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Carbon and Oxygen Usage in the EAF — Is More Always Better?

Post-combustion of carbon in electric furnaces:

CO into CO2 in an electric arc furnace, Post-combustion is the complete combustion carbon. improve energy utilization efficiency and reduce electrical energy consumption ways.considered is one. The complete combustion requirement in the furnace is because 2CO + O2 → CO2 reaction releases 6.25kWh / (Nm3O2),2C + O2 → CO means 1.46 kWh / (Nm3 O2) represents four times the incomplete combustion energy.

electric furnace before and after use Index

Under ideal conditions, the actual conditions in the furnace and the carbon-oxygen reaction must be observed. In the early stages of scrap melting, so the volatiles in the carbon material will change its balance, resulting in incomplete combustion without sufficient oxygen, and if the gas residence time in the furnace is too short, complete combustion will not occur in the furnace.

Adding carbon to the electric furnace

 the carbon-oxygen reaction Carbon adds gas arc furnace molten pool generate boiling,  the molten pool hydrogen and nitrogen are removed. Calculate the total carbon addition in the charge (scrap steel, including different types, pig iron, direct reduced iron / hot-pressed iron nuggets, mixing and carbon injection).

Steel remaining by maintaining the precise amount. considering the added flux and the slag flowing down the door of the electric furnace, the carbon addition can be determined through material balance efficiency. To do this, you need the following information:

  • Add toner component (Fixed C).

  • carbon added The amount.

  • of slag remaining after steel estimate the amount.

  • the molten steel after tapping Carbon content.

  • Tapping temperature.

What is excessive carbon injection?

carbon injection is slagging the main goal. the typical average injection consumption is usually between 8-12kg / t.

If carbon injected will increase the energy input increasing the data should support this. SMS electric furnace workshop in 2007collected a large amount. Figure 2 shows two data sets power consumption versus injection, oxygen injection consumption and R2 evaluation .there is no correlation, increased injection and reduced power consumption. but increasing oxygen blowing does seem to provide some benefits (most likely metal oxides at the expense ). Similarly, Figure 2 shows the electric furnace workshop data.  the four-carbon guns have been blocked, reducing the injection 22.3% amount. But the impact on power consumption is not significant (a 1.5% increase).


Carbon in pig iron or molten iron

use 10% to 30% pig iron, but in some extreme cases, the metal pig iron added total amount can reach 50%. 

It also has other uses, and steelmakers have found that pig iron is an ideal material because of it:

  • It can dilute the residual element content in the steel used.
  • Increase content in molten steel. The CO floating during the oxygen blowing process creates rolling boiling conditions for the molten pool. Removes hydrogen and nitrogen from the molten pool.
  • Pig iron has a low melting point and so is easy to melt quickly.
  • Pig iron has greater specific gravity than scrap steel piles. Increasing the basket loading capacity can create conditions for single basket charging.

On the other hand, silicon pig iron contains a large amount. Although this chemical energy can generate a large amount. this high silicon content requires the addition, increased slag and metal loss. When evaluating the value of high silicon pig iron, it must be considered. All these factors.

Sum up

Raw materials such as pig iron changes in availability or quality. DRI or HBI can have a huge impact on oxygen and injection. Sometimes these changes can ignore the production process. For example, a novice operator believes that the more injection, the better. The technical manager needs to look at the operation. It is the responsibility to evaluate the operation and aim for continuous process improvement.

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