United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-81-104 Aug. 1981
Project Summary
Source Test and Evaluation
Report: D. H. Mitchell Unit
No. 11, Northern Indiana
Public Service Co.
R. A. Orsini, T. L. Sarro, and J. A. Wilson
A comprehensive multimedia emis-
sions assessment was performed on
NIPSCO'a Dean H. Mitchell No. 11
boiler. This unit is equipped with an
ESP for particulate control and a
Wellman-Lord/Allied Chemical flue
gas desulfurization (FGD) system.
Level 1 and Level 2 procedures were
used to characterize pollutant emis-
sions in gaseous, liquid, and solid
waste streams.
Flue gas analyses indicated SO2
emissions of 266 ng/J after 89% re-
moval by the FGD. Primary sulfate
emissions of 20.8 ng/J comprised 5
mole percent of the total sulfur species
emitted. Average emissions of NO«(as
NO2) were 265 ng/J at the 70 percent
boiler load maintained during the test
period. Carbon monoxide emissions
were estimated to be 16 ng/J, on the
average, based on measurements at
the air heater inlet. Particulate emis-
sions (exclusive of HjSO* aerosol)
were 2.6 ng/J and 98 percent of the
particles were smaller than 3 /urn in
diameter. HUSO* aerosol emissions
were 3.7-10.4 ng/J, or more, and
were generally smaller than 0.5 //m in
diameter. Total organic emissions
ranged from 0.5 to 1.3 ng/J and
consisted primarily of Ci-Ce com-
pounds. POMs were not detected at
either the scrubber inlet or outlet.
Concentrations of elements in the flue
gas after scrubbing were below DMEGs
and AMEGs in all cases. Emissions of
NO3 , Cl~, and F" were 0.004, 0.25-
0.34, and 0.033 ng/J, respectively:
Emission concentrations of Cl~ and F"
were below their respective DMEGs.
Flue gas pollutant concentrations
were also determined at the air heater
inlet and scrubber inlet.
Elemental concentrations in clarif ier
overflow, the only liquid waste dis-
charged from the site, did not exceed
health DMEGs although concentra-
tions of Al, Ca, Cd, Fe, Ni. P, and Pb
exceeded ecology DMEGs. However,
Ca, Cd, Ni, and Pb are present in the
process feedwater from Lake Michigan
at concentrations similar to those
measured in the clarifier overflow.
Total organic concentrations in the
liquid waste were 0.108-0.117 g/m3
and consisted primarily of high molec-
ular weight compounds (>Ci6). Or-
ganic concentrations in the process
feedwater from Lake Michigan were
0.235-0.242 g/m3. No POMs were
detected in the liquid waste. Individual
liquid waste streams including the
prescrubber slurry liquids, thiosulfate
purge, and melt tank purge were also
evaluated.
Fly ash, prescrubber solids, and ash
pond sludge contained several ele-
ments at concentrations exceeding
DMEGs. Elements of principal con-
cern included Al, As, Fe, Ni, and P.
Organic concentrations were approxi-
mately 4.7 mg/kg and consisted pri-
marily of high molecular weight
-------
compounds (>Ci6). ROMs were not
detected in the solid waste. Sodium
salts in the thiosulfate and melt tank
purge streams, soda ash, and product
sulfur were also analyzed.
This Project Summary was devel-
oped by EPA's Industrial Environmen-
tal Research Laboratory, 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).
Introduction
A comprehensive multimedia emis-
sions assessment was performed on the
Northern Indiana Public Service Com-
pany's Dean H. Mitchell No. 11 boiler. A
simplified schematic of Unit No. 11 is
presented in Figure 1. This unit is a wall-
fired, dry-bottom radiant boiler with a
maximum steaming capacity of 103
kg/s and a corresponding turbo-gener-
ator output of 115 MW. Normal output
ranges from 46 MW to 115 MW with an
average load factor of 80% or 92 MW.
The unit is fueled with a high volatile
bituminous coal from the Captain Mines
No. 6 seam. Typical fuel ash and sulfur
contents are 9.5% and 3.2%, respec-
tively. Average ash and sulfur contents
during the test period were 12.5% and
3.5% (dry bases), respectively. Particu-
late emissions are controlled with a
cold-end American Standard Co. elec-
trostatic precipitator (ESP) and sulfur
dioxide emissions are controlled with a
Wellman-Lord/Allied Chemical flue gas
desulfurization (FGD) unit. The FGD
system represents the first application
of Davy McKee's Wellman-Lord (W-L)
process to a coal-fired boiler and thi
first combination of the W-L proces;
with Allied Chemical's S02 reductioi
process. A schematic of the W-L SO
recovery system is presented in Figun
2.
