gavin ritson optimum metal recovery from solutions

8/10/2019 Gavin Ritson Optimum Metal Recovery From Solutions

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Gavin Ritson, Hatch, Canada

Optimum metal recoveryfrom solutions: Design

considerations



Introduction

PregnantBarren

Heap Carbon in

Columns (CIC) C

T



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



Design



• 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



Solution Upflow Velocity

0

10

20

30

40

50

60

70

80

90

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



• Solution metal tenor drives

• Foulants reduce

• Carbon quality/activity affects

• Retention time in circuit

• Loading typically higher than CIP

Carbon Loading



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



• Variable – as few as three

• Mechanical Availability

• Layout and cost

• Suited to the particular application

• Solution tail requirements

• Commonly five

Number of Stages



• 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



• Typically from take-off above the distributor plate

• Maintain steep loading profile

• Minimise backmixing

• Best to start at first stage

Carbon Transfer



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



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



Innovation



Carousel Concept

Carbon

Feed

Feed

Tai

Tails



Carousel Advantages• No interstage carbon pumping

• Batch size remains constant (better control)

• Less attrition,

• Less backmixing

• Better carbon profile (higher loading)



Standard Tank Design

Loaded Solution

Barren Solution

Carbon

CIC Columns

Loaded Carbon



Improved Tank Design

Barren Solution

Loaded Solution

Loaded Carbon

Conical CIC

Columns



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



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

gavin ritson optimum metal recovery from solutions

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