FIELD OF THE INVENTION
The present invention relates to environmental friendly 25-40% alumina content type fire clay refractory
bricks having standards of IS 6(medium duty), IS 8 quality and low duty fire clay bricks, more particularly
environmental friendly fire clay refractory bricks for general-purpose refractory application from coal fly ash
and blast furnace granulated slag (inorganic solid waste materials). Furthermore the present invention is
directed to a method for manufacturing the said environmental friendly fire clay refractory bricks.
BACKGROUND OF THE INVENTION
A group of refractory clays, which can withstand temperature above pyrometric cone equivalent (PCE), 19
Orton are called fire clay. The clay which fuses below PCE-19 Orton is not included under refractory. Fire
clay is essentially of Kaolinite group and has a composition similar to that of china clay. In nature, it is
usually found to contain 24-32% Alumina (AI203), 50-60% Silica (Si02) and loss on ignition (LOI) 9 to
12%. Impurities like oxides of calcium, iron, titanium and magnesium and alkalis are invariably present,
making it white, grey and black in colour. Refractoriness and plasticity are the two main properties needed
in fire clay for its suitability in the manufacture of refractory bricks. A good fire clay should have a high
fusion point and good plasticity depending upon their capacity to withstand high temperature before
melting. The fire clays are graded into followings
Low duty - withstand temperature between 1515-1615 °C (PCE-19 to 28 Orton)
Intermediate duty - 1650 °C (PCE - 30 Orton)
High duty - 1700 °C (PCE - 32 Orton)
Super duty - 1775 "C (PCE - 35 Orton)
It practice it has been observed that higher the alumina content in the fire clay, higher is the fusion point, all
fire clays are not necessarily plastic clay. In such cases some plastic clay, like hall clay is added to
increase plasticity to a suitable degree.
Fire clay is classified under Acid Refractories, Acid refractories are those which are not attacked by acid
slag. In blast furnace iron ladles, the lining is done almost entirely with fire clay refractories. Other
application such as in boiler furnaces, cupola furnaces, safety lining of steel ladles, reheating and heating

. furnaces etc. This is because of the abundant availability of fire clay and its comparative low cost. The
refractories made out of it are most commonly and extensively used in all places as mentioned above. But
now situation has changed, environment regulations are much more stringent restricting fresh mining uses
to conserve forest reserves. Therefore, there is acute scarcity of raw material and this is really a problem
for refractory makers across the globe. This industry particularly the fire clay refractory bricks in the range
of 30-40% alumina content type is highly labour intensive, profit margin is not very lucrative and hence
major refractory makers do not want to make these kind of bricks.
Refractory products are manufactured largely by a replication of the natural geological process of forming
by high heat and pressure any naturally occurring or synthetic non-metallic mineral oxides (and some non-
oxides like carbides or nitrides) of course with technological progress, alternative bounding technique, such
as with chemicals, cements, resigns etc have also developed. Because refractory products are so resistant
to heat, erosion and corrosion, they are typically used in any process involving heat and corrosion such as
in kilns and furnaces. For examples in integrated steel plant units almost all the production units need
refractories such as sintering plant, coke oven, blast furnaces, hot metal transfer ladles, liquid iron storage
tank (mixer) steel melting vessels like BOF, THF, EAF, secondary steel ladles, tundishes, reheating
furnaces, soaking pit, annealing furnaces etc.
According to the main chemical component i.e fire clay or magnesia or zirconia etc. They are commonly
known as alumino-silicate or acid refractories, basic refractories and natural refractories products in
physical characteristics, refractories typically have relatively high bulk density, high softening point at
elevated temperatures and high crushing strength. They are produced as standard bricks over shapes as
per customer's requirement. Some refractories are also produced as unshaped and such refractories are
known as monolithic products.
The principal applications of refractories are in iron and steel industries, cement glass non-ferrous metals,
petrochemicals and fertilizer industry, chemicals, ceramics, thermal power stations and incinerators. But
the steel industry forms a major end-use segment for refractories consuming 50-80% of the total annual
refractory production depending upon the country. But for a variety of reasons, one of which is being the
continuous improvement of refractories. The specific refractories consumption for steel making in particular
has been on decline. In 1970, the steel industry in Japan and the US consumed 25-30 Kg of refractory per
tonne of steel produced and in India this was approximately 44-50 Kg/T of steel produced. The steelmakers
in other industrialized nations of the world have likewise had a similar decrease in refractory consumption.
According to research published by Global Industry Analysts Inc., Asia-Pacific, the largest refractories

.market in the world, is projected to reach 25.5 million metric tones in volume terms and USD 14.7 billion by
2009. The global refractories market is projected to costs 41 million metric tones in terms of volume and
USD 26 billion in value by 2010.
With development of high quality and durable refractories, a strong market orientation is seen towards
value based growth as against volume based growth. Significant growth potential is witnessed in
magnesia-carbon, high alumina, zircon / zirconia, silicon carbide and other more specialized refractory
materials that offer high performance in specific application. In general requirement of refractories in the
industries grade wise as follows of the total requirements.

This indicates that approximately V* of total of requirement is of fire clay refractories i.e around 25%.
These are basically alumina-silica refractory products. Some times fire clay refractories are also called as
low-medium-alumina refractories. The range of Alumina-silica refractory products has been shown in Table
No.1 below and this classification is based upon amount of alumina present in the refractory products.

Table No.1
Alumina-silica Refractory

Fire Clay: A group of refractory clays which can stand temperature above pyrometric cone equivalent
(PCE)-(Edward) (Orton) 19 are called fire clay. This type of clays normally having 24-26% plasticity and
shrinkage after firing 6-8% maximum. The clay which fuses below PCE-10 is not included under refractory.
Fire clay is essentially of kaolinte group and has a composition similar to that of china clay. In nature it is
usually found to contain 24-32% Al203, 50-60% Si02 and LOI between 9-12%. Impurities like oxides of
calcium, Iron, titanium and magnesium and alkalis are invariably present, making it white grey and black in
colour. Fire clay is generally of sedimentary origin, strictly speaking, fire clay is of sedimentary origin and
mainly found in the coal measures, as bedded deposits.
Refractoriness and plasticity are the two main properties needed in fire clay for its suitability in the
manufacturing of refractory bricks. Depending upon their capacity to with stand high temperature before
melting the fire clays are graded into following.
Low Duty - Withstand temperature between 1515-1615 °C (PCE - 19 to 28) Orton Cone.
Intermediate Duty - 1650 °C (PCE - 30 Orton)
High Duty - 1700 "C (PCE - 32 Orton)
Super Duty - 1775 °C (PCE - 35 Orton)
In practice it has been observed that the higher the alumina content in the fire clay, the higher is the fusion
point. All fire clays are not necessarily plastic clays. In such cases some plastic clay, like ball clay is added

