Reduction Behavior of Iron Ore Pellets with Simulated Coke ...
Transcript of Reduction Behavior of Iron Ore Pellets with Simulated Coke ...
Reduction Behavior of Iron Ore Pellets withSimulated Coke Oven Gas and Natural Gas
Elsayed A. Mousa,� Alexander Babich, and Dieter Senk
Recently a special attention is being paid on the combination of different ironmaking
technologies in the integrated steel plant to maximize the efficiency of the overall
process. The utilization of coke oven gas for production of direct reduced iron (DRI) in the
integrated steelmaking route is still under evaluation and discussion. In this study, iron
ore pellets were isothermally reduced with simulated original and reformed coke oven
gas (RCOG) at 700–9808C. The results were compared with those obtained by the
reduction of pellets with the original and reformed natural gas (RNG). The highest
reduction degree was obtained for the pellets reduced with RCOG while the lowest
reduction degree was exhibited by original natural gas. On the other hand the rate of
reduction with original coke oven gas was sharply increased at temperature of about
9008C to become higher than that of RNG. A slow down phenomenon appeared at the
later stage of reduction due to the intensive carbon deposition. The soot formation
increased as CH4 content and/or the temperature of reducing gas increased. Reflected
light microscope, scanning electron microscope with EDX, and high performance X-ray
diffraction analysis were used to estimate the reduction kinetics and mechanism.
1. Introduction
Steel production can be classified into four main routes
including blast furnace-basic oxygen furnace (BF-BOF),
direct reduction-electric arc furnace (DR-EAF), smelting
reduction-basic oxygen furnace (SR-BOF), and melting of
scarp in electric arc furnace.[1–3] The production of hot
metal in BF is dependent significantly on metallurgical
coke as a source of heat and reducing agent while it
dependent on natural gas in DR processes. The BF was
always referred as ‘‘traditional’’ ironmaking method while
DR and SR processes were often identified as ‘‘alternative’’
methods. Nowadays a combination of different routes and
technologies within an integrated steel works is being dis-
cussing more and more in order to reduce the energy
consumption and CO2 emissions.[4,5] It was reported that,
the production of DRI in the integrated steel route through
the addition of DR process (Midrex or HyL) depending
on the utilization of by-product gases has different
benefits.[6,7] From the economic view, the DRI could be
used in the blast furnace to decrease the consumption of
coke and/or pulverized coal as well as increasing of hot
metal production. An alternative application of DRI is to
use it as coolant in BOF either to replace scrap or increase
the production of crude steel. From the environmental
side, the utilization of DRI in BF or BOF will be very
effective in decreasing the CO2 emissions in steel
industry.[8,9]
The major fuel gases that can be recovered in the inte-
grated steel works are including blast furnace gas (BFG),
coke oven gas (COG), and basic oxygen furnace gas
(BOFG). The COG has the largest net calorific value in
the range of 16.4–18MJNm�3 (STP) compared to that of
BOFG (�8.8MJNm�3) or BFG (3.0–3.7MJNm�3).[6] The
specific amount of generated coke oven gas is in the range
from 410 to 560Nm3 t�1 coke depending on the volatile
matters in the coal charge.[6] In 2011, the worldwide coke
production reached a new record with 641.4million tonnes
with COG amounted to be more than 310 billion Nm3.[10]
The COG is currently used after its cleaning from tar,
naphthalene, raw benzene, ammonia, and sulfur for heat-
ing of blast furnace stoves, ignition furnaces in sintering
plant, heating furnace in rolling mills and electric power
generation in power plant.[7,11,12] The estimations which
carried out on optimizing the energy consumption in
the integrated iron and steel works indicated that the
[�] Dr. E. A. MousaCentral Metallurgical Research and Development Institute (CMRDI),PO Box 87-Helwan, Cairo, EgyptEmail: [email protected]. A. Babich, Prof. D. SenkDepartment of Ferrous Metallurgy, RWTH Aachen University,Intzestr. 1, 52072 Aachen, Germany
DOI: 10.1002/srin.201200333
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utilization of COG for power generation is not always the
optimal credits.[7] The COG consists of about 58% H2,
27% CH4, 7% CO, and small amount of CO2, N2, and other
elements.[13] This composition of COG which is rich with
hydrogen has attracting much attention in the recent years
for its utilization in the reduction processes.[13–18] The
injection of COG in BF is already put in practice.[1,13,16,19,20]
The application of COG for production of DRI in integrated
steel plant is still under discussion and evaluation.[6,7,21] In
addition the evaluation of the reduction kinetic and mech-
anism of iron burden with COG in direct reduction process
is not clear and the investigations which are carried out
on the reduction behavior using multicomponent gas
mixtures are little.[22–26]
The current study aims at investigation of the reduction
kinetics andmechanism of iron ore pellets using simulated
original and reformed COG. The results are compared with
that obtained from the application of either natural gas or
simulated reformed natural gas (RNG). The reduction has
been carried out isothermally at temperatures in the range
of 700–9808C. The temperature range was selected to
simulate the reduction zone in Midrex shaft furnace and
the maximum applied temperature in HyL process.[27,28]
The structure and morphological changes of reduced pel-
lets were intensively studied and correlated with the
reduction kinetics and mechanisms.
