A non linear model proposed by Perron and Bui (1994), which focuses on the dynamics of slow mode to predict the transient response induced by step changes in operating variables in the motion of the granular bed in a rotary kiln, was validated for different experimental conditions. The variables include feed rate of solids, inclination and rotational speed of the kiln, and dam height. The validity of the model for step changes in two or more variables at a time was also verified.
On a valid6 pour diffkrentes conditions exphimentales, un modhle non IinCaire propost par Perron et Bui (1994), reposant sur la dynamique du mode lent, dans le but de prkdire la rCponse transitoire induite par des changements de phases dans les variables de fonctionnement dans le dCplacement du lit granulaire dans un four rotatif. Ces variables comprennent la vitesse d'alimentation des solides, l'inclinaison et la vitesse rotationnelle du four et la hauteur de la digue. La validit6 du modkle pour les changements de phases en deux ou plusieurs variables en m&me temps a Cgalement 616 v6ritii.e. Keywords: step changes, transient response, granular bed motion, rotary kiln. otary kilns are the reactors of choice for a number of R processes in chemical and metallurgical industries.
Many of the processes using rotary kilns are at high temperatures where the feed undergoes physico-chemical transformation, which makes the operation in the established regime tin exception rather than a rule. The fluctuations in the material characteristics at the feed end, combined with changes in control variables, like the feed rate of solids, often lead to frequent adjustments to the operation. Hence, for formulating better control strategies, the knowledge of the kiln behaviour in the transient regime for sudden changes in operating variables is required.
Sai et al.
( 1 992) reported the experimental data on transient response of the rotary kiln in terms of the variation in the discharge rate of solids with time for a step change in operating conditions; namely, feed rate of solids, rotational speed and inclination of the kiln.
The movement of solids through the rotary kiln is a complex process involving two modes. The axial velocity of the active layer on top of the bed represents the fast mode, while