Claims:We Claim:
1. Crystalline Multi Wall Carbon Nano Tube (MWCNT) and modified graphite
incorporated refractory castable suitable for steel industry, comprising of:
white Fused Alumina (WFA) (Coarse) having particle size ranging from 2 mm to
3.5 mm and about 15-17 % by weight,
white Fused Alumina (WFA) (Coarse) having particle size ranging from 1 mm to
2.5 mm and about 6-8 % by weight,
white Fused Alumina (WFA) (Coarse) having particle size ranging from 0.5 mm
to 1 mm and about 15-17 % by weight,
white Fused Alumina (WFA) (Coarse) having particle size ranging from 0.5 mm
to 0.25 mm and about 7-9 % by weight,
white Fused Alumina (Fines) having particle size below 0.1 mm and about 15-19
% by weight,
white Tabular Alumina (Fines) having particle size below 0.044 mm and about 9-
11 % by weight,
calcined Alumina (Fines) having particle size below 0.044 mm and about 4-6 %
by weight,
reactive Alumina (Fines) having particle size below 0.002 mm and about 9-11 %
by weight,
fume Silica (Fines) having particle size below 0.044 mm and about 4-6 % by
weight,
graphite having (Fines) having particle size below 0.5 mm and about 4-6 % by
weight,
crystalline Multi Wall Carbon Nano Tube (MWCNT) (Fines) having diameter
below 4x10-5 mm (40 nm) and about 0.1-0.5 % by weight,
20
sodium Hexa-Meta Phosphate (SHMP) of LR/GR grade and about 0.04-0.06 %
by weight, and
carboxymethyl cellulose (CMC) of HLB ratio 8-10 and about 0.10-0.14 % by
weight.
2. The refractory castable as claimed in claim 1, wherein said White Fused Alumina
(WFA) comprises
Al2O3 (Min.), % 99.3
Fe2O3 (Max.), % 0.13
B.D. (Min.), gm/cc 3.55
A.P. (Max.), % 5
3. The refractory castable as claimed in claim 1, wherein said White Tabular
Alumina (WTA) comprises of
Al2O3 (Min.), % 99
Fe2O3 (Max.), % 0.10
Na2O (Max), % 0.50
True sp. gravity (Min.) 3.80
4. The refractory castable as claimed in claim 1, wherein said Reactive Alumina
comprises of:-
Al2O3 (Min.), % 99.4
Fe2O3 (Max.), % 0.03
21
Na2O (Max), % 0.50
SiO2 (Max.), % 0.03
Specific Gravity (Min.) 3.60
Specific Surface Area, m2/gm 5 – 8
L.O.I. (RT – 11000C, Max.),
%
1
5. The refractory castable as claimed in claim 1, wherein said Cacined Alumina
comprises of:
Al2O3 (Min.), % 99.4
Fe2O3 (Max.), % 0.03
Na2O (Max), % 0.40
SiO2 (Max.), % 0.03
Specific Gravity (Min.) 3.90
Specific Surface Area, m2/gm 0.6 – 1.5
L.O.I. (RT – 11000C, Max.), % 0.30
6. The refractory castable as claimed in claim 1, wherein said graphite comprises
of:
Fixed Carbon (Min.), % 96
NGC (Max.), % 0.50
Volatile matter (Max), % 2.0
22
Moisture (Max.), % 0.50
Size Range
(+) 44 mesh BSS (Max.)
(-) 60mesh BSS (Min.)
(-) 72 mesh BSS (Min.)
(-) 100mesh BSS (Min.)
