United States National Risk Management
Environmental Protection Research Laboratory
Agency Research Triangle Park NC 27711
Research and Development EPA/600/SR-94/140 April 1996
«>EPA Project Summary
The Environmental
Characterization of RDF
Combustion Technology—
Mid-Connecticut Facility,
Hartford, Connecticut
Theodore G. Brna and James D. Kilgroe
The environmental characterization of
refuse-derived fuel (RDF) semi-suspen-
sion burning technology was under-
taken jointly by Environment Canada
and the U.S. Environmental Protection
Agency (EPA) as part of ongoing pro-
grams of both agencies that assess
municipal solid waste combustion tech-
nologies. The facility tested is located
in Hartford, Connecticut, and represents
a state-of-the-art technology, including
a spray dryer/fabric filter flue-gas clean-
ing (FGC) system for each unit.
Results were obtained for a variety
of steam production rates, combustion
conditions, flue gas temperatures, and
acid gas removal efficiencies. All in-
coming wastes and residue streams
were weighed, sampled, and analyzed.
Key combustor and FGC system oper-
ating variables were monitored on a
real time basis. A wide range of analy-
ses for acid gases, trace organics, and
heavy metals was carried out on gas
emissions and all ash residue dis-
charges.
Very low concentrations of trace or-
ganics, heavy metals, and acid gases
in stack emissions were observed. High
removal efficiencies were attained by
the FGC system for trace organics and
metals in the flue gas. Trace organic
contaminants in the residues were not
soluble in water, while only very small
amounts of most trace metals present
in the residues were soluble in water.
A significant reduction in metal mobil-
ity was achieved for fabric filter resi-
due that was solidified using cement
and waste pozzolanic materials. Multi-
variate correlations were found between
trace organics at the furnace exit and
indicators of combustion conditions,
such as operating variables and easily
monitored combustion gases. These pa-
rameters could potentially be used to
control incinerator operating conditions
to ensure minimal trace organics in the
flue gas entering the FGC system.
This Project Summary was developed
by EPA's National Risk Management
Research 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
A joint Environment Canada (EC)/U,S.
Environmental Protection Agency (EPA)
program to evaluate the combustion and
air pollution control systems for a modern
RDF combustor was performed on Unit
11 at the Mid-Connecticut (Mid-Conn) fa-
cility in Hartford. The test program was
conducted with the cooperation and as-
sistance of the owner, Connecticut Re-
sources Recovery Authority (CRRA), and
the operator, ABB Resource Recovery
Systems [formerly Combustion Engineer-
ing, Inc. (CE)]. It involved characterization
and performance test phases. This Sum-
mary outlines the 13 valid performance
tests and describes the results of com-
bustion system, flue gas cleaning (FGC)
system and ash characterization/stabiliza-
tion evaluations.
-------
Test Facility Description
The Mid-Conn facility contains a pro-
cessing plant and a RDF power plant.
The power plant contains three CE steam
generating units, each consisting of a RDF
spreader stoker, a natural circulation
welded-wall boiler, a superheater, an
economizer, a tubular combustion air
preheater, FGC equipment, and ash han-
dling equipment (see Figure 1) All tests
were conducted on Unit 11, which is de-
signed to produce 105 tonnes/h of steam
at full load.
The fuel burning system for each unit
consists of a RDF injection system, a trav-
eling grate stoker, and a combustion air
system (see Figure 2) RDF is pneumati-
cally injected through four ports in the
front face of each combustor The lighter
fraction burns "in-suspension" and the
heavier falls onto the stoker where com-
bustion is completed Underfire air is pro-
vided at controlled rates to 10 zones under
the grate There are two separate overfire
air (OFA) systems: a tangential system
and a wall system. The tangential system
consists of four tangential overfire air
(TOFA) windbox assemblies located in the
furnace corners. Each TOFA assembly
contains three elevations of nozzles which
can be manually adjusted in the horizon-
tal plane. The wall system contains one
row of OFA ports on the front wall and
two rows on the rear wall.
