Explosive Mixtures Research Articles

Islamism in Pakistan and the Kashmir Conflict

The conflict in Kashmir is influenced by various interactive factors among which the Islamization of Pakistan and the following Talibanization of the entire Sub-Indian region undoubtedly have played a significant role. The emergence of the dispute is a consequence of the decolonisation process which peaked after the Second World War. Unfortunately, this same period was also marked by the beginning of the Cold War. Hence, it is argued that the Islamization of Pakistan is the product of the negative interaction of two main factors – the geopolitical rivalry of the superpowers at that time, especially considering the negative impact of the war in Afghanistan, and the rise of Islam as a consequence of the overall religious revival around the world. Adding to them is the local rivalry between the newly emerged states of India and Pakistan producing an extremely explosive mixture with the potential to ignite the entire region of South-East Asia, involving also the leading international powers. Thus, the conflict in Kashmir became an integral part of the post-Cold War world directly affected by the Islamic revival and the dissemination of the Islamist principles in Pakistan.

Experimental investigation and numerical analysis on the confined deflagration behavior of methane-air mixtures within the suppression of typical haloalkanes

To investigate the mechanisms of haloalkanes in promoting and inhibiting explosions in methane-air mixtures, the halon alternatives of CHF3, C3HF7, and C3H2F6 were selected as inhibitors. Experimental research was conducted in a 20-liter spherical explosion vessel to examine the promotional and inhibitory effects of these haloalkanes on methane-air mixtures. The adiabatic flame temperature, heat release rate, and concentrations of the key radicals were calculated. The results showed that C3H2F6, C3HF7, and CHF3 all exhibited a dual effect, initially promoting and subsequently inhibiting explosions in fuel-lean methane-air mixtures. The critical explosion suppression volume fractions of C3HF7 and CHF3 were 1.5 times and 2.25 times that of C3H2F6, respectively, for the suppression of methane explosion at Φ = 1.2. Furthermore, C3HF7 demonstrated a dual impact on the explosion of stoichiometric methane-air mixtures. From the perspective of reaction kinetics, for fuel-lean methane-air mixture (Φ = 0.8), a small volume of halogenated hydrocarbons led to an increase in the adiabatic flame temperature due to the heat release from critical fluorine-containing elementary reactions, thereby promoting the explosion. Under fuel-lean conditions, the introduction of a small volume of halogenated hydrocarbons led to an increase in the adiabatic flame temperature due to the heat release from critical fluorine-containing elementary reactions, thereby promoting the explosion. Simultaneously, these fluorine-containing reactions scavenged the key free radicals of H, O, and OH inhibiting the explosion process. These two effects competed with each other, ultimately determining the direction of the explosion process.

Fundamentals of forecasting explosive gas accumulation formation in working areas of coal mines

This article presents a methodological approach to solving the problem of predicting local methane accumulations in order to prevent occupational injuries resulting from explosions of methane-air mixtures. On the basis of the analysis of accidents that occurred in coal mines and industrial injuries of miners (mine workers) it is established that the leading role belongs to explosions of methane-air mixtures. The method/methodology considered in the article is based on a comprehensive analysis, first of all, of both mining and geological and other influencing factors and conditions of operating mines of the Pechersk coal basin, as well as aerogas-dynamic processes of mass transfer of air flows in mine workings. The assumption about influence of mining equipment on the process of formation of methane accumulation sites is made. The algorithm of consecutive actions of managerial engineering and technical personnel to reduce industrial injuries is proposed. The developed algorithm implies the use of applied software for modelling aerogas-dynamic processes in the mining excavation operating region. FlowVision and ANSYS Fluent application software packages were selected to determine the methane accumulation locations based on the analysis of existing application programmes.

