Explosive Concentration Research Articles

УСТАНОВКА ПРЕДОТВРАЩЕНИЯ ОБРАЗОВАНИЯ ВЗРЫВООПАСНОЙ КОНЦЕНТРАЦИИ СЖИЖЕННЫХ УГЛЕВОДОРОДНЫХ ГАЗОВ ПРИ СЛИВЕ/НАЛИВЕ АЦ

During the operation of the multi-fuel auto filling station, there are risks associated with the explosion and fire hazard of the facility, namely the transportation and shipment of explosive liquefied petroleum gas, with the depressurization of which it is possible to spread LPG vapors through the territory of the multi-fuel filling station, which can lead to ignition of LPG vapors and subsequent detonation. The issue of the safety of multi-fuel filling station (auto gas filling station) is relevant today. The regulatory document NPB-111-98 specifies the mandatory requirement for the already built the multi-fuel filling station. To meet the fire safety requirements for the multi-fuel filling station, an installation has been developed to prevent the formation of an explosive concentration of liquefied petroleum gases during the discharge/filling of the tanker truck. The installation for preventing the formation of an explosive concentration of LPG at the tanker truck shipment site is a system of supply and exhaust ventilation placed in such a way that on the one side of the edge the air flow creates a backstop with air inflow, on the other side a vacuum is created by the exhaust system. For the selection of equipment, the calculation of ventilation ducts, air flow velocity and system resistance was performed. The requirements for the mobility of the vapor phase on the surface have been achieved, which is at least 2 m/s. The project was implemented at a number of the multi-fuel auto filling station of a large oil company.

Экспериментальное исследование и моделирование процесса формирования взрывоопасных концентраций

Excess pressure is the main indicator characterizing the magnitude of explosive loads during emergency gas explosions. The value of this parameter and the entire accident scenario as a whole directly depend on the concentration of gas entering the room. Any typical room is characterized by the presence of two processes: laminar and turbulent diffusion. The laminar diffusion coefficient depends on the main characteristics of the gas (pressure, temperature). The laminar diffusion coefficient depends on the main characteristics of the gas (pressure, temperature). The coefficient of turbulent diffusion is determined only by the turbulent structure of the considered medium. It is established that the incomplete vortex mixing of gas with air is sufficient for flame propagation. This indicates the importance of studying the process of turbulent diffusion from the point of view of the formation of explosive gas-air mixtures. The purpose of the study is the experimental and computational determination of the coefficient of methane turbulent diffusion. This characteristic is required to assess the state of the gas-air environment in the room. It can be used in the development of explosion prevention measures, for example, in the design of a ventilation system. The study of the process of formation of explosive concentrations was carried out on the basis of an experiment and subsequent comparison of its results with a calculation model. In the course of the studies, it was established that the coefficient of turbulent diffusion, due to which explosive mixtures are formed, exceeds the coefficient of molecular diffusion by two orders of magnitude or more and is at least 4∙10–3 m2/s. The applied mathematical model and calculation scheme adequately describe the course of the experiments. Determination of the turbulent diffusion coefficient will allow assessing the state of the gas-air environment in the room and determining the required measures to prevent a possible emergency explosion.

Experimental research on flammability characteristics and ignition conditions of hybrid mixture emissions venting from a large format thermal failure lithium-ion battery

