PB276583
1
CD A U.S. Environmental Protection Agency Industrial Environmental Research EPA-600/7-77-Ofi
mm* f\. Office of Research and Development Laboratory •.§-*•» wvv/ i i I vw
Research Triangle Park, North Carolina 27711 JlH"tG 1977
INERTIAL CASCADE IMPACTOR
SUBSTRATE MEDIA FOR
FLUE GAS SAMPLING
Interagency
Energy-Environment
Research and Development
Program Report
KtPRODUCfD BY
NATIONAL TECHNICAL
INFORMATION SERVICE
t). S. DtPARTMENT OF COMMERCE
SPRIMGFIILO VA. 2216)
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of. and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
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.
-------
TECHNICAL REPORT DATA
(Please read Inunctions on the reverse before completing}
1. REPORT NO.
EPA-600/7-77-060
3. RECIPIENTS'A'CCESS'lOlVNQ "
'
4. TITLE AND SUBTITLE
Inertial Cascade Impactor Substrate Media for
Flue Gas Sampling
5. REPORT DATE
June 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHORtS)
'. r^v/ I • > w n v *s /
Larry G. Felix, George I. Clinard, George E. Lacey,
and Joseph D. McCain
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
10. PROGRAM ELEMENT NO.
EHE624
11. CONTRACT/GRANT NO.
68-02-2131
Technical Directive 10501
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
D COVERED
14. SPONSORING AGENCY CODE
EPA/600/13
is. SUPPLEMENTARY NOTES IERL_RTP project officer f0r this report is D. Bruce Harris
Mail Drop 62, 919/549-8411 Ext 2557.
16. ABSTRACT
The report summarizes Southern Research Institute's experience with
greases and glass fiber filter material used as collection substrates in inertial cas-
cade impactors. Available greases and glass fiber filter media have been tested to
determine which are most suitable for flue gas sampling. Greases are probably not
useful at above 177 C. For higher temperatures, glass fiber filter material can be
used. Of 19 greases tested by heating in the laboratory and by exposure to flue gas
in the field, only Apiezon H grease performed satisfactorily at above 149 C. In
experiments to evaluate the use of filter materials as impactor substrates, mass
increased as a result of exposure to flue gas for all of the fiber media tested. Labor-
atory and field studies are described which were directed toward developing a method
to passivate glass liber filter material to SOx induced mass gains. These studies .
indicate that a H2SO4 wash, followed by a thorough distilled water/is opropanol
rinse, drying, and baking, augmented by in situ conditioning, offers the best hope
for reducing SOx induced mass gains. Reeve Angel 934AH glass fiber filter material
performed best among the media tested.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Impactors
Substrates
Sampling
Flue Gases
Greases
Glass Fibers
Filters
Air Pollution Control
Stationary Sources
Cascade Impactors
Apiezon H Grease
Reeve Angel 934AH
13B 11E,11B
11D
14B
2 IB
11H
8. DISTRIBUTION STATEMENT
Unlimited
19, SECURITY CLASS (This Report)
Unclassified
21. NO. OF
EPA Form 2220-1 (9-73)
REPRODUCED BY
NATIONAL TECHNICAL
INFORMATION SERVICE
U. S. DEPARTMENT OF COMMERCE
SPRINGFIELD, VA. 22161
' (TMs pagei
72. PRICE
> fta i
-------
-------
EPA-600/7-77-060
June 1977
INERTIAL CASCADE IMPACTOR
SUBSTRATE MEDIA
FOR FLUE GAS SAMPLING
by
Larry G. Felix, George I. Clinard,
George E. Lacey, and Joseph D. McCain
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
Contract No. 68-02-2131
Technical Directive 10501
Program Element No. EHE624
EPA Project Officer: D. Bruce Harris
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, N.C. 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D.C. 20460
-------
ABSTRACT
This report summarizes Southern Research Institute's exper-
ience with greases and glass fiber filter material used as col-
lection substrates in inertial cascade impactors.
Tests have been performed to ascertain which of the avail-
able greases and glass fiber filter media are most suitable for
flue gas sampling. Greases are probably not useful for tempera-
tures above 177°C (350°F). For higher temperatures glass fiber
filter material can be used.
Of nineteen greases tested, by heating in the laboratory
and by exposure to flue gas in the field, only Apiezon H grease
was found to perform satisfactorily at temperatures above 149°C
(300°F).
In experiments designed to evaluate the use of filter mater-
ials as impactor substrates it was found that mass increases
occurred as a result of exposure to flue gas for all of the fiber
media tested. Laboratory and field studies are described which
were directed toward development of a method by which glass fiber
filter material can be passivated to SOX induced mass gains.
These studies indicate that a H2SO^ wash followed by a thorough
distilled water and isopropanol rinse, drying, and baking,
augmented by iri situ conditioning, offers the best hope for
reduction of SOX induced mass gains. Reeve Angel 934AH glass
fiber filter material performed best among the media tested.
-------
CONTENTS
Abstract ii
Figures iv
Tables . . . vi
1. Introduction 1
2 . Experimental Procedures 3
Evaluation of Greases 3
Preliminary Laboratory Screening Tests . . 3
Field Studies 7
Dow Corning Greases. .... 7
Apiezon Greases 7
Back-up Filters 18
Field Use of Apiezon H Grease 18
Summary of Results of Evaluation of Greases 23
Evaluation of Filter Media for Use as
Substrates and Back-up Filters 25
Previous Results 25
Preliminary Laboratory Screening Tests . . 27
Exposure of Media to S02 27
Sulfuric Acid Wash Treatment of
Filter Media 29
Field Studies 35
Effects of Flue Gas Temperature and
Sulfate Concentration 39
In Situ Preconditioning 43
Use of Laboratory Preconditioned
Filters in the Field 52
Summary of Results of Evaluation
of Filter Media 78
3. Conclusions and Recommendations. 79
Bibliography 80
Appendix A. Procedures for Acid Washing of Substrates. . 81
111
-------
FIGURES
Number
1 Apiezon L greased substrates, grease- toluene mixture
dropped on. Stages 2, 4, and 6. Stainless steel
substrates ..................... 13
2 Apiezon L greased substrate, grease-toluene mixture
dropped on. Closeup of Stage 4. Stainless Steel
substrate ...................... 14
3 Apiezon L greased substrates, grease-toluene mixture
painted on. Aluminum foil substrates ........ 15
4 Apiezon M greased substrates, grease-toluene mixture
painted on. Aluminum foil substrates ........ 16
5 Apiezon M greased substrate, grease-toluene mixture
painted on. Closeup of Stage 4. Aluminum foil
substrate . . ' .................... 17
6 Apiezon T greased substrate, grease-toluene mixture
painted on Stages 2 and 6, dropped on Stage 4. Stage
2 is stainless steel and Stages 4 and 6 are aluminum
foil ........................ 19
7 Apiezon T greased substrate, grease-toluene mixture
painted on. Closeup of Stage 2. Stainless steel
substrate .... .................. 20
8 Apiezon H greased substrates, grease-toluene mexture
painted on Stages 2 and 6, dropped on Stage 4.
Stainless steel substrates ............. 21
9 Apiezon N greased substrates, grease-toluene mixture
painted on. Aluminum foil substrates ........ 22
10 Diagram of experimental set-up for filter substrate
conditioning experiment ............... 28
11 Mass gains of four types of glass fiber filter materials
versus exposure time to water-air-5% SO2 gas mixture
at 260°C ...................... 30
IV
-------
Number
FIGURES (Continued)
Paqe
12 Mass increase per 47 mm filter as a function of labora-
tory conditioning time 32
13 Percent mass change for Reeve Angel 934AH glass fiber
filter substrate material as a function of time after
conditioning .36
14 pH of Reeve Angel 934AH glass fiber filter substrate
material as a function of time after conditioning . . 37
15 Comparison of mass of sulfate on blank Andersen
impactor substrates and observed anomalous mass
increases 40
16 Anomalous mass increases of Andersen glass fiber
impaction substrates at different flue gas
temperatures „ . 42
17 Anomalous mass gains of various 47 mm diameter glass
fiber filters at different temperatures (60 minute
samples at flow rates of 0.25 ACFM) 43
18 Anomalous mass gain of 64 mm diameter Reeve Angel 900AF
glass fiber filters 45
19 Anomalous mass gains of Andersen impactor glass fiber
impaction substrates 46
20 Substrate conditioning chamber, side view 66
21 Substrate conditioning chamber, interior components . . 67
22 Substrate conditioning chamber, end caps 68
23 Flow chart for acid wash treatment of glass fiber
filter material 82.
-------
TABLES
Number Page
1 Greases tested for mass change 4
2 Cumulative mass change. Four consecutive hourly
bakings at 160°C 5
3 Mass change after continuous baking at 160°C .... 6
4 Lab bakeout of Apiezon L. Greased substrates .... 8
5 Mass changes of Dow Corning silicone greases .... 9
6 Summary of flue gas test results. The flue gas
temperature average above 300°F for all tests.
Impactor flow rate was 0.7 ACFM 10
7 Typical physical properties of some Apiezon
greases 12
8 Apiezon H blank weight gains 24
9 Sulfur Dioxide pickup, mg/sheet - 20 hour exposure. . 26
10 Mass gains of 47 mm glass fiber filter substrate
materials from laboratory conditioning . 33
11 Barium, Calcium and soluble Sulfate content in two
glass fiber substrate materials 34
12 Filter types tested • 38
13 Soluble sulfate analyses of filters used at steam
plant B 41
14 Cement plant - substrate mass change 48
15 Steam plant A 50
16 Steam plant A 51
17 Filter blanks (untreated) 52
18 Cement plant 53
19 Steam plant A 55
VI
-------
Number
TABLES (Continued)
Page
20 Mass changes recorded in 47 nun glass fiber filters
exposed to 650°F flue gas for one week 63
21 Results of chemical analyses carried out on 47 nun
glass fiber filter substrate materials 65
22 Averaged stage mass gains for "blank" impactor runs
with Reeve Angel 934AH glass fiber filter substrate
material 69
23 Mass gains of 47 mm glass fiber filter substrate
materials exposed to flue gases in hot and cold side
precipitators at steam plant D, 25 June 1976. ... 71
24 Mass gains of 47 mm glass and quartz fiber filter
substrate materials exposed to flue gases in hot
and cold side precipitators at steam plant D,
31 August - 1 September 1976 , . 73
25 Mass gains of 47 mm glass fiber filter materials
exposed to flue gases in hot side precipitator at
steam plant E, November 1976 75
26 Blank impactor run mass gains at two different flue
gas sources, Reeve Angel 934AH glass fiber sub-
strate material 76
VI1
-------
-------
SECTION 1
INTRODUCTION
Cascade impactors are widely used to determine particle size
distributions in air pollution control device research programs.
In these research programs a large variety of flue streams are
encountered with temperatures ranging from ambient to around 370°C
(700°F). Gas analyses show that many of these sources contain
some SO components, particularly those associated with fossil
fuel fired boilers.
Most impactors have collection stages which are too heavy
to obtain accurate measurements of the mass of the particles
collected in each size fraction. Weighing accuracy can be improved
by covering the stage with lightweight collection substrate made
of aluminum foili teflon, glass fiber filter material, or other
suitable lightweight materials, depending upon the particular ap-
plication. Some manufacturers now furnish lightweight inserts to
be placed over the collection stages. With such arrangements it
is possible to collect enough material on each stage to make an
accurate determination of the mass collected and avoid overloading
the stage. If the stage is overloaded, once deposited particulate
matter can be reentrained and deposited on another stage or the
back-up filter and lead to erroneous results.
Substrate materials may also serve the purpose of changing
the surface characteristics from those of a bare metal or plastic
to something better suited to holding particles which impact.
Thus, various greases are often used, either on bare impactor
plates, or, more frequently, on metal foil substrates.
Presented in this report are the results of investigations
concerning the use of two classes of impactor substrates — greased
metal foils, and fiber filter materials. Tests were made under
both laboratory and field conditions to evaluate each of several
greases and filter materials. The general purpose of this study
is to identify specific materials and handling techniques which
may be used to improve the accuracy of weight measurements in
impactors by reducing uncertainties arising from changes in sub-
strate weights.
Although normal substrate preparation includes baking and
desiccation before the initial weighing, it is frequently found
-------
that weight losses can occur when sampling clean air. Tests have
been conducted to investigate this phenomenon in detail.1 It was
found that with careful handling, weight loss per glass fiber sub-
strate for Andersen impactors can be kept below 0.1 mg. This loss
is attributed to loss of fibers which stick to seals within the
impactor and to "superdrying" when sampling hot, dry air. Weight
losses of 0.1 mg are small compared to most stage catches when
sampling particulate matter, and thus are within an acceptable
range for sampling errors.
A more significant problem is excessive weight gain of the
glass fiber material itself due to gas phase reactions. These
reactions appear to be caused by the SO component in flue gases.
A series of studies was thus directed toward developing procedures
to passivate glass fiber materials against the effect of SO
components in flue gases.
Although greases offer good impedance to particle bounce on
substrates,'they are subject to temperature limitations. Sampling
clean, hot air while using greased substrates may result in severe
weight losses. These losses appear to result from one or more of
several mechanisms which may include continued loss of volatile
components, erosion of grease by the action of the gas jet in the
impactor, and occassional flow of grease from the substrate to
other surfaces within the impactor. In addition, chemical reactions
may play a role in some cases. Occasionally, some of the weight
lost on upper impactor stages has been found to reappear on a back-
up filter, which is an indication that the grease has been blown
off the collection surface or has chemically reacted to form a
"smoke" which was then collected by the backup filter.
In this report on evaluation of greases and an evaluation of
filter media are presented separately. A further division within
each of these sections is made between preliminary laboratory
screening tests and field studies. Under the latter headings,
detailed notes and information are presented for each substrate
medium.
-------
SECTION 2
EXPERIMENTAL PROCEDURES
In order to evaluate the suitability of various greases and
filter materials for application in cascade impactors, an investi-
gation, based on a program of preliminary laboratory screeni^c,
tests, followed up by field testing, was carried out. The labor-
atory tests were designed to characterize the behavior of the
materials being studied at elevated temperatures, and to identify
problems associated with specific materials. In the field studies,
direct exposure to flue gas was used as a means of examining the
behavior of greases and filter substrate mats in_ situ.
EVALUATION OF GREASES
The use of greases, usually on metal foil substrates, is an
important method for controlling particle bounce and scouring
effects on impaction surfaces. The principal difficulty with the
use of greases in general is the effect of elevated temperature on
their physical and chemical characteristics. Greases are complex
organic systems which may break down at high temperatures. A
decrease in viscosity might occur, in which case a grease could
flow easily from the surface on which it was applied*
Preliminary Laboratory Screening Tests
Since the principal concern regarding the use of greases on
impactor substrates is stability at elevated temperatures, the
laboratory screening tests consisted of heating samples in an oven
for periods of several hours, followed by examination of the mate-
rials for changes in consistency, color and mass.
