e) Maximum total baghouse pressure drop from inlet flange to
outlet flange with one module cleaning should be 8 in. w.g.
f) Bags are nominally 5 to 6 inches (0.127 to 0.157 m) in diameter
and 10 to 12 ft (3.04 to 3.66 m) long.
g) Space cage wire according to fabric filter supplier's
h) Woven glass or felted glass fabric can be used. An economic
analysis should be performed based on initial cost and expected bag life.
i) The design criteria comments for the reverse air collector
hoppers, access, inlet and outlet plenums, flue gas temperature control,
manufacturer's field representatives apply to the pulse jet collector.
Performance. The pulse jet collector has demonstrated performance
equal to that of the reverse air collector; the same comments apply to both.
Construction. The casing design requirements are the same as for
the reverse air collector. The module outlets are commonly provided with low
leakage butterfly type dampers in lieu of the poppet dampers. A walkway
should be provided in the plenum above the tube sheet of sufficient height to
allow for bag replacement.
Fabric Filter Media Types
Woven Glass. Woven fiberglass bags have established a good
operating record for continuous operation up to 500 degrees F (260 degrees C)
with surges to 550 degrees F (287.5 degrees C). These bags are coated with a
finish to provide increased chemical resistance to acid attack and improve
abrasion resistance between glass fibers for longer life. The designer shall
carefully evaluate temperature limitations, abrasive characteristics, and
chemical resistance as all affect maintenance and operational costs.
Felted Glass. At the present time there is one major manufacturer
of this fabric. Early experience was promising. However, the cost of this
fabric is high, and some bonding problems with the felted material have
occurred. This fabric has the same temperature limitations as the woven glass
bags. This fabric is fairly stiff and is only used on pulse jet applications.
Teflon. Teflon fabric is also quite expensive and shrinkage
problems have been experienced at temperatures at approximately 400 degrees F
(205 degrees C).
Other Fabric Filter Media. Other media types such as Nomex and
Acrylic are not suitable for fly ash applications due to the temperature
limitations of the fabric. Nomex is rated for 400 degrees F but deteriorates
in the presence of sulfur dioxide. Current filter technology should be
investigated with each project to make the best possible selection.