United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-87/009 May 1987
&ER& Project Summary
Evaluation of Fabric Filter on
Boiler 108 at the Naval
Amphibious Base,
Little Creek, VA
J. M. Foster, J. C. Mycock,
J. W. Richardson, and J. D. McKenna
The operating characteristics of the
reverse-air baghouse controlling emis-
sions from Boiler 108 at the Naval Am-
phibious Base (NAB), Little Creek, VA,
were determined via collection of data
(by Navy personnel) on boiler and bag-
house operation (hours of operation,
coal feed rate, steam load, air load, bag-
house inlet temperature, and baghouse
module pressure drop), and periodic in-
spection and testing of selected bags.
Tests of physical characteristics of
the fiberglass bags revealed normal de-
terioration of fabic strength with in-
creasing time of exposure to flue gas.
Fill fibers were more affected than warp
fibers. A long plateau in bag life was
observed; fabric characteristics after
1,500 hours of actual operation and
after 7,600 hours did not differ greatly.
Statistical analyses of fabric test data
indicated effects on fabric due both to
length of exposure time and position in
the baghouse, and interaction of those
effects. Other analyses indicated that
exposure time was the dominant effect.
Operating costs for reverse air and in-
duced draft fans were calculated for the
years 1983,1984, and 1985.
This Project Summary was devel-
oped by EPA's Air and Energy Engineer-
ing Research Laboratory, Research Tri-
angle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Boiler 108 at the Naval Amphibious
Base (NAB), Little Creek, VA, is stoker-
coal-fired, rated at 90,000 Ib/hr* of
steam but usually operated at 40,000-
60,000 Ib/hr. The baghouse controlling
participate emissions from Boiler 108 is
a reverse-air-cleaned Griffin Environ-
mental fabric filter employing 3 x 1 twill
fiberglass bags, and was studied from
its August 1983 start-up until Septem-
ber 1985, for the purpose of defining its
performance and operating characteris-
tics. The Navy collected data on boiler
and baghouse operation and mainte-
nance, and ETS, Inc. performed physical
tests on bags removed periodically
from the baghouse in order to monitor
wear on the bags and predict bag failure
and expected life.
Project Design
The project included:
• The collection of boiler operating
data.
• The collection of baghouse operat-
ing data.
• The calculation of fan power con-
sumption.
• The calculation of cleaning power
consumption.
• Graphic representation of relation-
ships between parameters.
•Users more familiar with the metric system may
use the conversion table at the end of this Sum-
mary.
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• Identification of problems of bag-
house operation and maintenance.
Navy personnel at the steam plant
collected operating data for the boiler
and baghouse. ETS laboratory person-
nel examined test bags for holes, abra-
sion, dust cake characteristics, and
other gross visual attributes. Randomly
selected bags were also examined
under magnification. Test bags were
subjected to the following laboratory
tests to determine fabric characteristics
and strength:
Permeability (as received and after
vacuuming to 10 and 30 in. of oil).
Organic Content (loss on ignition).
Tensile Strength (warp and fill fibers).
Mullen Burst.
MIT Flex (warp and fill fibers).
Fabric weights as received and after
vacuuming to 30 in. of oil also were
recorded.
Test bags were taken from near the
centers of modules (representative av-
erage bags) and from locations near
module doors (possible worst-case
bags, in the event of leakage around
doors).
Description of Baghouse 108
Design specifications for the emis-
sions control system included:
Baghouse Flow 49,800 acfm
Tempera- 350°F (maxi-
ture mum 500°F)
Pressure 7 in. h^O
drop (AP) (dirty)
Full load
dust load-
ing 1,000 Ib/hr
Gas-to- 2.5 max
cloth (G/C) (during
ratio cleaning)
Collection 99.9% (by
efficiency weight)
Coal—Bituminous with maximum
1.5% sulfur (S).
Bags—Woven fiberglass with a coat-
ing of Teflon B for 10% add-on
weight, or a combination of silicon
graphite and Teflon. Fabric weight of
14 oz/yd2 minimum, with a permeabil-
ity of 60 ft/min. Bags were rated for
maximum operating temperature of
500°F. Bags were 8 in. in diameter by
25 ft long.
Bag spacing inside the baghouse was
2 in. Anti-collapse rings were sewn
into the bags at 4- or 5-ft intervals.
Baghouse 108 had an optional pres-
sure drop-triggered cleaning control
(set at 6 in. H20) but was normally
cleaned twice every 24 hours on a tim-
ing cycle. During the winter, cleaning
might occur three times per 24-hour pe-
riod.
Baghouse 108 was equipped with an
automatic, pressurized fly ash handling
system.
Description of Test Bags
Three new bags were evaluated, as
well as three bags exposed to flue gas
but never actually in service in the bag-
house. Five series of nine bags each,
removed from the baghouse after vary-
ing hours of operation, were also
tested:
Series
Hours of Operation
I
IV
V
378
513
1189
1504
7602
Boiler and Baghouse 108 were oper-
ated intermittently, and the bags re-
mained in the baghouse during down-
time. The hours of operation given
above do not include downtime, but it
was assumed that downtime exposure
results in some additional stress to the
bags, although the type and amount
were not quantified.
Results of an Inspection of
Baghouse 108
Approximately 2 weeks after start-up
of Baghouse 108, ETS personnel con-
ducted a thorough inspection of each
module, noting conditions such as ash
build-up, holes in bags, and acid attack.
There was evidence of condensation
and acid attack, and dust was observed
on the outside of some bags, suggest-
ing dirty-side to clean-side leakage in-
side the baghouse.
