Explosion Suppression Research Articles

Mechanism and safety analysis of acetylene decomposition explosion: A combined ReaxFF MD with DFT study

• The ReaxFF MD method reveals the reaction path of acetylene pyrolysis, and the kinetic model is obtained by DFT calculation. • Acetylene reacts with itself in the form of vinylidene to generate methylene cyclopropene and vinyl acetylene as initial adducts. • Free radical polymerization initiates the explosive decomposition of acetylene. • Obtain the critical temperature and pressure curve for the explosive decomposition of acetylene. The internal reaction mechanism of the explosive decomposition of acetylene was systematically studied by the combination of reactive force field molecular dynamics simulation and density functional theory calculations. ReaxFF MD simulations reproduced the main pyrolysis products of acetylene observed in the actual pyrolysis experiments. Kinetics study showed that the pyrolysis of acetylene was predominated by molecular addition reactions at low temperatures, while the free radical chain reactions occur at higher temperatures. Density functional theory (DFT) is employed to calculate the activation energy barrier and other thermodynamic parameters for the reaction route steps revealed by ReaxFF simulations. Furthermore, the critical temperature and pressure of acetylene decomposition explosion were obtained by numerical calculation. These results elucidate the complicated reaction process of acetylene explosion and provide scientific guidance for the effective prevention and management of explosive accidents and a theoretical foundation for explosion suppression technology development.

Study on the preparation of green suppressors and their characteristics in coal dust flame propagation inhibition

The properties of a green waste molecular sieve-based powder suppressor in inhibiting the flame propagation of coal dust were studied. Waste molecular sieve (S) was pretreated and selected as the carrier, potassium oxalate (K) and ferric citrate (T) as the active components. The reverse dissolution crystallization method was adopted and S@K/T, S@T/K, S@ T -K suppressors with different core–shell structure were prepared by different loading sequences. Their particle size, morphology and thermal pyrolysis behavior were compared. The results showed that the particle distribution of three powders is uniform and the dispersity of them is good. The active components of explosion suppression are evenly loaded on the waste molecular sieve carrier and they have different coating structure. The thermal desorption heat of them is 44.64 J/ g, 66.95 J/g and 92.9 J/g, respectively. Furthermore, the flame propagation characteristics of coal dust were tested by the Hartmann flame propagation device. The results showed that all powders had the effect of inhibiting the flame propagation of coal dust and the inhibition effect is S@ T -K, S@T/K and S@K/T from strong to weak. Combined with characterization results, the influence mechanism of the difference in the flame propagation inhibition effect of three suppressants was investigated.

Influencing factors of coking coal dust explosion pressure and flame and effect of inert dust on its explosion suppression

Coking coal is a precious resource in the world and an important raw material for the production of steel, but it is easy to cause explosion accidents in the process of coking coal mining, which is very detrimental to safe production. In order to reveal the influencing factors of coking coal dust explosion intensity and the suppression effect of inert dust on coking coal dust explosion, an experimental study was carried out in this paper. The results show that the particle size and the mass concentration of coal dust have a great influence on the explosion pressure and flame. By analyzing the suppression effects of NaCl, KCl, and NH4H2PO4 on coking coal dust explosion, it is got that NH4H2PO4 has the best explosion suppression effect. When the mass percentage of NH4H2PO4 mixed into coking coal dust increases to 60%, the maximum explosion pressure decreases by 0.47 MPa, and the maximum flame length decreases by 0.50 m. As the particle size of NH4H2PO4 decreases, the explosion intensity continue to decrease. When the particle size of NH4H2PO4 is 0 ~ 25 μm, and the mass percentage of NH4H2PO4 mixed into coking coal dust is 50%, the explosion doesn’t occur anymore.

Effect of copper foam on the explosion suppression in hydrogen/air with different equivalence ratios

This study investigates the effect of copper foam sheets on explosion suppression in hydrogen/air mixtures with different equivalence ratios (φ). The explosion experiment is conducted in a circular tube with a large aspect ratio (108). The phenomenon of flame quenching can be observed distinctly in the case of φ = 0.5. In the case of φ = 1.5, the copper foam sheets are destroyed by the reflected shock wave, and the overpressure rises by 65 %. In addition, a longer duration of peak overpressure and a lower attenuation rate can be observed due to the interaction between the shock wave and flame front. For the cases of φ = 1.0 and 2.0, the copper foam sheet effectively prevents flames and shock waves from reflecting. The experimental results provide an essential reference for the design of hydrogen flame arresters, the safety of hydrogen pipeline transportation, and engineering application.

