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underflow slurry is pushed to
a carbon-in-leach circuit. Also
in the autoclaves, the carbon
contained in the sedimentary
materials is oxidized with the
combination of oxygen and high
temperatures.
Within the autoclaves, oxygen
is the primary reagent. During
design of the autoclaves, Hatch
included a heat recovery circuit
that, combined with the nature
of the exothermic reactions
that produce heat within the
autoclaves, makes the heat
autogenous by design. “Without
the heat recovery system, we
would need some external
heat source,” Fraser adds.
“This way, we keep the energy
needs down.” The Pueblo
Viejo autoclaves are the largest,
by weight, refractory-lined
autoclaves built to date globally,
with an onhook weight of 780
tonnes when shipped lead lined.
The massive structures are each
5.6 metres by 34.8 metres, and
will nominally operate at 230
degrees Celsius. There are four
in total.
The grand voyage
Hatch designed the autoclaves
and provided quality assurance
during fabrication. They were
built by KNM Process Systems
Sdn Bhd in Gebeng, Malaysia.
“We had two full-time quality
assurance inspectors on site
throughout the 33-month
fabrication,” Fraser recalls.
The autoclaves were then
shipped approximately
10 kilometres to the Kuantan
Port using a 24-line, selfpropelled
modular transporter
(SPMT) heavy-haul unit. At the
port, they were loaded on the
Beluga Bremen, a P2-class ship
owned by Beluga Charters out of
Germany, for its maiden voyage.
The autoclaves were transported
in two shipments of two
autoclaves each on the Bremen,
which used both of its 750-tonne
cranes and needed six hours
to load the autoclaves from the
SPMT into the cargo hold.
“We had two full-time
quality assurance
inspectors on site
throughout the
33-month fabrication”
The ocean voyage took four
weeks one way, heading
through the Panama Canal to
reach Samana in northeastern
Dominican Republic. “Samana
is basically an old and unused
former cruise ship pier that
was refurbished for the Pueblo
Viejo project, including the
autoclaves,” Fraser explains.
There, the autoclaves were
transferred from the Bremen
onto a 4.9-metre-wide 22-line
Goldhofer heavy-haul trailer unit
to transport the autoclaves over
120 kilometres to the Pueblo
Viejo site, a trek that took about
18 days, and had to be repeated
for each of the four autoclaves.
“I think I’ve walked every
kilometre of that route – I’ve
definitely driven it many times,”
says Fraser. “The Goldhofer
moves at an average of two
kilometres per hour and can only
operate during the daytime.”
Prior to the autoclaves arriving
in the Dominican Republic, the
project of readying the route to
get them to site took about
16 months. Due to the sheer
size of the autoclaves, there
were a lot of interference issues
to deal with: trees, power lines,
communications lines, signs in
villages that had been modified
so they could rotate, and bridges
(some had been temporarily
reinforced to support the excess
weight of the load; others had
metal ramp structures added
along each side to allow the
Goldhofer to drive over them).
The actual trek across the land
with the autoclaves required
a number of teams. Heavy
lifting and transport specialist
Mammoet Caribbean Inc. was
responsible for driving the
Goldhofer. A crane and ramp
team moved the ramps – the
team would go ahead, ramp
up a bridge, and then once the
Goldhofer crossed, dismantle
the ramp, move ahead of the
Goldhofer and ramp up the next
bridge. A safety team acted as
an escort and ensured all were
well-fed and hydrated, while
also providing necessary crowd
control near towns.
Upon reaching the massive
gates at Pueblo Viejo, which
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