Jean-Pierre Corriou

To What Extent Does Temperature Affect Absorption in Gas-Liquid Hollow Fiber Membrane Contactors?

Most models developed in the past for gas-liquid absorption accompanied by chemical reactions assumed isothermal conditions for an easy treatment of the experimental data. The reactions are often highly exothermic accompanied by a substantial temperature increase at the interface which affects not only the rate constants, but also the solubilities as well as the diffusivities. Analytical expressions are derived in this work to describe the diffusion-convection-reaction of a reacting solute component in a reactant solution in a hollow fiber membrane contactor in which the shell hydrodynamics is assumed as a plug flow. Results are presented for a classical bimolecular nonisothermal reaction to illustrate the effects of various parameters on the enhancement factor, efficiency, and temperature rise. The volatility effect of the liquid phase reactant on the absorption efficiency is also illustrated.

Spectrophotometric characterization of dissolved organic matter in a rural watershed: the Madon River (N-E France)

In the last 20xa0years, increasing dissolved organic carbon (DOC) concentrations have been observed in several rivers and lakes in Europe. This increase has reduced the quality of the aquatic environment. In this study, UV–vis spectroscopy and synchronous fluorescence spectroscopy with a difference of 50xa0nm between the excitation and emission (SF50) were used to characterize the DOC in a rural river (Madon River). The specific absorbance index at 254xa0nm (SUVA254) which is related to the aromaticity of DOC was extracted from UV–vis spectra, whose maximum of the second derivative (occurring near 225xa0nm) is related to nitrates. SF50 spectra which are characterized by well-defined peaks indicated large spatial and temporal variations. Two methods were used to analyze and compare these spectra. The first method was based on the decomposition of the SF50 spectra into four Gauss functions: B1 (related to tryptophan-like fluorescence), B2 and B3 (related to humic substances), and B4 (related to chlorophyll-like substances). The second method was principal components analysis (PCA), which results yielded three principal components that accounted for 95xa0% of the variance. Although PCA enables the consideration of the spectra without making assumptions regarding the number of fluorophores, the results from the decomposition in Gauss function were easier to interpret.

Estimation of a Reduced Model of the BSM1 Activated Sludge Wastewater Treatment Plant

The complete BSM1 model is recognized as representative of activated sludge plants. However, its large number of states may render it inadequate for development of state observers and for control. Thus, a reduced model has been developed for the two main sections of the plant, the anoxic and aerobic reactors. Concepts of model reduction of biological models based on the analysis developed by Bernard (Bernard2005a, Bernard2005b) have been used. The output data have been obtained by simulating the inlet by data representative of dry weather. After transformation and treatment of the data, it has been shown that a kinetic model reduced to two reactions is able to represent 80% of the total variance. The pseudo-stoichiometric coefficients have been estimated and the pseudo reaction scheme has been validated with respect to the actual concentrations at the outlet of a considered section. The dynamics are generally well represented by the reduced model.

Model predictive control of a fluid catalytic cracking unit

The dynamic model describing the FCC process is inspired from Lee and Groves model. The model uses three lump kinetics to describe the cracking reactions in the riser considered as a plug-flow system. The riser behavior is described by gasoil, gasoline, coke and energy balances as a plug flow reactor. The separator is considered as a CSTR. The regenerator mainly constituted by a dense and a dilute zone is also considered as a CSTR to represent the catalyst and its dynamic behavior is described by coke, oxygen and energy balances. This model is sufficiently complex to capture the major dynamic effects that occur in a FCC and to control the key variables which are the riser outlet temperature and the regenerator dense bed temperature. The manipulated inputs are the air inlet flow rate in the regenerator and the regenerated catalyst flow rate. Hard constraints are imposed with respect to the manipulated variables. In spite of the important nonlinearity of the FCC, Model Predictive Control is able to maintain a smooth multivariable control of the plant, while taking into account the constraints.

Dissolved oxygen control strategies for the industrial sequencing batch reactor of the wastewater treatment process in the papermaking industry

This paper proposes two strategies for controlling the dissolved oxygen concentration in the sequential batch reactor of the wastewater treatment process in the papermaking industry. Based on a previously developed sequential batch reactor simulation model, a fuzzy logic system and a neural network are integrated with a PID controller separately. According to the criteria defined in benchmark simulation model no. 1 (BSM1), three control strategies, namely, conventional PID, developed BP (back propagation)-PID and fuzzy-PID, applied in two cases with and without noise, have been investigated and assessed. For the cases without noise, both the developed controllers, i.e. BP-PID and fuzzy-PID, are superior to PID, wherein the fuzzy-PID controller not only improves the control performance but also reduces the aeration energy consumption. The results of further simulation with the interference of white noise reveal that the developed fuzzy-PID controller not only has better manipulated and controlled indexes than those of the BP-PID controller, it also demonstrates a good ability for anti-interference. These simulation results reveal the superiority of the developed fuzzy-PID control strategy in the dissolved oxygen control of the sequential batch reactor of the wastewater treatment process in the papermaking industry.

Boundary Geometric Control of Nonlinear Diffusion Systems

Abstract The paper addresses the boundary control of a nonlinear diffusion system submitted to Neumann actuation. The control law is designed in the framework of geometric control theory using directly the nonlinear partial differential equation model without any previous reduction. First, an equivalent linear model using the Cole-Hopf transformation is obtained, then the manipulated variable is inserted in the state equation of this equivalent linear model by means of a Dirac delta function to make the boundary condition homogeneous. Based on the resulting final model, the control law is derived using the characteristic index notion and the closed loop stability is demonstrated using concepts from the powerful semigroup theory. The control law performance is evaluated through numerical simulation by considering a nonlinear heat conduction control problem.

Dynamic Modelling of Chemical Processes

This chapter gives a general presentation of all types of models used in chemical engineering and continuous linear control. First, general models of processes based on first principles, mass and energy balances, are developed. Continuous linear and nonlinear models considered from the point of view of control are presented, either in the state-space or as transfer functions.

Improvement of Control Systems

The simple PID is not always sufficient. Many controller improvements commonly used in practice are presented such as the Smith predictor, cascade control, selective control, split-range control, feedforward control and ratio control.

Parametric Estimation Algorithms

The present chapter is devoted to the presentation and use of many algorithms used for parametric identification. Many of them are based on variants of least squares using gradient techniques. Various input sequences used for system excitation in view of model identification are detailed. Several examples of identification are given.

Design of Feedback Controllers

General considerations are given for the design of feedback controllers, and several rules are given for PID controllers with demonstration examples. Internal model control based on continuous transfer functions is presented. Finally, pole-placement and linear quadratic control are developed in the framework of continuous transfer functions.