A fire brick is a special type of brick made using fire clay and has a good resistance against high temperatures which are used in kilns, lining furnaces, fireplaces and fireboxes. These bricks are manufactured in a way similar to that of normal bricks, except during the burning process- Fire bricks are exposed to very high temperatures.
(ফায়ার ইট একটি বিশেষ ধরণের ইট যা ফায়ার
ক্লে ব্যবহার করে তৈরি করা হয় এবং এটি উচ্চ তাপমাত্রার বিরুদ্ধে ভাল প্রতিরোধ
করে থাকে যা কিল্ন, আস্তরণের চুল্লি, ফায়ারপ্লেস এবং ফায়ারবক্সে ব্যবহৃত হয়। জ্বলন্ত প্রক্রিয়া চলাকালীন এই ইটগুলি সাধারণ ইটের মতো একইভাবে তৈরি করা হয় , ফায়ার ইটগুলি খুব উচ্চ তাপমাত্রার সংস্পর্শে আসে।)
Fire clay
for Making Fire Bricks
Fire clay is used to make fire
bricks and is generally found under the coal seams. Fire clay contains two
major constituents- silica and alumina,
of which, the silica percentage varies from 60 to 70% and alumina varies from 25 to 35%.
Some other constituents such as
oxides of calcium, magnesium, iron, potassium and titanium are also present in
fireclay. However, the percentage of constituents other than silica and alumina
does not exceed 5% in the case of
good fire clay.
Fire clay
can be classified into three types based on its fire resisting capacity :
1.
High-grade fire clays
2.
Medium-grade fire clays
3.
Low-grade fire clays
Fire resistance
capacities of different fire clays are tabulated below.
1.
High
Duty. (1482 to 1648 Centigrade).
2.
Medium
Duty ( 1315 to 1481 Centigrade)
3.
Low
Duty (870 to 1314 Centigrade)
Size of
Fire Bricks
There are two standard sizes of fire-brick;
one is 9 in × 4 1⁄2 in × 3 in (229 mm × 114 mm
× 76 mm) and the other
is 9 in × 4 1⁄2 in × 2 1⁄2 in (229 mm × 114 mm × 64 mm).
Also available are
firebrick “splits” which are half the
thickness and are often used to line wood stoves and fireplace inserts. The
dimensions of a split are usually 9 in × 4 1⁄2 in × 1 1⁄4 in (229 mm × 114 mm × 32 mm). Fire brick was first
invented in 1822 by William
Weston Young in the Neath
Valley of Wales.
Properties
of Fire Bricks
They are yellowish white or white in color.
They are available in different sizes ranging from 9 X 4.5 X
2.5 inches to 9 X 2.75 X 2.25 inches.
One general fire brick weighs about 30 to 35 N.
The compressive strength of fire bricks ranges from 200 to
220 Kg/cm2.
The percentage of water absorption varies from 5 to 10%.
They have good chemical resistance.
Properties Of Fire Brick For Sale
|
Chemical Properties
|
Physical Properties
|
|
· High
temperature resistance
· Slag erosion resistance
· Thermal conductivity
|
· Wear resistance
· Shock resistance
|
Types of Fire Bricks
Fire
bricks are classified majorly into three types :
1. Acidic fire bricks
2. Basic fire bricks
3. Neutral fire bricks
1. Acidic Fire Bricks
Acidic Fire
brick, also called as acid resistant brick is used especially to
resist acidic actions of chemicals or weather.
Generally,
normal fire brick made of natural fire clay is as good as acid brick, but if
more acid resistance is needed then an additional amount of silica is added to
fire clay which may range up to 97% of its composition. For binding purposes, 1
to 2% lime may be added. Acid bricks are burnt at heavy temperatures for long periods.
2. Basic Fire Bricks
These are
good at corrosion resistance and chemical resistance. They
contain high amount of magnesia and here also lime is used as a
binding material. Different basic fire bricks available are Magnesite bricks,
Magnesia-carbon, magnesia-chrome bricks etc.
