EPA-600/2-76-168a
December 1976
Environmental Protection Technology Series
EPA FABRIC FILTRATION STUDIES: 1.
Performance of Non-woven Nylon
Filter Bags
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the
views and policy of the Agency, nor does mention of trade
names or commercial products constitute endorsement or
recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-168a
Etecembsr 1976
EPA FABRIC FILTRATION STUDIES:
1. PERFORMANCE OF
NON-WOVEN NYLON FILTER BAGS
bv
James H. Turner
Industrial Environmental Research Laboratory
Office of. Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Program Element No. EHE624
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
PREFACE
This report is the first in a series of reports, entitled EPA
Fabric Filtration Studies, which summarize the results of EPA laboratory
testing of new baghouse fabric materials and present the conclusions of
specialized research studies in fabric filtration. These tests have
been carried out over the past four years by the Industrial Environ-
mental Research Laboratory, Research Triangle Park, North Carolina, and
previously by predecessor agencies. The purpose of these investigations
was to evaluate the potential of various new fabrics as baghouse filters
and to obtain data for use by the fabric filtration community. The
testing consisted of simulating a baghouse operation in a carefully
controlled laboratory setting that allowed measurement and comparison of
bag performance and endurance. The simulation discussed in this paper
covered only a very narrow range of operating conditions:
1) Redispersed, classified flyash (mass median diameter between 5
and 6 urn) entrained in air was the only dust used.
2) All filtering was done at room temperature.
3) Humidity varied from about 20 to 40 percent for most of the
testing.
4) The air to cloth ratio varied between 4.3 and 8.7 fpm*.
5) The dust loading varied between 1.5 and 3 grains/ft .
6) The test cycle consisted of a constant 20 minute feed, 1
minute delay, 2 minute shake cleaning, and 1 minute delay,
regardless of the pressure drop across the bag.
*EPA policy is to use SI units only or to list both the common British
unit and its metric equivalent. For convenience and clarity, non-metric
units are used in this report. Readers more familiar with metric terms
may use the factors in the Appendix to convert to that system.
111
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Extreme caution should be used in extrapolating the results reported
here to the substantially different conditions that occur in all field
applications. The usefulness of the present results is primarily as an
initial screen of candidate fabrics for baghouse applications.
The projected EPA Fabric Filtration Studies series will contain:
1) Performance of Non-Woven Nylon Filter Bags (this report).
2) Performance of Non-Woven Polyester Filter Bags.
3) Performance of Expanded PTFE Laminate Filter Bags.
4) Aging Effects.
5) Bag Cleaning Technology.
6) Analysis of Particle Size Efficiency.
IV
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CONTENTS
Preface iii
Figures vi
Tables vii
List of Abbreviations and Symbols viii
Acknowledgments i*
Sections
1 Introduction 1
2 Conclusions 5
3 Experimental Methods 6
4 Results 9
4.1 Efficiency and Outlet Concentration 9
4.2 Specific Cake Resistance . . . 9
4.3 Effective Drag 16
4.4 Endurance 16
4.5 Humidity 19
4.6 Costs 19
4.7 Increased Velocity 19
4.8 Baghouse Operation 20
5 Limitations 22
6 References 23
Appendix 24
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FIGURES
Number Page
1 Cerex fabric photomicrograph. Fabric weight of
0.61 oz/yd2 4
2 Test equipment used for evaluation of spunbonded
nylons as fabric filter media 7
3 Dust mass collection efficiency of spunbonded
nylons 10
4 Outlet concentration for spunbonded nylons 10
5 Photomicrograph of spunbonded nylon after filtration
and cleaning, 0.61 oz/yd2 11
6 Photomicrograph of spunbonded nylon after filtration
and cleaning, 1.5 oz/yd2 12
7 Photomicrograph of spunbonded nylon after filtration
and cleaning, 2.9 oz/yd2 13
8 Photomicrograph of spunbonded nylon after filtration
and cleaning, 5.9 oz/yd2 14
9 Specific cake resistance of flyash on spunbonded
nylons 15
10 Effective drag of spunbonded nylons 17
11 Outlet concentration versus number of shakes for
5.9 oz/yd2 spunbonded nylon 17
VI
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TABLES
Number Page
1 Properties of Spunbonded Nylons used for Evaluation
as Fabric Filter Media 8
