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TECHNOLOGIE<br />
BMW setzt auf energieeffiziente Schmelzöfen von ZPF Therm<br />
Die ZPF Therm Maschinenbau GmbH<br />
hat an die neu gebaute Schmelzerei <strong>de</strong>s<br />
BMW-Werks in Landshut sechs gasbeheizte<br />
<strong>Alu</strong>minium-Schmelz- und Warmhalteöfen<br />
mit einer Schmelzleistung von<br />
je drei Tonnen pro Stun<strong>de</strong> geliefert. Die<br />
Anlagen bil<strong>de</strong>n das Herzstück <strong>de</strong>r neuen<br />
Schmelzerei.<br />
„Wir sind sehr stolz darauf, dass sich die<br />
Leichtmetallgießerei <strong>de</strong>s BMW-Werks Landshut<br />
im Zuge ihrer richtungweisen<strong>de</strong>n Än<strong>de</strong>rung<br />
im Produktionsprozess – nämlich <strong>de</strong>r<br />
Umstellung von Flüssig- auf Festmetallanlieferung<br />
– <strong>de</strong>r energieeffizienten Ofenanlagen<br />
von ZPF bedient“, sagt <strong>de</strong>r Geschäftsführer<br />
<strong>de</strong>r ZPF Group, Holger Groß. Die an das<br />
Werk Landshut gelieferten Ofenanlagen gehören<br />
zur ST-Baureihe von ZPF und damit zu<br />
<strong>de</strong>n großen Öfen <strong>de</strong>r Produktpalette – nicht<br />
nur hinsichtlich <strong>de</strong>r<br />
Schmelzkapazität. Die<br />
Abmessungen und das<br />
Gewicht von circa 70<br />
Tonnen je Anlage waren<br />
auch logistisch eine<br />
Herausfor<strong>de</strong>rung – sowohl<br />
bei <strong>de</strong>r Anlieferung<br />
als auch beim<br />
Platzieren am Standort,<br />
im oberen Stockwerk<br />
<strong>de</strong>r Schmelzerei.<br />
Die ST-Baureihe<br />
zeichnet sich durch das<br />
geschlossene Ofensystem<br />
und die umgekehrte<br />
Abgasführung<br />
aus. Die Schmelzbrenner erhitzen <strong>de</strong>n<br />
Schmelzschacht, dabei wer<strong>de</strong>n die Heißgase<br />
im Schacht verwirbelt. Um die verbleiben<strong>de</strong><br />
Wärmeenergie zu nutzen, wer<strong>de</strong>n die Heißgase<br />
anschließend über das Warmhaltebad<br />
geleitet, das sich durch die Restwärme <strong>de</strong>s<br />
Schmelzvorgangs erwärmt. Der Badbrenner<br />
greift nur regulierend o<strong>de</strong>r im reinen Warmhaltebetrieb<br />
ein. Die Heißgase gelangen nach<br />
<strong>de</strong>r Schmelzzone in die Nachverbrennungszone,<br />
wo die thermische Nachverbrennung<br />
einsetzt.<br />
Durch die hohe Temperatur und eine entsprechend<br />
lange Verweilzeit wer<strong>de</strong>n praktisch<br />
alle organischen Schadstoffe zersetzt. Dieses<br />
Verfahren ist das optimale und lufthygienisch<br />
beste Verfahren, da die Abgase bis auf die<br />
Frem<strong>de</strong>lemente Stickstoff, Schwefel und Halogene<br />
komplett zu Wasser und Kohlendioxid<br />
umgesetzt wer<strong>de</strong>n. Für die Nachverbrennung<br />
ZPF Therm supplies energyefficient<br />
smelting furnaces to BMW<br />
ZPF Therm Maschinenbau GmbH has<br />
supplied six gas-fired aluminium smelting<br />
and holding furnaces, each with a smelting<br />
capacity of three tonnes per hour, for<br />
the newly-built smelting plant at BMW<br />
in Landshut. The furnaces form the core<br />
of the new smelting plant.<br />
Die ST-Baureihe von ZPF zeichnet sich durch das geschlossene Ofensystem<br />
und die umgekehrte Abgasführung aus / ZPF’s ST series features an enclosed<br />
furnace system and inverted exhaust gas routing<br />
“We are very proud that the light alloy<br />
foundry at BMW’s Landshut works is <strong>de</strong>ploying<br />
ZPF’s energy-efficient furnaces in the<br />
course of their pioneering production process<br />
change from liquid to solid metal <strong>de</strong>livery,”<br />
says Holger Gross, general manager of<br />
the ZPF group. The furnaces <strong>de</strong>livered to the<br />
