Lightweight Insulating Castables by Temperature

Insulation refractory castable is also called lightweight refractory castable, also known as boiler insulation castable. Thermal insulation refractory castable thermal insulation castable is based on light thermal insulation aggregate. Add refractory powder, together with binding material and admixture, according to the optimal proportion, it is a kind of hydraulic unshaped thermal insulation material made by dry mixing. It has the characteristics of low bulk density, low thermal conductivity, and high thermal insulation performance, and can be constructed and poured on site. Also known as lightweight insulating castables. It is widely used in boilers, industrial kilns, and other equipment body thermal insulation engineering fields, mainly used for thermal insulation of kilns and to prevent the loss of heat sources.

lightweight insulating castables

Lightweight Insulating Castables by Temperature

Lightweight castable is made of aluminate cement, high alumina fine material, ceramsite, and several additives. Lightweight castables are light in volume, high in compressive strength, and resistant to acid and acid gas corrosion. Features such as heat insulation, heat preservation and low water absorption. Lightweight refractory castables can be divided into the following three categories according to the use temperature.

1. Low temperature lightweight refractory castable. Low-temperature lightweight refractory castables are used at temperatures below 900°C. Expanded vermiculite, expanded perlite, ceramsite, etc. are often used as aggregates. Ordinary Portland cement, bauxite cement or water glass are used as binders.
2. Medium temperature lightweight refractory castable. The use temperature of medium temperature light castable is 900-1200℃. Generally, porous clay particles, clay ceramsite, shale ceramsite, etc. are used as aggregates. Use bauxite cement, calcium aluminate cement or aluminum dihydrogen phosphate as a binder.
3. High-temperature lightweight refractory castable. High temperature lightweight refractory castables are used at temperatures above 1200°C. This refractory castable uses corundum, high alumina, mullite, clay, magnesia, magnesia-aluminum spinel, and other light particles or hollow spheres as aggregates. The combination system is calcium aluminate cement, aluminum dihydrogen phosphate, silica sol, aluminum sol, and silica fine powder.

Compared with other amorphous refractories, lightweight castables have a higher binder and moisture content and better fluidity, so they have a wider range of applications. Can be used in petroleum, chemical, non-ferrous metallurgy, and other industries. The materials and binders used can be selected according to the conditions of use. It can be directly cast into a lining body or can be used as a prefabricated block by casting or shaking.

Insulation Castables

Properties and Characteristics of Lightweight Thermal Insulation Castables

The bulk density of lightweight heat-insulating castables is generally 1.5-1.8g/cm, which is characterized by low thermal conductivity and thermal insulation properties.

Lightweight castables are divided into alumina hollow spheres, lightweight brick sand, porous clinker, expanded perlite, ceramsite, and other different lightweight castables, which are mainly used for thermal insulation in high-temperature furnaces and kilns.

In the soaking section and the heating section of the steel rolling heating furnace, lightweight insulating castables with a bulk density of 1.5g/cm³ are generally used to cast the working lining. The current service life is more than 2 years depending on the usage of the supply.

On the premise of ensuring the thermal insulation performance of thermal insulation castables, it is necessary to improve the mechanical properties, thermal shock resistance, and explosion-proof performance of the castables. Starting from the influencing factors of castable-related properties.

• (1) Reasonable selection of raw materials
• (2) The types of binders and composite components should be adjusted through multiple tests
• (3) Enhancement of powder-material combination and improvement of explosion-proof performance
• (4) Reasonable gradation of castable particles
• (5) Consider the thermal insulation performance of the castable. The selected lightweight aggregate is required to have high porosity, especially closed porosity, so as to exert the excellent thermal insulation performance of the gas and reduce the heat storage loss and heat dissipation loss of the castable lining. At the same time, under the premise of ensuring strength and fire resistance, the thermal insulation performance of the powder-material combination is improved.

Insulation refractory castable

To improve the performance of lightweight castables, micro powder technology should be used, which has good bonding strength under different service temperature conditions, and the amount of cement and the resulting heat of hydration should be reduced.

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