United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-96/019 April 1996
EPA Project Summary
Hazardous Air Pollutants from the
Combustion of an Emulsified
Heavy Fuel Oil in a Firetube
Boiler
C. Andrew Miller
Emissions of criteria and hazardous
air pollutants (HAPs) were measure
from the combustion flue gases of a #6
fuel oil, both with and without an emul-
sifying agent, in a 2.5x106 Btu/hr
firetube boiler, with the purpose of de-
termining the impacts of the emulsifier
on HAP emissions. The flue gases of
the boiler were sampled and analyzed
for both metal and organic HAPs, and
the effects of the emulsification on cri-
teria emissions such as carbon mon-
oxide (CO), nitrogen oxides (NOx), and
participate matter (PM) were also mea-
sured. Measured in pounds per million
British thermal units, the emulsified oil
showed a decrease in the CO emission
factor of 24%. A decrease of 35% in the
NOx emission factor, and a decrease of
37% in the PM emission factor com-
pared to emission factors measured
from burning the base oil (i.e., the same
oil without the emulsifying agent). Emis-
sions of sulfur dioxide (SO2), and met-
als were essentially unchanged for the
emulsified oil compared to the base
oil. Emissions of volatile organic HAPs
from the emulsified oil were 6% higher
than for the base oil, and emissions of
semivolatile organic HAPs were 29%
lower than for the base oil. No poly-
chlorinated dibenzodioxins or polychlo-
rinated dibenzofurans were detected in
the flue gases of either oil. There was a
notable shift in the particle size distri-
bution toward smaller size ranges for
the emulsified oil compared to the base
oil, although it is currently unclear
whether the reduction in total PM emis-
sions results in an overall reduction in
emissions of smaller (<2.5 urn) particles.
Additional work is planned to provide
quantitative informaton on the differ-
ences in size distributions and the to-
tal mass emissions for the different par-
ticle size ranges.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Overview
Tests were conducted to measure emis-
sions of criteria and hazardous air pollut-
ants (HAPs) from the combustion flue
gases of a #6 fuel oil, both with and with-
out an emulsifying agent, burned in a 732
kW (2.5x106 Btu/hr) firetube boiler. The
testing was conducted by EPA's National
Risk Management Research Laboratory
(NRMRL), Air Pollution Prevention and
Control Division (APPCD), at the Environ-
mental Research Center in Research Tri-
angle Park, NC. The purpose of the tests
was to determine the impacts of the emul-
sifier on emissions of metal and organic
HAPs.
The flue gases were sampled at the
stack of the boiler, and data were col-
lected to determine emissions of CO, NOx,
SO2, and PM. Continuous emission moni-
tors were used to measure CO, NOx, and
SO2, and the data were logged using a
computerized data acquisition system.
In addition to criteria pollutants, the tests
sampled and analyzed for the presence of
HAPs in the stack flue gases. Concentra-
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tions of 10 metal compounds were
sampled during the test program using a
standard EPA Method 29 sampling train.
Concentrations of antimony, arsenic, be-
ryllium, cadmium, chromium, lead, man-
ganese, nickel, selenium, and vanadium
were measured for both the base oil and
the emulsified oil stack flue gases. The
samples were analyzed for 45 volatile or-
ganic compounds (VOCs) using the Vola-
tile Organics Sampling Train (VOST). Of
the 45 compounds for which the samples
were analyzed, 24 are listed as HAPs
under Title III of the 1990 Clean Air Act
Amendments (CAAAs). Flue gas samples
were also analyzed for semivolatile or-
ganic HAPs using a Modified Method 5
sampling train and standard EPA analyti-
cal methods. The samples were analyzed
for 105 semivolatile compounds, of which
45 are listed as HAPs under CAAA Title
III. Included in the 105 compounds were
17 PAHs, which are listed as a single
HAP under CAAA Title III.
The boiler was operated at a steady
firing rate of 586 kW (2x106 Btu/hr) and a
nominal stoichiometry of 1.2. The emulsi-
fied fuel oil showed significant reductions
in emissions of criteria pollutants com-
pared with the base oil. CO emissions
from the emulsified oil were lower than
the base oil by 22%, NOx emissions were
35% lower for the emulsified oil than for
the base oil, and PM emissions were 30%
lower for the emulsified fuel than for the
base fuel. Because emulsification does
not impact the amount of sulfur in the oil
(but adds moisture and reduces oxygen in
the flue gas), little change was expected
in SO2 emissions. Although there was a
slight decrease in the concentration of SO2
in the measured flue gas of the emulsified
oil, the amount of change was not consid-
ered to be significant, and was consid-
ered to be unrelated to the use of the
emulsified oil.
