flammability of coal dust-air mixtures

lean limits, flame temperatures, ignition energies, and particle size effects
  • 70 Pages
  • 3.36 MB
  • 8806 Downloads
  • English
by
Dept. of the Interior, Bureau of Mines , [Washington]
Coal, Pulverized., Dust explosions., Coal mines and mining -- Dust con
Statementby Martin Hertzberg, Kenneth L. Cashdollar, and John J. Opferman.
SeriesReport of investigations - Bureau of Mines ;, 8360
ContributionsCashdollar, Kenneth L., joint author., Opferman, John J., joint author., United States. Bureau of Mines.
Classifications
LC ClassificationsTP325 .H4 1979
The Physical Object
Pagination70 p. :
ID Numbers
Open LibraryOL2818592M
LC Control Number83603535

The flammability of coal dust-air mixtures: Lean limits, flame temperatures, ignition energies, and particle size effects [Hertzberg, Martin] on *FREE* shipping on qualifying offers. The flammability of coal dust-air mixtures: Lean limits, flame temperatures, ignition energies, and particle size effectsAuthor: Martin Hertzberg.

Flammability of coal dust-air mixtures. [Washington]: Dept. of the Interior, Bureau of Mines, (OCoLC) Online version: Hertzberg, Martin. Flammability of coal dust-air mixtures.

[Washington]: Dept. of the Interior, Bureau of Mines, (OCoLC) Material Type: Government publication, National government publication. The present paper is a progress report on a comprehensive study of upper flammability limits of coal dust-air mixtures. The study was undertaken in the context of safety in pneumatic conveying systems.

An improved 8-liter combustion chamber was designed which allows dispersal of combustible particles up to concentrations around 5 kg/kg by: 8. The flammability of coal dust-air mixtures: lean limits, flame temperatures, ignition energies, and particle size effects / By Martin. Hertzberg, John J.

Opferman and Kenneth L. Cashdollar. Abstract. Item es bibliographical references (p. ).Mode of access: Internet. The present paper is a progress report on a comprehensive study of upper flammability limits of coal dust-air mixtures. The study was undertaken in the context of safety in pneumatic conveying.

flammability of coal dust/gas/air mixtures. The oxides of nitrogen or NO x radicals have influence upon the lean limits of flammability of hybrid mixtures and this is illustrated by use of three dimensional coordinate geometry.

Details flammability of coal dust-air mixtures FB2

Gases can be introduced to the underground environment through the exhaust gases of diesel equipment. A comprehensive study of the flammability behavior of air-dispersed coal dust was made using an 8-liter Bureau of Mines system which included the following: (1) an optical probe to continuously flammability of coal dust-air mixtures book the dust concentration; (2) measurements of ignition energy requirements; (3) the use of several narrow size distributions ranging from 3 to 65 um average diameter; (4) measurements of the.

At lower ignition energies, the curves have finite negative slopes, and it is only the ignitability of the mixture that is being measured. Clearly an electric spark discharge in the to joule range, which is adequate for lean methane- air, is not adequate for a lean coal dust-air mixture.

The coal dust/air mixture was ignited by a pocket exploding methane/air mixture. Results show that the maximum flame speeds of the explosion were m/s, and m/s in the long tube with m diameter and m at the dust concentration of g/m 3 and g/m 3 respectively.

This research program was a theoretical and experimental study of laminar flame propagation in pure methane air and coal dust air mixtures, flammability of coal dust-air mixtures book in such mixtures containing suppressant additives. The flames studied included methane air, coal dust air, coal dust air with size, volatiles content and concentration as variables, and coal dust air plus khco3, kno3, kbr, nacl, or caco3.

The apparent lean flammability limit of the coal dust-air mixtures was observed to decrease with increasing ignition energy. The decrease was rapid at low energies, with an approach to an.

The results obtained in the overall study carried out to characterize the explosion and flammability conditions of cork dust/air mixtures (Pilão, ; Pilão et al., a, Pilão et al., b, Pilão et al., ) have shown that the explosion of cork dust follows the propagation flame mechanism proposed by Hertzberg, Cashdollar, Ng and Conti ().

There is experimental evidence that coal dust/air mixtures do have a lower explosive limit (i.e., that concen- tration of coal in air below which an explosion does not occur), but do not have an upper explosive limit as long as the coal/ air mixture can be considered a cloud.

In practice, a fire occurring during normal pulverizer. Hybrid mixtures Flammable gas and combustible dust May each be present in concentrations less than their individual LFL (gas) and MEC (dust), and still be explosible Result in increased explosion severity and likelihood Examples Methane gas and coal dust Natural gas.

Nagy et al. () investigated the ignition behaviors of gas/coal dust mixtures and found that a gas/coal dust mixture was easier to ignite than either gas or coal dust.

