Rotary kilns are widely used in building materials, metallurgy, non-ferrous metals, chemical industries, and other fields. Due to different applications, types, and specifications of rotary kilns, as well as varying process requirements for different parts of the kiln, refractory materials must be appropriately selected.

There are many types of rotary kilns. Today, we will first explore the commonly used refractory materials for cement rotary kilns and discuss typical configuration schemes.

 Part.01 Commonly used refractory materials

Magnesia-Iron Aluminum Spinel Bricks

Used in the firing zone, where the flame temperature can reach up to 2000℃ and the material temperature remains above 1350-1400℃. Magnesia-iron aluminum spinel bricks exhibit excellent high-temperature resistance, erosion resistance, and spalling resistance. They can withstand severe high-temperature and chemical erosion, replacing the previously used magnesium-chromium bricks that easily produce toxic hexavalent chromium.

Magnesia-Aluminum Spinel Bricks

Used in the transition zone, where the temperature is slightly lower than that of the firing zone but still subjected to high temperatures and stress. Magnesia-aluminum spinel bricks demonstrate superior stability and thermal shock resistance at high temperatures, enabling them to adapt to the transition zone's working environment.

Silica-mullite brick

They are used in the pre-tropical zone, safety zone (a section after the upper transition zone), decomposition zone, and other areas. Silica-mullite brick feature high strength, excellent abrasion and erosion resistance, enabling them to withstand material abrasion and chemical corrosion. Additionally, their good thermal insulation properties help reduce heat dissipation.

High-Alumina Low-Cement Castables

They are used in the kiln head and kiln tail, where these areas are subjected to impact and abrasion from lumpy materials. High-alumina low-cement castables feature high strength, excellent toughness, and impact resistance, enabling them to withstand material impact and abrasion. Additionally, their good sealing properties help prevent hot gas leakage.

 Part.02 Common Configuration Options

Recommended schemes for refractory configurations for different parts of a cement rotary kiln are as follows:

Configuration of Traditional Cement Rotary Kiln Refractory Materials

Note: D is the effective inner diameter of the rotary kiln cylinder; L is the length of the cooler

 Part.03

Moreover, the shape quality of refractory bricks must also be emphasized. For the refractory bricks in the rotating state of rotary kilns and cylinder coolers, their external dimensions should be strictly specified. Unqualified bricks are prohibited from use. The specific requirements are as follows.

Dimension Tolerance

Height: ±2%

Width (big head/small head): ±2 mm

Width difference (big head vs. small head): ±1 mm

Length: ±1% (max. ±2 mm)

Edge Damage

Two edges on the hot or cold side may be damaged, with a maximum length of 40 mm and depth of 5 mm.

Corner Damage

Only one corner damage is allowed on either the hot or cold surface. The sum of the three edge lengths of the damaged corner shall not exceed 50 mm, while damage ≤20 mm is not classified as corner damage.

Cracks

Cracks parallel to the surface are prohibited.

Other cracks ≤40 mm in length and ≤0.2 mm in width, as well as micro-cracks on the brick face, are permitted.

Pits, Melt Stains, and Bulges

Pits and melt stains: max. diameter/depth 10 mm

Bulges: ≤0.5 mm, with a minimum interval of 1 m.

Circumferential lines should be parallel to each other and perpendicular to the kiln axis. Datum lines can be marked using a laser device and level, with kiln body axial/circumferential welds serving as auxiliary references when necessary.