The percentage changes between the
base and emulsified oil emission factors
(measured in pounds-per-million British
thermal units) are somewhat different from
the changes comparing the emissions
based on dry concentrations (measured
in parts per million). This is due to changes
in the fuel and gas flow rates from the
base to the emulsified fuel tests. When
comparing emission factors, the emulsi-
fied oil showed slightly greater, but con-
sistent, reductions on a percentage basis
than when comparing flue gas concentra-
tions. The CO emission factor was 24%
lower for the emulsified oil compared to
the base oil, the NOx emission factor was
35% lower for the emulsified oil compared
to the base oil, and the PM emission fac-
tor was 38% lower for the emulsified oil
compared to the base oil.
For the metal emission results in gen-
eral, the results followed the expected pat-
tern, and showed no significant differences
between the base oil and the emulsified
oil. Although there was a relatively large
difference in the antimony emission fac-
tors between the two oils, the data for
antimony showed a much larger scatter
than was present in the other metals. Be-
cause no metal was added in the emulsi-
fying agent, it was expected that the two
oils would show essentially the same total
emissions of metals per unit of energy.
Average values for VOC emissions are
presented, calculated using zero where
the compound was below the detection
limit. The values were quite low for both
oils, with total VOC emission factors of
less than 2.58 (im/MJ (6 lb/1012). The total
volatile organic HAP emissions from emul-
sified oil were about 6% higher than those
from the base oil. However, the emission
rates of individual organic compounds var-
ied considerably between the base oil and
emulsified oil. While the base oil emis-
sions of carbon disulfide were over twice
as high as for the emulsified oil, the emul-
sified oil had measured 2-butanone and
toluene emissions nearly 60% higher than
the base oil.
Emissions of semivolatile organic com-
pounds were slightly lower than the VOC
emissions, at approximately 1.5 mg/MJ
(3.5 lb/1012 Btu) for the base oil, and 1.1
mg/MJ (2.5 lb/1012 Btu) for the emulsified
oil. Most emissions from the base oil were
of benzyl alcohol at 1.06 mg/MJ (2.47 Ib/
1012 Btu), while phenol was the major emis-
sion from the emulsified oil at 1.02 mg/MJ
(2.37 lb/1012 Btu). Neither of these com-
pounds was present in the field blank used
to evaluate analytical contamination of the
samples.
The impact of the emulsifier on particle
sizes was also evaluated. Particle size
distributions were measured using a dif-
ferential mobility particle size instrument
and an impactor filter system which col-
lects particles in discrete size ranges. Both
methods indicated a shift of the particles
to smaller size ranges when the emulsi-
fied oil was being burned, compared to
the particle sizes resulting from the base
oil. However, discrepancies in the data
comparing the mass of PM captured in
the impactor to the total PM captured in
the Method 29 sampling train made it im-
possible to determine quantitative changes
with sufficient confidence. Therefore, only
qualitative results are reported here.
In conclusion, the emulsified oil showed
lower emissions of CO, NOx, and PM com-
pared to the base #6 oil, while no signifi-
cant change was noted in emissions of
SO2, total metals, or total organic HAPs.
For the boiler tested, operating at its full
load of 732 kW (2.5x106 Btu/hr) for a full
year, the total annual uncontrolled emis-
sions of organic HAPs are estimated to
be 0.089 kg/yr(0.197 Ib/year) for the base
oil and 0.083 kg/yr (0.183 Ib/year) for the
emulsified oil. This compares with annual
mass emission estimates of 140 kg/yr (308
Ib/year) of combined uncontrolled vana-
dium and nickel emissions for the base oil
and 152 kg/yr (335 Ib/year) of combined
uncontrolled vanadium and nickel emis-
sions for the emulsified oil. For both oils,
the uncontrolled annual emissions of HAPs
are well below the 9.07 tonnes/yr (10 tons/
yr) threshold defined by CAAA Title III for
a major source.
The primary potential disadvantage to
using emulsified oil was the shift of the
PM size distribution to smaller size ranges
compared to the base oil. It is not known
whether the amount of particulate in the
smaller size fraction increased, decreased,
or remained constant when compared to
baseline. Additional study of the impact of
emulsified fuels on particle size distribu-
tions is planned.
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The author C. Andrew Miller is also the EPA Project Officer (see below).
The complete report, entitled "Hazardous Air Pollutants from the Combustion of an
Emulsified Heavy Fuel Oil in a Firetube Boiler," (Order No. PB96-168281; Cost:
$28.00, 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:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
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EPA
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EPA/600/SR-96/019
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