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Abstract: In order to implement nonlinear control, nonlinear system identification must be performed, however, there are open questions concerning this field of process control, for example, experimental planning, model structure selection, parameter estimation, and validation. Therefore, the study of nonlinear model identification is a relevant unsolved problem that needs to be handled for nonlinear control synthesis. This paper presents the use of bifurcation theory, dynamic and stability analysis for nonlinear identification, and control of polymerization reactors. Peroxide‐initiated styrene‐solution polymerization reactors (lumped‐distributed) are investigated: batch, continuous stirred‐tank reactor (CSTR), and tubular reactors. Open and closed loop analyses are carried out using jacket temperature and weight average molecular weight setpoints as the bifurcation parameters. Phenomenological mathematical models, neural network nonlinear models, and an experimental data from a polymerization unit are employed for validating the proposed methodology in order to implement confident nonlinear controllers. [ABSTRACT FROM AUTHOR]

Simulation and experimental studies are carried out for peroxide-initiated styrene solution polymerization in a lumped-distributed reactor. Weight-average molecular weight (intrinsic viscosity measurements) and conversion (density data) are the output signals, while the manipulated variables are jacket reactor temperature and feed modifier ( tert-dodecylmercaptan) concentration. A simple in-line viscometrical method makes the in-line control of weight-average molecular weight in solution polymerization feasible, using independent conversion measurements from an in-line densitometer. Successful closed-loop servo and regulatory control results are obtained. [ABSTRACT FROM AUTHOR]

The article describes a low-cost thermocouple signal-conditioning module, which was built using the AD594C chip from Analog Devices Inc. This chip compensates for the drawbacks of the thermocouple because it amplifies the signal and provides the cold-junction temperature compensation. Thermocouples are widely used in industrial and laboratory activities. They are formed by two different metals that are typically welded together. The junction between the two metals generates a voltage that is temperature dependent, thus the voltage can be used to determine the temperature. The results show good linearity and reproducibility of the module. After testing, the module has been used to monitor the temperature of polymerization reactors in the laboratories.

The electrostatic dehydration of crude-oil emulsionswere investigatedusing pilot-plant and industrial data. The experimental data obtainedwith seven different crudes over a wide range of viscosities in apilot plant showed that the electric field and the residence timewere the most important operating variables. Various crude-oil propertiesinfluenced the emulsion stability, including the total acid numberand the resin, asphaltene, and metal contents, but their effects werestatistically correlated with the crude-oil viscosity and density.Using pilot-plant data, a power-law model relating the water contentin the treated oil to the dehydration operating conditions and thecrude-oil viscosity and density was developed to aid in the designand evaluation of industrial units. The model was tested against industrialdata and found to be able to predict very well the performance ofthe industrial units. [ABSTRACT FROM AUTHOR]