4. of Itakpe and Ajabanoko iron ore respectively. Table

4.         DISCUSSION

4.1       CHEMICAL COMPOSITION ANALYSIS

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The chemical composition analysis of itakpe iron ore
as represented in Table 1 show that Itakpe contains iron, silicate, aluminium,
magnesium, potassium and sodium elements, while Table 2 represents the chemical
composition of Ajabanoko deposit which is composed of iron, silicate,
aluminium, magnesium, potassium and sodium as well. It should be noted that
potassium, aluminium, magnesium and sodium occurs in a very small amount for
the two deposits. The chemical composition also confirmed that Itakpe iron ore
has average iron concentration of 36.18 % before carrying out any beneficiation
on it, while the Ajabanoko iron ore has average iron concentration of 34.4 %
before processing as presented in Table 1 and Table 2. The results revealed
that Itakpe has higher iron concentration than Ajabanoko prior to
beneficiation.

4.2       MINERALOGICAL ANALYSIS

Table 3 and Table 4 show the mineralogical analyses
of Itakpe and Ajabanoko iron ore respectively. Table 3 shows that Itakpe has
higher composition of hematite (29.67 %) than magnetite (24.18 %) with a
sub-metallic lustre. Table 4 which represent the Ajabanoko mineralogical
analysis has a higher composition of magnetite (26.54%) compare to hematite
(20.41 %). Although, both ore has higher composition of quartz mineral which can
be consider as the dominant gangue mineral of the ore.

 

4.3       BENEFICIATION STUDIES

The
general observations in the study show that separating fluid plays vital roles
in the separation of iron minerals from its ore and that the particle sizes
also aid the recovery. Although, there is appreciable recovery at fine particle
sizes, but the recovery was increased at coarse particle sizes.

 

4.3.1    Effects of Dilution Ratio

The
influence of dilution on the recovery of iron ore using Spiral is as revealed in
Tables 7, 8, 9, 10, 11, and 12. The highest grade of iron mineral was achieved
at 30% solid using the spiral gravity technique. The 40 % solid which is a low
dilution (higher percent solids) experienced a decrease in the falling rate of
particles leading to overcrowding of the particles during separation process
which makes the separation iron minerals from the gangue minerals to be less effective.
The volume of water in the agitator provides the necessary dilution required
for particles separation. Highest grade of Itakpe iron ore was gotten at 30 %
dilution using spiral separator as presented in Table 8 and Figure 11
respectively. Although, 20 % dilution ratio also recorded a reasonable grade,
but 30 % dilution is determined to be the optimum for Itakpe iron ore deposit
which has 62.0 % recovery using spiral separator. Beneficiation of Ajabanoko
iron ore recorded the highest grade at 30 % dilution using the spiral with a
recovery of 66.95 %. These indicate that separating fluid has a greater effect
on recovery using spiral separator.

 

4.3.2    Effects of Particle Size

The
effect of the particle size on the recovery of iron ore is also shown in Tables
7, 8, 9, 10, 11, and 12. The highest iron grade for Itakpe iron ore was
achieved at +300 ?m particle size
and +300 ?m was also determined to be optimum for Ajabanoko iron ore using
spiral separator as presented in Tables 8 and 11 respectively. Lower separation
efficiency in finer particles was observed and believed to be caused by the
negligible mass associated with these size particles. Particles so small that
settle in accordance with Stroke’s law are unsuitable for concentration (Wills,
2006).

 

4.3.3    Separation Effectiveness

The
results, as shown in Figures 4, 6, 8, 10, 12, and 14 revealed that iron ore
concentrate was effectively separated from the tailings, which are dominated
with quartz minerals. Theoretically, effective separation was possible because
the quotient of the difference in their specific gravities is greater than 2.5
(equation 1). From the same results, it was observed that the overflow, i.e.
the tailings still have a higher percentage of Fe at the end of the four stage
concentration processes. This Fe in the gangue may come from magnetite in the
ore, which was not effectively separated. The specific gravity of magnetite is
between 4.9 and 5.2, indicating that the quotient varies is between 2.4 and
2.8. Should there be more magnetite of specific gravity 4.6, the efficiency of
separation decreases. Recall from the above equation, as the quotient reduces,
the effectiveness of the separation reduces. Also, from the mineralogical
studies, it could be recalled that the Itakpe ore has higher percentage of
hematite and lower percentage of magnetite, while the Ajabanoko ore has higher
percentage of magnetite and lower percentage of hematite.

 

5.         CONCLUSION

It
has been observed that the quartz mineral present in the iron ore from the two
locations is the major gangue mineral, hence the nature of this mineral (quartz)
affected the recovery of iron minerals. The results revealed that the
concentration criterion is fulfilled for the effective separation of the
valuable minerals from the gangues using spiral gravity separation technique.
These results shows that gravity separation can as well be carried out in a
large scale on the two deposits which will be economical and profit driven if
invested on.

The
results of this study have clearly shown that optimum separation of iron ore
concentrate from Itakpe and Ajabanoko iron ore by spiralling operations is
possible. It is clearly revealed that the optimum separation was greatly
influenced and can be efficient with optimum dilution ratio and smaller
particle size of the ores. The result of the study has also shown that the
optimum Fe recovery could be achieved when the particle size is at +300 µm particle size
at 30 % dilution for Itakpe and +300 µm particle sizes
at 30 % dilution for Ajabanoko iron ore using 6-bowl spiral separator. The
spiral gravity separation technique was able to upgrade this type of ore to the
marketable grade as a result of the reasonable difference in specific gravity
between the iron mineral and the main associated minerals. Gravity separation
was a possible solution for pre-concentrating such ore before using other
concentrating technique in taking it to super concentrate. The result of both
deposits show little or no difference in terms of their recovery, which
interprets to both deposit having the same physicochemical properties. The result of beneficiation using spiral
separator shows particle size and dilution ratio plays a vital role on the
recovery of the iron minerals. Increase in dilution ratio gives increase in
recovery and grade of iron minerals but to a limit. Also, the smaller the
particle size the better the result of grade, but there is a limit at which
gravity concentration will be efficient when the dilution ratio is too high or
the particle size is too fine.