Baghouses should be operated within a reasonable design A/C ratio range. For example,
assume a permit application was submitted indicating the use of a reverse-air cleaning baghouse
using woven fiberglass bags for reducing particulate emissions from a small foundry
furnace. If the information supplied indicated that the baghouse would operate with an A/C
ratio of 6 (cm3/sec)/cm2 [12 (ft3/min)/ft2] of fabric material, you should question this information.
Reverse-air units should be operated with a much lower A/C ratio, typically 1 (cm3/sec)/
cm2 [2 (ft3/min)/ft2] or lower. The fabric would probably not be able to withstand the stress
from such high filtering rates and could cause premature bag deterioration. Too high an A/C
ratio results in excessive pressure drops, reduced collection efficiency, blinding, and rapid
wear. In this case a better design might include reducing the A/C ratio within the acceptable
range by adding more bags. Another alternative would be to use a pulse-jet baghouse with the
original design A/C ratio of 6 (cm3/ sec)/cm2 [12 (ft3/min)/ft2] and use felted bags made of
Nomex fibers. However, Nomex is not very resistant to acid attack and should not be used
where a high concentration of SO2 or acids are in the exhaust gas. Either alternative would be
more acceptable to the original permit submission.
Typical air-to-cloth ratios for baghouses used in industrial processes are listed in Tables 1
and 2. Use these values as a guide only. Actual design values may need to be reduced if the
dust loading is high or the particle size is small.When compartmental baghouses are used, the
design A/C ratio must be based upon having enough filter cloth available for filtering while
one or two compartments are off-stream for cleaning.
Table 1. Typical A/C ratios [(ft3/min)/ft2] for selected industries
Table 2. Typical A/C ratios for fabric filters used for control of particulate emissions from industrial boilers.
assume a permit application was submitted indicating the use of a reverse-air cleaning baghouse
using woven fiberglass bags for reducing particulate emissions from a small foundry
furnace. If the information supplied indicated that the baghouse would operate with an A/C
ratio of 6 (cm3/sec)/cm2 [12 (ft3/min)/ft2] of fabric material, you should question this information.
Reverse-air units should be operated with a much lower A/C ratio, typically 1 (cm3/sec)/
cm2 [2 (ft3/min)/ft2] or lower. The fabric would probably not be able to withstand the stress
from such high filtering rates and could cause premature bag deterioration. Too high an A/C
ratio results in excessive pressure drops, reduced collection efficiency, blinding, and rapid
wear. In this case a better design might include reducing the A/C ratio within the acceptable
range by adding more bags. Another alternative would be to use a pulse-jet baghouse with the
original design A/C ratio of 6 (cm3/ sec)/cm2 [12 (ft3/min)/ft2] and use felted bags made of
Nomex fibers. However, Nomex is not very resistant to acid attack and should not be used
where a high concentration of SO2 or acids are in the exhaust gas. Either alternative would be
more acceptable to the original permit submission.
Typical air-to-cloth ratios for baghouses used in industrial processes are listed in Tables 1
and 2. Use these values as a guide only. Actual design values may need to be reduced if the
dust loading is high or the particle size is small.When compartmental baghouses are used, the
design A/C ratio must be based upon having enough filter cloth available for filtering while
one or two compartments are off-stream for cleaning.
Table 1. Typical A/C ratios [(ft3/min)/ft2] for selected industries
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