&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA 600 7-79-154
July 1979
Quality Assurance of FBC
H2SO4 Measurements
Interagency
Energy/Environment
R&D Program Report
-------
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
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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
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EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
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This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-154
July 1979
Quality Assurance of FBC
H2SO4 Measurements
by
T. R. Acciani and R. F. Maddalone
TRW Defense and Space Systems Group
One Space Park
Redondo Beach, California 90278
Contract No. 68-02-2613
Task No. 3
Program Element No. INE624
EPA Project Officer: Frank E. Briden
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
ABSTRACT
The objectives of this report are to evaluate the existing data on
H?S04 measurements from FBC processes, determine the true value of the
sulfuric acid concentration which might have been obtained had the control
condensation procedure been used, and run a material compatibility study
to find possible alloys which could be used in the fabrication of a con-
trolled condensation sampling system.
The current sampling system at the Exxon FBC facility was reviewed
and it has been estimated that HUSO, values are 12% low with another
reduction of 10-25% because of low sampling temperatures and Balstron
filters. The Controlled Condensation System with an acid/base titration
using Bromophenol Blue as the indicator is the recommended sampling/analysis
method for sulfuric acid sampling at the Exxon FBC facility. The material
of construction for the Controlled Condensation System can be 316L Stain-
less Steel. 316L Stainless Steel had the best performance when subjected
to various tests used to simulate an FBC environment and will easily with-
stand the pressures found at the Exxon FBC facility.
-------
CONTENTS
Page
Abstract ii
Figures iv
Tables v
1. Introduction 1
2. Review of FBC Data 2
2.1 Conditions at FBC 2
2.2 H2S04 Sampling Systems 4
2.3 Critique of hUSO. Sampling at Exxon 6
2.4 Summary 9
3. Material Compatibility Studies 10
3.1 Preliminary Screening of Metals 10
3.2 Chemical Resistance 10
3.2.1 Experimental 10
3.2.2 Results 15
3.3 Catalytic Activity Study (Acid/Base Titration Method) ... 15
3.3.1 Experimental (Acid/Base Titration Method) 21
3.3.2 Results (Acid/Base Titration Method) 21
3.4 Catalytic Activity Study (Sulfate Titration) 21
3.4.1 Experimental (Sulfate Titration) 23
3.4.2 Results (Sulfate Titration) 23
3.5 Reactivity of Alloys with Condensed Sulfuric Acid 23
3.5.1 Experimental 23
3.5.2 Results 24
3.6 Summary of Material Compatibility Studies 25
4. Conclusions 26
5. References 27
m
-------
FIGURES
Number Page
1 Midget Impinger Sampling Arrangement
for Stream 3
2 Controlled Condensation System Set-Up 5
3 Dewpoint in °F for Various H-SO. Concentrations
and System Pressures 7 8
4 Metal Coupons Before Chemical Resistance Tests .... 12
5 Stainless Steel 316L at 100X Magnification 14
6 Stainless Steel 316L at 400X Magnification 14
7 A Pyrex Reaction Vessel 16
8 The Complete Laboratory Set-Up for the
Chemical Resistance Experiments 17
9 The Complete Laboratory Set-Up for the Catalytic
Effect Experiment 22
iv
-------
TABLES
Number paqe
1 Typical FBC Gas Phase Concentrations 2
2 Metal Composition 11
3 Compatibility 11
4 Chemical Environments 13
5 Pre-Test and Post-Test Analysis Results 19,20
6 Results of H2S04 Droplets on Metal Surface 24
-------
1. INTRODUCTION
This report has been prepared for the Process Measurement Branch of
the Industrial Environmental Research Laboratory of the Environmental
Protection Agency, Research Triangle Park, North Carolina, as Task 3,
Contract No. 68-02-2613. Task 3 is devoted to quality assurance of FBC
HpSO. measurements and is under the direction of EPA Project Officer,
Frank Briden.
The objectives of this report are to evaluate the existing data on
H S0d measurements from FBC processes, determine the true value of the
sulfuric acid concentration which might have been expected had the control
condensation procedure been used, and run a material compatibility study
to find possible alloys which could be used in the fabrication of a
Controlled Condensation System.
The pressurized fluidized bed combustion (FBC) of coal is a new
combustion technique which can reduce the emissions of S02 and NO from
/\
the burning of sulfur-containing coals. At Exxon, the FBC unit is
pressurized at 10 atm which contains a mixture of limestone or dolomite
and coal in the bed. To measure the effect of sorbent to coal ratios,
extractive sampling for S02 and S03 is performed on the outlet gas streams.
When the controlled condensation system was used at Exxon the results were
erratic. This report reviews the current sampling methods, points out the
problems which currently exist in the method and recommends the necessary
changes.
