ARC EFFICIENCY IN THREE-PHASE AND DC STEEL-SMELTING ARC FURNACES

摘要

The arc efficiency of small and moderate (3-25 tons) three-phase SAF is greater than that of dc furnaces of analogous capacity; consequently, the power consumption is 10-12 percent less in TPSAF than in DCSAF. The electrode consumption in small and moderate three-phase furnaces is larger by a factor of 1.5-2 than for dc furnaces of analogous capacity; this has the determining influence on the cost of 1 ton of steel, which is less for dc furnaces. On account of electromagnetic blowing of the arc, the arc efficiency of large (80-150 ton) three-phase SAF is less than that of dc furnaces of analogous capacity; typically, the power consumption in three-phase furnaces of larger capacity is 5-7 percent greater than that in large-capacity dc furnaces. The electrode consumption in large-capacity three-phase furnaces is 7-12 percent greater than for dc furnaces of analogous capacity; however, conclusions regarding the operational advantages of dc furnaces over three-phase furnaces would be premature, on account of the deficiencies of dc furnaces: the presence of a floor electrode of limited working life; operation with a liquid start; and the use of large electrodes. Currently, when the cost of 1 kg of electrodes is equal to the cost of 100-150 kW-hr/ton of power, the electrical operating conditions and structure of three-phase and dc steel-smelting arc furnaces are selected so as to reduce the electrode consumption, with possible increase in power consumption. The arc efficiency of large-capacity furnaces reached a maximum at the end of the 1970s (0.86-0.90), and is currently declining; it is 0.69-0.75 for current high-power furnaces. The power consumption of SAF may be reduced by using oxygen, fuel -oxygen burners, manipulators for foaming slag, coal, or coke, liquid iron, batch heating, waste-gas combustion, and bath mixing. Analysis of the structure and thermal operation of dc and three-phase SAF reveals that the scope for reducing electrode and power consumption in the furnaces has not been exhausted; new furnace designs could reduce power consumption by 5-10 percent and electrode consumption by 6-15 percent.