FIELD OF THE INVENTION
The present invention relates to carbon coated refractory grains and to a process for
developing such grains for the purpose of making refractory bricks or castables using such
coated grains. Carbon black used for the coating purpose is a nano material having particle
size of 24-36nm which is preferably about 99.9 % pure carbon and is amorphous in
nature. Advantageously, such coated carbon is provided such that it is insoluble in water
and form film over the grains. Also, the carbon coated on the surface of the grain forming
a thin film over it is adapted such as not to come out even in alkaline water and thus
favouring making carbon containing bricks/castables durable and avoids problems of
carbon being exposed during pressing or casting. The carbon coated grains are also
adapted to be used as nozzle filling compound of steel ladles. The carbon nano particle
based thin film coated refractory grains according to the present invention thus have wide
application in various industrial applications, for making refractory bricks and/or castables,
particularly for use in steel industries.
BACKGROUND ART
It is known in the art of manufacturing refractory bricks or castables that use of carbon
coated refractory oxide grains is quite common. Conventionally, refractory grains are
coated with graphite that is used in making carbon containing bricks or castables. Graphite
is a flaky material that could not coat the grains properly. As a result, the flaky graphite
comes to the surface of the brick at the time of pressing the grains to form brick. The main
obstacle in developing carbon containing castable resides in the use of graphite which is
non wettable in water and comes to the surface at the time of casting and thus making the
bricks or castables less durable and unable to provide desired thermal conductivity or like
properties.
Attempts have been made to try out different types of oils and organic
compounds/solvents to coat different types of refractory oxide grains with carbon black.
But none of the conventional process could result in the desired characteristics of the
coated grains suitable for use in refractory bricks or castables.

There has been thus a continuing need to developing carbon coating on refractory grains, by obtaining an appropriate_solvent at would provide a stable solution dissolving the
carbon black nano particles of selective size which would on one hand form coating on the
refractory oxide grains of a number of varieties in common use and on the other hand
form a stable thin film which would not be removed during formation of the bricks by
pressing or preparing castables.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for carbon coated refractory
grains which would on one hand form coating on the refractory oxide grains of a number
of varieties in common use and on the other hand form a stable thin film which would not
be removed during subsequent treatments/uses of such in variety of refractory materials.
Another objcet of the invention is direcetd to the development of a process of producing
such desired carbon coated refractory grains that would be insoluble in water and also
favourably form the desired film over the refractory grains.
A .further object of the present invention is directed to possible obtaining of bricks or
castables from the carbon nano particle coated refractory oxide grains which would provide
stable coating and do not get damaged during pressing or casting operation.
A further object of the present invention is directed to the carbon coated refractory grain
adapted to form bricks or castables which when subjected to alkalinesolution the carbon
would not come out of the grain and thus provide for a durable and effective coating of
the grains.
A still further object of the present invention is directed to developing the carbon nano
particle coated refractory grain used to form bricks or castables wherein said coated grains
are adapted to restrict the hydration of grains.

A still further object of the present invention directed to the carbon nano particle coated
refractory grains such that the coated grains are also useful as nozzle filling compound of
steel ladies.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided for carbon
coated refractory grains comprising :
refractory grains coated with a solution of carbon in organic hydrophihc Furancarbinol

thereby forming carbon coated refractory grains insoluble in water and forming film over
the grains.
Another aspect of the present invention directed to said Carbon coated refractory grains
wherein said carbon comprise nano particles of carbon black having particle size in the
range of 24-36 nm,_
A further aspect of the present invention directed to Carbon coated refractory grains
wherein said refractory grains comprise different types of oxide grains preferably selected
from Fused alumina, Quartzite and sintered and fused magnesite grains.
A still further aspect of the present invention is directed to Carbon coated refractory grains
wherein ratio of carbon black and organic compound vary with different types of grain.
A still further aspect of the present invention directed to Carbon coated refractory grains
wherein the coated grains are glazy in appearance and adapted such that (i) when put in
alkali solution carbon does not come out of the grain and (n) when put in water no carbon
comes out'from the grain.
An yet further aspect of the present invention directed to Carbon coated refractory grains
wherein the coated grain are adapted to restrict.the hydration of grain and are thermally
and electrically conductive.

