INSULATING REFRACTORY BRICK AND THE METHOD OF ITS MANUFACTURE
FIELD OF INVENTION
The present disclosure relates to a composition for the manufacture of insulating
refractory brick and a process of making such brick. More particularly, the present
disclosure is intended to use the waste materials of industry and wastes of fruits such
as coconut to cast refractory bricks used to form linings of vessels with improved
insulating value of such brick.
BACKGROUND OF THE INVENTION
Refractory brick are used, among other purposes, to form liners for vessels such as
rotary kilns, steel ladles, and other high temperature vessels. In some such brick,
insulation inserts are provided on the recessed cold face of the brick to improve the total
insulating efficiency. The inserts are generally manufactured from low density
compositions, such as ceramic fiberboard, which is an excellent insulator against heat
loss through conduction. However, it has been found that a relatively large quantity of
heat is radiated through the insulation insert. The radiation of such heat represents a
significant portion of the total heat transfer and has a profound effect on fuel
consumption.
The rapid increases in population in the world and the world economic growth have led
to an increase in demand for energy. Worldwide, coal reserves are the most stable and
available for fossil energy source. Utilization of coal as an energy source, however,
involves the generation of large amounts of waste material in the form of its arising
commonly known as fly ash. This is an alumina silicate material. It is estimated that
more than 300 billion tons of coal fly ash are produced annually worldwide and in our
country more than 120 million tons of coal ash is generated. Recycle rate of this ash is
very less, approximately 20-28%. That too, for construction industry for cement making,
house building brick making. This is used as landfills in many countries as main option.
This led to serious pollution (air, water and land pollution), and consequently socio-
economic problems. Another organic waste product is green coconut shell; disposal of
this is also a serious problem. Annual generation of waste green coconut shell is about
several thousand tones and at present this is purely used as landfill material only.
These enormous volumes of waste product such as coal fly ash and coconut shell,
because of their nature create disposal and environmental degradation problem can
potentially result into large scale pollution in all respects. The transport of waste product
such as fly ash to dumping sites and disposal result in increases of the cost of the final
manufactured product and thus has social and economic implications. It is of economic
and social importance to research the use of these wastes so as to develop new or
alternative applications to exploit them as raw materials for processing useful products
rather than dumping them where future inhabitant are at risk.
Refractory industry particularly the insulating refractory brick manufacturers make use
several thousands tones of traditional fireclay which comes out of mining operation from
the selected location of the earth in place of this major source for utilization or
application of fly ash, which is nothing but alumina silicate material. The chemical
composition of fly ash (Indian), the main inorganic waste in our research, lies in the
same AI2O3-S1O2 binary system as the fireclay currently used in refractories (Fig.1:
Al2O3-SiO2 binary phase diagram as applicable to refractories).
Mullite, an alumino silicate mineral, is a technologically attractive material for
refractories, due to its low thermal expansion and conductivity. Properties like chemical
inertness and excellent mechanical properties at elevated temp contribute to the
usefulness of mullite and alumino silicate minerals in applications like refractory
materials.
If minor oxides in the materials are ignored, the composition of the Indian fly ash lies in
the centre of the mullite area of the CaO-AI2O3-SiO2 ternary phase diagram (Fig.2
ternary phase diagram of the CaO-AbCb-SiCte system).
The performance of refractory materials mainly depends on the final phase diagram of
the combined raw materials and the amount of impurities present in the raw materials.
By carefully choosing the proportions of the mix, it is possible to design porous
refractory material from fly ash with green coconut shell that can be used as an
ingredient for the manufacturing of insulating refractories. More stringent measures for
special waste landfills, in combination with the emergency recycling philosophy, have
encouraged the policy of the three R's, which stand for recycle, reuse and reduce.
Coal fly ash, due to its mineralogical, physical and chemical composition and the
presence of some elements and compounds is an excellent substitutes to clay used for
insulating refractory brick making and green coconut shell is a best substitute of saw
dust.