7.0
80
60
30
7. The refractory castable as claimed in claim 1, wherein said Crystalline Multi Wall
Carbon Nano Tube (MWCNT) is of specification:
Purity (Min.), % 97
Outer diameter, nm 10 – 40
Length (Max), µm 15
Ash (Max.), Wt. % 3.0
Specific Surface area, m2/gm 40 – 300
Colour Black
8. The refractory castable as claimed in claim 1, wherein said Sodium Hexa-Meta
Phosphate (SHMP) comprises of :
P2O5 (Min.), % 65
9. The refractory castable as claimed in claim 1, wherein said Fume Silica
comprises of:
23
SiO2 (Min.), % 98
Cfree (Max.), % 0.70
Al2O3 (Max.), % 0.30
Fe2O3 (Max.), % 0.10
Na2O (Max), % 0.20
K2O (Max.), % 0.30
Coarse Particles >45 µm (Max.), % 0.50
B.D., kg/m3 250 – 350
L.O.I. (Max.), % 0.80
10. The refractory castable as claimed in claim 1, wherein said Carboxymethyl
cellulose (CMC) is of specification :
Material Powder/ Fine fibers
Colour White/ slightly yellowish
HLB Ratio 8 – 10
11. A process for the production of Crystalline Multi Wall Carbon Nano Tube
(MWCNT) and modified graphite incorporated refractory castable comprising the
steps of
a) premixing (Wet) of all Multi Wall Carbon Nano Tube (MWCNT) and all
Carboxymethyl cellulose (CMC) with about 4-5 % water by using a stirrer for 3
to 5 minutes;
b) dry mixing of all the coarse and fine grains (0.002 mm to 3.5mm) taken
together in a mixture for 5 to 7 minutes;
c) addition of all premixed liquid obtained in step ‘A’ and about 1-2 % water by
weight to the dry mix;
d) wet mixing for 5 to 7 minutes to get the green mixture;
24
e) casting of green mixture using required moulds for different shapes; and
f) subjecting the green casted body as obtained to dry and then coke to obtain
there from the said Multi Wall Carbon Nano Tube (MWCNT) and modified
graphite incorporated refractory castable.
12. A process as claimed in claim 11further comprising the steps of:
(i) air drying the green casted body obtained from step (e) for 24-32 hours to
get initial strength and thereafter releasing the green casted body from
mould;
(ii) subjecting air dried green cast body followed by further drying in
oven/tunnel drier at 1100C for 24-32 hours; and
(iii) coking of dried cast body at 10000C for 2-3 hours maintaining desired to
obtain refractory castable with high corrosion resistance.
13. A process as claimed in anyone of claims 11 or 12 wherein said mixing/addition
sequence of raw material ingredients further comprising the steps of:
(i) premixing (Wet) of all Multi Wall Carbon Nano Tube (MWCNT) and all
Carboxymethyl cellulose (CMC) with about 4-5 % water by using a stirrer for 3 to
5 minutes;
(ii) dry mixing of all the coarse and fine grains (0.002 mm to 3.5mm) taken
together in a mixture for 5 to 7 minutes;
(iii) adding of all premixed liquid obtained in step ‘(i)’ and about 1-2 % water by
weight to the dry mix; and
(iv) wet mixing for 5 to 7 minutes to get the green mixture.
14. A process as claimed in anyone of claims 11 to 13 wherein said coking process
of dried cast body further comprising the steps of:
25
(i) placing of the coke bed embedded dried casted body in a stainless steel
air tight container;
(ii) preheating of coke embedded casted body at a rate of 5 to 70C per minute
from ambient temperature to 300-400 0C;
(iii) heating the coke embedded casted body at 10 to 120C per minute from
400 to 10000C; and
(iv) allowing soaking time for 2 to 3 hours at the highest temperature to obtain
casted body with required properties.
Dated: this 30th day of July, 2015. , Description:CRYSTALLINE MULTI WALL CARBON NANO TUBE (MWCNT) AND MODIFIED
GRAPHITE INCORPORATED REFRACTORY CASTABLE AND THE PROCESS FOR
THE PRODUCTION THEREOF
FIELD OF THE INVENTION
The present invention relates to crystalline Multi Wall Carbon Nano Tube (MWCNT) and
modified graphite incorporated refractory castable. More particularly, the present
invention is directed to provide a refractory castable by incorporating aqueous system
compatible modified graphite and crystalline MWCNT having high corrosion resistance
suitable for use in steel industry and process of production of said castable.
