8/3/2019 Dolomitic Quicklime Practice
1/2
Dolomitic Quicklime PracticeSteel Manufacturers can lower flux
cost by 20% by using Dolomitic Quicklime to replaceChinese
Magnesite.
The use of Dolomitic Quicklime can extend furnace refractory
life and lower refractorymaintenance cost that was achieved with
the previous use of Chinese Magnesite are sustained.
Technical Discussion
Industry Research:
In a controlled study aimed at a critical evaluation of
Dolomitic Quicklime versus ChineseMagnesite*, Dr. R.J. Fruehan
demonstrated equivalent chemical slag performance in theapplication
of Chinese Magnesite-High Calcium Quicklime flux and Dolomitic
Quicklime-HighCalcium Quicklime. For the EAF steel maker, the
control of slag basicity (B=%CaO/%SiO) iscritical, along with
maintenance of a slag saturated with Magnesium (8-10%) to provide
optimum
protection to the refractory.
To produce an effective flux material, any MgO and CaO added to
the furnace mustbe in solution, and so the manner and rate of
dissolution of the added fluxes is ofprimary concern. The Fruehan
study looks in detail at the mechanisms and rates ofdissolutions of
the compared flux mixtures.
Once in the solution, the amount of MgO available is critical in
maintaining refractorylife. This recommended procedure ensures that
equivalent MgO is added to thefurnace, and that the MgO and CaO
chemistry is unchanged from the previouspractice when using Chinese
Magnesite. The cost difference is easily computed.
* "Comparative study on the dissolution of Dolomitic Quicklime
and Chinese Magnesia inSteelmaking", Dr. R.J. Fruehan and Y. Li,
Carnegie Mellon University.
Conclusions
Fruehan Concludes:"When (Chinese) Magnesia was added to the slag
together with (high calcium) lime, thedissolution rate is slightly
faster at the initial stage, but overall it dissolved slightly
slower thandolomitic quicklime. The differences are considered
insignificant for the steel maker".
Equivalent product calculations:In addition to MgO, the use of
dolomitic lime in place of Chinese Magnasite adds valuablecalcium
oxide to the steel making process, which is taken into account when
calculating therelative amounts of Dolomitic Lime and High Calcium
Lime that must added to the furnace.
Dr. Fruhan confirms "In addition, the CaO contributed from the
Dolomitic Lime is obviously of thesame value to the steelmaker as
the CaO derived from High Calcium Lime".
What does this mean for the Steel Maker in practical terms?The
Carmeuse calculator tool demonstrates the cost savings available
utilizing this approach fora typical steel maker.
http://www.carmeusena.com/page.asp?id=174&langue=ENhttp://www.carmeusena.com/page.asp?id=174&langue=EN
