Reduction behavior and kinetics of vanadium–titanium sinters under high potential oxygen enriched pulverized coal injection
Int. J. Miner. Metall. Mater.
Reduction behavior and kinetics of vanadium-titanium sinters under high potential oxygen enriched pulverized coal injection
Jin-fang Ma 0
Guang-wei Wang 0
Jian-liang Zhang 0
Xin-yu Li 0
Zheng-jian Liu 0
Ke-xin Jiao 0
Jian Guo 0
0 1) School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing , Beijing 100083 , China 2) Plans and Operations Department, Wanbao Mining Ltd. , Beijing 100053, China (Received: 19 August 2016; revised: 23 December 2016; accepted: 26 December 2016)
In this work, the reduction behavior of vanadium-titanium sinters was studied under five different sets of conditions of pulverized coal injection with oxygen enrichment. The modified random pore model was established to analyze the reduction kinetics. The results show that the reduction rate of sinters was accelerated by an increase of CO and H2 contents. Meanwhile, with the increase in CO and H2 contents, the increasing range of the medium reduction index (MRE) of sinters decreased. The increasing oxygen enrichment ratio played a diminishing role in improving the reduction behavior of the sinters. The reducing process kinetic parameters were solved using the modified random role model. The results indicated that, with increasing oxygen enrichment, the contents of CO and H2 in the reducing gas increased. The reduction activation energy of the sinters decreased to between 20.4 and 23.2 kJ/mol. Corresponding author: Guang-wei Wang E-mail: © The Author(s) 2017. This article is published with open access at link.springer.com
ore reduction; sintering; oxygen enrichment; pulverized coal; injection; kinetic models
Currently, China’s iron and steel industry is in a rigid
condition known as the “new normal.” One key objective of
iron and steel plants is to reduce costs and increase profits
while ensuring sufficient product quality. At present,
research into the raw and fuel materials used in blast furnaces
is focused primarily on the sinter ores and coke. With
respect to sinter, as the iron ore process environment becomes
increasingly complex, various iron ores are being used in the
sinter blending process [1–4]; among these sinters,
vanadium–titanium sinter has been studied broadly because of its
special characteristics. Previous studies on sinters have
concentrated on their mineral components, structure,
reducibility, strength, and furnace protection characteristics.
Deng  studied the reduction process of
vanadium–titanium sinter and the slag-iron formation process in
a blast furnace by observing the anatomy in a 0.8-m3 blast
furnace. Liu et al.  found that the controlling step in the
solid-state reduction of pre-oxidized vanadium–titanium
magnetite concentrate is the interface chemical reaction
when coal is used as the reducing agent, indicating that
vanadium–titanium magnetite concentrate is difficult to reduce.
Bai et al.  studied the mineralogical phase of
vanadium–titanium sinters during the reduction degradation
process. Other researchers have focused on the influence of
ω(MgO) on the strength of vanadium–titanium sinters and
on the sintering process [8–10]. Yang et al.  investigated
the influence of various addition ratios of
vanadium–titanium magnetite concentrate on the metallurgical
properties of vanadium–titanium sinter. Sun et al. 
studied the furnace protection role of titanium-containing
sinters in blast furnaces. With respect to coke, numerous
studies on substituting coal for coke to reduce the coke ratio
and strengthen the blast furnace smelting performance have
been reported; hence, oxygen-enrichment pulverized coal
injection in blast furnaces has emerged as an active research
Some recent studies have focused on the changing
conditions in blast furnaces after oxygen-enrichment
pulverized-coal injection. Zhu and Wang  reported that
iron-ore reduction in a blast furnace was improved after
oxygen-enrichment pulverized coal injection. Babich et al. 
noted the difficulty of pulverized coal injection and
indicated the possibility of increasing the pulverized coal
combustion ratio from both theoretical and practical viewpoints.