Filtration Conditions used for Evaluation of Spun-
bonded Nylons as Fabric Filter Media
Performance of Spunbonded Nylon Filter Medium with
Number of Shakes 18
Performance of Spunbonded Nylon Filter Media at Three
Levels of Filtration Velocity 21
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LIST OF ABBREVIATIONS AND SYMBOLS
A = filtration area of fabric, sq ft
C = mass outlet concentration, grains/1000 cu ft
o
E = mass collection efficiency, percent
F = fallout fraction (dust which goes directly to baghouse hopper
without contacting bag)
K? = true value of specific cake resistance, (in. H20/fpm)/(lb/sq ft)
1C, = measured value of specific cake resistance, (in. H20/fpm)/
(Ib/sq ft)
APF = pressure drop across bag at time zero filtration cycle (ex-
trapolated from straight line portion of pressure drop trace)
(in. H20)
APT = pressure drop across bag at end of filtration cycle (in. H20)
Q = flow rate through filter, cfm
q = flow rate through sampling system, cfm
R = average dust feed rate, grams/min
SE = effective drag, in. H20/fpm
ST = terminal drag, in. HLQ/fpm
T = filtration time, min
V = filtration rate, fpm (air/cloth ratio)
Wn = mass of dust collected in sampling system, grams
vm
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ACKNOWLEDGMENTS
The Monsanto Company, St. Louis, Missouri donated all the spun-
bonded polyester bags used in this study. They manufactured the fabric
and assumed all costs of sewing and preparing the bags to fit the EPA
test facility. Ralph DeBrunner of Monsanto supplied technical advice
in regard to the fabric.
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SECTION 1
INTRODUCTION
Fabric filtration is one of the major accepted methods of removing
participates from industrial effluent streams. Performance of fabric
filters (or baghouses) is dependent on properties of the gas stream to
be filtered, properties of the fabric used for the bags, and the modes
of operation used for filtration and for bag cleaning. Important per-
formance requirements are that the baghouse operate at the required
efficiency, that pressure drop be kept as low as practicable, and that
bag endurance be as great as possible. Efficiency is dictated by the
job to be done, but pressure drop and bag endurance (within limits) are
more in the nature of cost considerations.
Efficiency is often not a problem. Baghouses are inherently high-
efficiency devices, as long as the fabric used is tight enough either to
permit a good dust cake buildup on woven fabrics, or to prevent dust
particles from blowing straight through non-woven fabrics. The formula
used for calculating efficiency is:
E = 100
1 -
(WD)(Q)
(R - FR)(T)(qs) _,
(1)
Since efficiencies of bag filters are often greater than 99.9 percent,
it becomes a little inappropriate to talk of efficiency. An alternative
is to use outlet concentration:
(15.43 grains/gram) (WQ) (1000)
(T)(qs)
-------
Pressure drop through a bag filter increases as the dust load builds
up on the fabric. For a given dust-fabric system at specific filtration
conditions, a measure of pressure drop at the end of a cleaning cycle
(or just prior to the filtration cycle) is given by the filter effective
drags:
= APE/V. (3)
The drag can also be measured at the end of the filtration cycle
(just prior to cleaning) as:
= APT/V. (4)
The increase in pressure drop as the filtration cycle progresses
depends on the aust-fabric combination and the filtration conditions used.
Because the dust cake or dust mass will build up in a characteristic
fashion, a constant can be found for the system:
(JPT - APE)(A)2(7000 grains/lb)
(Q)(T)(1-F)(R)(T5.43 grains/gm)
(5)
K applies only to the region in which pressure drop increases linearly
with time. There is an initial "cake repair" period for each filtration
cycle during which pressure drop builds at a decreasing rate. Although
it was originally thought that K was a characteristic constant for any
-------
given dust, it is now realized that K is influenced by fabric construction
and filtration conditions [Ref. 1]. Flow and pressure drop through
fabric filters are discussed in the Handbook of Fabric Filter Technology
[Ref. 2].
Bag endurance for a given fabric depends upon its resistance to the
filtering environment and on the wear imposed by cleaning the fabric.
Mechanical shake cleaning is usually used with woven fabrics; for pulsed-
jet cleaning, a heavier felted material is preferred. A thorough discussion
of cleaning and its effects on bag endurance is given in the Fabric Filter
Cleaning Studies [Ref. 3].
