Imperial College London

DrBenoitChachuat

Faculty of EngineeringDepartment of Chemical Engineering

Reader in Process Systems Engineering
 
 
 
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b.chachuat Website

 
 
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609Roderic Hill BuildingSouth Kensington Campus

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Summary

 

Publications

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151 results found

Chachuat B, Srinivasan B, Bonvin D, 2008, Model Parameterization Tailored to Real-time Optimization, 18th European Symposium on Computer Aided Process Engineering (ESCAPE-18), Publisher: ELSEVIER SCIENCE BV, Pages: 1-13, ISSN: 1570-7946

Conference paper

Mitsos A, Chachuat B, Barton PI, 2007, Methodology for the design of man-portable power generation devices, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 46, Pages: 7164-7176, ISSN: 0888-5885

Journal article

Mitsos A, Chachuat B, Barton PI, 2007, Microfabricated fuel cell systems: Beyond process synthesis, ABSTR PAP AM CHEM S, Vol: 234, ISSN: 0065-7727

Journal article

Marchetti AG, Chachuat, Bonvin D, 2007, Batch process optimization via run-to-run constraints adaptation, European Control Conference (ECC), Publisher: IEEE, Pages: 2791-2798

© 2007 EUCA. In the batch process industry, the available models carry a large amount of uncertainty and can seldom be used to directly optimize real processes. Several measurement-based optimization methods have been proposed to deal with model mismatch and process disturbances. Constraints often play a dominant role in the dynamic optimization of batch processes. In their presence, the optimal input profiles are characterized by a set of arcs, switching times and active path and terminal constraints. This paper presents a novel method tailored to those problems where the potential of optimization arises mainly from the correct set of path and terminal constraints being active. The input profiles are computed between successive runs by dynamic optimization of a fixed nominal model, and the constraints in the optimization problem are adapted using measured information from previous batches. Note that, unlike many existing optimization schemes, the measurements are not used to update the process model. Moreover, the proposed approach has the potential to uncover the optimal input structure. This is demonstrated on a simple semi-batch reactor example.

Conference paper

Mitsos A, Chachuat B, Barton PI, 2007, What is the design objective for portable power generation: Efficiency or energy density?, JOURNAL OF POWER SOURCES, Vol: 164, Pages: 678-687, ISSN: 0378-7753

Journal article

Bernard O, Chachuat B, Steyer JP, 2007, State Estimation for Wastewater Treatment Processes, Wastewater Quality Monitoring and Treatment, Pages: 247-263, ISBN: 9780471499299

Book chapter

Marchetti A, Chachuat B, Bonvin D, 2007, Real-time optimization of continuous processes via constraints adaptation, Pages: 45-50, ISSN: 1474-6670

© Copyright 2007 IFAC. In the framework of process optimization, measurements can be used to compensate for the effect of uncertainty. The method studied in this paper combines a process model and measurements to iteratively improve the operation of continuous processes. Unlike many existing real-time optimization schemes, the measurements are not used to update the process model, but to adapt the constraints in the optimization problem. Upon convergence, all the constraints are respected even in the presence of large model mismatch. Moreover, it is shown that constraints adaptation can handle changes in the set of active constraints. The approach is illustrated, via numerical simulation, for the optimization of a continuous stirred-tank reactor.

Conference paper

Chachuat B, Singer AB, Barton PI, 2006, Global methods for dynamic optimization and mixed-integer dynamic optimization, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 45, Pages: 8373-8392, ISSN: 0888-5885

Journal article

Chachuat B, Bernard O, 2006, Probabilistic observers for a class of uncertain biological processes, INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Vol: 16, Pages: 157-171, ISSN: 1049-8923

Journal article

Bernard O, Chachuat B, Helias A, Rodriguez- Jet al., 2006, Can we assess the model complexity for a bioprocess: theory and example of the anaerobic digestion process, WATER SCIENCE AND TECHNOLOGY, Vol: 53, Pages: 85-92, ISSN: 0273-1223

