United States
Environmental Protection
Agency
Research and Development
Industrial Environmental
Research Laboratory
Cincinnati OH 45268
EPA-600/S2-84-148 Nov. 1984
v°/EPA Project Summary
Molten Salt Destruction of
HCB and Chlordane—
Bench- and Pilot-Scale Tests
S.J. Yosim, L.G. Kellogg, and S. Sudar
A research test program to demon-
strate the destruction of chlorinated
materials by the Molten Salt Destruction
(MSD) process was conducted. The
chlorinated materials tested were solid
hexachlorobenzene (HCB) and liquid
chlordane. The program consisted of
bench-scale and pilot-scale tests. The
bench-scale destruction and removal
efficiency (ORE) of HCB exceeded
99.999% at 900 to 1000°C. The HCB
concentration in the spent melt was
<0.001 ppm. The bench-scale ORE for
chlordane was >99.9999% with excess
air. The concentration of chlordane in
the melt was <0.01 ppm. The HCI
concentration in the off-gas for both
wastes was <100 ppm.
The pilot-scale DRE of HCB due to
the molten salt destructor alone ex-
ceeded 99.9999% in all cases. In some
tests, the DRE exceeded 8-9's
(99.999999%). The concentration of
HCB in the melt was < 0.1 ppm. In the
case of chlordane, the DRE due to the
molten salt destructor alone exceeded
99.9999% in all cases but one, in which
the DRE was 99.99983. In two cases, it
exceeded 7-9's. The chlordane concen-
tration in the melt was <1 ppm.
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory. Cincinnati, OH.
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
The resolution of problems associated
with the management of hazardous
waste is important to public health and
safety. Action by local, state, and federal
agencies in response to expressed public
concern has stimulated the industrial and
technical community to undertake signi-
ficant waste management efforts. Some
of the conventional methods previously
believed acceptable for treating these
wastes have subsequently proven to be
unacceptable. Thus, alternate methods
and particularly those that assure com-
plete and safe waste destruction as
opposed to land burial, surface impound-
ment, conventional incineration, etc. are
being investigated. An alternate method
that shows promise for efficient waste
destruction is the Molten Salt Destruction
(MSD) process.
This process is based on the use of a
molten turbulent bed of salt, such as
sodium carbonate, as a heat transfer and
reaction medium. Combustible waste
and air are continuously introduced
beneath the surface of the molten salt at
800 to 1050°C. The off-gas containing
carbon dioxide, steam, nitrogen, and
unreacted oxygen is cleaned of particu-
lates in commercial applications by
passing it through a baghouse. Acidic
gases, such as HCI and SC-2, produced
from halogenated organic compounds
and sulfur-containing organic compounds,
respectively, are neutralized and the
neutralized products are retained by the
alkaline NasCOa- The sodium carbonate
used as the active salt bed component
was selected because it is compatible
with the combustion products, C02 and
H20, and because it reacts with acidic
gases such as HCI produced from organic
chloride compounds. It is also relatively
inexpensive, nontoxic, stable, and non-
volatile.
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Although many tests on different types
of hazardous wastes demonstrated high
destruction efficiency on a bench-scale
level (—0.5 kg/h), no tests on hazardous
wastes had been conducted on the pilot-
scale level (~50 kg/h). Accordingly, a
research test program to demonstrate the
destruction of chlorinated materials was
conducted. The chlorinated materials
tested were solid hexachlorobenzene
(HCB) and liquid chlordane. The HCB was
considered to be a simulant for RGBs and
the chlordane was representative of
liquid chlorinated industrial wastes. The
overall objective of the test series was to
provide molten salt process performance
data and to challenge the molten salt
process limits for adequate waste de-
struction. The program consisted of
bench-scale and pilot-scale tests.
Description of Bench-Scale
and Pilot-Scale Units
The bench-scale molten salt destructor,
shown in Figure 1, consisted fo a 15.2-
cm-ID x 91,4-cm-high vessel mounted in
a Type 321 stainless steel container. The
3.7-cm ID metal downcomer was adjusted
so that its tip was —1 cm above the bottom
of the 15-cm diameter metal reactor tube.
Thus, the waste-air mixture was forced to
pass downward through the downcomer,
A'
Injector
Tube
Hopper
Sco
Screw
Feeder
Off-Gas Outlet
(Sampling System
Inserted Here)
Retainer
Vessel
Metal
Downcomer
Electric
Furnace
Metal
Tube
Molten
Salt
Soot
Blower
Cast Alumina
Melt
Overflow
Port
Fused Alumina
Liquid Injector
Figure 1.
Bench-scale molten salt destruc-
tor with solids feed.
