Claims:We Claim:

1. Castable suitable for producing cast refractory bricks for working refractory lining of pilot coke ovens comprising :
Sl. No. Parameters Requirement
1 Al2O3 (wt %),( Min.) 65-70
2 Fe2O3 (wt %), (Max.) 1.0-1.8
3 SiC (wt %), (Min.) 18 -25
4 Bulk density (B.D.) after drying at 110°C for 24 hrs. (gm/cc), (Min. ) 2.7 – 3.2
5 C.C.S.
After drying at 110°C for 24 hrs. (Min.)
After heating at 1000°C for 3 hrs. (Min.)
100-150
600 -800

2. Castables as claimed in claim 1 which is wooden mould castable.

3. Cast refractory bricks for working lining of bottom and walls of pilot coke oven involving the castable as claimed in anyone of claims 1 or 2 comprising good conductor of heat[4-5 Wm-1K-1 (IS 1528 (Part 16) :2007)]; good abrasion resistance [AI : 40-50 (B.S.1902:Section 4.6:1985)], good thermal shock resistance [>15cycles (IS 1528 (Part 3) :2010)], good stability in CO/ CO2 environment and non-sticky in nature to coal and coke and withstand maximum operating temperature of Pilot Coke Oven of upto about 1350°C.

4. Cast refractory bricks as claimed in claim 3 which is having shape and configuration comprising mainly three shapes of the bricks to complete the refractory lining, wherein two shapes are solid and one shape is having two cavities to reduce the total thickness for better heat transfer through the brick, and
wherein out of said two solid bricks, one brick is smaller in size called key-brick for adjustment of remaining gap of the lining from shell;
said hollow shaped bricks are having tongue on two sides and grooves on two sides of the thinner part of the bricks where the tongue and groove are to provide the stability of brick lining by locking of bricks during lining and also said tongue and groove also restricts the passage of hot gases through brick to brick gaps;
said shape and size of tongue, groove and also the cavities are maintained by careful de-molding after casting.

5. A process of manufacturing of working lining refractory bricks for pilot coke oven including the castable as claimed in claim 1 comprising
(i) providing said SiC containing castable of following specification:

Sl. No. Parameters Requirement
1 Al2O3 (wt %),( Min.) 65-70
2 Fe2O3 (wt %), (Max.) 1.0-1.8
3 SiC (wt %), (Min.) 18 -25
4 Bulk density (B.D.) after drying at 110°C for 24 hrs. (gm/cc), (Min. ) 2.7 – 3.2
5 C.C.S.
After drying at 110°C for 24 hrs. (Min.)
After heating at 1000°C for 3 hrs. (Min.)
100-150
600 -800

(ii) mixing water with the castable mix in a mixer;
(iii) casting the said wet mix in a wooden mould corresponding to the shaped bricks to be obtained;
(iv) de-moulding the cast brick and subjecting to drying; followed by
(v) firing the dried bricks following selected firing schedule; and
(vi) subjecting the fired bricks to natural cooling to room temperature to obtain the refractory bricks of desired properties suitable for application in pilot coke oven.

6. The process as claimed in claim 5 wherein said step of mixing water with castable mix comprising adding select amount (5 – 7%) of water to be mixed with said castable in a mixer for specified time (6 – 8 minutes).

7. The process as claimed in anyone of claims 5 or 6 wherein said step of casting comprising casting the wet mix thus prepared in the mixer in wooden mould with a select time (15 – 20 minutes).

8. The process as claimed in anyone of claims 5 to 7 comprising de-moulding and air curing for specified time (20 – 24 hours) and drying at specific temperature (1100C) for specific time (20 – 24 hours).

9.The process as claimed in anyone of claims 5 to 8 comprising firing of dried bricks at specific temperature (1180C – 1200C) for specific time (3.5 – 4 hours) with following firing schedule:

Firing Temperature Rate of heating (0C/Hour) Time required (Hour)
Room Temp.(~250C) to 2500C 20-25 6-9
At 2500C - 3-5
2500C to 5500C 20-25 10-12
At 5500C - 5-8
5500C to 12000C 40-50 10-13
At 12000C - 2-4
Then natural cooling to room temperature.

