An overview of the major types of insulating firebrick

Insulating Firebrick (IFB) also named thermal #insulation brick or lightweight #insulating #brick, is a kind of shaped refractory product with an application temperature greater than 600°C and a total porosity greater than 45%.

Insulating firebricks are mainly used for different kinds of #furnaces, #kilns, #stoves, #ovens, or reactors. Further fields of application include hot blast stoves, ceramics tunnel kilns, heat treatment furnaces as well as petrochemical plants such as reformers/cracker furnaces or carbon black reactors.

Light-weight & low thermal conductivity

Compared with dense refractory bricks, the insulating firebricks have a lower density and a lower thermal conductivity. It is a kind of energy-saving refractory material that can thinner the furnace lining, reduce furnace weight and decrease energy consumption.

Typically, the insulating firebricks have a density between 0.4g/cm3 to 1.5g/cm3. The low density is original from the big proportion of porosity inside. Due to the high porosity composition, the bricks have a lower thermal conductivity. The thermal conductivity is defined by the total porosity as well as pore shape and pore size distribution.

Normally, the porosity is produced by burnout materials and water. Burnout materials are e.g. Sawdust, plastic ball, coke, rice husk ash, or cellulose. Producers also choose the foaming method to create porosity by adding the chemical additive. The lightweight raw material e.g. perlite, diatomite, floating beads, recycled grog, are chosen in the hope of reducing finished brick density also.

Types of Insulating Firebrick

Insulating firebricks are classified according to ASTM C155, EN 1094-2, ISO 2245, JIS R2611, or GB/T 35845. It can also be classified according to different raw materials & main crystal phases such as fireclay, high alumina, diatomite, silica, mullite, bubble alumina, corundum, zirconia, perlite, sillimanite, anorthite, etc.

Below introduce some widely used insulating firebricks:

??Bubble Alumina Brick

Also named alumina hollow ball brick or ASTM 33/34 grade insulating firebricks, the main raw material is electro-fused alumina hollow ball, density is between 1.2g/cm3 to 1.8g/cm3, vibration or press to shape, sinter temperature over 1700°C.

Bubble alumina brick can be used in oxide or reducing furnace atmosphere, max service temperature can be up to 1850°C. Lower Al2O3 content bubble alumina bricks are more suitable for intermittent furnaces due to it is good thermal shock resistance ability. High purity bubble alumina brick with over 99% Al2O3 is suitable for reducing atmosphere furnaces.

?? ASTM C155 standard Insulating firebrick

It is a group of insulating firebricks with well-known grades 23, 26, 28, 30, 32. There are also 16, 20, 25, and 27 grades.

The grouping results from the classification temperature and the density of the insulating firebricks. Insulating firebrick of a certain class may not exceed a defined density and may not exceed a shrinkage of 2% after firing for 24 hours.

The raw materials of this group of insulating firebricks are based on Al2O3, SiO2, and CaO. CaO is typically used for anorthite insulating firebrick only. Raw materials are fireclay, calcined kaolin, kyanite, mullite, sillimanite, andalusite, alumina, etc.

Most bricks choose extrusion or casting method to shape, there is also press or foaming method, Bricks need cut & grind into sizes, which can reach accurate dimension tolerance with +/-1mm. Press to shape brick have a bigger tolerance compared with others, but the brick strength is good while thermal conductivity is lower when compared with same density brick.

Press to shape bricks no need to grind after sinter, which can realize automatic production easily while saving energy cost, labor cost. Unfortunately, most manufacturers now choose grind to shape methods now, they need to pay more research on press production shaping methods to reduce environmental problems.

?? JIS R2611 standard Insulating firebrick

Japan JIS R2611 standard classified the brick into A, B, C groups.

A group brick is lightweight, thermal insulation is high, but the strength is a bit lower.

B group brick density is a little higher, combining intensity and thermal insulation.

C group bricks have a higher density & strength, which is used for the place where the load is required.

