Ultrasonic Transmission Tomography Sensor Design for Bubble Identification in Gas-Liquid Bubble Column Reactors

Abstract

Scientists require methods to monitor the distribution of gas bubbles in gas-liquid bubble column reactors. One non-destructive method that can potential satisfy this requirement in industrial situations is ultrasonic transmission tomography (UTT). In this paper, an ultrasonic transmission tomography sensor is designed for measuring bubble distribution in a reactor. Factors that influence the transducer design include transmission energy loss, the resonance characteristics and vibration modes of the transducer, and diffusion angles of the transducers, which are discussed. For practical application, it was found that an excitation frequency of 300 kHz could identify the location and size of gas bubbles. The vibration mode and diffusion also directly affect the quality of the imaging. The geometric parameters of the transducer (a cylinder transducer with a 10 mm diameter and 6.7 mm thickness) are designed to achieve the performance requirements. A UTT system, based on these parameters, was built in order to verify the effectiveness of the designed ultrasonic transducer array. A Sector-diffusion-matrix based Linear Back Projection (SLBP) was used to reconstruct the gas/liquid two-phase flow from the obtained measurements. Two other image processing methods, based on SLBP algorithm named SLBP-HR (SLBP-Hybrid Reconstruction) and SLBP-ATF (SLBP-Adaptive Threshold Filtering), were introduced, and the imaging results are presented. The imaging results indicate that a gas bubble with a 3 mm radius can be identified from reconstructed images, and that three different flow patterns, namely, single gas bubble, double gas bubble with different diameters, and eccentric flow, can be identified from reconstructed images. This demonstrates that the designed UTT sensor can effectively measure bubble distribution in gas-liquid bubble column reactors.

Process intensification in multifunctional reactors: A review of multi-functionality by catalytic structures, internals, operating modes, and unit integrations

“…The gas bubbles aggregate and break apart while ascending. Their presence speeds up mixing the reactants particles, enhancing their contact efficiency and improving the transport (i.e., mass and heat) of these reactant particles [19][20][21][22][23][24]. In bubble column reactors, the bubble size varies across the reactor cross-section [22].…”

“…Their presence speeds up mixing the reactants particles, enhancing their contact efficiency and improving the transport (i.e., mass and heat) of these reactant particles [19][20][21][22][23][24]. In bubble column reactors, the bubble size varies across the reactor cross-section [22]. It is essential to understand the hydrodynamics of the gas-liquid flows in the bubble columns (e.g., size, distribution, and movement of the bubbles) as they are inherently unsteady, particularly under dense flows.…”

“…It is essential to understand the hydrodynamics of the gas-liquid flows in the bubble columns (e.g., size, distribution, and movement of the bubbles) as they are inherently unsteady, particularly under dense flows. The unsteady dynamics of the bubbles are known to influence the performance of mixing and transport properties, and subsequently, the chemical reaction rates, which will affect the overall reaction performance [22,25]. The gas holdup in bubble column reactors directly determines the reactor size as this parameter is related to the interfacial area, liquid back-mixing, and transport rate [26].…”

Oxygen Mass Transfer in Biopharmaceutical Processes: Numerical and Experimental Approaches

“…Essential extrusive methods include laser doppler anemometry (LDA) [117][118][119], ultrasonic [120][121][122][123][124] and shadow imaging (shadowgraphy) [125][126][127][128]. For LDA measurement, two laser beams cross each other in the transparent bioreactor.…”

A Lagrange-Newton Method for EIT/UT Dual-Modality Image Reconstruction

“…Thus, the mathematical model of UT can be referred to the geometrical optics or ray optics model, and the most commonly considered modes of the ultrasonic wave propagation are transmission and reflection modes, as shown in Figure 1. In addition, the piston transducer is used in the paper, where the energy of the ultrasonic wave is mainly concentrated in a narrow main lobe area [42]. The power of the transmission and reflection wave is mainly affected by the acoustic impedance of the media where the ultrasonic wave pass through, and it can be described as follows:αR=(PrPi)2=(Z2−Z1Z2+Z1)2, αT=(PtPi)2=(2Z2Z2+Z1)2, where Pi, Pr, Pt represent incident, reflection, and transmission sound pressures, respectively.…”