Reduction of oxygen to peroxide in a trickle electrode

1989 ◽  
Vol 54 (6) ◽  
pp. 1564-1574 ◽  
Author(s):  
Otomar Špalek ◽  
Karel Balogh
Keyword(s):  
Particle Size ◽  
Current Efficiency ◽  
Electrode Material ◽  
Pressure Loss ◽  
Peroxide Formation ◽  
Liquid Holdup ◽  
Electrolyte Flow ◽  
Electrode Thickness ◽  
Material Particle ◽  
Flow Rates

The effects of the electrode material particle size, electrode thickness, diaphragm properties and gas and electrolyte flow rates on the pressure loss and liquid holdup in the electrode and on the current efficiency of peroxide formation by oxygen reduction were studied in a trickle electrode. The results are discussed using trickle-bed electrode calculations.

scholarly journals The Influence of Structure on the Electrochemical and Thermal Response of Li-Ion Battery Electrodes

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Prehit Patel ◽  
George J. Nelson
Keyword(s):  
Particle Size ◽  
Heat Generation ◽  
Active Material ◽  
Thermal Response ◽  
Lithium Ion ◽  
Local Heat ◽  
Spherical Particles ◽  
Electrode Thickness ◽  
Material Particle ◽  
Fast Charging

Abstract Advancement of lithium-ion batteries for transportation applications requires addressing two key challenges: increasing energy density and providing fast charging capabilities. The first of these challenges can be met using thicker electrodes. However, the implementation of thick electrodes inherently presents a trade-off with respect to fast charging. As the thickness is increased, transport limitations reduce the ability of the battery to meet aggressive charge conditions. At the particle scale, interactions between solid diffusion and reaction kinetics influence the effective storage of lithium. At the electrode scale, diffusion limitations can lead to local variations in salt concentrations and electric potential. These short-range and long-range effects can combine to influence local current and heat generation. In the present work, a pseudo-2D lithium-ion battery model is applied to understand how active material particle size, porosity, and electrode thickness impact local field variables, current, heat generation, and cell capacity within a single-cell stack. The model was built assuming that the active particles are representative spherical particles. The governing equations and boundary conditions were set following the common Newman model. Cell response under varied combinations of charge and discharge cycling is assessed for rates of 1 C and 5 C. Aggressive charge and discharge conditions lead to locally elevated C-rates and attendant increases in local heat generation. These variations can be impacted in part by tailoring electrode structures. To this end, results for parametric studies of active material particle size, porosity, and electrode thickness are presented and discussed.

The Influence of Structure on the Electrochemical and Thermal Response of Li-Ion Battery Electrodes

2019 ◽  
Author(s):  
Prehit Patel ◽  
George J. Nelson
Keyword(s):  
Particle Size ◽  
Lithium Ion Battery ◽  
Heat Generation ◽  
Active Material ◽  
Lithium Ion ◽  
Spherical Particles ◽  
Electrode Thickness ◽  
Material Particle ◽  
Trade Off ◽  
Fast Charging

Abstract The continued advancement of lithium ion batteries for transportation applications requires addressing two key challenges: increasing energy density and providing fast charging capabilities. The first of these challenges can be met in part through the use of thicker electrodes, which reduce the electrochemically inactive mass of the cell. However, implementation of thick electrodes inherently presents a trade-off with respect to fast charging capabilities. As thickness is increased, transport limitations exert greater influence on battery performance and reduce the ability of the battery to meet aggressive charge conditions. This trade-off can manifest over multiple length scales. At the particle-scale, interactions between solid diffusion and reaction kinetics influence the effective storage of lithium within the active material. At the electrode scale, diffusion limitations can lead to local variations in salt concentrations and electric potential. These short-range and long-range effects can combine to influence local current and heat generation. In the present work, a pseudo-2D lithium ion battery model is applied to understand how active material particle size, porosity, and electrode thickness impact local field variables, current, heat generation, and cell capacity within a single cell stack. COMSOL Multiphysics 5.2 is used to implement the pseudo-2D model of a lithium ion battery consisting of a graphite negative electrode, polymer separator, and lithium transition metal oxide positive electrode. Lithium hexafluorophosphate (LiPF6) in 1:1 ethylene carbonate (EC) and diethylene carbonate (DEC) was used as the electrolyte. The model was built assuming that the active particles are representative spherical particles. The governing equations and boundary conditions were set following the common Newman model. Cell response under varied combinations of charge and discharge cycling is assessed for rates of 1C and 5C. Aggressive charge and discharge conditions lead to locally elevated C-rates and attendant increases in local heat generation. These variations can be impacted in part by tailoring electrode structures. To this end, results for parametric studies of active material particle size, porosity, and electrode thickness are presented and discussed.

