Gavin Ritson Optimum Metal Recovery From Solutions
Transcript of Gavin Ritson Optimum Metal Recovery From Solutions
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Gavin Ritson, Hatch, Canada
Optimum metal recoveryfrom solutions: Design
considerations
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Introduction
PregnantBarren
Heap Carbon in
Columns (CIC) C
T
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Innovation
• Carousel Operation
• Conical Design Conc
Design and Operation
• Solution Upflow velocity
• Carbon Loading
• Number of Stages
• Carbon Retention Time
•
Carbon Transfer • Carbon Attrition
• Carbon Elution and Regeneration
Content
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Design
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• Solution/carbon contact by fluidising
• Overall water balance dictates flow
• Steady throughput required
• Distributor plate designed to prevent channelling
• Carbon type affects the design
Solution Upflow Velocity
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Solution Upflow Velocity
0
10
20
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100
0 20 40 60 80 100 120 140
E x p a n s i o n ( % )
Upflow Velocity m/h
12X30
8X16
6X16
6X12
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• Solution metal tenor drives
• Foulants reduce
• Carbon quality/activity affects
• Retention time in circuit
• Loading typically higher than CIP
Carbon Loading
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Carbon Loading
y = 7629.8x0.8909
10
100
1000
10000
100000
0.0010 0.0100 0.1000 1.0000 10.0000
C a r b o n l o
a d i n g ( g / t )
Solution grade entering tank (mg/l)
Operation A
Operation B
Operation C
Operation D
Operation E
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• Variable – as few as three
• Mechanical Availability
• Layout and cost
• Suited to the particular application
• Solution tail requirements
• Commonly five
Number of Stages
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• Not consistently applied in industry
• Variable – five to fifty days, typically fourteen
• Short retention – better solution recovery, higher elution costs
• Longer retention – higher loading, higher solution tails
Carbon Retention
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• Typically from take-off above the distributor plate
• Maintain steep loading profile
• Minimise backmixing
• Best to start at first stage
Carbon Transfer
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Carbon Attrition• Most attrition from regeneration
• Interstage pumping with recessed impellers
• Fine carbon screen to prevent carbon to barren pond
• Filter for even finer fraction
• Carbon transfer system should be closed circuit
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Elution and Regeneration• Low eluted gold grade (high elution efficiency) beneficial
• Need consistent, good carbon activity
• Acid wash and regeneration to overcome fouling.
• Remove undersize carbon before returning to circuit
• Silica generally not consideration as with CIP/CIL
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Innovation
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Carousel Concept
Carbon
Feed
Feed
Tai
Tails
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Carousel Advantages• No interstage carbon pumping
• Batch size remains constant (better control)
• Less attrition,
• Less backmixing
• Better carbon profile (higher loading)
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Standard Tank Design
Loaded Solution
Barren Solution
Carbon
CIC Columns
Loaded Carbon
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Improved Tank Design
Barren Solution
Loaded Solution
Loaded Carbon
Conical CIC
Columns
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Conical tank advantages
• Easier for carbon to be recovered for elution
• With carousel need 100% carbon recovery
• Eliminates costly distribution plate
• Better fluidization/contact in lower region
• More flexibility in solution throughput
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Conclusions
• With lower metal prices it is important to optimise and inno
• Carousel arrangement has potential to improve economics
needs to be tried in a commercial operation