FEATURES OF HIGH-AMPERAGE ELECTROLYZER
V. M. Sizyakov,
V. Yu. Bazhin,
R. K. Patrin,
R. Yu. Feshchenko,
and A. V. Saitov
Translated from Novye Ogneupory,No.5,pp.5–8,May,2013.
Original article submitted February 8, 2013.
Reasons are discussed for shutdown for major overhaul of high-amperage (300 kA) electrolyzer OA-300M1
in the test section of the Ural Aluminum Plant. The electrolyzer service life is 1550 days. Results are provided
for a study of some electrolyzer lining specimens selected by a layer-by-layer pattern method.
Keywords: aluminum electrolyzer, cathode unit, lining, refractory materials, dry barrier layer (DBL)
Recently in the aluminum industry a number of engineer
ing and production measures have been taken aimed at im-
proving electrolyzer service life for aluminum production.
First this concerns new forms of hearths with graphitized and
silicon carbide materials, discretely fed with alumina in order
to create a stable protective build-up, automatically control-
ling electrolyte composition, and contemporary equipment
for anode replacement. The service life of a high-amperage
aluminum electrolyzer is limited mainly by the degradation
time for cathode materials, which occurs as a result of sev-
eral factors: chemical and electrochemical wear, and me-
chanical stresses [1, 2].
STUDY OF BREAKDOWN AREAS OF A CATHODE
UNIT AND REASONS FOR THEIR FORMATION
With visual examination of a cathode unit of a
OA-300M1 electrolyzer severe wear was detected for hearth
blocks with depletion up to 22 cm. The main reasons for
shutting down an electrolyzer was hearth breakdown and
breakthrough of metal into the 22nd blooms of the eleventh
cathode block. It was also revealed that joints between
electrolyzer blocks hardly undergo changes, and therefore a
relief nature is observed for the hearth surface (Fig. 1). The
uneven level of hearth depletion may be explained by pres
ence of localized areas with high density due to its uneven
distribution over a hearth, which is connected with hearth
section construction, with transverse arrangement of two
blooms, and the position of a hearth block beneath the anode.
Another reason for this wear may be metal and electro
lyte turbulence, which affects mechanical erosion and chemi-
cal corrosion with formation and dissolution of aluminum
carbide, which remains after sinking [3, 4]. It is noted that
the degree of erosion over the cathode periphery is greater
than in its central part. Processes of Al
formation and dis-
solution occur as follows:
4Al + 3C = Al C
(l) (so) 4 3
4NaAlF +12Na + 3C
=Al C +24NaF
Al C + AlF + 9F = 3Al CF
43 3 (soln)
3 8 (soln)
These chemical processes occur in certain areas of an
electrolyzer: at the carbon – metal boundary, and at inter
Refractories and Industrial Ceramics Vol. 54, No. 3, September, 2013
1083-4877/13/05403-0151 © 2013 Springer Science+Business Media New York
FGBOU VPO National Mineral and Raw Material University
Gornyi, St. Petersburg, Russia.
Fig. 1. Electrolyzer OA-300M1 hearth surface after shutdown.