ADVANCEMENTS IN CIVIL EXPLOSIVES: NOVEL FORMULATIONS AND SUSTAINABLE FUEL SOLUTIONS

ABSTRACT. The article presents the development of a new explosive mixture based on agricultural ammonium nitrate, possessing high detonation capability, increased water resistance, and physical stability. The concept for its creation is based on obtaining an oil-in-water (O/W) type microemulsion, produced using vegetable oil. Calculations conducted showed that the use of 100 % rapeseed oil methyl esters compared to diesel fuel improves emulsification by 14 %, reducing emulsification time by 15 %. Due to the structure of the microemulsion, ordinary agricultural ammonium nitrate can successfully retain around 7.5 % of the microemulsion. This amount of fuel phase is sufficient for obtaining an explosive composition with an appropriate oxygen balance. Substituting the porous ammonium nitrate (PAN) with agricultural ammonium nitrate - the cheapest oxidizer for the production of the newly developed explosive mixture, reduces its production cost and significantly increases the competitiveness of the product.

Considerations regarding the impulse ignition test for level of protection “eb” and ignition test for protection levels “eb” and “ec” stator insulation systems of Ex-proof electric motors

According to the provisions of the 5th edition of the standard IEC 60079 – 7, equipment protection by increased safety “e”, for Level of protection “eb” and “ec” electrical machines, if the rated voltage exceeds 1 kV, type tests in explosive mixtures have to be carried out, in order to certify such an electrical machine. The purpose of this paper is to provide some considerations regarding the impulse ignition test for level of protection “eb” and ignition test for levels of protection “eb” and “ec” stator insulation systems of explosion proof electric motors and also to present a case study regarding such tests conducted in the specialized laboratory of INSEMEX Petrosani, on a stator insulation winding system of a 6 kV electric motor type of protection Ex eb IIC Gb, case study which will assist manufacturers in designing appropriate stator winding insulation systems for increased safety type of protection electric motors.

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.

Virtual experiments about hydrogen explosions with linear propagation

The dangers associated with hydrogen mainly come from its wide flammability range, it’s extremely fast burning rate (having much more aggressive explosive properties than methane gas) and the considerable amount of energy released when it burns or explode. The development of new applications that use hydrogen as clean energy is constantly increasing, thus, hydrogen can be used on a large scale. This paper presents the use of computational fluid dynamics techniques, regarding the linear propagation of the explosion of air and hydrogen mixture in closed spaces, the main purpose being the determination of the overpressures to which a test stand of this processes is subjected.

Study on Marangoni explosion of binary mixtures in liquid layer

In this work, the process of forming micro-droplets due to instability and fragmentation after short chain alcohol solution spreads on the surface of oil layers is studied. Based on the free energy theory of the liquid-liquid interface, the relationship between the binary mixtures spreading on the surface of the liquid layer is derived, and the concentration range of short chain alcohol solution spreading as a thin film on the surface of the oil layer is calculated from the Hiskovsky formula. The Malangoni flow caused by the difference in evaporation rate between the center and edge of the droplet film perturbs the boundary of the liquid film, causing finger-shaped liquid columns to grow at the edge when the droplet spreads to its maximum. In this work, the expression for the critical wavelength and maximum wavelength of boundary instability are derived based on the perturbation model, and the reason for finger shaped liquid column fragmentation is explained based on the Plateau Rayleigh instability. A concentric cylindrical shell liquid column model is established to simplify the calculation and predict the location range of “droplet explosion” of droplets with different viscosity ratios on the liquid layer. Through theoretical calculations and experimental verification, it is found that the alcohol solution fragmented into small droplets within a length range of 4.51–5.98 times the width of the liquid column. This study provides theoretical guidance for existing application fields such as film forming technology and coating technology. The hypotheses, assumptions, and simplified models preliminarily verified experimentally provide solutions for some technical difficulties in the research fields of micro reactions and nanoparticle preparation in chemical industry.

