PROCEDE DE FABRICATION D'UNE ALIMENTATION DE GRANDE QUALITE POUR HAUT FOURNEAU A PARTIR D'ULTRAFINES DE MINERAI DE FER DE BASSE QUALITE

A PROCESS FOR PRODUCING HIGH GRADE BLAST FURNACE FEED FROM POOR GRADE IRON ORE ULTRA FINES

Abrégé français

L?invention concerne un procédé de fabrication d?une alimentation de grande qualité pour haut fourneau à partir d?ultrafines de minerai de fer de basse qualité, qui comprend le traitement d?ultrafines par dispersion sélective pour séparer les matériaux de gangue du matériau de fer déposé et le traitement du matériau de fer déposé par redispersion avec un dispersant non sélectif. Le matériau déposé dispersé est alors traité par floculation sélective avec de l?amidon modifié pour séparer du fer concentré pour une alimentation de haut fourneau et des résidus, en laissant les minéraux de gangue dans la phase dispersée. Le procédé de séparation des minéraux contenant du fer et des minéraux de gangue est réalisé en fonction des états de charge de surface à un pH particulier pendant la redispersion avec un dispersant non sélectif et par ségrégation des particules plus fines par un procédé d?hydrocyclone pour une meilleure floculation afin de produire le produit final qui contient 68 % de Fe, 1 % d?alumine et 1 % de silice.

Abrégé anglais

A process for producing high grade blast furnace feed from poor grade iron ore
ultra fines consists of processing
ultra fines by selective dispersion to separate gangue materials from settled
material iron and processing settled material of iron by
re-dispersing with non-selective dispersant The dispersed settled material is
then processed by selective flocculation with modified
starch to separate concentrate iron for blast furnace feed from tailings
leaving the gangue minerals in the dispersed phase. The process
of separation between iron bearing minerals and the gangue minerals is carried
out on the basis of surface charge conditions
at a particular pH during re-dispersing with non-selective dispersant and
segregating the finer particles by hydro-cyclone process
for better flocculation to produce the final product that contains 68% Fe, 1%
alumina and 1% silica.

Revendications

WE CLAIM
1. A process for producing high/qualified grade blast furnace feed from
poor/disqualified grade iron ore ultra fines, comprising:
processing the ultra fines by selective dispersion to separate gangue
materials from settled material comprising iron;
processing the settled material after separation of the gangue
materials by re-dispersing the settled material with a non-selective
dispersant;
processing the settled material after said re-dispersing by selective
flocculation with modified starch to separate concentrate iron for blast
furnace feed from tailings, leaving the gangue minerals in a dispersed
phase;
wherein a separation between iron bearing minerals and gangue
minerals is carried out on a basis of surface charge conditions at a
particular pH during said re-dispersing with the non-selective dispersant,
and segregating finer particles by a hydro cyclone process for better
flocculation to produce a final product that contains 68% Fe, 1.2%
alumina and 1.3% silica.
2. A process as claimed in claim 1, wherein the selective dispersant is a
polymer
of 5,000 to 10,000 molecular weight and the non-selective dispersant
includes sodium silicate and sodium hexameta phosphate, wherein the
dosage of said dispersant is in the range of 20 to 10,000 ppm.
8

3. A process as claimed in claim 1, wherein the dosage of flocculants is in
the
range of 20 to 10,000 ppm and includes a starch solution having a
concentration of said starch in the range of 0.1 to 10 wt%.
4. A process as claimed in claim 1, wherein the starch includes potato, wheat
and maize and the starch solution is plain as well as caustic starch solution
having starch concentration in the range of 0.1 to 10 wt%.
5. A process as claimed in claim 1, wherein the pH is 8-10.
6. A process as claimed in claim 1, wherein the concentration of ultra fines
in
solution is in the range of 2 to 25 wt%.
7. A process as claimed in claim 1, wherein the settling time is in the range
of
seconds to 20 hours.
8. A process as claimed in claim 1, wherein the mixing process comprises
magnetic stirring, mechanical stirring or mixing the ultra fines in solution
using ultra sound.
9. A process as claimed in claim 1, wherein the solvent is tap water,
distilled
water or double distilled water.
9

