Refractory bricks and insulating brick are two common refractory materials. Although they are both used in high temperature environment, there are significant differences in composition, properties, uses and ways of use. The following are the main differences between refractory bricks and insulating brick:

I. Composition and Structure

(1) Refractory bricks

Composition: Refractory bricks are mainly composed of refractory minerals, and common raw materials include clay, bauxite, magnesia, silica, etc. According to chemical composition and mineral composition, refractory bricks can be divided into clay bricks, high alumina bricks, silicon bricks, magnesium bricks and so on.

Structure: The structure of refractory brick is relatively compact, with high strength and corrosion resistance. Its internal porosity is low, usually below 15%, which makes the refractory brick able to withstand high temperature and chemical erosion.

(2) insulating brick

Composition: The main components of insulating brick are light refractories, such as expanded perlite, expanded vermiculite, foamed ceramics, etc. These materials have low density and good thermal insulation performance.

Structure: The structure of insulating brick is relatively loose, with a large number of pores inside, and the porosity is usually above 40%. These air holes can effectively prevent the conduction of heat, thus achieving heat insulation effect. Insulating brick's strength is relatively low, but its thermal insulation performance is excellent.

II. Performance

(1) Refractory bricks

Refractory: Refractory bricks usually have a high refractoriness and can withstand high temperatures above 1500℃. The fire resistance of high alumina bricks and magnesia bricks can even reach above 1700℃.

Corrosion resistance: Refractory bricks have good corrosion resistance, and can resist the chemical corrosion of high-temperature slag, acid-base gas and so on. For example, high alumina brick has good corrosion resistance to both acidic slag and alkaline slag.

Compressive strength: Refractory bricks have high compressive strength and can bear large mechanical load. For example, the compressive strength of high alumina brick can reach more than 100MPa.

Thermal conductivity: the thermal conductivity of refractory bricks is relatively high, and heat can be conducted through the brick body quickly.

(2) insulating brick

Fire resistance: insulating brick has a relatively low fire resistance, usually between 1000℃ and 1500℃. Although its fire resistance is not as good as that of refractory bricks, it is enough to meet the heat insulation requirements of most industrial furnaces.

Thermal insulation: The main feature of insulating brick is its excellent thermal insulation. A large number of air holes in it can effectively prevent the conduction of heat, which makes the thermal conductivity of insulating brick much lower than that of refractory bricks. For example, the thermal conductivity of insulating brick is usually between 0.1 and 0.5 W/(m k), while that of refractory bricks is between 1 and 5 W/(m k).

Compressive strength: The compressive strength of insulating brick is relatively low, usually between 10 MPa and 30 MPa. Because of its loose structure, insulating brick is not suitable for bearing heavy mechanical load.

Corrosion resistance: insulating brick's corrosion resistance is relatively weak, and it is mainly used for thermal insulation, without direct contact with high-temperature slag or corrosive gases.

III. Uses

(1) Refractory bricks

High-temperature furnace lining: Refractory bricks are mainly used for lining of high-temperature furnaces, which are in direct contact with high-temperature slag, molten metal or flame. For example, the lining of ironmaking blast furnace usually uses magnesia bricks, and the lining of steelmaking converter uses high alumina bricks or magnesia-carbon bricks.

Key parts of high-temperature equipment: Refractory bricks are also used in some key parts of high-temperature equipment, such as the tank wall of glass melting furnace and the firing zone of cement rotary kiln, which need to withstand high temperature and chemical erosion.

(2) insulating brick

Thermal insulation: insulating brick is mainly used for the thermal insulation of furnaces to reduce heat loss and improve energy efficiency. Insulating brick can be used alone or in combination with refractory bricks to form a composite lining structure.

Lightweight furnace lining: insulating brick can be used as a lightweight furnace lining material to reduce the overall weight of the furnace. For example, in some small industrial furnaces, insulating brick can replace some refractory bricks to reduce the weight and cost of the furnace body.

IV. Mode of use

(1) Refractory bricks

Masonry method: Firebrick usually adopts wet masonry method, and bricks are bonded together with refractory mud. When building, it is necessary to ensure the uniformity and compactness of brick joints to prevent the infiltration of high temperature gas or slag.

Construction requirements: the construction of refractory bricks should be carried out in strict accordance with the design requirements to ensure the dimensional accuracy of brick joints and the stability of the overall structure. Brick joints should generally be controlled between 1 and 3 mm.

(2) insulating brick

Installation method: insulating brick usually adopts dry masonry method, which is directly stacked on the furnace wall or roof. Insulating brick can be used in combination with refractory bricks in some places where higher thermal insulation effect is needed.

Construction requirements: The installation of insulating brick needs to ensure the close contact between bricks and avoid gaps. The surface of insulating brick needs to be flat to reduce heat loss.

V. Summary

The main difference between refractory bricks and insulating brick lies in their composition, structure, properties and uses. Refractory bricks are dense in composition, high in fire resistance and strong in erosion resistance, and are mainly used for lining of high-temperature furnaces. Insulating brick has loose composition and excellent thermal insulation performance, and is mainly used for thermal insulation layer. In practical application, refractory bricks and insulating brick can be used together as needed to form a composite lining structure to meet the needs of different high-temperature environments.