DEVELOPMENT OF ZERO EXPANSION SILICA BRICKS FOR HOT REPAIR OF COKE OVEN

摘要

Conventional dense silica bricks are extensively used for refractory lining of coke oven walls. These bricks are made from quartzite & the finished brick contents mostly tridymite phase which is so called stable at the operating temperature of coke oven. However, these bricks can not be used in hot repairing of coke oven wall as it gets cracked because of sudden change in temperature. In fact, any change in temperature in case of silica bricks means transformation from one phase to another which again accompanies a large volume change & generates cracks especially when the temperature rise and fall are sudden. To counter this problem, Zero Expansion silica brick is developed which is perfectly suitable for hot repair of Coke oven. Zero expansion silica bricks are manufactured from amorphous silica which has low Permanent linear change & low reversible thermal expansion. Very low volume expansion occurs when this brick undergoes sudden temperature change during hot repair. Thus, crack formation is prevented. As the name suggests this refractory has excellent volume stability at operating temperature. This developed brick is already in use in coke oven walls of an Integrated Steel Plant. This paper focuses on development of Zero expansion Silica bricks keeping special focus on selection of raw material, its granulometry & firing technique. Advantage & performance of these bricks have been highlighted with respect to use in actual practice for repair of coke ovens.