modelling of leaching of copper oxides in dumps and in-situ

7/31/2019 Modelling of Leaching of Copper Oxides in Dumps and in-situ

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MODELLING OF LEACHING OFCOPPER OXIDES IN DUMPS AND

IN-SITU

Joan Mahiques, Joaqun Martnez, and Luis Moreno

Department of Chemical EngineeringRoyal Institute of Technology

Stockholm, Sweden


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Outline

Introduction

Leaching modelling

( Calculated cases )

Results

Conclusions


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Particle size is crucial for leaching of copperoxides

For small particles, leaching is controlled by kinetics

For large sizes, diffusion controls leaching

In-situ leaching requires wells for injection and

extraction of the solution

Objectives

To assess the impact of minerals formed by particles with

different sizes on copper leaching To study the location of the injection and extraction wells

Introduction


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Simple case. One-dimensional model.

Injection at several wells along a line

Extraction at several wells along a line

Mass balances and others equations

Equation for the acid in the solution along the bed Equation for copper dissolved in the solution along the bed

Variation of the shrinking core with time. An equation for

each size.

Leaching modelling


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Acid concentration in the bed

Copper dissolved in the solution

Leaching modelling

+

+++

+

=

H

H

2

H

2

LH R

x

Cq

x

CD

t

C

2

222

Cu

Cu

2

Cu

2

L

Cu Rx

Cq

x

CD

t

C+

+++

+

=


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Shrinking core model for reaction within the particle

Two zones: copper depleted zone and unreacted zone

Reaction on the surface of the unreacted zone

Leaching modelling

Copper

depleted zone

Reaction zoneUnreacted zone

OHSOCuSOH2CuO 22

4

22

4 ++++++


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Shrinking core model. Copper generation including the

resistances due to:

Diffusion in the film around the particle.

Diffusion in the copper depleted zone

Reaction kinetics

One for each ore size

Leaching modelling

kr

R

Dr

R)rR(

K

1

SC5.0

t

N

2

C

2

effC

C

Cfilm

extHCuO

+

+

=

+


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Leaching modelling

Initial conditions

Boundary conditions At inlet

At outlet: only advective flow

0)0t,x(C0)0t,x(C 2CuH =


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Location of the injection and recovery wells in

different geometries, e.g. circular

A equation for the solution flow rate. Darcy equation

Steady-state is assumed to solve transport equations

Leaching modelling. 2-D model

iKAQq ==


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Data

Entity, unit Value

Initial H+ concentration, mol/m3 357

Solid copper concentration, mol/kg mineral 0.0365

Specific flow rate of leaching solution, m3/m2/s 1.3 10-6

Bed porosity 0.33

Bed length, m 10

Dispersivity, m 0.2 2.0

Particle effective diffusivity, m2/s 6.7 10-12


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One-D. One size

Results. Acid concentration

0

100

200

300

400

0 2 4 6 8 10

Distance, m

Acidconcentration,mol/m3

250 hr

500 hr

750 hr

1000 hr

1200 hr

1400 hr


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One-D. One size

Results. Copper concentration

-0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0 2 4 6 8 10

Distance, m

Solidco

pperconcentration,

mol/kg

0 hr

250 hr

500 hr

750 hr

1000 hr

1500 hr

2000 hr


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One-D. One size

Results. Recovery as a function

of the size

0

1000

2000

3000

4000

5000

6000

7000

0.015 0.025 0.035 0.045 0.055

size (R in m)

T

ime,

hr

Recov 90%

Recov 80%

Recov 70%

Recov 60%


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One-D. One size

Results. Time to reach a certain

copper recovery

0

2000

4000

6000

0 0.002 0.004 0.006 0.008 0.01

Q (m3/hr)

Time,

hr

Recov 90%

Recov 80%

Recov 70%

Recov 60%


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Distribution: three different sizes

Results. Comparing a given particle

size distribution with an average size

0

100

200

300

400

500

600

700

0 1000 2000 3000 4000 5000

Time, hr

Coppe

rrecovery,m

ol

R-ave

0.7 R-ave

0.8 R-ave

Distribution


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Stream lines for an extraction wells surrounded by

four injection wells.

Results 2-D modelling:

Stream lines


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Acid concentration for an extraction wells surrounded

by several injection wells

Results 2-D modelling:

Acid concentration


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The leaching model may be applied primarily to

copper recovery from oxide minerals

The results show that particle size has a great impact

on leaching performance A weighted averaged diameter is not a good

description for minerals of non uniform size. A size

distribution must be used in the simulations to obtainsatisfactory results

The Two-Dimensional model may be used to find an

adequate arrangement of injection and extraction wells

Conclusions

modelling of leaching of copper oxides in dumps and in-situ

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