CUPOLA FURNACE

                                                              CUPOLA

THE PRODUCT OF THE BLAST FURNACE THAT IS PIG IRON IS UNSUITABLE FOR CASTING AS IT CONTAINS IMPURITY IN HIGH PERCENTAGE. TO MAKE IT SUITABLE FOR DESIRED PURPOSE IT IS REFINED IN THE FURNACE KNOWN AS CUPOLA AND THE REFINED PRODUCT IS CALLED CAST IRON.

1.                   IT IS VERY SIMILAR TO A BLAST FURNANCE IN PRINCIPLE
2.                  IT IS A VERTICAL SHAFT FURNANCE IN TO WHICH THE ROW MATERIAL AND        FUEL ARE CHARGED AT THE TOP
3.                AIR FOR COMBUSTION OF FUEL IS INTRODUCED THROUGH ONE OR MORE              ROWS OF TUYERS A SHORT DISTANCE ABOVE THE BOTTOM. ITS DIAMETER          VARIES FROM 1-2 METER WITH A HEIGHT OF 4-5 TIMES DIAMETER

WORKING

IN A CUPOLA THE FIRST OPERATION IS TO LIT THE FIRE AT THE BOTTOM. WHEN A FIRE IS BURNING STRONGLY COKE IS ADDED SLOWLY TILL THE LEVEL ABOVE THE TUYERS IS 0.6 METER. THIS COKE SERVES AS A BED FOR THE ALTERNATE CHARGES OF METAL AND COKE WHICH FOLLOW WHEN THE CUPOLA IS FILLED UP TO THE CHARGING DOOR AND THE BLAST IS PUT ON AND THE COMBUSTION OF COKE NEAR THE TUYERS INCREASES RAPIDLY UNTILL A VERY INTENSE HEAT IS ATTAINED.

THE GASES OF COMBUSTION MOVES UPWARDS AND PASS ON A PORTION OF THE HEAT TO THE METAL AND COKE WAITING TO DESEND, IN 5-6 MINUTES THE FIRST CHARGE OF METAL STARTS MELTING AND TRICKLES DOWN THROUGH THE COKE AND FINALLY COLLAPSE AT THE BOTTOM OF THE CUPOLA. WHEN AN ADEQUATE QUANTITY COLLECTED/ACCUMULATED THE PLUG OF CLAY CALLED BOUT IS REMOVE FROM THE TAP HOLE AND METAL ALLOWS O RUN INTO THE LADDLE. THE TEMPERATURE OF  TAPPING IS 1200 -1400*C