United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-84/177 Dec. 1985
Project Summary
Engineering Assessment
Report—Hazardous Waste
Cofiring in Industrial Boilers
C. Castaldini, S. Unnasch, and H. B. Mason
The full report documents results of
42 hazardous waste combustion tests
performed on 11 full-scale industrial
boilers. The full report discusses the
boiler operating conditions, organic and
other gaseous emissions measured in
the stack, and the achieved destruction
efficiency of principal organic hazard-
ous constituents (POHCs) present in
the waste. The report is divided into two
volumes. Volume I presents a summary
of all test data, discusses conclusions,
and highlights trends in POHC destruc-
tion and other byproduct emissions with
respect to boiler operation and POHC
type. Volume II is a compendium of
boiler-specific test data summarized to
provide the readers with sufficient de-
tails to perform their own analyses.
Major volatile POHCs investigated were
carbon tetrachloride, chlorobenzene,
trichloroethylene, and toluene. The de-
struction efficiency of 14 other volatile
and semivolatile hazardous organics is
also reported. In general, industrial
boilers tested achieved individual POHC
destruction efficiencies in the range of
99.90 to 99.99996 percent under con-
ditions investigated. Although not clear-
ly evident, the collected data point out
lower destruction efficiencies with
transient or off-specification burner and
f eedrate conditions. Emissions of ident-
ifiable products of incomplete combus-
tion (PICs) were generally one to two
orders of magnitude greater than POHC
breakthrough emissions. These emis-
sions generally included dichlorometh-
ane, chloroform, tetrachloroethylene,
trichloroethanes, and benzene and tol-
uene when these compounds were not
POHCs in the waste fuel. Lower PIC
emissions accompanied greater POHC
destruction effSciences. These and other
trends are highlighted to point out areas
requiring further research.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH,
to announce key findings of the research
project that is fully documented in two
separate volumes (see Project Report
ordering information at back).
Introduction
Current estimates indicate that 264
million metric tons of hazardous waste
are generated annually.1 Much of this
waste has a high heating value so that
disposal by cofiring in industrial boilers
often provides an economic advantage
over other regulated disposal practices
such as landfill or incineration. In fact,
hazardous waste incineration in industri-
al boilers is a widespread practice. The
U.S. Environmental Protection Agency
(EPA) through the Office of Solid Waste
(OSW) and the Office of Research and
Development (ORD) sponsored field tests
on 11 full-scale industrial boilers to
evaluate the resultant air emissions of
this disposal practice and, in particular, to
determine the destruction efficiency
(DRE) of principal organic hazardous
constituents (POHCs) in the waste under
typical boiler operating conditions. The
following sections summarize the results
obtained during these tests and discuss
tentative conclusions with regard to
POHC DREs and other organic emissions
as a function of boiler type, waste type,
and selected operating conditions.
-------
Test Site Descriptions
The industrial boiler population com-
prises a diverse family of steam gener-
ators varying in design type, size, fuel,
and operating conditions, while industrial
organic wastes vary widely in physical
and chemical constituents. To obtain
results representative of current or
planned industry practice, a broad range
of boiler designs and waste types was
selected for testing. Within availability
and accessability constraints, preference
was given to sites which were regarded
as less likely to attain a high level of waste
destruction. See Table 1.
Overall, these test sites represent a
good sample of the industrial boiler
population. Watertube boilers are the
most likely candidates for hazardous
waste incineration. Their larger heat input
capacities allow higher waste firing rates
while still retaining low waste fuel ratios.
Furthermore, these units are often e-
quipped with multiple burners allowing
one or more burners to fire waste fuel
only. Steam-atomized oil guns for waste
firing are used in combination with
natural gas firing for single burner units.
Modifications to single burner arrange-
ments to allow oil and liquid waste
cofiring are feasible as demonstrated by
the site E boiler. Firetube boilers are less
likely to constitute a major equipment
category for cofiring practices because of
generally smaller capacities. However,
site G illustrates the versatility of these
units for full-scale incineration with heat
and resource recovery.