A new type of fabric is now being investigated for use as a filter
material. The fabric is non-woven, thinner than felted fabrics, and is
formed by laying a web of filamentous material in a continuous set of
processing steps which combine fiber formation, web formation, bonding,
and fabric windup. The resulting "spunbonded" fabric can be made from
such starting materials as polyamides, polyesters, or olefins. Spunbondeds
are tough, strong, available in numerous weights, and much cheaper than
woven fabrics of equivalent weight. Strength derives from the use of
continuous filaments which are bonded at points of contact. The fabrics,
if not given further treatment, are relatively stiff and parchment-like.
Figure 1 is a magnified view of some of the fabric used for the
present work. This fabric is a spunbonded nylon 66, contains no binders,
^
and is manufactured by Monsanto Company under the trade name Cerex .
It is the purpose of this work to investigate the performance of filter
bags made of spunbonded nylon.
-------
V i \\
Figure 1. Cerex fabric photomicrograph. Fabric weight of
0.61 oz/yd^.
-------
SECTION 2
CONCLUSIONS
The following conclusions are based on a limited amount of data
over a relatively narrow range of conditions:
1) On the basis of fabric weight, spunbonded nylons have higher
efficiency, lower outlet concentration, lower specific cake
resistance, and approximately equal effective drag when com-
pared with woven nylon.
2) The heaviest bag tested (5.9 oz/sq yd) will withstand shake
cleaning in excess of 8 million shakes. A lighter bag
(2.9 oz/sq yd) will withstand in excess of 40 million shakes.
3) Assuming endurance is sufficiently good, spunbonded nylon
filter bags would provide lower cost filtration when compared
to woven nylon bags.
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SECTION 3
EXPERIMENTAL METHODS
The test unit was a single-bag baghouse with dimensions as shown in
Figure 2. The bags, approximately 3.5 in. in diameter by 62 in. long,
had a total filter area of 4.6 sq ft. Inlet air of known humidity,
temperature, dust loading, and quantity was admitted to the top of the
bag, filtered, and passed out of the system. Pressure and flow were
measured and continuously recorded, using 0-10 in. HnO differential
pressure cells: one was connected across the baghouse; another, across
a flow venturi. Humidity was measured with wet and dry bulb thermometers;
inlet dust feed rate was measured by weighing the dust feeder discharge
over a known time interval. Efficiency and outlet concentration were
measured by passing a known fraction of the baghouse effluent through a
0.45 ym millipore filter and weighing the accumulated dust. Sample flow
rates were adjusted to give isokinetic flow. The dust used was flyash
taken from utility boiler dust collection equipment and sized to eliminate
large particles. Coulter analysis gave a mean particle diameter of 5.5 ym,
with 10 percent less than 2.5 ym and 90 percent less than 12 ym.
For each bag tested there was an equilibrium period of 24 hours,
after which performance was measured over three consecutive filtration-
cleaning cycles. The standard cycle was 20 minutes of filtration
followed by 1 minute of delay, 2 minutes of shake cleaning, and 1 more
minute of delay. Shake conditions included an amplitude of 0.81 in.
(stroke of 1.62 in.) and a frequency of 240 cycles per min. Fabric
properties and filtration conditions are listed in Tables 1 and 2,
respectively.
In addition to performance testing, two bags were put on an endurance
cycle of 2 minutes feed and 15 minutes shake with 1 minute delay periods.
-------
MECHANICAL
SHAKER
HUMIDITY
CONTROL CHAMBER
FLOW
VENTURI
DISPERSION
VENTURI
VARIABLE SPEED
DUST FEEDER (FLYASH)
CONTROL VALVE
COLLECTION HOPPER
MILLIPORE FILTER
SAMPLING TRAIN
EFFICIENCY
PORT
ROTARY BLOWER
Figure 2. Test equipment used for evaluation of spunbonded nylons as
fabric filter media.
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TABLE 1. PROPERTIES OF SPUNBONDED NYLONS USED FOR EVALUATION
AS FABRIC FILTER MEDIA3
Style
5706-11
578F-11
5715-11
5730-2F
5740-2F
4050-2F
Nominal Fabric
Weight (oz/sq yd)
0.60
0.85
1.50
3.00
4.00
6.00
Actual Fabric
Weightb (oz/sq yd)
0.613
1.010
Thickness
(in.)
