Method and apparatus for producing aluminum in an electrolysis cell with tile lining

In the electrolytic production of aluminum, in a cell having a side wall including a layer of carbon electrically insulated from a jacket of metal, the improvement including interposing a layer of tile (27) between the carbon layer (23,24) and the metal jacket (28).

BACKGROUND OF THE INVENTION 
The present invention relates to the lining of a cell for the electrolytic 
production of aluminum. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a new and improved process and 
cell for the electrolytic production of aluminum. 
This as well as other objects which will become apparent in the discussion 
that follows are achieved according to the present invention by providing, 
in the electrolytic production of aluminum, in a cell having a side wall 
including a layer of carbon electrically insulated from a jacket of metal, 
the improvement comprising interposing a layer of tile between the carbon 
layer and the metal jacket.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now in detail to the sole FIGURE of the drawing, it will be seen 
that a preferred cell for use in an embodiment of the present invention is 
similar to the Hall-Heroult-type cell shown in FIG. 1 of U.S. Pat. No. 
3,852,173 in that graphite block 23 is used here as carbon block as was 
done in FIG. 1 of U.S. Pat. No. 3,852,173. In the present embodiment, 
another type of carbon block, anthracite block 24, is placed on top of the 
graphite. Anthracite block is cheaper than graphite block, and it is used 
in the upper part of the side wall, where the greater thermal conductivity 
and erosion resistance of graphite block is not needed. 
Interposed between the top of the anthracite block 24 and the underside of 
the metal, e.g. steel, deck plate 25 is a layer of quarry tile 26. 
According to an embodiment of the present invention, an upwardly extending 
layer of quarry tile 27 is interposed between the carbon block and the 
metal, e.g. steel, jacket 28 of the cell. This quarry tile is held in 
place by a cement, e.g. silicon carbide mortar (not shown), at its joints 
29a, 29b and at its interfaces 31a, 31b with jacket 28 and the carbon 
blocks. 
It has been found that presence of tile 27 in a Hall-Heroult cell can 
permit electrolysis using a voltage across the cell at an average of at 
least 0.1 volts less than the average voltage for electrolysis in a cell 
without the tile. 
EXAMPLE 
Quarry tile 27 of the American Olean Tile Company, Lewisport, Ky., was 
installed in three cells in the manner shown in the FIGURE, using silicon 
carbide cement at the joints and at the interfaces. The average voltage 
across the three cells was 4.313 volts. This is to be compared with an 
average voltage of 4.448 volts for three similar cells in the same plant. 
Thus, an average savings of 0.135 volts per cell was realized. 
The tile was referred to by the supplier as its standard grade quarry tile. 
The individual pieces measured 6.times.6.times.1/2 inches thick. In a 
water absorption test according to ASTM C-20-70, such tile gives a percent 
water adsorption percentage between 0.5 and 0.6. In compression testing 
according to ASTM C-67-50, the tile shows a compressive crushing strength 
of between 25,000 and 30,000 psi. In thermal expansion testing according 
to ASTM C-372, a coefficient of linear thermal expansion is measured at a 
value of between 2.5.times.10.sup.-6 and 3.times.10.sup.-6 inches per inch 
per degree Fahrenheit. In thermal conductivity testing according to ASTM 
C-177, a "K" factor is recorded between 3 and 5. 
The silicon carbide cement was that of the Carborundum Company, 
Refractories Division, of Keasby, N.J., sold under the designation of 
Carbofrax No. 4 silicon carbide mortar/patch. Typically, this product will 
analyze 86.0% silicon carbide. The silicon carbide particle size is 36 
mesh and finer. Maximum use temperature is around 3200.degree. F. 
The carbon blocks measured 4 inches in thickness and were provided at their 
joints 30 with C-38 cement (not shown) of the Union Carbide Corporation, 
Carbon Products Division, of Niagara Falls, N.Y. This product is 
conductive approximately to the extent of the carbon blocks, resists 
oxidation, and can maintain bonding at service temperatures to 
1400.degree. C. and above. 
While the invention has been described in terms of preferred embodiments, 
the claims appended hereto are intended to encompass all embodiments which 
fall within the spirit of the invention.