BACKGROUND OF THE INVENTION
Refractories are non-metallic inorganic materials, they have high softening temperature.
They also possess good mechanical properties particularly at high temperatures and
most often at room temperature as well, good stability on rapid temperature change etc.
The materials also have good corrosion and erosion resistance to molten slag, metals
and hot gases. Refractories show good mechanical properties at high temperature and
as well as at low temperature. They have better corrosion and erosion resistance to
molten slag, metals and hot gases. Due to good thermo-mechanical and thermochemical
properties refractory materials are used in various high temperature
processes, including iron and steel making, non-ferrous metal processing, cement,
glass, chemical industries, in high temperature furnaces, kilns, boilers and incinerators.
The advantages of monolithic refractories in respect of ease of installation and thermomechanical
behaviour have made the replacement of conventional brick by refractory
castables - a natural process in refractory applications. In recent years refractory
castables have made considerable inroads into different areas of Iron & Steel making.
However, in spite of many advantages of castables, the major weak points which
restricted their wide application are excessive wear and penetration by slag leading to
structural spalling.
The incorporation of carbon materials especially graphite is known to significantly
enhance both corrosion and thermal shock resistance of refractories. For mixing and
placement of refractory castables, water is the most suitable liquid media due to its
3
availability, cost, non-hazardous characteristic and ease of handling. The main factors
limiting the development and use of carbon containing castables are the inferior
wettability of graphite by water and the hydration of metallic powders (e.g. alumina,
silicon etc.) commonly used to inhibit oxidation of carbon at high temperature (> 900oC).
Many of the scientific and technological developments would not have been possible
without refractory materials. Manufacturing of any metal without the use of refractory is
impossible. Refractories consumption in steel and iron industries is nearly 70% of total
refractories production. Iron and steel industries are the highest consumers of
refractories. So, the refractory production has to be in sync with the demand of iron and
steel industries. Better manufacturing and application environment is challenging a new
generation of refractory material with improved properties, performance and life with
eco-friendliness.
In the prior art, a Chinese specification CN 104311054 discloses a composite refractory
castable, includes the following components are made of by weight: 10 to 15 parts of
corundum, mullite 10 to 15 parts, silicon carbide, 10 to 15 parts, 5 to 10 parts of silica
fume, magnesia 15-20 copies of 10 to 15 parts of graphite, alumina powder 10 to 15
parts, 2 to 10 parts phenolic resin, 3 to 10 parts of carbon nano tubes; magnesite,
graphite, corundum, mullite, silicon carbide mixed with granulated powder, alumina
powder, silica fume, carbon nano tubes, a phenol resin as additives, wherein the fine
powder particles and parts by weight: 50 to 55 parts by particles, 45 to 50 parts of fine
powder, particle size in the range of 1.2 ~ 1.6mm, fine particle diameter of 0.4 ~ 0.8mm.
In another prior art, another Chinese specification CN 104311064 A discloses a
continuous casting machine tundish castable, by including the following components
made by weight: 30 to 35 parts of magnesia, graphite 20 to 25 parts, 20 to 25 parts of
alumina powder, silica 5 to 10 parts, 5 to 10 parts of phenolic resin, 5 to 10 parts of
carbon nano tubes; magnesia, graphite mixed with the granulated powder, alumina
powder, silica, carbon nano tubes, a phenol resin as additives, wherein the particles
parts by weight of fine powder: 55 to 60 parts by particles, 40 to 45 parts of fine powder,
particle size in the range of 1.0 ~ 1.5mm, fine particle diameter of 0.2 ~ 0.6mm.
