Wear-resistant and refractory castable for lining of circulating fluidized bed boilers

Wear-resistant and refractory castable for lining of circulating fluidized bed boilers

Wear-resistant refractory castables used in circulating fluidized bed boiler linings are a key type of refractory material, withstanding various complex operating conditions such as high temperatures and abrasion. The following is a detailed introduction to wear-resistant refractory castables.

Types and Characteristics

The commonly used wear-resistant refractory castables for circulating fluidized bed boiler linings mainly include the following:

Corundum-based wear-resistant refractory castables: With corundum as the main component, they possess high strength, high wear resistance, and good thermal shock resistance. They are mainly used in boiler combustion chambers, separators, and flues—areas prone to erosion and wear—effectively resisting the impact of high-speed fly ash and the effects of high-temperature thermal stress. However, it should be noted that corundum has relatively poor thermal shock stability. Frequent temperature changes during boiler operation, such as flame suppression and flame lifting, may shorten the service life of the refractory material.

High-alumina wear-resistant castables: With high-alumina materials as the main component, they possess excellent refractoriness and wear resistance. They are suitable for various parts of the boiler lining, especially performing well in high-temperature, high-pressure, and high-erosion environments.

Silicon carbide products: When used in a high-temperature, oxygen-free atmosphere, they exhibit high wear resistance and good thermal shock stability. After sintering at a certain temperature, a protective glaze layer can form on their surface. Sillimanite products: Adding sillimanite to refractory materials can increase the load softening temperature by 100-150℃, making it a high-quality refractory raw material. The molding and sintering temperature of sillimanite bricks reaches the temperature at which refractory materials begin to change (1450-1600℃), therefore, sillimanite bricks are an ideal wear-resistant refractory material for CFB (Conductivity, Heat, and Fulfillment).

In addition, there are low-cement refractory castables, lightweight insulating refractory castables, and steel fiber reinforced castables. These castables have the characteristics of high strength and good impermeability, light weight and good thermal insulation performance, strong anti-stripping and impact resistance, and are suitable for different parts of boilers.

Performance Requirements

The wear-resistant refractory castable used for the lining of circulating fluidized bed boilers must meet the following main performance requirements:

Refractory Resistance: The refractoriness of the refractory castable should be higher than the highest operating temperature of the boiler to ensure that the material does not soften or melt at high temperatures.

Abrasion Resistance: Due to the high-speed scouring of fly ash inside the boiler, the refractory castable must possess good abrasion resistance to reduce material wear and spalling.

Thermal Shock Resistance: Boilers experience significant temperature fluctuations during operation; therefore, the refractory castable must possess excellent thermal shock resistance to prevent material cracking or spalling caused by sudden temperature changes.

Erosion Resistance: Various chemical substances exist inside the boiler; the refractory castable must have good resistance to these substances to ensure the long-term stability of the material.

Workability: The wear-resistant refractory castable should possess good workability and plasticity to facilitate construction and repair. Before construction, ensure the base surface is clean and dry, and apply a layer of adhesive to improve adhesion. During pouring, mechanical or manual vibration should be used to ensure the material is uniformly compacted. After pouring, proper curing should be carried out to improve the strength and durability of the material.

Performance Requirements

The wear-resistant refractory castable used for the lining of circulating fluidized bed boilers must meet the following main performance requirements:

Refractory Resistance: The refractoriness of the refractory castable should be higher than the highest operating temperature of the boiler to ensure that the material does not soften or melt at high temperatures.

Abrasion Resistance: Due to the high-speed scouring of fly ash inside the boiler, the refractory castable must possess good abrasion resistance to reduce material wear and spalling.

Thermal Shock Resistance: Boilers experience significant temperature fluctuations during operation; therefore, the refractory castable must possess excellent thermal shock resistance to prevent material cracking or spalling caused by sudden temperature changes.

Erosion Resistance: Various chemical substances exist inside the boiler; the refractory castable must have good resistance to these substances to ensure the long-term stability of the material.

Workability: The wear-resistant refractory castable should possess good workability and plasticity to facilitate construction and repair. Before construction, ensure the base surface is clean and dry, and apply a layer of adhesive to improve adhesion. During pouring, mechanical or manual vibration should be used to ensure the material is uniformly compacted. After pouring, proper curing should be carried out to improve the strength and durability of the material.

Development Trends

With the continuous development and application of circulating fluidized bed boiler technology, wear-resistant refractory castables, as one of its key materials, are also constantly developing and innovating. In the future, with the continuous emergence and application of new materials and technologies, the performance of wear-resistant refractory castables will be further improved and optimized, making a greater contribution to the stable operation and energy conservation and emission reduction of circulating fluidized bed boilers.

In summary, wear-resistant refractory castables used in circulating fluidized bed boiler linings play a crucial role in the safe and stable operation of the boiler. Selecting suitable wear-resistant refractory castables and strictly following construction specifications are key to ensuring the service life and performance of the boiler lining.