Clemens Merten

Bubble size distributions in a bubble column reactor under industrial conditions

Abstract The design of gas liquid processes requires a detailed knowledge of bubble size distributions, since they determine the mass transfer. In this contribution the influence of operating conditions and physical properties of gas and liquid phase on initial and final (“stable”) bubble sizes is discussed. The measurements were performed in a lab scale bubble column for different liquids sparged with nitrogen for pressures up to 50 bars and temperatures up to 175 °C. Bubble size distributions were determined by image processing. Bubbles tend to become smaller with decreasing surface tension, increasing gas density and decreasing liquid viscosity, resulting in reduced stable bubble sizes at increased pressure and also at increased temperature as long as evaporation can be neglected. Impurities in aqueous and organic liquids can severely influence bubble sizes by restraining coalescence. For such systems bubble size distributions in a column mainly depend on the size of the primary bubbles, which are determined by the sparger design.

Strength Analysis of a Plate Type Evaporator

In this paper results from a complex strength analysis of a autothermic reactor are presented. The analysis has been carried out with the Finite Element software ANSYS. Calculations using a geometrical model with the same complex structure as the real device require high computational expense. Therefore a method for simplifying the geometrical structure was developed [1]. Afterwards elastic calculations with the simplified three-dimensional model of the device were carried out. The applied static loads are pressure and a steady state temperature field. Considering the stress categorization route the admissibility of the loads was checked in structural parts of the evaporator. These parts accord idealized structures for which the major design by analyses rules can be applied.Copyright

Design Procedure for Compact Chemical Reactors

A practical design procedure for compact chemical reactors under pressure and complex thermal loads is presented. The suggested method, which combines the mechanical design as well as the process design in a comprehensive manner, is validated at the example of a compact, micro structured evaporator. The considered reactor employs the combustion heat of waste gases for the evaporation of liquid process streams. The process design encloses experiments like flow visualization with high-speed photography and the determination of the temperature profile by means of IR-radiometry using a single plate arrangement. The mechanical design comprises the model reduction for less computing time and simulation studies on the mechanical stability of the considered reactor at realistic operation conditions using the finite-element method. For representative simulation results the experimental data is required to reproduce all relevant loads as precise as possible.Copyright