Dated this the 19th day of March, 2022
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199
, Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A PROCESS FOR MANUFACTURING OF REFRACTORY BRICKS FOR SPECIAL APPLICATION OVEN BY USING CASTING METHOD FROM SiC CONTAINING CASTABLE.



2 APPLICANT (S)

Name : STEEL AUTHORITY OF INDIA LIMITED.

Nationality : Indian.

Address : Research & Development Centre for Iron & Steel,
Doranda, Ranchi, Jharkhand, India. PIN-834002.






3 PREAMBLE TO THE DESCRIPTION

COMPLETE

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

FIELD OF THE INVENTION
The present invention relates to SiC containing castable, and particularly, to a process for manufacturing of refractory bricks for special application such as in pilot coke oven by using casting method from SiC containing castable.

BACKGROUND OF THE INVENTION
Applicant’s R & D center at RDCIS, Ranchi is having one 250 kg pilot coke oven manufactured by a foreign firm for which neither the stock of working lining refractory brick nor the drawing of refractory bricks and brick making mould was available with RDCIS. Shapes of the bricks are also very critical which is difficult to make by normal pressing method. Thus there was a need to develop such bricks indigenously.

Under prevailing operating conditions of pilot coke oven, the refractory working lining of bottom and walls need to be good conductor of heat. It should have good abrasion resistance, good thermal shock resistance, good stability in CO/ CO2 environment and also non-sticky in nature to coal and coke. The maximum operating temperature of Pilot Coke Oven is 13500C. Working lining of the Pilot Coke Oven had been done using SiC bricks. SAIL Refractory Unit (SRU) in its Bhandaridah plant is having facilities for manufacturing of SiC containing monolithic refractory. SiC containing monolithic refractory can be used for manufacturing of working lining refractory bricks for bottom and walls of Pilot Coke Oven.

Due to criticality in shapes of the bricks, casting method is preferred over normal pressing method. As drawings of working lining refractory bricks were not available, it was difficult to develop required drawings and to produce moulds for bricks by casting method.

There has been thus a persistent need in the existing operation of pilot coke oven to develop refractory bricks for Pilot Coke Oven working lining by casting method of profiled shaped bricks from SiC containing castable ensuring good abrasion resistant, good thermal shock resistant, good chemical stability in CO/CO2 environment and also non-sticky in nature to coal and coke.

OBJECTS OF THE INVENTION
The basic object of the present invention is directed to provide SiC containing castable based refractory bricks suitable for application in working lining of pilot coke oven and a process for manufacturing of such refractory bricks by using casting method from SiC containing castable.

A further aspect of the present invention is directed to developing refractory bricks for Pilot Coke Oven working lining by casting method including developing moulds of profiled shaped precast bricks from SiC containing castable ensuring good abrasion resistant, good thermal shock resistant, good chemical stability in CO/ CO2 environment and also non-sticky in nature to coal and coke.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to Castable suitable for producing cast refractory bricks for working refractory lining of pilot coke ovens comprising :
Sl. No. Parameters Requirement
1 Al2O3 (wt %),( Min.) 65-70
2 Fe2O3 (wt %), (Max.) 1.0-1.8
3 SiC (wt %), (Min.) 18 -25
4 Bulk density (B.D.) after drying at 110°C for 24 hrs. (gm/cc), (Min. ) 2.7 – 3.2
5 C.C.S.
After drying at 110°C for 24 hrs. (Min.)
After heating at 1000°C for 3 hrs. (Min.)
100-150
600 -800

