Dust Explosion Research Articles

Exploring the dynamics of passive isolation flap valves in dust explosion mitigation: a model-based approach and its implications

Passive isolation flap valves are relatively simple devices widely used in the process industries. However, as with any explosion mitigation technique, they work only within well-defined conditions, and the underlying physics makes any prediction difficult. The current paper presents new methods and findings, which rely on experiments on passive flap valves tested on 0.7 to 10 m3 vessels with 100 to 800 mm pipes. This study considers the simple configuration of a flap valve connected to a vented vessel-straight duct arrangement. The explosion in the vessel triggers the closure of the initially opened flap valve and should be effective within a short delay to prevent the flame from passing. The explosion in the vessel drives both the fluid flow in the pipes and the flap valve closing duration. The sudden closing of the pipe induces a complex fluid flow, including significant pressure and velocity fluctuations around the flap valve and a backflow towards the vessel. The commonly used empirical laws, such as those displayed in the EN standards on dust explosions, do not account for these fluid-structure interactions. A hybrid code has been developed to describe the fluid flow throughout the assembly. This code combines an integral model for the vessel and flap explosions, a 1D Eulerian method relying on a MacCormack scheme for the pipes, and a damped pendulum model for the flap solved using an RK4 scheme. The model results compare satisfyingly well with experimental results. The discussion focuses on analysing the problem's physics, from which design engineering rules are derived.

The Dust Explosion Threat within Biomass Thermal Operation in Industries: A review in Malaysia Cases

The Dust Explosion Threat within Biomass Thermal Operation in Industries: A review in Malaysia Cases

Prevention and suppression of coal dust explosion in underground coal mines: Role of rock dust type, particle size, proportion, concentration, and thermal properties

Rock dust inertant is commonly used for prevention and suppression of coal dust explosion in underground coal mines. The effects of rock dust type, proportion, particle size, thermal conductivity, and specific heat capacity on minimum ignition temperature (MIT) of coal-rock dust mixtures and intensity of explosion propagation under different experimental conditions were examined using Godbert-Greenwald furnace integrated with a high-speed camera. MIT of coal-rock dust mixtures significantly increased with increase in rock dust proportion. With decrease in particle size from < 850 to < 75 µm, the mean MIT increased from 616 to 657 °C and 627 to 665 °C for dolomite and limestone dust, respectively. With increase in dust concentration from 500 to 3000 g/m3, the ignition temperature (IT) of coal-rock dust mixtures decreased by 28 % and 30 % for dolomite and limestone dust, respectively. Moreover, the MIT significantly increased with increase in thermal conductivity and specific heat capacity of coal-rock dust mixtures. Limestone dust proved to be a better explosion suppressant compared to dolomite dust.

Methane and Coal Dust Problem in Underground Coal Mining and Alternative Ventilation Techniques

Methane and coal dust explosions are among the most important risk factors that cause fatal occupationalaccidents in underground coal mining. One of the most important reasons for these explosions is inadequate orunfavourable ventilation conditions. In cases where the generally used classical ventilation systems are insufficient,attempts are made to continue ventilation with classical methods instead of some methods that may be considered asalternatives, and these methods often lose their applicability due to high costs. In this study, methods that emphasize theirapplicability as alternatives in risky situations are proposed and the results of some study examples are evaluated.

Study on the effect of particle morphology on transient dispersion behavior and ignition of Al[sbnd]Mg alloy powder

Particle morphology has a significant effect on the explosion of energetic dust which includes heat transfer and transient dispersion behavior. This study aimed to investigate the differences in transient dispersion characteristics of Al-Mg alloy powders with different shapes using Particle Image Velocimetry (PIV) and to elucidate their effects on subsequent flame propagation and explosion parameters. The results demonstrated that irregular dust exhibited lower agglomeration and terminal fall velocity (TFV) compared to spherical dust, leading to a higher overall concentration of dust involved in the explosion. In addition, the turbulence intensity in the critical ignition zone of irregular particles was relatively high, resulting in particles having more active motion characteristics during the initial ignition phase. Therefore, irregular dust exhibited more intense flame phenomena and higher explosion parameters. These findings emphasize the importance of considering particle morphology when assessing the risk associated with metal dust explosions.