Ghanbari et al.  discussed the influence of using pulverized
coal and also proposed restricted conditions. Shen et al. 
used a model to investigate the influence of pulverized coal
characteristics and blast furnace conditions on the
pulverized coal injection process. Yan et al.  analyzed the
influence of high oxygen enrichment pulverized coal injection
on the tuyeres, gas, and smelting cost of blast furnaces. Hao
et al.  investigated the influence of the metallization
degree of burden on the oxygen enrichment pulverized coal
injection in the blast furnace smelting process and obtained
the corresponding complementary relationship between the
two sides. However, the literature lacks information
concerning the sinter reduction kinetics in the case of high
reduction potential conditions. Kinetics analysis is also
necessary for the design and operation of ironmaking systems,
which is essential for further studies in this field.
In summary, extensive works related to vanadium–titanium
sinters and oxygen enrichment pulverized coal injection
have been reported; however, their mutual effect has not
been investigated. In fact, the relationship between them
should be elucidated because they are used in blast furnaces
simultaneously, influencing the whole production process
and, in some cases, having complementary effects. The goal
of the present work is to investigate the isothermal reduction
behaviors of vanadium–titanium sinters under various high
potential pulverized coal injection conditions. The kinetic
parameters were also calculated using established kinetic
models. Hence, the results of this paper are expected to
provide theoretical support and reference data for further
studies of vanadium–titanium magnetite.
2. Experimental and methods
In this work, the vanadium–titanium sinters were
provided by Panzhihua Iron and Steel Company of China. The
size of the sinters used in the reduction experiments was
10–12.5 mm; their chemical composition is shown in Table
1. As shown in Table 1, the TFe of the sinters was only
48.7wt%, and the CaO and SiO2 contents were higher than
those of normal sinters produced using other iron ores. The
TiO2 and V2O5 contents were as high as 5.20wt% and
0.34wt%, respectively. The reduction of these sinters would
likely consume a relatively high volume of reducing gas and
produce a large amount of slag after reduction, adversely
affecting normal operation of the blast furnace.
CaO SiO2 MgO Al2O3 MnO
48.70 9.06 12.5 6.63
The isothermal reduction experiments were conducted
using five different reducing atmospheres. In each batch,
approximately 30 g of sinter was used. The experimental
temperature was increased from room temperature to the
reaction temperature at a rate of 10°C/min, and the sinters
were protected under an atmosphere of purified N2. Five
different reducing atmospheres were designed as follows.
Condition 1 (C1) represents the total coke smelting cycle,
which is the basic cycle shown in Table 2; condition 2 (C2)
represents the high potential pulverized coal injection with
non-oxygen enrichment; condition 3 (C3), condition 4 (C4),
and condition 5 (C5) represent the high potential pulverized
coal injection with oxygen enrichments of 9vol%, 19vol%,
and 39vol%, respectively. The gas composition was
calculated based on previous research . Because indirect
reduction strongly influences the economic and technical
indexes of the blast furnace, the quick indirect reduction
temperature zone was used as the isothermal reduction
temperature in this research; the investigated temperatures were
800, 900, 1000, 1100, and 1200°C, respectively. The flow of
the reducing gas was 10 L/min to eliminate the influence of
external diffusion on the reduction process.
9vol% oxygen enrichment
19vol% oxygen enrichment
39vol% oxygen enrichment
Gas flow / (L·min–1)
The vanadium–titanium sinters were reduced in a
thermogravimetric analysis apparatus as shown in Fig. 1.
Different gases were fully mixed in the blending device, and
the mixed gas was introduced through the bottom of the
furnace to participate in the reduction process. A computer
program monitored the reaction temperature, the flow of
various gases, and the weight of the sinters and recorded
the weight data every 0.5 s. After the reduction process, the
sinters were ground and analyzed by X-ray diffraction
(XRD). The reduction process was divided according to
the weight loss of the sinters. After reduction, the sinters
were polished and characterized by scanning electron
microscopy in conjunction with energy-dispersive X-ray
Fig. 1. Schematic of the reduction setup.
The reduction process of the sinters was also analyzed
based on the calculation of Eqs. (1) and (2), shown as below,
establishing the reduction kinetics models:
RI = (0.11×W ) (0.43×W2 ) + ( M 0 − M t ) ( M 0 − 0.43×Wt )
RI′ = dRI dt (2)
where RI is the reduction index of sinters; RI′ is the
reduction rate of sinters, s−1; M0 is the initial mass of sinters,
g; t is the reduction time, s; Mt is mass of sinters when the
reduction time is t, g; W1 is the FeO content in the sinters;
and W2 is the total content of Fe in the sinters.
