Infiltration Velocity and Thickness of Flowing Slag Film on Porous Refractory of Slagging Gasifiers

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Ramalakshmi Krishnaswamy ◽  
Tetsuya Kenneth Kaneko ◽  
Bishal Madhab Mazumdar ◽  
Peter Rozelle ◽  
Seetharaman Sridhar ◽  
...  
Keyword(s):  
Volumetric Flow Rate ◽  
Slag Viscosity ◽  
Slag Film ◽  
Cross Sectional ◽  
Porous Microstructure ◽  
Small Reynolds Numbers ◽  
Porous Refractory ◽  
Capillary Pressures ◽  
Slag Thickness ◽  
Refractory Surface

Two analytical formulations that describe the fluid interactions of slag with the porous refractory linings of gasification reactors have been derived. The first formulation considers the infiltration velocity of molten slag into the porous microstructure of the refractory material that possesses an inherent temperature gradient in the direction of infiltration. Capillary pressures are assumed to be the primary driving force for the infiltration. Considering that the geometry of the pores provides a substantially shorter length scale in the radial direction as compared with the penetration direction, a lubrication approximation was employed to simplify the equation of motion. The assumption of a fully developed flow in the pores is justified based on the extremely small Reynolds numbers of the infiltration slag flow. The second formulation describes the thickness of the slag film that flows down the perimeter of the refractory lining. The thickness of the film was approximated by equating the volumetric slag production rate of the gasification reactor to the integration of the velocity profile with respect to the lateral flow cross-sectional area of the film. These two models demonstrate that both the infiltration velocity into the refractory and the thickness of the film that forms at the refractory surface were sensitive to the viscosity of the fluid slag. The slag thickness model has been applied to predict film thicknesses in a generic slagging gasifier with assumed axial temperature distributions, using slag viscosity from the literature, both for the case of a constant slag volumetric flow rate down the gasifier wall, and for the case of a constant flyash flux distributed uniformly over the entire gasifier wall.

Meniscus behaviors and capillary pressures in capillary channels having various cross-sectional geometries

2018 ◽  
Vol 26 (10) ◽  
pp. 2014-2022 ◽  
Author(s):  
Yicun Tang ◽  
Jingchun Min ◽  
Xuan Zhang ◽  
Guiling Liu
Keyword(s):  
Cross Sectional ◽  
Capillary Pressures

Mathematical Analysis of a Novel Formaldehyde Remediation Process

2007 ◽  
Vol 2 (3) ◽  
Author(s):  
Norman W Loney
Keyword(s):  
Carbon Dioxide Laser ◽  
Volumetric Flow Rate ◽  
Oxidation Catalyst ◽  
Low Temperature Oxidation ◽  
Laser Applications ◽  
Cross Sectional ◽  
Temperature Oxidation ◽  
Design Variables ◽  
Smoke Stack ◽  
Remediation Process

The NASA low-temperature oxidation catalyst (Pt/SnO2), originally developed for space-based carbon dioxide laser applications has been recently adapted to address formaldehyde destruction in industrial smoke stack emission streams. A mathematical model is developed that can be used to correlate the observable chemistry occurring on the surfaces of a monolith with the volumetric flow rate of the gas and cross sectional area of catalyst surfaces as well as quantifying process design variables such as pressure or temperature of an exhaust gas stream.

scholarly journals Preparation of Porous F-WO3/TiO2Films with Visible-Light Photocatalytic Activity by Microarc Oxidation

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Chung-Wei Yeh ◽  
Kee-Rong Wu ◽  
Chung-Hsuang Hung ◽  
Hao-Cheng Chang ◽  
Chuan-Jen Hsu
Keyword(s):  
Visible Light ◽  
Dye Degradation ◽  
Microarc Oxidation ◽  
Band Gap Energy ◽  
High Specific Surface Area ◽  
Cross Sectional ◽  
Porous Networks ◽  
Transmission Electron ◽  
Porous Microstructure ◽  
Diffraction Patterns

Porous F-WO3/TiO2(mTiO2) films are prepared on titanium sheet substrates using microarc oxidation (MAO) technique. The X-ray diffraction patterns show that visible-light (Vis) enabling mTiO2films with a very high content of anatase TiO2and high loading of WO3are successfully synthesized at a low applied voltage of 300 V using electrolyte contenting NaF and Na2WO4without subsequent heat treatment. The cross-sectional transmission electron microscopy micrograph reveals that the mTiO2films feature porous networks connected by many micron pores. The diffused reflection spectrum displays broad absorbance across the UV-Vis regions and a significant red shift in the band gap energy (∼2.23 eV) for the mTiO2film. Owing to the high specific surface area from the porous microstructure, the mTiO2film shows a 61% and 50% rate increase in the photocatalytic dye degradation, as compared with the N,C-codoped TiO2films under UV and Vis irradiation, respectively.