Figure 2. MSTF destructor vessel.
outward at its bottom end, and then
upward through the salt The HCB mixed
with coke was metered from the hopper
by a screw feeder. The liquid chlordane
waste was fed with a peristaltic pump.
The Rockwell International Molten Salt
Test Facility (MSTF) was utilized for the
pilot-scale tests. The molten salt destruc-
tion vessel at the MSTF (shown m Figure
2) is a vertical steel tank approximately
6.7-m high with a 1.2-m outside diameter.
It is internally lined with a 0.15-m-thick
refractory liner made from high purity,
fused cast alumina blocks. Four injection
nozzles are provided on the combustor,
located 90° apart from each other. Two of
the opposing nozzles are used for
injection of preheated combustion air
only. The other two opposing nozzles are
horizontal and may be used for solids/
fuel/waste/salt injection Make-up salt
feeding iscontinuousandmeltwithdrawal
is accomplished in a continuous overflow
system. The balance of the MSTF equip-
ment consists of auxiliaries for materials
storage and feed, off-gas processing and
cleaning equipment, and supporting
analytical and control instrumentation.
South
Nozzle
The HCB was metered out of the lock
hopper using a variable speed rotary
valve. Chlordane was fed from a 0 25-m3
(65-gal) pressurized tank, filtered, and
then passed into the atomizer gun
through a flow control valve
Results of Bench-Scale Tests
A summary of the HCB results, which
includes the concentrations of HCB in the
off-gas and in the melt, is given in Table 1.
Excellent destruction was obtained in all
cases except in the 800°C test. The best
destruction efficiency (>99.9999960%)
was obtained at 1000°C (Test 2). Excellent
destruction efficiencies were also ob-
tained at 900°C (99.999971%) and at
1000°C, 70% of stoichiometric air
(99.999980%). No HCB was detected in
any melt sample (<0.001 ppm) even
though the samples were taken while
HCB was being fed. This is considered
significant due to the short residence
time of the feed in the expanded melt
(—3/4 s) and is indicative of the rapid
kinetics of HCB destruction in the melt.
The concentration of HCB in the off-gas
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was extremely low in all cases except for
the 800°C test.
Table 2 gives a summary of the
chlordane results and includes the
concentrations of chlordane in the off-
gas and in the melt. Excellent chlordane
destruction (>99.9999%) was obtained in
Test 2 and 3. In the off-spec test (Test 4),
the efficiencies determined from the gas
chromatograph/electron capture peaks
were 99 99%. However, when the sample
was examined by GC/MS, it was found
that the peaks were not due to chlordane
isometric. Thus, the destruction efficien-
cies were probably much greater than
99.99%.
No chlorine or phosgene was detected
and the HCI emissions were <100 pppm
in both HCB and chlordane tests.
Results of Pilot-Scale Tests
In the case of the HCB tests, the melt
temperatures varied from 918° to 985°C.
The HCB feed rate generally increased
with each succeeding test and ranged
from 21 kg/h to 122 kg/h. In the case of
chlordane, the melt temperature ranged
from 896°C to 991 °C. The chlordane feed
rate generally increased with each
succeeding test and ranged from 12 kg/h
to 33 kg/h. The destruction results for
HCB and chlordane are shown in Table 3
and 4, respectively. The top half of each
table shows the results from Sample
Location 1, which is just downstream of
the destructor vessel and thus gives an
indication of the performance of the
molten salt. The lower half of each table
shows the results from Sample Location
2, which is downstream of the baghouse
and thus gives an indication of the
performance of the entire destruction
system.
The HCB and chlordane DREs measured
at Sampling Location 1 were greater than
6-9's (>99.9999%) in all tests except for
chlordane Test 1, in which the ORE was
99.99983. Thus, the salt melt was very
Table 1. Summary of HCB Bench-Scale Results3
Test
No
2
3
4
5
Type of
Test
Baseline
Lower Temp
Minimum Temp
Off Spec
Temp
<°C)
1004
902
803
1009
% Stoich
Air
118
127
111
70
Cone of HCB
in Off -Gas
(ppmv) (mg/m3)
99.9999960
99.999971
99.87
99.999980
Destruction
and Removal
Efficiency
<%)
>99. 9999986
99.999974
99.87
99.999982
analyses of the HCB samples were done in accordance with EPA Method 612
Table 2. Summary of Chlordane Bench-Scale Results3
Test
No
2
3
4
Type of
Test
Baseline
900°C
Off-Spec
Temp
<°C)
999
898
1002
% Stoich
Air
121
118
81
Cone of Chlordane
in Off-Gas
(ppmv) (mg/m3)
<0.0013
<0.0027
<0.24
<0.022
<0.045
<4.18
Cone of Chlordane Destruction
in Melt Efficiency
(ppmw) (%)
<0.0086
<0.0072
<0.12
>99. 99989
>99. 99986
>99.9934
Destruction
and Removal
Efficiency
!%)
>99. 999951
>99. 999903
>99.9934
"The analyses of the extracted chlordane samples were done in accordance with EPA Method 608.
