NORDURAL, THE ICELANDIC SAGA CONTINUES

Abstract
On 17 July 2001, the last pot of the Norðurál Smelter Phase II
Project was put into operation. This expansion consisted of the
integration of 54 CA180/1 cells into the existing system and the
roll out of 6 VAW CA180/2 cells. These cells are the result of
extensive development work by VAW ATG’s modelling and
engineering team over the last few years.
The pots commissioned during Norðurál Phase I are operating
well and achieving world-class results. Since Norðurál was
designed as a modular smelter from the beginning, the owners,
CVC, decided to add a second module in early 2000. This paper
will deal with the Phase II Project, highlighting the concurrent
engineering used and the introduction of new technology. A
review and comparison of the theoretical and actual results will
also be given.
Introduction
In 1998, the first greenfield phase f the Norðural Smelter, located
in Grundartangi, Iceland, was put into operation. This smelter is a
wholly owned subsidiary of Columbia Ventures Corporation
(CVC). From the very beginning, this modular smelter was
designed to grow phase by phase to a final nameplate capacity of
180,000 tpy. Phase I amounted to 60,000 tpy, Phase II an
additional 30,000 tpy and, when completed, Phase III will
comprise 90,000 tpy. Details of the Phase I Project were published
elsewhere [1]. This paper will give detailed information about the
successful engineering, design, construction and operation of
Phase II. A plant photo of the actual Phase II smelter is shown in
Figure 1.
The main advantage of a modular approach is that a smelter like
Norðural can continue to grow at a steady pace. The rate of
growth is determined by such factors as the availability of energy,
capital and other constraints. Regarding the specific investment
costs, a modular approach has the advantage of degressive
investments, as parts of the infrastructure are already installed
during the first construction stage.
VAW Aluminium-Technology (VAW ATG) supplied the
reduction technology for the Phase I Project. It is based on the
state-of-the-art, side-by-side cell, operating at 180 kA (CA180/1).
VAW ATG’s pot control system, ELAS, was also employed. The
outstanding operational results of this first stage led to the owner’s
decision to proceed with Phase II using the same technology.
Consequently, 54 pots were to be commissioned. In addition, six
fully graphitised cells, based on a refinement of the existing
CA180/1 cell design, were to be installed in an integrated booster
Norðurál, the Icelandic Saga Continues
Detlef Vogelsang 1 , Joe Lombard 2 , Friedhelm Waldmann 1
1 VAW Aluminium-Technologie GmbH
P.O. Box 2468, D-53014 Bonn, Germany.
2 Aluminerie Alouette Inc.
CP 1650, Sept-Iles, Quebec, Canada
section. The design amperage of these cells is 210 kA
(CA180/2CA180/2). In the following, both cell types will be
compared with regard to design and operational results.
Figure 1: Plant photo of the Norðural Smelter Phase II
Project Organisation
Light Metals 2002
Edited by Wolfgang Schneider
TMS (The Minerals, Metals & Materials Society), 2002
The Norðural Phase II Project was managed and executed by a
team appointed by CVC. VAW ATG’s project team was fully
integrated into this Norðural II team.
VAW ATG performed several roles. It was the technology
supplier for the CA180/1 and CA180/2 reduction cells and the
supplier of key components, such as point feeder and dosing
system as well as the pot control system and the six
CA180/2CA180/2 superstructures. VAW ATG was also involved
in direct contract negotiations for technology-related equipment
and in quality assurance issues on-site and at the contractors’ sites
for busbars (Venezuela) as well as pot shells and CA180/1
superstructures (Dubai).
Unlike in Phase I, where an expatriate engineering company
conducted the EPCM activities, a local consortium of consulting
engineers (HRV) - using the knowledge and experience they had
gained then - handled all Phase II activities in co-operation with
the CVC/ATG project team. By keeping bureaucracy and red tape
to a minimum and by utilising short, efficient lines of
communication, the project team was able to execute the project
with pinpoint accuracy.

Planning for Phase II commenced after the stabilisation of Phase I
in September 1999. Following the same development strategy,
planning for the Phrase III expansion is now under the way after
the stabilisation of Phase II.
Site activities commenced in mid-February 2000. A busbar short
circuit test was concluded on 26 May 2001 and start-up was
completed on 17 July 2001.
The project was thus completed six weeks ahead of schedule and
within budget.
Technological Aspects
The reduction technology for the Phase II expansion of the
Norðural smelter is based on the proven technology installed in
Phase I. Details of this technology - the CA180/1 reduction cell
with a rated amperage of 180 kA - are published elsewhere [1]. Of
the 60 additional pots installed in Phase II, 54 cells are of the type
CA180; 6 fully graphitised cells were also installed with a rated
amperage of 210 kA
The prime objective during the development of this cell was to
achieve a reduction in the busbar and steel weights of at least 25
%. The pot-to-pot distance also had to be decreased from 6.3 to
5.9 m.