Jo increase plasticity to a suitable degree. A good fire clay should have 24-26% plasticity and firing
shrinkage after firing should be within 6-8% maximum. It should also not contain more than 25% Fe203. It
has been observed that some clays lacking plasticities when allowed to 'weather' i.e left in the open for few
months, become plastic due to the formation of humic add in the clay non-plastic fire clay is also known as
flint clay. It may be called semi-flint and semi-plastic depending upon the degree of plasticity.
Fire clay is classified under acid refractories. Acid refractories are those which are not attacked by acid
slag. In blast furnace iron ladles, the lining is done almost entirely with fire clay bricks. Other applications
such as the boiler furnaces, glass melting furnaces, chimney linings, pottery kiln blast furnaces, reheating
furnaces, cupola furnaces etc are made of fire clay. This is because of the abundant supply of fire clay and
its comparative cheapness. The refractory bricks made out of it are most commonly and extensively used
in all places of heat generation as mentioned above.
The typical properties and composition of fire clay refractory bricks are as follows:
Table No.2
Typical composition and properties of fire clay bricks


^But now situation has changed environmental regulations are much more strict then ever, no more fresh
mining leages, because of forest reserve. Therefore there is a acute scarcity of raw material and this is
really a problem for refractory makers across the globe. This industry particularly the fire clay refractories in
the range of 30-40% Alumina content type, is highly labour intensive and profit margin is not very lucrative,
major refractory makers do not want to make these kind of bricks.
Existing process & practice of Fire clay Refractory bricks making
As well know fire clay was probably the first refractory used by man. It occurs in most areas of the world
and being plastic when mixed with water was found singularly useful for the production of crucibles for
metal melting or glass manufacture. Inspite of the development of many more refractory and slag resistant
materials, it is still the most widely used. Other alumino-silicate, such as silimanite and bauxite are high
quality refractories for special purposes. Now in these days fire clay refractories 28 - 45%. Alumina types
are increasingly used, particularly in the iron and steel industries.
Manufacturing Process
Most present day fire clay bricks are manufactured either by dry pressing or by extruding a column of clay,
followed by repressing to give the desired shape. Limited quantity of fire clay refractory bricks are still
worked by hand, using the plastic process, but in general its use is limited to less modern factories or to the
production of small quantities of special shapes. The main raw material required to make fire clay
refractories are plastic clay, such as kaolin, china clay, ball clays etc and non-plastic clay such as flint clay
(non-plastic, hard, refractory clay, having a low firing shrinkage) and suitable fire clay grog. In the dry press
process the clay batch, which usually contains about 20% grog (such as chamotle or schamotle) is mixed
with a relatively small amount of water (4-5%), poured into press boxes and moulded by means of
mechanically or hydraulically applied pressure.
The grog is made by crushing waste refractory products, by firing dobies with some machines a vacuum is
applied to see press box to reduce the risk of lamination and cracking due to trapped air. In the second
process the clay passes through a pug mill, where it is mixed with a rather greater amount of water (10-
15%) and is then extruded through an auger machine, often under a partial vacuum, cut into lumps of the
desired size and then repressed. This latter process is particularly used for the production of hollow-ware
for use in the casting pit type requirement.
The drying and firing procedure vary considerably from one plant to another, some places tunnel driers are
used. Final firing is done mainly in down drought kilns, chamber kilns or in tunnel kilns depending upon
type of firing fuel availability. The finishing temperature for firing fire clay bricks varies greatly, but generally

.lies in the range between 1100 °C to 1400 °C. After completion of firing cycle soaking is done to a pre-
determined period after that, furnaces is cooled slowly and product is taken out for inspection and then
dispatch to the customer. The total process out line has been given in the Fig.No.A.
The physical and chemical properties of IS:6 anf IS :8 type bricks are given in table No. 6 and 7.

Lots of waste products are available, which are similar to fire-clay (alumino-silicate) in composition such as
fly ashes, granulated blast furnace slag, disposal of these inorganic wastes remain a major environmental
problem. Applications making use of these inorganic wastes materials would be of benefit to the
environment. The management of inorganic waste produced from diverse forms of Industrial activity such
as power generation from coal, iron and steel industries remains a major problem in many parts of the
world. These typical huge industrial wastes include coal-fly-ash, blast furnace granulated slag etc. This

. investigation focused on the used of coal fly ash and blast furnace granulated slag as a substitute for
natural fire clay (alumino-silicate) raw materials for manufacturing low cost fire clay refractory bricks for
general purpose use in industries such as boiler furnace, iron steel furnaces etc. Here the fly ash from
power plants and blast furnace granulated slag were selected on the basis of Alumina (Al203).
Higher alumina content in both the materials is better for refractory making purpose. As such different
mixtures were investigated to find a formulation that had refractory properties. More over it is of economic
and social importance to research the use of fly ash and blast furnace granulated solid wastes to develop
new or alternative applications to exploit them as raw materials for processing useful products rather than
dumping them where future inhabitants would be at risk.
The refractory industry with consumption of more than 1000 MT/Year of traditional fire clay products can be
a potential sink for utilization of these alumino-silicate waster materials, the granulated blast furnace slag
also comes in this category.
The chemical composition of most of the coal fly ash and blast furnace granulated slag, the main waste
materials is our investigation area in the Al203-Si02 binary system of the fire clay currently used in
refractory.
A study of the Al203-Si02 (Fig No.1) binary phase system is of particular interest as it is an aid in the
understanding of mullite formation, which possesses good thermo-mechanical properties. Fire clay
refractory materials also belong to the Al203-Si02 binary phase system.
Mullite, an alumino-silicate mineral is a technologically attractive material for refractory ceramics due to its
low thermal expansion and conductivity. Properties like chemical inertness and excellent mechanical
properties at high temperature contribute to the attractiveness of mullite and alumino-silicate minerals in
applications such as refractory materials. If minor oxides in the materials are ignored, the composition of
Rourkela Steel Plant's Power Plant No.Vs coal fly ash and BF granulated slag lies in the centre of the
mullite area of the CaO-AI203-Si02 ternary phase diagram (Fig No.2).
The performance of refractory ceramics depends mainly on the final phase diagram of the combined raw
materials and the amount of impurities in the raw materials. By carefully choosing the proportions of mix
(coal fly ash & BF granulated slag). It should be possible to design fire clay refractory bricks from above
waste materials that can be used as an ingredient for manufacturing refractories.

