Claims:WE CLAIM:

1. High Alumina based plastic refractory composition comprising in wt. % of total refractory mass Calcined Alumina (fines) 10-15%, Kyanite (fines) 8-12%, Fused Mullite (Fines) 27-33%, Fused Mullite (Fines to Medium) 8-12%, Bauxite (course) 5-9% and Liquid Binder 13-16%.
.
2. Plastic refractory composition as claimed in claim 1, which is high Alumina based refractory monolithic composition comprising Calcined Alumina(Fines) having particle size up to 0.1 mm, Raw Kyanite Powder (Fines) having particle size up to 0.1 mm, Fused Mullite (Fines to Medium) having particle size up to 0.1 mm, Fused Mullite (Medium) having particle size ranging from 1 mm to 3 mm, Bauxite (Course) having particle size ranging from 3 mm to 5 mm and a Binder system (Liquid) having a pH of 2.71 at 25deg C.

3. Plastic refractory composition as claimed in claims 1and 2, wherein Fused Mullite comprises Al2O3 (min.) 72.96% by wt., Fe2O3 (max.) 0.32% by wt. and SiO2 (max.) 25.7% by wt.

4. Plastic refractory composition as claimed in any of claims 1-3, wherein Calcined Alumina powder comprises Al2O3 (min.) 99.4% by wt., Fe2O3 (max.) 0.03% by wt., Na2O (max.) 0.50% by wt. and having particle size of 5 micron (D50).

5. Plastic refractory composition as claimed in any of the claims 1-4, wherein Raw Kyanite comprises Al2O3 (min.) 37% by wt., Fe2O3 (max.) 1.80% by wt. and PLC 1450 deg C/2 Hrs.(min.) 4% by wt.

6. Plastic refractory composition as claimed in any of the claims 1-5, wherein Bauxite comprising Al2O3 (min.) 87% by wt., Fe2O3 (max.) 2.5% by wt. and TiO2 (max.) 4% by wt.
7. Plastic refractory composition as claimed in any of the claims 1-6, wherein said Liquid Binder comprising Ortho Phosphoric Acid 87-92% by wt., Colloidal Silica 3-7% by wt., carboxymethyl cellulose 0.05-0.1% by wt. and SHMP 0.01-0.05% by wt.

8. A process for the synthesis of the Liquid Binder as claimed in claim 7, comprising the steps of:
i) Heating the organic gelling agent, deflocculating agent & silica sol with water (50%) up to 80degC. for proper mixing,
ii) Subjecting the above liquid to mixing with a liquid source of P2O5, and
iii) Allowing the composition as the binder to be stored in open condition.

9. A process for the production of plastic refractory composition as claimed in anyone of claims 1 to 7, comprising the steps of:
a. synthesizing the liquid binder
b. dry mixing of all the grains (upto 5mm) taken together in a Hobbert mixture for 5 to 7 minutes.
c. addition of 50% (by weight) premixed liquid binder obtained in step ‘A’ to the dry mix.
d. there after wet mixing for 5 to 7 minutes.
e. addition of the rest 50% of the premixed liquid binder obtained in step ‘A’ to the resultant mix and then final mixing for 5 to 7 minutes to get the final mixture.
f. storing the plastic mass as the desired composition in air-tight plastic container.

10. Plastic refractory composition as claimed in any of the claims 1-7, wherein granulometry of plastic refractory comprising Calcined Alumina (13% by wt) up to 0.1 mm, Kyanite (10% by wt.) up to 0.1 mm, Mullite (30% by wt.) up to 0.1mm, Mullite (10% by wt.) 0.1-1 mm, Mullite (30% by wt.) 1-2 mm, and Bauxite (7% by wt.) 3-5 mm.
11. Plastic refractory composition as claimed in any of the claims 1-7 & 10, wherein workability testing of plastic refractory comprising:
• 300 gms. of plastic mass has been taken out from air tight container.
• Preparing cylinder of 50 mm * 50 mm by 10 strokes in each side in sand rammer
• Measuring the initial height of the cylinder
• The cylinder was subjected to 5 strokes & final height has been measured.
• The percentage difference in the initial & final height without cracks in the sample is the workability Index.
• Every week the workability Index has been captured for more than 16 weeks.