In order to have a S02/SO., sampling system which could function at
higher than atmospheric pressure, a material compatibility study was
conducted to find an alloy to replace the all glass/quartz fabrication of
the current CCS. The compatibility study centered around three experiments
to determine the resistance of the alloy to corrosive vapors (HC1, S02,
HoSO^), catalytic activity (S02 -» $03), and the reactivity of the alloys
toward both dilute and concentrated sulfuric acid. This report will
describe the results of these tests and make recommendations on the
materials usable for the high pressure train.
-------
2. REVIEW OF FBC DATA
Under this phase of the task existing reports and procedures for
S02/S03 testing at the Exxon FBC facility were reviewed to determine the
error associated with data obtained. This review also provided a basis
for the critique of the sampling and analysis methods.
2.1 CONDITIONS AT -FBC
The FBC unit at Exxon is pressurized at 10 atm and uses a mixture of
limestone or dolomite and coal in the bed. The dolomite or limestone
controls the SO^ levels in the flue gas by trapping the S0? as CaSO..
Steam is produced by circulating water through tubes immersed in the bed.
The major components in the gas phase are shown in Table 1.
TABLE 1. TYPICAL FBC GAS PHASE CONCENTRATIONS
Species
so2
L
S°3
N0x
Cl"
F"
°2
co2
H20
Concentration
30-600 ppm
5-12 ppm
100-140 ppm
30-50 ppm
7-15 ppm
6-8%
10-14%
5-7%
Figure 1 is taken from Battelle's preliminary report on the compre-
hensive sampling and analysis at the Exxon mini-plant. As the diagram
shows, particulate material is removed by the Balstron filters in a heated
hot box at 177°C (350.7°F). The cleaned gas is distributed to the gas
sampling trains through a heated [177°C (350.6°F)] stainless steel manifold.
Connection between the trains and the manifold is made with a short length
of Teflon tubing.
-------
Slip Stream
from
PFBC Exhaust
VV\M
Exxon Hot Box, 350 F
4r
\\ \ \\ \\\ \ \\\\\
Balston
Filters
Goksoyr/Ross SO, collector, 160 F
\_ _3
x*-To gas meter
^
V
*
•»[_
\7
~r
A
*
Jfc'^'L
Silico Blank
gel
A. SOj-SOj Impinger Train
o
o
/
o
o
0
(. I
\
L'E
\
o
o
f
NoOH NoOH Blank S^cc qel
B. Chloride & Fluoride Imoinaer Trair
6
a
f
0
"
i
f )i\C 1 1C
<1 0
0
r
r
1
1
t
.[
o •
•3
'
a
il
KOH KOH Blank Siiico gei
C._Cyanide Impinger Train
VcnK —y To H. C. Anulyx.pr
H2S04 H2504 BlarA Silica
D. NHj Impinger Train
Figure 1. Midget Impinger Sampling Arrangement for Stream Ip
-------
Collection of the SCL (HUSO.) was accomplished by using a Goksoyr-
Ross coil (Controlled Condensation Coil — CCC). Sulfur dioxide was
trapped using a NaOH impinger system as a separate train.
Since the FBC was at 10 atm, flow through the sampling systems was
maintained by individual needle valves. During each run, the trains were
operated for approximately 100 minutes at flow rates between 7 to 12 1pm.
2.2 S03 SAMPLING SYSTEMS
The systems used to quantify H0SO. are based on selective absorption
(1 2 3)
or controlled condensation. A series of workersv ' ' ' have refined
the selective IPA absorption method. This approach uses an impinger with
80% isopropyl alcohol to collect the S03 and to pass the S0?. The S02
is collected in a back-up impinger of 3% H202. This method is currently
the basis of the EPA compliance test™) for sulfuric acid mist at acid
plants. The major problem with this procedure for combustion processes
is the lack of a pre-filter to effectively prevent particulate matter
from reaching the IPA impinger. The particulate matter in the impinger
can act either as a direct interferent by contributing SO. from sulfate
salts, or as an indirect interferent by catalyzing the S03= to S0.~
oxidation in the liquid phase through action of trace elements like Fe or V,
The controlled condensation (Figure 2) approach was first proposed
by Knor ' and has been further developed by Goksoyr and Ross/ '
The Goksoyr-Ross system is the basis of an ASTM procedure for SO .' '
X
In the controlled condensation approach, hLSO. is separated from the gas.
stream by cooling the temperature of the flue gas below the dew point
for S03 but above the dew point of H,>0. The resulting aerosol is either
collected on the walls of the cooling coil or on a back-up frit. Investi-
gators ' ' ' studying controlled condensation in the laboratory have
found the precision and accuracy to be +6% in synthetic gas streams.
Hillenbrand, et al, ' have also suggested that S02 can be oxidized by
fly ash.
Work' ' by this laboratory has defined the operating parameters
necessary to optimize a sampling system for H2S04. It was found that:
• The quartz filter system should be heated above 288°C (550.4°F)
to avoid acid fallout.