The manufacturing of fire clay refractory bricks mainly requires various types of clays and recycle
refractory grog or grog made out of calcined clay. The basic matrix is clay & alumina content adjuste
suitably. Here coal fly ash and BF granulated slag due to the minerological, physical and chemic;
composition and the presence of some elements and compounds are excellent substitutes, fly ash for cla
and BF granulated slag for refractory grog in fire clay refractory making. The general composition of fly as
and BF granulated slag has been given in Table No.3 & 4.


.All he composition mentioned in specification are in weight %.
Fly Ash present applications
Fly ash is a siliceous & aluminous material with pozzolanic properties and this is a residue resulting from
combustion of pulverized coal of lignite in thermal power plants. About 80% of total ash is in finely divided
form which is carried away with gases and is collected by electrostatic precipitator or other suitable
technology. This is called (dry) fly ash or chimney ash or hopper ash. The balance 20% of the ash is
collected at the bottom of the boiler and is referred as bottom ash. When fly ash, bottom ash is carried to
storage pond in the form of water slurry it is termed as pond ash. As evident from Table No.3, fly ash
consists of inorganic materials, mainly silica and alumina and some amount of organic material in the form
of unburnt carbon. It is refractory and alkaline in nature having fineness in the range of 4000-8000 sq.cm
per gram.
Although the material has been extensively studied for long, the potential of fly ash as a resource material
has been largely ignored. Its unique properties have now been proved as most useful to a wide range of
industries such as civil engineering, construction and building. Some of the major areas of civil engineering
where fly ash has been put to use are as follows:
Brick manufacturing for building houses.
Cement manufacture, replacement of cement in mortar concrete.
Roads and embankment construction
Dyke raising
Structural fill for reclaiming low lying areas
Hydraulic structures
Mine stowing material
Agriculture and forestry
Fly ash, when mixed with concrete, leads to make the same kind of glue that cement makes when added
with water, also used as substitute to cement with fly ash which in turn saves energy as well as reduction in
C02 emission.
Inspite of such application the utilization of fly ash is not increasing beyond 28%.

Thus call of the day is to find out some more areas where the conventional materials can be substituted
with fly ash. In our present work we have opened up one such new application of fly ash i.e manufacturing
of general-purpose fire clay brick with fly ash as main ingredient in place of conventional fire clays. If we
compare the chemical composition of conventional fire clay and fly ash then we find that its almost similar,
as shown in Table No.5, to granulated blast furnace slag.

The plasticity of fire clay varies 24-26% which is called good plasticity. Similarly the plasticity of dry coal fly
ash is also good. The LOI of fire clay varies from 9-12% while the LOI of fly ash varies between 10-18%.
For this reason we have selected to use Blast Furnace Granulated as one of the ingredients along with
conventional fire clay recycled grog of suitable granulometry.
The above table shows that coal fly ash is a good substitute to fire clay and blast furnace granulated slag
with 22-25% Al203 and about 10% MgO also a good refractory raw material. Here we are interested in
Al203 content of fly ash with low Fe203 content and Al203 + MgO content of blast furnace granulated slag.
At present the world production of blast furnace granulated slag is more than 300 million tones and about
50% of this being in use in different industries like cement, construction, road making etc. The balance 50%
is still a matter of concern and remains as read fill material causing land, air, water pollution.
Thus in this area also some more new applications are to be searched out which can increase the
consumption of blast furnace granulated slag. This work is being taken up in this direction only.
The disadvantage/problems faced of the above-mentioned prior art is that the amount of fly ash stockpiled
is increasing day-by-day inspite of application of fly ash in many industries in many ways. Major scarcity of
1 o

.refractory raw material is increasing day by day also. The naturally occurring raw materials/resources such
as fire clay minerals are not found in abundance these days as compared with the consumption of the fire
clay refractory bricks in the market. Further the conventional method of manufacturing of the fire clay
refractory bricks is costly and complicated. Moreover the industrial wastes such as coal fly ash and
granulated blast furnace slag cause environmental hazards.
Thus there is a need to provide an environmental friendly all varieties of 25-40% alumina content type fire
clay refractory bricks having standards of IS 6, IS 8 quality and low duty fire clay bricks, proper utilization of
coal fly ash and granulated blast furnace slag as raw materials which are industrial wastes to develop cost
effective (zero cost) and energy friendly for manufacturing fire clay refractory bricks of general purpose
(Fire clay refractory bricks-here means, fire clay refractory bricks such as IS: 6 & IS: 8).
OBJECTS OF THE INVENTION
The basic object of the invention is to overcome the disadvantages of the prior art.
One of the objects of the invention is to develop an environmental friendly all varieties of 25-40% alumina
content type fire clay refractory bricks having standards of low duty which can withstand temperature
between 1515 °C-1615°C ,IS 6 (medium duty) and IS 8 quality fire clay refractory bricks which can
withstand temperature upto 1630 °C.
Another object of the present invention is to develop fire clay refractory bricks for general-purpose
refractory application from coal fly ash and blast furnace granulated slag (inorganic solid waste materials).
Yet another object of the present invention is to develop fire clay refractory bricks, which help to recycle
waste products like coal fly ash and blast furnace granulated slag and utilize them in a proper economical
and environmental friendly way.
Yet another object of the present invention is to produce fire clay refractory bricks in a cost effective,
energy efficient and environmental friendly way.
Yet another object of the present invention is to a method for manufacturing the said environmental friendly
fire clay refractory bricks.

