Title of Invention	"AN IMPROVED PROCESS FOR PREPARATION OF SUPER CONCENTRA OF IRON FINES USEFUL FOR MAKING FERRITES"
Abstract	ABSTRACT TITLE OF THE ABSTRACT An improved process for super concentration of iron ore fines useful for making ferrites which comprises : An improved process for super concentration of iron ore fines useful for making ferrites by leaching the iron ore fines in caustic solution of strength varying from 10 to 30% at a temperature in the range of 150-240°C, decanting the leach solution obtained and subsequent filtering for solid/liquid separation, washing the solid iron concentrate thoroughly obtained with water to remove alkali, wash-leaching the caustic leached residue obtained in acid solution such as dilute hydrofluoric, hydrochloric acid solution having strength of 2 to 5%, filtering the slurry by known methods to obtain solid super concentrate, washing the solid super concentrate with water to remove acid for 15 to 30 minutes and drying the above said super concentrate at a temperature of 150 to 265°C for a period of 4 to 6 hours.

Title of Invention

"AN IMPROVED PROCESS FOR PREPARATION OF SUPER CONCENTRA OF IRON FINES USEFUL FOR MAKING FERRITES"

Abstract

ABSTRACT TITLE OF THE ABSTRACT An improved process for super concentration of iron ore fines useful for making ferrites which comprises : An improved process for super concentration of iron ore fines useful for making ferrites by leaching the iron ore fines in caustic solution of strength varying from 10 to 30% at a temperature in the range of 150-240°C, decanting the leach solution obtained and subsequent filtering for solid/liquid separation, washing the solid iron concentrate thoroughly obtained with water to remove alkali, wash-leaching the caustic leached residue obtained in acid solution such as dilute hydrofluoric, hydrochloric acid solution having strength of 2 to 5%, filtering the slurry by known methods to obtain solid super concentrate, washing the solid super concentrate with water to remove acid for 15 to 30 minutes and drying the above said super concentrate at a temperature of 150 to 265°C for a period of 4 to 6 hours.

