Scale Up of Hydrodynamic and Metallurgical Response in HeapLeaching OperationsJorge M. Menacho, De Re Metallica Ingeniería SpA, DRM Tech, Avda. del Valle 576, Huechuraba, Santiago, Chile

Contents

• Current Scale Up Criteria

• The Proposal

• Final Remarks

Conventional Scale Up CriteriaCase 1: Leach Ratio (LR)

The LR hypothesis should be always verified before applying it. Experiments atdifferent irrigation rates give the information to check this correlation. Thiscriteria is not directly deduced from the conventional kinetics formulations.

j ji iji

Ap Ap

1 2

q Δtq Δt

=ρ z ρ z

(3)

Case 2: Leach Time

Again, this criteria must be verified before applying it. Same experiments above-described allow to set the correlation degree between Extraction and Time.

(4)

j j ji i iji

i i j ji j1 2

q A Δtq A Δt

=q A q A

Other Related Scale Up CriteriaCase 3: Passed Acid

Same acid curing dosage is assumed the same at both scales. This criteria appliesbetter when the LR applies

(5)

Case 4: Consumed Acid

Here time affects the result; it applies better when t this the controlling variable.

(6)

A j j jAi i iji

Ap Ap

1 2

c q Δtc q Δt

=ρ z ρ z

M1 E M2E = f E

In all cases both maximum extractions are assumed directly proportional, that is:

(7)

A j j jAi i iji

Ap Ap

1 2

c q Δtc q Δt

=ρ z ρ z

Conventional Scale Up Criteria

DESIGN

DESIGN

Clearly, something is wrong with this method…

DESIGN

DESIGN

Parameter Column HeapHeight, m 1 5q, L/h/m2 7 4LR, m3/t 5.5 2.37Time, days 40 197

Parameter Column HeapHeight, m 1, 4 y 6 5q, L/h/m2 5 y 10 4LR, m3/t 4 a 16 2.37Time, days 90 197

What else can we do?

Quid Ultra Faciam?

S1 S SM

dc= -k c c

dt

Menacho (1998) suggested 2 (main) controlling leaching steps:

S2 S SM

dc q= -k c c

dt z

qt

ρz

S S0c t = c for t = 0

S SMc t = c for t

M 1 2

qE t = E 1 - exp - k + k t

ρz

Chemical Control

Convective Control; with Leach Ratio (LR)

Both phenomena occur in parallel; B.C. are as follows:

Assuming plug flow condition an integrated expression is obtained, widelyvalidated by DRM in most of the industrial heap/dump leach Chilean operations:

DRM Leach Kinetics

(8)

(9)

(10)

(11)

(12)

In this case k1 << k2 q/(z), that is:

M 2

qE t = E 1 - exp - k t

ρz

Limiting CasesCase 1: High solubility and fast kinetics (classical oxide ores)

The extraction is controlled by the leach ratio (LR), then:

M 2E t = E 1 - exp -k LR

In this case k1 >> k2 q/(z), then: M 1E t = E 1 - exp - k t

Case 2: Low solubility and slow kinetics (sulphide and refractory oxide ores)

Now the extraction yield is controlled by the leach time (t).

In this formulation EM, k1 and k2 are pseudo-kinetic parameters as they arefunction of operational conditions.

(13)

(14)

(15)

1 2

M1 1 2 1 E M2 1 2 2

1 1 2 2

q qE 1 - exp - k k t f E 1 - exp - k + k t

ρ z ρ z

General Scale Up CriteriaCase 3: Mixed Chemical/Convective Control (Most of Real Situations)

(16)

The following equality must be satisfied to get similar Extraction at scales 1 and 2:

A sufficient condition to satisfy Eq. 16 is given by:

M1 E M2E f E

2 1 1 2 2 2

1 1 2 2

k q t k q t

ρ z ρ z

1 1 2 2

1 1 2 2

q t q t

ρ z ρ z

1 1 1 2k t k t 1 2t t

E M1 M2f E E

1 1

1 2

2 2

zq q

z

(17)

(18)

Accordingly, same extraction is got if we run a 10 m column at 10 L/h/m2 and 1 mcolumn at 1 L/h/m2, keeping time and other conditions the same. P. Mayta et al.(2015) were the first applying this concept in the Sierra Gorda Leach Project.

