Displacement washing of lime mud

The sodium content in lime mud is one of the main parameters determining the quality or reburned lime mud. The content of sodium in lime mud is determined by the conditions in the lime mud washing system. Despite the fact that the sodium content is an important parameter, very few papers concerning the lime mud washing system can be found; no paper dealing with the mechanisms of lime mud washing has been found.The aim of this work was to make an introductory study of the mechanisms in the washing of a lime mud filter cake.In the experimental part of this work, the influence of liquid velocity, type of solute, bed length and cake formation were studied. It was found that the so-called dispersion model could be used to describe the washing operation, with the exception of a small tailing effect. From the experimental data and the dispersion model, a dispersion coefficient was calculated. The ratio between the dispersion coefficient and the diffusivity of the solute was found to be a function of the Peclet number.