Explosion Prevention Research Articles

Suppression of hydrogen-air explosions by isobutene with special molecular structure

Effects of isobutene (i-C4H8) with the unique molecular structure on hydrogen explosions are investigated in a 14 L spherical chamber at 100 kPa and 298 K. The results reveal that for lean hydrogen-air mixtures, the maximum explosion overpressure, maximum pressure rise rate, and deflagration index show a trend from rise to decline. However, for stoichiometric and rich hydrogen-air mixtures, pressure parameters decrease monotonously with increasing i-C4H8. The chemical suppression mechanism of i-C4H8 on hydrogen explosions is revealed in detail by numerical simulation. The relevant analyses show that i-C4H8 can not only change the chain reaction path and cut off the hydrogen-oxygen reaction, but also strengthen the consumption of oxygen and H radicals. This work will provide a novel theoretical foundation for hydrogen explosion prevention and control.

Synergistic effects of isobutene and carbon dioxide on suppressing hydrogen-air explosions

The effects of isobutene (i-C4H8) and carbon dioxide (CO2) on hydrogen explosions have been explored in a 14 L spherical chamber at 100 kPa and 298 K. The results show that compared with CO2, the cooperation of i-C4H8 and CO2 can more effectively suppress the explosion pressure, pressure rise rate, and deflagration index. The minimum suppression concentration of CO2 with 1.5% i-C4H8 is much lower than that of CO2 alone. Numerical simulation reveals the mechanism of the suppression of i-C4H8 and CO2. I–C4H8 changes the reaction paths, and the addition of CO2 further lowers the adiabatic flame temperature and the active radical concentration. The excellent performance of the cooperation of i-C4H8 and CO2 in hydrogen explosions will provide a new idea for the prevention and control of hydrogen explosions.

産業現場における静電気の発生と爆発・火災の防止

産業現場における静電気の発生と爆発・火災の防止

Kinerja Inert Gas Generator Untuk Mendapatkan Oksigen Konten 3% Pada Gas Lembam

Inert Gas System is a machine that functions as a security system to prevent explosions on tankers. Explosion prevention is carried out by introducing inert gas into the cargo tank with the aim of reducing oxygen levels in the cargo tank atmosphere so as to prevent the formation of a flammable gas mixture. Inert gas contains very little oxygen, namely 1-2% by volume. The device that produces the inert gas is called the Inert Gas Generator (IGG). The purpose of this study was to determine the factors that cause high oxygen content contained in the inert gas and the efforts made related to the factors mentioned so that the inert gas generator can work optimally. The research method used by the author is descriptive qualitative with Fishbone data analysis techniques and SWOT analysis. The results of the study stated that the factors causing oxygen content of more than 3% were dirty fuel filter, too much combustion air supply, oxygen analyzer that was rarely calibrated, flow sampling was too large, fuel quality was not good, lack of crew knowledge. to PMS (Plan Maintenance System) IGG. Efforts have been made to clean the fuel pump filter, close the air capacity valve a little, calibrate the oxygen analyzer according to the PMS schedule, reduce the sampling valve flow into the oxygen analyzer, add fuel oil treatment (additives) to the fuel, pay attention to the IGG maintenance schedule according to PMS, restore the maintenance implementation system based on the PMS inert gas generator schedule.

Explosion characteristics of coal dusts in O2/N2 ambience: A novel method to determine limiting oxygen concentration

