J.P. García-Sandoval

Regulation of the organic pollution level in anaerobic digesters by using off-line COD measurements.

A sampled delayed scheme is proposed to regulate the organic pollution level in anaerobic digestion processes by using off-line COD measurements. The proposed scheme is obtained by combining an error feedback control with a steady state estimator to track constant references and attenuate process load disturbances. The controller performance is tested experimentally for the treatment of tequila vinasses over a period of 68days under different set-point values and several uncertain scenarios which include badly known kinetic parameters and load disturbances. Experimental results show that the COD concentration can be effectively regulated under the influence of set-point changes and high load disturbances by using only a daily off-line COD measurement, which makes the industrial application of the proposed control scheme feasible.

Stability analysis and passivity properties for a class of chemical reactors: Internal entropy production approach

In this contribution, the stability and passivity properties of a class of chemical reactors are addressed from a thermodynamical point of view. For this purpose, a thermodynamical consistent model is derived from a generic gas reactor model whose rate is based on the reaction progress at the mesoscopic scale. It is shown that the internal entropy production may be used as a candidate Lyapunov function to prove the isolated system stability properties and as a storage function to emphasize the passivity properties when the chemical reactor interacts with the surroundings.

A robust monitoring tool for distributed parameter plug flow reactors

This paper deals with the design of an interval observer for plug flow reactors that are modeled by first-order hyperbolic partial differential equations. This model is considered to obtain the dynamics of an auxiliary variable that are further represented by a set of ordinary differential equations by means of the method of characteristics. Regarding these equations, the structure of the interval observer is deduced. This proposed estimation scheme is valid at a certain fixed specific axial point, is robust in the face of both uncertain parameters and load disturbances and is successfully implemented through simulations on an isothermal plug flow reactor within which a consecutive reaction is taking place and on a nonisothermal plug flow reactor with lateral feed where an irreversible reaction is carried out.

On the modelling of the shear thickening behavior in micellar solutions

AbstractThe steady and transient nonlinear rheological behaviors of dilute rod-like micellar solutions are predicted here with a particular case of the generalized Bautista–Manero–Puig (BMP) model that consists of the upper-convected Maxwell constitutive equation and a dissipative power-dependent kinetic equation, which takes into account the formation and disruption of shear-induced structures (SISs). This model has been derived using the extended irreversible thermodynamic (EIT) formalism. In steady shear, the model predicts a Newtonian region at low shear rates and a characteristic shear rate (γ̇c

Derivation of the mechanical and thermodynamic potentials from the generalized BMP model under shear-banding flow

{\dot{\upgamma}}_{\mathrm{c}}

The interface migration in shear-banded micellar solutions

) at which shear thickening develops. In the shear thickening region, the model predicts either a reentrant zone, which is caused by multi-valued shear stresses when the data are collected with a shear stress-controlled mode or a continuous increase in the shear stress-shear rate flow curve, when the data are collected with a shear rate-controlled mode; in this region, two coexisting phases are predicted. The coexisting phases at the same shear rate in the two-phase envelope and the spinodal-like region were evaluated from the extended Maxwell equal-area criterion, which was calculated from the equal values of the two minima of the plot of the extended Gibbs free energy versus shear rate. At higher shear rates, the model predicts a transition to shear thinning, and under transient flows, an induction time and a saturation time are obtained from the predicted and the experimental data as detailed in the text. The magnitudes of both, the induction and the saturation times, diminish as the shear rate departs from γ̇c

Saturated Output-Feedback control of continuous anaerobic digestors

{\dot{\upgamma}}_{\mathrm{c}}