Refractory materials for cement rotary kiln mainly include kiln bricks, insulation bricks, and castable refractory. According to the characteristics of the cement rotary kiln, the refractory materials used on the fireproof lining are required to have abrasion resistance, alkali resistance, and high-temperature resistance. Based on this feature, AGICO recommends several cement rotary kiln refractory bricks, such as high alumina bricks, high-strength alkali-resistant fire clay bricks, magnesia chrome bricks, lightweight insulation bricks, and castable refractory for cement kilns.
Kiln Bricks for Cement Rotary Kiln
High alumina bricks
The Al2O3 content of high alumina brick used for cement kiln is more than 75%, which has high compressive strength, softening temperature under load, and thermal shock resistance. In addition to the characteristics of ordinary high alumina brick, high alumina brick for cement kiln has other requirements, including wear resistance, alkali resistance, high-temperature resistance, and other properties.
Application process part of kiln bricks
- Traditional cement rotary kiln: firing zone, transition zone, cooling zone;
- New dry-process cement kiln: decomposition furnace, grate cooler, kiln door cover;
- Other types of rotary kilns: front and rear kiln doors, upper and lower transition zone, decomposition zone, preheating zone, and other locations.
| Item | Compressive strength at room temperature/MPa | Load softening temperature / ℃ (T0.6) | Thermal shock resistance/time (1100 ℃) ↔ water cooled) | Standards |
|---|---|---|---|---|
| Phosphate bonded high alumina brick | ≥ 60 | ≥ 1300 | ≥ 50 | JC350—1993 |
| Phosphate bonded high-alumina wear-resistant bricks | ≥ 65 | ≥ 1300 | ≥ 50 | JC350—1993 |
| Anti-stripping high alumina brick | ≥ 45 | ≥ 1470 | ≥ 20 | – |
| Chemically bonded high alumina brick | ≥ 60 | ≥ 1450 | ≥ 20 | – |
| Steel fiber wear-resistant phosphate bonded high alumina brick LZn1 | ≥ 80 | ≥ 1300 | ≥ 40 | – |
| Steel fiber wear-resistant phosphate bonded high alumina brick LZn2 | ≥ 80 | ≥ 1350 | ≥ 40 | – |
| Ordinary high alumina brick Lz75 | ≥ 55 | ≥ 1520 | ≥ 10 | GB2988—1993 |
| Ordinary high alumina brick Lz48 | ≥ 40 | ≥ 1420 | ≥ 10 | GB2988—1993 |
High-strength alkali-resistant fire clay bricks
High-strength alkali-resistant fire clay bricks used in cement rotary kilns are kiln bricks made of low-alumina clay bricks with 25-30% Al2O3 content by adding silica, scorched gemstones, and appropriate additives. The main function of the additive is to improve the compressive strength of fire clay bricks.
Kiln brick features: high strength, stable volume, penetration resistance, good alkali corrosion resistance, etc.
Application process part of kiln bricks
- The preheater, decomposition furnace and tertiary air duct of cement rotary kiln;
- Various high-temperature furnaces.
| Item | Composition | Value |
|---|---|---|
| Apparent porosity,% | – | ≤25 |
| Compressive strength at room temperature, MPa | – | ≥20 |
| Reheating line change (1350℃, 2h),% | – | +0.1–1.0 |
| Thermal shock stability (1100℃-water cooling), time | – | ≥10 |
| Alkali resistance, (1100℃, 24h) | – | First-class |
| Chemical composition | Al2O3，% | 25~30 |
| Chemical composition | SiO2，% | ≤60~70 |
| Chemical composition | Fe2O3,% | ≥2.0 |
Magnesia chrome bricks
AGICO recommends three types of magnesia chrome bricks for cement kilns, ordinary magnesia chrome bricks, direct-bonded magnesia chrome bricks, and semi-direct-bonded magnesia chrome bricks. They are all alkaline refractory products.
Kiln brick features: The magnesia chrome bricks used in cement kilns have high refractoriness, strong alkali corrosion resistance, good thermal stability, and a certain resistance to acid slag.
Application process part of kiln bricks
- Large-scale precalcining kiln: it is used for the central part and both sides of the kiln body, discharge port and other locations;
- Cement rotary kiln: burning zone;
- New dry process cement kiln: transition zone, firing zone and cooling zone.
| Item | Ordinary magnesia chrome bricks | Semi-direct-bonded magnesia chrome bricks | Direct-bonded magnesia chrome bricks | |||
|---|---|---|---|---|---|---|
| Load softening temperature / ℃T0.6 | ≥ 1530 | ≥ 1550 | ≥ 1580 | ≥ 1600 | ≥ 1600 | ≥ 1600 |
| Compressive strength /Mpa | ≥ 20 | ≥ 35 | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 40 |
| Number of thermal shocks/time (1000 ℃, water cooling) | ≥ 3 | ≥ 4 | ≥ 4 | ≥ 4 | ≥ 4 | ≥ 4 |
| Bulk density /kg·m -3 | 2850 | 2900 | ≥ 2980 | ≥ 2980 | ≥ 2950 | ≥ 2930 |
| Apparent porosity /% | 23~24 | 20~22 | ≤ 19 | ≤ 19 | ≤ 18 | ≤ 18 |
| Linear expansion rate /% (1000℃) | 1 | 1.1 | 1.01 | 1.03 | 1.05 | 1.05 |
| Cr2O3/% | 8~12 | 8~13 | ≥ 9 | ≥ 9 | ≥ 6 | ≥ 4 |
| MgO/% | 55·60 | ≥ 65 | ≥ 70 | ≥ 70 | ≥ 75 | ≥ 80 |
| SiO2/% | ≤ 5.5 | ≤ 4.0 | ≤ 3.0 | ≤ 2.8 | ≤ 2.8 | ≤ 2.5 |
Lightweight Insulating Brick for Cement Rotary Kiln
Lightweight insulating brick is a high-temperature thermal insulation refractory material, which is often used in cement kilns and various kiln linings and thermal equipment thermal insulation layers to play a role in thermal insulation.
