Effects of Frequency and Aeration Rate on Ultrasonic Oxidation of a Surfactant

The oxidation of surfactant (polyoxyethylene alkyl ether, C₁₄H₂₉O(CH₂CH₂)₇H, hereafter referred to as SS-70) induced by high power ultrasound is examined. The influences of aeration, bubble distribution, and frequency on the degradation rate are investigated. SS-70 is decomposed totally in a few hours. The optimum frequency for the degradation is observed. The decomposition rate of the surfactant is enhanced by the aeration and depends on the shape of the reactor. The optimum condition for the degradation process of ultrasonic oxidation is discussed.     

A Multimodal Tomography System Based on ECT Sensors

A new noninvasive system for multimodal electrical tomography based on electrical capacitance tomography (ECT) sensor hardware is proposed. Quasistatic electromagnetic fields are produced by ECT sensors and used for interrogating the sensing domain. The new system is noninvasive and based on capacitance measurements for permittivity and power balance measurements for conductivity (impedance) imaging. A dual sensitivity map of perturbations in permittivity and conductivity is constructed. The measured data along with the sensitivity matrix are used for the actual image reconstruction. The new multimodal tomography system has the advantage of using already established reconstruction techniques, and the potential for combination with new reconstruction techniques by taking advantage of combined conductivity/permittivity data. Moreover, it does not require direct contact between the sensor and the region of interest. The system performance has been tested on representative data, producing good results     

Electrical Capacitance Volume Tomography

A dynamic volume imaging based on the principle of electrical capacitance tomography (ECT), namely, electrical capacitance volume tomography (ECVT), has been developed in this study. The technique generates, from the measured capacitance, a whole volumetric image of the region enclosed by the geometrically three-dimensional capacitance sensor. This development enables a real-time, 3-D imaging of a moving object or a real-time volume imaging (4-D) to be realized. Moreover, it allows total interrogation of the whole volume within the domain (vessel or conduit) of an arbitrary shape or geometry. The development of the ECVT imaging technique primarily encloses the 3-D capacitance sensor design and the volume image reconstruction technique. The electrical field variation in three-dimensional space forms a basis for volume imaging through different shapes and configurations of ECT sensor electrodes. The image reconstruction scheme is established by implementing the neural-network multicriterion optimization image reconstruction (NN-MOIRT), developed earlier by the authors for the 2-D ECT. The image reconstruction technique is modified by introducing into the algorithm a 3-D sensitivity matrix to replace the 2-D sensitivity matrix in conventional 2-D ECT, and providing additional network constraints including 3-to-2-D image matching function. The additional constraints further enhance the accuracy of the image reconstruction algorithm. The technique has been successfully verified over actual objects in the experimental conditions     

Dynamics of spiral bubble plume motion in the entrance region of bubble columns and three-phase fluidized beds using 3D ECT

In this study, we have developed, for the first time in the field, a ‘dynamic’ three-dimensional image reconstruction technique for electrical capacitance tomography (ECT) imaging based on a neural-network multi-criterion optimization (NNMOIRT). This development enables a real time, 3D imaging of a moving object to be realized. The image reconstruction scheme of the 3D ECT is established by introducing a 3D sensitivity matrix into the NN-MOIRT algorithm, developed earlier by the authors. The sensitivity matrices employed are based on 6- and 12-electrode twin-plane cylindrical sensors. The NN-MOIRT algorithm reconstructs simultaneously the image voxels (volume pixels) on 20×20×20 resolutions from the capacitance data obtained using the twin-plane sensors which surrounds the 3D section of 8 cm in length in the cylindrical columns. The technique is successfully tested over a 3D simulated as well as actual experimental objects. The 3D ECT technique is used to investigate the transient phenomena in the entrance region of a 10 cm diameter column using a single nozzle gas distributor with paraffin liquid (Norpar), air, and glass-beads as flow media. Hydrodynamic characteristics of the gas-liquid and gas-liquid-solid flows, including 3D bubble plume spiral motion, 3D large scale liquid vortex dynamics and real time three-dimensional gas holdup distribution are studied.     

A model for simultaneous measurement of gas and solid holdups in a bubble column using ultrasonic method

The ultrasonic method developed to measure the dispersed phase holdups in dispersion systems is based on the fact that the velocity of ultrasound in the dispersion is different from that in the liquid. The relationships between velocity differences in the term of transmission time differences of ultrasound and gas holdup in a gas-liquid system and solid holdup in a liquid-solid system were derived. The holdups became linearly dependent on the time differences, which is in agreement with the experimental data. Based on those relations, a model for simultaneous measurement of gas and solid holdups in three-phase systems is proposed. The model permits measurement of the dispersed phase holdups by measuring the transmission time of ultrasound transmitted through the dispersions in two frequencies. It allows investigation of local holdups distributions in a bubble column and in a suspended bubble column.     

Dual imaging modality of granular flow based on ECT sensors

In this study, a previously developed dual modality imaging system is applied to image the flow of granular matter with different electrical properties in cylindrical vessels. The imaging system is based on both capacitance and power measurements acquired by an electrical capacitance tomography (ECT) sensor located around the vessel. The measurement data are then used to reconstruct cross-sectional images of both permittivity and conductivity distributions. A neural network multi-criterion optimization reconstruction technique (NN-MOIRT) is used for the inverse (reconstruction) problem. The contribution of this technology to the field of granular matters is explored through review of research articles that can be a direct application of this development. We discuss the capabilities of this dual-modality acquisition system using synthetic data for granular matter with different electrical properties.