Under EPA Contract 68-02-0273 laboratory tests were made on
the nineteen greases listed in Table I. Quantities ranging from
about 60 to 300 mg of undiluted grease were placed on a metal foil
and heated to 160°C (320°F) . Tables II and III show the experi-
mental results. Six greases were determined to be inert enough at
elevated temperature (160°C, 320°F) to warrant field tests with
filtered flue gas. These were Dow Corning Molykote 111, Dow Corn-
ing 11 Compound, Dow Corning High Vacuum Grease, Apiezon L and
Dow Corning 200 Fluid.
Under the current contract, Apiezon L grease was further
tested in the laboratory by baking prepared MRI impactor
substrate sets for extended times at 195°C (3.83°F) . These
-------
Table I
Greases Tested for Mass Change
1. Vaseline - Cheseborough-Pond's Inc., Greenwich, Conn. 06830
2. Molykote 111 Compound - Dow Corning Corp., Midland, Michigan 48640
3. Stopcock Grease - Dow Corning Corp., Midland, Michigan 48640
4. Dow Corning 11 Compound - Dow Corning Corp., Midland, Michigan 48640
5. Polyethylene Glycol 600 (Jefferson) - Applied Science Laboratories, Inc., State College, Pa. 16801
6. High Vacuum Grease - Dow Corning Corp., Midland, Michigan 48640
7. UCW:98 - Applied Sciences Laboratories, Inc., State College, Pa. 16301
8. Apeizon L - Applied Sciences Laboratories, Inc., State College, Pa. 16801
9. Kiln Bearing Grease - Citadel Cement Co., Birmingham, Ala.
10. 200 Fluid - Dow Corning Corp., Midland, Mich. 48640
11. Fluorolube GR-362 - Hooker Chemicals and Plastics Corp., Niagara Falls, N.Y.
12. Fluorolube GR-544 - Hooker Chemicals and Plastics Corp., Niagara Falls, N.Y.
13. --Fluorolube GR-470 - Hooker Chemicals and Plastics Corp., Niagara Falls, N.Y.
14. Fluorolube GR-290 - Hooker Chemicals and Plastics Corp., Niagara Falls, N.Y.
15. Fluorolube GR-660 - Hooker Chemicals and Plastics Corp., Niagara Falls, N.Y.
16. Carbowax 1000 - Applied Sciences Laboratories, Inc., State College, Pa. 16801
17. Carbowax 4000 - Applied Sciences Laboratories, Inc., State College, Pa. 16801
18. Carbowax 20M - Applied Sciences Laboratories, Inc., State College, Pa. 16301
19. STP Oil Treatment - STP Corporation, Fort Lauderdale, Fla. 33310
-------
Table II
Cumulative Macs Change
4 Consecutive Hourly Bakings at IGO'C
Original Original
Crease Shape Consistency
1.
2.
3.
4.
5.
6.
7.
0.
9.
10.
11.
12.
13.
14.
15.
16.
17.
It.
13.
Metal
Pointed Malleable
Pointed Malleable
Pointed Malleable
Pointed Malleable
Flat Liquid
Pointed Malleable
Rounded Highly Viscous
Pointed Malleable
Pointed Malleable
Flat Highly Viscous
Rounded Malleable
Rounded Malleable
Pointed Malleable
Pointed Malleable
Pointed Malleable
Pointed Slightly Viscous
Pointed Solid Crystals
Pointed Solid Crystals
Flat Viscous
Controls
Original
Color
Frosty White
Frosty White
Frosty White
Frosty White
Clear
Frosty White
Clear
Opaque Orange
Opaque Orange
Clear
Clear
Clear
Frosty White
Frosty White
Frosty White
Frosty White
Opaquo White
Opaque Brown
Clear Brovn
Standard Aluminum
Standard Ferrule
Initial
Mass
(mg)
70.18
92.75
89.97
75.99
86.34
125.24
02.98
79.50
120.52
173.55
229.25
300.04
139.48
161.42
137.01
131.34
54.30
87.15
69.12
73.31
69.56
1 hr
Mas 3
Change
1.14
0.23 .
0.45
0.25
7.79
0.66
0.53
+ 0.09
9.96
20.72
102.76
31.54
53.26
24.81
11.39
11.49
7.08
2.10
3.21
0.08
0.02
160'C
Change
1.62
0.25
0.50
0.33
9.02
0.53
0.84
0.11
8.26
11.94
44.82
10.51
38.19
15.39
8,31
S.72
13.04
2.41
4.64
2 hr
Mass
Change
2.73
0.30
0.53'
0.31
13.58
0.74
0.68
+ 0.00
12.95
20.92
137.59
51.97
70.07
41.56
20.33
25.03
14.49
8.15
5.41
0.06
+ 0.01
we
I
Change
3.89
0.32
0.59
0.41
15.73'
0.59
1.08
0.08
10.75
12.05
60.01
17.32
50.24
25.75
14.84
18.99
26.69
9.35
7.C3
3 hr
Mas:
Change
4.57
0.34
0.57
0.37
22.78
0.81
0.81
+ 0.08
16.97
20.96
159.28
71.50
00.12
56.17
28.70
33.13
18.07
13.63
7.49
0.08
0.01
IGO-C
Chanoo
6.51
0.37
0.63
0.49
26.38
0.65
1.29
0.10
14.08
12.08
69.48
23.83
57.44
34.80
20.95
25.13
33.20
15.64
10.82
4 hr
Change
5.50
0.36
0.57
0.39
28.69
0.81
0.82
+ 0.12
18.72
21.09
167.90
82.67
84.61
64.30
33.20
39.37
20.89
10.48
9.33
0.08
0.01
1GP-C
i
Charge
7.84
0.39
0.63
0.51
33.23
O.GD
1.30
0.15
15.53
12.15
73.24
27. 55
60.66
39.87
24.22
29.06
30.47
21.20
13.50
Final Shape,
Consistency, Color
Flat, Dry, Tacky, Yellow
Pointed, Malleable, Frosty
Rounded, Mallc.--.Lilo, Dlue
Rounded, Malleable, Frosty
Flat, Dry, Clear
P.oundc-d, >!ali
-------
Table III
Mass Chancje After
Continuous Baking at 160°C
Grease
1.
*2.
*3.
*4.
5.
*6.
7.
*8.
9.
*10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Initial
Mass
(mg)
69.43
97.09
49.82
41.07
66.75
49.55
57.37
34.77
50.65
63.25
104.30
101.32
161.31
133.89
120.59
81.01
60.16
49.60
81.41
4 hr
Mass
Change
- 5.91
- 0.09
- 0.20
- 0.25
- 64.85
+ 0.01
- 0.37
0.00
- 11.82
- 0.47
- 84.41
- 41.71
-100.53
- 57.01
- 36.90
- 49.62
- 44.54
- 24.65
- 17.74
160°C
%
Change
8.51
0.09
0.40
0.61
97.15
0.02
0.64
0.00
23.33
0.74
80.93
41.17
62.31
42.58
30.60
61.25
74.04
49.70
21.79
*These qualified for further field testing,
-------
substrates were prepared by dropping or painting on 10% Apiezon
L-Toluene solutions. Table IV shows the results of this study.
The conclusion of this study was that at elevated temperatures
(195°C, 383°P) Apiezon L grease was not a good candidate for sub-
strate coating because the thinly coated foils developed hard
enamel-like surfaces. Near the edges of more heavily coated sub-
strates grease accumulated, and in these deposits no such hard
coating was observed. However, these deposits had chp- -ed color.
Field Studies
Dow Corning Greases
Under Contract 68-02-0273 (EPA) limited tests were performed on
Dow Corning Molykote 111 and Dow Corning Silicone High Vacuum
Grease used as impactor substrate coatings. Substrates of a
University of Washington Source Test Cascade Impactor were
coated with these greases and used to sample flue gas for one
hour at a steam plant. The flue gas was first filtered using
a Gelman 47 mm Type A glass fiber filter. Table V shows the
results of this study. While the Dow Corning Molykote 111 was
much more stable than the silicone high vacuum grease a signifi-
cant weight loss did occur on each stage. Both back-up filters
had an abnormally high weight gain which was probably due to bake-
off or scouring of material from the greases. As a result of this
test it was decided that the Dow Corning greases are not suitable
for flue gas sampling. Note that only two out of the five Dow
Corning greases were tested. Therefore our conclusion represents
a generalization. However, the physical properties of these greases
are similar enough to make it reasonable.
Apiezon Greases
Under EPA Contract 68-02-2131 the behavior of Apiezon H, L,
M, N, and T greases in filtered flue gas streams were tested at
another steam plant. For the flue gas exposure tests, substrates
were made using either aluminum or stainless steel foils. The
greases were applied by dropping or painting on a 5% grease-
toluene solution of Apiezon H, M, N, or T or a 10% grease-toluene
solution of Apiezon L. After application the substrates were dried
in an oven at 165°C (329°F) for several hours.
Two University of Washington Source Test Cascade Impactors
were used in these tests. Gelman 47 mm prefilters were used to
precede the .impactors so that the substrates would be subjected
only to the flue gas. All impactor runs were made horizontally.
The impactor was allowed to warm-up for 30 to 45 minutes in the
flue gas stream before each run began. The runs were 2 to 2.5
hours in duration. The impactor flowrate was 0.7 ACFM, monitored
with an orifice and flowmeter. Table VI summarizes the results of
these runs. Note that each substrate set was subjected to the
149°C (300°F) flue gas for approximately 2.5 hours.
-------
TABLE IV
Laboratory Bakeout of Apiezon L. Greased Substrates
Mass (mg) of Grease on Plate During Bakeout at 195°C (383°F)
Preparation 2.5 hours 7 hours A(mg) A(%) 22 hours A(mg) A(%)
1. Paint on solution to
visibly wet surface
(foil) 11.66 11.31 -0.35 -3.0 10.75 -0.91 -7.8
2. 20 drops of solution
(foil) 47.92 46.95 -0.97 -2.0 45.70 -2.22 -4.6
3. 15 drops of solution
(MRI plate) 23.30 22.10 -1.20 -5.2 20.70 -2.60 -11.2
4. Paint on film one time
(MRI plate) 2.50 2.20 -0.30 -12.0 2.00 -0.50 -20.0
00 5. Paint on film 3 times
(MRI plate) 6.80 6.10 -0.70 -10.3 5.20 -1.60 -23.5
6. No treatment
(MRI plate) 0.5* 0.3 -0.2 -40.0 0.1 -0.4 -80.0
Appearance of grease after 2.5 hours: Yellow-orange film of grease on heavily coated surfaces
Appearance of grease after 22 hours: Orange-gold-brown color. Tacky sticky, still "greasy" on
heavily coated parts (near edge). Thinly coated parts
have hard enamel-like surfaces.
*Mass change of clean MRI plate after 2.5 hours bakeout in oven with other greases.
-------
TABLE V
Mass Changes of Dow Corning Silicone Greases
SUBSTRATE DOW DOW SILICONE
MOLYKOTE HIGH VACUUM GREASE
111 COMPOUND
TEMP 1490C (3QO°F) 138°C (280°F)
FLOWRATE 0.46 ACFM 0.45 ACFM
SAMPLE DURATION 60 MIN. 60 MIN.
STAGE MASS CHANGE.(mg)
1 -1.1 -4.06
2 -0.74 -1.74
3 -0.34 -3.60
4 -0.36 -3.76
5 -0.46 -1.32
6 -0.32 -1.90
7 -0.46 -0.64
Filter +1.86 +2.68
AVERAGE LOSS
PER STAGE 0.54 mg 2.43 mg
NET TOTAL LOSS 1.92 14.34 mg
FILTERS - UNPRECONDITIONED GELMAN TYPE A (OLD TYPE)
EXPECTED FILTER MASS CHANGE - 0.2 mg
-------
TABLE VI
Summ.iry of Flue Gas Test Results. The Flue fins Temperature AvcragcD
About 149°C (300°F) for All Tests. Impactor Flow Rate Was 0.7 ACFM.
Substr.ite
Set
1
(Apiezon L)
Grease on
Substrate flass Change
Stage
0
1
2
3
4
5
G
Back-up
(mg) (mg)
Blank +0
25.
13.
38.
11.
39.
12.
.05
.48
.33
.99
.36
.06
D -4.
P -7
D -27,
P -0,
D -24
P -0
+ 0,
.23
.96'
.29'
.98'
.64
.18'
.35
,15'
(*)
2
(Apiozcm L)
Substrate Mass
Change
(mg) (mg) (*)
Blank +o.
19.8
54.1
73.0
5.3
61.4
2.9
0.1'
35.28
7.51
37.24
9.14
29.28
8.69
D -3
P +0
D -26
P +0.
D -13.
P +0.
+0.
.18
.25'
.33
.54'
.15
.05'
.34
.17'
-
9.2
4.4
71.3
1.6
44.6
3.9
0.2'
3
(Apiezon M)
Grease on
Substrate Mass
(mg)
Blank
21.69 D
3.19 P
19.03 D
4.36 P
26.09 D
7 .10 P
(mg)
+ 0.
-0.
+ 0.
-7.
+0.
-10.
-0.
+ 4.
08
02'
04
143
10
11'
05
40"
Change
(*)
4
(Apiezon T)
Gzease on
Substrate
(mg)
Blank
0,
1 .
37.
2.
38
0.
3.
.1
.3
5
.3
.8
.7
.1'
23.
1,
3.
24.
24.
3.
.68 D
,B9 P
25 P
87 D
78 D
69 P
Mass
Change
(mg) (%)
+ 0
-1
-0
-0.
-0
-1.
+ 0
+ 5
.04
.10'
.25
.2]
.61
.07'
.09
.13*
4.
13.
6.
2.
4.
2.
3.
6
.2
5
5
.3
. 4
6s
5
(Apiezon H) s
Grease on
Substrate
(mg)
Blank
41.55 D
4.18 P
3.81 P
28.04 D
30.13 D
4.87 P
"
Mass
(mg)
+0.01
+ 1.56
+ 0.82
+0.80
+ 0.44
+ 0.53
-0.05
+4 .36"
Change
(%)
-
3.8
19.6
21.0
1.6
1.8
1.0
3.0*
6
(Apiezon N)
'Grease oTT
Substrate
(mg]
Blank
18.19 D
4.41 P
19 .00 D
3.37 P
18.79 r>
4 .14 r
Mass rh.inge
(mg)
+ 0.
-1 .
(0.
-1.
-0.
-1.
-0
+ 4
03
52'
OS
75
.06
.731
.10
.74
[»)
-
8.4
1.1
9.2
1 .8
9-2
2.4
3.3'
1. Grease lost to overflow, not recovered.
2. Rteve-Angel 934MI Filter Material, prnconditinned.
3. Some greaafi lost to overflow, most recovered and d.-posited hacV en foil.
4. Gelnian AC Filter Material, preconditioned. Weight gains mny he partially due to flue gas reactions.
5. Substrates contaminated with ambient dust. Probably not enough to alter results significantly.
6. Percent mass chanqe in filter calculated using final fiJtpr weight.
Note: D means that the ijredse-toluonc mixture was dropped on with an ayedropper
(20 to 25 drops).