Landshut factory come from ZPF’s ST series<br />
and are therefore the big furnaces in the<br />
product range – and not only in terms of their<br />
smelting capacity. Their size, and the fact that<br />
each furnace weighs around 70 tonnes, also<br />
meant that not only <strong>de</strong>livery to the site but<br />
also manoeuvring them into place on the upper<br />
floor of the smelting plant presented a<br />
major logistical challenge.<br />
The ST series features an enclosed furnace<br />
system and inverted exhaust gas routing.<br />
The smelt burners heat the melting shaft,<br />
which causes swirling in the hot gases in the<br />
shaft. In or<strong>de</strong>r to make use of the remaining<br />
energy, the hot gases are subsequently routed<br />
over the holding bath. The holding bath is<br />
therefore heated by residual heat from the<br />
smelting process. The bath burner only cuts<br />
in to regulate the temperature or purely in<br />
holding mo<strong>de</strong>. The hot gases reach the reburn<br />
zone behind the smelting zone where<br />
© ZPF Therm<br />
thermal post-combustion takes place.<br />
Practically all organic contaminants are<br />
broken down by the high temperature and<br />
a correspondingly long dwell time. Thermal<br />
post-combustion is the optimum process in<br />
relation to air quality because apart from<br />
external elements of nitrogen, sulphur and<br />
halogens the exhaust gases are completely<br />
converted to water and carbon dioxi<strong>de</strong>. No<br />
additional fuel is required for reburning. The<br />
necessary 750 to 1000 °C come exclusively<br />
from the smelting process.<br />
The purified exhaust gases are discharged<br />
from the furnace behind the post-combustion<br />
zone. No additional air filtering equipment<br />
is required. These extremely hot and<br />
clean gases can be used to further optimise<br />
energy management (heat recovery, water<br />
heating, cold production, factory heating, preheating<br />
chambers for aluminium).<br />
Hydraulic loading systems are used to load<br />
the smelting plants. The material containers<br />
used at BMW are transported into the loading<br />
system in a filling station. Between each<br />
of the three pairs of furnaces there is a loading<br />
system which fills either the furnace to<br />
the left or the right with recycled material as<br />
required. The compact packages of aluminium<br />
are placed directly on the smelting ramp<br />
by a fork lift truck. This permits an additional<br />
large lift door on the front of the furnace.<br />
In ZPF’s estimation, two major trends can<br />
be <strong>de</strong>tected amongst vehicle manufacturers.<br />
Firstly, the alloy nee<strong>de</strong>d for casting will in<br />
future be supplied mainly as solid metal and<br />
less as liquid metal. Secondly, manufacturers<br />
no longer send back most of the recycled<br />
material which accumulates during casting<br />
to a refining works but melt it down again in<br />
their own smelting and holding furnaces. Both<br />
<strong>de</strong>velopments point to growth potential for<br />
the ZPF group.<br />
ZPF Therm Maschinenbau has been building<br />
and supplying customer-specific furnaces<br />
for the light alloy processing industry for<br />
almost 20 years. The company pays particular<br />
attention in its products to the increasing<br />
<strong>de</strong>mands of the sector in terms of energy,<br />
raw materials and environmental efficiency.<br />
Each of ZPF’s furnaces is an illustration of<br />
the fact that highly cost-effective production<br />
and ecological sustainability are by no means<br />
mutually exclusive.<br />
■<br />
56 ALUMINIUM · 3/2013