In view of the great
demand for sponge iron in India for the last 8–10 years, there has been
a huge demand for refractories required for sponge iron industry.
Maithan has given focus towards meeting the requirement of this industry
and with such an impetus MCL has taken a lead in the introduction of the
ideally suitable refractories for sponge iron manufacture.
The different parameters in the selection of refractory for sponge iron
rotary kiln are summarized as follows:-
1) High abrasion resistance.
2) High load bearing capacity.
3) Lesser erosion of the refractory in view of the high hot strength at
the operational temperature (1050 – 1100°C).
4) Ability to withstand reducing atmosphere prevailing in the rotary
5) Longer refractory life.
6) Anti- accretion properties.
7) Lower outer shell temperature.
All the above stipulations are not possible to be achieved by any
particular type of refractory castable since it is a heterogeneous
mixture of different raw material.
The selection of refractories for the main rotary kiln, also known as
the reactor, is very vital and crucial while the refractories for the
other portions i.e. Cooler, ABC and DSC is not very critical. The
following combinations have been practiced at different plants for the
rotary kiln, as each option has its own advantages and disadvantages.
||Full bricks lining
||a) Easy accretion removal.
b) Lower shell temperature.
c) Lower installation cost.
|a) Due to cumulative effect
of shrinkage / expansion the brick lining can collapse leading to stoppage
b) Faster erosion.
||Brick & Castable
||Bricks lining in the
reduction zone provides lower shell temperature.
||Failure of brick lining even
in the pre-heating zone has been experienced.
||This is now widely practiced.
Selection of the correct type of Castable requires careful consideration.
a) Replacement of the damaged area can be done as per conventional
b) When castable thickness is reduced, patch repair can be done.
|If proper heat up is not
followed, refractory damage may occur. During shut downs, water sprinkling
for faster cooling will damage castable.
The following category
of refractories are normally used for sponge iron units
Mac Vib–60 (SI)
Mac Vib–60 M SPL
Mac Vib–80 (SI)
Mac Vib–80 (Spl/Li)
||Mac Heat–C (SI)
|Patching Castable **
||Mac Vib–60 (Patching)
Mac Vib–K (Patching)
Mac Vib–80 (Patching)
designed tailormade patch repair compatible to the previous refractory.
Combination of LC-60 & LC-80 castable with modification:
It provides much higher abrasion resistance since LC-80 consists
mainly of “Corundum” mineral which possess highest possible
hardness (Corundum has a hardness of 9 in the Moh’s scale of
hardness of 1 to 10, No. 10 being that of Diamond).
This configuration has been
modified by us at MCL to provide “ Anti –accretion property” by
lining with a special type known as Mac Vib-80 Spl. Li at
specific zones of the rotary kiln.
However, this configuration
results in a slightly higher outer shell temperature but this is
more than offset by virtue of the much lesser abrasion & erosion
and result in a longer life of the refractory.
We have also developed another
special type known as Mac Vib-80 LR which would possess better
abrasion resistance and also relatively lower outer shell
temperature as compared to normal LC-80 Castable.