Description

CA 02731355 2011-01-19
WO 2010/146596 PCT/IN2009/000434
FIELD OF INVENTION
The present invention relates to a process for producing high grade blast
furnace
feed from poor grade iron ore ultra fines. More particularly, the invention
relates
to a process of separation of iron bearing minerals from gangue minerals
contained in ultra fines by selective dispersion and selective flocculation
process.
BACKGROUND AND PRIOR ART OF THE INVENTION
Large quantities of ultra fines are generated during mining and washing of
iron
ores. At present 11 million tons of these ultra fines have accumulated at
various
slime ponds. Ultra fines contain iron with high alumina and silica generated
in
the iron ore mines and the iron ore washing plants. These materials contain
iron
bearing minerals namely hematite, goethite and magnetite and the gangue
materials composing of mostly clay and other alumina silicates. The fined
grained
clay mineral poses difficulties in beneficiation of these off grade fines to
make it
suitable for blast furnace feed, because the fines generated in the iron ore
mines
and also in the iron ore washing plants do not satisfy the stringent
specifications
of raw materials to be fed into the blast furnace.
1

CA 02731355 2011-01-19
WO 2010/146596 PCT/IN2009/000434
The prior art discloses process of separation between two elements namely iron
and alumina or iron and silica or alumina and silica from compounds where
these
items exist in different forms.
Therefore there exists a need to produce quality raw materials from the ultra
fines to make it suitable for blast furnace feed which will be of great
economical
significance by separating iron from alumina and silica contained in ultra
fines.
OBJECTS OF THE INVENTION
Therefore it is an object of the invention to propose a process for producing
high
grade blast furnace feed from poor grade iron ore ultra fines which is capable
of
separating iron from alumina and silica present in ultra fines for blast
furnace
feed.
Another object of the invention is to propose a process for producing high
grade
blast furnace feed from poor grade iron ore ultra fines which makes it
environmental friendly with zero waste.
Yet another object of the invention is to propose a process for producing high
grade blast furnace feed from poor grade iron ore ultra fines which is capable
of
separating iron from ultra fines that qualifies for blast furnace feed having
less
than 2% alumina and silica.
2

CA 02731355 2011-01-19
WO 2010/146596 PCT/IN2009/000434
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig. 1 - shows a flow chart describing the process according to invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
According to the invention, a process has been developed for producing
concentrate containing very high iron with very low alumina and silica from
the
ultra fines containing high alumina and silica generated in the iron ore mines
and
the iron ore washing plants. In this process, alumina and silica are
selectively
dispersed whereas the iron bearing minerals are selectively flocculated under
specific conditions. The final product contains more than 68 % Fe with only
around 1.2% alumina and 1.3% silica from the ultra fines containing around
57% Fe, 7.51% alumina and 7.15% silica, with iron recovery from 45-75%. The
tailings generated in this process can be utilized as building materials. This
process is environmental friendly with zero waste.
Quality of the raw materials for the iron and steel industries plays an
important
role in the down stream processes. The fines generated in the iron ore mines
and also in the iron ore washing plants do not satisfy the stringent
specifications
of raw materials to be fed into the blast furnace. It is therefore necessary
to
beneficiate these off grade fines to make it suitable for blast furnace feed.
In the
process of upgrading this ultra fines, with low gangue minerals containing low
3

CA 02731355 2011-01-19
WO 2010/146596 PCT/IN2009/000434
alumina and silica which would be suitable raw materials to be feed into the
blast
furnace. At the same time some part becomes rich in gangue materials
containing high silica and alumina which may be useful for making building
materials. The fine grained clay mineral poses difficulties in beneficiation
Selective dispersion followed by selective flocculation has been considered to
be
the most suitable beneficiation process for these materials due to the
fineness of
the materials. The characterization studies of these ultra fines show that the
particles are mostly below 35 micron and the major constituents are iron
oxide,
alumina, silica, alumina-silicates and iron-alumina silicates. Since the
surface
charge on the gangue minerals (silica and alumina-silicates) are quite
different
from that on iron oxide, at a particular pH, separation between iron bearing
minerals and the gangue minerals can be done on the basis of surface charge
conditions. In addition to the above consideration, a starch flocculant can be
used to selectively agglomerate the iron bearing minerals leaving gangue
minerals in the dispersed phase.
In the present invention suitable flocculation process has been developed on
different grades of slime material. The concentrate will be useful feed
material
for iron making through blast furnace route where as tailing will be suitable
feed
material to manufacture building material.
The difference in surface charge of the iron bearing minerals and the gangue
minerals has been utilized first to separate out some part of the gangue
minerals
present in the ultra fines. In the second stage, the materials from the first
stage
4

