NOVELTIES IN LEACHING, SOLVENT EXTRACTION AND ELECTROWINNING

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NOVELTIES IN LEACHING, SOLVENT EXTRACTION AND
ELECTROWINNING

• Carlos Avendaño V.

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• THE GENERAL OBJECTIVES OF TERRALS INNOVATIONS
  ARE

• Reduce risks and,

• Try to maximize economical benefits .

The Specific Objectives are

• Increase process efficiencies
• Obtaining higher recoveries, or quantities of
  recovered species, or decreasing reagents
  consumption.

• Optimize the business approach
• Discovering and analyzing the business risk
  factors.

• Reduce investments
• By means of plant and equipment configurations
  that take the best advantage of the knowledge,
  technology and available resources.

• Reduce exploitation costs
• By decreasing consumptions, or improving rich
  solutions, or reducing errors.

• Environmental improvements
• To avoid remediations and generation of
  environmental liabilities.

Novedades en Lixiviación, Extracción por
Solventes y Electro-obtención Intermín
Antofagasta Mayo 2005
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THE TLM METHODOLOGY (Targeted Leach Method)

• The traditional steps to evaluate a heap
  leaching imply performing mineralogical and
  chemical assays and other basic determinations,
  which are followed by column tests under
  different leaching conditions, to discover the
  ones that will bring the best results.

However, the real experience shows the leaching
conditions identified through these procedures
are seldom effective when applied in practice.
Terrals Approach - Recognizes the
characteristics and the behavior of the ore, -
Separates the conditions that must be observed
and the available degrees of freedom, -
Conciliates both aspects and establishes an
objective based on the economical criteria
of an operation
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THE TLM METHODOLOGY (Targeted Leach Method)

• Analyzes the leaching driving forces of the
  ore, under contexts different than the
  traditional ones,

Inserts preliminary Iso-pH column tests to
establish the mutual thermodynamic and kinetic
interactions between copper metallurgical
recoveries, impurity dissolution and acid
consumption and their related leaching ratios,
Defines the context of a complete LX-SX-EW
plant, to evaluate the possible interactions
between the various sections of a complete plant,
Enables clients to define their target PLS
quality conditions,
Performs a mathematical modeling of the most
optimal way to conciliate process conditions to
achieve the clients objectives and to leach
under optimal conditions, and
Performs verification tests on the compliance
of the objectives.
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THE TLM METHODOLOGY (Targeted Leach Method)
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THE TLM METHODOLOGY (Targeted Leach Method)

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THE TLM METHODOLOGY (Targeted Leach Method)
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THE TLM METHODOLOGY (Targeted Leach Method)
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THE TLM METHODOLOGY (Targeted Leach Method)
Table 2 Comparison of Objectives and
Results
Table 2 Comparison of Objectives and Results
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THE BC APPROACH (Business Configuration)

• This approach is located in the field of the
  project engineering methodologies.

• Every project is approached on the basis of
  profitable expectations, and whatever occurs
  against this objective should be considered as a
  risk.

• Both the success and risk factors are evaluated
  during the conceptual stages of the business
  study, under an economical point of view.

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THE BC APPROACH (Business Configuration)

• Sets up the general configurations of the heaps
  and plant processes and develops other detail
  aspects, and calculates the mass balances.

• Designs equipment and facilities for the plant
  implementation according to the selected
  alternatives, limited by the precision level of
  the available data.

• Calculates the demands of raw material, energy
  and services consumption, which are consistent
  with processes and configurations, to deduct
  direct costs from the considered alternatives.

• Calculates investments in the plant configuration
  alternatives and infrastructures, using data
  banks or quotations to conciliate calculations
  with the precision level of the basis data.

• Establishes the organization of each alternative
  such as personnel and external services demands
  - in order to calculate indirect costs.

• Calculates the econometric indexes of the project
  approach alternatives to compare them in the
  corresponding sceneries.