3. Results and discussion
3.1. Analysis of the sinter reduction process The isothermal reduction experiments of vanadium–titanium sinters were carried out at 800, 900, 1000, and 1100°C; the experimental results are shown in Figs.
2(a)–2(e). Fig. 2(f) shows the reduction conversion
corresponding to different working conditions at 1000°C. As
shown in Figs. 2(a)–2(e), the RI of the sinters increases
gradually with increasing reduction time. The increase of
the reduction temperature promotes RI in a rapid manner
under different working conditions. According to the law
of Arrhenius, the reduction rate increases exponentially
with increasing reduction temperature. The higher the
reaction activation energy, the more obvious the influence
of temperature on the reaction rate. During the sintering
reduction process by CO and H2, the constant rate of the
interfacial chemical reaction increases with increasing
temperature, whereas the reduction rate increases as the
other conditions remain unchanged. Under internal
diffusion control, the diffusion coefficient is proportional to
1.57 times the change in temperature. In addition, with
increasing temperature, the diffusion coefficient increases
and the diffusion resistance decreases for CO and H2 in the
product layer .
Fig. 2(f) reveals that the RI values of different reducing
atmospheres differed obviously. The main reducing agent of
C1 was CO; however, the concentration of CO was low,
resulting in a small increase of RI. The content of H2 in the
reducing gas increased after pulverized coal injection. As
known from the thermodynamics analysis, the reducing
ability of CO is stronger than that of H2 when the
temperature is less than 810°C; however, the opposite is true when
the temperature is greater than 810°C. Meanwhile, the
water–gas displacement reaction occurs, which would
accelerate the reduction process of iron oxide due to the existence
of H2, contributing to the reduction effect of CO. In addition,
in terms of kinetics, H2 has an advantage over CO in the
reduction process. The molecular dimension of H2 is smaller
than that of CO, and the diffusion velocities of H2 and H2O
are higher in the production layer than those of CO and CO2.
During the reduction process, H2 diffuses into the reaction
layer earlier than CO and the reaction product H2O diffuses
from the reaction layer into the main gas earlier than CO2.
Therefore, from a diffusion aspect, the reducing ability of H2
toward iron oxide is higher than that of CO. The RI is 0.478
for the sinters in C1, whereas the RI in the case of C4 is
To quantitatively analyze the reduction characteristic of
sinters under different conditions, we introduce the medium
reduction index (MRE), which is defined as
MRE = 0.5 t0.5 (3)
where t0.5 represents the time (in seconds) when the RI of
the sinters is 0.5.
Fig. 2. RI curves of the sinters under working conditions C1–C5 at different temperatures (a)–(e) and RI curves under five working
conditions at 1000°C (f).
Table 3 shows the MRE values under different working
conditions for the sinters. The MRE value increases
gradually with the increase of reduction temperature and the MRE
value increases from 1.39 × 10−4 to 2.68 × 10−4 s−1 for C3
when the reduction temperature is increased from 800 to
1200°C. At the same time, the increase of CO and H2 contents
in the reducing atmosphere would improve the reduction
properties. When the reduction temperature is 1000°C, the
MRE value increases from 1.63 × 10−4 s–1 in the case of C2 to
2.66 × 10−4 s−1 in the case of C5. In addition, the change of the
reduction properties between various oxygen enrichment
pulverized coal injections and the reducing atmosphere was also
investigated. Fig. 3 shows the relationship between the MRE
value corresponding to oxygen enrichment under different
working conditions. The MRE value increases and the range
of MRE decreases gradually with increasing oxygen
enrichment. The reason is that the increase in CO and H2 contents
has a decreasing characteristic in the reduction process.
