HIGH-GRADE CHROMITE CONCENTRATE

TECHNICAL FIELD

The present invention relates to a two-stage decomposition system developed for decomposing chrome ore from the other minerals existing together in nature.

PRIOR ART

Chrome ore has a higher specific weight when compared with lateral rocks (Serpentine, Olivine, etc.). This difference leads to preferring essentially gravimetric methods basically in enrichment of chrome ores. These methods are based on decomposition of materials by utilizing movement of particles in fluid medium (water or heavy liquid) with different speeds under the effect of different forces (gravity force, friction force, liquid buoyancy force, drifting, etc.) depending on the physical characteristics of the particles for instance like particle size, particle shape and particle density.

However, decomposition of chromite and olivine minerals, which are closer to each other when compared in terms of density, by means of gravimetric methods becomes more inefficient as the density difference in between decreases, and final concentrate at the desired tenor values cannot be obtained and the valuable material having economical value is lost in olivine mineral from time to time. Inefficient enrichment leads to reduction of the tenor of chromite concentrate and thus reduction of the value of chromite concentrate and moreover, inefficient enrichment leads to reduction in the totally obtained concentrate amount due to occurring losses and this leads to a big economical loss. This leads to loss of precious ores which have a national wealth characteristic and moreover this may lead to occurrence of environmental effect due to the special storage requirement of the wastes.

When the density of olivine, which is one of the minerals defined as lateral rocks, is compared with serpentine mineral, it is relatively closer to chrome ore. Since serpentine mineral has a lower density value when compared with other minerals during gravimetric enrichment (oscillating table, spiral, jig, etc.) stage, it can be easily removed from the system as waste. However, decomposition of chromite and olivine minerals by means of gravimetric methods becomes more inefficient as the density difference in between decreases depending on the elemental forms of the minerals, and chromite concentrate cannot be obtained with sufficient grade (tenor) or it may be lost inside olivine. In enrichment plants where such ores are processed, the metal obtaining efficiency decreases down to about 40%. Inefficient enrichment leads to decrease of the tenor of the chromite concentrate and thus, leads to reduction of the value of the chromite concentrate and the obtained total concentrate amount also decreases due to the loss occurrence, and a big economic loss occurs. For instance, Cr ₂ 0 ₃ tenor in the residue is 4% in a plant which processes a chrome ore with annually 100,000 tones of 10% Cr ₂ 0 ₃ tenor and which obtains concentrate with 42% Cr ₂ 0 ₃ , the plant will be able to produce 15,798 tones of saleable concentrate, and if the waste tenor is reduced to 3%, this amount will be 17,953 tones. In this case, when the price (-350 USD/tones in plant) of the updated chromite concentrate is taken into consideration, the plant, which can produce further 2155 tones, will be able to obtain a further income of 754,250 USD. As a result, because of all of the abovementioned problems, an improvement is required in the related technical field.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a chrome ore decomposition system, for eliminating the above mentioned disadvantages and for bringing new advantages to the related technical field.

An object of the present invention is to provide a chrome ore decomposition system where enriched chrome ore obtaining proportion is increased.

Another object of the present invention is to provide a two-stage chrome ore decomposition system developed for obtaining chrome ore. Another object of the present invention is to provide a chrome ore decomposition system where the efficiency is increased.

Another object of the present invention is to provide an environment-friendly chrome ore decomposition system where waste proportion is reduced.

Another object of the present invention is to provide a chrome ore decomposition system which provides recovery of present plant wastes having economical value. In order to realize all of the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a chromite decomposition system comprising a grinder which reduces run-of-mine ore and/or plant wastes to micronized sizes and developed for high-grade enriching the chrome ore existing in run-of-mine ore in nature and/or plant wastes, and at least one oscillating table provided at the continuation of said grinder and where the serpentine existing in the run-of-mine ore and/or plant wastes is decomposed. Accordingly, said invention is characterized by comprising a sizing unit connected to the oscillating tables and a magnetic separator provided at the continuation of said sizing unit and which decomposes chromite and olivine mixture, classified at specific particle length intervals, from each other.

In a preferred embodiment of the present invention, a drier is provided between said oscillating table and the sizing unit. In another preferred embodiment of the present invention, said magnetic separator comprises a magnetic drum/roll through which a conveyor band advances and whereon at least one magnet is positioned.

In another preferred embodiment of the present invention, said magnets are embodied in ring form and with a width of 1 mm and 20 mm.

