Process of exhausting gases from furnaces for production of aluminum by melt-electrolysis

Claim 1

IN THE OPERATION OF AN ALUMINUM SMELTING FURNACE WHICH INCLUDES A POT, A MOLTEN ELECTROLYTIC BATH THEREIN CONTAINING DISSOLVED ALUMINUM OXIDE, A CARBONACEOUS ANODE DESCENDING INTO THE POT, A DUCT AROUND THE LOWER PORTION OF THE ANODE FOR COLLECTING GASES EVOLVED DURING SMELTING WHICH INCLUDES MEANS FOR WITHDRAWING SUCH GASES FROM THE DUCT AND A SOLIDIFIED CRUST POSITIONED IN THE SPACE BETWEEN THE WALLS OF SAID DUCT AND POT TO PREVENT ESCAPE OF SMELTING GASES THROUGH SAID SPACE, THE METHOD WHICH COMPRISES THE STEPS OF ESTABLISHING DURING FURNACE OPERATION A FLOW OF OXIDIZING GAS CONTAINING FROM ABOUT 20% TO 100% OXYGEN BY VOLUME INTO THE POT BELOW THE CRUST AND BURNING IN SAID FLOW OF OXIDIZING GAS CARBON PARTICLES FLOATING ON THE SURFACE OF THE MOLTEN BATH FORMED AS A RESULT OF DISINTEGRATION OF THE ANODE, SAID FLOW OF OXIDIZING GAS BEING ESTABLISHED IN THE CASE OF 20% OXYGEN CONCENTRATION AT A RATE AVERAGING FROM ABOUT 50 TO 600 N/L PER HOUR PER 1000 AMPERES OF FURNACE LOAD AND AT EQUIVALENT RATES WHEN SAID OXIDIZING GAS CONTAINS GREATER OXYGEN CONCENTRATIONS.