Particle Scattering Photography Approach for Poorly Illuminated Multiphase Reactors. II: Experimental Validation and Optimization

Abstract

Based on the particle scattering photography approach proposed in Part I, a series of experiments are conducted in this work to validate the theoretical analysis, demonstrate the application features qualitatively and quantitatively, and evaluate the measurement errors. As expected, aided respectively by scattering light of four representative oxide powders (TiO2, Al2O3, CuO, and SiO2), the grayness differences between the bubbles and continuous phases in all images are improved with different extents, and especially the TiO2 particles perform the best. Grayness differences present a unimodal distribution with TiO2 concentration variation, and the optimum concentration is 7.3 mg/L. This particle scattering approach is proven to be more accurate, with an average error of <5% for the bubble size, in comparison with that of the reflector-aided method (>20%).

The bubble size and rise velocity of bubble‐induced three‐phase inverse fluidized bed (BIFB)

“…24 Usually, the photographic technique was mostly used in two-dimensional fluidized beds as it cannot obtain flow images inside a three-dimensional bed, or the image is severely distorted when an endoscope is used to capture flow images inside a three-dimensional bed. However, a new telecentric photographic probe developed by the Institute of Process Engineering, Chinese Academy of Sciences, 2,25,26 has effectively solved the problem of image distortion in a three-dimensional system. The new telecentric photographic probe can not only capture more accurate internal images with almost no distortion by employing a special telecentric lens but can also provide instantaneous full-field information of the particles and bubbles.…”

“…The bubble size and bubble rise velocity were obtained by taking pictures of the particles and bubbles inside the BIFB using the newly developed telecentric photographic probe, by the Institute of Process Engineering, Chinese Academy of Sciences. 2,25,26 The photographic system mainly consisted of a "vision probe" with a diameter of 22 mm, a light source control to adjust the light intensity, and a data acquisition computer to process the image using the acquisition software developed by the probe provider. The effective depth of each photograph is 8 mm and its effective area is 118.10 mm 2 .…”

Image‐based measurement of engulfment vortex to quantitatively assess micromixing efficiency in a gas–liquid stirred tank

“…41,42 Contrasting to (P)LIF and (micro-) PIV, light emitting diode (LED) as the light source of TVP is cheaper and safer than the laser. In addition, the TVP is qualified for the measurement of complex multiphase systems with high holdups of the dispersed phase and poor illumination, [42][43][44][45] but has not been applied in the micromixing field.…”

Circulating jet for enhancing the mass transfer in a gas–liquid stirred tank reactor

“…The hydrodynamics in large‐scale reactors are shown to be mainly a function of the superficial gas velocity in the system 8,9 . The local fluid dynamics in gas–liquid STR can accurately determine the flow state of the gas–liquid flow field 10,11 . Generally, viscosity has a negative effect on the mass transfer coefficient in STRs, and the negative effect of viscosity can be offset by increasing energy dissipation 12–14 .…”