0.0035
Air Permeabi
(cu ft/mi n/sq
791.0
0.0043 | 614.0
1.522 0.0067
2.862
4.161
5.870
0.0122
0.0157
383.0
99.2
65.6
0.0197 | 45.1
lity
ft)
Approximately 2 sq yd furnished for tests.
bASTM D 1910-64
CASTM D 1777-64
JASTM D 737-69
TABLE 2. FILTRATION CONDITIONS USED FOR EVALUATION OF
SPUNBONDED NYLONS AS FABRIC FILTER MEDIA
Air to Cloth Ratio (fpm)
Condition
4.3
6.3
i.7
Grain loading (grains/cu ft
Relative humidity (percent)
Temperature (°F)
3.0 2.0 1.5
20 to 40
75 to 80 —-
-------
SECTION 4
RESULTS
Results will be discussed by performance parameters and the
endurance test. Comparisons are made with the 4.1 oz/sq yd woven nylon
fabric tested and reported previously [Ref. 4]. The woven nylon was a
continuous-filament 2x2 twill with a 74 x 68 count.
4.1 EFFICIENCY AND OUTLET CONCENTRATION
Figures 3 and 4 dramatically show the effect of fabric weight on
collection efficiency. There is apparently a threshold fabric weight
for the test dust above which collection efficiency is good and below
which it is not. Figures 5 through 8 show the progressive reduction in
open pores available for passing dust as fabric weight increases. The
2.9 oz/sq fabric has very few open pores; the lighter fabrics have
obvious openings through which dust can pass (the pores are too large
for the dust to bridge). Outlet concentration is low for the 2.9 oz/sq
yd and heavier fabrics, but much higher for the lighter open fabrics.
Concentration was so high for the two lightest fabrics (0.61 and 1.0
oz/sq yd) that testing was discontinued. For the same weight of fabric,
the non-woven fabric appears to be much more effective at trapping
flyash particles.
4.2 SPECIFIC CAKE RESISTANCE
Figure 9 gives further evidence that fabric characteristics influence
the manner in which a dust mass builds up on the filter. As fabric
weight increases, so does specific cake resistance. For the same weight
fabric, spunbonded nylon has a resistance of about 60 percent of the
woven nylon.
-------
EFFICIENCY, %
3 § S g
—
. WOVEN SPUNBO
^ NYLON NYLO
NDED
NS
S:S|
F^
.-.•.•.-.•
:: ::::>
1
*:•:•:•:•:•
;.•.•.*.;.;
i
'.•.•.*.*.
—
4.1
1.5 2.9 4.2 5.9
FABRIC WEIGHT, oz/yd2
Figure 3. Dust mass collection efficiency of spunbonded nylons.
JJU
320
OUTLET CONCENTRATION, gr/1000 ft3
=> en s 5 s KH£SI
—
t^
—
:•$!:
• a^
WOVEN
^^ NYLON
^
> SPUNBONDED
/ NYLONS
ji-i-iS:
:::::::::::
:•:•:•:•
—
^i_
•^IM
.^
i^rt»
^
4.1
1.5 2.9 4.2 5.9
FABRIC WEIGHT, oz/yd2
Figure 4. Outlet concentration for spunbonded nylons.
10
-------
Figure 5. Photomicrograph of spunbonded nylon after
filtration and cleaning, 0.61 oz/yd2.
11
-------
Figure 6. Photomicrograph of spunbonded nylon after
filtration and cleaning, 1.5 oz/yd^.
12
-------
500pm
Figure 7. Photomicrograph of spunbonded nylon after
filtration and cleaning, 2.9 oz/yd^.
13
-------
Figure 8. Photomicrograph of spunbonded nylon after
filtration and cleaning, 5.9 oz/yd2.
14
-------
o
evi
8
CSI
JQ
6
j_f
= •;
i
£ 4
jj
a:
jj
*:
a:
_>
:£ 2
3 i
3_
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4.3 EFFECTIVE DRAG
Effective drag of the spunbonded nylons also increases with fabric
weight, as shown in Figure 10. This effect is expected as fabric thick-
ness and air permeability also increase with fabric weight. The woven
nylon has an effective drag about 80 percent of the spunbonded nylon.
This lower drag of the woven fabric would be offset by the lower K shown
for the spunbonded material. For the particular operating cycle used in
this work, the terminal drag results had higher numerical values, but
closely paralleled the effective drag results. The spunbonded fabrics
had slightly lower terminal drag (4.2 percent) than the woven nylon.