Potential distribution in a trickle-bed electrode

1989 ◽  
Vol 54 (12) ◽  
pp. 3144-3153
Author(s):  
Otomar Špalek ◽  
Karel Balogh
Keyword(s):  
Hydrogen Peroxide ◽  
Particle Size ◽  
Electrode Potential ◽  
Potential Distribution ◽  
Graphite Particle ◽  
Current Yield ◽  
Electrolyte Flow ◽  
Flow Rates ◽  
Voltage Loss ◽  
Trickle Bed

The performance of trickle-bed electrodes of crushed graphites in oxygen reduction to hydrogen peroxide has been investigated. Results are presented for the effects of the current density, gas and electrolyte flow rates, pressure, and graphite particle size on the electrode potential, voltage loss in the electrode material, and current yield of the process.

The effect of two-phase flow regime on hydrodynamics and mass transfer in a horizontal-tube gas-liquid reactor

1985 ◽  
Vol 50 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Andreas Zahn ◽  
Lothar Ebner ◽  
Kurt Winkler ◽  
Jan Kratochvíl ◽  
Jindřich Zahradník
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Liquid Flow ◽  
Horizontal Tube ◽  
Liquid Holdup ◽  
Two Phase ◽  
Flow Rates ◽  
Type Relation ◽  
Good Agreement

The effect of two-phase flow regime on decisive hydrodynamic and mass transfer characteristics of horizontal-tube gas-liquid reactors (pressure drop, liquid holdup, kLaL) was determined in a cocurrent-flow experimental unit of the length 4.15 m and diameter 0.05 m with air-water system. An adjustable-height weir was installed in the separation chamber at the reactor outlet to simulate the effect of internal baffles on reactor hydrodynamics. Flow regime maps were developed in the whole range of experimental gas and liquid flow rates both for the weirless arrangement and for the weir height 0.05 m, the former being in good agreement with flow-pattern boundaries presented by Mandhane. In the whole range of experi-mental conditions pressure drop data could be well correlated as a function of gas and liquid flow rates by an empirical exponential-type relation with specific sets of coefficients obtained for individual flow regimes from experimental data. Good agreement was observed between values of pressure drop obtained for weirless arrangement and data calculated from the Lockhart-Martinelli correlation while the contribution of weir to the overall pressure drop was well described by a relation proposed for the pressure loss in closed-end tubes. In the region of negligible weir influence values of liquid holdup were again succesfully correlated by the Lockhart-Martinelli relation while the dependence of liquid holdup data on gas and liquid flow rates obtained under conditions of significant weir effect (i.e. at low flow rates of both phases) could be well described by an empirical exponential-type relation. Results of preliminary kLaL measurements confirmed the decisive effect of the rate of energy dissipation on the intensity of interfacial mass transfer in gas-liquid dispersions.

scholarly journals Leaching Behaviour of Construction and Demolition Wastes and Recycled Aggregates: Statistical Analysis Applied to the Release of Contaminants

2021 ◽  
Vol 11 (14) ◽  
pp. 6265
Author(s):  
Alessandra Diotti ◽  
Giovanni Plizzari ◽  
Sabrina Sorlini
Keyword(s):  
Particle Size ◽  
Statistical Analysis ◽  
Raw Materials ◽  
Primary Source ◽  
Recycled Aggregates ◽  
Critical Parameters ◽  
Material Particle ◽  
Analysis Methodology ◽  
Construction And Demolition Wastes ◽  
Leaching Behaviour

Construction and demolition wastes represent a primary source of new alternative materials which, if properly recovered, can be used to replace virgin raw materials partially or totally. The distrust of end-users in the use of recycled aggregates is mainly due to the environmental performance of these materials. In particular, the release of pollutants into the surrounding environment appears to be the aspect of greatest concern. This is because these materials are characterized by a strong heterogeneity which can sometimes lead to contaminant releases above the legal limits for recovery. In this context, an analysis of the leaching behaviour of both CDWs and RAs was conducted by applying a statistical analysis methodology. Subsequently, to evaluate the influence of the particle size and the volumetric reduction of the material on the release of contaminants, several experimental leaching tests were carried out according to the UNI EN 12457-2 and UNI EN 12457-4 standards. The results obtained show that chromium, mercury, and COD are the most critical parameters for both CDWs and RAs. Moreover, the material particle size generally affects the release of contaminants (i.e., finer particles showed higher releases), while the crushing process does not always involve higher releases than the sieving process.

