Refractory Bricks: Types, Uses, and Pros and Cons

Refractory Bricks

Refractory Bricks are also known as Fire Brick. Refractory bricks are created by the dry-press, stiff-mud, soft-mud casting, and hot-pressing procedures utilized in the manufacture of building bricks.

Various materials, including magnesite and dolomite, require firing in rotary kilns to carry about sintering and densification before the crushed and sized material can be composed into refractory shapes and refired.

Refractory material consisting of nonmetallic minerals created in a variety of shapes for usage at high temperatures, particularly in structures for metallurgical undertakings and glass manufacturing.

What Are Refractory Bricks?

Refractory bricks are a block of refractory ceramic substance utilized in lining furnaces, kilns & Fireboxes. This brick is composed generally to withstand great temperatures, but will also usually have a low thermal conductivity for great energy efficiency.

Fire bricks can maintain excessive heat without melting or fusion. Fire brick usually includes silicon dioxide and aluminum oxide. The procedure involved in generating fire bricks is baking at a high temperature to obtain the desired result.

Generally, dense types of fire bricks are used in applications with extreme mechanical, chemical, or thermal stresses, like inside of a wood-fired kiln or a furnace, which is liable to abrasion from wood, fluxing from ash or slag, and great temperatures.

Read More: Fly Ash Bricks – Its Properties, Uses, Size, & Comparison With Red Clay Bricks

Types Of Refractory Bricks

There are generally three varieties of fire brick;

1. Acid Fire Bricks

• Ordinary Refractory Bricks
• Silica Bricks
• Ganister Bricks

2. Basic Refractory Bricks

• Magnesite Bricks
• Dolomite Bricks
• Bauxite Bricks

3. Neutral Refractory Bricks

• Chromite Bricks
• Carborundum
• Chrome Magnesite Bricks
• Spinal Bricks
• Forsterite Bricks

A brief description of these fire brick types is given below:

1. Acid Refractory Bricks

Acidic fire brick also called acid-resistant brick is utilized particularly to resist the acidic actions of chemicals or weather.

Mostly, normal refractory brick created from natural fire clay is as good as acid brick, but if additional acid resistance is required then an additional amount of silica is added to on fire clay which may range up to 97% of its composition.

For binding bases, 1 to 2% lime may be added. Acid bricks are burnt at large temperatures for lengthy periods.

2. Ordinary Refractory Bricks:

• The ordinary fire brick is generated from natural fire clay with a
• mixture of sand and crushed clay.
• It comprises 50-75% silica and 20-40% alumina with a fluxing matter below 10%.
• It can be utilized as good quality acid refractory lining to furnaces.
• It resists up to 1600℃.

3. Silica Bricks:

• Silica Brick contains 95% silica.
• It produced from sandstone or quartzite with an addition of 2-3% of lime to act as a bind substance and flux.
• It is favorable for the acid lining of furnaces for manufacturing glass for the walls and arches of basic open-hearth steel furnaces copper melting furnaces.
• It resists up to 2000℃.

4. Ganister Bricks:

• Ganister Bricks are generated from the siliceous category of ganister rock. This rock includes 85% of silica and 10% clay with an addition of 2% like.
• The brick is very tough, compact, and rigid at a great temperature of 2100℃.

2. Basic Refractory Bricks

These bricks are favorable for corrosion resistance and chemical resistance. They include a huge amount of magnesia and here also lime is utilized as a binding material. Various basic fire bricks usable are Magnesite bricks, Magnesia-carbon, magnesia-chrome bricks, etc.

Magnesite Bricks:

• Magnesite brick is generated from fire clay comprising 85% of magnesium oxide,3-5% iron oxide, and a balance of lime and alumina.
• This brick is utilized as the essential lining of furnaces.
• It resists up to 1800℃ – 2100℃.

Dolomite Bricks:

• The Dolomite brick is produced from fire clay including a high percentage of dolomite.
• It is a cheap substitute for magnesia bricks in furnace lining. Serpentine is utilized to enhance their strength.
• It resists temperatures up to 1400℃ – 1600℃.

Bauxite Bricks:

• Bauxite Bricks can be produced from fire clay including 86% Bauxite.
• It resists up to 1600℃.

3. Neutral Refractory Bricks

These are favorable for both acidic and basic lining purposes. They give good resistance against acidic fumes as well as corrosive actions. Neutral bricks are of two varieties namely high alumina bricks and chromite bricks.

High alumina bricks include alumina in huge amounts while chromite bricks include chromium, iron oxide, silica, bauxite, and iron ore in different proportions.

They are utilized to segregate the acid and basic linings of a furnace so that they cannot react with each other. They are not extremely significant as they are not utilized for fire-resisting purposes.

Chromite Bricks:

• Chromite brick is prepared from fire clay comprising 50% of chrome iron ore, 30% iron oxide (Ferrous oxide), and 20% bauxite with tiny silica.
• It resists temperatures up to 2000℃.

Carborundum:

• Carborundum is a unique variety of natural refractory bricks.
• It can be made from fire clay including a greater percentage of silicon carbide.
• It is used in electric furnaces.
• It resists temperatures up to 1900℃.