2. Experimental Work
The reduction of industrial iron ore pellets has been carried
out using a laboratory system as shown in Figure 1.[29]
The system consists of vertical tube Tammann furnace
connected with an automatic sensitive balance. Alumina
reaction tube is fitted inside the graphite heating tube
where the heat is mainly transferred through the radiation
to the iron ore pellets. The crucible containing samples are
hold by a Pt-Rh-wire, which is connected to a balance for
continuous measuring of the weight loss as a function of
time. With a pneumatic cylinder, the sample can be lifted
up and down within seconds into the Tammann furnace.
The temperature was measured with platinum (Pt 18)
thermocouple which fixed near to the sample. Purified
Ar with flow rate of 1.0 Lmin�1 is purged in the reaction
tube from the bottom during the heating up of the furnace
to the pre-determined temperature. At the applied
temperature, the pellets was placed in a basket and lifted
down to the middle of hot zone in the furnace. After
soaking the sample at this temperature for 10min, a reduc-
ing gas simulated the reformed coke oven gas (RCOG),
original coke oven gas (OCOG), RNG, and original natural
gas (ONG) as given in Table 1 is purged into the reduction
alumina tube with flow rate of 3.0 Lmin�1 while the Ar gas
is stopped during the reduction periods.
During the reduction experiment, the weight loss was
continuously recorded as a function of time. At the end of
experiment, the reduced pellet was lifted up and putted in
closed chamber under high flow rate of Ar to avoid the re-
oxidation during cooling. For partial reduction, the oxygen
weight loss required to achieve a certain reduction extent
was pre-calculated and the reaction is stopped when the
weight loss reached the predetermined value. The total
reduction degree was determined depending on the cal-
culation of oxygen represented in iron oxides of pellets.
The iron ore pellets were examined before and after
reduction by reflected light microscope (RLM – Leica
Aristomet) and scanning electron microscope-backscattered
electron image (SEM-EDX/BSE, ZEISSDSM 962). The formed
phases and its quantitative analysis were identified by high
performance X-ray diffractometers (Cu Ka1 radiation).
3. Results and Discussion
3.1. Characterization of Raw Materials
The chemical analysis of industrial iron ore pellets is given
in Table 2. The basicity (wt% CaO/wt% SiO2) of pellets is
Figure 1. Scheme of the Tammann furnace experimental set:1: flow controller; 2: pneumatic cylinder; 3: electronic balance,4: computer, 5: thermocouple; 6: graphite tube; 7: sample;8: alumina tube; 9: alumina balls; 10: quartz glass; 11: gas supply.[29]
H2 (vol%) CO (vol%) CH4 (vol%)
RCOG 77.5 22.5 0
OCOG 60 10 30
RNG 55 35 10
ONG 0 0 95þ 5% CnHm
Table 1. Composition of the applied reducing gases.
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equal to 0.67 which indicates the acidic properties of the
applied pellets. X-ray diffraction analysis of the applied
pellets exhibited that the pellets were composed of two
main phases: Fe2O3 and SiO2 as given in Figure 2. The
microstructure of the pellet was examined with optical
light microscope and SEM–EDX in order to determine
the most common structure of the identified phases as
shown in Figure 3 and 4; respectively. Figure 3a illustrates
the distribution of dark gray color grains all over the matrix
structure in addition to the presence of pores with different
diameters. Figure 3b gives more focus on the microstruc-
ture of pellets showed the presence of pale white grains and
light gray phase filled the micropores. These phases are
identified with SEM–EDX as shown in Figure 4. The main
phase was hematite (Fe2O3) and the gray color grains were
silica (SiO2) while the gray patches between hematite
grains were calcium silicate (Ca2SiO4).
