Arsenic Control in Mining Processes and Extractive Industry

Report
Arsenic and Nitrogen handling
in Mining Areas and Processes
Green Mining Seminar
12.9.2013
EUROMINING 2013, Tampere
Raisa Neitola, GTK Mintec
12.9.2013
1
Content
GREEN MINING PROJECTS:
1. ARSENAL – Arsenic Control in
Mining Processes and Extractive
Industry
2. MINIMAN – Solutions for
Control of Nitrogen Discharges at
Mines and Quarries
Raisa Neitola, GTK Mintec
12.9.2013
2
WHY WE NEED GREEN MINING PROJECTS?
• The increased extraction of mineral resources and mining
activities will place added pressure on the environmental
issues and a proper water management in mining areas
• The presence of arsenic and nitrogen compounds in mining
areas and beneficiation processes creates the need to develop
eco-efficient solutions to control different types of
discharges in mining areas
ARSENAL and MINIMAN concentrate on
developing technologies for management of arsenic
and nitrogen discharges at the whole chain operations
from quarrying and mining to end product and waste
management.
Raisa Neitola, GTK Mintec
12.9.2013
3
ARSENAL – Arsenic Control in Mining Processes and
Extractive Industry
Timetable: 1.1.2011 -31.8.2013 Budget: 1 400 k€
NEEDS
• Arsenic is a world-wide challenge
• Arsenic is commonly associated with ores containing metals such as gold
• It is easily solubilized in water phase
Control of arsenic in all mining operations is a necessity
APPROACH
• New mineral processing and water treatment solutions for arsenic removal
• Novel bio-based treatment processes for arsenic containing wastes and streams
• Monitoring and environmental risk assessment tools
BENEFITS
• Better knowledge and new management tools on arsenic in the mining area
• Eco-efficient solutions for mining industry to control and remove arsenic
• Minimization of health and environmental risks related to arsenic
USERS & COMPETITION
• Technology companies, mines, consults, authorities, other stakeholders
(Outotec Oyj, Kemira Oyj, Ekokem-Palvelu Oy, Agnico Eagle Oy, Endomines Oy, Nordic
Mines AB, Pyhäsalmi Mine Oy, YARA Suomi Oy, Mondo Minerals B.V. Branch Finland)
• Arsenic behavior is highly depend on prevailing conditions and processes
Special, tailor-made and global approaches are a challenge and a possibility
©Loukola-Ruskeeniemi,
Arseeni Suomen luonnossa
ympäristövaikutukset ja riskit, 2004
12.9.2013
WP1 Management of Arsenic in Beneficiation
Process by Mineral Processing Methods
• OBJECTIVES
– To get preliminary understanding of the mineralogical and environmental
characteristic of arsenic-containing tailings and their behiaviour in ponds
– To develop beneficiation process to produce high quality gold concentrate
with very low arsenic grade and environmentally friendly tailings
• EXPERIMENTAL WORK
– Mineralogical and chemical characterization of arsenic containing ores,
concentrates and tailings by MLA and XRF
– Environmental characteristic of As-containing tailings
• Batch leaching tests, pH-dependency and static tests
– Laboratory scale flotation tests for arsenic containing gold ores
• OUTCOMES
– Flotation flowsheet to produce
• rougher high quality gold concentrate
• scavencer As-containing marginal concentrate, which is later treated by
bio- and cyanide leaching methods
• Sulphide free and low arsenic containing tailings for disposal
– Insight for tailings characteristics at disposal
Raisa Neitola, GTK Mintec
12.9.2013
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WP2 Sorption-based As-removal Technologies
• OBJECTIVES
– To develop techniques for removal of trace
level As-concentrations as a polishing step
before discharge to the environment
– To find and apply cost-effective sorption
materials for As-removal from mine waters
• EXPERIMENTAL WORK
• OUTCOMES
– Results suggest sorption to be a viable option
for trace level As-removal from mine waters
– Promising As-removal capacities found for
pre-treated cast iron chips
– Challenges remain in technical performance
of the material (e.g clogging)
Raisa Neitola, GTK Mintec
50