Case I: Reduced Flow Scaling Criteria

A key aspect for success is the strictapplication of the protocol for: (i) Samplepreparation, especially for drilling coretesting, (ii) Agglomeration, (iii) Columnloading and (iv) Irrigation calendar, includingthe hydrodynamic wetting ramp.

Results here shown come from tests designedby DRM and executed by ASMIN S.A.

Case I: Reduced Flow Scaling Criteria

Case II: Reduced Flow Scaling Criteria

Case II: Reduced Flow Scaling Criteria

In Summary…

1m

4m 4m

HYDRODYNAMICS

REDUCED FLOW UNITARY TEST

• …GOOD NEWS, but still a task is PENDING: How these resultsare scaled up to real Heap/Dump Operation in a reliable way?

Hydrodynamics is the Key aspect

The New Way to Run Small-Scale Leach Tests

• The Reduced Flow Unitary Test is disruptive in terms ofconceptual support, simplicity, cost and reliability of results…

• We strongly believe this soon will be the new way to run leachtests everywhere…

Reflexions…

Flow Pattern Scale Up

OBSERVATION:

Flow is constrained by

the column wall thus

changing the flow pattern

and also the copper

extraction kinetics, driving

to a FLAT liquid front, that

is a flow pattern close to

PLUG FLOW condition.

A A

ij iz

i i

hK K K

x

t x

iij s

i j i

c s c q cD s

t t x x x

Solution to the Navier-Stokes Equations in a bidimensional field:

Solute transport – Convectionand dispersion equation

Liquid flow – Richards equation

Boundary conditions:

- First type or Dirichlet type- Second type or Neumann type- Third type or Cauchy type

Time

RT

D, T

ime

-1

COLUMN

HEAP

Flow Pattern is a Major Dissimilitude…

A Phenomenological Model is Appropriate to Solve this Problem

System of Integral Equations (Menacho, 1999)

* * *

Column i Column PF i0R p ,t = φ t R p ,t, t dt

PF i PF j

R p ,t R p ,t

* * *

Pad j Pad PF j0R p ,t = φ t R p ,t, t dt

(19)

(20)

(21)

Hydrodynamic andMetallurgical Heap Leach Model

Variable-saturation liquid infiltration throughout a porous beds is described by theRichards´ equation (Continuity and Momentum equations). In one dimension it is,

θ h= k h + 1

t z z

Where θ is the saturation, k is the hydraulic conductivity, h is the matric potential,z is the height coordinate and t is the time. Boundary conditions are as follows:

0 0

z=0

hθ z,0 = θ and k h + 1 = q 0,t

z

The dynamic liquid inventory inside the heap and the effluent flowrate are themain responses of the model. Relations {h / / k} are needed to solve theRichards equation

L.A. Richards (1931), "Capillary Conduction of Liquids through Porous Mediums“, Physics, 1(5): 318- 333.J.M. Menacho and F.J. Troncoso (2013), “Scale Up of Heap and Dump Leaching Results”, COPPER 2013.

(22)

(23)

Matric or Characteristic SWCC Curve (h vs. Relationship)

Range accordingto hydrodynamicquality or the ores

Liq

uid

Co

nte

nt

, %

v/v

CV

CV

CV

Soil Suction h, kPa

Non-Saturated PermeabilityCurve ( vs. k Relationship)

Increase in Physical Quality

Usual Heap Leaching Operating Region

Saturated HydraulicConductivity

Hyd

rau

licC

on

du

ctiv

ity

k, m

/s

Liquid Content , % v/v

Volume of the LiquidLiquid Content =

Volume of the Heap

LIX-SX-EW Dynamic Simulator

SX/EW

RaffinatePLS

Aeration

MINE PLAN

BLASTINGCRUSHINGAGGLOMERATION

Copper Cathodes

...

