Title of Invention	A PROCESS FOR PRODUCTION OF CHEMICAL-GRADE CHROMITE CONCENTRATES FROM CHROMITE ORE
Abstract	A non-lime process for production of chemical grade chromite concentrates from chromite ore is disclosed. The process comprises the steps of grinding mined ore with around 45% Cr2 O3 to - 1 mm size. The ground ore is fed to primary floatex for gravity-cum-size separation. The tailings contain magnesium silicate over silica materials are separated from under flow of - 0.25 mm of the primary floatex by reverse floatation , thereby obtaining feed materials required for producing chemical grade chromite concentrates by no-lime method.

Title of Invention

A PROCESS FOR PRODUCTION OF CHEMICAL-GRADE CHROMITE CONCENTRATES FROM CHROMITE ORE

Abstract

A non-lime process for production of chemical grade chromite concentrates from chromite ore is disclosed. The process comprises the steps of grinding mined ore with around 45% Cr2 O3 to - 1 mm size. The ground ore is fed to primary floatex for gravity-cum-size separation. The tailings contain magnesium silicate over silica materials are separated from under flow of - 0.25 mm of the primary floatex by reverse floatation , thereby obtaining feed materials required for producing chemical grade chromite concentrates by no-lime method.

Full Text	FIELD OF APPLICATION The present invention relates to a process for production of chemical-grade chromite concentrates from chromite ore. More specifically it relates to a process to produce concentrates from metallurgical grade mined ores like ores from Sukinda mines in India and from their beneficiated concentrates and tailings. BACKGROUND OF THE INVENTION Chemical - grade chromite concentrates are used to produce chromium chemicals. Chromium chemicals find applications in tanning, plating, pigment, wood preservation, and metallurgical Industries. Presently, 8 -10% of total chromite ore mined in the world is consumed for the production of chromium chemicals. South Africa is a major producer of chemical grade chromite in the world. Most of the Indian chromite ores are inherently suitable for metallurgical applications, in particular to produce ferrochrome with more than 63 % chromium. For producing chemical grade chromite concentrates from these ores, the lime process is used. The mined ore is added to lime (CaO) and heated to produce calcium chromate. However, in the lime process the residue left out is highly carcinogenic and more alkaline in nature resulting in problems in the disposal of the residue. Thus the lime process of producing chromium chemicals is metallurgically inefficient and environmentally unfriendly. In the no - lime process of producing chemical grade chromite concentrates, the chromite ore or concentrate should have a desired mineral chemistry. The ore should have sufficient iron in the form of Fe2+ in the chromite mineral lattice, silica less than 1 %, MgO less than 10 % and Cr2 O3 around 46 %. In this process, the ore is mixed with sodium carbonate Na2 CO3 and heated upto a temperature of 1100 -1200° C for producing sodium chromate. The chromite spinel, Fe-sesquioxide, gibbsite and silicates are the major phases present in the Indian chromite deposits particularly in Sukinda. Present mineral beneficiation process at chrome ore beneficiation (COB) plant, Sukinda is "grinding-teetered bed separation and spiraling unit operation combinations". The finished product of this process i.e. chromite fine concentrates contains more than 51% Cr2O3, more than 10% MgO and less than 12% total Fe is not suitable for chemical applications in "no lime" process. However, an environmental friendly and metallurgically efficient "no lime" chemical process requires stringent specifications of chemical grade chromite concentrates. These concentrates should have Fe about 20% with a ratio of Fe2+ to Fe3+ of 70:30; less than 1 % SiO2, less than 10% MgO and Cr2O3 should be preferably around 46%. By conventional normal gravity circuit, if the process is properly tuned, it is possible to produce concentrates with SiO2 less than 1 %, but the total Fe will be less than 11 %, Cr2O3 more than 51% and MgO more than 10%. If we target 46% Cr2O3, the silica level will be high and total Fe will still be low. Thus there was a need for providing a no - lime process for production of chemical grade