Eduardo Coselli Vasco de Toledo

Dynamic modelling of a three-phase catalytic slurry reactor

Two dynamic models for a three-phase catalytic slurry reactor with appropriate solution procedures were developed in this work. The models consist of mass and heat balance equations for the catalyst particles, for the gas and liquid bulk phases as well as for the heat exchange through the jacket of the reactor. The models of the tubular reactor were applied to describe the dynamic behaviour of the reactor during the hydrogenation of o-cresol on Ni/SiO2 catalyst. These models differ in solid phase modelling, which allows to evaluate the reactor dynamic behaviour prediction capacity. The models successfully reproduce the main characteristics of the reactor dynamic behaviour.

A tuned approach of the predictive–adaptive GPC controller applied to a fed-batch bioreactor using complete factorial design

Abstract This work presents a novel tuned approach of the Generalized Predictive Control controller in both adaptive and nonadaptive configurations applied to a fed-batch penicillin process using the complete factorial design method. The controller stabilizes the dissolved oxygen concentration through agitation manipulation. The operating process variables were calculated by a mathematical model solved numerically. This new approach employed complete factorial design methodology to provide the optimal set of parameters, estimating the design parameters influence on the integral of the absolute error between the controlled variable and the set point (IAE). The controller parameters analyzed were prediction and control horizons, suppression factor, reference trajectory and integral factor. Moreover, the robustness performance was evaluated using the white noise presence in the measured variable, different polynomial orders of the internal model, several delay time and sampling periods of the controlled variable, and the presence of the internal polynomial. This controller performed better than PID and DMC controllers

Off-line optimization and control for real time integration of a three-phase hydrogenation catalytic reactor

Abstract In order to develop and test the integration procedure, in this paper a real time process integration involving the optimization and control of the process is presented, in this case, with the two-layer approach. The used optimization algorithms were Levenberg–Marquardt and SQP that solve a non-linear least square problem subject to bounds on the variables. The two-layer approach is a hierarchical control structure where an optimization layer calculates the set points and manipulated variables to the advanced controller, which is based on the dynamic matrix control with constraints (QDMC). The non-isothermal dynamic model of the three-phase slurry catalytic reactor with appropriate solution procedure was utilized in this work (Vasco de Toledo, E. C., Santana, P. L., Maciel, M. R. W., & Maciel Filho, R. (2001). Dynamic modeling of a three-phase catalytic slurry reactor. Chemical Engineering Science , 56 , 6055–6061). The model consists on mass and heat balance equations for the catalyst particles as well as for the bulk phases of gas and liquid. The model was used to describe the dynamic behavior of hydrogenation reaction of o -cresol to obtain 2-methil-cyclohexanol, in the presence of a catalyst Ni/SiO 2 .

Process intensification for high operational performance target: Autorefrigerated CSTR polymerization reactor

The concept of process intensification is applied to a CSTR polymerization reactor, where bulk reactions take place via styrene-free radicals, connected to a semi-flooded horizontal condenser; the aim is to operate the system in a safe and efficient way. The model developed was able to reproduce the major dynamic characteristics, even with the presence of non-condensable gases. The existence of such gases prevents the reactor from ever reaching a steady state, increasing the condenser pressure and the reactor temperature and reducing the area of contact and the mass of liquid in the condenser. To circumvent this problem, the control strategy of this work proposes a regular purge of the condenser gases in order to avoid a collapse of the system. In this context, different control algorithms were also analysed and it was concluded that a fast and reliable control of the reactor is only possible when advanced controllers are used.

Development of a software for simulation analysis of the phenomenon of phase change of three-phase catalytic slurry reactor

Abstract This work deals with the development of a software capable to simulate via deterministic modelling the phenomenon of phase change observed in three-phase catalytic slurry reactors, that occurs in the reacting medium and in the refrigerant fluid. The software is based on a detailed dynamic model formulation and considers different tools to evaluate the phase change. The developed software allows the simulation of different possibilities introduced in the model, aiming a better reproduction of chemical plant data.

Detailed deterministic dynamic models for computer aided design of multiphase slurry catalytic reactor

Abstract The non-isothermal dynamic models of the three-phase slurry catalytic reactor with appropriate solution procedure were developed in this work. The models consist on mass and heat balance equations for the catalyst particles as well as for the bulk phases of gas and liquid, and momentum balance equations for the fluid phase. The models were used to describe the dynamic behaviour of a hydrogenation of phenol in catalyst of Ni-Rhaney, producing cyclohexanol and cyclohexane (undesired product). These heterogeneous models include the heat exchange through the jacket of the reactor, evaluates the effect of the phase change of the reacting medium (flash) and the cooling fluid, as well as the variation of the physical properties and the coefficients of heat and mass transfer. The proposed model has shown to be able to predict the main characteristics of the dynamic behaviour of reactor.