When the concentration of gas is below its lower flammable limit and the content of the particles is below its minimum explosible concentration, it can be explosible. Thermal abuse tests for 50 Ah lithium-ion batteries were conducted under an inert atmosphere. The battery failure venting emissions were collected and their composition was identified previously. It still needs further research for the flammability characteristics and ignition conditions for hybrid mixture emissions venting from a large format lithium-ion battery thermal failure. In this study, the likelihood, severity, and kinetics of the batteries' hybrid mixture emissions flammability have been researched. To analyze battery emission flammability characteristics, five indexes have been investigated; they are ignition temperature (Tig), ignition time (τig), maximum explosion pressure (Pmax), pressure rise maximum rate ((dP/dτ)max), and size-normalized maximum rate pressure rise (KSt). Based on quantitative analysis for the hybrid mixture flammability characteristics, it indicates that particle size and gas content can impact hybrid mixture emission flammability characteristics. As for the mixture with finer particles, the optimum combustion condition of the particle and gas concentration pairs were 0.3 and 0.7. The ignition temperature for the optimum combustion conditions was 495 °C. The pressure rising velocity was 23 Mpa/s during ignition. High solvent content and low particle concentration are the conditions for optimum combustion. This indicates that the gas admixture solvent plays a major role in the combustion kinetics of the mixture emission. This research offers a fundamental perspective and provides preventive and protective thermal safety designs that are more suitable for large format commercial battery thermal systems.

Experimental Study of the Suppression Effect of N2/CO2 On the LPG Explosion Behavior in a Half-Open Duct with Large Aspect Ratios

ABSTRACT This work aims to investigate the effect of N2/CO2 on the explosion behavior of premixed liquefied petroleum gas (LPG)-air in a half-open duct. Experiments were performed in a duct (L/D = 47.5) with the ignition end closed and the other end open. Firstly, the optimal explosion concentration of LPG was determined using the stepwise approximation method, secondly, the effects of different volume fractions (VFs) of N2/CO2 on the pressure dynamic process, flame propagation velocity, and explosion severity of LPG-air explosion were analyzed, and finally the inerting effects of N2 and CO2 were compared using the control variable method. The results show that the explosion pressure and flame propagation velocity reach a maximum when the VF of LPG is 4.8% (without inert gas), and two pressure peaks (the first pressure peak (P 1 ) and the second pressure peak (P 2 )) are observed. When the VF of LPG is 4.8%, the maximum pressure and the average flame propagation velocity in the tube decrease and the explosion intensity inside and outside the duct was effectively mitigated as the VF of N2/CO2 increases, and the explosion is completely suppressed as the VF of inert gas reached 30%. P 2 is significantly suppressed, and the maximum explosion pressure (P max ) occurs at when the VF of N2/CO2 is above 15%. The suppression effects of CO2 are more remarkable at a lower VF (below 18%), those of N2 are more significant at a higher VF (above 18%), and P 1 also follows this rule. For a given volume fraction of inert gas, the suppression effect of N2/CO2 on the degree of explosion severity becomes more significant when approaching the optimal LPG explosion concentration (4.8%).

Uncovering the structure and function of specialist bacterial lineages in environments routinely exposed to explosives.

Environmental contamination by hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the two most widely used compounds for military operations, is a long-standing problem at the manufacturing and decommissioning plants. Since explosives contamination has previously been shown to favour the growth of specific bacterial communities, the present study attempts to identify the specialist bacterial communities and their potential functional and metabolic roles by using amplicon targeted and whole-metagenome sequencing approaches in samples collected from two distinct explosives manufacturing sites. We hypothesize that the community structure and functional attributes of bacterial population are substantially altered by the concentration of explosives and physicochemical conditions. The results highlight the predominance of Planctomycetes in contrast to previous reports from similar habitats. The detailed phylogenetic analysis revealed the presence of operational taxonomic units related to bacterial members known for their explosives degradation. Further, the functional and metabolic analyses highlighted the abundance of putative genes and unidentified taxa possibly associated with xenobiotic biodegradation. Our findings suggest that microbial species capable of utilizing explosives as a carbon, energy or electron source are favoured by certain selective pressures based on the prevailing physicochemical and geographical conditions.

