Page 14 - Energize June 2022

NEWS

Upgraded boiler units to meet gas distribution should be as homogenous
as possible,” adds Brook.
new emission regulations a series of electrodes or plates strung
He explains that an ESP is a box with
vertically inside of it. The dust particles
are charged, creating a flow to the
collector electrodes upon which the dust is
abcock has come full circle at a major power station, where it will be upgrading deposited and collected. When these plates
electrostatic precipitators (ESPs) on six boiler units that Babcock designed and built in get full, they are rapped (struck), and all the
Bthe 1980s. dust slides down into the hopper.
Using technology not available at the time, Babcock will bring the boiler units into the Babcock will use computational fluid
2020s, enabling the power station to comply with latest emission regulations of below 50 mg dynamics modelling, which was not
of dust per normal cubic metre (Nm ) of flue gas, essentially halving the impurities. available in the 1980s, to model the gases
3
This power station has provided reliable power to the utility for more than four decades, from the outlet of the boiler into the
ranking as the best-performing and lowest-cost generating station in the utility’s fleet. The precipitator cases, to better understand
boiler was designed to burn coal with a low calorific value and an ash content above 40%. and manage what is happening with the
Producing fly-ash with a low carbon content proved beneficial for the cement industry, which gases under different load conditions
relies on these properties to improve water resistance in cement. and improve dust distribution, thereby
improving dust collection and removal.
To meet the latest emission regulations, a three-part programme is required to enhance the Also included in Babcock’s scope of
total precipitator capability in order to achieve levels of below 50 mg: work is the replacement of the current
• Upgrade and refurbish the SO 3 conditioning plant. wire-type discharge electrodes with
• Change the technology on the ESP’s transformers to convert them into high-frequency sets. modern and more reliable rigid discharge
• Upgrade and refurbish the ESPs to maximise dust collection efficiency to comply with new electrodes. After time, the 12-metre long
legislation. weighted discharge electrode wires have
started to perish, diminishing the electric
Babcock has been awarded the third portion of the programme and will refurbish four (or corona) field, causing the collector
precipitator cases in each boiler beginning in 2023. electrodes to lose efficiency and collect less
Dave Brook, a Technical Director at Babcock, explains that ESPs use an electric charge to dust. The new rigid discharge electrodes,
remove impurities from air or gases through a series of collector and discharge electrodes. which will be manufactured in South Africa,
“Fly ash is a very fine dust found in hot flue gases from coal combustion. It travels through cannot break and will create a more stable
the heat transfer surfaces of the boiler and the air heater, and eventually emerges through corona field, thereby maximising efficiency
the ducting and through electrostatic precipitators. After it is removed and deposited in the of the ESPs.
hoppers below, the fly ash is either removed or sold to the cement industry,” Brook says. Babcock is the lead contractor
“The fine dust in the gas travels a torturous route in the boiler, resulting in areas where responsible for all project management,
there is more dust, and others with less dust. In order for the ESPs to function optimally, the integration, delivery and construction
for the project, and will be working in
partnership with USA-based Babcock &
Wilcox (B&W). B&W owns the technology
of the original design of the precipitators
and will be undertaking the process and
detailed engineering.
As one of the most established and
experienced steam generator and industrial
plant suppliers in Africa, Babcock has
delivered solutions to many of the power
stations in the country. Babcock is present
at several sites undertaking projects that
include high-pressure piping, coal burner
overhauls and mill maintenance.

Contact David Brook, Babcock,
Phone 010 001-0730,
david.brook@babcock.co.za,
www.babcock.co.za

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