Results of Fabric Tests
The woven fiberglass bags, with
about 5% organic finish according to
loss-on-ignition test results, were 8 in.
in diameter by 25 ft long. Visual and mi-
croscopic examination revealed, in gen-
eral: abrasion along the seam, some
holes, pearling, and fill fibers dirtier
than warp fibers.
Fabric weights varied little from one
series of test bags to another.
Table 1 shows the average results of
all fabric tests, expressed as percent-
ages of new bag test values. It ap-
peared, despite some low values in fab-
ric strength measurements (e.g.,
breakage of fill fibers at under 1 00 flexes
in the MIT flex test), that fabric strength
remained on a plateau. As of July 1986,
the original bag set was still in place,
and no massive bag failures had oc-
curred.
Visible emissions were not a problem
with Baghouse 108. They were meas-
ured at under 20% during acceptance
tests at full boiler load in 1983, and re-
mained low as of July 1986.
Effect of Position in the
Baghouse and Length of
Exposure on Fabric Test Values
ETS personnel performed a statistical
analysis of data including values from
fabric tests, position in the baghouse,
and length of exposure time, in order to
gauge the effects of baghouse position
and exposure time on fabric test results.
Generally, both baghouse position and
exposure time affected fabric test re-
sults, and there was interaction be-
tween those effects.
Although statistical tests indicated
that there were separate (but interact-
ing) effects on fabric test values due to
length of exposure time and postition in
the baghouse, it was found that the ef-
fect due to position probably was not
the major reason for differences be-
tween fabric test values. A more obvi-
ous effect was due to length of expo-
sure time on fabric characteristics.
Comparing fabric test values showed
that permeability declined steadily with
exposure time, as did values in tests of
fabric strength (Mullen burst, tensile
strength, and MIT flex), particularly for
fill fibers.
Calculation of Fan Power Costs
Operating costs for the induced draft
(I. D.) and reverse air (RA) fans were cal-
culated using hours of operation during
1983,1984, and 1985, and Virginia Elec-
tric and Power Co. (VEPCO)-quoted cost
of electricity.
/. D. Fan Data
Baghouse 108 inlet average gas flow
at full boiler load (data from acceptance
test, 12/10/83) was 47,561 acfm <&> 371°F.
I. D. fan power cost was calculated
using the representative inlet volume of
50,000 acfm (fv 370°F. Baghouse 108
flange-to-flange pressure drop normally
ran 2-4 in. H20, according to NAB per-
sonnel.
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1 Tmble 1. Summary of Physical Characteristics of Test Bags
(Expressed as % of New Bag Values)
Series
1
II
III
IV
V
Date Pulled
09/07/83
11/08M3
01/24/84
after 05/15/84
after 09/27/85
Date
Rec'd
09/09t83
11/18/83
01/26/84
06/08/84
10/24/85
Actual
Operating
Time, hr
378
513
1189
1504
7602
Permeability
As Vacuum
Rec'd 10 in. 30 in.
7
7
6
8
7
34
23
37
42
27
46
36
54
67
45
Mullen
Burst
96
90
86
70
68
Tensile
Strength
Warp Fill
99
89
91
63
57
105
87
91
61
62
MIT Flex
Warp Fill
190
101
75
23
28
94
54
45
13
14
Loss
on
Ignition
89
82
93
89
109
RA Fan Data
An RA gas flow of 10,000 acfm was
assumed. RA fan power costs were cal-
culated for pressure drops across the
RA fan of 0.5, 1.0, and 1.5 in. H2O.
Baghouse 108 Operating Hours
Operating hours for Baghouse 108
were: 1983—1519 hours, 1984—4081
hours, and 1985—2002 hours (as of the
last bag pull).
Cost of Electricity for NAB,
Little Creek, VA
The April 1986 quotation by VEPCO
for industrial power cost in Norfolk, VA
(schedule 6, Virginia jurisdiction) was
$0.045446/kWh.
Metric Conversions
Readers more familiar with the metric
system may use the following values to
convert the nonmetric units used else-
where in this Summary.
Nonmetric Times Yields Metric
acfm
°F
ft
ft/min
in.
in. H20
in. (vac)
Ib/hr
oz/yd2
0.000472
5/9(°F-32)
0.305
0.00508
0.0254
0.249
3.38
0.000126
0.0339
am3/s
°C
m
m/s
m
kPa
kPa
kg/s
kg/m2
Fan Power Costs
System AP,
in. H20
2
3
4
1983
$1350
2025
2700
1984
$3627
5440
7253
1985
$1779
2669
3558
1983
$ 67
135
202
1984
$ 181
363
544
1985
$ 89
178
267
RAAP,
in. H2O
0.5
1.0
1.5
Assuming round-the-clock baghouse
operation for 50 weeks a year and a vol-
ume of 50,000 acfm with the baghouse
operating at 4 in. H2O pressure drop, the
I. D. fan power cost would be just under
$15,000 per year, and each inch of pres-
sure drop would cost over $3,700 per
year
Conclusions
Baghouse 108 performed well in con-
trolling paniculate emissions from the
coal-fired boiler it serves. The original
set of fiberglass bags, with very few re-
placements, remained in service 3 years
after start-up.
Joyce M. Foster, John C. Mycock, John W. Richardson, and John D. McKenna
are with ETS, Inc.. Roanoke. VA 24018-4394..
Dale L. Harmon is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of Fabric Filter on Boiler 108 at the
Naval Amphibious Base, Little Creek, VA," (Order No. PB 87-171 286/AS;
Cost: $13.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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U S EN¥IR PROTECTION ASENCY
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