MRE values of sinters under different working
conFig. 3. Relationship between the MRE value and the oxygen
3.2. Phase evolution analysis during the reduction
The change of the phase evolution of sinters was also
investigated. The divided samples were treated under the
following conditions: (1) the working condition of C3; (2) a
reduction temperature of 1000°C; and (3) a reduction time
of 5, 10, 20, 40, or 60 min. After reduction, the samples
were protected under an N2 atmosphere until they had
cooled to room temperature. A portion of each sample was
ground for XRD analysis, and a portion was polished for
Fig. 4 shows the SEM results for the samples subjected to
reduction for different times. The surface of the sinters was
Fig. 4. SEM micrographs of the sinters subjected to 1000°C and the C3 working condition for various reduction times: (a) 5 min;
(b) 10 min; (c) 20 min; (d) 40 min; (e) 60 min; (f) zoomed image of the area denoted with a red square in Fig. 4(e).
reduced to some extent; however, the inner part of the
sinters was unreacted when the reduction time was 5 min. As
shown in Figs. 4(a)–4(f), based on the analysis of the
microstructure, the reduced zone increased with increasing
reduction time and the reduced interface moved into the
inner part. When the reduction time was 20 min, the
ferrous phase was formed in the surface of the sinters while
there was not any of that in the inner part, but it could be
seen that there exited wustite. When the reduction time
was 60 min, metallic iron was formed at the boundary of
the sinters, and the reaction interface shifted to the center
of the sinters. As shown in Fig. 4(f), most of the inner
particles of the sinters were reduced to metallic iron, whereas
a few unreduced iron oxides were surrounded by the dense
iron product layer; small particles of iron oxide were
observed as “unreacted cores.”
For the further analysis of the sinters’ microstructure after
60 min of reduction, Fig. 5 shows more detailed SEM
images; the EDS analysis results corresponding to points 1–6
in Fig. 5 are shown in Table 4. The goal of these analyses
was to deduce the relationship between titanium and ferrous
ions in vanadium–titanium sinters during the reduction
process. According to the results shown in Table 4, point 1 is
wustite, which is still in the process of reduction; points
2–4 are the slag formed after reduction, where points 3
and 4 are the slag mainly composed by titanium. The
interface between point 3, which is slag with titanium, and
point 1, which is wustite, becomes much clearer with
increasing the reduction time; by contrast, point 4 contains
titanium combined strongly with wustite. Hence, point 3
Microstructure of the sinters after reduction (1000°C, C3, 60 min).
is reduced from point 4 to finally realize the reduction
process of vanadium–titanium sinters. The EDS analysis
results show that point 5 is wustite with small amount of
titanium and point 6 is metallic iron with little titanium.
We concluded that the reductive separation of titanium
and ferrous ions during the reduction process is the
critical controlling step influencing the separation between the
iron and the slag.
Fig. 6 shows the XRD patterns of the sinter samples
reduced for different times. The main minerals of the
unreacted sinters are hematite, magnetite, and ilmenite. When
the reduction time was 5 min, the peak of wustite appeared
and the intensity of the hematite peak decreased; however,
the intensity of the magnetite peak increased. When the
reduction time was 20 min, the peak associated with metallic
iron appeared and the intensity of the hematite peak
continued to decrease, whereas the intensities of magnetite and
wustite peaks increased and the ilmenite peak emerged.
When the reduction time was 40 min, the intensity of the
ilmenite peak disappeared and the peak of metallic iron was
the most intense peak in the spectrum; in addition, the
intensity of the wustite peak continually increased. According to
the aforementioned analysis, the reduction process of sinters
can be expressed as Fe2O3 → Fe3O4 → FeO → Fe . The
reduction from hematite to magnetite was relatively fast. The
hematite was reduced completely to magnetite when the
reduction time was 20 min. In addition, the magnetite was completed
reduced to wustite when the reduction time was 40 min.
Fig. 6. XRD results of the sinters reduced for different times (1000°C, C3): (a) unreduced sinters; (b) 5 min; (c) 10 min; (d) 20 min;
(e) 40 min; (f) 60 min.
3.3. Construction of the reduction kinetics model For the gas–solid non-catalytic reaction, the reduction kinetic equation can be expressed as
dα = k ( Pg ,T ) f (α ) (4)
where α is the conversion rate (i.e., the RI); dα is the
reaction rate (i.e., RI′); k is the apparent reaction rate
constant, whose value is influenced by the reaction temperature
(T) and the gas-phase pressure (Pg); f(a) is the function of
the reaction kinetics mechanism; and t is the reaction time.