Bartknecht () studied the explosion behavior of methane/coal dust mixtures and found that a small amount of methane could induce a significant increase in the explosion. Flammability of Dust Clouds The ignition and propagation of flame in a dust cloud depend on a number of factors such as dust concentration, the composition of the dust and moisture content, particle size and shape, and turbulence in the system.

These factors not only determine the severity of the explosion but also influence the type and degree of precautions which it may be necessary and. Explosion pressure rate rise (dp/dt) experiments for coal dust and methane-coal dust-air hybrid mixtures in a modified 20 L explosion apparatus were conducted to provide data on explosion.

Flammability, pulverized bituminous coal dust, limestone mixture, Flammability limits, 5 coal dust/limestone mixtures, effect of varying dust concentration, gaseous mixtures, initial temperature and pressure effect, lean limit concentration, 21 particle size effect, Flammable mixtures, CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): An investigation into different aspects of importance in the understanding of explosibility of hybrid mixtures of coal dust, air and gases potentially found within mine workings through a comprehensive laboratory program of explosibility tests was conducted.

Plotting of test results revealed that conditions of. Potentially Explosive Atmospheres, Explosion Prevention and Protection, Determination of Minimum Ignition Energy of Dust/air Mixtures, European Standard EN Jan CEN, The experimental system of 10 m3 large-scale multiphase combustion explosion tank was used for research into the explosion development process under the ignition conditions of methane-coal dust-air mixture, and the overpressure development processes of the mixture at different distances were obtained.

For the methane-coal dust-air mixture with an equivalence ratio of 1, the explosion.

Description flammability of coal dust-air mixtures EPUB

The limiting oxygen concentration (LOC) of flammable dust/air mixtures is usually determined in time consuming and expensive experiments. However, when using an assumption for the flame. Flammability or Explosive Limits of coal dust  It is defined as its ability of coal dust, when in the form of a cloud, to spread or propagate ignition to all points where dust- air mixtures of corresponding concentration are present.

 The range of flammable limits or explosive limits is very wide, much wider than in the case of firedamp mixture. Flammable Properties Dust/air mixtures may ignite or explode. During fire conditions, vapors and decomposition products may be released, forming flammable/explosive mixtures in air.

Contact with heat may generate toxic and/or flammable gases. Sensitivity to Mechanical Impact Not available Sensitivity to Static Discharge Not available. [Note: The Mine Safety and Health Administration (MSHA) PEL for respirable coal mine dust with 5% silica is mg/m³, or (10 mg/m³) / (% respirable quartz + 2) for coal dust with > 5% silica.] See Appendix G.

In addition to laboratory testing the acceleration of flames in coal dust/air mixtures has been investigated in an experimental mine. These have shown that flame velocities can attain values on the order of hundreds of meter meters per second.

The transition from deflagration to detonation has also been observed in the experimental mixtures. “Explosion Characteristics of H2/CH4/Air and CH4/Coal Dust/Air Mixtures” This paper presents interesting data related to gas and dust explosion in coal mines.

Although previous literature has shown enhanced effects from methane gas addition to coal dust, the effect of the hydrogen content of the coal is worthwhile to consider.

A triangular flammability diagram is the most useful tool to display the flammability region, and to determine if a flammable mixture is present during plant operations.

This paper describes how to draw and use a flammability diagram. A procedure to estimate the flammability region using the available and sometimes limited data is discussed. Clearly, steady-state combustible coal and air mixtures are fuel rich, as discussed in Refs.

[ 1- 3].

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An analysis to predict the (adiabatic, laminar flow) propagation of coal dust flames must also model rich mixtures. All one-dimensional, laminar flame propaga- tion models for coal dust and air mixtures have. The flammability or explosibility of coal dust-air mixtures had been the subject of many investigations carried out in.

Laboratories Surface experimental galleries and Experimental coal mines. The experimental work was centered around the Origin Propagation and Control of coal dust explosions.

This paper is an overview of and introduction to the subject of dust explosions. The purpose is to provide information on the explosibility and ignitability properties of dust clouds that can be used to improve safety in industries that generate, process, use, or transport combustible dusts.

The requirements for a dust explosion are: a combustible dust, dispersed in air, a concentration above.The effects of two processes used to treat coal on the flammability characteristics of the coal are presented.

Experiments were conducted on an Entrained Dust Flow Facility which supports a stationary premixed coal dust and air flame.

Flame speeds of the coal and air mixtures were determined based on the inlet velocity of the flow and the.Characteristics of Dust Explosions When a mass of solid flammable material is heated it burns away slowly owing to the limited surface area exposed to the oxygen of the air.

The energy produced is liberated gradually and harmlessly because it is dissipated as quickly as it is released. The result is quite different if the same mass of material is ground to a fine powder and intimately mixed.