A rapid method for flow pattern, mixing time estimation and turbulent dissipation rates in turbulent stirred mixers based on 2-D network-of-zones (NoZ) model

A rapid non-iterative method for estimating flow patterns in stirred vessels in fully turbulent regime was defined and evaluated starting from limited known data near the core regions based on the 2-D network-of-zone (NoZ) model. Flow pattern induced by impeller of arbitrary diameter could be generated non-iteratively from known NoZ data with impeller of same type but another diameter, before mixing time was estimated within minutes on a standard PC. Case studies on six different impeller diameter and types representing typical radial flow impellers and axial flow impellers respectively was presented, errors of mixing time predicted in which were all within a maximum of ±33% compared to mixing time predicted via experimental correlation. A rapid method for estimating turbulent dissipation rate profiles were also introduced and evaluated quantitatively

Towards application of vortex chamber technology as a rotating fluidized bed reactor

This work focuses on the development of vortex chamber technology for the generation of rotating fluidized beds of fine particles and the evaluation of potential application as chemical reactor. Major design aspects are studied, such as the influence of the gas inlet design on the solids retention in a vortex chamber and this as a function of the particle type. The influence of separate solids outlets located on the end walls was also studied. High-G fluidization in vortex chamber results in very short gas-solid contact times, this work addresses this issue by evaluating the application of a RFB-SG to fluid catalytic cracking by means of CFD simulations using a Eulerian multiphase model and the Kinetic Theory of Granular Flow, using a 10-lump reaction kinetics model. A process intensification of one order of magnitude can easily be achieved, while operation with a more active catalyst or a higher cracking temperature opens the way for additional process intensification. Finally, a multi-zone reactor concept is also explored, which can be of great importance to efficiently deal with catalyst regeneration and with the effects of the heat of reaction, by coupling exo- and endothermic reaction zones.(FSA - Sciences de l'ingénieur) -- UCL, 201

Influence of solids outlets and the gas inlet design on the generation of a gas-solids rotating fluidized bed in a vortex chamber for different types of particles

Two design aspects of vortex chambers for the generation of gas-solids rotating fluidized beds are experimentally studied for different types of particles: the solids outlet(s) and the gas inlets. Efficient solids retention and minimal solids losses via the chimney are aimed at so that the gas and solids residence times can be controlled independently. The importance of a strong vortex in the central particle bed freeboard region is demonstrated. It is shown that separate, well-dimensioned and -positioned solids outlets prevent a significant presence of particles in the freeboard region, increasing the vortex strength in this region. This is found to be particularly important when fluidizing small/light particles. The ratio centrifugal force-to-radial gas-solid drag force that is generated by the gas injection is shown to also have an important impact. Theoretically it is shown that this ratio strongly depends on the particle characteristics and to what extent it can be increased by increasing the gas injection velocity, preferentially by reducing the gas inlet slot size and otherwise the number of gas inlet slots. Experiments with different vortex chambers and particles qualitatively confirm the theoretical expectations, but show that limitations are encountered. A very high gas injection velocity prevents efficient penetration of especially fine/light particles in the gas inlet jets which is detrimental for the transfer of tangential momentum between the gas and the particle bed. Slots smaller than the particle size are also shown to be inefficient, as they generate rotational motion of the particles around their own center of gravity

High-Gravity Operation in Vortex Chambers for the Generation of High-Efficiency Fluidized Beds

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Computational Fluid Dynamics Simulation of Fluid Catalytic Cracking in a Rotating Fluidized Bed in a Static Geometry

The application of a rotating fluidized bed in a static geometry to fluid catalytic cracking is evaluated by means of computational fluid dynamics (CFD) simulations using an Eulenan-Eulenan model and the kinetic theory of granular flow The reactions arc described by a 10-lump model. First, the reaction kinetics is based on currently allowable clacking temperature and catalyst activity. Typical reactor dimensions required are presented, and an evaluation of the process intensification potential is made, based on a comparison with riser technology Next, the possibility of using a higher cracking temperature or a more active catalyst is evaluate

Fluid catalytic cracking in a rotating fluidized bed in a static geometry: a CDF analysis accounting for the distribution of the catalyst coke content

Computational Fluid Dynamics is used to evaluate the use of a rotating fluidized bed in a static geometry for the catalytic cracking of gas oil. A Eulerian–Eulerian flow model is used in combination with the Kinetic Theory of Granular Flow. The catalytic cracking reactions are described by a 10-lump model. Catalyst deactivation by coke formation is included. To operate at low catalyst coke content, the catalyst residence time is small and the catalyst makes on average only a limited number of rotations in the reactor. Therefore,the catalyst bed cannot be considered well-mixed and a local distribution of the catalyst coke content is to be accounted for. The catalyst coke content distribution function has no pre-described functional form and is discretized. A continuity equation is then solved for each of the classes of catalyst with a given coke content. The impact of the strongly endothermic cracking reactions on the particle bed temperature uniformity is also studied