Hydrodynamic and mass transfer efficiency of ceramic foam packing applied to distillation.

In addition to a high void volume and specific area, solid foams possess other properties (low density, good thermal, mechanical, electrical, and acoustical behaviour) that make them attractive for applications such as heat exchangers and reformers. Applications using foams as catalysts or structured catalyst supports have demonstrated higher performance than classical catalysts. Several studies have explored the hydrodynamic behaviour of foams in monophasic and counter current systems and have reported very low pressure drops. This paper describes the application of ceramic foam to distillation. The β-SiC foam contains 5 pores per inch (PPI) with a 91% void volume and a surface area of 640 m2/m3. Performance parameters including pressure drop for the dry and wet packing, flooding behaviour, and dynamic liquid hold-up were measured in a column of 150 mm internal diameter. The mass transfer efficiency in terms of the height equivalent to theoretical plate (HETP) was determined by total reflux experiments using a mixture of n-heptane and cyclohexane at atmospheric pressure. The experimental results were used to develop a set of correlations describing pressure drop and liquid hold-up in terms of a dimensionless number. The hydrodynamic performance and mass transfer efficiency were compared with classical packing materials used in distillation

Startup of a reactive distillation process with a decanter

The startup of a reactive distillation process for the production of propyl acetate including a decanter is studied. A simulation model is presented which describes the whole startup from a cold and empty state and takes into account the liquid phase split in the decanter. The simulation model is successfully validated with own dynamic experimental data. Different startup strategies are developed and analysed in simulation studies showing the high influence of the initial charging of decanter and reboiler on the startup time

Conception and optimization of heat integrated distillation column (HIDIC)

Distillation is the most applied separation technology. Its major drawback is the low thermodynamic efficiency (typically around 10%) [1]. In response to the environmental issues that concerns energy consumption of distillation column, HIDiC (heat integrated distillation column) is expected to have a large impact on energy saving. The mixtures with close boiling point are confirmed to be the best candidates for HIDiC [2]. In fact, in this configuration the rectifying section and the stripping section are separated. Heat is transferred inside the distillation column from the rectifying to the stripping section, because the operating pressure (and thus the temperature) of the rectifying section is increased by means of the compressor. First, the aim of this study is to develop a simulation model of HIDiC by using commercial software ProSimPlus. The influence of design variables (distribution of heat all along the column, reflux ratio and rectifying section absolute pressure) on energy saving are studied. In addition, in order to minimize the energy consumption and the total annual cost (CAPEX, OPEX), sensitive parameters are defined and optimized. Please click Additional Files below to see the full abstract

Mass transfer and hydrodynamic characteristics of new carbon carbon packing: Application to CO2 post-combustion capture

A novel structured packing, the 4D packing, has been characterized in terms of hydrodynamics, effective area and gas side mass transfer coefficient. The increase of the 4D opening fraction allows to reduce pressure drop and to get a better capacity than Mellapak 500Y and 750Y, for which the geometric areas are similar. The 50% open 4D packing, 4D-50%, leads to effective areas which are higher than Mellapak 500Y ones, and doubled compared with Mellapak Plus 252Y ones. Effective areas for the 4D do not decrease when the opening fraction increases from 30 to 50%, this indicates that a non-negligible amount of droplets is generated at 50%. Gas side mass transfer coefficient had been measured with an original experimental method: water evaporation. Corresponding results seem to be in agreement with the literature, and with the fact that a large amount of droplets is generated. Correlations are proposed for both effective area and gas side mass transfer coefficient for the 4D-50%.The 4D-50% packing could be very interesting for post-combustion CO2 capture since it generates low pressure drop and a very high interfacial area. This will be further confirmed by an economic study for which the absorber plant will be designed with a rate based model