Suppression of methane/air deflagration-to-detonation transition in the linked vessel

A set of experimental equipment for suppression of methane/air deflagration-to-detonation transition (DDT) was proposed. In this investigation, a 113-L cylindrical vessel and a 6-m long linked pipe with a 100-mm internal diameter were used to investigate the suppression characteristics of methane/air deflagration-to-detonation transition (DDT) in a linked vessel. The experimental results showed that multi-layer mesh and aluminum silicate wool were effective in preventing DDT in this setup. All the aluminum silicate wool and wire mesh used in the experiments except for the 5-layer 40-mesh mental wire mesh can suppress DDT in the linked vessel. There is a significant pressure difference at the end of pipe when multi-layer metal mesh was used. The suppression effect was obvious, the pressure at the end of the pipe was reduced by about 70% when 25 layers wire-mesh were used. With the increase of mesh layer, the suppression effect is better. In general, the explosion suppression effect of mesh layers on 40 mesh wire mesh is more significant than that on 60 mesh wire mesh. In addition, an increase of thickness and length of aluminum silicate wool can enhance the explosion suppression performance. The aluminum silicate wool with a length of 900 mm and a thickness of 5 mm reduces the maximum pressure by about 61%.

Suppression of methane explosion in pipeline network by carbon dioxide-driven calcified montmorillonite powder

To minimize the damage and loss caused by methane explosions, and improve the safety of methane extraction, transportation, and utilization, we conducted a study on the explosion suppression performance of carbon dioxide-driven calcified montmorillonite powders with different particle sizes in a custom-designed experimental platform. The explosion suppression performance under different working conditions was evaluated according to the peak explosion overpressure, explosion power index, and the time required to reach the two outlets of the pipe network, and the explosion suppression mechanism was analyzed and discussed. The results indicated that calcified montmorillonite powder showed excellent explosion suppression performance. When the particle size of the powder was 21–32 μm and successively increased to 61–72 μm, both the explosion overpressure and explosion flame were effectively suppressed. In addition, when the particle size of the powder continued to increase to 81–92 μm, it had little enhanced suppression effect on the methane explosion. Therefore, considering the cost of use in practical applications, the calcified montmorillonite powder with a particle size of 61–72 μm was the optimal detonation inhibitor. Based on calcified montmorillonite, compound explosion suppression using carbon dioxide could serve as a theoretical reference and support for further improving the safety of methane extraction, transportation, and utilization.

Experimental Research on the Suppression Effect of Different Types of Inert Dust on Micron-Sized Lignite Dust Explosion Pressure in a Confined Space.

Coal is an important strategic resource in the world; coal production safety has always been widely concerned. In coal mine production, inert dust can effectively reduce coal dust explosion accidents in mine tunnels. To reveal the suppression effect of inert dust on lignite dust explosion, CaCO3, SiO2, and NH4H2PO4 are selected for suppression experiments. It is found that the lignite dust explosion pressure decreases continuously as the mass percentages of inert dust mixed into lignite dust increase. By calculating the molar mass, the suppression effects of CaCO3 and SiO2 on lignite dust explosion are compared. The lignite dust no longer explodes when the mass percentage of NH4H2PO4 dust mixed into lignite dust is 70%, indicating that NH4H2PO4 is more effective than that of CaCO3 and SiO2. The smaller the particle size of NH4H2PO4, the better the suppression effect on explosion. The lignite dust does not explode when the mass percentage of NH4H2PO4 is 60% and the particle size of NH4H2PO4 is 25–38 μm, which proves that decreasing the particle size of NH4H2PO4 is important to suppress explosion. The research results are of great significance for grasping the explosion suppression effect of inert dust on lignite dust.

Study on Methane Explosion Suppression in Diagonal Pipe Networks Using a Fine Water Mist Containing KCl and an Inert Gas.

To explore an effective approach for suppressing methane explosions in actual pipe networks, we used a custom-made diagonal pipe network experimental system to assess the suppression of methane explosions using a fine water mist containing KCl and an inert gas. The shock wave pressure, flame wave velocity, and flame wave temperature under different suppression conditions were compared to characterize the effects of explosion suppression under different working conditions, and the mechanism of explosion suppression was analyzed. The results showed that under single-factor explosion suppression conditions the optimal explosion suppression results were achieved when the volume fraction of N2 was 25%, the volume fraction of CO2 was 20%, and the concentration of KCl was 7%. The suppression effect of CO2 on the flame wave temperature was better than fine water mist containing KCl and N2, and the suppression effect of fine water mist containing KCl on the shock wave overpressure and flame wave velocity was more significant. Under the working conditions of fine water mist containing KCl, which was coupled with an inert gas to suppress the explosion, the suppression effect of the fine water mist containing KCl coupled with 20% CO2 on the shock wave overpressure, flame wave velocity, and flame wave temperature was considerably better than fine water mist containing KCl coupled with 25% N2.

Study on Combustion Kinetic Characteristics of Lignite and Semi-coking Dust.