SUMMARY OF THE INVENTION
According to one aspect of the present there is provided an environmental friendly fire clay refractory brick
composition especially adapted for the use in general purpose refractory applications, having 25-40%
alumina (Al203) content, said composition comprising:
(i) coal fly ash as the main matrix comprising
45 to 51 wt. % Si02;
22-30 wt. % Al203;
7.3 to 9.5 wt. % Fe203;
2 to 3 wt. % CaO;
0.5 to 1.0 wt. %Ti02;
1.1 to1.5%MgO;
18 to 21 wt. %LOI;
(ii) blast furnace granulated slag as the gorging agent comprising
about 32.3 wt. % Si02;
about 23.2 wt. % Al203;
about 0.37 wt. % FeO;
about 31.9 wt. % CaO;
about 10.3 wt. %MgO;
about 0.04 wt. % MnO;
about 0.53 wt. % Sulphur;
about 0.85 wt. % Ti02;
about 0.448 wt. % K20;
(iii) recycled fire clay grog; and
(iv) fresh plastic and non plastic/fresh clay (fire clays);
wherein said components of (i), (ii), (iii) and (iv) being mixed with 4 to 6 wt % of water.
According to another aspect of the present invention there is provided a method of manufacturing
environmental friendly fire clay refractory brick as described above comprising steps of:

(i) selecting raw materials such that it comprises 60 to 70 wt. % of said coal fly ash, blast furnace
granulated slag; upto 30 % fire clay grog and fresh plastic and non-plastic fire clays;
(ii) mixing said raw materials with 4.5 to 5.5 % of water in a mixer/blending machine to get a
mixture;
(iii) moulding said mixture of step (ii) by putting the mixture in mould followed by ramming with
rammers to import compactness in the brick after which the said bricks were removed from the
mould;
(iv) air drying said bricks of step (iii) for about 24 hours in air;
(v) oven drying said bricks of step (iv) for removal of moisture from it and to ensure about 0.05 %
maximum moisture at a temperature of 110°C for 24 hours;
(vi) firing said bricks of step (v) for 24 hours at four different temperatures between 1150°C and
1320 °C for soaking purpose followed by slow cooling upto room temperature, and
(vii) inspection of said brick prepared in step (vi) for apparent porosity, cold crushing strength,
refractoriness, permanent line or change as per low duty ,IS :6, IS: 8 fire clay refractory bricks.
DETAILED DESCRIPTION OF THE INVENTION
The present work focuses on the recycling of coal fly ash combined granulated blast furnace slag to make
fire clay refractory bricks, withstand temperature between 1515 °C-1615°C having standards of low duty
and further which can withstand upto 1630 °C like IS: 6 / IS: 8 (30-42% alumina content refractory bricks).
The conventional such bricks are made from different type of fire clay, grog and other aluminous materials
with different percentages, which nowadays, not found in abundance and are not economical.
Waste product used as main raw material for manufacturing of fire clay refractory bricks:
1. Coal Fly Ashr. The coal fly ash used for the present invention was received from the Captive Power
Plant No.1 of Rourkela Steel Plant (SAIL) India. This is an inorganic waste material from the coal fired
power plants. The oxides present in coal fly ash make it an ideal raw material. Coal fly ash will
introduce to the mixer the necessary oxides (mainly Al203) needed to manufacture the fire clay

refractory bricks. The physical and chemical compositions of coal fly ash so used in the present
invention are given in Table No.8 & 9.

This chemical analysis was done at the Research & Control Laboratory of Rourkela Steel Plant (SAIL),
Rourkela. This contents relative high silica (45-51%) and alumina (22-30%) indicates fair refractoriness
computable with normal fire clays and rather better than fire clays. This gives an indication that the
Rourkela Steel Plant Captive Power Plant No.Vs coal fly ash can be used at relative high temperature
before reaching its melting point and grain or particle size indicates a fair plasticity. In view of these two
properties, coal fly ash was considered as the main ingredient of the body composition for the fire clay
refractory bricks in place of conventional plastic and non plastic fire clay minerals.
2. Granulated Blast Furnace Slag: It is well known that the disposal of industrial wastes is one of the
major world wide environmental problems. In India for example, dumping of industrial wastes such as
granulated blast furnace slag, fly ash has become a major environmental problem. Further more as a

consequence of environmental and financial consideration, there is a growing demand for wastes to
be reused or recycled. At present, the utilization of granulated blast furnace slag is in cement industry
and about 30-35% of total generation is recycled & balance is dumped in landfill sites. Thus there is
an urgent environmental and ecological demand to solve this problem. Blast furnace slag is a
nonmetallic by product from iron and steel industry. It is generated during the conversion of iron ore
into iron metal. Production of one tonne of molten iron leads to the generation of 450-500 Kg of slag.
The granulated blast furnace slag is cooled and solidified by rapid water quenching to fragments. The
chemical composition of Blast furnace granulated so used in this study for manufacturing of fire clay
refractory bricks (collected from Blast Furnace No.1 of Rourkela Steel Plant (SAIL), Rourkela, India)
has been given in Table No. 10. The present study focuses on the recycling feasibility of coal fly ash
and Blast furnace granulated slag to make fire clay refractory bricks for general purpose for
application in industries at relatively low cost and with good physical, chemical and mechanical
properties. Further more out come of this study will maximize the industrial profitability and abate both
wastes and environmental impacts.

In addition to above two waste products another two raw material were also used i.e recycled fire clay
refractory grog and fresh plastic clay of appropriate PCE value. But there both were in very small quantity.

Recycled fire clay refractory grog 20% by weight of 55 - 60% alumina content and plastic clay 10% by
weight of 28 - 29 (OC) PCE.
Method and Process
Hand moulding and forming method were used for manufacturing of fire clay refractory bricks from above
two industrial waste product with suitable quantity of high alumina refractory grog make out of used
refractory bricks and some quantity of fresh non plastic and plastic fire clay, the methodology adopted was
as follows:
Dry coal fly ash from Power Plant's collection hopper → Chemical analysis after removal of any foreign
particles → simultaneously collection of Blast furnace granulated slag and removal big particles and any
other foreign material → chemical analysis (as shown in Table No. 10) → mixing of coal fly ash with known
quantity of Blast furnace slag and known quantity of Refractory grog and known quantity of fresh plastic
and non plastic fire clays → mixing the same in pan mixer with some known quantity of water → putting the
mixture into mould and ramming with the rammers → forming → removal of the mould → keeping the
specimen so manufacture in air for air drying → drying the specimen in oven for removal of moisture →
firing the same to a appropriate temp → Cooling → removal of the specimen → from the firing furnace →
testing the specimens for apparent porosity, cold crushing strength, permanent line or change as per IS : 6
& IS : 8.
Foreign matter, means metallic particles and big particles means any things more than +5mm.
a. Raw Material
(i) Coal fly ash as per Table No.9
(ii) Blast furnace granulated
(iii)Recycled fire clay grog
(iv)Fresh plastic & non-plastic fire clays
b. Coal fly ash and blast furnace granulated slag about 60-70% and balance 30% is fire clay grog and
fresh plastic & non-plastic fire clays. This was mixed with 4.5-5.5 of water in a mixer. The mixing
was done till entire was is homogenized for this a blending machine was also used.
Out of 30%, 20% is the recycled fire clay refractory grog in which alumina content is between 55 -
60% & 10% is fresh plastic clay of 28 - 29 PCE (OC).