3.2. Reduction Behavior
Typical reduction curves of pellets isothermally reduced
with RCOG, OCOG, RNG, and ONG at different tempera-
tures (700–9808C) are given in Figure 5a–d, respectively.
The reduction degree of pellets was increased with increas-
ing the applied temperature in all cases. A slow down
phenomenon was appeared at the final stage of reduction
Element Fe FeO SiO2 Al2O3 CaO MgO P Mn CaO/SiO2
wt% 64.54 0.2 3.75 0.91 2.51 0.04 0.034 0.12 0.67
Table 2. Chemical analysis of industrial pellets.
Figure 2. XRD phases analysis of the applied iron ore pellets.
Figure 3. Photomicrographs of the applied iron ore pellets: (a) x¼ 50 (b) x¼ 1000.
Figure 4. SEM–EDX photomicrographs of the applied iron orepellets.
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with OCOG, RNG, and ONG at 900–9808C. The reduction
with RCOG was not accompanied by such phenomenon
and the reduction degree was reached about 99% at 9808C.A comparison between the reduction curves at the same
temperature is given in Figure 6a–d. The reduction with
RCOG showed the highest value amongst all gases while
the reduction with ONG showed the lowest value of
reduction. The reduction rate with OCOG became higher
than that of RNG until certain extent (�80%) after which
the slow down phenomenon took place which attributed to
the carbon deposition. The reduction with ONG at 700–
8008C was sluggish (�15%) while it was reached to 70–89%
for the other gases at the same temperature. As the
temperature increased the reduction with ONG was
sharply increased to reach about 50 and 80% at 900 and
9808C, respectively.The relationship between the rate of reduction (dr/dt) at
both the initial (20% reduction degree) and advanced
reduction stages (70% reduction degree) against tempera-
ture is given in Figure 7a and b, respectively. This relation
was not adequate for the pellets reduced with ONG due to
the very low reduction degree at 700 and 8008C. It can be
seen that, the reduction rate increased with temperature
for all reducing gases at both the initial and final stages. It is
remarkable that, the rate of reduction of pellets with OCOG
became higher than that of pellets reduced with RNG at
temperatures higher than 8008C.
3.3. Reduction Kinetics and Mechanisms
The rate controlling mechanism at different reduction
stages can be determined from the correlation between
the apparent activation energy values, application ofmath-
ematical models and the microstructure investigation of
the reduced pellets at different reduction degrees. The
values of apparent activation energy (Ea, kJmole�1) were
Figure 5. Isothermal reduction curves of pellets reduced at different temperature with: (a) RCOG (b) OCOG (c) RNG (d) ONG.
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computed from Arrhenius equation as given in Equation 1
and 2.
Kr ¼ Ko e�Ea=RT (1)
Ea ¼ RT ln Ko=Kr (2)
where Kr is the reduction rate constant (s�1), Ko the
frequency factor (s�1), Ea the apparent activation
energy (kJmole�1), R the universal gas constant
(8.314� 10�3 kJmole�1 K�1), and T is the absolute
temperature (K).
From the Arrhenius plots (log dr/dt vs. 1/T� 104) given
in Figure 8, the apparent activation energy values were
calculated at different reduction degrees. The computed
values are given in Table 3. At the initial stages of reduction
(20% R), the rate controlling mechanism seems to be inter-
facial chemical reaction for RCOG and OCOG while it is a
combination of gaseous diffusion and interfacial chemical
reaction for RNG. At higher reduction degree (70% R),
the rate controlling mechanism could be solid state diffu-
sion in all cases with some contribution of interfacial
chemical reaction. The higher values of activation energy
(119.46 kJmole�1) obtained for the reduction with OCOG
at the later stages is mainly attributed to the slow down
phenomenon due to the soot carbon formation.
In order to confirm the validity of the rate controlling
mechanism which estimated from the apparent activation
Figure 6. Comparison between reduction curves of pellets reduced with different gases at: (a) 7008C, (b) 8008C, (c) 9008C, and (d)9808C.