4.4 ENDURANCE
The bag tested for endurance was periodically run for several
cycles at the 20 minute filtration, 2 minute shake conditions in order
to measure outlet concentration. Equipment repair was required at
approximately 3.3 million shakes. Inspection showed a crack or fissure
about 2 in. long on the bag surface, presumably at a point where the bag
had been folded or creased in handling (the stiff nature of the material
makes it difficult not to get such folds and creases). Further handling
may have enlarged the crack, although there was no clear open space
between the edges of the crack. Figure 11 shows changes in outlet con-
centration with number of shakes. Up to the point of equipment failure
the outlet concentration decreased; however, Table 3 shows there was no
significant change in terminal drag (or terminal pressure drop). Effective
drag increased, but there was a compensating decrease in specific cake
resistance.
After the equipment failure and subsequent bag handling, outlet
concentration immediately increased, but then started decreasing again.
The implication is that cracks in spunbonded bags tend to be "repaired"
with continued usage. After 8.2 million shakes the bag failed. A second
bag (2.9 oz/sq yd) failed at 40.5 million shakes with average outlet con-
centration of about 30 grains/1000 cu ft.
16
-------
I 0.6
o
•F 0.5
cs~ 0.4
0.3
0.2
0.1
0
o
LU
SPUNBONDED
NYLONS *
WOVEN
NYLON
4.1
1.5 2.9
FABRIC WEIGHT, oz/yd2
4.2 5.9
Figure 10. Effective drag of spimbonded nylons.
30
a
I I I
EQUIPMENT FAILURE
v
d
20
o
I 10
LU
i
1
2 3 4
MILLIONS OF SHAKES
Figure 11. Outlet concentration versus number of shakes for
5.9 oz/yd2 spunbonded nylon.
17
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oo
TABLE 3. PERFORMANCE OF SPUNBONDED NYLON FILTER MEDIUM WITH NUMBER OF SHAKES
Number of Shakes
(millions)
Characteristic
Efficiency, %
Outlet Concentration (CQ), grains/1000 cu ft
0.
99.
11.
Specific Cake Resistance (K), (in. HLO/fpm)/ |
(lb/sq ft)
Effective Drag (Sr), in. H20/fpm
Terminal Drag (Sj), in. H^O/fpni
7.
0.
0.
Terminal Pressure Drop (APy), in. H20 | 3.
27
63
30
70
51
80
45
1.
99.
4.
5.
0.
0.
3.
55 1 3.
84
50
20
54
73
99.
2.
4.
0.
0.
13 | 3.
06
91
80
80
3.92b
99
19
7
65 | 0
83 | 1
55
4
4.
.37 | 99.
.00 | 10.
1
.90
.75
.04
.48
6.
0.
1.
4.
97
6.05
64 | 99.54
80 | 13.50
90 | 8.00
80
05
50
0.79
1.08
4.64
aFabric weight = 5.780 oz/sq yd
After equipment failure
-------
4.5 HUMIDITY
All of the reported performance figures were collected for air at
20 to 40 percent relative humidity. It has previously been found that
humidity affects flyash collection on nylon [Ref. 4], so attempts were
made to correlate performance with humidity over the range of 10 to 60
percent. Results were inconclusive from the work that was done, but the
ranges of values found for a 2.8 oz/sq yd bag were:
Efficiency: 99.34 - 99.87 percent
CQ: 4.7 - 19.7 grains/1000 cu ft
K: 3.5 - 4.6 (in. H20/fpm)/(lb/sq ft)
SE: 0.29 - 0.52 in. H20/fpm
4.6 COSTS
Cerex is much cheaper than woven nylon. As of February 1973, the
price of 4 oz/sq yd Cerex was $0.46/sq yd. One supplier quoted a
quantity price of $1.60/sq yd for a heat-set, continuous-filament woven
nylon, 3.93 oz/sq yd, approximately 74 x 68 count. Sewing costs for
small lots of bags 5.5 in. in diameter by 71 in. long were quoted by one
bag fabricator as $1.95 for woven nylon and $2.00 for the spunbonded
nylon. For bags of this size, Cerex bags would cost about 70 percent of
that of woven bags.
