Wave model for longitudinal dispersion: Application to the laminar‐flow tubular reactor
The wave model for longitudinal dispersion, published elsewhere as an alternative to the commonly used dispersed plug-flow model, is applied to the classic case of the laminar-flow tubular reactor. The results are compared in a wide range of situations to predictions by the dispersed plug-flow model as well as to exact numerical calculations with the 2-D model of the reactor and to other available methods. In many practical cases, the solutions of the wave model agree closely with the exact data. The wave model has a much wider region of validity than the dispersed plug-flow model, has a distinct physical background, and is easier to use for reactor calculations. This provides additional support to the theory developed elsewhere. The properties and the applicability of the wave model to situations with rapidly changing concentration fields are discussed. Constraints to be satisfied are established to use the new theory with confidence for arbitrary initial and boundary conditions.
A critical comparison between the wave model and the standard dispersion model
For the description of the phenomena occurring in packed-bed reactors a wave model (WM) has been proposed by Kronberg and Westerterp (Chem. Eng. Sci. 54 (1999) 3977) as an alternative to the standard dispersion models (SDM). In this work the WM is investigated. The capabilities of the WM have been tested on the basis of three industrially important reactions: (1) partial oxidation of methanol to formaldehyde; (2) synthesis of vinyl acetate from acetic acid and acetylene and (3) methanation of carbon dioxide. The predictions of the WM have been compared with the predictions of the SDM and experimental data taken from literature. In case of moderate reaction rates very good agreement was found between the predictions of both models and the experimental data. In case of highly exothermic reactions with steep temperature and concentration profiles the SDM fails to describe the experimental data, whereas the WM gives a good agreement with the experiments.
Modeling of chemical reactors—XXIX mixing-cell model for packed bed reactors. Steady state considerations. Problems of multiplicity
Abstract The axial heat and mass transfer in tubular catalytic reactors may be described by mixing-cell model and diffusion model as well. The diffusion description yields for a strong exothermic reaction and adiabatic conditions three steady state profiles, on the other hand the mixing-cell model gives rise to more than three steady states. A simple numerical and graphical analysis for mixing-cell model is presented.