Studies on Ring Forming Mechanism in Lime Kiln with Coal Fuel via Modelling Tools

Abstract

Ring formation in limestone-calcining kiln is the most troublesome problem and a persistent obstacle to the efficient operation. To understand the factors that lead to ring formation, the ring formation mechanism in the lime kiln using pulverized coals with some ash contents as fuel was analyzed. FactSage software and viscosity model were employed for the prediction of slagliquid quantity and quality related to the ring formation in the complex coal ash slag system. The amount and compositions of slag-liquid from melted coal ash were determined by FactSage model; its viscosities were determined by Urbain model. The ring compositions mainly included CaO, 3CaO·SiO2, CaO·SiO2 and MgO. The amount and viscosities of slag-liquid from the blended ash were 75% at 1400 °C and 102~263Pa·s at 1300~1400 °C, respectively. The ring forming mechanism was extrapolated to include lime particles clinging to kiln wall, dissolving in slagliquid, reacting with slag-liquid and hardening via liquid-phase sintering.