TECHNICAL FIELD

The present subject matter generally relates to sillimanite separation process, and more particularly, to a process for separating sillimanite from beach sand.

BACKGROUND OF THE INVENTION

Sillimanite is a very important raw material for the manufacture of refractory bricks used in iron, steel, cement and glass industries. Sand in coastal stretches (beach sand) contains sillimanite along with other minerals like quartz, shell, ilmenite, rutile, zircon, garnet etc. Sillimanite is separated from the beach sand using flotation process.

In the existing commercial separation process, the non-conducting, non-magnetic portion consisting of sillimanite, zircon, quartz, and shell is subjected to froth flotation process for sillimanite separation. In the flotation process, sodium silicate, oleic acid and sodium carbonates are added to aid in the sillimanite flotation. During the process, oleic acid forms a layer on the sillimanite surface which is removed by heating the mineral to high temperature. However, some oleic acid remains on the sillimanite surface as residue. The residual oleic acid in the mineral reduces the quality and affects the end use.

Hence, there is a requirement of a process to separate sillimanite from beach sand which eliminates the use of chemical additives and which overcomes aforementioned and other challenges. SUMMARY

The following presents a simplified summary of the subject matter in order to provide a basic understanding of some aspects of subject matter embodiments. This summary is not an extensive overview of the subject matter. It is not intended to identify key/critical elements of the embodiments or to delineate the scope of the subject matter.

Its sole purpose is to present some concepts of the subject matter in a simplified form as a prelude to the more detailed description presented later.

It is therefore an object of the present subject matter to provide a process for separating sillimanite from beach sand.

It is another object of the present subject matter to subject the non-magnetic minerals portion of the beach sand namely zircon, sillimanite, rutile, quartz and shell through wet operation (Spiral and cross flow) after the magnetic separation, where zircon and rutile are separated as Very Heavy Minerals (VHM).

It is yet another object of the present subject matter to use electrostatic plate separator for separating sillimanite.

These and other objects, embodiments and advantages of the present disclosure will become readily apparent to those skilled in the art from the following detailed description of the embodiments having reference to the attached figures, the disclosure not being limited to any particular embodiments disclosed.

In an embodiment, the present subject matter aims at disclosing a method to separate sillimanite from beach sand. The method comprising the includes passing the beach sand through a preliminary filter screen to achieve uniform grain size of beach sand; subjecting the beach sand of uniform grain size through a magnetic separation process to separate out non-magnetic minerals of the beach sand; subjecting the non-magnetic minerals to a matrix of wet operations; drying and processing a concentrate of sillimanite and quartz, said concentrate being an output of the matrix of wet operations; and separating sillimanite from said concentrate through utilization of difference in surface conductivity of sillimanite with respect to other minerals.

In another embodiment, the non-magnetic materials comprise zircon, sillimanite, rutile, quartz and shell.

In yet another embodiment, minerals like zircon, rutile, silica and shell are separated out when the non-magnetic minerals are subjected to the matrix of wet operations.

In yet another embodiment, the concentrate of sillimanite and quartz is processed through electrostatic plate separator.

In yet another embodiment, the quartz turns conductive due to triboelectric charging and sillimanite is separated as the non-conductive mineral after processing through electrostatic plate separator.

In yet another embodiment, said concentrate is passed through electric field and the particles having opposite charges are pulled towards respective electrodes thereby creating different trajectories for occurrence of sillimanite separation.

In yet another embodiment, an induced roll magnetic separator is positioned after electrostatic plate separator for separation of sillimanite.

In yet another embodiment, the sillimanite is passed through a magnetic separator to remove any traces of entrapped magnetic minerals present. In yet another embodiment, the resultant non magnetic sillimanite achieved as output of the magnetic separator is high grade commercial sillimanite.

In yet another embodiment, the preliminary filter screen is a filter screen having size 425 microns

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the embodiments of the systems and methods described herein, and to show more clearly how they may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, wherein:

Figure 1 illustrates a flowchart depicting the sillimanite separation process starting from beach sand in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

The following presents a detailed description of various embodiments of the present subject matter with reference to the accompanying drawings.

The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to a person skilled in the art of the present disclosure. In the accompanying drawings, like reference numerals are used to indicate like components. The present subject matter provides a sillimanite separation process which improves quality of sillimanite mineral obtained after separation from beach sand. The sillimanite separation process avoids use of oleic acid used in the flotation process whose residue remains with the sillimanite product.

