Insulation Refractory

What are the Commonly Used Fibrous Insulation Materials?

Release Time: 2025-02-06
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Fibrous insulation materials are renowned for their lightweight nature, low thermal conductivity, minimal heat capacity, excellent thermal shock resistance, and ease of installation, all contributing to significant energy savings. These materials primarily encompass inorganic and composite fibers, with common types including asbestos, rock wool, glass fiber, and refractory fibers.

Ceramic fiber wool

Asbestos

Asbestos refers to a group of naturally occurring fibrous hydrated silicate minerals. It has been extensively used as a raw material in industries for insulation, thermal protection, fireproofing, electrical insulation, and sealing applications.

 

Rock Wool

Rock wool is an artificial mineral fiber insulation material produced from natural rocks such as blast furnace slag, basalt, and diabase. It is known for its excellent thermal insulation properties and is widely used in various industrial applications.

 

Glass Fiber

Glass fiber is created by transforming molten glass into fibrous form using methods like steam blowing, flame blowing, or centrifugal techniques. Depending on its form, it can be categorized into continuous long fibers and short fibers. Composition-wise, it includes alkali-free glass fiber, alkali-containing glass fiber, and zirconium-containing glass fiber. Long fibers are typically utilized in insulation materials and as reinforcement for plastics, while short fibers are employed in energy-saving insulation applications.

 

Refractory Fiber

Refractory fibers, commonly referred to as aluminosilicate fibers, are produced using raw materials such as kaolin, kyanite, or bauxite, with the addition of B₂O₃ to enhance melt viscosity and reduce slag formation. The prepared mixture is melted in an electric arc or resistance furnace. A constant-temperature working channel at the furnace’s base ensures the appropriate temperature and viscosity of the molten material. Forming is achieved through blowing methods, with pressure adjusted based on raw material properties and melting temperature, typically around 0.6 MPa. The resulting short fibers are collected, settled in a chamber, and compressed with binders to form mats of certain strength. Needle punching enhances the structural integrity of these mats. Aluminosilicate fibers are suitable for use below 1200°C, with variations depending on Al₂O₃ content. By incorporating Al₂O₃ to achieve a 95% content, alumina fibers are produced. Adding components like Cr₂O₃ or ZrO₂ can elevate the usage temperature to 1400°C. Centrifugal methods can also form short fibers, where high-speed centrifuges spin molten streams into fibers.

Refractory Fiber board

Aluminosilicate fibers, commonly used in high-temperature applications, exhibit a tendency to crystallize into mullite and cristobalite phases when exposed to temperatures between 900 and 1200°C. This crystallization increases thermal conductivity and reduces elasticity, leading to the degradation of the vitreous structure. Despite these challenges, aluminosilicate fibers are favored for their lightweight, softness, low usage volume, ease of installation, low thermal conductivity, low molar heat capacity, excellent insulation properties, chemical stability, and thermal shock resistance.

 

Alumina Fibers

Alumina fibers are characterized by low thermal conductivity, minimal heating shrinkage, and low heat capacity. They can be used continuously at temperatures ranging from 1300 to 1400°C, surpassing the typical range of standard aluminosilicate fibers (1000 to 1100°C). These fibers maintain good chemical stability, making them suitable for acidic environments, oxidizing and reducing atmospheres, and vacuum conditions. They also exhibit some resistance to alkaline environments but are susceptible to corrosion by lead vapor and vanadium pentoxide. Alumina fibers are primarily utilized as insulation linings in various industrial furnaces, such as heat treatment furnaces in the steel industry, ceramic kilns, and cracking furnaces in petrochemical processes, offering significant energy-saving benefits. In intermittent kilns, they can substantially increase production output. Additionally, alumina fibers serve as catalyst carriers in the chemical industry, known as alumina carriers, and are used in applications like thermal insulation in nuclear reactors and space shuttles, as well as reinforcement materials for light alloys.

 

Zirconia Fibers

Zirconia fibers are polycrystalline refractory materials composed of pure tetragonal or cubic phase ZrO₂ nanoceramic grains. With a purity exceeding 99.7%, these fibers consist of fully stabilized cubic phase grains and appear as white, cotton-like continuous filaments with diameters ranging from 3 to 8 μm. Due to the high melting point of ZrO₂ (2700°C) and its non-oxidizing nature, zirconia fibers offer superior high-temperature performance compared to other refractory fibers like alumina or mullite fibers. They exhibit chemical stability, corrosion resistance, oxidation resistance, thermal shock resistance, and non-volatility at elevated temperatures.

 

Polycrystalline Mullite Fibers

Polycrystalline mullite fiber products are suitable for long-term use in high-temperature equipment operating below 1600°C, such as silicon carbide and molybdenum disilicide electric furnaces, various steel heating furnaces, and mechanical forging furnaces. Their application can significantly enhance equipment thermal efficiency, conserve energy, boost productivity, and improve product quality.

 

These advanced refractory fibers are employed in various high-temperature industrial furnace insulation applications, including ceramic kilns, mechanical and metallurgical heating furnaces, heat treatment furnaces, and other industrial furnace linings. They are also used for high-temperature fire barriers, kiln doors, kiln cars, expansion joints, and glass furnace insulation.

 

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