Full Text	This invention relates to an improved process for super concentration of iron ore fines useful for making ferrites. High quality iron oxide having low silica, alumina and calcia has great demand for making different grade of ferrites. India has vast reserves of iron ore and considerable amount of this is exported to several countries. Large amount of iron ore fines are generated during mining. Utilisation of the iron ore fines for making value added products like soft ferrites has been of great importance, particularly because of the fact that the iron oxide required by soft ferrite industry can safely use beneficiated iron ore of desired specification in order to achieve desirable magnetic properties in the final product. In the hitherto known dry process (Lamb F.D and Woodard D.A. Pilot-plant production of high grade Magnetic concentrates. Cranberry N.C U.S Bur. Mines. Report No. Inv. 3980 December 1946 pp.7) which uses magnetic separation technique on wilfley tables to remove silica. In another hitherto known acid leaching process (C.V Firth 'Method of producing iron oxide for production of iron oxide powder', U.S Patent 2,413,492 December 31, 1946) which involves dissolution of iron in mineral acid, precipitation of iron hy¬droxide from acid solution and subsequent calcination of iron hydroxide producing pure iron oxide. Yet another process (T.D. Tiemann 'Extraction of Silica from Low Grade Siliceous Iron Ore by Digestion in Sodium Hydroxide Solution' Trans. Soc. Min. Eng. AIME 232 (1965) pp.307-308) where sodium hydroxide solution was used to dissolve silica and alumina from the iron ores. The hitherto known process have the following drawbacks : In the physical beneficiation process, the silica level in the super concentrate can not be brought down below 0.5% and the super concentrate produced is not suitable for making ferrites. In the acid leaching process, acid consuming gange materials also go in solution along with iron and the solution needs puri¬fication. The number of unit operation is more. The high cost of the process defeats the commercial application. Moreover, the process corrodes the processing equipments. The caustic leaching process alone cannot bring down the silica content below 0.5% and final product (super concentrate) is not suitable for ferrite making. Therefore, R&D efforts have been done to develop an economic and viable process to produce high quality iron oxide from iron ore fines to be used for making soft ferrites. The main object of the present invention is to provide an improved process for super concentration of iron ore fines useful for making ferrites, particularly soft ferrites. Another object of the present invention is to provide an improved process for super concentration of iron ore fines useful for making ferrites whereby processing cost is reduced. Yet another object of the present invention is to provide an improved process for super concentration of iron ore fines useful for making ferrites whereby super concentrate is produced with minimum loss of iron value. Still another object of the present invention is to provide an improved process for super concentration of iron ore fines useful for making ferrites whereby costly chemical such as sodium hydroxide is recovered and recycled and thereby reducing the cost of production. In the process of the present invention iron ore fines containing impurities like silica, alumina, calcia etc. are subjected to leaching in caustic solution under temperature and pressure where silica and alumina etc. present in the iron ore fines are chemically reacted with caustic solution such as caus¬tic soda, caustic potash producing water soluble slicate and aluminate etc. leaving the unreacted iron oxide in the residue. The chemical reactions occuring during caustic leaching may represent as below: -2 + SiO2 + 2H2 O + 4MOH = Si (OH) + 4M + 2OH (1) 6 Al2 03 + 2MOH = 2M AlO2 + H O (2) where M represents alkali metal. After leaching, the solid/liquid separation is done by decanta-tion. The iron containing residue is repeatedly washed with water to free it from alkali and entrapped soluble salts. After final washing, the product is further leached in dilute acid solution such as hydrofluoric acid, hydrochloric acid solution at ambient temperature where unreacted silica left in caustic leaching is gone in solution. After wash leaching the solid is separated by filtration and dried. The super concentrate thus produced can be used for making soft ferrites. After alkali leaching treatment, the leach liquor is further processed for recovery of pure caustic solution by conventional processes. The recovered caustic solution can be recycled. Accordingly, the present invention provides an improved process for super concentration of iron ore fines useful for making ferrites which comprises : i) leaching the iron ore fines in caustic solution of strength varying from 10 to 30% at a temperature in the range of 150-240°C for a period of 1 to 6 hours, ii) decanting the leach solution obtained in step (i) and subsequent filtering for solid/liquid separation, iii) washing the solid iron concentrate thoroughly obtained from step (ii) with water to remove alkali, iv) wash-leaching the caustic leached residue obtained from step (iii) in acid solution such as dilute hydrofluoric, hydrochloric acid solution having strength of 2 to 5%, v) filtering the slurry by known methods to obtain solid super concentrate, vi) washing the solid super concentrate with water to remove acid for 15 to 30 minutes, vii) drying the above said super concentrate at a temperature of 150 to 265°C for a period of 4 to 6 hours. vii) Drying the super concentrate. According to a feature of this invention, the iron ore fines employed may be selected from iron ore fines having the following composition range : Fe O3 - 75.5 - 85.9% 2 5.9 20.4% 62.0 69.0% 2.5 10.6% FeO Total