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

www.steel-research.de

� 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim steel research int. 84 (2013) No. 11 1085

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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.


1086 steel research int. 84 (2013) No. 11 � 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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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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References

[1] D. Babich, H. W. Senk, K. Gudenau, Th. Mavromatis,

Ironmaking Textbook, Mains GmbH, Aachen 2008,

p. 402, ISBN 3-86130-997-1.

[2] H. W. Gudenau, J. Fang, T. Hitara, U. Gebel, Steel

Research Int. 1989, 60(314), 138.

[3] R. Degel, Eisenerzreduktion in der Wirbelschicht mit

wasserstoffreichem Gas, Dr. -Ing. Dissertation,

IEHK, RWTH Aachen, 1996, Shaker Verlag Aachen.

[4] P. Diemer, H. B. Lungen, M. Reinke, Utilization of

coke oven for the production of DRI, Proc, METEC

InSteelCon, VDEh, 27 June–1 July 2011, Dusseldorf,

Germany.

[5] A. Babich, D. Senk, Hydrogen Rich Blast Furnace,

Coal Use in Iron and Steel Metallurgy, (Ed: D.

Osborne) Woodhead, Publishing Ltd, Cambridge,

England 2013, forthcoming.

[6] P. Diemer, K. Knop, H. B. Lungen, M. Reinke,

C. Wuppermann, Stahl Eisen 2007, 127(1), 19.

[7] P. Diemer, H.-J. Killich, K. Knop, H. B. Lungen,

M. Reinke, P. Schmole, Proc, 2nd International

Meeting on Ironmaking, 12–15 September 2004,

Vitoria, Espirito Santo, Brazil.

[8] P. Diemer, H. B. Lungen, M. Reinke, Proc METEC

InSteelCon, VDEh, 27 June–1 July 2011, Dusseldorf,

Germany.

[9] K. Knop, Stahl Eisen 2002, 122(11), 43.

[10] http://www.resource-net.com/files/Sample

Pages.pdf: Coke market survey, 2011.

[11] P. Diemer, H.-J. Killich, K. Knop, H. B. Lungen,

M. Reinke, P. Schmole, Stahl Eisen 2004, 124(7), 21.

[12] Z. Yang, Y. Zhang, X. Wang, Y. Zhang, X. Lu, W.

Ding, Energy Fuel 2010, 24(785), 785.

[13] I. G. Tovarovskii, A. E. Merkulov, Steel Translation

2011, 41(6), 499.

[14] E. Proface, S. Pivot, Proc, METEC InSteelCon, VDEh,

27 June–1 July 2011, Dusseldorf, Germany.

[15] D. Andahazy, G. Loffler, F. Winter, C. Feilmayer,

T. Burgler, ISIJ Int. 2005, 45(2), 166.

[16] S. Matsuzaki, K. Higuchi, A. Shinotake, K. Saito,

Proc, International Congress on the Science and

Technology of Ironmaking (ICSTI), 14–18 October

2012, Rio de Janeiro, RJ, Brazil, p. 977.

[17] M.-S. Chu, T.-I. Guo, Z.-G. Liu, X.-X. Xue, J.-I. Yagi,

Proc, International Congress on the Science and



[18] T. Miwa, H. Okuda, M. Osame, S. Watakabe,

K. Saito, Proc, METEC InSteelCon, VDEh, 27 June–1

July 2011, Dusseldorf, Germany.

[19] P. E. Kovalenko, A. P. Chebotarev, V. F. Pashinskii,

V. M. Zamuruev, I. G. Tovarovskii, N. G. Boiko,

V. S. Plevako, B. S. Trunov, Metallurg 1989, 9, 22.

[20] T. H. Burgler, G. Braunnbauer, A. Ferstl, Stahl Eisen

2004, 124(2), 39.

[21] J. Zhou, W. Liu, J. Sun, D. Zhang, Z. Ma, Proc,

International Congress on the Science and



[22] V. I. Zenkov, V. V. Pasichnyi, Powder Metall. Met.

Ceram. 2010, 49(3–4), 231.

[23] A. Bonalde, A. Henriquez, M. Manrique, ISIJ Int.

2005, 45(9), 1255.

[24] G. Tsvik, Proc, METEC InSteelCon, VDEh, 27 June–1

July 2011, Dusseldorf, Germany.

[25] J. C. D’Abreu, M. M. Otaviano, H. M. Kohler, Proc,

International Congress on the Science and



[26] L. A. Hass, J. C. Nigro, R. K. Zahl, Rep. Invest. U. S.

Bur. Mines, 1985, 8997, 14.

[27] B. Alamsari, S. Torii, A. Trianto, Y. Bindar, Int.

Scholary Res. Network ISRN Mech. Eng., 2011,

5402(324659), 12.

[28] R. G. Morales, Proc 2nd Latin American Steel and

Iron Ore Conference, April 2000, Rio de Janeiro,

Brazil.

[29] A. Babich, D. Senk, H. W. Gudenau, Ironmaking

Steelmaking 2009, 36(3), 222.

[30] Y. H. Han, J. S. Wang, R. Z. Lan, L. T. Wang, X. J.

Zuo, Q. G. Xue, Ironmaking Steelmaking 2012, 39(5),

313.

[31] D. Ghosh, A. K. Roy, A. Ghosh, Trans. ISIJ 1986, 26,

186.

[32] W. H. Chen, M. R. Lin, A. B. Yu, S. W. Du, T. S. Leu,

Int. J. Hydrogen Energy 2012, 37, 11748.

[33] L. von Bogdandy, H.-J. Engell, The Reduction of Iron

Ores, Springer Verlag, Berlin 1971, 576 p.

[34] Y. S. Karabasol, V. M. Chizhikova, Physico-

Chemistry of Iron Oxide Reduction from Iron

Oxides (in Russian), Moscow, Metallurgie, 1986,

200 p.

[35] A. Chatterjee, Sponge Iron Production by Direct

Reduction of Iron Oxide, PHI Learning Private

Limited, New Delhi, 2010, 353 p.



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Reduction Behavior of Iron Ore Pellets with Simulated Coke