Transcript Development of the TATI Activox BMR Ammonia Recovery Circuit

Development of the TATI Activox® BMR
Ammonia Recovery Circuit
D.A. van den Berg (Hatch), P. Maré (Hatch), G.J. Nel
(Norilsk Nickel)
Agenda
•
– Background to TA®P
– TA®P flow sheet
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Introduction
•
Selection of SX neutralizing reagent
– General SX neutralizing reagent options
– Benefits of ammonia recovery for TA®P
•
Ammonia recovery technology
– Traditional lime boil process
•
TA®P ammonia recovery process
– Vibrating mills
– Reaction tanks
– Stripping column and design
Conclusion
•
Conclusion and key benefits
2
Tati Activox® Project
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
3
The Tati Activox® Project (TA®P)
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
• Greenfields project for Activox hydrometallurgical
plant located outside Francistown, Botswana
• Process tested at HDP (demo plant)
• Uses Activox® technology to treat nickel sulphide
concentrate.
Feed Conc
506 000 dt/a
Ni
4.2 - 5.3%
Cu
2.7 - 5.1 %
Co
0.11 - 0.18 %
Fe
47%
Product
t/a
Nickel metal
25 000
Copper metal
22 000
Cobalt carbonate
640
• Ammonia recovery eased key location challenges
• Project indefinitely suspended mid 2008 with
detailed process design complete and
construction underway.
4
The Tati Activox® Plant
Concentrate
Activox® Leach
Ultra-Fine
Grinding
CCD
PGE Circuit
Copper PLS
Pond
Second Stage Iron
Removal
First Stage Iron
Removal
Copper Raff Pond
Copper Solvent
Extraction
Copper Electrowinning
Ammonia
Copper
Product
Ammonia
Recovery
Cobalt Product
Cobalt Solvent
Extraction
Nickel Electrowinning
Cobalt
Precipitation
Nickel
Product
To Tailings
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SX Neutralizing Reagent
Selection
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
General Factors which were considered:
1. What are the by-products created and
how are they handled?
•
•
Marketable?
Safe disposal?
2. What is the transportation requirements
for the reagent & by-product?
3. What is the impact on plant water
balance?
4. What is the impact on overall plant
process conditions (impurities)?
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Typical Reagent Options for pH
control in SX
•
–
–
Introduction
Reagent
Selection
•
Conclusion
•
Supplied as 50% solution or pellets
Sodium sulphate can be crystallised for detergent
filler, pulp & paper or glass industry
Sodium Carbonate
–
–
•
Supplied as anhydrous liquid
Ammonium sulphate can be crystallised for
fertilizer
Sodium Hydroxide
–
–
Ammonia
Recovery
TAP Ammonia
Recovery
Ammonia
Supplied as anhydrous solid
Similar sodium sulphate product
Location
–
No local market for ammonium sulphate or sodium
sulphate by-product
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Indicative Reagent Supply Costs
R6500 /t
Increasing Cost
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
R150 /t
Sodium Hydroxide (NaOH)
Ammonia (NH3)
Sodium Carbonate (Na2CO3)
Quicklime (CaO)
Conclusion
•
•
Quicklime is by far the cheapest alkali
Ammonia recovery uses “cheap” base to
recover more expensive ammonia
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Tati Neutralising Reagent Selection
for SX
No. Reagent
Introduction
Required
Reagent
(Kg per t acid)
Reagent
Selection
1
Ammonia
Recovery
2
Option 1 with 90% 34.7 kg ammonia
ammonia
and 515 kg lime
recovery
per ton acid
3
Sodium hydroxide 408 kg/t
4
Sodium carbonate 1081 kg/t
TAP Ammonia
Recovery
Conclusion
•
Ammonium
hydroxide
347 kg ammonia
prt ton acid
Ammonia recovery has significantly less
ammonia reagent costs
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Traditional Ammonia Recovery
• The lime boil process:
Quicklime+ Water
Introduction
Reagent
Selection
Cooling
Water
Lime Slaking
Ammonia
Recovery
Ammonia and
Water Vapour
TAP Ammonia
Recovery
Conclusion
Cooling
Water
Condenser
Lime
Slurry
Feed Slurry
Cooling
Water
Ammonia Product
Tank
Steam
Lime Boil Reactors
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Traditional Ammonia Recovery
• Advantages
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
– Only need reaction tanks and condensers (and
slaking equipment)
– Ammonia make-up by adding ammonium
sulphate to lime boil feed or anhydrous
ammonia to recovered ammonia.
