New Aluminium Melting Furnaces have reduced emissions and save energy
Five years ago, regulations were introduced for limits for emissions from aluminium melting furnaces. Metal melting facilities had until October 30th 2007 to meet the new limits. While many companies will have to invest in complicated systems of filtration, a German company is offering the aluminium casting industry an alternative.
ZPF therm GmbH of Siegelsbach guarantees compliance with the mandatory emissions limits from its aluminium melting furnaces – without filtering systems. Norbert Feth, Marketing Manager of ZPF therm GmbH, German market leader in the production of aluminium melting furnaces, has in the meantime determined an unexpected trend. “Within the past few months, we have been getting increasingly more orders from customers whose melting furnaces are still functioning quite well but do not meet emissions specifications” he says. “From the business viewpoint, it doesn’t make much economic sense to retrofit older furnaces with expensive filtration systems, which anyway would be capable of being used for only a few years”. The price of retrofitting an old furnace would be around EUR 50,000 to EUR 150,000 depending on size. Due to the capital and installation costs of a filtration system, in many cases it may be economically worthwhile to invest in new melting facilities that will guarantee conformity without the need for filtering systems.
ZPF therm provides a compliance guarantee in writing since the measured emissions values of their furnaces fall far below the statutory limits. The proportion of particulate matter in waste gases is less than three milligrams per cubic meter, for nitrogen oxide, the value is about eleven milligrams and only 0.4 milligrams for hydrogen fluoride. Herr Feth speculates: “Even if the limits become yet stricter in five years time, we will still be able to meet the limit values”.
The reason for such low emission lies in the unique design of ZPF therm´s furnaces. The crux of the system is the combustion chamber which is made of refractory concrete and weighs several tonnes. The thick encasement functions as a protective layer between the external steel skin and the insulation layers on one hand and the aggressive liquid aluminium on the other. The heavy refractory also serves as heat accumulator that maintains a steady state interior temperature of the furnace. A sophisticated system of insulation keeps the thermal energy in the interior of the furnace and thus contributes to the saving of fuel.
A different exhaust gas flow from the melting chamber plays a very significant role in the reduction of the furnace’s emissions to air. Rather than being expelled directly to atmosphere from the melting shaft through a chimney as is typical in other furnaces, flue gases in ZPF therm´s furnaces are first kept in the interior of the self-contained system. In the process, residues from the melting process are subsequently virtually combusted. This renders complex filtration unnecessary. Moreover, the longer dwell of the hot gases in the chamber also contributes greatly to the high energy efficiency of the furnace. In the case of the ZPF therm furnace, an average of 20 to 30 percent more performance capacity can be attained through this method of optimal heat utilization as opposed to comparable melting furnaces with open waste gas systems.
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