Predicting bulk powder flow dynamics in a continuous mixer operating in transitory regimes

Chawki Ammarcha (1) , Cendrine Gatumel (1) , Jean-Louis Dirion (1) , Michel Cabassud (2) , Vadim Mizonov (3) , Henri Berthiaux (1)

1 RAPSODEE - Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement
2 LGC - Laboratoire de Génie Chimique
3 Department of Applied Mathematics (Ivanovo, Russie)

Over recent years there has been increasing interest in continuous powder mixing processes, due mainly to the development of on-line measurement techniques. However, our understanding of these processes remains limited, particularly with regard to their flow and mixing dynamics. In the present work, we study the behaviour of a pilot-scale continuous mixer during transitory regimes, in terms of hold-up weight and outflow changes. We present and discuss experimental results concerning the start-up dynamics of a Gericke GCM 500 mixer, for which a specific experimental protocol has been developed to determine the evolution of the hold-up in the mixer and the real outflow. Empirical relationships are derived so as to link hold-up weight variations with operating conditions. A simple stochastic approach, based on a non-homogeneous Markov chain, is developed to simulate the bulk particle flow and transport in the continuous mixer at a macroscopic level. Although this simple model is only based on the start-up behaviour, it provides a full description of the mixer dynamics in response to strong perturbations on the flow rate or on the rotational speed of the stirring device, such as negative or positive steps. This model is validated experimentally for a wide range of operating conditions, and constitutes a first approach to process control.

Mots clés: Powder mixing; Transitory regime; Continuous mixing; Markov chain; Stochastic process

Domaines: Génie chimique; Génie des procédés

Chawki Ammarcha, Cendrine Gatumel, Jean-Louis Dirion, Michel Cabassud, Vadim Mizonov, et al.. Predicting bulk powder flow dynamics in a continuous mixer operating in transitory regimes. Advanced Powder Technology, 2012, vol. 23, pp. 787-800. ⟨10.1016/j.apt.2011.10.008⟩. ⟨hal-00878622⟩