P means that the grense-toluene mixture was painted on with a paint brush
(3 to 4 times).
-------
A problem of grease overflow occurred in some of the tests
as a result of reduced grease viscosity at elevated temperature.
This normally resulted in unaccounted loss of mass. Moreover,
excessive loss of grease due to overflow would generally be con-
sidered sufficient grounds for rejection of the grease, since
behavior leading to overflow could not be tolerated in actual
use on impactor substrates.
The results of these tests are summarized below. A total of
6 substrate sets were made up: two sets for Apiezon L and one set
each for the rest. Table VII gives the published physical proper-
ties of the Apiezon greases. Figure numbers refer to photographs
of greased substrates.
Apiezon L (Figures1, 2, and 3)--
Substrate sets 1 and 2 were prepared with Apiezon L grease.
The substrates that were heavily coated (>20 mg of grease) developed
a hard, black, enamel-like surface and the grease showed evidence
of being blown away from beneath the jets. Lightly coated sub-
strates did not develop the "enameled" appearance; however, the
grease was blown away from beneath all the jets, and the grease
was not hardened. Considerable grease overflow occurred during
these runs; the low viscosity of Apiezon L grease at 149°C (300°F)
combined with horizontal impactor operation is probably respon-
sible for this overflow. When thick overflow deposits were found
beneath the foils, these deposits remained "greasy" and were not
discolored.
Apiezon M (Figures 4 and 5)—
Substrate set 3 was coated with Apiezon M grease. Apiezon
M has a melting point which is nearly that of Apiezon L, although
its molecular weight is much lower. (See Table VI.) This grease
behaves much like Apiezon L, exhibiting vivid flow patterns
beneath the jets and evidence of chemical reactivity as well as
overflow onto the substrate support plate. After exposure to the
flue gas stream, this grease solidified at room temperature into
a black, waxy solid. Figure 5 shows where all the grease had been
scoured from directly beneath the jets on stage 4.
Apiezon T (Figures 6 and 7) --
Substrate set 4 was prepared with Apiezon T grease. Apiezon
T has a melting point of 125°C (257°F) and although this is a
fairly high melting point for grease, the aluminum and stainless
steel substrates showed clear jet patterns and flow of grease.
The grease was slightly discolored after exposure to the flue gas
but afterwards remained "greasy". Some overflow occurred.
11
-------
TABLE VII
Typical Physical Properties of Some Apiezon Greases*
PROPERTY
GREASE H
GREASE L
GREASE M
GREASE N
GREASE T
K)
Approximate melting point, C (a)
Specific gravity at: 20°C
30°C
Viscosity cP of molten grease at:
50°C
100°C
Average molecular weight
Coefficient of expansion per C
over 20°C-30°C
Thermal conductivity Btu in/ft2
h.deg F 1=50
w/m deg C 0.216
Specific heat at 25°C: cal/g 0.42
Joule/g 1.7
Latent heat of fusion, cal/g
fusion peak, °C
Volume resistivity, ohm-cm
Permittivity
Loss tangent
Surface breakdown, kV at flash-
over
Electric strength, volts/mil
47
0.896
0.889
766
62.3
1300
0.00076
1.40
0.202
(b)
(b)
15.1
32
1.2 x 101S
2.3
less
24
730
44
0.894
0.887
413
29.8 .
950
0.00075
1.33
0.192
(b)
(b)
18.7
34
2.6 x 1016
2.1
than 0.0001
28
850
43
0.911
0.904
0.00072
1.31
0.189
(b)
(b)
15.0
31
2.0 x 1016
2.3
27
820
125
0.912
0.905
0.00073
1.22
0.176
(b)
(b)
3.3 x 1012
2.3
24
730
a. Grease H does not melt at high temperatures and consequently many of the above physical proper-
ties cannot readily be measured.
b. Specific heats of Greases L, M, N and T cannot be measured as their fusion peaks are too close
to room temperature.
*Prom Bulletin 43a, Apiezon Oils, Grease and Waxes, James G. Diddle Co., Plymouth Meeting, PA 19462,
-------
rH
X 0)
•H 0>
E *J
CO
0)
c v>
0) (0
3 IV
—I rH
O C
•U -H
I It
0) -P
to 10
rd
OJ
l-i •
CPVO
-'O
W C
0) O
t-l TT
4J
W «
A rsl
3
ui ui
0)
T3 0^
0) 10
(n -u
10 w
OJ
M
CT1 • .
C w
J O 0)
^J
C 13 HJ
0 0) M
HI Oi W
•H O -Q
a M 3
< T3 W
0)
U(
3
13
-------
TJ
01
a
a
o
a> 01
M 4J
3 m
4J J-(
x -u
•H in
e ja
3
o> in
c
01 i-H
3 01
i-H 0)
O 4J
4J UJ
I
H
>-i C
a>
01
X) 0)
3 cn
W (0
±>
TD in
a>
^ a
ET3
a>
!-J U)
0
C ^H
o u
N
01
•H •
a c
< o
0)
IH
3
!T>
•H
14
-------
0)
J-l
3
•U
X
0)
c
0
4J .
I W
in
J2
» 3
in oo
m -H
M o
4-> U-l
3
-------
Figure 4. Apiezon M greased substrates, grease-toluene mixture
painted on. Aluminum foil substrates.
-------
-p
to
0) X)
M 3
3 to
-P
X f-t
•H .H
6 0
m
0)
c §
Q> 3
3 G
F-l -H
O 6
JJ 3
I H
01 <
cn
(0
-P -P
(0 C/3
3 Q,
tn 3
-------
Apiezon H (Figure 8)--
Substrate set 5 was made up with Apiezon H grease. This
grease melts above 250°C (482°F) and during this test showed no
signs of having melted. Some discoloration took place but the
grease remained "greasy". The discoloration could be partially
due to contamination. A thin layer of room dust (^20 ym-50.ym
diameter) appears uniformly distributed over all these substrates.
This could have occurred as the substrates were being prepared, as
they were being unloaded or during weighing. Thus the nearly uni-
form weight gain of these substrates may be connected with this
contamination. Jet patterns were barely visible on some stages;
however, a uniform coating of grease remained on each. No over-
flow of the grease was observed.
Apiezon N (Figure 9)—
Substrate set 6 was prepared with Apiezon N grease. Apiezon
N is similar to Apiezon L and M in that it melts between 40°C
(104°F) and 50°C (122°F) . When exposed to 149°C (3006F) flue gas
streams this grease is scoured from beneath the jets so that none
would be left to catch particulate. Grease overflow occurred on
two stages. The grease showed slight evidence of having reacted
chemically, turning very dark and becoming slightly waxy in places.
Back-Up Filters
Two types of glass fiber back-up filters were used in the
flue gas tests. Reeve Angel 934AH was used with the Apiezon L
grease and Gelman AE was used with the rest. Both types of filters
took on a visibly gray color after each test. This may be due to
volatile components being driven off the substrates. However,
this same coloration was noticed with the Apiezon H grease which
had an overall weight gain. We have seen this coloration before
when greased substrates were used in field tests.
On the basis of this study we concluded that Apiezon H grease
is the best available of the greases tested.
Field Use of Apiezon H Grease
In May of 1976 during a field test at a steam plant, University
of Washington (UW)Source Test Cascade Impactors were used with
Apiezon H greased substrates. Flue temperatures averaged 124°F
(255°F) and run times were 30 minutes. All runs were made at the
outlet of the electrostatic precipitator where SO2 and S03 concentra-
tions averaged 450 ppm and 0.8 ppm respectively.
Blank runs were made with the UW impactors- in order to deter-
mine the magnitude of weight changes that could be expected from
loss or flow of the Apiezon H grease. For a blank impactor run
18
-------
QJ
-P H
C fl
-H 'H
(fl
0)
>-l 10
3 -H
-P
X -P 3
M W rH
tn (0
C
- o a>
0) ^
4J ^3 fO
ra a)
-P &
tn o 13
X3 M Pi
a T3 fl
tn
Q
05 t3
-------
'O
0)
-p
c
•H
KJ
0) O
1-1 -p
3 to
-P l-i
X -P
•H Cfl
G .Q
0) in
C
0) .H
P 0)
H (1)
O -P
I
Q) Cfi
Ul U)
m CD
Q) rH
1-1 C
(0
•* -P
0) CO
4J
-P CN
cn
X! 0)
3 en
W (0
^J
T3 CD
0)
W M-i
ra O
G)
n &
Oi 3
(1)
EH U)
O
C rH
O U
N
0
•H •
a c
< o
r^
0)
20
-------
CO
w
CD
M <0
2 -P
-P CO
X
OJ
C CD
CD tP
D id
rH 4J
O CO
-P
I C
CD O
en
CD QJ
5-i CL,
{Ji p,
O
CD
-P
CO C
X) (0
CO CM
T3 CO *
(D CD CO
to Cn CD
to ta -p
(D -P rd
i-l CO M
tjl -p
X O
LQ
w
c ^
O CD
N 4-» r-i
QJ C
-------
O
-P
C
ft
-p
X
•H
5
0)
c
0)
o
-p
I
Q)
0)
M
cn
•
< tn
in 0)
to JJ
-p to
« s-i
^ 4J
•H
O
tn
in
tn C
•H
X £
3
C -H
O <
N
(U
•H •
ft Ci
< O
CTi
a>
cn
•H
Cn
22
-------
the impactor is preceded by a Gelman 47 nun stainless steel filter
holder fitted with a glass fiber filter. Next, the impactor is
inserted into the precipitator duct and operated as in a normal
run. No attempt is made to sample isokinetically, but a flow
rate and run time is chosen which is typical of impactor operation.
Table VIII shows the individual stage mass changes that oc-
curred during each blank run. The coupling between the stainless
steel Gelman 47 mm filter holder and the impactor was not made of
stainless steel and was subject to some' corrosion. This corro-
sion occasionally flaked off during impactor disassembly and de-
posited on stage 0. Consequently, larger than average weight
gains occurred on runs 4 and 5. Examination of individual sub-
strates of the blank runs showed the following:
1. Stage 0 for each run was contaminated with some debris.
2. All substrates in run 6 were discolored.
3. The back up filters, 47 mm Reeve Angel 934AH material
showed no large weight gains with the exception of run
5, and none of the filters were discolored.
4. With the exception of run 5, discoloration of the grease
was infrequent and unrelated to weight gains.
5. The grease showed no sign of chemical degradation or
flow for all runs.
Since these weight gains are not much different from those
observed when glass fiber substrates jare used (see Tables XXII
and XXVI) we conclude that Apiezon H grease will be a suitable sub-
strate material when flue temperatures do not exceed 177°C (350°F).
At higher temperatures some material bakes out of the grease and
weight losses occur. A limited laboratory test shows that at 288°C
(550°F), Apiezon H grease loses weight and undergoes chemical
change.
Summary of Results of Evaluation of Greases
Upon preliminary screening by static heating tests in the
laboratory, six of the nineteen greases tested were found to have
acceptable characteristics at.elevated temperatures. Among those
greases eliminated by these te'sts, large changes in mass or in
consistency had occurred.
In the field tests greases were applied to metal foil impactor
substrates and were subjected to a flue gas sampling procedure.
Particulate matter was removed by a prefilter so that the effects
of the flue gas alone on the greased substrates could be observed.
23
-------
TABLE VIII
Apiezon H Blank Mass Gains for University of Washington
Mark III Source Test Cascade Impactors. Coal fired power
boiler source, cold side precipitator operating at 107OC
(225°F), 30 minute runtime. All masses in milligrams.
M
Stage
0
1
2
3
4
5
6
Filter*
Run 1
5/17/76
0.22
0.06
0.04
-0.03
0.02
-0.06
-0.14
-0.32
Run 2
5/1-7/76
0.08
0.09
0.01
-0.11
-0.08
-0.13
-0.12
-0.18
Run 3
5/19/76
0.16
-0.18
0.04
0.09
0.09
0.05
0.13
0.02
Run 4
5/20/76
0.55
0.11
0.10
-0.13
-0.05
-0.03
-0.05
0.08
Run 5
5/21/76
0.65
0.85
0.64
0.64
0.47
0.31
0.16
0.34
X
0.33
0.19
0.17
0.09
0.09
0.03
-0.004
-0.01
0
0.25
0.39
0.27
0.32
0.22
0.17
0.14
0.25
* Reeve Angel 934AH 47 mm disc,
-------
As a result of the field studies it was concluded that Apiezon H
grease performed best of the greases tested. Other greases studied
displayed changes in consistency or a tendency to flow under the
influence of the gas stream.
Further tests on Apiezon H have demonstrated that this grease
is a suitable substrate material for applications where the temp-
erature does not exceed approximately 177°C (350°F).
EVALUATION OF FILTER MEDIA FOR USE AS SUBSTRATES AND BACK-UP FILTERS
Substrate mass gains have been found to be a source of very
large errors when sampling industrial flue gases with inertial im-
pactors in which glass fiber material is used for substrates.
Ideally, the only mass change in a substrate should be that result-
ing from collection of particulate matter from the flue gas. How-
ever, if gas-phase reactions take place, involving components of
the glass fiber substrate, then it is possible for substantial
mass gains to occur, unrelated to the particle size distribution.
Previous Results
A report by Forest and Newman2 indicates that mass gains in
glass fiber filters are possible by conversion of S02 to various
suflates.
The work of Charles Gelman and J. C. Marshall of the Gelman
Instrument Company, makers of various filter media and equipment,
seems to confirm that S02 absorption is the cause of the mass
gains.3 They acknowledge that a high pH glass fiber can absorb
sulfur dioxide and thus cause erroneously high particulate weights.
Pate and Lodge's work1* using Na2C03 treated glass filters as "dosi-
meters" for S02 exposure chambers, with mass gain of the filters
being a time function of exposure to S02 was mentioned.
According to Gelman and Marshall, the SO2 reaction on glass
fiber could cause "a 30% error in the measurement of total sus-
pended particulate matter" in an urban atmosphere. The new
automotive catalytic mufflers could increase this error. It is
possible that flue gases would give even higher errors, especially
if the gases have a high moisture content, because the reactivity
of SO2 appears to increase at higher humidity.
Both quartz and glass fiber filter material were tested by
Gelman. The quartz was found to be non-reactive to S02. The glass
fiber materials, Type II and SpectroGrade, prepared with HjjSO^,
were low in S02 pickup. The SpectroGrade glass, prepared with
HC1, picked up significant amounts of S02. (See Table IX.) Their
explanation is that the glass prepared with H-jSO,, has reacted to
form CaSO^ to prevent further reaction with S02 to form sulfates.
The test used for SO2 reactivity was to expose the filters to a
water saturated atmosphere of S02 for 20 hours. Mass change of the
filter was measured.
