Mechanisms of multiphase reactive flow using biogenically calcite-functionalized micromodels

Lab on a Chip ◽  
2018 ◽  
Vol 18 (24) ◽  
pp. 3881-3891 ◽  
Author(s):  
Wen Song ◽  
Folake Ogunbanwo ◽  
Marianne Steinsbø ◽  
Martin A. Fernø ◽  
Anthony R. Kovscek
Keyword(s):  
Reactive Transport ◽  
Reactive Flow ◽  
Reaction Products ◽  
Storage Media ◽  
Protective Reaction

Biogenically calcite-functionalized microfluidics reveals a new grain-engulfment mechanism where protective reaction products alter reactive transport through porous CO2 storage media.

scholarly journals Pore-Scale Modeling of Mineral Growth and Nucleation in Reactive Flow

2022 ◽  
Vol 3 ◽  
Author(s):  
Vitalii Starchenko
Keyword(s):  
Reactive Transport ◽  
Surface Reaction ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Reactive Flow ◽  
Natural Environments ◽  
Pore Scale ◽  
Arbitrary Lagrangian Eulerian ◽  
Mineral Precipitation

A fundamental understanding of mineral precipitation kinetics relies largely on microscopic observations of the dynamics of mineral surfaces exposed to supersaturated solutions. Deconvolution of tightly bound transport, surface reaction, and crystal nucleation phenomena still remains one of the main challenges. Particularly, the influence of these processes on texture and morphology of mineral precipitate remains unclear. This study presents a coupling of pore-scale reactive transport modeling with the Arbitrary Lagrangian-Eulerian approach for tracking evolution of explicit solid interface during mineral precipitation. It incorporates a heterogeneous nucleation mechanism according to Classical Nucleation Theory which can be turned “on” or “off.” This approach allows us to demonstrate the role of nucleation on precipitate texture with a focus at micrometer scale. In this work precipitate formation is modeled on a 10 micrometer radius particle in reactive flow. The evolution of explicit interface accounts for the surface curvature which is crucial at this scale in the regime of emerging instabilities. The results illustrate how the surface reaction and reactive fluid flow affect the shape of precipitate on a solid particle. It is shown that nucleation promotes the formation of irregularly shaped precipitate and diminishes the effect of the flow on the asymmetry of precipitation around the particle. The observed differences in precipitate structure are expected to be an important benchmark for reaction-driven precipitation in natural environments.

In-situ Raman study of the thermal decomposition of LiBH4

2009 ◽  
Vol 1216 ◽  
Author(s):  
Daniel Reed ◽  
David Book
Keyword(s):  
Thermal Decomposition ◽  
Hydrogen Storage ◽  
Peak Position ◽  
Ex Situ ◽  
Liquid Lithium ◽  
Reaction Products ◽  
Lithium Borohydride ◽  
Storage Media ◽  
Liquid Phases

AbstractWith relatively high gravimetric and volumetric hydrogen storage capacities, borohydrides have attracted interest as potential hydrogen storage media. Lithium borohydride has a maximum theoretical gravimetric hydrogen storage density of 18.4 wt%, and has been shown to be reversible when heated to 600°C in 350 bar hydrogen1. It is hoped that a greater understanding of the decomposition and reformation mechanisms, may lead to the development of LiBH4-based materials that can absorb and desorb hydrogen under less extreme conditions. However, these studies have proved a challenge: currently most in-situ investigations have used x-ray diffraction or neutron diffraction however these cannot readily give information on non-crystalline or liquid phases. The preparation of samples measured ex-situ via XRD, NMR2 and Raman3 have shown the reaction products and stable intermediates during the thermal decomposition, however, it is very difficult to detect short lived intermediate (or byproduct) species. Raman spectroscopy has the advantages that: materials with only short-range order can be analysed; and by focusing the laser on regions in a sample the reaction path can be monitored with changing temperature with a rapid scan rate.After heating lithium borohydride through its phase change and melting point, shifts in peak position and peak width were observed, which agreed with other studies4. A sample was also heated to 500°C (under 1 bar Ar) to decompose the sample. A number of intermediates and reaction products have been predicted and observed ex situ. This work shows the in situ formation of lithium dodecaborane (Li2B12H12) and amorphous boron from liquid lithium borohydride. It is therefore possible to determine at what temperatures certain intermediates and products form.

