Selection Of Kiln Refractory Materials

Industrial kilns are core equipment in the chemical, metallurgical, and building materials industries. Their high-temperature resistance, service life, and production safety are directly determined by the refractory material selection. Improper selection can easily lead to premature kiln failure and production interruption. Understanding the following four points can help accurately match kiln requirements and reduce subsequent maintenance costs.

1.Matching Materials to Working Conditions

Temperature: For medium-low temperatures (800-1200°C, such as ceramic bisque-fired kilns), choose clay-based refractory bricks for their low cost and adaptability. For medium-high temperatures (1200-1600°C, such as cement rotary kilns), use high-alumina materials (alumina ≥ 60%) for excellent resistance to high-temperature shrinkage. For high temperatures (above 1600°C, such as glass melting furnaces), choose corundum or silicon carbide materials for their extreme heat resistance.

Medium: For acidic media (such as sulfuric acid industrial kilns), choose siliceous materials for excellent acid resistance. For alkaline slag (such as steel blast furnaces), choose magnesia materials (magnesia-alumina spinel bricks) for strong resistance to alkali corrosion. For areas subject to high-velocity airflow, prioritize dense refractory bricks with reinforcing agents or wear-resistant castables.

2. Selecting Forms by Location

For general areas (furnace walls, linings): Use refractory bricks (high-alumina bricks, clay bricks). They are easy to lay, structurally stable, and suitable for large areas.

For irregularly shaped areas (vaults, corners): Use refractory castables, which can be cast on-site to perfectly fit the structure and prevent heat leakage and media penetration through gaps.For areas prone to wear (doorways, feed inlets): Use wear-resistant refractory bricks or a combination of castables and wear-resistant coatings to enhance wear resistance and reduce downtime and replacement costs.

3. Focus on indicators to avoid inferior products

When looking at core specifications, pay attention to three key points: First, the refractory temperature must be 50 to 100°C higher than the maximum kiln temperature; second, the compressive strength must be at least 25 MPa at room temperature; and third, the thermal shock stability must be able to withstand more than 10 cycles of rapid cooling and heating without cracking. All of these factors should be reviewed in the product test report.

Next, consider the appearance: Good refractory bricks have a smooth surface, free of cracks and chipping; the refractory castable must be free of lumps and have a uniform texture. If there are impurities or uneven color on the surface, it is definitely a low-quality product and should be avoided.

4. Standardized Construction and Maintenance

Construction: Refractory bricks should be laid with staggered joints. Mortar joints should be filled with refractory mortar of the same material, with a thickness of 2-3mm. Refractory castables should be mixed according to the proper proportions and vibrated to compact them to prevent residual bubbles that could lead to later damage.

Maintenance: Before first use, the furnace should be “baked out.” The temperature should be gradually increased by 100-200°C per day to avoid sudden temperature rises that could cause cracking of the material. Reduce frequent temperature fluctuations and regularly clean the furnace of accumulated slag to prevent the long-term adhesion of corrosive media.