temperatures. Additionally, the gas flow rate of 0.8 m/s is not favourable since even
the limestone of the middle layer (its dissociation degree makes up 40–70%) did not
have time to react completely during the time of the process (Fig. 3).
Table 3 Dependence of the magnetite oxidation degree within the depth of the
layer on the gas temperature and the gas flow rate (within the preheating zone)
Gas
temperature,
о
С
1000
1050
1100
Pellet layer
depth, mm
Gas rate, m/s
0.8
1.0
1.2
0.8
1.0
1.2
0.8
1.0
1.2
The degree of
magnetite
oxidation, %
91.9
93.9
95
93.6
95.2
96.2
95.1
96.4
97.2
300
77.6
84.4
88.1
81.1
86.9
90.1
84
89
91.8
240
54.2
71
79
61.1
75
81.9
66.3
78.3
84.3
180
17.4
50.9
66.8
20.3
57.6
70.9
34.6
62.8
74.4
120
3.7
17.1
49.3
7.2
26.9
55.7
9.1
38
60.7
60
Figure 3. Dependence of the limestone decomposition degree on the gas
temperature and the gas flow rate in the layer depth (in the preheating zone)
The preheating temperature kept within the range of 1000–1100°C and the
changes in the gas flow from 0.8 m/s to 1.2 m/s did not show the significant affect on
the magnetite oxidation degree in the middle part of the pellets layer (Fig. 4). However,
the different picture was observed in the lower part of the pellets layer, as the influence
of these parameters was revealed to be stronger.
Thus, for the gas rate of 0.8 m/s and the preheating temperature of 1100 °C, the
magnetite oxidation degree was approximately 10%. With the gas rate of 1 m/s, the
same temperature enabled the magnetite oxidation degree of approximately 40%.
Figure 4. Dependence of the magnetite oxidation degree on the gas temperature
and the gas flow rate within the depth of the pellets layer (the preheating zone)
Middle of the layer
0
20
40
60
80
100
980
1020
1060
1100
Heating temperature (°С)
De
gr
ee
of lime
stone
d
iss
oc
iation
(%)
1,2
1
0,8
Bottom of the layer
0
20
40
60
80
100
980
1020
1060
1100
Heating temperature (°С)
De
gr
e
e
of
li
m
e
ston
e
d
is
soc
iation
(
%)
1,2
1
0,8
Middle of the layer
0
20
40
60
80
100
980
1020
1060
1100
Heating temperature (°С)
De
gr
ee
of m
agn
etit
e
oxid
ation
(%)
1,2
1
0,8
Bottom of the layer
0
20
40
60
80
100
980
1020
1060
1100
Heating temperature (°С)
De
gr
ee
of m
agn
etit
e
oxid
ation
(%)
1,2
1
0,8
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