Boiler Operation and Test
Conditions
The test protocol at each site consisted
of a baseline test and replicate waste-
fuel-fired tests. During the baseline test,
emission measurements were performed
with the boiler firing only the primary
fossil fuel. The intent of this test was to
measure the level of organic emissions
attributable to the combustion of fossil
fuel only. Three replicate cofired tests
were then performed. Baseline heat input
and fuel feed conditions were maintained
constant between these tests. At some
sites, the protocol was extended to meas-
ure the impact of high and low boiler
loads and variable excess air levels.
Table 2 summarizes the test conditions
investigated for each of the eleven sites.
Sites A through D were tested with as-
is waste fuels. Following these four initial
test sites, waste fuels were spiked with a
mixture of carbon tetrachloride, chloro-
benzene, and trichloroethylene to broad-
en the results on POHC destruction and
facilitate intrasource comparison. At site
H, 1,1,1 -trichloroethane was substituted
for trichloroethylene.
Criteria Gas Emissions
Table 3 summarizes criteria gas emis-
sions measured at each site and high-
lights general boiler operation pertinent
to combustion stability and combustible
emissions. Highest CO emissions were
measured at site A. The wood combustion
Table 1. Summary of Test Site Boilers
Furnace
Steam Capacity. Volume.
Site Boiler Type kg/s (1ff> Ib/hr) m'/ft3/
Furnace Number of
Waterwall Burners
Surface. /Injection
rrffft2) Primary Fuel Ports)
Typical Waste
Fuels
Injection
Mechanism
Control
Device
Typical Operation
A Watertube 13 (101 17.41613) 106 11,144) Wood waste
stoker
Creosote sludge
Mixed with wood
Mult/cyclone
Fluctuating loads.
combustion air and
waste teed
B Packaged I 1 (8.51 1.1 1391 8.0 (831 Natural gas
firetube
I Alkyd wastewater
Air atomized None Low boiler load. Maximum
oil gun waste fire rate of
42 ml/s I4O gph)
C Field-erected 29 (230) 322 (11.400) 170 (1.800) Natural gas
watertube . or oil
6 Phenolic waste
One or two steam
atomued burners
None
Low load with reduced
number of burners
High excess air.
D Field-erected 11.4 (90) 62 (2.2OO) 14O (1.520) No. 6 oil
convened
watertube
stoker
E Packaged 13.9 (110) 42 (1.48O) 666 (7.160) No. 6 oil
watertube
4 Methanol and
toluene wastes
with chlorinated
organics
1 Methylmethacrylate
byproduct wastes
One of the lower
level steam
atomized burners
Two steam atomized
waste guns in main
burner throat
None About 50 percent capacity
with 3 or 4 burners in
service
None Part toed with maximum
250 ml/s (240 gph)
waste firing rate for loads
above 50 percent
F Field-erected 7.6 (60) 96 (3.390) 100 (1.1001 No 6 oil. 2 Paint solvents Lower steam
converted gas. or atomized oil burner
watertube propane
None Part load with maximum
190 ml/s (180 gph) waste
firing rate for loads above
50 percent
G Modified
packaged
firetube
5.0 (40) 6.4 (226) 20 (220) None
1 Highly chlorinated
organics
Available air 2 scrubbers Part load with startup on
atomized oil gun in series natural gas. Total chlorine up
to 80 percent of waste fuel.
H Field-erected 32 (250) 520 (18.400) 515 (5.54O) Pulverized 12 coal. Methyl acetate One or two steam
tangentialfy coal 6 oil waste fuel atomized oil
fired watertube burners
ESP
At boiler capacity with
maximum 440 ml/s (420 gph)
waste firing rate
I Packaged 7.8 (62) 41 (1.430) 76 (820) Natural gas 2 Aniline waste high
watertube in nitrate organics
Either upper or None Staged combustion for low
lower steam NO, with maximum 130 ml/s
atomized burner (120 gph) waste flow
J Packaged 1.3 (1O) 1.5 (51) 2.6 (91) None
firetube
I Artificially
blended fuels
Available oil
burner
None
Typical excess air of
17 percent
K Packaged 7.6 (60) 65 (2.270) 47 (508) No 6 oil 1 Blended waste with
watertube light oil
Mixed with heavy
oil
None
Typical 70/30 percent heavy
and light oil mixture
-------
Table 2. Summary of Tests with Waste Fuel firing
Number of
Waste-Fuel-
Site Fired Tests
Volumetric
Heat
Release
Rate,
kW/m*
{1O> Btu/
hr-ft1)
Surface Heat
Release Kate,
kW/m3
11O> Btu/
hr-ft1)
Bulk
Furnace*
Temperature,
Bulk
Furnace*
Residence
Time, sec
Waste Fuel
Heating
Value. MJ/kg
U&Btu/tb)
Waste Heat
Input,
Percent of
Total
POHCs of Interest
3OO (29)
48 (16) 1,370 (2,SOO)
1.2 39(17) 40 Phenol, pentachlorophenol.
