CPT International 01/2018

SIMULATION
The flue gas’ outlet temperature is a
suitable parameter for rating the furnace’s
energy efficiency, since it represents
the result of the combined heat
transfer processes inside the furnace.
As a general rule, a higher efficiency is
obtained at a lower flue gas temperature.
Figure 4 depicts the chronological
course of flue gas temperatures at
the melting shaft’s exit (position A in
figure 2) as well as the furnace’s outlet
(position B).
The effect of the fluctuating filling
level on the flue gas temperature can
be seen at measurement position A.
Charging procedures lead to significant
drops of the measured temperature,
which are then followed by a steady
increase. However, the temperature of
the flue gas at the furnace’s outlet (position
B) which ranges between 850 °C
and 1,000 °C shows a more consistent
trend. Furthermore this illustrates that
the flue gas still contains a lot of heat
energy when leaving the furnace.
a
b
Figure 5:perature
inside the melting shaft
Figure 6: Aluminum mass inside a melting shaft with optimized charging strategy
Simulation model
In order to analyze different process
parameters, such as the die casting machine’s
demand for aluminum and its
effect on the melting furnaces, a simulation
model following the depiction
in figure 1 has been created. The
simulation is qualified for developing
new strategies for the in-plant aluminum
distribution or suitable operation
modes for the die-casting machines
and furnaces. Furthermore the simulation
tool offers the derivation of suitable
reactions for different problems,
such as an unexpected breakdown of a
melting furnace or delays in the delivery
of external melted aluminum. The
simulation allows in a risk-free and
cost-efficient virtual environment to
analyze procedures which would otherwise
have major impact on the operation,
e.g. the changing of charging
intervals of the melting furnaces or the
preheating of the raw materials.
The simulation consists of a material
flow model and an energy model,
representing the thermodynamic processes
inside the furnaces. The material
flow section comprises the transport
and processing of aluminum (see figure
1). In addition to the various components,
such as die-casting machines,
furnaces and forklifts, the model also
includes the control measures for the
entire process. In this context strategies
for distribution of liquid aluminum
to the die-casting machines as
well as the order of charging the melting
furnaces with solid material are implemented.
The link between the material flow
model and the energy model of the
furnace is realized by the processes af-
44 Casting Plant & Technology 1 / 2018