.c. From above mixture standard bricks in the size (230x115x65mm) were made and also some other
ladle shops as shown in Fig.3, 4, 5, 6 & 7 though hand moulding process. In order to investigates
the feasibility of manufacturing the fire clay refractory brick batches of mix, namely Fd, Fc2, Fc3 &
Fc4 were designed for the current innovation. These mixture composed of upto 70% of coal fly ash
+ Blast furnace granulated slag and upto 30% of fire clay grog + Fresh plastic and non-plastic fire
clays. The process of brick machine was based dry basis, where requirement of water is less i.e
4.5-5.5% only.
d. Moulding and Forming : From each batch of Fc1, Fc2, Fc3 & Fc4, 10 standard bricks were made by
hand moulding process which means, the mixture was poured in the mould and then ramming was
done to import compactness in the product. After forming, the green bricks were removed from the
mould and numbered as F1: F2, F3 F10.
The raw materials so identified (coal fly ash and blast furnace granulated slag) for manufacturing of fire
clay refractories can be called as "green materials" because making fire clay refractory bricks from above
two requires low manufacturing energy consumption and thus low waste gas emission therefore called
green bricks also.
e. Air Drying : These bricks as numbered as F1, F2... and so on were allow to be air dried for 24 Hrs.
f. After air drying the bricks of each batch they were kept in a oven at a temperature of 110 °C for 24
Hrs. After this moisture content of each brick was tested by moisture meter to ensure (0.05% max)
moisture.
g. Firing : The above dried samples were fired in the reheating furnace at four different temperatures
1150 °C, 1250 °C, 1280 °C, 1300 °C & 1320 °C. The brick samples were kept at above temperature
for soaking purpose for 24 Hrs and then slow cooler was done up to room temperature.
h. Inspection : After cooling, visual inspection was done with respect to crack, wrapage and any other
physical defects. However, no such abnormality was seen. In order to assess the physical,
chemical and mechanical characteristics of the fired specimens, each batch composition is
examined against the requirement of the IS : 6 & IS : 8 standard specification (Low duty fire clay,
medium duty fire clay as per Table No.2). Volumetric changes, firing weight loss, bulk density were

also calculated. According, the successful and promising batches were identified and suggested for
making fire clay refractory bricks.
i. Setting of Batch Composition : The set composition after testing the specimen of Fc1, Fc2, Fc3, Fc4
... has come out as per Table No. 11 for low duty fire clay bricks and as per Table No. 12 as per
medium duty (IS : 6) quality fire clay bricks and as per Table No. 13 for IS : 8 type fire clay bricks.



Physical properties of fire clay refractory bricks so manufactured from coal fly ash and Blast furnace
granulated slag
The physical properties of the fire clay refractory bricks/specimen so manufactured from coal fly-ash and
blast furnace granulated slags were determined Indian Standards Institution guidelines. Samples bricks
were so made from different compositions of coal fly ash and blast furnace granulated slag as main raw
material were tested at Research & Control Laboratory of Rourkela Steel Plant (SAIL), Rourkela, India. The
bricks samples were fired at three different temperatures as shown in Table No.11, 12 & 13 were tested
separately for cold crushing strength, apparent porosity, refractoriness (PCE), permanent linear change,
refractoriness under load (RUL). There were tested as per the procedure laid down in the IS : 1528-1974
(Indian Standard Institution). The results so obtained has been shown in Table No. 14, 15 & 16 chemical
composition w.r.t Al2O3 and SiO2 was done by chemical analytical method. For each five composition of the
batch 10 samples were tested and average value has been shown in the Table.

Discussion on Chemical and Physical properties of fire clay refractory bricks so manufactured from fly ash
and Blast furnace granulated slag
The main aim of this innovation work was to make fire clay refractory bricks from coal fly ash and blast
furnace granulated slag. The chemical composition of coal fly ash as shown in Table No.9, it is clear that fly
ash is composed essentially SiO2, Al2O3 as main component and Fe2O3 so present is less than 10%. Thus
the composition is very much similar to fire clay materials normally used for fire clay refractory bricks
making in the range of 25-40% alumina content. Similarly the chemical composition of blast furnace slag as
shown in Table No. 10. Here also is clear that main constituents are SiO2, Al2O3, CaO and with very less
amount of FeO. From the chemical composition of the above two wastes material, it is clear that the fire
clay refractory bricks so made are giving constituents within the equilibrium diagram of ternary phase. The
chemical composition of Rourkela Steel Plant fly ash the main inorganic waste in innovation lies in the
same Al2O3-SiO2 binary system as the fire clay currently used in refractories. If minor oxides in the
materials are ignored the composition of Rourkela Steel Plant's coal fly ash lies in the centre of the mullite
area of the CaO-AI2O3-SiO2 ternary phase diagram Fig No.2. Addition of lime will move the composition
closely along the lime anortile tie line in the graph. Here there is enough lime in the blast furnace
granulated slag. The performance of refractory ceramics depends mainly on the final phase diagram of the
combine raw material and the amount of impurities in the raw materials. Thus by carefully choosing the
proportion of the mix, it should be possible to design fire clay refractories in the range of 25-40% Al2O3
content from fly ash and blast furnace granulated slag that can be used as an ingredient for the
manufactured of fire clay refractories. This innovation has shown the ways that coal fly ash and granulated
blast furnace slag due to its mineralogical, physical and chemical composition and the presence of some
elements and compounds are excellent substitute for fire clay in fire clay based refractory industry.
The chemical composition of the fly ash used in this work is given in Table No.9. The relative high silica
(45-51%) and alumina (22-30%) content of the coal fly ash indicate fair refractoriness. This has given us an
indication that the Rourkela Steel Plant's coal fly ash can be used relatively at high temperature before
reaching its melting point. Therefore, coal fly ash was considered as the main ingredient of the body
composition for the fire clay refractory product of 25-40% alumina content. The addition of granulated Blast
furnace slag which is a coarser material enhanced moisture release and prevented crack during drying and
firing, this is the additional advantage of using Blast furnace granulated slag. Varieties of fire clay refractory
bricks were made. For each type necessary calculation was done carefully of the mix, necessary external
oxides were introduced in the mixture for production of required quality of fire clay refractory bricks. These
oxides were in the form of grog (from used refractory brick of particular variety and fresh calcined plastic
and non plastic fire clays).

