United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S2-82-091 Jan. 1983
Project Summary
Organic Emissions from
Iron Ore Sintering Plants:
Determination of Causes and
Methods of Abatement
Robert A. Stoehr
This report summarizes a laboratory
project to develop basic information
on the emission of organics from iron
ore sinter beds. Samples of sinter mix
and sinter mix components (including
several types of iron ore fines, blast
furnace flue dust, rolling mill scale,
anthracite coal, and limestone) ware
obtained from three sinter producers.
Small samples were heated in a tube
furnace under a 100 ml/min flow of
N2 or air. A combination of total
organic analysis and full chromato-
graphic analysis was used to determine
the rate of organic emissions as a
function of temperature and to char-
acterize the nature of the emissions.
Maximum emissions were observed
between 300° and 500°C. Substantial
emissions occurred as low as 100°
and as high as 800°C. They were less
in air than in Na. indicating that combustion
occurred even at comparatively low
temperatures where the fixed carbon
does not burn. Mill scale and blast
furnace flue dust were shown to be the
major sources of the organic emis-
sions.
These results suggest procedures
for recycling the hydrocarbon bearing
gases through the hot sinter bed to
produce complete combustion and for
thermally pretreating the offending
components.
This Project Summary was developed
by EPA's Industrial Environmental
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
The goal of this project was to develop
basic information on the conditions
under which organics are emitted from
iron ore sinter beds and to investigate
techniques for their elimination at the
source.
Iron ore sintering is one of the prin-
cipal methods for agglomerating iron
ore fines into a feed material suitable for
the blast furnace. Furthermore, it is a
unique agglomerating method in that it
permits the recycling of certain waste
materials which are high in iron value
and fuel value, including rolling mill
scale and blast furnace flue dust and
filter cake. Iron ore fines, iron ore con-
centrates, coke, coke breeze, anthracite
coal, and limestone are used in various
proportions to complete the mix.
The materials are blended, mixed
with a controlled amount of moisture,
agglomerated on a balling drum or disc,
then fed onto the travelling grate of a
downdraft sintering machine. The
material is ignited from the top. Suction
in the windboxes pulls air down through
the bed. The ignited layer, or "flame
front," moves down through the bed as
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the bed moves along the machine on the
travelling grate. The flame front reaches
the bottom of the bed just before the bed
reaches the discharge end of the fine.
Hydrocarbons enter the sinter mix
with a number of components; princi-
pally with blast furnace flue dust and
filter cake, and oil-coated mill scale.
They are volatilized in the preheating
zone below the flame front: since the
conditions are reducing, they either do
not burn or burn incompletely.
Temperatures are not high enough in
the windboxes to ensure burning of the
hydrocarbons after they leave the bed.
The organics emitted from the bed may
be subsequently condensed or allowed
to escape into the atmosphere.
The experiments of this project were
designed to obtain basic information on
the conditions under which organics are
emitted from sinter bed materials to aid
in the control of the process and the
design of systems for improved
pretreatment of components and
recycling of the off-gas.
Experimental Procedures
Sinter mix samples were obtained
from three major producers of iron ore
sinter: Bethlehem Steel, Jones and
Laughlin Steel, and United States Steel.
Samples .were shipped in sealed cans.
In addition to samples of the complete
mix, samples of the sinter mix
components were supplied by the
producers. These components included
rolling mill scale, .blast furnace flue
dust, Quebec ore concentrate, Mesabi
ore fines, Venezuela fines, calcine,
black sand, and anthracite coal.
The general experimental procedure
was to place the specimen on a porous
support in a vertical combustion tube,
heat it at a prescribed rate while passing
a controlled atmosphere through it, and
analyze the effluent gases for organics
using a gas chromatograph (GC) with a
flame ionization detector.
From the beginning, it was realized
that the emissions should be analyzed
continuously so that the total quantity of
organics emitted could be determined.
This proved to be impossible when the
GC was used in a conventional manner,
because a long time (nearly 1 hr) was
needed to provide good separation
between the organics from Ci to C24.
