Universität Stuttgart

Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1

Browse

Institute: search.filters.UBSInstitut.Sonstige EinrichtungAuthor: search.filters.author.Eigenberger, Gerhart

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Dynamic modelling of multitubular catalytic reactors
    (1991) Stankiewicz, Andrzej; Eigenberger, Gerhart
    This paper presents a study on modelling and simulation of transient operational characteristics in multitubular fixed-bed reactors. The dynamic model of the reactor is based on a porous body approach which regards the intertubular space as a pseudo-homogeneous environment. Such an approach permits to take into account most factors in the geometrical design of the unit and thus to study the influence of various shell-side geometrical and operational parameters on the reactor behaviour. Based on the model, the dynamic responses of the two most common industrial reactor designs, i.e. the parallel flow unit with distributing plates and the crossflow reactor with disk-and-doughnut baffles have been investigated and compared. In addition, some problems of correct space discretization and use of time-dependent regridding procedures, are discussed.
  • Thumbnail Image
    ItemOpen Access
    Catalyst poisoning and fixed bed reactor dynamics
    (1975) Weng, Hung Shan; Eigenberger, Gerhart; Butt, John B.
    The poisoning kinetics of thiophene on Ni-kieselguhr catalysts and the deactivation behavior of nonisothermal fixed bed reactors have been studied experimentally using benzene hydrogenation as a model exothermic reaction. The time dependent axial temperature profiles in the reactors were measured and compared with values evaluated from a dispersion model, the parameters of which have been determined in separate experimentation. Poisoning kinetics were measured in a series of differential reactor experiments at atmospheric total pressure, thiophene partial pressures of 0·037-0·19 torr, hydrogen to benzene molar ratios >8/1 and temperatures from 60-180°C. Excellent agreement was found with a power law equation for the rate of change of activity with time, first order in catalyst activity and in thiophene concentration, with an experimental activation energy of 1080 kcal/kmole. This correlation of poisoning kinetics, however, was not able to predict the propagation of the zone of activity (hot-spot) on poisoning of an integral fixed bed reactor. Initial (steady state) temperature profiles were modeled satisfactorally, but the rate of migration of the hot spot was found experimentally to be more rapid than that predicted from the correlation of poisoning kinetics. A semi-empirical two site deactivation model is shown to resolve the discrepancy.
  • Thumbnail Image
    ItemOpen Access
    A modified Crank-Nicolson technique with non-equidistant space steps
    (1976) Eigenberger, Gerhart; Butt, John B.
    A finite difference method with non-equidistant space steps, based upon the Crank-Nicolson technique is presented. Its prime feature is the automatic positioning of axial grid points at required positions. Thus reducing considerably the total number of grid points and hence the amount of computer time. The method is demonstrated for a number of examples of tubular reactor calculations. It proves to be well suited for the solution of all kinds of diffusion type models, especially if steep gradients or moving profiles occur, and can be used even on moderate size process computers.
  • Thumbnail Image
    ItemOpen Access
    Reactor stability and safe reaction engineering
    (1989) Eigenberger, Gerhart; Schuler, Hans
    Stable operation of a chemical reactor and stability (in the stability-theory sense) of a chemical process are not necessarily synonymous concepts. Thus, appropriate control can permit reliable operation at an unstable operating point, while even global stability does not necessarily rule out a runaway reaction, e.g., when a strongly exothermlc reaction has a pronounced parametric sensitivity. The concepts of stability and parametric sensitivity are explained in relation to strongly exothermic reactions in stirred-tank and tubular reactors. The conventional view of reaction engineering and the theory of thermal explosions, commonly used in safety engineering, are considered in detail. Practical problems of safe reaction engineering are discussed in relationship to the control of batch and semibatch reactors and to the behavior of tube-bundle reactors.