According to a further aspect of the present invention, said Castable is wooden mould castable.
A still further aspect of the present invention is directed to said Cast refractory bricks for working lining of bottom and walls of pilot coke oven involving the castable comprising good conductor of heat [4-5 Wm-1K-1 (IS 1528 (Part 16) :2007)]; good cold abrasion resistance [AI : 40-50 (B.S.1902:Section 4.6:1985)] , good thermal shock resistance [>15cycles (IS 1528 (Part 3) : 2010)], good stability in CO/ CO2 environment and non-sticky in nature to coal and coke and withstand maximum operating temperature of Pilot Coke Oven of upto about 1350C.
A still further aspect of the present invention is directed to said Cast refractory bricks which is having shape and configuration comprising mainly three shapes of the bricks to complete the refractory lining, wherein two shapes are solid and one shape is having two cavities to reduce the total thickness for better heat transfer through the brick, and
wherein out of said two solid bricks, one brick is smaller in size called key-brick for adjustment of remaining gap of the lining from shell;
said hollow shaped bricks are having tongue on two sides and grooves on two sides of the thinner part of the bricks where the tongue and groove are to provide the stability of brick lining by locking of bricks during lining and also said tongue and groove also restricts the passage of hot gases through brick to brick gaps;
said shape and size of tongue, groove and also the cavities are maintained by careful de-molding after casting.

A still further aspect of the present invention is directed to said a process of manufacturing of working lining refractory bricks for pilot coke oven including the castable as stated above comprising
(i) providing said SiC containing castable of following specification:

Sl. No. Parameters Requirement
1 Al2O3 (wt %),( Min.) 65-70
2 Fe2O3 (wt %), (Max.) 1.0-1.8
3 SiC (wt %), (Min.) 18 -25
4 Bulk density (B.D.) after drying at 110°C for 24 hrs. (gm/cc), (Min. ) 2.7 – 3.2
5 C.C.S.
After drying at 110°C for 24 hrs. (Min.)
After heating at 1000°C for 3 hrs. (Min.)
100-150
600 -800

(ii) mixing water with the castable mix in a mixer;
(iii) casting the said wet mix in a wooden mould corresponding to the shaped bricks to be obtained;
(iv) de-moulding the cast brick and subjecting to drying; followed by
(v) firing the dried bricks following selected firing schedule; and
(vi) subjecting the fired bricks to natural cooling to room temperature to obtain the refractory bricks of desired properties suitable for application in pilot coke oven.

A still further aspect of the present invention is directed to said process wherein said step of mixing water with castable mix comprising adding select amount (5 – 7%) of water to be mixed with said castable in a mixer for specified time (6 – 8 minutes).

Another aspect of the present invention is directed to said process wherein said step of casting comprising casting the wet mix thus prepared in the mixer in wooden mould with a select time (15 – 20 minutes).

Yet another aspect of the present invention is directed to said process comprising de-moulding and air curing for specified time (20 – 24 hours) and drying at specific temperature (1100C) for specific time (20 – 24 hours).

A still further aspect of the present invention is directed to said process comprising firing of dried bricks at specific temperature (1180C – 1200C) for specific time (3.5 – 4 hours) with following firing schedule:

Firing Temperature Rate of heating (0C/Hour) Time required (Hour)
Room Temp.(~250C) to 2500C 20-25 6-9
At 2500C - 3-5
2500C to 5500C 20-25 10-12
At 5500C - 5-8
5500C to 12000C 40-50 10-13
At 12000C - 2-4
Then natural cooling to room temperature.

The above and other objects and advantages of the present invention are described hereunder with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: schematic drawing of Precast refractory bricks for Pilot Coke Oven.
Figure 2: photo image of the Precast refractory brick for Pilot Coke Oven produced by casting method from SiC containing castable according to present invention showing cavity and grooves.
Figure 3: photo image of the Precast refractory brick showing cavity and tongue(to be inserted in groove of adjacent brick during lining installation).

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention is directed to provide SiC containing castable based refractory bricks suitable for application in working lining of pilot coke oven and a process for manufacturing of such refractory bricks by using casting method from SiC containing castable.