12. Plastic refractory composition as claimed in any of the claims 1-7 & 10, wherein physical & chemical properties of plastic refractory are as follow:
Properties at different temperature
BD (gm/cc) 850°C, 2 hrs 2.3
1250°C, 2 hrs 2.34
1550°C, 2 hrs 2.14
CCS (kg/cm2) 850°C, 2 hrs 325.96
1250°C, 2 hrs 351.74
1550°C, 2 hrs 345.76
MOR (kg/cm2) 850°C, 2 hrs 99.2
1250°C, 2 hrs 107.02
1550°C, 2 hrs 98.3
PLC (%) 850°C, 2 hrs 0.29
1250°C, 2 hrs 0.46
1550°C, 2 hrs 2.2

Chemical analysis:
Elements %
Al2O3 65.0
SiO2 22.0
Fe2O3 0.6
TiO2 0.5
CaO 0.1
Alkalies 0.3
P2O5 11.2

Dated: this 29th day of August, 2016


(N. K. Gupta)
Patent Agent,
Of NICHE,
For SAIL

To,
The Controller of Patents,
The Patent Office, Kolkata.
, Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(Section 10 and rule 13)

TITLE

HIGH ALUMINA BASED REFRACTORY COMPOSITION AND A PROCESS FOR ITS MANUFATURE

APPLICANT
STEEL AUTHORITY OF INDIA LIMITED,
A GOVT. OF INDIA ENTERPRISE,
RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL,
DORANDA, RANCHI-834002, STATE OF JHARKHAND

The following specification particularly describes the nature of the
invention and the manner in which it is to be performed

HIGH ALUMINA BASED REFRACTORY COMPOSITION AND A PROCESS FOR ITS MANUFATURE

FIELD OF THE INVENTION
The present invention relates to Plastic refractory for reheating furnace & its process for manufacture. More particularly, the present invention is directed to provide a plastic refractory for the roof of reheating furnace having high strength, good thermo-mechanical stability & workability by incorporating special binder system and raw material in composition & maintaining the granulometry. It also provides a method of manufacturing of said Plastic Refractory.