Разработка средств локализации взрывов угольной пыли

The aim of the research was to increase the speed of the device for localizing coal dust explosions to reliably suppress the fire front by creating a barrier from a cloud of fire extinguishing agent and, as a result, stopping the spread of an explosion in a mine working. The result is an increase in the safety of a mine personnel. In the paper, an integrated approach was applied, including the following: analysis and generalization of statistical data on explosions of the methane-air and dust-air mixtures in the mines of Ukraine; critical analysis of means of localization of explosions of coal dust; computer simulation of stress propagation in a rock mass during an explosion. The obtained data on the propagation of stresses in a rock mass allowed to scientifically substantiate the new approach to obtaining information about a shock front approaching. The results of the study confirmed that the transfer of dust accumulations into a suspended state under the influence of seismic waves moving along the working with a significant advance of the explosion front creates conditions for the formation of an explosive concentration of dust ahead of the fire front. Earlier receipt of an explosion signal from a seismic sensor can contribute to the formation of an explosion-proof environment even before the fire front approaches, which will allow taking measures to prevent the creation of a combustible environment and the formation of a non-combustible zone in the path of the fire front. Thanks to the discovery of the mechanism of propagation of explosion energy in a mountain environment, a fundamentally new approach to detecting an explosion in a mine working was substantiated, and a new design of a device for localizing coal dust explosions was developed. The introduction of this device will speed up the localization of dust explosions by creating an efficient barrier from a cloud of fire extinguishing agents. At the same time, an explosion-proof environment will be formed in the mine working, which will lead to an increase in the level of protection of miners from the harmful and hazardous explosion factors.

Redefining of potential dust explosion risk parameters for additives in the petrochemical manufacturing process

Petrochemicals are an indispensable part of our everyday life, necessitating large-scale production facilities. Additive aids play a pivotal role in the petrochemical production process, which are required for the final product to have certain desired properties. The additives used are prone to ignition and combustion, but are frequently overlooked as a source of potential hazard. This study examines the hazard profile of five common powder additives in the petrochemical manufacturing process. The inherent combustion and explosion characteristics were investigated in detail. Each sample’s potential to produce a dust explosion was evaluated based upon the parameter test results, e.g., minimum ignition energy (MIE), minimum ignition temperature (MIT), and minimum explosible concentration (MEC). MIT of all five samples was between 350 and 390 °C, and MEC was less than 45 g/m3. Two of the powders had a KSt explosion rating of “extremely strong” (St-3). After a comprehensive evaluation of dust explosion sensitivity and dust explosion severity, all five additive samples were categorised as high-level potential dust explosion risks. Process safety staff and engineers working with petrochemical production should be aware of the risks posed by dust additives and be prepared to implement more stringent loss prevention measures to curtail the likelihood of dust explosions.

Characterization of the explosiveness of wood dust

Factors that influence the explosiveness of wood dust, like particle size distribution, moisture content and microscopic structure, have been characterised. Sawdust flammability has been tested in a Hartmann tube. The Minimum Explosive Concentration and Minimum Ignition Temperature of dust clouds and layers have also been measured. Dust granulometry linked to the regularity of its structure and moisture are the essential parameters to generate or not an explosive atmosphere. Smaller particle size dust with a lower moisture content is much more likely to create an ignition and/or explosion risk. The samples have been classified into two groups, those collected from cutting processes and those found in the ventilation ducts or deposited in the facilities. The most dangerous samples are those from Group 2. In some cases, dust samples up to 35 % moisture or with particle size greater than 500 µm at maximum dryness are able to produce an explosion.

Continuous Supply of Non-Combustible Gas Mixture for Safe Autotrophic Culture to Produce Polyhydroxyalkanoate by Hydrogen-Oxidizing Bacteria.

