| As the modification in the clinkerization technology has been a
continuous process over the years, the trend of refractory application
in Cement Rotary Kiln {CRK) system has also undergone
a considerable change. The fireclay/alumino-silicate bricks, high
alumina bricks of different grades and conventional castables
have been replaced by aluminous bricks with specific characteristics,
e.g. coating repellent type, high strength insulating bricks,
basic bricks of different types including dolomite, silicon
carbide bricks and special castables with low cement, ultra-low
cement and no cement along with new anchoring system to
optimize the lining life.
The recently reported performance data of periclase spinel
bricks in a large capacity kiln reveal that apart from minor
problems, the changeover from mag-chrome bricks to these
bricks can be carried out successfully. However, the result
achieved cannot be generalized as these can be influenced by
kiln system, kiln feed and fuel parameters etc. The magnesia
spinelide refractory {MSR) brick, with high affinity to protective
coating and increased resistance to clinker melt, developed
by National Council for Cement and Building Materials {NCB)
has now emerged as a dependable indigenous basic refractory
for burning zone of CRK system. The brick will soon be available
to cement industry as its commercial production is to be
launched shortly. The service conditions in transition zone of
CRK are many times as severe as those in burning zone.
Periclase spinel brick and direct bonded basic bricks have been
used in transition zone with varying degree of success. A modified,
highly spall resistant high alumina brick has been developed
and used abroad in this zone. A brick of this type has
also been developed indigenously by NCB.
Based on the different experiences in preheating and calcining
zones, an effective alternative material for lining of these
areas subjected to high thermal and chemical stresses has been
developed. It is a new seal tight brick with maximum resistance
to alkalis, with requisite mechanical characteristics. For specific
applications and to withstand the stresses like high impact,
abrasion, alkali attack and coating formation, special castables
have been developed. It has been established that the areas, e.g.
critical locations in different types of coolers, kiln hoods,
tertiary airducts, kiln outlets, preheaters and precalciners etc
where shaped products fail, sometimes miserably, an appropriately
selected and applied castable provides the best solution
to the problem of lining life. Some of these refractory products
are described in the paper. |