naphthalene, fluorene.
2-4-Oimethylphenol
B
C
D
E
F
G
H
1
J
K
3
3
3
3
1
6
1
3
3
3
2
6
1
745 (72)
78 (7.5)
40O (39)
230 (22)
580 (55)
380-770
(37-74)
420 (40)
114 (11)
820 (79)
180 (17)
340 (33)
690-1.750
(65-170)
270 (26)
106 (34)
150 (48)
180 (57)
100 (33)
37(11)
24-49
(7.6-15)
26 (8.1)
104 (34)
262 (81)
183 (58)
180 (57)
1 18-3OO
(37-95)
370 (120)
1.320 (2,400)
1.320 (2.4OO)
1,430 (2.600)
1,370 (2,500)
1,550 (2,800)
1,480-1.590
(2,700-2,900)
1,480 (2.7OO)
1.370 (2,500)
1,350 (2.450)
1.370 (2.500)
1.430 (2,600)
1.310-1.370
(2.40O-2.5OO)
1.370 (2.500)
0.8
2.0
1.1
1.3
0.7
0.5-1.0
1.1
2.0
0.4
2.0
1.8
0.3-0.7
1.8
0.03-O.18
(0.013-O.077)
39 (17)
21 (8.8)
42 (18)
27 (12)
25-27 (11-12)
37 (16)
33 (14)
21 (9.0)
17 (7.0)
25 (11)
42 (18)
40 (17)
<1
38
18
48
22
19-43
56
9.0
100
2.4-4.3
8.2
100
65
Toluene
Phenol
Tetrachloroethylene
Bis(2-chloroethyl)ether, toluene
Methylmethaerylate, a-hydroxy methyl
isobuty-rate and a-hydroxy isobutyrate
methyl ether
Above plus carbon tetrachloride,
chlorobenzene and trichloroethylene
Toluene, methylmethacrylate
Carbon tetrachloride, chlorobenzene,
trichloroethylene, toluene
Carbon tetrachloride, epichlorohydrin,
bis(2 -chloroisopropyl)ether
Carbon tetrachloride, chlorobenzene,
1, 1, 1 -Trichloroethane
Carbon tetrachloride, chlorobenzene,
trichloroethylene, toluene, aniline,
benzene, nitrobenzene
Carbon tetrachloride, chlorobenzene,
trichloroethylene, toluene
Carbon tetrachloride, chlorobenzene,
trichloroethylene, toluene, benzene
*Not measured values. Estimates of bulk gas temperature in the furnace were used to calculate bulk furnace residence time. Values to be considered
approximate.
Table 3. Criteria Gas Emissions and Test Conditions
Criteria Emissions, as Measured, Dry Basis*
Site
A
B
C
D
Test
1.
4
2.
2.
2,
2.
3.
3,
3.
5,6,
3.
4
4
4
7
Fuels
Wood waste and creosote
Natural gas and alkyd
wastewater
Natural gas and phenolic
waste
No. 6 oil and methanol
with tetrachloroethylene
No. 6 oil and toluene with
bis(2-chloroethyl)ether
02
(percent)
6.2-16.7
(10.4)
3.8-6.0
(5.3)
7.8-11.3
(10.3)
4.3-6.4
(5.2)
5.2-6.8
(6.1)
CO2
(percent)
15.4-4.4
(9.9)
8.8-12.4
(9.6)
6.2-8.7
(7.3)
11.6-15.0
(12.7)
10.7-12.6
(12.0)
CO
(ppm)
470->1.000
O530)
35-96
(54)
10-15
(13)
70-128
(93)
89-107
(93)
NO.