149 Evaluation of Hammermill Tip Speed, Air Assist, and Screen Hole Diameter on Ground Corn Characteristics

2021 ◽  
Vol 99 (Supplement_1) ◽  
pp. 134-135
Author(s):  
Michaela B Braun ◽  
Kara M Dunmire ◽  
Michael Sodak ◽  
Jerry Shepherd ◽  
Randy Fisher ◽  
...  
Keyword(s):  
Particle Size ◽  
Geometric Mean ◽  
Air Flow ◽  
Hole Diameter ◽  
Experimental Unit ◽  
Flow Index ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Composite Flow ◽  
Ground Corn

Abstract This study was performed to evaluate hammermill tip speed, assistive airflow and screen hole diameter on hammermill throughput and characteristics of ground corn. Corn was ground using two Andritz hammermills (Model: 4330–6, Andritz Feed & Biofuel, Muncy,PA) measuring 1-m in diameter each equipped with 72 hammers and 300 HP motors. Treatments were arranged in a 3 × 3 × 3 factorial design with 3 tip speeds (3,774, 4,975, and 6,176 m/min), 3 screen hole diameters (2.3, 3.9 and 6.3 mm), and 3 air flow rates (1,062, 1,416, and 1,770 fan RPM). Corn was ground on 3 separate days to create 3 replications and treatments were randomized within day. Samples were collected and analyzed for moisture, particle size, and flowability characteristics. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with grinding run serving as the experimental unit and day serving as the block. There was a 3-way interaction for standard deviation (Sgw), (linear screen hole diameter × linear hammer tip speed × linear air flow, P = 0.029). There was a screen hole diameter × hammer tip speed interaction (P < 0.001) for geometric mean particle size dgw (P < 0.001) and composite flow index (CFI) (P < 0.001). When tip speed increased from 3,774 to 6,176 m/min the rate of decrease in dgw was greater as screen hole diameter increased from 2.3 to 6.3 mm resulting in a 67, 111, and 254 µm decrease in dgw for corn ground using the 2.3, 3.9, and 6.3 mm screen hole diameter, respectively. For CFI, increasing tip speed decreased the CFI of ground corn when ground using the 3.9 and 6.3 mm screen. However, when grinding corn using the 2.3 mm screen, there was no evidence of difference in CFI when increasing tip speed. In conclusion, the air flow rate did not influence dgw of corn but hammer tip speed and screen size were altered and achieved a range of dgw from 304 to 617 µm.

Influence of hydrodynamics of electrolyte flow during electrochemical treatment on the quality of the treated surface

2021 ◽  
pp. 55-60
Author(s):  
Keyword(s):  
Electrical Conductivity ◽  
Current Density ◽  
Electrochemical Treatment ◽  
Flow Lines ◽  
Electrolyte Flow ◽  
Flow Rates ◽  
Average Flow ◽  
Electrochemical Processing ◽  
Interelectrode Gap

The features of the hydrodynamics of the electrolyte in the interelectrode gap during electrochemical processing of a profile axisymmetric workpiece are considered. The distribution of average flow rates and flow lines is calculated for a specified electrolyte supply. The nature and rate of the electrolyte flow are established. The unevenness of the current density is determined taking into account the change in the electrical conductivity of the electrolyte from heating and gas filling of the interelectrode gap, as well as the quality of the treated surface. Keywords: electrochemical treatment, roughness, electrolyte, electrical conductivity, gas filling. [email protected]

Assessment of Lost Circulation Material Particle-Size Distribution on Fracture Sealing: A Numerical Study

2022 ◽  
pp. 1-15
Author(s):  
Lu Lee ◽  
Arash Dahi Taleghani
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Numerical Study ◽  
Fluid Loss ◽  
Material Particle ◽  
Lost Circulation ◽  
Fracture Sealing ◽  
Discrete Element Methods ◽  
Lost Circulation Materials

Summary Lost circulation materials (LCMs) are essential to combat fluid loss while drilling and may put the whole operation at risk if a proper LCM design is not used. The focus of this research is understanding the function of LCMs in sealing fractures to reduce fluid loss. One important consideration in the success of fracture sealing is the particle-size distribution (PSD) of LCMs. Various studies have suggested different guidelines for obtaining the best size distribution of LCMs for effective fracture sealing based on limited laboratory experiments or field observations. Hence, there is a need for sophisticated numerical methods to improve the LCM design by providing some predictive capabilities. In this study, computational fluid dynamics (CFD) and discrete element methods (DEM) numerical simulations are coupled to investigate the influence of PSD of granular LCMs on fracture sealing. Dimensionless variables were introduced to compare cases with different PSDs. We validated the CFD-DEM model in reproducing specific laboratory observations of fracture-sealing experiments within the model boundary parameters. Our simulations suggested that a bimodally distributed blend would be the most effective design in comparison to other PSDs tested here.

scholarly journals Effect of Material Particle Size on Reduction rate of Hematite and Quaternary Calcium Ferrite Mixtures

2013 ◽  
Vol 99 (6) ◽  
pp. 401-406 ◽  
Author(s):  
Daisuke Noguchi ◽  
Ryouta Ikezaki ◽  
Ko-Ichiro Ohno ◽  
Takayuki Maeda ◽  
Kouki Nishioka ◽  
...  
Keyword(s):  
Particle Size ◽  
Reduction Rate ◽  
Calcium Ferrite ◽  
Material Particle
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