Behavior Of Fixed-bed Reactors Research Articles

Prediction of the fixed-bed reactor behaviour using dispersion and plug-flow models with different kinetics for immobilised enzyme

The behaviour of fixed-bed reactors, which have an immobilised enzyme on the packing surface, was studied considering steady-state conditions and external mass transfer resistance in the fluid around catalyst spherical particles. Solutions were obtained by integration of the plug-flow model equation and by the orthogonal collocation method of the second order differential equation of the axial dispersion flow model. Both models were analysed for lactose hydrolysis with β-galactosidase immobilised on chitosan using different kinetic reaction mechanisms after determining the specific parameters. The calculated results show the importance of the hydrodynamic and kinetic reaction parameters for error reduction in the prediction of the experimental behaviour.

Simulation of tubular reactors packed with large-pore catalysts with spherical geometry

The effect of intraparticle convection on the behavior of fixed-bed reactors with spherical catalyst particles is analyzed. In the model equations for the particles, both radial and angular coordinates are accounted for. The study concerning the number of discretization points to be used in the numerical solution of the intraparticle profiles is presented. For the reactor, a comparison between unidimensional heterogeneous models with and without intraparticle convection and with spherical and slab geometry for the solid particles is also performed.

Effect of intraparticle convection on the steady-state behavior of fixed-bed catalytic reactors

The effect of intraparticle convection on the behavior of fixed-bed reactors containing large-pores catalysts (e.g. selective oxidation catalysts) is analysed by comparing three reactor models : pseudohomogeneous model ( PH), heterogeneous diffusion ( HT d ) and heterogeneous diffusion/convection model ( HT dc ). Runaway diagrams were constructed based on the “maxima-curve”, allowing system properties to change with temperature and on the method of isoclines. It is shown that the “maxima-curve” method fails in the case of the HT dc model since then the “maxima-curve” P bm = f( T bm ) has two maxima. The stable region of operation predicted by the HT dc model. Energy savings can be obtained by using large-pore catalysts since then it is possible to operate at lower wall/feed temperatures than those used with conventional catalysts. New catalysts can be designed to take advantage of the improvement on the effectiveness factor due to intraparticle convection and energy savings due to the use of more favorable operating conditions.