Polyhydroxyalkanoates (PHAs) are eco-friendly plastics that are thermoplastic and biodegradable in nature. The hydrogen-oxidizing bacterium Ralstonia eutropha can biosynthesize poly[(R)-3-hydroxybutyrate] [P(3HB)], the most common PHA, from carbon dioxide using hydrogen and oxygen as energy sources. In conventional autotrophic cultivation using R. eutropha, a gas mixture containing 75–80 vol% hydrogen is supplied; however, a gas mixture with such a high hydrogen content has a risk of explosion due to gas leakage. In this study, we aimed to develop an efficient cell culture system with a continuous supply of a non-combustible gas mixture (H2: O2: CO2: N2 = 3.8: 7.3: 13.0: 75.9) for safe autotrophic culture to produce P(3HB) by hydrogen-oxidizing bacteria, with a controlled hydrogen concentration under a lower explosive limit concentration. When the gas mixture was continuously supplied to the jar fermentor, the cell growth of R. eutropha H16 significantly improved compared to that in previous studies using flask cultures. Furthermore, an increased gas flow rate and agitation speed enhanced both cell growth and P(3HB) production. Nitrogen source deficiency promoted P(3HB) production, achieving up to 2.94 g/L P(3HB) and 89 wt% P(3HB) content in the cells after 144 h cultivation. R. eutropha NCIMB 11599, recombinant R. eutropha PHB-4, and Azohydromonas lata grew in a low-hydrogen-content gas mixture. R. eutropha H16 and recombinant R. eutropha PHB-4 expressing PHA synthase from Bacillus cereus YB-4 synthesized P(3HB) with a high weight-average molecular weight of 13.5–16.9 × 105. Thus, this autotrophic culture system is highly beneficial for PHA production from carbon dioxide using hydrogen-oxidizing bacteria as the risk of explosion is eliminated.

Development of a model for the prediction of the ignition properties of combustible dusts undergoing homogeneous combustion: Application to sulfur dust

The determination of ignition properties such as the minimum explosible concentration (MEC) is critical for the control of the risks associated with handling combustible dust. This work describes a novel approach for the determination of the MEC of combustible dusts undergoing homogeneous combustion, using sulfur dust as a case study. The proposed model is developed based on the heat and mass transfer occurring when a sulfur dust particle in a control volume is exposed to a hot planar surface acting as an ignition source. The model includes radiative and convective heat transfer from the ignition source to the particle and predicts the dust particle’s fusion and vaporization. Ignition criteria of sulfur vapor accumulation in the control volume are based on the material’s lower flammability limit (LFL) and the comparison of accumulated energy in the control volume to the activation energy of the vapor-air combustion initiation reaction. The model also includes a correlation describing a time to ignition which accounts for necessary dynamic changes like the exposure time of the dust to the ignition source. The model is capable of predicting the influence of the dust particle diameter on the MEC of sulfur dust and was validated with experimental data.

Экспериментально-аналитические исследования формирования пожаровзрывоопасных паровоздушных облаков в атмосфере при утечках и проливах жидкого водорода

Experimental and numerical studies of the process of formation of fire-explosive steam-air clouds in the atmosphere during leaks and spills of liquid hydrogen were carried out. Within their framework, the tasks were performed to determine the size and lifetime of a hydrogen-air cloud with a hazardous concentration of hydrogen from the point of view of explosion and fire hazard (including at the boundary of a visible cloud), and the relationship between the temperature and concentration of combustible gas in a gas-air cloud; studying the effect of cloud temperature on its parameters, the role of atmosphere involvement in the convective hydrogen jet; establishing the influence of moisture content in the atmospheric cloud and the mobility of the environment (wind exposure) on the dynamics of changes in the level of its fire and explosion hazard. It is shown that the humidity of the environment affects the concentration of hydrogen at the boundary of the visible cloud, and, consequently, its fire and explosion hazard. The assessment of the influence of humidity on the parameters of the studied turbulent convective jet indicates that the rate of change in the mass concentration of hydrogen on the axis of the low-temperature jet from the height of ascent depends on the humidity of the medium. The higher the humidity, the sharper the decrease in the mass concentration of hydrogen along the height of the convective jet becomes. In accordance with the calculations, the time for dissipation of a cloud to a fireproof hydrogen concentration in the presence of moisture condensate is reduced by 30 %, and the dissipation time to an explosive concentration of hydrogen is reduced by about 20 %. The coefficient of air involvement α in convective jets of hydrogen-air mixtures with positive buoyancy is 0.12 considering the real enthalpy and absolute humidity of the surrounding air of 15 g/m3 (90 % humidity at 20 °C). This coefficient can be used in the calculations of turbulent convective jets formed during stationary hydrogen evaporation. Wind at low speeds leads to an increase in the maximum transverse dimensions of the cloud, regardless of the concentration in the hydrogen jet, and at high speeds, to their decrease. For emergency hydrogen spills, the most dangerous case when a hydrogen-air cloud of large volumes is formed in the atmosphere, is the case with zero humidity and no wind (in a wide range of values of the initial mass flow of hydrogen: 0.1–100 kg/s).