Journal article

Mitsos A, Chachuat B, Barton PI, 2005, A design and operation methodology for man-portable power generation, Pages: 7313-7315

A integrated design methodology for portable power generation based on fuel cell systems was presented. Various fuels, including hydrogen, ammonia, various hydrocarbons, and alcohols, and fuel cells including solid oxide fuel cell, polymer electrolyte membrane, single chamber solid oxide fuel cell, direct methanol fuel cell, and proton conducting fuel cell based on ceramic technology were considered. The system level analysis provided limits of performance and could be used to determine at an early stage if a proposed device is worth pursuing; e.g., the use of methane. The use of detailed two- and three-dimensional computational fluid dynamics allowed geometrical improvements as well as the derivation and validation of modeling assumptions that were employed in the system-level and intermediate fidelity models. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).

Conference paper

Chachuat B, Barton PI, 2005, Constructing tight convex/concave relaxations of the solutions of parameter-dependent nonlinear odes, Pages: 6825-6826

Optimization problems embedding initial value problems in nonlinear ordinary differential equations (ODEs) that depend on parameters are frequently encountered in chemical engineering as well as in many other engineering and scientific fields ẋ ((t, p) = f(t, p, ×)(t, p)), ∀t ∈ (t0, t⌈] x (t0, p) = h (p) with p ∈ P, x (t, p) ∈ ℝnI and P ⊆ ℝnp a nonempty convex set. This paper is concerned with the problem of obtaining pointwise in time convex/concave bounds for the solutions x of (5) on P. More precisely, the general goal is to construct auxiliary differential systems, the solutions of which underestimate/overestimate the solutions of the original differential system (5), and are guaranteed to be pointwise in time convex/concave on P. Note that the idea of constructing such auxiliary differential systems is not new to this paper for it has already been proposed by Singer and Barton [1]. However, in this former work, the authors considered pointwise in time affine relaxations only. The main contribution of this work lies in the development of a theoretical framework enabling the construction of general nonlinear relaxations for the solutions of parameter dependent nonlinear ODEs on subsets of a Euclidean space. The practical application of these results is also closely considered. More precisely, a procedure for constructing such relaxations under mild assumptions is proposed, based on McCormick's relaxation technique [2], Finally, several illustrative examples are presented which demonstrate the construction and practicality of the relaxations. An important application of these results is in algorithms capable of solving dynamic optimization problems to guaranteed global optimality [3,4,5] as well as mixed-integer dynamic optimization (MIDO) [6] and hybrid discrete/continuous dynamic optimization [7] problems.

Conference paper

Chachuat B, Mitsos A, Barton PI, 2005, Optimal start-up of micro power generation processes employing fuel cells, Pages: 7002-7003

Conference paper

Chachuat B, Singer AB, Barton PI, 2005, Global mixed-integer dynamic optimization, AICHE JOURNAL, Vol: 51, Pages: 2235-2253, ISSN: 0001-1541

Journal article

Chachuat B, Mitsos A, Barton PI, 2005, Optimal design and steady-state operation of micro power generation employing fuel cells, CHEMICAL ENGINEERING SCIENCE, Vol: 60, Pages: 4535-4556, ISSN: 0009-2509

Journal article

Fikar M, Chachuat B, Latifi MA, 2005, Optimal operation of alternating activated sludge processes, CONTROL ENGINEERING PRACTICE, Vol: 13, Pages: 853-861, ISSN: 0967-0661

Journal article

Chachuat B, Roche N, Latifi MA, 2005, Optimal aeration control of industrial alternating activated sludge plants, BIOCHEMICAL ENGINEERING JOURNAL, Vol: 23, Pages: 277-289, ISSN: 1369-703X

Journal article

Chachuat B, Roche N, Latifi MA, 2005, Long-term optimal aeration strategies for small-size alternating activated sludge treatment plants, CHEMICAL ENGINEERING AND PROCESSING-PROCESS INTENSIFICATION, Vol: 44, Pages: 593-606, ISSN: 0255-2701

