Modelling and Discrimination Studies in a Catalytic Fluidized Bed Reactor

Abstract

<p>The object of this research program was to develop a strategy and methodology for modelling existing large-scale chemical reactors by coupling bench-scale studies with plant data.</p> <p>By way of example, the hydrogenolysis of n-butane on a 10% nickel on silica gel catalyst was carried out in a pilot-scale fluidized bed reactor (8 in. in diameter by 3 ft. bed depth). Integral reaction data were obtained from a small fixed bed reactor, packed with the same catalyst. A kinetic model, based on adsorption-desorption and reaction of activated hydrocarbon species, was developed and the ten kinetic parameters in it were estimated from the packed bed data. Statistical methods for the design of experiments for parameter estimated and for model discrimination were employed. This chemical kinetic model was used with a number of available two-phase mechanistic models to describe the fluid mechanical behaviour in fluidized beds. A catalyst activity and an interchange factor, which provides a prediction of the interchange of gas between the bubble and the emulsion phase in a fluidized bed were estimated from the plant data. Statistical methods were used to plan the experiments to allow a combination of maximum discrimination among models and a test of the models over the full range of possible operating conditions. A model discrimination criterion which takes into account the effect of errors in parameter estimates is developed and applied to determine the best model for this system at two fluidized bed heights.</p> <p>Fluidized bed models are evaluated in the light of this experience. Some of the problems associated with obtaining estimates of parameters in one experimental system and applying them in another are delineated. General guidelines are indicated for modelling large industrial-scale reactors.</p>