Designing flow and temperature uniformities in parallel microchannels reactor

Flow Characteristics and Switching Mechanism of Bistable Slit Flow Actuated by Temperature

The bistable flow is attractive as it can be analogous to a switch to realize flow control. Based on the previous studies on actuation technique, the present study first proposed temperature-driven switching of bistable slit flow. A two-dimensional numerical simulation was conducted to investigate the flow deflection characteristics and switching mechanism. It was concluded that the temperature gradient not only biases the slit flow but also locks it to the high-temperature side. The flow deflection angle became larger with the increase in temperature gradient. Being driven by the temperature, the flow can be switched from one side to the other. Furthermore, the fluid viscosity, which varies with temperature, determines the degree of flow deflection and the entire switching time. This research can enrich the active regulation of flow and has significant potential applications in thermal sensors, thermal detectors, microelectromechanical systems, biomedicine, and other equivalent fields.

Reactor Selection for Upgrading Hemicelluloses: Conventional and Miniaturised Reactors for Hydrogenations

This work presents an advanced reactor selection strategy that combines elements of a knowledge-based expert system to reduce the number of feasible reactor configurations with elaborated and automatised process simulations to identify reactor performance parameters. Special focus was given to identify optimal catalyst loadings and favourable conditions for each configuration to enable a fair comparison. The workflow was exemplarily illustrated for the Ru/C-catalysed hydrogenation of arabinose and galactose to the corresponding sugar alcohols. The simulations were performed by using pseudo-2D reactor models implemented in Aspen Custom Modeler® and automatised by using the MS-Excel interface and VBA. The minichannel packings, namely wall-coated minichannel reactor (MCWR), minichannel reactor packed with catalytic particles (MCPR), and minichannel reactor packed with a catalytic open-celled foam (MCFR), outperform the conventional and miniaturised trickle-bed reactors (TBR and MTBR) in terms of space-time yield and catalyst use. However, longer reactor lengths are required to achieve 99% conversion of the sugars in MCWR and MCPR. Considering further technical challenges such as liquid distribution, packing the reactor, as well as the robustness and manufacture of catalysts in a biorefinery environment, miniaturised trickle beds are the most favourable design for a production scenario of 5000 t/a galactitol. However, the minichannel configurations will be more advantageous for reaction systems involving consecutive and parallel reactions and highly exothermic systems.

Photoelectric Sensor for Fast and Low-Priced Determination of Bi- and Triphasic Segmented Slug Flow Parameters

Applying multiphase systems in microreactors leads to an intensification of heat and mass transport. Critical aspects of the well-studied segmented slug-flow, such as bubble generation and pump control, can be automated, provided a robust sensor for the reliable determination of velocity, phase lengths, and phase ratio(s) is available. In this work, a fast and low-priced sensor is presented, based on two optical transmission sensors detecting flow characteristics noninvasively together with a microcontroller. The resulting signal is mainly due to refraction of the bubble-specific geometries as shown by a simulation of light paths. The high performance of the processing procedure, utilizing the derivative of the signal, is demonstrated for a bi- and triphasic slug flow. The error of <5% is entirely reasonable for the purpose envisaged. The sensor presented is very fast, robust, and inexpensive, thus enhancing the attractiveness of parallelized capillary reactors for industrial applications.

Process intensification

Process intensification (PI) is a rapidly growing field of research and industrial development that has already created many innovations in chemical process industry. PI is directed toward substantially smaller, cleaner, more energy-efficient technology. Furthermore, PI aims at safer and sustainable technological developments. Its tools are reduction of the number of devices (integration of several functionalities in one apparatus), improving heat and mass transfer by advanced mixing technologies and shorter diffusion pathways, miniaturization, novel energy techniques, new separation approaches, integrated optimization and control strategies. This review discusses many of the recent developments in PI. Starting from fundamental definitions, microfluidic technology, mixing, modern distillation techniques, membrane separation, continuous chromatography, and application of gravitational, electric, and magnetic fields will be described.

Liquid–liquid microflow reaction engineering

Engineering characteristics of liquid–liquid microflow and its advantages in chemical reactions.