The principal waste streams from thi!
system are bottom and fly ash, pre
scrubber slurry from a venturi contactor
and flue gas. Bottom ash samples frorr
the No. 11 boiler could not be obtainec
because the sluice system combine!
ash from all units at the Mitchell station
Solid and liquid wastes are dischargee
to a system of three primary ash storage
ponds totaling 122,000 m3 in capacity
Solid wastes are dewatered and hauled
to off-site disposal areas. Supernatant
liquids are processed through either ol
two 14,000 m3 clarifying ponds and
discharged into Lake Michigan.
Dry
By-Product
Raw
Coal
*-H2o YYY z
Dredged
Sludge
Figure 1. Schematic of Dean H. Mitchell No. 11 Unit.
2
-------
Cooling
Water
7.
2.
3.
*
6.
7.
8.
9.
10.
11.
12
13.
Clean
Flue Gas
Sodium Carbonate
Solution Makeup
Thiosulfate
Purge (to Dryer)
Sulfate
Purge Stream
To Allied S02
Reduction
Plant
Flue Gas
From Unit
No. 11
Fly Ash
Purge to
Pond
Booster Blower
Venturi Contactor
Absorber
Absorber Surge Tank
Evaporator-Crystallizer
Dump-Dissolving Tank
Condenser
SOz Compressor
Chiller Crystallizer
Centrifuge
Dryer
Storage Bin
Absorber Feed Tank
SOZ0
Vapors
Dried
Sulfate
Product
Figure 2. Schematic of the Wellman-Lord SOz recovery system.
Two additional streams were being
discharged from the FGD system during
the test period: 1) the melt tank liquor
and 2) the thiosulfate purge. These
streams would be dried to produce a
solid by-product during normal opera-
tion; however, equipment problems
necessitated the discharge of these
streams into the ash pond during the
entire test period.
Summary and Conclusions
Average measured flue gas emis-
sions are summarized in Table 1. Emis-
"ions data indicated an S02 scrubbing
ficiency of 89% based upon scrubber
inlet and outlet data. Sulfur dioxide
levels measured at the air heater inlet
appeared to be erroneously low based
upon feed coal sulfur concentrations;
this can be partially attributed to instru-
ment drift, although the cause is not
entirely understood. Primary sulfate
(SO3 as S04° plus paniculate sulfate)
comprised 0.6% of the flue gas sulfur
species at the scrubber inlet and 5% at
the scrubber outlet. Primary sulfate at
the scrubber inlet and outlet consisted
of essentially equal mole fractions of
80s and paniculate sulfate. However,
data from the source assessment samp-
ling system (SASS) indicate particulate
sulfate levels of 2.2 and 0.6 ng/J at the
scrubber inlet and outlet, respectively,
compared to the 10 ng/J levels indi-
cated by the controlled condensation
system (CCS). These data may indicate
that S03 was adsorbing on the particu-
late filter of the CCS, resulting in
inordinately high measured particulate
sulfate levels. Because of the large duct
width and the proximity of the sampling
ports to a right-angle bend at the econ-
omizer outlet, particulate stratification
is probable at the air heater inlet. For
this reason, measured primary sulfate
levels at the air heater inlet are consid-
ered to be low.
Total oxides of nitrogen were deter-
mined during a period of 70% boiler load.
-------
Table 1. A verage Measured Flue Gas Emissions
Emission Factor, ng/J
Pollutant Air Heater Inlet Scrubber Inlet
Scrubber Outlet
S02*
Primary SO/f
/VOxt (as N02 at
70% load)
CO**
Total Paniculate^
Total OrganicsQ
/VOa-ftt
crt
ft
1968 ± 145***
24.8 ±3.0***
224 ±68***
16 ±13***
1590
0.6 - 1.0
0.215 - 0.219
3.4 ±0.56***
1.3 ±0.34***
2482 ± 158***
21. 7 ±5.6***
271 ±50***
No Data
39.8
0.5 - 0.9
0.003 - 0.006
4.5 ±0.89***
1.2 ±0.38***
266 ±39***
20.8 ±2.9***
263 ±43***
No Data
2.65
0.9 - 1.3
O.O04
0.25 - 0.34
0.033 ±0.011***
* SOz was determined by continuous pulsed fluorescence analysis at the air heater
inlet and by ultraviolet analysis at the scrubber inlet and outlet (Level 2).
t Primary S0<= (SOa as S0*= plus paniculate sulfate), chloride, and fluoride were
measured with the CCS (Level 2).