If the gas pressure is assumed to be constant during the
reduction process, the apparent reaction rate constant is
mainly influenced by the reaction temperature, which can be
expressed by the Arrhenius formula:
k = k0e−E RT
where kGM, kVM, and kHM are the pre-exponential indices of
the GM, VM, and HM gasification reactions, respectively; n
represents the reaction order.
In previous studies, the modified random pore model
(MRPM)  was proposed; its formula is
RI′ = kHMe−E RT (1 − RI)n 1 −ψ ln (1 − RI) (9)
where ψ is a parameter of the particle structure, with the
expression of ψ = 4πL0S(102−ε 0 ) (here, S0, L0 and ε0 are the
pore surface area, pore length, and solid porosity, respectively).
Eqs. (6)–(9) are four explicit formulae that describe the
gasification fractional conversion RI′, the conversion rate RI,
and temperature T. The kinetic parameters, including E, k0, n,
and ψ, can be calculated from experimental datasets using
nonlinear least square fitting methods. The objective
function can be written as
OF= N ( RI′exp,i − RI′calc,i )2 (10)
where RI′exp,i is the experiment data; RI′calc,i is the value
RI′ = kGMe−E RT (1 − RI)2 3
RI′ = kVMe−E RT (1 − RI)
RI′ = kHMe−E RT (1 − RI)n
calculated using a model; and N is the number of test values
Fig. 7(a) shows the contrasting relations between the
experimental data and values calculated using the four models.
Obvious deviations were observed when the GM and VM
were used to express the reduction process, whereas the HM
and MRPM exhibited better agreement, especially the MRPM.
A comparison of Eqs. (8) and (9) suggests that the MRPM
provided better agreement because it was modified according
to the HM. In addition, the MRPM considers multiple pore
structures resulting from the structure of sinters. The reduction
process of the sinters in this research was complicated. When
CO was used to reduce the sinters, iron oxides were reduced
in the sequence of Fe2O3 → Fe3O4 → FeO → Fe , which
resulted in three interfaces; the existence of H2 divided the
reduction process into another three interfaces. For simplicity,
the reduction process of the sinters under different working
conditions was considered to result in six interfaces. The GM
could only express one interface during the reduction, whereas
the VM, which considered the reduction activity, considered
diffusion into and from the particles simultaneously, which is
not consistent with the phenomenon of obvious reaction zones
and unreduced zones discussed in Section 3.2. The HM is an
empirical formula, but it can only express the reaction
mechanism process under multiple conditions; it cannot express
the phenomenon of samples with multiple pore structures.
Although the MRPM is an empirical formula, it combines the
properties of both the RPM and the HM, and is therefore able
to express the more complicated reaction mechanism. The
lines in Fig. 7(a) represent the calculation curves by different
models at various temperatures. From the calculation curves
and experimental curves, the MRPM provides a better fit than
the other investigated models. Figs. 7(b)–7(f) shows the
contrasting relation of the experimental data and the values
calculated using the MRPM. Good agreement was obtained
between the calculated values and experimental data,
demonstrating that the MRPM can express the reduction process of
iron ores under different reducing atmospheres.
Table 5 shows the reduction kinetic parameters of the
sinters under different working conditions obtained using the
MRPM. The contents of CO and H2 in the reducing atmosphere
increased with increasing oxygen enrichment. The reduction
apparent activation energy of the sinters decreased gradually:
the values for C1 and C5 were 23.2 and 20.4 kJ/mol,
respectively. The decrease of the apparent activation energy
promoted the reduction process of the sinters at the same
reduction temperature and accelerated the reaction rate of the
system. The results also show that the reduction kinetic parameter
n decreased gradually with increasing oxygen enrichment: the
values for C1 and C5 were 1.27 and 0.89 kJ/mol, respectively.
Compared with the calculated values of Ψ, the values were
small for all of the investigated working conditions. The
sinters contained numerous large pores but few small pores,
which was the critical factor influencing the value of Ψ.
However, for smaller values of Ψ, the MRPM and HM results
became more similar, consistent with Eqs. (8) and (9). When
the Ψ value was limited to zero, the results obtained using the
MRPM and the HM were the same, which is the main reason
why the calculated values were so similar for the two models.
Fig. 7. Comparison of the calculated results of RI and RI′ and the experimental results of the sinters under different working
conditions: (a) different models for C1, (b) C1, (c) C2, (d) C3, (e) C4, and (f) C5.
