부산대학교 도서관

Lime is used extensively in steel industry as fluxing material. Lime is produced by calcination of limestone in a lime kiln. The calcination process takes place at elevated temperatures near 900 °C to convert limestone into quick lime. Lances are distributed along the periphery of the kiln to provide uniform heating with by-product gases LD, COG, and BF as fuel. During the operation, lance tip is immersed in limestone and gets choked eventually which results in premature cracking. This reduces the length of the lance tubes which can be found only during their highly labor-intensive manual inspection performed every fortnight. Hence, a non-destructive method was developed, wherein an ultrasonic waveguide made of the same material of the lance was inserted to estimate chokage and real-time length of the lance. Additionally, the acoustic resonance of the air column-based method was also attempted to measure the length of the lance. These methods were able to guide operations by predicting remnant length with an accuracy > 95% and aiding in pre-planning shutdowns for replacement of damaged lances.