Use of fly ash and green coconut shell as raw materials for insulating refractory brick
making has many advantages such as use of a zero value raw material (fly ash - due to
huge generation - available free of cost from coal based powder plants). Secondly, the
conservation of natural resources and finally the elimination of solid waste.
Now question arises, why so much importance to insulating bricks? Currently one of the
most important points for the industry is energy conservation; Therefore, there is an
increase in the use of insulating refractory bricks, made for different temperature
ranges, fully taking care of 'save energy' mission. They are used in the metallurgical
furnaces such as Reheating furnace, heaters, boilers, incinerators and almost in all kind
of furnaces in gas and petroleum industry, iron and steel related furnaces. The new
demand on the exploitation of unconventional material where material is not required to
be mined from the earth, does not disturb the ecology and environment, available at low
cost or at very nominal cost. Insulating refractory bricks:- conventionally refractory
insulating bricks are formed from clay mixed with saw dust or a polymer powder. The
saw dust or polymer powder is burnt away during the firing of the brick, thereby
rendering the brick porous and hence insulating. By the term refractory is meant the
ability to with stand high temperature of 800 °C or more, and upto 1400 °C. The term
insulation in this context or the present invention means a thermal conductivity of 1.0
w/mkat 1000 °C.
Existing process or conventional process of insulating brick making
Conventionally, refractory insulating bricks are often formed from clay mixed with saw
dust or a polymer powder. The saw dust or polymer powder is burnt away during the
firing of the brick, thereby rendering the brick porous and hence insulating.
By the "term refractory" is meant the ability to withstand high temperature for example
temp of 800 °C or more, preferably 1000 °C or more, most preferably 1400 °C or more.
The term insulating in this context or the present invention means a thermal conductivity
at 1000 °C of less than 1.0 w/mk.
The insulating bricks so made with fly ash and green coconut shell, in term of
technological characterization. The insulating bricks made with fly ash and green
coconut shell were seen at par with commercial insulation bricks, rather better, density
thermal conductivity, cold crushing strength, PB & AP revealed to be similar the
commercial products. Thus they are use of fly ash and coconut shell is economically
attractive and technically feasible.
In India major electricity needs (more than 70%) are being met by thermal power plants
and in the world as a whole, out of total electricity generated more than 50% is being
produce by thermal power plant and here coal is the major fuel. As stated above these
power plants generates huge amount of fly ash as waste product. In India alone more
than 120 MT fly ash is generated every year, out of this only 10-20% is utilized in some
area mainly in house construction industry and in cement industries. Balance of about
80-85% of fly ash so generated is returning towards to pit mine causing major
environmental problem. Therefore, a huge amount is available for utilization in
production of a product. As a consequence of this fact this fly ash of low commercial
value can be made as economically attractive.
FLY ASH : A definition and origin
The fly ash produced from the burning of pulverized coal in a coal fired boiler is a fine
grained powder, particulate material that is carried off in the flue gas and is usually
collected from the flue gas by electrostatic precipitators, bag houses or mechanical
collection devices such as cyclones. In general, there are three types of coal fired
furnaces used in the electric utility industry. They are, dry bottom boilers, wet bottom
boilers and cyclone furnaces. The most common type of coal burning furnace is the dry
bottom furnace.
Chemical composition and classification of coal fly ash
Fly ash material solidifies while suspended in the exhaust gases and is collected by
electrostatic precipitators or filter bags as stated above. The particles solidify while
suspended in the exhaust gases; Fly ash particles are generally spherical in shape and
range in size from 0.5Nm to 100Nm. They consist mostly of silicon dioxide (Si02)
present in two forms, amorphous which is round and smooth, crystalline, which is sharp,
pointed and hazardous aluminium oxide (AI2O3) and iron oxide (Fe2O3). Fly ash is
generally highly heterogeneous, consisting of a mixture of glassy particles with various
identifiable crystalline phases such as quartz, mullite and various iron oxides.
