CPT International 04/2014

SPS
Pressure vessel
Pulse
generator
Oxygen
Basic
load control
Figure 1: SIP plant with two pressure
vessels
Figure 2: Functional principle of the Sequence Impulse Process (SIP) [5]
In 2011, Luitpoldhütte AG installed
such a SIP plant at its foundry in Amberg,
Germany (Figure 1).
Principle of the Sequence Impulse
Process (SIP)
The Sequence Impulse Process feeds
additional process gases (e.g. oxygen)
in pulses into shaft furnaces. The
pulsed oxygen is injected by pressure
pulses via tuyere lances [3, 4].
The objective of this technique is to
use the potential energy generated inside
the pressure vessel by compression
of the oxygen so as to achieve maximum
oxygen penetration in the furnace
charge.
The pipes and lances are constantly
supplied with a basic load of oxygen in
order to avoid weakening pulses due to
increasing friction and ensure that the
injection lances in the tuyeres are permanently
cooled.
The pulses are generated at defined
intervals. In a fraction of a second, a
large volume of oxygen is released from
the pressure vessel and impulse-fed
into the furnace [5]. The principle of
the SIP is shown in Figure 2.
Underlying metallurgical and
technological features
The aim is to achieve uniform gas
penetration over the entire furnace
cross-section by means of energy-rich,
cyclical pulses in the low-frequency
range [6].
Figure 3: Coke bed temperature in front of the tuyeres [8]: reference campaign,
SIP campaign (from left to right)
In the cupola process, the SIP provides
energy saving potentials as it reduces
energy losses due to cooling. For
example, the wall effect, i.e. high thermal
load on the furnace walls, can be
avoided.
Additionally, effective gas penetration
improves the convective heat
flux and reduces the sensible heat in
the top gas.
The minimum required calorific value
of the top gas is determined by the
hot-blast temperature or the efficiency
of the recuperator. In other words, here
the energy saving potential is highest.
This means that energy or heat is to be
extracted from the reduction zone of
the furnace as quickly as possible to reduce
the zone in which Boudouard reaction
equilibrium exists (i.e. the equilibrium
between carbon dioxide (CO 2
)
and carbon monoxide (CO) which occurs
when oxygen reacts with glowing
carbon). This can be achieved by an optimal
location of the melting zone and
an efficient convective heat flux from
the coke and/or the shaft gas to the
iron. Here, a solution is provided by
the Sequence Impulse Process which
allows the localized and timed injection
of additional oxygen [7].
Within the framework of the research
project “Automated Sequence
Impulse Process for Large Shaft Furnaces”
(German acronym: ASIPGO),
the temperatures in the coke bed of a
cupola, measured by means of a quotient
pyrometer with integrated video
camera, were investigated. Compared
to the injector process (reference process),
the SIP technology achieved
a temperature reduction by approx.
200 K in front of the tuyeres with the
same amount of oxygen. This indicates
that the combustion zone was shifted
towards the furnace centre as a result
of the oxygen being fed in pulses.
This reduces the wall effect in the fur-
Casting Plant & Technology 4/2014 11