Measurement of gas phase characteristics using a monofibre optical probe in a three-phase flow

Abstract

The study of gas-liquid-solid systems structure requires reliable measurement tools. In this paper, preliminary results on the potential use of a monofibre optical probe to investigate such flow are presented. This probe, manufactured at LEGI, allows the simultaneous measurement of the gas phase residence time and gas phase velocity. This specificity makes this probe more interesting than classical single tip probes (which measure only the gas residence time) or double tip probes (which are more intrusive). Although extensively used in two-phase gas-liquid, this probe was never used in gas-liquid-solid systems. First, the probe signal response is studied for three-phase flow conditions in the presence of solids. Results show that for soft solids, the probe tips can be contaminated when the probe pierces the solid. The signal processing procedure was modified accordingly to take into account these events. Second, the probe results are validated by comparing global results (global void fraction, gas flowrate) deduced from profile measurements with measurements performed by independent means. Lastly, void fraction profiles and interfacial area are studied more in detail. Depending on the solid loading, these profiles exhibit different behaviours. These features are associated to characteristics of the flow such as the transition from an homogeneous regime to an heterogenous regime, and are consistent with global observation performed by independent means. This demonstrates the ability of the probe to connect local information to the global behaviour and structure of the flow.

Bed height and material density effects on fluidized bed hydrodynamics

“…There are two types of probes, optical fiber and resistive conductive probes, with optical fiber probes being used frequently. For example, Mena et al (2008) used a monofiber optical probe to measure the gas phase characteristics (residence time and velocity) in a three phase flow system.…”

Customization of an optical probe device and validation of a signal processing procedure to study gas–liquid–solid flows. Application to a three-phase internal-loop gas-lift Bioreactor

“…It is indeed a prerequisite before studying the complete bioreactor behaviour with biomass. More specifically, given the industrial applications targeted, the solid considered in this paper is spent grain whose properties are different from the solids used in previous work (Mena et al, 2008). Therefore specific developments were required.…”

“…The reactor wall transparency, out of focus, illumination and image analysis are among other known limitations (Ferreira et al, 2012). The reactor wall, focus and illumination can be solved/reduced experimentally (Mena et al, 2008(Mena et al, , 2005b. Concerning image processing, automatic image analysis is not an easy task mainly because of the identification of single and overlapping bubbles.…”

“…Moreover, due to their small size the spatial resolution is very high. The optical probe principle as well as a complete description of the LEGI optical probes signal processing methods (treatment for gaseous velocity -TGV) and main measurement errors can be found in the literature (Cartellier, 1998(Cartellier, , 1992Mena et al, 2008). Let us just stress that the probe manufacturing allows to control the diameter and shape of the sensitive tip (which is an almost perfect cone).…”

“…Sensors are based on temperature, capacitance, optical and conductivity properties of the system. Frequently, they are applied on two-phase flow (Jhawar and Prakash, 2007;Olivieri et al, 2007) and more recently to three-phase flow systems (Mena et al, 2008;Hooshyar et al, 2010;Wu et al, 2008), usually at low solids holdup (Boyer et al, 2002).…”