Other variants insulating firebrick based on JIS R2611 standard are classified by specific application working environment.

?? ISO 2245 standard Insulating Firebrick

According to ISO 2245 standard, the shaped insulating firebrick are subdivided into groups according to:

a)?the temperature at which the permanent change in dimensions, determined in accordance with ISO 2477, is 2 % or less (see Table 1);

b)?the bulk density, rounded to two decimal places, determined in accordance with ISO 5016, to distinguish Class L products from those with the same grouping according to a), but with a higher porosity. Products with average bulk densities equal to or below that given in Table 2 shall be designated as Class L.

A shaped insulating firebrick shall be designated by:

a) a reference to this International Standard;

b) the group to which it belongs;

c) an indication of its bulk density;

d) the fact that it belongs to class L (where applicable).

EXAMPLE 1

Shaped insulating product in accordance with ISO 2245, group to which it belongs (120), bulk density (0,8):

ISO 2245-120-0,8

EXAMPLE 2

Shaped insulating product by ISO 2245, group to which it belongs (140), bulk density (1,2):

ISO 2245-140-1,2

??Silica Insulating Firebrick

Silica insulating firebrick is a kind of acid refractory brick, which has high refractoriness under load and great thermal stability. The working temperature is between 1220-1550oC.

Silica insulating firebrick is normally used as backup insulation of dense silica bricks e.g. glass furnace melter crown insulation, hot blast stove dome insulation, etc

The bricks typical density is 1.2g/cm3, 1.0g/cm3, 0.8g/cm3 & 0.6g/cm3. Normally is pressed to shape, except 0.6g/cm3 density which is extrusion to shape, sintered in a tunnel kiln. The brick is easy to occur crack defects during production, a proper sinter temperature & holding time can reduce cracks.

Silica insulating firebricks easily occur corner broken during handling, a proper handling procedure & safe suitable packing should be conducted.

??High Alumina Insulating Firebrick

High alumina insulating firebrick choose bauxite as the main raw material with Fe2O3 over 48%, extrusion or press to shape, sintered by pusher slab or kiln car tunnel kiln. Due to high Fe2O3 & TiO2 content, the brick appearance color is changeable from dark yellowish to off-white. Due to high Fe2O3 content, the brick cold crushing strength is higher.

High alumina insulating firebrick can be used at temperatures between 1000°C to 1300°C. Density is 0.6g/cm3 to 1.2g/cm3 normally. It is an economic choice for medium-temperature furnace insulation.

??Fireclay Insulating Firebrick

Fireclay insulating firebrick choose fireclay and perlite as main raw material with Al2O3 30% to 46%, press to shape, sinter in pusher slab kiln. Brick density is ranging from 0.4g/cm3 to 1.5g/cm3. Normal grade brick max service temperature is 900°C to 950°C. When changing raw material proportion, the max service temperature can reach 1200°C.

Fireclay insulating firebrick is an economic choice for furnace low-temperature insulation such as aluminum smelter, coke oven, blast furnace, anode baking furnace, etc.

??Diatomite Insulating Firebrick

Diatomite insulating firebrick is manufactured with natural porous raw materials diatomaceous earth, with low thermal conductivity. The bricks are used as backup insulation of CFB, coke oven, etc. The typical density in China is 0.7g/cm3 with a max service temperature of 900°C.

Summary

Insulating firebricks are used as industrial #furnaces hot face or backup insulation. The bricks are #energy-saving material, chosen suitable quality insulating firebrick to have the advantages such as reduce fuel consumption, keep stable furnace temperature, extend furnace lifespan, etc. Compared with dense refractories, the insulating firebricks cost is much lower, thus many furnace owners pay less attention to it, which is a very costly mistake under furnace long-period operation.

One furnace needs different kinds & different grades of insulation materials which is quite a complicated job on material selection. We suggest you choose one professional insulation refractory supplier to realize your furnace insulation.

For more information about our insulation #refractory, drop your message here or email [email protected] to see how we can help you on reducing costs without quality concession.

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