Several unsuccessful techniques
were used in efforts to overcome this
problem before a truly effective
procedure was developed. The
unsuccessful techniques included
capturii
bottles
could
organic
analysis
conden;
tures,
measur
is heate
A su
combin
which d
continu
graphic
perform
The
sinter
Figure
a vertic
tube (C
the sarr
resistan
thermo
measur
penden
The
connec
(0.125-
steel li
filter (E)
The eig
was in
theGC.
Figure
the off-gas in gas sampling
hich were stored until they
e analyzed, absorbing the
n hexane or benzine for later
capturing the organics by
tion at liquid nitrogen tempera-
d measuring emissions by
g weight loss as the specimen
essful technique involved a
on of total organic analysis,
uld be performed on a nearly
us basis, and full chromato-
analysis, which could be
d at selected temperatures.
entual apparatus for testing
x components is shown in
A 3,0-g sample was placed on
13-mm diameter silica glass
A fritted silica disc supported
le. The tube was heated in a
e-wound tube furnace (B). A
uple directly in the sample
I the sample temperature inde-
f of the furnace temperature.
ample heating tube was
d to the GC through a 3.17-mm
) diameter heated stainless
e (0). A heated glass fiber
the line removed particulates.
-port gas sampling valve (F)
leated compartment on top of
ach time the sample valve was
actuated, a 1-ml gas sample was
injected into the GC. This sample valve
resulted in much less variability than
the hypodermic syringes used
previously.
A 3.0-g sinter mix sample size was
chosen because it allowed all of the off-
gas to go through the sample line and
valve without overloading the flame
ionization detector in the GC. The gas
flow rate was standardized at 100
ml/min.
To perform total organic analysis, a
short (25.4 cm or 10 in. long) column of
SP 2100 on 80/100 Supelcoport was
used at a constant oven temperature of
250°C. This caused all of the organics to
be eluted to the flame ionization
detector (FID) in a single peak. The FID
responded specifically to organic
carbon. Tests have verified that other
carbon (such as C02> does not interfere.
Because only one peak needs to be
observed, sample repetition time could
be as short as 15 sec.
For full chromatographic separation
of the organics, a 1.83 m (6 ft) long
column of SP 2100 on 80/100
Supelcoport was used. The column
oven temperature was programmed,
starting at 50°C and heating at 10°C per
minute to a final temperature of 250°C.
This produced a separation of the or-
II
I I
H
A = Gas Supply
B = Tube/Heating Furnace
C = 13-mm Vycor Sample
Tube with Fritted Disc
D = Heated Line
E = Filter
F = fight-port Sample Valve
G = Gas Chromatograph
H = Flame Ionization
Detector
Sinter mix component apparatus.
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ganics from d to €24, but it took more
than 1 hour from sample to sample,
including the oven cooling time.
Results and Conclusions
Major conclusions from these
experiments include:
1. Mill scale and blast furnace flue
dust are the major sources of
organic emissions from sinter
beds.
2. The range of temperatures over
which substantial emissions
occur varies with the producer
and the components used in the
mix. It may extend from 100° to
nearly 800°C.
3. Higher oxygen potentials result in
lower organic emission rates.
Combustion of some of the hydro-
carbons occurs, even though the
temperatures are too lowfor igni-
tion of the fixed carbon.
4. The full chromatographic
analyses reveal that the
emissions are predominantly of
low molecular weight, indicating
that thermal decomposition is
occurring. This effect becomes
more pronounced at highertemp-
eratures. The percentage
reduction of emissions in air is
much greater in the complete
sinter mix than in the individual
components. The greater
reductions achieved on the
complete mix probably indicate
that the oxidation of organics at
these temperatures requires a
surface, and that the iron oxides
and other materials, which are
more prevalent in the complete
mix, provide such a surface.
5. Thermal pretreatment of the
offending components could
effectively remove the hydrocar-
bons while leaving the fixed
carbon.
6. The analytical procedures
developed for this project could
be applied to monitoring organic
emissions on industrial sinter
lines.
Robert A. Stoehr is with the University of Pittsburgh, Pittsburgh, PA 15261.
Robert C. McCrillis is the EPA Protect Officer (see below).
The complete report, entitled "Organic Emissions from Iron Ore Sintering
Plants: Determination of Causes and Methods of Abatement," (Order No. PB
83-116 897; Cost: $8.50, 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
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
U S. GOVERNMENT PRINTING OFFICE: 1983 - 659-O17/O
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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