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

Performance characteristics of a new structured packing

A new structured packing using carbon fibres, called Sepcarb® 4D, is presented. This packing has several attractive properties, such as high voidage (ε=94%) and high effective area (a=420 m2 m−3). These properties are advantageous for packing used as a gas–liquid contactor for separation units. To determine the internal characteristics of this packing, we performed several experiments using a 150-mm-internal-diameter column. Firstly, hydrodynamics experiments were conducted using an air–water counter current flow to determine the pressure drop (for both dry and wet packing) and flooding point. Secondly, the mass transfer efficiency was determined in terms of HETP (height equivalent to theoretical plate) by total reflux experiments with an n-heptane/cyclohexane mixture at atmospheric pressure. Hydrodynamic performance and mass transfer efficiency were compared with those of packings generally used in distillation and absorption

Design and conception of an innovative packing for separation column—Part I: Hydrodynamic study on wire intersections

Packed columns are crucial equipment established in the process industry in order to per­form several separation operations (e.g. distillation, absorption, etc.). The scientific challenge is to improve the performance of these separation columns. This work aims to develop an innovative wire-based packing, where the liquid flow on the wire will have an interfacial surface greater than the geometric surface of the packing structure. A study of the liquid film behavior on inclined wires and their intersections is carried out based on experimen­tal observations and a numerical simulation. The result is a mapping of the liquid flow regimes favored for the distillation process. Hence, it will be possible to orient the design of the wire-based packing, especially the wire diameter and inclination and the shape of the intersections

Design and optimization of Heat Integrated Distillation Column “HIDiC”

Distillation is the most applied separation technology. However, its major drawback is the low thermodynamic efficiency (typically around 10%). In response to environmental issues that concern energy consumption of distillation columns, HIDiC (heat integrated distillation column) is expected to have a large impact on energy saving. The aim of this study is to optimize the HIDiC sensitive parameters so as to minimize the Total Annual Cost (TAC). For this, a HIDiC simulation model is developed by using commercial software ProSimPlus. GA (Genetic Algorithm) is used to find the optimal HIDiC configuration where multivariable are optimized without initialization. Binary (Benzene/Toluene) separation case is examined. As a result, 7.4% and 13.9% TAC reductions are realized in comparison with the reported solutions in previous works

Cooperative WebLab in chemical engineering between France and Brazil: Validation of the methodology

A WebLab is an experiment operated remotely via Internet. Besides the strictly technical aspects of such an experiment, which may contribute to the learning of Chemical Engineering fundamentals, there is also important feedback when teams of students of two different countries are working together: the WebLab becomes an intercultural experience, enhancing the communication skills of the students. A WebLab between Universidade Federal de São Carlos (DEQ/UFSCar) and the Ecole Nationale Supérieure d’Ingénieurs en Arts Chimiques et Technologiques (ENSIACET) is presented in this work. A mass transfer experiment in a bench scale reactor (stirred and aerated) had to be studied by mixed teams, thus emulating challenges that will be common in future working environments. In order to perform the experiment, students in Brazil and in France were put into groups. The students had to make decisions about the procedure for executing the experiments. All the students were able to control the equipment, no matter where they were physically. Students communicated using video conference software. The students' and teachers' opinions of this experience were very positive. This methodology is an important contribution to the education of engineers in a world integrated by modern communication technologies

Design and simulation of divided wall column: Experimental validation and sensitivity analysis

This article deals with design and simulation of divided wall column. Design parameters are provided to the rigorous simulation in the ProSimPlus® software. The results show that the procedure can determine parameters quickly in the case studies and can give a good initialization for rigorous simulation. Secondly, a pilot plant has been design, built and operated in our laboratory. The pilot plant will provide necessary experimental evidence to validate the previous procedure. Ternary mixture and four-component mixture of alcohols have been used in our pilot plant in steady state conditions. The results show that the composition of products, composition and temperature profile along the column are in very good agreement with simulation results. Finally, in order to determine the optimal parameters of divided wall columns, the effects of the structural parameters of the divided wall column such as the height of the wall, the vertical position of the wall and number of stages of each section are analyzed. Ternary diagram is used as an indicator both in showing what the most economical configuration is and in showing the distillation boundary