-------
STACK
ADAPTER FOR CONNECTING HOSE
TC WELL
ASBESTOS CLOTH
INSULATION
GLASS-COL
HEATING
MANTLE
\
RUBBER VACUUM
HOSE
DRY TEST
METER
THREE WAY
VALVE
3%
•SILICA GEL
EMPTY
Na2co3
3% H.
RECIRCULATOR
THERMOMETER
Figure 2. Controlled Condensation System Set-up
-------
• Fly ash at the level of 0.3 g on the surface of the filter
can reduce the amount of ^$04 recovered by 12% when a 10
ppm gas stream of ^$04 was passed through the system.
• Extensive field evaluation under high (11 g/m ) mass loading
and high S02 (4000 ppm) concentrations showed that as little
as 0.1 ppm of H,>SO. can be detected.
• The coefficient of variance for the percentage removal of
H2S04 by wet scrubbers at a coal-fire utility was found to
be ±18%. This value compares well with the +_ 16% for the
estimated field accuracy.
• Oxidation of S02 at the recommended filter holder temperatures,
4000 ppm S02 and 8% 02 did not occur. When fly ash from a
coal-fired utility was placed on the filter, it did not have
a catalytic effect under those conditions.
On the basis of this work it was possible to evaluate the quality of
samples taken at the Exxon plant.
2.3 CRITIQUE OF S03 SAMPLING AT EXXON
Using the Controlled Condensation System (CCS) to sample 803(^504)
requires precise control of filter and condensation coil temperatures.
The Exxon hot box in Figure 1 has several potential problems that could
lead to low SO^ values since the hot box and manifold temperature is ~176°C
Experiments with quartz liners and filters showed combined retention values
of -25% of the H2S04 input at 200°C (392°F). At 176°C (348.8°F) the reten-
tion of HpSO* would be higher, but experiments have shown that quantitative
H^SO. recovery is only attainable above 288°C.
The inertness of the Balstron filters toward H2SO, is unknown, since
TRW's experience to date has been with quartz filters. It can be stated
that with the higher capacity by these types of filters, the highly
alkaline nature of the participate matter (CaO + fly ash), and the lower
sampling temperature would all lead to ^$04 recovery values than the 88%
normally expected.
The use of a short piece of unheated Teflon line to connect the
trains to the manifold can lead to serious errors. It has been found
that even unheated ball/socket joints in the CCS can lead to premature
condensation of water. Normally this will lead to a positive error due
to S0£ being scrubbed out of the gas and measured as ^$04. If a
connecting line must be used, then it should be heated above 250°C. In
-------
this case a 316 SS line with a Teflon ball or socket could be used to
connect the train to the manifold.
Figure 3 shows plots of dew point vs SO, concentration at two
pressures. The dew point data at 10 atm and 1 atm were calculated
(13)
and a second set at 1 atm was obtained experimentallyv '. The normal
operating temperature for the controlled condensation coil is 60°C (140°F),
Exxon had sampled with the CCC at 73°C (163.4°F). The high operating
temperature should not affect the results because Figure 3 shows that
73°C (163.4°F) is low enough to remove most of the SO, from the gas
phase. It is recommended that the temperature be reduced further, to
ensure that the gas is completely cooled below the S03 dewpoint in the
confines of the Controlled Condensation Coil (CCC).
Use of an 80% IPA impinger to collect sulfuric acid in the presence
of SOp can cause large positive errors due to pick-up of S02 by the IPA
solution. It has been found that the IPA lots contain small quantities
of peroxides. The IPA can be checked colorimetrically by adding a KI
solution to an aliquot of the IPA. Formation of a straw brown color
indicates the IPA cannot be used. Furthermore, the CCC has been shown to
be~100% efficient in removing H2SO., so a back-up impinger is not
required. It is recommended that the impinger system consist of two
HpOp impingers, a sodium carbonate impinger, a blank and a silica gel
impinger. This system, together with the CCC, will quantitatively
collect H2S04(CCC), S02(H202) and HC1 or HF (Na2C03).
The recommended analysis method for the sulfuric acid collected in
the CCC is an acid/base titration using Bromophenol Blue as the indicator.
An alternate method is to perform a sulfate titration with Sulfonazo III
as the indicator. This approach is less sensitive, but still accurate,
and it also can be used to measure the sulfate collected in the ^2
impingers. Current EPA methodology (Methods 6 and 8) uses Thorin as
the indicator, however, Thorin has an indistinct end point and suffers
from interferences by Cl", F" and P04". Sulfonzao III exhibits little
or no effect from those anions.
