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Book ChapterDOI

Mathematical Modelling and Analysis of Nano-dust Explosion

01 Jan 2019-pp 1033-1046
Abstract: Dust is common in process industries that manufacture, store and handle particulate material. More than half of dusts processed in industries are combustible. Explosive dust clouds can be generated from most organic materials, many metals and even some non-metallic inorganic materials. Studies have reported techniques to control explosions occurring in coal mines and other process industries and such occurrences in varied locations due to different types of dusts, point to the fact that this issue needs further investigation. Industrial practices in India are similar to developed countries but information relevant to dust explosion occurring in India is almost negligible as the type of explosion remains uninvestigated. Further, use of nanoparticles and nano-dusts in upstream oil and gas industry is increasing significantly. Under conducive conditions, storage, transport and pumping down nanoparticles downhole can be considered to be potentially vulnerable situations, leading to explosions with catastrophic consequences, not only financial but including human loss. It is difficult to eliminate dust explosion, but it can be mitigated using different methods. Such events can be prevented if technical safety parameters of dust are known. One of the important measures is the determination of worst case explosion overpressure and provision of blast resistant walls or structural components. This work investigates the dust explosion characteristics of nano-dusts, by taking into account the settings and the circumstances in which the dust is being accumulated. In order to study these changing characteristics of dust particles from an explosion as well as a technical safety perspective, a mathematical model is developed to determine a practical solution for screening in terms of an equation and demonstrate that the equation is doing fair against the experimental data. Various types of nano-dusts and their explosions are simulated using the constructed model. A sensitivity analysis for all the relevant critical parameters is undertaken with this model, after it has been validated with experimental data. The model represents explosions carried out using both micro-powders as well as nano-powders, which can assist the end-user in estimating the approximate value of overpressure and thus, in turn would largely govern further handling and analysis.

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Topics: Dust explosion (64%), Overpressure (51%)
Citations
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Journal ArticleDOI
Abstract: Dust explosion, one of the most serious and wide spread explosion hazards, which is recently a topic of concern for the developed countries are not even identified as a serious threat in developing countries. In this paper we present a review on the concept of dust explosion, by critically reviewing the work done in this domain, a brief on the equipment used for studying this field, followed by possible directions this research could be furthered in.

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23 Sep 2021-
Abstract: Despite extensive research and efforts in handling and mitigation of dust explosion, accidents involving dust explosion take place. The mention of dust explosion in the literature dates to 1785, but industry professionals from oil and gas are unaware of this hazard. An incident is reported leading to the demise of two workers while attempting to unload barite powders. The process industry is highly dependent on powdered chemicals which are used as an additive in drilling fluid and cements such as barite, bentonite, calcium carbonate, lead sulphides, NaOH, etc. The explosive behaviour of these dusts can be determined with the help of the Kst values. The Kst value is dependent on the confinement, dispersion of particles, size of the dust particle, the source of ignition, and presence of free oxygen. Usually, an experimental setup of 20L sphere with two different types of nozzles i.e., perforated annular nozzle or rebound nozzles are majorly used to calculate the value of Kst. While the setup is being prepared at our end, this work presents a comparison of the performance of these nozzles using Computational Fluid Dynamics (CFD) as a tool, to understand the different parameters of dispersion, and the impact they have on the dust explosion.

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References
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Journal ArticleDOI
Abstract: An experimental investigation was carried out on the influences of dust concentration, particle size distribution and humidity on aluminum dust explosion. Tests were mainly conducted thanks to a 20 L explosion sphere. The effect of humidity was studied by storing the aluminum particles at constant relative humidity until the sorption equilibrium or by introducing water vapour in the explosion vessel. The tested particles sizes ranged from a volume median diameter of 7 to 42 μm and the dust concentrations were up to 3000 g m−3. Among other results, the strong influence of the particle size was pointed out, especially when the Sauter mean diameter is considered. These results stressed the predominance of the specific surface area on the mass median particle diameter. The effect of water on aluminum dust explosion was decoupled: on the one hand, when water adsorption occurs, hydrogen generation leads to an increase of the explosion severity; on the other hand, when the explosion of dried aluminum powder occurs in a humid atmosphere, the inhibiting effect of humidity is put forward. A model based on mass and heat balances, assuming a shrinking core model with chemical reaction limitation, leads to a satisfactory representation of the pressure evolution during the dust explosion.

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92 citations


Journal ArticleDOI
Manju Mittal1Institutions (1)
Abstract: Explosion characteristics of micron- and nano-size magnesium powders were determined using CSIR-CBRI 20-L Sphere, Hartmann apparatus and Godbert-Greenwald furnace to study influence of particle size reduction to nano-range on these. The explosion parameters investigated are: maximum explosion pressure (Pmax), maximum rate of pressure-rise (dP/dt)max, dust explosibility index (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE), minimum ignition temperature (MIT), limiting oxygen concentration (LOC) and effect of reduced oxygen level on explosion severity. Magnesium particle sizes are: 125, 74, 38, 22, 10 and 1 μm; and 400, 200, 150, 100, 50 and 30 nm. Experimental results indicate significant increase in explosion severity (Pmax: 7–14 bar, KSt: 98–510 bar·m/s) as particle size decreases from 125 to 1 μm, it is maximum for 400 nm (Pmax: 14.6 bar, KSt: 528 bar·m/s) and decreases with further decrease of particle size to nano-range 200–30 nm (Pmax: 12.4–9.4 bar, KSt: 460–262 bar·m/s) as it is affected by agglomeration of nano-particles. MEC decreases from 160 to 30 g/m3 on decreasing particle size from 125 to 1 μm, its value is 30 g/m3 for 400 and 200 nm and 20 g/m3 for further decrease in nano-range (150–30 nm). MIE reduces from 120 to 2 mJ on decreasing the particle size from 125 to 1 μm, its value is 1 mJ for 400, 200, 150 nm size and <1 mJ for 50 and 30 nm. Minimum ignition temperature is 600 °C for 125 μm magnesium, it varies between 570 and 450 °C for sizes 38–1 μm and 400–350 °C for size range 400–30 nm. Magnesium powders in nano-range (30–200 nm) explode less violently than micron-range powder. However, likelihood of explosion increases significantly for nano-range magnesium. LOC is 5% for magnesium size range 125–38 μm, 4% for 22–1 μm, 3% for 400 nm, 4% for 200, 150 and 100 nm, and 5% for 50 and 30 nm. Reduction in oxygen levels to 9% results in decrease in Pmax and KSt by a factor of 2–3 and 4–5, respectively, for micron as well as nano-sizes. The experimental data presented will be useful for industries producing or handling similar size range micron- and nano-magnesium in order to evaluate explosibility of their magnesium powders and propose/design adequate safety measures.