Fly ash also contains environmental toxins such as arsenic, barium, beryllium, boron,
cadmium, chromium, cobalt, copper, fluorine and many other such elements in ppm. As
per ASTM C 618, fly ash has been divided into two classes Class F and Class C. The
difference between these classes is the amount of calcium, silica, alumina and iron
content in the ash. The chemical properties of the fly ash are largely influenced by the
chemical content of the coal burned as shown in the table given below as Table No. 1.

Accordingly, it is an object of the invention to decrease the amount of heat transferred
through the refractory brick, to decrease the amount of fuel consumption, and to reduce
the shell temperature of the vessel.
SUMMARY OF THE INVENTION
Therefore it is one of the object of the present invention to work out the use of following
waste materials for the development of porous thermal refractory insulating bricks.
> Coal fly ash
> Green coconut shell
> Lime powder waste
The materials used in this work were employed in various compositions, finally to
achieve the properties of improved refractory insulating bricks.
Another object of the present invention is to develop a refractory insulating brick that
complies with the specifications of conventional refractory insulating bricks.
Another object of the present invention is to provide a developing process of bricks
manufacturing which is easy, economical fuel and environment friendly.
Another object of the present invention is to characterize the physical and chemical
properties of the refractory insulating bricks so manufactured from fly ash and the waste
green coconut shell.
Comparison of different mixtures to achieve a mix formulation with refractory insulating
properties.
Another object of the present invention is to provide a method for the manufacturing of
such refractory insulating bricks which are economical and further the production is
carried out in an economic manufacturing route.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1, illustrates the Al203-Si02 binary phase diagram applicable to refractory in
accordance with the present invention;
Fig 2, illustrates the ternery phase diagram of the CaO-AI203-Si02 system in
accordance with the present invention;
Fig 3, illustrates the brick sizes made from fly ash and waste green coconut shell in
accordance with the present invention.
DETAILED DESCRIPTION
The present disclosure covers all aspects of the use of coal fly ash and green coconut
shell (waste product) for manufacturing commercial and economically viable refractory
insulating bricks for application in industrial furnaces.
The main function of refractory insulating bricks is to save energy and obtain acceptable
furnace shell temperature. Insulating refractory bricks are normally used as a back lining
for the vessel. Thermally insulating refractories function by providing stagnant or "dead"
gas space i.e they contain large volume fractions of voids (low bulk density). The prime
criteria for refractory insulating bricks selection are refractoriness and dimensional
stability sufficient for application. The service temperature limit of an insulating
refractory brick relates to composition, sintering temperature and void volume. Two
reasons for interpolating an insulating layer between a hot working lining and the
"outside" of the vessel are:
1. To cool the back face e.g. to preserve the mechanical integrity of an
enclosing metal shell or for reason of safety outside a wall or roof.
2. To reduce the heat flux (thermal conductivity) through the lining and hence
improve process fuel economy.
The melting point of the various oxides present in an insulating refractory brick is the
first of several indicators to decide the behavior thermally, chemically and mechanically
at high temperatures of all the ternary oxide compounds that are possible. Only a few
have high melting points. A list of oxides that would be considered for industrial
refractories are listed in the Table as given below which include the melting point of
each substance and also gives the approximate tammann temperature. The melting
points will serve as a basis for considering the thermal stability of refractory mixtures.

The coal fly ash is the major source of oxides for the manufacturing of refractory
insulating bricks.
Existing Process & Practices of Refractory Insulating Brick Making
Insulating refractory bricks are made from variety of oxides, most commonly fire clay
which is known as calcined fireclay (30/42% AI2O3 and balance is Silica (SiCh) and
others). The desirable features of these bricks are their light weight and low thermal
conductivity, which usually result from a high degree of porosity. The high porosity of
the brick is created during manufacturing by adding a fine organic material to the mix,
such as saw dust. During firing, the organic addition bums out, creating internal pores.
Another process of making insulating refractory bricks in which high porosity is achieved
by the addition of a foaming agent to the slip. Using this process the insulating
refractory bricks are cast instead of dry pressed. Because of their high porosity,
refractory insulating bricks inherently have lower thermal conductivity and lower heat
capacity than other refractory materials.