25
-------
TABLE IX
SULFUR DIOXIDE PICKUP3
rag/Sheet - 20 Hour Exposure
Initial
PH
SpectroGrade-HCl
Siliconized 3 7.1
SpectroGrade HCl 17 9.4
SpectroGrade
H2SCU 3 6.8
Type II Fiber
H2SO^ 3 6.8
Quartz ° 7-°
Quartz
Alkali Strengthened 23 (est.) 9.5
26
-------
Another type of SpectroGrade coated with an organic silicone
resin showed low SO2 pickup. This type of SpectroGrade with the
silicone treatment is now standard type. Use of the siliconized
SpectroGrade at elevated temperatures can result in the disappearance
of the coating and S02 absorption by the filter medium since the
filter is prepared with HCl.
Although the work by Gelman and Marshall showed quartz fiber
media to be non-reactive with SOa, the material has been found to
be too fragile to be used successfully as an impactor substrate
material.
Teflon is nearly inert and might be a good choice, although
it cannot be used in hot electrostatic precipitators where flu'e
temperatures regularly exceed 260°C (500°F). Another disadvantage
of teflon is that particles tend not to adhere upon impaction,
leading to scouring and particle bounce.
On the basis of strength, material integrity and particle
retention, only glass fiber materials (or greases, used below 177°C
[350°F])are left as suitable substrates, in spite of the problem
posed by S02 uptake. These results imply that there is no inert
filter material which is a usable substrate for cascade iinpactors
as obtained directly from the manufacturers. Of the glass fiber
materials tested, Whatman GF/A, GF/D, and Reeve Angel 934AH show
the least mass gains when exposed to flue gases.
Preliminary Laboratory Screening Tests
The purpose of the laboratory screening tests was to gain an
understanding of the mass changes that occur and to facilitate the
selection of sufficiently inert filter material for impactor sub-
strates. A suitable substrate material would be one which has
stable low mass characteristics and is mechanically strong to resist
cutting, tearing, and loss of material. Since the mass changes
are apparently a result of chemical reactions involving the pro-
duction of sulfates, the laboratory work was principally concerned
with exposure of the substrate materials to sulfuric acid and/or
S02 gas. The stability of mass changes over long time periods
was investigated in order to evaluate the prospects for precon-
ditioning techniques as a means for controlling mass changes. Two
laboratory test methods were employed. One approach used a flow
of gaseous SOz through the filter material, and the second involved
soaking the material in hot sulfuric acid solution.
Exposure of Filter Media to SOa
In this laboratory study glass fiber substrate materials were
exposed to air, SOz, and water vapor at an elevated temperature.
Figure 10 shows a diagram of the conditioning apparatus. Dry air
was preheated in the conditioning oven and then bubbled through a
27
-------
Flowmeter
CD
S02
Plowmeter
D
I
Air
Preheat
coils
'1
Sample conditioning
chamber
Oven
Humidifier
Heater tape
\* V?
VJater heater
Air-S02 exhaust
Air flow direction
S02 flow direction
Air-SC>2 mixture
flow direction
Figure 10 Diagram of experimental set-up for filter substrate
conditioning experiment
-------
heated water container 60°C (140°F). Next, S02 was introduced to
the heated and humidified air stream. All lines carrying SOz laden
air was then passed through a chamber containing the filter media
being tested. The chamber was designed so that conditioning gases
flowed through the filter stack being conditioned.
Both gravimetric and pH determinations were used in investigat-
ing the rate of S02 uptake by the sample material. The procedure
used to determine the filter pH was a modification of Gelman's
method for 8" x 10" filter sheets.3 Two 47 mm filters were used
for each pH determination.
In one series of tests, four different kinds of glass fiber
substrate materials were treated in the laboratory conditioning
chamber on an hour-by-hour hasis. After each hour of conditioning
the substrates were weighed, desiccated, reweighed, and the weights
were recorded. It was found that desiccation resulted in no change
in the weights, so this practice was discontinued. The four sub-
strate materials tested were Reeve Angel 934AH, Gelman AE, Gelman
SpectroGlass, and Whatman GF/A. All filters were 47 mm in diameter.
Eight groups of twenty filters each were prepared and conditioned
in the following order:
1. Reeve Angel 934AH
2. Gelman AE
3. Gelman SpectroGlass
4. Whatman GF/A
5. Reeve Angel 934AH
6. Gelman AE
7. Gelman SpectroGlass
Gas flow was such that the Reeve Angel material was exposed
first. Figure 11 shows the results for the first nine hours of
conditioning. The conditioning temperature was 260°C (500°F).
Water saturated air with 5% SOa was pumped through the chamber
at a rate of 2.1 1pm. Note that after nine hours of conditioning
the Reeve Angel material had not gained but lost weight. However,
the weight loss is miniscule and is probably due to handling^ All
others had gained significant amounts.
Sulfuric Acid Wash Treatment of Filter Media
Another approach to passivating impactor substrates was also
investigated. Bundles of Reeve Angel 934AH and Gelman AE 47 mm
filters were soaked in hot sulfuric acid-water mixtures for 90
minutes. These filters were then washed in distilled water, washed
again in ethanol (ETOH) or isopropanol (IPA), dried, baked and
desiccated. Upon conditioning for one hour under the conditions
described above (260°C [500°F], air-water gas mixture with 5%
S02 ) eighteen Gelman AE 47 ram filters gained 11.9 mg or 0.66mg/
filter. Twenty untreated Gelman AE 47 mm filters gained 67.7 mg
or 3.39 mg/filter with the same conditioning. Therefore, the
29
-------
• •
a; _,
ii o
£
n
oo
CO
m 9
O
cc
o
O)
S s
< in
0)
Q 7 -7
> 5? 5?
i- < <
OJ _J _J
£ UJ UJ
u_ O CJ
^
J2 4 •
E
>
CO
o
I<
CD LU
O
_ z
Z < 44 • • • -^
^
p UJ
*^ UJ
x Hi
5 CC
4« • • • • 4
• •
I i i i ' '
o
> pj
o
o
d
q o q q q ' o q
to iri ^ to CN t-^ o
q
o>
q
00
p
r-'
o
to
o
UJ
z
q o
.
O
o
-» S
H
0)
CP
•H
/ (
asvauoNi SSVIAI
30
-------
sulfuric acid wash can make a difference when the filters are known
to gain weight. The Reeve Angel material again showed no weight
gains.
The hour-by-hour conditioning of the four different types of
glass fiber filter substrate materials was continued, and mass gains
were monitored for a total of 26 hours of conditioning. In addition,
the sulfuric acid washed Gelman AE and Reeve Angel 934AH materials
were laboratory conditioned on an hour-by-hour basis for a total of
18 hours. Figure 12 shows the mass gain per 47 mm filter versus lab-
oratory conditioning time. Data for Gelman AE,'AE acid washed, Gel-
man SpectroGlass, and Whatman GF/A are presented. Reeve Angel 934AH
plain and acid washed filter materials were also conditioned, but
since mass increase in this material was negligible these data were
not graphed. The Gelman AE acid washed material gained approximately
one third as much mass as the plain Gelman AE. Figure 12 also shows
that even after 26 hours of laboratory conditioning mass gains may
be expected with further conditioning.
Gas analyses were conducted on the conditioning gas at the in-
let to the conditioning chamber. SO2 and SO3 concentrations were
measured at approximately 10,000 ppm, and 3 to 5 ppm, respectively.
Iron is a catalyst for the conversion of SOa to SO3 at the condition-
ing temperature (22°C, 428°F). The conversion efficiency is small,
less than one percent, but still enough SO3 is produced to be detected,
Since all the SOz carrying lines are stainless; steel and since the
conditioning chamber is stainless steel we should expect that the
filters which have been SOz conditioned have also been exposed tc SO =.
Table X summarizes the end-point results presented in Figure 12.
These data are presented in the order in which the 47 mm filters were
conditioned in the stainless steel conditioning chamber (alundum
filter holder). Results are presented on a mass gain per filter
and percent mass gain basis.
In another series of tests, chemical analyses were made on
the laboratory conditioned and unconditioned filters. Table XI
shows the barium, calcium, and soluble sulfate concentration in
two types of glass fiber filter material conditioned at SRI:
Reeve Angel 934AH and Gelman AE. These 47 mm filters were
analyzed when received, after being baked-out and desiccated and
after being conditioned. The Reeve Angel material shows large
amounts of calcium and miniscule amounts of barium and soluble
sulfates,' even after 12 hours of conditioning. The Gelman AE
materials show large amounts of calcium as well, but after condi-
tioning there is a great gain in soluble sulfates. This is re-
flected in the mass gains for this material. Each 47 mm filter
gained on an average 2.93 mg. The initial pH of the Gelman AE
material after baking was 9.8. With two hours of conditioning
the pH dropped to 8.8. This is in contrast with the behavior of
the Reeve Angel material. The pH of this substrate material stayed
rather constant at about 5.9 to 6.7 before and after conditioning.
Mass' gains on conditioning for any length of time were very small.
31
-------
0
-5
o
— c
0
u
< n»
*" 2 '55
«j
° 0 g -
O «£,
o OO O F I < IS
o OO 01 o ~~ IL ••=
» 00 O iu £ uj O S
« oo a ,X, ^ ^K UJ UJ IU I <
o oo < o (3 a o 3 QJ
OO <0 oO«0*.
o OO . O
o OO 4 D
o OO D
o OO <• D
o O O O
o O'O < a
o O O O -
0 O O « O
O O < CD -
1 1 1 1 1 1 l_l ^ \^ 1 4. 1 .4,-^
_: o o o o o o o o oweor^u
^OiOOrsCDUS^r CO p4 T^OOOti
o
"ml"
d
o 0
1)
u
c
3
° nl
rt a)
E
!H -H
i
in Z yj J-i
C> nj 0
E ° ^
« 5 u 2
o ^ ^
O -H X3
(C
M W rH
cn
(C U-l
S 0
fN
CM H
(D
S-l
cn
•H
D
3
U3d NIVO SSVW
32
-------
TABLE X MASS GAINS OF 47 mm GLASS FIBER FILTER SUBSTRATE MATERIALS
FROM LABORATORY CONDITIONING1
Batch Number of 47 nun Conditioning Mass Before Mass After Mass -Gain Percent Mass
u>
Material2
Reeve Angel
934AH
Gelman AE
Gelman Spectro
Glass
Whatman
GF/A
Reeve Angel
Gelman AE
Caiman Spectro
Olass
Wiatman GF/A
R^eve Angel
934 AH
(Acid Washed)
Gelman AE
(Acid Washed)
Number Filters Conditioned Time
3307
8204
8192-
20232
3563
3307
8204
8192-
20232
3563
4292
8206
20
20
20
20
20
20
20
20
20
20
(Hours)
26
26
26
26
26
26
26
26
18
18
Conditioning Conditioning per
2
2
2
1
2
2
2
1
2
2
(grams)
.1888
.6644
.6717
.7695
.2149
.6266
.6522
.7361
.0968
.6939
2.
2.
2.
1.
2.
2.
2.
1.
2.
2.
(grams)
1881
8735
8160
8349
2166
8375
8051
8272
0975
7699
filter
Gain
(mq)
-0.
10.
7.
3.
0.
10.
7.
4.
0.
3.
04
46
22
27
09
55
65
56
04
80
-0.
7.
5.
3.
0.
8.
5.
3.
0.
2.
03
84
40
70
08
03
77
64
03
82
'U S02, 3-5 ppm SO*, Saturated H20, 220°C (428°F)
'Filter materials ore listed in order of conditioninq in a stainless steel Alundum thiniblc- holder.
-------
TABLE XI
Barium, Calcium, and Soluble Sulfate Content in Two
Glass Fiber Substrate Materials
Original
After Bakeo-ut
After Conditioning
(2 hours)
After Conditioning
(12 hours)
Reeve
Angel
934AH
BARIUM
Ba++
Mass
63
54
135
(yg)
%BaO
.06
.05
.13
Substrate
Material
CALCIUM
Ca++
Mass
14202
14055
14531
(yg)
%CaO
17
17
18
.9
.8
.2
SO 4-
Mass
3.
3.
4.
Soluble
SULFATE
-
I
5
5
5
(wg)
%s
.0
.0
.0
<0.01
13820
17.6
92
.C
Gelman AE Substrate Material
Original
After Bakeout
After Conditioning
(2 hours)
BARIUM
Ba++
Mass (ug)
<10
<10
<10
%BaO
<0.01
<0.01
<0.01
CALCIUM
Ca++
Mass (yg) %CaO
6094 6.5
5470 6.1
5758 5.9
Soluble
SULFATE
S04
Mass (yg)
<10
<10
3013
%£
-------
These results indicate that a laboratory induced sulfate
mass gain can be made to occur in glass fiber filter materials.
Whether or not this mass gain, or "conditioning" lasts is another
question. To determine if the conditioning is a temporary effect,
samples of these filters (16 to 20 filters per sample) were con-
ditioned for 2 to 12 hours. Some were exposed to ambient air after
conditioning, while others were desiccated.
Figures 13 and 14 show the results of these tests for the
Reeve Angel 934AH material. Figure 13 shows the percent weight
change versus days after conditioning for groups of filter con-
ditioned for 2 hours and 12 hours. One group was exposed to
ambient air after conditioning and another group was desiccated
after conditioning. In both cases minute mass gains were seen
for 12 hour conditioning and minute mass losses were seen for
2 hour conditioning. In either case there appears to be no re-
action after conditioning resulting in an appreciable mass gain
or loss. Figure 14 shows the pH of single filter samples measured
after conditioning for 2 and 12 hours. As in Figure 13, one group
was exposed to ambient laboratory conditions while another group
was desiccated. This substrate material appears to have essentially
no change of pH upon conditioning, and it is possible that since the
material is only slightly acidic, changes in the pH of water used
in the pH determination could have caused the changes shown in
Figure 14. Whenever pH of a filter sample is measured, the pH of
the water used is also measured. We believe this to be the case
for the low pH recorded on day 2 of the desiccated sample and day
3 of the exposed sample. In this case the raw distilled water used
in the pH determination had a measured pH of 4.32.
From these tests it would appear that, if pH is a good moni-
tor, the conditioning has a lasting effect. Samples of this
material, conditioned for 12 hours, which were stored under desicca-
tion for as long as 77 days show no mass change and small change in
pH (6.10 before, 6.77 after).
Field Studies
The effects of industrial flue gases on various filter sub-
strate materials were studied in a series of field tests. Several
types of filter material, listed in Table XII, were obtained from
commercial suppliers for testing. In these experiments, uncondi-
tioned, laboratory conditioned, and acid washed glass fiber sub-
strate materials were subjected to flue gases under various sampl-
ing conditions. Since the purpose of the evaluation is to determine
procedures and identify materials which exhibit minimum weight
changes for sampling applications, the filter media were exposed to
flue gases for time intervals characteristic of an impactor run
during stack sampling.
