

resin residence time [Figure 7, Option 2]; and

pulp pH [Figure 7, Option 1 and Option 2].

4.1.1 Copper feed concentration

Two feed concentrations, designated high feed and low feed, were evaluated for the

copper RIP campaign. The copper, nickel and calcium concentrations obtained on the

resin and solution at steady state are shown in Table 2. The pH for adsorption was

controlled at 3 and a pulp residence time of 1 hour per stage was allowed. The resin

residence time for the high feed was 3 hours per stage, while that for the low feed was 4

hours per stage. Resin volumes were adjusted for the feed concentrations to allow for the


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required resin-to-pulp flowrates, with 25%(v/v) resin being used for the high feed and

5%(v/v) for the low feed.

Table 2 : Solution and resin loading profiles

High feed Low feed

Cu Ni Ca Cu Ni Ca

Solution profile, g/l

Feed

Comp. Barren

7.5

0.03

44 0.6 0.8

0.05

3.6 0.6

Resin profile, g/l

Stage 1

Stage 2

Stage 3Stage 4

43

26

81

16

26

4242

0.3

0.4

0.40.4

39

28

167

17

23

3131

0.8

0.9

11

The high feed copper concentration in the solution phase of the pulp was reduced from 7.5

g/l to 0.03 g/l over 4 adsorption stages. Copper loading on the resin in stage 1 was 43 g/l,

with co-loading of 16 g/l nickel. Calcium co-loading onto the stage 1 (loaded) resin was

around 0.3 g/l, which should not cause any gypsum precipitation problems during a fixed

bed elution with sulphuric acid eluant. The displacement of nickel (from 42 g/l in stages 3

and 4 to 16 g/l in stage 1 for the high feed) by copper can be seen from the resin loadingprofile in Table 2.

The low feed copper content was reduced from 0.8 g/l to 0.05 g/l in the composite barren

across 4 adsorption stages. Copper loading on the resin was about 10% less than the

loading obtained with the high feed. Similar nickel co-loadings of around 17 g/l were seen

for the feed solutions containing 42 and 3.6 g/l nickel. Although calcium co-loading

increased to 0.8 g/l, problems with gypsum precipitation during sulphuric acid elution in a

fixed bed are not anticipated.

4.1.2 Effect of pulp and resin residence times

The effects of pulp and resin residence times were tested with the feed containing 0.8 g/l

copper at a pH value of 3. The upgrading ratio of copper from solution onto the resin

determines the relative flowrates of the resin and pulp. Hence, in order to maintain the

resin-to-pulp flowrates required for different pulp residence times, the resin concentrations

were adjusted appropriately. Results are shown in Figure 8 and Table 3.


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0.00

0.20

0.40

0.60

0.80

1.00

Feed S1 S2 S3 S4 Barren

Cu/Cuinfeed

PULP=1h; RESIN=4h PULP=0.5h; RESIN=3h PULP=0.5h; RESIN=2h

Figure 8 : Solution profile

Table 3 : Metal loadings on resin at copper feed tenor of 0.8 g/l

pulp

h

resin

h

Resin concentration

%

Curesin

g/l

1

0.5

0.5

4

3

2

5

7.5

5

39

36

34

Results indicate that both the solution and resin residence times affected the resin loading

and the solution profile over the circuit.

4.1.3 Effect of pH

Two pH values were tested for the adsorption of copper, namely 2.5 and 3. The copper

loadings achieved for the feed pulps containing 7.5 and 0.9 g/l copper are shown in Table

4. For each feed concentration, the adsorption circuit pH was varied, whilst pulp and resin

residence times, and resin concentrations, were kept constant.

Table 4 : Effect of pH on copper loading

Cufeed, g/l Curesin, g/l

pH = 2.5 pH = 3

7.5 43 43

0.9 36 41

At the high feed copper concentration of 7.5 g/l, copper loadings of 43 g/l were achieved at

both pH values of 2.5 and 3, while at the lower feed concentration, a pH dependency was


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observed. A final loading of 41 g/l was achieved at pH 3 and a reduced loading of 36 g/l at

pH 2.5.

4.2 NICKEL AND COBALT MINI-PLANT CAMPAIGN

During the mini-plant campaign for simultaneous recovery of nickel and cobalt (Figure 7 -

Options 1 and 2), the parameters evaluated included:

nickel and cobalt feed concentrations ;

pulp and resin residence times; and

pulp pH.

4.2.1 Feed concentration

The feed tenor to the Ni-Co RIP circuit will be determined by the washing efficiency of the

upstream solid-liquid separation step. Two feed concentrations, as shown in Table 5, were

tested.

