Explosive Reaction Research Articles

Effect of CO2 on the explosion limit parameters and kinetic characteristics of ammonia-hydrogen-air mixtures

To explore the effect of CO2 on the explosion limit parameters and kinetic characteristics of the NH3-H2-air mixtures, the standard combustible gases explosion limits device was utilized to test and analyze the explosion limit, critical oxygen concentration, and explosion triangle. Based on the CHEMKIN software, the suppression mechanism of CO2 on NH3-H2-air mixtures explosion with 0.4 R (hydrogen ratio) and a near-inerting critical concentration was simulated and analyzed. The results indicated that increasing F (volume fraction of CO2) led to a decrease in the upper explosion limit (UEL) of NH3-H2-air mixtures and an increase in the lower explosion limit (LEL). When F increased to 36%, the explosion of the NH3-H2-air mixtures with 0.4 R was completely suppressed. As R increased, the UEL and LEL decreased and increased linearly, respectively, the critical explosion-suppression concentration of CO2 increased, the critical oxygen concentration decreased, and the explosive zone area also increased. In addition, based on the analysis of the changing characteristics of the UEL and LEL, prediction models for the UEL and LEL of NH3-H2-air mixtures with different hydrogen ratios under the effect of CO2 were provided. Reaction kinetics analysis found that less CO2 had a more pronounced impact on ·H and ·OH. However, when F increased to 20-30%, the maximum mole fraction of ·O decreased the most. At this point, the sensitivity of·NH2 towards decreasing oxygen concentrations became comparable to that of ·H and ·OH. When F increased to a near-critical explosion-suppression concentration of 30%, ·H, ·OH, ·O, and ·NH2 were in a critical state of disappearing, and the chain initiation of the explosion was destroyed. Sensitivity analysis indicated that ·H+O2(+M)<=>HO2(+M) and ·NH2+·NH=N2H3 performed a more significant inerting effect on ·H and ·NH2, which ultimately led to the termination of the explosive chain reactions.

Detection of Organic Explosive Residues from Outdoor Detonations using Confocal Raman Microscopy

The detection of post-blast residues in the aftermath of an explosion involving organic explosives with spectroscopic techniques is challenging as, typically, no microscopically visible unreacted particles remain after the explosion. However, some low-order explosions may leave visible particles behind, as well as the presence of significant amounts of unreacted material. In this study, four authentic open-air detonations using two simulated improvised explosive devices (IEDs) containing a mixture of military explosives (TNT and RDX), and two IEDs containing smokeless powder were conducted. The various materials they contained, including plastic, wood, and metal, were swabbed and extracted with acetone to create post-blast liquid extracts. The extracts were then dried and examined using confocal Raman microscopy, alongside a 50 ppm reference mixture of smokeless powder constituents, which was created to evaluate the effects of Raman scattering within the full smokeless powder mixture. Smokeless powder constituents, such as ethyl centralite, diphenylamine, nitroglycerin, and dibutyl phthalate, were successfully identified by comparison to the reference mixture on most substrates, with the exception of the paint stick (wood) substrate. TNT/RDX was also able to be identified in the extracts, with RDX crystals being observed in some dried extracts after solvent evaporation. However, the detection of TNT/RDX in the second detonation was unsuccessful, possibly due to an explosive chain reaction that was highly efficient. No trends were seen in substrate affinity for TNT/RDX. The challenges and benefits with the developed methodology for the detection of organic explosive residues from a variety of substrates are discussed in detail.

Explosion dynamics for thermal runaway gases of 314 Ah LiFePO4 lithium-ion batteries triggered by overheating and overcharging

