An Algorithm to Estimate the Effectiveness Factor in Catalytic Pellets

SERGIO DARÍO KEEGAN; SERGIO PATRICIO BRESSA; NÉSTOR JAVIER MARIANI; GERMÁN DÉLFOR MAZZA

Praga, Republica Checa

Congreso; 15th International Congress of Chemical and Process Engineering (CHISA 2002),; 2002

Czech Society of Chemical Engineering - European Federation of Chemical Engineering

The 1D model proposed by Burghardt and Kubaczka (1996) to approximate the behavior of 3D catalytic pellets has been recently found able to provide accurate results for evaluating effective reaction rates when its parameter ċ is suitable adjusted (Mariani et al., 2002). This parameter represents the contraction of the cross section available for diffusion. The well known 1D geometries result for some specific values: slab (s=0), infinitely long circular cylinder (s=1), sphere (s=2). In general, the range of interest is -1/5<s<5 (Mariani et al., 2002). A formulation coupling a first order Galerkin approximation with a truncated asymptotic expansion is proposed here to evaluate the effectiveness factor of single reactions in the range 1/5<s<5. The formulation provides a 3% level of precision for essentially all normal kinetics of practical interest and a large range of abnormal kinetics. In particular, this conclusion includes reaction rates approaching a zero order reaction, for which large deviations arise from the use of previous approximations proposed in the literature. On the other hand, the extent of abnormal kinetics being accurately approximated is significantly enlarged.