David Rouzineau

Evaluation of coupled reactive distillation performances by means of a rigorous simulation procedure

Publisher Summary This chapter discusses the non equilibrium model (NEQ) for multicomponent separation processes, including liquid and/or gas reactions. This model includes the finite mass-transfer rate described by Maxwell–Stefan equations. The bulk of both the vapor and liquid are perfectly mixed, and the resistance to mass and heat transfer is located in two films at the liquid/vapor interface (film theory). There are no restrictive hypotheses as to the nature and the localization of the chemical reactions. The chapter describes the original formulation of mass transfer and solves it to avoid the bootstrap problem. The resulting differential algebraic equations (DAEs) system is then solved. The chapter presents the resolution and focus on two keys points: the coherent initial state and the reduction of differentiation index. With several examples, a comparison between equilibrium stage model (EQ) and the NEQ model is affected and a sensitivity analysis is done to highlight the importance of the film thickness.

Production Zone Method: a New Non-ideal Shortcut Method for Distillation Column Design

Graphical shortcut methods are useful tools for the design of distillation columns. The proposed nonideal shortcut method includes a graphical representation and is based on the concept of operation leaves. This new method uses a production segment rather than a completely specified product, which eliminates any sensitivity to the composition of the minor product. Concerning phase equilibria, no restrictive assumptions are made. The study aimed (1) to determine whether a specified separation respects the mass balance and thermodynamic feasibility and (2) to find the minimum reflux ratio for a preliminary design of the column. Designs obtained with this new method for ideal, non-ideal, and azeotropic mixtures give purity and recovery rates close to the specifications, which might be impossible to obtain with a conventional ideal shortcut like the well-known Fenske–Underwood–Gilliland shortcut method. The distillation boundaries of azeotropic mixtures are taken into account thanks to a non-ideal thermodynamic model applied to the calculation, which is not the case with a conventional ideal shortcut. The paper examines the following mixtures: an ideal mixture of ethanol, n-propanol, and n-butanol; a non-ideal mixture of acetone, water, and acetic acid; and an azeotropic mixture of acetone, isopropanol, and water.

Reactive distillation modelling and sensitivity analysis based on NEQ model

Abstract Firstly, a non-equilibrium model (or NEQ model)has implemented for multi component reactive separation processes. The mass transfer description is based on the Maxwell Stefan approach and the hydrodynamics on the film theory model. We have excluded other restrictive assumptions. The code calculation is implemented in the simulation software ProSim Plus TM . Secondly, an experimental packed reactive distillation pilot has been developed in order to obtain experimental. The experiments were performed for homogeneously catalysed esterification of acid acetic and methanol into methyl acetate and water. Five runs have been performed for which the inlet flow rate and compositions, as well as the concentration in catalyst are modified. For each run, the simulation results are in good agreement with the vapour composition and the liquid temperature profile, without any parameter adjustment. Finally, a sensitive analysis of the NEQ model parameters has been done. It seems for the various physical parameters (e.g. the liquid and vapour film thickness, the liquid hold-up and the interfacial area), that the interfacial area is the most sensitive. For the other parameters, their sensitivity depends where the reaction and the mass transfer resistance take place. Moreover, a step discretisation analysis in regard to the axial coordinates shows that the type of flow inside the column could be compared to a plug flow. In addition, the need of taking into account the reaction contribution in the diffusional layers is clearly shown.