Combustion of liquid and solid aerosols

Essenhigh, Robert H.; Fells, I.

doi:10.1039/df9603000208

Cited by 15 publications

(7 citation statements)

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“…If, therefore, we now concentrate solely upon the k2' term, what our fitting procedure has done is to correct the data for the k2 component, and it now allows us to treat the data as if the k2 term were very large-i.e., the low temperature resistance, St, is very small. But, under these circumstances, the original Equation 9 reduces to the familiar resistance approximation of Equation 10, which can be written in the alternative form: Rs = kipi/(\ + ki/k0) (for k2 large) (14) and this can now be compared with the empirically derived equation:…”

Section: Identificationmentioning

confidence: 99%

Combustion Behavior of Small Particles

Essenhigh¹,

Froberg²,

Howard³

1965

Ind. Eng. Chem.

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Recent work has confirmed the conclusions of Hottei and Stewart that the resistances to combustion of small particles in flames are due to the combined effects of diffusion and adsorption-not simply to diffusion atone. The reexamination of the classic data of Hottei, Tu, and Davis in the light of more advanced theory has established that adsorption controls the combustion of particles under 100 microns in diameter. The theory of one of the more important processes of our time-the combustion of carbon-is thus made consistent with experimental observation to an extent not previously known, permitting more confident design of combustion apparatus Despite intense research on the combustion of carbon in the last 30 years, the classic experiments of Tu, Davis, and Hottei (41) on 1-inch spheres are still the most widely quoted. The theory of carbon combustion has advanced in several particulars since then (13,15,39,42) and it has long been known that the original Tu theoretical analysis was inadequate. In the original analysis, only desorption and boundary layer diffusion were considered as possible rate-controlling steps in the reaction; chemisorption and internal reaction were neglected. At the time of writing, these two latter concepts had not been formulated, or not generally accepted. There was also a bias against considering adsorption, which was always assumed to be, effectively, instantaneous.According to Brunauer (9), the concept of activated adsorption was first formulated in the early 1930's-about the time of writing of the Tu paper, or soon after-but, even a decade later, it still had not been generally accepted, with the consequence that many true chemisorption processes even then were being incorrectly interpreted in terms of solution, diffusion, migration (mobile adsorption), or reaction at the solid surface itself (9). Analysis of the internal reaction processes came even later and has been developed only in the last decade or so.

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Section: Identificationmentioning

confidence: 99%

Combustion Behavior of Small Particles

Essenhigh¹,

Froberg²,

Howard³

1965

Ind. Eng. Chem.

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“…Equation B-l has been depicted in their papers, which can be approximated by the straight line shown in eq 15. Although eq 15 and 16 appear to conflict mathematically with each other, eq 15 is very simple to use for further derivations, and the numerical confirmation was also made as to = 1 -|2, which does not conflict theoretically with eq 16 (Essenhigh and Fells, 1960). Further mathematical development becomes tedious in the latter, but the final results were not affected entirely by whether = 1 -or = 1 -|2.…”

Section: Appendix Bmentioning

confidence: 86%

“…Assuming that the rate of combustion of a particle is controlled by the diffusion of oxygen, it is reported Kunii, 1953,1955) that { ), the particle size at time , ignited at = 0, is approximately related to (see Ap- where Dp0 is the particle size at = 0 and is the time needed for complete combustion of a single particle, which takes the same form as that of a liquid droplet, as originally expressed by Essenhigh and Fells (1960…”

Section: Combustion Of Dust Particlesmentioning

confidence: 99%

“…where KD is called the burning constant. According to Essenhigh and Fells (1960), it takes about 2000 s/cm2 for solid on the average. Then the mass of one particle burnt at time , ( ), is geometrically expressed by using eq 15 m(9) = mQ\ 1where m0 = ^p03Ps Hence, after igniting at the center of the vessel at time t = 0, M(t), the total mass of particles burnt until the time, i, when the flame propagates up to the nth spherical surface, is obtained by summation of the mass of particles burnt on each spherical surface in Figure 2 M(t) =m0¿Mi)[l-…”

Section: Combustion Of Dust Particlesmentioning

confidence: 99%

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Prediction of Maximum Rate of Pressure Rise Due to Dust Explosion in Closed Spherical and Nonspherical Vessels

Nomura¹,

Tanaka²

1980

Ind. Eng. Chem. Proc. Des. Dev.

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“…On the other hand, when q 1 is more than q 2 , the reaction of combustion makes continuous progress. A steady state can be kept only on the conditions ofq1 =q2 anddq1/dTs =dq2/dT 8 …”

Section: Prediction Of Ignition Temperaturementioning

confidence: 99%

Theoretical Approach to Dust Explosion

Tanaka

1983

KONA

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A number of experimental researches on dust explosion have been published with measured data of the explosive characteristics such as the ignition temperature, the flame propagation velocity, the upper and lower limit explosible concentrations and the rate of pressure rise.In this study the above-mentioned explosive characteristics are dealt with systematically based on a simple model of uniformly dispersed dust cloud consisting of particles of the same size, from the viewpoint of heat transfer process.Comparing the computed results with the empirical law and the experimental data, it is assured that the explosive characteristics can be predicted theoretically. In addition, the analysis of the area for the pressure relief venting is conducted to minimize the damage, leading to a new dimensionless vent ratio. Prediction of ignition temperaturethe heat emitting from the solid surface into the atmosphere by convection q 2 are taken on the ordinate. When q 1 is less than q 2 , the reaction is always kept at the level of oxidation. On the other hand, when q 1 is more than q 2 , the reaction of combustion makes continuous progress. A steady state can be kept only on the conditions ofq1 =q2 anddq1/dTs =dq2/dT 8 •The reading of the horizontal axis T (surrounding temperature) on this condition is experimentally defined as the ignition temperature. 1 Definition of ignition temperature')The ignition temperature is defined as the gas temperature at which a mass of particles begin to burn, when they are heated in an oven with a certain shape and size. It has been measured with a great number of materials. In Fig. 1, the surface temperature of solid T 8 is displayed on the abscissa and the heat of reaction q 1 and The reaction rate of oxidation of a single spherical particle with a diameter of Dp is given by Hottel eta!. s) as follows:where m is mass of the particle, t time, ks rate constant of reaction, E activation energy and Cg concentration of oxygen. The number of the particles n in the dust cloud with a diameter land the dust concentration Cd isfor the particle of a density Ps· The generated heat G in the lump of the particles and the emitted heat U from them are calculated in the KONA No.1 (1983)

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Combustion of liquid and solid aerosols

Cited by 15 publications

References 4 publications

Combustion Behavior of Small Particles

Combustion Behavior of Small Particles

Prediction of Maximum Rate of Pressure Rise Due to Dust Explosion in Closed Spherical and Nonspherical Vessels

Theoretical Approach to Dust Explosion

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