TITLE:
Enrichment of chromite value from ultrafine chromite tailings of COB Plant
Sukinda by desliming followed by selective flocculation using CMC flocculant.
FIELD OF THE INVENTION:
The present invention relates to a process for enrichment of chromite value from
ultrafine chromite particle of COB plant.
The present invention also relates to upgrade ultrafine chromite particle present
in the chromite tailing pond by selective flocculation followed by desliming
technique. The selective flocculation was conducted using medium grade of
CMC (carboxyl methyl cellulose) as flocculant. In this method the Cr2O3 (%) was
upgraded to 36.21 (%) with 29 yield (%).
BACKGROUND OF THE INVENTION:
During beneficiation of low grade chromite ores, huge quantity of tailings was
generated and these tailings were stored in the tailing pond. For further recovery
of metals from the tailings many attempts was taken by physical separation
method, magnetic separation method, physico chemical method of separation ie

flotation etc. All these methods are not much effective because of particle size
limitations. Selective flocculation is another alternative physicochemical method
for beneficiation of the ultrafine chromite particles.
Few attempts was taken at Turkey to establish the process using artificial
mixtures of chromite ore and its associated gangue minerals i.e serpentine
[Akedemir and Hieylmaz, 1998; Bekioglu and Arol, 2004]. But they could not
establish the process effectively.
Lopamudra etal, 2013; 2014 has taken an attempt to establish the selective
flocculation using synthetic mixture of chromite and its associated gangue
minerals kaolinite. They had achieved Cr2O3 (%) 45.19% with (%) 56.48(%)
recovery from 24.3% of feed assay. Few works was done to establish the
selective flocculation process using degraded wheat starch as the flocculant
(291/KOL/2013; 316/KOL/2014).
In the patent 291/KOL/2013 enrichment of ultrafine chromite tailing was carried
out by selective flocculation followed by magnetic separation process. The
findings shows it was possible to obtain Cr2O3 (%) upto 28.11% with 31.89% of
Fe (T) % from 14% Cr2O3 of feed assay.

In the patent no. 316/KOL/2014, enrichment of ultrafine chromite particles was
attempted by desliming followed by selective flocculation method using degraded
wheat starch as flocculant. They had achieved Cr2O3 (%) 44.04 %, 12.01% Fe(T)
with 31.7 yield (%)in the concentrate from the deslimed product of feed assay
(%) of 24.9% Cr2O3(%), 21.9% Fe(T).
For all the above cases degraded wheat starch was used. In commercial
practice, preparation of the flocculant is a challenging part. In addition to this, the
flocculant remains active only for 24 hours.
In one patent IN 201631008680, selective flocculation for enrichment of ultrafine
chromite tailings was attempted using medium grade CMC flocculant. They used
chromite particles which was generated by wet sieving from the as received
chromite tailings. They achieved approximately 31.34 (%) Cr2O3(%) with 32.086
yield (%) from 16.81(%) of Cr2O3feed assay (%). But the developed process is
having limitations for commercial application.

OBJECTS OF THE INVENTION:
An object of the present invention is to propose a process for enrichment of
chromite value from ultrafine chromite tailings of COB (Chrome Ore Beneficiation
Plant.Sukinda district of Odisha, Tata steel Ltd) plant.
Another object of the present invention is to develop a process flow sheet to
upgrade the ultrafine chromite particles using CMC reagent by selective
flocculation method.
Still another object of the present invention is to generate ultrafine feed particles
from the as received tailing which will be used as a suitable feed for selective
flocculation by grinding followed by desliming.
Yet another object of the present invention is to grind the chromite tailings for
better liberation in a ball mill prior to desliming in a 2" hydrocyclone.

Further object of the present invention is to do the assay analysis, size analysis
of the desliming products i.e both under flow and over flow.

Still further object of the present invention is discard the overflow of the deslimed
product if assay(%) is less than 10(%).
Another object of the present invention is to use the deslimed under flow product
in selective flocculation by further grinding.
A still further object of the invention is to enrich the ultrafine chromite values by
selective flocculation process to achieve Cr2O3 (%) grade upto 36.21 % with
29.8% yield (%).

Yet another object of the present invention is prepare the CMC (Carboxy Methyl
Cellulose) as the flocculant is by preparing the flocculant by addition of sodium
hydroxide with Carboxyl methyl cellulose.
BRIEF DESCRIPTION OF THE PRESENT INVENTION:
According to the invention there is provided a process for enrichment of chromite value from ultrafine chromite tailings of COB plant comprising the steps
of collecting the chromite tailing sample from representative point of tailing pond,

grinding the sample to generate less than 150 µm of particle size, subjecting the
grinded sample to desliming in a hydrocyclone by varying difficult operating
process parameters, separating the products of the hydroclone into two parts ie
the overflow and the under flow. Furthermore introducing the under flow products
to a ball mill for further grinding to generate ultrafine particles of 37 micron and
rejecting the hydrocyclone over flow products as discard. The underflow sample
was introduced as the feed for selective flocculation process.The feed sample
was subjected for dispersion phase after addition of the dispersants,
subsequently maintaining the pH of the feed slurry the feed sample was mixed
with 2000RPM by a mechanical stirrer for proper mixing of the dispersants with
the feed sample and after addition of flocculent , speed reduced to 200 RPM
subsequently to prevent the breakage of formed floe.
After maintain the flocculation time, the dispersed phase was separated from the
flocculated phase and subjected for analysis,
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS-
w
Figure 1 shows that flow sheet of the developed process.

