Synopsis:
The authors applied the dephosphorization equilibrium formula reported by Chipman to mostly the final slag and metal samples of the 3 ton experimental LD converter.
The results obtained were as follows.
(1) The observed values of
Kp, dephosphorization constant calculated from oxygen in metal, were in fairly good accordance with Chipman's equilibrium values, while the values of
Kp, dephosphorization constant calculated from (FeO) in slag showed a definite descrepancy from Chipman's equilibrium values.
Furthermore the descrepancy increased almost proportionally with the increase of (FeO)% or T.Fe% in slag.
Experessing this descrepancy as Δlog
Kp'(=log
Kp'
(ehip)-log
Kp'
(obs)) the ahthors obtained the following relations statistically.
(2) During the final stage of the blow, the oxygen in bath did not increase proportionally with (FeO) in slag and at the end of the blow the oxygen in bath was generally lower than the value predicted from the distribution equilibrium of oxygen between metal and slag.
Therefore less effect of "after-blow" to dephosphorization could be expected compared to the bottom blown converter.
(3) In the final slag of the converter there existed somewhat a definite relation between
NCaO' and
NFeO according to the operation condition such as the amount of lime charged, [Si]% of pig iron, pig ratio, etc.
NCaO' tended to decrease with the increase of
NFeO because of the dilution effect of (FeO).
For the slag they studied, the following relation was obtained.
(4) The relation between phosphorus-distribution ratio, log
NCa
4P
2O
9/[%P]
2 and
NFeO was calculated as follows.
from Eq. (2), (5) and (4)
from Eq. (3) and (6)
With the increase of
NFeO the value of log
NCa
4P
2O
9/[%P]
2(obs) increased to a maximum value at about
NFeO=0.3 but with the further increase of
NFeO it began to decrease.
This relation is very interesting when they consider the practical phenomenon that during "after-blow" dephosphorization is not so much improved in spite of the rapid increase of (FeO) content in slag.
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