The explosion characteristics of anthracite and bituminous coals in O2/N2 ambience were experimentally studied via a 20-L spherical explosion chamber with various ignition energies of 2, 5 and 10 kJ. A novel method based on combustion duration time was proposed for the first time, with an emphasis on the determination of the limiting oxygen concentration (LOC). The values of LOC determined by the alternative method were almost consistent with those obtained by using the standardized overpressure method, where the LOCs were above 21.6%, 19.8%, and 13.2% for anthracite coal and 11.4%, 9.6%, and 9.0% for bituminous coal when the ignition energy is 2, 5, and 10 kJ, respectively. But the newly proposed method was found to be much less affected by the ignition energy compared with the standardized overpressure method, taking combustion duration time as an explosion criterion thus had a higher efficiency and required fewer experiments. The results also showed that as oxygen concentration decreases from 21.6% to 14.4%, the maximum explosion pressure decreases from 0.4334 MPa to 0.1034 MPa for anthracite coal and from 0.5664 MPa to 0.3981 MPa for bituminous coal, respectively. Moreover, the effect of ignition energy varied with varying volatile matter content and ignition mechanism of coal dusts. The higher the volatile content, the less sensitive it is to the ignition energy. The newly proposed method will provide a reference for the new standard development, hazard analysis, explosion prevention and suppression by involving the use of inert gases of combustible powder industries.

Experimental study on the lower explosion limit and mechanism of methanol pre-mixed spray under negative pressure

Equally as important as gas and dust explosions, the lower explosion limit(LEL) of spray is an important parameter for explosion prevention and control. The impact of ambient temperature(298.15–323.15 K), pressure(0.8–1.0 bar) and injection pressure(1.3–2.1 bar) on the LEL of methanol spray under negative pressure was studied. The development of a typical spray explosion accident and the mechanism of spray explosion were analyzed. Results showed that the impact of oxygen content on the LEL of methanol spray was minor and could be ignored. Under negative pressure, the LEL increased with increasing ambient pressure with a linear relationship. The increasing ambient temperature promoted the decrease of the LEL. The reduction of LEL was facilitated by the air drive at 13 bar to 17 bar. Under the combined effect of ambient pressure and injection pressure, the LEL of methanol spray varied in line with the effect of single factor. When ambient temperature and injection pressure combined, the injection pressure had less impact on the LEL, while the impact of ambient temperature took the lead. The slope of the fitting curve was greater at ambient temperatures above 308.15 K(material temperature) when ambient pressure and temperature were combined, and the LEL of methanol spray was more significantly impacted by ambient pressure. The combined effect of ambient pressure and temperature resulted in a 43.64% reduction of the LEL, much greater than the sum of the reductions caused by the single factors. Apart from the three factors of combustion, a suitable vapour-liquid two-phase concentration was needed for the spray explosion. In the initial stage, the explosion pressure increased, the rate of pressure rise decreased and the combustion between droplets spread relatively slowly. When the explosion developed fully, the rate of pressure rise increased, the pressure reached a peak. The flame brightness was extremely high. Droplet flaming continued after the termination of the explosion. The hazards of spray explosions included debris from the explosion, fireballs, shock waves, and the scalding of flaming droplets.

Modelling of turbulent hydrogen-blended premixed flames using algebraic flame surface wrinkling closure for the Lewis numbers and mean local burning velocity

Hydrogen-blended fuel is of fundamental interest due to difficulties in modelling and its practical significance for the development of high-performance hydrogen combustion devices and safety technologies for the prediction and prevention of fire or explosion. In this analytical study, we validate an algebraic premixed turbulent model [13] for molecular transport effects in both spherical expanding methane flames enriched with hydrogen and Bunsen burner flames. Experiment comparisons are supported with theoretical ideas. Bunsen flames are measured at varied turbulence, equivalence ratios, temperatures, and pressures. We also consider other, very recent, experimental data [32] of similar fuel mixtures to support the trends.In the study of outwardly evolving spherical expanding flames, we present three variants of this model, with two functions based on the Lewis number Le, and one based on the experimentally measured mean local flame burning velocity SFm. The Lewis number is significant in understanding the role of the diffusion of deficient reactants, which is particularly noticeable in blended fuels. The utilitarian part of this work is to demonstrate that the Le-based premixed turbulent models take into account the preferential diffusion effect, and to embed a term that quantifies turbulent flame speed explicitly for mixtures, for example, having the same unstretched burning velocity as the model input. We show that in the modelling of turbulent burning velocity, the use of SFm avoids the use of input parameters the unstretched laminar flame speed and the Lewis number. Moreover, we validate high-pressure experiments by Bagdanavicius [12] to show that the pressure has less significant impact on the Bunsen flames and, therefore, we model without the pressure term. The model correlates well with most of the data.