Further cost reduction with spunbonded bags is possible. Instead
of being sewn, bags may be seamed ultrasonically or by various thermal
techniques. Equipment is presently in use and commercially available
for performing such operations.
4.7 INCREASED VELOCITY
In addition to testing at a filter velocity of 4.3 fpm, some testing
was done at 6.3 and 8.7 fpm, but with constant dust feed rate (decreased
19
-------
grain loading). Table 4 shows the performance results. At the highest
velocity, the lighter fabrics showed lower efficiency and higher outlet
concentration than for the lowest velocity. This result may imply the
formation of a more open cake allowing more seepage; however, values of
the specific cake resistance and effective drag showed just the opposite
effect. Presumably aerodynamic forces at the higher velocity were great
enough to push more particles through the dust-fabric combination. For
the heaviest fabric, the results were different: efficiency was nearly
the same as for the 4.3 fpm, outlet concentration was lower, cake
resistance increased by nearly 3 units, but effective drag decreased and
terminal drag changed only marginally.
4.8 BAGHOUSE OPERATION
The stiff nature and resulting ease of creasing or cracking of the
heavier weights of Cerex has been noted. Not enough experience has been
gained during the present series of tests to tell if there would be any
problems in industrial usage. The apparent cost and performance advantages
of the fabric certainly warrant more testing in larger scale installations.
On a fabric weight basis the spunbonded nylon has higher efficiency,
lower outlet concentration, lower specific cake resistance, lower cost,
and approximately equal pressure drop characteristics when compared with
woven nylon. Endurance in the laboratory has extended to more than 6
million shakes without catastrophic failure.
20
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TABLE 4. PERFORMANCE OF SPUNBONDED NYLON FILTER MEDIA AT THREE
LEVELS OF FILTRATION VELOCITY
Fabric weight ( oz/sq yd )
Characteristic
1.5
2.9
4.2
5.9
Efficiency, %
*A/C =4.3 88.68
A/C = 6.3 90.19
A/C = 8.7 86.09
Outlet Concentration (C ), i
grains/1000 cu ft '
A/C - 4.3 328
A/C = 6.3 212
A/C =8.7 201
Specific Cake Resistance (K),
(in. H20/fpm)/(lb/ sq ft)
A/C =4.3 3.7
A/C = 6.3 1.5
A/C = 8.7 0.9
Effective Drag (SF),
in. H20/fpm
A/C = 4.3 0.02
A/C = 6.3 0.04
A/C = 8.7 0.02
Terminal Drag (ST),
in. H20/fpm
A/C = 4.3 0.15
A/C = 6.3 0.10
A/C = 8.7 0.05
Terminal Differential Pressure
(APT), in. H20
A/C = 4.3 0.66
A/C = 6.3 0.62
A/C = 8.7 0.47
99.84
98.97
99.31
4.7
21.1
10.0
3.9
6.4
8.2
0.25
0.42
0.31
0.44
0.58
0.61
1.91
3.63
5.30
99.90
98.90
99.40
3.1
22.7
9.4
4.5
4.3
6.9
0.29
0.34
0.36
0.46
0.50
0.63
1.99
3.07
5.39
99.79
99.40
99.75
7.0
13.6
3.7
7.2
4.7
10.2
0.52
0.42
0.48
0.79
0.61
0.85
3.43
3.85
7.38
*A/C = air to cloth ratio, fpm.
21
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SECTION 5
LIMITATIONS
This work was done with only one test dust (redispersed flyash)
and no variations were made in feed rate, cleaning conditions, or (with
the exception of endurance testing) operating cycle. Lack of
familiarity with the fabric undoubtedly caused operation at less than
optimum conditions. Humidity control was imperfect and probably
affected the results. Inaccuracies in flow rate measurement, used for all
performance calculations, probably amounted to as much as 5 percent.
22
-------
SECTION 6
REFERENCES
Draemel, D. C., "Relationship Between Fabric Structure and Fil-
tration Performance in Dust Filtration," EPA-R2-73-288, NTIS No. PB
222 237, July 1973.
Billings, C. E. and J. Wilder, Handbook of Fabric Filter Technology,
Vol. I, Fabric Filter Systems Study, EPA publication APTD 0690,
NTIS No. PB-200 648, 2-1 to 2-219, December 1970.