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energy values, the experimental results were tested against
the integral expressions derived from an approximation of
‘‘un-reacted core model.’’[30] The integral expression of the
reduction kinetics of iron oxide is given in Equation 3.
roroCoA � Ce
A
f
Kgþ ror
2o
6De CoA � Ce
A
� � 1� 3 1� fð Þ2=3 þ 2 1� fð Þ� �
þ K
Kþ 1þ Kð Þroro
CoA � Ce
A
1� 1� fð Þ1=3� �
¼ t
(3)
where t is the chemical reaction time, po the density of
oxygen of solid phase constant, CoA the initial concentration
of reducing gas, CeA the equilibrium concentration of
reducing gas, Kg the mass transfer coefficient of gas phase
in the phase boundary layer, De the effective diffusion co-
efficient of the reducing gas in the product layer, Kþ the
positive interface reaction rate constant, and K is the reac-
tion equilibrium constant.
Under the applied conditions, the external gas diffusion
resistance can be neglected due to the proper gas flow rate
(3.0 Lmin�1) which is able to overcome the gas boundary
layer around the pellets. Therefore the reaction time (t)
is proportional to ½1� 3ð1� f Þ2=3 þ 2ð1� f Þ� when the
reduction process controlled by internal gaseous diffusion
while it is proportional to ½1� ð1� f Þ1=3� when the
reduction process controlled by interfacial chemical reac-
tion. If the gas–solid reaction is hybrid controlled by com-
bined effect of internal gaseous diffusion and interfacial
Figure 7. Effect of temperature on the reduction rate of pelletsreduced with different gases at: (a) 20% reduction degree and(b) 70% reduction degree.
Figure 8. Arrhenius plots for pellets reduced with different gasesat: (a) 20% reduction degree and (b) 70% reduction degree.
Gas mixtures Regression equations Ea, kJmol�1 (�3.0)
20% Reduction 70% Reduction 20% R 70% R
RCOG log K¼ 3.4350� 0.31� 1/T log K¼ 4.203� 0.415� 1/T 59.15 79.19
OCOG log K¼ 3.7642� 0.33� 1/T log K¼ 5.846� 0.626� 1/T 62.97 119.46
RNG log K¼ 2.6304� 0.21� 1/T log K¼ 4.6147� 0.490� 1/T 40.07 93.5
Table 3. Activation energy values for the pellets reduced with different gases.
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chemical reaction, the reduction time t will proportional to
½ð1� 3ð1� f Þ2=3 þ 2ð1� f ÞÞ þ ð1� ð1� f Þ1=3Þ�.On applying the mathematical formulations corre-
sponded to the interfacial chemical reaction, a set of
straight lines was obtained for the pellets reduced with
RCOG andOCOG at the initial stages of reduction as shown
in Figure 9a and b, respectively. It can be seen some
deviations of experimental results from the straight lines
at temperature�8008C as the reduction proceeded. On the
other hand a set of straight lines was obtained by appli-
cation of the hybrid control mathematical equation on the
experimental results of pellets reduced with RNG as shown
in Figure 9c. This confirmed the reduction mechanism
which exhibited by apparent activation energy calculation
at the initial stages. At the advanced reduction stages, a set
of straight lines with different deviations at the later stages
was obtained on the application of interfacial chemical
reaction equation on the experimental results of RCOG,
OCOG, and RNG as shown in Figure 10a–c, respectively.
This indicates that the reduction mechanism at the
advanced reduction stages was controlled by chemical
reaction followed by solid state diffusion mechanism at
the final reduction stages as the sharp deviation from the
straight lines took place.
The microstructure investigation was carried out to
clarify the controlling mechanism at both the initial and
final stages of reduction. The microstructure of pellets
reduced with the different gases at 9808C up to 20%
reduction degree is given in Figure 11a–d. Figure 11a
and b showed some grains of metallic iron (white grains)
randomly distributed on the structure which indicated the
lower resistance of gaseous diffusion and the prevailing
contribution of the interfacial chemical reaction. A similar
behavior can be observed for the reduction with ONG at
the initial stages of reduction as shown in Figure 11d. This
can be attributed to the high diffusivity of H2. On the other
hand Figure 11c illustrates a structure of metallic iron
grains with lower iron oxides at the outer layer and the
appearance of metallic iron decreased in going to the core
of pellets showed an interface between the outer and
Figure 9. Testing of experimental data against the mathematical equations at the initial stages of reduction with: (a) RCOG, (b)OCOG, and (c) RNG.
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middle layers. This confirmed that the rate controlling
mechanism was a mixture of interfacial chemical reaction
and gaseous diffusion for the reduction with RNG at the
initial stages of reduction.