Insulating refractories are used as back up lining materials and also used as lining in
furnaces where abrasion and wear by aggressive slag and molten metal are not a
concern. Refractory insulating bricks offer several distinct advantages:
• Decreased heat losses through the furnace lining and less heat loss to the main
refractory lining leads to saving in fuel cost.
• The insulating effect causes a more rapid heat up of the lining and lowers heat
capacity of the insulating refractory.
• Thinner furnace wall construction to obtain a desired thermal profile.
• Less furnace mass due to lower mass of the insulating refractory.
Generally, insulating refractory bricks are distinguished from light weight materials
because of a total porosity of 45 to 75%. Extremely lightweight materials have a porOSity
of 75 to 85% and ultra-lightweight, high temperature insulating refractories have a total
porosity greater than 85% with respect to application Insulating refractory bricks are
classified as follows:
Temperature resistant heat insulating materials for application temperature up to
800-850 "C, known as type III as per IS 2042-1972. Normally these classes of
refractory insulating bricks are called thermal insulating bricks and not refractory
products.
• Heat resistant refractory insulating bricks for application temperature upto 1250
°C, they are type II insulating bricks covered under IS 2042-1972.
• Refractory insulating bricks for application temperature up to 1500 °C, light
weight chamotte and kaolin bricks etc. These are known as type I as per IS
2042-1972.
• High refractory insulating bricks for application temperature up to 1700 °C, light
weight mullite and alumina bricks, light weight hollow sphere corundum castables
and bricks, special high refractory fibers.
• Ultra high refractory insulating materials for application temperature up to 2000
°C, zirconia, light weight bricks and fibers, non-oxide compounds carbon.
International standards classify high temperature insulating materials according to three
criteria. These are
• The bulk density and with it the porosity and indirectly the thermal conductivity as
well as heat capacity.
• The temperature (indicated as temperature limit for classification and application)
at which the product shows a linear shrinkage of 1 to 7% and hence volume
stability, taking into consideration the maximum application temperature.
The main material components, such as chamotte, silica, basic materials or
specials, sometimes crushing strength and thermal conductivity are included for
classifying refractory insulating bricks.
The present process of manufacturing general purpose insulating refractory bricks,
which can withstand up to a temperature range 850-1550 °C and based on calcined
refractory clay (chamotte) is as follows:

Shaping is done by cutting or grinding the above clots as per customer requirement.
The main raw material in above process is based on AI2O3, SiO2 and sometimes CaO
are also used. The "Burnout" process is applied to the production of this type of
insulating refractory bricks. Fine saw is used; this is to be burnt out. Normally burnt out
materials with low ash content are used in order to prevent negative effects on the hot
properties of the insulating refractory bricks. Some place petroleum coke, lignite
abrasion. Fine waste products of cellulose and paper board are also utilized as organic
materials to be burnt out.
The insulating refractory so manufactured from above process, which is most commonly
used at present, are generally classed into three varieties based all application
temperature and meeting the properties as shown in table as shown below.

Coal fly ash is a solid material extracted by electrostatic and mechanical means from
the flue gases of furnaces of thermal power plant fired with pulverized bituminous coal.
The coal ash, a ceramic material is essentially an aluminosilicate glass with inclusion of
mullite, spinel, quartz and lime. The properties of this caol fly ash are determined mainly
by its unique chemical and mineralogical composition. The primary components of
power plant coal fly ash are silica (SiO2), Alumina (AI2O3) and Iron Oxide (Fe2O3) with
varying amount of carbon, calcium (as lime), magnesium and sulphide (sulphides and
sulphates). These oxides so present in coal fly ash are it an idle raw material for
manufacturing of insulating refractory bricks in place of conventional calcined plastic fire
clay. The carbon so present in the fly ash is an extra advantages to act as fuel and the
upon firing it generates gas inside the brick and forms spherical voids, this helps in
getting excellent thermal insulating properties.
