Please explain the effect of minerals which are added as additive in coke on slag compostion of iron making. For example if some extra calcite is added upon the amount of calcite present in the coal
The simple answer is that minerals must come out of the furnace somehow.
The primary exit is through the slag, secondarily with the iron, thirdly out the top of the furnace as dust. Different elements will partition differently. And the partitioning ratio will vary with the presence of other elements (and, of course, the furnace operating conditions). More specifically, Calcium should come out in the slag and therefore will affect its properties. I think that if calcium comes in via coke or via PCI it may have some effect on slag properties, mainly in the variability in slag basicity, but am not sure.
Richard
thank you. do you recommend any paper which discusses about this?
I haven't come across any recent overviews over the fate of the elements.
Dear Mr.Ananthan
I would like to add some more points to Mr. Richard answer.
In any means (coke /coal/sinter/pellet) , if CaO input increases/decreases it will definitely affect the final BF slag basicity and its properties. It effects the hot metal quality like Sulphur and Silicon content. It has huge impact in the subsequent processes.
But above said issues can be eliminated by optimizing your process.
1) Constant CaO input to the blast furnace ( reduce the CaO input from sinter/pellet which is added with the coke )
2) While doing the step 1, you should consider the effect of CaO added with coke on coke property and its effect on blast furnace performance.
For example, CRI of coke has improved by 2% with the addition of CaO in coke making.
You should estimate how much coke rate will decrease with CaO added coke which has increased CRI
Regards
Venkatesan J
If the calcium is present in the coal as carbonate, then it will form CaO in the coke reaction zone and help catalyse gasification of the coke. If gaseous sulphur is present, CaS will be formed too. (does CaS catalyse gasification?) If Ca is present as silicates it is far more stable and not so likely to gasify coke in the reaction zone. It will eventually report to the slag and it is assumed (but not demonstrated) that only total calcium is important in determining the slag viscosity. Note that CaO and CaS can be formed during the coking process itself (see work by M.Grigore et al who tracked the fate of minerals during coking and gasification in a series of papers around 2008-2012)
Sorry, I should have said that, as far as the contribution of calcium to slag viscosity is concerned, usually only the total amount of calcium is considered in the equations that aim to predict viscosity.
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