The benefits arising due to the use of high metalized DRI in charge materials must be considered along with the production cost of metalized burden. Overall economics of metalized DRI in electric steelmaking is important while deciding % metallization in the feed.

Another important issue in case of DRI is the proportion of DRI in the charge. For this purpose 1000 kg sponge iron of 90% metallization is to be used in different proportions. We consider charge mix is scrap and DRI. Calculations show that 1288.66 kg iron ore would be needed to produce 1000 Kg DRI with 90% metallization. The following table illustrates the influence of proportion of DRI on the free iron and other variables of DRI:

We note the following:

i)    Increase in proportion of DRI increases the free iron in the charge.

ii)      which is combined with oxygen as  increases with increase in the proportion of    DRI     .       This would require extra amount of heat energy both chemical and thermal to reduce  to         and to raise the temperature of reactants to .

iii)    Gangue content of the DRI increases with the increase in proportion of DRI. This would lead to          increase  in slag volume and heat load.

What is the consequence?

A) Tap to tap time may decrease with the increase in DRI but more proportion of DRI may increase tap to     tap time for two reasons, namely more time is required to reduce  and, to handle increase     volume of slag.

B) Increased proportion of DRI beyond a limit may increase electrode consumption and refractory wear.