Maximum As-removal capacity, mg/g
– Batch tests with selected industrial byproducts to assessment of sorption capacity
and kinetics (commercial sorption material as
reference)
– Column experiments with real mine water to
simulate the end-use application
46
40
30
20
14
7,9
10
0,02
2,3
0
Waste rock
Granulated
steel slag
Ash pellet
Granulated Cast iron chips
ferric oxohydroxide
(CFH 12)
12.9.2013
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WP3 Management of As-containing Side
Streams and Waste Materials by Bioprocessing
• OBJECTIVES
– To develop biobased methods to process eco-efficiently industrial side
stream
– To reduce the amount of released arsenic and minimize environmental
impacts of arsenic containing streams and waste materials
– To stabilize arsenic from waste waters binding it into the iron precipitate
• EXPERIMENTAL WORK
– Mineralogical and chemical characterization of concentrates and
bioleaching residues by MLA and XRF
– Bioleaching of nickel concentrate, which is flotation by-products of talc
production
• Laboratory batch tests and continuous leaching tanks
– Fluidized-bed reactor for waste waters
• OUTCOMES
– Knowledge and data for supporting the desing of
new industrial plant for utilization of arsenic bearing side stream
– Treatment of arsenic-containing wastewaters through sorption
on biogenic iron precipitates was proved to be efficient
– Stability of arsenic in the iron precipitate was pH-dependent
Raisa Neitola, GTK Mintec
12.9.2013
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WP4 Environmental research
• OBJECTIVES
Siilinjärvi
– To study and compare natural and anthropogenic As at two
geologically different mine sites (Kittilä Suurikuusikko gold
mine, Yara Siilinjärvi industrial area)
– To assess and compare ecological risks at study sites
– To model the behaviour of natural and anthropogenic As
• EXPERIMENTAL WORK
–
–
–
–
Desk study of As geochemistry in mine environments
Water, soil and bedrock sampling & geochemical analysis
Modelling study (PHREEQC)
Assessment of ecological risks
Kittilä
• OUTCOMES
– Despite of the geology of mine site, mining activity has increased
the proportion of available and potentially mobile As in soil
– Mining activities have increased the ecological risks by
•
•
changing As into more soluble and mobile form
elevating As concentrations in the surrounding environment
– As mobility in soil depends on adsorption by iron oxyhydroxides
– Desorption of arsenic is potential risk to environment (e.g.
wetlands)
Raisa Neitola, GTK Mintec
12.9.2013
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MINIMAN – Solutions for Control of Nitrogen
Discharges at Mines and Quarries
Timetable: 1.1.2012 -31.12.2013 Budget: 920 k€
NEEDS
• Better understanding of the behaviour of nitrogen compounds
• Minimizing of nitrogen transport
• Removal of N-compounds from mine waters
APPROACH
• Analysis of sources, behaviour and management
opportunities of nitrogen compounds
• Biological reactor process and electrochemical
/adsorption process for nitrogen removal
BENEFITS
• Knowledge, tools and technological solutions
for nitrogen control at mines
USERS & COMPETITION
• Technology companies, mines, consults, authorities, other stakeholders
(Outotec Oyj, Kemira Oyj, Ekokem-Palvelu Oy, Outokumpu Chrome Oy,
Agnico Eagle Finland Oy, Yara Suomi Oy, FQM Kevitsa Mining Oy,
Nordic Mines AB, Nordkalk Oy Ab, Infra ry, Kiviteollisuusliitto ry,
BK-automation Ky)
• Non-nitrogen explosives/explosion techniques (not in near future)
Explosion
fumes to air
•Gases: N2, NOx
Spillage to
surface and
groundwater
Mined ore
and waste
rock
•Ions : NO3-, NH4+
•Remnants of
explosives to the
extraction facility →
tailings
•Remnants of
explosives to the
waste rock area →
potential leaching
Final
product
Major nitrogen sources at mine sites
• Ammonium nitrate based explosives
• Cyanide used in gold extraction
Challenges
• Behaviour and release of nitrogen
compounds from waste rock and tailings
• Water: Relatively low (NO3-, NH4+)
concentrations, high volumes, high ionic
