heap leaching technology implementation, lessons learned
DESCRIPTION
TRANSCRIPT
Lessons Learned
Growth & Innovation – Copper Group
Heap Leaching
Technology
Implementation
Processing Route Reserves Resources
Existing
Operations
Milling 83% 86%
Leaching 17% 14%
Projects
Milling 93% 89%
Leaching 7% 11%
Copper Outlook
0%
5%
10%
15%
20%
25%
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
%
% of Copper Production from Leaching
Actual Forecast
Only 20% of projects in the pipeline are
considering a Heap Leaching / SXEW circuit
Can we do something
different?
Project
Mining & Geology
Metallurgical Process
Environmental Aspects
Legal & Social Issues
Opex, Capex & Business Evaluation
Project vs. Process Development
Engineering & Infrastructure
Market Analysis
Profit, Profit, Profit
Shareholder value
Market share
Social/Environmental impacts
Process Development
Geomet
Theory Kinetics
Process Engineering
Flow Sheet
Design Criteria Testwork
Project Development
Exec Plan
Value Eng Specs
Concept Study
• Ore Body Knowledge
Pre-Feasibility
• Processing options
• Testwork
• Design criteria
• Location
• Capacity Trade-Off
Feasibility
• Value Engineering
• Main equipment selection
• Project Execution Plan
Project Development Path *Considering the metallurgical/engineering section only
6 to 12 months 2 to 3 years
Maybe 4 depending
on ore body complexity
12 to 18 months
• Exploration is not sufficiently advanced to allow a proper understanding of the ore
body
• Geometallurgical characteristics are not understood
• Mining sequencing is not clear
• Ore deposit information is just two numbers: Tons and average grade
• Urgency for getting some tests done and using assumptions to put together inputs for
business valuation without validating its real applicability/representativeness
• Benchmark data is used ignoring project-specific aspects (i.e. mineral association,
gangue minerals, location, climate, etc.)
Concept Study
• Testwork:
• Non-representative samples, or samples not linked with the mine production plan
• Wrong scale
• Site specific conditions ignored
• Sample preparation for test different from ore preparation at commercial scale
• Focus on chemistry (i.e. recovery), ignoring the physics (i.e. hydrodynamics)
• Focus only on core unitary processes in the flowsheet (i.e. leaching) but not integrated
• Done by a third party with limited contextual information, results usually late in the engineering process, lack of cross communication and follow up from the owners team
Pre-feasibility Study – Design Criteria
• Benchmark data
• Used incorrectly or at convenience
• Ignoring the project specifics (i.e. climate conditions)
• Too many processing options, complex flow sheets
• Mine production plan continuously modified without assessing the impact on process design criteria
• Technology development versus Project development
• Water balance not considered an issue, even in high rainfall environments
• Leach pad design based on assumed geotechnical / hydrodynamic characterization of the project site location
Pre-feasibility Study – Engineering
• Metallurgical test work still in progress, flowsheet is modified
• Additional resources added to the mineral inventory not covered by
previous testwork but within the payback period. Impact on risk/cost is not
assessed
• Design criteria not honored during engineering development, process
changes introduced to “improve” project economics
• Lack of metallurgical process details to support operating costs estimation
Feasibility Study
We need a plan …
Concept Study
•Understanding the Geometallurgy of the ore deposit
•Not a continuation of the exploration activities
•Narrow the processing options based on ore body knowledge
•Use range analysis to complete a probabilistic evaluation of the business case using benchmark and realistic assumptions based on the ore body knowledge
Pre-Feasibility
Study
•Selecting the preferred processing route, process flowsheet finalized
•First, define the design criteria, based on representative samples and at the right scale
•Then, complete the engineering study
•Re-do the range analysis now using the project data
Feasibility Study
•Optimizing the business case to finalize the project execution plan
•Complete the value engineering and risk management to improve chances of success
•Finalize the detail project execution plan
•Kick-off the operational readiness team
Is there enough mineral
resources to support a strong
business case?
How will the mineral
resources be developed to
deliver the most value?
How can the business
case be optimized to
minimize risk and ensure
value realization?
Concept Study
• Ore Body Knowledge
Pre-Feasibility
• Processing options
• Testwork
• Design criteria
• Location
• Capacity Trade-Off
Feasibility
• Value Engineering
• Main equipment selection
• Project Execution Plan
Project Development Path
6 to 12 months 2 to 3 years
Maybe 4 depending
on ore body complexity
12 to 18 months
1. Ore Body Knowledge
• Finish the exploration program first, at least having it sufficiently advanced to
ensure enough information is available to define viable options for processing
• Change management must be applied every time a new mineral inventory is
issued to validate that the process design criteria is still applicable. Same
with any new mine production plans
Lessons Learned
2. Testwork
• Select the right scale for your tests
o Reactor tests, bottle roll tests, mini column tests are just indicative and must not be used to define any process design criteria – Common for Process Development
o Define upfront the purpose of every tests and the information that will be provided to be used later in the design.
o Understand first the process drivers (i.e. liquid/air permeability, gangue reactivity, ore/liquid temperature, etc.) then define the scale
o The more complex the metallurgical system; the higher the scale that must be used to produce the required data (i.e. temperature dependent, high rate of gangue reactions)
o Full height columns / cribs / pilot heap tests are necessary to reduce scale-up risks. The lower the scale the highest the scale up penalty
Summary of Lessons Learned
Operational
Parameter Units
Commercial
Scale
Pilot / Large
Scale Test
Medium
Scale Test
Small
Scale Tests
Heap Height m 10 10 5 1
Solution Application
Rate L/m2/h 5 5 5 5
Solution to Ore Ratio L / h / t 0.28 0.28 0.56 2.78
Example
2. Testwork
• If you don’t have the right samples (type and quantity), wait for them…
• Technology development is different than project development. In projects, tests are
done to produce the design criteria; not to understand the technology. Keep them
separated
• Differences in ore preparation between the lab scale tests and the commercial scale
design can introduce significant risk to the project
• Lab test conditions must be aligned with the future operational conditions
Summary of Lessons Learned
2. Testwork
• Getting hydrodynamic and geotechnical data from testing fresh ore samples is a huge
mistake
• Maintain consistency in the way tests are done to be able to do comparison and
validation
• Accept the results as they are; use ranges to evaluate the feasibility of the project.
• Numerical models cannot replace the metallurgical test work program
Summary of Lessons Learned
3. General
• Heap Leaching cannot be fast-tracked; the way to shorten the development
time is by doing the right things in the right order
• Benchmark data is indicative only, be careful with copy and paste
• Keep the level of technology innovation under control managing the risk
profile
• Maintain focus on what needs to be done in each stage of project
development
• Do not outsource the definition of the process design criteria and flow sheet
Summary of Lessons Learned
• Define the mineral resources
• Short list the processing options based on ore body knowledge
Concept Study
• Define the processing route and its design criteria
• Define the production capacity, location and general layout
• Complete the range analysis to evaluate the probabilistic outcomes
Pre-Feasibility Study
• Finalize the risk management plan and value engineering
• Complete the project execution plan
Feasibility Study
Study deliverables
Questions ? Comments ?