Unstable miscible displacements in radial flow with chemical reactions

Endothermic phenomena were identified during the regeneration of the porous ceramic diesel particulate trap. These phenomena were experimentally investigated and they were found to be related to the cerium content of the fuel used for the trap loading and regeneration and to the soot mass accumulated in the trap. Carbon mass and energy balance through the regeneration process reveals that these phenomena cannot be attributed to chemical reactions in the trap. It is assumed that they are due to the effect of regeneration on the radial flow distribution through the trap, an assumption remaining to be experimentally tested.

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A Numerical Simulator for Modeling the Coupling Processes of Subsurface Fluid Flow and Reactive Transport Processes in Fractured Carbonate Rocks

Water ◽

10.3390/w11101957 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1957 ◽

Cited By ~ 2

Author(s):

Yuan ◽

Wei ◽

Zhang ◽

Qin

Keyword(s):

Fluid Flow ◽

Chemical Reactions ◽

Reactive Transport ◽

Radial Flow ◽

Transport Processes ◽

Coupled Processes ◽

Rock Properties ◽

Brinkman Equation ◽

Fractured Carbonate ◽

Carbonate Formations

Water–rock interactions can alter rock properties through chemical reactions during subsurface transport processes like geological CO2 sequestration (GCS), matrix acidizing, and waterflooding in carbonate formations. Dynamic changes in rock properties cause a failure of waterflooding and GCS and could also dramatically affect the efficiency of the acidizing. Efficient numerical simulations are thus essential to the optimized design of those subsurface processes. In this paper, we develop a three-dimensional (3D) numerical model for simulating the coupled processes of fluid flow and chemical reactions in fractured carbonate formations. In the proposed model, we employ the Stokes–Brinkman equation for momentum balance, which is a single-domain formulation for modeling fluid flow in fractured porous media. We then couple the Stokes–Brinkman equation with reactive-transport equations. The model can be formulated to describe linear as well as radial flow. We employ a decoupling procedure that sequentially solves the Stokes–Brinkman equation and the reactive transport equations. Numerical experiments show that the proposed method can model the coupled processes of fluid flow, solute transport, chemical reactions, and alterations of rock properties in both linear and radial flow scenarios. The rock heterogeneity and the mineral volume fractions are two important factors that significantly affect the structure of conductive channels.

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Surface reactions observed by photoemission electron microscopy (PEEM)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121831 ◽

1992 ◽

Vol 50 (1) ◽

pp. 286-287

Author(s):

H.H. Rotermund

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Work Function ◽

Chemical Reactions ◽

Reaction Diffusion ◽

Dynamic Processes ◽

Clean Surface ◽

Crystal Surfaces ◽

Single Crystal Surfaces ◽

Photoemission Electron

Chemical reactions at a surface will in most cases show a measurable influence on the work function of the clean surface. This change of the work function δφ can be used to image the local distributions of the investigated reaction,.if one of the reacting partners is adsorbed at the surface in form of islands of sufficient size (Δ>0.2μm). These can than be visualized via a photoemission electron microscope (PEEM). Changes of φ as low as 2 meV give already a change in the total intensity of a PEEM picture. To achieve reasonable contrast for an image several 10 meV of δφ are needed. Dynamic processes as surface diffusion of CO or O on single crystal surfaces as well as reaction / diffusion fronts have been observed in real time and space.

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Microwaves: Application in Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100158248 ◽

1990 ◽

Vol 48 (3) ◽

pp. 140-141

Author(s):

Anthony S-Y Leong ◽

David W Gove

Keyword(s):

Electron Microscopy ◽

Light Microscopy ◽

Chemical Reactions ◽

Electromagnetic Waves ◽

Tissue Fixation ◽

Primary Method ◽

Dipolar Molecules ◽

Wide Range ◽

Time Required ◽

Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

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Fine structure and properties of defects in naturally occurring silicates and oxides

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100175430 ◽

1990 ◽

Vol 48 (4) ◽

pp. 460-461

Author(s):

David R. Veblen

Keyword(s):

Chemical Reactions ◽

High Resolution Electron Microscopy ◽

Extended Defects ◽

Single Chain ◽

Naturally Occurring ◽

Resolution Electron ◽

Fine Structures ◽

Image Simulations ◽

Similar Crystal Structure

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

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