chromite concentrates from metallurgical grade chromite ores mined in India. SUMMARY OF THE INVENTION One object of the present invention therefore, is to provide a process for production of chemical grade chromite concentrate directly from chromite ore used as feed in wno - lime" chemical production process. Another object of the present invention is to provide a process for production of the concentrate from the tailings of the main process flow sheet of the chrome ore benefication plant Yet another object of the invention is to provide a process for production of the concentrate from the chrome ore benefication plant products. The desliming, multi gravity separation followed by floatation stages were developed for tailoring the chemical grade concentrate from already existing tailings. These and other objects are achieved by the process of the present invention, description of the preferred embodiments of which will now be described. Thus the present invention provides a non-lime process for production of chemical grade chromite concentrates from chromite ore comprising the steps of grinding mined ore with around 45% Cr2 to - 1 mm size; feeding the ground ore to primary floatex for gravity cum size separation; and separating the tailing containing magnesium silicate and other silica minerals from underflow of - 0.25 mm of the primary floatex by reverse flotation; thereby obtaining feed materials required for producing chemical grade chromite concentrates by no- lime method. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The process flow sheets of the present invention are illustrated in the figures of the accompanying drawings, where Figure 1A shows the process flow sheet for production of chemical grade chromite from chromite ore mined. Figure 1B shows the flow sheet of chromite ore benefication plant for production of chemical grade chromite. Figure 2 shows the process flow sheet for production from tailing dumps of chromite ore benefication plant. Figure 3 show the process flow sheets for production from chromite ore (A to E) benefication plant products. DFTAILED DESCRIPTION The process flow sheets for the process of the present invention for production of chemical grade chromite concentrate from mined ore, the chromite ore benefication plant tailing dumps and the chromite ore benefication plant products are shown respectively in Figures 1A, 1B, 2 and 3 (3A, 3B and 3C). Mined low grade chromtie ore with around 45% Cr2 O3 is ground to -1 mm size and fed to primary floatex for gravity cum size separation. The under flow of below 0.25 mm is made into ore pulp with 30% ore and 70% water (30% pulp density). Fatty acid emulsion is added as collector. The froth containing silica minerals, that include magnesium silicate can be collected. This is illustrated in Figure 1. This process will allow the Si O2 and MgO contents to be kept to the desired levels of less than 1% and 10% respectively. The ore can now be used as feed material for making chemical grade chromite concentrates by no - lime process. The present and earlier generated chromium ore benefication plant tailings can be treated in a hydrocyclone as shown in Figure 2 for rejecting 15 micron size particles as overflow. The underflow is to be treated in fines gravity separation like multigravity separator (MGS) to separate silica rich and low density particles from chromite and iron rich particles using gravity difference between them. The concentrate so obtained is to be treated further in MGS as a second stage to get further separation of silica minerals. The second stage MGS concentrate is to be treated in the same manner as described earlier to get the desired concentrate with lower Si O2 and MgO content. The processes shown in Figures 3A - 3D are similar to the process illustrated in Figure 2. However the starting material is different and the inputs are from COB plant different stream products as mentioned in the COB plant process flow sheet of Figure IB. In the flow sheet illustrated in Figure 3E, the COB plant fines concentrate is taken and blended with mined iron rich (~ 30 % Fe Cr) chromite ore (with ~ 38 - 40 % Cr2 O3) and it is possible to get desired chemical grade concentrate as a feed to "No - lime" process. The chemical grade chromite concentrates produced by the method of the present invention were