An alternative explosion criterion of combustible dusts based on combustion duration time: Applications for minimum explosion concentration and limiting oxygen concentration

A novel method based on combustion duration time was newly proposed as an explosion criterion to determine minimum explosion concentration (MEC) and limiting oxygen concentration (LOC) in our recent works. This work further studies the reasonability and reliability of the alternative method experimentally and theoretically. Six different dust samples were tested via a 20-L spherical explosion chamber. The experimental results showed that the data of MEC and LOC determined by using the alternative and the standardized methods are in good agreement. The minimum flame propagation velocity ( S f ) and the corresponding maximum combustion duration time ( t c ) were found at its MEC and LOC, suggesting that the theoretical analysis can well explain all the experimental data. It is the first time to study the theoretical basis of the explosion criterion, thus helping to improve our understandings of dust explosion characteristics, and to amend the explosion criterion in future test standards. • An alternative method based on t c was proposed to determine MEC and LOC. • The alternative method was found to be reliable and feasible. • A theoretical analysis on flame propagation velocity was performed to explain the proposed method. • The alternative method compensates the deficiency of the current standardized explosion criterion.

Experimental study of explosion overpressure and flame propagation of micro‐sized and nanosized iron powder

AbstractIn order to study the explosion of micro‐sized and nanosized iron powder, the explosion overpressure and flame propagation were measured in a 20‐L near‐spherical explosion pressure experiment and a Hartmann tube experiment. The explosion overpressure experiments show that the optimum explosion concentrations of micro‐sized and nanosized iron powder are 750 and 375 g/m3, respectively. The maximum explosion pressure and the maximum explosion pressure rise rate of nanosized iron powder are 0.56 MPa and 46.41 MPa/s, which are 144% and 225% of that of micro‐sized iron powder, respectively. Under the optimum explosion concentration, the explosion flame of nanosized iron powder is brighter, and the propagation time is shorter. The maximum propagation velocity of micro‐sized and nanosized iron powder flame is 0.84 and 6.55 m/s, respectively, and the flame pulsation degree of micro‐sized iron powder is larger. The spherical particles and the cracks on the surface of the product particles were observed in the micro images of the explosion products, and the explosion mechanism model of micro‐sized and nanosized iron powder was obtained. It was observed that the deformation of micro‐sized iron particles intensifies, forming regular and complete spherical iron oxide particles.

Predicting continuous dispersion and deposition of explosive dust in confined spaces using a discrete phase model

Dust dispersion and deposition are of great concern when designing dust control systems. In this study, suspension and deposition of dust in an enclosed chamber was simulated using a computational fluid dynamics (CFD) - discrete phase model (DPM) with a particle-wall stick-rebound feature. The dispersion and deposition of dust at explosive concentrations of 15, 30, and 45 g/m 3 were simulated in this study. The dust rebounding at particle-wall interaction and particles sticking to wall were also simulated. The rate of dust-deposition and particle-size distribution of settled dust were obtained during simulation from selected locations within the chamber. The results showed that the larger particles tend to settle closer to the dispersion nozzle when compared with the smaller particles. The suspended dust concentration increased with the rate of dispersion, but after 30 s of continuous dispersion, the rate of dispersion did not alter the suspended dust concentration changing rate. The low prediction errors showed that the CFD-DPM model is accurate in predicting the rate of dust-deposition in confined chambers by tracking the particle motion. • A CFD-DPM approach was used to simulate the dust dispersion and deposition. • With time, the rate of dust dispersion did not influence suspended dust concentration. • Tracking particle motion aids in accurate prediction of dust-deposition.