Experimental investigation on the suppression of aluminum dust explosion by sodium carbonate powder

To prevent the potential explosion accidents in industries involving aluminum powder, the effectiveness of Na2CO3 in inhibiting aluminum dust explosions was investigated using thermal methods and explosion tests. Furthermore, the surface morphologies and chemical compositions of the resultant explosion products were characterized to illustrate the inhibition mechanism of Na2CO3 powder. The results revealed a marginal increase in ignition temperatures and a decrease in combustion peak temperature as the proportion of Na2CO3 increased. Notably, within the range of 0–450%, a notable reduction was observed in both the maximum explosion pressure (from 0.68 to 0.06 MPa) and the maximum pressure rising rate (from 91.93 to 2.87 MPa/s). In particular, as the percentage of Na2CO3 increased, a gradual decrease in flame brightness and average flame velocity was observed. Moreover, a negative relationship was observed between ignition temperature and apparent activation energy with maximum explosion pressure and maximum pressure rising rate. An analysis of the explosion residues indicated the presence of Na2CO3, NaOH, Al2O3, Al(OH)3, Na(AlO)2, Na2O and unburned aluminum. The inhibition mechanisms of Na2CO3 involved heat absorption, isolation, and the consumption of free radicals. These results offer valuable insights that can aid in mitigating the risks associated with aluminum dust explosion.

Application of microencapsulated fibrous carrier inhibitors in suppressing flake aluminum dust explosion: Performance and mechanism

Flake aluminum powder (FAl), due to its larger specific surface area and higher reactivity, posing a potential threat to the process safety of involved enterprises. To mitigate the explosion caused during the production of FAl, a green composite inhibitor, Sep@CS@PA-Na, was successfully prepared in the aqueous phase using microencapsulation technology with sepiolite (Sep), chitosan (CS), and sodium phytate (PA-Na) as raw materials. The suppression of FAl explosions in a vertical combustion duct system by inhibitors with different inerting ratios (α) was investigated. The results showed that after adding Sep@CS@PA-Na with an α of 0.75, the maximum flame propagation velocity (Vmax), the average flame velocity (Vavg), and the velocity of the flame reaching the pipeline top (Vtop) decreased by 79.6%, 75.1%, and 86.2%, respectively, and the reduction of the maximum flame front pressure (Pmax) and the maximum flame pressure rise rate ((dP/dt)max) were 90.4% and 89.8%, respectively, and the peak temperature (Tp) dropped to 505°C. Combined with TG-DSC and explosion product analysis, Sep@CS@PA-Na possessed both gas-phase reaction and surface reaction suppression functions, which were mainly reflected in the dilution effect, quenching effect, and barrier effect. This work will provide technical support for the emergency prevention and control of energetic metal dust explosions.

Investigation of marginally explosible dusts

“Marginally explosible dusts (MEDs)” are a group of combustible dusts that are distinguished by relatively low volume-normalized maximum rate of pressure rise (KSt) and maximum explosion pressure (Pmax) values. Earlier studies have suggested that dusts with KSt values less than 45 bar m/s in the laboratory-scale 20-L chamber would not explode in the 1-m3 chamber and therefore not on an industrial scale. Conversely, for some metallic dusts, significantly higher KSt values are generated in the 1-m3 chamber. Industries that handle MEDs continue to search for answers to the questions “are they explosible or not?” and “should we protect or not protect against potential explosions of these dusts?“. To answer these questions, four well-characterized materials namely, carbon black, oat grain flour, urea, and zinc were tested in the current study. These materials were selected because they exhibit different combustion behaviors and also cover a range of industries. Five ignition energies (i.e., 0.5, 1, 2.5, 5, and 10 kJ) were used in the 20-L chamber tests. The results show a clear case of overdriving (as a result of the high ignition energy density in the 20-L chamber) with respect to urea and carbon black dusts. Nevertheless, the urea dust is non-explosible. The data also suggests that the choice of test chamber to generate suitable explosion data is strongly dictated by the combustion path of MEDs. However, there are exceptions. The study also establishes the importance of both chemico-physical and thermal analyses to understanding the explosion behavior of MEDs. With reference to urea dust, a new definition for MEDs has been suggested as dusts having Pmax < 3.0 bar(g), KSt < 20 bar m/s (in the 20-L chamber), MEC >1000 g/m3, MIE >1000 mJ, and MIT >600 °C. This work provides guidelines to industries that handle MEDs on the explosibility classification of these dusts, thus addressing the existing difficulty, and informing industry on the safety strategies required when handling this group of dusts.