The FGC system consists of a lime-
based spray dryer absorber (SDA) fol-
lowed by a reverse-air-cleaned fabric filter
(FF) or baghouse. The SDA is capable of
controlling the temperature at the FF inlet
and the sulfur dioxide (S02) concentration
at the FF outlet. The FF inlet temperature
is controlled by the lime slurry flow rate.
The S02 removal rate is controlled by
adjusting the lime concentration in the feed.
Each baghouse has 12 compartments,
each with 168 Teflon-coated glass fiber
bags.
Measurement Method and Test
Conditions
All tests were run at slightly derated
load conditions because of problems with
wet RDF and performance of the induced
draft fan. Combustion and FGC process
test conditions for the performance tests
were based on the results of 28 charac-
terization tests conducted in January 1989.
During the performance tests, a comput-
erized data acquisition system was used
to continuously record combustion and
FGC process conditions. Continuous emis-
sion monitors (CEMs) were used to mea-
sure the concentration of oxygen (02),
carbon monoxide (CO), carbon dioxide
(C02), total hydrocarbons (THC), hydro-
gen chloride (HCI), S02, and nitrogen ox-
ides (NOx) at the SDA inlet and FF outlet.
CEMs were also used to measure the
concentration of CO, HCI, and S02 at the
mid-point between the SDA and FF.
Modified Method 5 (MM-5) sampling
trains were used to collect organic samples
at the SDA inlet and FF outlet during all
tests. Organic samples were also collected
at the air heater inlet during four tests
(PT07, PT08, PT09, and PTIO) Method 5
(M-5) sampling trains were used to collect
total particulate samples at the SDA inlet
and FF outlet. All sampling and analysis
was done in accordance with protocols
approved by EC and EPA. Test program
sampling locations are shown in Figure 1.
The duration of each test was from 4 to
6 hours. Combustion and FGC process
conditions were set, and the test was be-
gun after stable operating conditions were
obtained. The tests were terminated after
sufficient volumes of samples had passed
through the MM-5 sampling trains.
All polychlorinated dibenzo-p-dioxin and
polychlorinated dibenzofuran (PCDD/
PCDF), CO, S02, and HCI data presented
in this summary have been corrected to
12% C02 All PCDD/PCDF data are given
in nanograms per standard cubic meter
[25°C, 101.3 kPa (77°F, 1 atm)] as noted
by ng/Sm3.
A total of 14 performance tests were
conducted. However, performance test 1
(PT01) did not meet all sampling require-
ments, and the results are not given Com-
bustion and FGC process conditions were
varied independently. The combustion
tests were structured to evaluate the ef-
fects of good and poor combustion condi-
tions on organic concentrations at the SDA
inlet.
The primary combustion test variables
were boiler steam load, underfire-to-OFA
ratio, and OFA distribution. During testing,
the criterion forjudging good or poor com-
bustion conditions was the CO concentra-
tion at the SDA inlet. The effects of load
were evaluated by conducting tests at low
Economizer
Superheater \
Air Heater
Sampling
(Organics)
RDF
Distributors
Front
Overfire Air
Inlet Sampling (Organics, Metals, Particles. Loading & Size)
and CEMs (CO, C02 , HCI, NOx , 02 , S02 , TCH, Moisture)
Outlet Sampling (Organics, Metals, Particles: Loading & Size)
and CEMS (C02, HCI, 02 , S02, TCH)
Midpoint
CEMs (C02 , HCI, S02)N
TTTTT
Fabric Filter (Baghouse)
Combustor \ Grate Sittings
•Dry Bottom Ash Off Grate
Fabric Filter Residue
CEMs = Continuous Emission Monitors
Stack
Inducted Draft Fan
Figure 1. RDF Spreader stoker with spray dryer absorber and fabric filter.
2
-------
RDF
Distributors
Grate
Surface
Tangential
Overfire Air
Water Seal
Drive Shaft
Undergrate
Air
Compartment
Idler Shaft
Sifting Screw
Conveyor
Figure 2. RDF spreader stoker boiler (Combustion Engineering).
