Process Heat

Energy-efficient process for heating aluminium billets

The newly developed furnace preheats combustion air and lowers the specific consumption of natural gas in the system, reducing CO2 emissions by up to 160 tonnes per annu

Summary

Initial situation

F.W. Brökelmann Aluminiumwerk GmbH & Co. KG produces semi-finished parts, profiles and pipes of aluminium for use in the fields of traffic engineering, building technology, industrial engineering and heat exchange technology.

Around 10,500t of aluminium are made into a variety of profiles in extrusion presses each year. Until now, the aluminium billets were preheated by gas burners in a furnace prior to extrusion. Approx. 313 kWh/t of gas were needed for this process. The hot flue gases generated in the preheating zone were extracted.

The project aimed to make the production of aluminium profiles more energy-efficient whilst increasing productivity at the same time by increasing furnace throughput by 25 per cent.

Technical solution

In order to improve the efficiency of the furnace, the aluminium processing plant developed a billet heating furnace with an innovative combustion air preheating system in collaboration with an engineering firm. The other main characteristics of the new furnace are:

  • A larger number of burner nozzles
  • The innovative positioning of the nozzles producing the flames within the billet heating furnace
  • An adaption of the interior of the furnace to the diameters of the billets
  • The use of a high-convection preheating chamber with ventilators

The flue gases escaping from the preheating chamber are led through a heat exchanger to preheat the combustion air used for the gas burners.

This process facilitates both a more effective transfer of heat to the material and the use of the flue gases that had previously been discharged.

In addition, the head of the aluminium billet is induction heated immediately prior to extrusion in order to facilitate the extrusion process.

Findings

These measures made it possible to reduce the quantity of natural gas used in full-load operation to 192 kWh/t. In relation to an annual quantity of 10,500t of aluminium, average CO2 emissions will go down by 15.8% to around 141t p.a. Once part-load operation has been optimised, the target of reducing CO2 emissions by 160 tonnes per annum will also be feasible.

The modification of the furnace made it possible to reduce the energy used for the induction heating of the billets from 23 kWh to 15.1 kWh per tonne of aluminium.

Furnace capacity was increased from 4,800 kg/h to 6,000 kg/h. This corresponds to an increase in capacity of 25%.

Conclusions

If all plants of this type operating in Germany were to implement this innovative process, harmful carbon dioxide emissions could be reduced by a total of approximately 7,000 tonnes each year.

Source: Final report

More Project Information

Project title: Umsetzung eines innovativen energieeffizienten Aluminiumbolzenerwärmungsverfahrens

Project number: 20109

Project period: 2007 - 2008

Project region: Germany (North Rhine-Westphalia)

Project contact:

Frau Fischer
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+49 (340) 2103 3067
+49 (340) 2104 3067

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Source: Environmental library of the Federal Environment Agency (UBA)