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Table 1. Installation Year by Type of Melting Furnaces


Furnace Type Number Average Year Installed


All


EAF IF


58 24 34


1977 1960 1992


Furnace Type Number Average Capacity (lb.)


All


EAF IF


58 24 34


12,368 26,433 2,440


527


Standard Deviation 65


Oldest Year Installed


1938 1938 1976


Table 2. Capacities of Steel Melting Furnaces (lb.)


Minimum Capacity (lb.)


400


6,000 400


Table 3. Energy Consumption (kWh/Ton) for Steel Melting Average


Minimum 350


• Increasing “tap to tap time” increased energy consumption (strong influence).


• EAF has lower energy consump- tion than IF (strong influence).


• Newer equipment decreased energy


heat balances. Figure 2 shows an example of the heat balance from an electric arc furnace. Supplemental chemical energy is


2


one way to decrease electrical energy consumption and increase the effi- ciency and productivity of melting


Procedure Te MS&T team visited


five metalcasting facilities, observed the melting of several heats and calculated


Maximum Capacity (lb.)


110,000 110,000 9,500


Maximum 700


Fig 1. This chart shows the refractory linings used in melting furnaces in the 19 facilities surveyed.


consumption (strong influence).


• Increasing “furnace capacity” decreased energy consumption (weak influence). In addition to the statistical data


collected, operators were asked to report


steel in EAFs. Many technologies can introduce supplemental chemical energy into the process. Preheating of the scrap charge and using oxyfuel burners can increase melting efficiency of the solid scrap charge. Two supple- mentary chemical energy methods, post-combustion of CO in the furnace to CO2


and exothermic heat from


oxidation reactions to the melt, could increase energy efficiency during the flat bath period.


what they considered to be major factors with the greatest influence on energy losses during melting at their facilities. Te three most frequently cited were: refractory (75%), scheduling (70%) and casting yield (25%).


Opportunities to increase energy


efficiency are greatest during the superheating and correction period because the electrical energy effi- ciency drops significantly when heating liquid steel with an open arc in air. A significant portion of the arc energy is reflected from the arc and bath surface to the sidewalls and roof where the energy is lost in heating (and often melting) refractory rather than steel. In addition to using


Newest Year Installed


2003 1977 2003


Fig. 2. This Sankey diagram (energy flows) depicts melting steel in a 15-ton EAF. 48 | MODERN CASTING February 2013


Fig. 3. This Sankey diagram shows the decrease in electrical energy consumption by the addition of chemical energy (0.4% SiC in charge).


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