In another preferred embodiment of the present invention, said magnets are embodied in ring form and with a width of 2 mm and 8 mm. In another preferred embodiment of the present invention, said magnets are placed with predetermined intervals on the magnetic drum.

In another preferred embodiment of the present invention, said magnets are placed with intervals of at least one 1 mm on the magnetic drum.

In another preferred embodiment of the present invention, said magnets are positioned on the magnetic drum such that 2 mm gap is formed between the two magnet couples positioned side by side with thickness of 8 mm. In another preferred embodiment of the present invention, said magnets show natural magnetic characteristic of which the magnetic field is stable and sensitive. In another preferred embodiment of the present invention, said magnets are electromagnetic magnets.

In another preferred embodiment of the present invention, said magnets comprise neodymium.

In order to realize all of the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a chromite mineral decomposition method developed for high-grade enrichment of chrome ore existing in plant wastes and/or run-of-mine ore existing in nature, comprising the steps of:

(a) reducing run-of-mine ore and/or plant wastes in a grinder to a particle size which is 500 microns or lower;

(b) decomposing serpentine, existing in run-of-mine ore and/or plant wastes after grinding, in an oscillating table;

Accordingly, said invention is characterized by comprising:

(c) classifying the particle sizes of chromite and olivine mixture, which remains after said oscillating table, in a sizing unit;

(d) decomposing the chromite and olivine mixture, classified in specific particle size intervals, from each other by means of a magnetic separator.

In another preferred embodiment of the present invention, before step (c), the chromite and olivine particles, which remain after serpentine decomposition on the oscillating table, are dried in a drier having a medium temperature between 50 ^e C and 400 ^e C. In another preferred embodiment of the present invention, in step (d), the temperature value where the particles in chromite and olivine mixture exit the drier is at most 150 ^e C.

In another preferred embodiment of the present invention, in step (d), the temperature value where the particles in chromite and olivine mixture enter into the magnetic decomposition system is at most 80 ^e C.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a schematic general view of the decomposition system of chromite mineral.

Figure 2 is a representative view of the magnetic separator. Figure 3 is a representative view of magnetic drum / roll and magnets.

REFERENCE NUMBERS 10 Chromite decomposition system

1 1 Grinder

12 Oscillating table

13 Drier

14 Sizing unit

15 Magnetic separator

151 Conveyor band

152 Magnetic drum/roll

153 Magnet DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the subject matter chromite mineral decomposition system (10) is explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

Chromite, which is one of the natural components of the earth, is one of the basic elements of metallurgy, chemistry and refractory industry. The only mineral of which the ferro-chrome metal is economically produced is chromite. Chromite exists together with serpentine and olivine minerals in rock form in nature. The ore charge, where chromite, serpentine and olivine minerals exist together, is named as run-of-mine ore.

The subject matter chromite mineral decomposition system (10) essentially comprises a grinder (1 1 ), an oscillating table (12) positioned at the continuation of said grinder (1 1 ), a drier (13) positioned at the continuation of said oscillating table (12) and a sizing unit (14) where the dried minerals from said drier (13) are dimensioned. At the continuation of the sizing unit (14), there is a magnetic stirrer (15) where the mineral mixture, decomposed to the desired dimensions, is magnetically decomposed. There is a conveyor band (151 ) of the magnetic stirrer (151 ) and there is a magnetic drum/roll (152) provided in at least one end of said conveyor band (151 ). In an application of the present invention, at least one magnet (153) is positioned on said magnetic drum/roll (152). Said preferred magnet (153) is preferably in ring form. In another application, for the enrichment process, a fixed magnet (153) arrangement is used at the center and a rotating drum-type magnetic stirrer (15) is used.

The chromite existing in run-of-mine ore ingredient can be decomposed from each other by means of the following process steps of serpentine and olivine mineral,

a- Grinding

b- Oscillating table

c- Drying and dimensioning

d- Magnetic decomposition

(a) In this step, run-of-mine ore and/or plant wastes are grinded in the grinder (1 1 ) until the freeing particle size of at least the ores for a predetermined duration by means of methods known in the art. In the preferred application, grinding is realized for particle dimensions of 500 microns and lower. Thus, the physical contact of chromite, serpentine and olivine mineral to each other is broken.

(b) The serpentine mineral which has a different density from the chromite and olivine mineral is decomposed by means of usage of oscillating table (12) known in the art.