(L), intermediate (I), normal (N), and high
(H) boiler steam flow rates Underfire-to-
OFA ratios, which influence the relative
amount of RDF burned in suspension and
the entrainment of particulate matter (PM)
in the flue gases (PM carryover), were
controlled by changing the number of lev-
els of OFA Distributional mixing effects
were evaluated by changes in the
underfire-to-OFA ratio and by using rear
wall overfire air (ROFA) in combination
with different levels of TOFA.
Combustion test conditions, in order of
increasing load, and the resultant average
CO and PCDD/PCDF concentrations are
summarized in Table 1. The CO values
are reconstructed averages based on mea-
sured values at the SDA inlet and FF
outlet. The PCDD/PCDF values are from
the SDA inlet.
FGC tests were run at nine different
test conditions corresponding to high [166
to 171°C (330 to 339°F)], medium [141 to
142°C (285 to 287°F)], and low [122 to
124°C (252 to 255°F)] temperature at the
SDA outlet and high (>100 ppm), medium
(21 to 100 ppm), and low (<21 ppm) S02
concentration at the FF outlet The SDA
outlet temperature was used as a surro-
gate for approach to saturation tempera-
ture since the latter parameter was not
directly measurable The S02 concentra-
tion served as an on-line indicator of sor-
bent-to-acid gas ratio (or lime stoichiom-
etry) during the test program and was
used as a qualitative measure of stoichi-
ometry for evaluation of test data. The
plant's lime slurry density measurement
was inoperative during the test program
and the lime stoichiometry could only be
estimated. Stoichiometry is used in this
summary to denote the ratio of lime sor-
bent to acid gases (HCI and S02) corre-
sponding to high, medium, and low lime
flow rates. FGC tests conditions and aver-
age acid gas control results are summa-
rized in Table 2.
The four ash streams—bottom ash (BA),
grate sittings (GS), economizer (EC) ash,
and FF residues (collected combustor
flyash and SDA reaction products—that
were sampled during the 13 performance
tests were also subjected to ash charac-
terization and treatment tests. Note that,
while the ash products generated by the
facility are normally combined and dis-
posed of in a monofill, no sampling or
analysis was done on this combined prod-
uct. Ash characterization and treatment
work included trace organic and trace
metal analyses on ash samples from all
13 performance tests; chemical analyses
of leachates generated from EC's Sequen-
tial Chemical Extraction Procedure; and
chemical analyses and engineering tests
on solidified mixtures of FF ash, waste
pozzolanic material, and Portland Type II
cement.
Table 1. Combustion Conditions and Results at SDA Inlet
Test No.
Load
Comb.
Overfire Air
CO,
NOx
PCDD/PCDF
(PT)
1000 kg/h
Cond."
TOFAb
ROFAc
OFAd
ppm
ppm
na/Sm3e
13
71 (L)
G
2
nil
47
158
157
599
14
74 (L)
G
2
nil
49
70
177
428
10
87(1)
G
2
nil
52
77
186
667
02
88(1)
G
2
nil
52
108
184
946
05
84(1)
P
1
65
38
903
149
1861
09
95 (N)
G
2
65
51
92
188
449
08
96 (N)
G
2
65
48
89
193
1162
11
96 (N)
G
2
65
52
68
175
536
07
101 (N)
P
3
nil
51
387
172
1003
04
98 (N)
P
3
nil
54
214
172
774
03
99 (N)
P
1
65
44
432
160
1008
12
117(H)
G
2
65
53
116
180
282
06
118(H)
P
2
nil
57
397
157
1202
Good (G) or poor (P) combustion conditions
Number of levels of TOFA
Pressure in ROFA plenum, mm Hg
OFA as a percentage of total combustion air
Standard conditions: 25°C, 101.3 kPa
3
-------
Table 2. Flue Gas Cleaning (FGC) System Performance: Acid Gases
Concentrations, ppm
Test
Runa
FGC Cond.
