Tomographic Measurement Techniques – Visualization of Multiphase Flows

Abstract

Tomographic measurement techniques have become increasingly popular for the application in the field of chemical and process engineering. With this techniques, the fields of density, concentration, temperature, velocity or local void fraction can be measured without interfering with the multiphase flow. These fields are often either instationary or even have transient character. Therefore, the used tomographic measurement techniques have to have a high spatial and temporal resolution. In this paper known tomographic measurement systems are described and compared to each other. The sensor systems and reconstruction methods are explained. As an example, the applications of electrical and x-ray tomography are described for the imaging the flow inside random and structured packings. With the electrical tomographic measurement technique a temporal resolution of up to 100 frames per second is achieved, whereas with the x-ray tomography spatial resolutions of 0.4mm are possible.

Liquid Distribution in Trickle-Bed Reactor

“…Influence of the distributor on the pressure drop in Column 2 provided with a 2-mm glass beads packing (U L = 6 mm·s -1 ). Reinecke et al (1996aReinecke et al ( , 1996bReinecke et al ( , 1998 Kennedy and Jaffe (1986), this model gives a good description of data obtained in industrial plants: Figure 4 shows an RTD obtained by using radioactive tracing in a commercial HDS plant and the best fit of the two-zone model.…”

“…Tomographic measuring techniques are more and more widely used in the investigation of the hydrodynamics of multiphase reactors, as shown in a number of recent review papers (Williams and Xie, 1993;Beck et al, 1997;Chaouki et al, 1997;Reinecke et al, 1998). Each of the different possible tomographic techniques has its advantages and drawbacks: the X-ray tomography used by Toye et al (1996Toye et al ( , 1997 is well suited for very small velocities, since the gasliquid repartition has to be constant during a measurement, which is quite slow.…”

“…Each of the different possible tomographic techniques has its advantages and drawbacks: the X-ray tomography used by Toye et al (1996Toye et al ( , 1997 is well suited for very small velocities, since the gasliquid repartition has to be constant during a measurement, which is quite slow. In the present work, the capacitive tomography developed by the team of Hanover was used (Reinecke, 1996;Mewes, 1996a, 1996b;Reinecke et al, 1998) found in the mentioned papers. The main advantage of this technique is that it is very fast (response time of the order of magnitude of a few milliseconds).…”

Opaque Multiphase Reactors: Experimentation, Modeling and Troubleshooting

“…Here emission or transmission tomography of accuracy higher than our current setup is needed for experimental validation of the porosity distribution in the packing. Several techniques claim success with imaging of packed and trickle beds (Kantzas, 1994;Reinecke et al, 1998;Sederman et al, 1998). CFD codes are then used to generate the most likely flow pattern and its possible deviations and this in turn represents the basis for the cell model which can then be used for kinetic-transport calculations and evaluation of reactor performance.…”

Experimental analysis and evaluation of the mass transfer process in a trickle-bed reactor

“…These reactors can be used in the development of chemical processes such as catalytic hydrodesulfurization, production of calcium acid sulfite, oxidation of formic acid in water, synthesis of butynediol, production of sorbitol, hydrogenation of aniline to cyclohexylaniline and oxidation of sulfur dioxide on activated carbon (Larachi et al, 1991;Burghardt et al, 1990;Burghardt et al, 1995;Gianetto and Specchia, 1992;Latifi et al, 1997;Pawelec et al, 2001;Pironti et al, 1999;Rajashekharam et al, 1998;Wu et al, 1996;Reinecke et al, 1998).…”