Current Efficiency
Raw Materials
Cell Operation
Measurements
ATab Table of Contents Examples
This page reports several examples that are published in the literature and compares them with the corresponding ATab version.
V. Mann et al. (2008) [Lit.]
To improve in essence anode covering with crushed bath and/or alumina of the existing anode setting pattern (next picture Figure 8) several new patterns were tested (Figure 9):
Existing and Modeled Anode Setting Patterns.
To improve essentially the anode covering with crushed bath and/or alumina of the existing anode setting pattern (Figure 8) three patterns were tested (Figure 9): A) "opposite", B) "staircase", C) "overtaking". Most efficient among the patterns reviewed was the pattern C), tested under industrial conditions on test cells.
The experiments applied the following criteria: 1. uniformity of thermal and electrical resistance of the anode carbon during the entire anode shift life, 2. symmetry of horizontal currents in the melt, 3. permanence of jack load, 4. even surface of the anode carbon to form reliable coverage.
Test in industrial cells showed that anode setting pattern C) was most efficient. No layout pattern is published therefore these layouts could not be compared with ATab results.
V. Mann et al. (2008) [Lit. A, B]
A. V. Knizhnik form JSC (Siberian Research and Design Institute for Aluminium and Electrode Industry) developed the software Zamena (change) to investigate the properties of the anode table in dependence of the anode change sequence. Zamena calculates anode life andvalue of conditional days in hours automatically. The program shows the following values: residual height of the anode pair (in percentage terms), time intervals between change of the anodes standing side by side, of the anodes standing opposite, time till the anode change, time till the corner anode change. Zamena also calculates a coefficient that is a measure for current distribution irregularity in the anodes.
Comparison of the Zamena Window with the ATab Anode Table Representation.
Zamena is a software developed form JSC (Siberian Research and Design Institute for Aluminium and Electrode Industry). It investigates among other things the properties of the anode table in dependence of the anode change sequence.
V. Gusberti et al. (2007) [Lit.]
In this paper several anode change sequences are examined. The next figure compares the published anode table layouts with the ATab anode change paths.
Comparison of published Anode Table Layouts with the ATab Anode Change Paths.
This paper examines several anode change schemas (Rota-1 to Rota-4). This figure compares the published with the ATab anode change paths.
The study uses in a transient non-linear shallow water stability model the rate of increase of the wave amplitude as criterion to evaluate and select the layouts. Three different change sequences were tested in industrial electrolytic cells. The current efficiencies for the three anodechange patterns achieved in real cells are in excellent agreement with the model instability predictions and the waves growth rates.
M. Iffert et al. (2005) [Lit.]
This publication treats among other things the influence of anode change on the electrolyte temperature. During this process a mass of cold carbon is introduced into a cell causing significant, especially local, cooling. This effect was investigated for two different anode changing sequences namely Rota-A and Rota-B. These anode table layouts corresponds to Rota-1 and Rota-2 of the publication above.
Rota-A and Rota-B Anode Table Layouts.
The Rota-A and Rota-B anode table layouts correspond to Rota-1 and Rota-2 of the Gusberti paper.
The next figures compare the fluctuations of the electrolyte temperature during a complete anode change cycle period. The temperature deviations of Rota-B cells are greater compared to Rota-A. An interesting finding since the total mass of cold anodes to be inserted into the cells is the same for both cell types.
J. Purdie et al. (2001) [Lit.]
This paper reports about two standard setting patterns that are called the "odd butterfly" and "even butterfly", for odd and even numbered cells respectively. The two patterns are mirror-reversed, with the aim being to optimise crane movements by setting the upstream side of one cell and the downstream side of the adjacent cell at the same time.
A number of other setting patterns were investigated, with the aim to reduce thermal cycling associated with the setting cycle and to reduce overall voltage.
The next table shows the actual voltage and voltage noise for each of the patterns, measured over 13 months. Data is adjusted for age, cathode type and location (values in italics in the grey fields are significantly different from odd butterfly (see Relative Cycle Period Averages).
Results.
Pattern A shows significantly lower temperature variation than the standard patterns. Voltage noise and actual voltage are also lower. There is a significant difference in noise, voltage and temperature standard deviation between the two standard patterns, "Odd" and "Even Butterfly". All the other trial patterns tend to perform worse than the standard patterns.
The results indicate that the "Odd Butterfly" seems to be the best setting pattern. Pattern A must be compared with the "Odd Butterfly" pattern on a larger trial group of cells, before a decision can be made to adopt pattern A. The impact of making such a change on anode cover integrity, and potentially net carbon consumption, will need to be considered in the decision.
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