United States
Environmental Protection
Agency
Environmental Sciences Research;
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-82-068 Feb. 1983
Project Summary
Comparison of Automated and
Manual Sulfuric Acid
Sampling Systems
Walter R. Dickson
Three sampling systems designed to
measure gaseous sulfuric acid (H2SO<)
in combustion source emissions were
evaluated. The three systems are: (1) a
commercially available monitor pro-
duced by Severn Science Limited (SSL)
of Great Britain, (2) a prototype sulfuric
acid mist monitor (SAMM) designed
and constructed by the Environmental
Sciences Research Laboratory (ESRL)
of EPA, (3) a miniaturized acid-conden-
sation system (MACS) for performing
manual HUSO* measurements, also
designed by ESRL. All three systems
were evaluated in the laboratory using a
thermal generator to produce H2SO4.
Following the laboratory evaluation the
three systems were evaluated at a coal-
fired utility plant equipped with an
electrostatic precipitator (ESP) control
device. Sampling was conducted for
one week at the ESP inlet and for
another week at the ESP outlet. The
commercially available monitor (SSL)
was compact and simple to operate but
gave unexplainable positive responses.
The prototype monitor (SAMM) was
found to be sound in measurement
principle but in need of significant
packaging improvements to be practi-
cal. The manual sampling system
(MACS) was highly practical and simple
to operate but gave lower results than
the automated systems due to the equi-
librium of H2SO4 with the surface of the
probe and filter holder.
This Project Summary was developed
by EPA's Environmental Sciences Re-
search Laboratory, Research Triangle
Park. NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
Due to the possible correlation between
primary sulfate emissions and visibility
degradation, acid rain, inhalable particu-
late formation, and surface materials
damage, there has been increased atten-
tion on measurements of such emissions.
Measurements of primary sulfate emis-
sions from fossil-fuel-fired systems usu-
ally attempt to separate gaseous HaSCh
from the metal sulfate salts. As the H2SO4
can react with the paniculate matter in
such emissions, both reversibly and irre-
versibly, such separation can be difficult
and unpredictable. Studies have shown
that the.measurement of gaseous H2S0.4
is best achieved, either manually or
automatically, by first separating the
particles with a high-temperature quartz
media.
Much of the pioneer work on gaseous
HaSO* measurements was performed by
researchers interested in corrosion stud-
ies in Great Britain and Germany. From
these early studies emerged an auto-
mated method that measures H2SCU
colorimetrically after reaction with
Barium Chloroanalate. The gaseous
H2SC>4 is separated from paniculate sul-
fate with a high-temperature quartz probe
plug. This measurement concept has been
packaged into an automatic monitor and
is available commercially from Severn
Science Limited (SSL) of Great Britain.
More recently developed methods have
focused on the temperature-controlled
condensation of the acid after particle
removal. The acid is condensed in a
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temperature-controlled Goksoyr-Ross
type coil that avoids the collection of
water and sulfur dioxide, common inter-
ferents. This technique, now accepted as
the manual procedure for HzSCu measure-
ments, was also recently incorporated
into an automated monitor. This prototype
Sulfuric Acid Mist Monitor (SAMM) col-
lects the H2SC>4 in a Goksoyr-Ross type
coil and then measures the conductivity
of the collected acid. Both the SAMM and
the manual Miniature Acid Condensation
System (MACS), which uses the temper-
ature-controlled condensation of HjSCU,
were developed by EPA's Environmental
Sciences Research Laboratory.
Procedure
This study involved the side-by-side
evaluation of the three methods (SSL,
SAMM, and MACS). The evaluation
included a laboratory study using a ther-
mal generator to produce particle-free
H2S04. Over an HzSCU concentration
range of 2 to 20 ppm (v/v), the two
automated methods (SSL and SAMM)
agreed (±10%) with the manual method
(MACS). In the SAMM, a small electro-
static separator was used as an alterna-
tive to filter media.
The three sampling systems also were
field-tested at a coal-fired utility plant. A
full week of sampling at an electrostatic
precipitator (ESP) inlet resulted in average
HzSCu concentrations of 12, 12, and 10
ppm using the SSL, SAMM, and MACS,
respectively. Sampling at the ESP outlet
during the second week gave average
concentrations of 4, 4, and 3 ppm for the
SSL, SAMM, and MACS, respectively.
Summary of Results
1. During field evaluation, the commer-
cially available SSL monitor operated
well and was compact and simple to
operate. The average results agreed
well with results from the SAMM.
The instrument did give transient
positive responses that did not agree
with responses from the other two
methods, could not be explained, and
should be investigated further.
The SAMM was found to be extremely
cumbersome in its prototype form
and in need of major design changes.
The monitor produced results that
agreed with the SSL results. While
the measurement principle of the
prototype was acceptable, the system
appeared to offer no advantages over
the SSL monitor.
The MACS operated well and was
highly portable and easy to use. Its
results were consistently low when
compared to results from the two
monitors. These low results were
attributed to the retention of some of
the H2S04 in the MACS probe. Such
probe losses are not encountered
with the monitors due to the estab-
lishment of an equilibrium between
the acid and the surface areas of
those systems. For sources with low
H2SC>4, the MACS requires a more
sensitive 864determination than the
conventional Barium-Thorin proce-
dure.
Walter R. Dickson is with Southern Research Institute, Birmingham, AL 35255.
James L. Cheney is the EPA Project Officer (see below).
The complete report, entitled "Comparison of Automated and Manual Sulfuric
Acid Sampling Systems," (Order No. PB 83-144 840; Cost: $10.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
U.S. GOVERNMENT PRINTING OFFICE: 19B3 659-O17/OB9:
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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