\ /VOX was determined by continuous chemiluminescent analysis (Level 1).
** CO was determined by non-dispersive infrared analysis (Level 2).
tt Totalparticulates were determined by SASS measurements (Level 1) and do not
include HiSO* aerosol which is a vapor at the collection temperature of 477 K.
tt Ci-Cie fractions were determined by gas chromatograph while the >Ci6 fraction
was determined gravimetrically (Level 1).
***lndicated ranges of values represent one standard deviation.
was determined by extraction of the SASS paniculate catch (Level 2).
Because this is nearly the average boiler
load, the 265 ng/J emission level should
be similar to that of normal operation.
Somewhat higher or lower emissions
would result from higher or lower load
boiler operation.
Carbon monoxide was monitored only
at the air heater inlet. While leakage
across the air heater may reduce CO
levels slightly, neither the ESP nor the
scrubber affect flue gas CO levels.
Hence, the 16 ng/J CO level measured
at the air heater inlet should accurately
reflect actual emission levels.
Total paniculate data indicate an ESP
removal efficiency of 97.5% and a
scrubber efficiency of 93.3%; however,
the actual ESP removal efficiency pro-
bably exceeds 97.5% since paniculate
stratification apparently resulted in a
low paniculate catch at the air heater
inlet. Paniculate at the air heater inlet
and scrubber inlet consisted primarily of
particles larger than 3//m. At the air
heater inlet, 44% of the paniculate were
larger than 10//m, 42% were 3-1 O^m,
13% were 1 -3/um, and 1 % were smaller
than 1^m. At the scrubber inlet, 25% of
the paniculate were larger than 10//m,
39% were 3-10/L/m, 20% were 1-3/am,
and 17% were smaller than 1//m. Only
2% of the paniculate emissions to the
atmosphere were larger than 3 fjrn,
while 98% were less than 3fjm in
diameter. Size distribution data obtained
with an MRI impactor indicate that more
than 76% of the paniculate and H2S04
aerosol emissions to the atmosphere
are less than 1 fjm in diameter and are
capable of deep lung penetration. Sulfate
analyses of the impactor plates indicated
H2S04 aerosol emissions ranging from
3.7 to 10.4 ng/J with a diameter gen-
erally less than 0.5 urn.
Total organic emissions ranged from
0.5 to 1.3 ng/J and consisted primarily
of Ci-C6 organics. The light hydrocar-
bons were not removed by flue gas
processing although decreases in high-
er molecular weight organics were
observed across the ESP and the scrub-
ber. Flue gas processing removed 87%
of the C7-Ci6 organics and 82% of the
>Cie organics. Higher molecular weight
organics were found to consist of aro-
matics, unsaturated hydrocarbons, and
either esters or phenols. ROMs were not
detected at the scrubber inlet or outlet.
At the air heater inlet, phenanthrene
was detected at 0.7 /ug/m3 (0.2 pg/J),
and fluoranthene and dibenzanthracene
were detected at concentrations below
0.6 /ug/m3 (0.2 pg/J). With the possible
exception of dibenzanthracene (which
could be dibenz(a,h)anthracene), mea-
sured concentrations of these com-
pounds do not appear to pose a hazard to
human health.
Inorganic analyses for cations i
cated at least 14 elements exceeded
their respective Discharge Multimedia
Environmental Goal (DMEG) levels at
the air heater inlet while only four
elements exceeded their DMEG levels
at the scrubber inlet. Elemental concen-
trations in the flue gas after scrubbing
did not exceed DMEG levels nor did they
exceed Ambient Multimedia Environ-
mental Goal (AMEG) levels. Hence, with
respect to detected cations, flue gas
emissions did not pose a health hazard
for short term direct exposure or contin-
uous exposure after dispersion.
