The Influence of Coal Rank on the Burning Times of Single Captive Particles

1963 ◽  
Vol 85 (3) ◽  
pp. 183-188 ◽  
Author(s):  
R. H. Essenhigh
Keyword(s):  
Burning Rate ◽  
Particle Diameter ◽  
Porous Matrix ◽  
Coal Rank ◽  
Fixed Carbon ◽  
Initial Particle ◽  
Proportionality Constant ◽  
Coal Particles ◽  
Rank Dependence ◽  
Experimental Values

Measurements of volatile and residue burning times of captive coal particles have shown them to vary in proportion to the square of the initial particle diameter; this was true for each of 10 coals tested. For the volatiles, the measured constant of proportionality was found to be independent of coal rank when allowance was made for swelling, the burning rate apparently being controlled by the diffusional rate of volatile escape through a porous matrix of fixed carbon. For the residues, the experimental “square-law” relation confirms Nusselt’s prediction; and agreement between predicted and experimental values of the proportionality constant was found to be good. An apparent rank dependence, showing shorter burning times with less fixed carbon, was simply a consequence of there being less fixed carbon to burn. There was no influence of rank-dependent “reactivity.” The relevance of the results to flames is also discussed.

Development of a High Pressure Dry Coal Feed System for a 100 kWt Oxy-Coal Reactor

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Taylor Schroedter ◽  
Bradley R. Adams ◽  
Jacob Tuia ◽  
Andrew Fry
Keyword(s):  
Particle Diameter ◽  
Flow Ratio ◽  
Feed System ◽  
Horizontal Pipe ◽  
Bench Scale ◽  
Coal Particles ◽  
Simplifying Assumptions ◽  
Coal Flow ◽  
Co2 Flow ◽  
Burner Operation

Abstract A design concept to feed dry coal from a hopper to a 100 kWt pressurized oxy-coal (POC) reactor using CO2 at 2 MPa was developed using transient computational fluid dynamics (CFD) simulations and bench-scale measurements. The feed system was required to maintain a steady flow of gas and solids at a coal flowrate of approximately 3.8 g/s and a CO2-to-coal mass ratio in the range 1–2. A 5.08-cm diameter vertical coal hopper feeding into a 0.635-cm diameter horizontal pipe was used to represent key elements of the feed system. A fluidized bed concept was found capable of providing the desired coal flowrate and CO2-to-coal flow ratio. Use of separate fluidization and dilution flows allowed the coal flowrate and CO2-to-coal flow ratio to be controlled independently. The amount of coal transported from the hopper was dependent on the net CO2 flow in the hopper but independent of the CO2 dilution flow. Pipe exit coal flowrates were found to fluctuate at levels acceptable for steady burner operation. Tests from a bench-scale apparatus using Pittsburgh 8 coal with a median particle diameter of 50 µm and moisture content of 6% confirmed the feasibility of the fluidization design. However, for a given CO2 fluidization flowrate, experimental coal flowrates were lower than predicted coal flow, in part due to simplifying assumptions of dry, spherical coal particles and smooth piping in the simulations.

Melting Behavior of In-Flight Particles and Its Effects on Splat Morphology in Plasma Spraying

2002 ◽  
Author(s):  
H. Zhang ◽  
H. B. Xiong ◽  
L. L. Zheng ◽  
A. Vaidya ◽  
L. Li ◽  
...  
Keyword(s):  
Particle Size ◽  
Numerical Simulations ◽  
Plasma Spraying ◽  
Particle Diameter ◽  
Deposition Efficiency ◽  
Melting Behavior ◽  
Splat Morphology ◽  
Initial Particle ◽  
Unknown Parameters ◽  
Group Parameter

Effects of particle size, velocity, and temperature on the splat morphology have been well studied in the open literature. Effects of melt fraction on deposition efficiency and splat morphology are, however, not well understood. In this paper, we will focus on the melting behavior of in-flight particles and their impact on splat morphologies. A group parameter, “melting index”, has been derived to correlate the melting status of in-flight particles with particle size, velocity, and temperature which can be measured experimentally. Numerical simulations have been used to determine the unknown parameters in the melting index. The effects of initial particle diameter on the melting behavior have also been investigated.