tested for performance in "no lime" process which is used for production of chromium chemicals. The results of test confirmed that the blends are suitable for "no lime" process with extraction efficiency of about 75% as against 79% from South African Chemical grade concentrates (reference sample). The process for production of chemical-grade chromite of the present invention will provide a new product from metallurgical grade mined chromite ore. This process will increase the utilization of tailing and thereby add-value to the waste. Cr2O3 concentration in chemical grade chromite is about 46 % as compared to metallurgical grade chromite where higher concentrations of Cr2O3 are preferred. The process will also help to exploit the low grade chromite deposits in Sukinda, which are not suitable for metallurgical chromite production. Indian chromite ores are used mostly for the production of metallurgical grade chromite concentrates. A significant quantity of Cr2O3 is lost in the tailings of this process. Value added product can be generated from these tailings using the process of the present invention. WE CLAIM : 1. A non-lime process for production of chemical grade chromite concentrates from chromite ore comprising the steps of : - grinding mined ore with around 45% Cr2 O3 to - 1 mm size ; and - feeding the ground ore to primary floatex for gravity cum size separation; characterized in that the tailings containing magnesium silicate and other silica minerals are separated from underflow of -0.25 mm of the primary floatex by reverse floatation ; thereby obtaining feed materials required for producing chemical grade chromite concentrates by no-lime method. 2. The process as claimed in claim 1, wherein said reverse floatation comprises the step of preparing an ore pulp with water of 30% pulp density; and adding a fatty acid emulsion for collecting the froth containing silica minerals. 3. The process as claimed in claim 1, wherein said separated tailings are subjected to further processing comprising the steps of : - treating the tailings in a hydrocyclone for rejecting 15 micron size particles as overflow; - treating the underflow of the hydrocycloning in a fines gravity separator to separate silica rich low density particles ; - repeating the fines gravity separating step to separate further silica rich low density particles ; and - subjecting the output from the preceding step to reverse floatation to separate magnesium silicate and other silica numerals; thereby obtaining feed materials required for producing chemical grade chromite concentrates by no-lime method. 4. The process as claimed in claim 3, wherein said fines gravity separator is a multigravity separator (MGS). 5. The process as claimed in claim 3, wherein lower grade chromite ores can be used as a starting material for producing chemical grade chromite concentrates, in place of the COB tailings. 6. The process as claimed in claims 1 and 3, wherein the overflow from said primary floatex is fed to a secondary floatex for hydrocycloning the overflow therefrom at 15µ size to obtain the feed material required for producing chemical grade chromite. 7. The process as claimed in claim 1, wherein the tailings from said spiral circuit is subjected to spiral scavenging for obtaining the chemical grade chromite concentrate. 8. The process as claimed in claims 1 and 3, wherein said COB plant fine concentrate is taken and blended with mined iron rich chromite ore to obtain chemical grade chromite concentrate. 9. The process as claimed in claim 8, wherein said iron rich chromite ore is preferably 30 % Fe (total) and 38-40 % Cr2 O3. 10. A process for production of chemical-grade chromite concentrates from chromite ore, substantially as herein described and illustrated in the accompanying drawings. A non-lime process for production of chemical grade chromite concentrates from chromite ore is disclosed. The process comprises the steps of grinding mined ore with around 45% Cr2 O3 to - 1 mm size. The ground ore is fed to primary floatex for gravity-cum-size separation. The tailings contain magnesium silicate over silica materials are separated from under flow of - 0.25 mm of the primary floatex by reverse floatation , thereby obtaining feed materials required for producing chemical grade chromite concentrates by no-lime method.

