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ALUMINIUM SMELTING INDUSTRY
KPI
Unit
Dec 2010
to
July 2011
Aug 2011
to
Feb 2012
Mar 2012
to
Sept 2012
1 Oct 2012
to
21 Nov 2012
Amperage kA 419.6 430.2 439.7 440.1
Current efficiency % 95.1 94.9 94.5 94.9
Metal production kg/pot-day 3214 3291 3345 3366
Volts per cell V 4.22* 4.22** 4.24*** 4.24***
DC specific energy kWh/kg Al 13.22* 13.25** 13.37*** 13.37***
Net carbon consumption kg/kg Al 407 412 404 0.398
Fe % 0.040 0.039 0.043 0.036
Si % 0.028 0.029 0.028 0.026
AE frequency AE/pot-day 0.191 0.085 0.071 0.046
AE duration s 9.6 10.3 10.1 10.3
PFC emissions,
CO 2 equivalent****
kg/t Al 33 16 13 9
Fig. 2, above: Historical data on HMI
Fig. 3, below: Pot voltage trend graph on HMI
Table 2: KPIs of Dubal DX+ technology –
average of the five cells
*Based on 4.35 V actual minus 0.13 V for design changes in
the industrial version of DX+
**Based on 4.32 V actual minus 0.10 V for design changes
in the industrial version of DX+
***Based on 4.31 V actual minus 0.07 V for design changes
in the industrial version of DX+
****CO 2 equivalent is calculated as in Reference [4], using
the Tier 2 method
nology has been optimised in many other ways
with respect to its sister DX technology. In spite
of increased length and width, the mass of the
DX+ optimised potshell was reduced by 21%
without any reduction in strength, thanks to improved
structural characteristics of the design.
The cell superstructure height was lowered by
more than 400 mm, and in spite of its increased
size, its mass was decreased by 12%. The overall
volume of the concrete in the potshell and busbar
supports was reduced by 35%.
Considering the amperage increase to 440
kA, the productivity of potroom in tonnes of aluminium
per square metre of covered building has
increased by 16% to 7.12 tonnes of aluminium
produced per square metre of covered building,
calculated for 360 cells and one central passage
per potroom. Capex improvement is the result of
cell productivity, which is proportional to amperage,
and of the higher number of cells per potline
corresponding to the higher rectiformer voltage
of 2,000 V DC. Further optimisation is under way.
The design of DX+ busbars has already been optimised
and the results are: decrease of cell centreline
distance by approx. 5%, reduction of busbar
mass by 20% and reduction of busbar voltage
drop by 26%. Reduced cell-to-cell distance
increases the building productivity by 4.6%.
In Table 1, the actual voltage and the corresponding
specific energy consumption have been
corrected with respect to demonstration cells
to allow for the expected improvements due to
design changes in the industrial DX+ cells to be
installed at Emal Potline 3. These improvements
include larger cross-sections of busbars and cathode
collector bars. A substantial voltage gain has
been obtained with the introduction of four-stub
anodes at the end of 2011 instead of the threestub
anodes previously used. This explains a different
voltage correction for DX+ industrial cells
for the four periods given in Table 2.
Excellent performance has been maintained in
conjunction with amperage increase. As per tradition
at Dubal, the metal purity is excellent in DX
potlines at both Dubal and Emal as well as in DX+
demonstration cells at Dubal: the metal’s low
iron and silicon content did not deteriorate with
amperage increase. Low anode effect frequency
and duration result in very low PFC emissions
(expressed in CO 2 equivalent kg/t Al in Table 1)
which are a benchmark within the industry [7].
20 ALUMINIUM · 1-2/2013