RATH: Successful new refractory lining
for hearth-type melting furnace of Aluminium GmbH Nachrodt
with sophisticated technical solution

It is a pivotal element in the aluminum industry, without which nothing works: The melting furnace. For almost four decades now, RATH has been offering mature refractory solutions for the optimal operation of aluminum melting furnaces. Such a solution has now been developed also for the relining of a hearth-type melting furnace in the aluminum smelter of Aluminium GmbH Nachrodt (AGN) in the Sauerland of Germany: The core service in this project was a technically demanding solution with components in the floor and side wall despite a furnace being tiltable to either side.

Since the acquisition by Alu-met GmbH in 1999, the annual capacity of the aluminum smelter of Aluminium GmbH Nachrodt near Dortmund has more than doubled, thanks to extensive investments into technical innovations. While 30,000 tons were produced before the merger, currently around 65,000 tons of extrusion billets of Alloy 6000 are produced and delivered.

An optimal, long-lasting refractory lining of the melting furnaces is an essential component for a melting plant to work with highly efficacy. Thanks to more than 125 years of experience in refractory technology, RATH possesses extensive expertise and has developed a comprehensive range of refractory and thermal insulation products for the aluminum industry. Expertise from which Aluminium GmbH Nachrodt, too, is now benefiting: In the context of the relining for a hearth-type melting furnace, the RATH engineering team developed a design solution with the components in the bottom and side wall despite a furnace being tiltable to either side. Here, RATH-produced precast blocks, LC castables, gunning castables, insulating bricks, lightweight refractory bricks and plates were used.

Numerous challenges successfully mastered

“As there were no steel construction and refractory drawings available, all the measurement had to be taken on site”, explains Stephan Holze, Sales & Application Consulting RATH, illustrating the special challenges of this project. Another customer request: Lining of the complete bath area with prefabricated parts. “A further essential requirement was the creation of a bath volume concept including the formation of a melting ramp with increased bath volume”, says Stephan Holze. Last but not least, the conversion had to take place during ongoing production with rail-bound feeding and cleaning manipulations. “All of these were requirements that we were able to meet to our customer’s complete satisfaction in close cooperation with them,” summarizes Stephan Holze.

From the dismantling of the old refractory lining to the external heating up

Moreover, RATH also provided numerous other services for this project: In addition to the planning by the engineering team, RATH also provided the coordination with other trades in order to ensure a smooth overall process. The removal of the existing refractory lining was also carried out by RATH, using robot technology; this was followed by the assembly of the new refractory lining for the complete furnace system, including the construction site equipment. Furthermore, Aluminium GmbH Nachrodt relied on the experts from RATH for heating up as well: The plant was heated up externally, with concomitant thermographic monitoring as well as additional control of the heating depending on the steam pressure in the concrete area in order to achieve optimum quality. Consequently, Frank Hildebrandt, plant manager at Aluminium GmbH Nachrodt, also expressed his satisfaction: “RATH was more than convincing in this project, with high technical competence and smooth execution.”

Major benefits of RATH’s refractory lining

The new refractory lining was installed over a period of about four weeks in total. Now the smelter benefits from long service life of the refractory lining, high operational reliability, low wear, and better cleaning. The prefabricated, heat-treated and factory-tested components are likewise very beneficial: These ensure higher quality than possible with on-site lining. In addition, assembly errors that could lead to hidden damage can thus be excluded. A further benefit: All the components used in the bath area of the furnace have very smooth surfaces with minimum open porosity, which further increases resistance to infiltration.

Full-range supplier of services and products

For almost four decades now, the international refractory materials producer has been supporting companies in the aluminum industry with comprehensive consulting expertise – from planning and installation to maintenance and care of the furnaces. Since then, more than 300 plants have been planned or built by RATH. However, RATH is not only a full-range supplier in terms of consulting and services, but also in the production of all the refractory materials required for all layers in furnace construction. As one of the few manufacturers in the refractory sector, the company produces the complete portfolio of refractory materials required for the refractory lining of a wide range of aluminum furnaces itself.