BACKGROUND OF THE INVENTION
Reheating furnaces are used for heating the steel ingots, slabs or bar to an even temperature throughout their body so that they can be properly rolled or pressed into strip, plate, rod, angle or any other shape as required. In large steel plants, pusher or walking beam type furnaces are used. The operating temperature is generally reaches up to 1250°C, depending upon the quality of the steel, size of the product, etc.
In earlier days reheating furnaces are lined with High Alumina bricks. Various shaped refractory compositions have been employed previously for the same purpose. However, such products are not well suited for use as lining because of their high density & difficulty in lining. Moreover, the use of brick and other preformed refractory materials is limited to relatively simple shapes and to applications which can accommodate the shape of the brick. Although there are available refractory castables which can be cast in place, these materials normally demand high curing & drying time, have high density, high thermal conductivity which make their use undesirable. In an effort to enhance the moldability plastic material have been developed. The composition should maintain its adhesion during
drying and should set up to a relatively crack-free refractory mass which will retain its strength and adherence during subsequent heating operation up to the 1300° C. Range.
To avoid complicacy in lining various monolithic refractories such as Plastic refractory came in to the light. Monolithic refractory materials have widely superseded conventional brick shaped refractory materials which must be in a variety of shapes and require much labor and time for lining. Lining operations for monolithic refractory materials are carried out by various techniques such as spraying, casting, stamping or vibration forming. Vibration forming is accepted as the best lining method because it easily provides the final desired shape, and the molded structure has a uniform texture without the occurrence of lamination.
Due to the operating flexibility of reheating furnace, the requirements for refractory are a) high thermal shock resistance, b) user friendly installation, c) good lining performance & d) overall energy cost savings. Plastic refractory is gaining more and more preference for lining of roof of reheating furnaces due to high thermal shock resistance, lesser weight and monolithic construction.
Like other Steel plants in India and abroad, SAIL has also started using plastic refractory in reheating furnaces. In modernization, the new reheating furnaces are installed by the technology provider & materials are imported by them. During repair & maintenance job procurement of refractory from foreign suppliers becomes very critical due to their high lead time. Moreover, due to lower shelf life of plastic material it cannot be stored for a very long time and this poses problem for the unplanned shut downs in plants.
In view of above, RDCIS has been working for development and application of Plastic refractory for Reheating Furnace of Iron and Steel industries. A comprehensive laboratory based study was done for development of Plastic Refractory with the potential of improving lining life of Furnace.
OBJECTS OF THE INVENTION
The basic object of the present invention is directed to manufacture in-house Plastic refractory composition with incorporation of fused high Alumina bearing raw material ensuring high strength and better thermo-mechanical behaviour to make them suitable for use in steel industry and a process for its production.
Another objective of the present invention is directed to incorporation of proper granulometry for better theology & thermal shock resistance.
Another objective of the present invention is directed to synthesis of a binder system for better workability & high strength at high temperature.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to provide Al2O3-SiO2 based plastic refractory composition comprising Calcined Alumina (Fines) 10-15 wt. %, Kyanite (Fines) 8-12 wt. %, Fused Mullite (Fines) 27-33 wt. %, Fused Mullite (Fines to Medium) 8-12 wt.%, Fused Mullite (Medium) 27-33 wt. %,Bauxite (Course) 5-9 wt. % and Liquid Binder 13-16 wt. %.
A further aspect of the invention is directed to provide Al2O3-SiO2 based monolithic refractory composition which is plastic refractory composition particularly comprising:
Calcined Alumina (Fines) having particle size up to 0.1 mm,
Raw Kyanite Powder (Fines) having particle size up to 0.1 mm,
Fused Mullite (Fines) having particle size ranging from 0 mm to 0.1 mm,
Fused Mullite (Fines to Medium) having particle size ranging from 0.1 mm to 1 mm,
Fused Mullite (Medium) having particle size ranging from 1 mm to 3 mm,
Bauxite (Coarse) having particle size ranging from 3 mm to 5 mm,
A Binder system (Liquid) having pH of 2.71 at 250C.
A still further aspect of the present invention is directed to provide plastic refractory composition wherein said Fused Mullite comprises: Al2O3 (min.) 72.96 wt. %, Fe2O3 (max) 0.32 wt. % and SiO2 (max) 25.7 wt. %.
A still further aspect of the present invention is directed to provide plastic refractory composition wherein said Calcined Alumina comprises: Al2O3 (min.) 99.4 wt. %, Fe2O3 (max.) 0.03 wt %, Na2O (max.) 0.50 wt. % and (D 50) 5 micron size.
A still further aspect of the present invention is directed to provide plastic refractory composition wherein said Raw Kyanite Powder comprises: Al2O3 (min.) 37 wt. %, Fe2O3 (max.) 1.80 wt. % and PLC 1450oC/2 hrs (min.) 4 wt. %.
Another aspect of the present invention is directed to provide Plastic refractory composition wherein said Calcined Bauxite comprising :Al2O3 (Min.) 87wt.%,Fe2O3 (Max.) 2.5wt.%, TiO2 (Max.) 4wt.%, and SiO2 (Max.) 6 wt. %.
Yet another aspect of the present invention is directed to provide Plastic refractory composition wherein said Binder comprising :Ortho-Phosphoric Acid 87-92 wt. %, Colloidal Silica 3-7 wt. %, Water 3-7 wt. %, Carboxy Methyl Cellulose 0.05-0.10 wt. % and SHMP 0.01-0.05 wt. %.
A further aspect of the present invention is directed to a process for the synthesis of said liquid binder composition as described above comprising the steps of:

• Synthesizing a liquid binder mix incorporating a source of P2O5, a thixotropic agent (SiO2 Sol), an organic gelling agent & a deflocculating agent selectively in the composition containing

Component Wt. %
Ortho-Phosphoric Acid 87-92
Colloidal Silica 3-7
Water 3-7
Carboxy Methyl Cellulose 0.05-0.1
SHMP 0.01-0.05

• Heating the water (50%) up to 80°C for proper mixing of the organic gelling agent, deflocculating agent & silica sol with it.

