Dust Cloud Concentration Research Articles

Dust cloud combustion characterization of a mixture of LiBH4 destabilized with MgH2 for reversible H2 storage in mobile applications

This study discusses results of an experimental program to determine dust cloud combustion characteristics of 2LiBH4 + MgH2 binary system in air. The determined parameters of hydrided and partially-dehydrided states of this system include: maximum deflagration pressure rise (PMAX), maximum rate of pressure rise (dP/dt)MAX, minimum ignition temperature (TC), minimum explosible concentration (MEC), minimum ignition energy (MIE), and explosion severity index (KSt). Impact of dust particle size on the measured parameters is evaluated for the partially-dehydrided state. For dust of same mean particle size, results show the hydrided state to be more explosible in air compared to its partially-dehydrided state. Moreover, MIE of the partially-dehydrided mixture is identified in the test with lowest ignition delay time (IDT) and highest dust cloud concentration (DC). Taguchi's mixed-levels design of experiments (DoE) methodology is employed to calculate dust's MIE response surface as a function of DC and IDT. The one-at-a-time effect and interaction effect between DC and IDT on dust MIE are determined. The core insights of this contribution are useful for quantifying risks in mobile and stationary H2 storage applications, informing H2 safety standards, and augmenting property databases of H2 storage materials.

Overall characterization of cork dust explosion

Explosibility and ignitability studies of air/cork dust mixtures were conducted in a near-spherical 22.7 L explosibility test chamber using pyrotechnic ignitors and in a furnace of 1.23 L. The suspension dust burned as air-dispersed dust clouds and the uniformity of the dispersion inside the chamber was evaluated through optical dust probes. The range of tested particle sizes went from a mass median diameter of 47.4 to 438.3 μm and the covered dust cloud concentration was up to 700–800 g/m 3. Measured explosion parameters included minimum explosible concentration, maximum explosion pressure, maximum rate of pressure rise and minimum autoignition temperature. The effect of dust particle size on flammability was evaluated and it was found that the minimum explosible concentration is around 40 g/m 3 and it is relatively independent of particle size below 180 μm. Maximum explosion pressure of 7.2 bar and maximum rate of pressure rise of 179 bar/s were detected for the smallest tested sizes. The limitations on the rates of devolatilization of the solid particles became rate controlling at high burning velocities, at high dust loadings and for large particle sizes. The effect of initial pressure on the characteristic parameters of the explosion was studied by varying the initial absolute pressure from 0.9 bar to 2.2 bar, and it was found that as initial pressure increases, there is a proportional increase of minimum explosion limit, maximum explosion pressure, and maximum rate of pressure rise. The influence of the intensity of the ignition energy on the development of the explosion was evaluated using ignition energies of 1000 J, 2500 J and 5000 J, and the experimental data showed that the value of 2500 J is the most convenient to use in the determination of minimum explosion concentration. The behavior of the cork dust explosion in hybrid methane air mixtures was studied for atmospheres with 2% and 3.5% (v/v) of methane. The effect of methane content on the characteristic parameters of the explosions was evaluated. The conclusion is that, the hazard and explosion danger rise with the increase of methane concentration, characterized by the reduction of the minimum dust explosion concentration. The minimum autoignition temperature obtained with the thermal ignition tests was 540 °C and the results have shown that this value is independent of particle size, for particles with mass median diameters below 80 μm.

Explosibility of cork dust in methane/air mixtures

Explosibility studies of hybrid methane/air/cork dust mixtures were carried out in a near-spherical 22.7 L explosibility test chamber, using 2500 J pyrotechnic ignitors. The suspension dust burned as methane/air/dust clouds and the uniformity of the cork dust dispersion inside the chamber was evaluated through optical dust probes and during the explosion the pressure and the temperature evolution inside the reactor were measured. Tested dust particles had mass median diameter of 71.3 mm and the covered dust cloud concentration was up to 550 g/m 3 . Measured explosions parameters included minimum explosion concentration, maximum explosion pressures and maximum rate of pressure rise. The cork dust explosion behavior in hybrid methane/air mixtures was studied for atmospheres with 1.98 and 3.5% (v/v) of methane. The effect of methane content on the explosions characteristic parameters was evaluated. The conclusion is that the risk and explosion danger rises with the increase of methane concentration characterized by the reduction of the minimum dust explosion concentration, as methane content increases in the atmosphere. The maximum explosion pressure is not very much sensitive to the methane content and only for the system with 3.5% (v/v) of methane it was observed an increase of maximum rate of pressure rise, when compared with the value obtained for the air/dust system. q 2005 Elsevier Ltd. All rights reserved.

