A revolutionary hydrometallic process
developed by Cominco Engineering Services Ltd. (CESL) for
processing copper concentrate is on the cusp of being
commercialized by Cia. Vale do Rio Doce (CVRD), which is poised
to start up the first commercial-scale plant using the
technology before the end of this year.
CVRD's $100-million Usinas Hidro Carajas
plant in the Carajas region of Brazil will soon begin refining
copper concentrate from its Sossego Mine, with production
forecast to reach 10,000 tonnes of copper cathode per year.
CESL, a Vancouver, British Columbia, subsidiary of Teck Cominco
Metals Ltd., is providing process design, engineering input and
startup support, said David Jones, chief metallurgist for Teck
CVRD also has plans for a much larger plant
with a capacity of between 200,000 and 250,000 tonnes of copper
cathode per year that will use the CESL approach to process
concentrates from two new mines Salobo and Alemao.
The CESL process is said to offer a myriad of
advantages, ranging from an enhanced environmental profile to
the ability to treat classes of concentrates not suitable for
traditional smelter refining.
One of the process' biggest benefits, Jones
said, is its elimination of the sulfuric acid by-product, which
results in lower production costs and reduced environmental
risk. Smelting copper produces about 3 tonnes of sulfuric acid
for every 1 tonne of copper produced, he explained, and a large
smelter can store only a few days of by-product acid on site.
It must be disposed of regularly and there must be a nearby,
ready market for the acid.
"As a result, smelter economies are tied to
the market for sulfuric acid," Jones said. "The hydromet
process allows the de-linking of sulfuric acid disposal from
Besides lowering any potential environmental
risk, the hydromet process also allows for significant freight
cost savings. Since a smelter must be located to provide
convenient disposal of the acid, it generally is far from the
mine supplying concentrates, which translates to significant
freight costs to transport the concentrates to the smelter plus
the cost of moving the acid for disposal. With the CESL
process, the copper refinery can be located close to whatever
mine is supplying the concentrates, eliminating the freight
costs to ship concentrates as well as those incurred to move
acid for disposal.
Versatility is another key asset of CESL
hydromet, which is capable of refining concentrates that might
not be suitable for smelting using more conventional
technologies. "Hydromet could lead to processing material which
might not have been smelted," Jones said. "There have always
been quite a lot of low-grade concentrates which may not have
been economical to treat." The process can handle concentrates
with a copper content as low as 20 percent, Jones said, whereas
smelters prefer levels closer to 40 percent.
The hydromet process also is well-suited for
processing bulk concentrates that contain more than one metal.
While copper is frequently found in company with nickel, zinc
or even gold, smelters are designed to recover one metal at a
time. Indeed, Jones said that in some cases a penalty is
assessed for contained nickel or zinc in copper smelting.
"Typically, bulk concentrates have held
limited market appeal to smelters because smelters are designed
to recover one metal or another, not both," Jones said. "The
hydromet process unlocks the possibility of processing
previously unprocessable bulk concentrates. Metals can be
recovered simultaneously, which is a huge advantage." CESL is
now in the process of piloting a nickel-recovery circuit for
its hydromet process, he added.
The CESL hydromet process also opens the
possibility of refining so-called "dirty concentrates"-material
that contains deleterious impurities, including mercury and
arsenic, the two most commonly found impurities. Smelters can't
process dirty concentrates, Jones said. "Some mines which were
never developed due to impurities are now developable, because
the impurities are transparent to the hydromet process; they
pose no trouble."
Developing the CESL hydromet process has been
no small task for Teck, which to date has spent more than $100
million on research and development and is now plowing another
$20 million annually into the project.
There are currently 140 employees working on
the project, and Teck has had more than 1,000 students involved
in the effort over the past 12 years, during which the company
has been testing concentrates from all over the world to
fine-tune the process. "We have pretty exhaustive test data,"
Jones said. To run the tests, CESL has been using both a pilot
plant with a capacity to treat about 150 kilograms of copper
concentrate daily and a larger demonstration plant that can
treat up to 5 tonnes of concentrates per day.
While the CESL hydromet refining process
holds significant promise, the program is just now reaching
commercial potential and is not likely to affect copper markets
for some time. "It won't change the supply-demand balance,"
Jones said. "This is a long-term project."