Main Raw Materials for this Invention
These were
1. Fly ash: Source of fly ash was captive power plant of No.1 of Rourkela Steel
Plant (SAIL) Rourkela. The physical and chemical properties of fly ash collected
from captive power plant No.1 of Rourkela Steel Plant (SAIL), India are as shown
in the tables as under: (This was collected directly from the storage hopper of the
Boilers - in dry condition)

2. Waste Green Coconut Shell: The waste green coconut shell were collected from
the market. These are the shell which people throw away after drinking water
from this.
3. Calcined Fire Clay: This was taken from the refractory material suppliers. The
range of AI2O3 content was kept 30^42%.
In order to make insulating refractory bricks, above mentioned fly ash was used as main
raw material in place of conventional calcined fire clay (plastic clay) and waste green
coconut shell's paste as 'burnt out' material in place of conventional saw dust. Some
amount of plastic vergin clay was also added to the above mixture. Entire range of type
I, type II & type III refractory insulating bricks can be made from above three items and
will meet the requirement of refractory insulating bricks as per IS 2042-1972.
In India, thermal power plants generate more coal fly ash than the other countries. It is
estimated that currently more than 126 MT of coal fly ash is generated every year in
India alone. Only a small amount of the total coal fly ash generated is utilized in making
bricks for construction industry or concrete building blocks or blending with cement. For
this reason it is of utmost importance to develop new applications and uses for coal fly
ash. One such new area is use of coal fly ash for manufacturing of refractory insulating
bricks for its morphological characteristics, physicochemical properties and pozzolanic
activity. Coal fly ash has potential for use in the production of refractory insulating bricks
in combination with clays and suitable "burnt out" material.
4. Waste Lime Power: This was collected from the acetylene plant, which is also a
waste product in the major steel plants.
In utilization of Coal Fly Ash (Dry one directly from the hopper of the boiler) in place of
calcined fire clay as main raw material, one new area has been created. Utilization of
waste green coconut shell in the paste form in place of conventional saw dust will
require less water for making the mixture for insulating refractory brick making as well.
The starch so present in the waste green coconut shell is enough to act as binder for
green strength that is another advantage of using waste green coconut shell.
Production method employed in the manufacturing of refractory insulating bricks
from coal fly ash and waste green coconut shell
Plastic forming, i.e extrusion and casting methods were used for manufacturing
refractory insulating bricks. Green coconut shell in the fine paste form from fibers was
the burning out additive. This on firing was burnt out and thereby increases the porosity
of the product. The process production steps were as follows:
Captive Power Plant ? dry coal fly ash from the hopper ? removal of any bigger size
particle and foreign material ? chemical analysis of fly ash ? mixing with known
quantity and quality calcined plastic clay ? mixing with ground fibers (paste form) waste
green coconut ? Initially dry mixing all above three items (fly ash + fire clay + green
coconut shell) ? mixing of the above with water so as to obtain a consistency of mud ?
pouring of the same into the mould / extrusion in hand extrusion machine in the clot /
brick form ? leaving it for 24 hrs ? removal of mould ? air drying for 24 hrs ? taking
out the product so obtained from the mould / extrusion machine into open sun rays for
48-60 hrs which means removal of maximum possible moisture by sun rays ? putting
the same in to heating oven at 110 "C for 24 hrs or checking the moisture with moisture
meter for no moisture or less than 0.5% ? shifting the bricks so produced for firing in
the furnace at a temperature of 1280 - 1340 °C for 3 to 4 days (for this purpose soaking
zone of the reheating furnace was used) ? slow cooling ? testing in the laboratory for
CCS, AP: BP, thermal conductivity and PLC ? recording the result and comparing the
same with the standard like IS 2042, type I, II & III.
Further as per one of the exemplary embodiment of the present invention the steps of
drying in sunlight, preheating for reducing moisture can be eliminated by controlled firing
of the bricks is a furnace at a temperature of 1280 - 1340 °C for 3 to 4 days.