In this research, the reduction behavior of sinters was
investigated under different oxygen enrichment working
conditions and the influence of reduction time and atmosphere
on the reduction process was also analyzed, where the
MRPM was used to investigate the reduction kinetic
behavior under different working conditions. The results are
summarized as follows:
(1) With increasing oxygen enrichment, the contents of
CO and H2 in the blast furnace coal gas increased, resulting
in an increase in reduction rate of the reduction process of
sinters. When the reduction temperature was 1000°C, the
MRE value increased from 1.63 × 10−4 s−1 in the case of C2
to 2.66 × 10−4 s−1 in the case of C5.
(2) The MRE value increased from 1.39 × 10−4 to 2.68 ×
10−4 s−1 under 9vol% oxygen enrichment when the reduction
temperature was increased from 800 to 1200°C. However,
the range of the MRE decreased gradually with increasing
oxygen enrichment, indicating that the influence of the CO
and H2 contents in the coal gas on the reduction of sinters
(3) Both the HM and the MRPM showed the changing
relationship between the reduction rate and RI based on the
analysis of the reduction process of sinters; however, the
values calculated using the MRPM agreed better with the
experimental data than those calculated using the HM.
According to the calculation results of reduction kinetic
parameters by the MRPM under different conditions, the
reduction activation energy decreased to between 20.4 and
23.2 kJ/mol with increasing oxygen enrichment.
This work was financially supported by the Fundamental
Research Funds for Central Universities (FRF-TP-15-063A1).
Open Access This article is distributed under the terms of
the Creative Commons Attribution 4.0 International License
permits unrestricted use, distribution, and reproduction in any
medium, provided you give appropriate credit to the original
author(s) and the source, provide a link to the Creative
Commons license, and indicate if changes were made.
 X.P. Hu and M.Y. Liu , Application research on a high grade brazilian concentrates in sintering process , Res. Iron Steel , 38 ( 2010 ), No. 2 , p. 17 .
 L.J. Yan , S.L. Wu , Y. You , Y.D. Pei , and L.H. Zhang , Assimilation of iron ores and ore matching method based on complementary assimilation, J. Univ. Sci. Technol. Beijing , 32 ( 2010 ), No. 3 , p. 298 .
 J.G. Hu and Z.M. Gao , Characteristics of Marra Mamba iron ore fines and the application technology in sintering process , Res. Iron Steel , 36 ( 2008 ), No. 5 , p. 25 .
 H.G. Li , G. An , Z.X. Zhao , and S.H. Ou , Experimental research on sintering performances of imported powder iron ores with high and medium ignition loss , Met. Mine, ( 2006 ), No. 8 , p. 41 .
 C.S. Deng , The reduction behavior and iron slag formation characteristics of vanadium-titanium sinter in blast furnace by dissecting 0.8 m3 blast furnace , Sichuan Metall., ( 1985 ), No. 2 , p. 4 .
 S.S. Liu , Y.F. Guo , G.Z. Qiu , T. Jiang , and F. Chen , Solid-state reduction kinetics and mechanism of pre-oxidized vanadium-titanium magnetite concentrate , Trans. Nonferrous Met. Soc. China , 24 ( 2014 ), No. 10 , p 3372 .
 Y.Q. Bai , S.S. Cheng , H.B. Zhao , and S.F. Huo , Study of V-Ti sinter reduction degradation by mineralogical analysis , Sintering Pelletizing , 36 ( 2011 ), No. 2 , p. 1 .
 Q. Lu , F.M. Li , W.S. Wang , and B.S. Hu , Influence of w(MgO) on sinter strength and sintering process of vanadium-titanium magnetite , Res. Iron Steel , 35 ( 2007 ), No. 1 , p. 5 .
 M. Zhou , S.T. Yang , T. Jiang , and X.X. Xue , Influence of MgO in form of magnesite on properties and mineralogy of high chromium, vanadium, titanium magnetite sinters , Ironmaking Steelmaking , 42 ( 2015 ), No. 3 , p. 217 .