The complete design of this cell was worked out from first
principles on a clean sheet of paper. Hence, the potential for
original, lateral thinking was not compromised by the need to use
existing components or systems. The design was based on a
proven set of busbar design tools and tools for the optimisation of
the pot lining developed at VAW ATG. Features of these
modelling instruments were published earlier [3,4,5]. The new pot
shell was designed applying a fully 3-dimensional finite element
model that takes the temperature distribution of the steel parts as
predicted by thermo-electrical modelling into account.
The CA180/2 refinement project was characterised by a
concurrent engineering approach. After the definition of such
basic data as the pot-to-pot distance, size of pot shell, layout of a
first lining approach, an initial budget estimate was worked out.
Using the preliminary modelling results from the conceptual
designs of the busbar, superstructure, pot shell and lining
available, the basic engineering of these components could
commence and the tender drawings completed. This meant that
the commercial aspect of tendering could begin with the enquiry
for the various technology-related components. Revision loops
ensured that improvements to the conceptual design were
integrated into the final detailed engineering of the CA180/2. By
the time the tenders were ready for awarding, the final
manufacturing drawings were issued and any modifications
included in the final contract negotiations.
Concurrent activities in all fields of modelling, engineering and
commerce resulted in a total fast-track development time of only
15 months for this new cell technology.
A computer model of the CA180/2 cell is shown in Figure 2.
Figure 2: Computer model of the CA180/2 cell
The busbar system was optimised with respect to weight and
voltage drop. A four-riser solution was formulated to give a potto-pot
distance of 5.9 m for the CA180/2 cells compared with 6.3
m for the CA180/1 cells used in Phase I. The weight of aluminium
required for the busbar system decreased from 36.6 to 21.7 t. The
voltage drop for the external busbar system was reduced by 20
mV. Due to the position of the risers, the theoretical width of the
potroom building was reduced by 1.3 m. The cost of installing the
busbar system was cut by having major parts of the busbar ring
system prefabricated in workshops and supplied to the
construction site as subassemblies.
Magneto-hydrodynamic computations indicated an improved
magneto-hydrodynamic stability for the CA180/2 compared with
that of the CA180/1 operating at a 30 kA lower amperage. The
smooth start-up of the CA180/2 fully graphitised cells confirmed
these theoretical predictions. Metal and bath velocities increased
slightly but had no impact on the practical pot performance and
heat transfer at the long side of the pot. The crossover of the
busbar at the end of both potrooms as well as the positioning of
the booster rectifier for the CA180/2 fully graphitised cells was
optimised with regard to the magnetic field conditions for the end
cells and the neighbouring CA180/1 cells.
The cathode design is characterised by fully graphitised twin
cathode blocks. The four collector bars per cathode element are
cast iron rodded. Compared with the CA180/1 lining, the height of
the bottom insulation was reduced, which means that the CA180/2
pot shell is 100 mm lower than its CA180/1 counterpart.
The predicted cell voltage based on the thermo-electrical model
[3] was 4.2 V; the predicted current efficiency was 95 %. Both
figures were verified by the operational results achieved during
the first three months of pot operation.
The pot shell was optimised to give low weight, high stiffness and
optimal ventilation of the cooling ambient airflow. As published
earlier [7], cooling fins were employed to give improved heat
transfer and higher stiffness of the shell sidewalls. The ventilation
of the pot shells was further improved by the installation of floor
grids around the periphery of the pot stall. Compared with the

CA180, fewer cradles were required since twin cathode blocks
were installed. The installation of welded cradles together with
improved bracing of the short ends of the shell resulted in a pot-
The same anode assembly as used for the CA180/1 was
employed. The design principles of the superstructure, however,
are novel. The anode-jacking system was constructed as a
scissor jacking system, see Figure 4. This resulted in a
significant reduction in the anode beam weight.
A second positive effect is the reduction in the height of the
potroom building that will be achievable in the Phase III project.
The hopper/point-feeder system comprises three alumina
hoppers with pneumatically operated crust breakers and dosing
valves and one hopper for aluminium fluoride. A feedback
signal to the ELAS pot control system is used to indicate a
successful breaking operation [6] and supply other essential
operational information to ensure early fault detection and
reliable dosing of alumina. The breaker units are height
adjustable and easily adapted to different bath level heights.