Rock splitting with pyrotechnic compositions and secondary propellants

In some cases of resources extraction, as well as in construction at industrial and urbanized territories, commercial explosives are not safe enough for the surroundings with regard to the generated fly-rocks, air-blast, toxic fumes, seismic waves and vibrations. The main reasons for these harmful impacts of explosion are the velocity and the mechanism of the chemical reaction of explosive decomposition. The authors shifted the focus of their researches from detonating explosives to high-speed combusting energetic materials. The production of low explosive non-detonating mixtures from long-term stored smokeless gunpowders and ammonium nitrate prills in different configurations, and popular pyrolant compositions were studied. The samples of different cartridge casings, filled with non-detonating propellant mixtures or pyrotechnic compositions were examined by two methods - for velocity of propagation and by field tests. It was made investigations for application of waste single-base-powders and double-base-powders for obtaining non-detonating explosive cartridges, suitable in dimension stone mining, as well as in blasting activities at tender and complicated conditions.

Optical evaluation of the surfaces of the CuAlBe samples after the test of resistance to harsh wear stresses in an explosive atmosphere

A material with both non-sparking and good mechanical properties based on CuBe-Al elements was proposed for anti-sparking materials intended for use in potentially explosive atmospheres (design and manufacture of technical equipment, tools and implements intended for use in potentially explosive atmospheres). The alloy was obtained using a classical induction furnace from Cu-Be master alloy and pure Al. Using hot-rolled bands (heated to 800 °C and rolled from ingots with 10 mm diameter to 2 mm thickness plates) experimental devices were made to perform laboratory tests in explosive mixtures for the acceptance of spark arresting materials intended for use in potentially explosive atmospheres. A hard wear process by forcefully applying some steel elements to the experimental CuAlBe alloy was carried out in an enclosure with an explosive atmosphere consisting of an atmosphere with 10% H2. The main purpose of the tests is to verify whether or not the tested materials produce mechanical sparks. They are considered non-sparking materials and are checked/tested accordingly. Their appearance was not observed in the first 16000 friction tests between the two materials. The tests left deep traces of wear on the surface of the experimental alloys, leading to damage to their surface. The wear marks were analyzed macroscopically by optical microscopy (LOM). The test response after 16 000 frictions was negative to explosion and the material can be used as non spark alloy.

Design of an experimental stand for hydrogen explosions

Hydrogen, with its remarkable potential as a clean and abundant energy carrier, has gained significant attention as a promising solution for a sustainable future. However, the handling, storage, and utilization of hydrogen come with inherent risks, particularly the potential for explosions. The present work deals with the design of an experimental stand for hydrogen explosions in interconnected spaces, based on previous experience in the field of air-methane mixtures explosions. Considering the explosive properties of hydrogen, much more aggressive than methane gas, a comparative analysis is carried out between the results of a physical experiment of a methane explosion carried out on a spiral stand and the results obtained from a computational simulation of a hydrogen explosion on a similar geometry. The purpose of the comparative analysis is to highlight the vulnerable points of the future construction, bringing improvements to the new experimental model in the sense of increasing operational safety, while preserving, at the same time, the possibilities of recording the explosion parameters (pressures, velocities, flame front behavior) at a higher level of accuracy.

Fundamentals of Gas Permeation in PEM Water Electrolyzers Operated at High Pressures