concentrations, Nordic conditions
12.9.2013
WP1 Removal of Nitrogen compounds by
Biological techniques
• OBJECTIVES
– To evaluate the feasibility of biological methods
to remove nitrate and ammonium from metalrich mine wastewaters at low-pH
• EXPERIMENTAL WORK
– PCR/DGGE analysis for monitoring the
evolution of microbial community
– Batch tests for the assessment of metal toxicity
and pH effect on microbial activity
– Fluidized-bed and membrane bioreactors for
denitrification and nitrication experiments
• OUTCOMES SO FAR
– Denitrification of acidic water is feasible
whereas nitrification is more pH sensitive
– Both nitrification and denitrification tolerate
metal concentrations that are typical in AMD
12.9.2013
WP2 Nitrogen sorption experiments
• OBJECTIVES
– To find and apply cost-effective sorption materials for
nitrogen compounds from mine waters
– To compare different sorption materials and their
ability to remove low concentrations of ammonia and
nitrate from mine waters
• EXPERIMENTAL WORK
– Desk study of the potential sorption methods and
materials based on existing knowledge
– Batch and column tests using natural minerals based
materials (e.g. zeolite, vermiculite) and other sorbent
materials (e.g. carbon) with real/synthetic water
– Regeneration tests of sorbent materials
• OUTCOMES SO FAR
– Zeolite sorption is potentially a functioning method of
ammonia removal from mine waste water
– Case dependant feasibility study and pilot scale testing
are needed to confirm economics and feasibility
12.9.2013
WP3 Electrochemical nitrogen capture
•
OBJECTIVES
– To develop novel electrochemical technique for nitrate and
ammonia capture suitable also for Nordic conditions
•
EXPERIMENTAL WORK
– Laboratory scale research using a continuous flow cassette reactor
•
Synthetic wastewater used in a self constructed reactor
• Cooperation with University of Queensland Advanced Water
Management Centre
•
OUTCOMES SO FAR
– Electrochemically enhanced stripping is
potentially a feasible technology for variety
of inorganic streams for nitrogen capture in
the future – including mine wastewaters
– More research is needed for material
selection and development and process
optimization and reactor configuration
– High ion concentration of mine waste water
can cause fouling problems
12.9.2013
WP4 Aging tests
• OBJECTIVES
– To evaluate the nitrogen discharge from the mine sites
•
‘Nitrogen smudging’ (contamination by explosive originated nitrogen
compounds) of otherwise mineralogically and chemically inert waste rocks of
good technical quality hinders the utilization of these product streams
– To gather essential data on the behaviour of nitrogenous compounds present
in the environments of mines and quarries
• EXPERIMENTAL WORK
– Monitoring the surface waters around the quarries
– Aging tests at the quarries
• 1000 m3 IBC-container + waste rock
• OUTCOMES SO FAR
– Data forms a basis for a holistic view on need and
options for nitrogen management in mining and quarrying that takes into
account the scale of the operations
Mining activity seems to have relatively low nitrogen emissions, ”nitrogen
smudging” should not prevent the utilization of waste rock material
• The ”first flush” of nitrogen from waste rocks comes fast and is relatively short
•
12.9.2013
CONCLUSIONS
• The results of ARSENAL project suggest that by novel
mineral processing methods and proper water treatment
methods the amount of As-compounds in tailings and
effluents can be reduced to levels that satisfy the regulations
concerning mining waste management.
• So far, MINIMAN project generated new know-how on the
behaviour of N compounds in mining areas and better
understanding of the nitrogen discharge issue as well as
developed advanced technologies for the removal of nitrogen
compounds from mine waters.
Raisa Neitola, GTK Mintec
12.9.2013
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Thank You for Your Attention!
Raisa Neitola, GTK Mintec
24.10.2012
15

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