SINTERING OF CALCINED LIME MUD - THE INFLUENCE OF THE SODIUM AND SULFATE CONTENT IN THE LIME

The influence of sodium carbonate, calcium sulphate and sodium sulphat e on the intra-particle sintering of calcined lime mud was investigate d. This was done by calcining and sintering doped lime mud with differ ent concentrations of the investigated substances. The concentrations were varied up to approx. 12 weight-% (salt concentration), the temper ature between 760 and 910 degrees C and the sintering time between 0 a nd 60 minutes. It was found that sodium carbonate and sodium sulphate increase the sintering rate, while calcium sulphate has a very small i nfluence, if any. It was found that not only are the ions important bu t also in which compound they exist, since the melting point of the so lid strongly influences the sintering process. A model was developed t o describe the influence of sodium carbonate and sodium sulphate on th e reduction of the specific surface area. Depending on the washing eff iciency in the washing unit before the lime kiln, the lime mud enterin g the calcination reactor has different concentrations of sodium. The results indicate that the higher the washing efficiency in the washing unit, the greater the specific surface area of the calcined lime mud.