In the typical experimental procedure several filters are cut
to size, if necessary, and mounted in 47 mm Gelman stainless steel
35
-------
g
•H
-P
in
in u-i
(d o
iH
CP C
O
K-H
< -U
-* 0
to C
CT> 3
M-t
rH
O fd
t7>
c to
< rt
4) .H
> -H
0) )-(
« QJ
•P
j-« d
o g
tw
QJ
0) -!-»
cr> d
£ M
(C 4^
x: tn
O J2
-H Q) -r^
Q) 4-1 13
5 r-i C
•rH O
-P «4-t O
a
(U H l-<
u
-------
pH
9.0
8.0
7.0
6.0
5.0
4.0
pH BEFORE CONDITIONING
CONDITIONED FOR 2 HOURS
mini i i i i i i i i i ; i i i i i 111 M i i i i
CONDITIONED FOR 12 HOURS
SAMPLE EXPOSED TO AMBIENT AIR
AFTER CONDITIONING
m
u>
pH
9.0
8.0
7.0
6.0
5.0
4.0
'Tiimiiiiiiim'inu'-i'iiiiinnii
pH BEFORE CONDITIONING
Jmmii i i i i i i i i i i i i i i i i 11 11 i i i i j~
CONDITIONED FOR 2 HOURS t-
Mllllllll I I I I I I I I I I I I I I II II I 1 I I I I l~
1 CONDITIONED FOR 12 HOURS -
SAMPLE DESSICATED AFTER CONDITIONING
DAYS AFTER CONDITIONING
(conditioning occurs on day one)
Figure 13. pH of Reeve Angel 93f AH glass fiber filter substrate
material as a function of time after conditioning.
-------
TABLE
FILTER TYPES TESTED
Gelman Type A GA
Gelman Type AE GAE
Gelman SpectroGrade SA
Mine Safety Appliance 1106 BH MSA 1106 BH
Reeve,'Angel 900^ RA 900AF
Reeve. Angel 9-34AH RA 93-4AH
Whatman GF/A GF/A
Whatman GF/D GF/D
Chemplast Teflon Filter Teflon
Pallflex Tissuquartz 2500 QAD Quartz
38
-------
filter holders. The filter holders were assembled as a series filter
arrangement and run as an Andersen Stack Sampler would be run. The
first filter holder was a pre-filter which removed the particulate
material. The remainder of the filters, each in its holder, were
exposed only to the flue gas. Isokinetic sampling was not considered
important in order to approximate the exposure of the substrates to
flue gases in typical sampling situations. In some cases, impactors
loaded with substrates in the usual fashion were used with prefilters
rather than using the series of 47 mm filters described above.
The field test sites included ESP applications at a gas fired
cement kiln and six different coal fired steam plants, covering a
temperature range from about 100 to 350°C {212 to 662°F).
The results of tests made at two steam plants, A and B, are
especially interesting. The substrates were supplied by Andersen
2000, Inc. At steam plant A the gas temperature was 149°C (300°F)
and at steam plant B the gas temperature was 316°C (600°F).
Determinations of soluble sulfates were made on the substrates after
each run. The results of those suflate determinations are plotted
against the gain in mass per substrate in Figure 15. The solid
line indicates a perfect one-to-one correspondence between the ob-
served mass gains and amount of soluble sulfates found on each
filter. These data fall very close to this line of perfect agree-
ment. No correlation was found between flue gas SO2 concentration
and blank mass gains in this test series. Data from two tests at
Plant B are shown in Table XIII. These data show a similar near
perfect agreement between the weight increases determined gravi- .;
metrically and the chemically determined sulfate content on the v
second test. No weight increases were observed during the first
test. When queried as to whether they had changed suppliers for
their substrate material in the time between the first and second
tests at steam plant B, Andersen 2000, Inc. replied that they had
used and were using Gelman Tyep A glass fiber filter substrate
material but that Gelman had changed their manufacturing process
so that the Type A material used in the second plant B test was
washed in hydrochloric acid whereas the material used in the first
test at plant B was made with a sulfuric acid wash.
Effects of Flue Gas Temperature
Figure 16 shows the relation between substrate mass gain and
flue gas temperature. With the exception of the "pre 6/74" point,
a linear relationship seems to hold. The "pre 6/74" represents data
from the first of the two tests conducted at steam plant B where
the substrate was quite neutral compared to the basic substrates in
the second test.
Figure 17 shows the results of tests of several types of 47 mm
glass fiber filter substrate material at different flue gas condi-
tions and temperatures. This again illustrates the apparent relation-
ship between flue gas temperature and substrate mass gain as well
as the insensitivity of SO 2 concentration.
39
-------
3 4
MASS GAIN, mg
Figure 15. Comparison of mass of sulfate on blank
Andersen impactor substrates and observed
anomalous mass increases.
40
-------
TABLE
SOLUBLE SULFATE ANALYSES OF FILTERS USED AT STEAM PLANT B
Unused samples from batch used at steam plant B (6/74). No
samples from actual blank runs (where no mass gains were observed)
are available.
Sample No.
11
18
IF
Tptal mg
SO ., "/filter
^0.2
Reported
wt gain, mg
Set 1 from second steam plant B test (1/75)
Unused, perforated, unbaked 9,4
Unused, perforated, baked 9,4
Sll 7,6
S12 7.7
S13 7.4
S14 7.0
S15 7.1
S16 7.1
SI? 7.0
S18 • 8 = 8
^0.2
^0.2
4.4
4.2
5.1
5.0
5=6
5.6
6.0
5.6
4.98
4.96
5.58
5.56
6.06
6.10
5.94
6.04
Set 2 from second, steam plant B test (1/75)
Unused/ perforated, baked 9.3
Unused, solid, baked 9.7
S20 6,8
S21 6.7
S22 7.1
S23 7.4
S24 7.2
S25 7.3
S26 7.2
S27 7.1
S28 7.0
S2F 8.2
.
7.3
5.1
4.6
5.2
4.5
5.0
4.6
4.9
4.6
5.5
8.34
5.30
5.22
5.40
4.80
5.44
5.24
5.50
4.S6
6.24
L> .
pH determined after the filter sample was in contact vvith 10 ml
of distilled water (pH 5.6) for 1 hr.
The total soluble sulfate was determined' by a Ba(ClO^)2
titration following a water extraction of the sample.
41
-------
""
E
Z
5 —
100
o
£
a
L COAL FIRED POWER BOILERS
0 PORTLAND CEMENT KILN
150
200 250
GAS •; EMPERATURE, °C
300
3630-001
Figure 16- Anomalous mass increases of Andersen glass
fiber impaction substrates at different
flue gas temperatures.
42
-------
1.5
1.0
2
0
CO
CO
• GELMAN TYPE A (OLD)
O GELMAN SPECTRO GRADE TYPE A
& MSA 1106 BH
0 REEVE ANGEL 900 AF
CEMENT
PLANT
50 PPM
200
303
TEMPERATURE, °C
400
3630-003
Figure 17. Anomalous mass gains of various 47mm diameter
glass fiber filters at different temperatures
(60 minute samples at flowrates of 0.25 ACFM)
43
-------
In situ Preconditioning
Because mass gains in filter substrate media are related to
chemical reactions occurring as a result of the action of hot flue
gas on filter components, it may be possible to force the reactions
to occur by a preconditioning process before using substrates in
actual impactor runs. An approach that can be followed is to ex-
pose substrates to filtered flue gas for preconditioning.
The results of in_ situ preconditioning experiments carried
out with two different types of filter materials are shown in
Figures 18 and 19. Substantial reductions in mass increases were
produced by the preconditioning procedure.
Figure 18 presents the gain in mass for Reeve Angel 900AF
glass fiber filters as a function of the duration of exposure to
the flue gas; The most rapid mass changes in the unconditioned
filters occur within a short time after the onset of exposure to
the gas. Figure 19 shows the mass gains of Andersen Impactor sub-
strates versus exposure time for preconditioned and unconditioned
"substrates. The dates at the top of the figure indicate the time
at which these substrates were acquired from Andersen 2000, Inc.
The 6/74 Normal Substrates show an increase and leveling off with
exposure time while the 6/74 preconditioned sub'strates show some-
what smaller mass gain. The "HOT" 6/74 preconditioned substrates
would seem abnormal compared to Figure 11 but the conditioning
with hot flue gas apparently reduced the mass gains for this
filter set. The 1/74 Normal Substrates show a possible linear
relationship, although certainly not conclusively. The precondi-
tioned 1/75 Substrates indicate a satisfactorily low mass gain
versus exposure time.
One problem with these data is that there was no positive
identification of the filter media supplied to us by Andersen 2000,
Inc. Therefore, experiments with these filters are, in a sense,
uncontrolled. The results in Figure 17 showed that mass gains are
far from uniform among different types of filter media when exposed
to identical concentrations of SO and temperature.
«n>
With this problem in mind, further tests were designed to gain
an understanding of the mass changes and to facilitate the selection
of a sufficiently inert filter material for impactor substrates.
A suitable substrate material would be one which has stable mass
characteristics and is mechanically strong to resist cutting, tear-
ing, and loss of material.
Several types of filter material were obtained from commercial
suppliers for testing: Gelman Types A, AE, and SpectroGrass glass
fiber filter material, Mine Safety Appliance 1106-BH glass fiber
filter material; Reeve Angel 900AF and 934AH glass fiber material;
Whatman GF/A and GF./D glass fiber material; Chemplast teflon filter
membranes; and Pallflex Tissuquartz 2500 QAD (see Table XII). The
-------
2.0
s"
o
to
1/3
O NORMAL
PRECONDITIONED
234
EXPOSURE, hours
3630-005
Figure is. Anomalous mass gain of 64mm diameter Reeve
Angel 900AF glass fiber filters.
45
-------
• NORMAL SUBSTRATES
D PRECONDITIONED SUBSTRATES
A NORMAL SUBSTRATES
& PRECONDITIONED SUBSTRATES
1.5
1.0
0.5
EXPOSURE, hours
3630-004
Figure 19. Anomalous mass gains of Andersen impactor
glass fiber impaction substrates.
46
-------
method chosed to test the filter media was to expose them directly
to the flue gases for time intervals characteristic of an impactor
run. Several Gelman stainless steel 47 mm filter holders were used
to accomplish this. These holders were assembled as a series fil-
ter arrangement and run just as an Andersen Stack Sampler would be
run. The first filter holder was a pre-filter which removed the
particulate material. The remainder of the filters, each in its
holder, were exposed only to the flue gas.
Before the weighed filter samples were loaded in the Gelman
holders, they were cut to 47 mm diameter where necessary, baked
.in a laboratory oven at 287°C (550°F) for two to three hours, and
desiccated for at least twenty-four hours. The samples remained
in the desiccator until just prior to.use.
Two sampling sites were chosen for testing of the filter
media. Both sources were placed where previous impactor runs had
been made, and the sources were of different types. The first
testing was done at the outlet of a hot-side ESP at a cement plant
between February 12th and February 21st, 1975. Two gas fired kilns
were in operation while the tests were being performed. Outlet
temperatures were in the neighborhood of 260°C (500°F). Other
data, including flow rates and mass gains, are listed in Table XIV.
Filter la includes the particulate catch in each case.
The second site was a power plant (steam plant A). Here tests
were performed at the coal-fired boiler precipitator outlet during
two periods. The first period was February 25 to February 28, 1975,
Flue gas temperatures ranged from 130°C (275°F) to 180°C (335°F).
Other data are listed in Table XV. The second testing at steam
plant A was April 1 to April 3, 1975, with flue temperatures vary-
ing from 138°C (280°F) to 174°C (345°F). Table XVI contains these
data.
In the test at the cement plant and the first test at steam
plant A, there was a problem with the filter material sticking to
the 0-ring and the support screen of the holder. This created a
nuisance, and also added the possibility that some material might
be overlooked. For the tests in April at steam plant A, teflon
gaskets were cut which fitted directly under the O-ring and on the
support screen. The filter sample was held between teflon gaskets
and the gaskets were preweighed with the filter sample.
Two identical 47 mm filters were run in each holder. Origin-
ally, it was hoped that we might be able to obtain mass gain data
from each of these, but because of a tendency of the filters to
adhere to one another, the mass gains of both were lumped together.
All the results are shown in Table XVI.
The sampling times and flow rates used were supposed to approx-
imate the sampling time and flow rate of a typical Andersen Stack
Sampler test. Sampling times varied from thirty minutes to eight
47
-------
CD
TABLE XIV
CEMENT PLANT - SUBSTRATE MASS GAINS
Run Number
cc-i
CC-2
CC-l
dig)
(°F)
(°F)
(ft1)
(°F)
(rain)
(ml)
(acfn)
CHg)
CH,0|
„
O)
£
V)
2
<
O
in
-------
hours, which met the above requirement. The flow rates used, how-
ever, were somewhat below that of the ideal Andersen Flow Rate of
0.5 cfm. On all of the tests in which the teflon membranes were
used, the flow rates were only half as high as the desired flow
rate of 0.5 cfm because the pressure drop across the membrane was
large. (Even so, the ratio between flow rate and filter surface
area at these lower flow rates approximated the same ratio of
these quantities for an Andersen Stack Sampler.) No attempt was
made at isokinetic sampling since only the flue gas was of interest.
After each run, the filters were desiccated for at least 24 hours
and weighed. Any gas-phase reaction was then detected by a mass
change.
The results of all the tests are listed in the tables. From
these results, no definite trend emerged to indicate that the mass
gains depended upon flow rate. However, there seems to be a rela-
tion between mass gain and total exposure time of the filter to
the flue gas, regardless of the flow rate.
Both Whatman types GF/A and GF/D, and the Reeve Angel 934AH
showed little tendency for mass gain. The Pallflex quartz showed
loss of mass, but it was very fragile and tended to break and
tear easily, which may have resulted in a loss of some of the fil-
ter material.
Chemical analyses were performed on all the filter materials
that had been tested in the Gelman holders. This includes the
tests at the cement plant and those at steam plant A. Soluble
sulfate determinations and pH tests were run on each sample except
the teflon samples, which had shown very little mass change. These
results are shown in Tables XVII, XVIII, and XIX.
The data in these tables indicate that sulfate is responsible
for the majority of the observed mass gain on each filter. (Some
filters which had small mass gains appeared to have picked up
little sulfate, but this may only reflect the limits of accuracy
in the determination of sulfate.) In each case, the pH of the
sample was more acidic after it had been run, indicating possible
sulfate gain.
The results of these tests can be summarized as follows:
The pH of the filters varied widely from batch to
batch before testing.
There was a definite correlation between high initial
pH and mass gains upon testing.
The pH decreased during testing.
A large fraction of the mass gain in every case was found
to be the result of sulfate formation on the filter media.
49
-------
TABLE XV
STEAM PLANT A
Ln
O
Run Numb
<""''
(°F)
<•>••)
(ft1!
("PI
(-in)
(-11
(•elm}
CHO)
(•111 0|
cn
E
W
Z
<
Ul
4
UJ
r-
^
1C
H
V)
m
D
(/)
Date
Anb. Prav.
Anb. Temp.
Stack TeBp.
Cn Vol.
ivg. caB
Meter Toap.
Hun Tine
Orl. 10
Cond. B,0
I B,0
Flow latei
-otl.