Multi-Layered Numerical Model Development of a Standard Cylindrical Lithium-Ion Battery for the Impact Test

For safety issues in lithium-ion batteries (LIBs), international standards and regulations for various abusive environments have been developed, and UL1642 in Underwriters Laboratories (UL) currently covers electrical, mechanical, environmental, and fire exposure tests. An impact test is one of mechanical abuse tests in UL1642, which aims to determine the safe prevention of fire or explosion. As the energy density of a lithium-ion battery is continuously increasing, it is difficult to pass the regulation. Therefore, it is necessary to predict failure mode due to an internal short circuit in developing high-capacity cells. For a sudden and measured mechanical force, we speculate that damage to a separator consisting of LIBs makes the battery experience an exothermic phenomenon due to an internal short circuit because a separator is a key component for preventing the electrical contact between two electrodes. Therefore, if we can find mechanical stresses of each component in LIBs, we can evaluate whether each component is severely damaged or not. In the present study, we propose a finite element model consisting of a multi-layered structure, which will permit us to assess the possible onset location of the short circuit, and to predict the sequence of failure at a cell level. We applied the proposed method to a cylindrical cell, and the accuracy of the model was verified through the comparison of the experiment results. Additionally, simulation results showed that it is possible to track mechanical stress variations of each component progressively. Furthermore, we performed the numerical experiment evaluating the thickness effect of a center-pin. We expect the proposed finite element model to be used in order to devise cell level abuse-tolerant design from a mechanical point of view before conducting mechanical abuse tests as part of the product development process.

Effects of volatile contents on the deflagration characteristics and soot formation of methane/coal volatiles hybrid explosion using reaction kinetics simulation

The volatile content of coal dust has a great influence on the explosion features and reaction process for methane/coal dust mixtures. The present work aims at exploring the specific influence and underlying mechanisms of coal volatiles on explosions of the mixture. For this purpose, the reaction kinetics model of coal volatiles deflagration in methane-air atmospheres was established based on Wang-Frenklach (WF) mechanism and Appel-Bockhorn-Frenklach (ABF) mechanism, with the numerical modeling presenting excellent consistency with previous reports. In addition, with the aid of the CHEMKIN-PRO program, the explosion characteristics of coal volatiles with different contents in various methane-air atmospheres were numerically investigated. The primary chain-reaction paths and significant features of key radicals for the mixtures were firstly explored, the variation laws in temperature, pressure, and ROP (Rate-of-Production) for the mixtures were then quantitatively analyzed, and finally, we discussed the formation rules and reaction mechanisms of the soot particles generated in the explosions. Results showed that for a given methane-air atmosphere, as the volume fraction of volatile content increased from 0.1% to 1.6%, the explosion reactions of the mixtures occurred prematurely, indicating the coal volatile content has a positive influence on the hybrid explosion of the mixtures. Meanwhile, methane concentration is dominant in provocating the explosion severity and the maximal temperature of the mixtures. For the methane concentrations of 7%, 9.5%, and 11%, as the volume fraction of coal volatile increased from 0.1% to 1.6%, the maximal explosion pressure decreased by 0.34%, 0.26%, and 0.23%, whereas the maximal explosion temperature increased by 0.25%, 0.19%, and 0.17%, respectively. In addition, the ROP of the free radicals exhibited an increasing tendency as the volume fraction of coal volatile increased from 0.1% to 1.6%, particularly, the two most active free radicals H and O obtained different increases in content. Furthermore, as the volume fraction of coal volatile increased from 0.1% to 1.6%, the time for the growth rate of soot particles reaching its maximum reduced by 71.06% and the growth rate decreased by 37.51%. This study can provide theoretical references and effective strategies for accident prevention and disaster control of methane-coal dust explosions.

