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MODELS FOR DESIGN, OPTIMISATION AND CONTROL IN

HYDROMETALLURGY

Jorge M. Menacho, General Manager, De Re Metallica Ingeniera drm@drm.cl

Extended Summary

This paper summarizes the experience of the author in developing and applying

mathematical model tools to solve process industrial problems, specific engineering tasks

as well as to develop new solutions to modern metallurgy.

The general approach faced along the time is shown in Figure 1. First step is always

experimentation, either on macroscopic phenomena or microscopic characteristics which

after interaction produce the macroscopic result. Next steps are: direct modeling of the

experiments; scale up to industrial level and then tuning with real industrial data. This

allows running simulations on different scenaries in the field of technical innovations,

process engineering and operation of actual plants.

Figure 1. General Approach in modelling tools application.

Tables 1 and 2 list some of the tools developed along the time by the author and co-workers to face the above-described tasks in the field of Hydrometallurgy and Mineral

Processing. These tools are currently managed by the consulting company De Re

Metallica (DRM).

Tech innovation

Process design

Machine design

Operation

Mine Planning

Stabilization

Optimisation

Control

Continuum media

Discrete media

DEM

Extended DEM

Navier Stokes

PBM

Object modelling Object Programming

Macroscopic

Microscopic

Empirical

Transport Phenomena

Kinetics

Thermodynamics

Experimentation

Modelling

Scale up

Tuning

Simulations

Validation

Design parameter

Flowsheet

Equipment sizing

Risk analysis

Engineering

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Table 1. DRM-Model Library: Hydrometallurgy.

Table 2. DRM-Model Library: Mineral Processing.

Selected applications performed by the author at DRM are described below.

(i) Reliable Scale Up Leaching Procedure

A novel scale up procedure to project results from small-size column to industrial heap

leaching has been developed with noticeable results, starting from the Navier-Stokes

equations applied to liquid infiltration through porous bed of variable saturation. Many

applications in the last ten years support this statement.

(ii) Anticipating Ponding and Failure Conditions

Irrigation and mechanical stability of the heap are quite linked. Pad deformation and failure

depend on the saturation level, as shown by the Mohr-Coulomb equation. From these

relationship an operational criteria was supplied as an alternative to the classical

geotechnical safety factor with simplicity advantages.

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(iii) New Tools for Process Risk Analysis

A classical problem in heap leaching is the handling of high/low physical quality ores. Mine

Plans handle average values of the clayish/competent ores but in practice daily variability

drives to a statistical distribution of saturation in the pads. New tools for process risk

analysis have been developed to answer the key question:

What is the probability to have ponding/collapse?

(iv) Plant Ramp Up Assistance

Another interesting application is to assist ramp up of new operations. This is a difficult

stage in any new project as all is transient; dynamic models have been successfully used

to assist this task. An example is given related to a new Ripios Secondary Leach operation

started up this year 2012. Questions are:

How the effluent rate is going to behave? How about Cu levels? How much are we going

to produce this year and next one?

Model answers are illustrated in Figures 2 and 3.

Figure 2. Effuent rate forecast.

0

200

400

600

800

1000

1200

1400

1600

1800

25/05/2012

14/06/2012

04/07/2012

24/07/2012

13/08/2012

02/09/2012

22/09/2012

12/10/2012

01/11/2012

21/11/2012

11/12/2012

31/12/2012

Flowrate,m3/h

Time, days

Model Off-Flowrate On Flowrate Real Off-Flowrate

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Figure 4. Mine-to-Cathode overall strategy.

(viii) Variability Management

Another DRM development is related to a new management tool called Variability KPI,

useful to estimate the effect of bottle neck, idle capacity and lack of control in the technical

and economical results at a given plant. This tool can be used for Mine Planning purposes

as well as to supply diagnosis of actual plant results.

(ix) New Intelligent Automatic Irrigation System

A novel intelligent automatic control system has been developed by DRM together with

MiningSystem Co. in Chile. This system is driven to maximize the copper extraction in

addition to get uniform liquid application. It has been successfully applied at Minera

Escondida, BHP Billiton since January to August 2012, obtaining a net +2 point extraction

increment in copper recovery. The system is currently available for new industrial

applications.

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Figure 5. Intelligent Irrigation Automatic Control System.

(x) New Integral System to Assess Agglomerate Quality

A novel system to control the physical and chemical quality of agglomerates has been

developed by DRM. The system is composed by a sampling device, a measurement

station provided with a robotic arm and a phenomenological which process the data

producing updated set point to manipulate valves feeding the acid and raffinate solution in

the rotary drum. The system is completely automated.

Figure 6. Agglomerate Quality Control Robotic System.

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(xi) Cloud Computing and Web Applications

DRM and WiseConn offer nowadays Web monitoring and automatic control solutions for

the Mining Industry. Water and energy management are typical applications as shown in

Figure 7 as well as process applications along the whole production chain.

Figure 7 Water management by means of Internet facilities.

(xii) Research with Multiphysics

DRM is currently using Multiphysics Package Software to investigate new options leading

to better results compared to standard technology: Figure 7 shows the impact of a

chimney set at the upper surface of the pad in order to promote aeration.

Conclusion

Companies may get large profit by using modeling tools, either to diagnose high impact

problems, to design sustainable solution, to optimize and control their operations, as well

as to assist in development of technology.

We are currently transiting from continuum mechanics domain to the discrete element

domain with an increasing number of applications eventhough current computing

capabilities slow down its spreading.

The Mining Industry is quite conservative but modern communication technology will

penetrate it sooner than later.