This document discusses approaches for reducing liabilities in tailings management. It describes how dewatering tailings can allow for safer storage by increasing the density and reducing the volume of tailings stored. Dewatering also has advantages like recycling metals from the tailings, increasing storage capacity, and extending the life of storage facilities. The document provides an example of a zinc smelter in Belgium that implemented a dewatering system to manage its goethite and gypsum tailings, allowing it to safely store the dried filter cakes and recover zinc from the process.

1. DEC:
MSc Eng. Xavier LEPERE – R&D Project Engineer – Process Technology & Remediation Design
17/09/2014
APPROACHES FOR
REDUCING LIABILITIES IN TAILING
MANAGEMENT

2. DEC (DEME ENVIRONMENTAL
CONTRACTOR)
15/10/2014 2

3. DEC (DEME ENVIRONMENTAL
CONTRACTOR)
3
DEC is an environmental contratctor that provides worldwide solutions for
the remediation of contaminated soil and sediments.
DEC is familiar with lots of different techniques:
 Soil washing
 Sediment / Sludge dewatering
 Chemical stabilization
 Immobilization
 Bioremediation
 Environmental dredging
 Tailing management
 Acid Tar Remediation
 …

4. CONTENTS
1. Tailing Ponds
2. Problems with storage in Tailing Ponds
3. Technical solutions for a safer storage
4. Case Study
5. Conclusions
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5. risks associated with wet storage of tailings1. TAILING PONDS
Tailings: residues after separating or extracting the valuable metals
from the ores or concentrate.
 Red mud
 Goethite
 Fayalite
Former practice: wet storage
Risks associated with wet storage

6. Tailings management is not the core business of the companies
 Stability issues of the tailing dykes
- No real geotechnical study
- Dykes are always raisen up
 Groundwater contamination
- No membrane underneath
- Tailings are not treated (high leachability)
 After a few years the ponds are full
- Very often no permit can be obtained to build new ponds or raise
the dykes
2. PROBLEMS WITH TAILING PONDS
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7. 2. PROBLEMS WITH TAILING PONDS
THE AJKA ALUMINA PLANT ACCIDENT
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Dam Failure – Red Mud:The Ajka Alumina Plant
Hungary 10/2010

8. Dam Failure – Cyanide Water: Aurul Gold Mining Baia Mare Romania
2. PROBLEMS WITH TAILING PONDS
BAIA MARE ROMANIA ACCIDENT (2000)
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9. Objectives
- Store dry matter, not
water
- Volume reduction
- Recycling of metals
3. TECHNICAL SOLUTIONS FOR A
SAFER STORAGE
Solution: DEWATERING
- Existing lagoons –
create storage
capacity
- New lagoons
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10. Mass and volume reduction as function of DM content
(grain density of 3.7 g/cm³)
0%
10%
20%
30%
40%
50%
60%
70%
80%
40% 50% 60% 70% 80%
Dry matter content (%)
Reductionmassor
volume(%)
m reduction
V reduction
 Final goal is storing dry matter, not water.
 This means storing the minerals at the highest dry matter content
or highest density
3. TECHNICAL SOLUTIONS FOR A
SAFER STORAGE
INCREASE OF CAPACITY BY DEWATERING
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11.  Increase stability of tailing ponds
- Good geotechnical characteristics of filter cake
 Recycling of metals/chemicals from tailings during dewatering
- Reduction of the residual metals or chemicals.
 Post treatment: Chemical stabilization of filter cake
- Reduction of mobility of metals, anions,… regarded as
pollutants.
 Post treatment: Solidification of filter cake
- Decrease permeability of filter cake: use as geotechnical barrier
- Reduction of the volume of percolate
3. TECHNICAL SOLUTIONS FOR A
SAFER STORAGE
ADVANTAGES OF DEWATERING
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12. 4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
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13. Process residues
 Goethite (FeOOH):
75,000 tons dry
matter a year.
 Gypsum
(neutralisation
sludge): 30,000
tons dry matter a
year
4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
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14. 4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
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Old Goethite pond
18 ha - 2,000,000 m³
Old Gypsum pond
30 ha - 3,000,000 m³

15. 4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
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Increase capacity for
40 years by
heighering dykes
Capping
(+ 500,000 m³
contaminated soil)
New Goethite pond
4.5 ha - 500,000 m³

16. Construction of the new Goethite pond in 2002
4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
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17. Capping of the old Goethite pond 2004
4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
17

18. Capping of the old Goethite pond in 2004
4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
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19. 4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
2005
Lab- and pilot scale design
2006-2007
Temporary mobile plant
for fresh Goethite
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20. 4. CASE STUDY
TAILINGS MANAGEMENT AT ZINC SMELTER BELGIUM
2006-2007
Construction fixed plant
2007-2017
Residue management
and plant operation
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21. COMPLEX SITE LOGISTICS
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Fresh Goethite buffers
Dry storage and
compaction of filter cakes Dredging & excavation
of wet gypsum
Fresh Goethite from zinc smelter
Filtrate to zinc smelter

22. Fresh Goethiete buffer
DREDGING & EXCAVATION
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23. Historical gypsum
DREDGING & EXCAVATION
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24.  Two membrane filter presses of 20 m³ volume each.
 Normal production: one filter press per type of material
- Goethite: very acid and corrosive medium, high density.
- Gypsum: alkaline nature.
 Production: 30 ton DM/h each press
DEWATERING IN MEMBRANE FILTER PRESSES
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25. OPERATION DEWATERING
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26. OPERATION – FILTER CAKE STORAGE
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27. INTEGRATION IN THE ZINC PROCESS
Liming
Goethite
buffer
Storage and compaction
GYPSUM POND
Fresh
Gypsum
Recuperation of zinc
from filtrates
FILTER PRESS
Liming +H2SO4
Gypsum
buffer
DEWATERING PLANT
ZINC PLANT
Liming
Fresh
Goethite
FILTER PRESS
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28. RECUPERATION OF ZINC FROM GYPSUM TAILING
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29.  Dewatering is a technical solution to reduce liabilities in
tailings management, it offers:
- Safer storage of the residues (dry storage)
- Increase storage capacity and extend production
time
- Possibility to recover valuable metals
5.CONCLUSIONS
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