-------
CJ
o
o
O_
3
TOO
atm
O = 1 atm
EXPERIMENTAL
(1 atm)
300
1000
S03 CONCENTRATION (ppm)
Figure 3. Dewpoint in °C for Various S00 Concentrations and Pressures
-------
2.4 SUMMARY
Using the current sampling system at Exxon, it is estimated that the
HpSO. values are a minimum of 12% low compared to the best attainable
recoveries of the standard CCS. Due to the combination of the low
sampling temperatures and Balstron filters, the H^SO. recovery was
reduced by another 10-25%. The exact amount of HpSO. fallout is impossible
to estimate accurately, since the above estimates are based on laboratory
(12)
studies of a fly ash/quartz filtration system. ' In order to improve the
SCL sampling at the Exxon mini-piant it is recommended that:
• The hot box temperature be increased to provide a gas-out temp-
erature >250°C (482°F) with 288°C (550.4°F) as an optimum average.
• Heat the connecting line from the manifold to the gas trains.
i Reduce the CCC temperature to within 4°C (39.2°F) of the
maximum water dew point.
t Eliminate the 80% IPA impinger and use a system of ^02 and
NaOH impingers to trap S02, HC1 and HF.
• Quantitate the h^SO^ in the coil using an acid/base titration
on the coil rinse with Bromophenol Blue indicator.
• Use Sulfonazo III indicator for the sulfate titration of the
H0 impingers.
-------
3. MATERIAL COMPATIBILITY STUDIES
The investigation of material compatibility with the FBC gas streams
was initiated to find a suitable metal to be used in the probe and coil
sections of a Controlled Condensation System (CCS) designed for high pres-
sure sampling at a FBC facility. The most important properties
the probe and coil material must have are: resistance to HC1, SC^, and
H2S04 fumes; low reactivity with condensed H2S04; lack of catalysis of
S02 to S03.
3.1 PRELIMINARY SCREENING OF METALS
In order to ascertain the most appropriate metal for use in fabrica-
tion of a probe and coil, a preliminary evaluation of various materials
was made. Several materials were selected based on general compatibility
and suspected reactivity (or lack thereof) with an FBC environment.
Tables 2 and 3 list the composition of various alloys and compatibility of
these alloys with chemicals which are found in an FBC environment. The
final selection of material was based upon probable chemical resistance,
strength, availability, and ductability. The initial materials selected
were: 316L Stainless Steel, Hastelloy C-276, Durimet 20, Chlorimet 2,
Tantalum, and Inconel 671.
3.2 CHEMICAL RESISTANCE
A preliminary screening was initiated to examine the chemical resis-
tance of the various materials. Since the environment of an outlet flue
gas stream at a FBC facility consists of HC1, h^SO/i, S02 and H20 vapors
at 300°C (572°F) and 150 psi, these experiments consisted of exposing
various metal coupons to HC1, S02 and H2S04 vapors individually and to all
three vapors collectively.
3.2.1 Experimental
Table 4 gives a complete listing of the chemicals and conditions
employed for each environment. The initial pressure in the reaction vessel
was 75 psi which increased to 150 psi when heated to 300°C (572°F).
Hydrochloric acid and H2S04 were initially introduced into the reaction
vessel as solutions and later vaporized during the experiment.
10
-------
TABLE 2. METAL COMPOSITION*
Fe
Cr
Ni
C
Mo
N
Cu
Si
Mn
Ta
SS316
Base
16-18
10-14
0.1 max
1.75-2.75
-
-
-
-
-
SS446
Base
23-27
-
0.35 max
-
0.25 max
-
-
-
-
Monel
1.4
-
67
0.15
-
-
30
0.1
-
-
Hastaloy B
3-7
-
Base
0.02-0.12
24.32
-
-
-
-
-
Durimet T
Base
19
22
0.07 max
2
-
1
1
-
-
Durimet 20
Base
20
29
0.07 max
2
-
4
1
-
-
Chlorimet 2
3 max
-
63
0.15 max
32
-
-
1
1
-
Ni chrome
-
20
78.5
-
-
-
-
1.5
-
-
Tantalum
-
-
-
-
-
-
-
-
99.9+
TABLE 3. COMPATIBILITY*
Vapor
Hydrochloric
Acid
Sulfur
Dioxide
Sulfuric
Acid
SS316
NG
OK
NG
SS446
NG
OK
OK
Monel
<0.5% OK
dry-OK
wet-NG
OK<19%
boil
Hastaloy B
OK
wet-NG
OK<60%
Durimet T
OK
OK
OK<10%
Druimet 20
OK
OK
OK<25%
NG >78% hot
Chlorimet 2
OK
OK except
with high
temp
OK except
>80% hot
Ni ch-
rome
?
?
?
Tantalum
OK 662° max
OK 392° max
OK 347° max
at 98%
*Referenced from "Chemical Engineers Handbook"
-------
316L STAINLESS STEEL
DURIMET 20
INCONEL 671
TANTALUM
HASTELLOY C-276
CHLORMET 2
Figure 4. Metal Coupons Before Chemical Resistance Tests
12
-------
TABLE 4. CHEMICAL ENVIRONMENTS
Test
Series
1. Control
2. S02
3. HC1
4. H2S04
5. Total
H?0
10%
X
X
X
X
X
Op
8&
to
X
X
X
X
X
SOo
2000 ppm
X
X
H2S04
500 ppm
X
X
HC1
500 ppm
X
X
Remainder N2
X
X
X
X
X
*Total pressure in system was 75 psi at 25°C (77°F).