Analysis on the disaster chain evolution from gas leak to explosion in urban utility tunnels

Gas leakage and explosion are the main disasters associated with utility tunnels. The ongoing challenge is to establish a precise and efficient disaster chain model to describe the process from the gas leakage to explosion in the utility tunnel, which are regarded as the initial and final status during the disaster, respectively. In this paper, a disaster chain model is proposed to analyze the evolution process from gas leak to explosion in a concurrent way. The risk area of the gas explosion, which could change with gas leakage dynamically, was calculated by the proposed model. The evolution analyses of the gas leakage and explosion were systematically studied. Results showed that the CH4 mass fraction was stratified and focused on the top of the utility tunnel during gas leakage, which provides initial conditions for the gas explosion. The explosion reaction considering the gas cloud location and stratification effect is insufficient and unstable since the gas concentration is out of the optimal explosion concentration. Additionally, the propagation velocity and temperature were decreased since the explosion intensity was weakened.

Experimental study on the minimum ignition energy of cornstarch particle-air flows in a horizontal pipeline

Pipelines and process equipment are commonly interconnected in a network of dust extraction or pneumatic conveying in lines industry. History has shown that the severity of a dust deflagration could be much accentuated if the initial fireball is allowed to propagate further through pipelines. However, less is known about the hazard of a primary ignition in a pipeline conveying system with combustible dust and high airflow velocity. This paper presents an experimental study on the ignitability of cornstarch particle-air flow in a lab-scale piping system. The results show that minimum ignition energy (MIE) of dried cornstarch flow at 12–28 m/s was less than 300 mJ, and the minimum explosible concentration (MEC) was less than 100 g/m3. An increase in airflow velocity increased both MIE and MEC, as well as stretching the spark plasma. Moisture in the dust significantly decreased its ignitability, with this being a more marked factor than airflow velocity in influencing the ignition hazard in a pipeline.

Evaluation of time series artificial intelligence models for real-time/near-real-time methane prediction in coal mines

ABSTRACT Atmospheric monitoring systems are critical in underground coal mine ventilation where methane explosion hazards can develop. The number and location of sensors are important for ventilation monitoring. Atmospheric monitoring system sensors should be installed near the most critical locations like the shearer cutting drum and along the longwall face. Sensors can provide information for a limited area, and their readings may have delays caused by sensor response time, gas diffusion rate, and temperature. Computational fluid dynamics modeling can provide relatively accurate predictions regarding the location of possible explosive gas concentrations. However, it requires significant computational resources and time, which is not conducive to real-time decision-making. This paper evaluates artificial intelligence systems for predicting near-real-time explosion hazards. The prediction performance of 10 time series algorithms is compared by using seven datasets and assessed by classification accuracy. Accurate real-time/near-real-time methane predictions are possible with two algorithms: HIVE-COTE and RISE. Initial results demonstrate that near-real-time decision-making for explosive hazard warning systems is accurate and robust, and artificial intelligence modeling of explosion hazards enhances mine safety.