According to yet another aspect of the present invention directed to a process for the
manufacture of carbon coated refractory grains comprising :
i) providing a solution of carbon black in organic hydrophilic Furancarbmol ; and
n) subjecting the thus coated grain to drying.
A further aspect of the present invention directed to said process for the manufacture of
carbon coated refractory grains wherein said ratio of carbon black to the grain is selected
based on the grain and its end uses.
A still further aspect of the present invention is directed to a process for the manufacture
of carbon coated refractory grains as claimed in anyone of claims 7 or 8 wherein the step
of drying comprises drying the coated grains in the temperature range of 80°C to 120°C for
a period of 0.5 hr to 2 hr and preferably 110°C for a period of about 1 Hr.
The present invention and its advantages and objects are described in further details with
reference to the following non limiting illustrative examples:
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO FOLLOWING
ACCOMPANYING EXAMPLE
As already described , the present invention is directed to developing carbon coated
refractory grains and a process for developing such grains for the purpose of making
carbon containing refractory bricks or castables using such coated grains. Such coated
carbons are insoluble in water and form film over the grains providing a stable coating
which do not get damaged or removed during pressing/casting operation for
manufacturing of bricks or castables.
The process of developing the carbon coated refractory oxide grains of a number of types
to suit different application were developed following a number of experiments to arrive at
the optimum result. The process involving the various input materials such as selective
carbon particles, different solvents and different alternative refractory oxide grains and the
various selective steps to develop the carbon coated refractory grains for use in making

bricks and castables of desired characteristics are illustrated through the folllowing
examples:
EXAMPLE:! (PRIOR ART PROCESS^
Different natural oils like mustard oil, Karanj oil, Custard oil and Kerosene oil have been
mixed separately with different percentage of carbon black ranging from 0.25%wt to 2.0 %
wt having particle size in the range of 0.5mm to 5mm, to coat the grains of quartz, alumina,
sintered and fused magnesia. The observed results are as given below:
- Mustard oil made a solution with carbon black but could not coat the grain well.
- Karanj oil and custard oil made a solution better than mustard oil and coat the
grain but the coating did not stick on the grain and came out easily.
- Kerosene oil could not make a solution with carbon black.
Also the organic compounds of different varieties have been used to coat the grain with
carbon black namely Formaldehyde, Ethylene glycol, Ethyl alcohol.
- Formaldehyde, Ethylene glycol made a solution well with carbon black but could
not coat the grains which could stick on the grains.
- Ethyl alcohol could not make a solution with carbon black.
i *
EXAMPLE-2
To obtain a stable coat of carbon solution on refractory grains of a number of types of oxide
materials which are used for manufacturing carbon containing bricks or castables, following
process steps in accordance with the present invention were followed :
1. The carbon particles used for the purpose of coating on grains are taken to be Carbon
black which is a nano material, amorphous in nature and is 99.9% pure carbon. The particle
size of black carbon is in the range of 24-36nm.
2. Organic solvent Furancarbinol used to form a solution with carbon black and coat the
grain well.

3. Nano carbon material carbon black coated the oxide grains well with organic hydrophihc
compound Furancarbinol.
4. The grains of different type like quartz, alumina, sintered and fused magnesia were
coated with different ratio of carbon black and Furancarbinol such as,
Solvent Furancarbinol to carbon black in the ratio of:
Type of Grains Preferred range of ratios
Quarzite: 0.25% to 2.0% by wt.
Fused Alumina: 0.25% to 2.0% by wt.
Sintered and
fused magnesite: 0.25% to 1.0% by wt.
5. With the carbon solution obtained as above , the carbon solution was coated on the
surface of the grains to form a film over the grains.
6. The coated grain thus produced were dried in the temperature range of 80°C to 120°C
for a period of 0.5 hr to 2 hr and preferably 110°C for a period of about 1 Hr.
7. Resulting grains obtained from the process was found to have a stable coating on
drying, which is glazy in appearance and is not easily removed by rubbing or do not come
out even when rubbed with hands or is subjected to alkali solution.
8. The carbon coated refractory oxide grains thus produced were next used for making
carbon containing bricks by pressing or producing castables by casting, which demonstrate
the desired thermal or electrical characteristics of the coated refractory particles for
respective end uses.
In particular, the properties of the carbon-coated grains were found to have the following
properties favourable for producing carbon containing bricks or castables:
The carbon coated the surface properly and forms a film over the grain;
When rubbing it in hand carbon is not coming out from the grain that confirms
carbon coated the grain well;
The coated grain is glazy in appearance;

