INTRODUClTON
The advantages of a spouted bed are well known for physical processes with coarse particles. These. processes involve drying, particle coating, granulation and heat transfer operations (Mathur and Epstein, 1974).
The fluid from an inlet orifice penetrates through a bed of particles forming a central spout surrounded by an annular region. The fluid in this spout carries a stream of particles upward and thus creates a spout with a high voidage (low particle concentration). On the top of the bed, particles leaving the spout,form a fountain. The particles from the top of the bed move downwards, opposite to the fluid flow in the annulus. The conventional spouted-bed contactor consists of both conical and cylindrical parts. The angle of the conical part determines the mixing of solid particles in this region. A detailed knowledge of the solid circulation pattern in a spouted bed is very important in order to evaluate the effectiveness of gassolid contact and to help determine the gas distribution in both spout and annulus. These characteristics are necessary for mathematical modelling of a spoutedbed reactor. Mathur and Lim (1974) proposed a one-dimensional flow model to characterize the spouted-bed reactor with a catalytic first-order reaction. Piccinini et al. (1979) modified this model by taking into account diffusional mass transfer. In addition they also introduced a "streamtube" model. Streamtube boundaries and the gas residence time in each streamtube can be derived for the annulus in the manner described by Lim and Mathur (1976). A complete theoretical model for a first-order isothermal catalytic reaction in a spouted-bed was presented by Littman et al. (1981). The authors evaluated all required quantities in a completely general way. Smith et of. (1982) extended the theory of spouted-bed reactors to the non-isothermal case and exploited the effects of the major design variables on reactor performance. This theoretical dynamic model accounts for temperature changes and explicitly includes the effect of solids circulation on the temperature and concentration profiles. These effects should be considered in an assessment of spouted-bed industrial reactors. The numerical results demonstrate the influence of design variables such as hed height and diameter, particle size, cone angle and inlet flow rate on steady-state performance.