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THE BC APPROACH (Business Configuration)
The BC Approach counts on calculation modules
that transfer their information through links in
order to keep it permanently coordinated, and to
reduce revision arising from changes, to save
time and costs
Configuration and Mass Balance Module. Heap
Leaching Configuration Module. Pre-Sizing of
Equipment and Facilities Module. Investment
Calculation Module. Cost Calculation
Module. Econometric Indicators Calculation
Module. Design of Equipment Details Module.  
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THE BC APPROACH (Business Configuration)
Business Organization Stage The objectives of
the first calculation exercise are to show the
project implementations to discover the risk
factors caused by high investment costs or by
other reasons.
Project calculations are carried out with the
available data, considering the desired
production, or the estimated ore treatment rate,
and metallurgical data or any other project
conditioning aspect.
The configuration alternatives are then
parallely modeled, either regarding capacity or
any other aspect, mainly related to mass balance
and implementations for different process
approaches.
The important issue about the solution of the
mass balance module (from the studied
alternatives), relies on the fact that the
decisions to solve and construct it are based on
the project configuration.
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THE BC APPROACH (Business Configuration)
The comments, observations and corrections to the
first exercise of the business organization lead
us to new and consecutive calculation exercises,
in order to
- Explain the project advances to the owner, in
order to incorporate his indications,
restrictions, and perceptions on risk factors,
and carry out the desired solution assays.
- Consider evaluation factors and start
discarding, until the best option is selected
upon the basis of objective factors.
- Even though the engineering is only an
organizational factor in this stage, the project
is conceptualized, the predictable risk factors
are under control, with the flexibility degrees
upon any unexpected events.  
- Under the traditional engineering concepts, it
will look as if a conceptual engineering at a
very advanced stage in technical issues between
Basic and Detail Engineering has taken place.
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THE BC APPROACH (Business Configuration)
Design Stage The BC Approach elements can
be perfectly used to formulate the official,
traditional engineering documents, such as
specification plans, reports and others. Detail
design modules are used in this stage, containing
the information on the best alternative selected.
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OTHER NOVELTIES IN LEACHING
Practically all the novelties are related to the
TLM Methodology. In some cases they are part
of its grounds and, in others, they are a
consequence of such methodology.
Interfering Agents Control. One of the TLM
grounds is a more careful recognition of the
mineral. As a result of such recognition, we can
find a series of natural species that interfere
with the leaching process, such as
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Control of Interfering Agents
Reductants Species with the ability to
precipitate copper, previously dissolved by the
reagents, thus copper remains in the ore as a
metallic precipitate, unlikely to re-dissolve, as
a consequence of a loss of recovery capacity
phenomenon.
Copper Precipitate from the solution by
ore-extracted reductants
Cu precipitate
Remaining reductant
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Control of Interfering Agents
Ion Exchangers Usually consist of clays that
exchange their ions with the copper ions
dissolved by reagents thus, the metal remains in
the gravel as a complex unlikely to re-dissolve
Complex Silicates Complex compounds formed
during leaching, starting from previous
dissolution of silicates, which form colloidal
compounds with similar properties to those of the
ion exchanging clays, able to fix cations and
previously dissolved copper.
Those interfering compounds (or the possibility
that they appear from the dissolved species) are
identified by means of mineralogy and preliminary
tests, and are controlled through oxidation
(reductants) or by pre-impregnation with ions
with no value (exchangers) or by the adoption of
unfavorable conditions to silicate dissolution,
to avoid further formation of silicates.
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Identification of the Redox Potential as a
Driving Force in Leaching.
The Redox potential is highly significant in
sulphide leaching. It also controls the mineral
reductants and iron oxidation states in oxide
mineral leaching, and thus determines the type of
secondary compounds they form.
For example, within a reductant environment, the
iron will be in ferrous state and will not form
colloidal precipitates from hydroxides or from
jarosites, and will not interfere in the ore bed
porosity.
In case of an oxidizing environment, the acid
consumption increases to keep the ferric ions in
the solution however, it appears the risk of
jarosite formation, which can affect the ore bed
porosity as well as diffusion inside its own
particles.
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Identification of the Redox Potential as a
Driving Force in Leaching.
The ferrous to ferric oxidation in low acidity
environments, has the capacity to return free
acid to the system and reduce its consumption.
Also the controlled formation of jarosites
represents a mechanism to abate impurities in a
virtually permanent form to control its
concentration in the solutions, provided that
once this compound is formed, its structure can
be changed from the gel colloidal state to the
permeable sol state.
Terral uses diverse mechanisms for air injection,
for addition of reagents, and for irrigation and
resting pulses to activate the oxidizing
mechanisms and the change of state of jarosites,
to affect positively the leaching metallurgical
results and develop specific leaching techniques
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Identification of the Redox Potential as a
Driving Force in Leaching.
Sulphide Leaching Bacteria-assisted leaching
techniques use the mechanisms associated to their
activity to generate ions and conditions for
sulphide leaching. Given the large extent of
this topic and abundant bibliography available,
we will not present it in this opportunity.
Cleaning of precipitation solutions Terral has
developed an alternative process based on the
recirculation of the precipitation ferrous
solutions to the irrigation of the exhausted
gravel, in order for oxidizing and precipitating
the ferric ions to recover up to about 85 of the
water with purity compatible with leaching.
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Identification of the Redox Potential as a
Driving Force in Leaching.
Acid generation. The high price and consumption
of some minerals encouraged Terral to incorporate
sulphur to oxidize it in heaps to sulphuric
acid. This research is at an initial promisory
stage, still solving the issue on bacteria
adaptation to changing environments in the heap,
due to the recirculation of the leaching
solutions to adjust the copper concentration in
the PLS, based on the TLM concepts.
Leaching of Gold and Other Metals in Acid
Environment. Upon inclusion of oxidizing ions in
leaching, to reach gold oxidizing potentials and
to supply the anions that can keep the ore in
solution within an acid environment, recoveries
of around 80 have been achieved from samples
containing 3 gr gold/MT (and 0,6 total copper,
in mixed ores), verifying gold recovery from the
solutions through any of the existing techniques.
Also, the response of other metals to this same
methodology is being explored.
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Control of the PLS Characteristics
The irrigation ratio is a leaching driving
force, which activates the physical-chemistry of
dissolution. An interpretation in terms of a
countercurrent extraction unit operation, infers
the possibility of adjusting the concentration of
species at will, by means of recirculations.
In copper conditioned by recovery, kinetics,
and recirculations. It is independent from the
heap height and the irrigation rate, provided
that the other factors have been adjusted the
cycle durations remains as a variable depending
from all of them.
In acid conditioned by the controlled acid
contribution from different sources and by the
mineral consumption during the PSL generation
stage, by irrigation with recirculation and with
raffinate until reaching the irrigation ratio.
In impurities conditioned by the controlled
acid contribution, by redox environments, by iron
and jarosite handling, and other chemical
complexes.
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Control of the PLS Characteristics
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Transtec Proposal (Technological Transfer)
Transtec is a business proposal consisting
of
Terral evaluates a leaching operation, assuming
the corresponding costs and risks determines the
applicability of its TLM methodologies and
evaluates the prospective improvements and their
economical value. Delivers a report to the
company on the results obtained, but not on the
used methodologies.
If the results are interesting Terral will
submit a Transtec program, which implies the
transference of its methodologies under
confidentiality terms, and the development of all
the required tests - to be charged to Terral.
Protocols state that the implementation of the
methodologies will take place once the companys
success criteria have been satisfied.
At the same time, it is agreed on - the
objective forms of measurements of the results
obtained, - the partition of the resulting
benefits between the Company and Terral, and -
the validity period of the agreement.
The program is approached under the compromise
that the modifications will only affect the
leaching processing aspects and will have minimum
effect on the plant implementation thus, there
will be practically no new investments.
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Novelties in Solvent Extraction
Topics on Processes
Maintenance of Clean Organic An impure PLS may
induce contaminate the organic with micelles,
which affect the separation times of the phases
and increase the tendency to crud formation.
The operational strategy turns to maintaining
the organic phase as clean as possible, by means
of a preventive treatment over an organic flow,
parallely to the circuit in the normal operation.
Use of Impregnated Extractant in Inert Substrate
The mixer-settlers are not adequate to recover
elements with concentrations within the ppm
range. Terral has started tests with a 100 pure
extractant impregnated in an inert porous medium
to apply the operational concepts and unitary
processes of the ionic exchange resins, in order
to recover the elements under such conditions.
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Configuration of SX Equipment
Mixers
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Configuration of SX Equipment