Journal article

Barton PI, Mitsos A, Chachuat B, 2005, Optimal start-up of micro power generation processes, 15th European Symposium on Computer Aided Process Engineering (ESCAPE-15), Publisher: ELSEVIER SCIENCE BV, Pages: 1093-1098, ISSN: 1570-7946

Conference paper

Bernard O, Chachuat B, Helias A, Le Dantec B, Sialve B, Steyer JP, Lardon L, Neveu P, Lambert S, Gallop J, Dixon M, Ratini P, Quintaba A, Frattesi S, Lema JM, Roca E, Ruiz G, Rodriguez J, Franco A, Vanrolleghem P, Zaher U, De Pauw DJW, De Neve K, Lievens K, Dochain D, Schoefs O, Fibrianto H, Farina R, Gonzalez VA, Alvarez VG, Lemaire P, Martinez JA, Esandi F, Duclaud O, Lavigne JFet al., 2005, An integrated system to remote monitor and control anaerobic wastewater treatment plants through the internet, WATER SCIENCE AND TECHNOLOGY, Vol: 52, Pages: 457-464, ISSN: 0273-1223

Journal article

Chachuat B, Singer AB, Barton PI, 2005, Global solution of mixed-integer dynamic optimization problems, 15th European Symposium on Computer Aided Process Engineering (ESCAPE-15), Publisher: ELSEVIER SCIENCE BV, Pages: 133-138, ISSN: 1570-7946

Conference paper

Chachuat B, Mitsos A, Barton PI, 2004, Optimal design and operation of micro power generation processes, Pages: 7749-7758

The optimal design and operation of a micro power generation process that consists of a reactor, a solid-oxide fuel cell (SOFC), and two burners in a stack fed with ammonia and butane fuels are presented. Hydrogen is produced from ammonia decomposition, while butane is catalytically oxidized to produce heat and maintain the stack at a sufficiently high temperature. The developed steady state model is used as a basis to study and determine the optimal design and operation of the system. The optimization problem is formulated so that the consumption rate of utilities (ammonia and butane) is minimized, while meeting a specified power demand and maintaining the stack in thermic equilibrium. Radiative heat losses play a central role in the operation and design of micro power generation processes. This is an abstract of a paper presented at the AIChE Annual Meeting (Austin, TX 11/7-12/2004).

Conference paper

Chachuat B, Mitsos A, Barton PI, 2004, Optimal design and operation of micro power generation processes, Pages: 2369-2378

This paper presents the optimal design and operation of a micro power generation process that consists of a reactor, a solid-oxide fuel cell (SOFC) and two burners in a stack fed with ammonia and butane fuels. Hydrogen is produced from ammonia decomposition, while butane is catalytically oxidized to produce heat and maintain the stack at a sufficiently high temperature. In the first part, a novel model is developed for predicting the steady-state performance of the process. Subsequently, this model is used as a basis to study and determine the optimal design and operation of the system. The optimization problem is formulated so that the consumption rate of utilities (ammonia and butane) is minimized, while meeting a specified power demand and maintaining the stack at its thermal equilibrium. The dependence of the optimal design and operating strategy on the operating temperature and the heat losses of the system is emphasized.

Conference paper

Chachuat B, Roche N, Latifi MA, 2003, Reduction of the ASM 1 model for optimal control of small-size activated sludge treatment plants, Revue des Sciences de l'Eau, Vol: 16, Pages: 5-26, ISSN: 0992-7158