The coated grain when put in alkali solution carbon is not comes out of the grain;
The coated grain when put in water no carbon is coming out from the grain which
is good for development of carbon containing castables;
The coated grain are capable of restricting the hydration of grain;
The coated grains are thermally and electric conductive.
It is thus possible by way of this invention to produce carbon coated refractory grains and
in particular, carbon black nano particle in organic Furancarbmol based solution, providing
a stable coating of carbon on different variety of refractory oxide grains such as the fused
alumina, quartzite, sintered and fused magnesia and the like, whereby the grains are
rendered suitable for use for producing the bricks by pressing or the castables by casting
process, without any damage to the carbon coating and maintaining desired thermal and <
electrical properties for longer term with a stable performance in a number of application/
of such carbon coated refractory particles including such as refractory bricks or castables
in steel industries.

WE CLAIM:
1. Carbon coated refractory grains comprising :
refractory grains coated with a solution of carbon nano particles in organic hydrophilic
Furancarbinol thereby forming carbon coated refractory grains insoluble in water and
forming film over the grains for refractory bricks or castables which avoids carbon
exposure during pressing or casting operation.
2. Carbon coated refractory grains as claimed in claim 1 wherein said carbon nano
particles comprise of carbon black having particle size in the range of 24-36 nm.
3. Carbon coated refractory grains as claimed in anyone of claims 1 or 2 wherein said
refractory grains comprise different types of oxide grains preferably selected from
Fused alumina, Quartzite and sintered and fused magnesite grains.
4. Carbon coated refractory grains as claimed in anyone of claims 1 to 3 wherein ratio of
carbon black and organic compound vary with different type of grain.
5. Carbon coated refractory grains as claimed in anyone of claims 1 to 4 wherein the
coated grains are glazy in appearance and adapted such that when (i) when put in
alkali solution carbon does not come out of the grain and (n) when put in water no
carbon comes out from the gram.
6. Carbon coated refractory grains as claimed in anyone of claims 1 to 5 wherein the
coated grain are adapted to restrict the hydration of grain and are thermally and
electrically conductive.
7. A process for the manufacture of carbon coated refractory grains as claimed in anyone
of claims 1 to 6 comprising :
i) providing a solution of nano carbon black particles in organic hydrophihc
Furancarbinol maintaining solvent Furancarbinol to nano carbon black particles
ratio in the range of 0.25 to 2.0% by wt. and coating said refractory grain to
thereby provide a coated refractory grain; and

II) subjecting the thus coated refractory grain to drying.
8. A process for the manufacture of carbon coated refractory grains as claimed in claim 7
wherein ratio of said carbon black to the grains is selected based on the type of grain
and its end uses and the carbon black used have particle size in the range of 24-36 nm
with 99.9% pure carbon being amorphous in nature; and
step of drying comprises drying the coated grains in the temperature range of 80°C to
120°C for a period of 0.5 hr to 2 hrs and preferably at 110°C for a period of about 1 hr.
9. Carbon coated refractory grains as claimed in claim 1 for use in manufacture of
refractory bricks.

ABSTRACT

TITLE: CARBON COATED REFRACTORY GRAINS AND A PROCESS FOR ITS MANUFACTURE.
The present invention relates to carbon coated refractory grains and a process for
developing such grains for the purpose of making refractory bricks or castables using such
coated grains. Such coated carbon are insoluble in water and a carbon solution form film
over the grains. Carbon black used for the coating purpose is a nano material having
particle size of 24-36nm which is 99.9 % pure carbon and is amorphous in nature. The
carbon black when mixed with organic compound hydrophilic Furancarbinol to form a
solution and mixed with the different type of refractory oxide grain in a mixer, it forms
carbon thin film over the grains. The carbon coating on drying, do not come out even in
alkaline water and thus carbon containing bricks/castables durable made of such grains.
These grains are also used as nozzle filling compound of steel ladles and thus having wide
application in various industrial applications, for making refractory bricks and/or castables,
particularly for use in steel industries.