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.
Highlights
Gas-liquid bubble column reactors are widely used in the chemical industry
The behavior of the gas bubbles can be evaluated by measuring the gas concentration, the bubble velocity, and the size and distribution of bubbles of varied sizes across the reactor when viewed in cross-section [1,2]
16-transducer ultrasonic transmission tomography (UTT) systems, the imaging results from double gas bubble models reconstructed using the Sector-diffusion-matrix based Linear Back Projection (SLBP)-HR method are better than the imaging results constructed using the SLBP-ATF algorithm
Summary
Gas-liquid bubble column reactors are widely used in the chemical industry. The gas phase is a discrete phase, while the liquid phase is a continuous phase, so bubble column reactors can be treated as two-phase flow reactors. Bubble column reactors are suitable for supporting slow chemical reactions or high heat release reactions. Gas flows in from the pipe attached to the lower left side of the reactor and flows part of the vessel. Gas flows in from the attached pipe attached to the lower leftofside of the reactor and out flows of the. Gas flows inatfrom the of pipe to the lower left side the flows of out of vessel. The separate component of reactor attached to the the pipe attached at the top of the vessel The separate component ofreactor reactorand attached to the out of the pipe attached at the top of the vessel.
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