|It is an established practice all over the world to operate blast furnaces with higher Titanium contents, which ultimately gives a very safe, trouble-free and long life of the hearth.
Titanium content in the hot metal is maintained between 0.08 to 0.2% depending on the condition of the hearth and the age of the furnace. Titanium also helps in the production of low Nirtogen steel. The normal requirement of this ore varies between 20-30 kg/thm. Solubility of carbon in hot metal increases with drop in Silican content of the hot metal. Titanium Carbonitride protection on the wall helps in preventing carbon pick-up from the wall with low Silicon hot metal.
There are two other sources of Titanium, Viz. Ferro-titanium and Illmenite sand. The former is generally expensive to be used in blast furnaces as feed material and Illmenite sand is available only as fines (like sand), which cannot be charged directly in a blast furnaces. Addition of Illmenite sand in sinter making causes sharp deterioration in the quality of sinter with respect to RDI. Judicious use of
Titanferrous ore in blast furnace as feed material will help in achieving a trouble-free long campaign life of the blast furnace hearth. Moreover, the iron oxide part of what is charged reports to the metal after reduction and therefore, full advantage is taken of what is added at the top of the furnace.
Comparative Study -
Titaniferrous Iron Ore Vs Illmenite bearing Formed Coke
Titaniferrous Iron Ore
TiFe is a dense magnetite ore with a high specific gravity. It reaches the hearth at a faster rate then any of the other burden material and gets deposit there giving extensive protection.
Average Tio2 contents = 14%
Illmenite bearing Formed Coke:
This is a briquette made from Illmenite sand and coke breeze with pitch as a binder.
Average Tio2 content = 10%
The average Tio2 content in TiFe ore is 14% whereas in Illmenite bearing formed coke, it is 10%.
TiFe ore has an added advantage of the presence of Fe that reports to the hot metal and therefore full advantage is taken from what is added at the top of the furnace, whereas, no such advantage exists in Illmenite bearing formed
In formed coke, pitch is usually used as a binder. The softening temperature of pitch is below 125° C while the top gas temperature of blast furnace is higher than 150°C all the time. Temperature from the top gradually increases to 1900°C at the tuyer level. As the Formed Coke travels down along with the burden, it is exposed to higher and higher temperature. The formed coke must be getting crumbled and adversely affecting the permeability and most of it getting blown out of the furnace along with the dust. Only part of Tio2 in Illmenite sand can reach high temperature zone for reduction to Ti. The Ti pick up in hot metal is poor and it further adds to the cost of hot metal without commensurating benefit of hearth protection.