Expanding the potlines by 60 reduction cells also called for
enhanced pot-tending equipment. Using an advanced logistics
Figure 3: Loading forces for the CA180/2 pot shell
shell weight reduction of 30%. Despite this, the load bearing
capacity of the shell was increased by a factor of 1.8. A FEM
result for the loading forces is shown in Figure 3.
model [2], which incorporated detailed smelter logistics, VAW
ATG investigated various alternatives for pot-tending
equipment. The most reliable and economical solution turned
out to be the installation of a dense-phase system for supplying
alumina throughout the whole Norðural smelter, together with
an additional crane for pot tending. An additional gantry at the
end of the extended potrooms also improved the traffic load and
flow.
The smelter’s power supply was sufficient for the increased
number of reduction cells. Only an additional seawater-cooling
loop had to be installed. The anode-rodding shop also had
sufficient capacity for the increased production. The casthouse
was equipped with an additional 70-t holding furnace as well as
a 12-t/h sow caster carousel. Besides the civil engineering works
for the extended potrooms, a 6-bay lining shop was also
installed. It is insulated and heated to create “normal”
temperature conditions especially for winter lining operations.

This lining shop proved invaluable time and time again during
the lining phase.
Figure 4: Plant photo of the CA180/2 cell at Norðural
Start-up and Early Operations
Both the CA180/1 and CA180/2 pots were started up under full
current load. A graphite resistor bed was placed underneath the
anodes. Typical preheating times were 72 hours. Besides regular
control of the CA180/1 cells, an extended and comprehensive
measurement programme was carried out on the CA180/2 fully
graphitised cells. During preheating, cathode temperature,
current pick-up of the anodes and anodic risers were measured at
2-hour intervals. Strain gauge measurements were conducted on
the pot shells and superstructures.
After bath addition and start-up, the cathodic current distribution
and anodic riser currents were determined every 12 hours. A
typical preheating result is shown in Figure 5.
Due to the decreasing electrical resistance of the fully
graphitised cathodes, the average heating rate as measured on
the top surface of the cathodes, decreased from 25°/h to about
5°/h. It was seen that the CA180/2 cells, equipped with fully
graphitised cathodes, are much more sensitive to variations
during start-up than the amorphous cathode of the CA180/1
pots. Hence, tight control during this critical period of cell life is
extremely important.
The operational data obtained during the first three months of
operation have been encouraging with a current efficiency of
95% and a specific D.C. energy consumption of 13.1 kWh/t Al.
Anode effect frequencies have been as low as 0.03/pot day. The
ELAS pot control system together with the sophisticated point
breaker/feeder system have achieved success rates of 75% for
extinguishing anode effects.
60
50
40
30
20
10
0
-10
3
6
9
12
Figure 5: Typical preheating for the CA180/2 cell.
Conclusions
The modular approach of building a greenfield aluminium
smelter phase by phase has proved to be successful. The specific
investment costs are substantially lower than those of a fullsized
smelter investment. The planning of the expansion steps
can also be adjusted to external constraints, such as availability
of energy and capital.
The development concept and project strategy for the new
CA180/2 cell demonstrated that the bundling of computer
models for the conceptual design with novel approaches for
engineered solutions could result in very low investment costs.
The concept of concurrent engineering with revision loops
helped to reduce the development time to only 15 months.
In addition, this new VAW CA180/2 reduction cell provided
outstanding operational results at the first attempt.
References
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1. Joe Lombard, “Norðural: A Fast-Track Modular Smelter”,
Light Metals 1999, pp. 159-163.
2. Ingo Eick, Detlef Vogelsang, Andrae Behrens, “Planning
Smelter Logistics: A Process Modeling Approach”, Light
Metals 2001, pp. 393-398.
3. Detlef Vogelsang, Ingo Eick, Martin Segatz, Christian
Droste, “From 110 to 175 kA: Retrofit of VAW Rheinwerk,
Part I: Modernisation Concept”, Light Metals 1997, pp.
233-238.
4. Detlef Vogelsang, “Application of Integrated Simulation
Tools for Retrofitting Aluminium Smelters”, 4 th
Australasian Aluminium Smelter Technology Workshop,
25-30 October 1992, pp. 641-643.
5. Martin Segatz, Christian Droste, “Analysis of Magnetohydrodynamic
Instabilities in Aluminium Reduction Cells”,
Light Metals 1994, pp. 313-322.
6. Klaus Hofenbitzer, “Improved Concept of Alumina
Feeding”, Light Metals 1999, pp. 293-296.
7. Ingo Eick, Detlef Vogelsang, “Dimensioning of Cooling
Fins for High-Amperage Reduction Cells”, Light Metals
1999, pp. 339-345.
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