Hydrogen Inhibition as Explosion Prevention in Wet Metal Dust Removal Systems

Hydrogen energy attracts an amount of attention as an environmentally friendly and sustainable energy source. However, hydrogen is also flammable. Hydrogen fires and explosions might occur in wet-dust-removal systems if accumulated aluminum dust reacts with water. Hydrogen inhibition is a safe method to address these issues. For this purpose, we used sodium citrate, a renewable and nontoxic raw material to inhibit H2 formation. Specifically, hydrogen inhibition experiments with sodium citrate were carried out using custom-built equipment developed by our research group. When the concentration of sodium citrate solution was in the range of 0.4–4.0 g/L, a protective coating was formed on the surface of the Al particles, which prevented them from contacting with water. The inhibitory effect was achieved when the concentration of sodium citrate was in a certain range, and too much or too little addition may reduce the inhibitory effect. In this paper, we also discuss the economic aspects of H2 inhibition with this method because it offers excellent safety advantages and could be incorporated on a large scale. Such an intrinsic safety design of H2 inhibition to control explosions in wet-dust-removal systems could be applied to ensure the safety of other systems, such as nuclear reactors.

Simulation Study of Gas Explosion Propagation Law in Coal Mining Face With Different Ventilation Modes

In ventilation working face, different ventilation way is one of the important factors affecting the propagation of gas explosion shock wave. In order to study the gas explosion shock wave propagation laws in coal mining faces with different ventilation methods, using Fluent simulation software, combined with pipeline gas explosion experiments and the actual situation of gas accumulation area explosion in the corner of 415 coal face in Chenjiashan coal mine, Shaanxi Province, and on the basis of building a three-dimensional mathematical and physical model, the gas explosion simulations under Y-type and W-type ventilation methods were carried out, respectively. The results are described as follows: (1) The attenuation trend of overpressure peak value of inlet roadway 1 and working face with Y-type ventilation conforms to the power function form. Intake airway 2 and return airway have the same peak overpressure attenuation trend, but the peak value of overpressure in return airway is generally 10.6% higher than that in intake airway 2, and its attenuation rate is a process from low to high and then to low. (2) The peak attenuation trend of overpressure in intake airways 1 and 2 with W-type ventilation conforms to the form of power function, and the peak attenuation trend of overpressure in return airway conforms to the form of exponential function. The peak value of overpressure decreases with the increase in the distance from the explosion source, and its attenuation rate decreases gradually. The research results have important theoretical significance for improving the prevention of gas explosion in coal mining face with different ventilation modes.

Inhibiting effects investigation of pulverized coal explosion using melamine cyanurate

To ensure the safety of industrial process related to pulverized coal, inhibition capacity of melamine cyanurate (MCA) on pulverized coal explosion was investigated. Oxidation process and explosion characteristics of the pulverized coal mixed with MCA were conducted, and the characteristics of explosion products were detected to demonstrate the inhibiting processes of MCA. The results demonstrated that the maximum mass loss rate and heat release of the pulverized coal oxidation decreased with the mass fraction of MCA increasing. When the addition amount of MCA ranged from 0% to 70%, maximum explosion pressure, maximum pressure rising rate and average flame velocity were decreased. The explosion was completely inhibited when 65% MCA was added and the optimum inhibiting concentration was approximately 195 g/m3. The inhibiting mechanism of MCA on pulverized coal explosion included isolation, heat absorption and oxygen consumption. The results of this work provide basic parameters for coal dust explosion prevention.

Brief Discussion on Dangerous Gas Release and Explosion Prevention Measures of Valve-regulated Lead-acid Battery in Power Plant

Brief Discussion on Dangerous Gas Release and Explosion Prevention Measures of Valve-regulated Lead-acid Battery in Power Plant

Analysis of the Interaction Mechanism of the Risk Factors of Gas Explosions in Chinese Underground Coal Mines.

