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.

Membrane fouling is a troublesome factor in the design and scale-up of stirred membrane reactors. Many efforts have been made to study the fouling mechanism in traditional membrane filtration. However, it is still ambiguous in stirred membrane reactors (SMRs). For this purpose, we investigated the effects of hydrodynamics on membrane filtration performance in SMRs under constant-pressure operation by combining experiment and computational fluid dynamics (CFD) simulation. The results indicate that the strong axial flow is beneficial in maintaining the stability of membrane permeation, while the strong radial flow works oppositely. In addition, the formation of the filtration cake increases the total membrane filtration resistance but keeps smaller particles from blocking the membrane surface channels, which leads to filtration resistance multiplying rapidly. Hence, the formation of the thick cake, strong axial flow, and weak radial flow is conducive to maintaining permeation flux in order to reduce the replacement of the membrane and improve the period of continuous production.

Although the image-based method is considered to be the most direct and accurate measurement method compared to some other methods, there are some factors that add uncertainties to the measurements. In this study, a newly developed inline image-based method consisting of a telecentric vision probe and automatic particle identification software is evaluated by comparing with other recognized measuring technologies for regular and irregular particles. The subject technique provides pretty good repeatability for both regular (σ D 50 = 0.65%) and irregular particles (σ D 50 = 1.26%). From an engineering perspective, the measurement results of average diameters reveal the reliability of this image-based method. The maximum relative deviations are respectively 6.56% and 3.90% compared to the laser diffraction. Future work should be devoted to further improvement of the accuracy of this image-based method including contour identification, the particle shape-based reconstruction models, and the 3D image techniques based on binocular or multiple vision probes.

Little research on the microbubble-aided transport characteristics in stirred vessels is reported. This motivates the present efforts to experimentally analyze the effects of operating condition, impeller, baffle, and sparger on the gas dispersion characteristics in a stirred tank with microbubble aeration. It is found that the number of large bubbles gradually increases with the increase of impeller speed, which is completely opposite of the results in the conventional gas−liquid stirred tank. Without baffles installed, k L a is greater than that in baffled ones, especially at the higher impeller speed. Under the same P v , the impeller type has little effect on k L a. The ring sparger shows more efficient gas−liquid mass transfer performance than a single tube distributor. Under the combination of an axial impeller and a draft tube without baffles installed, the maximal k L a exceeds 0.01 s −1 . The present study provides a useful reference for the design of stirred reactors in some applications.