Fe SiO 2 Al O - 0.3 - 0.4% 2 3 CaO - 0.02 - 0.03% MgO - 0.04 - 0.06% The caustic salts used for leaching of iron ore fines may be of commercial grade. Strength of caustic solution used forleach-ing may vary from 10 to 30%. The pulp density of slurry may vary from 1.45 to 1.75 gm/cc. The temperature of leaching may vary from 150 to 240oC and pressure may vary from 25 to 40 kg/cm2. Time of leaching may vary from 1 to 6 hours. The hydrofluoric/hydrochloric acid used for wash leaching may be of commercial grade. Strength of acid solution used for wash leaching may vary from 2 to 5%. The solid/liquid ratio for wash leaching may vary from 1:2 to 1:5 (w/v) and time of wash leaching may vary from 15 to 30 minutes. The super concentrate produced may be dried at a temperature in the range of 150 to 265oC for period of 4 to 6 hours. According to feature of this invention, the leach-liquor produced on pressure leaching contains free caustic hydroxide and soluble silicate of sodium, potasium, calcium which on further processing by conventional process produce pure caustic hydroxide to be used for recycling. By the process of present invention most of silica and alumina are removed and iron oxide of 99.8% purity is produced which is suitable for making soft ferrites. The following examples are given by way of illustration and should not be construed to limit the scope of the present inven¬tion. The iron ore fines treated were of the following composi¬tion: Total Fe - 62.19% Fe O - 80.83% 2 3 FeO - 7.30% SiO - 10.57% 2 Al 0 - 0.38% 2 3 CaO - 0.02% MgO - 0.05% K O - 0.02% 2 S - 0.03% P - 0.03% Example - 1: 100 gms of iron ore fine sample was leached under similar conditions of agitation, oxygen pressure, pulp density and same solution strength of caustic soda at varied temperature in the range of 150 to 240oC for 5 hours. After leaching, the solid/liquid separation was done by decantation followed by washing with water. The solid concentrate was then leached in 5% dilute hydrofluoric acid solution for 30 minutes at ambient tem-perature with solid/liquid ratio 1:5 (w/v) and then filtered. The residue was washed with water and then dried at 265oC for 6 hours. The results of the super concentrate produced are given in Table-1. (Table Removed) Example - 2: 100 gms of iron ore fines were subjected to pressure leach-ing in 10 to 30% sodium hydroxide solution. The concentrate of alkali leach residue was washed in dilute hydrofluoric acid solution. The results are given in Table-2. (Table Removed) Example - 3: 100 gm iron ore fine sample was subjected to pressure leaching in 25% strength of sodium hydroxide solution at 225oC for 5 hours. The leaching was carried out under different oper¬ating oxygen pressure as per Table-3. The results of super concentrate produced are given in table-3. TABLE – 3 (Table Removed) Example - 4: 100 gm of iron ore fine sample was subjected to pressure leaching at 225oC for different time as per Table-4. The alkali leach residue was further washed leach in 5% hydroflouric acid solution for 30 minutes. The results of produced super concen¬trate are given in Table-4. Table- 4 (Table Removed) Example - 5: 100 gm of iron ore fines sample was subjected to alkali pressure leaching with different slurry pulp density as per Table-5. The results super concentrate produced are given in Table-5. Table- 5 (Table Removed) The main advantages of the present invention are : 1) In the improved process of present invention, silica con¬ tent in super concentrate has been brought down below 0.05% whereas in the existing processes the silica level cannot be brought down below 0.5%. 2) In the present invention, percent of iron yield is more than 80% whereas in the existing processes it is below 60 percent. 3) In the present invention the process stipes are less when compared to the existing processes leading to less operating cost. 4) In the present invention caustic solution solution is recycled leading the less processing cost We claim : 1. An improved process for super concentration of iron ore fines useful for making ferrites which comprises : i) leaching the iron ore fines in caustic solution of strength varying from 10 to 30% at a temperature in the range 150-240°C for a period of 1 to 6 hours,to obtain leach solution ii) decanting the leach solution obtained in step (i) and subsequent filtering for solid/liquid separation to obtain solid iron concentrate iii) washing the solid iron concentrate thoroughly obtained from step (ii) with water to remove alkali, iv) wash-leaching the caustic leached residue obtained from step (iii) in acid solution such as 'dilute hydrofluoric, hydrochloric acid solution having strength of 2 to 5%, to obtain slurry v) filtering the slurry by known methods to obtain solid super concentrate, vi) washing the solid super concentrate with water to remove acid for 15 to 30 minutes, vii) drying the above said super concentrate at a temperature of 150 to 265°C for a period of 4 to 6 hours. 2. An improved process as claimed in claim 1 wherein the iron ore fines used has the following composition range. Fe2O3 75.5 85.9% FeO 5.9 20.4% Total Fe 62.0 69.3% SiO2 2.50 10.6% AI2O3 0.30 0.40% CaO 0.02 0.03% MgO 0.04% 0.06% 3. An improved process as claimed in claims 1-2 wherein the leaching is done under pressure in the range of 25 to 40 kg/cm2. 4. An improved process as claimed in claims 1-3 wherein the leaching is done with slurry having pulp density in the range of 1.45 to 1.75 gm/cc. 5. An improved process as claimed in claims 1-4 wherein wash leaching was done in hydrofluoric/hydrochloric acid solution in the range of 2 to 5% at ambient temperature for the period of 15 to 30 minutes with solid liquid ratio in the range of 1:2 to 1:5 (w/v). 6. An improved process for super concentration of iron ore fines useful for making ferrites substantially as herein described with reference to the examples.

Full Text

This invention relates to an improved process for super concentration of iron ore fines useful for making ferrites.
High quality iron oxide having low silica, alumina and calcia has great demand for making different grade of ferrites. India has vast reserves of iron ore and considerable amount of this is exported to several countries. Large amount of iron ore fines are generated during mining. Utilisation of the iron ore fines for making value added products like soft ferrites has been of great importance, particularly because of the fact that the iron oxide required by soft ferrite industry can safely use beneficiated iron ore of desired specification in order to achieve desirable magnetic properties in the final product.
In the hitherto known dry process (Lamb F.D and Woodard D.A. Pilot-plant production of high grade Magnetic concentrates. Cranberry N.C U.S Bur. Mines. Report No. Inv. 3980 December 1946 pp.7) which uses magnetic separation technique on wilfley tables to remove silica.
In another hitherto known acid leaching process (C.V Firth 'Method of producing iron oxide for production of iron oxide powder', U.S Patent 2,413,492 December 31, 1946) which involves dissolution of iron in mineral acid, precipitation of iron hy¬droxide from acid solution and subsequent calcination of iron hydroxide producing pure iron oxide.
Yet another process (T.D. Tiemann 'Extraction of Silica from Low Grade Siliceous Iron Ore by Digestion in Sodium Hydroxide
Solution' Trans. Soc. Min. Eng. AIME 232 (1965) pp.307-308) where sodium hydroxide solution was used to dissolve silica and alumina from the iron ores.
The hitherto known process have the following drawbacks :
In the physical beneficiation process, the silica level in the super concentrate can not be brought down below 0.5% and the super concentrate produced is not suitable for making ferrites.
In the acid leaching process, acid consuming gange materials also go in solution along with iron and the solution needs puri¬fication. The number of unit operation is more. The high cost of the process defeats the commercial application. Moreover, the process corrodes the processing equipments.
The caustic leaching process alone cannot bring down the silica content below 0.5% and final product (super concentrate) is not suitable for ferrite making.
Therefore, R&D efforts have been done to develop an economic and viable process to produce high quality iron oxide from iron ore fines to be used for making soft ferrites.
The main object of the present invention is to provide an improved process for super concentration of iron ore fines useful for making ferrites, particularly soft ferrites.
Another object of the present invention is to provide an improved process for super concentration of iron ore fines useful
for making ferrites whereby processing cost is reduced.
Yet another object of the present invention is to provide an improved process for super concentration of iron ore fines useful for making ferrites whereby super concentrate is produced with minimum loss of iron value.
Still another object of the present invention is to provide an improved process for super concentration of iron ore fines useful for making ferrites whereby costly chemical such as sodium hydroxide is recovered and recycled and thereby reducing the cost of production.
In the process of the present invention iron ore fines containing impurities like silica, alumina, calcia etc. are subjected to leaching in caustic solution under temperature and pressure where silica and alumina etc. present in the iron ore fines are chemically reacted with caustic solution such as caus¬tic soda, caustic potash producing water soluble slicate and aluminate etc. leaving the unreacted iron oxide in the residue. The chemical reactions occuring during caustic leaching may represent as below:
-2 +
SiO2 + 2H2 O + 4MOH = Si (OH) + 4M + 2OH (1)
6
Al2 03 + 2MOH = 2M AlO2 + H O (2)

where M represents alkali metal.
After leaching, the solid/liquid separation is done by decanta-tion. The iron containing residue is repeatedly washed with water to free it from alkali and entrapped soluble salts. After
final washing, the product is further leached in dilute acid solution such as hydrofluoric acid, hydrochloric acid solution at ambient temperature where unreacted silica left in caustic leaching is gone in solution. After wash leaching the solid is separated by filtration and dried. The super concentrate thus produced can be used for making soft ferrites.
After alkali leaching treatment, the leach liquor is further processed for recovery of pure caustic solution by conventional processes. The recovered caustic solution can be recycled.
Accordingly, the present invention provides an improved process for super concentration of iron ore fines useful for making ferrites which comprises :
i) leaching the iron ore fines in caustic solution of strength varying from 10 to 30% at a temperature in the range of 150-240°C for a period of 1 to 6 hours, ii) decanting the leach solution obtained in step (i) and
subsequent filtering for solid/liquid separation, iii) washing the solid iron concentrate thoroughly obtained from
step (ii) with water to remove alkali,
iv) wash-leaching the caustic leached residue obtained from step (iii) in acid solution such as dilute hydrofluoric, hydrochloric acid solution having strength of 2 to 5%, v) filtering the slurry by known methods to obtain solid super
concentrate, vi) washing the solid super concentrate with water to remove
acid for 15 to 30 minutes,
vii) drying the above said super concentrate at a temperature of 150 to 265°C for a period of 4 to 6 hours.
vii) Drying the super concentrate.
According to a feature of this invention, the iron ore fines employed may be selected from iron ore fines having the following composition range :
Fe O3 - 75.5 - 85.9% 2
5.9 20.4%
62.0 69.0%
2.5 10.6%
FeO Total Fe
SiO 2
Al O - 0.3 - 0.4% 2 3
CaO - 0.02 - 0.03% MgO - 0.04 - 0.06%
The caustic salts used for leaching of iron ore fines may be of commercial grade. Strength of caustic solution used forleach-ing may vary from 10 to 30%. The pulp density of slurry may vary from 1.45 to 1.75 gm/cc. The temperature of leaching may vary from 150 to 240oC and pressure may vary from 25 to 40 kg/cm2. Time of leaching may vary from 1 to 6 hours.
The hydrofluoric/hydrochloric acid used for wash leaching may be of commercial grade. Strength of acid solution used for wash leaching may vary from 2 to 5%. The solid/liquid ratio for wash leaching may vary from 1:2 to 1:5 (w/v) and time of wash leaching may vary from 15 to 30 minutes.
The super concentrate produced may be dried at a temperature in the range of 150 to 265oC for period of 4 to 6 hours.
According to feature of this invention, the leach-liquor produced on pressure leaching contains free caustic hydroxide and soluble silicate of sodium, potasium, calcium which on further processing by conventional process produce pure caustic hydroxide to be used for recycling.
By the process of present invention most of silica and alumina are removed and iron oxide of 99.8% purity is produced which is suitable for making soft ferrites.
The following examples are given by way of illustration and should not be construed to limit the scope of the present inven¬tion.
The iron ore fines treated were of the following composi¬tion:
Total Fe - 62.19%
Fe O - 80.83%
2 3
FeO - 7.30%
SiO - 10.57%
2
Al 0 - 0.38%
2 3
CaO - 0.02%
MgO - 0.05%
K O - 0.02%
2
S - 0.03%
P - 0.03%

Example - 1:
100 gms of iron ore fine sample was leached under similar conditions of agitation, oxygen pressure, pulp density and same solution strength of caustic soda at varied temperature in the range of 150 to 240oC for 5 hours. After leaching, the solid/liquid separation was done by decantation followed by washing with water. The solid concentrate was then leached in 5% dilute hydrofluoric acid solution for 30 minutes at ambient tem-perature with solid/liquid ratio 1:5 (w/v) and then filtered. The residue was washed with water and then dried at 265oC for 6 hours. The results of the super concentrate produced are given in Table-1.
(Table Removed)
Example - 2:
100 gms of iron ore fines were subjected to pressure leach-ing in 10 to 30% sodium hydroxide solution. The concentrate of alkali leach residue was washed in dilute hydrofluoric acid solution. The results are given in Table-2.
(Table Removed)
Example - 3:
100 gm iron ore fine sample was subjected to pressure leaching in 25% strength of sodium hydroxide solution at 225oC for 5 hours. The leaching was carried out under different oper¬ating oxygen pressure as per Table-3. The results of super concentrate produced are given in table-3.
TABLE – 3
(Table Removed)
Example - 4:
100 gm of iron ore fine sample was subjected to pressure leaching at 225oC for different time as per Table-4. The alkali leach residue was further washed leach in 5% hydroflouric acid solution for 30 minutes. The results of produced super concen¬trate are given in Table-4.

