One would think that aluminium melting furnaces do not have much in the way of refractory problems because of the relatively low temperatures involved, generally below 800 degrees.  In fact they can give very severe problems due to thermit reactions.  Aluminium has an extremely strong affinity for oxygen, only beaten by magnesium and calcium.  Molten aluminium can reduce silica in refractories, leaving you with a composite material called a cermet, composed of aluminium oxide with a silicon metal matrix.  This cermet is extremely tough and difficult to remove.  The reaction is very highly exothermic.  If you see it starting it makes a very bright spot like a welding arc.  From there it grows and spreads and can go right into the insulation and up to the furnace shell.  It has a high thermal conductivity and gives a very strange effect in the furnace.  It can turn the whole lining into a cermet.  The operator experiences difficulty getting high temperature inside the furnace and yet the shell starts to glow red hot.  Very perplexing.  The cermet is so tough that it can't be broken out.  You have to cut the whole furnace shell off and remove the lining in one piece.  This thermit reaction often occurs in aluminium holding furnaces where the aluminium is heated from above and the refractory directly above the molten metal level gets hotter than the actual aluminium itself.  This can be prevented by smearing a layer of silica free material on the metal line.  Phosphate bonded alumina such as Alpatch is very effective but green chrome oxide containing paint also works to some extent.  

Rotating aluminium furnaces receive most of their refractory wear by de-drossing.  The scraper removes the dross and any attached thermit (also called corundum build up) but it removes the surface of the refractory as well.  These furnaces are generally lined with a very hard dense aluminosilicate refractory castable.  This gives them poor heat retention and thermal inefficiency.  The best solution to this situation is to use a very good insulation material but at intervals of about 150 mm you put very hard silicon carbide skid rails down the length of the furnace.  The skid rails keep the scraper from touching the insulation material and the damage from de-drossing is minimized.