(ppm)
90-124
(105)
38-60
(44)
38-43
(40)
200-23O
(216)
162-168
(165)
TUHC
(ppm)
0-50"
(4.3)
8-170
(74)
0
11-32"
(20)
14-42C
(27)
Genera/ Test Conditions
Transient boiler emissions
resulting from probable boiler load
changes, insufficient fuel-air
mixing of fuel bed combustion
Unsteady waste feed rate caused by
insufficient mixing. Several
episodes of waste fuel cut off.
Steady-state boiler operation at
very low boiler load and high excess
air
Variable concentration of
trichloroethylene in waste fuel.
Several smoke episodes during test
2 and 3 primarily. Burner flameout
and high CO during lightoff.
Steady boiler operation with well
mixed waste fuel
-------
Table 3. Table 3. (continued)
Site Test
E 2
3,4,5
6
7
8
9
F 2,3.4
G 1.2,3
H 2.3.4
1 2
4
J 1-6
K 1
Fuels
No. 6 oil and methyl-
methacrylate (MMA)
No. 6 oil and MMA waste
spiked with carbon tetra-
chloride, chlorobenzene.
and trichloroethylene
No. 6 oil and MMA waste
spiked with carbon tetra-
chloride, chlorobenzene.
and trichloroethylene
No. 6 oil and MMA waste
spiked with carbon tetra-
chloride, chlorobenzene.
and trichloroethylene
Natural gas and MMA
waste spiked with carbon
tetrachloride, chloro-
benzene, and
trichloroethylene
Natural gas with toluene/
MMA mix
No. 6 oil and solvents with
carbon tetrachloride.
chlorobenzene. and
trichloroethylene
Highly chlorinated organic
wastes with carbon
tetrachloride
Pulverized coal and methyl
acetate with carbon
tetrachloride, chloro-
benzene, and
1, 1, 1 -trichloroethane
Natural gas and aniline/
nitrobenzene waste with
carbon tetrachloride.
chlorobenzene, and
trichloroethylene
Natural gas and mixture of
toluene, benzene, carbon
tetrachloride, chloro-
benzene, and
trichloroethylene
Heavy oil and light oil with
carbon tetrachloride.
chlorobenzene, and
trichloroethylene
02
(percent)
5.3-6.9
(5.5)
5.3-8.0
(6.9)
5.2-7.4
(6.3)
6.5-8.5
(7.4)
5.3-6.8
(6.2)
6.4-8.5
(7.4)
7.0-11.3
(8.3)
8.2-9.4
(8.7)
5.7-11.9
{6.3)
2.4-2.7
(2.6)
2.5-2.7
(2.6)
3.2-7.6
(5.4)
3.8-4.3
(4.0)
Criteria Emissions, as Measured. Dry Basis*
COz
(percent)
9.5-12.8
(11.6)
9.0-12.8
(10.2)
10.0-12.8
(11.7)
9.3-11.0
(10.4)
9.0-10.4
(9.6)
7.8-10.4
(8.6)
6.7-10.4
(8.9)
8.4-10.2
(9.4)
8.4-13.6
(12.4)
. 10.2-10.7
(10.4)
10.6
10.5-14.2
(12.5)
10.5-11.7
(11.0)
CO
(ppm)
88-101
(92)
80-155
(114)
80-120
(100)
95-100
(98)
49-80
(65)
50-123
(77)
93-133
(103)
85-140
(107)
110-128
(118)
63-242
(180)
22-112
(63)
10-119
(76)
87-150
(108)
/vo.