On oblique liquid curtains

2019 ◽  
Vol 876 ◽  
Author(s):  
Steven J. Weinstein ◽  
David S. Ross ◽  
Kenneth J. Ruschak ◽  
Nathaniel S. Barlow
Keyword(s):  
Surface Tension ◽  
Steady State ◽  
Characteristic Length ◽  
Volumetric Flow Rate ◽  
Liquid Sheet ◽  
Length Scale ◽  
Characteristic Length Scale ◽  
Cross Sectional ◽  
Average Speed ◽  
Theoretical Results

In a recent paper (J. Fluid Mech., vol. 861, 2019, pp. 328–348), Benilov derived equations governing a laminar liquid sheet (a curtain) that emanates from a slot whose centreline is inclined to the vertical. The equations are valid for slender sheets whose characteristic length scale in the direction of flow is much larger than its cross-sectional thickness. For a liquid that leaves a slot with average speed, $u_{0}$, volumetric flow rate per unit width, $q$, surface tension, $\unicode[STIX]{x1D70E}$, and density, $\unicode[STIX]{x1D70C}$, Benilov obtains parametric equations that predict steady-state curtain shapes that bend upwards against gravity provided $\unicode[STIX]{x1D70C}qu_{0}/2\unicode[STIX]{x1D70E}<1$. Benilov’s parametric equations are shown to be identical to those derived by Finnicum, Weinstein, and Ruschak (J. Fluid Mech., vol. 255, 1993, pp. 647–665). In the latter form, it is straightforward to deduce an alternative solution of Benilov’s equations where a curtain falls vertically regardless of the slot’s orientation. This solution is consistent with prior experimental and theoretical results that show that a liquid curtain can emerge from a slot at an angle different from that of the slot centreline.

Numerical Simulation of Volcanic Ash Infiltration into Thermal Barrier Coatings

2019 ◽  
Vol 827 ◽  
pp. 367-372
Author(s):  
Masayuki Arai ◽  
Yuta Fukushima ◽  
Kiyohiro Ito
Keyword(s):  
Numerical Simulation ◽  
Phase Transformation ◽  
High Temperature ◽  
Volcanic Ash ◽  
Thermal Barrier ◽  
Cross Sectional ◽  
User Subroutine ◽  
Barrier Coating ◽  
Temperature Environment ◽  
Porous Microstructure

CMAS attack is known to occur owing to the deposition of volcanic ash onto thermal barrier coating (TBC) surface at a high-temperature environment. The serious problem is TBC spallation resulting from the infiltration of molten volcanic ash into the porous microstructure of TBC. The infiltration induces inner stress and phase transformation, which directly results in those serious problems. In this study, the diffusional equation for expressing the infiltrating process of the molten ash into the porous structure of TBC and the associated constitutive equation considered regarding phase transformation are formulated. The equations are installed into commercial finite element (FE) code (MARC) using the user subroutine. The numerical simulation results are compared with the cross-sectional SEM observation for the volcanic-ash-deposited TBC sample exposed at a high-temperature to confirm verification of the model proposed herein.

scholarly journals A network model for fluid transport through sea ice

2006 ◽  
Vol 44 ◽  
pp. 129-133 ◽  
Author(s):  
J. Zhu ◽  
A. Jabini ◽  
K.M. Golden ◽  
H. Eicken ◽  
M. Morris
Keyword(s):  
Sea Ice ◽  
Fluid Transport ◽  
Laboratory Data ◽  
Grid Method ◽  
Two Dimensions ◽  
Cross Sectional ◽  
Fluid Permeability ◽  
Porous Microstructure ◽  
Polar Biology ◽  
Fully Connected

AbstractThe flow of liquid through porous sea ice is a fundamental process affecting problems in polar biology, oceanography and geophysics. The geometry and connectedness of the pore microstructure of sea ice determine its fluid permeability, which depends strongly on temperature. Here we analyze a simple pipe network as a basis for modeling fluid flow through the complex porous microstructure, and for numerical approximations of the fluid permeability of sea ice as a function of temperature. For slow flow the fluid system is equivalent to an electrical resistor network, and the network is solved using a fast multi-grid method. The radii of the pipes in the network are chosen randomly from distributions describing measured cross-sectional areas of brine inclusions in sea ice. At this stage, the model reflects only the most general features of brine microstructure and its evolution with temperature. Preliminary results for a basic implementation in two dimensions are presented. They are consistent with theoretical bounds on the vertical fluid permeability of sea ice found recently. Moreover, the results agree roughly with laboratory data for higher porosities. For lower porosities and colder temperatures, the fully connected network of pipes in the model, albeit with smaller radii, overestimates observed values. This finding provides evidence that the brine network becomes more disconnected with lower temperatures, which is consistent with transitional behavior near a percolation threshold.