Thermal runaway (TR) of LiFePO4 lithium-ion batteries (LFPs) can produce significant amounts of smoke, posing serious explosion hazards. This paper systematically investigated TR gas generation, explosion limits, explosion overpressure, and post-explosion gas compositions of 314 Ah LFPs under overcharging and overheating. Quantum chemical and explosion reaction kinetics calculations clarified the elementary reactions and compositional alterations occurring in gases and free radicals during the explosion process. The findings revealed that H2 constituted the primary component of TR gases, comprising 47.64 % and 53.12 % of the overcharging and overheating, respectively, followed by CO2 and CO. The ranges of explosion concentration for TR gases, when subjected to overheating and overcharging conditions, were 6.32–29.3 % and 6.83–26.91 %, respectively. At the point of maximum explosion overpressure (Pmax), the gas concentrations peaked at 15.86 % and 16.25 %. The elementary reaction R1 held a pivotal position in enhancing the explosion overpressure. As the TR gas concentration escalated, the Rate of Production (ROP) of R31 and R35 also surged, ultimately resulting in elevated concentrations of CO. The reactions R123, R250, and R279 facilitated the generation of H2 while simultaneously consuming hydrocarbon gases. This resulted in a risk of secondary explosion of the TR gas after the explosion. Post-explosion gas residual quantities followed the order: C2H6 < C2H4 < CH4 < H2 < CO. The results revealed crucial insights for developing explosion prevention and suppression in the process safety industry and Energy Storage Systems.

Experimental Investigation and Chemical Kinetics Analysis of Carbon Dioxide Inhibition on Hydrogen-Enriched Liquefied Petroleum Gas (LPG) Explosions

The utilization of hydrogen-enriched liquefied petroleum gas (LPG) is an effective means of reducing carbon emissions, but the special physical and chemical properties of hydrogen have raised concerns among the public. To delve into the intricate chemical kinetic mechanisms governing the inhibitory effect of CO2 on the explosion of hydrogen-enriched LPG, this study systematically investigated the influence of varying CO2 concentrations (3%, 6%, and 9%) on the explosion characteristics of hydrogen-enriched LPG (hydrogen ratio ranging from 0 to 0.5) within a 20 L spherical explosion chamber. Subsequently, a chemical kinetic analysis was conducted, focusing on the explosion reaction dynamics of the H2/LPG/CO2/Air mixture, encompassing temperature sensitivity assessments and the production rates of key free radicals. The findings reveal that although hydrogen incorporation does not significantly alter the maximum explosion pressure of LPG, it markedly accelerates the explosion reaction rate, posing a challenge for CO2 in effectively inhibiting the explosion of hydrogen-enriched LPG. CO2 functions as a stabilizing third body within the reaction system, diminishing the collision frequency among free radicals, hydrogen molecules, hydrocarbon molecules, and oxygen molecules, thereby slowing down the reaction rate. As the proportion of hydrogen increases, the concentration of ·H radicals, known for their high reactivity, escalates, rapidly completing the propagation phase of the chain reaction and intensifying the overall generation rates of critical free radicals, including ·H, ·O, and ·OH. Notably, the key reaction H+O2⇋O+OH, which governs the reaction temperature, undergoes significant enhancement, further accelerating the explosion reaction rate and ultimately diminishing the inhibitory efficacy of CO2 against the hydrogenated LPG explosion. Furthermore, as the amount of hydrogen added increases, hydrogen’s competitiveness for oxygen within the reaction system markedly improves, attenuating the oxidation of hydrocarbons. Concurrently, the alkane recombination reaction, exemplified by C3H6+CH3(+M)⇋sC4H9(+M), is strengthened. These insights provide valuable understanding of the complex interactions and mechanisms during the explosion of hydrogen-enriched LPG in the presence of CO2, with implications for the safe application of hydrogen-enriched LPG.

Numerical Study on the Explosion Reaction Mechanism of Multicomponent Combustible Gas in Coal Mines

Combustible gases, such as CO, CH4, and H2, are produced during spontaneous coal combustion in goaf, which may cause an explosion under the stimulation of an external fire source. It is of great significance to study the influence of combustible gases, such as CO and H2, on the characteristics of a gas explosion. In this study, CHEMKIN software (Version 17.0) and the GRI-Mech 3.0 reaction mechanism were used to study the influences of different concentration ratios between CO and H2 on the ignition delay time, free radical concentration, and key reaction step of a gas explosion. The results show that the increase in the initial CH4 and CO concentrations prolonged the ignition delay time, while the increase in the H2 concentration shortened the time and accelerated the explosion reaction. The addition of H2 promoted the generation of free radicals (H⸱, O⸱, ⸱OH) and accelerated the occurrence of the gas explosion. CO generated ⸱OH free radicals and dominated the methane consumption through the R119 and R156 reactions. As the concentrations of CO and H2 increased, the R38 reaction gradually became the main driving factor of the gas explosion.