(c) The chromite and olivine mineral are subjected to drying process in the drier (13) which is the preferred application before the magnetic decomposition process. The drying medium temperature is preferably between 50 ^e C and 400 ^e C. Afterwards, in order to decompose chromite and olivine minerals from each other, chromite and olivine particles are dimensioned in the sizing unit (14) at desired intervals. The dimensioning is optional, and in case dimensioning is not realized, the chromite particles are scattered as a result of the effect of the weight and centrifugal force, may be mixed in the olivine ingredient. Thus, in the preferred application, dimensioning is realized for obtaining product with the highest grade.

(d) The chromite and olivine particles dimensioned in various proportions are passed through magnetic separators (15) by utilizing the magnetic sensitivity difference in between. Thus, the chromite and olivine minerals are decomposed from each other at a high grade. In the magnetic decomposition process which is the second stage enrichment process, aqueous or dry magnetic decomposition can be realized. Preferably due to usage easiness and low cost, dry magnetic decomposition is used.

As the magnetic separator (15), magnets (153) like neodymium which show natural magnetic characteristic and of which the magnetic field is stable and sensitive are used. During magnetic decomposition, the temperature of feeding of the chromite + olivine mixture to the magnetic separator system shall be preferably at most 80 ^e C. In the preferred application, the temperature of feeding the chromite + olivine mixture to the magnetic separator system is 50 ^e C.

In the alternative embodiment of the present invention, various types of magnets can be used like wet magnetic separators and electromagnetic magnet. In case electromagnetic magnet is used, the temperature of the chromite + olivine mixture which is subjected to magnetic decomposition can be above 80 ^e C. For the wet magnetic separation process, usage can be realized when a medium is created which provides the same field intensity and where the drifting force is eliminated.

The used magnet (153) is in the form of a rotating magnetic drum/roll (152). Magnets (153) which have diameter suitable for particle size dimensioned are positioned on the magnetic drum/roll (152). The conveyor band (151 ) passes through the magnetic drum/roll (152) and while the chromite + olivine mixture passes through said magnetic drum/roll (152), the mineral, of which the magnetic characteristic is high, adheres to the conveyor band (151 ) and passes to the lower side and it is thrown to the mineral collection section of which the magnetic characteristic is low. Thus, decomposition is realized.

The transverse thicknesses of magnets (153) which are in sleeve form used on the magnetic drum (152) change between 1 mm and 20 mm. During dimensioning, thin magnets (153) can be sufficient for thin materials, and thick magnets (153) are used for greater particle groups. In the preferred application, the transverse thicknesses of the used magnet (153) are between 2 mm and 8 mm. The magnet (153) rings are placed on the magnetic drum (152) with intervals of at least 1 mm. In an application of the invention, positioning of the magnets (153) on the magnetic drum (152) are such that the gap between two magnet (153) couples, positioned side by side and having thickness of 8 mm, is 2 mm. The positioning manner of the magnets (153) may change depending on the ore ingredient and tenor.

In Table 1 , the magnetism, specific weight and chemical formula of the chromite, olivine and serpentine mineral are given.

Table 1

Serpentine 1 100-6300 2.5 - 3.2 (Mg,Fe,Ni,AI,Zn,Mn) ₂ -

₃ (Si,AI,Fe)20 ₅ (OH) ₄

In practice, while the dried and dimensioned chromite + olivine mixture advances on a conveyor band (151 ) and while said mixture passes through the magnetic drum/roll (152) whereon magnet (153) is provided and provided at the end/rotation section of the conveyor 5 band (151 ), the chromite, of which the magnetic characteristic is higher, is held onto the conveyor band (151 ) as a result of magnetic effect and advances to the lower side of the conveyor band (151 ). From here, said mixture falls to the chromite collection chamber through the section where magnetic field ends on a stripping unit or on a conveyor band (151 ). Olivine, of which the magnetic characteristic is lower, is scattered and removed from 10 the magnetic field as a result of the effect of centrifugal force, and olivine falls into the olivine collection chamber.

In the preferred application, the data related to the magnetic drum (152) and to the conveyor band (151 ), where the magnetic decomposition process is realized, is given in Table 2.

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Table 2

The protection scope of the present invention is set forth in the annexed claims and cannot be restricted to the illustrative disclosures given above, under the detailed description. It is because a person skilled in the relevant art can obviously produce similar embodiments under the light of the foregoing disclosures, without departing from the main principles of the present invention.

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