(62b) Project “Multi-Phase” – a Combined Effort of Industry and Academia to Investigate Bubble Column Hydrodynamics

Project “Multi-Phase” – a combined effort of industry and academia to investigate bubble column hydrodynamics

Bubble columns are widely employed multiphase reactors within the chemical industry.  Important technical multiphase processes include the production of terephthalic acid, acetic acid, oxo alcohols, acetone, and hydrogen peroxide. Annual production in terms of intermediates and end products for the above-mentioned production processes alone amounts to over 30 million metric tons. Despite of the importance of these reactors there is a significant gap between academic research and industrial demands. This gap consists of reliable design equations with respect to gas holdup, liquid backmixing and heat and mass transfer applicable at high pressures and temperatures. In addition the majority of the available equations do not consider organic solvents as liquid phase. As most industrial processes take place at elevated pressures and temperatures including organic solvents uncertainties arise during the design process of bubble column reactors which may lead to significant economic and environmental consequences. Another problem is that the availability of reliable measurement techniques suited for the task to investigate the hydrodynamics of multiphase systems at industrial relevant conditions is limited. Therefore it is not only necessary to develop design equations derived from technical scale columns operated at process conditions with industrial relevant media but it is also vital to simultaneously develop measurement devices to fulfill this task.

One approach to contribute to the solution of these problems is the recently started german scientific project “Multi-Phase”, which arose as a lighthouse project from the ProcessNet initiative “Campus Bubble Columns”. This project consists of a network of several companies and institutions which combine scientific knowledge ranging from single bubble behavior to the description of the overall flow field in gas liquid vessels. Evonik Industries AG provides the necessary infrastructure to operate three experimental facilities. Two of them, 160 and 300 mm diameter glass columns, can be operated at atmospheric pressure with organic solvents in order to investigate the influence of internals and scale on gas holdup and backmixing. Another 330 mm diameter bubble column can be operated with organic liquids at elevated pressures and temperatures. This column will serve to demonstrate the applicability of newly developed measurement techniques and will also provide gas holdup and residence time measurements which can be directly used to validate existing correlations and models to predict hydrodynamic parameters.

This presentation includes a more detailed introduction into the structure and aims of the project. Furthermore first results of the experimental studies regarding gas holdups in water, aqueous mixtures, organic liquids at atmospheric and elevated pressure in columns of different diameters are presented and discussed. A comparison with literature data and correlations proves that further research is necessary and points out several difficulties which arise if comparable experimental data are to be obtained. A brief survey of how uncertainties in the prediction of hydrodynamic parameters of bubble columns can affect the modeling results will also be given.

The Multi-Phase project (full title: Increasing Energy Efficiency and Reducing Greenhouse Gas Emissions by Multiscale Modeling of Multiphase Reactors) is supported by the BMBF under support no. 01RC1102.