Description of experimental process for development of refractory insulation
bricks from fly ash and waste green coconut shell
a) Raw Material
(i) Fly ash
(ii) Calcined plastic clay
(iii) Waste green coconut shell
(iv) Waste lime power
b) Mixture preparation
Fly ash about 60-85% + calcined plastic clay (32-42% Al203) 30-15% + 5-15% of
waste green coconut fibers in very fine from / paste form + 2 to 3% waste lime
powder.
c) Enough water was added to this in a pan for mixing so as to obtain moldable /
extrusionable mixture, water % varied from 20-30%.
d) This mixture was extruded using a hand extruder so as to get standard shape
bricks of (230x115x65mm) and some other shapes as shown in Fig 3, 4, 5.
e) Each brick sample was marked number as 1, 2, 3......and so on.
f) All the bricks were air dried in the sun rays. Thereafter they were dried overnight
at 110 "C in a drying oven.
g) 20 samples were then fired at 850-900 °C.
h) Another 20 samples were fired at 1000-1050 'C
i) Balance 20 samples were fired at 1150-1280 °C.
In all the cases temperature was same like 900 °C, 1050 "C, 1280 °C. Samples
were pushed into the temperature zones for 24 hrs. This to avoid forced firing
which means actual firing at respective temperature was started only after 24 hrs
(as the firing was done through the inspection and cleaning window of a
reheating furnace of the hot strip mill).
j) Firings of the samples were done for 30 hrs.
k\ After this, all the samples were taken out from the respective firing zones while
continuous slow cooling is taking place. The removal takes 10-12 hrs. This is to
avoid forced cooling.
I) After cooling visual impaction was done with respect to crack, warpage or any
kind of physical defect. No such abnormality was seen.
r;;vu;vu; rrc^srims of Refractory insulating Bricks manufactured with Fly Ash
The physical properties of the refractory insulating bricks/samples so manufactured
from coai fly ash and waste green coconut sheii were determined as per the IS 2042-
1372 (Indian Standard insulation). The samples of bricks so made were tired in three
different temperature range i.e 900 "C, 1050 C 1250 =C, the physical properties ot
these were determined separately for, cold crushing strength in Kg/cm2, bulk density
(gni/cc), apparent porosity (%), permanent change after heating for 24 hrs at different
temperature of application, pyromeiic cone equivalent (standard pyromeilc cone, ASTM
No.). The testing was done at the Refractory Testing Section of Research « Control
Laboratory of Rourkeia Steel Plant (SAIL), Rourkela.
For all the three cases, thermal conductivity was also tested. The results are
summarized below in the Table No.A, B C.
Discussion on physical properties obtained on refractory insulating bricks from
coal fly ash and waste green coconut shell
The aim of this work was to produce refractory insulating bricks mainly from coal fly ash
as same is available without any coast and by utilizing the bulk of such unused material
accumulated on the mother earth. The chemical composition of the coal fly ash from
power plants used in this work is given above in Table No.1 & 5. The basic ingredients
of fly ash, silica (51 %) and Alumina (>30%) indicates fair refractoriness. This gives an
indication that the fly ash of Rourkela Steel Plant's Captive Power Plant No.1 can be
used at relatively high temperature before reaching its melting point. Therefore coal fly
ash was considered as the main ingredients of the body composition for the refractory
insulating brick product. The new combustible organic matter i.e waste green coconut
shell in the fine paste form (fiber paste) was introduced in place of conventional saw
dust had resulted in higher porosity after burn out, and resulted in porous refractory
insulating product. And this porosity had resulted in lower bulk density, which ultimately
resulted in lowering down the thermal conductivity of the product resulting into a thermal
insulating refractory brick.
The product developed from coal fly ash and waste green coconut shell reveals physical
properties almost similar to traditionally made refractory insulating brick as shown in
Table No.A, B & C. Thus the specific objective of making refractory insulating brick has
been successfully achieved.
5. Salient features of the innovation
• New area for increasing use of coal fly ash.
• Elimination of use of saw dust.
• Utilization of waste green coconut shell in place of saw dust.
• Cheapest way of manufacturing / production of refractory insulating bricks.
• Environment friendly process as waste product is converted in to productive
use.
