Page 96 - Air Pollution Control Engineering

02_chap_wang.qxd 05/05/2004 12:40 pm Page 76
76 Lawrence K. Wang et al.

Table 7
Comparison of Calculated Values and Values Supplied by the Permit Applicant for
Fabric Filters
Process Calculated value Reported
variables (example case) a value
Continuous monitoring of system
pressure drop and stack opacity Yes —
Emission stream temp. range b 365–415°F —
Selected fabric material Fiberglass or Teflon TM —
Baghouse cleaning method Mechanical shaking, reverse-airflow, pulse jet —
A/C ratio 2.5 ft/min for mechanical shaking
or reverse air; 5 ft/min for pulse jet —
Baghouse configuration Negative pressure —
a Based on the municipal incinerator emission stream.

5.5. Filter Bag Replacement
The cost of replacement bags is obtained from Eq. (12):
RB [ L]
C = C + C CRF B (12)
B
where C is the bag replacement cost ($/yr), C is the initial bag cost ($), C is the bag
RB B L
replacement labor [$ (C = $0.14A )], and, CRF is the capital recovery factor, 0.5762 (indi-
L nc B
cates a 2-yr life, 10 % interest). Because the bag replacement labor cost is highly variable,
2
a conservative high cost of $0.14/ft of net bag area has been assumed (8).
6. MANAGEMENT

6.1. Evaluation of Permit Application
One can use Table 7 to compare the results from this section and the data supplied
by the permit applicant (13). The calculated values are based on the typical case. As
pointed out in the discussion on fabric filter design considerations, the basic design
parameters are generally selected without the involved, analytical approach that char-
acterizes many other control systems. Therefore, in evaluating the reasonableness of
any system specifications on a permit application, the reviewer’s main task will be to
examine each parameter in terms of its compatibility with the gas stream and particu-
late conditions and with the other selected parameters. The following questions should
be asked:
1. Is the temperature of the emission stream entering the baghouse within 50–100°F above the
stream dew point?
2. Is the selected fabric material compatible with the conditions of the emission stream (i.e.,
temperature and composition) (see Table 3)?
3. Is the baghouse cleaning method compatible with the selected fabric material and its con-
struction (i.e., material type and woven or felted construction) (see Section 4.3 and Table 6)?
4. Will the selected cleaning mechanism provide the desired control?
5. Is the A/C ratio appropriate for the application (i.e., type of dust and cleaning method used)
(see Table 4)?