The microstructure of pellets reduced with different
gases up to 70% at 9808C is given in Figure 12. The outer
layers in all cases consisted mainly of metallic iron grains.
The connections between the metallic iron grains are sig-
nificant in the case of RCOG while it is small in the case of
ONG. The middle and core layers showed wustite grains
which are entrapped inside shells of metallic iron. The
formation ofmetallic iron shells prevents the direct contact
of reducing gas with wustite and consequently the
reduction proceeded mainly with solid state diffusion
mechanism.
Figure 13 illustrates the effect of temperature on the
microstructure of reduced samples. There is no remarkable
difference between the microstructure of samples reduced
with different gases at 8008C except that reduced with ONG
where no metallic iron was developed because the
reduction process was inactive (only �15% reduction).
As the temperature increased up to 9808C, the metallic
iron grains became denser especially in the case of
OCOG and ONG with the development of macropores.
The effect of temperature appeared clear on the micro-
structure of the pellets which are reduced with ONG at
9808C (�80% reduction) compared to that reduced at
8008C (�15% reduction).
3.4. Carbon Deposition Phenomenon
In order to clarify the influence of temperature on the
higher reduction rate of pellets reduced with OCOG and
ONG and the sharp slowdown at the later stage of
reduction, the samples were analyzed using high perform-
ance X-ray diffractometers as shown in Figure 14a–d. It
was found the formation of Fe3C and carbon in the pellets
reduced with OCOG, RNG, and ONG while it was not
Figure 10. Testing of experimental data against the interfacial chemical reaction mathematical equation at the final stages ofreduction with: (a) RCOG, (b) OCOG, and (c) RNG.
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appeared in the case of RCOG. The quantitative analysis of
the different phases that developed after reduction at
9808C is given in Figure 15. The pellets reduced with
OCOG andONG exhibited higher ratios of Fe3C and carbon
deposition compared to that formed with RNG which is
mainly attributed to the higher content of CH4. The pres-
ence of CH4 in the reducing atmosphere was responsible
for the carbon deposition and iron carbide formation
which resulted in weight gain or ‘‘slow down phenom-
enon’’ at the later stage of reduction. Figure 16 showed
the outer surface of the pellets reduced with RCOG and
OCOG compared to that of original pellets. It can be seen
extensive development of cracks on the outer surface of the
pellet reduced with RCOG due to the high reduction rate of
the applied gas. The pellets reduced with OCOG were
completely coated with a layer of soot carbon. In order
to clarify the deposition of soot on the outer layer of pellets,
a cross is given Figure 17. The external layer is soot carbon
followed by a diffused layer of carbon and iron carbide and
the core of metallic iron.
During the reduction with gases containing methane,
the cracking of CH4 to H2 and carbon took place at
temperature higher than 8008C as given in Equation 4.
At temperatures �8008C the cracking was inactive and
the reduction ceased at low reduction extent (Figure 8).
At temperatures �9008C, the developed H2 and soot are
participated in the reduction process as given in
Equation 5–7.[31] In such multicomponent mixture, the
developed H2O and CO2 from the reduction process could
be in situ react with CH4 or developed active carbon to
generate further H2 and CO as given in Equation 8–12.[32]
The developed gases were enhanced the reduction rate
through increasing the reduction potential of the sur-
rounding atmosphere. Therefore the overall reaction
(Equation 5) was controlled primary by the rate of CH4
decomposition and the actual reduction rate was con-
trolled by the developed H2 and carbon.[31] In the case
of OCOG which contains 30% CH4, the reduction rate
was sharply increased at temperature higher than 8008Cdue to the positive effect of the input and developed H2
compared to that in RNG. It was reported that, the rate of
reduction by H2 is 3–6 times faster than that of CO and 4.5
times faster compared to that of CH4.[31,33,34]
CH4 ðgÞ ¼ CðsÞ þ 2H2 ðgÞ DHo298 ¼ þ74:5kJmol�1 (4)
½O�oxide þ H2ðgÞ ¼ H2OðgÞ (5)
½O�oxide þ CðsÞ ¼ COðgÞ (6)
Figure 11. Photomicrographs of pellets reduced up to 20% reduction degree at 9808C with: (a) RCOG, (b) OCOG, (c) RNG, and (d)ONG.
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Figure 12. Photomicrographs of pellets reduced with different gases up to 70% reduction at 9808C.