CA 02731355 2011-01-19
WO 2010/146596 PCT/IN2009/000434
have been subjected to the selective flocculation by using modified starch. By
this process, value added products, the concentrate becomes the raw material
for blast furnace and the tailing containing high alumina and silica becomes
building materials.
As shown in figure 1, ultra fines are subjected to selective dispersion
process
which separates tailings with higher alumina and silica from settled material
comprising mainly of iron with some tailings. This is then subjected to re-
dispersing process with non selective dispersant. In the next stage, the
materials
from the first stage is subjected to a selective flocculation by a
flocculating agent
like modified starch which separate out iron rich concentrate from further
left out
gangue materials of clay, alumina and silica which goes out to tailing already
collected. Now this concentrate of iron can be used for blast furnace feed.
The
gangue materials containing high silica and alumina thus separated can be used
for building material so that no wastage results out of the process.
The advantages of the process over prior art are:
1. Separation takes place among three compounds of iron, alumina and
silica existing in ultra fines in various forms.
2. The final product containing 68% Fe with only round 1.2% alumina and
1.3% silica from the ultra fines is qualified as blast furnace feed. More
than 2% of alumina and silica disqualifies the product as blast furnace
feed.

CA 02731355 2011-01-19
WO 2010/146596 PCT/IN2009/000434
Iron containing ultra fines is the mixture of Fe, Si,Al oxide with different
particle
size. The particle size of ultra fines is in the range of 100 micron to 100
nm. Both
the alumina and silica levels in ultra fines are in the range of 3 to 8 wt.%.
The dispersant used includes selective and non-selective dispersant with
different
dosage. The selective dispersant includes polymer of 5000 to 10,000 molecular
weight. The non-selective dispersant includes sodium silicate and sodium
hexameta phosphate. The dosage of dispersant is in the range of 20 to 10,000
ppm. The flocculants includes different starch solution with varied dosage in
the
range of 20 - 10,000 ppm. The starch includes potato, wheat and maize while
the starch solution used is plain as well as caustic starch solution with
starch
concentration in the range of 0.1 to 10 wt%. The process is feasible under
varied
pH condition when the range of pH is 2.5 to 11 with a preferred pH range as 8-
10. The concentration of ultra fines in this process is in the range of 2 to
25 wt%
The settling time of the process also varies from 10 seconds to 20 hours. The
method of mixing is carried out either by magnetic stirring, mechanical
stirring or
mixing the ultra fines in solution using ultra sound. The solvent includes tap
water, distilled water, double distilled water.
By this process of selective dispersion and selective flocculation, the
alumina and
silica levels in concentrate iron has been dropped down to a level of 1
whereas
both the alumina and silica level in tailing can be up to 14 wt.%.
From the present invention, various grades of rejected ultra fines can be
separated out into two (1) iron rich concentrate and (ii) tailing (with rich
in
6

CA 02731355 2011-01-19
WO 2010/146596 PCT/IN2009/000434
alumina and silica) by selective dispersion and selective flocculation
process. The
concentrate is most suited feed material for iron making through blast furnace
rout whereas the tailing is the most suited feed material to make building
material. Added advantage is that this process is environmental and eco
friendly
with zero waste.
Movement of different particles of oxide mineral in solution depends on degree
of surface charge/zeta potential of those particles. Particles are expected to
be
coagulated or settled if surface charge/zeta potential becomes zero. Surface
charge/zeta potential characteristics of iron bearing minerals (hematite,
goethite
and magnetite) are quite different from clay minerals (alumina and silica)
under
different conditions. This variation can be shorten or extend by varying pH
and
using different chemicals. Using all this conditions alumina level in rejected
ultra
fines can be drop down to 4. This material is unsuitable as feed material for
operation of blast furnace.
In this present invention, better charge neutralization happens when particles
are made finer. Hence segregating the finer particles of iron oxide, alumina
and
silica by hydro cyclone process and subjecting that to selective flocculation,
the
final product that contains 68% Fe, around 1.2% alumina and 1.3% silica is
obtained that qualifies as blast furnace feed.
7

Dessin représentatif