Modelling of the batch treatment of wet granular solids with superheated steam in fluidized beds

This article deals with the batch treatment of granular solids with superheated steam. The treatment of these solids by fluidisation, drying and roasting is described. The benefits of this treatment above other alternatives are energety savings, better product quality and higher plant safety. A physically justified mathematical model was set up, which makes the calculation of the time-dependent process parameters possible (e.g. apparatus wall temperature, bed height-dependent steam temperature and average steam temperature, steam outlet temperature, solid temperature as well as the solid humidity). For a process evaluation dimensionless characteristic numbers are formed. Experimental investigations for different operating conditions are in agreement with numeric calculations of the model. For a dynamic control of the desired final humidity of the solid, the temperature of the steam outlet should be constantly observed.