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ALUMINIUM SMELTING INDUSTRY
Anode paste with
high coarse and fine porosity
(continuous kneader)
Fig. 3: Green paste porosity as an indicator of mixing efficiency [1]
Anode paste with low porosity
and evenly coated coke particles
(continuous kneader + Eirich mixing cooler)
products is performed entirely batchwise. Especially
the so-called Ultra High Power (UHP)
qualities for graphite electrodes with large diameters
require an optimally prepared press
body. The very fact that up to three months
elapse between paste mixing and the quality
control of the final product, shows the high
cost of uncertain quality in such a process;
with the mixer being one of the key elements.
A lot of manufacturers are using Eirich highperformance
compact systems because they
need this reliable quality.
Optimisation of the three
important process steps
pensation of short-term variations in paste
composition, especially efficient and thus
moderate energy input, etc. come into their
own. On top of that, the machines are available
for a wide range of throughput rates, so
that even most modern smelters with more
than 600,000 tonnes a year of aluminium production
can be supplied from an anode plant
with just one single preparation line.
After the triumphant start of a pilot system
in a Swiss aluminium smelter, and following
comprehensive tests in Norway, it took about
ten years to commercialise this new idea successfully.
After launching a comparatively small plant
in Cameroon in 1998 [8, 9], the breakthrough
occurred in 2003 with the sale of three plants
to several customers in China [3] In the meantime
the EMC has gained ground in India as
well as in the Persian Gulf. At the Qatalum
greenfield smelter the magical limit of 60 t/h
was achieved in one single line for the first
time.
The concentration on only one preparation
line, even for extremely large anode factories,
is based on economic reasons, which require
a system with maximum reliability and high
availability, but in parallel with short downtimes
for maintenance work. Thanks to decades
of experience, an in-house production of
high quality standards, and a worldwide service
organisation, the EMC systems reach the
same performance as the well-known Eirich
remixer-coolers. Meanwhile, there are 14
EMC lines under construction or in operation.
Carbon products for other
metallurgical purposes
Intensive mixers have been successfully used
for manufacturing graphite electrodes for
electric arc furnaces, cathode blocks for primary
aluminium smelting [4] and carbon blocks
for linings of blast furnaces.
Based on the given task definition, the
paste preparation for these high-quality final
In the mid-1980s, Eirich was able for the first
time to replace a series of conventional batch
mixers of an Austrian graphite electrode manufacturer
by one single Eirich high-performance
mixer. The new batch preparation system
used the following principles:
• Separation of dry substance heating and
mixing process
• Application of a direct electric coke heater
of high performance
Fig. 4: Conventional two-step paste preparation Fig. 5: Eirich Mixing Cascade EMC Fig. 6: 35 t/h paste plant at Aostar/China [3]
42 ALUMINIUM · 1-2/2013