Table 5 : Feed concentrations for Ni-Co RIP campaign

Metal High Feed, g/l Low Feed, g/l

Ni

Co

Ca

3.8

0.19

0.6

1.7

0.07

0.6

During these tests the pH was controlled at 5 (based on results in Figure 3) and a pulp

residence time of 0.5 hour per stage was allowed. The resin residence time for the high

feed was 2 hours per stage, while 3 hours per stage was allowed for the low feed. Figures

9 and 10 show the average solution profiles at steady state over the circuit for nickel and

cobalt. Average metal loadings on the resin for both feed solutions are listed in Table 6.

For the high feed the resin concentration was 20%(v/v) per stage, while that for the low

feed was 15%(v/v) per stage.


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3875

2974

1430

29532 24 46

17271435

926

448106

0

1000

2000

3000

4000

5000


Niinsolution,mg/l

High feed Low feed

Figure 9 : Nickel solution profiles

158

75

142 3

68 68 59

38

19

2

189

0

50

100

150

200


Coinsolution,mg/l

High feed Low feed

Figure 10 : Cobalt solution profiles

Table 6 : Metal loadings on resin

High feed, g/l Low feed, g/l

Ni Co Ca Ni Co Ca

Stage 1Stage 2

Stage 3

Stage 4

4331

13

2.7

1.91.7

0.8

0.2

1.63.5

7

9

4335

20

6.8

1.61.5

1

0.3

3.22.8

8

11

Under the conditions employed, the nickel and cobalt concentrations were decreased to

less than 0.05 g/l over 4 contact stages for both feed pulps. Similar nickel loadings of 43

g/l were obtained on the loaded resin for both feed solutions. The solution and resin

profiles for the lower feed concentration indicated that the resin loadings were much closer

to the predicted equilibrium loadings, than were those for the higher feed. This indicated


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that the resin residence time of 2 hours per stage, used during the test with the higher

feed, was insufficient.

The resin showed some selectivity for nickel over cobalt, and the circuit had to be operated

carefully in order to prevent cobalt leakage into the barren. This can be seen from the

solution and resin profiles for the lower feed concentration, where about 17% extraction of

nickel was achieved over stage 1, with no extraction of cobalt over the same stage.

Calcium co-loading of about 1.6 g/l was seen on the loaded resin for the high feed, with co-

loading in excess of 3 g/l for the low feed solution. Calcium co-loading during the copper

trial, which was operated at pH values between 2.5 and 3, was less than 1 g/l in all four

stages. This indicates the pH dependence of calcium loading on the resin. Co-loaded

calcium could cause problems during elution with sulphuric acid and care should be taken

during the design of the elution circuit to avoid gypsum precipitation.

4.2.2 Effect of pulp and resin residence times

The effects of pulp and resin residence times were tested for the high nickel feed (Table

5). Both tests were conducted at a pH of 3. Results are shown in Figure 11 and Table 7.

3783

736

56 5 6

1430

29532 24

2593

3875

2974

0

1000

2000

3000

4000

5000


Niinsolution,mg/l

PULP=1h; RESIN=3.5h PULP=0.5h; RESIN=2.2h

Figure 11 : Solution profile across the mini-plant

Table 7: Metal loadings on resin

pulp

h

resin

h

Resin concentration

%

Niresin

g/l

1

0.5

3.5

2.2

20

25

47

43


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When both the solution and resin residence times were reduced, nickel loading decreased

from 47 g/l to 43 g/l. Results indicated that the barren concentration could probably be

reduced to about 0.05 g/l in three stages if residence times of 1 hour for pulp and 3.5 hours

for resin are allowed. However, the CAPEX saving for a larger plant with one less

adsorption stage will probably not off-set the savings for a plant where the adsorption tank

volumes and total resin inventory are much lower. The final decision on the configuration

of the plant would be based on an economic evaluation taking both CAPEX and OPEX into

account.

4.2.3 Effect of pH

Nickel and cobalt loadings onto the resin at pH values 4 and 5 are shown in Table 8. The

high feed (Table 5) was used at pulp and resin residence times of 1 and 3.5 hours

respectively.

Table 8 : Effect of pH on nickel and cobalt loadings

Metal Resin loading, g/l

pH = 4 pH = 5

Ni

Co

Ca

44

1.9

1.9

48

2

2.3

Results indicated a decrease in nickel, cobalt and calcium loadings when the pH was

reduced from 5 to 4.

4.3 SIMULTANEOUS RECOVERY OF COPPER, NICKEL AND COBALT

A single test was done to determine the feasibility of simultaneous copper, nickel and

cobalt recovery. The high Ni-Co RIP feed pulp (Table 5) was spiked with copper to have

0.8 g/l of copper present, but as a result of the high pH value of 4 copper precipitation

occurred. The circuit was operated at pH 4, because mini-plant results indicated a

relatively small change in nickel and cobalt loadings between pH 5 and 4, and conditions

were aimed at maximising copper re-dissolution over the adsorption circuit. Pulp and resin

residence times of 1 and 3.7 hours respectively, and 25%(v/v) resin, were used per stage.