TempJSOf
Inlet
Outlet
Removal, %
HCI
S02
HCI
S02
HCI
S02
2,5
UH
470
173
20
121
95.7
35.3
3,11
HA
416
187
20
17
95.2
90.9
4
H/M
471
186
31
44
93.4
76.3
6
MA-
404
192
10
32
97.5
95.3
7
UL
399
183
8
17
98.0
90.7
8
M/H
538
184
41
126
92.4
31.5
9
H/H
432
178
98
189
77.8
-6.2°
10
UM
429
194
19
74
95.6
61.9
12,13,14
M/M
444
187
18
59
95.9
68.5
a Values are averaged for multiple runs.
b High temperatures (H) ranged from 166 to 171°C (330to339°F), medium temperatures (M) from 141
to 142°C (285 to 287°F), and low (L) temperatures from 122 to 124°C (252 to 255 °F) forthe spray
dryer outlet gas Fabric filter S02 outlet concentrations were above 100 ppm for high (H) concentra-
tion, between 21 and 100 ppm for medium (M) concentration, and 20 ppm or less for low (L)
concentration. All concentrations are referenced to 12% C02in dry gas [25°C (77°F), 101.3 kPa (1
atm)]
c Desorption of S02 in the filter cake is suspected for low lime stoichiometry and relatively high HCI
concentration.
Combustion Test Results
Test results were evaluated to assess
the effects of combustion conditions on
furnace emission of organics, NO,,, and
metals using the concentration of these
pollutants at the SDA inlet
Although organic compounds (such as
PCDD/PCDF) may be in the waste feed, it
is unlikely that they will pass through the
combustor undestroyed. They may also
be formed in high temperature regions of
the furnace from the thermal decomposi-
tion products which are incompletely oxi-
dized due to insufficient combustion air,
mixing, temperature, or residence time
They may also originate from catalytic re-
actions on the surface of flyash down-
stream of the combustion chamber.
Multiple regression analyses show that
PCDD, PCDF, chlorophenol (CP), chlo-
robenzene (CB), and polynuclear aromatic
hydrocarbon (PAH) concentrations at the
SDA inlet can be best correlated with two
or more of the following easily monitored
furnace/flue gas properties' CO concen-
tration, THC concentration, NOx concen-
tration, moisture (H20) concentration, and
temperature in the furnace or at the econo-
mizer outlet
For example, the best correlation for
PCDD concentrations at the SDA inlet
(R2=0 9)* is based on the CO, N0X, and
H20 concentrations at this location.
* R' is the correlation coefficient; R2=1 0 indicates a
perfect (exact) correlation.
Multiple regression analyses provide cor-
relations that indicate that the combustor
operating variables (steam load, combus-
tion air flows, RDF moisture content, etc )
can be used to control PCDD, PCDF, CP,
CB, and PAH concentrations at the SDA
inlet. These operating variables control
combustion in the furnace by impacting
the fundamental combustion parameters
time, temperature, air/fuel ratio, and mix-
ing
Multiple regression analyses based on
easily monitored flue gas properties pro-
vide for better correlations of organics
(R2=0.8 to 0.98) than combustor operating
variables (R2=0 6 to 0.8). Optimum control
systems for limiting the furnace emission
of organics will probably require both flue
gas property measurements and combus-
tion operating variables as inputs.
Single parameter regression analyses
using average test values show that ei-
ther CO or THC tracks the furnace de-
struction of organics While only
moderately strong correlations were ob-
tained between CO (or THC) and PCDD/
PCDF at the SDA inlet [R2=0.70 (or 0 68)],
they provided the strongest correlation for
any single monitoring or control variable
(see Figures 3 and 4). Single parameter
correlations between average CO (or THC)
concentrations and CP, CB, or PAH con-
centrations at the SDA inlet provided bet-
ter correlations [R2=0.88 (0 92), 0.83 (0 87),
and 0.83 (0.85), respectively] than those
for PCDD or PCDF. There were no signifi-
cant correlations between average CO (or
THC) and PCB at the SDA inlet. Thus,
either CO or THC concentration at the
SDA inlet is a good relative indicator of
furnace emission of most trace organics
of concern.