Kiln brick features: high strength, good thermal shock stability, small linear change on reheating, small thermal conductivity, efficient heat preservation, and heat insulation.
Application process part of kiln bricks
It is suitable for cement rotary kilns, blast furnaces, hot blast stoves, coke ovens, boilers, glass kilns, and various kiln linings and thermal equipment, etc.
| Item | NG-0.6 | NG-0.8 | NG-1.0 | NG-1.2 |
|---|---|---|---|---|
| Bulk density g/cm3 | 0.6 | 0.8 | 1 | 1.2 |
| Compressive strength at room temperature/Mpa | 2 | 3 | 3.5 | 4.5 |
| Heating permanent linear change% (℃xh) | 1200 | 1250 | 1350 | 1350 |
| Thermal conductivity W/m.k(350±25℃) | 0.25 | 0.35 | 0.4 | 0.5 |
Castable Refractory for Cement Kiln
Compared with kilns in other industries, cement rotary kilns have higher temperatures and greater corrosivity, so the requirements of castable refractory materials for cement kilns are relatively high. There are many types of cement kilns, such as vertical kilns, dry hollow rotary kilns, new dry process kilns, wet process kilns, etc. The diameter of the kiln body of various kiln types is also different. Therefore, suitable castable refractory materials should be selected according to the use environment.
Classification of castable refractory materials
AGICO provides you with five types of castable refractory materials for cement kilns: high-strength type, steel fiber reinforced type, low-cement type, ordinary type, and alkali-resistant type. According to the material, they can be divided into three types: corundum, bauxite, and clay.
Application process part of castable refractory materials
- Rotary kiln: front kiln mouth, firing zone, transition zone, decomposition zone, discharge port, kiln door cover, cooling zone, rear kiln door, etc.
- New dry process kiln: preheater, calciner, tertiary air duct, etc.
- Large-scale precalcining kiln: discharge port, outside of burner and lower half of cold end, cooling belt, etc.
| Item | Temperature | High-strength type | Steel fiber reinforced type | Steel fiber reinforced type | Low-cement type | Ordinary type | Ordinary type | Alkali-resistant type |
|---|---|---|---|---|---|---|---|---|
| Material type | Corundum | Corundum | Bauxite | Bauxite | Bauxite | Clay | Clay | |
| Chemical composition /% | Al2O3 | ≥ 93 | ≥ 87 | ≥ 74 | 75-78 | ≥ 70 | ≥ 45 | ≤ 40 |
| Chemical composition /% | CaO | ≤ 5.5 | – | – | 1.5-2.0 | – | – | ≤ 9 |
| Chemical composition /% | SiO2 | ≤ 0.5 | ≤ 2 | ≤ 12 | 12-15 | – | – | ≥ 55 |
| Bulk density /g·cm -3 | 110 ℃ | ≥ 2.88 | 2.89-2.96 | 2.50-2.62 | ≥ 2.70 | 2.6 | 2.2 | 2 |
| Bulk density /g·cm -3 | 1100 ℃ | ≥ 2.70 | 2.80-2.88 | 2.42-2.51 | ≥ 2.70 | – | – | – |
| Compressive strength /MPa | 110 ℃ | ≥ 80 | 70-100 | 70-100 | 100 | ≥ 40 | ≥ 40 | ≥ 40 |
| Compressive strength /MPa | 1100 ℃ | ≥ 80 | 40-60 | 40-60 | 110 | ≥ 25(1000℃) | ≥ 25(1000℃) | ≥ 20(1000℃) |
| Compressive strength /MPa | 1400 ℃ | ≥ 80 | – | – | 130 | – | – | – |
| Flexural strength /MPa | 110 ℃ | ≥ 8 | – | – | 14.3 | – | – | ≥ 5 |
| Flexural strength /MPa | 1100 ℃ | ≥ 8 | 9-12 | 9-12 | 15.7 | – | – | ≥ 2.5(1000℃) |
| Flexural strength /MPa | 1400 ℃ | ≥ 8 | 6.5-11 | 5.5-9 | 15.8 | – | – | – |
| Hot flexural strength /MPa | 110 ℃ | ≥ 9 | – | – | 16.7 | – | – | – |
| Hot flexural strength /MPa | 1100 ℃ | ≥ 9 | – | – | 16 | – | – | – |
| Hot flexural strength /MPa | 1400 ℃ | ≥ 9 | – | – | – | – | – | – |
| Linear expansion rate /% | 1000 ℃ | 0.8 | 0.72-0.77 | 0.60-0.66 | – | 0.5 | 0.4 | 0.4 |
| Linear expansion rate /% | 1100 ℃ water cooling | ≥ 15 | – | – | ≥ 15 | – | – | – |
| Reheating line change /% | 110 ℃ | – | – | – | -0.4 | ＜ 0.4(1000℃) | ＜ 0.5(1000℃) | ＜ 0.5(1000℃) |
| Reheating line change /% | 400 ℃ | ＜ 1 | – | -0.1~ -0.2 | -0.77 | – | – | – |