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An incredible journey
The design, manufacture
and global transportation
of the world’s largest autoclaves
Each 780-tonne autoclave
took 18 days to be
transported just over
120 kilometres from
the port at Samana,
Dominican Republic,
to the Pueblo Viejo
operation.
The Pueblo Viejo gold operation
in the Dominican Republic is on
track for its first gold pour in the
first quarter of 2012. But getting
to this point has not exactly
been easy sailing. Because
the ore is double refractory, in
order to access it, the project
had to commission the largest
autoclaves ever built and
transport them halfway across
the world from Malaysia to the
Caribbean.
Accessing gold
Pueblo Viejo, a joint venture
between Barrick Gold
Corporation and Goldcorp Inc.,
boasts gold reserves of
approximately 23.7 million
ounces. Barrick owns 60 per
cent and is the managing
partner. The sulphidic refractory
gold deposit is being constructed
to a 24,000 tonne-per-day design
capacity. In the first five years, it
will produce an average of 1.042
to 1.125 million ounces annually
(100 per cent basis).
Hatch Autoclave Technology
Group has been on the project
since 2006 with the engineering,
procurement, construction
management (EPCM) contract
for the core part of the refractory
process, namely, the autoclaving
facility and supporting oxygen
plant. “It’s a double refractory
gold ore, associated with two
mineralogical issues: sulphides,
in the form of pyrite and minor
base metals such as silver,
copper and zinc, which prevent
cyanidation from directly
recovering the gold; and a
natural carbon component to the
ore, which causes issues with the
recovery under a conventional
system,” explains Hatch project
manager Kevin S. Fraser. The
incorporation of autoclaving
in the processing of the ore
addresses these challenges.
In the autoclaves, all sulphides
are oxidized, producing
sulphuric acid as a by-product.
The iron, copper and zinc
dissolve into the solution; then
the acid is washed out in a
counter-current decantation
(CCD) circuit leaving free
microscopic gold to allow
for leaching in cyanide. The
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