K. Vasudeva

Parametric sensitivity in fixed-bed reactors☆

Parametric sensitivity in fixed-bed reactors has been analysed by previous workers using the quasihomogeneous model [i.e. for the kinetic regime only]. In the present paper a general treatment is proposed in which transport limitations are also considered. It is shown that the critical inlet partial pressure is strongly dependent on the transport processes. Based on the analysis presented, four regimes of fixed-bed reactor operation are postulated and conditions are stated to identify the regime in which a given system would operate. These conditions are applied to some industrially important reactions to show that the regimes represent realistic systems. Procedures are developed to obtain the critical inlet partial pressure for systems lying in the various postulated regimes. Illustrative examples are then solved to demonstrate the procedures developed in the text. The correctness of the procedures is established by comparing the values of the critical inlet partial pressure obtained from the present analysis with those obtained from numerical solution.

On mean residence times in flow systems

Abstract A widely accepted result of residence time theory namely mean residence time is equal to the system volume divided by the flow rate was first offered by Danckwerts[l] and later extended by Buffham[21 and Gibilaro[3] to more general cases. Taking a two section system it is argued and experimentally demonstrated that the above theoretical result is not universal. A possible implication of this result is that even for a single section system the above result may not hold in all the cases. This is also supported by experimental data on a single section system.

Effectiveness factors in Langmuir-Hinshelwood and general order kinetics☆

Abstract The heat and mass balance equations for diffusion accompanied by chemical reaction in a catalyst pellet are solved for reactions following a common class of Langmuir-Hinshelwood kinetics and general-order kinetics. An explicit algebraic expression is developed relating the effectiveness factor to the kinetic, adsorption, and transport parameters under nonisothermal conditions. This equation can be directly used in fixed-bed reactor calculations to take into account the influence of adsorption and intraparticle processes.