The solution and resin loading profiles for nickel, cobalt and copper are shown in Table 9.


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Table 9 : Solution and resin profiles

Feed Stage 1 Stage 2 Stage 3 Stage 4 Barren

Solution profile, g/l

Ni

Co

Cu

Ca

3.8

0.21

0.23 [a]

0.6

2.5

0.17

0.04

0.57

0.04

0.006

0.03

0.002

0.002

0.005

0.002

0.002

0.005

0.002

0.002

Resin profile, g/l

Ni

Co

Cu

Ca

36

2.0

6.8

1.9

17

1.2

2.2

4.4

2.7

0.20

0.83

8.8

0.15

0.04

0.27

8.8[a] 0.8 g/l copper was added to feed the lower concentration was attributed to

precipitation at pH 4.

Recoveries of greater than 99% nickel and cobalt was achieved over 3 contact stages

under the test conditions employed. Based on a feed copper content of 800 mg/l and a

stage 1 loading of 6.8 g/l, the copper recovery was in excess of 77%. However, the

degree of copper recovery would have to be quantified.

5. PLANT SIZING AND PRELIMINARY ECONOMIC ANALYSIS

For calculation of the plant size and preliminary economic feasibility, a filter efficiency of

90% was assumed. During detailed economic evaluation, the overall process should be

considered and options compared to determine the economic optimum with regard to the

solid-liquid separation and RIP. For example, CAPEX to have 98% metal recovery from

the filter vs. the CAPEX for reduced filter capacity followed by RIP with an overall metal

recovery of greater than 99%.

5.1 Plant sizing

The preliminary economic evaluation was based on slurry flowrates of 60 m3/h. A three

hour resin transfer time was used, to allow for resin handling. Although only four active

adsorption stages were required for effective metal recovery, a fifth adsorption stage had

to be incorporated during the design of the carousel RIP plant to make provision for resin

handling. The resin concentration was maintained below 25% to limit resin loss through

resin-on-resin attrition. Thus, within these limits, solution residence times and resin

concentrations were adjusted according to the required resin-to-pulp flowrates. The plant

sizings for Options 2 and 3 (Figure 7) are shown in Table 10.


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The total resin inventory comprised:

the required resin volume in each adsorption stage to allow for adsorption of the total

load of metal in the feed; and

two equivalent resin volumes in the elution circuit to allow sufficient time to drain

stage 1, separate the resin from the pulp, and elute and wash the resin.

Table 10 : Summary of important sizing parameters for RIP circuits

2 separate plants 1 plant

Figure 7

Option 2

Cu

Figure 7

Options 1&2

Ni-Co

Figure 7

Option 3

Ni-Co-Cu

Feed:Cu

Ni

Co

Flowrate

% solids

g/l

g/l

g/l

m3/h

0.9

3.8

0.2

60

25

0.05

3.8 [a]

0.2 [a]

60

25

0.9

3.8

0.2

60

25

RIP:

Pulp residence time per stage

Number of stagesActive volume

Resin volume

h

m3

m3/stage

0.5

541

3.6

0.65

559

15

0.75

572

17

[a] Ni recovery in Cu RIP excluded

5.2 CAPEX calculation

A CAPEX estimate was prepared (to within 15% accuracy) by Grinaker-LTA Process

Engineering, during February/March 2001, for a RIP plant employing adsorption tanks with

an active volume of 80m3. This CAPEX was scaled using the six-tenths factor rule, using

the adsorption tank active volumes as a basis, in order to obtain an indication of the

CAPEX requirement for the current RIP application. The resin inventory requirement was

based on the resin loadings obtained during the mini-plant campaign. The scaled CAPEX

figures for the three design scenarios are presented in Table 11.


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Table 11 : Scaled CAPEX for the three proposed RIP plants.

CAPEX item Figure 7

Option 2

Cu

Figure 7

Options 1&2

Ni-Co

Figure 7

Option 3

Ni-Co-Cu

Scaled plant CAPEX (R [a], million) 13 16.1 18.1

Actual resin CAPEX (R, million) [b] 1.3 5.1 6.1

TOTAL CAPEX (R, million) 14.3 21.2 24.2

[a] South African Rand [b] Resin cost = R58 500/m3

5.3 Revenue

The revenue was calculated using the following metal tonnage and prices:

Cu 400 tonne/annum at R 13 000/tonne

Ni 1 750 tonne/annum at R 55 000/tonne

Co 90 tonne/annum at R140 000/tonne

An exchange rate of R8/US$ was used for revenue and OPEX calculations, which was the

exchange rate at the time of the CAPEX estimate. It was decided that, because the eluate

produced by the resin-in-pulp circuit must undergo further treatment before a saleable

product is formed, the revenue should be discounted by 20%.

