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Title: Dynamics and modelling of fixed bed tubular reactors
Author: Romero-Ogawa, M. A.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1991
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The behaviour of a pilot scale tubular fixed bed catalytic reactor for the catalytic oxidation of SO2 under non-reactive and reactive conditions for both steady-state and unsteady-state regimes is analysed by means of heterogeneous, pseudo-heterogeneous and pseudo-homogeneous models. The equations involved are solved by double orthogonal collocation employing both global and finite element approaches. Steady-state and unsteady-state non-reactive experiments have been performed in order to estimate heat transport parameters. A Smith predictor scheme was implemented for the control of the reactor inlet temperature and its performance compared with that of a conventional PID controller. Radial heat transfer parameters are estimated from the steady-state experimental information and axial heat transfer parameters from dynamic experimental data. Individual heterogeneous heat transport parameters are evaluated by employing equivalence relationships and the estimated effective parameters. Radiant heat transport (a mechanism rarely included) is considered throughout and an average value of 0.9 has been obtained for the particle emissivity. Four different methods were employed to determine the contribution of radiant heat transport to the effective parameters. Although the predicted steady-state behaviour of the system shows good agreement with experimental data and the dual stage parameter estimation strategy yields fair equivalence between the three model representations, the values of the estimated heat transfer parameters are outside normal ranges (viz. effective axial conductivities around 4x10-2 W m-1K-1, an asymptotic fluid Peclet number of 3 and a solid-wall Biot number of 4.7x106). The transient behaviour of the reactor under non-reactive conditions is predicted well enough in terms of shape but exhibits an offset in the final steady-state in relation to the experimental measurements. The predicted dynamic response under reactive conditions is compared to experiments reported by other workers. The heterogeneous model gives a good qualitative prediction of the transients involved, whilst the other structures fail to reproduce the observed behaviour. The physical meaning of the values obtained for the estimated parameters are considered doubtful and it is recommended that the models employed should be considered as predictive structures. The finite element approach showed better numerical stability and speed of convergence than global collocation, especially in parameter estimation (where it had not been applied previously) and in the prediction of dynamic reactive behaviour as it updates the element boundaries to follow the movement of the reactor hot spot.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available