 |
Visits: 86087423
AMS now reading: 1
|
|
|
|
|
 |
|
|
| Mikloš V. |
| EXPERIMENTAL VERIFICATION OF THE INFLUENCE OF ARBITRARY VARIABLES ON COBALT RECOVERY FROM LATERITE ORE INTO AMMONIA SOLUTION |
Abstract
The intention of presented work is to describe the possibilities of utilisation of information on common cobalt oxides reduction to cobalt oxides reduction from Albanian lateritic Fe-Ni ore. The definition of two independent variables: the reduction temperature and oxygen partial pressure in the gaseous atmosphere is sufficient to define FeNi lateritic ore reduction equilibrium.
The constant reduction time of 40 minutes and reduction temperatures 600, 650, 700, 750, and 800°C were chosen for experimental tests. In further experiments, the reduced sample was cooled at different rates in reduction or inert atmosphere of purified argon because of gaseous atmosphere influence on the reduction efficiency. Only suitable ore reduction stage and the corresponding roasted ore phase content ensure sufficient cobalt transfer into the ammoniacal solution.
Sample reduction efficiency was evaluated by standard leaching test, reduced sample leaching in the ammoniacal solution of ammonium carbonate. Concentrations of cobalt and iron were stated by means of atom absorption spectrometry method.
Thermodynamic analysis of Co and Fe oxides reduction leads to an important finding that in spite of Co oxides seem to reduce easy, when they are bind with other oxides present in a lateritic ore, their reducibility lowers sharp. For the reduction, the high reduction potential of reducing gas is needed, what is clear at their binding with Fe oxides, when the equilibrium curves of individual oxidoreduction reactions are shifted to the higher reduction potentials region.
A selective reduction of the FeNi lateritic ore is not possible. The reduction is accompanied by the Fe-Ni alloy (?-phase) creation.
The efficiency of Co transfer into g-phase alloy increases with increasing Fe oxides reduction stage, at simultaneous decrease of cobalt content in the reduced alloy.
Cobalt yield increases up to the reduction temperature of 700°C, then, with the increasing temperature, it decreases. The highest cobalt yields have been achieved at fast cooling of the reduced ore in the inert atmosphere.
Dissolution of iron into ammoniacal solution begins to increase markedly above the temperature of 650°C, pCO/pCO2 ratio 4.98 in reduction atmosphere, and at the core cooling in inert atmosphere. The iron precipitation from ammoniacal solution decreases Co yield into ammoniacal solution.
During the reduced ore cooling in an reduction atmosphere, the reoxidation of reduced metallic ?-phase takes place at simultaneous decrease of Co and Fe yields into ammoniacal solution. With the amount of reduced metallic phase, the influence of reoxidation increases, as well.
|
| Keywords: |
| No 3 (1998), p. 211-219 |
|
|
|
|
|
|
|
Editors and press
AMS online