Previous field tests have shown a strong
positive correlation between the amount
of PM entrained in flue gas (PM carryover)
and emissions of PCFF/PCDF. The Mid-
Conn data show a fair correlation (R2=0.61)
between PCDD/PCDF and PM concentra-
tions at the SDA inlet for good combus-
tion conditions (CO<200ppm), yet, no
significant correlation between these vari-
ables was seen for all combustion condi-
tions. Possibly for good combustion, the
emission rate of PM (as PM is postulated
to provide reaction sites where PCDD/
PCDF are formed) is the principal variable
affecting the furnace PCDD/PCDF emis-
sion rate. For poor combustion, the ef-
fects of other parameters obscure the
relationship between PM and PCDD/
PCDF.
PCDD/PCDF and other chloro-organic
compounds can be formed downstream
of the furnace by de novo synthesis reac-
tions on the surface of flyash. The amount
formed is believed to be proportional to
the amount of flyash and the time indi-
vidual particles with reaction sites exist in
the temperature range of about 450 to
150°C (750 to 300°F). Mid-Conn has an
air heater just upstream of each SDA with
flue gas in the upper end of this range.
Thus, an increase in PCDD/PCDF con-
centrations across the air heater due to
de novo synthesis was expected. The flue
gas temperature at the economizer outlet
(which approximates that at the air heater
inlet) typically ranges from 343 to 388°C
(650 to 730°F), while the temperature at
the outlet of the air heater ranges from
177 to 210°C (350 to 410°F) To evaluate
the hypothesis that PCDD/PCDF form on
particulate deposits within the air heater,
PCDD/PCDF measurements were made
during four test runs just upstream of the
air heater inlet simultaneously with those
at the SDA inlet (air heater outlet) Con-
trary to expectations, a comparison of
measurements at the inlet and outlet of
the air heater indicated a reduction of
PCFF/PCDF concentrations during three
of four runs. No explanation for these un-
expected results is presently available.
Average NOK emissions ranged from
149 to 193 ppm. Generally, NOx emis-
sions increase with increased combustion
temperatures and improved mixing Ac-
cordingly, low CO emissions corresponded
with high NOx emissions. Conversely, the
lowest NOx emissions were associated with
4
-------
2000
§ 1500
CO
73
O)
C
O
o
CL
O
Q
O
CL
1000
500
•
o
i
I
o
0° 0
#
•
O Good Operation
• Poor Operation
o
o
o
0 200
R2 = 0 70
Values corrected to 12% CO'
400 600
CO (ppm)
800
1000
Figure 3. Uncontrolled PCDD/PCDF vs CO
emissions.
~
A
~
<
< <
1
A Good Operation
~ Poor Operation
A A
A
1
1
0 10
R2 = 0.68
Values corrected to 12% CO.
20
30
THC (ppm)
40
50
60
Figure 4. Uncontrolled PCDD/PCDF vs. THC at SDA inlet.
high concentrations of CO, THC, and or-
ganics at the SDA inlet. An evaluation of
30-second emission averages from the
CEM data indicates that, to obtain NOx
emission less than 180 ppm (the new
U.S New Source Performance Standards
requirement for large municipal waste com-
bustors), the Mid-Conn units would have
to operate at a CO emission concentra-
tion of 71 ppm or higher.
There were no apparent correlations
between combustion conditions and the
concentration of metals in flyash at the
SDA inlet.
Flue Gas Cleaning Test Results
The HCI and S02 concentrations were
monitored continuously, and their aver-
aged values along with removals for each
test run are shown in Table 2. Note that
the test conditions for Runs 2 and 5; 3
and 11; and 12, 13, and 14 have been
grouped, since the FGC system setpoints
(SDA gas outlet temperature and FF out-
let S02 concentration) were the same.