scholarly journals Deepening roots can enhance carbonate weathering

2020 ◽  
Author(s):  
Hang Wen ◽  
Pamela L. Sullivan ◽  
Gwendolyn L. Macpherson ◽  
Sharon A. Billings ◽  
Li Li
Keyword(s):  
Carbon Cycle ◽  
Reactive Transport ◽  
Numerical Experiments ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
Base Case ◽  
Reaction Products ◽  
Soil Co2 ◽  
Carbonate Weathering ◽  
Weathering Rates

Abstract. Carbonate weathering is essential in regulating atmospheric CO2 and carbon cycle at the century time scale. Plant roots have been known to accelerate weathering by elevating soil CO2 via respiration. It however remains poorly understood how and how much rooting characteristics (e.g., depth and density distribution) modify flow paths and weathering. We address this knowledge gap using field data from and reactive transport numerical experiments at the Konza Prairie Biological Station (Konza), Kansas (USA), a site where woody encroachment into grasslands is surmised to deepen roots. Results indicate that deepening roots potentially enhance weathering in two ways. First, deepening roots can control thermodynamic limits of carbonate dissolution by regulating how much CO2 transports downward to the deeper carbonate-rich zone. The base-case data and model from Konza reveal that concentrations of Ca and Dissolved Inorganic Carbon (DIC) are regulated by soil pCO2 driven by the seasonal fluctuation of soil respiration. This relationship can be encapsulated in equations derived in this work describing the dependence of Ca and DIC on temperature and soil CO2, which has been shown to apply in multiple carbonate-dominated catchments. Second, numerical experiments show that roots control weathering rates by regulating the amount of water fluxes that flush through the carbonate zone and export reaction products at dissolution equilibrium. Numerical experiments explored the potential effects of partitioning 40 % of infiltrated water to depth in woodlands compared to 5 % in grasslands. Soil CO2 data from wood- and grasslands suggest relatively similar soil CO2 distribution over depth, and only led to 1 % to 12 % difference in weathering rates if flow partitioning was kept the same between the two land covers. In contrast, deepening roots can enhance weathering by 17 % to 207 % as infiltration rates increased from 3.7 × 10−2 to 3.7 m/yr. Numerical experiments also indicated that weathering fronts in woodlands propagated > 2 times deeper compared to grasslands after 300 years at the infiltration rate of 0.37 m/yr. These differences in weathering fronts are ultimately caused by the contact time of CO2-charged water with carbonate rocks. We recognize that modeling results are subject to limitations in representing processes and parameters, but we propose that the data and numerical experiments allude to the hypothesis that (1) deepening roots can enhance carbonate weathering; (2) the hydrological impacts of rooting characteristics can be more influential than those of soil CO2 distribution in modulating weathering rates. We call for co-located characterizations of roots, subsurface structure, soil CO2 levels, and their linkage to water and water chemistry. These measurements will be essential to improve models and illuminate feedback mechanisms of land cover changes, chemical weathering, global carbon cycle, and climate.

scholarly journals Quantitative Model of the Formation Mechanism of the Rollfront Uranium Deposits

2018 ◽  
Vol 20 (3) ◽  
pp. 213
Author(s):  
D.Y. Aizhulov ◽  
N.M. Shayakhmetov ◽  
A. Kaltayev
Keyword(s):  
Reactive Transport ◽  
Redox Reactions ◽  
Reaction Rates ◽  
Quantitative Model ◽  
Production Costs ◽  
Reactive Flow ◽  
Uranium Deposits ◽  
Geological Processes ◽  
Exploration And Production ◽  
Favorable Conditions

The rollfront type deposits are crescent shaped accumulation of mineralization including uranium, selenium, molybdenum in reduced permeable sandstones. It generally forms within a geochemical barrier between mostly reduced and predominantly oxidized environments. Redox reactions between oxidant and reductant creates favorable conditions for uranium precipitation, while constant flow of oxidant continuously dissolves uranium minerals thereby creating a reactive transport. Several previous works had either focused on the characteristics of the rollfront type deposits, or on the description of chemical and geological processes involved in their genesis. Based on these previous works, authors aimed to mimic laboratory experiments numerically by reactive flow and numerical simulation. Data from one particular experiment was used to determine reaction rates between reactants to produce a model of reactive transport and chemical processes involved in the formation of rollfront type deposits. The resulting model was used to identify the causes of crescent like formations and to determine main mechanisms influencing rollfront evolution. A better understanding and simulation of the mechanism involved in the formation of rollfront type deposits and their properties would contribute to decreased exploration and production costs of commodities trapped within such accumulations. The results of this work can be used to model other deposits formed through infiltration and subsequent precipitation of various minerals at the redox interface.