Microballistics in fungi and plants

Ballistic movements in biology are powered by muscle contraction, explosive chemical reactions, the formation and collapse of gas bubbles, merger of fluid droplets, and release of hydrostatic pressure. At the macroscopic end of this kinetic carnival we find jumping fleas, violent spider jaws, shrimp claw hammers, and squirting beetles and cucumbers. The speeds are startling, but the mechanisms seem familiar because they occur on a spatial scale that overlaps with our physical experiences. We jump, albeit more slowly than fleas, for example, and it does not seem strange that seeds will spurt from a swollen cucumber when it hits the ground. Ballistics in microscopic dimensions are very different, operating in a seemingly alien world of fluid mechanics where thin air becomes soup and gravity vanishes.

Effect of mesh aluminum alloy on hydrogen and propane explosion characteristics

In order to explore the effect of mesh aluminum alloy (MAA) on the explosion characteristics of different types of gases, experiments were conducted by filling MAA in hydrogen and propane explosion pipes. The explosion characteristic parameters of hydrogen and propane with different volume fractions under the action of MAA were obtained. The chain reaction process and thermodynamic reaction mechanism of hydrogen and propane explosions were studied using the numerical simulation software CHEMKIN-PRO and Materials Studio. The experimental results show that MAA significantly promotes hydrogen explosions but inhibits propane explosions. Simulation results show that ·H, ·O, and ·OH are key radicals in the hydrogen explosion process. As the hydrogen volume fraction increases, the number of radicals in the reaction system also increases. When MAA is filled in the hydrogen explosion test pipe, the turbulence of the flame structure inside the pipe increases the collision probability between key radicals such as ·H, ·O, and ·OH, sharply increasing the temperature of the explosion reaction system, resulting in a promoting effect of MAA on hydrogen explosions. When MAA is introduced into the propane explosion test pipe, it creates a barrier and wall effect. This reduces the number of key radicals in the reaction system and lowers the likelihood of radical collisions, which slows down the rates of multiple chain reactions and inhibits the propane explosion. Thermodynamically, it can be seen that propane requires more energy than hydrogen for key elementary reactions to explode, making it more difficult to react.

Experimental and numerical study on the suppression of brown coal explosion characteristics by different types of solid explosion suppressants

A 20L spherical explosion testing system was used to characterize the explosion characteristics of brown coal powder and its mixing with different explosion suppressants. and the free radical reaction mechanism was studied through numerical simulation. Research has shown that sodium bicarbonate (NaHCO3) has a low decomposition temperature and a fast reaction rate in the early stages. A significant amount of phosphorous groups are produced when ammonium dihydrogen phosphate (NH4H2PO4) and melamine polyphosphate (MPP) react, consumes explosive free radicals and blocks heat transmission between coal dust, delaying and inhibiting explosion. In the explosive reaction, H and O free radicals are continually consumed during the breakdown of cyanuric acid melamine (MCA). Finally, the suppression mechanism of different explosion suppressants on coal powder explosions was revealed, and specific recommendations were made for the selection and application of explosive suppressants.

Variable air blast fireball of HMX/Al with tailored gradient structures

Air blast fireball of the composite explosive is an important way to destroy the target and effectively determines the damage effect. Herein, based on the effect of aluminum powder content on the explosion reaction kinetics of HMX-based aluminized explosives, the cylindrical charges with positive gradient structure (PGS) and negative gradient structure (NGS) were designed and prepared to control the structure and size of air blast fireball. The PGS cylinders exhibited lateral shuttle-shaped flame/fireball and the width of the fireball was 3.901 m, which was increased by about 14% compared with homogeneous cylinders. The NGS cylinders led to the vertical shuttle-shaped flame/fireball that the height of the air blast fireball reached 4.049 m, and had longer durations of the fireball. The numerical fitting results show that the lateral shuttle-shaped flame/fireball and vertical shuttle-shaped flame/fireball gradually changed into spherical-like flame/fireball with an increase from 0 to 30 wt% of outer and inner layer HMX content, respectively. The vertical shuttle flame/fireball gradually changed into a spherical-like flame/fireball with the increase of HMX content. This is a feasible way to regulate the shape and size of the air blast fireball through gradient adjusting the distribution of HMX and Al, which could provide an effective strategy to improve the damage effect.

