Clement Festila

Dynamic modeling and validation of 2-ethyl-hexenal hydrogenation process

Abstract The paper evaluates, by modeling and simulation, 2-ethyl-hexenal hydrogenation process in catalytic trickle bed three-phase reactors. The mathematical model consists of balance equations for gas and liquid phases. Reaction rate equations, transport models and mass balances were coupled to generalized heterogeneous models which were solved with respect to time and space with algorithms suitable for partial differential equations. The importance of mass transfer resistance inside the catalyst pellets as well as the dynamics of the different phases being present in the reactor is revealed. The dynamic mathematical model presented can be used to analyze and understand the interaction of various processes that take place inside the hydrogenation reactor and also to make preliminary calculation of experimental parameters. Another important use of the mathematical model is to determine the optimal operation conditions and to design the control system. The model is implemented in Matlab and tested in simulations achieving successful results.

Feedback linearization control design for the 13C cryogenic separation column

The separation of carbon isotopes represents a major research area due to the numerous uses of the least abundant carbon isotope, 13C. One of the methods used for separating these isotopes is the cryogenic distillation, in large counter- current columns. Such industrial plants represent a difficult problem in terms of automatic control, since they are characterized by nonlinearities, large delay times and extremely severe control input constraints. The paper presents a control strategy based on a feedback linearization technique as an inner loop controller and a robust controller as the outer loop. The two are combined to result in a nonlinear robust control that achieves robust stability and robust performance for a certain amount of model uncertainties.

Robust Feedback Linearization Applied to a Separation Column for 13C

In the present developing plan to apply the cryogenic technology for the production of the 13C, an efficient and safe operation is a strong reason to conceive and to apply a modern computer based control strategy. The authors are concerned with the problem of developing effective and readily implemental techniques for modelling and control of the isotope separation plant. These columns are characterized by complex nonlinearities, with large time‐delays. Furthermore, are subject to external disturbances, which are difficult to model. The present paper presents two models of the plant: a nonlinear model and a linear system obtained by robust feedback linearization.

Fault Detection and Diagnosis for Continuous Time Process

Abstract Recent advances in microelectronic circuit have enabled the application of process diagnostics to a variety of systems to improve performances and the reliability. Failure detection and isolation strategies monitor a system’s operation for degradations and if detected, classify the failure source. One of the most important methods for failure detection and diagnosis is the analysis of the variations of the estimated process parameter. In this paper is presented a structure of a method for failure detection and diagnosis based on continuous time parameter estimation of a mathematical model of the process. Continuous time parameters can be related easily to the physical characterizations of process. The parameter is to directly estimate by well-known prediction error method of identification for dynamic systems. The failure detection it is based on process coefficient’s changes and statistical decision methods. Unlike usual papers, the failure can be detected whether others process parameters are not constant.

A one-step procedure for frequency response estimation based on a Switch-Mode Transfer Function Analyzer

Frequency response analysis is a well established system identification method. In this paper, a simple and efficient method based on the classical Transfer Function Analyzer (TFA) technique is implemented for system identification. The novel algorithm has been called Switch-Mode-TFA. The originality of the proposed approach consists of: i) using a chirp TFA test input instead of a pure sine function, ii) using a variable sampling period instead of the traditional fixed sampling period and iii) a simplified implementation using switched electric circuits. The advantage of our approach is thus threefold: i) the frequency response of the system is obtained for the entire range of frequencies by means of only one identification test; ii) the number of samples per cycle remains constant, independent of the excited frequencies and iii) it can be easily implemented in hardware platforms. The results in both simulation and real-life examples indicate that the proposed Switch-Mode-TFA method can be reliably used for frequency response analysis in many other applications.

Monitoring and control of liquid nitrogen level of the 13 C separation column using NI PXI-1031

This paper is a step forward by making real time control system design to monitor and control process variables to ensure its smooth operation and desired reliability. Liquid nitrogen level in the condenser is a core component of isotopic separation process to obtain (13C), so is needed a special focus on monitoring and control. The goal of the work is to design a controller for the liquid nitrogen in the condenser of (13C) isotope separation column using NI-PXI 1031 (PCI eXtensions for Instrumentation) from National Instruments. The designed ON-OFF controller is implemented in LabVIEW and are discussed the advantages and disadvantages.

Fractional order controller design for 13 C separation column

Controller design for an isotope separation column is recognized as a difficult and challenging problem, especially when the controller used is of fractional order. The objective of this work is to find out optimum settings for a fractional PIλ controller in order to fulfill three different robustness specifications of design for the compensated system, taking advantage of the fractional order, λ. Since this fractional controller has one parameter more than the conventional PI controller, one more specification can be fulfilled, improving the performance of the system and making it more robust to plant uncertainties, such as gain and time constant changes. For the tuning of the controller, an iterative optimization method has been used based on a nonlinear parametric minimization routine‥

Drinking water quality improvement by physical methods, using middle-frequency inverters

The actual paper deals with the general problem of the water purification with the aim to be accepted as potable water, using two physical methods: in the first stage, the ozone-treatment and then, the ultraviolet (UV) radiation treatment in water transport pipes. A higher treatment efficiency is achieved by superposition of both methods: higher reaction rate, smaller ozone dose and UV-radiation times. The more expensive component of the water disinfection system by physical methods is the inverter - with frequency control - supplying the ozone generator, which uses the corona discharge. The authors propose also a second middle-frequency inverter to supply the UV-lamps. Some results of the experimental water treatment station are also given in the last part.

Diesel-Engine Intelligent Control in Railway Traction

The European laws are more and more restrictive regarding the environment pollution: exhaust gases, noise, etc. The authors present some modern solutions for improvement of the Diesel engine operation in railway traction. Using dedicated electronic systems for injection control and monitoring, the main advantages - economical, technical and environmental - are presented. The new control strategy is based on the general linearized model of the Diesel engine

Modeling and simulation of the liquid phase 2-ethyl-hexenal hydrogenation

Actual computer based process simulations are recognized as essential tool in chemical process. The aim of this paper is to develop a mathematical model that describes the chemical processes that occur in a reactor used for hydrogenation of 2-ethyl-hexenal to 2-ethyl-hexanol. The developed model is based on the mass balance and reaction kinetics equations. The equations include both ordinary differential equations and partial differential equations. The evolution (in time and space) of the process variables (liquid and gaseous flows, composition of the streams) were studied for the hydrogenation process. Process models can be used to get information about the process behavior and can also be used for control and optimization studies.