RDCIS has been working on building up of knowledge base for development and
application of new generation castables for Iron and Steel industries. A comprehensive
4
laboratory based study was done on how to make graphite compatible to the aqueous
system, which would help in the development of modified graphite and crystalline
MWCNT containing castables, with the potential of improving lining life under severe
corrosive environment.
OBJECTS OF THE INVENTION
The basic object of the present invention is directed to provide a crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated
refractory castable having high corrosion resistance suitable for use in steel industry
and a process for its production.
Another objective of the present invention is directed to incorporation of aqueous
system compatible modified graphite and MWCNT in refractory castable.
SUMMARY OF THE INVENTION
Nano scale silicon particles have many current and potential commercial uses1,
including electronics, sensors, high-hardness chemoabrasives3, optoelectronics4,
optomagnetic switches5, electronic storage6, silicon ink7, photoelectric solar cells8,
high power density batteries9, thermoelectrics10, light emitters11, seed crystals, and
catalysts12. There are a wide variety of (generally expensive) ways to prepare silicon
nanoparticles13. But such production methods typically have cost, shape, and/or
product characteristic drawbacks. Accordingly, there is a need for inexpensive bulk
manufacturing methods capable of producing nano silicon powders with a broad range
of product characteristics and uses.
There is also a need for energetic nano powders, compositions and composites which
are designed for specific uses with various characteristics including composition,
structure size, shape, phase structure (eg, amorphous, multicrystalline or
monocrystalline condition), reactant structure, surface/layer composition(s), grafting,
purity, doping, and compatibility within composite compositions. Flake like
noncontinuous fluorocarbon coatings have been applied to relatively large silica
particles by expensive plasma-enhanced chemical vapour deposition (PECVD) with a
goal of being able to coat alumina particles14. In attempts to limit progressive alumina
nano particle surface oxidation, coatings have also been applied to alumina by
5
perfluoroalkyl carboxylate reaction with surface Al—OH groups, leaving an intermediate
oxygenated layer, and nickel coatings have been attempted to address the oxidative
storage-instability of alumina nano particles. AlB2 (perhaps as a coating on) alumina
nano particles formed by expensive electrical resistance explosion of alumina/boron has
been tested to protect against alumina surface oxidation15. However, nano silicon
powders are inherently more storage-stable than alumina nano particles. Accordingly, to
realize and facilitate practical storage-stable and affordable propellant and explosives
applications, new scalable methods and composition designs which facilitate storage
stability and minimize oxide surface layer formation and oxidative aging are important
for manufacture of inexpensive high energy nano silicon powders which do not
substantially degrade over time.
The basic aspect of the present invention is directed to provide crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory castable
suitable for use in steel industry, comprising:
White Fused Alumina (WFA) (Coarse) having particle size ranging from 2mm to
3.5 mm and about 15-17 % by weight,
White Fused Alumina (WFA) (Coarse)having particle size ranging from 1 mm
to2.5mm and about 6-8 % by weight,
White Fused Alumina (WFA) (Coarse) having particle size ranging from0.5 mm to
1 mm and about 15-17 % by weight,
White Fused Alumina (WFA) (Coarse) having particle size ranging from 0.5 mm
to 0.25 mm and about 7-9 % by weight,
White Fused Alumina (Fines) having particle size below 0.1 mm and about 15-19
% by weight,
White Tabular Alumina (Fines) having particle size below 0.044 mm and about 9-
11 % by weight,
Calcined Alumina (Fines) having particle size below 0.044 mm and about 4-6 %
by weight,
6
Reactive Alumina (Fines) having Specific size below 0.002mm and about 9-11 %
by weight,
Fume Silica (Fines) having particle size below 0.044 mm and about 4-6 % by
weight,
Graphite having (Fines) having particle size below 0.5 mm and about 4-6 % by
weight,
Hexa-Meta Phosphate (SHMP) of LR/GR grade and about 0.04-0.06 % by
weight, and
Carboxymethyl cellulose (CMC) of HLB ratio 8-10 and about 0.10-0.14 % by
weight.
