Selection of Refractory Materials for Different Boiler Types
2025-08-15 09:15:49
The primary purpose of using wear-resistant refractory materials for the lining of circulating fluidized bed boilers is to protect the furnace steel shell from erosion and wear by the combusted materials.
The most commonly used lining materials for boilers include amorphous castables, refractory and wear-resistant castables, plastic castables, low-cement castables, corundum castables, steel fiber refractory castables, and lightweight castables.
A power generation boiler consists of a combustion chamber, water-cooled tube walls, superheater, economizer, preheater, and steam drum. The combustion chamber temperature of a power generation boiler is approximately 1550°C. Steam-cooled walls are installed in the high-temperature flue of the water-cooled tubes near the furnace wall, so the temperature inside the furnace wall is relatively low, generally not exceeding 900°C. For membrane-type water-cooled wall structures, the furnace wall temperature is only 500-600°C, or even lower.
Chain-type or pulverized coal furnaces operate at temperatures around 1000°C. Fluidized bed boilers have higher temperatures, with many pipes passing through the furnace wall. Therefore, the refractory castable used in the lining of fluidized bed boilers requires high-grade refractory castables.
For lightweight boilers, the working layer is generally lined with clay refractory castables or clay refractory plastics. The insulation layer is insulated with lightweight castables, or insulation boards or fiber wool. Some manufacturers apply a sealing layer to the outer surface of the furnace shell to enhance the airtightness of the boiler lining. This provides better insulation and fuel conservation.
Pulverized coal furnaces are sparged by a combination of pulverized coal particles and airflow. High-aluminum and clay refractory castables are used for casting, and the furnace roof is rammed with high-aluminum refractory plastics. If coal particle abrasion or dust-laden airflow is severe, a highly wear-resistant castable, such as silicon carbide refractory castable, is used for the working layer lining to extend its service life.
Refractory bricks are used in circulating fluidized bed boilers for applications such as return hoppers, economizer walls, mixed suffocation walls, flues, and chimney linings.
Refractory and wear-resistant castables are primarily used in boiler cyclones, furnaces, dense phase zones, furnace outlets, water-cooled air chambers, slag coolers, return hoppers, and ignition air ducts. High-alumina refractory castables are used in boiler flue corners, air chambers, economizer guards, and fire doors. Lightweight insulating castables are used for thermal insulation of boiler roofs and furnace walls.
Wear-resistant plastics offer easy installation and quick repair, high strength, wear resistance, excellent thermal shock resistance, crack resistance, and excellent sealing properties. It is primarily used for repairing and localized tamping of fluidized bed boilers. Micro-expanding refractory plastics offer strong plasticity and adhesion at room temperature, high strength after natural drying, and slight expansion at high temperatures, resulting in high refractory resistance, excellent sealing properties, and easy installation. Corrosion-resistant and wear-resistant ramming materials offer excellent thermal conductivity, facilitating heat transfer and are used in areas of circulating fluidized bed furnaces requiring wear and corrosion resistance.
Of course, different furnace types and sizes require different castables and refractory bricks. The selection is based on the specific requirements of the equipment.