Shockproof refractory castable anode assembly

Abstract

An anode system ( 10 ) in contact with a molten salt bath ( 34 ) in an electrolysis apparatus, contains a 50% to 95% dense refractory support ( 12 ) which comprises refractory material and from 2 wt %. to 20 wt. % of metal fibers ( 40 ), where the metal fibers are from 1 cm to 4 cm long.

What is claimed is:  
     
         1 . A support for an anode system in contact with a molten salt bath in an electrolysis apparatus, said support comprising a 50% to 95% dense castable refractory subject to attack by gases from the bath, where the refractory comprises refractory material and from 2 wt % to 20 wt. % of metal fibers, where the metal fibers are from 1 cm to 4 cm long and have a length to thickness ratio of 500:1 to 20:1.  
     
     
         2 . The support of  claim 1 , comprising at least 55% of alumina castable refractory.  
     
     
         3 . The support of  claim 1 , wherein the metal fibers are selected from the group consisting of stainless steel, nickel alloy, copper alloy and mixtures thereof.  
     
     
         4 . The support of  claim 1 , wherein the metal fibers are stainless steel and the metal fibers have a coating comprising an oxide of phosphorous.  
     
     
         5 . The support of  claim 1 , wherein the metal fibers have a concave cross-section.  
     
     
         6 . The support of  claim 1 , wherein the electrolysis apparatus is an aluminum producing apparatus, the molten metal salt bath is molten cryolite at about 850° C. to 1050° C., and the gases include HF and O 2 .  
     
     
         7 . A support assembly for an inert anode system comprising at least one inert anode in contact with a molten salt bath in a metal electrolysis apparatus, where the at least one inert anode is attached to a support system having an outer side subject to attack by gases from the bath, the support system consisting essentially of a 50% to 95% dense castable refractory material having from 2 wt % to 20 wt % of metal fibers dispersed therethrough, where the fibers are from 1 cm to 4 cm long, and where no more than 20 fibers per sq. cm. on average protrude through the outer side of the support system.  
     
     
         8 . The support assembly of  claim 7 , comprising at least 55% alumina castable refractory.  
     
     
         9 . The support assembly of  claim 7 , wherein the metal fibers are selected from the group consisting of stainless steel, nickel alloy, copper alloy and mixtures thereof.  
     
     
         10 . The support assembly of  claim 7 , wherein the metal fibers are stainless steel and the metal fibers have a coating comprising an oxide of phosphorus.  
     
     
         11 . The support assembly of  claim 7 , wherein the metal fibers have a concave cross-section and a length to thickness ratio of 500:1 to 20:1.  
     
     
         12 . The support assembly of  claim 7 , wherein the electrolysis apparatus is an aluminum producing apparatus, the molten salt bath is molten cryolite at about 850° C. to 1050° C., and the gases include HF and O 2 .  
     
     
         13 . The support assembly of  claim 7 , wherein the support consists essentially of 3 wt. % to 10 wt. % stainless steel fibers and from about 1 wt. % to about 45 wt. % filler, with the remainder a mixture of an Al 2 O 3 , SiO 2 , CaO material system having a maximum service temperature of at least 1200° C.  
     
     
         14 . The support assembly of  claim 7 , wherein the fibers have a non-circular cross-section and have a generally random dispersal arrangement to themselves, the fibers are present at from about 3 wt % to 10 wt. % and the support system is 50% to 95% dense.  
     
     
         15 . The support assembly of  claim 7 , wherein the fibers have a length to thickness ratio of 100:1 to 50:1  
     
     
         16 . The support assembly of  claim 10 , wherein the phosphate coating is from about 0.5 nanometers to about 5 nanometers thick.  
     
     
         17 . An electrolytic reduction cell for the production of aluminum comprising at least one inert anode attached to a castable refractory support where the anodes and support are in contact with a molten salt bath in an electrolysis apparatus, where the support comprises a 50% to 95% dense castable refractory subject to attack by gases from the bath, where the refractory comprises refractory material and from 2 wt. % to 20 wt. % of metal fibers, where the metal fibers are from 1 cm to 4 cm long and have a length to thickness ratio of 500:1 to 20:1.  
     
     
         18 . The cell of  claim 17 , wherein the support comprises at least 55% of alumina castable refractory.  
     
     
         19 . The cell of  claim 17 , wherein, in the support, the metal fibers are selected from the group consisting of stainless steel, nickel alloy, copper alloy and mixtures thereof.  
     
     
         20 . The cell of  claim 17 , wherein, in the support, the metal fibers are stainless steel and the metal fibers have a coating comprising an oxide of phosphorus.  
     
     
         21 . The cell of  claim 17 , wherein, in the support, the metal fibers have a concave cross-section.  
     
     
         22 . The cell of  claim 17 , wherein the electrolysis apparatus is an aluminum producing apparatus, the molten metal salt bath is molten cryolite at about 850° C. to 1050° C., and the gases include HF and O 2 .  
     
     
         23 . An electrolytic process for making a metal where an electrolyte reduction cell comprising at least one inert anode is attached to a castable refractory support where the anodes and support contact a molten salt bath in an electrolysis apparatus at up to about 1000° C. and where corrosive gases contact the inert anode and the support, and where metal is deposited from the molten salt bath, where said support comprises a 50% to 95% dense castable refractory subject to attack by gases from the bath, where the refractory comprises refractory material and from 2 wt. % to 20 wt. % of metal fibers, where the metal fibers are from 1 cm to 4 cm long and have a length to thickness ratio of 500:1 to 20:1.