Showing papers by "Laurent E. Prat published in 2005"

Performance Evaluation of a Novel Concept “Open Plate Reactor” Applied to Highly Exothermic Reactions

Abstract: The implementation of chemical reactions in batch or semi-batch reactors is strongly limited by the constraints linked to the dissipation of the heat generated by the reactions. The novel concept of heat exchanger reactors offers enhanced thermal performances in a continuously operating reactor. A study program is proposed to assess the feasibility and potentialities of this novel concept. Two kinds of reactions are carried out to characterize simultaneously the reactor performances in terms of reaction and heat exchange: the oxidation of sodium thiosulfate by hydrogen peroxide and an acido-basic reaction (NaOH/H2SO4). The resultant experimental data emphasize a significant thermal efficiency : the reactant concentrations and therefore the heat generation can be increased without risk of thermal runaway.

A New Pulsation Policy in a Disk and Doughnut Pulsed Column Applied to Solid‐Liquid Extraction of Andrographolide from Plants

Abstract: Classically, sinusoidal oscillations are imposed to enhance mixing and mass transfer between two phases contacted. But, in any case of solid/liquid contact, it was noticed that this pulsation mode was not efficient enough to allow a controlled behaviour of the solid phase. The problem is particularly met for the treatment of raw plants or polydispersed populations with complex physical properties. The objective of this study is to demonstrate the viability of using a non-sinusoidal pulsation in a continuous contactor to replace a traditional batch sinusoidal mode. A review of the different pulsation techniques is firstly presented. The example of solid-liquid extraction of Andrographolide from plants has then been choosen to bring out the advantages of the new pulsation mode. The development of this application as a continuous process in a column has indeed encountered difficulties due to the important heterogeneity of the matter : one of these classes tends to float and the other to sink, which always leads to a definitive flooding in classical operations. Typically, the proposed signal is composed of two different periods : in one hand, a classical sinusoidal pulsation step used to mix the liquid and solid phases in the active part of the column and allow an optimal mass transfer and, in a second hand, an impulsion phase, used generally for the transport of solid. The extraction is carried out in a disc and doughnut column of 54 mm in diameter, and 3.5 m in height. Liquid and solid are flowing cocurrently and downwardly. Experiments have been performed to know the global characteristics of the process in steady state and to suggest some elements for industrial design. The results showed that an optimal tuning of the geometric characteristics of the column, the level of interface and the parameters of the pulsation, could increase the operated domain where flooding is avoided.

Optimisation d'une reaction chimique dans un reacteur ouvert du type a plaques

Abstract: Procede d'optimisation d'une reaction chimique dans un reacteur ouvert du type a plaques, qui consiste a :- etablir un modele dynamique du reacteur pour cette reaction,- appliquer un outil logiciel d'integration a ce modele dynamique pour resoudre ses equations,- determiner et optimiser un ensemble de parametres du reacteur a partir d'evaluations des objectifs a atteindre, des contraintes a respecter et des donnees variables du reacteur et de la reaction,- construire un reacteur conforme a l'ensemble optimise de parametres,- et faire des mesures de parametres physiques lors de la mise en oeuvre de la reaction dans le reacteur construit, pour valider son fonctionnement

Measurement-based run-to-run optimization of a batch reaction-distillation system

Abstract: Recently, measurement-based optimization schemes have been developed to deal with uncertainty and process variations. One of the methods therein, labeled NCO tracking, relies on appropriate parameterization of the input profiles and adjusts the corresponding input parameters using measurements so as to satisfy the necessary conditions of optimality (NCO). The applicability of NCO-tracking schemes has been demonstrated on several academic-size examples. The goal of this paper is to show that it can be applied with similar ease to more complex real-life systems. A batch reaction-separation system for the production of propylene glycol is used for illustration. A simple parameterization of the optimal solution with four input parameters is derived and only the active terminal constraints are tracked in a run-to-run manner. With this strategy, near optimality is achieved within a few batches.

Pulsed column for solid/liquid system

Abstract: The invention concerns a pulsed column for treating a system comprising a liquid phase and a solid phase. More particularly, the invention concerns a column for controlling and adjusting the retention time of the solid phase in the column independently of the retention time and flow rate of the liquid phase. Said column comprises means for applying low-amplitude and high-frequency pulses. The plates comprise an orifice for circulating all the phases between the stages or volumes of the column. Said orifices include closure means actuated into open position during the application of high-amplitude pulses. The inventive column enables the retention time of the solid phase to be controlled independently of the liquid phase retention time.