A further aspect of the present invention is directed to said crystalline Multi Wall Carbon
Nano Tube (MWCNT) and modified graphite incorporated refractory castable wherein
said White Fused Alumina (WFA) comprises:
Al2O3 (Min.), % 99.3
Fe2O3 (Max.), % 0.13
B.D. (Min.), gm/cc 3.55
A.P. (Max.), % 5
A still further aspect of the present invention is directed to said crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory castable
wherein said White Tabular Alumina (WTA) comprises
Al2O3 (Min.), % 99
Fe2O3 (Max.), % 0.10
Na2O (Max), % 0.50
True sp. gravity (Min.) 3.80
7
A still further aspect of the present invention is directed to said crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory castable
wherein said Reactive Alumina comprises
Al2O3 (Min.), % 99.4
Fe2O3 (Max.), % 0.03
Na2O (Max), % 0.50
SiO2 (Max.), % 0.03
Specific Gravity (Min.) 3.60
Specific Surface Area, m2/gm 5 – 8
L.O.I. (RT – 11000C, Max.),
%
1
Yet another aspect of the present invention is directed to said crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory castable
wherein said Calcined Alumina comprises
Al2O3 (Min.), % 99.4
Fe2O3 (Max.), % 0.03
Na2O (Max), % 0.40
SiO2 (Max.), % 0.03
Specific Gravity (Min.) 3.90
Specific Surface Area, m2/gm 0.6 – 1.5
L.O.I. (RT – 11000C, Max.), % 0.30
8
A further aspect of the present invention is directed to said crystalline Multi Wall Carbon
Nano Tube (MWCNT) and modified graphite incorporated refractory castable wherein
said Graphite comprises
Fixed Carbon (Min.), % 96
NGC (Max.), % 0.50
Volatile matter (Max), % 2.0
Moisture (Max.), % 0.50
Size Range
(+) 44 mesh BSS (Max.)
(-) 60mesh BSS (Min.)
(-) 72 mesh BSS (Min.)
(-) 100mesh BSS (Min.)
7.0
80
60
30
A still further aspect of the present invention is directed to said crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory castable
wherein said Crystalline Multi Wall Carbon Nano Tube (MWCNT) comprising
Purity (Min.), % 97
Outer diameter, nm 10 – 40
Length (Max), µm 15
Ash (Max.), Wt. % 3.0
Specific Surface area, m2/gm 40 – 300
Colour Black
A still further aspect of the present invention is directed to said crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory castable
wherein said Sodium Hexa-Meta Phosphate (SHMP) comprising
9
P2O5 (Min.), % 65
Yet another aspect of the present invention is directed to said crystalline Multi Wall
Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory castable
wherein said Fume Silica comprising
SiO2 (Min.), % 98
Cfree (Max.), % 0.70
Al2O3 (Max.), % 0.30
Fe2O3 (Max.), % 0.10
Na2O (Max), % 0.20
K2O (Max.), % 0.30
Coarse Particles >45 µm (Max.), % 0.50
B.D., kg/m3 250 – 350
L.O.I. (Max.), % 0.80
A further aspect of the present invention is directed to said crystalline Multi Wall Carbon
Nano Tube (MWCNT) and modified graphite incorporated refractory castable wherein
said Carboxymethyl cellulose (CMC) comprises
Material Powder/ Fine fibers
Colour White/ slightly yellowish
HLB Ratio 8 – 10
A further aspect of the present invention is directed to a process for the production Multi
Wall Carbon Nano Tube (MWCNT) and modified graphite incorporated refractory
castable as described above, comprising the steps of:
A. Premixing (Wet) of all Multi Wall Carbon Nano Tube (MWCNT) and all
Carboxymethyl cellulose (CMC) with about 4-5 % water by using a stirrer for 3
to 5 minutes.