The metal coupons shown in Figure 4 were cut, ground, and vapor honed
to help assure a uniform surface and eliminate any large physical differences
in textures. The mass of each sample was determined and photographs
(100X and 400X magnification) of the grain structure were taken initially to
give a reference point for the starting material. Figures 5 and 6 show
the grain structure of 316L Stainless Steel at 100X and 400X magnification.
The metal coupons were then placed into the reaction vessels where they
were pressurized, sealed, and heated. After 72 hours of heating, the
specimens were immediately vented to atmosphere and removed from the
reaction vessel to prevent any condensation of gases on the metal coupons.
The exposed metal coupons were weighed, photographed at 100X and 400X
magnification, and critically examined for degradation.
In order to carry out the above evaluation, the reaction vessels
which had to maintain a corrosive environment, and a gas manifold which
was needed to fill the vessels, had to be constructed. The reaction vessels
13
-------
Figure 5. Stainless Steel 316L at 100X Magnification
Figure 6. Stainless Steel 316L at 400X Magnification
14
-------
were constructed from 1" I.D. standard wall pyrex tubing. Figure 7 shows
a pyrex reaction vessel which held six metal coupons. To prevent dissimilar
metal contact with the resultant galvanic corrosion, metal coupons were
first placed into quartz boats, which were then placed into the reaction
vessel. Additional quartz boats were placed into the reaction vessel to
hold the HC1 and H2$04 solutions.
Figure 8 shows the complete laboratory set-up for the chemical re-
sistance experiments. The gas manifold along with the various valves and
gauges were all stainless steel. Since very specific quantities of S02
were required for the FBC environments, a (zero to 1600 Torr) Wallace and
Tierman pressure gauge, which accurately measures pressure to one Torr,
was incorporated into the manifold system. Two zero-to-100 Ibs. pressure
gauges which accurately measure pressure to one Ib. were used to monitor
the filling of 02 and Ng gases into the reaction vessel.
3.2.2 Results
The results of the initial investigation indicated that only tantalum
could not withstand the FBC environment. The high temperature [300°C (572°F)]
along with the chemical environment caused the tantalum to oxidize.
Durimet 20, Inconel 671 and Chorimet 2 were fairly resistant to the FBC
environment but some slight staining and pitting of the metals' surface
was observed. Hastelloy C-276 and 316L Stainless Steel had the best over-
all performance with some slight discoloration of the metals but no apparent
chemical attack. The results are summarized in Table 5,
3.3 CATALYTIC ACTIVITY STUDY (Acid/Base Titration Method)
A second evaluation was designed to examine the lack of catalytic
activity of the metal to participate in the S02 to S03 oxidation. Both
Hastelloy C-276 and 316L Stainless Steel would have been tested for their
catalytic property but a problem arose. The manufacturer of Hastelloy
C-276 would not sell the necessary material needed for the experiment
because their stock of material was defective. This problem did not
seriously impair the results of the study, since 316L Stainless Steel
was shown to be a suitable material for the train fabrication and was
readily available.
15
-------
12" M—— 2
C
BOAT
METAL
1" I.D.
1/4" TUBING
Figure 7. A Pyrex Reaction Vessel
-------
WALLACE TIERNAN
PRESSURE GAUGE
PRESSURE GAUGES
PROTECTIVE METAL CYLINDER
GLASS
REACTION
VESSEL
GLASS TO METAL
INTERFACE
Figure 8. The Complete Laboratory Set-up for the Chemical
Resistance Experiments
17
-------
TABLE 5. PRE-TEST AND POST-TEST ANALYSIS RESULTS
00
MATERIAL
HASTELLOY
C-276
316 L
DURIMET 20
TEST
ATMOSPHERE
so2
HC1
H2S04
SOp , HC1 , HnSO.