Table- 4
(Table Removed)

Example - 5:
100 gm of iron ore fines sample was subjected to alkali pressure leaching with different slurry pulp density as per Table-5. The results super concentrate produced are given in Table-5.
Table- 5
(Table Removed)
The main advantages of the present invention are :
1) In the improved process of present invention, silica con¬
tent in super concentrate has been brought down below 0.05%
whereas in the existing processes the silica level cannot be
brought down below 0.5%.
2) In the present invention, percent of iron yield is more than
80% whereas in the existing processes it is below 60 percent.

3) In the present invention the process stipes are less when
compared to the existing processes leading to less operating cost.
4) In the present invention caustic solution solution is recycled
leading the less processing cost

We claim :
1. An improved process for super concentration of iron ore fines useful for making ferrites which comprises : i) leaching the iron ore fines in caustic solution of strength varying from 10 to 30% at a temperature in the range 150-240°C for a period of 1 to 6 hours,to obtain leach solution
ii) decanting the leach solution obtained in step (i) and subsequent filtering for solid/liquid separation to obtain solid iron concentrate
iii) washing the solid iron concentrate thoroughly obtained from step (ii) with water to remove alkali,
iv) wash-leaching the caustic leached residue obtained from step (iii) in acid solution such as 'dilute
hydrofluoric, hydrochloric acid solution having strength of 2 to 5%, to obtain slurry
v) filtering the slurry by known methods to obtain solid super concentrate,
vi) washing the solid super concentrate with water to remove acid for 15 to 30 minutes,
vii) drying the above said super concentrate at a temperature of 150 to 265°C for a period of 4 to 6 hours.
2. An improved process as claimed in claim 1 wherein the iron ore fines used has the following composition range.
Fe2O3 75.5 85.9%
FeO 5.9 20.4%

Total Fe 62.0 69.3%
SiO2 2.50 10.6%
AI2O3 0.30 0.40%
CaO 0.02 0.03%
MgO 0.04% 0.06%
3. An improved process as claimed in claims 1-2 wherein the
leaching is done under pressure in the range of 25 to 40
kg/cm2.
4. An improved process as claimed in claims 1-3 wherein the
leaching is done with slurry having pulp density in the range
of 1.45 to 1.75 gm/cc.
5. An improved process as claimed in claims 1-4 wherein wash
leaching was done in hydrofluoric/hydrochloric acid solution in
the range of 2 to 5% at ambient temperature for the period of
15 to 30 minutes with solid liquid ratio in the range of 1:2 to
1:5 (w/v).
6. An improved process for super concentration of iron ore fines useful for making ferrites substantially as herein described with reference to the examples.

Documents:

334-del-1999-abstract.pdf

334-del-1999-claims.pdf

334-del-1999-correspondence-others.pdf

334-del-1999-correspondence-po.pdf

334-del-1999-description (complete).pdf

334-del-1999-form-1.pdf

334-del-1999-form-19.pdf

334-del-1999-form-2.pdf

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Patent Number

217674

Indian Patent Application Number

334/DEL/1999

PG Journal Number

17/2008

Publication Date

25-Apr-2008

Grant Date

28-Mar-2008

Date of Filing

25-Feb-1999

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SAHA ANIL KUMAR	NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR 7, BIHAR,INDIA.
2	KHAN ZAHID HUSAIN	NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR 7, BIHAR,INDIA
3	PATCHA RAMACHANDRA RAO	NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR 7, BIHAR,INDIA

PCT International Classification Number

C21D 7/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA