United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S7-86/004 May 1986
*
Project Summary
Environmental Assessment of a
Watertube Boiler Firing a Coal/
Water Slurry
R. DeRosier and L. R. Waterland
This report describes emission results
obtained from field testing of flue gas from
a watertube industrial boiler firing a
coal/water slurry (CWS). Previously, an
emission test of this same unit was made
while burning a coal/oil mixture (COM).
Emission measurements performed in-
cluded continuous monitoring of flue gas
emissions; source assessment sampling
system (SASS) sampling of the flue gas,
with subsequent laboratory analysis of
samples to obtain total flue gas organics
in two boiling point ranges, compound
category information within these ranges,
specific quantitation of the semlvolatile
organic priority pollutants, and flue gas
concentrations of 73 trace elements; EPA
Method 5 sampling for paniculate; EPA
Method 8 sampling for SO2 and SO3
emissions; and grab sampling of fuel and
ash for inorganic composition. Two tests
were performed firing a CWS containing
nominally 60 percent coal by weight: an
abbreviated set of tests with flue gas O2
of about 2.8 percent, and a complete set
of tests with flue gas O2 of about 2.1
percent.
NOX, S02, CO, and TUHC emissions
were in the 230-310, 880-960,170-200,
and 1-3 ppm ranges (corrected to 3 per-
cent O2), respectively, over the two tests.
Particulate levels at the boiler outlet
(upstream of the unit's paniculate control
device) apparently increased from 3.5
g/dscm in test 1 to 7.3 g/dscm in test 2.
The increase may have been due to in-
creased combustibles loss with the boiler
flyash. Coarse paniculate predominated:
over 60 percent (weight) of the boiler
outlet flue gas paniculate was greater than
10 nm diameter, almost 70 percent was
greater than 3 //m diameter.
Total organic emissions were quite high,
almost 50 mg/dscm. About 70 percent of
this organic matter was in the nonvolatile
(>300°C) boiling point range. The bottom
ash organic content was quite high as
well, 8 mg/g, with 80 percent of this be-
ing in the nonvolatile boding point range.
Of the polynuclear aromatic hydrocar-
bons (PAHs) analyzed for, only naphtha-
lene was detected in flue gas samples (on
the paniculate) with emission levels of 8.6
fjg/dscm. Several PAHs were found in the
bottom ash, at levels ranging from 0.4 to
over 40 pg/g.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of the
research project that is fully documented
in two separate volumes (see Project
Report ordering information at back).
Introduction
Coal/water slurries have received atten-
tion in recent years as an alternative to oil
fuels. CWS has the advantage of allowing
certain oil-fired boilers to eliminate their oil
fuel requirements without completely
redesigning the boiler. Thus, CWS has the
potential for application as a near-term
technology for conversion of certain oil-
burning facilities to coal firing and thereby
offsetting high oil prices and frequently
uncertain supply situations. This report
presents the results of an emission assess-
ment of a CWS-fired watertube industrial
boiler.
The tests were performed at the Pitts-
burgh Energy Technology Center's
(PETC's) combustion test facility. This
facility consists of a 3.0 kg/s steam
-------
(24,000 Ib/hr) watertube boiler, an air-
cooled steam condenser and deaerator,
CWS preparation and storage facilities,
and pollution control devices. The boiler
is a package, two-drum "D'-type water-
tube originally designed by Nebraska Boiler
Company to fire No. 6 fuel oil. Table 1 sum-
marizes the boiler specifications.
CWS is prepared by charging a predeter-
mined amount of water to a 6,800 L
(1,800 gal.) steam-jacketed mix tank with
agitator before adding coal through a
gravimetric coal feeder. The CWS is then
transferred to a 10,600 L (2,800 gal.)
holding tank with an agitator and recircula-
tion pump. The CWS is pumped to the
burner by a Moyno pump. The original
burner was modified for abrasive service.
Summary and Conclusions
Boiler Operation
The test program called for flue gas
emission measurements with the boiler
operating at constant, near-rated capac-
ity with the CWS fuel. Two tests were per-
formed: test 1 with a 60.9 weight percent
coal slurry at 14 percent excess air, and
test 2 with a 58.9 percent coal slurry at
11 percent excess air. An abbreviated
sampling protocol was completed for test
1; test 2 included the complete, planned
comprehensive sampling protocol.
Table 2 lists the boiler operating condi-
tions during both tests. Except for the
fraction of coal in the fuel and the excess
air, the boiler was operated at essentially
the same conditions for both tests. Table
3 summarizes the fuel compositions for
both tests.