Figure 13. Photomicrographs of pellets reduced with different gases at 800 and 9808C.
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½O�oxide þ COðgÞ ¼ CO2ðgÞ (7)
CH4ðgÞ þ H2OðgÞ ¼ 3H2ðgÞ þ COðgÞ DHo298 ¼ þ205:8 kJmol�1
(8)
CH4ðgÞ þ CO2ðgÞ ¼ 2H2ðgÞ þ 2COðgÞ DHo298 ¼ þ247:4kJmol�1
(9)
H2OðgÞ þ CðsÞ ¼ H2ðgÞ þ COðgÞ DHo298 ¼ þ131:3kJmol�1 (10)
CO2ðgÞ þ CðsÞ ¼ 2COðgÞ DHo298 ¼ þ172:5kJmol�1 (11)
3FeðsÞ þ CðsÞ ¼ Fe3CðsÞDHo298 ¼ þ4:7kJmol�1 (12)
At the initial stages of reduction, the generated H2O and
CO2 were relatively high due to the fast reduction rate of
Fe2O3 and Fe3O4. The product gases could react directly
with the active formed carbon and/or CH4 as given in
Equation (8–11). Therefore the carbon deposition was
insignificant at this stage. At the later stages of reduction,
the rate of oxygen removal from the remained wustite
became very slow compared to that at the beginning of
reduction. Therefore the carbon deposition became sig-
nificant at this stage of reduction. The calculated
reduction degree at this stage could be pseudo due to
the intensive soot formation not only on the surface of
reduced pellets but also in the basket and inside the
reaction tube. The deposited carbon resulted in sharp
slow down in the reduction curve.[22] The carbon depo-
sition started at lower reduction extent in the case of
OCOG and ONG due to the high concentration of CH4
compared to that in RNG. In the case of RNG the carbon
deposition was slightly appeared at higher reduction
extent (�85%) due to the lower CH4 content. Generally
the rate of carbon deposition increased with temperature
and/or CH4 content in the applied atmosphere. The high
carbon DRI has important benefits in terms of steel pro-
duction costs, productivity, storage, and transpor-
tation.[25,35] The complete reforming of coke oven gas
to H2 and CO results in the development of extensive
cracks which decrease the pellets strength. The appli-
cation of OCOG which is rich with CH4 (30%) results in
soot formation on the outer surface of pellets. Therefore
the utilization of partial RCOG in direct reduction process
is expected to be efficient method for production of
carburized DRI in the integrated steel plant.
Figure 14. XRD analysis of pellets reduced at 9808C with: (a)RCOG, (b) OCOG, (c) RNG, and (4) ONG.
Figure 15. Quantitative analysis of the different phases devel-oped in pellets reduced with different gases at 9808C.
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4. Conclusions
In this study, iron ore pellets were isothermally reduced
with simulated RCOG, OCOG, RNG, and ONG at 700–
9808C. The main finding can be summarized as follows:
(1) The highest reduction degree was obtained for the
pellets reduced with RCOG at all temperatures while
the lowest reduction degree was exhibited by ONG.
(2) The reduction with OCOG was lower than that of RNG
at �8008C while it became higher at �9008C due to the
cracking of methane and the development of more H2
and active carbon.
(3) The reduction was controlled by interfacial chemical
reaction at the initial stages of reduction (20%) with
RCOG and OCOG while it was controlled by hybrid
control of gaseous diffusion and interfacial chemical
reaction for reduction with RNG. At the advanced
reduction stage (70% reduction), the interfacial chemi-
cal reaction became the rate controlling mechanism
while it converted to solid state diffusion at the later
stage of reduction.
(4) The reduction with gases containing CH4, the carbon
deposition was observed at the later stage of reduction.
The rate of carbon deposition increased as CH4 content
in the gas increased and/or temperature increased.
(5) The addition of DR unit in integrated steel plant for
production of carburized DRI through utilization of
COG is expected to be very efficient.
Acknowledgments
The authors wish to acknowledge gratefully the financial
support provided to the corresponding author of this
research by Alexander von Humboldt Foundation in
Germany.
Received: December 11, 2012;
Published online: April 17, 2013
Keywords: COG; DRI; gaseous reduction; carbon
deposition; kinetics and mechanism
Figure 16. External shape and outer surface of pellets: (a) Before reduction (b) After reduction with RCOG (c) After reduction withOCOG.
Figure 17. Cross section of pellets reduced with OCOG at 9808C.
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