Table 3.
Pilot-Scale HCB Destruction Results
Sample Location 1
Test
No.
1
2A
2B
3A
3B
HCB
Feed
Rate
(kg/h)
21 4
20.9
34.4
508
122
Concentration of
HCB
(ppmv)
2.4 x 70"5
<7.0 x W~5
2.0 x 10~3
<1.1 x 10'4
6.3 x 10~3
in Off-Gas
(mg/m3)
2.7 x ro~4
<80x 10~'
2.2 x J0~2
<1.3 x 10~3
7. 1 x 10~2
Conc'n of
HCB in
Melf
(ppmw)
NM"
NMa
0.001
NMa
0.10
% of HCB Feed
Found in
Off-Gas
039 x W~s
<1 3 x 70~6
21 x 10~6
<0.84 x 10~6
19 x 10~e
a
Melt
NM"
NMa
4.1 x 70~6
NMd
230 x 10~e
Destruction
Efficiency
(%)
NM°
Nlvf
6-9's 74
Ntvf
5-9's 77
Destruction
and Removal
Efficiency
(%)
8-9's 61C
>7-9's 87
6-9's 79
>8-9's 19
6-9's 81
Sample Location 2
Test
No.
1
2B
3B
HCB
Feed
Rate
(kg/h)
21.4
34.4
122
Concentration of HCB
in Stack Gas
(ppmv) (mg/m3)
<5.2 x 7CT7 <6.0 x 10~6
<2.4 x ;cr6 <27xio~5
9.4 x ;cr6 1.6 x io~"
%of
HCB Feed
Found in
Stack Gas
<9 x J0~9
<2 7 x 10~a
44 x /O"8
Destruction
and Removal
Efficiency
(%)
>10-9's 09C
>9-9's 73
9-9's56
a
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Table 4.
Pilot-Scale Chlordane Destruction Results
Sample Location 1
Test
No
1
2A
2B
3
4
Chlor-
dane
Feed
Rate
(kg/h)
12.1
24.6
30.8
32.7
25.0
Concentration of
Chlordane in Off Gas
(ppmv) fmg/m3)
35x10~3 59x7CT2
2.1x10~3 3.5 x 70~2
4.1x10~3 6.8x10'*
3.4x70"4 5.7 x 70~3
32x70~4 53x10~3
Conc'n of
Chlordane
in Melt
(ppmw)
<0.005
<0.004
<1 2
<1 2
<043
% of Chlordane Feed
Found in
Off-Gas Melt
170 x 70"6
43 x 10's
68 x 70"6
53 x 7CT6
65 x 70'6
<2 6 x 70"5
<2 0 x 70 5
<3.0 x 70~3
<3 9 x 70"3
<7 4 x 10~3
Destruction
Efficiency
5-9's 87a
6-9's 37
>4-9's 70
>4-9's 61
>4-9's 85
Destruction
and Removal
Efficiency
5-9's 83
6-9's 55
6-9's 32
7-9's 47
7-9's 34
Sample Location 2
Chlor-
dane
Test
No.
1
2A
2B
3
4
Chlor-
dane
Feed
Rate
(kg/h)
12 1
246
308
32.7
25.0
Concentration of Chlordane
in Stack Gas"
(ppmv) (mg/m3)
<2.5 x W5 <4 1 x 70""
<3 7 x 7CT5 <5. 7 x 70""
<2.2xW~5 <36x10~A
<27 x 10~* <4.4 x 10'*
<47x10'5 <7.8x10'<
%of
Chlordane
Found in
Stack Gas
<1.2x 70"6
<064 x 70~6
<0.36x 70'6
<4.1 x 70~6
<0.86 x 70~6
Destruction
and Removal
Efficiency
<%)
>7-9's 88"
>8-9's 36
>8-9's 64
>7-9's 59
>8-9's 14
*5-9's 81 denotes 99.99981%, 7-9's 88 denotes 99.9999988%
b
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S. J. Yosim, L. G. Kellogg, andS. Sudar are with Rockwell International, Canoga
Park, CA 91304.
Richard A. Carries is the EPA Project Officer (see below).
The complete report, entitled "Molten Salt Destruction of HCB and Chlordane—
Bench- and Pilot-Scale Tests, "(Order No. PB 84-246 354; Cost: $14.50, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PA
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
*6ENCt
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