Emission Measurements and
Results
The sampling and analysis procedures
used in this test program conformed to a
modified EPA Level 1 protocol. All flue gas
samples were taken at the boiler outlet,
upstream of the unit's particulate control
device (baghouse). Emission measure-
ments included:
• Continuous monitoring for 02, C02,
NOX, CO, S.02, and TUHC
• Source Assessment Sampling
System (SASS) for trace elements
and organic emissions
• Combined EPA Methods 5/8 for par-
ticulate and sulfur oxides
• Grab sample for C, to C6 hydrocar-
bons by gas chromatography (GO
Table 1. Boiler Specifications
Convection heating surface, m2
(ft2)
Radiant heating surface, m2 (ft2)
Furnace dimension, m (ft)
Design steam capacity, kg/s (Ib/hr)
Design pressure, MPa (psigi
Operating pressure, MPa (psig)
Soot blower
Year installed
182 (1,956)
48 (518)
1.92 x 4.O5 x 2.26 (6.3 x 13.3 x 7.4)
3.0 (24,000)
1.7 (250)
1.2 (175)
One Boyer-type VH valve-in-head
1978
Table 2. Boiler Operating Conditions
Test 1
Test 2
Steam flow, kg/s
(Ib/hr)
Drum pressure, MPa
(psi)
Furnace draft, Pa
(in. H20)
Fuel flow, kg/s
(Ib/min)
Steam temperature, °C
Boiler feedwater temperature, °C
Combustion air temperature, °C
Flue gas temperature, °C
furnace exit (°F)
Excess air, percent11
3.03
(24,000)
1.3
(189)
112
(0.47)
0.410
(54.2)
186
(367)
101
(213)
24
(76)
272
(522)
14
3.03
(24,000)
1.3
(189)
116
(0.466)
O.39
(51.8)
188
(371)
_a
28
(83)
291
(556)
11
aNot available.
bCalculated from PETC fuel composition and O2 concentrations.
• Grab sample for N2O analysis
In addition, samples of the fuel, bottom
ash, and baghouse hopper ash were col-
lected for analysis.
The analysis protocol included:
• Analyzing the fuel, ash, and SASS
train samples for 73 trace elements
using spark source mass spec-
trometry (SSMS), supplemented by
atomic absorption spectrometry
(AAS)
• Analyzing the SASS train and ash ex-
tract samples for total organic con-
tent in two boiling point ranges: 100
to 300 °C by total chromatograph-
able organics (TCO) analysis and
>300°C by gravimetry (GRAV)
• Analyzing the SASS train and ash ex-
tract samples for the 58 semivolatile
organic priority pollutants, including
many of the PAH compounds of in-
terest from combustion sources
• Performing infrared (IR) spectrometry
analysis of organic sample extracts
• Performing liquid chromatography
(LC) separation of selected sample
extracts with subsequent TCO,
GRAV, and IR analyses of LC fractions
• Performing direct insertion probe low
resolution mass spectrometry
(LRMS) analysis of selected sample
extract LC fractions
Bioassay tests were also performed on
SASS train and ash samples to estimate
their potential toxicity and mutagenicity.
Table 4 summarizes flue gas emissions
measured in the test program. Emissions
are presented as ng/J heat input and as
-------
Table 3. Fuel Analyses {Percent By Weight)
CWS (as fired)
Test 1
Test 2
Carbon
Hydrogen
Oxygen (by difference)
Nitrogen
Sulfur
Ash
Additive
Water
Higher heating value.
kJ/kg
(Btu/lb)
Coal
(dry basis)
PETC?
82.23
5.60
6.76
1.60
1.19
2.62
—
—
34,459
(14,8291
PETC*
50.08
3.41
4.12
0.97
0.72
1.60
0.50
38.60
20,986
(9,031)
This
study3
47.90
3.34
8.56
1.02
0.80
1.93
—
36.45
21,341
(9,184)
PETC*
48.43
3.30
3.98
0.94
0.70
1.54
0.50
40.6
20,296
(8,734)
'Measured.
bCalculated based on coal ultimate analysis and reported proportion of coal, additive,
and water in the CWS formulation.
mg/dscm of flue gas. As a measure of the
potential significance of the emissions
levels for further analyses, an occupational
exposure guideline for most pollutants is
also noted in the table. The occupational
exposure guideline noted is either the
time-weighted-average Threshold Limit
Value (TLV) established by the American
Conference of Governmental Industrial
Hygienists, or the 8-hr time-weighted-
averaged exposure limit established by the
Occupational Safety and Health Admin-
istration (OSHA). These are noted only to
aid in ranking the potential significance of
the emission levels for further analyses. In
this respect, pollutants emitted at levels
several orders of magnitude higher than
their guidelines might warrant further con-
sideration, while species emitted at levels
significantly lower than their guidelines
might be considered of little potential con-
cern for further analyses. Only elements
emitted at levels exceeding their guidelines
in these tests are noted in Table 4.
