Effect of ring formation on burner flame stability in lime kilns

Ring formation in lime kilns is a common problem in pulp mills. Unstable burner operation that causes wide temperature variations within the kiln has been shown to be a main contributor. As rings grow thicker and longer, they are expected to affect the burner flame pattern, alter the temperature distribution, and further aggravate the problem. This study systematically examines the effect of rings on burner operation as a function of primary air and ring characteristics, using a laboratory mock kiln. The results show that primary air greatly affects the burner flame pattern and stability. Without a ring, the flame is brighter and shorter, with an increase in primary air (PA) up to 17%, and blows out at 20% PA or higher. In the presence of a ring, the flame becomes unstable and blows out when the ring is placed near the burner, but it is more stable when the ring is placed away from the burn - er. Thick and long rings destabilize the flame more than thin and short rings.This work was conducted as part of the research program on “Increasing Energy and Chemical Recovery Efficiency in the Kraft Process - III”, jointly supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and a consortium of the following companies: Andritz, Arauco, AV Group, Canadian Kraft Pulp, Celulose Nipo-Brasileira, Clyde- Bergemann, Domtar, DMI Peace River Pulp, Eldorado, ERCO Worldwide, Georgia Pacific, Fibria, FPInnovations, International Paper, Irving Pulp & Paper, KFS, Klabin, Stora Enso, Suzano, Tembec, Valmet, and WestRock