Lightweight Fire-Resistant Raw Material - Vermiculite

I. Source of Vermiculite
Vermiculite is a complex hydrated iron-magnesium silicate mineral, which is a regenerated mineral formed by the hydrothermal metamorphism or weathering of mica minerals. When heated at a certain temperature, it undergoes a rapid expansion and becomes an excellent insulating material.

II. Main Characteristics of Vermiculite
1. Low density: The density of vermiculite is usually between 1100 to 1200 kg/m³, while the density of expanded vermiculite is only 50 kg/m³ to 200 kg/m³, significantly lower than that of traditional clay-based or high-alumina refractory bricks (with a density often above 2000 kg/m³). This characteristic enables it to effectively reduce the overall structural load of thermal equipment such as kilns.
2. Low thermal conductivity: The internal structure of expanded vermiculite is filled with closed air pores, which greatly hinders heat conduction. Its normal temperature thermal conductivity is generally within the range of 0.04 W/(m·K) to 0.07 W/(m·K). When used as an insulation layer in high-temperature industrial kilns, it can effectively reduce heat loss and lower energy consumption.
3. Excellent refractory properties: The refractory temperature of vermiculite is usually between 1300℃ to 1380℃. After being expanded through high-temperature firing, because the mineral lattice is not completely destroyed during the expansion process, its refractory temperature can still remain above 1300℃, enabling it to be used as a refractory and insulation material in many medium-high temperature industrial scenarios.
4. Strong chemical stability: Vermiculite is neutral to weakly alkaline. At high temperatures, it is not prone to intense chemical reactions with most molten metals, slag, or atmospheres, maintaining relatively stable performance.
5. Good thermal shock stability: The porous structure of expanded vermiculite helps buffer the thermal stress caused by sudden temperature changes such as those due to furnace start-up or shutdown. It has good resistance to thermal shock.
6. Natural and environmentally friendly: Vermiculite itself is non-toxic and non-radioactive, a natural mineral. The expansion process has relatively low energy consumption. Within the normal usage temperature range, it does not release harmful gases or substances. The porous layered structure of vermiculite has a strong affinity for heavy metal ions such as lead (Pb), cadmium (Cd), and mercury (Hg). After disposal, it has a relatively small impact on the environment, conforming to the trend of green industrial development.
7. Limitations: Due to its porous structure, expanded vermiculite has strong water absorption. Attention should be paid to moisture-proof treatment or its use in dry environments. Its strength is generally lower than dense refractory materials and is usually not used as a working layer in direct contact with high-temperature melts or under severe mechanical wear.

III. Main Applications of Vermiculite in Industry and Construction
Industrial High-Temperature Equipment:
(1) Furnace Insulation Layer: As a backfill or pre-formed product for the furnace lining of industrial furnaces such as metallurgical furnaces, glass melting furnaces, cement kilns, and ceramic kilns, it significantly reduces heat loss and improves thermal efficiency.
(2) Pipe and Equipment Insulation: Used as insulation filler or wrapping material for high-temperature pipes, flues, and hot air ducts.
(3) Steel Ladle Covering Agent/Casting Insulation Agent: Utilizing its thermal insulation properties, it covers the surface of molten steel to reduce heat loss, or is used for casting risers insulation to improve casting quality.
Building Fire Prevention and Insulation:
(1) Fireproof Door Core Material: Expanded vermiculite particles or boards made with inorganic binders, are important filling and insulation materials for fireproof doors. They can effectively block heat transfer when exposed to fire.
(2) Steel Structure Fireproof Coating Aggregate: As a key component of expansive fireproof coatings, it expands and carbonizes at high temperatures, forming a thermal insulation protective layer.
(3) Building Insulation Mortar/Board: Used as insulation layers for walls and roofs (especially in areas where both insulation and fire prevention requirements need to be met).
(4) Fireproof Board: Fireproof boards made mainly from expanded vermiculite.