Numerical Modelling of a Carryover Deposition in Kraft Recovery Boileres, 1998 Engineering Conference Proceedings

The deposition of carryover, or molten and partially molten smelt and black liquor particles, is a primary source of plugging of flue gas passages within kraft recovery boilers. An improved understanding of how an individual particle impacts onto a heat transfer surface may result in strategies for reducing the deposition rate. A numerical model has been developed to simulate molten carryover droplet impact, to assess the influence of particle size, velocity and particle fluid properties on the consequent impact dynamics. Results of parametric studies using the model show that the liquid surface tension and the wetting behaviour of the liquid on the surface strongly affect the impact of small particles (diameter < 0.5="" mm).="" small="" particles="" are="" shown="" to="" spread="" uniformly="" and="" without="" disruption,="" and="" are="" likely="" to="" stick="" on="" impact.="" as="" the="" particle="" size="" and="" impact="" velocity="" increase,="" inertial="" effects="" become="" more="" significant.="" particles="" larger="" than="" 1="" mm="" will="" tend="" to="" splash="" on="" impact,="" forming="" small="" satellite="" particles="" which="" do="" not="" stick,="" and="" which="" may="" account="" for="" the="" presence="" of="" the="" small="" carryover="" particles="" found="" in="" precipitator="">