Contact

Prof. Dr. Uwe Hampel
Head Experimental Thermal Fluid Dynamics
u.hampel@hzdr.de
Phone: +49 351 260 - 2772
Fax: 12772, 2383

Dr. Markus Schubert
Experimental Thermal Fluid Dynamics
m.schubertAthzdr.de
Phone: +49 351 260 - 2627
Fax: +49 351 260 - 2383

Johannes Zalucky
Experimental Thermal Fluid Dynamics
j.zaluckyAthzdr.de
Phone: +49 351 260 - 3774

Experimental investigation of hydrodynamics in SiSiC foam packed reactors

Motivation

Consuming about 40% of the primary energy in industry the chemical and petrochemical sector are two of largest energy consumers in the industrialized world though both are already using high-level system of thermal and energetic integration. Most of the energy consumption has been identified to arise in the downstream processing of product and by-product which emerge for technical reasons. In the joint project “Helmholtz Energy Alliance – Energy Efficient Chemical Multiphase Processes” the main focus of studies was set on two types of chemical reactors as most-important upon many processing steps of a chemical processing chain. Hereby, bubble column reactor based and trickle-bed reactor based processes were chosen after a holistic analysis. By implementing innovative reactor internals such as solid foams, POCS or monoliths, both reactor concepts are believed to gain significant improvement in the overall efficiency.

Being one of seven project partners, the group at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) studied the multiphase hydrodynamics in solid foam packed trickle-bed reactors. The open-cell solid foams, consisting of a continuous network of solid material and hydraulic open void cavities, are characterized by comparable small pressure drops, high specific surfaces and improved thermal conductivity. Compared to conventional reactor internals, such as packings of spheres or extrudates, significant improvements of flow and temperature field homogeneity as well as improved catalyst exploitation. At HZDR, the studies covered the investigation of flow regimes, liquid distribution and liquid holdup which were studied by fast electron beam X-ray computed tomography. The fast X-ray tomography enables insights of the dynamic flow behavior in the reactor cross section with spatially and temporally high resolved tomographic images.

At the gas and liquid throughputs studied at HZDR, the trickle flow as well as the pulse flow were encountered as flow regimes at cocurrent downflow of water and air [4, 7]. The highly dynamic pulse flow is characterized by continuous alternation of gas- and liquid-rich periods in the cross-section which are driven through the reactor by the succeeding gas and liquid. The high input of shear stress and the continuous exchange liquid are key mechanisms which especially contribute to an improved reaction control of highly exothermal reactions. For the investigation of pulse dynamics, water and air throughputs, axial position and solid foam pore density were varied [5, 6, 8].

Measurement system

The investigations of hydrodynamics in foam packed columns were carried out with the ultrafast electron beam X-ray computed tomography system ROFEX III. The measurements were carried out with a temporal resolution of 1 ms and a spatial resolution of 1 mm. Having two measurement planes with an axial distance of about 14 mm, the system provides a detailed insight in the morphology and statistical key parameters of the liquid pulses.

Micro CT images of the applied foams with pore densities of 20 ppi, 30 ppi and 45 ppi

Set-up of the ultrafast electron beam X-ray tomograph ROFEX III

Micro-CT images of the applied foams with pore densities of 20 ppi, 30 ppi and 45 ppi (from left to right) Schematical drawing of the ultrafast X-Ray scanner ROFEX III

Results

Comparison pulse flow regime

Depending on operation conditions, partially and fully developed pulse flow ocurrs in solid foam packed reactors. Within the investigated measurement range pulse flow has been found at three gas/liquid velocity combinations (A, B, C) corresponding to gas and liquid superficial velocities uG and uL, respectively, of:

  • A: uL=0.03 m s-1 | uG=1.0 m s-1
  • B: uL=0.04 m s-1 | uG=0.8 m s-1
  • C: uL=0.04 m s-1 | uG=1.0 m s-1.

Varying operation conditions, the trend of cross sectional liquid saturation measured within solid foams can be seen in the following table.

Attention, large data traffic! Each video may cause data traffic of up to 6 MB!


Presentation pulse flow Presentation pulse flow Presentation pulse flow Scalebar for saturation images

20 ppi

30 ppi

45 ppi

© HZDR
The videos shown below are representative excerpts of one second length from a comprehensive set of experiments which provide insight in the complex dynamics of pulse flow. The data is presented in terms of liquid saturation βL, i.e. liquid volume per void fraction. A detailed analysis on the pulse morphology and key characteristics like pulse frequency, velocity and volume is given in the literature [5].

Peer-reviewed publications

  • [1] Fischer, F.; Hoppe, D.; Schleicher, E.; Mattausch, G.; Flaske, H.; Bartel, R.; Hampel, U., An ultra fast electron beam x-ray scanner, Meas. Sci. Technol., 2008, 19(9), DOI:10.1088/0957-0233/19/9/094002
  • [2] Fischer, F.; Hampel, U., Ultra fast electron beam X-ray computed tomography for two-phase flow measurement, Nuclear Engineering and Design, 2010, 9, DOI:10.1016/j.nucengdes.2009.11.016
  • [3] Wagner, M.; Barthel, F.; Zalucky, J.; Bieberle, M.; Hampel, U., Scatter analysis and correction for ultrafast X-ray tomography, Phil. Trans. R. Soc. A, 2015, 373(2043), DOI:10.1098/rsta.2014.0396
  • [4] Zalucky, J.; Möller, F.; Schubert, M.; Hampel, U., Flow Regime Transition in Open-Cell Solid Foam Packed Reactors: Adaption of the Releative Permeability Concept and Experimental Validation, Ind. Eng. Chem. Res., 2015, 54(40), pp 9708-9721, DOI:10.1021/acs.iecr.5b02233
  • [5] Zalucky, J.; Claußnitzer, T.; Schubert, M.; Hampel, U., Pulse flow in solid foam packed reactors: Analysis of morphology and key characteristics, AIChe J., 2016, submitted.

Other publications


Further links


Contact

Prof. Dr. Uwe Hampel
Head Experimental Thermal Fluid Dynamics
u.hampel@hzdr.de
Phone: +49 351 260 - 2772
Fax: 12772, 2383

Dr. Markus Schubert
Experimental Thermal Fluid Dynamics
m.schubertAthzdr.de
Phone: +49 351 260 - 2627
Fax: +49 351 260 - 2383

Johannes Zalucky
Experimental Thermal Fluid Dynamics
j.zaluckyAthzdr.de
Phone: +49 351 260 - 3774