These data show that the HCI and S02
values at the SDA inlet averaged 445 and
185 ppm, respectively, over the tests, with
the individual test values being +10% of
these averages, except that for Run 8
when the HCI concentration was about
20% higher.
As expected the HCI and S02 removals
increased with decreasing SDA outlet gas
temperature (approach to saturation tem-
perature) and increasing lime stoichiom-
etry. The HCI removal averaged 95% or
more, and the S02 removal was greater
than 90% when the lime stoichiometry was
high (low FF outlet S02 concentration)
and showed only a slight decrease with
temperature as the average SDA outlet
temperature increased from the 122 to
166°C (252 to 330°F). The HCI removal
was above 92% for all temperature and
stoichiometry combinations tested, except
for high temperature (171°C or 339°F)
and high stoichiometry when it was about
78% The S02 removal was more sensi-
tive to the change in stoichiometry than to
temperature: 91 to 95% for high stoichi-
ometry and 62 to 76% for medium stoichi-
ometry over the tested SDA outlet
temperature range [122 to 171°C (252 to
339°F)]. At low stoichiometry, the S02 re-
moval fell from 35 to 32% as the SDA
outlet gas temperature increased from
122°C (252°F) to 142°C (287°F); how-
ever, the S02 removal was -6% at 171°C
(339°F) (i e , the S02 concentration at the
FF outlet was greater than the SDA inlet),
suggesting that S02 was being desorbed
in the filter cake. This suspected desorp-
tion was similar to that observed in the
Mid-Conn characterization test series, is
5
-------
consistent with pilot study findings, and is
likely due to displacement of S02 by the
more reactive HCI in the filter cake. These
results suggest that normal operation of
the SDA/FF system [140°C (285°F), mod-
erate stoichiometry] would be expected to
yield 95% or more HCI removal and about
70% S02 removal.
Table 3 provides inlet concentrations
and removal efficiencies for selected or-
ganics. With the exception of run 9 (high-
est SDA outlet temperature and low
stoichiometry), the PCDD removal was at
least 99.8% for SDA inlet concentrations
ranging from 95 to 397 ng/Sm3 This low
PCDD removal efficiency was probably
the result of low inlet concentration and
high SDA outlet temperature. The PCDF
removal was 99 9% or greater for all runs,
although the SDA inlet PCDF concentra-
tion changed almost three-fold from 341
to 1007 ng/Sm3 CP control was usually
slightly better than CB control, with CP
control generally being 97% or more and
CB control being 95% or more. The CP
inlet concentration ranged from 11,329 to
62,938 ng/Sm3, being more than double
that for CB. The PAH removal generally
increased with inlet concentration, rang-
ing from 58 6 to 97.7% as the concentra-
tion rose from 6,289 to 88,626 ng/Sm3.
The lowest PAH removals in the FGC
system correspond to the lowest inlet con-
centrations and occurred during good com-
bustion (low CO). However, the PAH (as
well as other organic) emissions varied
with FGC system variables. Generally, or-
ganics removal was high (over 95%), ex-
cept PAH removal which was usually
moderately high (over 92%), for all test
runs and conditions so that changes in
the FGC process variables had little effect
over the range evaluated; e.g., the re-
moval of combined PCDD and PCDF was
99.7% or higher for all test runs.
As shown in Table 4, the PM concen-
tration in the flue gas at the SDA inlet
ranged from 3,274 to 4,949 mg/Sm3, while
the outlet concentration ranged from 2.68
to 7.62 mg/Sm3. The corresponding PM
removal was 99.8% or more Because of
the low outlet concentration for all runs,
the effects of FGC process changes on
PM removal efficiencies could not be dis-
tinguished. Table 4 also presents selected
metals control data, with control of ar-
senic (As) and cadmium (Cd) to concen-
trations below detection limits for all test
runs.
The removal of lead (Pb) followed very
closely the removal of PM, usually being
above 99%, despite a five-fold ratio of the
maximum to minimum inlet concentration
for the tests. Surprisingly, Hg control was
over 96% for all the tests The chromium
(Cr) removal was high and paralleled that
of mercury (Hg).