3. Neutral Fire Bricks
These are
good for both acidic and basic lining purposes. They offer good resistance
against acidic fumes as well as corrosive actions. Neutral bricks are of two
types namely- high alumina bricks and chromite bricks.
High alumina
bricks contain alumina in large amounts while chromite bricks contain chromium,
iron oxide, silica, bauxite, and iron ore in various proportions.
Uses of Fire Bricks
Fire
bricks are used for the following purposes.
- These
are used for Inner surface lining of kilns, furnaces, chimneys etc.
- To
build fire-resistant structures thereby reducing the damage of the
structure against fire accidents.
- For
inner lining of wood-fired ovens.
- As an insulating material for
furnaces, ovens because of their lower thermal conductivity.
Manufacturing Process of
Lightweight High Alumina Brick
Foam Method
1. Adopt heavy high aluminium bauxite abrasive powder with about 55% Al2O3 content and binding clay fines with about 31~32% Al2O3 content as the raw materials. The proportion of bauxite chamotte and binding clay fines is 9:1. Add 48~50% water into ball mill and grind for 1~2 hours. Mud all go through the 0.2mm sieve. Specific gravity of slip is 1.7~1.9, ph value is 7.
2. Adopt sodium abietate to make foaming agent. Sodium abietate foaming agent is made of rosin and alkaline saponification by adding stabilizer osseocolla liquor.
3. Firstly dissolve 322g caustic soda into 2L water and make caustic soda liquor with 14.4% density and 1.16 proportion. Add rosin with lower 5mm particle size into the boiling caustic soda liquor according to proportion and boil for 1~2 hours.
4. Adopt white animals bone glue or hyaline bone glue. The proportion of bone glue and water is 1:1. Boil bone glue for 5~10 min at 5℃.
5. Pour bone glue that is heat uo to 40℃ into the rosin soap slowly and make foam with frothing machine for 5~10min. Prepare mud in the blender. Put mud, aluminium potassium sulfate liquor and sulphite cellulose sulfite lye into blender for 1~2min mixing according to the proportion of design. Add foaming agent for 5~10min mixing. Make all kinds of lightweight high alumina bricks with 0.4~0.8 bulk density through controlling the different specific gravity of slip.
6. Pouring lightweight high alumina brick on the steel plate placed under the porous aluminium mold. Pad 5~6 layer papers for the lining of mold. Pour the molded mud into the mold slowly till full. Shock for structure balance and reduce the cracking.
7. Demould the green body after 24 hours drying under the temperature of 35~45℃. Moisture of green body will be lower than 1% after 7 days, and then put the green body into the kiln for firing at the temperature of 1300~1340℃.
8. The physical and chemical indicators of brand 0.4 foaming lightweight high alumina bricks as follows: 0.4g/cm3 bulk density, 0.7~1.5Mpa cold crushing strength, -0.1% reheating linear shrink, 1770℃ refractoriness, 52% Al2O3 and 33.3% FAe2O3.
9. Manufacture lightweight high alumina bricks with different bulk density which is mainly depend on the proportion of mud. Meantime, it also affected by foaming agent stability and sintering temperature. Better foaming agent stability, the proportion of fire brick will be lower. Higher sintering temperature, the shrink of fire bricks will be lager and bulk density will be higher. So, it is the key point to produce quality lightweight high alumina fire bricks according to adopt different raw materials, make sure the sintering temperature for exactly and prepare pug with good stability.
Inclusion of Combustible Materials
1. Use the method of adding combustible materials into the pug to make the lightweight fire brick with 0.8 density. There are saw powder, rice hull, coke blacking and anthracite that can be chosen as the combustible materials. Require that the combustible materials should be easy burning up and contain low ash content and low detrimental impurity. Generally adopt 30~40% content of saw powder and rice hull. Saw powder need to be sieved. Grind rice hull and bauxite. Add pug and combustible materials into the wet pan mill for 4~5min mixing, or make into clay lath through screw extruder. Moisture of clay is about 40~50%.
2. The clay through mulling can be shaped in the wooden pattern. Wet the wooden pattern with water, coat with saw powder, then enclose clay and demould after slicking. The green body will be fired in the required temperature after drying.