THE STUDY OF LIQUID AND GAS PHASES INTERACTION
DURING THE REDUCTION OF METAL OXIDES FROM THE
MELTS BY GAS REDUCTANT IN BUBBLED LAYER1
A.S. Vusikhis, A.N. Dmitriev, D.Z. Kudinov, L.I. Leontiev
Institute of Metallurgy, Urals Division of Russian Academy of Sciences
101, Amundsen street, Ekaterinburg, 620016, Russia
ABSTRACT. Analyses of the former results allowed to apply thermodynamic balance
calculation to the description of the oxide melt reduction kinetics. Step by step
balance equation solution permitted to build a series of kinetics curves for interaction
process between multicomponent oxide melt and reducing gas during barbotage.
Studying gas interacting processes during the barbotage at the multicomponent
oxide melt with the purpose of testing the selective extraction possibility is of both
scientific and practical interest.
The solution of this problem within the scope of the complex solution of the
rational raw material resources development problem is of especial interest for the
Urals and for the Sverdlovsk region in particular.
As a rule, thermodynamic balance calculations for various systems are
performed in order to estimate the reaction possibility. In this work an attempt to
apply thermodynamic balance calculation to the description of the oxide melt
barbotage kinetics with various reduction gases was made.
The technique was tested on a NiO-FeO-Al2O3-SiO2-CaO-MgO-CO-CO2
system. The gas and melt composition are analogous to those used earlier during
studying the blow of the ore melt containing nickel oxide (1.8% wt.) and iron oxide
(17.4% wt.) with the mixture of CO (97% vol.) and CO2 (3% vol.).2
Initial data for calculations was following: temperature — 1550°C, pressure —
1 atm, initial melt contents: nickel oxide — 1 mole, iron oxide — 10 moles, total
gases amount in a portion — 1 mole, gas contents: CO — 0.97 mole, CO2 — 0.03
mole.
Comparative analysis of calculated (drawn as lines) and experimentally
acquired (drawn as rectangles) data (Fig. 1 – 4) has shown that proposed technique
may be used for qualitative analysis of the interaction processes between
multicomponent oxide melt and reduction gases of various composition.
A work of kinetics description of melted multicomponent system barbotage
with various reduction gases has been done on a basis of the conclusions that have
been made. Initial data for calculations are the same (excepted of gases composition):
temperature — 1550°C, pressure — 1 atm, gas amount in a portion — 1 mole.
Composition and amount of components in the systems shown in Table 1, gas
composition — Table 2.
1
Work is executed at support of Council under grants for conducting scientific
schools of Russia (№ 1997.2003.3).
2
Leontiev L.I., Vatolin N.A., Shavrin S.V., Shumakov N.S.: Dry metallurgy
processing of complex ores. Moscow, Metallurgy, 1997.
1 - 72
Fig. 1. Nickel contents in an alloy
Fig. 2. Nickel oxide contents in the melt
1 - 73
Fig. 3. Nickel extraction into the alloy
Fig. 4. Slag ratio
Table 1. Oxide system composition and amount of components
NiO
FeO
SiO2
Al2O3
CaO
MgO
Unit
1
10
40
3
10
2
Mole
0,015
0,152
0,606
0,045
0,152
0,03
Molefraction
1,8
17,4
58,0
7,4
13,5
1,9
% wt
1 - 74
Table 2. Initial gas composition in a bubble (portion), % vol.
Version
CO
CO2
H2
H2O
1
100
0
2
97
3
3
95
5
4
92,5
7,5
5
87,5
12,5
6
80
20
7
75
25
8
0
0
100
0
9
33,1
0,01
66,3
0,6
10
30,9
2,4
55,8
10,9
11
26,3
6,9
40,4
26,4
Versions 1 through 7 are CO-CO2 mixtures with various amounts of
components, version 8 is pure hydrogen, and versions 9 through 11 are results of rock
gas oxygen conversion at different oxygen flow factors. Thermodynamic calculation
results are represented at Fig. 5 – 8.
Analysis of the results that have been got shows that a joint iron and nickel
reduction process with reduction gases barbotage depends on their composition.
During the reduction with pure gas (H2, CO or their mixture) one with the carbonic
oxide is the slowest. Rising the amount of hydrogen speeds the process up; reduction
with pure hydrogen is the most effective. During barbotage nickel reduction speed
decreases, and irons one increases. During melt blowing with H2+CO mixture
reduction process is performed basically with hydrogen, CO Influence is much less.
Nickel extraction degree is great, but with barbotage duration increase iron extraction
degree increases also, which can lead to significant ferrous alloy dilution. During the
reduction with a gas mixture containing reaction products (CO2 and H2O) both oxides
reduction degree decreases, their reduction speeds fall, and so do metal extraction
degrees. Thus, depending on the chosen aim, reduction gas of various compositions
may be used, which can be generated with various kinds of solid, liquid or gas fuel
usage. The reduction with hydrogen is the most effective, but such gas generation
leads to a great expenditure. Converted rock gas usage is much less expensive. Rock
gas conversion may be accomplished with various oxidizers: oxygen, water vapor,
and carbon dioxide. Depending on the oxidizer concentration converted gas will
contain different CO, H2, CO2 and H2O amounts. As shown by calculations, gas made
of CO and H2 with maximal hydrogen amount is the most effective. Gas of such
composition may be generated with rock gas vapor conversion; oxygen conversion
product contains 8% more CO, though energy expenditures for its generation are
much less.
1 - 75
Fig. 5. Nickel contents in an alloy
Fig. 6. Nickel oxide contents in the melt
1 - 76
Fig. 7. Nickel extraction into the alloy
Fig. 8. Slag ratio
1 - 77