Influence of initial pressure on the explosibility of cork dust/air mixtures

Abstract Flammability studies of air/cork dust mixtures were conducted in a near-spherical 22.7 l explosibility test chamber, using 2500 J pyrotechnic ignitors. The suspension dust burned as air-dispersed dust clouds and the uniformity of the dispersion in the chamber was evaluated through optical dust probes. Tested particle dust had mass median diameters of 71.3 and 222.1 μm and the covered dust cloud concentration was up to 700–800 g/m3. Measured explosion parameters included minimum explosion concentration, maximum explosion pressure and maximum rate of pressure rise. The effect of initial pressure on the explosion characteristics parameters was studied by varying the initial absolute pressure from 0.9 to 2.2 bar, and it was found that as initial pressure increases, there is a proportional increase of minimum explosion limit, maximum explosion pressure, and maximum rate of pressure rise.

Influence of initial pressure on cork dust/air mixtures explosibility

Flammability studies of air/cork dust mixtures were conducted in a near-spherical 22.7 L explosibility test chamber, using 2500 J pyrotechnic ignitors. The suspension dust burned as air-dispersed dust clouds and the uniformity of the dispersion in the chamber was evaluated through optical dust probes. Tested particles dust had mass median diameters of 71.3 μm and 222.1 μm and the covered dust cloud concentration was up to 700-800 g/m 3 . Measured explosion parameters included minimum explosion concentration, maximum explosion pressure and maximum rate of pressure rise. The effect of initial pressure on the explosion characteristics parameters was studied by varying the initial absolute pressure from 0.9 bar to 2.2 bar, and it was found that as initial pressure increases, there is a proportional increase of minimum explosion limit, maximum explosion pressure, and maximum rate of pressure rise.

Recent development of standardization of testing methods for dust explosion in Japan

The Dust Explosion Committee of the Association of Powder Process Industry and Engineering (APPIE) of Japan has acted to establish the standard for the member of the Association. Two testing methods have been authorized by the Association. The methods are established to evaluate sensitivity and severity for dust explosion. The ignition sensitivity is evaluated by the minimum explosive dust cloud concentration. Tapping sieve equipment and a strictly-specified Hartmann-type explosion tube have been selected as the testing apparatus. The tapping sieve equipment is applied to measure the minimum explosive concentration by forming a dust cloud supplied from a sieve on the top of the explosion chamber. The Hartmann-type tube is used to investigate roughly whether the test powder is explosive or not. A lot of explosion tests had been carried out to standardize the equipment and evaluate the sensitivity. This APPIE standard is being revised. Along with the ISO standard for explosion severity, Research Institute of Industrial Safety, the Ministry of Labour published a Guide to Test Method for Explosion Pressure and Rate of Pressure Rise for Combustible Dusts in 1994. Based on this Guide, The APPIE Committee has made the draft for the member. These standards and drafts are aimed to be the Japanese Industrial Standard (JIS). No other similar standard exists in Japan. In the present paper, technical data and explosion statistics which are the background of the APPIE standard for the ignition sensitivity are to be described.

Improved optical probe for monitoring dust explosions

An improved optical probe was developed to monitor dust-cloud concentration in explosions even in the presence of dust flame radiation. Principal features of the probe include a pulsed light-emitting diode and a photodetector with optical interference filter to reduce flame radiation. The probe has a U-shaped configuration and air jets to keep the windows dust free. Experimental data are presented for a coal dust explosion.

Dust cloud concentration probe

An optical probe was developed to measure dust cloud concentration during the propagation of dust flames or explosions. Principal features of the probe are a miniature light-emitting diode and photosensor in a U-shaped configuration and air jets to keep the windows of the device dustfree.