Field Controlled Charge and Heat Transfer Involving Macroscopic Charged Particles in Liquids

1975 ◽  
Vol 97 (3) ◽  
pp. 429-434 ◽  
Author(s):  
P. W. Dietz ◽  
J. R. Melcher
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Charged Particles ◽  
Particle Diameter ◽  
Particle Migration ◽  
Electrically Conducting ◽  
Fluid Convection ◽  
Experimental Values ◽  
Insulating Liquid ◽  
Parallel Electrode

When an electric field is applied to a system of electrically conducting particles in an insulating liquid, the rates of charge and heat transfer are augmented. Charged during collisions in the field, the particles execute field-induced excursions between the electrodes interrupted by collisions with other particles. Thus a combination of particle migration and particle-induced fluid convection results in the increase in heat transfer. Experimental values for the Nusselt number are obtained for heat transfer across the parallel electrode configuration. The model developed using these results consists of a well-mixed central region with thermal boundary layers about one particle diameter thick near each electrode.

Studies on Coal Ignition and Combustion Characteristics

2017 ◽  
Author(s):  
Xue Chen ◽  
MingYan Gu ◽  
XianHui He ◽  
Dan Yan ◽  
Jimin Wang ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Coal Particle ◽  
Gas Flow ◽  
Ignition Time ◽  
Particle Diameter ◽  
Combustion Characteristics ◽  
Gas Temperature ◽  
Flow Temperature ◽  
Particle Ignition ◽  
Coal Particles

A 2-D numerical model of flow, heat transfer, and combustion of coal particles in a laminar gas flow at O2/CO2 atmosphere was developed based on the Eulerian-Lagrangian methodology. The gas-phase combustion was modeled using the GRI-Mech 3.0. The motion of coal particles was simulated using a trajectory model. The model was employed to study the coal ignition time, temperature and mass changes. The effects of particle diameter, the flow temperature and oxygen concentration on the ignition time and the combustion characteristics of coal particles were also investigated. The results obtained show that smaller size particle experiences a shorter ignition time with a higher coal temperature. A higher gas temperature leads to a shorter coal particle ignition time; increasing the flow temperature the difference in the ignition time of different sized coal particles decreases. The coal particle ignition time is decreased when the oxygen concentration is increased.

scholarly journals Numerical investigation of ibuprofen removal from pharmaceutical wastewater using adsorption process

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yan Cao ◽  
Ali Taghvaie Nakhjiri ◽  
Mahdi Ghadiri
Keyword(s):  
Diffusion Coefficient ◽  
Activated Carbon ◽  
Adsorption Process ◽  
Negative Impact ◽  
Particle Diameter ◽  
Considerable Change ◽  
The Finite Element Method ◽  
Pharmaceutical Wastewater ◽  
Experimental Values ◽  
Function Time

AbstractIn the present study, a mathematical modelling was developed to investigate ibuprofen adsorption from pharmaceutical wastewater into activated carbon and sonicated activated carbon. The developed model was dissolved based on the finite element method. Effect of different operating parameters including particle porosity and diameter as well as ibuprofen diffusion coefficient in solution on the amount of ibuprofen adsorption at different time point and position in the particle were evaluated. It was found good agreement between experimental values and modelling results in terms of ibuprofen adsorption as a function time. The 84.5% and 92.5% of maximum adsorption was achieved for the AC and SAC at the centre of particle after 150 min. Increasing the particle porosity and ibuprofen diffusion coefficient was improved the ibuprofen adsorption into the adsorbent. However, the particle diameter had negative impact on the system performance. There was a decrease in solute adsorption from 84.10 to 7.30 mg/g and from 106 to 15.73 mg/g for the AC and SAC respectively with increasing the particle radius from 173 to 500 µm. Finally, it was concluded that the particle specifications play important role in the adsorption process as it was observed considerable change in the amount of adsorption at different positions in the particle with changing the particle specifications.

Direct measurement of the coating thickness on spherical particles

1994 ◽  
Vol 52 ◽  
pp. 904-905
Author(s):  
U. Admon ◽  
K. Coakley ◽  
M. P. Dariel ◽  
A. A. Giuseppetti ◽  
C. Hagwood ◽  
...  
Keyword(s):  
Cross Sections ◽  
Coating Thickness ◽  
Size Range ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Initial Particle ◽  
Initial Particle Size ◽  
Powder Particles ◽  
Third Dimension ◽  
Spacing Measurement

In the course of the development of an coating process of metallic powders, the dependence of the coated layer thickness on the process variables and on the initial particle size had to be determined. The initial, atomized powder particles in the 5-80 μm size range, were perfect spheres to a good approximation.We chose to employ a “particulate” approach according to which individual powder particles were repeatedly cross-sectioned and examined at known intervals, sufficiently close to allow the same spheres to be cross-cut more than once. Micrographs of selected particles were taken at each stage. Simple chord measurements taken from the micrographs, which provide two-dimensional information, and the measured spacing between the corresponding cross-sections, giving the third dimension, allows to calculate both the particle diameter and the coating thickness. The accuracy of the results depends critically on the accuracy of the spacing measurement. The present communication describes a simple, practical, and precise method for this measurement, eliminating the necessity for precision alignment and dedicated tools.