(ppm)
292-415
(325)
270-450
(336)
325-398
(365)
320-308
(270)
345-440
(405)
100-180
(124)
168-207
(190)
43-54
(48)
322-344
(332)
384-452
(420)
1.090-1.160
(1.150)
74-192
(116)
143-151
(146)
TUHC
(ppm)
32-322"
(142)
38-142"
(91)
27-29"
(28)
17-31°
(24)
97-109°
(104)
52-61"
(56)
0-1.1
(0.4)
0.2-0.5"
(0.3)
0-2
(0.6)
5-7
(6.4)
5-6
(5.3)
NA
NA
General Test Conditions
Steady boiler/burner operation
with no smoke or high CO
emissions
Several periods of smoke and high
CO emissions due to fluctuating
waste feed and moderate burner
settings. Most transient operations
occurred during tests 3 and 4.
Low load test; no smoke emission
episodes.
Three short periods of high CO
emissions attributed to surge in
waste feed. High load test.
No significant transients. Steady
burner and waste feed operation
with low CO and smoke.
Slightly higher stack opacity
necessitated slight increase
in excess air. No significant upsets.
Inadequate burner settings caused
several flameouts and some high
CO and smoke emissions
Steady-state combustion
conditions. No recorded
operational upsets.
Steady boiler load with slightly
variable waste feed. Test 4
performed at higher excess air
condition.
Staged combustion during test 2.
Unstaged combustion during test 4.
No significant boiler transients.
Experienced feed pump problems.
Tests performed at three separate
boiler loads. High and low excess
air. No significant boiler or waste
feed transients.
No significant boiler or burner
transients. Typical load and excess
air conditions.
^Numbers in parentheses are the average.
"Based on results for test 1 only.
CTUHC for sites D and E based on the sum of Ci to Ce
hydrocarbon emissions.
"7 to 16 ppm was measured by on-site GC.
NA — not available.
-------
on a fuel bed typically results in insuf-
ficient fuel-air mixing which leads to
transients in excess O2, CO, and hydro-
carbon emissions. Unsteady test condi-
tions at site B resulted in significant
hydrocarbon emissions. Unstable burner
conditions were the result of initial tests
at site D (tests 2 and 3) and site E (tests 3
and 4 primarily). These conditions, which
caused intermittent high CO and smoke
emissions, often resulted in burner flame-
outs. Improper waste and primary burner
settings at site F also caused combustion
instability and sudden f lameouts. Several
test periods were accompanied by peaks
in high CO emissions which generally
lasted less than 1 min. During most of the
high smoke emission periods at these
sites gas sampling was interrupted. Sites
G through K showed no significant opera-
tional transients with the exception of
test 4 at site H where excess air surged on
a few occasions and during the staged
combustion test at site I where CO
emissions increased.
POHC Destruction
Table 4 summarizes site-specific ORE
results for volatile POHCs. These results
are based on about 120 separate gas
measurements and a total of 35 individual
tests at 9 boiler sites. Test sites A and C
are not included in the table because
POHCs were semivolatile. Results indi-
cate DREs ranging from about 99.90 to
99.99996 percent for all POHCs with a
total mass average for all sites of 99.998.
The bulk of the data is available for four
POHCs: carbon tetrachloride, trichloroeth-
ylene, chlorobenzene, and toluene. On
the average, DREs for carbon tetrachlo-
ride and trichloroethylene were higher
than chlorobenzene and toluene. The
ranges in DREs, however, show nearly
equal results independent of POHC.
On a site-specific basis, DREs of volatile
organics at site F showed the lowest
mass average DRE (99.98 percent). Next
lowest mass average DREs were recorded
for site H and B both at 99.991 percent
and site E at 99.995 percent. It should be
pointed out that chlorobenzene results
for site J are misleading since low DREs
were calculated based on high analytical
detection limits. In reality, chlorobenzene
DREs were probably much higher and site
J mass average DRE would be increased
passing the 99.9997 percent listed in
Table 4.
A comparison of site-specific DREs
highlights some important trends. The
site F boiler was the only test site with a
total mass average DRE less than 99.990
percent for volatile POHCs. In fact, low
DREs were measured for all three cofired
tests at this site. Burner operation at site
F was characterized by nozzle coking,
probable fuel jet impingement on the
burner throat, intermittent periods of high
CO and smoke emissions and burner
flameouts. These problems were brought
about by improper placement of the fuel
guns in the burner ports. Similarly, lower
DRE results at site E were recorded during
tests characterized by fluctuating waste
feedrates combined with intermittent
periods of high CO and smoke emissions.
