Relevance of Multiphase Reaction Engineering to Modern Technological Challenges

Analysis and simulation of multiphase hydrodynamics in capillary microseparators

The capillary microseparator is an important microfluidic device for achieving the inline separation of biphasic segmented flows. While it has found wide applications in areas such as on-chip synthesis of pharmaceuticals and fine chemicals, many aspects regarding its operating ranges and hydrodynamic details remain to be elucidated. In this work, we employ OpenFOAM computational fluid dynamics (CFD) method to systematically simulate the performance of the capillary microseparator under the retention, normal operation and breakthrough regimes. The three distinct operating regimes are in accordance with experimental observations. In addition, the simulations enable quantification of the instantaneous flow rate through each micron-scale capillary microchannel and provide detailed predictions even under very low pressure differences (∼10 Pa), both of which are difficult to achieve experimentally. Furthermore, inspired by high-resolution hydrodynamics from the CFD simulations, we develop a simple analytic expression that predicts the retention threshold of the microseparator in good agreement with the simulated results and recent computations and experimental data.

CFD Analysis of BED Textural Characteristics on TBR Behavior: Hydrodynamics and Scaling-up

In recent years, CFD has played an important role in the understanding and design of TBR’s. In this work, through CFD with Eulerian approach, a three-phase heterogeneous reactor model was developed, were the accuracy of Interfacial Momentum Exchange Model (IMEM) for the gas-solid interaction, the effect of a more detailed catalytic bed geometry description, and the pellet shape over TBR hydrodynamics of two fluid phases interacting with the solid phase was studied. Then, a second model was developed, where the validated hydrodynamic model was coupled with mass transport for an HDS process of light gasoil. Additionally, in order to insight into the scaling up process of a TBRs, the proposed columns behaviors were compared against literature columns using four different ways, and it was found that the best predictions were obtained when the models’ holdup were equaled to those evaluated in literature columns. Since in reliable literature deviations in pressure drop predictions of around 30% can be found, the model results show significant improvement against literature, achieving 5 times better accuracy in predicting pressure drops, and 50% improvement in holdup prediction; the coupled model reproduces the same conversion values compared with literature data, and predicts conversions with 95% accuracy

An alternative method for tracking a radioactive particle inside a fluid

The proposed tracking method describes the trajectory of a radioactive particle moving in a fluid as a sequence of small cubic cells occupied by successive particle positions. In addition, the EM reconstruction algorithm was applied to get the image of the unique cell which had the greatest probability to contain the particle at a given time of a test. Next, this information was useful to calculate the coordinates and velocities of the particle at that time. The method was tested in laboratory using a gamma radiation detection system, the radioisotope (198)Au and a mixer. According to the results, the maximum deviation found between theoretical and experimental values of the average rotating period was less than 8% and the particle's reconstructed trajectories are representative of its real movement. Thus, a paradigm shift permitted us to begin the development of an alternative method to solve the complex problem of tracking the movement of a radioactive particle inside an opaque unit.

Bubble Columns with Internals: A Review

Most industrial bubble column reactors require the utilization of internal structures for heat transfer and/or for controlling the flow structures and back mixing in the system. The internals denote all types of innards added to a bubble column, such as perforated plates, baffles, vibrating helical springs, mixers, and heat exchanger tubes. In commercial scale bubble columns, instrumentation probes, down-comers, and risers with heat exchangers are all considered. This review presents the state-of-knowledge of bubble columns with internals. It starts with an introduction. The second section discusses the horizontal internals, and the following section examines the studies involving vertical internals.