Explosion characteristics of wood dust and its suppression in typical powder-related environments

To reduce the explosion hazard caused by wood dust, the effects of dust concentration and ammonium polyphosphate (APP) on the explosion of wood dust were carried out in a vertical combustion pipeline and the suppression mechanism was revealed. The explosion intensity of the wood dust increased and then decreased with increasing concentration, and the bottom of the pipeline remained bright due to continuous ignition. APP could effectively suppress the propagation of wood dust explosion flame. When the mass fraction of APP was 10%, there was no obvious flame, and the flame pressure dropped by up to 98%. The effect of APP on wood dust pyrolysis was analyzed using TG-DSC, and the explosion products were characterized by physicochemical analysis using EDS. The results showed that APP could improve the stability of the carbon layer on the surface of wood dust particles, and its decomposition products could enhance the thermal shielding and oxygen isolation effects of the particle surface protective layer. In addition, the APP significantly suppressed wood dust explosion by absorbing heat from the reaction zone, capturing and consuming free radicals, and reducing the oxygen concentration per unit volume.

Effects of explosion suppressants on the dust explosion and pyrolysis characteristics of the fungicide fenaminstrobin

In this study, the explosion and pyrolysis characteristics of fungicide fenaminstrobin dust were studied, and the inhibitory effects of three explosion suppressants, namely, NH4H2PO4, KH2PO4, and KCl, on dust explosion were compared. A combined thermogravimetric (TG)–Fourier transform infrared (FTIR)–mass spectrometry (MS) technique was adopted to analyze the inhibition mechanism. The results showed that the minimum ignition energy (MIE) was 5 mJ, the explosion index (Kst) was 305.7 bar m/s, and the dust explosion hazard was severe. We found that all three compounds (NH4H2PO4, KH2PO4, and KCl) could be used as explosion suppressants. When the addition dose of NH4H2PO4 was 35%, the Kst value dropped by 40.7%, and MIE exceeded 1000 mJ. When the addition of KH2PO4 was 50%, the Kst value dropped by 37.3%, and the MIE increased to 300 mJ. In comparison, NH4H2PO4 showed the best inhibitory effect, while KCl demonstrated the worst inhibitory effect. The pyrolysis of fenaminstrobin produced organic gases, including quinoline, benzonitrile, and methyl isocyanate, and generated large quantities of free radicals. The explosion suppressants could inhibit the explosion through physical pathways (endothermic, coating, and oxygen-diluting processes) and chemical pathways (free-radical capture).

Study on the inhibition of explosion and combustion of coal dust based on the structure of core-shell microencapsulated polyurethane

In order to study the effect of core-shell microencapsulated ammonium polyphosphate modified materials on the suppression of explosion and combustion of different metamorphic coal, a core-shell microencapsulated ammonium polyphosphate explosion inhibitor was prepared using in-situ polymerization method. Through experiments on flame suppression and overpressure suppression during explosive combustion, the inhibitory effect of core-shell microencapsulated ammonium polyphosphate explosion suppressant on coal dust explosion was studied, revealing the coupling inhibition mechanism of thermal propagation isolation obstruction effect and group reaction reduction of key atoms. The experimental results show that when 60 wt% core-shell microencapsulated ammonium polyphosphate explosion suppressant is added, the suppression effect on the explosion and combustion of different metamorphic coal is significant, and the flame propagation and pressure rise of coal dust explosion can be basically achieved. By analyzing the substances before and after the explosion through characterization experiments, the inhibitory mechanism of core-shell microencapsulated ammonium polyphosphate explosion suppressant on different metamorphic coal was obtained. Expanding the application field of microcapsule materials provides important methods and theoretical basis for developing core shell microcapsule flame retardant and explosion suppression materials to prevent coal dust explosion disasters.

Methane and Coal Dust Problem in Underground Coal Mining and Alternative Ventilation Techniques

Methane and coal dust explosions are among the most important risk factors that cause fatal occupationalaccidents in underground coal mining. One of the most important reasons for these explosions is inadequate orunfavourable ventilation conditions. In cases where the generally used classical ventilation systems are insufficient,attempts are made to continue ventilation with classical methods instead of some methods that may be considered asalternatives, and these methods often lose their applicability due to high costs. In this study, methods that emphasize theirapplicability as alternatives in risky situations are proposed and the results of some study examples are evaluated.