Highly Porous Co-Al Intermetallic Created by Thermal Explosion Using NaCl as a Space Retainer.

Co-Al porous materials were fabricated by thermal explosion (TE) reactions from Co and Al powders in a 1:1 ratio using NaCl as a space retainer. The effects of the NaCl content on the temperature profiles, phase structure, volume change, density, pore distribution and antioxidation behavior were investigated. The results showed that the sintered product of Co and Al powders was solely Co-Al intermetallic, while the final product was Co4Al13 with an abundant Co phase and minor Co2Al5 and Co-Al phases after added NaCl dissolved out, due to the high Tig and low Tc. The open porosity of sintered Co-Al compound was sensibly improved to 79.5% after 80 wt.% of the added NaCl dissolved out. Moreover, porous Co-Al intermetallic exhibited an inherited pore structure, including large pores originating from the dissolution of NaCl and small pores in the matrix caused by volume expansion due to TE reaction. The interconnected large and small pores make the open cellular Co-Al intermetallic suitable for broad application prospects in liquid-gas separation and filtration.

Effect of hydrogen concentration, initial pressure and temperature on mechanisms of hydrogen explosion in confined spaces

Hydrogen as a renewable clean energy raises industrial safety and environmental issues. Studying the mechanism of hydrogen explosion in confined space is significant for guiding the risk assessment and efficient use of hydrogen energy. This paper used a 20 L explosion chamber to explore the effect of initial concentration changes on the hydrogen explosion and verify the model, the CHEMKIN simulation software was used to qualitatively and quantitatively evaluate the dynamic behavior characteristics of hydrogen explosion in confined space under different initial conditions, and the variation law of physical process of hydrogen explosion under different influencing factors in confined space was revealed from macro-micro perspectives. This study shows that the maximum explosion temperature and pressure under fuel-rich conditions are generally higher than those under fuel-lean conditions. The induction period of the hydrogen explosion reaction gradually shortens as the initial pressure increases, there is a negative temperature coefficient effect of ignition delay at the initial temperature of 800 K. In addition, compared with the initial pressure, higher explosion temperature and faster reactant mixing speed significantly affect the gas explosion reaction rate. The molar fractions of free radicals H, O, and OH show an inverted V-shaped relationship with the initial hydrogen concentration, and there is a hysteresis phenomenon in the final molar fraction peak of H free radicals; Sensitivity analysis indicates that free radicals are mainly responsive to the intermediate reaction R16 (forward direction) and R9 (reverse direction), thereby affecting parameters such as explosion pressure and temperature. These research findings can provide theoretical support for developing hydrogen explosion suppression technology.

Ignition mechanism and chemical reaction of the micro-damage polymer-bonded explosives under different inertial loading conditions

Understanding the impact-induced ignition properties and energy release behavior of polymer-bonded explosives (PBXs) is critical for the safety of explosive systems. In this study, a new impact test component was designed using a light gas gun to quantify the ignition mechanism and chemical reaction of micro-damaged PBXs under different inertial loading conditions. A constitutive model was developed to describe the mechanical-thermal-chemical response of the PBXs. This model was employed to further investigate the correlation between microcracks, debonding, hot spots, and chemical reactions. The results show that the stress state of the material is not uniformly distributed due to the micro-inhomogeneities and structural defects of PBXs. The shear friction of the microcracks contributes to localized hot spots, thereby inducing ignition. The critical loading condition for ignition is the length of the steel pillar is 32 mm. The damage and hotspot temperatures of the anterior lateral and posterior lateral regions are greater than those of other locations. The ignition response is accentuated with longer steel pillars, resulting in a more violent release of energy.

