XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1815
Considering the leaching effect and energy consumption,
the appropriate high-temperature reoxidation roasting tem-
perature is 850 °C.
The data from the gas flow and oxygen content experi-
ment were shown in Figure 5(b) and Figure 5(c), respec-
tively. Both curves show a trend of rapid rose at first and
then a slow rise. With the increase of gas flow from 150 ml/
min to 600 ml/min, the leaching rate of V2O5 increased
from 56.35% to 64.25%. Similarly, the oxygen content
increased from 7% to 35%, and the leaching rate of V2O5
increased from 55.32% to 68.09%. This indicated that the
vanadium leaching rate of the roasted product was posi-
tively related to gas flow and oxygen content. Because oxy-
gen participates in the oxidation of low-valence vanadium
to high-valence vanadium in the roasting process. When
the oxygen supply was insufficient, a large amount of low-
valent vanadium in vanadium-bearing minerals cannot be
fully oxidized, and thus it is not easy to be leached by acid.
To ensure sufficient oxygen supply and good fluidization
effect of materials, the total gas volume of 600 ml/min and
35% O2 were considered as the appropriate roasting condi-
tions. In addition, when the roasting time was extended
from 1 h to 3 h, the leaching rate of V2O5 increased from
63.69% to 68.89% (Figure 5(d)). The leaching rate of
vanadium increased slowly due to the continuous exten-
sion of time. 3h was determined as the appropriate time for
high-temperature reoxidation roasting.
The vanadium leaching rates of raw ore and roasted
products were given in Table 3. The leaching rate of the
primary oxidation product improved by 13.73 percent.
Moreover, The leaching rate of roasted products effectively
improved by 36.23 percent to that of raw ore. Therefore,
the suitable conditions of high-temperature reoxidation
were 850 °C, 3 h, 35% O2, and 600 ml/min of gas volume.
68.89% was the optimum V2O5 leaching rate of a roasted
product under suitable conditions.
Analysis of the Roasting Process of Carbonaceous Shale
Phase Transformation Analysis
The effect of primary oxidation roasting on the phase trans-
formation of carbonaceous shale was analyzed by XRD(Hu
et al., 2012), as shown in Figure 6. With the roasting tem-
perature rising to 650 °C, all diffraction peaks of pyrite
in the sample disappear. This indicated that the oxidation
reaction of pyrite occurred at this time. This was consis-
tent with the results of the thermal decomposition analy-
sis of carbonaceous shale in Section 3.1. In addition, the
characteristic peaks of mica, quartz, dolomite, and barite
in carbonaceous shale had no obvious change. This showed
that these minerals, except pyrite, were unchanged during
the primary oxidation roasting. Further, the effect of high-
temperature reoxidation roasting on the phase of carbona-
ceous shale was analyzed by XRD, as shown in Figure 6. At
850 °C, the diffraction peak of mica in the sample disap-
peared, and the diffraction peak of tremolite appeared. This
indicated that the lattice structure of mica was destroyed at
high temperatures (Bai et al., 2022b Dong et al., 2020).
When the temperature rose to 1050 °C, the diffraction
peak of barite in the sample disappeared. It indicated that
the decomposition reaction of barite occurred.
Therefore, the removal of reducing substances such
as carbon and pyrite in carbonaceous shale is the func-
tion of the primary oxidation roasting process. This elimi-
nates the effect of reducing substances on the oxidation of
low vanadium to high vanadium in carbonaceous shale.
Furthermore, the effect of the reoxidation roasting process
is on the lattice structure of vanadium-containing mica.
Because of the stable lattice structure of mica, it is difficult
to release the vanadium element which is isomorphic in the
mica lattice, and then difficult to be oxidized and dissolved.
However, the binding of mica with a broken structure to
vanadium is weakened after high-temperature roasting.
Low-valent vanadium in mica lattice is more easily exposed,
which makes the low-valent vanadium converted into high-
valent vanadium. Then the vanadium dissolution rate is
improved.
FTIR Analysis for the Oxygen Effect on Roasting
To explore the effect of different oxygen contents on high-
temperature roasting, the FTIR analysis results are shown
in Figure 7. The high-temperature roasting stage is impor-
tant, which determines the leaching rate of the roasting
process. Because the lattice damage of vanadium-bearing
minerals occurs in high-temperature reoxidation roasting.
In Figure 7, 3438 cm–1 was the stretching vibration band
of hydroxyl in structural water. The strong absorption band
at Si-O: 1086 cm–1 in the silicon oxide tetrahedron belongs
to Si(Al)-O(Al), Si-O-Si(Al) stretching vibration (Bai et al.,
Table 3. Vanadium leaching rates of raw ore and roasted products
Sample Raw Ore
Primary Oxidation
Product
The Cascade Suspension
Roasting Product
Leaching rate, %32.66 46.39 68.89
Considering the leaching effect and energy consumption,
the appropriate high-temperature reoxidation roasting tem-
perature is 850 °C.