Chrome Magnesite Bricks:

Chrome Magnesite Brick is created from a mixture of chrome and magnesite.

Spinal Bricks:

• Spinal bricks are produced from a mixture of alumina and magnesia taken in comparable proportions.

Forsterite Bricks:

• Forsterite bricks are produced from magnesium silicone oxide mineral ( 2MgO SiO2).

Read More: 30+ Types of Bricks used in Construction

Uses Of Refractory Brick

Uses of Refractory Bricks are as follows

• Refractory Bricks are utilized for lining the inner floor of kilns, furnaces, chimneys, and various others.
• To construct fire-resistant structures in order to decrease structural defects to fire accidents.
• For the inner lining of an oven created from wood.
• As an insulating element for furnaces, ovens because of their lower thermal conductivity.

Properties Of Refractory Bricks

Properties Of fire refractory or fire bricks are listed below;

• Refractory Bricks are yellowish-white or white in color.
• They are available in various sizes ranging from 9 X 4.5 X 2.5 inches to 9 X 2.75 X 2.25 inches.
• One common fire brick weighs nearly 30 to 35 N.
• The compressive strength of fire brick ranges from 200 to 220 Kg/cm².
• The percentage of moisture absorption varies from 5 to 10%.
• They have decent chemical resistance.
• It can be better wear resistance.
• Thermal Conductivity – The unit temperature gradient situations, through the material per unit area of the heat flow rate, with the porosity.
• The impact resistance of brick is decent, big service life.
• At increased temperatures to resist the role of slag erosion and not be demolished.

Refractory Brick Production Process

• The production procedure of a refractory brick is divided into the raw material selection, calcining, forming, crushing, batching, mixing, placing material, molding, drying, burning, assessment and packing.
• The rate of refractory brick and raw material price, physical and chemical index, and production procedure is quickly specified.
• Raw material choice, beneficiation, and purification, High purity raw materials are the premise for producing high-quality refractories.
• Natural mineral materials usually comprise lean ore and rich ore, with unequal composition and large-quality variations, sometimes directly usage of refractories will cause problems and weak quality, even can not be utilized, therefore, mineral processing, enrichment, and category are essential.
• Calcining, except for some raw materials, most of the raw materials utilized as refractory aggregate must be calcined at great temperatures.
• A series of physical and chemical reactions are generated when the raw material is calcined, which plays a vital role in enhancing the composition, increasing mineral composition and structure of the refractories, and assuring the volume stability of the refractory and the precision of the apparent size.
• The indexes of material sintering contain apparent porosity, bulk density, and water absorption, etc.
• Sorting, crushing, and proportioning, the raw material requires to be screened after a crushing and grinding, because the semi-finished material is graded by various sizes of powder, and ensures received the dense body with the greatly compact.
• Each variety of equipment can generate various fineness of finished powder by grinding, 80 mesh -425 mesh, 500 mesh -2000 mesh, the finest can achieve about 2500 mesh.
• Mixing, placing material, in order to homogenate the components and particles of raw meal and clinker, It is essential to mix and add binder at a similar time to improve the bonding strength of the semi-finished material.
• After molding, drying, and press by great pressing equipment and molded, the green refractory bricks should be placed for a particular time to dry.
• Burning, the complete product was sintered by high-temperature sintering at a high-temperature kiln.
• Checking and packing.

Advantages Of Refractory Bricks

Refractory Bricks advantages as follows,

• Insulating Nature – A refractory brick is utilized especially for its insulating capabilities. It has the ability to stop heat and prohibits it from penetrating to the other side. Utilizing it in constructing a house will maintain a cozy interior during summer and winter.

• Better Durability – Aside from their insulating power, fire bricks are more durable compared to ordinary bricks which are prepared from ordinary clay. The additional cool thing about fire bricks is that they are amazingly lightweight considering their durability.

• Excellent Weather Resistance – One of the considerably common difficulties in construction sites is the damages that normal bricks receive due to the modifications in climate conditions or inappropriate storage. Utilising refractory bricks will only need you a dry storage place.

• Customized Bricks – One big thing about fire is that they can be ordered from manufacturers that demand customized fire brick. You can get them in your desired shape, size, and specification to perfectly suit your necessities.

• Having these advantages bring the price of these firebricks reasonable. Not only that you can achieve the excellent advantages they offer, but you can also order them in style to add your unique and intelligent touch.

• Stronger Than Normal Bricks – fire brick is tougher than normal clay-made bricks and this is why they are evaluated as more durable than ordinary bricks. Though these bricks are tough, they are amazingly light-weighted.

• Easy Storage – In extensive or big constructional projects, it has been always found that due to inappropriate storage and due to modifications in climate conditions, various bricks get destroyed easily. With refractory or fire brick, there is no difference with the storage. Just make sure they are conserved in a dry place,  as moisture may defect such bricks.

• Fireproof – Refractory or fire bricks are incredibly good at heat insulation because they are fireproof. This makes them a decent choice to utilise all sorts of high-heat products to line up.

