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What type of lightweight refractory brick is used in the Maerz kiln?

Release time:

2025-12-26 10:00

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The lightweight refractory bricks commonly used in kilns include high-alumina/mullite-based lightweight thermal insulation bricks, supplemented by ceramic fiber modules or blankets in areas requiring even higher thermal insulation performance. These lightweight thermal insulation bricks are typically employed as the insulation layer in the kiln shell, the outer lining, and the thermal insulation layer in the preheating and cooling sections. However, the kiln’s firing zone (the combustion/high-temperature zone) still requires a dense magnesium brick or high-alumina brick as the refractory lining.

Key points to select:
The lining of a Maerz-type dual-chamber/parallel-flow regenerative kiln is typically designed in layers: the inner layer consists of dense refractory bricks—such as magnesia bricks or high-alumina bricks—that are alkali-resistant, corrosion-resistant, and wear-resistant; the outer layer is made of lightweight thermal insulation materials to reduce heat loss and conserve energy. The lightweight bricks primarily serve to provide thermal insulation rather than directly withstand the chemical erosion associated with calcination.
The density of commonly used lightweight insulating bricks typically ranges from 0.6 to 1.2 g/cm³ (with two common grades available on the market: 0.6 g/cm³ and 1.0 g/cm³). The maximum service temperature they can withstand varies depending on their formulation, usually falling within the range of 1200–1500°C (high-alumina and mullite-based bricks exhibit even higher temperature resistance). Therefore, when selecting bricks, it’s important to match their density and temperature rating to the specific temperature conditions of the kiln section.
In areas requiring higher thermal insulation and allowing for thinner layers, ceramic fiber blankets/modules can be used in combination to enhance the insulation performance (fiber materials have low thermal conductivity, are thin in thickness, and improve overall thermal insulation efficiency).

As recommended by the kiln section:
Calcination Zone (High-Temperature Zone): Do not use lightweight bricks alone; instead, employ dense magnesia bricks or high-alumina bricks as the protective layer, and supplement the outer side with lightweight insulating bricks of higher density (≈1.0–1.2 g/cm³) as the thermal insulation layer.
Preheating Section / Intermediate Temperature Zone: Lightweight insulating bricks made of high-alumina or mullite with a density of 0.6–1.0 g/cm³ can be used, offering both thermal insulation and mechanical strength.
Cooling section / casing and outer insulation layer: Lightweight bricks or fiber modules with lower density and primarily thermal-insulating properties can be used (saving weight and space).

Common optional materials:
Lightweight clay bricks (clay-based insulating bricks): With an Al₂O₃ content of 30–48%, they have a lower bulk density (0.4–1.0 g/cm³), are relatively inexpensive, and can be used at temperatures ranging from 1200 to 1400℃. They are commonly employed in low-temperature insulation layers or as auxiliary components.
Lightweight high-alumina bricks (high-alumina insulating bricks): Al₂O₃ content ≥ 48%; low bulk density (typically 0.8–1.3 g/cm³); low thermal conductivity; service temperature up to 1300–1500℃. Suitable for use in the outer layers of preheating zones and cooling zones, or in medium-temperature sections. They offer excellent thermal insulation performance and strong resistance to thermal shock.
Lightweight mullite bricks: Primarily composed of mullite, these bricks feature high strength and excellent thermal shock resistance. They can withstand higher service temperatures (up to over 1500℃) and are suitable for applications requiring superior thermal insulation and durability.
Ceramic fiber blanket / module
In actual engineering practice, the above materials are typically used in layered combinations.

Selection suggestion:
1. Selection based on kiln section: The density and temperature resistance grade of lightweight bricks are determined by the kiln’s operating temperature, chemical environment (whether it contains strong alkalis or is prone to slagging), and stress conditions. The calcination zone must not be lined exclusively with lightweight bricks.
2. Typical specifications: Commonly used lightweight high-alumina insulating bricks for engineering applications, with a density of 0.8–1.1 g/cm³ and a temperature resistance of approximately 1350°C. On the outer side of the high-temperature zone, ceramic fiber or higher-density lightweight bricks are added to extend service life.

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