Side Lining Materials

The side-wall lining of reduction cells should withstand the following  

The side lining materials of reduction cells are carbon blocks and silicon carbide blocks. Anthracite-based carbon side blocks were used for many years. As a continuation of R D in the application of carbon side blocks, many approaches were offered (Table 2.12)  

The technology of carbon side-wall blocks is very similar to the technology of anthracitic graphitic cathode bottom blocks (Figs. 2.20 and 2.21). The requirements for carbon side-wall blocks are similar to the requirements for bottom blocks but easier moderate strength, moderate sodium swelling, relatively high resistance to oxidation and to corrosion by bath and by aluminium. 

Material Anthracitic Anthracite + graphite Anthracitic, with increased oxidation resistance Anthracitic, with increased oxidation and erosion resistance Graphitic, with increased oxidation resistance Graphitic, with increased oxidation resistance 

2 Refractories and Carbon Cathode Materials for Aluminium Reduction Cells 

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The immersed tests are usually produced in big crucibles, filled with at least one corrosive agent. The dimension of the tested rods (usually rectangular bars) is 25 mm x 25 mm x 100 mm or 10 mm x 10 mm x 150 mm (Fig. 1.33). The bars may rotate or be dipped and pulled out or may be tested without rotation. The corrosion resistance tests for silicon carbide side lining materials are discussed in detail in Chap. 2. The corrosion resistance tests for A1 melt are discussed in Chap. 3. The tests for sodium swelling of carbon materials are discussed in Chap. 2, devoted to the lining materials for electrolysis, rather than in the chapter devoted to corrosion resistance. 

Table 2.12 Properties of carbon side lining materials...

Attempts to use silicon carbide as a side lining material started in the 1980s when the problems with carbon side lining began at the reduction cells with increased current. The technical solution was the application of nitride-bonded silicon carbide. Within the next 20 years, several variants of SiC side lining designs were tested (Fig. 2.64a-f) ... 

Nitride-bonded silicon carbide (silicon nitride-silicOTi carbide material) is not the only variant for application as a side lining material. Here is a list of variants ... 

Figure 9 Close-up of packed-bed weir-SMEC using 20-pm-particle-sized polymeric support material. The homogenious packing structure of the packed bed can be seen on the left-hand side lining up close to the eight-channel microfluidic grid...

Tasopoulos, T dagger, R. G. dagger, D. C. Griffiths, A. E. Eneigy absorption and hardness of chair-side denture soft lining materials. Eur. J. Pmsthodont Rest. Dent., 2010,18(4), 189-194. 

Table A lists all those solvents denoted by a letter in Table B and should be referred to when indicated in the chemical listing. Always use the lowest temperature recommendation shown for either the chemical or the solvent. Table B shows lining materials, chemicals, solvents, concentration and temperature limits for use. The lining materials are described across the top as column headings. The various rubber groups are listed in their approximate order of relative cost, with natural rubber being the lowest. The chemicals are listed on the left hand side. These tables contain not only the common names of the chemicals, but also any names which may be synonymous.

The side-wall blocks from carbon or silicon carbide are placed on a refractory shoulder side line. This side line is above the refractory layers under the cathode bottom blocks. It may be made of bricks or from castables, usually together with heat insulation boards. This sideline has two purposes. First, side lining is installed in the refractory side line, and, second, it helps to compensate for the mechanical tensions due to the sodium swelling (and thermal expansion) in carbon bottom blocks. Heat insulation materials are easily deformed due to tension, but the construction of the refractory lining remains tmdamaged. 

Carbon anthracite side-wall blocks were used for a long time. The reactimi between air oxygen and the carbon starts begiiming at 400-500 °C at 900 °C, the reaction rate is considerable. Additives to the material of carbon side-wall blocks make oxidation slower. The carbon side lining deteriorates due to oxygen in the upper part (Fig. 2.63) or in the lower part from the side of the shell (in case of air leakage through busbar windows). 

The producers of carbon materials offered several decisions to increase the properties of carbon side lining (Table 2.12). There were variants of anthracite-... 

There were no significant results in the application of carbon side-wall materials with enhanced characteristics in the reduction cells, and the current technical decision is silicon carbide side lining. Yet it is necessary to mention that a carbon side lining is in use in low-current cells, especially in Soderberg technology. 

Variants of Silicon Carbide Materials (and Others) as a Side Lining... 

As shown in laboratory experiments, nitride-bonded SiC is sufficiently more corrosive-resistant, comparing with aluminosilicate-bonded SiC (sintered in air). Currently, nitride-bonded silicon carbide is the main and only material for SiC side lining. 

The rods are 10 x 10 x (100-130) mm, in the melt of the bath and aluminium. The existing variants of the rod test imitate the service of the SiC side lining in slightly different ways, giving a different corrosion resistance for the materials of different producers. 

Self-bonded SiC, sintered SiC, aluminium nitride (AIN), SiAlON-bonded SiC, titanium boride—SiC compositiOTi, oxide materials were considered to be promising for application as a side lining of the reduction cell. 

Currently, N-SiC refractory, for one thing, is a material that satisfies the requirements of the Hall-Heroult process on corrosion resistance and thermal conductivity additionally, it is considered to be cost-effective although it is not an optimal material for side lining of the HaU—Heroult process from a materials science viewpoint. 

Yurkov A, Danilova O, Dovgal A. N-SiC side lining - variations of materials structure. Light Met. 2014 143 1245-9. 

Sometimes the gaps for the compensation of the thermal expansion are made near the walls under the side lining, and the gaps are filled with ceramic fiber materials, taking into account 50 % shrinkage of this fiber material. 

Carbon ramming paste a semifinished product used to fill in the gaps between the end of carbon cathode blocks and the refractory side lining. The raw materials are the same as for carbon cathode blocks, but the material receives its final properties during the preheating and startup. 

The Z-trajectory ensures excellent separation of ions from neutral molecules at atmospheric pressure. In line-of-sight or conventional electrospray sources, the skimmer is soon blocked by ions and molecules sticking around the edges of the orifice. In Z-spray sources, the final skimmer, being set off to one side, is not subjected to this buildup of material. 

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