• Solving disposal problem of coal fly ash and waste green coconut shells.
• Creating new market for coal fly ash.
• Less fuel requirement for producing refractory insulating bricks made from fly
ash as compared to convention refractory insulating bricks made from plastic
fire clay.
6. Usefulness of the Innovation
a. Technological
(i) The chemical composition of the fly ash is suitable for making refractory
insulating bricks as the relative high silica and alumina (>30%) content
indicates fair refractoriness.
(ii) Product so made with coal fly ash and waste green coconut shell has
shown equally good refractory properties even better than conventional
one w.r.t to strength and bulk density.
(iii)These products can replace conventional refractory insulating bricks
from all the related application fields.
As such product is technically suitable for lining of metallurgical and other
furnaces.
B. Economic
(i) Saving of production cost as no expensive mining and milling operation
are necessary in the utilization of coal fly ash (dry - directly from
hoppers of boilers of thermal power plants) as main raw material for
the production of refractory insulating bricks.
(ii) Use of low cost material i.e waste material like green coconut shell in
place of saw dust.
(iii)Conservation of natural resources by finding new application (refractory
insulating bricks) for fly ash instead of natural mineral.
(iv)Due to inherent quality of coal fly ash (carbon content in the form of
unburnt coal is more than 12%). The requirement of fuel for making
refractory insulating brick will be less. Thus overall product cost will be
very less as compared to conventional refractory insulating bricks.
C. Impact in Industry
> The refractory insulating refractory makers will be free in respect of
acquiring mining lease, cost of mining operation etc.
> New refractory insulating bricks making units can be opened near the
power plants so that the fly ash will be available at no cost.
> To user industry, refractory insulating bricks can be made available at
low cost and thereby will reduce their installation cost.
D. Advancement of knowledge and science
> Because of higher silica & alumina content in the fly ash, it is possible
to make higher quality of refractory insulating bricks and other
refractory products by careful calculation of a mix. Necessary oxides
can be introduced into this.
> Utilization of solid waste such as coal fly ash and waste green coconut
shells.
Highlight of the Inventive Step
• The chemical composition of the fly ash indicates fair refractoriness. This gives
an indication that the Rourkela Steel Plant's Captive Power Plant No.1, fly ash
can be used at relatively high temperature before reaching its melting point. As
such, suitable for making refractory insulating bricks in place of conventional
plastic clay.
The basic properties of saw dust and green coconut shell are same, as such the
green coconut shells in the ground paste form can be used as burn out material
for creating pores in the refractory brick matrix and making the brick thermally
insulative.
• The outcome of this innovation offers an insulating refractory brick to be used in
application up to 1500 °C.
• The innovation focused on the utilization of coal fly ash and other waste (green
coconut shell) as raw material to develop cost effective and production friendly
procedure for production of refractory insulating bricks by casting / extrusion
process.
• The properties of the newly developed refractory insulating brick are comparable
to traditionally manufactured refractory insulating bricks.
• The process is economical as the major raw materials are waste materials. The
use of these materials further helps to resolve the problem of waste disposal and
benefit the environment.
• This developed refractory insulation bricks comply with the specification of IS
2042-1972 (Table No.3) laid down for insulation refractory bricks.
• Refractory insulating bricks so developed with coal fly ash and waste green
coconut shells are very good product which avoids the waste disposal problem,
helps environment upgradation efforts and the bricks so developed are very
much useful.
• Process demonstrate, that refractory insulation bricks with coal fly ash and waste
green coconut shell, do not requires any extra equipments or investment. These
can be manufactured with existing set ups.
Thus we can say that the successfully developed refractory insulation brick from coal fly
ash and waste green coconut shells can adequately replace fire clay + saw dust based
refractory insulation bricks in high temperature application furnaces / vessels used in
industry. The newly developed product is cost effective, manufacturing can easily be
automated.