While high carbon content in flyash,
which is characteristic of RDF combus-
tors, may be a factor in the observed high
control of Hg emissions, conclusive test
data were not obtained on carbon content
during the test program. However, the loss-
on-ignition data in Table 5 range from
4.26 to 10.45% and suggest high carbon
content, since these values are believed
representative of the carbon plus water of
hydration content of the fabric filter ash.
Since the carbon concentration in flyash
from highly efficient mass burn combus-
tors is from 1 to 2%, the values in Table 5
suggest carbon values greater than this
range even for water of hydration con-
tents as high as 50%. Also, the higher PM
loading in RDF combustor flue gases may
lead to increased mercury control because
of the relatively higher particulate surface
areas for absorption of volatile metals.
Ash/Residue Results
The average loss on ignition (LOI) in
bottom ash/grate sittings (0 7 to 1.5%)
was lower than that measured in bottom
ash from waterwall mass burn systems
(1.5 to 5.0%) and much lower than in
bottom ash from two-stage combustion
systems (12 to 30%).
Concentrations of PCDD/PCDF in the
bottom ash and grate sittings were at or
below the detection limit. PCBs were be-
low detection limits in all ash/residue
streams.
Generally, the organics concentrations
in the combustor ash (BA, GS, and EC
ash) were considerably less than in the
FF residue. For example, over 99% of the
total PCDD/PCDF associated with the resi-
dues was measured in the FF residue.
Table 3. Flue Gas Cleaning (FGC) System Performance: Organics
Test
Runb
FGC Cond.
Temp/SO /
Inlet Concentrations, ng/Sm38
Removal, %
PCDD
PCDF
CB
CP
PAH
PCDD
PCDF
CB
CP
PAH
2,5
L/H
397
1,007
10,860
62,938
60,176
99.9
99.9
96.2
97.4
92.0
3,11
H/L
161
611
6,159
20,798
46,976
99.8
100"
95.2
99.1
92 2
4
H/M
151
623
5,964
16,964
22,519
99.8
99.9
98.4
99.0
91.3
6
WI
317
885
9,403
41,588
88,626
99.9
100*
94.3
96.9
97.7
7
UL
207
796
7,074
25,168
51,774
99.9
10Cf
98.5
99.1
97.3
8
M/H
211
951
7,071
20,226
10,259
99.9
100d
98.4
99.1
76.7
9
H/H
71
378
4,848
11,329
32,421
99.2
99.9
97.7
96.6
92.5
10
UM
243
424
6,170
16,198
6,289
99.9
10Cfi
99.3d
99.5
58.6
12,13,14
M/M
95
341
4,647
14,419
7,747
99.9
10&
100d
99.4
63.2
8 Organics are polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF), chlorobenzenes (CB), chlorophenols (CP), andpolynucleararomatic
hydrocarbons (PAH).
b Values are averaged for multiple runs.
c High temperatures (H) ranged from 166 to 171°C (330 to 339T), medium temperatures (M) from 141 to 142°C (285 to 287°F), and low temperatures (L)
from 122 to 124°C (252 to 255"F) for the SD outlet gas. Fabric filter S02outlet concentrations were above 100 ppm for high (H) concentrations, between
21 and 100 ppm for moderate (M) concentration, and 20 ppm or less for low (L) concentration. All concentrations are referenced to 12% CO, in dry gas
[25 °C (77°F), 101.3 kPa (1 atm)].
d Value is based on rounding off to three significant figures.
6
-------
Table 4. Flue Gas Cleaning (FGC) System Performance: Particulate Matter and Selected Metals
Particulate Matter
Test FGC Cond. (PM) mg/Sm3 Inlet Concentration, /tg/Sm3 Removal, %
Runa
TempJSO*
Inlet
Outlet
As
Cd
Cr
Pb
Hg
PM
As°
C 250
ppm)
Organic contaminants in the ashes, in-
cluding PCDD, PCDF, CB, and PAH, were
not soluble in water
Typically, concentrations of less volatile
metals [e.g , chromium (Cr), nickel (Ni),
copper (Cu)] were higher in the combined
bottom ash/grate sittings, whereas con-
centrations of relatively volatile metals
[e.g., Cd, Hg, zinc (Zn)] were higher in the
FF residue Lead concentrations were rela-
tively high in both grate sittings and FF
residue, and relatively low in the bottom
and economizer ashes.
