Zhengzhou Tyreen Refractory Co.,Ltd
Alkali resistant brick is a low-alumina silica-alumina refractory specifically developed for areas exposed to strong alkali attack. It is produced from low-alumina refractory clay or pyrophyllite clinker as the main raw material, with controlled additions of silica and strength-enhancing additives, then high-pressure formed and high-temperature fired.
The key performance mechanism is chemical: at high temperature the brick reacts with alkali metal oxides (mainly K₂O and Na₂O) to form a high-viscosity liquid phase. This liquid phase quickly creates a dense glaze-like protective layer on the brick surface, sealing the pores and effectively blocking further penetration of alkali melts. As a result, the brick resists “alkali cracking” and corrosion that commonly destroy ordinary fireclay or high-alumina bricks in the same environment.
Key Performance Characteristics
- Excellent alkali corrosion resistance through the formation of a protective glaze layer
- High cold crushing strength (especially the high-strength grade)
- Good volume stability at high temperature
- Reliable resistance to thermal shock
- Low permeability that limits alkali vapor and melt penetration
- Suitable mechanical strength and abrasion resistance for gas-flow and dust-laden zones
Typical Technical Data
| Item | Ordinary Type | High-Strength Type | Insulation Type | Vault Type |
|---|---|---|---|---|
| Al₂O₃ (%) | 25–30 | 25–30 | 25–30 | 30–35 |
| SiO₂ (%) | 65–70 | 65–70 | 60–70 | 60–65 |
| Fe₂O₃ (%) | ≤2 | ≤2 | ≤2 | ≤2 |
| Bulk Density (g/cm³) | ≥2.15 | ≥2.25 | ≤1.65 | ≥2.20 |
| Apparent Porosity (%) | ≤21 | ≤20 | ≥35 | ≤21 |
| Cold Crushing Strength (MPa) | ≥35 | ≥60 | ≥15 | ≥35 |
| Refractoriness under Load 0.2 MPa (°C) | ≥1350 | ≥1300 | ≥1250 | ≥1400 |
| Refractoriness (°C) | ≥1650 | ≥1650 | ≥1650 | ≥1710 |
| Thermal Conductivity (350°C, W/m·K) | ≤1.28 | ≤1.28 | ≤0.70 | ≤1.28 |
Main Applications
The primary and most important use is in cement kiln systems, especially modern dry-process precalciner kilns where alkali circulation is severe:
- Preheater cyclones and riser ducts
- Calciner / decomposition furnace
- Tertiary air duct
- Transition zone of the rotary kiln
- Vertical flue and cyclone cones
High-strength grades are preferred in areas with higher mechanical stress or stronger gas flow. Insulation-type alkali resistant bricks are sometimes used in kiln hood, cooler and other lower-temperature sections where both alkali resistance and heat insulation are needed.
Although the product is optimized for cement industry alkali attack, it can also be considered for other thermal equipment that experiences moderate alkali vapor or alkali-containing dust, such as certain sections of lime kilns or waste incinerators. However, its core design and largest application remain cement kiln linings.