The high cost of clean hydrogen (H2) remains a major hurdle to drive large scale adoption and achieve zero emission goals. For large scale deployment using low cost renewable electricity, polymer electrolyte membrane water electrolyzers (PEMWEs) show high potential based on their high faradaic efficiency and high operating current density. Operation of PEMWEs at high differential pressures can significantly reduce the per kilogram price of H2 and increase the overall energy efficiency while also eliminating the necessity to compress H2 during storage and transportation.1 Thinner membranes reduce the voltage losses from ohmic resistance and achieve high faradaic efficiencies. However, a higher crossover of hydrogen from the cathode through the membrane to the anode is observed for thinner membranes at high cathode operating pressures. As Ir/IrO2 (anode catalyst) is inefficient in oxidizing H2 1, this increased crossover of H2 not only reduces the PEMWE efficiency but also results in formation of an explosive gas mixture. Some initial studies also suggest critical effect of crossover H2 on durability of the anode catalyst. Addition of a gas recombination catalyst (GRC) in the membrane is a highly useful strategy to oxidize permeating H2 and prevent the formation of such explosive gas mixtures. Despite the importance, fundamentals of gas recombination reaction mechanism along with the effects of GRC and its properties on it is not well established.In this study, effect of the GRC and its properties (loading, particle size, distribution, and location) on H2 permeation will be elucidated using a high pressure (up to 30 bar) electrolyzer setup coupled with online gas chromatography (Figure 1). The role of H2 and O2 partial pressures and operating current densities (simulated by varying the flow rates) will also be closely examined. Effects caused by the addition of anode and cathode catalyst layers on H2 permeation will also be presented in addition to long-term membrane durability results.Figure 1. Decreased H2 permeation rate observed with GRC (Membrane A) at different cathode (H2) operating pressures at 80 °C using ex-situ electrolyzer setup. Deactivation of the GRC reaction is observed when switching the anode gas from O2 to N2. Figure 1

Impact of Position and Platinum Loading of Recombination Interlayers in Proton Exchange Membranes on the Anodic Hydrogen Content in Water Electrolysis

Hydrogen crossover through the membrane is a significant safety concern in proton exchange membrane water electrolyzers (PEMWEs). This issue is predominant at low loads, which contradicts the application of PEMWEs in conjunction with fluctuating renewable energy sources that require the electrolyzer to switch between low- and high-load operation. The risk of flammable or explosive oxygen-hydrogen mixtures on the anode side of the electrolyzer prevents the application of membranes as thin as in fuel cells, which results in relatively large Ohmic losses. A means to mitigate the accumulation of hydrogen in the oxygen compartment is the integration of platinum nanoparticles as a recombination catalyst interlayer within the membrane that catalyzes the recombination of hydrogen and oxygen to water. It was shown that such an interlayer effectively minimizes the hydrogen concentration on the anode side without reducing the cell performance.1 Thus, this technology can pave the way toward thinner membranes and more efficient electrolyzers.However, the interlayer should not increase the costs of the membrane electrode assembly by excessive Pt loading. Hence, we investigated the ideal position of this recombination interlayer within the membrane,2 and we performed a parameter study on the minimum required catalyst loading for an effective hydrogen-in-oxygen reduction.3 We find that the best position for the interlayer is close to the anode due to the lower oxygen permeability of the membrane. Also, a loading of 10 µg per cm² of platinum nanoparticles is sufficient to reduce the anodic hydrogen content from more than 2.5 vol.% (without interlayer) to approx. 0.5 vol.% when operating a PEMWE cell with a 110 µm thick membrane at 0.5 A/cm² and a differential pressure of 10 barc/1 bara. In summary, we are able to show that low platinum loadings within the membrane are sufficient to reduce the anodic hydrogen content in PEMWEs to safe values without impairing the electrochemical performance of the cell.References C. Klose, P. Trinke, T. Böhm, B. Bensmann, S. Vierrath, R. Hanke-Rauschenbach and S. Thiele, J. Electrochem. Soc., 165(16), F1271-F1277 (2018).A. Martin, D. Abbas, P. Trinke, T. Böhm, M. Bierling, B. Bensmann, S. Thiele and R. Hanke-Rauschenbach, J. Electrochem. Soc., 168(9), 94509 (2021).D. Abbas, A. Martin, P. Trinke, M. Bierling, B. Bensmann, S. Thiele, R. Hanke-Rauschenbach and T. Böhm, J. Electrochem. Soc., 169(12), 124514 (2022).

