A CFD Study of the Effects of Rings on Flow and Temperature in Lime Kilns

Abstract

Rotary lime kilns, used in the kraft chemical recovery process to convert lime mud into lime, suffer from the formation of ring-shaped deposits called rings. Prior research has led to better understanding of ring growth, although it is still not fully understood, since the process is concealed within the kiln. For this reason, a steady state, 2D axisymmetric lime kiln, ring, and virtual bed heat sink model has been developed in this work, and was validated by predicting the shell temperature of a real kiln with good accuracy. Various ring configurations were then simulated in a typical lime kiln in order to study their effects on flow and temperature. The results show that ring-related jets and recirculation zones form in the gas, temperature deviations occur upstream and downstream of the rings, and, recarbonation, causing ring hardening, occurs over a wide range of ring thickness for both front-end and mid-kiln rings.