Typical Process for Heap Leach Gold Mines - Oxus International

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6 Δεκ 2012 (πριν από 4 χρόνια και 8 μήνες)

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Produced by Oxus International with the help of
EcoSafety
, and the
Biotechnology Institute of the National
Academy of
Sciences of the Kyrgyz
Republic

The Biotechnology Institute
of the National Academy of
Sciences of the
Kyrgyz
Republic


This presentation provides information on cyanide, and how it is
used
by environmentally responsible gold mining
companies in
close proximity to communities. It also aims to dispel myths
about cyanide’s environmental impacts and health risks.


The
research has been produced by
a
Kyrgyzstan
-
based
research company, Oxus International,
working with the NGO
EcoSafety

and
the
Biotechnology Institute of the National
Academy of Sciences of the Kyrgyz Republic.


It
has been funded by the mining company
Manas

Resources,
who exercised no editorial control over the findings of the
research
or
the construction of this slideshow.


Cyanide is a chemical that is produced from
both natural and industrial sources.


Cyanide exists in small amounts in nature,
such as in almonds, apples and sweet
potatoes.


Cyanide in mining only accounts for 18% of its
total usage.


Cyanide is mainly used for industrial purposes
in pharmaceuticals and plastics, but also has
medicinal and artistic uses.

18%

82%

Mining
Other Industries

Exploration


Geologists study an area to gain more specific
knowledge of the geology and mineral composition
and decide where and how to proceed with mining
operations.

Drilling rig
in Crescent
Valley
Nevada,
USA

Three
-
dimensional
model of
geology at
Kubi

mine,
Ghana


Construction and
Mining


The mine, leach heap,
processing plant and
other facilities
are constructed.


Blasting and heavy machinery are used to expose and loosen
layers of rock. Rocks that contain traces of gold are called
“ore”.


Heap leach pad
at
Elansdrift

mine, South
Africa

Blasting at
Silver Bell mine,
Arizona, USA


Loading and Crushing


The
ore that result from blasting and mining are
collected, crushed into finer pieces, and
transported to the leach heap.


A pile of
crushed rock
in South
Dakota, USA

A rock
crushing
machine in
Australia


Heap Leaching Process


The crushed ore is sprayed or dripped

with a cyanide
solution, which binds to the gold and collects at the
bottom the heap. This step can also occur in large
containers. The cyanide solution is carefully prepared
to ensure its chemical stability.

Construction
of the leach
pad at
Kişladağ

mine
in Turkey

Cyanide
solution soaks
the ore below
at the
Mesquite
mine in
Nevada, USA


Extraction and Smelting


The cyanide and gold mixture is pumped
into
containers
loaded with
carbon, which absorbs the gold. The remaining
rocks in the heap are washed to remove traces of cyanide.


The carbon
and
gold
mixture transfers
to a stripping column
to separate the gold from the carbon.


The gold sludge is sent to a smelter to produce gold
bars at
98% concentration.


Gold bars in
various sizes

Processing
plant at
Kalgoorlie
,
Australia


Water Recycling


Water containing low amounts of cyanide is
reused in the heap leaching process.


There is zero discharge from the processing plant.


Golden Cross
Mine before
rehabilitation,
New Zealand


Rehabilitation and
Closure


Most mining companies determine an appropriate
closing scheme before mining operations begin.


This step ensures that the environment is protected
and returns to its pre
-
mine state as closely as
possible.



The same
mine
following
rehabilitation


Cyanide leaching is the
safest

economically
viable method of
extracting gold
from low
-
concentration ore deposits.


It is used
in 80
% of all gold mines in the
world.


Due to heavy regulations and safety
procedures, there have been only 8 major
cyanide spills since 1992.


There are about 460 gold mines around the
world that use cyanide.



Since 1992, there have been only 8 major
cyanide incidents.



The International Cyanide Management Code
was created in 2000 to improve the
management of cyanide in the mining
industry and help prevent major incidents.


If used improperly, cyanide can be dangerous

to humans, birds, fish and other wildlife.


Humans can experience breathing and nerve
issues if exposed to toxic levels of cyanide.



Research shows cyanide
does not

accumulate in the body or environment. It
does not

cause cancer or birth defects in
humans.



Cyanide is quickly broken down by sunlight
and other natural processes that transform it
into harmless compounds.


In
May
1998, a truck accident caused the
loss
of about 1,800 kg
of sodium cyanide
into
the
Barskoon

River.


Despite media reports, the long
-
term effects
of the spill were negligible.


Levels of cyanide in the air and soil never
reached dangerous amounts in populated
areas.


After two weeks, the cyanide had dissipated
to 1/1000
th

of its peak levels.


Many large gold mines that use cyanide run
successful operations in close proximity to
residential populations all over the world.
Examples include:


Super Pit in
Kalgoorlie
, Australia.


Population: 32,390


Martha Mine in
Waihi
, New Zealand.


Population: 4,503


Morro do
Ouro

in
Paracatu
, Brazil.


Population: 81,599



The gold mining industry is very heavily
scrutinized, causing constant improvements in
safety and environmental practices. Because of
the attention that many mining companies
receive, it is in their best interest to minimize
environmental impacts and to mine safely.



Many of the world’s largest gold mines are in
North America and Australia
where there are
very strict cyanide
regulations. These companies
use cyanide responsibly for gold extraction, even
in close proximity to local communities.


Mining companies can
minimize pollution, dust,
noise, and changes in landscape by installing
water
or air emission treatment
facilities, regularly
testing
air and water
for
pollutants,
implementing water
-
spraying systems
and
planting natural vegetation
barriers.


Blasting is a required part of many gold
mining processes in order to loosen the rock
which contains gold.


The main impact of blasting is the potential
for disruptive levels of noise and vibration in
nearby communities.


Blasting can also have negative impacts on
animals in nearby communities.


Mining companies undertake extensive studies to
develop blasting designs that mitigate negative
impacts on communities and animals as much as
possible.


The blasting process is as follows:


Informing
the community of blast times;


Drilling
holes in the ground according to the blast
design;


Inserting
blast charges into the bores;


Detonating
the charges sequentially with minimal
duration to mitigate effects of vibration and noise;


Monitoring
and recording blasting data to ensure
stringent
safety and environmental standards are met.



Mining operations create direct and indirect
employment opportunities for nearby
communities.


Many mining companies seek to hire as many
local workers as they can and use local
suppliers for mining needs.


In addition, many
mining companies provide
vocational
training to
local workers to
help
them find jobs elsewhere after mine
operations
finish.


Many mining companies implement development
initiatives in the local
communities
such as road
upgrades,
school
improvements, and long
-
term
income generating
projects
(vegetable gardens,
vineyards, tourism projects).