• Terral adopts permanent changes in the
  direction of the phases flows that gradually
  separate in settlers the phases move separately
  both horizontally and vertically from the
  interphase.

The concept on specific flows is modified and
becomes apparent , while the real settling
surface becomes larger when distributed both
vertically and horizontally.
The real specific flow becomes substantially
smaller than the apparent one, and also changes
into specific for each of the phases as they
can adjust to a longer vertical path, to favor
settling of the phase that should be recovered
cleaner.
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Configuration of SX Equipment
Settlers
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Configuration of SX Equipment
After-Settlers
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Configurations of SX Equipment
Organic Tank
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Configuration of SX Equipment
Electrolyte Filters
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Novelties in Electrowinning

• Agitated and Ventilated Cell.
• This cell shows the characteristics to improve
  the technical, economical and environmental
  performance of the electrowinning process.

The development and design objectives are
To operate at very high current densities, up
to 600 Amp/m2, to reduce the considerable
investment required in this plant section.
To produce better quality cathodes than those
obtained under conventional current densities,
due to evident market reasons.
To solve the maximum operational problems to
facilitate the operations performed during
electrowinning.
To solve problems caused by acid mist, to
improve the environment and reduce the
tankhouse corrosion
Allow update of the existing cells, which will
be easier if this technology is implemented in
an existing unit
To combine with other operations, so that it is
possible to comply with the new electrolyte
feed requirements, and to transfer the benefits
gained in this cell to other sections.
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Agitated and Ventilated Cell
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Agitated and Ventilated Cell
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Agitated and Ventilated Cell
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Agitated and Ventilated Cell
DOWTURN (Upon covering the only open cell)
Mist (mg/m3
Time (min)