In order to meet the stricter wastewater effluent guidelines adopted by the European Union, wastewater treatment plants require better management strategies. Wastewater treatment process models have become a major tool to design closed-loop control schemes. However, the dynamic models that are currently used in the simulation of activated sludge treatment plants (ASM 1, ASM 2 and, more recently, ASM 3 models) are highly dimensional and are not appropriate for on-line implementation (e.g., for model predictive control or optimal control). It is therefore important to develop reduced models that could be used for this purpose. A reduced model was developed to describe the behaviour of alternating activated sludge treatment plants, with the aim of applying it to the optimal control of an aeration system. The reduction scheme was based on appropriate simplifications to the ASM 1 model (which is more appropriate for open-loop control). The objective was to verify if accurate predictions could be made time periods of several hours (about 8 h). The present results are related to an existing small-size wastewater treatment plant. This plant was designed for 15000 population-equivalents (p.e.) and consists of a primary treatment stage (screening, grit removal, primary sedimentation), followed by a secondary treatment stage (biological treatment). The latter consists of a single aeration tank of about 2050 m3equipped with 3 turbines which are operated cyclically to create alternating aerobic and anoxic conditions. Ammonia is converted into nitrate during air-on periods (nitrification step) and nitrate is subsequently removed during air-off periods (denitrification step). It is important to note that a dynamic model, based on the ASM 1 model and calibrated from a set of input/output measurements over a one-day period (CHACHUAT, 2001), was used here as a reference to perform model reduction. The following two-level simplification procedure was applied: • A homotopy method

Journal article

Fikar M, Chachuat B, Latifi MA, 2003, Dynamic optimisation of alternating activated sludge processes, Pages: 3189-3193

© 2003 EUCA. The study presents dynamic optimisation of a small size single basin wastewater treatment plant. The objectives are to determine an optimal sequence of aeration/non-aeration times and the corresponding periodical steady state subject to minimisation of energy consumption. Based on the optimal trajectories, two simple feedback rules are proposed that follow from properties of the optimal solution. Simulation results with these simple rules show very satisfactory control performance.

Conference paper

Fikar M, Chachuat B, Latifi MA, 2003, Dynamic optimisation of alternating activated sludge processes, Pages: 3189-3193

© 2003 EUCA. The study presents dynamic optimisation of a small size single basin wastewater treatment plant. The objectives are to determine an optimal sequence of aeration/non-aeration times and the corresponding periodical steady state subject to minimisation of energy consumption. Based on the optimal trajectories, two simple feedback rules are proposed that follow from properties of the optimal solution. Simulation results with these simple rules show very satisfactory control performance.

Conference paper

Chachuat B, Latifi MA, 2003, A new approach in deterministic global optimisation of problems with ordinary differential equations, 4th International Conference on Frontiers in Global Optimization, Publisher: KLUWER ACADEMIC PUBLISHERS, Pages: 83-108

Conference paper

Chachuat B, Roche N, Aberentz P, 2001, A new approch for the optimum management of aeration in a small activated sludge treatment plants, Eau, l'INDUSTRIE, les Nuisances, Pages: 53-59, ISSN: 0755-5016

Most of small size wastewater treatment plants use simple control strategies based on dissolved oxygen concentration, redox potential or ammonia concentrations. Dynamic optimisation methods are here applied to improve both economic and reliability performances of small size wastewater treatment plants equipped with mechanical surface aerators. The aeration policy which minimises the energy consumption and satisfies discharge requirements under specified constraints (process and physical constraints) is then determined. The comparison between rule-based control policies and optimised aeration strategies showed that the optimised aeration profiles lead to reductions of energy consumption of about 40%.

Journal article

Chachuat B, Roche N, Latifi MA, 2001, Dynamic optimisation of small size wastewater treatment plants including nitrification and denitrification processes, COMPUTERS & CHEMICAL ENGINEERING, Vol: 25, Pages: 585-593, ISSN: 0098-1354

Journal article

Chachuat B, Roche N, Latifi MA, 2000, Dynamic optimisation of small size wastewater treatment plants including nitrification and denitrification processes, Computer Aided Chemical Engineering, Vol: 8, Pages: 853-858, ISSN: 1570-7946

In this paper, dynamic optimisation of small size wastewater treatment plants is studied. The problem is stated as a hybrid dynamic optimisation problem which is solved using a gradient-based method. The aeration policy which minimises the energy consumption and satisfies discharge requirements under specified constraints (process and physical constraints) is then determined. The comparison between usual rule-based control policies and optimised aeration strategies showed that the optimised aeration profiles lead, to reductions of energy consumption of at least 30%. © 2000 Elsevier B.V. All rights reserved.

Journal article

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