The sillimanite separation process consists of subjecting the non-magnetic minerals portion of the beach sand namely zircon, sillimanite, rutile, quartz and shell through a matrix of wet operation (spirals, upstream classifier and attritioner) after the magnetic separation, where minerals like zircon, rutile and a portion of silica and shell are separated out. The remaining concentrate of sillimanite and quartz are dried and further processed through the electrostatic plate separator. Due to the triboelectric (contact) charging, quartz turns conductive and hence sillimanite is separated as the non conductive mineral in its pure form. Electrostatic plate separator is a mineral sorting device which utilizes the difference in the surface conductivity of the minerals to separate them. Since the surface conductivity of sillimanite is different from the other minerals present therein, sillimanite can be separated out. As the mineral is passed through an electric field the particles having opposite charges are pulled towards respective electrodes thereby creating different trajectories thereby separation occurs.

Figure 1 illustrates a flow diagram 100 showing various steps associated with the sillimanite separation process in accordance with an embodiment of the present subject matter. Initially, beach sand is passed through a preliminary filter screen 102 to achieve uniform grain size of beach sand for further process. The screened beach sand is then passed through a magnetic separator 104 to further remove magnetic particles. The remaining non magnetic portions which contain minerals namely zircon, sillimanite, rutile, quartz and shell are subjected to a series of wet operations. The wet operations include spiral concentrator 106, attritioner 108 and upstream classifier (cross flow) 1 1 0. The spiral concentrator 106 is a high capacity low cost device developed for inexpensive pre concentration of low value ores. It is a static machine that uses the principle of minerals specific gravity and centrifugal force to separate the denser minerals from the lighter gauge materials. When a homogeneous slurry flows around the helix of a spiral concentration, stratification occurs in the vertical plane due to a combination of hindered settling, interstitial settling, bangnold forces & also stream cross sectional rotation. The result is that, in the vertical plane, the heavier minerals proceed to the lower velocity zones near the trough surface, while the lighter minerals tend to stratify above them in the higher velocity zones. The helical twist of the spiral concentrator 106 causes a radial, or centrifugal, velocity gradient related to the other, in a horizontal plane. This difference in centrifugal force shifts the heavy minerals inward towards the collection ports and the light faster flowing slower settling minerals outwards that is away from the collection ports.

The upstream classifier 1 10 also known as cross flow is a high capacity low cost device developed for inexpensive pre concentration of low value ores. It is a static machine that uses the principle of hindered settling and minerals specific gravity to separate the denser minerals from the lighter gauge materials. Feed materials descend against a rising flow of water and a fluidized bed is established having the specific gravity equal to the slurry on the teeter bed. Particles having densities higher than the teeter bed sinks and particles having lower densities are floated away.

After going through the spiral concentration stage of wetting operations, middling fractions containing enriched sillimanite and quartz are obtained as spiral output. The said fractions are passed through the attritioner 108 to remove attached impurities such as dust or any light surface coating. The attritioner 108 liberates any surface coating present in the concentrate and upstream classifier 1 10 removes it from the resultant mass. The product thus obtained is dried through a drier 1 12 to remove any moisture and is passed through an electrostatic plate separator 1 14, where sillimanite and quartz are separated. The sillimanite thus obtained is further passed through a magnetic separator 1 16 to remove any traces of entrapped magnetic minerals present. The resultant non magnetic fraction of the magnetic separator is high grade commercial grade Sillimanite.

In accordance with an embodiment of the present subject matter, beach sand is passed through a preliminary filter screen of 425 microns to achieve uniform grain size of beach sand for further process. The screened beach sand is then passed through a magnetic separator to further remove magnetic particles. The remaining non magnetic portions which contain minerals namely zircon, sillimanite, rutile, quartz and shell are subjected to a series of wet operations including spiral concentrator, attritioner and upstream classifier (cross flow). Middling fractions containing enriched sillimanite and quartz are obtained as spiral output after this step. The said fraction is passed thought an attritioner to remove attached impurities such as dust or any light surface coating. After this stage the concentrate is again subjected to a spiral operation where the sillimanite content is further upgraded. The said enriched concentrate is further cleaned using attritioner and upstream classifier. The attritioners liberate any surface coating present in the concentrate and upstream classifier removes it from the resultant mass. The product thus obtained is dried to remove any moisture and is passed through Electrostatic plate separator where sillimanite and quartz are separated. The sillimanite thus obtained is further passed through a magnetic separator to remove any traces of entrapped magnetic minerals present. The resultant non magnetic fraction of the magnetic separator is high grade commercial grade Sillimanite. Further, an Induced Roll Magnetic Separator (IRMS) can be placed after the electrostatic plate separator. Induced Roll Magnetic Separator (IRMS) is a mineral separation device used mainly in the pre concentration of ores. In induced roll magnetic separators, separation occurs at the roll surface due to combination of magnetic, centrifugal & gravity forces. The magnetic pull induced on the particle based on its magnetic susceptibility changes the trajectory of the mineral resulting in separation of the mineral.

The sillimanite separation process in accordance with an embodiment of the present subject matter is shown below:

The data retrieved through the analysis of aforementioned wet operations is given below: Wet Process Analysis Report