Refining of iron

Claim 1

IN THE OPERATION OF A TANDEM FURNACE FOR THE PRODUCTION OF STEEL, SAID FURNACE COMPRISING TWO ELONGATED REFRACTORY VESSELS WITH A CONNECTING PASSAGE ADJACENT ONE END ONLY THEREOF FOR THE TRANSFER OF GASES FROM ONE VESSEL TO THE OTHER VESSEL AND WHEREIN EACH VESSEL IS ALTERNATELY USED AS A REFINING FURNACE WHILE THE OTHER IS THEN USED AS AN INPUT MATERIAL PREHEATING FURNACE, AND WHEREIN THE VESSEL FUNCTIONING ON ITS METAL REFINING CYCLE CONTAINS A MOLTEN CHARGE OF FERROUS METAL WITH A CARBON CONTENT HIGHER THAN THE DESIRED CARBON CONTENT OF THE FINISHED STEEL, SAID MOLTEN CHARGE HAVING AN OVERLYING SLAG LAYER, AND THE VESSEL WHICH IS THEN ON ITS INPUT PERHEATING CYCLE CONTAINS AN INPUT MATERIAL CHARGE OF SCRAP TO BE PREHEATED, THE METHOD WHICH COMPRISES: (A) INJECTING A HIGH VELOCITY JET OF REFINING OXYGEN FROM A LANCE INTO THE VESSEL CONTAINING THE MOLTEN METAL ONLY AT THE END OF SAID VESSEL REMOTE FROM THE CONNECTING PASSAGE AND ONLY IN A DIRECTION WHICH IS DOWNWARD AT AN ACUTE ANGLE TO THE SURFACE OF THE METAL AND TOWARD THE END OF THE VESSEL AT WHICH THE CONNECTING PASSAGE IS LOCATED AND THEREBY GENERATE HEAT IN THE METAL BY THE REACTION OF CARBON AND OXYGEN AND RELEASE CO INTO THE VESSEL ABOVE THE METAL, (B) MAINTAINING THE TEMPERATURE OF THE CO IN THE SPACE ABOVE THE SLAG AT A TEMPERATURE NO HIGHER THAN THE TEMPERATURE OF THE MOLTEN METAL BY THE EXCLUSION OF OXYGEN FROM CONTACT THEREWITH IN AN AMOUNT SUFFICIENT TO RAISE THE TEMPERATURE OF THE FURNACE GASES TO A LEVEL WHERE THE SLAG TEMPERATURE MAY BE HIGHER THAN THE TEMPERATURE OF THE MOLTEN METAL BY CONTROLLING THE VELOCITY OF THE OXYGEN STREAM IN THE RANGE BETWEEN 1 AND 2 MACHS, THE SPACING OF THE OXYGEN LANCE WITH RESPECT TO THE METAL TO MINIMIZE-ENTRAINMENT OF THE CO IN THE VESSEL INTO THE OXYGEN STREAM AND BY ADJUSTING THE ANGLE OF THE JET TO AVOID REFLECTION OF THE OXYGEN FROM THE SURFACE OF THE METAL, (C) CONDUCTING THE CO FROM THE REFINING VESSEL THROUGH SAID CONNECTING PASSAGE INTO THE PREHEATING FURNACE AND BURNING THE CO WITH OXYGEN IN THE PREHEATING FURNACE TO THEREBY PREHEAT THE SCRAP.