FF residue was more soluble in water
(approximately 34% solubilized) than ei-
ther the combined bottom ash/grate sitt-
ings or economizer ashes (approximately
7% solubilized). A substantial portion of
the solubilized material from the FF resi-
due consisted of sulfate and chloride an-
ions (14% sulfate and 27% chloride).
Only very small amounts (typically less
than 10%) of most trace metals present in
the ashes/residue were soluble in water
In general, under simulated acidic con-
ditions, larger fractions of Cd, Cr, Pb, man-
ganese (Mg), and Zn were potentially
available for leaching from the FF residue
than from the bottom and grate sittings
ashes. However, note that, under most
controlled disposal conditions, an acidic
leaching environment is unlikely given the
high acid neutralization capacity of the FF
residue.
Samples of FF residue were solidified
using cement and three types of waste
pozzolanic materials. Engineering test re-
sults indicate that these solidified materi-
als were physically strong, durable, and
relatively impermeable. In addition, results
from different leach tests indicate that a
significant reduction in metal mobility was
achieved through both physical encapsu-
lation and chemical fixation.
7
-------
Table 5. Fabric Filter Ash Content: Organics and Selected Metals
Test
Runa
FGC Cond.
TempJSO?
Ash Rate
kg/h
Concentration, ng/g
Concentration, jig/g
LOIc
%
PCDD
PCDF CB
CP
PAH
As
Cd
Cr
Pb
Hg
2,5d
UH
429
96
71
1,085
2,870
9,437
15
70
264
1,987
25
6.52
3,11e
HA.
2,140
49
100
704
2,225
1,087
18
97
240
2,405
30
4.50
4
HM
1,385
84
172
1,059
3,320
1,806
20
96
179
3,413
48
8.15
6
MA.
1,238
227
282
1,684
6,09 5
7,431
19
96
154
3,666
36
10.45
7
UL
550
154
271
941
4,997
1,992
17
90
147
3,051
37
9.97
8
M/H
434
62
96
729
1,636
2,905
22
62
210
2,439
25
5.00
9
H/H
1,317
112
222
1,266
4,33 6
4,780
21
119
287
4,545
37
9 30
10
UM
1,166
27
47
684
1,924
1,402
19
87
274
2,352
27
4.26
12,13,14'
M/M
707
102
111
1,218
1,832
4,093
19
118
207
2,812
39
8.89
Values are averaged for multiple runs.
High temperatures (H) ranged from 166 to 171°C (330 to 339°F), medium temperatures (M) from 141 to 142°C (285to 287°F), and low temperatures (L)
from 122 to 124°C (252 to 255°F) for the SD outlet gas in the FGC system.
LOI is loss on ignition.
Data shown are based solely on Run 5.
Data shown are based solely on Run 11
Data shown are based solely on Runs 12 and 14.
1000
PCDD PCDF " CB ' PCB
Combustion Conditions:
U POOR
|U INTERMEDIATE
B GOOD
Figure 5. Organics concentrations in fabric filter ash.
PAH
TOTAL
8
-------
Theodore G. Brna and James D. Kilgroe are with the U.S. EPA Air and Energy
Engineering Research Laboratory, Research Triangle Park, NC 27711.
James D. Kilgroe is the EPA Project Officer (see below).
The complete report, entitled "The Environmental Characterization of RDF Combus-
tion Technology—Mid-Connecticut Facility, Hartford, Connecticut," (Order No.
PB96-153432; Cost: $35.00, 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
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
National Risk Management
Research Laboratory (G-72)
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use
$300
EPA/600/SR-94/140
9
------- |