Table 4 shows that several elements
were present in the boiler outlet at signifi-
cant levels. However, flue gas particulate
accounts for the major fraction of these
elements in the flue gas at this location.
Ultimate flue gas discharge concentrations
would be significantly reduced after
passage through the unit's particulate
control device.
The data in Table 4 show that emissions
of the vapor phase pollutants NOX, SO2,
CO, and TUHC were essentially equivalent
in both tests performed. However, par-
ticulate emissions approximately doubled
in test 2. This test was run at slightly lower
excess air than test 1: flue gas 02 of 2.1
percent in test 2 and 2.8 percent in test
1. Also, the CWS in test 2 had slightly
more water (less coal) than in test 1. Both
of these would be conducive to poorer
combustion efficiency. This, in turn, could
lead to increased particulate mass emis-
sions as the combustibles losses in the
flyash increased. Indeed, the baghouse
hopper ash from test 2 was found to con-
tain over 60 percent carbon (dry basis).
Unfortunately, no such carbon content
data were taken for the test 1 flyash;
although, it is interesting that complete
emissions of all the ash content of the fuel
fired would result in particulate emissions
of about 3.1 g/dscm. This is just below the
measured value in test 1, but less than half
that measured in test 2.
The size distribution of test 2 boiler
outlet particulate favored coarse par-
ticulate as shown in Table 5. Over 60 per-
cent (weight) of the flue gas particulate
was greater than 10 u.m diameter; almost
70 percent was greater than 3 u.m
diameter.
Table 4 shows that total organic emis-
sions (C, to C6, TCO, and GRAV) were
quite high, at 48 mg/dscm. The nonvolatile
(GRAV) boiling point range accounted for
most of the organics measured.
SASS train and ash extract samples for
the semivolatile organic priority pollutant
species, a grouping which contains several
polynuclear aromatic hydrocarbon com-
pounds, were analyzed. Results of these
analyses are summarized in Table 6. As
noted, only naphthalene and several
phthalates (which are suspected con-
taminants) were found in SASS train
samples.
The bottom ash extract contained the
greatest number and concentration of the
priority pollutants sought. This is consis-
tent with the very high total organic (TCO
plus GRAV) content of this sample (8
mg/g). As with the SASS train samples,
most of the total organics in the bottom
ash (80 percent) were in the nonvolatile
(GRAV) boiling point range.
The SASS train organic module extract
and the bottom ash extract samples were
subjected to liquid column chroma-
tography (LC) separation, with TCO, GRAV,
IR, and LRMS analyses of eluted fractions,
in an attempt to elucidate the chemical
character of the organic material in these
samples. These analyses suggested that
the flue gas organic consisted largely of
oxygenated organics such as carboxylic
acids. Oxygenated organics and alkyl
aromatics were suggested in the bottom
ash extract.
Bioassay tests were performed on the
SASS train and ash stream samples. The
health effects bioassay tests performed
were the Ames mutagenicity assay, and
the CHO cytotoxicity assay. The results of
these assays, summarized in Table 7, sug-
gest that the flue gas was of low to
moderate toxicity and low mutagenicity.
The ash streams were of low to moderate
toxicity and nondetectable mutagenicity.
The positive Ames response of the
XAD-2 extract is typical of such extracts
from SASS tests of combustion sources.
Current studies sponsored by EPA's Air
and Energy Engineering Research
Laboratory are investigating if such
bioassay responses are due to artifact
compounds formed when combustion
product gas containing NOX is passed
over XAD-2 resin.
Results of several quality assurance
(QA) activities performed in these tests
are discussed in Volume I of the full report.
Most analysis precision determinations
achieved project QA objectives. However,
two precision challenges and one accuracy
challenge failed project QA objectives (one
only marginally). Discussion in the report
indicates that these failures have no effect
on conclusions derived from data obtained
in these tests.
