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 superhe ated steam. The treatment of these solids by fluidisation, drying and roast ing is described. The benefits of this treatment above other alternatives a re energety savings, better product quality and higher plant safety. A phys ically justified mathematical model was set up, which makes the calculation of the time-dependent process parameters possible (e.g, apparatus wall tem perature, bed height-dependent steam temperature and average steam temperat ure, steam outlet temperature, solid temperature as well as the solid humid ity). For a process evaluation dimensionless characteristic numbers are for med. 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 outle t should be constantly observed. (C) 1999 Elsevier Science S.A. All rights reserved.