Full Text

FIELD OF APPLICATION
The present invention relates to a process for production of chemical-grade chromite
concentrates from chromite ore. More specifically it relates to a process to produce
concentrates from metallurgical grade mined ores like ores from Sukinda mines in India
and from their beneficiated concentrates and tailings.
BACKGROUND OF THE INVENTION
Chemical - grade chromite concentrates are used to produce chromium chemicals.
Chromium chemicals find applications in tanning, plating, pigment, wood preservation, and
metallurgical Industries. Presently, 8 -10% of total chromite ore mined in the world is
consumed for the production of chromium chemicals. South Africa is a major producer of
chemical grade chromite in the world.
Most of the Indian chromite ores are inherently suitable for metallurgical applications, in
particular to produce ferrochrome with more than 63 % chromium. For producing
chemical grade chromite concentrates from these ores, the lime process is used. The
mined ore is added to lime (CaO) and heated to produce calcium chromate.

However, in the lime process the residue left out is highly carcinogenic and more alkaline in
nature resulting in problems in the disposal of the residue. Thus the lime process of
producing chromium chemicals is metallurgically inefficient and environmentally unfriendly.
In the no - lime process of producing chemical grade chromite concentrates, the chromite
ore or concentrate should have a desired mineral chemistry. The ore should have sufficient
iron in the form of Fe2+ in the chromite mineral lattice, silica less than 1 %, MgO less than
10 % and Cr2 O3 around 46 %.
In this process, the ore is mixed with sodium carbonate Na2 CO3 and heated upto a
temperature of 1100 -1200° C for producing sodium chromate.
The chromite spinel, Fe-sesquioxide, gibbsite and silicates are the major phases present in
the Indian chromite deposits particularly in Sukinda. Present mineral beneficiation process
at chrome ore beneficiation (COB) plant, Sukinda is "grinding-teetered bed separation and
spiraling unit operation combinations". The finished product of this process i.e. chromite
fine concentrates contains more than 51% Cr2O3, more than 10% MgO and less than 12%
total Fe is not suitable for chemical applications in "no lime" process.
However, an environmental friendly and metallurgically efficient "no lime" chemical process
requires stringent specifications of chemical grade chromite concentrates. These
concentrates should have Fe about 20% with a ratio of Fe2+ to Fe3+ of 70:30; less than 1
% SiO2, less than 10% MgO and Cr2O3 should be preferably around 46%.

By conventional normal gravity circuit, if the process is properly tuned, it is possible to
produce concentrates with SiO2 less than 1 %, but the total Fe will be less than 11 %,
Cr2O3 more than 51% and MgO more than 10%. If we target 46% Cr2O3, the silica level
will be high and total Fe will still be low.
Thus there was a need for providing a no - lime process for production of chemical grade
chromite concentrates from metallurgical grade chromite ores mined in India.
SUMMARY OF THE INVENTION
One object of the present invention therefore, is to provide a process for production of
chemical grade chromite concentrate directly from chromite ore used as feed in wno - lime"
chemical production process.
Another object of the present invention is to provide a process for production of the
concentrate from the tailings of the main process flow sheet of the chrome ore benefication
plant
Yet another object of the invention is to provide a process for production of the
concentrate from the chrome ore benefication plant products.
The desliming, multi gravity separation followed by floatation stages were developed for
tailoring the chemical grade concentrate from already existing tailings.

These and other objects are achieved by the process of the present invention,
description of the preferred embodiments of which will now be described.
Thus the present invention provides a non-lime process for production of
chemical grade chromite concentrates from chromite ore comprising the steps
of grinding mined ore with around 45% Cr2 to - 1 mm size; feeding the ground
ore to primary floatex for gravity cum size separation; and separating the
tailing containing magnesium silicate and other silica minerals from underflow
of - 0.25 mm of the primary floatex by reverse flotation; thereby obtaining feed
materials required for producing chemical grade chromite concentrates by no-
lime method.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The process flow sheets of the present invention are illustrated in the figures of
the accompanying drawings, where
Figure 1A shows the process flow sheet for production of chemical grade
chromite from chromite ore mined.
Figure 1B shows the flow sheet of chromite ore benefication plant for
production of chemical grade chromite.
Figure 2 shows the process flow sheet for production from tailing dumps of
chromite ore benefication plant.
Figure 3 show the process flow sheets for production from chromite ore
(A to E) benefication plant products.

DFTAILED DESCRIPTION
The process flow sheets for the process of the present invention for production of chemical
grade chromite concentrate from mined ore, the chromite ore benefication plant tailing
dumps and the chromite ore benefication plant products are shown respectively in Figures
1A, 1B, 2 and 3 (3A, 3B and 3C).
Mined low grade chromtie ore with around 45% Cr2 O3 is ground to -1 mm size and fed to
primary floatex for gravity cum size separation. The under flow of below 0.25 mm is made
into ore pulp with 30% ore and 70% water (30% pulp density). Fatty acid emulsion is
added as collector. The froth containing silica minerals, that include magnesium silicate
can be collected. This is illustrated in Figure 1. This process will allow the Si O2 and MgO
contents to be kept to the desired levels of less than 1% and 10% respectively. The ore
can now be used as feed material for making chemical grade chromite concentrates by
no - lime process.
The present and earlier generated chromium ore benefication plant tailings can be treated
in a hydrocyclone as shown in Figure 2 for rejecting 15 micron size particles as overflow.
The underflow is to be treated in fines gravity separation like multigravity separator (MGS)
to separate silica rich and low density particles from chromite and iron rich particles using
gravity difference between them. The concentrate so obtained is to be treated further in
MGS as a second stage to get further separation of silica minerals.
The second stage MGS concentrate is to be treated in the same manner as described
earlier to get the desired concentrate with lower Si O2 and MgO content.

