Coal intake, storage, export and import: a single-source solution
The logistics of storage and reclaim of the vast volumes of coal
required annually to fuel the bulk of the world’s energy demand
represents a considerable challenge at each stage in the supply
chain. Australia alone exports some 250mt (million tonnes),
including both steam and metallurgical coal; whilst this is shipped
worldwide, the lion’s share goes to Asia, including substantial
volumes to China. Although China is a net importer, the bulk of
demand is satisfied from its own mining operations.
Nevertheless, logistical challenges remain with pressure on
railroads and ports both for deep sea, coastal and barge freight.
Economical and efficient solutions for the coal miner and
consumer are critical to deliver the scale of performance
required and the level of environmental protection demanded.
PERFORMANCE AT THE MINE SITE
At the mine site, after crushing and screening, the coal must be
blended to ensure a controlled quality from a mix of different
sources within the mine complex. Circular storage systems with
bridge reclaimers provide homogenization by generating a
layered stockpile using a radial and luffing boom stacker working
continuously in a circular motion, raising incrementally after each
pass such that at any point in the stockpile length a section
through will yield layers of every quality.
Using the bridge reclaimer with oscillating harrows covering
the full inclined face of the stockpile, the reclaimer recovers
elements of every layer, ensuring the final output is a mix of all.
Working continuously around a central column, the circular
storage provides a constant uninterrupted output to the
Fast train loading at the preparation plant is essential tospeed
the transfer of coal between mine site and export terminal.
For this purpose, longitudinal strategic stockpiles are
preferred to stack out the coal from the washery into discrete
sections for rapid recovery by high performance portal
reclaimers. The twin boom reclaimer from SCHADE, part of the
international AUMUND Group, can work at rates to 4,000tph
(tonnes per hour) per unit, transferring the coal from the live
stockpile to the train loading hoppers, allowing rail wagons to be
loaded rapidly, on the move, avoiding any delays.
EFFICIENCY AT THE POWER UTILITY
At the power plant, the situation is reversed, requiring fast
discharge of deep sea vessels or wagon rakes. Particularly in the
case of Capesize vessels, fast unloading is critical to minimize the
vessel time in port and eliminate any risk of high demurrage
charges. High-performance circular storage systems are able to
receive the coal direct from either continuous or grab ship
unloaders with stacking rates to 5,000tph per storage.
Enclosed circular storage offers many advantages, particularly
for power plants, by eliminating any risk of wind-blown fugitive
dust and with the minimum footprint per tonne. It also has a
relatively attractive appearance to minimize visual intrusion.
Using the lightweight geodesic dome, the enclosure structure
supports no machinery load and can be mounted directly to the
stockpile retaining walls. By fully enclosing the stockpile, there is
no risk of runoff water contamination; particularly important in
ports and terminals.
At the Kemen Electric Power (China) for example, two
storage facilities are linked to the powerplant complex, including
twin gantry crane-type grab ship unloaders, each able to recoveraround 2,000tph in ideal digging conditions. Each of the two
circular storage facilities can hold 260,000m3 of coal, and both
include a radial stacking conveyor as well as a semi-portal style
circular reclaimer. These are both mounted to the central
column which also supports the head of the incoming belt
conveyor. SCHADE has now delivered some 50 circular storage
systems of 120 metres diameter, helping to fuel China’s insatiable
demand for energy. With these installations, the company covers
the demands both of the mine operator and power utility or
steel works as well as each stage of the handling process
in-between, including the export and import terminals.
These huge systems are not required in every project or
business sector. The storage experts from Herne, Germany,
therefore offer similar technology scaled down to suit the
demands of the cement industry for kiln fuels handling both coal
and petcoke plus such as the paper, chemical and similar
industries for boiler fuels and raw materials also. As of today
approximately 600 reference installations around the world
demonstrate the reputation of SCHADE storage solutions; operating
in continuous process applications where availability is hypercritical..
OPERATING IN EXTREME WEATHER CONDITIONS
There are alternatives available, particularly for facilities that operate
in extreme weather conditions, such as on the Great Lakes where the port
may be icebound for a large part of the year and where the ambient
temperatures range from +30°C to –30°C. In these conditions, the
rotary discharge machine or paddle feeder is an attractive solution.
Mounted beneath the stockpile the rotary discharge machine is
unaffected by weather and may recover coal from an enormous
stockpile using dozers to bring the coal to the extractors. An excellent
example is the American Superior Midwest Energy Terminal in Wisconsin
USA (see picture above).
Coal is delivered mainly by rail wagon from the mines of the Powder
River Basin year round and must be accumulated in the winter
months when the port is ice bound. The terminal provides 5mt
of open coal storage for recovery by a total of nine AUMUND
rotary discharge machines.
The BEW-BL rotary discharge machine comprises a rotating
paddle wheel mounted to a block frame, carried on rails, that
travels beneath the stockpile, recovering coal from any point to
a troughed belt conveyor below at a controlled rate proportional
to the paddle wheel speed.
At the Midwest Energy Terminal, machines work in sets of
three with each set functioning as a single unit with a combined
peak capacity of over 10,000tph. Using all three sets of
discharge machines together, coal of differing qualities may be
blended to the reclaim conveyor. Installed in 1975, and at peak
times running 24/7, they remain today among the highest
performing reclaimers of this type worldwide and are a fine
testament to the AUMUND product design philosophy.
FLEXIBLE MOBILE SOLUTIONS
Building a new terminal with permanent port infrastructure
represents a significant long-term investment. Nevertheless
short-term market positions exist, and operators may wish to
take advantage of particular opportunities and, in this situation,
the professional mobile stackers and shiploaders offered by
B&W are an economical option.
This is amply demonstrated in a recent project at the port of
Jorf Lasfar in Morocco where two StormajorTM mobile stackers
are employed to stockpile coal imported by grab cranes from
small bulk carriers (see picture below, and on the front cover of
this issue of DCI). The grabs discharge to trucks and the trucks
move the coal inland to the stockyard for stacking, using the
StormajorTM; and final distribution.
Mobile solutions are flexible and fast track with minimum
THE AUMUND GROUP
The AUMUND Group, headquartered in Germany along with its
subsidiary SCHADE Lagertechnik acquired in 2001, has a long
and illustrious history in the mining and use of steam and
metallurgical coals going back to 1879 and the early days of coal
mining in the Ruhr. AUMUND and SCHADE equipment will be
found from the coal preparation plant at the mine site through to the
export terminal and power plant or steel works. Back in 1991
AUMUND acquired the Louise Company of Germany
including all of the original Louise products such as the CentrexTM silo
discharger and the rotary discharge machine, now known as the
BEW-BL and fully integrated to the AUMUND Fördertechnik product
range. To complete the picture, B&W Mechanical Handling Ltd. was
acquired by AUMUND back in 2002 bringing the SamsonTM surface feeder
plus mobile stacking and ship loading solutions to the group portfolio
adding the benefit of performance with flexibility where permanent
fixed solutions would not be viable.