8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Silica Bricks are made from Quartzite which mostly contents quartz phase. During making, the quartz is converted into phases like Tridymite and Cristobalite along with some amorphous phases. This polymorphic transformation in Silica brick is governed by the impurities present in parent quartzite and also with the addition of mineralizers. However in this process very little amount (<1%) of quartz may remain unaltered. The behaviour/ properties of silica bricks is governed by its physical properties (AP/BD/CCS), thermal and thermo-mechanical properties. Out of these, thermal expansion is considered to be one of the major criterion. Thermal expansion plays a vital role in designing and lining of coke ovens. Consistency in thermal expansion of silica bricks is controlled by the quantity of different phases (Tridymite, Cristobalite, Residual quartz etc) present in bricks. In our conventional silica bricks the thermal expansion ranges between 1.28-1.34% at 1000 deg C and these bricks are widely used in Indian coke ovens in normal and tall batteries. Extensive research has been carried out in Dalmia-OCL to develop low thermal expansion bricks ranging between 1.12 -1.25% by controlling the mineralogical phases during manufacturing with available quartzite. In this paper the authors are trying to highlight how the thermal expansion of silica bricks can be reduced by increasing Tridymite content in the brick and then how content of Tridymite formation is linked with the composition and production process like chemistry of mineralizers, firing cycles and quality of quartzite.