The processes shown in Figures 3A - 3D are similar to the process illustrated in Figure 2.
However the starting material is different and the inputs are from COB plant different
stream products as mentioned in the COB plant process flow sheet of Figure IB.
In the flow sheet illustrated in Figure 3E, the COB plant fines concentrate is taken and
blended with mined iron rich (~ 30 % Fe Cr) chromite ore (with ~ 38 - 40 % Cr2 O3) and it
is possible to get desired chemical grade concentrate as a feed to "No - lime" process.
The chemical grade chromite concentrates produced by the method of the present
invention were tested for performance in "no lime" process which is used for production of
chromium chemicals. The results of test confirmed that the blends are suitable for
"no lime" process with extraction efficiency of about 75% as against 79% from South
African Chemical grade concentrates (reference sample).
The process for production of chemical-grade chromite of the present invention will provide
a new product from metallurgical grade mined chromite ore. This process will increase the
utilization of tailing and thereby add-value to the waste. Cr2O3 concentration in chemical
grade chromite is about 46 % as compared to metallurgical grade chromite where higher
concentrations of Cr2O3 are preferred. The process will also help to exploit the low grade
chromite deposits in Sukinda, which are not suitable for metallurgical chromite production.
Indian chromite ores are used mostly for the production of metallurgical grade chromite
concentrates. A significant quantity of Cr2O3 is lost in the tailings of this process. Value
added product can be generated from these tailings using the process of the present
invention.

WE CLAIM :
1. A non-lime process for production of chemical grade chromite
concentrates from chromite ore comprising the steps of :
- grinding mined ore with around 45% Cr2 O3 to - 1 mm size ; and
- feeding the ground ore to primary floatex for gravity cum size
separation;
characterized in that
the tailings containing magnesium silicate and other
silica minerals are separated from underflow of -0.25 mm of the
primary floatex by reverse floatation ;
thereby obtaining feed materials required for producing chemical
grade chromite concentrates by no-lime method.
2. The process as claimed in claim 1, wherein said reverse floatation
comprises the step of preparing an ore pulp with water of 30% pulp
density; and adding a fatty acid emulsion for collecting the froth
containing silica minerals.

3. The process as claimed in claim 1, wherein said separated tailings are
subjected to further processing comprising the steps of :
- treating the tailings in a hydrocyclone for rejecting 15 micron size
particles as overflow;
- treating the underflow of the hydrocycloning in a fines gravity
separator to separate silica rich low density particles ;
- repeating the fines gravity separating step to separate further silica
rich low density particles ; and
- subjecting the output from the preceding step to reverse floatation
to separate magnesium silicate and other silica numerals;
thereby obtaining feed materials required for producing chemical
grade chromite concentrates by no-lime method.

4. The process as claimed in claim 3, wherein said fines gravity separator
is a multigravity separator (MGS).
5. The process as claimed in claim 3, wherein lower grade chromite ores
can be used as a starting material for producing chemical grade
chromite concentrates, in place of the COB tailings.

6. The process as claimed in claims 1 and 3, wherein the overflow from said primary
floatex is fed to a secondary floatex for hydrocycloning the overflow therefrom at
15µ size to obtain the feed material required for producing chemical grade
chromite.
7. The process as claimed in claim 1, wherein the tailings from said spiral circuit is
subjected to spiral scavenging for obtaining the chemical grade chromite
concentrate.
8. The process as claimed in claims 1 and 3, wherein said COB plant fine concentrate
is taken and blended with mined iron rich chromite ore to obtain chemical grade
chromite concentrate.
9. The process as claimed in claim 8, wherein said iron rich chromite ore is preferably
30 % Fe (total) and 38-40 % Cr2 O3.
10. A process for production of chemical-grade chromite concentrates from chromite
ore, substantially as herein described and illustrated in the accompanying drawings.