Experimental and chemical kinetic modeling study on the inhibition performance of pentauoroethane blended with carbon dioxide in methane-air mixture explosions

To explore the inhibition effectiveness and mechanisms of pentafluoroethane (C2HF5), carbon dioxide (CO2), and their blends, 9.5% methane (CH4)-air mixture explosions under different inhibitors were tested by employing a 20 L spherical explosion system. A quadratic regression model was developed to predict impacts of factors on maximum explosion pressure (pm) through response surface method. The reactions and mechanisms under blended inhibitors were numerically investigated. Results depicted that increasing volume fractions of inhibitor led to decrease in pm, maximum rate of pressure rise, and delay in explosion induction time. Blended inhibitors demonstrated superior inhibition effectiveness, optimal inhibition-environmental was achieved at 4.5% C2HF5 blended with 5.5% CO2. A quadratic polynomial relation existed among pm, volume fractions of C2HF5, CO2, and CH4 during the explosion. Key free radicals were weakened and the promoted explosive elementary reactions were primarily inhibited. CH4+OHCH3+H2O and CH4+HCH3+H2 were the most diminished reactions by blended inhibitors compared to CO2 alone. Carbon-containing reactions R82 and R84, and fluorinated reactions R1025 and R1099 reduced the key free radicals, interrupted the chain reactions and promoted the production of HF. Findings will provide new ideas for prevention of CH4-air mixture explosions and reduce hazardous effect.

Research on the Explosion Reaction Mechanism of Volatile Gases from Coal Dust Pyrolysis

ABSTRACT It is imperative to have an in-depth understanding of the coal dust explosion reaction mechanism to control and prevent coal explosions in the coal mining industry and promote the safe and efficient utilization of coal resources. The volatile gases are the primary components involved in coal dust explosion reactions. Therefore, studying the explosion reaction mechanism of volatile gases in coal dust is of great significance for revealing the process of coal dust explosion. This study conducted a thermogravimetric mass spectrometry (TG-MS) experiment to analyze the mass loss characteristics and volatile gas components during coal dust pyrolysis. Experimental results showed that the pyrolysis process of coal dust is mainly divided into three stages. The main components of volatile gases escaping from coal dust pyrolysis are CO, CH4, CO2, and H2O. Then, the Chemkin-Pro numerical simulation method was also introduced to analyze the mixture explosion reaction process of coal dust pyrolysis volatile gas. The sensitivity analysis and the rates of production analysis (ROP) of reactants, products, and intermediate products during the volatile gas explosion reaction were conducted. Furthermore, 14 components and 27 key elementary reactions involved in the reaction process were simplified and extracted. A simplified reaction pathway for the mixture explosion of coal dust pyrolysis volatile gas was constructed. This study introduces a novel approach to investigate the mechanism of homogeneous combustion of volatile gases in coal dust explosion reactions.

Analysis of Sodium–Water Reaction as heat source for district heating and cooling

Finding new alternatives is a need to develop disruptive solutions that could be applied to the decarbonized, sustainable, circular systemic change for the energy system transition. In this case, a complete new approach, sodium as energy resource, is described. Traditionally, sodium has been considered a risky element even if it were proposed as coolant in many applications, as nuclear or solar thermal plants. Such applications have been concerned by the explosive reaction of alkali as Na with water. We analysed the alternative of profiting of such highly exothermic reaction for an energy use. Previously, we experimentally tested the utilization of sodium as propellant, as reported in Guerrero et al. (2019), what produced the correlation between the energy release and the sodium consumption in excess of water. We are now developing a boiler fuelled by sodium and water. Based on these previous and ongoing activities, this paper shows the proposal and the process analysis of a sodium–water boiler applied to heating and cooling networks,as one of the sectors to be decarbonized in the energy system. A tentative configuration for the design of such heater, and the heat exchangers to adapt heated water temperatures will be presented. We present the conceptual design of a 13.5 MW district heating plant for a ΔT=10°C heating water from 60 to 70 °C, consuming 1 kg/s Sodium, reaching an efficiency of 95%, comparable with existing boilers.

Isolation of the contribution of viscous flow to initiation of pentaerythritol tetranitrate during sub-shock impact

The drop weight impact experiment is used routinely to provide an initial screening of the handling sensitivity of new explosives. Despite the ubiquity and simplicity of the drop weight impact test, the physical mechanisms responsible for generating temperatures sufficiently high for the initiation of explosive reactions are not well understood. Preliminary work has shown that temperatures sufficient for ignition are in theory achievable in steady-state Poiseuille flow at the flow velocities observed experimentally with temperature-dependent shear viscosities. However, it is far from certain that such steady-state flow conditions can be achieved in the drop weight impact test because of its short duration. Therefore, here we study heat generation both experimentally and numerically to quantify the temperature distributions in molten pentaerythritol tetranitrate (PETN). Drop weight experiments have been performed starting with PETN that has been melted on a transparent anvil. The experimental results are consistent with our finite element calculations that indicate that the temperature does not approach the level needed for ignition on the time scales of the experiment. Interestingly, ignition regularly occurs in solid samples under the same conditions, so we discuss the phenomenology of ignition of both solid and molten PETN in the drop weight test and provide constraints to numerical simulations.

