“Melting is a core step in the processing of primary and secondary aluminium but also extremely energy intensive and can impact both the productivity and total cost of aluminium production,” says Simphiwe Molefe, Applications Specialist for Bulk Markets at Afrox.

“With the growing need for reducing production costs, increasing productivity and yield, enhancing quality and environmental awareness in the aluminium industry, Afrox – through its parent company, the Linde Group – is evolving and refining its technologies to increase productivity in the aluminium process chain. From melting and dross handling to refining, extrusion and annealing, Afrox has the technical competence and process knowledge to add value throughout the aluminium process chain.”

Low-temperature oxyfuel combustion technology
“This technology is designed for the aluminium industry and is based on flameless oxyfuel combustion. The combustion in the process occurs under a diluted oxygen concentration. Basically, the flame is diluted by mixing it with hot furnace gases and this slows down oxyfuel combustion reactions and results in lower flame temperatures, comparable to those of an airfuel system. The mixing of flue gases with the flame also disperses the energy throughout the entire furnace for a faster and more uniform heating. The dispersed flame contains the same amount of energy as a normal airfuel burner, but with more effective distribution. The dilution of the flame also slows down the oxyfuel combustion reactions and results in lower flame temperatures, lower emissions, higher melt rates and lower fuel consumption, while avoiding hot spots and dross formation.”

“Air consists of approximately 20,95% oxygen by volume with approximately 78,09% being nitrogen. With this amount of nitrogen by volume, during airfuel combustions nitrogen tends to absorb heat, in a way acting as an extinguisher. By increasing the amount of oxygen in the melting process, you reduce the amount of inert nitrogen in the combustion reaction. This has several advantages which include increased thermal efficiency, reduced fuel consumption, improved control over the process and less fuel emissions,” explains Molefe.

He adds that this is applicable to both primary and secondary aluminium processing as well as new or existing furnaces. While this is not new technology, it is often challenging for smelters to determine the exact suitable combustion solution to meet their individual needs.

“Together with the Linde Group, we have extensive experience with oxyfuel for aluminium melting which enables us to provide our customers with suitable combustion solutions that meet individual demands.”

“As a member of the global Linde Group, Afrox has access to cutting-edge gas solutions, and is able to assist customers in the aluminium sector in the use of oxygen to enhance the combustion process, increase efficiency and reduce emissions. Afrox’s oxyfuel solutions for the aluminium industry have shown to increase melting rates by as much as 100%, reduce fuel consumption by up to 50% and cut flue gas and emissions by anything up to 90%.”

Afrox’s oxyfuel solutions include a wide range of oxyfuel burners and technologies designed by the Linde Group to suit different processes and requirements for aluminium melting.

Airox® Combustion Technology
“The Airox® burner solution is an advanced tool for flexible and economic melting. The technology allows furnace operators to easily switch between oxygen, or oxygen-enriched gases during the melting process, and air during the holding phase. This results in greater melting capacity and flexibility as well as lower emission rates and energy consumption. Airox® combustion technology is well suited for furnaces that are used for melting and holding intervals, light metal foundries, extrusion companies and foil producers.”

Wastox® Combustion Technology
“This solution is most suitable for the economic melting of low-grade scrap and turns unwanted contaminants into valuable fuel. The secondary aluminium industry is often challenged to find economic, environmentally sound ways of melting scrap contaminated with organic compounds, as emissions can limit productivity and restrict the choice of raw material. Wastox® provides a powerful answer to these challenges by using oxygen lances to combust emissions within the furnace that are simple to install and operate.”

For more information contact Simphiwe Molefe of Afrox on TEL: 011 490 0470 or email simphiwe.molefe@afrox.linde.com.