|ICESP X CONFERENCE PAPER ABSTRACTS 7C SERIES
Held in Cairns,
Conference on Electrostatic Precipitation (ICESP)
is the official conference of the International Society for Electrostatic
ROD HANSEN AND ROBBIE VAN RENSBURG
3 600 Mw Duvha Power Station situated near Witbank in Mphumalanga Province presents aunique opportunity to make a direct comparison of operating and maintenance costs between electrostatic precipitators (ESP’s) and retrofitted pulse jet fabric filters (PJFF’s). Units 1 to 3 have the ABB Flakt design PJFF’s and Units 4 to 6 have the originally installed Lurgi design ESP’s with 5 field 141 m2/m3/s specific collecting area (SCA). These ESP’s have subsequently been retrofitted with sulphur trioxide flue gas conditioning (SO3 FGC). This comparison is particularly interesting when viewed in the context of the Legislation which compels either a load reduction or an outage in order to avoid contravening particulate emission Limits and this at a time when there is little reserve margin on the total Eskom System. The trade-off between operational costs and the ability to generate MW’s can be complex.
This paper will briefly review some of the early problems experienced with the PJFF’s andmeasures taken to increase bag life, ultimately resulting in a change to a more expensive fabric type. It also reviews some of the day by day operational demands of the ESP’s.
FRANCIS D. FEREDAY, TODD W. FOLMSBEE, JAMES FISHER AND GARY KLEIN
Actual operating results have been used to empirically determine the relationship betweenfabric filter (baghouse) differential pressure and stack gas flow in a reverse gas cleaned fabric filter. Assumptions are made that the tubesheet pressure drop is the sum of the pressure loss across the filter media and the dust cake. The dust cake is comprised of a component that remains on the bag after cleaning and a removable component that accumulates between cleaning cycles. The component that accumulates between cleaning is proportionate to the inlet dust concentration, the filter velocity and the time between cleaning. This relationship was examined with conventional fiberglass filter bags and with filter bags that have an ePTFE membrane laminated to the woven fiberglass. On average, the results show a 41% decrease in fabric filter drag that allowed actual stack gas flow to increase by 5% and baghouse pressure differential to decrease by 39%. Results suggest the lower drag is attributable to improved ash removal from the bag during cleaning and not due to lower resistance through the filter media itself. Maximum electric power generation increased by 2.8% during the peak summer demand period due to the higher gas flow achieved with the ePTFE membrane bags.
Last updated: May 10, 2009.
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