The data from the gas flow and oxygen content experi-
ment were shown in Figure 5(b) and Figure 5(c), respec-
tively. Both curves show a trend of rapid rose at first and
then a slow rise. With the increase of gas flow from 150 ml/
min to 600 ml/min, the leaching rate of V2O5 increased
from 56.35% to 64.25%. Similarly, the oxygen content
increased from 7% to 35%, and the leaching rate of V2O5
increased from 55.32% to 68.09%. This indicated that the
vanadium leaching rate of the roasted product was posi-
tively related to gas flow and oxygen content. Because oxy-
gen participates in the oxidation of low-valence vanadium
to high-valence vanadium in the roasting process. When
the oxygen supply was insufficient, a large amount of low-
valent vanadium in vanadium-bearing minerals cannot be
fully oxidized, and thus it is not easy to be leached by acid.
To ensure sufficient oxygen supply and good fluidization
effect of materials, the total gas volume of 600 ml/min and
35% O2 were considered as the appropriate roasting condi-
tions. In addition, when the roasting time was extended
from 1 h to 3 h, the leaching rate of V2O5 increased from
63.69% to 68.89% (Figure 5(d)). The leaching rate of
vanadium increased slowly due to the continuous exten-
sion of time. 3h was determined as the appropriate time for
high-temperature reoxidation roasting.
The vanadium leaching rates of raw ore and roasted
products were given in Table 3. The leaching rate of the
primary oxidation product improved by 13.73 percent.
Moreover, The leaching rate of roasted products effectively
improved by 36.23 percent to that of raw ore. Therefore,
the suitable conditions of high-temperature reoxidation
were 850 °C, 3 h, 35% O2, and 600 ml/min of gas volume.
68.89% was the optimum V2O5 leaching rate of a roasted
product under suitable conditions.
Analysis of the Roasting Process of Carbonaceous Shale
Phase Transformation Analysis
The effect of primary oxidation roasting on the phase trans-
formation of carbonaceous shale was analyzed by XRD(Hu
et al., 2012), as shown in Figure 6. With the roasting tem-
perature rising to 650 °C, all diffraction peaks of pyrite
in the sample disappear. This indicated that the oxidation
reaction of pyrite occurred at this time. This was consis-
tent with the results of the thermal decomposition analy-
sis of carbonaceous shale in Section 3.1. In addition, the
characteristic peaks of mica, quartz, dolomite, and barite
in carbonaceous shale had no obvious change. This showed
that these minerals, except pyrite, were unchanged during
the primary oxidation roasting. Further, the effect of high-
temperature reoxidation roasting on the phase of carbona-
ceous shale was analyzed by XRD, as shown in Figure 6. At
850 °C, the diffraction peak of mica in the sample disap-
peared, and the diffraction peak of tremolite appeared. This
indicated that the lattice structure of mica was destroyed at
high temperatures (Bai et al., 2022b Dong et al., 2020).
When the temperature rose to 1050 °C, the diffraction
peak of barite in the sample disappeared. It indicated that
the decomposition reaction of barite occurred.
Therefore, the removal of reducing substances such
as carbon and pyrite in carbonaceous shale is the func-
tion of the primary oxidation roasting process. This elimi-
nates the effect of reducing substances on the oxidation of
low vanadium to high vanadium in carbonaceous shale.
Furthermore, the effect of the reoxidation roasting process
is on the lattice structure of vanadium-containing mica.
Because of the stable lattice structure of mica, it is difficult
to release the vanadium element which is isomorphic in the
mica lattice, and then difficult to be oxidized and dissolved.
However, the binding of mica with a broken structure to
vanadium is weakened after high-temperature roasting.
Low-valent vanadium in mica lattice is more easily exposed,
which makes the low-valent vanadium converted into high-
valent vanadium. Then the vanadium dissolution rate is
improved.
FTIR Analysis for the Oxygen Effect on Roasting
To explore the effect of different oxygen contents on high-
temperature roasting, the FTIR analysis results are shown
in Figure 7. The high-temperature roasting stage is impor-
tant, which determines the leaching rate of the roasting
process. Because the lattice damage of vanadium-bearing
minerals occurs in high-temperature reoxidation roasting.
In Figure 7, 3438 cm–1 was the stretching vibration band
of hydroxyl in structural water. The strong absorption band
at Si-O: 1086 cm–1 in the silicon oxide tetrahedron belongs
to Si(Al)-O(Al), Si-O-Si(Al) stretching vibration (Bai et al.,
Table 3. Vanadium leaching rates of raw ore and roasted products
Sample Raw Ore
Primary Oxidation
Product
The Cascade Suspension
Roasting Product
Leaching rate, %32.66 46.39 68.89