Contrary to site F, low DREs for site E
were most evident with the POHC methyl-
methacrylate resulting in DREs as low as
99.95 percent. Chlorinated POHCs at site
E also showed lower DREs during these
tests with unstable combustion condi-
tions, however, destruction was always
greater than 99.990 percent.
Table 4. Summary of Test Average DREs for Volatile POHCs*
POHC B
Carbon
tetrachloride
Trichloro-
ethylene
1,1,1-Tri-
chloroethane
Chloro-
benzene
Benzene
Toluene
99.991
Tetrachloro-
ethylene
Methylmeth-
acrylate
Mass weighted 99.991
average
D
99.9992-
99.99990
(99.9996)
99.994-
99.9992
(99.998)
99.994-
99.99990
(99.998)
E
99.9990-
99.9998
(99.9996)*
99.994-
99.9995
(99.998)
99.995-
99.99990
(99.998)
99.997
99.95-
99.997
(99.991)
99.95-
99.99990
(99.995)
F
99.98-
99.9990
(99.995)
99.98-
99.998
(99.996)
99.96-
99.992
(99.98)
99.90-
99.97
(99.95)
99.90-
99.9990
(99.98)
Site
G H
99.995- 99.97-
99.9990 99.9994
(99.998) (99.98)
99.97-
99.9996
(99.994)
99.990-
99.997
(99.992)
99.995- 99.97-
99.9990 99.9996
(99.998) (99.991)
1
99.9990-
99.9993
(99.9993)
99.99990-
99.99992
(99.99991)
99.997-
99.9990
(99.998)
99.97-
99.98
(99.97)
99.998
99.97-
99.99992
(99.998)
J
99.997-
99.9998
(99.9990)
99.998-
99.99993
(99.9996)
99.8-
99.97
(99.95)
99.9990-
99.9997
(99.9990)
99.8-
99.99993
(99.9990)
K Range
99.97-
99.9998
99.9998
99.98-
99.99993
99.99990
99.97-
99.9996
99.8-
99.99992
99.99992
99.97-
99.996
99.996
99.90-
99.99996
99.99996
99.994-
99.9992
99.95-
99.995
99.996- 99.8-
99.99996 99.99996
(99.9997)
Weighted
Average
99.9992
99.9994
99.994
99.992
99.990
99.998
99.998
99.991
99.998
'Each test average DRE is generally based on the weighted average of triplicate measurements.
"Numbers in parentheses represent the site-specific POHC average DRE.
-------
These trends suggest that lower DREs
are more likely to occur during unstable
combustion conditions leading to high
combustible emissions. Therefore, an
attempt was made to correlate DREs with
combustion efficiency, defined as the
percent carbon utilization (1 -CO/CO2) x
100. Figure 1 illustrates the mass average
(total POHC fired taken as a whole) site-
specific DREs as a function of the combus-
tion efficiency. Site average DREs plotted
in Figure 1 and in all other graphical
presentations are based on all volatile
and semivolatile POHCs detected in the
waste fuels. A complete listing of Re-
source Conservation and Recovery Act
(RCRA) Appendix VIII POHCs tracked for
DRE measurement is presented in Ap-
pendix A, Volume I of the full report.
The data presented in Figure 1 indicate
no definitive trend of lower DRE with
higher CO. This is not entirely surprising
because this attempted correlation does
not account for site-specific considera-
tions such as combustion characteristics
of waste (POHC) types, boiler type and
capacity, waste feedrate and feed mech-
anism, and temperature and residence
time profiles. Furthermore the bulk of the
data was obtained when CO emissions
were in the narrow range of 70 to 140
ppm as measured corresponding to about
99.94 to 99.84 percent combustion ef-
ficiency as defined here. The only clear
evidence of low DRE with high CO
emissions is offered by the site A data
where CO emissions were in excess of
500 ppm and the mean average DRE was
lower than 99.990 percent. A tentative
conclusion may be that DREs of 99.990
99.99999-1
99.9999-
8 99.999-
01
1
99.99
99.9
99.0
£
BH F
99.99 99.97 99.90 99.68 99.0
It - CO/COA100. percent
Figure 1. Site average DREs versus com-
bustion efficiency.
percent or greater are more likely to result
from combustion conditions leading to
CO less than 80 to 100 ppm. However, in
some cases low CO emissions may
represent an overly conservative require-
ment for high POHC DRE. Although the
validity of CO as a surrogate for DRE
results remains speculative at this time,
the effect of transient boiler operation
and high CO emissions on DRE should be
investigated in greater detail.