Enhancing Durability of Polymer Electrolyte Membrane Water Electrolyzer through Incorporation of Gas Recombination Catalyst in Membrane

Hydrogen will become a critical component of the future energy landscape driven primarily by the growing use of renewable energy sources. Polymer electrolyte membrane water electrolyzer (PEMWE) is a superior technology to facilitate hydrogen production from renewable electricity. However, durability remains a significant challenge for the widespread commercialization of electrolyzers.1 Cross-over of H2 from cathode to anode could lead to explosive mixtures in the anode causing safety concerns during operation. Hydrogen crossover also impacts the durability of the anode catalyst.2 Hydrogen permeation from the cathode to the anode through the membrane reduces the anodic Ir catalyst to a low valence state leading to increased dissolution of the Ir catalyst at a high cell voltage. Utilizing thin membranes (~50µm) can improve the electrolyzer system’s efficiency but also increase the hydrogen permeation, particularly at high pressures.In this study, we present a methodology to incorporate platinum as a gas recombination catalyst (GRC) layer into commercial membranes, significantly reducing hydrogen permeation rates and mitigating anode catalyst degradation. Membranes with GRC can mitigate the degradation of PEMWE, leading to more efficient and durable PEM electrolysis systems for hydrogen production. The methodology developed enables higher control of the GRC layer properties (Pt particle size and location in the membrane). Ex-situ measurement of hydrogen permeation, shown in Figure 1, indicates a significant reduction in the permeation rate for GRC incorporated NR 212. This study presents a systematic electrochemical evaluation of anode degradation in PEMWE with and without GRC in the membrane using accelerated stress tests. The durability of the GRC during long-term operation is also presented. Acknowledgment This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.

Assessment of Banknotes as a Matrix for Detecting Post-Explosion Residues of Fuel-Oxidizer Explosive Mixtures Using Ion Chromatography

Banknotes are commonly subjected to chemical analysis in forensic laboratories in the search for post-explosion residues. This matrix presents unique challenges due to the potential presence of target analytes resulting from everyday use, as well as the lack of control samples for comparison. In addition to their relevance in attacks against Automated Teller Machines (ATMs), banknotes are of significant interest when confiscated from suspicious individuals, vehicles, and locations, as they can provide valuable evidence in establishing a connection to this type of crime scene. In such cases, the absence of bulk particles, alternative materials, and control samples is common. This study employed ion chromatography to analyze uncirculated, circulated, and seized banknotes, aiming to determine their ionic profiles. This investigation provides insights into the background levels of target ions in banknotes and aids in the analysis of post-explosion residues. A simple, fast, and precise extraction method was proposed, yielding RSD values below 10% for most analytes in uncirculated banknotes. The study revealed the presence of various ions of interest, some in significant concentrations, even in uncirculated banknotes. PCA analysis demonstrated a clear separation of uncirculated notes based on their banknote value. However, this clustering behavior was not observed in circulated banknotes due to natural variations in analyte concentrations. Interestingly, when uncirculated, circulated, and seized R$ 100 banknotes were analyzed together, the seized samples from an ATM robbery showed a distinct separation from the other groups, indicating the potential for developing classification models.

Amorphous Ni(OH)2 -Ni3 S2 /NF nano-flower heterostructure catalyst promotes efficient urea assisted overall water splitting.

Urea assisted overall water splitting represents a cost-effective and efficient technology for hydrogen production, which not only obviates the generation of explosive H2 and O2 gas mixture but also minimizes the energy cost for the water splitting. In this study, we employed a one-pot hydrothermal method to directly synthesize Ni(OH)2 -Ni3 S2 /NF hybrid nanoflowers on a nickel foam (NF) substrate, resulting in efficient and stable bi-functional electrocatalysts for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Under alkaline conditions, the Ni(OH)2 -Ni3 S2 /NF catalyst exhibits low voltage requirements of 1.346 V and -0.014 V vs. RHE with a current density of 10 mA cm-2 for UOR and HER, respectively. Furthermore, when employing the Ni(OH)2 -Ni3 S2 /NF catalyst as both anode and cathode for urea-assisted overall water splitting, it requires a cell voltage of merely 1.396 V with a current density of 10 mA cm-2 , which is notably lower than the voltage required for complete water decomposition at the same current density (1.568 V vs. RHE). The one-step synthesis of the Ni(OH)2 -Ni3 S2 /NF catalyst lays a foundation for further exploration of other transition metal complexes as dual-function electrocatalysts, enabling energy-efficient electrolytic hydrogen production and the treatment of urea-rich wastewater.

