Present invention relates to a process for the pelletization of graphite powder.
Mixing carbon in steel manufacturing is a very important process to manufacture different grades of carbon steel. The various grades of steel is required for a variety of applications both for making industrial tools and machinery and for making steel for manufacture of general; purpose articles like utensils. The carbon is added to the steel during the melt process in the making of the steel and for effectively incorporating this additive, carbon is used in powder form. The quantity of carbon to be used may vary from the requirement imposed on the property of steel based on the end use. Say for instance the steel may be required for final use in making of railway tracks. In such a case the strength of the final steel may have to be really high keeping in view of the fact that the material has to bear a very high dynamic load.
Reference may be made to a US patent (#4,005,170) wherein a wet pelletizing process for preparing improved carbon black pellets has been disclosed. The wet pelletization process uses water as the pelletizing medium giving a control of shape and size of the pellets. The amount of pelletizing liquid normally used is in a range of about 3 to 75 percent of the total amount of liquid required for preparing pellets in a conventional manner. High speed of 550 rpm has been used for effecting mixing of the carbon black powder to form agglomerates.
Reference may be made to yet another disclosure on method of producing iron oxide pellets (US Patent # 6,579,505). The invention discloses method for producing an iron oxide pellet including the steps of adding water to a raw material mixture comprising iron oxide serving as a primary component, a carbonaceous material in an amount sufficient for reducing the iron oxide, an organic binder in an amount sufficient for binding the iron oxide and the carbonaceous material. The pelletization process used consists in using starchy organic binder in an amount sufficient for binding the iron oxide and the carbonaceous material, and an inorganic coagulant in an amount of not less than
0.05 mass % and less than 1 mass %; and adding water to the uniformly mixed raw material mixture.
Main objective of the present invention is to provide a process for the pelletisation of graphite powder.
Another objective of the present invention is to provide a process using natural starch as a binder for pelletisation.
Still another objective of the present invention is to provide a process capable of extrusion of graphite mixed with binder in wet condition.
A further objective of the present invention is to provide a process capable of producing graphite pellets with low affinage.
Still further objective of the present invention is to provide graphite pellets with the process of the present invention, the said pellets being capable of being used in carbonisation of steel during the melting process.
Present invention discloses a process for the peptization of graphite powder. The process essentially uses natural starch in a proportion in a range of 4-5% of graphite as binder to facilitate in pelletization. The affinage of the pellets so formed is in the range of 15-30% and thus helps in reducing the dust pollution during steel melting process. Further due to the low affinage the palletised graphite leads to better carbon dissolution in the steel melt and is capable of being transported without any dust formation during transportation. The graphite pellets are characterised by low moisture content (not more than 0.4%) low volatile matters (less than 5%) and high carbon fixation (not less than 95%).
Accordingly the present invention provides a process for the pelletisation of graphite powder which comprises: mixing of graphite fine, binder and a pelletizing liquid medium, the quantity of the said binder being in a range of 1-5% of graphite fine by weight, the pelletizing liquid medium in the said mixture is in a range of 40-50% of graphite fine by weight, the said mixture being stirred thoroughly for a time period of 15 minutes, the said mixture being extruded under a maximum force of 6 ton to give a graphite pellet of diameter in a range of 2mm
to 10mm, the said pellets being dried at a temperature of 110° C for a time in
the range of 2-8 hours or optionally allowed to cool dry in a natural way in
sunshine
In an embodiment of the present invention the binder used may be a natural
starch, carbohydrates.
In another embodiment of the present invention the palletising liquid medium may
be water.
In another embodiment of the present invention the palletised graphite by the
process of the present invention may have affinage in a range of 15-30%.
The process is hereby described to produce a batch of say 20 Kgms of graphite
pellets of diameter in the range of 3.5to 10mm , more particularly with diameter of
less than 3.5mm. Graphite fine powder is mixed with a binder preferably a
natural carbohydrate. The amount of binder taken is preferably in a range of 1-
5% by weight of graphite. To this is added the palletising medium preferably
water in a range of 40-50% by weight of graphite fines. The mixture is then
thoroughly mixed and is then extruded to pellets under a force of preferably 6
ton. This extrusion gives pellets of diameter of about 3.5 mm. These pellets are
allowed to dry in natural way without any heating. The main desirable
'SPECIFIC property of these pellets are that (1 ) it has least strength at
temperature of liquid metal ( 2 ) it has no obnoxious volatiles The inclusion of
carbon is uniform in the steel melt. Because of the above properties there is no
dust pollution in the environment nor are there any obnoxious gases from the
steel melt during the (Addition of these Pellets ) carbonisation process.