Specific anion analyses indicated
emission levels of NOs", CI", and F'to be
0.004, 0.25-0.34, and 0.033 ng/J,
respectively. DMEG values have not
been established for N03~. Concentra-
tions of CI" and F" exceeded their
respective DMEG values at the air
heater inlet and scrubber inlet although
they were both below their DMEG
concentrations at the scrubber outlet.
Hence, the specific anions analyzed did
not appear to pose a health hazard with
short term direct exposure.
Elemental concentrations in the clari-
fier overflow, the only liquid waste
discharged from the site, did not exceed *
health-based DMEG values in any case. I
Ecology-based DMEG values were ex-
ceeded by concentrations of Al, Ca, Cd,
Fe, Ni, P, and Pb. However, Ca, Cd, Ni,
and Pb are present in the process
feedwater from Lake Michigan at con-
centrations similar to those measured
in the clarifier overflow. Elemental con-
centrations in the prescrubber slurry
liquids exceeded health-based DMEG
values for 8, Cr, and Fe, and exceeded
ecology-based DMEG values for numer-
ous elements (notably Al, Cd, Fe, Ni, and
P). Concentrations of numerous ele-
ments in the thiosulfate purge liquids
and melt tank liquor exceeded DMEG
values.
Organics in the liquid waste streams
consisted primarily of >C16 compounds.
C7- Cie organic concentrations in liquid
wastes were generally below the detec-
tion limit of 0.001 g/m3. Total organic
concentrations in the prescrubber slurry
liquids and clarifier overflow were
0.351-0.361 g/m3and0.108-0.117
g/m3, respectively. Organics were
present in the process feedwater from
Lake Michigan at a concentration of
0.235-0.242 g/m3. No POMs were
detected in liquid wastes or process*
water streams.
Solid waste streams (fly ash, pre-
scrubber solids and ash pond sludge) I
-------
reach contained 4 to 6 elements at
concentrations exceeding health-based
DMEG values and 11 or 12 elements at
concentrations exceeding ecology-based
DMEG values. Elements of primary
concern included At, As, Fe, Ni, and P.
Solids present in the thiosulfate purge
and melt tank liquor appear to be rela-
tively pure Na2S03 and NaHSO3, re-
spectively. Elemental impurities present
in the soda ash and product sulfur
streams did not exceed 265 mg/kg, and
most elements were present at levels
below 10 mg/kg.
Organics in the fly ash and ash pond
sludge consisted primarily of high mo-
lecular weight compounds; C7-C16 or-
ganics were present at concentrations
of 0.345 and 0.245 mg/kg, respectively,
while >Ci6 organics were present at
concentrations of 4.42 and 4.48 mg/kg,
respectively. Solid wastes were found to
contain saturated hydrocarbons, aro-
matics, esters, and ethers. Additionally,
the fly ash contained ketones, and the
ash pond sludge contained unsaturated
hydrocarbons and alcohols. POMs were
not detected in fly ash or ash pond
sludge samples. The average pre-
scrubber slurry solids content was
0.47% and insufficient solids were
collected to enable organic analyses.
R. A. Orsini, T. L Sarro. andJ.A. Wilson are with TRW, Inc., Environmental Engi-
neering Division, One Space Park, Redondo Beach, CA 90278.
Michael C. Osborne is the EPA Project Officer (see below).
The complete report, entitled "Source Test and Evaluation Report: D. H. Mitchell
Unit No. 11. Northern Indiana Public Service Co.."(Order No. PBS 1-218 489;
Cost: $11.00, 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Recommendations
This test effort has provided detailed
characterization data for the NIPSCO
Dean H. Mitchell No. 11 boiler system.
However, limited supplemental panicu-
late and sulf ate data would be desirable.
Additional MRI impactor size distribu-
tion data are required to more thoroughly
characterize paniculate at the scrubber
inlet. Also, additional CCS data at the
scrubber inlet and outlet would serve to
clarify existing data regarding the SO3
and paniculate SO/ loadings.
it US GOVERNMENT PRINTING OFFICE 1981 -757-012/7277
-------
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
PS 0000329
U S EWVia FROTECXIUN AGENCX
KfelGiOW 5 LIBRARY
230 S DEARBORM Si'R^Ei*
CHICAGO 1L 60ftu4
------- |