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Residence time distribution in an inclined rotating fixed-bed reactor

Härting, H.-U.; Lange, R.; Schubert, M.

Abstract

Trickle bed reactors (TBR) are widely applied in the chemical industry for heterogeneous catalytic reactions. Besides their wide application, their performance often suffers from inherent drawbacks, like liquid maldistribution and poor mass and heat transfer rates; and are therefore a promising target for process intensification (PI). PI in such reactors can be realised by a periodic operation of the reactor, which is usually implemented by the modulation of liquid flow rate or liquid inlet concentration. Flow rate modulation is known to increase the mass and heat transfer rates and to significantly increase the time-averaged reaction rates compared to steady state results. On the other hand, the positive effects of the flow rate modulation vanish rapidly along the reactor length due to the fading pulse shape.
An alternative reactor concept for PI is the inclined rotating fixed-bed reactor, which retains the positive effects of flow rate modulation but eludes the deficiencies. The reactor inclination results in phase segregation, whereas the superimposed reactor rotation generates a periodic wetting and draining of the particles in the co-rotating fixed-bed (see Figure 1), thus, transforming the temporal periodic operation into a spatial periodic operation, which is present along the whole reactor length.
To optimize the reactor performance for a given chemical reaction, a reactor model is required, which considers the macro-mixing behaviour. Thus, the aim of this study is the systematic investigation of the influence of reactor inclination and rotation on the residence time distribution (RTD) for selected combinations of gas and liquid superficial velocities. The RTD is examined by the imperfect pulse method, whereat inhouse developed wire-mesh sensors are applied to measure the tracer concentration as well as the in-plane spatial phase distribution at two axial positions in the reactor. The experimental data are fitted to the axial dispersion model with open-open boundary conditions, from which the mean residence time and the Péclet number are extracted.
The results will be discussed with respect to flow regime maps that are based on tomographic imaging. Furthermore, the mean residence time and the Péclet number will be compared with data for the vertical reactor configuration (TBR) and with correlations from the literature.

Keywords: Residence time distribution; process intensification; fixed bed reactor; inclination; rotation

  • Lecture (Conference)
    21st International Congress of Chemical and Process Engineering (CHISA 2014), 23.-27.08.2014, Praha, Česká republika

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