• Subjecting the above liquid to mixing with liquid source of P2O5 .

• Allowing the composition as the binder to be stored in open condition for checking its stability in the gel form.

Another aspect of the present invention is directed to said process for the production of Plastic refractory comprising the steps of:
A. Synthesizing a liquid binder
B. Dry mixing of all the grains (0mm to 5mm) taken together in a Hobbert mixture for 5 to 7 minutes.
C. Addition of 7% (by weight) premixed liquid binder obtained in step ‘A’ to the dry mix.
D. There after wet mixing for 5 to 7 minutes.
E. Addition of rest 50% of the premixed liquid obtained in step ‘A’ to the resultant mix and then final mixing for 5 to 7 minutes to get the final mixture.
F. Storing the plastic mass in air-tight plastic container for further evaluation.
G. Ramming of green mix thus obtained by using sand rammer for different cylinders of 50 mm height & 50 mm dia.; and 150 mm × 25 mm × 25 mm Bar samples are also prepared.
H. Subjecting the green samples thus obtained to dry at 150°C in heating oven & fired at different temperatures to evaluate the physical properties.
A further aspect of the present invention is directed to said process wherein granulometry of said raw material ingredients comprising

Calcined Alumina (13%, by wt.) 0-0.1 mm
Kyanite (10%, by wt.) 0-0.1 mm
Mullite (30%, by wt.) 0-0.1 mm
Mullite (10%, by wt.) 0.1-1 mm
Mullite (30%, by wt.) 1-2 mm
Bauxite (7%, by wt.) 3-5 mm

Another aspect of the present invention is directed to said process for the measuring the workability of Plastic refractory comprising the steps of:
• 300 gms. of plastic mass has been taken out from air tight container.
• Preparing cylinder of 50 mm * 50 mm by 10 strokes in each side in sand rammer
• Measuring the initial height of the cylinder
• The cylinder was subjected to 5 strokes & final height has been measured.
• The percentage difference in the initial & final height without cracks in the sample is the workability Index.
• Every week the workability Index has been captured for more than 16 weeks.

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 Plastic refractory with high strength, good thermo-mechanical behaviour & good workability suitable for use in the reheating furnace of steel industry and in particular related to process of manufacturing such Plastic refractory and development of its formulation. The batch composition of the plastic refractory and its method of production is illustrated with following example:
Example:
In manufacturing of plastic refractory with fused high Alumina bearing raw material according to the present invention, a base composition of fused high alumina bearing raw material incorporated plastic refractory is developed. A liquid binder was prepared containing liquid ortho phosphoric Acid, liquid colloidal silica in 9:1 (by wt.) ratio by mixing it with a mixture of hot & cold water, a gelling agent (CMC) & a deflocculating agent (SHMP). All the grains (0 mm to 5 mm) are taken in appropriate proportions and dry mix it in a mixer for 5 to 7 minutes. Then additions of 50% (by weight) premixed liquid binder to the dry mix and mix it for another 5 to 7 minutes. Again, addition of rest 50% of the premixed liquid to the resultant mix and then final mixing for 5 to 7 minutes. After sufficient mixing, mix taken out and keep in air tight plastic container for more than 16 weeks. Then ramming of plastic mass by sand rammer to get the cylinders of 50mm *50 mm & hand ramming to get the bar sample of 25 mm *25 mm *150mm for testing of properties. All green pressed bodies are Oven dried at 1500C for 24 hours & fired at different temperatures to evaluate the properties. Considering the workability test of plastic refractory, following process is followed in every week for more than 16 weeks:
• 300 gms. of plastic mass has been taken out from air tight container.
• Preparing cylinder of 50 mm * 50 mm by 10 strokes in each side in sand rammer
• Measuring the initial height of the cylinder
• The cylinder was subjected to 5 strokes & final height has been measured.
• The percentage difference in the initial & final height without cracks in the sample
is the workability Index.
• Every week the workability Index has been captured for more than 16 weeks.