The aim of this innovation was to produce refractory body from coal fly ash and granulated blast furnace
slag, which will provide fire clay refractory bricks in the range of 25-40% alumina content. Associated with
low cost the three type bricks so made have the similar properties of same kind of bricks made from
traditional raw materials. Thus the specific objective of making fire clay refractory bricks from coal fly ash
and blast furnace granulated slag has been successfully achieved.
Usefulness of the Innovation
A. Technological
(i)The chemical composition of coal fly ash from Rourkela Steel Plant, lies in the Al2O3-SiO2 binary
system as in the conventional fire clay currently used in refractories, thus on the basis of this
innovation, entire range of 25-40% alumina content variety of fire clay refractories can be
manufactured from coal fly ash and blast furnace granulated slag in which alumina content
varied from 25-31% and lies in CaO-AI2O3-SiO2 ternary system.
(ii)New application to exploit fly ash and blast furnace granulated slag as raw materials for making
useful product such as fire clay refractories rather than dumping them where future inhabitants
are at risk.
(iii)Range of fire clay refractories so manufactured in this work from coal fly ash and granulated
blast furnace slag have shown equally good refractory properties as from conventional raw
materials.
(iv)Fly ash and blast furnace granulated slag can replace conventional raw material up to certain
extent for making fire clay bricks. Here fly ash as main matrix and blast furnace granulated slag
as gorging agent.
B. Economic
(i) Product so made is cheaper than conventional use of a zero to very low cost raw material.
Because enormous volume of unused coaly fly ash and granulated blast furnace slag, and due
to their nature create disposal and environmental degradation problem. That can potentially
result in large scale air and water pollution.

(ii) Conservation of natural wealth such as fire clay mineral, by finding new substitute of fire clay
minerals for making fire clay refractories.
(iii)By use of fly ash and blast furnace granulated slag, overall profitability of users and supplier
industry is increased because fly ash is zero cost material, fly ash supplier saving disposal cost
and users are not to pay for buying huge amount of fire clay mineral for fire clay brick making.
(iv)The requirement of energy is less as compared to conventional raw materials process. Because
when we use coal fly ash and granulated blast furnace slag in place of conventional fire clay
minerals, the expensive mining and milling operation are eliminated. The coal fly ash and
granulated blast furnace slag (both are industrial wastes) are being used as they are without
any further processing.
C. Impact in Industry
(i) Fire clay refractory industry will not be dependent on fire clay minerals. Thus reduction in mining
operation and this will aid the profitability of the refractory industry.
(ii) Expenditure on dumping of coal fly ash and blast furnace granulated slag will go down. Thus
solving the dumping and disposal problem of these two industrial wastes.
(iii)New raw material for fire clay refractory makers at zero cost or at much cheaper rate as
compared to the conventional method.
(iv)To the user industry, fire clay refractories can be made available at low cost.
(v) Industries will be having main advantage by using above two industrial wastes as raw materials,
first the use of a zero to very low cost raw materials, secondly the conservation of natural
resource and finally the elimination of solid waste.
(vi)Reduction in the amount of stock pilled of fly ash and granulated blast furnace slag.
D. Advancement of Knowledge and Science
The group of alumino-silicate refractory bricks are called fire clay refractory and is the most important
and common group of refractories. The raw material based on Al2O3, SiO2 and CaO (sometimes) are
used to produce these bricks. Raw materials such as clay, kaolin, fire clay, sillimanite, audalusite,

kyanite, mullite, alumina, bauxite are used as source of alumina. The chemical composition of coal fly
ash and granulated blast furnace slag shows presence of good amount of alumina and lies in the
mullite region of Al2O3-SiO2 binary system, similarly the blast furnace granulated slag belongs to ternary
system CaO-AI2O3-SiO2. Good amount of alumina, lime and magnesia is present in this slag. Thus it is
possible to make higher grades and quality fire clay refractory bricks at much lower cost than with the
conventional raw materials.
Recycling waste materials would aid in the protection of the environment when the properties of waste
products (coal fly ash and granulated blast furnace slag) are such that it is possible to use them for
value added applications. These products stand a better chance of competing than products made from
primary materials. Here coal fly ash, granulated blast furnace slag's have chemical and physical
properties that in principle, make them suitable for making fire clay refractory materials.
Main features of the invention are as follows:
Nil to low coast raw material is coal fly ash and blast furnace granulated slag (inorganic waste material) for
manufacturing of fire clay refractory bricks.
The conservation of natural resources by finding new application for coal fly ash and blast furnace
granulated slag instead of natural minerals.
Elimination of inorganic solid waste such as coal fly ash produced by power stations and granulated slag
produced by blast furnace.
The coal fly ash and blast furnace granulated slag were combined and the mix was investigated for
refractory bodies confirming to set standards of IS:6 & IS:8 quality and low duty fire clay bricks.
Chemical composition of the coal fly ash and blast furnace granulated slag compare favorably with the
chemical composition of natural fire clay minerals used in the manufacture of variety of fire clay refractory
bricks. It is therefore evident that coal fly ash and blast furnace granulated slag can be utilized as mineral
sources for developing fire clay refractory bricks at low cost.
A saving of production cost is evident as no expensive mining and rolling operation is necessary in the
utilization of the coal fly ash and granulated blast furnace slag as raw materials for production of fire clay
refractory bricks.