Gas explosion accidents easily cause severe casualties in Chinese underground coal mines. Systematic analysis of accident causation is crucial for the prevention of gas explosions. This study identifies the representative risk factors of gas explosions and determines the interrelationship among these risk factors to highlight weak links and develop countermeasures. A total of 21 representative risk factors of gas explosions were identified through 128 case studies and front-line investigations. On this basis, a five-level hierarchical structure model of gas explosions was established to explore the complex interrelationships among the representative risk factors based on a combination of the Decision-Making Trial and Evaluation Laboratory (DEMATEL) and Interpretive Structural Modeling (ISM) methods. Moreover, the Matrix of Cross Impact Multiplications Applied to Classification (MICMAC) method was applied to achieve risk factor classification into four clusters, namely, driving factors, linkage factors, dependent factors and autonomous factors. The results indicated that the interrelationships and emergence properties among the risk factors may cause gas explosions, which should give more attention to the interrelationships among multiple factors and multiple subsystems for coal enterprises. Meanwhile, the complex geological conditions, poor safety supervision, inadequate safety education and training, incomplete execution safety regulations and poor safety technology and input are the long-term focus of risk management for coal enterprises. Finally, 10 countermeasures were proposed to control these representative risk factors and interrelationships. The results are helpful to the development of gas explosion risk management policies and to the preferential allocation of limited resources to resolve these issues.

The inhibiting effects of sodium carbonate on coal dust deflagration based on thermal methods

To aid the development of safe procedures, the inhibiting effects of sodium bicarbonate (NaHCO3) on coal dust explosions were investigated by employing a simultaneous thermal analyzer and a standard 20-L spherical chamber. The thermal behaviors and explosion parameters of the coal dust/NaHCO3 mixtures were characterized and the surface morphology, functional groups and chemical composition of the explosive residue were conducted. Finally, the inhibiting mechanism of NaHCO3 on coal dust explosions was proposed. The results demonstrated that the thermal decomposition temperature of coal dust was increased and the thermal decomposition rate, maximum heat flow, and heat release were decreased after the addition of NaHCO3. The apparent activation energies and pre-exponential factors of coal dust were also increased. The maximum explosion pressure and maximum explosion pressure rising rate during deflagration decrease with an increase in the NaHCO3 mass fraction, and the optimal inhibiting ratio of NaHCO3 powder to pulverized coal explosion is 400%. NaHCO3 powder covers the surface of coal dust particles promoting heat absorption and isolation, and the functional groups, such as C=C, C–O and C–H, are protected by NaHCO3, preventing coal dust pyrolysis and inhibiting the explosions. The results provide guidance for the prevention of coal dust explosion.

Explosion prevention and mitigation in plants which process, generate and store combustible dusts

Combustible dusts which are present in workplaces are a significant hazard which cannot be ignored by the plant owners, managers and workers. Combustible dust deflagrations and explosions have caused large numbers of deaths and catastrophic property damages in various industries, ranging from pharmaceutical plants to sugar factories. One may say that dust explosions in process industries always start inside process equipment such as mills, dryers, filters. Such events may occur in any process in which a combustible dust is handled, produced or stored, and can be triggered by any energy source, including static electricity, friction and hot surfaces. For any combustible dust type, several important parameters have to be taken into account when designing and using protective systems: i.e. the ease with which dust clouds ignite and their burning rates, maximum explosion pressure, maximum rate of explosion pressure rise. These parameters vary considerably depending on the dust type, their knowledge being a first step for carrying out a proper explosion risk assessment in installations which circulate combustible dusts. The paper presents the main aspects concerning explosion protection which have to be taken into account when designing protective systems intended to be used in explosive atmospheres generated by combustible dusts and the importance of selecting the proper explosion protection technique.

Aspects regarding the explosion risk assessment of installations in atmospheres with combustible dust

Many industrial processes involving the presence of dust and combustible dust, suspended or accumulated in the form of deposits, have the potential to lead to a fire, explosion or decomposition in the presence of oxygen. As the damage caused by an explosion of dust is generally greater than that caused by explosions of flammable gases and vapours, a special attention must be paid to measures and means of protection and prevention of explosions of dust. A dust explosion can only occur if there is mainly a potentially explosive atmosphere generated by the air / dust mixture and a source of ignition. The level of safety is given by the operational efficiency of the employees and technical equipment involved in the production process to ensure that at least one of the above conditions is eliminated. The probability of a dust explosion is related to the physicochemical properties of the processed materials, together with the nature of the operations performed and the equipment used. This paper highlights the principles and factors that must be taken into account when conducting an explosion risk assessment in installations with combustible dust atmospheres in order to establish prevention and protection measures, with the aim of ensuring a tolerable level of risk.