-Ca> Mater
Avg.. Probe
AP
(* AP acroaa
orifice)
Orl. AP
la
Ib
I
,
4
J
6
I" BRSP-l
2-25-7S
}9.0»
54
I7i
11.062
ai
60
1148-
.059
6.0
(l.ll 7.5 uied
In (low-
rato cal
culatloni
0.181
0.189 "-1"
I.I
(.1
GA 11.29 aq
USA 0.41
1106 BB
CA 0.143
DA 0.17
900 AT
Ttflon 0.01
MCA 0.27
1106 OK
CA 0.19
BRSF-2
2-25-75
29.08
61
265
It. 767
71
60
1148-
.059
11.4
14. (1 7.5
0 249
0*258 °'Z5<
11. (5
14.9
GA 26.50
CA 0.44
BA 0.69
900 AT
KtA -0.1. J«**
"»« " o-rln,
i support
aevarely
Teflon 0.00
IU 0.56
900 Kt
CA -0.74 Stuck
to
o-rlng
6 out by
it.
All filters Btuck
allgntly to aupport.
Aa nuch BB pOBeiblo
rocovvraJ .
BRSP-]
2-26-75
19.44
51
m
BO. 428
81
240
1141-
.059
57. S
(5.«) 7.5
0 286
0.265 °'286
12. (
18.5
CA
RA 0.7>
900 AT
MSA O.H
teflon 0.01
EA O.U
CA -0.04 Icvecely
cut
GA 0.11
Thla (and all that
follow) are Spactro
Gratia A from batch
III 12.
BBSr-4
2-26-75
29.42
69
775
14.269
82
120
1141-
.059
21.8
IS. 7) 7.5
0 211
0.21* 8-131
12.7
12.8
CA 17.99
KSA 0.88
1106 BH
RA 0.81
900 AT
CA 0.14
SA O.H
CA 0.41
Teflon 0.07
BRSP-5
2-27-75
BKSf-6
2-JO-J5
1
29.16
64
100
140.245
79
4(0
1141-
.059
90.8
(1.7) 7.J
0.110
0.215 '•'"
11.95
12.7
CA
CA 1.17 Hodarate-
ly brown
on 0due.
MSA l.<5 nodcrata-
1106 BH ly brown
near
o-rlng.
SA 0.61 Severely
cut light
brown
CA 0.51 NO
discol-
oration
Ttflon 0.00
MSA 1.00 Slight
1106 Ell brown-
inq
39.10
41
155
• .«!)
74
10
1148-
.059
4.B
14.6) 7.!
0.266
ol26» °-"B
12.5
12.9
CA 23.41
MSA 0.69
not BH
SA -0.12 Td.n
CA 0.17
SA 0.66
Teflon -0.01
MSA ft. 71
Hut nit
i-U-7-,
J9 . 10
50
Jii
.
0
.
-
,
-
f
CA 0.)4
CA 0.11
MSA 0.77
1106 BH
SA -0.10 Tor
CA 0.18
K5A 0.70
1106 BH
Teflon n.nt,
nl'Il"! "!,J ij'i'r,,
innndi airly.
-------
TABLE XVI
STEAM PLANT A
Run Number
BRSP-8
BRSP-9
DRSP-10
ilHSP-11
DRSP-13
THg)
(°F)
(°F)
(ft')
( F)
(min.)
(ml.)
CHjO)
("Hg)
(acfm)
U|
2
O
8
S 9
IE
fc
IS
D
M
Date
Amb. Pres.
Amb. Temp.
Stack Temp.
Gas Vol.
Avg. Gas
Meter Temp.
Run Time
Cond. H20
t H20
Ori. ID
Ori. AP
Avg. Probe
AP
Flowrate:
- Ori.
- Gas meter
* ib
2a
2b
3a
3b
4a
4b
ba
5b
6a
6b
4/1/75
29.28
84
315
52.172
103
240
48.9
4/2/75
29.15
78
315
13.004
92
60
11.0
(6.6) 7.5 used (5.2) 7.5
in flow-
rate
calculations
3348 - .059
9.7
7.1
0.242
0.238
GA
GA 3.68
GAE
GAB
£ 2-02
Quartz _„ M
Quartz «.->«
GF/A
GF/A °'52
RA 934 AH . ,,
RA 934 AH °'46
3348 - .059
10.3
4.35
0.267
0.272
GA
GA 1.74
GAE
GAE
SA 0>0°
SES -1-96
SS °-°2
RA 934 AH
RA 934 AH
4/2/75
29.15
92
315
6.531
107
30
6.0
(5.9) 7.5
3348 - .059
10.3
4.75
0.261
0.262
GA
GA 1.00
GAE
GAE '
SA °'08
Quartz
Quartz *
GF/A °'08
£ 9341 AH °"2<
4/2/75
29.15
89
315
6.516
99
30
5.8
(5.6) 7.5
3348- .059
10.3
4.65
0.262
0.266
GA
GA 0.84
GAE
GAE °-96
IA -°-12
Krt*-1-"
GF/D °-°°
^9^^°-"
4/3/75
29.1,?
48
345
50.284
53.5
240
48.8
(6.1) 7.5
3348 - .059
10.3
6.6
0.272
0.266
GA
GA 2.74
GAE
GAE
SA ...
SA "-06
Juart z *
GF/D
GF/D *
s la3: «i °-°8
4/3/75
29 12
280
1 ' 097
69
00
13.3
(6.2) 7.5
3348- .059
10. 3
4.35
0. 260
0.265
GA
GA 0.12
CAF
GAE 1"°8
SA °->°
0.66
GF/D 0 18
Gf/0 °'1B
RA 934 ftH
RA 934 AH
NOTE:
GA - Celman Typo A
GAE - Gelman Type AE
SA - Gelman Spectro Glass Fiber, Type A
Quartz - Pallflex Tisguquartz 2500 QAD
GF/A - Whatman GF/A
GF/D - Whatman GF/D
RA 934 AH - Reeve Angel 934 AH
•Combined weight of the two filters pec holder, except
for holder 1 whore the weight of the ptefilter (la)
has been eliminated.
-------
TABLE XVII
FILTER BLANKS (UNTREATED)
Type mg Spj*"' pH
GA 0.04 8.6
MSA 0.18 9.3
RA 900 AF 0.06 9.8
SA Negligible 5.6
Quartz Negligible 6.6
GAE Negligible 9.2
RA 934 AH 0.06 7.2
GF/A Negligible 8.1
GF/D Negligible 7.0
52
-------
TABLE XVIII
CEMENT PLANT
Run Number
CC-1
CC-2
CC-3
w
la
Ib
2
3
4
S
6
Filter Filter
Mass Gain Sulfate Portion Mass Gain Sulfate Portion Mass Gain Sulfate
(mg) (mg) P Analyzed « (mg) (mg) p Analyzed (mg) (mg)
GA 3.22 2.1 7.1 %
_ -
SA 0.28 0.44 B.I Whole
GA -0.48
- — _ - -
_
_
Silicons
o-rings
stuck
to
filters
GA 10.58 5.02 8.1 '.
GA 0.44 0.10 8.0 Whole
SA 0.92 0.94 8.1 H
Slight
brown
ring
RA 1.16 0.83 7.7 Ij
900 AF
MSA 1.02 0.76 7.7 >i
1106 BH Slight
brown
ring
- -
_ _
Teflon
o- rings
GA 9.48 4.8J
GA 0.84 0.27
MSA 1.42 0.90
1106 BH
RA 1.70 1.45
900 AF
SA 1.66 1.85
Stuck
to
metal
support
-
-
Teflon
o-rings
Filter
H Portion
** Analyzed
7.7 k
7.2 ij
7.7 »,
8.1 H
8.7 H
-
-
*0n those filters containing relatively large amounts of particulate, only a portion of the filter was analyzed.
Sulfate was calculated on a whole filter basis.
-------
TABLE XVIII
(CONTINUED)
CC-4
Mass Gain Sulfatei Filter Portion
(rag) ; (ing) 1 J>H Analyzed
GA
MSA
1106 BH
Teflon
GA
RA
900 AF
MSA
1106 BH
Teflon
4.38 2.0 7.4
2.1.4 1.67 6.9
-0.02
0.90 0.30 7.1
2.40 2.27 7.0
1.92 1.52 7.5
0.00
Teflon
o-rings
*
\
-
h
\
\
-
54
-------
tn
TABLE XIX
STEAM PLANT A
Run Number
BRSP-1
BKSP-2
To
lb
2
3
4
5
6
•Same
Filter Portion
Mass Gain (mg) Sulfate (mg) PH Analyzed*
GA" IT! ' ~~
MSA 0.
1106 BH
GA 0.
RA 0.
900 AF
Teflon 0.
MSA 0.
1106 BH
GA 0.
note as Citadel
29 0.56 576 "j
43 0.17 5.7 Whole
16 0.06 5.5 Whole
37 0.26 5.6 Whole
01
27 0.11 6.7 Whole
19 0.04 6.4 Whole
GA
GA
RA
900 AF
MSA
1106 BH
Teflon
RA
900 AF
GA
All fi
stuck
slight
Mass Gain (mg)
'H.50
0.44
0.69
-0,14
0.00
0.56
-0.74
Itcrs
at least
iy
Filter Portion
Sulfate (mg) pn Analyzed
" 0".9l 5.4 i, • - .
0.04 5.9 Whole
0.20 6.9 Whole
Stuck
to
o-ring
and
support
0,26 7.7 Whole
Stuck
-------
Wj CJ
O N
0. >,
O C
I
o,
2
o
TABLE
(CONTI
1J O
O N
b >-
01 G
jj 5
K "S
-O
3
o
3
o
3
O 0
S 3
in
O
10 XI
56
-------
TABLE XIX
(CONTINUED)
Run Number
BRSP-5
BRSP-6
Filter Portion
Mass Gain (mgl Sulfoto (mgl PH Analyzed Mass Gairi (mg) Sulfatc (mgl
la GA
Ib GA 3.27
2 MSA 3.65
1106 BH
(Jl
-J 3 SA 0.68
4 GA 0.53
5 Teflon 0.00
6 MSA 1.00
1106 BH
— _ —
1.95 Moderately 3.0 ^
brown on
edge
2.34 Moderately 3.0 >j
brown near
o-ring
1.40 Severely 3.0 Whole
cut
0.103 5.6 Whole
_
0.52 Slight 5.8 ^
brown
ring
GA 23.41 1.28
MSA 0.69 0.24
1106 BH
SA -0.12 Torn
GA 0.27 0.02
SA 0.66 0.10
Teflon -0.01
MSA 0.71 0.28
1106 BH
Filter Portion
pH Analyzed
3.9 ^
6.4 Whole
-
6.5 Whole
5.7 Whole
-
6.4 Whole
-------
TABLE XIX
(CONTINUED)
Run Number
BUSP-7
BRSP-8
00
la
Ib
2
3
4
5
6
Mass
GA
GA
MSA
1106 BH
SA
GA
MSA
1106 BH
Teflon
Gain (mg)
0.34
0.38
0.77
-0.10
0.38
0.70
0.06
This set not run;
heated
Sulfate (mg)
0.12
0.12
0.37
Torn
0.08
0.31
-
placed in
for 30 minutes, and
PH
6.8
6.9
7.8
-
7.2
7.8
-
stack
taken
Filter Portion
Analyzed
Whole
whole
Whole
-
Whole
Whole
-
t
out.
Ib
2a & b
3a & b
4a & b
5a f, b
5a & b
6a c. b
Mass
GA
GAE
GSA
Quartz
GF/A
GF/D
RA 934
Ga
3.
8.
2.
-0
0.
0.
in (mg)
68
54
02
50
52
24
Sulfate (mg)
1.62
5.16
1.54
Negligible
Negligible
-
Negligible
PH
3.4
3.3
3.5
3.6
5.9
-
5.6
Filter Portion
Analyzed
«,
!< each filter
S each filter
•5 each filter
2 wnolc filters
-
2 whole filters
-------
TABLE XIX
(CONTINUED)
Run Number
BRSP-9
BRSP-10
Filter Portion
Mass Gain (mg) Sulfote (mg) gH Analyzed Mass Gain (mg) Sulfate (mg)
Ul
vo
Ib
2a
3a
4a
5a
5a
6a
t b
t b
£ b
t b
t b
t b
GA
GAE
GSA
Quartz
GF/A
GF/D
RA 934
AH
1,74 0.92 3.4 »i
1.26 0.46 5.8 H each filter
0.00 0.05 5.3 2 whole filters
-1.96 -
0.02 Negligible 6.6 2 whole filters
_
0.02 Negligible 6.1 2 whole filters
GA 1.00 0.42
GAE 1.76 0.29
GSA O.OB 0.04
Quartz 0.12 Negligible
GF/A O.OB
GF/D
PA 934 AH 0.24 Negligible
Filter Portion
pH Analvzed
3.7 Whole
7.2 ^ each filter
5.9 2 whole filters
3.5 2 whole filters
-
-
6.3 2 whole filters
-------
TABLE XIX
(CONTINUED)
Run Number BRSP-11
Mass Gain |mg) Sulfato (mg)
Filter Portion
Analyzed
BRSP-12
Mass Gain (mg) Sulfate (mg)
Filter Portion
£H Analyzed
Ib
2a & b
3a i b
4a 6 b
5a & b
5a & b
6a (. b
GA
GAE
GSA
Quartz
GF/A
GF/D
RA 934 All
0.84
0.96
-0.12
-1.40
-
0.00
0.04
0.37
0.44
0.04
-
-
0.05
0.02
4.1
7.8
5.0
-
-
6.6
5.9
Whole
2 whole
2 whole
-
-
2 whole
2 whole
filters
filters
filters
filters
GA
GAE
GSA
Quartz
GF/A
GF/D
RA 934
AH
2.74
6.66
4.06
-5.16
-
-0.04
0.08
1.48
4.B2
4,99
-
-
0.13
0.14
2.8
2.7
2.7
-
-
5.9
5.6
s
s
2
2
Whole-
each
each
-
-
whole
wholu
filter
filter
filters
filters
-------
Run Number
TABLE XIX
(CONTINUED)
BRSP-13
Mass Gain Sulfate
(mg) {mg)
Filter Portion
Analyzed
Ib
2a &
3a &
4a &
5a &
Sa &
6a &
b
b
b
b
b
b
GA
GAE
GSA
Quartz
GF/A
GF/D
RA 934AH
0.
1.
0.
0.
-
0.
0.
12
08
10
66
18
32
0
0
c
.03
.32
.05
Negligible
0
r,
V*
-
.06
.05
6.
5.
5.
3.
-
6.
50
0
3
7
3
4
5
Whole
2
2
2
2
2
whole
whole
whole
-
whole
whole
filters
filters
filters
filters
filters
61
-------
For a given temperature, the filters seem to "saturate"
and not gain much additional mass after a period of time
(2-6 hours) .
Use of Laboratory Preconditioned Filters in the Field
Two techniques were employed for laboratory preconditioning
of filter media. One was an exposure to a controlled mixture of
air, water and SO2 at elevated temperature, as described in the
preliminary laboratory screening tests. The other method was a
sulfuric acid wash as previously described which is detailed in
Appendix A. In the following paragraphs, those filters treated
by the former method are termed "laboratory conditioned" and the
filters for which the second method was used are referred to as
"acid washed" filters.
In the field tests, unconditioned, laboratory conditioned,
and acid washed glass fiber substrate materials were exposed to
flue gases of differing temperatures. In order to obtain an esti-
mate of what would be the maximum mass gains caused by flue gas,
samples of various manufacturers glass fiber filter material were
taken to the outlet of a hot side electrostatic precipitator (343°C,
650°F) and exposed to the flue gases for one week during a field
test at steam plant C. Included in this sample were 27 Reeve
Angel 934AH, 47 mm filters which were laboratory conditioned at
SoRI for 12 hours. An alundum thimble holder was used to hold the
samples and was placed in the flue gas stream on a probe preceded
by a Gelman 47 mm stainless steel filter holder. The flow rate
used was 0.4 ACFM and the pressure drop was approximately 10 inches
of mercury, indicating that the flue gas was passing through the
filter stack (81-47 mm filters) . The inside diameter of the thimble
holder is almost exactly 47 mm, insuring a good fit with the filters
Table XX shows the mass changes recorded in this experiment.
The filters are identified by manufacturer, name, and batch.
Three observations can be made immediately:
1. Reeve Angel filter material conditioned at SoRI behaves
as unconditioned Reeve Angel material behaves.
2. Reeve Angel filter material shows the lowest mass gains
of all the filter materials exposed to the flue gas.
3. The Gelman Quartz material lost weight.
Since the Reeve Angel 934AH material, which was laboratory pre-
conditioned, gained mass this means that such a procedure might not
be useful. On the other hand, the laboratory conditioning was done
at 232°C (450°F) and the flue temperature was 343°C (650°F). we
know from previous work1 that there is a strong dependence on temp-
erature when mass gains occur. Other factors are that the exposure
time was one week and that the filters were not handled during the
test.
62
-------
Ul
TABLE XX
Mass Chanaus Recorded in 47 mm Glass Fiber Filters
Exposed to 3430C (650°F) Flue Gas for One Week
Number Averaqe Mass Chanqe/ Percent Mass Chanqe
Filter Manufacturer Name Batch No.
Reeve Angel*
Reeve Angel
Reeve Angel
Reeve Angel
Whatman
MSA
Gelman
Gelman
Gelman
Gelman
934AH
934AH
934AH
934AH
GF/A
1106BH
Spectroglass
fiber
AE
AE
Quartz
3307
3307
3307
4292
3563
J888
8192-
20232
8204
8206
8198
in Sample
27
27
3
20
3
3
3
5
5
5
Filter (mq)
0
0
0
0
6
12
16
17
18
-2
.89
.90
.91
.58
.19
.06
.36
.36
.10
.53
0
0
0
0
7
10
12
13
13
-1
.79
.81
.82
.55
.0
.9
.3
.1
.3
.6
• Conditioned at SRI for 12 hours.
-------
The mass gains reported in Table XX probably are good maximum
values. Previous experience with Reeve Angel 934AH material shows
no mass gains as large as those recorded in the week's exposure.
This last point will be discussed in greater detail later in this
report.
Table XXI shows the results of chemical analyses made on 47 mm
glass fiber substrate materials exposed to hot side electrostatic
precipitator (ESP) flue gases and laboratory simulated flue gases.
These substrates were prepared in various ways. Some were condi-
tioned at SoRl, and some were conditioned at the hotside ESP.
Others were not exposed to flue gases but analyzed in an unused
state. Comparison with Table XX shows that the mass gains recorded
were almost exclusively due to sulfate compounds formed on the sub-
strates.
Of interest is the fact that calcium and magnesium content
appear to be unrelated to sulfate mass gains. Filters which were
washed in sulfuric acid solutions and then in distilled water and
ethanol (ETOH) showed no significant amount of sulfate content.
This is perhaps due to the washing out of sulfates, which were
formed by the sulfuric acid, by the water and ETOH. In subsequent
conditioning of the acid washed filter media, mass gains occurred
which were much less than that caused in unconditioned substrates.
Since the sulfate mass gain by glass fiber substrates when
they are exposed to hot flue gases is well documented, one approach
to passivation is to expose or condition substrates to these gases
prior to use in an impactor. Figures 20 through 22 show a condi-
tioning chamber designed at SoRI. It is fabricated from 316 stain-
less steel which has been treated in hot nitric acid to remove any
iron near metal surfaces. This chamber will hold enough Andersen
substrates for a typical field test of one week duration. The
chamber, with a Gelman 47 mm prefilter, is inserted into an outlet
port and the enclosed substrates are exposed to filtered flue gas
at 0.5 ACFM for periods from several hours to several days. Table
XXII shows the averaged stage mass gains from blank Andersen and
Brink impactor runs made at a variety of flue gas sources with
Reeve Angel 934AH substrate material. These substrates were condi-
tioned in hot flue gas for varying lengths of time. In no case were
the stage mass gains as great as those found in the week-long ex-
posure test (Table XX). Note than an Andersen substrate is typically
one and one-half times as massive as a 47 mm filter (^150 mg as
opposed to 100 mg for Reeve Angel 934AH).
If preconditioning is to be useful then it is desirable to
reduce the blank mass gains below these reported in Table XXII,
as close to zero as possible. Figure 12 shows that a sulfuric
acid wash reduces laboratory induced mass gains in Gelman AE material
by a factor of 4. A sulfuric acid treatment of Reeve Angel 934AH
material similarly should reduce mass gains in this substance.
64
-------
TABLE XXI RESULTS OF CHEMICAL ANALYSES CARRIED OUT ON 47 mm GLASS FIBER FILTER SUBSTRATE MATERIALS
EXPOSED AND UNEXPOSED TO FLUE GASES, LABORATORY SIMULATED FLUE GASES (1% SO2, 3-5 ppm
S03, SATURATED HjO, 220°C (428°F)) and H SO WASHES
Filter Material
Reeve Angel 934AH'
-------
cr»
A. ^ JKC/, (W
6
SOUTHJW HStAKH INSTITUTl
1IIMINCHAK »1AI*MA 3»01
Figure 20. Substrate conditioning chamber, side view.
-------
cr>
--J
to i
50UTHIIN HSIAKM INSTITUn
illMINGMAw ALAlAMA JJJOi
Figure 21. Substrate conditioning chamber, interior components.
-------
U)
a
03
o
13
C
-------
TABLE XXII
Averaged Stage Mass Gains for "Blank" Impactor Runs with
Reeve Angel 934AH Glass Fiber Filter Substrate Material1
VO
Source
Aluminum Smelter
- (Scrubber)
Power Plant
(Utah)
Power Plant
(St. Louis)
Paper Mill
(Kraft Recovery)
Power Plant
(Pennsylvania)
Cement Kiln
Power Plant
(Alabama)
Power Plant
(North Carolina)
Preconditioning
Temperature Time SO2 Concentration Run Time
49 120
149 300
166
177
177
138
138
330
350
350
280
280
104 220
Power riant
(Tennessee)
160
160
160
327
327
338
338
338
338
154
160
320
320
320
620
620
640
64C
640
640
310
320
(hours)
(ppm)
24
12
12
15
5
12
12
12
12
12
12
0
12
12
12
12
<1
330
95
107
760
760
3500
3500
3500
900
900
900
900
900
900
2500
2500
(hours)
3.B
1.75
16
0.5
.80
1.60
0.50
0.50
2.0
2.0
4.0
1.5
6.0
2.0
2.0
2.0
0.4
0.2
0.65
4.0
Average Mass
Gain per Stage
(mg)
-0.03
-0.05
0.30
0.24
0.14
0.13
0.20
0.43
0.15
0.49
0.06
0.28
0.41
0.18
0.25
0.63
0.02
0.082
0.032
0.16
Usually there is more than
2. Brink impactor blank run, all others are Andersen impactor blank runs.
1. Stage mass gains are averaged for each condition.
one blank run tor any given temperature.
-------
Experiments were conducted in which unconditioned, labora-
tory conditioned, and acid treated glass fiber filter material were
to be exposed to flue gases at an electric power generating station,
steam plant D. This plant has both hot-side and cold-side electro-
static precipitators operating off boilers fired with the same coal.
Flue gases at the hot-side outlet and cold-side outlet are hotter
and colder, respectively, than the laboratory conditioning temper-
ature. Two trips were made to this plant for the purpose of expos-
ing glass fiber filter material to filtered hot- and cold-side flue
gases in simultaneous runs.
Table XXIII shows the mass gains which occurred during the first
trip when different kinds of 47 mm glass fiber filter substrate media
were exposed to flue gases in the hot- and cold-side precipitators.
The filters were subdivided into three broad classes: (1) uncondi-
tioned filters, (2) filters conditioned in the laboratory at SoRI,
(3) acid washed filters. Two identical stacks of filters were made
up and placed in identical stainless steel alundum filter holders.
Twelve different samples were placed in each filter holder in the
order and numbers given in Table XXIII. For example, 20 Reeve Angel
934AH filters which had been laboratory conditioned at SoRI for a
total of 26 hours were at the top in each filter holder, and 10
Gelman AE sulfuric acid washed filters were at the bottom of each
filter holder.
These filter holders, loaded with filters, were exposed for
six hours each at the hot- and cold-side precipitators. Flow rates
were adjusted to pull total volume of gas (reduced to standard
conditions) through each group of filters. The cold-side temp-
erature was 143°C (290°F) and the hot-side temperature was 321°C
(610°F). Filters conditioned at SoRI were conditioned at 221°C
(430°F).
Several comments may be made about the results presented in
this table:
1. The Reeve Angel 934AH filter material which was washed
in sulfuric acid, rinsed in distilled water and ethanol
(ETOH), and then laboratory conditioned for 18 hours at
SoRI had the lowest mass gains of all materials tested:
zero for the cold side, and -0.01 mg/filter for the hot
side.
2. Material which had been conditioned at SoRI (26 or 18
hours) and then exposed to flue gases in the hot-side
precipitator generally lost weight. This may be due
to handling losses as some black particulate matter was
inadvertantly allowed to fall in among the filters when
the Gelman prefilter was removed from the front of the
filter holder, and some of these filters had to be dusted
off. This was done with a soft camels' hair brush.
70
-------
Oi4 91 JOJ IHS 4" pAU(j^TPuooaJd,
uoi^uDoiBap ttjno\i \i io^j^t
P103 '(HoOTS) DoTZC - OPTS }°H,
»>'0 8fl
6!'0- Sl'O-
6TO O'O
OO'O lO'O-
SS'O C9'l
61-0 t»'0-
T,-0
oz-o zro-
<6-T iff
9?'0 OZ'O-
eo'O afo
ii'o ao'o
SPTS Pioo apis qoH
Uip"i3 9BCH "J1I55253-
009'0
OOt '0-
09fO
ooo-o
StfO
OiT'O
StS'O
Mr.
OOiT
StE'O
060'0
szi-o
3P1S Ploo
Oli'l 5i»Z'T IJSZ'l S1»Z'T
Oifo- to»o't 8i»o't tr»o't
OtS'O iB8C-T 6I6C'l TSifT
OTO-0- 86,0-1 M..-I 86>0-1
S«fT EZC£'l »itfl BZZfl
06C'0- 6B£8"t OOZS'I SS£8"I
SS6'Z 1969'Z t»i'l C6»i'Z
S91'0- BtZB'Z OtOB'Z OfOS't
09f9 S06i'Z tlOfZ S9ti'Z
ssz'o- ezsfl-z rttB'Z srtB'z
06fO if 01 '1 ttOl'l 6TOT'Z
SBO-0 6T6T-Z 6B1Z-Z tttl'l
3PTS 3OH apTS Ploo apT9 '°H OPTS P1OD
tSEZ'l
SISO'T
098C-T
9i»0't
SSOi-I
BU8'1
ZS69-Z
ItTB'Z
ms-t
BBC8-Z
tOOI'Z
Ztl'Z
apTS }°H
qs>n O'H
'Ajp "OS'H
M«B« O'H
•Alp "OS'H
-O'H "OS'H
-O'H "OS'H
BUON
qOT 'B^noH ,j
OUOH
W -«nOB 9Z
3UON
q.1 '.JKOR 9Z
auoH
qua 'ejnoH 9Z
OT
OT
01
01
OZ
OZ
OZ
oz
01
oz
oz
oz
•WTH 'ON
>OZ«
z«z»
90Z8
ztz»
E95E
E9SE
ZCZOZ
-Z6Z8
ZCZOZ
-Z6Z8
»oca
»OZ8
Z«Z»
tOEE
•oN MOW
av UIUT33 zi
tnttt fafani BASag n
av ur»it»o 01
By,c6 1.6U, aA.TO 6
v/ia uB«A»mi a
»/jo u«m«nn i
...t0 —B »-.«
...to OI,^S «,«
3V uwrjao »
3V UMTT30 E
HVt£6 T»t»«V dAO9H Z
tfV»C6 T»fiuv 0A99U [
adAj, ja^tTJ ^apTOH ^T<7i
ut uojiysi
9161 'eimr tz 'itrtnd uvais SV3IJ03 iv , saoxviidiDTdd aais aioo anv xou
NI sasva an-u 01 aasodxa s-wraaiw ai\raisans M30.1U naau ssxno um t> jo sum SSVN mrx
-------
3. In general, filter material which has been conditioned at
SoRI, acid washed, or both, showed much less mass change
per filter than unconditioned filter media.
4. Unconditioned filters gained more mass when exposed to
hot-side precipitator flue gases than when exposed to
cold-side precipitator flue gases. This was expected
from previous experience..
Table XXIV shows the mass gains which occurred during the second
trip. The acid treated Reeve Angel 934AH and Whatman GF/A material
exposed during this trip were prepared according to the following
procedure: One/tundred-fifty 47 mm filters were conditioned in a
50-50 mixture by volume of distilled water and sulfuric acid at
88°C (190°F) for one hour. The filter stack was then separated
into three groups of 50. All three groups were washed first in
distilled water and then ethyl alcohol (ETOH). Finally, one group
was rinsed in distilled water; one group was rinsed in isoprophyl
alcohol (IPA) , and the last group was rinsed in ETOH. After
draining, each group was baked in a laboratory oven at approximately
104°C (220°F) for 6 hours.
Along with the laboratory conditioned material, unconditioned
glass fiber and quartz fiber filter substrate materials were also
exposed to the flue gases. These materials included Reeve Angel
934AH, Whatman GF/A, Gelman AE, Gelman SpectroGlass, Old Gelman
Type A (pre-1975), and a quartz fiber material supplied by Mr. D.
B. Harris, Project Officer of this contract.
The mass changes recorded in Table XXIV differ somewhat from
those observed in the other test (first trip). All acid washed
substrates lost mass. But, examination of unused, acid treated
substrates prepared for this test showed that the mass losses were
due to inadequate washing of the filter media after acid treatment.
Samples of the Whatman GF/A material which showed a hot-side loss
of 2.29 mg/filter were placed in a nearly neutral distilled water
solution (pH = 6.0). After mixing for several minutes the pH of
the filter-water slurry had dropped to 4.4. Other samples of
these filters which had been exposed to air for several weeks
showed 2 to 3 mg/filter mass losses upon baking at 100°C (212°F)
for 2 hours. When exposed to ambient air after baking, these fil-
ters regained 1 to 2 mg/filter of the baking weight loss. The high
boiling point of sulfuric acid (338°C, 640°F) means that the usual
bakeout (100°C-200°C) of substrates following acid treatment will
be insufficient to remove most residual acid. To be sure that most,
if not all, of the acid is removed after treatment, the pH of the
substrate water should be compared with that of the distilled water
used for washing. Wash water should be left in the container hold-
ing the substrates for several minutes prior to making a pH determin-
ation.
The unconditioned material behaved much like that exposed on
the first trip. The Gelman Type A (pre-1975) material gained mass
72
-------
TABLE XXIV
MASS GAINS OF 47 mm GLASS AND QUARTZ FIBER FILTER SUBSTRATE MATERIALS
EXPOSED TO FLUE GASES IN HOT AND COLD SIDE PRECIPITATORS1 AT STEAM
PLANT D, 31 AUGUST - 1 SEPTEMBER 1976
position in
Thiablif Holder
1 thieve
2 HhaLme
3 Oualtz
4 Golnun
5 GelUfl
6 GelBtn
7 Reevr
9 Roovc
9 Rcorfo
10 Kheuu
11 Kh*uu
12 tfhutne
'Supplied by Pr
\11rt ft^Inuin Tvn
Filter Type
Angel 914AH
Jl CP/A
'
Type A'
Type AJ8
3pocl.ro ClflflB
Angel 934AH
Angel 934AH
Angel 934AB
.n GP/A
It GP/A
Jl GP/A
oject Of Citvi .
* A al»an I Ibci
EtAteh No.
3563
-
D204
8292-
20232
429!
4292
4292
3563
35.3
3563
It 0.35 ACFH.
20
20
4
4
«
8
20
20
20
20
20
None 2. lOOt
Hop* 1.7051
rtonn 3.W12
None 0.5484
Hone 1.0638
Wane 0.9846
H,SU.-H,O 3.127B
H,.Vl,-rPA 2.09J5
HiSO.-KTOII 2.102U
H,BO.-lliO 1.6797
H|EOk-lPA 1.7374
n.,CCI.-ETOI 1.7189
Cold 6ida
2.0945
1 .7089
O.tlH
0.5527
1.0653
0.9990
2.1061
2.0931
2.0841
1.6761
1.7675
1 7115
Hot Side
J.1013
1.7277
0.6079
0.5560
1. 1050
1 0184
2.V954
2.U920
2.0961
1 €676
1.7250
1.6931
Cold Side
2.094!
1.
0.
0.
1 1
] .
2
.7141
.61/Pllter !f»el
-0.015
0.260
-2.100
0.475
1.24
0.538
-0.510
-0.245
-0.145
-0. 160
-1.625
-1.510
Percent
0.13
1.J3
-l.lt
1.39
J.B7
1.4]
-1.5!
-0.09
-0. 28
-0.72
-0.71
-2.63
Hie* Chenae
-0.01
0. 10
-1.47
0.34
0.4]
n.
-------
but not as much as contemporary Gelman AE. Finally, the quartz
fiber material lost a considerable amount of mass. This material
is much stronger than the Pallflex Tissuquartz tested earlier but
is still fragile. One final hot-side, cold-side exposure test
was planned at steam plant D, but boiler outages-forced the test
to be moved to another source. During November, 1976, a field
test was executed at steam plant E, and some substrates were pre-
pared for flue gas exposure tests there.
Differently preconditioned 47 mm glass fiber filter materials
were exposed fcr 8.5 hours to 321°C (609°F) flue gas. Gas flow
through the filter stack was 0.3 ACFM. An attempt was made to
expose a similar set of preconditioned 47 mm filters to flue gas
after the air preheater (117°C, 242°F), but this attempt failed
when the filters were moistened.
Table XXV shows the recorded mass changes. Reeve Angel
934AH shows almost negligible mass changes on a "per filter"
basis, regardless of conditioning. On the other hand, the Whatman
GF/A material shows small mass gains for sulfuric acid wash pre-
conditioning and much larger gains with no pre-treatment. The
acid washed filters were conditioned in a 50-50 (by volume) solu-
tion of concentrated sulfuric acid and distilled water at a temp-
erature of 115°C (239°F) for two hours. After this treatment,
the filters were rinsed with distilled water until the pH of the
rinse water from the filters (5.0) was nearly the same as the pH
of the distilled water (5.5). Some of the filters were further
rinsed in isopropanol or ethanol. The filters were next spread out
and allowed to dry in an oven at 104°C (220°F) . When dry they were
baked at 228°C (550°F) for four hours to drive off any remaining
sulfuric acid. Then the filters were desiccated until use. Ade-
quate rinsing in distilled water is crucial to the conditioning
of these filters. Otherwise residual sulfuric acid will be driven
off by the flue gas if above 650°F and the filters will show a
mass loss.
The low mass changes for Reeve Angel 934AH material reported
in Table XXV are at variance with some of the mass changes recorded
for blank Andersen and Brink impactor runs shown in Table XXVI.
Table XXVI shows average mass gains per filter for Andersen and
Brink impactor blank runs at two flue gas sources. These sources
were the steam plant E, which has a hot-side precipitator operat-
ing from 316° to 372°C (600° to 700°F), and the steam plant F with
a cold-side electrostatic precipitator operating from 93° to 121°C
(200° to 250°F). The acid washed material used here was prepared
as indicated above with careful attention to adequate rinsing.
.The average mass of an Andersen impactor glass fiber substrate
is near 150 mg. Scaling up the mass changes seen in Table XXV for
47 mm Reeve Angel 934AH acid washed material gives an average
of 0.05 to 0.07 mg per Andersen substrate. Most of the blank mass
gains of Andersen substrates reported in Table XXVI are much larger
74
-------
TABLE XXV. MASS GAINS OF 47 mm GLASS FIBER FILTER MATERIALS EXPOSED TO FLUE GASES
IN A HOT SIDE PRECIPITATOR1 AT STEAM PLANT E, NOVEMBER 1976.
Position in Thimble
Holder Filter Type
1
2
3
-4 4
U!
5
«
7
8
9
Reeve Angel
934AR
Whatman GF/A
Reeve Angel
934AH
Reeve Angel
934AH
Whatman GP/A
Reeve Angel
934AB
Whataan GF/A
Reeve Angel
934AR
Whatman GF/A
Batch No.
4292
3563
4292
4292
3S63
4292
3S63
4292
3563
Type of
No. Filters Preconditioning Initial Weight
20
20
20
20
20
20
20
20
20
none
none
Flue gas at Gorgas1, 6 hrs
HzSOn-HjO-Isopropanol
B2SOu-H20-Isopropanol
BzSOt. -Hj 0-Ethanol
BzSOn-HzO-Ethanol
B5SOi,-HjO
n2S(K-H20
(grams)
2.0923
1.7432
2.1025
2.0996
1.6823
2.0757
1.7971
2.0728
1.8218
Final Weight
(grams)
2.0915
1.7640
2.1010
2.1005
1.6852
2.0764
1.8001
2.0735
1.B258
Mass Change/
Filter
(mg)
-0.040
1.040
-0.075
0.045
0.145
0.035
0.150
0.03S
0.200
Percent
Mass Chai
-0.04
1.19
-0.07
0.04
0. 17
0.03
0.17
0.03
0.22
NOTES: 1. Exposure time was 8.5 hours ? 321°C <609°F)
Gas flowrate was 0.3 ACFM
2. Six hours at 321°c (610°F). Gas flowrate
was 0.35 ACFM
-------
TABLE XXVI Blank Impactor Run Mass Gains at Two Different Flue Gas Sources,
Reeve Angel 934AH Glass Fiber Substrate Material
Type of
Jmpacrtor
Location
Type ol Preconditioning1
Temperature
Flowrate
(ACMM) (ACFM)
Run Time Number of Dlank Runs Average Mass
(min) of this type Gain
-------
than this with the important exception of the data from steam plant
E, Test 2. Substrates for this test were prepared as described
above but were baked at 370°C (700°F) for one-half hour. Mass
gains by these substrates are uniformly low and quite acceptable.
Blank substrates in Brink impactors showed larger mass gains as
compared to Test 1, but during Test 2 silicone rubber 0-rings
were used for sealing, and these 0-rings disintegrated on dis-
assembly of the impactor causing fouling of the substrates. The
good set of data from Test 2, steam plant E, for the Andersen
blank impactor runs does not necessarily indicate that the problem
of substrate mass gains due to flue gas reactions has been solved.
What it does show is that acid washing, baking, and in_ situ condi-
tioning can provide a lowered average mass gain coupled with a
much lower standard deviation of mass gain. The lower standard
deviation of mass gain is important in itself since it means that
the substrates all behave in a similar manner.
Summary of Results of Evaluation of Filter Media
Untreated filter materials used as impactor substrates will
almost invariably increase in mass when subjected to the hot flue
gases normally encountered in field applications. Conversion of
SOz to various sulfates appears to be the cause of mass gains.
The various filter materials tested vary widely in the amount of
mass change which occurs under a particular set of flue gas
conditions.
Preconditioning techniques can be used to force the produc-
tion of sulfates in a filter medium, leaving a minimal number of
sites available for chemical reaction in the flue gas, and hence,
providing substrate material for which minimum mass gains occur
during use in an impactor. The best results were achieved when
substrates were washed in sulfuric acid, following the procedure
detailed in Appendix A, baked, and conditioned in_ situ.
Of the filter materials studied only the Reeve Angel 934AH
was found to be suitable in all respects for use as cascade
impactor substrates.
77
-------
SECTION 3
CONCLUSIONS AND RECOMMENDATIONS
Collection stages of most types of cascade impactors are very
heavy in comparison with the amounts of particulate material nor-
mally collected. It is therefore the usual practice to augment
each collection stage with a lightweight substrate to improve weigh-
ing accuracy. Generally, two classes of substrates are used —
greased metal foils, and fibrous filter material.
Greased foils provide resistance to particle bounce and scour-
ing effects, but greases tend to be unstable at elevated tempera-
tures. Some tend to harden, and in others the viscosity may become
reduced so that they may flow or be blown off the surface by the
high velocity gas flowing through the impactor. Of the greases
tested, Apiezon H was found to perform most satisfactorily. This
grease may be used at temperatures up to approximately 177°C (350°F)
No greases were found to be useable at higher temperatures.
Mass gains exhibited by glass fiber filter materials when they
are exposed to the SOX components in flue gas streams pose a compli-
cated problem. Experiments show that these mass gains are caused
by formation of sulfates due to a gas phase reaction with SOX.
Laboratory and field experiments indicate that the only glass fiber
filter material suitable for use as a cascade impactor substrate
is Reeve Angel 934AH. When this material is acid treated, accord-
ing to a procedure given in Appendix A, mass gains caused by flue
gas reactions can be kept quite small.
It is recommended that acid washing, baking and in situ con-
ditioning be used whenever large blank mass gains with large stand-
ard deviations are expected. In this context, "large" refers to
substrate mass gains greater than several tenths of a milligram.
Further research may provide a technique for passivating glass
fiber materials to all mass gains. It has been suggested that a
high temperature polymer or silicone compound might be developed
to coat the glass fibers in much the same way that the Gelman
SpectroGlass material is prepared for use at low temperatures.
78
-------
BIBLIOGRAPHY
1. W. B. Smith, et al, "Particulate Sizing Techniques for Control
Device Evaluation, Appendix A," U.S. Environmental Protection
Agency Report EPA-650/2-74~102a prepared by Southern Research
Institute under Contract No. 68-02-0273.
2. Forrest, j. and Newman, L., "Sampling and Analysis of Atmospheric
Sulfur Compounds for Isotope Ratio Studies", Atmospheric
Environment, 7: 561, 1973.
3. Gelman, C. and Marshall, J. C., "High Purity Fibrous Air
Sampling Media", J. Amer. Ind. Hygiene Assoc, 36: 512, July 1975.
4. Pate, J. B., Lodge, J. p., Jr., and Neary, M. P., "Use of
Impregnated Filters to Collect Traces of Gases in the Atmosphere.
Part II, Collection of Sulfur Dioxide on Membrane Filters",
Analytica Chemica Acta 28: 341, 1963
79
-------
APPENDIX A
Procedure for Acid Washing of Substrates
1. Submerge the substrates to be conditioned in a 50-50
mixture (by volume) of distilled water and reagent grade con-
centrated sulfuric acid at 110°-115°C (230°-239°F) for 2 hours.
This operation should be carried out in a hood with clean glass-
ware. Any controllable laboratory hotplate is suitable.
The substrates may need to be weighted down to keep them
from floating. For this purpose, place a teflon disc on the
top and bottom of the substrate stack. The top disc can be held
down with a suitable glass or teflon weight.
2. When the substrates are removed from the acid bath
they should be allowed to cool to room temperature. They are
next placed in a distilled water bath and rinsed continuously with
a water flov; of 10-20 cm3/min. The substrates should be rinsed
until the pH of the rinse water, on standing with the substrates,
is nearly the same as that of the distilled water. The importance
of thorough washing cannot be over-emphasized.
3. After rinsing in distilled water the substrates are
rinsed in reagent grade isopropanol (isopropyl alcohol). They
should be submerged and allowed to stand for several minutes.
This step should be repeated four to five times, each time using
fresh isopropanol.
4. Allow the substrates to drain and dry. They can be
spread out in a clean dry place after they have partially dried
(dry enough to handle).
5. When the filters are quite dry to the touch they should
be baked in a laboratory oven to drive off any residual moisture
or isopropanol. Bake the substrates at 50°C (122°F) for about
two hours, at 200°C (392°F) for about two hours, and finally at
370°C (700°F) for about three hours. The substrates are now
ready for in situ conditioning.
As a final check, place two substrates in'about 50 ml of
distilled water, and check the pH. The substrates to be checked
for pH should be torn into small pieces, placed in the water, and
stirred for about 10 minutes before the pH is measured. If the
pH is significantly lower than that of the distilled water, then
80
-------
the filters should be baked out at 370°C (700°F) for several hours
more to remove any residual sulfuric acid. The boiling point of
sulfuric acid is 338°C (640°F), so high temperatures must be used.
Figure 23 is a flow chart representing the acid wash procedure
described in the foregoing paragraphs.
81
-------
WASH SUBSTRATES IN
50% H2S04 SOLUTION
RINSE IN WATER
(ROOM TEMPERATURE!
RINSE IN ISOPROPANOL
(ROOM TEMPERATURE)
DRY SUBSTRATES
IN AMBIENT AIR
BAKE OUT
RESIDUAL MOISTURE
pH TOO LOW
TEST pH OF
SUBSTRATES
STORE IN
DESSICATOR FOR
ULTIMATE USE
Fiaure 23.
Flow chart for acid wash treatment of glass
fiber filter material.
82
------- |