The influence of pipeline deposited dust on the explosion propagation of dust collector

An explosion experiment involving corn starch was conducted using a small tank directly connected to the pipeline. The objective was to investigate how the mass and location of deposited dust in the pipeline affect the explosion pressure and flame propagation characteristics of the dust cloud. The results revealed that when the container was at the optimum dust explosion concentration, as the mass of deposited dust increased, the maximum explosion pressure of both the container and pipeline increased and then decreased. Additionally, the maximum flame propagation velocity and flame propagation length gradually decreased as deposited mass increased. Furthermore, as the distance between the location of deposited dust in the pipeline and the container increased, the maximum explosion pressure increased and then decreased. Similarly, the maximum flame propagation velocity demonstrated a similar trend, whereas the flame propagation length gradually increased. In conclusion, the study's findings offer a theoretical foundation for scientifically assessing and effectively preventing and controlling explosion disasters in dust removal systems.

Factors Influencing Worker Safety in Grain Handling: An Advisory Panel Perspective

HighlightsFindings confirmed that out-of-condition grain is a primary causal factor in grain entrapment and engulfment.The advisory panel confirmed that grain quality has implications for grain dust explosions.Findings highlighted a lack of in-depth knowledge expected from an expert panel, specifically on aspects of protective grain quality traits.Abstract. Out-of-condition grain has been identified as a primary causal factor in grain entrapments and engulfments. The quality of grain also has implications for grain dust explosions. Limited research has examined exactly which elements of grain condition influence worker safety in grain handling. This research project aimed to establish an advisory panel to examine and provide input on how elements of grain condition relate to worker safety risks in grain handling. A purposeful sampling technique was used to obtain a sample of grain handling and storage experts to function in an advisory role for the project. A primary aim of this research was to understand the problem further, provide input on tested variables, and guide educational and dissemination efforts. As is true for qualitative methodologies, those selected as part of the targeted sample cannot be generalized to other experts in the field of grain handling. The final sample contained six industry representatives, five academic professionals, and two insurance/regulatory professionals. Participants interviewed had varied expertise with grain-based safety events. Of those interviewed, 23% of participants had personal experience, 54% had bystander or investigator experience, and 23% had training experience. Semi-structured interviews were conducted to further understand the problem, provide input on important elements in safe grain handling, and guide educational and dissemination efforts. Interviews were analyzed with a primary objective to identify elements of grain condition that play a role in the incidence of grain entrapment, grain engulfments, or grain dust explosions. NVivo 14 was used to conduct a thematic analysis, and four overall themes were identified, which included challenges to worker safety in the grain handling industry, areas where improved communication is needed, grain quality indicators that may play a role in safety incidents, and available mitigation strategies. The themes are the opinions of the advisory panel and may not reflect those of the entire grain handling industry. Keywords: Expert panel, Grain bin safety, Grain handling hazards, Grain quality.

Method of calculation of satellite flow parameters behind the point of Mach reflection

A mathematical model for the calculation and express analysis of triple configurations of air shock waves arising from an “elevated” explosion of a condensed high-energy material is presented. The considered blast waves with a long duration of the positive phase (compression phase) can take place in industrial and agricultural applications: in the explosion of fuel-air mixtures, explosive dust in elevators and granaries, as well as high-energy materials for agricultural and industrial applications based on ammonium nitrate and explosive saltpetre mixtures with petroleum products. The developed mathematical model uses exact and semi-empirical relationships developed earlier in the theory of optimal shock wave systems.

Fire and Explosion Hazard Aspects for Bucket Elevators

Technological installations for the vertical transport of cereal products, are affected by the presence of combustible dusts that can be mixed with air, in suspension, or in the form of dust layers of different thicknesses. The presence of these combustible dusts is a constant danger of fires or even explosions. In combustible dusts are swirled in the air in concentrations in their explosive range and there is also an ignition source, the dusts can burn quickly and even give rise to explosions, in which case the force and pressure developed is considerable. Since, in most cases, following a fire and especially a combustible dust explosion, the damage caused is quantified by immeasurable material damage and even by recording human losses, special attention must be paid to how they are identified and implemented protection and prevention measures to prevent fires and combustible dust explosions. In this paper, the principles and main factors that must be considered when quantifying the risk of fire and/or explosion for a bucket elevator used for the vertical transport of cereal products are highlighted. A number of recommendations for the safe use of these lifts are also presented.

