Quantitative characterizations of long-period fluctuations in a large-diameter bubble column based on point-wise void fraction measurements

Kajishima

Tsuchiya

2011

JEE

Self Cite

To mitigate global warming, a system that can dissolve huge amount of gaseous CO 2 expelled from a fossil fuel-fired power plant into the ocean, which must be at the same time eco-friendly to the ocean environment, is indispensable. We propose a system of sequestrating such CO 2 in the deep ocean water based on gas-lift effects, the so-called GLAD (Gas-Lift Advanced Dissolution) system. The primary system is an inverse-J (originally) pipeline set in the ocean at a depth of 200−3000 m. In the system, pumping powered by buoyancy of the dissolving CO 2 bubbles is used to transport CO 2-rich seawater to great depths. In the present paper, we outline the GLAD system and summarize its related fundamental studies for the purpose of designing a highly efficient and extremely reliable system.

Section: Discussion Of the Environmental Acceptability Of The Glad Symentioning

confidence: 99%

Deep Ocean CO2 Sequestration via GLAD (Gas-Lift Advanced Dissolution) System

Kajishima

Tsuchiya

2011

JEE

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“…Although electric conductivity probes have been studied, proposed and used frequently (e.g., Hibiki and Ishii, 2002), such probes present the problem of explosion protection for their application in some industrial plants. They also have no means of counteracting changes in the electric conductivity of the liquid phase.…”

Section: Introductionmentioning

confidence: 99%

Improvement of Optical Fiber Probing in Multiphase Systems, and the Possibility of Practical Application in Chemical Engineering Processes

J. Chem. Eng. Japan / JCEJ

Sato

Nihei

et al. 2018

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Optical ber probing (OFP) is a very useful and practical technique for investigating and monitoring multiphase systems, and it is particularly suitable for simultaneously measuring a bubble's/droplet's chord length, velocity and number density in an industrial-scale apparatus, as well as a laboratory-scale setup. Here, we outline the principles of OFP and propose several types of optical ber probes that meet the requirements for particular purposes of the multiphase systems in chemical engineering processes. We describe measurement methods that use an optical ber probe suitably tuned for liquid lm and foam, as well as for bubble measurement. The basic measurement principle of OFP is very simple: the probe tip's detection of changes in the refraction indices from a gas phase to a liquid phase or vice versa. For example, to precisely measure a bubble's properties such as the chord length and velocity, it is necessary to determine the precise relationship between the process of the optical ber probe's penetration into the bubble and the optical signal. Since the probing signal provides a variety of information due to the complicated interaction of the laser beams, optical ber and gas-liquid interfaces, it is necessary to use both experimental and computational approaches in order to extract the physical meanings of the probe's signals. Using our own fully-3D ray-tracing simulator and well-arranged high-speed visualization setups, we discuss how to improve the measurement accuracy of OFP. We rst computationally analyze the OFP signals under several penetration conditions, and we explain our recommendations regarding how to improve the accuracy of a single-tip optical ber probe used for measurement in multiphase systems. On the basis of our present ndings and the improvement in measurement accuracy, we then propose several applications of OFP to chemical engineering processes.

“…Mudde and Saito reported that the flow regimes were described as the functions of the superficial gas velocity and geometrical property of bubble columns by using OFP and Laser Doppler Anemometry (LDA) (Mudde and Saito, 2001). Higuchi and Saito characterized long-period fluctuations in a bubble column, from point-wise time-series void fractions by using an OFP (Higuchi and Saito, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…In the present study, we propose a signal-centric analysis based on experiments and computations. At first, we conducted computational ray tracing ) in a Single-Tip Optical fiber Probe (S-TOP, Saito et al 2010). The ray tracing is a technique to trace paths and intensity of light and simulate the effects of its encounters with objects.…”

mentioning

confidence: 99%

Measurement technique of bubble velocity and diameter in a bubble column via single-tip optical-fiber probing with judgment of the pierced position and angle

Mizushima

Sakamoto

Chemical Engineering Science

2013

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Our objective is to improve the accuracy of bubble measurement with Single-Tip Optical fiber Probe (S-TOP) in a bubbly flow. The STOP measures a point-wise void fraction and a velocity and diameter of a bubble simultaneously, by using only a single Mizushima, Sakamoto, and Saito CES 2 wedge-shaped tip. The STOP structure is very simple but raises an issue of an unclear touch position/angle between the STOP and a bubble. We propose a pre-signal threshold method in order to solve this issue. The pre-signal is one of the noisy optical signals from the STOP. First, the STOP signals are quantitatively analyzed with a newly developed 3D computational ray tracing method; the simulator can trace enormous ray segment trajectories in an optical fiber and render complicated optical boundary conditions. Moreover, in the simulator, evaluation of the complex output signals is achieved by computing the polarization and energy of every ray. We discovered that the intensity of the pre-signal indicates whether the STOP touches normally the center region of the bubble, or does not. We applied this characteristic to practical STOP measurement of a bubbly flow. As a result, the difference between the measured chord length via the STOP and the bubble minor axis from visualized images was significantly improved from 42 % (existing signal process) to 15 % (with processing through the method).