Yongchen Song

Measurement on CO_2 Solution Density by Optical Technology

The optical technology based on Mach-Zehnder interferometry was successfully applied to a high-pressure liquid CO2 and water system to measure CO2 solution density. Experiments were carried out at a pressure range of from 5.0 to 12.5 MPa, temperatures from 273.25 to 284.15 K, and CO2 mass fraction in solution up to 0.061. CO2 solution density data were obtained from two sets of experiments. These data were calculated through the fringe shifts induced by density changes inside of the high-pressure vessel, which were directly recorded during the experiments, and a modified version of Lorentz-Lorenz formulation. The experimental results indicated that the density ratio of CO2 solution to that of pure water at the same pressure and temperature is monotonically linear with the CO2 concentration in the solution. The slope of this linear function, calculated by the experimental data fitting, is 0.275.

Measurement of the Density of CO2 Solution by Mach-Zehnder Interferometry

Abstract: The density of CO2 solution was measured by using Mach‐Zehnder interferometry in the pressure range from 5.0 to 12.5 MPa, at temperatures from 273.25 to 284.15 K, and CO2 mass fraction in solution up to 0.061. It was found that the density difference between the CO2 solution and pure water at the same pressure and temperature is monotonically linear with the CO2 mass fraction. The slope of this linear function, calculated by experimental data fitting, is 0.275.

Numerical Simulation of the Inner Structure of a Two-phase Plume Formed in a Stratification Environment

The inner structure of a two-phase plume, driven by air bubble buoyancy and formed in a stratification ambient fluid in a rectangular tank, is numerically simulated by means of two-phase flow theory and Large-eddy simulation technology. Focusing on the discrete nature of the buoyant dispersed phase and on the role of momentum exchange between two phases during plume formation, we investigated the phenomena of mass “entraining-in” and “peeling-out” that occurs inside the stratified ambient plume. These phenomena are thought to result from an intricate interplay among phase interaction, static stability of the stratification ambient fluid itself, and dynamic stability due to turbulence. Numerical simulations show that there exists an inner-out structure of the stratified ambient plume, while at the same time predicting that the re-entraining-in mass flux is on the same order of magnitude as that of the inner peeling-out mass flux within the annular region centered around the plume. This further explains the mechanism underlying the formation of multi-scale eddies at the edge of the air bubble plume, which also constitutes the boundary between the inner and outer zones of this inner-out stratified fluid plume. Within the inner part of the plume, the mass entraining-in and peeling-out appeared as a spatial discontinuity. The numerically visualized three-dimensional density fields are consistent with the two-phase plume characteristics.

Numerical visualization of two-phase plume formation in a stratification flow environment.

Abstract: Evolution of two‐phase plumes driven by air bubble buoyancy in a stratification ambient in a rectangular tank is visualized numerically by means of two‐phase flow theory and large‐eddy simulation technology. With a focus on the discrete nature of the buoyant dispersed phase and the role of momentum exchange between two phases in plume formation, we investigated the phenomena of mass entraining‐in and peeling‐out for continuous phase plume, which may result from a complicated and intricate interplay with phase interaction and dynamic stability of the stratification ambient, respectively. Numerical simulations show that although mass entraining‐in and peeling‐out appear to be distinguished entirely in the vertical direction, they interact or couple locally within inner of the plume and present a discontinuity in nature. The numerically visualized three‐dimensional density field also indicates the same plume characteristics.

Density change of underground water due to CO2 dissolution

Publisher Summary As an alternative technology to mitigate the carbon dioxide (CO2) concentration from the atmosphere, geological sequestration had been widely accepted as a practical option because of the potential capacity and the relative safety in comparison with another option—ocean sequestration. To investigate the sciences and technologies concerned with it, Research Institute of Innovative Technology for the Earth (RITE) initiated a research and development project for CO2 geological sequestration. The field experiment had been conducted at Nagaoka, Japan. For this technology, one of the geophysical dynamics additionally induced to the original geosystem is the dissolution of injected CO2 into the reservoir water, which is a way for storage. The density of dissolved water is changed leading to a gravity flow. This flow can make contribution to the evolution of CO2 enriched water in the terms of buoyancy.

A mathematic model of anothite dissolution in CO2 solution

Publisher Summary This chapter focuses on the study on the dynamics occurred at the interface among cap rocks, Anorthite, and CO2 solution because of CO2 geological sequestration. The efficient CO2 sequestration in the underground reservoir is mostly dominated by the porous structure of the cap rocks that are either essentially impermeable strata such as thick rock salt layers (aquicludes) or with lower permeability such as shale rocks and mudstones (known as aquitards). With basis on the fundamental theories of geochemistry and mass transfer, a mathematical model of Anothite dissolution in CO2 solution is developed for describing the dynamics of interface chemistries and transport physics. The model developed is convenient to be implemented into the existed geo-hydrological numerical model for simulating the long-term CO2 geological sequestration performance. The preliminary results obtained from the model analysis shows that Anorthite dissolution in a CO2 solution is mostly dominated by chemical reaction rather than the mass transfer when local Sherwood number is larger than 5 and temperature is lower than 325K. For the environment of the CO2 geological sequestration at depth about 1000m, temperatures range from 313 to 338K, the dissolution may be governed alternatively by chemical reaction or by fluid mass transfer depending on the variation in local Sherwood number.