Microstructure and Electrochemical Behavior of Sm0.5Sr0.5CoO3 Deposited by Solution Precursor Plasma Spraying

2013 ◽  
Vol 683 ◽  
pp. 60-63
Author(s):  
Xiao Ming Wang ◽  
Le Yi Zhang ◽  
Ming Yan Chen ◽  
Lin Lin Wang
Keyword(s):  
Specific Surface ◽  
Plasma Spraying ◽  
Electrochemical Behavior ◽  
Surface Resistance ◽  
Electrochemical Measurement ◽  
Solid Oxide ◽  
Cross Sectional ◽  
Solution Precursor Plasma Spraying ◽  
Solution Precursor ◽  
Porous Microstructure

Solution precursor plasma spraying (SPPS) was employed to prepare porous Sm0.5Sr0.5CoO3 (SSC) cathode for solid oxide fuel cell (SOFC). The surface and cross-sectional morphology of the SSC deposit were characterized by scanning electron microscopy. The effect of annealing on SSPS SSC microstructure was examined. The electrochemical behavior was investigated through the impedance spectroscopy. The results showed that the SPPS SSC cathode exhibits multidimensional porous microstructure. The electrochemical measurement result showed that the specific surface resistance of SSC decreased significantly with the increase of test temperature and yielded a specific surface resistance of 2.6 Ω•cm2 at 800oC.

scholarly journals Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections

2021 ◽  
Vol 18 (21) ◽  
pp. 11080
Author(s):  
Mingjie Zhang ◽  
Zhi Gao ◽  
Xin Guo ◽  
Jialei Shen
Keyword(s):  
Wind Direction ◽  
Flow Characteristics ◽  
Volumetric Flow Rate ◽  
Pollutant Concentration ◽  
Canopy Layer ◽  
Cross Sectional ◽  
Significant Difference ◽  
Wall Zone ◽  
The Impact ◽  
Near Wall

To gain further insight into the ventilation at urban street intersections, this study conducted 3D simulations of the ventilation at right- and oblique-angled intersections under eight wind directions by using the Reynolds-averaged Navier–Stokes (RANS) κ-ε turbulence model. The divergent responses of ventilation and pollution concentration for the pedestrian zone (ped), the near-wall zone (nwz), and the canopy layer to the change in intersection typology and wind direction were investigated. The flow characteristics of the intersections, taken as the air flow hub, were explored by employing indices such as the minimum flow ratio (β) between horizontal openings. The results show that oblique wind directions lead to a lower total volumetric flow rate (Qtotal) but a higher β value for right-angled intersections. For T-shaped intersections, a larger cross-sectional area for the outflow helps to increase Qtotal. Oblique-angled intersections, for example, the X-shaped intersection, experience a more significant difference in Qtotal but a steady value of β when the wind direction changes. The vertical air-exchange rate for the intersection was particularly significant when the wind directions were parallel to the street orientation or when there was no opening in the inflow direction. The spatially averaged normalized pollutant concentration and age of air (τ*¯) for the pedestrian zone and the canopy layer showed similar changing trends for most of the cases, while in some cases, only the τped*¯ or τnwz*¯ changed obviously. These findings reveal the impact mechanism of intersection configuration on urban local ventilation and pollutant diffusion.

Pore-Scale Modeling of Waterflooding in Mixed-Wet-Rock Images: Effects of Initial Saturation and Wettability

SPE Journal ◽  
2013 ◽  
Vol 19 (01) ◽  
pp. 88-100 ◽  
Author(s):  
Y.. Zhou ◽  
J.O.. O. Helland ◽  
D.G.. G. Hatzignatiou
Keyword(s):  
Contact Angle ◽  
Capillary Pressure ◽  
Water Saturation ◽  
Solid Surfaces ◽  
Initial Water ◽  
Cross Sectional ◽  
Flow Rates ◽  
The Cross ◽  
Capillary Pressures ◽  
Saturation Profiles

Summary We simulate transient behavior of viscous- and capillary-dominated water invasion at mixed-wet conditions directly in scanning-electron-microscope (SEM) images of Bentheim sandstone by treating the pore spaces as cross sections of straight tubes. Initial conditions are established by drainage and wettability alteration. Constant rate or differential pressure is imposed along the tube bundle. The phase pressures vary with positions along the tube length but remain unique in each cross section, consistent with 1D core-scale models. This leads to a nonlinear system of equations that are solved for the interface positions as a function of time. The cross-sectional fluid configurations are computed accurately at any capillary pressure and wetting condition by a semianalytical model that is based on free-energy minimization. The fluid conductances are estimated by newly derived explicit expressions that are shown to be in agreement with numerical computations performed directly on the cross-sectional fluid configurations. An SEM image of Bentheim sandstone is taken as input to the developed model for simulating the evolution of saturation profiles during waterfloods for different flow rates and several mixed-wet conditions, which are established with various initial water saturations and contact angles. It is demonstrated that the simulated saturation profiles depend strongly on initial water saturation at mixed-wet conditions. The saturation profiles exhibit increasingly gradual behavior in time as the contact angle, defined on the oil-wet solid surfaces, increases or the initial water saturation decreases. Front menisci associated with positive capillary pressures promote oil displacement by water, whereas for large and negative capillary pressures at small flow rates, oil displaces water because the associated front menisci retract. This results in the development of pronounced gradual saturation fronts at mixed-wet conditions. The waterfloods simulated at conditions established with a large initial water saturation and small contact angle on the oil-wet solid surfaces exhibit sharp Buckley-Leverett saturation profiles for high flow rates because the capillary pressure is small and less important. The shape of the saturation profiles is interpreted on the basis of the simulated capillary pressure curves and the corresponding fluid configurations occurring in the rock image.

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