A non-lime process for production of chemical grade chromite concentrates
from chromite ore is disclosed. The process comprises the steps of grinding
mined ore with around 45% Cr2 O3 to - 1 mm size. The ground ore is fed to
primary floatex for gravity-cum-size separation. The tailings contain
magnesium silicate over silica materials are separated from under flow of -
0.25 mm of the primary floatex by reverse floatation , thereby obtaining feed
materials required for producing chemical grade chromite concentrates by
no-lime method.

Documents:

00339-kol-2005-description provisional.pdf

00339-kol-2005-drawings.pdf

00339-kol-2005-form 1.pdf

00339-kol-2005-form 2.pdf

00339-kol-2005-form 3.pdf

339-KOL-2005-ABSTRACT 1.1.pdf

339-kol-2005-abstract.pdf

339-KOL-2005-AMANDED CLAIMS.tif

339-KOL-2005-AMANDED PAGES OF SPECIFICATION.pdf

339-KOL-2005-CANCELLED PAGES.pdf

339-kol-2005-claims.pdf

339-KOL-2005-CORRESPONDENCE 1.1.pdf

339-KOL-2005-CORRESPONDENCE 1.2.pdf

339-kol-2005-correspondence.pdf

339-kol-2005-correspondence1.3.pdf

339-KOL-2005-DESCRIPTION (COMPLETE) 1.1.pdf

339-kol-2005-description (complete).pdf

339-kol-2005-description (provisional).pdf

339-KOL-2005-DRAWINGS 1.1.pdf

339-kol-2005-drawings.pdf

339-kol-2005-examination report.pdf

339-KOL-2005-FORM 1 1.1.pdf

339-kol-2005-form 1.pdf

339-KOL-2005-FORM 13 1.1.pdf

339-kol-2005-form 13.2.pdf

339-kol-2005-form 13.pdf

339-kol-2005-form 18.1.pdf

339-kol-2005-form 18.pdf

339-KOL-2005-FORM 2 1.1.pdf

339-kol-2005-form 2.pdf

339-KOL-2005-FORM 3 1.1.pdf

339-kol-2005-form 3.2.pdf

339-kol-2005-form 3.pdf

339-kol-2005-form 5.1.pdf

339-kol-2005-form 5.pdf

339-kol-2005-gpa.pdf

339-kol-2005-gpa1.1.pdf

339-kol-2005-granted-abstract.pdf

339-kol-2005-granted-claims.pdf

339-kol-2005-granted-description (complete).pdf

339-kol-2005-granted-drawings.pdf

339-kol-2005-granted-form 1.pdf

339-kol-2005-granted-form 2.pdf

339-kol-2005-granted-specification.pdf

339-KOL-2005-REPLY TO EXAMINATION REPORT.pdf

339-kol-2005-reply to examination report1.1.pdf

339-kol-2005-specification.pdf

« Previous Patent

Next Patent »

Patent Number

249623

Indian Patent Application Number

339/KOL/2005

PG Journal Number

44/2011

Publication Date

04-Nov-2011

Grant Date

31-Oct-2011

Date of Filing

21-Apr-2005

Name of Patentee

TATA STEEL LIMITED

Applicant Address

RESEARCH AND DEVELOPMENT DIVISION, JAMSHEDPUR

Inventors:

#	Inventor's Name	Inventor's Address
1	RAO N D	C/O TATA STEEL LTD RESEARCH AND DEVELOPMENT DIVN, JAMSHEDPUR 831 001
2	M. RAO. SARIPALLI	C/O TATA STEEL LTD RESEARCH AND DEVELOPMENT DIVN, JAMSHEDPUR 831 001
3	U. KAPURE GAJANAN	C/O TATA STEEL LTD RESEARCH AND DEVELOPMENT DIVN, JAMSHEDPUR 831 001
4	K. DAS ROMEO	C/O TATA STEEL LTD RESEARCH AND DEVELOPMENT DIVN, JAMSHEDPUR 831 001
5	TATHAVADKAR VILAS	C/O TATA STEEL LTD RESEARCH AND DEVELOPMENT DIVN, JAMSHEDPUR 831 001

PCT International Classification Number

C22B 23/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA