AU2010330717B2 - A process for producing high purity Fe2 O3 for value-added applications including blast furnace feed for a poor-grade iron ore slime - Google Patents

Description

IN/PA-210 A PROCESS FOR PRODUCING HIGH PURITY Fe 2

O

3

FORVALUE

ADDED APPLICATIONS INCLUDING BLAST FURNACE FEED FOR A POOR-GRADE IRON ORE SLIME

--------------------------------------------------------------------

FIELD OF INVENTION The present invention generally relates to a method of producing a concentrate containing very high purity iron oxide with very low alumina and silica from a poor grade iron ore fines. More particularly, the invention relates to a process for producing high purity Fe 2 0 3 for value added applications including blast furnace feed from a poor grade iron ore slime. BACKGROUND OF INVENTION Quality of the raw materials for the iron and steel industries plays an important role in the downstream 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 used either for value added application or blast furnace. Iron ore are beneficiated all over the world for which several techniques are being used namely spiral, floatex density separators, jigs, multi-gravity separator, low and high intensity magnetic separator, flotation, selective 1 IN/PA-210 dispersion and flocculation and many more with advanced technologies. Iron ore production entails generation of fines (10-25%) containing high alumina (6-8%), which is unsuitable for direct use in the blast furnace. Assuming an annual production of 150 tons of iron ore, the iron values to the tune of 15 25 million tones is lost every year. The main drawback for use of iron ore ultra fines is that high level of clay are associated with it. As a consequence, this ultra fines being rejected and getting wasted including causing environmental hazards. The particle size of these ultra fines is not suitable to beneficiate it by known beneficiation processes such as (i) gravity or (ii) magnetic separation. The known benefication processes separate minerals from the mixture of two oxides. But, iron ore ultra fines are mixtures of different oxides, which have no utility . It is mixed with goethite, silica, alumina, alumina silicate,refractory minerals. An efficient benefication technology is thus needed which is enabled to effectively produce two valuable products from the waste which are respectively suitable for fine magnetic particles for value added appiication and making building material, refractory material, nano paint or nano coolant. Large quantities of ultra fines are generated during mining and washing of iron ores. If the alumina content of the slimes can be reduced to below 2%, in the beneficiated product, the following benefits can be derived immediately: 2 IN/PA-210 (1) High mine out put. (2) Optimum utilization of the natural resources (3) Reduction at the environmental hazardgenerated due to storage and disposal of the unsuitable products. (4) Higher productivity in the blast furnace and the sinter plant (5) Inerface in production of value added products like application in medical science, paint formulation, removal of hazardous element from contaminated water and soil. Due to ultrafineness of the particles, a process-selection from among the established techniques has become difficult. Accordingly, it requires a more dominating property than gravity or magnetic separation of such ultra fines. The selective flocculation process is known to be adapted to separate iron oxide as red mud from bauxite. It is expected that such a process could be considered to beneficiate such ultra fines. Also this process can be deployed to improve the brightness of selectively separated silica. Thus, a selective flocculation of these fines could be a viable option for efficient separation of alumina and silica from the iron bearing minerals. OBJECTS OF INVENTION It is therefore an object of the invention to propose a process for producing high purity Fe 2 0 3 for value added application and blast furnace feed from a poor grade iron ore slime , which eliminates the prior art disadvantages. 3 IN/PA-210 Another object of the invention is to propose a process for producing high purity Fe 2 0 3 for value added application and blast furnace feed from a poor grade iron ore slime, which provides a first grade of product containing only very low amount of alumina and silica adaptable for high-valued product or blast furnace feed. A further object of the invention is to propose a process for producing high purity Fe 2 0 3 for value added application and blast furnace feed from a poor grade iron ore slime, which provides a second grade of product containing high alumina and silica suitable for making building or refractory material. SUMMARY OF THE INVENTION According to the invention, various grades of rejected ultra fines can be separated out into two categories, (i) a concentrate for value-added applications including blast furnace feed by the selective flocculation followed by pelletization process, the concentrate can be further separated into a good concentrate and a high grade concentrate, the later requiring a two step selective flocculation process; and (ii) a tailing (with rich in alumina and silica) containing mostly as sillimanite and quartz by selective dispersion and selective flocculation process. Both the alumina and silica levels in the ultra fines are in the range of 2.5 to 14wt/o. The alumina and silica levels in the 4 IN/PA-210 concentrate can be dropped down to a level of 0.8 whereas both the alumina and silica level in the tailing can be up to 21 wt/o with varying level of yield of concentrate. The concentrate is most suited as the feed material for iron making through the blast furnace route, whereas the tailing is most suited as the feed material to make building material. The tailing material may be potentially suited for other applications like feed material for formulation of nano paint and nano coolant. Added advantage is that this process is environmental and eco friendly with zero waste. Accordingly, the invention provides a process for producing a high purity Fe 2 0 3 for value added application and blast fumace feed from a poor grade iron ore slime . The process provides a concentrate containing a very high purity iron with very low alumina and silica from the slime containing high alumina and silica generated in the iron ore mines and the iron ore washing plants. According to the process, all the oxide minerals are dispersed and subsequently flocculated selectively under specific conditions. Two products are produced in this process, namely a concentrate, and a tailing. The concentrate contains 68.5% Fe with only around 0.8% alumina and 1.0% silica from the slime containing around 54.5% Fe, 7.61 % alumina and 7.42% silica. This concentrate is suitable for value added applications like in medical science, paint formulation, removal of hazardous elements from contaminated water and soil, and also as the blast furnace feed. The tailing are generated 5 in this process contains 29.8% Fe with 20.5% A1 2 0 3 and 19.68% SiO 2 present mainly as the sillimanite and quartz. This tailing can be utilized as building and refractory material. This process is environmentally friendly with zero waste. Thus the inventive process can effectively produce two valuable products from the ultra fines of iron ore. One product is suitable for fine magnetic particle application or for pelletization whereas the other product is suitable for refractory making, nano paint or nano coolant. A definition of the specific embodiment of the invention claimed herein follows. In a broad format, the invention provides a process for producing a high-grade concentrate comprising more than 97wt% Fe 2

