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pic1.gif (132 bytes) Refractories for Sponge Iron Making
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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 kiln.
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.

Sl.No. Configuration Advantage Disadvantage
1. 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 of campaign.

b) Faster erosion.
2. 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.
3. Full Castable 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

Low Cement Castable Mac Vib–45
Mac Vib–60 (SI)
Mac Vib–60 M SPL
Mac Vib–80 (SI)
Mac Vib–80 (Spl/Li)
Dense Castable Mac Heat–C (SI)
Mac Cast
Insulating Castable Maclite–11 (SI)
Patching Castable ** Mac Vib–60 (Patching)
Mac Vib–K (Patching)
Mac Vib–80 (Patching)
** Specially designed tailormade patch repair compatible to the previous refractory.

 

Combination of LC-60 & LC-80 castable with modification:

a)  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).
b) 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.
c) 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.
d) 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.

 

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