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

Abstract

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.

Slug flow as tool for selectivity control in the homogeneously catalysed solvent-free epoxidation of methyl oleate

“…Arsenjuk et al and Vietinghoff et al developed systems where the slug length at the reactor inlet is measured by an optical sensor shown in Fig. 7 consisting of a double infrared gate, where the passage of aqueous slugs through the infrared beam results in a reduction in measured beam intensity [29,30]. The slug flow is formed in the slug generator shown in Fig.…”

“…Data is gathered from the sensors using an analogue data acquisition device (National Instruments NI-9205) and Gemoets, Su et al state that the overall performance of an oxidation reaction is mainly determined by intrinsic kinetics and transport properties inside the reactor. They also make a case that for a fast liquid-phase oxidation reaction, the reaction rate and selectivity are influenced by the mass transfer rate and internal circulations within the slugs along with reaction kinetics [30]. The individual effects of the setpoints, i.e., volumetric flow rate, phase ratio, and the length of the slugs, on the solvent-free Aliquat® 336 assisted oxidation of MO are discussed in the following sections.…”

A computer vision sensor for the parallelization of actively regulated capillary slug flow microreactors

“…Prior research shows that for even fluid distribution in all parallel channels of a multi-capillary liquid-liquid contactor, some additional considerations must be made (Kashid et al 2010): Although all parallel capillaries are nominally identical, manufacturing tolerances, corrosion, solid precipitation, or deposition are non-negligible for the fluid distribution across parallel capillaries at the micro scale. Therefore, to achieve uniform results across all units, vs, φ and Ls must be measured and regulated in each capillary (Arsenjuk et al 2020b;Vietinghoff et al 2020). For this purpose, Arsenjuk et al (2020b) developed a concept for the active regulation of multichannel liquid-liquid contactors with the ability to control all slug flow parameters across several parallel capillaries.…”

“…Wolffenbuttel et al (2002) provides a summary of the four most common sensing techniques employed in liquid-liquid slug flow monitoring, including impedance-, absorbance-and reflectance sensors, as well as video imaging, which is concluded to be slow and elaborate. In addition, Arsenjuk et al (2020b) andVietinghoff et al (2020) describe the use of infrared (IR) optical sensors. While the IR-based sensor may be realized in a non-intrusive and cost-effective way, at least one sensor per parallel capillary is required and the sensor is prone to irregularities in the slug flow pattern as well as requiring precise positioning.…”

Near Infrared Sensor Setup for General Interface Detection in Automatic Liquid-Liquid Extraction Processes

“…Taking advantage of the optical features of interfaces and how they affect intensity measures, an optical sensor can more reliably discover the interface location under different conditions. In Vietinghoff et al [27], for example, optical properties of interfaces in capillary tubes are used to detect different phases in the flow of a micro reactor.…”