A mathematical model is developed for a styrene pilot plant reactor.The steady state version of this model was used to optimize the location of a steam injection port part way along the catalytic bed. Significant improvement in reactor performance was predicted by splitting the steam feed between the reactor inlet and the injection port. Performance was measured in terms of market value of products minus a utility cost for the steam. Studies were also carried out via computer simulation to determine optimal operating conditions. An important result was the relationship of optimal steam-to-ethylbenzene feed ratio to the kinetic parameters which describe the main dehydrogenation reaction. A pilot plant was constructed and operated in order to investigate experimentally the predictions of the mathematical model. Instrumentation was designed and installed so that an on-line digital computer could acquire process measurements directly and establish operating conditions. The experimental program confirmed the improved performance by operation of the reactor with a steam injection port and the existence of an optimum of the steamto-ethylbenzene feed ratio as indicated by simulation.

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Liapunov analysis techniques employing a general quadratic functional are used to derive stability conditions for tubular reactor systems. The adiabatic tubular reactor without axial dispersion is shown to be locally stable, which excludes the possibility of multiple steady states, and the reactor with axial dispersion is proven locally stable if a condition involving only system parameters and steady state values is satisfied. Peclet numbers for heat and mass transfer are not specified equal for the latter proof.Results of simulation studies are used to confirm the validity of the derived stability condition, and it is shown that the parametric region of multiplicity is quite well defined. For the nonlinear equations, single steady state cases appear to possess nonuniform stability.This paper investigates the stability of tubular reactors using both theoretical and computational techniques. Liapunov's direct method employing a functional based on a general quadratic norm is used as the theoretical method. The theoretical analysis yields through straightforward algebraic manipulation stability results without the need for a solution of the partial differential equations describing the system. Dynamic simulations were computationally carried out by finite differencing the describing equations and using the quasilinearization technique.In the literature much attention has recently been devoted to stability studies of distributed parameter systems. Murphy and Crandall (19) applied Liapunov stability theory to the catalyst particle problem using a theorem somewhat similar to that to be presented here. Their analysis yielded stability conditions depending on system parameters and steady state values. Han and Meyer ( 1 5 ) used bounded-input-bounded-output concepts to analyze the stability of a nondispersive, catalytic bed reactor. They obtained a stability condition based on discretized nonlinear equations which was different from previous results based on linearized equations. Other work has been done on nondispersive models, and an example is the recent article by Agnew and Narsimhan (1). that is, positive away from a given steady state and zero only at the steady state is specified, and stability is ensured if it can be shown that the time derivative of this function is negative definite. This time derivative involves time derivatives of the state variables, and these are conveniently available in the system differential equations.Liapunov's first method, according to Bertram and Kalman ( 7 ) , "deals with stability questions via an explicit representation of the solutions of a differential equation," whereas Aris ( 4 ) is more specific in stating, "His so-called first method shows how the process of linearization about the steady state may be justified and exploited."The difficulty in the application of the second method is usually found in the search for the Liapunov function. An inverse formulation involving first the specification of a negative definite Liapunov function derivative has been widely used for line...

DateThe final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline.iii can preserve product quality and maintain stable product compositions, resulting in a more efficient and cost-effective operation, which can ultimately lead to scale-up and commercialization of solar thermochemical technologies. ABSTRACTIn this work, we propose a model predictive control (MPC) system for a solar-thermal reactor for the steam-gasification of biomass. The proposed controller aims at rejecting the disturbances in solar irradiation caused by the presence of clouds. A first-principles dynamic model of the process was developed. The model was used to study the dynamic responses of the process variables and to identify a linear time-invariant model used in the MPC algorithm.To provide an estimation of the disturbances for the control algorithm, a one-minute-ahead direct normal irradiance (DNI) predictor was developed. The proposed predictor utilizes information obtained through the analysis of sky images, in combination with current atmospheric measurements, to produce the DNI forecast.In the end, a robust controller was designed capable of rejecting disturbances within the operating region. Extensive simulation experiments showed that the controller outperforms a iv finely-tuned multi-loop feedback control strategy. The results obtained suggest that our controller is suitable for practical implementation.v

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