-------
Table 4. Summary
Compound
SO2
S03
NOX (as N02)
N20
CO
TUHC (as CH4
Solid particulate
Total volatile
organics (C, to C@)
Total semivolatile
organics (TOO)
Total nonvolatile
organics (GRAV)
Trace Elements
Iron, Fe
Phosphorus, P
Aluminum, Al
Arsenic, As
Silicon, Si
Vanadium, V
Chromium, Cr
Beryllium, Be
Copper, Cu
Lead, Pb
Barium, Ba
Nickel, Ni
Calcium, Ca
Lithium, Li
Potassium, K
Cobalt, Co
Titanium, Ti
Uranium, U
Magnesium, Mg
of Exhaust Gas
Test
Emissions8
1
(ng/J heat input) (mg/dscm)
786
0.86
136
18
62
0.2
1,064
4.3
_c
-
—
—
—
_
—
_
—
—
—
—
—
—
—
_
—
—
—
—
—
2,550
2.8
448
58
202
0.73
3,485
14.0
-
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
Test 2
(ng/J heat input)
680
<0.5
172
41
66
0.53
1,991
2.5
1.6
9.1
55
3.6
82
0.3
148
0.46
0.33
0.01
0.56
0.23
2
0.37
6.9
0.07
5.3
0.17
5.4
0.02
4.1
(mg/dscm)
2,480
<2
624
148
239
1.9
7,255
9.1
5.9
33.1
201
13.2
297
1.06
537
1.67
1.19
0.045
2.03
0.85
7.95
1.33
25.3
0.27
19.3
0.64
20
0.09
15
Occupational
exposure
guideline
(mg/dscmp
5
1
6
d
55
d
1tf
d
d
d
1
0.1
2
0.01f
10s
0.05
0.05
0.002
0.1'
0.05f
0.5
0.1
2
0.025
23
0.1
10*
0.05f
10
"Exhaust O2 and CO2 levels averaged 2.76 and 14.9 percent, and 2.08 and
15.7 percent, respectively for the two tests.
b Time-weighted-average TLV unless noted.
c Double dashes indicate that sample was not obtained; abbreviated test.
dNo occupational exposure guideline applicable.
eFor nuisance paniculate.
f 8-hr time-weighted-OSHA exposure limit.
9 Ceiling limit.
Table 5. Flue Gas,Particulate Size
Distribution
Emission Rate
Particle Size
>1Q\im
3 to 1Q\on
1 to 3um
Filter «1ifn)
Ig/dscm)
4.34
0.38
1.19
0.91
(ng/J)
1,190
100
330
250
(percent
of total)
63.6
5.6
17.4
13.4
Total
6.82
1,870 100.0
-------
Table 6. PAH and Other Sent/volatile Organic Priority Pollutant Species Detected
Sample
10 + 3 pm
paniculate
1\rn + filter
paniculate
XAD +
condensate
extract
Bottom
ash
Species
Img/kg)
(ng/dscm)
Img/kg)
fag/dscmi
fag/dscm)
fmg/kg)
Baghouse
ash
Img/kg)
PAHs
Acenaphthene ~a
Acenaphthylene
Anthracene
Benzfaianthracene
Benzo(/+k)fluoranthenes
Chrysene
Fluoranthene
Fluorene
Naphthalene 0.2 0.9 3.7 7.7
Phenanthrene
Pyrene
1
2
1
0.4
0.4
0.8
2
2
42
11
2
—
-
—
-
-
--
—
-
0.3
—
-
Other priority pollutants
Bis(2-ethylhexyl)phthalate <0.1S <0.7 3.4 7.2
Butylbenzylphthalate <0.07 <0.3 0.2 0.4
Diethylphthalate - - 0.4 0.8
2,4-dimethylphenol <0.2 <0.9
-------
R. DeRosier and L R. Water/and are with Acurex Corp., Mountain View, CA
94039.
Robert E. Hall is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Environmental Assess-
ment of a Watertube Boiler Firing a Coal/Water Slurry:"
"Volume I. Technical Results." (Order No. PB 86-159 845/AS; Cost: $ 11.95)
" Volume II. Data Supplement," (Order No. PB 86-183 308/A S; Cost: $ 16.95)
The above documents will be available only from: (cost subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S7-86/004
\ ''' -'lO,'' '"' 'JTTf. 1
3
y o /
0000329 PS
U Z ENVIR PROTECTION AGENCY
CHICAGO
IL
------- |