The critical parameter to ascertain the novelty of the process is the measurement
of the affinage of the pellets. This is done as follows.
150 cc of -3 + 14 mesh Pellets are taken and weighed. The pellets are kept in
cylinder of dia 100 mm, these are spreaded in the cylinder and a plate is placed
on the top of Pellets. A load of 4000 kg is applied on the Pellets by Universal
Testing Machine for 90 seconds. The pellets are then taken out and screened on
14 mesh to find out the generation of minus 14 mesh pellets or dust. Then the %
of minus 14 mesh is calculated.
Novelty of the present invention lies in providing graphitised pellets capable of use in steel melting for incorporating carbon with high fixation (not less than 95%) without producing any hazardous gases and dust pollution in the environment.
The said novelty has been achieved by the inventive step of extruding the wet mixture of graphite with natural carbohydrate and drying under sunshine for longer period or optionally with heat treatment at a low temperature of 110° C for a short duration not exceeding 10 hours.
Following examples are given by way of illustration only and should not be construed to limit the scope of the invention.
Example-1 100 gm of Graphite powder - 60 mesh was taken. Raw Water in a proportion of 50% of Graphite Powder and Starch Powder in a proportion 5 % of Graphite Fines were mixed in mixer. The mixing temperature was kept at 90° C by oil heating. The mixing was done for 20 minutes. The mix was taken out and kept in Extrusion pot. The mix was pressed by a Hydraulic Press at 100 Kg /cm2 pressure for peptization. The pellets were sun dried for 48 hours giving the graphite pellets ready for use.
Example-2 100 gm of Graphite powder - 60 mesh was taken. Raw Water in a proportion of 55% of Graphite Powder and Starch Powder in a proportion 4.5 % of Graphite Fines were mixed in mixer. The mixing temperature was kept at 90° C by oil heating. The mixing was done for 15 minutes. The mix was taken out and kept in Extrusion pot. The mix was pressed by a Hydraulic Press at 150 Kg /cm2 pressure for peptization. The pellets were dried at 110° C for 2 hours giving the graphite pellets ready for use.
Example-3 100 gm of Graphite powder - 60 mesh was taken. Raw Water in a proportion of 55% of Graphite Powder and Starch Powder in a proportion 4.0 % of Graphite Fines were mixed in mixer. The mixing temperature was kept at 90° C by oil heating. The mixing was done for 15 minutes. The mix was taken out and kept
in Extrusion pot. The mix was pressed by a Hydraulic Press at 150 Kg /cm2 pressure for pelletization. The pellets were dried at 110° C for 2 hours giving the graphite pellets ready for use.
The properties of the pelletized graphite are summarised in table-l
Table-I

(Table Removed)
Abreviations used : GM : Gross Moisture VM : Volatile Matters FC Fixed Carbon ( Calculated )
The main Advantages of the invention are:
1 - The pelletized graphite has quick dissolution in steel.
2 - The pellets result in better carbon recovery.
3 - There is no dust Pollution during its addition in the steel melting.
4 - The use of the pellets leads to eco friendly volatiles during steel melting.
5 - Handling losses during storage & transportation are minimised.

We claim :
1. A process for the pelletization of graphite powder which comprises: mixing of graphite fine, binder and a pelletizing liquid medium, the quantity of the said binder being in a range of 1-5% of graphite fine by weight, the pelletizing liquid medium in the said mixture is in a range of 40-50% of graphite fine by weight, the said mixture being stirred thoroughly for a time period in a range of 15 -20 minutes, the said mixture being extruded under a maximum force of 6 ton to give a graphite pellet of diameter in a range of 2 mm to 10 mm, the said pellet then being dried at a temperature of 110° C for a time in the range of 2-8 hours or optionally allowed to cool dry in a natural way in sunshine, the palletised graphite being characterized in that the gross moisture is not more than 0.4%, volatile matters not being more than 5% and carbon fixation in steel not being less than 95% .
2. A process as claimed in claim 1, wherein the binder used is a natural starch, a carbohydrate.
3. A process as claimed in claims land 2, wherein the pelletising liquid medium may be water.
4. A process as claimed in claims 1to 3, where in the pelletised graphite fines by the process of the present invention has affinage in a range of 15-30%.
5. A process for the peptization of graphite powder substantially here in as described with reference to the examples accompanying this specification.