The Effect of Burning NCG on Lime Kiln Flame Patterns

The stability of the burner flame is critically important in lime kiln operation. It can be affected greatly if noncondensible gases (NCG) are burned in the kiln. A Flow Simulation Apparatus was used to study the mixing and interaction between a simulated main burner jet and a simulated NCG burner jet in a confined cylindrical duct. The results show that the angle of the NCG jet with respect to the duct axis is the dominant factor in determining the mixing and interaction between the two jets. The lateral expansion rate of both jets decreases with an increase in Reynolds number (Re) and in Craya-Curtet number (Ct) of the jets. The expansion of the jet is important, because it determines the shape of the flame (long or bushy), the temperature and heat transfer in the kiln, and whether the flame may impinge on the kiln walls. The results also show that the recirculation zones in the confined duct are longer with two jets than they are with a single jet. This implies that burning NCG tends to lower the temperature of the main burner.This work was part of the research program on “Increasing the Throughput and Reliability of Recovery Boilers and Lime Kilns” jointly supported by Alstom Power Inc., Andritz Corporation, Aracruz Celulose S.A., Babcock & Wilcox Company, Boise Paper Solutions, Bowater Canadian Forest Products Inc., Canfor Inc., Clyde-Bergemann Inc., Daishowa-Marubeni International Ltd., Domtar Inc., Georgia Pacific Corporation, International Paper Company, Irving Pulp & Paper Limited, Kvaerner Power, MeadWestvaco, Stora Enso Research AB, Tembec, Votorantim Celulose e Papel, and Weyerhaeuser Company, and by the Natural Sciences and Engineering Research Council of Canada. Fuel Combustion Technology is also acknowledged for its donation of the Flow Simulation Apparatus used in this study