FIELD OF THE INVENTION
The present invention generally relates to a process to utilize low grade
manganese ore fines for manganese based ferroalloy making. More particularly,
the present invention relates to a froth floatation process for benefication of low-
grade manganese ore fines to improve manganese content to a desired level
(Mn>36, Mn/Fe:> 2) adaptable in silicomanganese making process.
BACKGROUND OF THE INVENTION
According to the prior art, high grade manganese ore lumps of >10mm are
generally preferred for the ferromanganese making process to maintain the
furnace performance. Low grade ore fines of <10mm generated in the mining
are normally discarded as a waste, because these fines cannot be used due to
low manganese content (Mn <35%), low Mn/Fe ratio (<1) high gangue
concentration (A12O3 0-10%, SiO2: 0-15% ) and finer size.
Manganese ores are primarily used in the silicomanganese making. These
ferroalloys are used in steel making process to refine the steel. Quality of
manganese alloys depends on the feed grade ores and the ore should contain
Mn:>36% and Mn/Fe>2 to produce the SiMn. The mined high-grade manganese

ore lumps (+10mm) are generally used in the submerged arc furnace at
silicomanganese plant. The low-grade fines generated in the mining and sizing of
the high grade manganese ores, are disposed at waste dumps. These fines
usually contain Mn: 25-34% and Mn/Fe:0.7-1. The high-grade manganese ore
resources are depleting rapidly and there is an economic requirement to
beneficiate the low-grade manganese ore fines to use in silicomanganese
production.
Benefication of Manganese ore fines however, entail the following
disadvantages:
1. Low density difference in manganese and iron minerals, so gravity
separation methods do not work.
2. Narrow difference in magnetic susceptibility of hematite and pyrolusite
makes the magnetic separation process difficult.
3. Existing floatation techniques are used for separation of silica and alumina
but separation of iron and manganese minerals is difficult.
4. Lower yield in magnetic separation of fines.

OBJECT OF THE INVENTION
It is therefore an object of the invention to propose a froth floatation process
for beneficiation of low-grade manganese ore fines to improve manganese
content adaptable in silicomanganese production process.
SUMMARY OF THE INVENTION
According to the invention, low-grade manganese ore fine samples are collected,
and processed to recover the siliceous ferromanganese grade concentrate. The
recovered ore concentrate is briquetted and used into silicomanganese making
process to replace the high grade lumpy ores.
Substantial amount of silico manganese grade ore concentrate can be recovered
from low grade manganese ore fines generated during mining. According to the
invention, low grade manganese ore fines of 0-0.500mm with Mn: 25-34%,
Mn/Fe: 0.7-1, Si02: 6-37%, AI203: 2-7 is beneficiated to remove aluminosilicates
and iron content using floatation agents. The ore fines are grounded into
<0.2mm size and fed to a floatation cell. Oilec acid is used as collector and
operational PH is kept around 5 and a product of Mn>36%, Mn/Fe>2, Si02<2%
and AI203 <5% was recovered at weight recovery varying between 49-60%.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a process flow-sheet according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The process developed according to the invention for Upgradation of low
ferruginous manganese ore fines substantially reduces the cost. The impact of
the process is more profound as it produces a product which can be used in
silicomanganese production. The developed process provides a methodology for
beneficiation of manganese ore fines.
The first stage of the process is to crush the oversize fines (>0.5mm) into
<0.5mm size. Further fine grinding results in the loss of softer pyrolusite
particles in the magnetic fraction with iron particles. Size distribution and
chemical analysis of fines is given in table 1 and 2.

Table-1 : Chemical analysis of Manganese ore sample

According to the invention, detailed data on liberation and association
characteristics of the minerals were studied before selecting the process
parameters and achieving desired quality product. Characterization studies were
carried out using XRD and QEMSCAN. It was found that major manganese
mineral is pyrolusite and major iron bearing mineral is hematite, Quartz, Kaolinite
and mica and other major gangue minerals. In liberation studies it was found
that >80% iron and manganese minerals are liberated at 200 micron size which
will be helpful for separation of these minerals.

Flotation experiments are carried out in a flotation cell with Oilec acid collector at
a dosing rate of 1 to 3 Kg/T. Feed slurry was conditioned at 30-40% solids with
oleic acid for 15 minutes. Percent solids in the feed are maintained is 10-15%
solids with airflow rate of 2.5 liters per minute, stirrer speed of 1000 rpm and
pine oil was used as frother. Test was conducted for 15 minutes. Slurry pH 5 to 7
is adjusted using _ sodium hydroxide and HCL. The result obtained in the 2nd
stage of floatation test is shown in Table 3. In the first stage PH was maintained
around 7 and aluminosilicates were removed. In the second stage, iron and
manganese minerals were separated at pH of 5. Final concentrate produced
contains 38.23 % Mn, 18.54 % Fe, 4.80% Al2O3 and 1.44% SiO2 with Yield of 50-
60%.
Table-3 : Floatation test conditions


A product of Mn > 36, Mn/Fe: ~2, Si02< 10 and A1203 < 5% was achieved in
this process with the manganese recovery >60 % with an yield of 50-60%. The
iron particles of finely disseminated in the manganese minerals cannot be
removed further. The optimized conditions used in the invention, are for
example, collector dosing of 1 Kg/T, percent solids 25% in slurry with airflow
rate of 2.5 liters per minute, and stirrer speed of 1000 rpm. Slurry pH for first
stage was 7 and for the second stage 7 is maintained with sodium hydroxide.
Detailed process flow sheet is given in Figure 1.

WE CLAIM:
1. A method to recover silicomanganese grade ore concentrate from low
grade manganese ore fines, comprising the steps of :
- grinding of the low-gradient ore fines of >0.2mm into <0.2mm size fines;
- removing the aluminosilicates in a first stage floatation step at pH 7 using
Oilec acid collector;
- floating iron bearing minerals from manganese minerals at pH 5 in a
second stage floatation step;
- discarding the iron, alumina and silica bearing gangue minerals in a two
stage reverse floatation of low grade manganese ore; and
- recovering in an ore concentrate containing a product of Mn > 36, Mn/Fe:
~2, SiO2< 10 and A1203 < 5% with manganese recovery >60 % and
weight recovery between 50-60%.

2. The method as claimed in claim 1, wherein the dosing rate of the collector
is 1 to 3 Kg/T, and wherein the feed slurry was conditioned at 30-40%
solids with the collector for about 15 minutes.
3. The method as claimed in claim 1 or 2, wherein air-flow rate of 2.5
liters/minute and stirring speed of 1000 rpm is maintained.
4. The method as claimed in claim 1, where the pine oil is selected as the
frother.
5. The process as claimed in claim 1, wherein the product is used for
silicomanganese production.

ABSTRACT
The invention relates to a method to recover silicomanganese grade ore
concentrate from low grade manganese ore fines comprising the steps of
grinding of the low-gradient ore fines of >0.2mm into <0.2mm size fines;
removing the aluminosilicates in a first stage floatation step at pH 7 using
Oilec acid collector; floating iron bearing minerals from manganese minerals
at pH 5 in a second stage of floatation step; discarding the iron, alumina and
silica bearing gangue minerals in a two stage reverse floatation of low grade
manganese ore; and recovering in an ore concentrate containing a product of
Mn > 36, Mn/Fe: ~2, SiO2< 10 and A1203 < 5% with manganese recovery
>60 % and weight recovery between 50-60%.