Alkali Proof Castable

Jun 29, 2021

Alkali proof castable will react with alkali metal oxidizes at high temperature and produce high viscosity liquid phase, which will form a layer of enamel-like protection layer to resist the further permeation and corrosion of molten alkali metals. Lightweight alkali proof castable is made from alkali resistant ceramsite, porous fireclay clinker, waste ceramics, high strength expansile perlite and so on. Calcium aluminate cement or water glass is often used as binder of lightweight alkali proof castable.

Dense alkali proof castable is made from bauxite and fireclay clinker aggregate, binders and powder materials are the same as lightweight alkali proof castable. Chemical compositions of dense alkali proof castable are: 35%~60% of Al2O3 and 35%~60% of SiO2. Calcium silicate cement and silica micro powder are often used as binders of low cement alkali proof castable. Silica micro powder can not only increase medium temperature binding strength, but contributes to the formation of anti-permeation layer.

Alkali proof Castable Physiochemical Index

Item	Light alkali resistant castable	Heavy alkali resistant castable
Al2O3 %	35~65	45~65
SiO2 %	35~45	23~35
Bulk density g/cm3(1100℃, 3h)	1.4~1.5	2.1~2.3
Crushing strength Mpa (1100℃, 3h)	6~6.5	6~10
Linear change rate % (1100℃, 3h)	-(0.3~0.5)	-(0.3~4)
Thermal shock resistance(1100℃, water cooling)	—	20
Thermal conductivity/ W·（m·K-1）	0.4~0.5	1.2~1.3

Alkali Proof Castable Applications

Alkali resistant castable is mainly used at places where surfers severe alkali metal oxides corrosion and alkali metal vapor corrosion. The main applications of dense alkali proof castable are: rotary cement kiln end, kiln hood, pre-heater, discharge hole, blast tuyere and other parts, besides it is also widely used in rotary alumina roasting kilns.
The main applications of lightweight alkali proof castable are: pre-heater top cover, cylinder body and insulating lining of rotary alumina kilns and rotary cement kilns.

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