Wet coal is obviously less efficient as fuel. But, most importantly,
dust from open stockpiles can travel on air currents to coat
surrounding landscape with a fine black film. And, water running
through open-air stockpiles carries contaminants to aquifers.
Far-sighted organizations and countries are requiring their fuel
stockpiles to be covered, so besides protecting the environment,
it makes economic sense.
USING DOME STRUCTURES
Domes are known to be efficient and effective in covering large
expanses of space. They are used for many different bulk
materials. The efficiency of domes comes in part from using
geometry to create strength and stiffness. The curvature in
domes permits these slender and lightweight structures to span
up to 300m.
Because coal is often transported long distances, and stocked
at various points between the mine and the end-user, coal piles
can come in variety of shapes: longitudinal piles
frequently found at ports, ring blending beds at
large power plants, and simple conical or
irregular piles common at industrial plants.
The shape of the pile and the available space
dictate the shape of dome that is built to
Geometrica has developed unique
technology that realizes the efficiency of
domes even when the stockpiles are of any
shape, whether circular, longitudinal or freestyle.
With this technology, domes may sit
directly on a ground-level foundation, or sit on
a concrete wall to contain additional material.
Also, domes can be built over existing piles
with little or no down-time allowing stocks to
continue operating while they are being covered. And the
effectiveness comes in meeting (and exceeding) each individual
Next we look at some cases in point for domes built by
Geometrica addressing various customers’ needs.
When the largest power producer in Taiwan, Taiwan Power Co.,
was expanding its capacity near Kaohsiung, it had to store
720,000 tonnes of coal. That the piles would be open-air was
never considered, as Tai Power's policy is quite strong in
environmental protection. But the decision on what type of
cover to use was subject to years of study and engineering.
In addition to meeting their basic functional requirement of
covering the coal, the consulting design professionals, Gibsin
Engineering, specified four dome-silos to be designed for
typhoon winds of up to 94m/s and resist the highly corrosive
environment of its location (industrial
adjacent to the ocean). Tai Power added
the requirement of a tight schedule to be
set in coordination with the installation of
the stacker/reclaimer equipment.
Joining forces with Triumstar
International of Taiwan, Geometrica
proposed galvanized steel space-frame
domes to be clad with aluminium sheeting.
It also proposed conducting wind
simulations and tunnel testing to
determine the appropriate design loads
under the specified wind conditions, and
an accelerated construction schedule with
just-in-time deliveries. All the while,
competing with alternative solutions, both
local and foreign. Tai Power awarded the contract to
Geometrica and Triumstar.
The four circular domes were built simultaneously in about
one year after site work started. They feature skylights, natural
and forced ventilation, firefighting provisions, lightning protection,
external platforms and an extensive network of catwalks.
In Ras Al Kahimiah, UAE, the eponymous company needed to
store coal for its power plant. This structure was also close to
the ocean, but the environment is not as corrosive as that of
Kaohsiung. A galvanized steel structure with galvanized and
painted cladding was selected. Galvanized steel allows for a
stronger, lighter, and corrosion-resistant dome resulting in
longevity and reduced maintenance.
Following the stringent European Environmental Standards,
RAK Cement was also concerned about dust emissions from the
coal stockpiles. The area is exposed to winds of up to 140kph.
The domed structure would protect the environment and
community from the dust emissions and protect the coal
stockpile from wind and rain. Another concern, as with all coal
stockpiles, is the high risk of conflagration of coal. The structure
needed to be designed so that the restacker/reclaimer could
keep the coal aerated and dust confined. This equipment could
run the length of the longitudinal dome.
They also had ‘space’ restraints. Geometrica’s proprietary
engineering and fabricating software created the end product —
a barrel vault of 140m long, 40m wide, and 20m tall with two
vertical walls at either end of the building, sitting on top of a
rectangular concrete bin, also designed by Geometrica. The
domed silo covers a 30,000-tonne coal stockpile.
Jacksonville Electric Authority
In Jacksonville, Florida, twin fuel/coal storage domes were
designed and built as part of the Clean Coal Technology
Demonstration Program that was charged with developing
“innovative, environmentally friendly coal utilization processes
for the world energy marketplace.”
Because of its location to adjacent wetlands, the development
of this project included consulting with various community and
environmental groups, with the end result being that emissions
limits are significantly lower than EPA regulations.
Solid fuels are stored in the two 400ft diameter by 140ft-high
all-aluminium domes, each having a capacity of 60,000 tonnes.
These domes serve to keep the fuel dry and to reduce fugitive
dust emissions as well as storm water runoff. As per the
National Fire Protection Association recommendations, these
domes are built with internal cladding to minimize coal dust
Moctezuma Cerritos Cement Plant
This plant had a need to store coal for kiln fuel in a conical pile.
Stacking in such pile shape produces large amounts of dust, and
the dome shape was selected to minimize the entrapped air
volume and thereby prevent the suspension of dust in the air.
Also, the cladding was affixed on the inside of the structure to
avoid coal dust to accumulate
on the structural members.
In each of these, as in other industrial storage domes,
protecting employees, the community, and the stockpiles
are all the major considerations. Depending
on location, other factors such as high winds, rain,
maintenance issues and available space will dictate the
type of storage dome that is needed. But more often than
not, nowadays, a storage dome is the answer for each
of these considerations.