It is quite possible to make higher variety of fire clay brick by careful calculation of a mix. The necessary
oxides can be introduced in a mixture. The oxide means some minerals containing higher amount of
alumina, such as corundum, bauxite, kainite etc.
Fly ash and BF granulated slag based fire clay refractory composites have been developed using fly ash as
main raw material. 40-65% of suitable fly ash can directly be substituted for fire clay minerals as main raw
material for manufacturing of fire clay refractory bricks.
Cost effective, energy efficient & environment friendly.
Fuel requirement is considerably reduced as fly ash contains some percentage of unburnt carbon.
Utilization of fly ash in fire clay refractory making minimizes the emission problem. As total energy
requirement as low as compared to conventional raw materials due to elimination of crushing, grinding
operations.
It has been shown that both fly ash and granulated blast furnace slag are being used as major feed stock in
manufacturing of variety of fire clay refractories.
New field of applications for fly ash - this will bring the stock piling of fly ash from different parts of world.
Solving disposal problem of fly ash which ultimately resulting in cost reduction at both sides (Suppliers &
users).
Use of fly ash and blast furnace granulated slag for manufacturing of fire clay refractories results in
reducing the demand for virgin materials that need quarrying and substituting for materials that may be
energy intensive.
Utilization of coal fly ash and blast furnace granulated slag for fire clay refractory making does not require
any additional technological facilities or investment as demonstrated in the work.
The development of fire clay refractory bricks with coal fly ash and blast furnace granulated slag was done
successfully and bricks so made are having all the characteristics of low duty, IS:6 & IS:8 quality. These

were deployed in the relining of iron and steel ladles of Foundry department in place of conventional IS:6
bricks. The bricks so deployed have performed well and found suitable to replace conventional fire clay
refractory bricks. The developed refractory brick is cost effective and manufacturing process is environment
friendly.
The characteristics of fire clay refractories made from cola fly ash and Blast furnace granulated slag were
investigated in this work and were found similar to low duty fire clay refractories, IS:6 & IS:8 quality fire clay
refractories and similar performance in actual application but with much reduced cost.
Based on this work environmentally friendly fire clay refractory bricks with good commercial characteristics
were successfully made using emerging recycling philosophy of the three R's which stand for recycle,
reuse and reduce.
Fire clay refractories so developed with coal fly ash and blast furnace granulated slag without shifting the
waste disposal problem by creating different waste products.
The raw materials so identified (coal fly ash and blast furnace granulated slag) for manufacturing of fire
clay refractories can be called as "green materials" because making fire clay refractory bricks from above
two requires low manufacturing energy consumption and thus low waste gas emission.
Making fire clay refractories from coal fly ash and blast furnace granulated slag is much more cheaper than
the similar product made from primary materials.
Adoption of process at commercial production level will help in reducing the stock piling of fly ash and aid in
the protection of the environment.
New application of these two waste materials and helping to solve the waste disposal problem.
Fire clay refractory brick making from coal fly ash and blast furnace granulated slag will lead to the
preservation of natural resources. The environment will benefit from this utilization as the demand on
mining activities for raw materials will be reduced and discarded waste (coal fly ash - BF granulated slag)
that degrades the environment will be utilized.
The properties of the newly developed varieties of fire clay refractory bricks comply with the specification of
fire clay refractories.

Fire clay refractory bricks making with coal fly ash and granulated blast furnace slag does not require any
extra investment.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure A illustrates Existing (conventional) process of manufacturing of fire clay refractory bricks.
Figure 1 illustrates Al2O3-SiO2 binary phase diagram as applicable to refractory.
Figure 2 illustrates ternary phase diagram of the CaO-AI2O3-SiO2 system.
Figure 3 illustrates Fire Clay Bricks from Fly-Ash and granulated Blast Furnace Slag.
Figure 4 illustrates Fire Clay Bricks from Fly-Ash and granulated Blast Furnace Slag.
Figure 5 illustrates Fire Clay Bricks from Fly-Ash and granulated Blast Furnace Slag.
Figure 6 illustrates Fire Clay Bricks from Fly-Ash and granulated Blast Furnace Slag.
Figure 7 illustrates Fire Clay Bricks from Fly-Ash and granulated Blast Furnace Slag.
Figure 8 illustrates the present invention process for manufacturing of fire clay refractories from coal fly ash
and blast furnace granulated slag
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 of the present invention describes AI2O3 - SiO2 phase diagram this diagram shows various
phase transformation at various composition of AI2O3 & SiO2. This, AI203 binary phase diagram is
applicable to fire-clay Refractories. The chemical composition of Rourkela Steel Plant's coal-fly-as lies in
the same AI203 - Si02 binary system as the fire-clay currently used in Refractories. This binary phase
system is of particular interest as it is an aid in the understanding of mulite formation which possesses
good thermo-mechanical properties.
Figure 2 of the present invention describes Cao - AI2O3 - SiO2 ternary phase diagram,

If minor oxides in the coal fly as of Rourkela Steel Plants are ignored then the composition of this fly as lies
in the center of the mullite area of the CaO - AI2O3 - siO2 ternary phase diagram as shown in the figure.
Addition of lime the performance of refractory ceramics depends mainly on the final phase diagram of the
combined raw materials and the amount of impurities in the raw materials. This diagram helps in choosing
the proportions of the mix for manufacturing the fire clay Refractories. The tick curves represents three
phase labeled areas show the liquidus surface of various solids the tin curves represent the isothermal
sections.
Figure 3 of the present invention discloses Fire clay bricks so made with the present technology for
application in lining of iron and steel ladle as safety lining refractory bricks.
Figure 4 to 7 of the present invention discloses various shapes of fire clay Refractories made for relining of
iron ladles.
Figure 8 describes present invention process for manufacturing of fire clay refractories from coal fly ash
and blast furnace granulated slag that are as stated below:-
Dry coal fly ash from Power Plant's collection hopper → Chemical analysis after removal of any foreign
particles → simultaneously collection of Blast furnace granulated slag and removal big particles and any
other foreign material → chemical analysis (as shown in Table No. 10) → mixing of coal fly ash with known
quantity of Blast furnace slag and known quantity of Refractory grog and known quantity of fresh plastic
and non plastic fire clays → mixing the same in pan mixer with some known quantity of water → putting the
mixture into mould and ramming with the rammers → forming → removal of the mould → keeping the
specimen so manufacture in air for air drying → drying the specimen in oven for removal of moisture →
firing the same to a appropriate temp → Cooling → removal of the specimen → from the firing furnace →
testing the specimens for apparent porosity, cold crushing strength, permanent line or change as per IS : 6
& IS : 8.