O

3 from iron ore slime comprising at least 6wt% alumina, the process comprising the steps of: - separating through a non-selective dispersion of oxides in iron-containing ultra fines having different particle sizes ranging between 100 micron to 100 nm, into coarser and finer categories in a plurality of hydrocyclones of different sizes, wherein the coarser category comprises oxides with a particle size of more than 15 microns and the finer category comprises oxides with a particle size of less than 15 microns, wet-grinding the coarser category particles under varied concentration to convert into finer category particles; and allowing the produced particles to undergo a selective flocculation in a single benefication step by use of a starch solution which generates a first concentrate containing around 68.5% Fe, 0.8% alumina, and 1% silica, and a first tailing containing around 29.8% Fe, 20.5% alumina, and 19.67% quartz; - allowing the first concentrate to undergo a further non-selective dispersion of oxides followed by a further selective flocculation to produce a high grade concentrate and a second tailing, the high grade concentrate being suitable for value-added applications; and - allowing the first tailing to undergo a selective flocculation to produce a second concentrate and a second tailing, the second tailing being suitable as material for refractory and building construction, wherein the second concentrate suitable for pelletization. 6 BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING Figure 1 - schematically illustrates in the form of a flow-chart, the process steps according to the invention. DETAILED DESCRIPTION OF THE INVENTION According to the invention, the difference in surface charge of the iron bearing minerals and the gangue minerals is utilized first to separate out a first part of the gangue minerals present in the ultra fines. In the second stage, the materials from the first stage are subjected to a selective flocculation by adapting modified starch. By this process, the concentrate [Text continues on page 7.] 6a IN/PA-210 gets converted and suitable for use as the raw material for blast furnace, and the tailing containing high alumina and silica suitable for use as the building materials. As shown in figure-1, a non-selective dispersion followed by a selective flocculation process is proposed to separate out different levels of iron containing ultra fines into (i) an iron rich concentrate, and (ii) a tailing having high level of clay and refractory materials. The ultra fines are processed according to the invention include the ground rejected material of various beneficiation processes and hydro cyclone over-flow. The processable iron containing ultra fines is the mixture of Fe, Si and Al oxides with different particle size. The alumina and silica level of each includes in the range of 2.5 to 14 wt/o. The particle size of the ultra fines is in the range of 100 micron to 100nm, and separated into coarser (more than 15 micron) and finer (less than 15 micron) categories, by adapting a hydro-cyclone of different sizes. The coarser particles are caused to undergo wet grinding under varied concentration to make it finer, finer particles being more suitable for the process because they offer better liberation and better floc formation. The dispersant used in the process includes different non-selective dispersant with different dosages for example, sodium silicate and sodium hexameta phosphate. The dosages of the dispersant are selected in the range of 20 to 150000 ppm, preferably in the range of 20 to 10000 ppm. The flocculant 7 in this process contains 29.8% Fe with 20.5% A1 2 0 3 and 19.68% SiO 2 present mainly as the sillimanite and quartz. This tailing can be utilized as building and refractory material. This process is environmentally friendly with zero waste. Thus the inventive process can effectively produce two valuable products from the ultra fines of iron ore. One product is suitable for fine magnetic particle application or for pelletization whereas the other product is suitable for refractory making, nano paint or nano coolant. A definition of the specific embodiment of the invention claimed herein follows. In a broad format, the invention provides a process for producing a high-grade concentrate comprising more than 97wt% Fe 2 0 3 from iron ore slime comprising at least 6wt% alumina, the process comprising the steps of: - separating iron-containing ultra fines having different particle sizes ranging between 100 micron to 100 nm, into coarser and finer categories by hydrocyclones having different sizes, wherein the coarser category comprises oxides with a particle size of more than 15 microns and the finer category comprises oxides with a particle size of less than 15 microns, and wherein the coarser category particlesare converted to finer category particles by a process of wet-grinding; - subjecting the produced ultra fines having a particle size less than 15 microns to non selective dispersion to ensure stable dispersion of all oxide particles; - followed by selective flocculation in a single benefication step of the dispersed oxide particles by use of a starch solution to generate a first concentrate containing around 68.5% Fe, 0.8% alumina, and 1% silica, and a first tailing containing around 29.8% Fe, 20.5% alumina, and 19.67% quartz; - allowing the first concentrate to undergo a further non-selective dispersion of oxides followed by a further selective flocculation to produce a high grade concentrate and a second tailing, the high grade concentrate being suitable for value-added applications; and - allowing the first tailing to undergo a selective flocculation to produce a second concentrate and a second tailing, the second tailing being suitable as material for refractory and building construction, wherein the second concentrate suitable for pelletization. 6

Claims (2)

1. A process for producing a high-grade concentrate comprising more than 97wt% Fe 2 0 3 from iron ore slime comprising at least 6wt% alumina, the process comprising the steps of: - separating iron-containing ultra fines having different particle sizes ranging between 100 micron to 100 nm, into coarser and finer categories by hydrocyclones having different sizes, wherein the coarser category comprises oxides with a particle size of more than 15 microns and the finer category comprises oxides with a particle size of less than 15 microns, and wherein the coarser category particles are converted to finer category particles by a process of wet-grinding; - subjecting the produced ultra fines having a particle size less than 15 microns to non selective dispersion to ensure stable dispersion of all oxide particles; - followed by selective flocculation in a single benefication step of the dispersed oxide particles by use of a starch solution to generate a first concentrate containing around

68.5% Fe, 0.8% alumina, and 1% silica, and a first tailing containing around 29.8% Fe, 20.5% alumina, and 19.67% quartz; - allowing the first concentrate to undergo a further non-selective dispersion of oxides followed by a further selective flocculation to produce a high grade concentrate and a second tailing, the high grade concentrate being suitable for value-added applications; and - allowing the first tailing to undergo a selective flocculation to produce a second concentrate and a second tailing, the second tailing being suitable as material for refractory and building construction, wherein the second concentrate suitable for pelletization. 2. The process as claimed in claim 1, wherein the ultra fines constitute a mixture of Fe, Si, and Al-Oxides, and wherein the aluminium and silica comprises 2.5 to 14 wt%. 3. The process as claimed in claim 1 or claim 2, wherein non-selective dispersion is achieved by dosage of a non-selective dispersant. 4. The process as claimed in claim 3, wherein the non-selective dispersant comprises sodium silicate and sodium hexameta phosphate. 9 5. The process as claimed in claim 3 or claim 4, wherein the dosage of the non selective dispersant is within the range of 20 to 15000 ppm. 6. The process as claimed in claim 5, wherein the dosage of the non-selective dispersant is within the range of 20 to 10000 ppm. 7. The process as claimed in any one of claims 1 to 6, wherein the starch solution comprises one or more of potato, wheat, and maize starch. 8. The process as claimed in claim 7, wherein the starch solution comprises a caustic starch solution. 9. The process as claimed in claim 8, wherein the caustic starch solution has a concentration in the range of 0.1 to 10.0 wt%. 10. The process as claimed in any one of claims 1 to 9, wherein the process is implemented within a pH range of 2.5 to 11. 11. The process as claimed in claim 10, wherein the process is implemented within a pH range of8 to 10. 12. The process as claimed in any one of claims 1 to 11, wherein the concentration of the ultra fines is in the range of 2 to 25 wt%. 13. The process as claimed in claim 12, further comprising a settling time following selective flocculation, wherein the settling time is between 10 seconds and 20 hours. 14. The process as claimed in any one of claims 1 to 13, further comprising mixing the fine particles in a solvent using an ultrasonic treatment comprising a treatment time in the range of 1 to 100 minutes under variable ultrasonic power prior to selective flocculation, and wherein the solvent comprises double-distilled water, tap water, or industrial process water. 15. A process for producing a high-grade concentrate comprising more than 97wt% Fe 2 0 3 from iron ore slime comprising at least 6wt% alumina, as substantially described and illustrated herein with reference to the accompanying drawing. Date: 8 July 2013 10