Control
so2
HC1
H2S04
SOp i HC1 , HpSO*
Control
so2
HC1
H2S04
S02, HC1, H2S04
Control
WEIGHT IN GRAMS
PRE-TEST
7.6555
8.9545
7.9626
8.5847
7.8274
3.5107
4.1576
3.8447
3.7728
3.8574
5.7834
5.7016
6.1724
6.1544
5.8666
POST-TEST
7.6551
8.9545
7.9619
8.5844
7.8274
3.5103
4.1572
3.8443
3.7728
3.8576
5.7832
5.7017
6.1717
6.1541
5.8667
A9
-.0004
.0000
-.0007
-.0003
.0000
-.0004
-.0002
-.0004
.0000
+.0002
-.0002
+.0001
-.0007
-.0003
+.0001
POST-TEST OBSERVATIONS
NO APPARENT ATTACK
NO APPARENT ATTACK
OVERALL STAINING, NO APPARENT ATTACK
NO APPARENT ATTACK
NO APPARENT ATTACK
AMBER COLOR, NO APPARENT ATTACK
DARK AMBER, CONTINUOUS COLOR, NO APPARENT
ATTACK
BLUE-PURPLE COLOR, NO APPARENT ATTACK
LIGHT AMBER COLOR, NO APPARENT ATTACK
LIGHT BLUE COLORATION, NO APPARENT ATTACK
AMBER COLORATION, NO APPARENT ATTACK
CRYSTALLINE FORMS, SLIGHT SURFACE ATTACK
SOME STAINING & CRYSTAL FORM
AMBER COLORATION, NO APPARENT ATTACK
SOME CRYSTAL FORMATIONS, AND SLIGHT ATTACK
- Continued -
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TABLE 5. PRE-TEST AND POST-TEST ANALYSIS RESULTS (Continued)
MATERIAL
CHLORIMET 2
TANTALUM
INCONEL 671
TEST
ATMOSPHERE
so2
HC1
H2S04
S02, HC1, H2S04
Control
so2
HC1
H2S04
S02, HC1, H2S04
Control
so2
HC1
H2S04
jOn , Hl> 1 , H«oU«
Control
WEIGHT IN GRAMS
PRE-TEST
12.0106
10.1746
11.7105
11.2442
10.6229
18.2257
14.5883
20.7296
18.9315
14.0782
9.9561
9.7145
9.4317
10.0606
9.5944
POST-TEST
12.0103
10.1741
11.7100
11.2438
10.6227
18.2256
14.5884
20.7299
18.9320
14.0786
9.9554
9.7141
9.4311
10.0605
9.5940
A9
- . 0003
-.0005
-.0005
-.0004
-.0002
-.0001
+.0001
+.0003
+.0005
+.0004
-.0004
-.0004
-.0006
-.0001
-.0004
POST-TEST OBSERVATIONS
SLIGHT ATTACK ON ONE SIDE
LOCALIZED CRYSTAL FORMATIONS, SLIGHT ATTACK
LOCAL STAINS AND CRYSTAL
NO APPARENT ATTACK
DISCOLORATION, NO APPARENT ATTACK
METAL TURNED BLUE (OXIDATION)
METAL TURNED BLUE (OXIDATION)
METAL TURNED BLUE (OXIDATION)
METAL TURNED BLUE (OXIDATION)
METAL TURNED BLUE (OXIDATION)
LOCAL STAINS
LOCAL STAINS
LIGHT AMBER COLOR, LOCAL CRYSTALS AND STAINS
LOCAL STAINS
DISCOLORATION
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3.3.1 Experimental (acid/base titration method)
The experiment consisted of passing a gas stream of N2 (90%), 0? (10%),
and S02 (8000 ppm) through a 1.5M (0.635 cm I.D.) 316L Stainless Steel
pipe at 300°C for one hour at a flow rate of 8 1/min. The N2 and 02 gases
were saturated with H20 before mixing with S02. After the gases passed
through the metal pipe, they entered a controlled condensation coil which
would condense any H2SO. generated during the experiment. The remaining
gases were then passed through two 3% H202 impingers which converted SO?
to H2S04- The actual amount of S02 in the gas stream was determined by
titrating the acid in the impingers after the test run. Figure 9 shows
the complete laboratory set-up for the catalytic effect experiment.
3.3.2 Results (acid/base titration)
After running the gases through the experimental system for one hour
the controlled condensation coil and the 316L Stainless Steel pipe were
rinsed with D.I. water and each solution was titrated with NaOH (Bromophenol
Blue indicator) to determine the amount of H2SO^ present. The impinger
solutions were also titrated with NaOH (Bromophenol Blue indicator) to
determine the amount of S02 passing through the system. The rinse solution
from the controlled condensation coil had 0.27 ^0.02 ppm of H2S04 and
no H2S04 was found in the 316L Stainless Steel pipe.
3.4 CATALYTIC ACTIVITY STUDY (Sulfate Titration)
The results of the S02 catalysis by 316L Stainless Steel were based
on an acid/base titration. There was a possibility that any H2S04 formed
in the 316L Stainless Steel pipe might have reacted with the pipe and
never have reached the Controlled Condensation Coil (CCC). Consequently
an acid/base titration of the pipe would not show any H2S04 formed. In
order to eliminate this possibility, a sulfate titration was performed
on the rinse solution after the catalytic effect experiment was repeated.
20
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ro
Controlled Condenstation Coil
Figure 9. The Complete Laboratory Set-up for the Catalytic Effect Experiment
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3.4.1 Experimental (stil fate titration)
The same experimental conditions were employed as in Section 2.3.1.
3.4.2 Results (sulfate titration)
At the end of one hour, the Controlled Condensation Coil and the 316L
Stainless Steel pipe were rinsed with D.I. water and each solution was
titrated with BalClO^ and Sulfonazo III indicator to determine the amount
of S0| ion present. These titrations showed that the pipe and the
Controlled Condensation Coil did not contain any S0| ion. The minimum
detectable quantity of SOj for the Ba(C104) titration was 0.01 millimoles,
which corresponds to a minimum detection gas concentration of 0.02 ppm
under the conditions of the test. These results confirm that 316L Stain-
less Steel does not catalyze S02 to S03 at the conditions tested.
3.5 REACTIVITY OF ALLOYS WITH CONDENSED SULFURIC ACID
The third evaluation was designed to examine the reactivity of the
metal with condensed ^504. Both Hastelloy C-276 and 316L Stainless
Steel were tested for reactivity in two different sets of experiments.
3.5.1 Experimental
The first experiment was to depost lOOyl of concentrated sulfuric
acid on the metal surface, place the metal in a closed environment of air
saturated with 50°C D.I. H,>0 for one hour. At the end of the time
period, the acid was rinsed off with 50 ml of D.I. ^0 and the rinse was
titrated with NaOH (Bromophenol Blue indicator) to determine the acidity
of the solution. The same procedure was performed on a piece of Teflon
which was used as control. By comparing the acidity of the rinse solution
of the metals to the rinse of the control, the amount of reactivity was
determined. Also, the acidity of a solution made up of lOOyl of concen-
trated ^$04 and 50 ml of D.I. HgO was determined and compared to the
rinse from the metals and control.
22
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The second experiment for reactivity was to place the metal into
a IN H2$04 solution at 50°C for one hour. The degree of reactivity of
the metal toward the acid was determined by a change in the acidity of
the solution and the weight of the metal sample. If a reaction occurred
between the acid and metal, the acidity of the solution would drop and
the sample would be reduced. The acidity of the IN ^SO^ solution was
determined by titration with NaOH (Bromophenol Blue indicator).
3.5.2 Results
The results of the first experiment with concentrated sulfuric acid
are listed in Table 6 and indicate that both 316L Stainless Steel and
Hastelloy C-276 are inert toward h^SO^
The results of the second experiment with dilute sulfuric acid
showed that the weight of the Hastelloy C-276 and 316L Stainless Steel
samples did not change and the normality of the 1^04 solution remained
constant. The results indicate that both metals are inert toward the
solution.
TABLE 6. RESULTS OF H2S04 DROPLETS ON METAL SURFACE
Type of Surface
Blank
Teflon
Hastelloy C-276
Stainless Steel 31 6L
Amount of H2S04
Placed on Surface
100 fjil
100 nl
100 H-l
100 (J
Average titration volume
3.65
3.66
3.68
3.70
23
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3.6 SUMMARY OF MATERIAL COMPATIBILITY STUDIES
The initial materials selected, based upon a literature survey were:
316L Stainless Steel, Hastelloy C-276, Durimet 20, Chlorimet 2, Tantalum,
and Inconel 671. This preliminary screening indicated that 316L Stainless
Steel had two advantages over the other alloys, cost and availability.
The chemical resistance experiments have shown that both Hastelloy
C-276 and 316L Stainless Steel are resistant to the FBC flue gas environ-
ment. Tantalum had oxidized in the FBC environment. Durimet 20, Chlorimet
2, and Inconel 671 had shown signs of chemical reactions which would
indicate that these alloys would break down under constant exposure to
the FBC environment.
The catalytic activity experiments have shown that 316L Stainless
Steel does not act as a catalyst for S02 to S03 oxidation.
The chemical reactivity experiments have shown that both 316L Stainless
Steel and Hastelloy C-276 were inert toward both dilute and concentrated
sulfuric acid.
The results of the material compatibility studies have shown that
316L Stainless Steel can be employed as the probe and coil material for
the Controlled Condensation System. 316L Stainless Steel had the best
overall performance for the three chemical tests. Hastenoy C-276 is
another possible alloy to be employed as probe and coil material but
further experimentation must be done on its ability not to catalyze
to S03.
24
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4. CONCLUSIONS
The current sampling systems employed at the Exxon FBC facility was
reviewed and it is estimated that the KLSO. values are 12 to 37% low
compared to the actual amount of output.
The H2S04 sampling at the Exxon FBC can be improved by:
• Increasing the hot box temperature so a gas-out temperature
of at least 250°C is obtained with 288°C as an optimum average
• Maintaining a uniform heat throughout the entire CCS
t Employing a H?0? and NaOH impinger system to trap SO?, HC1,
and HF
• Using an acid/base titration method with Bromophenol Blue
indicator to quantitate ^$04 in the coil
• Using Sulfonazo III indicator for the sulfate titration of the
impingers.