Sputtering Coating on the Surface of Diamond Particles Using High Temperature Generated by Thermal Explosion Reaction

Sputtering Coating on the Surface of Diamond Particles Using High Temperature Generated by Thermal Explosion Reaction

Effect and Mechanism of NH4H2PO4/Montmorillonite Composite Powder on Al-Mg Alloy Dust Explosion

ABSTRACT The explosion of energetic metal dusts represents a major threat to the machining industry. It is therefore crucial to develop inexpensive, high-performance explosion inhibitors. For better protection of production, by using solvent-antisolvent approach, we prepare a uniquely clustered composite inhibitor by combining a natural clay mineral – Montmorillonite. In a 20-L spherical explosion apparatus and a vertical combustion tube, our examination shows that adding 80 wt% NH4H2PO4/Montmorillonite composite powder inhibitor can fully inhibit the explosion of Al-Mg alloy dust; adding 60 wt% composite powder inhibitor can inhibit the flame propagation. And that our new composite powder inhibitor outperforms pure monomer powder inhibitors. Through XRD, XPS, etc analysis, we gain a deeper insight into the inhibitory mechanism of NH4H2PO4/Montmorillonite. On the one hand, the decomposition of NH4H2PO4 and the resulting products combine to inhibit reaction; on the other hand, Montmorillonite contains plenty of voids that not only limits the propagation of flames, but also well absorbs the products generated from explosion reaction. Through research and experiments, we obtain a cheap, environmentally friendly and efficient composite dust explosion-proofing agent, which provides new ideas for the design of dust explosion-proofing materials and broadens the application prospects of natural clay minerals as dust explosion-proofing agents.

Study of CO Gas Dilution in Forcing Ventilation System at Ramp Down KKRB 4 Utama, Pongkor, West Java

CO is a hazardous gas formed from the reaction of explosives that lack oxygen balance. These explosives have the potential to generate toxic gases, including CO. It is crucial to minimize CO concentration at the work site by ensuring proper air circulation. This study aims to examine the impact of varying ducting distances on CO gas dilution, using the gas diffusion coefficient value as a basis. The research method employed is observational, involving the assessment of CO gas dilution in the tested tunnel at varying distances from the working front to the sensor. The research was conducted on the Ramp Down KKRB 4 Utama. Result of the research is the most ideal carbon monoxide reduction time at RD KKRB 4 Utama is shown at sensor placement distance 1 using the blow system, where A Sensor takes 2.21 hours and B Sensor takes 1.06 hours to reach a concentration level below the TLV (Threshold Limit Value) 50 ppm.

Chemical reaction process and dynamic characteristics of urea pyrolysis products in inhibiting gas explosion

During the coal mining process, gas explosions pose significant hazards, causing casualties and property losses. In order to develop new types of inhibitors for gas explosions, this paper explores the reaction mechanisms of urea pyrolysis products NH3 and HNCO inhibiting gas explosions based on density functional theory (DFT), transition state theory, and grand canonical ensemble Monte Carlo method (GCMC). It analyzes the reaction processes and kinetic characteristics of urea pyrolysis products with key radicals and gas molecules involved in explosions from a microscopic dynamic perspective. The results show that urea pyrolysis products exhibit good inhibition effects on active radicals involved in explosion reactions·NH3 and HNCO show stronger van der Waals forces in electrostatic attraction towards O2 and *H, respectively, and faster rate advantages in reaction rate constants. The lower Gibbs free energy barrier indicates higher reaction activity of pyrolysis products, thereby diluting the concentration of key radicals involved in explosion reactions and effectively inhibiting explosion key elementary reactions (R32, R38, R53, R57, R156, and R170). This study provides new insights into the microscopic inhibition mechanism of urea pyrolysis products on gas explosions, offering a new approach for designing more targeted modified inhibitors, which helps reduce the hazards of gas explosions during coal mining and provides scientific support and technical guidance for safe coal mining production.