 Z.G. Liu , M.S. Chu , H.T. Wang , W. Zhao , and X.X. Xue , Effect of MgO content in sinter on the softening-melting behavior of mixed burden made from chromium-bearing vanadium-titanium magnetite, Int . J. Miner . Metall. Mater., 23 ( 2016 ), No. 1 , p. 25 .
 G.Q. Yang , J.L. Zhang , J.G. Shao , Y.C. Wen , J.T. Rao , and W.G. Fu , Influence of vanadium titano-magnetite concentrate proportion on metallurgical properties of V-Ti bearing sinter , Sintering Pelletizing , 37 ( 2012 ), No. 2 , p. 6 .
 Y.P. Sun , P.J. Liu , J.L. Lü , and J. Wang , Practice of blast furnace protection with titanium-containing sinter , Iron Steel Vanadium Titanium , 34 ( 2013 ), No. 5 , p. 48 .
 J.J. Zhu and W.Z. Wang , Effects of PCI with oxygen enriched blast on the temperature field of the middle and upper zone in BF , Iron Making, 13 ( 1994 ), No. 4 , p. 19 .
 A. Babich , S. Yaroshevskii , A. Formoso , A. Isidro , S. Ferreira , A. Cores , and L. Garcia , Increase of pulverized coal use efficiency in blast furnace , ISIJ Int ., 36 ( 1996 ), No. 10 , p. 1250 .
 H. Ghanbari , F. Pettersson , and H. Saxén , Sustainable development of primary steelmaking under novel blast furnace operation and injection of different reducing agents , Chem. Eng. Sci. , 129 ( 2015 ), p. 208 .
 Y.S. Shen , B.Y. Guo , A.B. Yu , and P. Zulli , Model study of the effects of coal properties and blast conditions on pulverized coal combustion , ISIJ Int ., 49 ( 2009 ), No. 6 , p. 819 .
 C.J. Yan , X.L. Cheng , J.J. Gao , and Y.S. Zhou , Effect of high oxygen enrichment PCI on BF blast ironmaking , Iron Steel , 48 ( 2013 ), No. 6 , p. 25 .
 Z.Q. Hao , X.C. Li , and Q. Wang , Effect of metallization degree of burden on ironmaking operation of BF with oxygen enriched blast and coal injection , J. Iron Steel Res ., 12 ( 2000 ), Suppl. 1 , p. 81 .
 G.W. Wang , J.L. Zhang , J.G. Shao , H.B. Zuo , and J.Q. Qiu , Model for economic evaluation of iron production with oxygen-enriched and pulverized coal injection , Iron Steel , 48 ( 2013 ), No. 11 , p. 21 .
 J.X. Li , P. Wang , and L.Y. Zhou , Technique of oxygen blast furnace with high injection of PC and hydrogenous fuel , J. Iron Steel Res ., 21 ( 2009 ), No. 6 , p. 13 .
 J. Szekely and J.W. Evans , A structural model for gas-solid reactions with a moving boundary , Chem. Eng. Sci., 25 ( 1970 ), No. 6 , p. 1091 .
 J. Ochoa , M.C. Cassanello , P.R. Bonelli , and A.L. Cukierman , CO2 gasification of Argentinean coal chars: a kinetic characterization , Fuel Process. Technol., 74 ( 2001 ), No. 3 , p. 161 .
 S. Kasaoka , Y. Sakata , and C. Tong , Kinetic evaluation of the reactivity of various coal chars for gasification with carbon dioxide in comparison with stream , Int. Chem. Eng., 25 ( 1985 ), No. 1 , p. 160 .
 J.Y. Shang and E.E. Wolf , Kinetic and FTIR studies of the sodium-catalyzed steam gasification of coal char , Fuel , 63 ( 1984 ), No. 11 , p. 1604 .
 C. Shuai , Y.Y. Bin , S. Hu , J. Xiang , L.S. Sun , S. Su , K. Xu , and C.F. Xu , Kinetic models of coal char steam gasification and sensitivity analysis of the parameters , J. Fuel Chem. Technol. , 41 ( 2013 ), No. 5 , p. 558 .
 J.L. Zhang , G.W. Wang , J.G. Shao , and H.B. Zuo , A modified random pore model for the kinetics of char gasification , BioResources , 9 ( 2014 ), No. 2 , p. 3497 .