Refractory Systems — Rethought

Refractory materials for tunnel kilns must withstand extreme chemical and thermal stresses. The increasing use of alternative fuels and raw materials, as well as the need for durable solutions for extended production cycles, present the industry with new challenges. Given the current geopolitical environment, energy efficiency and resource conservation are becoming increasingly important. At the same time, the focus is on systems that are easy to install and improve the reliability and maintainability of the structures. Refratechnik addresses these requirements by developing innovative, sustainable, and energy-efficient solutions.

1.1 The ECO Wall System: Ecological, Efficient, and Future-Proof

The design of refractory wall systems for tunnel kilns must withstand very high mechanical, thermal, and chemical stresses. At the same time, quick and easy installation as well as an energy-efficient design are essential. Refratechnik’s ECO Wall System offers an innovative solution to these complex requirements. Energy losses are effectively minimized through weight reduction and the use of highly insulating materials. Mechanical stability and chemical resistance are ensured by the use of appropriate materials. In addition, large panel sizes increase installation speed, reduce the number of joints, and thereby lower both maintenance requirements and operating costs.

1.2.1 The Refratechnik Suspended Ceiling – A Lightweight Solution

Refratechnik’s lightweight suspended ceiling was developed specifically for oxidizing atmospheres and meets the highest standards for stability and energy efficiency. It is designed for a support spacing of 600 to 800 mm and a maximum firing temperature of 1150 °C. With an inter-panel thickness of just 70 mm, it is a true lightweight and combines mechanical strength with significant energy savings.

The design, which uses only one type of hanging brick per row, reduces the variety of shapes, lowers production costs, and significantly simplifies installation. The transverse overlap of the hanging bricks and their longitudinal connection to the intermediate bricks ensure the ceiling meets airtightness requirements. Fewer joints enhance airtightness, effectively minimizing heat loss and significantly optimizing thermal insulation and energy efficiency.

In addition, the one-piece burner tubes, each 880 mm long, contribute to further improving airtightness, which additionally increases the efficiency of the entire structure.

1.2.2 The Basic Suspended Ceiling—The Solution to Alkali Stress

Refractory suspended ceilings must be precisely tailored—both structurally and in terms of materials—to the specific firing temperatures and chemical properties of the furnace atmospheres. If alkalis from the mass fired enter the kiln atmosphere, they can react with the refractory material at temperatures above 700 °C and form new mineral phases such as leucite. These reactions lead to an increase in volume, causing the material to swell and flake off—a phenomenon known as “alkali bursting.” Refratechnik has developed a basic suspended ceiling that significantly reduces the risk of “alkali bursting.” This design is particularly well-suited for the heating and firing zones of tunnel kilns, as it withstands alkaline attacks much better than conventional standard ceilings. This ensures a longer service life and greater operational reliability.

1.3 Efficient Tunnel Kiln Cars: Saving Energy, Reducing CO₂

An analysis of energy losses in the tunnel kiln shows that the exit of the tunnel kiln cars from the kiln accounts for a significant portion of these losses. To minimize these losses, the use of energy-saving materials and optimized designs in this area is particularly effective. The refractory supplier’s influence on the tunnel kiln car’s energy consumption is considerable, accounting for approximately 20 to 30%.

1.3.1 BURCOLIGHT—the proven lightweight material

Refratechnik’s BURCOLIGHT refractory material offers the ceramics industry an innovative solution for saving energy and reducing CO₂ emissions. By reducing the weight of the tunnel kiln car’s refractory structure, energy consumption is significantly lowered; BURCOLIGHT enables energy savings of up to 30% compared to the standard material BURCOTOP 125 H. For the kiln as a whole, the savings can amount to up to 10%.

BURCOLIGHT offers outstanding thermal shock resistance, as demonstrated by tests conducted in accordance with DIN 51068/T1, in which no cracking was observed even after more than 100 cycles. With an extremely low thermal expansion of just 0.30% at 1000 °C (DIN 51045), movement within the tunnel kiln car platform is significantly reduced. The material is ideally suited for use in short cycle times. Furthermore, BURCOLIGHT is recyclable and contributes to sustainable production by effectively reducing CO₂ emissions and conserving resources. BURCOLIGHT has been used successfully worldwide for over 20 years and offers a forward-looking solution for efficient and environmentally friendly ceramic production.

1.3.2 REFRATHERM Eco – Maximum Energy Efficiency and Climate Neutrality

Refratechnik relies on state-of-the-art insulation technologies to maximize the efficiency of tunnel kiln cars and reduce energy consumption. REFRATHERM Eco is a highly insulating material that, thanks to its high microporosity and the resulting high air content, exhibits exceptionally low thermal conductivity. This results in outstanding insulation and energy efficiency, which is further enhanced by the material’s low weight. Since REFRATHERM Eco is made from plant-based waste materials, it is CO₂-neutral and, in addition to saving energy, also helps reduce the CO₂ footprint.

REFRATHERM Eco excels in the installation of tunnel furnace cars thanks to its optimal flow properties, which ensure a homogeneous distribution of the insulation material within the car’s core. This property simplifies the installation process and significantly reduces assembly time.

1.3.3 REFRATHERM LF – Smart Insulation, Reduced Costs

REFRATHERM LF is a high-performance alternative for insulating tunnel kiln cars. Thanks to its high porosity, the material has a low density (75–110 kg/m³) and reduced thermal mass, resulting in significant energy savings with every firing. Furthermore, REFRATHERM LF is easy to install, free of refractory ceramic fibers, and not classified as hazardous waste. It exhibits excellent stability and is reusable, which significantly simplifies repairs and maintenance work.

1.3.4 Streamlined Viaducts – Energy-Efficient Yet Stable

To further optimize the energy efficiency of the tunnel kiln car, Refratechnik has developed viaducts with reduced refractory thickness. As a result, these firing aids achieve enormous energy savings, as they significantly reduce weight by using 20% less material compared to the standard product.

Conclusion

The solutions developed with the overall concept in mind are focused on energy savings. Refratechnik’s R&D Center sets new standards in the development of refractory systems by combining stability, service life, and resource efficiency. Through close collaboration with plant manufacturers and brickmakers, the company creates innovations for walls, ceilings, cars, and firing aids that meet the requirements of modern tunnel kilns.