What refractory materials are used in heating furnaces?

The selection of refractory materials in heating furnaces needs to comprehensively consider the furnace structure, working temperature, thermal system and chemical properties of the use environment (such as furnace atmosphere, slag composition, etc.). According to the differences in their functional requirements and use locations, they can be summarized into the following main categories of refractory materials and their characteristics:

1. Clay and high alumina refractory materials

• Composition and performance: Clay bricks are made of kaolin with an Al2O2 content of about 30% as the main raw material, while high-alumina bricks contain more than 48% Al2O2, and the latter has better high-temperature performance.

• Application scenarios: Suitable for parts with medium heat loads such as furnace walls and furnace roofs, while high-alumina bricks are often used for furnace linings and refractory layers that bear higher heat loads.

• Advantages and disadvantages:

• Clay bricks: Excellent thermal shock stability, low price, but limited high-temperature performance.

• High-alumina bricks: High compressive strength, high load softening point (1350~1600℃), suitable for areas with higher temperatures.

2.Silica refractory

• Composition and performance: The SiO₂ content of silica bricks is usually higher than 94%, maintaining good volume stability at high temperatures, and the load softening temperature can reach above 1650℃.

• Application scenarios: Mainly used in high-temperature areas such as furnace tops and regenerators, especially suitable for oxidizing furnace gas environments.

• Limitations: Poor thermal shock resistance, not suitable for areas with frequent temperature fluctuations.

3.Basic refractory materials

• Composition and performance:

• Magnesium brick: mainly composed of magnesium oxide (MgO), with excellent high temperature performance (upper temperature limit can reach 2000℃).

• Magnesium aluminum brick: by introducing alumina to improve thermal shock stability, suitable for more complex working conditions.

• Application scenario: suitable for furnace bottom and slag line, especially in areas exposed to alkaline slag or high temperature flame.

• Advantages: strong resistance to alkaline corrosion, suitable for high temperature environment.

• Disadvantages: weak resistance to corrosion of acidic slag.

4.Castables and refractory concrete

• Composition and performance: Castables can be selected from high-alumina, corundum or silicon carbide substrates according to needs, supplemented with micropowder and binder. Its high-temperature performance and thermal shock resistance can be further optimized by adding modified ingredients.

• Application scenarios: Used in complex structural parts such as furnace walls, furnace bottoms and flues, which can achieve overall construction and reduce joints.

• Features: High construction flexibility and good thermal stability.

5.Lightweight insulation material

• Composition and performance:

• Lightweight bricks: such as lightweight clay bricks and lightweight high-alumina bricks, with low thermal conductivity and good thermal insulation performance.

• Ceramic fiber products: such as fiber blankets and modules, with extremely low thermal conductivity and excellent thermal insulation performance.

• Application scenarios: used for heating furnace insulation layer, significantly reducing heat loss and improving thermal efficiency.

• Advantages: significantly reducing furnace heat capacity and energy consumption.

• Disadvantages: low mechanical strength, need to be used in conjunction with other refractory materials.

6.Special refractory materials

• Corundum refractory materials:

• Features: Contains more than 90% Al₂O₃, excellent temperature resistance (>1800℃).

• Application: Suitable for high-temperature parts directly contacted by flames or areas with severe slag corrosion in the furnace.

• Silicon carbide bricks:

• Features: Good thermal shock resistance, high thermal conductivity, and strong wear resistance.

• Application: Furnace bottom, slag line, flue and other parts.

• Zirconia corundum bricks:

• Features: Outstanding resistance to acidic atmosphere and high temperature performance.

• Application: Used in high-temperature areas for treating acidic furnace gas.

The selection of appropriate refractory materials depends not only on the operating temperature and chemical environment of the furnace, but also on the expected service life, cost-effectiveness and maintenance requirements. The right choice can ensure that the heating furnace maintains performance during long-term operation, reduces downtime and improves production efficiency. In addition, the installation and maintenance of refractory materials are also crucial and need to be completed by experienced technicians to ensure the integrity and durability of the furnace lining. By carefully selecting and correctly installing these refractories, the heating furnace can operate normally, provide stable thermal energy support for industrial production, and thus promote the smooth progress of the entire production process.