Stacking DischargeDrainage

Wetting Irrigation Washing

DRM Simulator

Block Diagram of the DRM.BioLeach® Simulator.

Multi-Layer Dump Leach Simulator

Subsequent leach in the lower layers supplies additional Copper dissolution.Exposed area per unit mass is reduced as the dump grows. At the same time,inner temperatura increases and hydrodynamics and kinetics change.

L a y e r 1

L a y e r 2

L a y e r 3

L a y e r 4

U n d e r i r r i g a t i o n

N o i r r i g a t i o n

I r r i g a t i o n r a t e qL 1

A e r a t i o n r a t e qA 1

[ C o m p o s i t i o n ]1

T e m p e r a t u r e 1

I r r i g a t i o n r a t e qL 2

A e r a t i o n r a t e qA 2

[ C o m p o s i t i o n ]2

T e m p e r a t u r e 2

I r r i g a t i o n r a t e qL 3

A e r a t i o n r a t e qA 3

[ C o m p o s i t i o n ]3

T e m p e r a t u r e 3

C o m p o s i t i o n - 1

T e m p e r a t u r e - 1

C o m p o s i t i o n - 2

T e m p e r a t u r e - 2

. . .

L a y e r 1

L a y e r 2

L a y e r 3

L a y e r 4

U n d e r i r r i g a t i o n

N o i r r i g a t i o n

I r r i g a t i o n r a t e qL 1

A e r a t i o n r a t e qA 1

[ C o m p o s i t i o n ]1

T e m p e r a t u r e 1

I r r i g a t i o n r a t e qL 2

A e r a t i o n r a t e qA 2

[ C o m p o s i t i o n ]2

T e m p e r a t u r e 2

I r r i g a t i o n r a t e qL 3

A e r a t i o n r a t e qA 3

[ C o m p o s i t i o n ]3

T e m p e r a t u r e 3

C o m p o s i t i o n - 1

T e m p e r a t u r e - 1

C o m p o s i t i o n - 2

T e m p e r a t u r e - 2

. . .

Multiple-Floor 3D DRM Dynamic Dump Leach Simulator®.

Performance of the DRMHydro-Met Heap Leach Simulator

• A correct scale up procedure mustinclude both the hydrodynamics and themetallurgical mechanisms

• A phenomenological model is the besttool to project results from small columnto industrial heap/dump operations

PLS Flowrate

Cu Concentration in PLS

Cu Production

Hydrodynamic Saturation Profiles:Geotechnical Constrains

Safety Limit

Clayish Ore

Competent Ore

The physical ore quality is

detected in the Unitary

Leach Test and it is scaled

by hydrodynamics

Solution Channeling, Ponding and Landscapes

Safe and EfficientLeach Operation

Volume of the Liquid in the HeapSaturation =

Volume of the Heap Porosity

NO FIT OF DATA; PREDICTION FROM 1 m/1 ton crib TO 18 m, 7 millions tons pad

Notable Study Case: 100% PredictionCop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 1PAD 02

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 03

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 04

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 05

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 06

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 07

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 08

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 09

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

PAD 10

Cop

per

Extr

acti

on, %

Time, days

Industrial Pad Scaled from Mini Crib

DRM.BIOLEACH MODEL

Final Remarks

Conceptual frame for correct scale up and improvedmethodology to perform hydrometallurgical column testing hasbeen given

The UNITARY COLUMN properly used is much powerful thanwe think…especially when sample availability is scarce

Scale up involves not only metallurgical aspects but alsohydrodynamics, often neglected by the Metallurgists

Liquid infiltration through variable saturation porous mediaprovides the right frame to scale up and predict industrialheap/dump leaching results in a safe way

To getthe right

results…

Use the right tools…

In theright

way…

Jorge M. Menacho, De Re Metallica Ingeniería SpA, DRM Tech, Avda. Del Valle 576, Huechuraba, Santiago, Chile, HydroProcess 2017, Gecamin, June 21 – 23, Santiago - Chile