1 st of June 2017 The task A smelter introduced slotted anodes to improve performance Green anodes were formed with two transversal slots Dusting was already ID: 610912
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Slide1
ICPMA - Group VII
1
st
of June, 2017Slide2
The task
A smelter
introduced
slotted anodes to improve performanceGreen anodes were formed with two transversal slotsDusting was already a problemCE 92.5 %, net anode consumption 430kg/t AlInitial experience with slots good – lower bubble voltage drop raised amperage3 months after implementation: increased dusting, CE drop of 1%Reasons for the problems?
2Slide3
Anode geometry
Figure
not to
scale, all measures in mm3Slide4
Some initial
reflections
Why
would you want slots?Reduced voltage drop due to bubblesTurbulence in center channelLess disturbance of metal padLongitudinal slots would be preferableLead the gas to the center channelEquipment limitations during forming could dictate orientationThe green anodes are formed with slots - machining slots after
baking is more usualAvoid cleaning
after
baking
Potentially
lower
scrap rateAvoid inhomogeneitiesChoice may be related to investment costThe slots amount to ≈15.4kg of carbon assuming consumption of 30kg/day, this corresponds to roughly half a day of anode life
4Slide5
Root
cause
of the problemMechanisms for dusting: air burn, CO2 burnHypothesis: slots increase the surface area, with a corresponding increase in CO2 burn and dustingOriginal contribution of CO2 burn to net anode consumption: ≈35kg/t AlSurface area without slots: ≈4m2 Additional surface area effectively open to CO2 burn due to slots: 0.72m2
18% increase, amounts to 6kg/t Al
net
anode
consumption
,
which
could
explain the dustingThe positive effects of introducing slots could outweigh the increased net anode consumptionHowever, the significant loss in CE probably means that the introduction of slots would not make financial sense for this plant Dusting problem should be solved first, then slots
may be
introduced
5