• Inexpensive – They may be creative, but they are inexpensive as well. They don’t cost much, unlike the additional fire bricks. The lighter editions could be more expensive than the heavier ones. Still, regardless of what their density is, they can be greatly durable.

• Moisture-proof – Refractory brick has a powerful moisture-proof characteristic, as well as it gives the advantages of heat insulation, fire insulation, and absorption of water.

Disadvantages Of Refractory Brick

The Disadvantages Of Refractory Bricks are as follows;

• Heavy Weight – They are created of concrete, which creates them heavier than bricks. Take this into account, since this will impact the extra weight or cost of the commodity you are constructing.

• Poor Soundproof – Refractory bricks are not sound resistant. This does not affect the end output of your product, but you may need to rethink utilizing your products if it may lead to an interruption if you generate something for the house.

Refractory Brick Features

The Various features or characteristics of the refractory or fire brick are as follows

• Chemical Composition – The major elements determine the quality and characteristics of the refractory.
• The Bulk Density – Unit volume weight, density is large, demonstrating good density, strength may be high, but the thermal conductivity may be enormous.
• Apparent Porosity – They did not do particular requirements, but as a manufacturer must rigidly restraint the sensible porosity.
• Load Softening Temperature – It is also known as high-temperature load started up to deformation temperature, this parameter is incredibly significant, marking the high-temperature resistance of materials.
• Thermal Shock Resistance – The ability to resist sudden differences in temperature without being demolished.
• Compressive Strength – The ultimate pressure capability to withstand (ambient temperature).
• Bending Strength – The capacity to withstand shear pressure.
• The Linear Rate Of Change – It is also called a “burn line change”, or “residual line change”, which implies that each time under the similar temperature in the volume of expansion and contraction differences, and if every expansion contraction is the same, we define such a linear rate of difference of 0.

Read More: 7 Brick Test to Decide Quality of Bricks

The Explanations For The Recycling Of Used Refractory Brick

• Every used refractory brick will be recycled. The major reason is that the refractory brick is not completely used as the lining of the kiln.
• Refractory Bricks have a certain kind of use-value, which is connected to the refractory brick material along with the strength.
• The recovery of utilized refractory bricks can not only save resources but also create refractory bricks nicely utilized.
• The additional reason for the recycling of refractory bricks is the rate problem, the rate of the used refractory bricks is commonly low, which also generates some firebrick manufacturers to add some users to decrease the cost of a generation when the refractory brick is processed.
• In current years, the considerable environmental safety situation has added a tiny pressure to the refractory industry. Several manufacturers of refractory raw materials have stopped generation.
• The refractory brick manufacturers can not buy better refractory raw materials when they purchase refractory raw materials. Therefore, the used refractory bricks are properly obtained to better complete the refractory bricks generation.
• Through the above analysis, you must understand why some people recycle utilized firebricks and utilized resources.
• REVELL as a manufacturer of refractories, the generation, and processing of refractory bricks are based on the generation of refractory bricks and creating better foundation work for users.

Composition Of Fire Clay Or Refractory

Fire clay should include a higher percentage of ‘non-detrimental silica and alumina. They should have a relatively tiny quantity of detrimental lime, magnesia, iron oxide, and alkalis.

Silica – Silica (SiO2) becomes soft at about 2800℉ and ultimately fuses and becomes a glassy material at about 3200℉. It melts around 3300℉. This great softening and melting point has established it as the principal substance for the generation of refractory bricks.

Alumina – Alumina (Al2O3) has an even greater softening and fusion temperature than silica. It melts at about 3800℉. It is, accordingly, utilized in a mixture with silica.

Lime, Magnesia, Iron oxide, And Alkalis – The existence of these detrimental ingredients acts as fluxes to reduce the softening and fusion temperature.

Properties Of Good Refractory Brick

Properties of good Refractory Bricks are given below;

• To fulfill the desired objective the refractory bricks must be decent in quality. Followings are the properties of decent Fire bricks.
• Refractory bricks must withstand stress created at high temperatures in furnace walls and arches.
• They must conserve their rigidity at great temperatures.
• Irreversible volume fluctuation should not happen at the furnace temperature. Because shrinkage leads to the opening of junctions and effects in a leaky furnace.
• They must withstand the tendency to crack and split off fragments when uncovered to a rapid change of temperature.
• They must not easily form fusible commodities with slags.
• They can not react with furnace gases.
• They should obtain a compressive strength of about 20000 to 30000 psi.
• They should not consume more than 6% of water by weight when maintained in water for 24 hours.

Conclusion

In conclusion, refractory bricks are commonly known as fire bricks, and it essential material for applications requiring resistance to high temperatures and harsh conditions, this specialized bricks are made from various ceramic materials and it used in industries such as glass manufacturing, cement manufacturing, metallurgy.

Refractory bricks offer excellent thermal insulation, heat resistance, durability, chemical attacks and abrasion. Their ability to with stand extreme temperatures makes them crucial for lining furnaces, boilers, kilns and other high-temperatures environments. Proper selection and installation of refractory brick is vital for maintaining the structural integrity and efficiency of these industrial systems, with their exceptional properties.

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