Reactive flow and homogenization in anisotropic media

2020 ◽  
Author(s):  
Einat Aharonov ◽  
Roi Roded ◽  
Ran Holtzman ◽  
Piotr Szymczak
Keyword(s):  
Flow Field ◽  
Reactive Transport ◽  
Flow Direction ◽  
Anisotropic Media ◽  
Space Structure ◽  
Reactive Flow ◽  
Advective Transport ◽  
Void Space ◽  
Bulk Fluid ◽  
Reactive Fluid

<p>Dissolution by reactive fluid flow is a fundamental process in geological systems. It controls diagenesis and karst evolution and has broad implications for groundwater hydrology. Specifically, reactive flow controls the evolution of the void-space structure via the feedback between the reaction and transport. In some instances, advective transport rate is high compared to that of geochemical reactions (low Damkӧhler number, Da), such that the reactive fluid penetrates the system before its reactivity is exhausted, resulting in a relatively spatially-uniform dissolution. Despite the importance of low Da conditions, the emerging transformations in the medium structure, flow field, and its bulk properties are not well understood. Likewise, our ability to decipher diagenetic history and preexisting structure is lacking.</p><p>Here, using a network model, we investigate the evolution of heterogeneous and anisotropic medium during dissolution at low Da conditions. The numerical simulations show that the medium progressively becomes more homogeneous as well as isotropic, which consequently makes the flow field more uniform. Homogenization is particularly notable for anisotropic media, in which the transverse channels are wide relative to the channels parallel to the main flow direction. In this case, flow is initially focused within a few highly tortuous pathways, hence emphasizing the effect of dissolution on flow heterogeneity and tortuosity. The homogenization process is further enhanced when the surface reaction is transport-controlled—that is, when diffusion of dissolved ions away from the mineral surface to the bulk fluid is slow, reducing the reactivity adjacent to the surface: At first, since diffusive transport is more effective in narrow channels, they undergo faster dissolution, which selectively enlarges them leading to an initial steep rise in permeability. Later, however, as dissolution proceeds and the channels broaden, the overall dissolution rate drops, diminishing the growth rate of permeability. Our findings provide fundamental insights into reactive transport and hydrogeological processes in fractured and porous media.</p>

Pore-Network Modeling Dedicated to the Determination of the Petrophysical-Property Changes in the Presence of Reactive Fluid

SPE Journal ◽  
2010 ◽  
Vol 15 (03) ◽  
pp. 618-633 ◽  
Author(s):  
Lionnel Algive ◽  
Samir Bekri ◽  
Olga Vizika
Keyword(s):  
Transport Equation ◽  
Reactive Transport ◽  
Surface Reactions ◽  
Flow Regimes ◽  
Pore Network ◽  
Reactive Flow ◽  
Petrophysical Properties ◽  
Pore Scale ◽  
Reactive Fluid ◽  
Effective Transport

Summary A pore-network model (PNM) is an efficient tool to account for phenomena occurring at the pore scale. Its explicit 3D network of pores interconnected by throats represents an easy way to consider the topology and geometry effects on upscaled and homogenized petrophysical parameters. In particular, this modeling approach is appropriate to study the rock/fluid interactions. It can provide quantitative information both on the effective transport property modifications caused by the reactions and on the structure evolution resulting from dissolution/precipitation mechanisms. The model developed is based on the resolution of the macroscopic reactive transport equation between the nodes of the network. By upscaling the results, we then determined the effective transport properties at the core scale. A sensitivity study on reactive and flow regimes has been conducted in the case of single-phase flow in the limit of long times. It has been observed that the mean reactive solute velocity and dispersion can vary up to one order of magnitude compared with the tracer values because of the concentration-profile heterogeneity at the pore scale resulting from the surface reactions. As for the reactive apparent coefficient, when the kinetics is limited by the mass transfer, it can decrease by several orders of magnitude with regard to that calculated by the usual perfect-mixing assumption. That is why scale factors should be added to the classical macroscopic transport equation implemented in reservoir simulators to predict accurately the reactive flow effects. For each study case, we also obtained the permeability variation vs. the porosity evolution in a physical way that accounts for reactive transport conditions. It appears that the wall-deformation pattern and its effect on petrophysical properties must be explained by considering both microscopic and macroscopic scales of the reactive transport, each one governed by a dimensionless number comparing reaction and transport characteristic times. This work helps improve the understanding of surface-reactions effects on reactive flow on the one hand and on permeability and porosity modifications on the other. Using the PNM approach, scale-factor parameters and permeability-vs.-porosity relations can be determined for various rock types and reactive flow regimes. Once integrated as inputs in a reservoir simulator, these relations form a powerful and convenient means of enhancing the modeling accuracy of the change in petrophysical properties during injection of a reactive fluid, such as brine rich in carbon dioxide (CO2).

