Vermiculite bricks are high-quality thermal insulation materials developed by meticulous aerospace engineers, while refractory bricks are a type of refractory material with outstanding fire resistance. There are significant differences between the two. Vermiculite bricks are manufactured using natural expanded vermiculite, inorganic additives, and high-strength binders. They undergo multiple processes of light pressing and forming, followed by drying or baking, to produce various sizes of thermal insulation and refractory brick products. They exhibit excellent fire resistance, maintaining their original physical form and chemical properties at temperatures up to 1100°C without releasing any toxic substances. Their outstanding characteristics include refractory properties and environmental friendliness. The density of vermiculite bricks ranges from 0.4 to 0.8 g/cm³, with a thermal conductivity coefficient at room temperature of 293–502.4 J/(m·h·℃) (70–120 cal/(m·h·℃)). Compressive strength is <2.45 MPa, with water absorption around 6%. As an excellent soundproofing and thermal insulation material, vermiculite bricks effectively reduce noise impact, lower energy consumption, and improve living environments. Industrial applications include steel frame cladding, iron production, casting slag removal, and high-rise building steel frame insulation. However, it is important to note that vermiculite bricks have relatively low strength and should not be used in load-bearing applications. To balance various properties, vermiculite bricks feature lower strength and melting point, with refractoriness and high-temperature performance inferior to other lightweight refractory materials. They are generally unsuitable for load-bearing structures or as medium-to-high-temperature insulation materials, with typical operating temperatures ranging from 800 to 1100°C.
Refractory bricks are typically shaped refractory materials fired from refractory clay or other refractory materials. They feature high density, high strength, excellent wear resistance, and corrosion resistance. They find extensive applications across numerous industries. The primary types of refractory bricks available on the market include: high-alumina refractory bricks, clay refractory bricks, and lightweight refractory bricks. The foremost advantage of refractory bricks lies in their exceptional heat resistance. They represent an outstanding refractory material, and among numerous refractory options, the quality of refractory bricks is arguably superior. They not only deliver highly efficient heat resistance but also exhibit excellent wear resistance. Their thermal conductivity is significantly influenced by the size of pores within the bricks. Larger pores accelerate heat transfer, while smaller pores slow it down. Refractory bricks boast a long service life and high impact resistance. They exhibit strong corrosion resistance, making them highly resistant to damage—meaning they possess excellent slag resistance.
Vermiculite bricks primarily serve for insulation and heat retention, though their direct flame resistance is inferior to that of refractory bricks. Refractory bricks are designed to withstand intense flame exposure, excelling in thermal endurance. Key distinctions between vermiculite and refractory bricks include:
1. Thermal Insulation Properties
The thermal conductivity of vermiculite bricks typically ranges from 0.2 to 0.4 W/m·K (at an average temperature of 350±25°C), while that of refractory bricks exceeds 1.0 W/m·K (at the same average temperature). Consequently, vermiculite bricks demonstrate significantly superior thermal insulation compared to refractory bricks.
2. Refractoriness
Vermiculite bricks exhibit refractoriness below 1100°C, whereas refractory bricks maintain refractoriness above 1400°C.
3. Density
Vermiculite bricks are typically lightweight insulation materials with densities ranging from 0.4 to 0.8 g/cm³. Refractory bricks, however, generally have densities exceeding 2.0 g/cm³. Higher density per unit volume indicates greater compactness, higher strength, and a larger thermal conductivity coefficient.
Overall, refractory bricks offer high mechanical strength, extended service life, and excellent chemical stability. They do not react chemically with materials and exhibit superior high-temperature resistance, withstanding temperatures up to 1900°C. They are particularly suitable for use in fertilizer plants within high-low temperature shift reactors, reformers, hydrogenation converters, desulfurization tanks, and methanation furnaces. Vermiculite bricks differ significantly from refractory bricks, as their operating environments, applications, and functions are distinct. Different locations require different materials. When selecting materials, we must determine which refractory material is suitable for our specific application based on actual conditions.
