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emission stream temperature above the dew point and insulating the baghouse should
eliminate the need for stainless steel.
4.6. Design Range of Effectiveness

Awell-designed fabric filter can achieve collection efficiencies in excess of 99%,
although optimal performance of the system may not occur for a number of cleaning
cycles as the new filter material is “broken in.” The fabric filter collection efficiency
depends on the pressure drop across the system, component life, filter fabric, cleaning
method and frequency, and the A/C ratio (13,14,26).
Performance can be improved by changing the A/C ratio, using a different fabric, or
replacing worn or leaking filter bags. Collection efficiency can also be improved by
decreasing the frequency of cleaning or allowing the system to operate over a greater
pressure drop before cleaning is initiated. Section 5.2 will discuss the above filtration
performance parameters in detail.

5. OPERATION

5.1. General Considerations
Many times, optimization of the fabric filter’s collection efficiency occurs in the
field after construction. The following discussion does not pertain to the preliminary
design of the fabric filtration control system; however, the information presented
should be helpful in achieving and maintaining the desired collection efficiency for the
installed control system.
5.2. Collection Efficiency

To discuss fabric-filter “collection efficiency” is somewhat of a misnomer because
a properly operated system yields very constant outlet concentrations over a broad
range of inlet loadings. As such, the system really does not operate as an efficiency
device—meaning that the performance of a fabric filter is not judged by the percent
particulate matter (PM) reduction from initial PM concentration. Outlet concentrations
are not a strong function of inlet loading. Typical outlet concentrations range between
0.001 and 0.01 g/dscf, averaging around 0.003–0.005 g/dscf. However, the term “col-
lection efficiency” applies to a fabric-filter system when describing performance for a
given application. The above given outlet concentration usually corresponds to very
high collection efficiencies (17).
Awell-designed fabric filter can achieve collection efficiencies in excess of 99%,
although optimal performance of a fabric-filter system may not occur for a number of
cleaning cycles, as the new filter material achieves a cake buildup. The fabric-filter
collection efficiency is related to the pressure drop across the system, component life,
filter fabric, cleaning method and frequency, and A/C ratio. These operating parameters
should be modified to meet the required fabric filter performance. Modifications to
improve performance include changing the A/C ratio, using a different fabric, replacing
worn or leaking filter bags, and/or modifying the inlet plenum to ensure that the gas
stream is evenly distributed within the baghouse. Collection efficiency can also be
improved by decreasing the frequency of cleaning or allowing the system to operate
over a greater pressure drop before cleaning.