• Disadvantages
– Gypsum Scaling
– Lime Slurry Dilution
– Energy Intensive
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TA®P Ammonia Recovery Process
Introduction
Reagent
Selection
•
•
•
•
Vibrating mills
Reaction tanks
Steam stripping, condensing, make-up
Barren slurry to tailings, process water
recovered
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
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Vibrating Mills
CaO(s) + H2O(l) = Ca(OH)2(s)
(NH4)2SO4(aq) + Ca(OH)2(s) = CaSO4(aq) + 2 H2O (l) + 2 NH3(aq)
Reaction mills
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Reaction Tanks
CaSO4(aq) + 2 H2O(l) = CaSO4.2H2O(s)
Gypsum formation
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Steam Stripping
NH3(aq) = NH3 (g)
Ammonia stripping
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Steam Stripping
Theoretical stages plotted on McCabe Thiele
(Confirmed by ASPEN modelling, Stuart Bradbury of PPT)
McCabe Thiele Diagram for Ammonia- Water System
Introduction
0.12
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
0.11
Y - mol fraction Ammonia in Vapour
Reagent
Selection
1
0.1
0.09
2
0.08
0.07
3
0.06
4
0.05
0.04
5
0.03
6
0.02
7
8
0.01
0
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
X - mol fraction Ammonia in Solution
Equilibrium Line
Operating Line
Stages
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Ammonia Stripping Column Design
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
Demo plant
• Small (6” diameter) column
• 10% tray efficiency duration operation
TA®P Design
• Design for 15% tray efficiency
– Larger column diameter and tray spacing
– Typical efficiency (for dual flow trays) is 20-40%, but
reduced due to slurry environment.
• Design for reduced steam consumption
– Higher L/V ratio than demo plant to reduce steam
requirements
– Discharged into flash cooler to recover steam
•
live steam requirement reduced by 30%
• Gypsum handling
– Includes seeded reaction tanks to reduce scaling in
stripping column
– Included full redundant train to increase availabilities
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Stripping
Columns
Plant Layout :
Note:
Mills, reaction tanks
and stripping column
have a duplicate train
(interchangeable)
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
Reaction
Tanks
Quicklime
Silo
Condensers
Flash
Reboilers
Vibrating
Mills
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Summary of Key TA®P
Ammonia Recovery Benefits
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
• As compared to other neutralising
reagents:
– Reduced reagents costs
– Flexibility in reagent make-up (anhydrous
ammonia or ammonium sulphate crystals)
• As compared to traditional lime boiling
– Gypsum scaling is abraded off vibrating mill
walls
– Seeded reaction tanks promote crystal growth
– Quicklime added directly to feed slurry, no
slaking required, no water dilution.
– Exothermic slaking energy captured in feed
slurry
– Reduced steam requirements
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Conclusion
Introduction
Reagent
Selection
Ammonia
Recovery
TAP Ammonia
Recovery
Conclusion
The TA®P ammonia recovery circuit
incorporates technologies resulting in the
following advancements over the
traditional lime boil process:
• higher quicklime utilisations
• improved plant availabilities
• lower energy requirements
• improved management of gypsum
scale.
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Thank-you
Introduction
Pieter Mare (Hatch)
Gerhard Nel (Norilsk Nickel)
Reagent
Selection
Ammonia
Recovery
Questions?
TAP Ammonia
Recovery
Conclusion
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