Large-Eddy Simulation of Small-Scale Ocean Turbulence Coupled with Buoyant Plumes

To examine the turbulent characteristics of a small-scale ocean (length scale at L=O(103m)) disturbed by buoyant plumes, a numerical experiment is performed by employing Large-eddy simulation technology and two-fluid theories. This includes a simulation of reconstruction of the statistically stationary state of a small-scale ocean and the simulation of two-fluid plumes. For numerical reconstruction of a small-scale ocean, the observation data of the instantaneous flow field on the West Coast of Hawaii Island is applied to the determination of the turbulent structure with the aid of the forced-dissipative mechanism. The dynamics of buoyant droplets is described by an Eulerian scheme with the assumption of treating the droplets as a quasi-fluid. The two-way coupling between turbulent ocean and droplets is performed through exchange sub-models for momentum and mass. The predictions of turbulence spectra indicate that the buoyant plumes improved indistinctly the horizontal turbulent characteristics, however, they significantly modified the temperature spectrum in the lower wavenumber range. For plumes, the dynamics in the regime near the injection exit are dominated by interactions between turbulent ocean and droplets/solution. Outside of this regime, water column of solution is governed by the ocean turbulent flow.

Measurement of clathrate hydrate precipitation from CO2 solution by a nondestructive method

Abstract Using recorded data of pressure and temperature, we developed a nondestructive method to estimate the precipitation rate of carbon dioxide (CO2) hydrate by considering the CO2 solution density equation in association with the mass conservation equation. We applied this method to the investigation of the dynamic process of clathrate hydrate precipitation from CO2 solution using a high-pressure dissolution system consisting of a high-pressure vessel and optical detecting instruments. The role of stirring was examined. The temperatures studied in the experiments were from 275 to 288 K over a pressure range of 4∼8 MPa. Experimental results showed that our method can quantitatively monitor this dynamic process. The volume ratio of precipitated hydrate to that of the pressure-vessel approached 0.09 when a steady state was reached, which took about 100 seconds; more than 60% of the total clathrate hydrate precipitated within 10 seconds at the cooling rates of this experiment. For precipitation, stirring enhanced the cooling and led to a large hydrate precipitation rate from 0.004 to 0.008 in volume ratio per second. For nucleation, however, the residual structure of the solution decreased the amount of hysteresis in the formation of hydrate nuclei during supercooling, of which induction times were reduced by 4∼9 minutes.

Numerical Prediction of the Effects of Oceanic Flow Characters on the Evolution of CO2 Eniched Plumes

The near-field dynamics of CO2 rich plume draw attention of assessment of the local impacts of CO2 ocean sequestration on natural oceanic environment. In this study, we attempt to predict numerically the role of ocean flow characters, including the current profile and the turbulent intensity, and of the injection parameters, including the injection rate and initial droplet diameters, on the evolution of liquid CO2 (LCO2 ) droplet and CO2 enriched seawater plumes. The numerical model we used in this study is a two-phase large-eddy simulation model. From numerical experiments we found: 1). The plume height (both LCO2 plume and CO2 enriched seawater plume) is insensitive to ocean currents and turbulent intensity but do sensitive to initial droplet diameter. For releasing rates of 0.6kg/sec, the estimated plume heights at initial droplet diameters of 8.0 and 5.0 millimeter are approximately 170 and 80 meters for different oceanic flows. 2). The physics of CO2 enriched seawater plume, for instance CO2 concentration distribution and local largest concentration, however, are governed sensitively by seawater flow characters and alternatively by injection rate and initial droplet diameter. 3). Strong turbulence enhanced the dispersion and mixing of droplets and CO2 enriched seawater with fresh seawater to produce an improved CO2 concentration distribution.Copyright

Experimental Study of Dissolution Rate of a CO2 Droplet and CO2 Solubility in High Pressure and Low Temperature Seawater With Hydrate Free

Against the background of carbon dioxide (CO2 ) ocean sequestration technology, we investigated the solubility of CO2 in seawater at a thermodynamic state similar to that at an ocean depth of 1000 m. The experiment was performed in two steps. In the first step, we reexamined and modified the fundamental relationship between Sherwood (Sh) number and Rayleigh (Ra) number in a natural convective flow over an up-down CO2 droplet. We derived a new expression of the Grashof number for CO2 dissolution in water and seawater with the aid of the relation between the density of CO2 solution and CO2 concentration. In the second step, this new expression was applied to the estimation of solubility of CO2 from experiments examining the dissolution of an individual CO2 droplet in seawater at hydrate-formable pressure and temperature states. We found from our experiments: that (1) at hydrate-formable conditions (step two), no hydrate appeared at interface between liquid CO2 and seawater throughout the experiments within 5 hours, which suggested that a thermodynamic state (pressure and temperature) is indispensable but not a complete condition for hydrate formation; and (2) associated with this dual nature, the data of CO2 solubility estimated from this experiment are much larger than those obtained by Kimuro et al [1] from experiments of hydrate coexistence. Our data ranged from 0.052 to 0.062 in mass fraction.Copyright