Iron dust explosion characteristics with small amount of nano-sized Fe2O3 and Fe3O4 particles

Iron powder, as one of the most abundant metal fuels that can be used as recyclable carriers of clean energy, is a promising alternative to fossil fuels in a future low-carbon economy. It may pose a potential explosion hazard during the process of processing, storage, transport, and reduction/oxidation (redox). The explosion characteristics of iron dust in air were undertaken via a 20 L spherical explosion chamber with an emphasis on minimum explosion concentration (MEC) of iron dust. The alternative method of combustion duration time (tc) was used to determine MEC and compared with the standardized over pressure method. Two kinds of nano-sized iron oxides (Fe2O3 and Fe3O4) were used as inertants to determine the inhibition effect of different oxidation products. The iron dust explosion products with various shapes and sizes were found to be able to grow up 4–6 times of the iron dust for the first time. Adding small amount of Fe2O3 or Fe3O4 could reduce the explosion severity and sensitivity of iron dust. The MEC data determined by both methods were comparable. The addition of 5 % oxide has obvious inhibition effect under 1500 g/m3 concentration. With the increase of oxide concentration to 10 %, the inerting effect increases, and the MEC of iron dust increases more than 3 times. The increase of dust concentration will weaken the inerting effect. When the concentration increases from 500 g/m3 to 3000 g/m3, the weakening effect of 10 % Fe2O3 on the explosion pressure decreases from 38.45 % to 2.24 %, and 10 % Fe3O4 decreases from 46.21 % to 10.63 %. Unlike coal, biomass or aluminum dusts, the iron dust explosion was found to have a unique secondary acceleration of pressure rise rate for the first time. These results provide a fundamental basis to mitigate the iron dust explosion via solid inerting method without adding extra elements.

Effect of CaCl2, Al(OH)3 and NH4H2PO4 on the explosion sensitivity of pulverized coal

ABSTRACT In this paper, the effects of 30 wt%, 50 wt% aluminum hydroxide, calcium chloride and ammonium dihydrogen phosphate three explosion inhibitors on the two sensitivity parameters of the minimum explosion concentration and the minimum ignition energy of pulverized coal were investigated. It was found that for the same explosion inhibitor, the higher the content of explosion inhibitor, the higher the increase of MEC and MIE of pulverized coal-explosion inhibitor. At the same time, dust reduction measures should be taken in time when the coal dust concentration will be close to 70 g/m3. It was found that for the same explosion inhibitor, the higher the content of explosion inhibitor, the higher the increase of MEC and MIE of pulverized coal-explosion inhibitor. In the meantime, dust reduction measures should be taken in time when the coal dust concentration will be close to 70 g/m3. Furthermore, 150 g/m3 was the critical concentration of the ignition energy of pulverized coal. In order to prevent the occurrence of coal dust explosion accidents, it was necessary to resolutely prevent the concentration of pulverized coal from approaching this value on site. In addition, when the pulverized coal-explosion inhibitor concentration was 100 g/m3-250 g/m3, whether it was 30 wt% NH4H2PO4 or 50 wt% NH4H2PO4, the ignition energy required for mixing with pulverized coal was greatly increased. Overall, in the concentration range of 30–50 wt%, 50 wt% NH4H2PO4 was more advantageous in the suppression of coal dust explosion.

Explosion characteristics and mechanism of aluminum-reduced graphene oxide composite powder

Aluminum-based fuel in energetic formulations has favorable ignition and combustion characteristics, but it is also prone to an explosion. To ensure safe production and prevent accident, explosion characteristics and the mechanism of aluminum-reduced graphene oxide (Al-RGO) composite were investigated. Thermal analysis showed that after adding RGO, the activation energy of Al dust in the initial oxidation stage decreased from 241.5 kJ/mol to 90.0 kJ/mol. With the addition of 5 wt% RGO, PTFE, and Ni inclusions, the minimum explosible concentration increased by 40%, 10%, and 25%, the maximum explosion pressure increased by 20.8%, 13.8%, and 7.5%, respectively. Moreover, the addition of RGO could significantly improve the flame propagation speed and oxidation efficiency of aluminum but with a slight effect on the burning time of single Al particles. XPS results revealed that the major explosion product of Al-RGO is Al2O3. Based on these results, the explosion mechanism of Al-RGO was discussed in-depth.