Proposal of a new injection nozzle to improve the experimental reproducibility of dust explosion tests

Murillo, Carlos A.; Amín, Mariangel; Bardin‐Monnier, Nathalie; Muñoz, Felipe; Pinilla, Andrés; Ratkovich, Nicolás Ríos; Torrado, David; Vizcaya, Daniel; Dufaud, Olivier

doi:10.1016/j.powtec.2017.12.096

Cited by 20 publications

(20 citation statements)

References 33 publications

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“…In this paper, the method of dust lifting has been used as well as dust injection by a pressurised container. The efficiencies of the standard rebound nozzle and a symmetric one, developed in a previous study (Murillo et al, 2018), have also been compared in order to break the agglomerates and approach an 'ideal homogenous dust cloud', or at least, ensure a better homogeneity. As the dispersion conditions have an impact both on the initial turbulence of the dust cloud and on its particle size distribution, it can be interesting to determine the 'best ignition delay time' for each (nanoparticles / operating conditions) couple.…”

Section: Introductionmentioning

confidence: 99%

Nanopowders explosion: Influence of the dispersion characteristics

Santandréa

Pacault

Praly

et al. 2019

Journal of Loss Prevention in the Process Industries

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This work aims to study the influence of the dispersion conditions in a standard 20L sphere on the explosibility of a nanopowder. Even more than for micropowders, the dispersion conditions have a strong impact on the dust cloud homogeneity and its particle size distribution (PSD). Due to their high surface energy, nanoparticles are prone to agglomeration, but such structures can be broken during the dispersion process. Varying the dispersion pressure, the ignition delay time and even the nozzle type (rebound or symmetric) leads to modifications of the dust specific surface area, and thus of its reactivity. Tests were performed on aluminum and carbon black nanopowders. They were characterized before and during their dispersion in the sphere, notably using in situ laser PSD measurement. The initial turbulence level of the dust cloud was determined by particle image velocimetry. It appears that using the symmetric nozzle, less fragmentation occurs due to a lower shear stress exerted on the agglomerates. This results in a decrease in the explosion severity and an improved experimental reproducibility. Because preignition phenomenon was observed for aluminum nanopowders during their injection through the electrovalve, the dust dispersion by dust lifting was experimented. With regard to the standard procedure, the maximum rate of pressure rise decreased by approximately 30% whereas the maximum overpressure remains nearly unchanged. It means that the same amount of dust reacts in both kinds of experiments but that less fragmentation occurs, which is confirmed by PSD measurements. This work brings some questions about the interpretation of the explosivity results related to nanopowders and highlights the potential need to introduce recommendations in the current standards.

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Section: Introductionmentioning

confidence: 99%

Nanopowders explosion: Influence of the dispersion characteristics

Santandréa

Pacault

Praly

et al. 2019

Journal of Loss Prevention in the Process Industries

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“…Aluminum (Al) powder is an important solid fuel due to its high density and energy; it is widely used in the civilian and military industry, especially for the purpose of propulsion in advance aerospace devices, for example, rockets and missiles . On the other hand, Al powder is extremely dangerous because of its flammable and explosive properties.…”

Section: Introductionmentioning

confidence: 99%

“…Benedetto et al and Valeria Di Sarli et al developed a computational fluid dynamics model to simulate the dispersion of dust within a 20‐L chamber; the particle tracks and dust concentration distribution were analyzed. Murilloet al and Chen et al numerically investigated turbulence and some important factors that affect dust dispersion.…”

Section: Introductionmentioning

confidence: 99%

“…The dust cloud was formed by two symmetrical porous nozzles. Murillo et al proposed a new symmetric nozzle and made a comparison of dust clouds in the chamber with a standard rebound nozzle. Wu et al studied the dust concentration in a 20‐L cylindrical vessel with two nozzles.…”

Section: Introductionmentioning

confidence: 99%

“…aluminum powder, dispersion, ignition delay time, transmission 1 | INTRODUCTION Aluminum (Al) powder is an important solid fuel due to its high density and energy; it is widely used in the civilian and military industry, especially for the purpose of propulsion in advance aerospace devices, for example, rockets and missiles. [1][2][3][4][5] On the other hand, Al powder is extremely dangerous because of its flammable and explosive properties. When Al powder mixes with air and generates dust clouds, explosions of dust clouds have been recognized as a great threat to human life, safety, and property in the past few decades.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of dispersion behavior of aluminum powder in a 20 L chamber with two symmetric nozzles

Yao

Wang

Chen

et al. 2019

Process Safety Progress

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Although aluminum (Al) powder is a potential fuel that has been widely used in many important fields, Al powders are dangerous because of its flammable and explosive characteristics. From this point of view, the investigation of the explosion characteristics of Al powders is of critical importance. The characteristics of a dust explosion are closely related to the dispersion behavior of the powders. The purpose of this research is to analyze the dispersion behavior of Al powder and the uniformity of dust cloud. The dispersion process of Al powders was studied using a high‐speed camera. Image processing technology was applied to obtain the transmission value of the light beam passing through the Al dust cloud at different locations within a vessel. The images obtained by the high‐speed camera indicated that the dispersion process had three stages, that is, a fast injection stage, diffusion stage, and stabilization stage. By examining the transmission‐time histories at 13 different locations in the chamber and at various Al concentrations (from 100 to 800 g/m3), the decay behavior of transmission under different concentrations was obtained, and the decay time fluctuated from 44 to 68 ms. By comparing the deviation of transmission at different locations and for various concentrations in the stabilization stage, the maximum SD obtained was 8.2%, that meant the dust clouds were relatively uniform. Finally, based on the experimental results, the ignition delay time (after which the powder/air mixture is considered homogeneous) corresponding to different dust concentrations should be different to ensure the accuracy of explosion characteristics test.

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