Numerical Simulation of Gas Explosion with Non-uniform Concentration Distribution by Using OpenFOAM.

Gas explosions in coal mines have occurred occasionally, which may cause casualties and economic losses. In the actual mine roadway, the gas concentration distribution is uneven because the gas density is lower than that of air. Gas explosion characteristics of uneven gas distribution with the concentration gradient in mine roadways were analyzed by using the open-source computational fluid dynamic code OpenFOAM. The flame and pressure characteristics were calculated, and the flame and shock wave propagation laws of the non-uniform gas-air mixture explosion with different concentration gradients were analyzed and compared with the uniform gas-air mixture gas. The results show that when the overall gas concentration is the same, the flame velocity and the pressure growth rate of the uniform gas explosion are lower than those of the non-uniform, but the pressure peaks of both are similar. At the same time, when the initial volume concentration is 10%, the non-uniform gas explosion has the highest flame propagation velocity and peak value. The peak explosion pressure of different concentration gradients is proportional to the initial concentration. The above studies clarified the characteristics of gas-air mixture explosions with concentration gradients and provided theoretical support for the prevention and control of gas explosion disasters.

Structure, Phase Composition, and Hardness of Ni3Al–TiC Composite Fabricated by Thermal Explosion of Nickel, Aluminum, and Titanium Carbide Powder Mixture

Structure, Phase Composition, and Hardness of Ni3Al–TiC Composite Fabricated by Thermal Explosion of Nickel, Aluminum, and Titanium Carbide Powder Mixture

Experimental investigation on initiation mechanism, overpressure, and flame propagation characteristics of methane-air mixtures explosion induced by hexogen in a closed pipeline

Gas explosion accidents under shock wave stimulation cause more severe hazards than electric spark ignition. To explore the initiation mechanism and explosion characteristics of methane induced by shock waves. A series of experimental investigations of methane-air mixtures initiated by hexogen (RDX) was performed based on a self-developed closed pipeline. The effects of incident shock wave intensity and methane concentration on the characteristics of methane explosion were studied. The results indicate that methane participating in the reaction can significantly increase the positive pressure duration compared with RDX explosion. With the increase of incident shock Mach number (Ma), methane deflagration pressure increases and counteracts the attenuation of RDX detonation pressure. When the ignition distance is 0 cm, the overpressure inside the pipeline is directly proportional to the methane concentration from 5 vol% to 13 vol%. When the concentration approaches the upper explosion limit, the flame velocity exceeds the theoretical detonation velocity, resulting in the unstable detonation of methane in the pipeline.

Analytical Modeling of a Hydrogen Sensor Based on Exfoliated and Reduced Graphene Oxide

Hydrogen can be considered a clean energy carrier with zero carbon emissions, produced from renewable energy sources. However, hydrogen is a highly flammable gas and can form explosive mixtures with oxygen; hence, sensing techniques are essential for timely leak detection. This paper presents the experimental characterization of a hydrogen sensor based on sensing material consisting of thermally exfoliated/reduced graphene oxide (rGO) films deposited on a sensor device by the drop-coating technique. The measurement of changes in electrical resistance due to hydrogen gas exposure operating at different temperatures (27°C, 90°C, and 150°C) is carried out in a gas chamber with a known concentration of hydrogen in constant air flow. In addition, a generalized mathematical formulation is provided for the dependence of hydrogen gas concentration, temperature, and sensor resistance for the hydrogen gas sensor based on exfoliated/reduced graphene oxide.