DETAILED DESCRIPTION OF THE INVENTION:
Tailing pond sample of COB (Chrome Ore Beneficiation Plant, Sukinda) was
. used in the study. Size analysis of the as received tailing sample shows the
tailings contains particle size variation from 1mm. The collected tailing sample
was subjected for detail characterization study i.e. assay analysis, physical
property analysis, mineralogical analysis, surface property analysis etc.
The mineralogical analysis shows better liberation was found in the size less than
150 Mm. The as received tailing sample was grounded to pass through 150 urn.
Furthermore the grounded sample was subjected for assay analysis. The assay
analysis of <150um shows the sample contains Cr2O3(%) 20.66, Al203
20.39(%),6.32(%) SI02. 24.6(%) Fe(T) etc These grounded (<150 urn) particles
subjected for desliming by 2" hydrocyclone. The desliming process was done
varying different operating process parameters i.e. bed pressure (.5, 1,1 5 and 2)
kg/cm2, vortex finder (14.3, 11.1 and 8.3) mm and apex diameter (9.4,6.4,5 and
3.2) mm etc. Analysis shows at bed pressure 1.5 kg/cm2,apex dia of 6.4mm and

vortex finder of 11.1 mm approximately 24.99% Cr2O3 (%) with 21.36% of Fe (T)
% with 78% of yield was achieved in the underflow, whereas 7-8% of Cr2O3 (%)
with 30-34% of Fe (T) % was achieved in the overflow. The product analysis
details is presented in Table 1. The overflow material was rejected as it contains
Cr2O3 (%) less than 10%. The underflow product was further processed and used
as the feed for selective flocculation process. The underflow products was
grounded in the ball mill to generate particle size of less than (37 um), which was
used as feed for selective flocculation process.
All selective flocculation test work was conducted by maintaining 12% of
solid concentration. Test works were conducted in a 1000ml of glass beaker. In
selective flocculation process sodium hexametaphosphate solution was used as
dispersant and the medium grade CMC was used as the flocculant. While
conducting the experiment, the mechanical stirrer speed was maintained at a
high rate approximately 2000RPM, so that the added dispersant can add on each
and individual minerals. Subsequently required pH of the feed slurry was
maintained. After addition of the flocculant dose, mechanical stirrer speed
reduced to a slower speed approximately to 100 rpm. After maintaining the

required conditioning time, supernant liquid was separated from the flocculated
part, subsequently subjected for assay analysis. The chemical analysis was
presented in Table 2. The detail process flow sheet is presented in Fig.1.


WE CLAIM:
1. A process for enrichment of chromite value from ultrafine chromite tailings
of COB plant comprising the steps of collecting tailing sample of ultrafine
chromite,
grinding the trailing sample to less than 150 µm particle size,
subjecting the grinded sample to the step of desliming in a hydrocyclone by
varying the difficult operating process parameters,
separating the contents of the hydroclone into two parts the overflow and the
under flow,
introducing the under flow products to a ball mill to generate (-37 µm of ultrafine
particles) and discarding the over flow products as reject,
subjecting the grand product of the underflow(-37 µm) to the step of selective
flocculation process,
stirring the mixture at a speed of approximately 2000 RPM,
separating the supernatant liquid from the flocculated part,
subjecting both the products (supernant part & the flocculated part)to the step of
further analysis.

2. The process as claimed in claim 1, wherein the said step of desliming was
preferred varying different operating process parameters i.e bed pressure
between .5 to 2 kg/cm2, vortex finder 14.3 and 8.3mm and apex diameter is 9.4
and 3.2 mm.
3. The process as claimed in claim 1 wherein the preferred parameters for
desliming are bed pressure 1.5 kg/cm2, apex diameter of 6.4mm and vortex
finder of 11.1mm.
4. The process as claimed in claim 1, wherein the said under flow has
24.99% Cr2O3 and 21.36% of Fe.
5. The process as claimed in claim 1 wherein the overflow has 7 to 8% of
Cr2O3% with 30-34% of Fe and the same was discarded.
6. The process as claimed in claim 1 wherein the said underflow products
were grounded in a ball mill to produce particle size of less than 37 µm.

7. The process as claimed in claim 1, wherein flocculation process was done
using sodium hexametaphosphate solution as dispersant and CMC was used as
flocculant.