5.4 OPEX calculationThe following components were considered for the OPEX calculations:

Eluant consumption

Resin could be eluted with fresh H2SO4, spent electrolyte or solvent extraction raffinate.

For this evaluation a consumption of 1.2 moles of fresh sulphuric acid per litre of resin was

used at a cost of R360/tonne (as 98% sulphuric acid). However, it may be argued that

acid consumption for elution may not be considered an operating expense, owing to the

fact that each mole of copper, nickel or cobalt returned to a solvent extraction

electrowinning plant would produce an equivalent amount of acid. In this case, thesulphuric acid cost will only be that associated with the stripping of co-loaded impurities.

Limestone consumption

The limestone consumption for neutralisation during adsorption was taken to be 1.2 moles

per litre of resin at a price of R110/tonne. It can also be argued that the neutralising agent

may be omitted as an OPEX, owing to the fact that the CCD underflow would have to be

neutralised and the metals precipitated prior to disposal even in the absence of a RIP

plant.


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Resin replacement

During the operation of the RIP plant, resin will be lost due to degradation and handling.

Resin losses should be determined on a relatively large scale for a specific application. A

replacement figure of 50% of the inventory per annum was used for the purposes of the

OPEX calculations.

Metal losses

For the Cu RIP plant a metal loss of 0.05 g/l (6%) in the barren exiting the adsorption

cascade was assumed. For the Ni-Co and Ni-Co-Cu RIP circuits, a nickel loss of 0.05 g/l

was assumed in the barren. This translated to a 1.3% nickel loss, which is the figure that

was also used for cobalt loss for the Ni-Co RIP and cobalt and copper losses for the Ni-

Co-Cu RIP circuits. The metal prices used for these calculations are given in Section 5.3.

The OPEX associated with reagents and potential metal loss in the RIP operation is shown

in Table 12. Eluant and limestone consumptions, and resin replacement are a function of

the level of resin loading, which in turn is dependent on the feed concentration.

Table 12 : Reagent cost breakdown

Figure 7

Option 2

CuR/tonne Cu

Figure 7

Options 1&2

Ni-CoR/tonne Ni

Figure 7

Option 3

Ni-Co-CuR/tonne Ni

Eluant

Limestone

Resin replacement

Metal loss (barren)

TOTAL REAGENTS

1 000

1 200

2 300

900

5 400

900

1 200

2 200

1 100

5 400

1 100

1 400

2 600

1 200

6 400

5.5 Cash flow analysis

Cash flow analysis was conducted in order to obtain an indication of the payback periods

and the internal rates of return of the proposed RIP plants. The composition of the

breakdown of the total CAPEX, as well as the associated depreciation schedule, is shown

in Table 13.


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Table 13 : CAPEX composition and depreciation schedule

CAPEX item Percentage of total Depreciation schedule

Buildings 10% Not depreciated

Productive plant 80% Written off at 20% per annum over 5 years

Permanent works 10% Written off at 5% per year over 20 years

In addition, the cash flow analysis was subject to the following assumptions:

Tax rate was taken as 35%.

Discount factor was taken as 10%.

Life of plant was taken as 10 years.

No variation in the metal and reagent prices was taken into account.

Working capital was calculated as 10% of the total CAPEX [4].

The results of the cash flow analysis, carried out for each option, are presented in Table

14.

Table 14 : Cash flow analysis of the proposed RIP plants.

Parameter Figure 7

Option 2

Cu

Figure 7

Options 1&2

Ni-Co

Figure 7

Option 3

Cu-Ni-Co

Payback period (years) > 10.0


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7. REFERENCES

1. Green B.R., Kotze M.H., and Engelbrecht J..P. (1998) Resin-in-pulp - After gold, where

next? EPD Congress, San Antonio, Texas. B. Mishra (ed.). The Minerals, Metals and

Materials Society, Warrendale, Pennsylvania. (Pages 119-136)

2. Taylor M.J.C., Green B.R., Wyethe J.P., Padayachee D.P. and Mdlalose K.E. (2000)

Recovery of vanadium from waste solids and solutions using an ion exchange process.

MINPREX 2000, Melbourne, Victoria.

3. Greager I.P, Wyethe J.P., Kotze M.H., Dew D., Miller D. (2001) A resin-in-pulp process

for the recovery of copper from bioleach CCD underflows. Copper Cobalt Nickel and

Zinc Recovery Conference, The South African Institute of Mining and Metallurgy in

collaboration with The Institution of Mining and Metallurgy (Zimbabwe Branch), Victoria

Falls, Zimbabwe.

4. Peters M.S. and Timmerhaus K.D. (1991) Plant design and economics for chemical

engineers. Mc-Graw-Hill Book Company. Fourth edition.

Cobalt Nickel and Copper Recovery With Resin-In-pulp

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