Figure 2 illustrates the dependence of
measured DRE results on POHC concen-
trations in the waste fuel. The DREs are
plotted versus the concentration of
POHCs in the waste fuel (ppm) normalized
by the ratio of the waste fuel heat input to
the total heat input (W/T). The data, also
based on mass average DRE for each site,
suggest that higher DREs are likely with
increasing POHC concentration in the
waste fuel and higher waste/fuel ratios.
This trend may indicate the importance of
PIC formation from baseline fuels as well
as the level of background contamination
and error associated with low-level de-
tection of volatile organics. PIC emission
data clearly suggests that both fossil fuels
such as oil and coal as well as waste fuels
result in significant emissions of PICs.
Furnace waterwall heat release rate
and NO, formation can be indicators of
the thermal environment in the flame and
throughout the furnace. Waterwall sur-
face heat release rate is a measure of the
temperature profile through a furnace.
Although radiative properties of combus-
tion products play a predominant role,
generally the higher the waterwall sur-
face heat release rate, the higher the
temperature profile through the furnace.
Similarly, high flame temperature, long
residence time, and turbulent mixing are
conducive to high thermal NO formation.
These combustion characteristics are also
desirable from a POHC destruction view-
point. Therefore, higher thermal NO may
be linked with high POHC destruction.
Figure 3 illustrates the trend of weighted
average DREs with test loads surface
heat release rates calculated for each
site. The data illustrate a general trend of
higher DREs with increasing waterwall
surface heat release rates. This trend
suggests that thermal environments
throughout the boiler furnace may be
more important for high POHC DREs than
flue gas residence time. Furthermore,
firetube boilers can be as effective in
thermal POHC destruction as watertubes.
This is evidenced by results obtained at
sites G and J.
DRE results for sites A, B, F. and H fall
below the trend indicated by the other
99.99999-,
99.9999-
§
99.999-
O 99.99
Q.
99.9-
99.0-
K
CD J
HF
A
1.0 10* 10* 10*
POHC Concentration, ppm x HW/HT
Figure 2. Site average DRE versus waste
fuel POHC concentration.
test sites. As discussed earlier, boiler
operation at sites A, B, and F was
generally characterized by unstable com-
bustion and burner conditions often lead-
ing to high combustible emissions. Low
DRE results for site H, the only pulverized
coal-fired boiler tested, may be attributed
in part to low POHC concentration with
respect to total heat input of the boiler
and the contribution of background or-
ganic emissions from eombustion of coal.
Stated differently, this trend indicates
that the lower limit of POHC DRE is likely
to increase with furnace waterwall heat
release rate. This trend is similar for DRE
versus measured NOX emissions.
Other Organic Emissions
Table 5 summarizes chlorinated organ-
ic emissions identified as products of
incomplete combustion (PICs) during
waste fuel firing for test sites D through
H. PIC identification was based on blank
corrected emission of organic compounds
not detected in the waste fuels. Total
chlorinated PIC emissions ranged be-
tween 0.3 and 32 mg/s. These emissions
were one to two orders of magnitude
greater than measured emissions of
breakthrough chlorinated POHCs. Dichlo-
romethanefmethylene chloride) and chlo-
roform generally constituted the bulk of
these emissions followed by tetrachloro-
ethylene and trichloroethanes. Methylene
chloride PIC emissions are in part suspect
because of possible contamination. This
compound is widely used in both field test
-------
c
01
Q
O
99.99999-1
99.9999-
99.999-
99.99-
99.9-
99.0-
FB
H
7
20
1
40
I
60
I
80
100
120
SHRR, 1.000 Btu/hr-ft2
Figure 3. Effect of surface heat release rate on DRE—site average data.
activities and laboratory analyses. Non-
chlorinated PICs were generally toluene
and benzene.