Effect of the particle diameter of the chemical foaming agent on the foaming process and the cellular structure of one-shot compression molded polyethylene foams

2018 ◽  
Vol 38 (1) ◽  
pp. 41-50 ◽  
Author(s):  
Junichiro Tateishi ◽  
Tsuyoshi Nishiwaki ◽  
Sathish K. Sukumaran ◽  
Masataka Sugimoto
Keyword(s):  
Thermal Decomposition ◽  
Time Dependence ◽  
Cellular Structure ◽  
Particle Diameter ◽  
Cavity Pressure ◽  
Number Density ◽  
Foaming Agent ◽  
Proportionality Constant ◽  
Foaming Process ◽  
Chemical Foaming

Abstract We investigated the effect of varying the particle diameter and the particle content of a chemical foaming agent on the foaming process and the cellular structure of one-shot compression molded polyethylene foams. We foamed metallocene linear low-density polyethylene (LLDPE) crosslinked by dicumyl peroxide using azodicarbonamide (ADCA) as the foaming agent. We used a purpose-built metal mold equipped with a built-in pressure sensor to monitor the time evolution of the cavity pressure. The time dependence of the cavity pressure, which is indicative of the thermal decomposition of the ADCA, was s-shaped. The s-shaped time dependence of the cavity pressure indicates that, after an initial induction phase during which there is no thermal decomposition of the ADCA, the ADCA rapidly decomposes until the reaction is essentially complete. The cavity pressure at saturation, which corresponds to the mass of the generated gas, was linearly proportional to the ADCA content but only weakly dependent on the particle diameter of the ADCA. Upon decreasing the particle diameter of ADCA, rise in the cavity pressure at intermediate times, which indicates the thermal decomposition of the ADCA, began earlier and was faster. The cell size in the final foam decreased with a decrease in the particle diameter of the ADCA. The cell number density in the unfoamed samples (NF) was proportional to the ADCA particle number density in the unfoamed samples (NC), with a proportionality constant less than 1. A model for the foaming process where the ADCA particles nucleate cells and the nucleated cells then coalesce, thereby reducing the number of remaining cells, can offer an explanation for the observed proportionality between NF and NC and the proportionality constant being less than 1. Furthermore, it is proposed that cell coalescence occurs if the increase in the moduli of the LLDPE due to crosslinking is not sufficient to prevent the coalescence of the cells triggered by the rapid increase in the cavity pressure due to the rapid decomposition of ADCA.

scholarly journals Obtaining and characterizing microemulsion systems containing Alkali-Surfactant-Polymer (ASP) for advanced oil recovery application

2021 ◽  
Vol 10 (5) ◽  
pp. e33010514807
Author(s):  
Helton Gomes Alves ◽  
Gregory Vinicius Bezerra de Oliveira ◽  
Flávia Freitas Viana ◽  
Marcos Allyson Felipe Rodrigues ◽  
Afonso Avelino Dantas Neto ◽  
...  
Keyword(s):  
Surface Tension ◽  
Oil Recovery ◽  
Rheological Behavior ◽  
Particle Diameter ◽  
Coconut Oil ◽  
Micellar Aggregates ◽  
Droplet Sizes ◽  
Slight Elevation ◽  
Polymeric Solutions ◽  
Experimental Values

Fluids in terms of rheological behavior can be classified into Newtonians and non-Newtonians. Newtonians are fluids that have unique and absolute viscosities, because the ratio between shear stress and shear rate is constant. In the oil industry, most fluids, such as microemulsions, oil and polymeric solutions, do not exhibit Newtonian behavior. To understand the behavior of chemical fluids, it is necessary to analyze some parameters to interpret their properties and applicability. In this context, the present work aims to obtain and characterize microemulsion systems containing Alkali, Surfactant, and Polymer, and verify their applicability in advanced oil recovery. Thus, we obtained five microemulsion systems consisting of saponified coconut oil (surfactant), Butan-1-ol (co-surfactant), kerosene (oil phase), Na2CO3 (alkali), water and different percentages of the polymer. The systems were characterized by analyzes of particle diameter, surface tension, viscosity and rheological behavior using mathematical models. Droplet sizes showed characteristic values of micellar aggregates. Surface tension presented a slight elevation when the percentage of polymer in the microemulsion increased. Through the rheological study, it was possible to observe that experimental values were better adjusted to the Ostwald-de Waele “power-law” model. As the percentage of polymer in the system increased, we calculated the apparent viscosity of the systems and observed an increasing change in viscosity values, a result of great interest to enhanced oil recovery studies.

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