Microporous Calcium Silicate Insulation Material

Calcium silicate, also known as microporous calcium silicate, refers to a porous thermal insulation material made from the CaO-SiO2-H2O ternary system. It is a new type of thermal insulation material. In the CaO-SiO2-H2O system, there are currently 22 known minerals. However, there are only two types of thermal insulation materials widely used in industry, namely Xonotlite and Tobermorite. The chemical formula of the former is close to 6CaO·6SiO₂·HO. The chemical composition of its actual product is as follows: SiO2 46.3%, Al2O3 0.3%, CaO 43.3%, MgO 0.7%, Fe2O3 2.5%, and ignition loss 5.9%. The maximum operating temperature of this product is 1000℃. The chemical formula of Tobermorite is close to 5CaO·6SO₂·5H2O. The chemical composition of an actual product is as follows: SiO2 44.4%, Al2O3 3.7%, CaO 4.7%, MgO 0.6%, Fe2O3 1.8%, and ignition loss 13.8%. Tobermorite has a layered structure, and the interlayer distance of 11.3A is called 11ÁTobermorite, and the interlayer distance of 14Á is called 14ATobermorite. Its maximum operating temperature is 650℃.

Microporous Calcium Silicate Insulation Material

Microporous calcium silicate insulation material

Preparation process of calcium silicate insulation material

Calcium silicate insulation material is synthesized by hydrothermal method using quartz sand, ordinary silica or highly active silica and lime raw materials. Usually inorganic fibers such as asbestos and alkali-resistant glass fiber are added as reinforcing agents. In recent years, organic fibers have also begun to be used. After drying, the product needs to be further processed to ensure the size of the product.

The shape of calcium silicate insulation products is usually plate-shaped, tubular or block-shaped. According to the shape of the product and the requirements for performance, there are generally the following molding methods.

• 1. Wet pressing method. After the raw materials and water are mixed evenly, they are gelled to make gel. Then they are pressed, dehydrated and boiled. The apparent density of the product is controlled by pressure, thereby controlling the strength and thermal conductivity of the product.
• 2. Bagging method. Use a special bagging machine to scoop the raw material slurry into sheets. Then stack several thin sheets to form a board. The manufacturing process is similar to the method of manufacturing asbestos board. The characteristic of this method is that the reinforcing fibers are arranged along the direction of the sheet, and the reinforcing effect is significant. The product has high strength and is particularly suitable for producing thin plates with a thickness of 6~12mm.
• 3. Casting method. The raw materials are dispersed with water or hot water to make mud, and the mud is injected into the mold for molding. Foaming treatment can also be performed during the casting process.
• 4. Pressing and rolling molding. Add an appropriate amount of water to the raw materials, mix them evenly, and make semi-dry mud. The apparent density of the product can be adjusted by roller rolling or extrusion molding through an extruder, and the rolling pressure can also be controlled.

The cooking temperature of Tobrermorite is usually 160℃~180℃, while the cooking temperature of Xonotlite is 180℃~220℃. The cooking method can be continuous or intermittent.

Microporous calcium carbonate block

Microporous calcium silicate is made by calcining and melting calcium oxide and silicon dioxide at high temperature. It is a new type of insulation product with relatively ideal performance indicators among the current hard insulation materials. It has the advantages of light bulk density, low thermal conductivity, high bending and compressive strength, no deformation when exposed to water, long service life, sawing, easy processing, non-toxic, and no corrosion to pipes and equipment. It is a new type of hard insulation material currently welcomed by power, petrochemical, metallurgy and other departments. According to the different use temperatures, calcium silicate is divided into two categories: ordinary type and high temperature type.

Ordinary calcium silicate is divided into three types according to different densities: 240 type, 220 type, and 170 type, all of which can be used for insulation of equipment and pipes below 650℃. Hydrophobic calcium silicate is a performance-improved type of ordinary calcium silicate, and waterproof components are added during the production process. In addition to the various properties of ordinary calcium silicate, it also has the characteristics of non-absorption and moisture-proof. It is particularly suitable for underground direct buried pipelines in swamps and trenches and overhead pipelines in humid areas.

High temperature microporous calcium silicate belongs to the hard calcium silicate stone type, and its use temperature is below 1000℃. It is mainly used in boilers, kilns and pipes and equipment below 1000℃.

Microporous calcium silicate products are used for thermal insulation of chemical equipment and process pipelines. The thermal insulation construction is convenient and the effect is good. It is especially used in the thermal insulation of industrial furnaces and high-temperature reactors, and its performance is relatively stable. The disadvantage is that its toughness is not as good as other fiber materials.