Due to criticality in shapes of the bricks, casting method is preferred over normal pressing method. As drawings of working lining refractory bricks were not available, drawings for working lining refractory bricks and also for brick making moulds have been developed. Wooden moulds were selected for ease of handling and cost optimization. Desired quality was ensured by close monitoring of each manufacturing steps. Laboratory evaluation of different properties of castable has also been done. One set spare working lining refractory bricks for bottom and walls of Pilot Coke Oven manufactured successfully, so that Pilot Coke Oven need not to remain idle for the want of working lining refractory.

Refractory working lining of bottom and walls of Pilot Coke Oven/other special application metallurgical oven need to be good conductor of heat. It should have good strength & abrasion resistance, good stability in CO/ CO2 environment and also non-sticky in nature to coal and coke.

Shapes of the bricks of bottom and walls of Pilot Coke Oven/other special application metallurgical oven are very critical which is difficult to make by normal pressing method. Casting is a favourable way of manufacturing of these types of bricks. Accompanying Figure 1 shows the schematic drawing of Precast refractory bricks for Pilot Coke Oven.

Mainly 3 shapes of the bricks are used for complete the refractory lining, two shapes are solid and one shape is having 2 cavities to reduce the total thickness for better heat transfer through the brick. Out of 2 solid bricks 1 brick smaller in size is called key-brick for adjustment of remaining gap of the lining from shell. Bricks are having tongue in 2 sides and grooves on 2 sides of the thinner part of the bricks. The purpose of this tongue and groove is to provide the stability of brick lining by locking of bricks during lining. Tongue and groove also restricts the passage of hot gases through brick to brick gaps. After casting careful de-molding is required to maintain the shape and size of tongue, groove and also the cavities as shown in accompanying Figure 2 & 3.

Wooden moulds are cost effective and easy to handle where required production volume is less and manual operation is more.

In order to have Bricks for working lining of bottom and walls of Pilot Coke Oven/other special application metallurgical oven, it should have good thermal conductivity, good strength, abrasion resistance, good stability in CO/ CO2 environment and also non-sticky in nature to coal and coke. So, SiC containing refractory is the most suitable for the purpose.

Thus the process of manufacturing of working lining refractory bricks for pilot coke oven by casting method using SiC containing castable having following specification:

Parameters Requirement
1 Al2O3 (wt %),( Min.) 65-70
2 Fe2O3 (wt %), (Max.) 1.0-1.8
3 SiC (wt %), (Min.) 18 -25
4 Bulk density (B.D.) after drying at 110°C
for 24 hrs. (gm/cc), (Min. ) 2.7 – 3.2
5 C.C.S. :
After drying at 110°C for 24 hrs. (Min.) 100-150
After heating at 1000°C for 3 hrs. (Min.) 600 -800

The process for making castable mix for manufacturing of refractory bricks for pilot coke oven from above ingredients wherein specified amount (5 – 7%) of water is mixed with said castable in a mixer for specified time (6 – 8 minutes).
Mix thus prepared in the mixer is cast in wooden mould with a specified time (15 – 20 minutes).
Cast bricks are next subjected to de-moulding and then air curing for specified time (20 – 24 hours) followed by drying at specific temperature (1100C) for specific time (20 – 24 hours).

Finally, dried bricks are subjected to firing at specific temperature (1180C – 1200C) for specific time (3.5 – 4 hours) with following firing schedule:

Firing Temperature Rate of heating (0C/Hour) Time required (Hour)
Room Temp.(~250C) to 2500C 20-25 6-9
At 2500C - 3-5
2500C to 5500C 20-25 10-12
At 5500C - 5-8
5500C to 12000C 40-50 10-13
At 12000C - 2-4

The fired bricks are then subjected to natural cooling to room temperature.
It is thus possible by way of the present invention manufacturing of working lining refractory bricks for bottom and walls of Pilot Coke Oven from SiC containing monolithic refractory castable that ensure properties like good conductor of heat, good abrasion resistance, good thermal shock resistance, good stability in CO/ CO2 environment and also non-sticky in nature to coal and coke, which can sustain the maximum operating temperature of Pilot Coke Oven at 1350°C.