Figure 4 illustrates a trend in PIC emis-
sions versus POHC breakthrough for total
PICs (including toluene and benzene).
The data indicate a general trend of lower
PIC emissions with increasing POHC destruc-
tion. This suggests that combustion con-
ditions leading to more efficient POHC
destruction are also likely to result in
lower PIC formation.
Conclusions and
Recommendations
Field tests conducted at 11 industrial
boilers burning hazardous wastes indi-
cate that POHC OREs generally exceeded
99.990 percent under relatively steady or
normal boiler operating conditions. Al-
though trends were not definitive, POHC
DREs generally increased with higher
waterwall surface heat release rates
(furnace or temperature), lower CO
emissions, and higher POHC firing rate.
Additional research is necessary to de-
termine the effect of unsteady or trans-
ient boiler operation on POHC DRE mani-
fested by high CO and smoke emission.
Table 5. Volatile Chlorinated PICs Versus POHC Breakthrough
Selected Chlorinated PICs. Percent of Total
Site
D
E
F
G
H
Chlorinated Waste
FuelPOHCs
Tetrachloroethylene
Bis(2-chloroethyl)ether
Carbon tetrachloride.
chlorobenzene. and
trichloroethylene
Carbon tetrachloride.
chlorobenzene, and
trichloroethylene
Carbon tetrachloride.
epichlorohydrin. and
bis (2-chloroisopropyll
ether
Carbon tetrachloride.
chlorobenzene, and
1,1,1 -trichloroethane
Total
Chlorinated
POHC
Break-
through
(U9/s)
630-880
(790)
3.0-6.8
14.7 >
56-570
(220)
51-133
(85)
95-307
(170)
290-4.100
(1,600)
Total
Chlorinated
PICs
(fjg/s)
2.600-7.700
(4,300)
330-3,100
(1.800)
500-32.000
(7,400)
700-23.000
(8,400)
710-7,300
(4,900)
4,000-12,000
(6.900)
Carbon
Tetra- Chloro-
chloride methane
3.6 0
1.7 0
0
12
5.2
92
Dichloro-
methane
75
49
NA
43
2.9
0
Chloro-
form
6.0
14
61
39
58
2.7
1,1.1-
TCA
and
1.1,2-
TCA
6.4
7.5
2.9
5.7
0
0.5
Dichloro-
ethylene
and
Dichloro-
ethane
2.1
4.4
0
0.09
17
0
Tetra-
chloro-
ethylene
__
23
33
0.04
6.9
2.6
PICs/
POHCs
5.4
380
34
99
29
4.3
Average Results
4.7-1,600
(570)
1,800-8,400
(6.700)
2.7
18
34
30
3.8
3.9
11
92
'Dashes indicate POHC in the waste fuel.
NA—not analyzed.
-------
a.
H
£)G
£
H
H
10'
1 1 1 1
93.0 99.5 99.99 99.999
POHC ORE, percent
Figure 4. PIC emissions versus test average POHC-DRE.
1
99.9999
1
99.99999
The contribution of PIC emissions to
POHC-DRE determination should also be
investigated further.
Reference
1. Dietz, S. et al., "National Survey of
Hazardous Waste Generators and
Treatment, Storage and Disposal
Facilities Regulated under RCRA in
1981," prepared by Westat Inc. for
the Office of Solid Waste, U.S.
Environmental Protection Agency
under contract no. 68-01-6861,
April 1984.
C. Castaldini, S. Unnasch, and H. B. Mason are with Acurex Corporation,
Mountain View, CA 94039.
Robert Olexsey is the EPA Project Officer (see below).
The complete report, entitled "Engineering Assessment Report—Hazardous
Waste Coining in Industrial Boilers," consists of two volumes:
"Volume I. Technical Results," (Order No. PB 85-197 838/AS; Cost: $ 16.00.
subject to change).
"Volumell. Data Supplement," (Order No. PB85-197846/AS; Cost: $23.50.
subject to change).
The above reports 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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U. S. GOVERNMENT PRINTING OFFICE:]986/646-l 16/20737
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