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June 2015
AFRICAN FUSION
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Above: Afrox’s CSP solutions have been
supplied to the Bokpoort parabolic trough
plant, which requires 20 000 km of pressure
piping to be welded, along with the support
structures for a solar field consisting of
588 600 m² of mirrors.
Above right: Afrox’s modular and portable
skid-based container system consists of a
series of containerised bulk LPG storage
tanks along with all of the evaporators
necessary to supply the fuel for the initial
salt melt.
Centre right: The Bokpoort CSP plant has
a molten salt storage system to provide
over nine hours of generation capacity after
sunset or during cloudy weather.
Right: Onsite pipe welding is done using the
TIG process for root runs followed by fill and
capping passes using low hydrogen MMA
electrodes.
In order to ‘blanket’ the thermal storage medium,
Afrox has developed a custom-designed nitrogen
storage and reticulation network comprising a
pressure swing absorption (PSA) nitrogen generation
system backed up by a high-pressure liquid nitrogen
storage and supply system.
toprevent thehot salt fromreactingwith
moisture and atmospheric gases. “Afrox
has developed a custom-designednitro-
gen storage and reticulation network to
provide the inert atmosphere necessary
for the salt storage tanks, the expansion
tanks and the high temperature fluid
boiler. The system comprises an on-site
nitrogen production system, using pres-
sure swing absorption technology (PSA),
backed up by a high-pressure liquid
nitrogen storage and supply system,”
says Pieterse.
Afrox’s parent, the LindeGroup Engi-
neering division, is supplying the on-site
nitrogen generating facility, while the
cryogenic storage facility and custom
designed nitrogen reticulation system
has been installed by Afrox. A long-term
nitrogen supply agreement between
Afrox and Bokpoort CSP has been con-
cluded to ensure an uninterrupted and
reliable nitrogen supply to the project.
Bulk liquid supply is ideal for ap-
plications where flexibility is required
or uneven demand patterns are preva-
lent. Once the demand at the CSP plant
has been established, however, on-site
nitrogen generation or a combination of
bulk and on-site supply are options that
can be considered.
Through the Bokpoort CSP project,
Afrox has demonstrated its ability to
design and deliver reliable systems and
services for both the construction and
operation phases of CSP projects. “Our
supply network covers almost every
region in South Africa, but it becomes
increasingly less cost effective as the
distance from a source increases. We
have already opened a branch in Up-
pington and are in the final stages of
planning for a branch in Katu to support
this growing industry,” reveals Afrox’s Pi-
eterse. “When you consider that several
of coal fired plants may be adding CSP
systems to improve their efficiencies,
we anticipate up to 22 CSP plants being
built by 2030.
“And Afrox is well positioned to sup-
port this futurepotential. Basedonan in-
depthunderstandingoftherequirements
and challenges during the construction
phase of CSP projects, along with our
knowledge of the ongoing operating and
maintenance needs, we have developed
a comprehensiveCSPsolutions offering,”
Pieterse concludes.