10
B. Dry mixing of all the coarse and fine grains (0.002mm to 3.5mm) taken
together in a mixture for 5 to 7minutes.
C. Addition of all premixed liquid obtained in step ‘A’ and about 1-2 % water
by weight to the dry mix.
D. Thereafter wet mixing for 5 to 7 minutes to get the green mixture.
E. Casting of green mixture immediately using required moulds for different
shapes; and
F. subjecting the green casted body thus obtained to dry and then coke such
as to thereby obtains there from the said Multi Wall Carbon Nano Tube
(MWCNT) and modified graphite incorporated refractory castable.
A still further aspect of the present invention is directed to said process comprising the
steps of
(i) Air drying the green casted body obtained in step (E) for 24-32 hours to
get initial strength and thereafter releasing the green casted body from
mould;
(ii) subjecting air dried green cast body followed by further drying in
oven/tunnel drier at 1100C for 24-32 hours;
(iii) Coking of dried cast body at 10000C for 2-3 hours maintaining desired to
obtain refractory castable with high corrosion resistance.
Yet another aspect of the present invention is directed to said process wherein said
mixing/addition sequence of raw material ingredients comprising:
(i) Premixing (Wet) of all Multi Wall Carbon Nano Tube (MWCNT) and all
Carboxymethyl cellulose (CMC) with about 4-5 % water by using a stirrer for 3 to
5 minutes.
(ii) Dry mixing of all the coarse and fine grains (0.002 mm to 3.5mm) taken
together in a mixture for 5 to 7 minutes.
11
(iii) Addition of all premixed liquid obtained in step ‘(i)’ and about 1-2 % water by
weight to the dry mix.
(iv) There after wet mixing for 5 to 7 minutes to get the green mixture.
A still further aspect of the present invention is directed to said process wherein
said coking process of dried cast body comprises
(i) In a stainless steel air tight container, coke bed embedded dried casted
body is placed.
(ii) Preheating of coke embedded casted body at a rate of 5 to 70C perminute
from ambient temperature to 300-4000C.
(iii) Heating up of coke embedded casted body at 10 to 120C per minute from
400 to 10000C.
(iv) Allowing soaking time for 2 to 3 hours at the highest temperature to obtain
casted body with required properties.
The objectives and advantages of the present invention are described hereunder in
greater details with reference to the following accompanying illustrative example.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to provide crystalline Multi Wall Carbon Nano Tube
(MWCNT) and modified graphite incorporated refractory castable with high corrosion
resistance suitable for use in steel industry and in particular related to process of
manufacturing such crystalline Multi Wall Carbon Nano Tube (MWCNT) and modified
graphite incorporated refractory castable and development of its formulation. The batch
composition of the crystalline Multi Wall Carbon Nano Tube (MWCNT) and modified
graphite incorporated refractory castable and its method of production is illustrated with
following example:
12
Example 1:
Use of Multi-Walled Carbon nano tubes (MWCNTs) and Ultrafine Micro Crystalline
Graphite (UMCG) Powders:
Another study reported that microstructures and mechanical properties of Al2O3-C
refractories with Al, Si and SiO2 as the additives fired in the temperature range from 800
to 1400 °C wherein vestigated ,when multi-walled carbon nano tubes (MWCNT) were
used as the carbon source to partially or totally replace graphite flake in the materials.
The results showed that specimens with only graphite flake, specimens containing 0.05
wt. % MWCNTs possessed better mechanical properties at further increased of
MWCNTs amount from 0.1 to 1 wt. % properties deteriorated.
The Cold modulus of rupture (CMOR) and flexural modulus (E) values are 23.70 MPa
for CMOR and 3733.36 for E, secondly 14.11 MPa for CMOR and 2540.91 for E were
reported at 1200 °C for 0.05% and 0% MWCNTs. [66] A recent study addition of
ultrafine micro crystalline graphite (UMCG) powders in Al2O3–C refractory showed that
microstructure and mechanical properties were improved with the addition of UMCG in
comparison to the graphite.