316L Stainless Steel can be employed as the material of construction
for the probe and coil sections of the CCS* Hastelloy C-276 could be a
second possible alloy.
25
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5. REFERENCES
1. P.P. Corbett, "A P ho to lurbidi metric Method for Estimation of SO, in
the Presence of S02", J.. Soc. Chem, Ind. . 67 227 (1948). J
2. D. Flint, "Determination of Small Concentrations of S03 in the Pre-
sence of Larger Concentrations of $02", Ibid, 2.
3. R. S. Fielder, P. 0. Jackson and E. Raask, "Determination of SOo and
in Flue Gases", _J_. Inst., Fuel, 33, 84 (1960).
4. Environmental Protection Agency, "Determination of Sulfuric Acid
Mist and Sulfur Dioxide Emmisions from Stationary Sources", Fed.
Reg., 41, (111), 23087 (1976).
5. B.P. Knol, "Improvements in Determination of S03 and S0? in Combustion
Gases", Riv. Combust ibli. 4, 542 (1960).
6. H. Goksoyr and K. Ross, "The Determination of Sulfuric Trioxide in
Flue Gases", J_. Inst. Fuel. .35, 177 (1962).
7. American Society of Testing Materials, Part 26, ASTM Method D3226-73T,
1974.
8. J. N. Driscol and A. W. Berger, "Improved Chemical Methods for Sam-
pling and Analysis of Gaseous Pollutants from Combustion of Fossil
Fuels Volume I, Sulfur Oxides", Walden Research Corporation, PB 209-
267, June, 1971.
9. H. F. Hamil, R. F. Thomas, D. Comann, "Collaborative Study of Methods
for the Determination of Sulfuric Acid Mist and Sulfur Dioxide
Emissions from Stationary Sources", S. W. Research Institure, PB-240-
752/6, November, 1974.
10. L.J. Hillenbrand, et al, "Chemical Composition of Particulate Air
Pollutants from Fossil Fuel Combustion Sources", Battelle Columbus
Laboratories, PB-219-009, March, 1973.
11. R. F. Maddalone, S. F. Newton, R. G. Rhudy, and R. M. Statnick,
"Laboratory and Field Evaluation of the Controlled Condensation
System for (Goasoyr/Ross) for S03 measurements in Flue Gas Streams."
This was presented at the 70th APCA Annual Meeting and Exhibition,
Toronto, June 20 - 24, 1977.
12. Communication from, Dr. Larry Cooper, Acurex Corporation.
13. E.S. Lisle and J. D. Sensenbaugh, "The Determination of Sulfur
Trioxide and Acid Dew Point in Flue Gases", Combustion, 36, 12 (1965).
14. R. F. Maddalone and N. Garner, "Process Measurements Procedures for
Sulfuric Acid Emissions", TRW DSSG, EPA Contract # 68-02-2165 Task
No. 13, February, 1977.
26
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
TREPORT NO.
EPA-600/7-79-154
2.
3. RECIPIENT'S ACCESSION NO.
AND SUBTITLE
Quality Assurance of FBC H2SO4 Measurements
5. REPORT DATE
July 1979
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
Acciani and R. F. Maddalone
OROANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
TRW Defense and Space Systems Group
One Space Park
Redondo Beach, California 90278
INE624
11. CONTRACT/GRANT NO.
68-02-2613, Task 3
7 SPONSORING AGENCY NAME AND ADDRESS
J3PA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 5/77 - 8/78
14. SPONSORING AGENCY CODE
EPA/600/13
NOTES
541-2557.
. RTF project officer is Frank E. Briden, Mail Drop 62, 919/
16.
report gjves results of a study to: evaluate existing data on H2SO4
measurements from fluidized-bed combustion (FBC) processes; determine the true
value of the H2SO4 concentration which might have been obtained had the control con-
densation (Goksoyr/Ross) procedure been used; and run a material compatibility
study to find alloys that can be used to fabricate a controlled condensation sampling
system . The sampling system at Exxon's FBC facility was reviewed: H2SO4 values
aje about 12% low with another reduction of 10-25% because of low sampling temper-
atures and Balstron filters. The control condensation system with an acid/base ti-
tration using bromophenol blue as the indicator is the recommended sampling/analy-
sis method for H2SO4 sampling at the Exxon facility. Construction material for the
controlled condensation system can be 316L stainless steel, which had the best
performance when subjected to various tests used to simulate an FBC environment
will easily withstand the pressures found at the Exxon facility.
17-
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
. COSATI Field/Group
pollution
gulfuric Acid
gulfur Trioxide
Measurement
Combustion
Bed Processing
Condensing
Quality Assurance
Alloys
Pollution Control
Stationary Sources
Goksoyr/Ross Method
13 B
07 B
14B
21B
13H,07A
07D
11F
---DISTRIBUTION STATEMEN1
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
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31
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
form 2220-1 (9-73)
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