Dennis, R. and J. Wilder, "Fabric Filter Cleaning Studies," EPA-
650/2-75-009, NTIS No. PB-240 372/AS, January 1975.
Durham, J. F. and R. E. Harrington, "Influence of Relative Humidity
on Filtration Resistance and Efficiency of Fabric Dust Filters,"
Filtration and Separation 8, July/August 1971, pp. 389-393.
23
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APPENDIX
CONVERSION FACTORS
To__Convert f r OIIK
foot?
2
inch
yard
grains/foot ^
grains/1000 ft
Ib (force)
foot
inch
mi 1
yard
grain
Ib (mass)
oz (mass)
inch of water (60°F)
Ib (force)/inch2 (psi)
Ib (force)/foor
foot/min (fpm)
foot^
inch.,
yard
2
oz/yd o
Ib (mass)/foot
in. H~0/fpm
in. H-O/fpm
lb(m)/ft2
To
2
meter~
meter~
meter
kg/in3
g/m3
newton
meter
meter
meter
meter
kilogram
kilogram
kilogram
*•
newton/meter^
newton/meter
r
newton/meter^
meter/sec
3
meter3
meter-
meter
kg/m?
kg/m
newton-sec
meter
newton-sec
meter-kg
9.29 x
6.45 *
8.36 *
2.29 *
2.29 >
4.45
3.05 x
2.54 x
2.54 x
9.144 x
6.48 x
4.54 x
2.83 x
2.49 x
6.89 x
4.79 x
5.08 x
2.83 x
1.64 x
7.65 x
3.39 x
4.88
4.90 x
io:
10 :
ID'1
10^
10 J
10"J
10~r
1Q-5,
_
10 '
'»:?
10 '
10"^
<
10 J
10+1
ID'3
"1
10_=
10 '
ID'2
4
10^
•(-I/sec)
10
24
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TECHNICAL REPORT DATA
(Please read Inunctions on the reverse be lore con>.ri--l:ng/
. REPORT NO.
EPA-600/2-76-168a
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
EPA FABRIC FILTRATION STUDIES:
1. Performance of Non-woven Nylon Filter Bags
5. REPORT DATE
December 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James H. Turner
8. PERFORMING ORGANIZATION REPORT NO.
IERL-RTP-274
9. PERFORMING ORGANIZATION NAME AND ADDRESS
See Block 12.
10. PROGRAM ELEMENT NO.
EHE624
11. CONTRACT/GRANT NO.
NA--InlioJse Report
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; b/72-3/73
14. SPONSORING AGENCY CODE
EPA/600/13
is. SUPPLEMENTARY NOTES Author Turner's Mail Drop is MD-61: his phone is SIS/549-8411
Ext 2925.
is. ABSTRACT
e report gives results or testing bags made of spunbonded nylon 66 in
single-bag baghouses at flyash grain loadings of 1. 5-3. 0 grains/cu ft. at air-to-cloth
ratios of 4. 3-8. 7 fpm, and at relative hum'dities of 20-40%. Results showed increa-
sed filtration efficiency with increased fabric weight. Compared to woven nylon of
the same weight (4 oz/sq yd), spunbonded nylon was more efficient (99. R9 vs. 95.02%),
produced lower specific cake resistance (4.5 vs. 7.6 (in. H2O/fpmX/(lb/sq ft)), and
had slightly higher effective drag (0.2? vs. 0.23 in. H2O/fpm). Endurance for a 2.9
oz/sq yd bag was over 43 million shakes. Spuibonded bag costs ware estimated to
be 70% o.f woven bag costs. Conclusions based on limited testing were that spunbonded
nylon bags have higher efficiency, lower outlet concentration, lower specific cake
resistance, and approximately equal effective drag when compared with woven nylon
of the same weight. The heaviest bag tested will withstand shake-cleaning in excess
of 8 million shakes. Assuming endurance is sufficiently good, spunbonded nylon
filter bags would provide lower cost filtration when compared to woven nylon bags.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
'0. IDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Air Pollution
Filtration
Dust Filters
Nylon 65
Non-woven fabrics
Dust
Fly Ash
Air Pollution Control
Stationary Sources
Particulate
Baghouses
Fabric Filters
Spunbonded Fabrics
Collection Efficiency
13B
11D
13K
HE
11G
2 IB
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report!
Unclassified
21. NO. OF PAGES
37
20. SECURITY CLASS (This page!
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
25
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