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Reducing Power Station Emissions With FGD
Cyclones
Automated gypsum dewatering
cyclone distributor. |
Acknowledged for its contribution to local
leading cyclone technology, Multotec Process Equipment is at
the forefront of flue gas desulphurisation (FGD) scrubbing
systems both locally and internationally.
Through its research and development department and test
facilities, Multotec has analysed and tested various
reinforced designs and flow control methods in order to cope
with the change in the operating conditions when moving over
from standard coal fired power stations to the more
demanding brown coal fired equivalent. Through continually
improving the materials of construction and the performance
criteria of its FGD cyclone range, Multotec has ensured that
these units are able to perform at elevated temperatures and
pressure.
The company has the ability to offer polyurethane, rubber
and ceramic materials of construction, together with
composites; all manufactured in house. By using a variety of
materials of construction, Multotec can provide a range of
wear solutions, allowing for optimum flexibility in terms of
all mineral sectors, and also FGD.
Flue gas desulphurisation is the chemical process to remove
sulphur oxides from the flue gas at coal-burning power
plants. Ninety percent of the FGD systems use limestone or
lime as the absorbent. As the flue gas comes into contact
with the slurry of calcium salts, sulfur dioxide (SO2)
reacts with the calcium to form hydrous calcium sulfate or
gypsum which is used in the manufacture of wallboard.
Recent trends in the technology development of the FGD
systems, as well as the stringent manufacturing
specifications of power stations, have called for fewer
numbers of larger capacity cyclones in order to optimise
plant efficiencies and provide more economically viable
installations.
The Multotec cyclones used for primary dewatering can be
designed to separate a stream rich in the smaller size
solids for returning to the absorber, while allowing the
larger size gypsum solids to leave the system as a
byproduct. Multotec supplies into both the primary and the
secondary dewatering device stations to various forms of
construction regulations.
Segregating the unreacted ultra fine limestone to the
overflow stream and returning this stream to the FGD process
also allows the FGD system to maintain higher levels of
limestone in the absorber slurry than in the byproduct
solids. This, in turn, allows the process to maximise SO2
removal while still achieving high overall limestone
utilisation. It also allows for the removal of undesirable
materials such as gypsum fines, inerts, fly ash, and
chlorides.
A number of devices such as vacuum filters and centrifuges
are used for final dewatering of the FGD byproduct solids,
in order to lower the solids moisture content below what can
be achieved with a cyclone or thickener alone. However, in
the return line of these products, the Multotec cyclones are
again used for waste water recovery to the waste water
management system on the plant.
Multotec continues to develop products for the mining,
minerals beneficiation and power generation industries that
have a proven reputation in extended wear life and process
reliability, with the latest addition to its FGD range being
no exception.
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