14 research outputs found
A simple photoacoustic method for the in situ study of soot distribution in flames
This paper presents a simple photoacoustic technique capable of quantifying soot volume fraction across a range of flame conditions. The output of a high-power (30 W) 808-nm cw-diode laser was modulated in order to generate an acoustic pressure wave via laser heating of soot within the flame. The generated pressure wave was detected using a micro-electro-mechanical microphone mounted close to a porous-plug flat-flame burner. Measurements were taken using the photoacoustic technique in flames of three different equivalence ratios and were compared to laser-induced incandescence. The results presented here show good agreement between the two techniques and show the potential of the photoacoustic method as a way to measure soot volume fraction profiles in this type of flame. We discuss the potential to implement this technique with much lower laser power than was used in the experiments presented here
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Electrostatic Beneficiation of Coal. Quarterly Technical Progress Report, April 1, 1996--June 30, 1996
Progress reports are presented for the following: modification to the electrostatic separator; review of DOE specifications for minimum beneficiation and calculations of grinding requirements based on washability; two-pass beneficiation; analysis of different sieve fractions; measurement of charge to mass ratio as a function of height of deposition; and charging of coal against different materials
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Electrostatic Beneficiation of Coal. Quarterly Technical Progress Report, October 1, 1996--December 31, 1996
From previous study, we know that oxidation of the coal surface will decrease the efficiency of electrostatic beneficiation by increasing the negative charge of the carbon particles. The polarity and magnitude of charge acquired by the nonconducting particles varied depending on the state of ``oxidation`` of the surfaces and the work function relative to the metal surface. The formation of oxide layer on the coal particles are rather rapid, therefore, the grinding and charging processes are needed to be carried out in a nitrogen or argon atmosphere. It is clear that impaction efficiency between coal particle and charger will decrease with decreasing particle size and particle velocity. So, it is necessary to charge small particles in a different process. We plan to size classify the coal particles into three size fractions: (1)fine (<40{mu}m). (2) medium (40{approximately}100{mu}m). (3) coarse (100{approximately}200{mu}m). Static mixer and a new designed charger (powder pump connected with a circular tubing) are used in the experiment. And we planned to measure the charge to mass ratio distributions as a function of the particle size distribution on the separator plates. This report discusses the following: determination of the charge to mass ratio distributions as a function of particle size distribution; and method to measure the mass, charge and size of the particle
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Electrostatic Beneficiation of Coal
It was suggested in the proposal that small particles, due to low inertia, may not impact on the surfaces of the tribocharger. They would, thus, not receive charge and would not be beneficiated in the electrostatic separation. A milling process was proposed in which the small particles are stirred together with larger carrier beads producing the desired contact charge exchange. A force is necessary for removing the coal particles from the carrier beads. In copying machines electrostatic force is used to pull toner particles away horn iron carrier particles which are held back by magnetic force. Aerodynamic force is used in test instruments for measuring the charge to mass ratio on toners. A similar system of milling and removal is desired for use with the small coal particles. The carrier beads need to be made of copper rather than iron. This complicates the separation process since copper is non-magnetic. We are working on coating of iron beads with a layer of copper. Dr. Robert Engleken of Arkansas State University has supplied us with several test batches of copper-coated iron in the size range of -40 +70 mesh. ` We are currently testing whether the milling process used with the copper coated iron beads produces the desired charge on the coal particles
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Electrostatic Beneficiation of Coal. Quarterly Technical Progress Report, July 1, 1996--September 30, 1996
Progress reports are presented for the following tasks: single particle measurement of size and charge; electrodynamic balance for trapping single particles for measurement; and tribocharging of coal particles passed through a circular tube
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Electrostatic Beneficiation of Coal. Quarterly Technical Progress Report, January 1--March 31, 1996
Two methods of examining the decay rate of charge on powders deposited on the separator plates were examined. In the first method the charge transferred from ground to the separator plate was measured directly with an electrometer after completion of the powder deposition and after turning off the electric field. In a second method an electrostatic field meter (Trek model 354A) was used to measure the field due to the charge on the plates or on thin Teflon or aluminum plates which had been placed over the metal separator plates. In addition the paper discusses the fabrication and use of a resistivity cell for coal powder; charging of small particles by milling; observations with silica gel; and a review of articles on particle charging. A separate section presents the electrostatic charging properties of coal macerals
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Electrostatic Beneficiation of Coal. Quarterly Technical Progress Report, July 1--September 30, 1995
The report discusses the progress made during the eighth quarter on the following tasks: assessing beneficiation (sulfur vs. ash); effect of weathering on charging and separation; charge measurement with E-SPART analyzer; particle measurement using image processing; and petrographic analysis. Some experimental data are included