Development of high performance operational strategies for polymerization reactor

Abstract This work presents the modeling and control of the temperature of a CSTR polymerization reactor connected to a semi-flooded horizontal condenser. The objectives of this work were to evaluate the cooling potential and the development of different algorithms to control the reactor temperature where bulk polymerization reactions take place via styrene free radicals. The control algorithms studied were classic PI, long-range predictive GPC and predictive-adaptive STGPC (GPC connected to the identification algorithm ‘RLS’). The results obtained here show that the system provides quick, efficient and highly competitive refrigeration compared with other systems when this system is associated with a control algorithm which adapts perfectly to its dynamics characteristics. The new approach presented in this work, which associates the system ‘CSTR + semi-flodded horizontal condenser’ to the control algorithm (GPC and STGPC), makes the process highly competitive regarding refrigeration and performance.

Alternative Designs for Fixed Bed Catalytic Reactors

The scope of this paper is to explore the benefits of both conventional operation design co-current and counter-current, to propose a new alternative design for fixed bed catalytic reactor. Steady state and dynamic behavior were considered in the analysis. Additionally for the steady state, a study on the possible alternatives for the patterns of cooling fluid was also realized, searching for an efficient refrigeration, as well as, minimum energy cost, for the fixed bed catalytic reactor. These new alternative designs consist of using the main advantages of both conventional configurations in an unique design. The results show that the proposed alternative design for fixed bed catalytic reactor has considerable advance compared to conventional system.

Optimization of a Three-Phase Catalytic Slurry Reactor Using Reduced Statistical Models

The main contribution of this work is to propose the use of a statistical procedure to generate simplified models from a detailed deterministic one for Real Time Optimization. Such models are also used as a tool to map the optimal and feasible region. These simplified models are useful in online optimization coupled to control implementations, since detailed rigorous models may demand time and high computational burden for their solution, which hampers the success of online purposes. In order to illustrate the application of the procedure, a three-phase catalytic reactor was considered. A dynamic heterogeneous mathematical model formulation of the o-cresol hydrogenation reaction was used to simulate the reactor steady-state response to different inlet conditions. The proposed statistical procedure (factorial design) generated simplified models for the reactor exit temperature and the reactant conversion, two useful pieces of process information. The use of these models in an optimization problem is then presented as an illustration of their application in an online real time optimization in a two-layer fashion. The simplified models turn possible the identification of the range of optimal solutions as well as the mapping of the region of optimal solutions very quickly compared to the use of full models, allowing the system to be flexibly operated at high level of performance.

Development of Rigorous and Reduced Heterogeneous Dynamic Models for Fixed Bed Catalytic Reactor and Three-Phase Catalytic Slurry Reactor

In this work, the dynamic behavior of two chemical reactors (Fixed Bed Catalytic Reactor and the Three-Phase Reactor), in which different reactions of great industrial interest take place, is presented. Rigorous and reduced models were developed and their capabilities to adequately predict the dynamic behavior of these reactors were compared, indicating which model is more suitable for a specific application (design, optimization and control). Different approaches [Classic, Hermite, Finlayson, Pirkle, Dixion, Generic and Orthogonal collocation (one point)] were used to obtain the reduced models. With these techniques, a mathematical order reduction was carried out, which eliminates the spatial co-ordinate (of the catalyst particle or of the reactor) and promotes radially lumped-differential formulations. The proposed rigorous models were able to predict the main characteristics of the dynamic behavior of the fixed bed catalytic reactor as well as of the three-phase reactor, including the inverse response phenomena and the hot spot present in the former. This knowledge is essential to design and control these reactors. The computational time demanded for the solution of the rigorous models is high in comparison to the reduced ones, which restricts the use of the rigorous models to cases where time is not a limiting factor. Otherwise, when on-line applications are required, the reduced models are more adequate. The models based on reduction techniques overcame computational burden with a faster and easier numerical solution, as well as other difficulties found in rigorous heterogeneous models, especially related to the large number of parameters and sophisticated numerical procedures required by the solution.