Veiling Effects in the Measurement of Poly-disperse Particles with a Photographic Probe

Abstract

The current study aims to clarify how much the measurement results using the image-based method are affected by two types of total overlaps in the images. By ensuring the homogeneous suspension of particles and simultaneous optimization of the probe location, it has been proven that using the overall holdup of particles as the benchmark data is reasonable. In a bidisperse particle system, the larger the particles, the more significant the effect of large particles veiling small particles. The maximal relative error nears 50%. In a poly-disperse system, the measurement error heavily depends on the veiled particle size. The larger the particles, the smaller the deviation. For the components of 1 and 3 mm, the relative errors under multiple conditions exceed 50%. The veiling effect of small particles on large particles is qualitatively evaluated. The results of the current study are helpful in promoting the inline image-based method for the actual multiphase reactor method.

Multivision Probe Combination Measurement for Polydisperse Particles in Multiphase Reactors

“…Except for the 20 mm particles exceeding the view field of the ϕ22 mm probe, all other particle sizes are smaller than the view field of both probes. The holdups of the 1, 3, 5, and 8 mm particles are measured using the ϕ22 mm probe, and then, the measurement results are compared with those by the ϕ68 mm probe . As shown in Figure , the measurement results by the ϕ22 mm probe are clearly closer to the standard value for the 1, 3, and 5 mm particles.…”

“…As large and small particles have conflicting requirements for optical lens parameters, another vision probe with an external diameter of 22 mm is used to measure the small particles in a bidisperse particle system consisting of 1 mm and 10 mm particles (see details in Section 3.2.1 in ref 14). During image analysis, images with large particles occupying a large area of the field of vision are eliminated, and then, the remaining images are analyzed using the above method described in Section 2.…”

“…In our previous work, it has been found that the measurement error heavily depends on the veiled particle size in a polydisperse system and the larger the particles, the smaller the deviation. 14 In the above section, the measurement accuracy for the small particles is improved significantly using the ϕ22 mm probe. If the measurement results of large and small particles using two vision probes with different fields of view are combined in an appropriate way, a quite acceptable particle property distribution could be obtained.…”

“…In the first set of experiments, the overall holdup of 1 mm particles is always kept at 0.30% and the loading of 10 mm particles is gradually increased from 1.00 to 7.00%. In the second set of experiments, the overall holdup of 10 mm particles is always kept as 3.00% and the loading of 10 mm particles is gradually increased from 0.025 to 0.225% (see details in Section 3.2.1 in ref ). For the bidisperse particle system, it is easy to cut the measured particles into two size classes, i.e., 1 mm size class and 10 mm size class.…”

“…However, serious measurement errors of small particles are found because of the veiling effect. 14 On the other hand, if only a small probe is used, the size of large particles may exceed the field of view. Based on such a situation, we might as well make some trade-off, that is, measure large and small particles separately using appropriate probes for each individual and then combine their results in a certain way to get the particle distribution.…”