In manufacturing of improved crystalline Multi Wall Carbon Nano Tube (MWCNT) and
modified graphite incorporated refractory castable according to the present invention, A
base composition of crystalline Multi Wall Carbon Nano Tube (MWCNT) and modified
graphite incorporated refractory Castable is developed. Modification of graphite is done
by extrusion method. Graphite and calcined alumina in an optimum ratio is mixed with
distilled water to make a extrudable paste. Then this paste istaken inside the cylindrical
part and extruded through the required head in thread form by putting pressure with
rotating top pressure handle. Extruded threads are kept for air drying for 24 hrs. and
then kept in dryer at 1100C for 8 hours. Properly dried extruded threads are then ground
to desired fineness to use in castable. A pre-mix was prepared for each composition
containing Multi Wall Carbon Nano Tube (MWCNT), Carboxymethyl cellulose (CMC)
and 4-5% of water. All the raw materials are taken in appropriate proportions and dry
mix it in a mixer. Then all pre-mix and 1-2 % water is added to the dry mix. After
sufficient mixing for consistency, castable is taken out and put in mould on a vibrating
table for casting. After casting, samples are left to dry in open air for about 24-32 hours.
13
After drying in open air samples are de-moulded and kept in oven/tunnel dryer for drying
at 1100C for 24-32 hours. All the samples are coked at 10000C for 2 to 3 hrs.
Considering the composition and granulometry of the developed formulation of the
crystalline Multi Wall Carbon Nano Tube (MWCNT) and modified graphite incorporated
refractory castable, following coking process is followed:
(i) In a stainless steel air tight container, coke bed embedded dried casted
body is placed.
(ii) Preheating of coke embedded casted body at a rate of 5 to 70C per minute
from ambient temperature to 300-400 0C.
(iii) Heating up of coke embedded casted body at 10 to 120C per minute from
400 to 10000C.
(iv) Allowing soaking time for 2 to 3 hours at the highest temperature to obtain
casted body with required properties.
The starting batch composition for producing such bricks is given in Annexure-I:
Annexure I: Batch Composition of crystalline Multi Wall Carbon Nano Tube
(MWCNT) and modified graphite incorporated refractory castable
Raw Material % (By Weight)
WFA (Coarse + Middle) 46 – 50
WFA (Fines) 15 – 19
WTA (Fines) 9 – 11
Reactive Alumina 9 – 11
Calcined Alumina 4 – 6
Fume Silica 4 – 6
14
Graphite 4 – 6
crystalline Multi Wall Carbon Nano
Tube (MWCNT)
0.1 – 0.5
SHMP 0.04 – 0.06
Surfactant 0.10 – 0.14
Details of different components of raw materials in a batch have been given in following
Annexure II.
Annexure II: Details of different Raw Materials, Additives and Binder
White Fused Alumina (WFA)
Al2O3 (Min.), % 99.3
Fe2O3 (Max.), % 0.13
B.D. (Min.), gm/cc 3.55
A.P. (Max.), % 5
White Tabular Alumina (WTA)
Al2O3 (Min.), % 99
Fe2O3 (Max.), % 0.10
Na2O (Max), % 0.50
True sp. gravity (Min.) 3.80
Reactive Alumina
15
Al2O3 (Min.), % 99.4
Fe2O3 (Max.), % 0.03
Na2O (Max), % 0.50
SiO2 (Max.), % 0.03
Specific Gravity (Min.) 3.60
Specific Surface Area, m2/gm 5 – 8
L.O.I. (RT – 11000C, Max.),
%
1
Calcined Alumina
Al2O3 (Min.), % 99.4
Fe2O3 (Max.), % 0.03
Na2O (Max), % 0.40
SiO2 (Max.), % 0.03
Specific Gravity (Min.) 3.90
Specific Surface Area, m2/gm 0.6 – 1.5
L.O.I. (RT – 11000C, Max.), % 0.30
Graphite
Fixed Carbon (Min.), % 96
NGC (Max.), % 0.50
Volatile matter (Max), % 2.0
16
Moisture (Max.), % 0.50
Size Range
(+) 44 mesh BSS (Max.)