WE CLAIM
1. An environmental friendly fire clay refractory brick composition especially adapted for the use in
general purpose refractory applications, having 25-40% alumina (Al2O3) content, said composition
comprising:
(i) coal fly ash as the main matrix comprising
45 to 51 wt. % Si02;
22-30 wt. % Al203;
7.3 to 9.5 wt. % Fe203;
2 to 3 wt. % CaO;
0.5 to 1.0 wt. %TiO2;
1.2 to 1.5%MgO;
18 to 21 wt. %LOI;
(ii) blast furnace granulated slag as the gorging agent comprising
about 32.3 wt. % Si02;
about 23.2 wt. % Al203;
about 0.37 wt. % FeO;
about 31.9 wt. % CaO;
about 10.3 wt. %MgO;
about 0.04 wt. % MnO;
about 0.53 wt. % Sulphur;
about 0.85 wt. % TiO2;
about 0.448 wt. % K2O;
(iii) recycled fire clay grog; and
(iv) fresh plastic and non plastic/fresh clay (fire clays);
wherein said components of (i), (ii), (iii) and (iv) being mixed with 4 to 6 wt % of water.
2. Brick composition as claimed in claim 1 wherein said coal fly ash has high percentage particle size
<325 Sieve.
3. Brick composition as claimed in claim 1 wherein said blast furnace granulated slag has Basicity of
about 0.9%.
4. Brick composition as claimed in claim 1 wherein said blast furnace has Granulometry ranging from
1 to 4 mm.

5. Brick composition as claimed in claims 1 to 4 adapted to prepare low duty fire clay refractory brick,
IS: 6(medium duty) quality fire clay refractory brick and/or IS: 8 quality fire clay refractory bricks.
6. Brick composition as claimed in claim 5 wherein said low duty fire clay refractory brick has batch
composition comprising
upto 60% coal fly ash;
upto 20% blast furnace granulated slag;
upto 10 % fire clay grog;
upto 10 % fresh clay (fireclay); and
4 to 6 % water.
7. Brick composition as claimed in claims 5 and 6 having firing temperature ranging from 1150 to 1200
°C.
8. Brick composition as claimed in claims 5 and 6 having apparent porosity ranging from 17.5 to 20 %.
9. Brick composition as claimed in claims 5 and 6 having coal crushing strength ranging from 150 to
200 Kg/cm2.
10. Brick composition as claimed in claim 5 wherein said IS: 6(medium duty) quality fire clay refractory
brick has batch composition comprising
upto 50 % coal fly ash;
upto 30 % blast furnace granulated slag;
upto 10 % fire clay grog;
upto 10 % fresh clay (fireclay); and
4 to 6 % water.
11. Brick composition as claimed in claims 5 and 10 having firing temperature ranging from 1200 to
1280 °C.
12. Brick composition as claimed in claims 5 and 10 having apparent porosity ranging from 19 to 25 %.
13. Brick composition as claimed in claims 5 and 10 having refractoriness of more than 30.
14. Brick composition as claimed in claim 5 wherein said IS: 8 quality fire clay refractory bricks has
batch composition comprising
upto 60% coal fly ash;
upto 20% blast furnace granulated slag;
upto 10 % fire clay grog, upto 10 % fresh clay (fireclay); and

4 to 4.5 % along with 0.5 % mollesus water.
15. Brick composition as claimed in claims 5 and 14 having firing temperature ranging from 1300 to
1340 °C.
16. Brick composition as claimed in claims 5 and 14 having apparent porosity ranging from 27 to 30 %.
17. Brick composition as claimed in claims 5 and 14 having refractoriness of more ranging from 32.5 to
33 %.
18. A method of manufacturing environmental friendly fire clay refractory brick as described above
comprising steps of:
(i) selecting raw materials such that it comprises 60 to 70 wt. % of said coal fly ash, blast furnace
granulated slag; upto 30 % fire clay grog and fresh plastic and non-plastic fire clays;
(ii) mixing said raw materials with 4.5 to 5.5 % of water in a mixer/blending machine to get a
mixture;
(iii) moulding said mixture of step (ii) by putting the mixture in mould followed by ramming with
rammers to import compactness in the brick after which the said bricks were removed from the
mould;
(iv) air drying said bricks of step (iii) for about 24 hours in air;
(v) oven drying said bricks of step (iv) for removal of moisture from it and to ensure about 0.05 %
maximum moisture at a temperature of 110°C for 24 hours;
(vi) firing said bricks of step (v) for 24 hours at four different temperatures between 1150°C and
1320 °C for soaking purpose followed by slow cooling upto room temperature, and
(vii) inspection of said brick prepared in step (vi) for apparent porosity, cold crushing strength,
refractoriness, permanent line or change as per low duty ,IS :6, IS: 8 fire clay refractory bricks.
19. An environmental friendly fire clay refractory brick composition and method as herein substantially
described and illustrated with the accompanying figures.

The present invention relates to an environmental friendly fire clay refractory brick composition
especially adapted for the use in general purpose refractory applications having 25-40% alumina
(Al2O3) content. The composition comprises (i) coal fly ash as the main matrix comprising 45 to 51 wt.
% Si02; 22-30 wt. % AI203; 7.3 to 9.5 wt. % Fe203; 2 to 3 wt. % CaO; 0.5 to 1.0 wt. % TiO2; to 1.5 %
MgO; 18 to 21 wt. % LOI; (ii) blast furnace granulated slag as the gorging agent comprising about
32.3 wt. % Si02; about 23.2 wt. % Al203; about 0.37 wt. % FeO; about 31.9 wt. % CaO; about 10.3 wt.
% MgO; about 0.04 wt. % MnO; about 0.53 wt. % Sulphur; about 0.85 wt. % TiO2; about 0.448 wt. %
K2O; (iii) recycled fire clay grog; and (iv) fresh plastic and non plastic/fresh clay ( fire clays). The
components of (i), (ii), (iii) and (iv) are mixed with 4 to 6 wt % of water. The invention also relates to a
method of manufacturing environmental friendly fire clay refractory brick. The steps comprises of (i)
selecting raw materials such that it comprises 60 to 70 wt. % of said coal fly ash, blast furnace
granulated slag; upto 30 % fire clay grog and fresh plastic and non-plastic fire clays; (ii) mixing said
raw materials with 4.5 to 5.5 % of water in a mixer/blending machine to get a mixture; (iii) moulding
said mixture of step (ii) by putting the mixture in mould followed by ramming with rammers to import
compactness in the brick after which the said bricks were removed from the mould; (iv) air drying said
bricks of step (iii) for about 24 hours in air; (v) oven drying said bricks of step (iv) for removal of
moisture from it and to ensure about 0.05 % maximum moisture at a temperature of 110°C for 24
hours; (vi) firing said bricks of step (v) for 24 hours at four different temperatures between 1150°C
and 1320 °C for soaking purpose followed by slow cooling upto room temperature, and (vii) inspection
of said brick prepared in step (vi) for apparent porosity, cold crushing strength, refractoriness,
permanent line or change as per low duty ,IS :6, IS: 8 fire clay refractory bricks.