MATHEMATICAL-MODELING AND APPARATUS ARRANGEMENTS OF DEEP DRYING PROCESS OF GRANULAR POLYMERS

A computer - aided analysis is made of the factors influencing the kin etics of the continuous deep drying of granular polymers on the basis of a two-level mathematical model. In terms of the lower (microkinetic ) level, which deals with the drying of separate granules, considerati on is given to the accuracy of determining the moisture diffusion coef ficients in polymers as functions of temperature and concentration D=f (U,t). The expedience of employing the solution of linear and non-line ar differential diffusion equations in microkinetic calculations is al so considered. In terms of the macrokinetic level, which rakes account of the influence of the hydrodynamic and heat-and-mass transfer dryin g conditions in the dryer, a numerical study is undertaken of how the kinetics is influenced by the granules' dimension nonuniformity and by the difference in the granules' residence time in the dryer. The resu lts are graphically presented in generalised variables. The travel of 12 granular polymers in the shaft (column) dryers is experimentally st udied depending on definite determining parameters. Accordingly, some recommendations aimed at ensuring the uniform drying are given. Presen ted are also the experimental results on the longitudinal mixing for d ifferent polymers for a continuous shaft dryer with a ring material la yer and with the drying agent performing the radial motion. The findin gs make it possible to determine the mixing rate and to outline some p ractical recommendations. The investigations carried out allow one to find the rational construction of the dryer for the deep drying of gra nular polymers and to refine the kinetic calculations.