(-) 60mesh BSS (Min.)
(-) 72 mesh BSS (Min.)
(-) 100mesh BSS (Min.)
7.0
80
60
30
Crystalline Multi Wall Carbon Nano Tube (MWCNT)
Purity (Min.), % 97
Outer diameter, nm 10 – 40
Length (Max), µm 15
Ash (Max.), Wt. % 3.0
Specific Surface area, m2/gm 40 – 300
Colour Black
Sodium Hexa-Meta Phosphate (SHMP)
P2O5 (Min.), % 65
Fume Silica
SiO2 (Min.), % 98
Cfree (Max.), % 0.70
Al2O3 (Max.), % 0.30
Fe2O3 (Max.), % 0.10
Na2O (Max), % 0.20
K2O (Max.), % 0.30
Coarse Particles >45 µm (Max.), % 0.50
17
B.D., kg/m3 250 – 350
L.O.I. (Max.), % 0.80
Carboxymethyl cellulose (CMC)
Material Powder/ Fine fibers
Colour White/ slightly yellowish
HLB Ratio 8 – 10
Further aspect of the present invention is that the above components are added and
mixed in the order as indicated in Annexure III. The Properties of developed brick are
given in Annexure IV.
Annexure III: Mixing sequence of ingredients
1. Premixing (Wet) of all Multi Wall Carbon Nano Tube (MWCNT) and all
Carboxymethyl cellulose (CMC) with about 4-5 % water by using a stirrer for 3 to 5
minutes.
2. Dry mixing of all the coarse and fine grains (0.002 mm to 3.5mm) taken together in a
mixture for 5 to 7 minutes.
3. Addition of all premixed liquid obtained in step ‘(i)’ and about 1-2 % water by weight
to the dry mix.
4. Thereafter wet mixing for 5 to 7 minutes to get the green mixture.
Annexure IV:
Properties of Developed crystalline Multi Wall Carbon Nano Tube (MWCNT) and
modified graphite incorporated refractory castable
Properties Value
Al2O3 (%),Min. 85
Fe2O3 (%),Max. 0.2
Bulk Density (B.D.) (gm/cc),Min. (IS–1528, Part–XII)
18
After heating at 1100C for 24 – 32 hours 2.95
After reheating at 10000C for 2 – 3 hours at
reducing atmosphere (Coked)
2.80
Apparent Porosity (A.P.) (%), Max. (IS–1528, Part–VIII)
After heating at 1100C for 24 – 32 hours 20
After reheating at 10000C for 2 – 3 hours at
reducing atmosphere (Coked)
22
Cold Compressive Strength (C.C.S.) (kg/cm2), Min. (IS–1528, Part–IV)
After heating at 1100C for 24 – 32 hours 550
After reheating at 10000C for 2 – 3 hours at
reducing atmosphere (Coked)
400
Although the foregoing description of the present invention has been shown and
described with reference to particular embodiments and applications thereof, it has
been presented for purposes of illustration and description and is not intended to be
exhaustive or to limit the invention to the particular embodiments and applications
disclosed. It will be apparent to those having ordinary skill in the art that a number of
changes, modifications, variations, or alterations to the invention as described herein
may be made, none of which depart from the spirit or scope of the present invention.
The particular embodiments and applications were chosen and described to provide the
best illustration of the principles of the invention and its practical application to thereby
enable one of ordinary skill in the art to utilize the invention in various embodiments and
with various modifications as are suited to the particular use contemplated. All such
changes, modifications, variations, and alterations should therefore be seen as being
within the scope of the present invention as determined by the appended claims when
interpreted in accordance with the breadth to which they are fairly, legally, and equitably
entitled.
19