Lead aspartate: a new en bloc stain for electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 34-35
Author(s):  
J.R. Walton
Keyword(s):  
Electron Microscopy ◽  
Calcium Ion ◽  
Enzyme Reaction ◽  
Lead Citrate ◽  
Reaction Products ◽  
En Bloc ◽  
Thin Sections ◽  
Lead Salts ◽  
Thin Sectioning ◽  
High Alkalinity

In electron microscopy, lead is the metal most widely used for enhancing specimen contrast. Lead citrate requires a pH of 12 to stain thin sections of epoxy-embedded material rapidly and intensively. However, this high alkalinity tends to leach out enzyme reaction products, making lead citrate unsuitable for many cytochemical studies. Substitution of the chelator aspartate for citrate allows staining to be carried out at pH 6 or 7 without apparent effect on cytochemical products. Moreover, due to the low, controlled level of free lead ions, contamination-free staining can be carried out en bloc, prior to dehydration and embedding. En bloc use of lead aspartate permits the grid-staining step to be bypassed, allowing samples to be examined immediately after thin-sectioning.Procedures. To prevent precipitation of lead salts, double- or glass-distilled H20 used in the stain and rinses should be boiled to drive off carbon dioxide and glassware should be carefully rinsed to remove any persisting traces of calcium ion.

Radiation Damage in Ceramics

1982 ◽  
Vol 40 ◽  
pp. 600-603
Author(s):  
T. E. Mitchell ◽  
M. R. Pascucci ◽  
R. A. Youngman
Keyword(s):  
Radiation Damage ◽  
Outer Space ◽  
Point Of View ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
Storage Media ◽  
Transmission Electron ◽  
Fundamental Point ◽  
Small Defect ◽  
Present Understanding

1. Introduction. Studies of radiation damage in ceramics are of interest not only from a fundamental point of view but also because it is important to understand the behavior of ceramics in various practical radiation enyironments- fission and fusion reactors, nuclear waste storage media, ion-implantation devices, outer space, etc. A great deal of work has been done on the spectroscopy of point defects and small defect clusters in ceramics, but relatively little has been performed on defect agglomeration using transmission electron microscopy (TEM) in the same kind of detail that has been so successful in metals. This article will assess our present understanding of radiation damage in ceramics with illustrations using results obtained from the authors' work.

Studies of Oxide Formation on Copper Thin Films by Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 316-317
Author(s):  
G. G. Hembree ◽  
M. A. Otooni ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Crystal Surface ◽  
Crystal Defects ◽  
Diffraction Reflection ◽  
Reaction Products ◽  
Intermediate Energies ◽  
Crystal Films ◽  
Reflection Electron Microscopy

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.

Precipitation in silicon: Microanalysis

1988 ◽  
Vol 46 ◽  
pp. 474-475
Author(s):  
R.W. Carpenter
Keyword(s):  
Transition Metals ◽  
Spatial Resolution ◽  
Thin Foil ◽  
Precipitation Reaction ◽  
High Current ◽  
Reaction Products ◽  
Carbon And Nitrogen ◽  
Dielectric Layers ◽  
Precipitation Processes ◽  
Areas Of Interest

Interest in precipitation processes in silicon appears to be centered on transition metals (for intrinsic and extrinsic gettering), and oxygen and carbon in thermally aged materials, and on oxygen, carbon, and nitrogen in ion implanted materials to form buried dielectric layers. A steadily increasing number of applications of microanalysis to these problems are appearing. but still far less than the number of imaging/diffraction investigations. Microanalysis applications appear to be paced by instrumentation development. The precipitation reaction products are small and the presence of carbon is often an important consideration. Small high current probes are important and cryogenic specimen holders are required for consistent suppression of contamination buildup on specimen areas of interest. Focussed probes useful for microanalysis should be in the range of 0.1 to 1nA, and estimates of spatial resolution to be expected for thin foil specimens can be made from the curves shown in Fig. 1.

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