Although the foregoing description of the present invention has been shown and
described with reference to particular embodiments and applications thereof, it has
been presented for purposes of illustration and description and is not intended to be
exhaustive or to limit the invention to the particular embodiments and applications
disclosed. It will be apparent to those having ordinary skill in the art that a number of
changes, modifications, variations, or alterations to the invention as described herein
may be made, none of which depart from the spirit or scope of the present invention.
The particular embodiments and applications were chosen and described to provide the
best illustration of the principles of the invention and its practical application to thereby
enable one of ordinary skill, in the art to utilize the invention in various embodiments and
with various modifications as are suited to the particular use contemplated. All such
changes, modifications, variations, and alterations should therefore be seen as being
within the scope of the present invention as determined by the appended claims when
interpreted in accordance with the breadth to which they are fairly, legally, and equitably
entitled.
We Claim
1. An insulating refractory brick comprising a mixture of:
fly ash about 60-85%, calcined plastic clay 30-15%, waste green coconut fibers in very
fine from / paste form 5-15%, waste lime powder 2 to 3% and water is added so as to
obtain moldable / extrusionable mixture wherein quantity of water is varied from 20-
30%.
2. An insulating refractory brick as claimed in claim 1, wherein the fly ash comprises
essentially of Si02 (45-51%), Al2O3 (22-30%), Fe2O3 (7.3-9.5%), CaO (2-3%), Ti02 (0.5-
1.0%), MgO (1.1-1.5%) and LOI (Carbon) (18-21%)
3. An insulating refractory brick as claimed in claim 1, wherein the calcined plastic
day contains 32-42% of Al2O3.
4. A method for manufacturing insulating refractory bricks comprising the steps of:
dry mixing fly ash, calcined plastic clay, waste green coconut fibers in very fine
from/paste and waste lime powder;
adding water to the said mixture so as to obtain moldable / extrusionable mixture;
pouring the mixture in the mould / extrusion machine in the clot / brick form;
leaving the mixture in the mould for 24 hours;
removing the mould followed by air drying for 24 hours;
drying the brick in open sun light for 48-60 hours;
heating the dried bricks in a pre heated oven at 110°C for 24 hours;
checking the moisture in the bricks with a moisture meter;
firing the bricks in a furnace at temperature 1280 - 1340 °C for 3 to 4 days;
slow cooling is carried out for the fired bricks
5. A method for manufacturing insulating refractory bricks as claimed in claim 4
wherein the mixture comprises of Fly ash about 60-85%, calcined plastic clay 30-15%,
waste green coconut fibers in very fine from / paste form 5-15%, waste lime powder 2 to
3% and the quantity of water is varied from 20-30%.
6. A method for manufacturing insulating refractory bricks as claimed in claim 4
wherein the allowance of moisture content in the bricks after heating in a preheated
oven at 110°C is 0.5%.
7. A method for manufacturing insulating refractory bricks as claimed in claim 4
wherein firing of the bricks is carried out in the soaking zone of reheating furnace is
used.
8. A method for manufacturing insulating refractory bricks as claimed in claim 4
wherein
the slow cooling is carried by air cooling.
9. A method for manufacturing insulating refractory bricks comprising the steps of:
dry mixing fly ash, calcined plastic clay, waste green coconut fibers in very fine from /
paste and waste lime powder;
adding water to the said mixture so as to obtain moldable / extrusionable mixture;
pouring the mixture in the mould / extrusion machine in the clot / brick form;
leaving the mixture in the mould for 24 hours;
removing the mould followed by air drying for 24 hours;
firing the bricks in a furnace at temperature 1280 - 1340 °C for 3 to 4 days;
slow cooling is carried out for the fired bricks
10. A method for manufacturing insulating refractory bricks as claimed in any of the
preceding claims wherein the bricks conform to IS 2042-1972.

The present disclosure relates to an insulating refractory brick comprising a mixture of
fly ash about 60-85%, calcined plastic clay 30-15%, waste green coconut fibers in very
fine from / paste form 5-15%, waste lime powder 2 to 3% and water is added so as to
obtain moldable / extrusionable mixture wherein quantity of water is varied from 20-
30%, and method of manufacturing the same.