MINIMUM EXPLOSIBLE CONCENTRATION MEASUREMENTS OF HYBRID ROCKET SOLID FUEL DUST

Hybrid rockets are considered safe because there is no affinity between the fuel and oxidizer. However, if the solid fuel turns to dust, the dust might cause rapid combustion. Therefore, the dustification of fuel has been evaluated using crushing tests. In an earlier study by the authors, wax was used as a specimen. It was crushed by explosives in a balloon filled with air and oxygen. Then pressure waves near the balloon were measured. Results show that the pressure fluctuation in the oxygen-filled case was greater than that in the air-filled case, but it could not be ascertained whether this result was attributable to the combustion of the wax that had become dust or to the combustion of the wax surface which the explosive contacted. Therefore, the authors measured the lower explosion limit concentration of wax dust under atmospheric conditions and in an atmosphere with a high oxygen concentration to obtain knowledge related to the wax dust mixture flammability. A blow-up type dust explosion test apparatus was used to measure the lower explosion limit. The specimens were produced by grinding and sieving the wax pellets. Powders of four types were produced: 850 &amp;mu;m, 500 &amp;mu;m, 212 &amp;mu;m, and 53 &amp;mu;m. The dust concentration was calculated by dividing the sample mass by the volume of the explosion cylinder. Based on the test results, the lower explosion limits were identified for 212 &amp;mu;m and 53 &amp;mu;m, but not for 850 &amp;mu;m and 500 &amp;mu;m.

Physico-chemical analysis and characterization of the flammability of metallic powders

When fine particles known as flammable powders are suspended in the air under specific circumstances, they have the potential to explode. There could be many serious fatalities, injuries, and structural damage as a result of a dust explosion. By being aware of the flammability parameters and the physico-chemical analysis for flammable powders and taking additional protective measures as a result of the occurrence of these kinds of catastrophic mixes, the risk of such incidents can be decreased. The goal of this study was to determine the flammability characteristics of two combustible powders, magnesium and aluminum powder. These characteristics included the lowest ignition temperature of the dust cloud and dust layer as well as certain physicochemical studies of the composition.

Effect of silver inhibition on the ceramic foam as flame suppression

Aluminium dust explosions pose significant safety and economic challenges in various industrial processes. Due to this, the current research explores an innovative approach by inhibiting the silver nanoparticles (Ag NPs) to ceramic porous form substrate as a flame suppressant in order to mitigate the risks associated with these explosions. The antimicrobial and non-toxic qualities of silver are also attractive to be applied in medical and food technology. However, the interfacial adhesion between the metallic (nanosilver) and non-metallic (silica-based-ceramic) is still vaguely studied due to the mechanical and surface energy mismatch between the organic surface and the inorganic layers. From this study, the physicochemical and mechanical properties of the silver-coated ceramic foam were analyzed using X-ray diffraction, field emission scanning electron microscopy with energy dispersive X-ray, thermogravimetric analysis, and compression test. From the mechanical testing, it was found that the percentage increase of maximum load for silver-ceramic foam from the original ceramic foam was about 60%. The results indicate that silver-coated foam has a better compressive strength of 0.93 MPa as compared to 0.58 MPa by the original ceramic. The inhibition effect of Ag NPs powder on the explosion pressure evolution and flame spread mechanism of aluminium powder at different concentrations and particle sizes was tested using the Hartmann experimental system.

Experimental study of the effect of coal dust on the flame dynamics of partially premixed gas-coal dust explosion in a vertical pressure relief pipe-line

To further study the gas-coal dust explosion hazards under complex conditions. Experiments were conducted in pipe-line systems containing explosive pipe-line and pressure relief pipe-line. The effect of coal dust concentration and particle size on the flame dynamics of gas-coal dust explosion was investigated. The flame structure in the explosion pipe-line is divided into two-stages: spherical and round-finger. In the pressure relief pipe-line, the flame structure e varies at working conditions. Flame front position increases with time, showing a class exponential growth trend. The flame front velocity increases in the explosion pipe-line, has a short drop during the entry into the pressure relief pipe-line, and then increases. With the increase of coal dust concentration, flame propagation time has been increasing in the pipe-line system and the explosion pipe-line, with the shortest time at 25 g/m?. Flame propagation time first increases and then decreases in the pressure relief pipe-line, the shortest time at 50 g/m?. The maximum flame front velocity first increases and then decreases. The maximum flame front velocity is maximized at 50 g/m?. With the increase of coal dust particle size, flame propagation time has been increasing in the pipe-line system, and in the explosion pipe-line, flame propagation times have been decreasing in the pressure relief pipe-line. The maximum flame front velocity first increases, then decrease, and increases again. The maximum flame front velocity is minimal at 45 ?m.