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68 citations


Journal ArticleDOI
Olivier Dufaud1, Alexis Vignes, François Henry1, Laurent Perrin1  +1 moreInstitutions (1)
06 Jul 2011-
Abstract: This work deals with the study of ignition and explosion characteristics of nanoparticles. It has been carried out on various powders: zinc, aluminum, carbon blacks... Specific behaviours have been highlighted during the first phase of this project (Nanosafe 2). For instance, it has been demonstrated that there mainly exists two combustion regimes that are either kinetically controlled, for small size particles, or diffusion controlled, for large size particles (generally with diameters greater than 1 or 2 µm). It has been found that as the particle size decreases, minimum ignition temperature and minimum ignition energy decrease (even lower than 1 mJ), indicating higher potential inflammation and explosion risks for metallic nanopowders. Moreover, the presence of agglomerates in the nanopowders could modify their reactivity. Thus, the explosion severity of Al powders tends to increase as the specific surface area decreases, before reaching a peak for 1 µm particle size. These results are essential for industries producing or handling nanopowders in order to propose/design new and proper prevention and protection means. Nevertheless, the validity of the classical characterization tools with regard to nanopowders should be discussed. For example, the experimental laminar flame velocity of Al dusts has been compared to a theoretical one, determined by Huang's model, which assumes that the propagation of the flame is run mainly by conduction. It has shown a good agreement. However, under certain conditions, the Al flame propagation is expected to be mainly conducted by radiation. Two hypotheses can then be made. On the one hand, it can be assumed that the 20 L sphere probably disturbs the flame propagation and thermal mechanisms by absorbing radiation (wall quenching effect). On the other hand, it has been observed, thanks to the use of a high speed camera that the preheating zone is smaller for some nanopowders than for micro-particles (figure below). It could notably be explained by the fact that the flame radiation is absorbed by the cloud of unburnt Al nanopowders. Several other factors may have an impact on the explosion severity. If these points are correctly addressed, it will be possible to get more reliable ignition and explosion characteristics.

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45 citations


Journal ArticleDOI
Niansheng Kuai1, Jianming Li1, Zhi Chen1, Weixing Huang1  +2 moreInstitutions (1)
Abstract: An experimental investigation was carried out on magnesium dust explosions. Tests of explosion severity, flammability limit and solid inerting were conducted thanks to the Siwek 20 L vessel and influences of dust concentration, particle size, ignition energy, initial pressure and added inertant were taken into account. That magnesium dust is more of an explosion hazard than coal dust is confirmed and quantified by contrastive investigation. The Chinese procedure GB/T 16425 is overly conservative for LEL determination while EN 14034-3 yields realistic LEL data. It is also suggested that 2000–5000 J is the most appropriate ignition energy to use in the LEL determination of magnesium dusts, using the 20 L vessel. It is essential to point out that the overdriving phenomenon usually occurs for carbonaceous and less volatile metal materials is not notable for magnesium dusts. Trends of faster burning velocity and more efficient and adiabatic flame propagation are associated with fuel-rich dust clouds, smaller particles and hyperbaric conditions. Moreover, Inerting effectiveness of CaCO 3 appears to be higher than KCl values on thermodynamics, whereas KCl represents higher effectiveness upon kinetics. Finer inertant shows better inerting effectiveness.

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40 citations


Journal ArticleDOI
Weiguo Cao1, Liyuan Huang1, Jianxin Zhang, Sen Xu1  +2 moreInstitutions (1)
Abstract: The parameters of explosive characteristics of the coal-dust are assessed systematically with the test device of minimum ignition temperature of dust clouds and 20L sphere explosion test units. The minimum ignition temperature of dust is a main safety index when handling combustible dusts in industrial production, and while hazard evaluation, the maximum explosion pressure and the explosion index are key parameters. Five kinds of coal-dust with different particle diameters were tested in order to determine the temperature sensitivity and the ferocity under the given conditions, which can be used as the criteria to classify dust explosion hazards. The experiment results indicate that the minimum ignition temperature of coal-dust cloud reduces with the decrease of particle diameter under temperature of (293±5) K and powder spraying pressure of 0.08MPa, and when the particle size reduces to (25-48) μm, the minimum ignition temperature is between (793-803)K; Besides that, the results can also show that minimum explosive concentration of coal-dust cloud is between 20 gam-3 and 30 gam-3under temperature of (293±5) K, powder spraying pressure of 2MPa and ignition energy of 10kJ, the maximum explosion pressure is 0.45MPa and the maximum explosion index is 11.14 MPaamas-1, which classifies coal-dust explosion hazards to Level I. The conclusions drawn from the experimental results are of great significance to the safe application of these combustible substances.

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22 citations


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