Batch Composition of invented fused high Alumina based raw material incorporated plastic refractory brick for use in the reheating furnace of steel industry
The present invention is directed to provide fused high alumina based raw material incorporated plastic refractory with higher strength, good thermo-mechanical behaviour & good workability for use in reheating furnace of steel industry. The starting batch composition for producing such bricks is given in Annexure - I:
Annexure - I: Batch Composition of plastic refractory
Raw Material Wt. %
Calcined Alumina (Fines) 10-15
Kyanite (Fines) 8-12
Fused Mullite (Fines) 27-33
Fused Mullite (Fines to Medium) 8-12
Fused Mullite (Medium) 27-33
Bauxite (Coarse) 5-9
Liquid Binder 13 – 16

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
Fused Mullite
Al2O3 (Min.), % 72.96
Fe2O3 (Max.), % 0.32
SiO2 (Max.), % 25.7

Calcined Alumina Powder
Al2O3 (Min.), % 99.4
Fe2O3 (Max.), % 0.03
Na2O (Max), % 0.50
Size (D 50), micron 5

Raw Kyanite Powder
Al2O3 (Min.), % 37
Fe2O3 (Max.), % 1.80
PLC 1450°C/2 hrs (Min), % 4

Calcined Bauxite
Al2O3 (Min.), % 87
Fe2O3 (Max.), % 2.5
TiO2 (Max.), % 4
SiO2 (Max.), % 6

Liquid Binder

Component Wt %
Ortho-Phosphoric Acid 87-92
Colloidal Silica 3-7
Water 3-7
Carboxy Methyl Cellulose 0.05-0.1
SHMP 0.01-0.05

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 plastic mass are given in Annexure - IV.

Annexure - III: Mixing sequence of ingredients
A. Synthesizing a liquid binder
B. Dry mixing of all the grains (0 mm to 5mm) taken together in a Hobbert mixture for 5 to 7 minutes.
C. Addition of 7% (by weight) premixed liquid binder obtained in step ‘A’ to the dry mix.
D. Thereafter wet mixing for 5 to 7 minutes.
E. Addition of rest 50% of the premixed liquid obtained in step ‘A’ to the resultant mix and then final mixing for 5 to 7 minutes to get the final mixture.
F. Storing the plastic mass in air-tight plastic container for further evaluation.
G. Ramming of green mix thus obtained by using sand rammer for different cylinders of 50 mm height & 50 mm dia; and 150 mm × 25 mm × 25 mm Bar samples are also prepared.
H. Subjecting the green samples thus obtained to dry at 150°C in heating oven & fired at different temperatures to evaluate the physical properties.
Annexure - IV: Properties of Developed plastic mass
a) Physical properties:
Properties at different temperature
BD (gm/cc) 850°C, 2 hrs 2.3
1250°C, 2 hrs 2.34
1550°C, 2 hrs 2.14
CCS (kg/cm2) 850°C, 2 hrs 325.96
1250°C, 2 hrs 351.74
1550°C, 2 hrs 345.76
MOR (kg/cm2) 850°C, 2 hrs 99.2
1250°C, 2 hrs 107.02
1550°C, 2 hrs 98.3
PLC (%) 850°C, 2 hrs 0.29
1250°C, 2 hrs 0.46
1550°C, 2 hrs 2.2

b) Chemical Analysis:
Elements %
Al2O3 65.0
SiO2 22.0
Fe2O3 0.6
TiO2 0.5
CaO 0.1
Alkalies 0.3
P2O5 11.2

Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the appended claims.