Investigation on the Inhibition of Aluminum Dust Explosion by Sodium Bicarbonate and Its Solid Product Sodium Carbonate.

To characterize the inhibiting effects of sodium bicarbonate (NaHCO3) on aluminum dust, the inhibiting capacities of NaHCO3 and its solid product sodium carbonate (Na2CO3) on the explosions of 10 and 20 μm aluminum dusts were studied using a standard 20 L spherical chamber. Explosion parameters were analyzed based on the induction period and explosion stage to evaluate the inhibiting effects. The results show that the induction period of 10 μm aluminum dust explosion is 18.2 ms, which is shorter than that of 20 μm aluminum dust. Two aluminum dust explosions can be completely inhibited during the induction period when inert ratios of NaHCO3 are 350 and 150%, respectively, but that is not observed after adding the corresponding amount of Na2CO3. When the inert ratio ranges from 0 to 150%, the physical effect of NaHCO3 on 10 μm aluminum is poor and the chemical effect is the essential process. But as the inert ratio increased from 200% to 350%, the physical effect of NaHCO3 is higher than the chemical effect, suggesting that the physical effect is the key factor. With the increase of NaHCO3, the physical effect increases gradually. However, the chemical effect changes little. The physical effects of NaHCO3 including heat absorption and isolation play an essential role in the inhibiting process, which has a significant impact on the pyrolysis process and explosion parameters. The results of the present work provide guidance for the prevention and control of aluminum dust explosions.

Explosion hazard and prevention of Al–Ni mechanical alloy powders

Al–Ni mechanical alloys containing nickel are synthesized to explore the explosion hazard of fuel additives in energetic formulations in this study. Explosion severity and ignition sensitivity of Al and Al–Ni powders are measured. The results show that as the nickel content increases, the synthesizing heat of Ni-aluminide will firstly increase, and then decrease, which may also make the explosion severity of aluminum powder increase firstly and then decrease accordingly. The powder's sensitivity to electrostatic ignition will grow as the nickel content increases. As the nickel content increases from 0 to 17%, the average activation energy of Al–Ni powder decreases by 77.5%. The increase of ignition energy mainly affects the flame propagation, but with few effects on the process of Al–Ni combustion. Therefore, as the ignition energy increases, the explosion severity of the Al and Al–Ni powders decreases slightly. For safety's sake, the production and storage devices must be inert, and the concentration of oxygen should be less than 5%.

Effects of Void Scale of Coal Accumulation on Methane-Air Flame Propagation and Overpressure Dynamics

ABSTRACT With the coal mining toward depth, there is an increased probability of gas explosion accidents. While the propagation characteristics of gas explosion on account of goaf environment have not been determined yet, which has great significance for the prevention of the goaf fire spreading to working face. This paper investigates the critical void scale of coal piles that allowed for the propagation of gas explosion flames using a closed duct with the dimensions of 100 × 20 × 10 cm. The void ratios of the stacked coals varied in 0.554, 0.521, 0.492, and 0.471. The results show that the increased flame speed in the coal accumulations poses a greater explosion hazard. While the smaller coal particle sizes are more advantageous for the suppression effect on flame velocity. The explosion duration is inversely proportional to the void ratio, which mainly depends on the void diffusion stage and the flame extinction stage. Moreover, the maximum overpressure and (dP/dt)max of the explosions attenuate with the decrease in the void scale. The critical void ratio of coal accumulation is between 0.47 and0.49 for premixed methane-air flame with an equivalence ratio of 1. The irregular coal geometry makes flame quenching easier. The void-scale effect of accumulations on flame propagation should be fully considered in the explosion prevention works.