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Dive into the research topics where Diogo Rodrigues is active.

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Featured researches published by Diogo Rodrigues.


Computers & Chemical Engineering | 2015

Variant and invariant states for chemical reaction systems

Diogo Rodrigues; Sriniketh Srinivasan; Julien Billeter; Dominique Bonvin

Chemical reaction systems State decoupling Reaction variants Reaction invariants Reaction extents a b s t r a c t Models of chemical reaction systems can be quite complex as they typically include information regarding the reactions, the inlet and outlet flows, the transfer of species between phases and the transfer of heat. This paper builds on the concept of reaction variants/invariants and proposes a linear transformation that allows viewing a complex nonlinear chemical reaction system via decoupled dynamic variables, each one associated with a particular phenomenon such as a single chemical reaction, a specific mass transfer or heat transfer. Three aspects are discussed, namely, (i) the decoupling of reactions and transport phenomena in open non-isothermal both homogeneous and heterogeneous reactors, (ii) the decoupling of spatially distributed reaction systems such as tubular reactors, and (iii) the potential use of the decoupling transformation for the analysis of complex reaction systems, in particular in the absence of a kinetic


Computer-aided chemical engineering | 2015

Control of Reaction Systems via Rate Estimation and Feedback Linearization

Diogo Rodrigues; Julien Billeter; Dominique Bonvin

The kinetic identification of chemical reaction systems often represents a time-consuming and complex task. This contribution presents an approach that uses rate estimation and feedback linearizati ...


27th European Symposium on Computer Aided Process Engineering (ESCAPE) - 10th World Congress of Chemical Engineering | 2017

Global Identification of Kinetic Parameters via the Extent-based Incremental Approach

Diogo Rodrigues; Julien Billeter; Dominique Bonvin

The identification of reaction kinetics represents the main challenge in building models for reaction systems. The identification task can be performed via either simultaneous model identification (SMI) or incremental model identification (IMI), the latter using either the differential (rate-based) or the integral (extent-based) method of parameter estimation. This contribution presents an extension of extent-based IMI that guarantees convergence to globally optimal parameters. In SMI, a rate law must be postulated for each reaction, and the model concentrations are obtained by integration of the balance equations. The procedure must be repeated for all combinations of rate candidates. This approach is computationally costly when there are several candidates for each reaction, and convergence problems may arise due to the large number of parameters. In IMI, the identification task is decomposed into several sub-problems, one for each reaction [1]. Since IMI deals with one reaction at a time, only the rate candidates for that reaction need to be compared. In addition, convergence is facilitated by the fact that only the parameters of a single reaction rate are estimated. In rate-based IMI, the parameters are estimated by fitting the simulated rates to the experimental rates obtained by differentiation of measured concentrations. In extent-based IMI, the simulated rates are integrated to yield extents, and the parameters are estimated by fitting the simulated extents to experimental extents obtained by transformation of measured concentrations [2]. The simulated rates are functions of concentrations. Hence, since each reaction is simulated individually, the simulated rates must be computed from measured concentrations. Most parameter estimation methods converge to local optimality, which may result in an incorrect model. It turns out that extent-based IMI is particularly suited to global optimization since each estimation sub-problem (i) involves only a small set of parameters, and (ii) can be rearranged as an algebraic problem, where the objective function is polynomial in the parameters with coefficients computed only once prior to optimization using a Taylor expansion. These features facilitate the task of finding a global optimum for each reaction. Instead of the classical branch-and-bound approach, this technique relies on reformulating the estimation problem as a convex optimization problem, taking advantage of the equivalence of nonnegative polynomials and conical combination of sum-of-squares polynomials on a compact set to solve the problem as a semidefinite program [3]. A simulated example of an identification problem with several local optima shows that extent-based IMI can be used to converge quickly to globally optimal parameters. References: [1] Bhatt et al., Chem. Eng. Sci., 2012, 83, p. 24 [2] Rodrigues et al., Comput. Chem. Eng., 2015, 73, p. 23 [3] Lasserre, SIAM J. Optim., 2001, 11(3), p. 796


Computers & Chemical Engineering | 2017

On decoupling rate processes in chemical reaction systems – Methods and applications

Julien Billeter; Diogo Rodrigues; Sriniketh Srinivasan; Michael Amrhein; Dominique Bonvin

Abstract Models of chemical reaction systems can be complex as they need to include information regarding the reactions and the mass and heat transfers. The commonly used state variables, namely, concentrations and temperatures, express the interplay between many phenomena. As a consequence, each state variable is affected by several rate processes. On the other hand, it is well known that it is possible to partition the state space into a reaction invariant subspace and its orthogonal complement using a linear transformation involving the reaction stoichiometry. This paper uses a more sophisticated linear transformation to partition the state space into various subspaces, each one linked to a single rate process such as a particular reaction, mass transfer or heat transfer. The implications of this partitioning are discussed with respect to several applications related to data reconciliation, state and rate estimation, modeling, identification, control and optimization of reaction systems.


Chemical Engineering Science | 2017

Semi-analytical Solutions for Tubular Chemical Reactors

Diogo Rodrigues; Julien Billeter; Dominique Bonvin


Chemical Engineering Science | 2017

Generalization of the concept of extents to distributed reaction systems

Diogo Rodrigues; Julien Billeter; Dominique Bonvin


Foundations of Computer Aided Process Operations (FOCAPO) - Chemical Process Control (CPC) | 2017

Concept and Applications of Extents in Chemical Reaction Systems

Dominique Bonvin; Sriniketh Srinivasan; Diogo Rodrigues; Julien Billeter; Michael Amrhein


109th Annual Meeting of the American Institute of Chemical Engineers (AIChE) | 2017

Optimal Control Laws for Batch and Semi-batch Reactors Using the Concept of Extents

Diogo Rodrigues; Julien Billeter; Dominique Bonvin


Archive | 2016

Fast Estimation of Plant Steady State, with Application to Static RTO

Diogo Rodrigues; Michael Amrhein; Julien Billeter; Dominique Bonvin


IFAC-PapersOnLine | 2015

Incremental Model Identification of Distributed Two-phase Reaction Systems

Diogo Rodrigues; Julien Billeter; Dominique Bonvin

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Dominique Bonvin

École Polytechnique Fédérale de Lausanne

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Michael Amrhein

École Polytechnique Fédérale de Lausanne

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Sriniketh Srinivasan

École Polytechnique Fédérale de Lausanne

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Nirav Bhatt

Indian Institute of Technology Madras

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