In order to master the combustion kinetic characteristics of semi-coking dust in the early pyrolysis stage of lignite combustion explosion, a vacuum tube furnace was used to prepare semi-coking dust with different pyrolysis degrees, and the experimental samples were studied by a synchronous differential thermal analyzer. By means of theoretical analysis, the reaction mechanism of lignite and semi-coking dust was revealed. The results show that when the final pyrolysis temperature rises to 920 °C, the percentage of volatile matter decreases by 94.6%. The reaction in this process also causes the original pores to be cross-linked and collapsed, and a large number of new pores are generated, and the original pore structure is significantly enlarged. With the increase of the final temperature of pyrolysis, the ignition temperature (Tb) of the dust increased from 354 to 455 °C, the fastest reaction temperature (Tc) increased from 399 to 495 °C, and the ember temperature (Td) increased from 558 to 658 °C. The maximum combustion rate decreased by 65.97%, and the average combustion rate decreased by 84.67%. The apparent activation energy increased by 4.7 times from 45.219 to 257.665 kJ/mol, and the combustion kinetics of semi-coke became worse. The thermal reaction of lignite and semi-coking dust conforms to the diffusion mechanism of the three-dimensional spherical symmetry model. The research results provide a new idea for discussing the mechanism of coal dust explosion and the development of explosion suppression technology.

Study on the Effect of KHCO3 Particle Size and Powder Spraying Pressure on the Methane Explosion Suppression Characteristics of Pipe Networks.

To achieve the best explosion suppression effect of an active powder spraying system, the KHCO3 powder suppression test for a 9.5% methane–air premixed methane explosion was studied based on an independent test platform consisting of a pipe network. The suppression effect of KHCO3 powder particle size and powder spraying pressure on the methane explosion shock wave pressure, flame wave velocity, and flame wave temperature were studied, and the explosion suppression mechanism was analyzed. The results indicated that both the particle size of the KHCO3 powder and powder spraying pressure had a significant effect on the explosion inhibition. When the spraying pressure was in the range of 0.1–0.2 MPa, the increase in KHCO3 powder spraying pressure on the effect of explosion suppression was significantly enhanced, and when the powder spraying pressure exceeded 0.2 MPa, the explosion suppression effect did not obviously increase. With a reduction in the KHCO3 powder particle size, the effect of explosion suppression significantly improved, and when the KHCO3 powder particle size was reduced to 50–75 μm, we observed the best shock wave pressure, flame wave velocity, and flame wave temperature suppression effect.

Experimental study on the effectiveness and safety of cement powder on extinguishing metal magnesium fires based on pneumatic conveying technology

A pneumatic conveying powder device was carried out to investigate the fire-extinguishing performance of cement powder against metal magnesium fire. The fire suppression test shows that pneumatic conveying can effectively transport cement powder to the combustion area for suppressing metal magnesium fire, and the fire-extinguishing time increases with the fire load of metal magnesium. The fire suppression effect of cement powder in metal magnesium fire is ascribed to the formation of a thermally insulation layer as physical barrier concomitant with heat absorption during pyrolysis process that effectively weaken the heat transfer and reduces the combustion intensity, as supported by the morphology and DSC analysis. The results of explosion suppression test reveal that cement powder has a significant inhibitory effect on reducing the explosion max-pressure and max-pressure rise rate of methane explosion, exhibiting a high-level security in the fire-extinguishing process. This work provides an effective and safe strategy for extinguishing metal magnesium fires. • A pneumatic conveying device was designed to transport cement powder in fire extinguishing field. • Pneumatic conveying cement has excellent extinguishing effect in metal magnesium fires. • Inhibition effect of cement powder on methane explosion verifies the safety in extinguishing process. • The fire suppression mechanism of cement powder in metal magnesium fires is proposed.

Suppression of methane explosion in a pipe network by carbon dioxide‐driven montmorillonite powder with different masses

Suppression of methane explosion in a pipe network by carbon dioxide‐driven montmorillonite powder with different masses

Preparation and characterization of flower-like Mg-Al hydrotalcite powder for suppressing methane explosion

A novel flower-like Mg-Al hydrotalcite powder was successfully prepared using coprecipitation method and then characterized for suppressing methane explosion. The influences of Mg-Al hydrotalcite on the explosion pressure and flame propagation characteristics of methane were studied using a 5 L pipeline explosion experimental setup, and its explosion suppression performance was compared with that of magnesium hydroxide and aluminum hydroxide. The results show that the novel Mg-Al hydrotalcite powder prepared in this study has an excellent methane explosion suppression performance. The maximum explosion pressure of methane after adding 0.2 g/L Mg-Al hydrotalcite powder was decreased by 77.72%, and the average flame propagation velocity of methane explosion was decreased by 66.34%. With an increase of the Mg-Al hydrotalcite powder concentration, the main methane flame structure became progressively discrete. Combined with the physical and chemical properties of Mg-Al hydrotalcite powder, its explosion suppression mechanism on 9.5% methane was discussed.

Explosion suppression flame and mechanism of energetic dust with distinct morphologies: Aluminum-containing metal as a typical

A series of explosion suppression experiments on aluminum powder with diverse morphologies were carried out in vertical pipelines. By combining the flame propagation images and flame temperatures, the physical and chemical effects of inhibitors on the flame propagation of spherical aluminum powder (S Al ) and flaky aluminum powder (F Al ) were explored. The results demonstrated that the amount of inhibitor required for F Al was greater than S Al , and the chemical effects of piperazine pyrophosphate (PPAP) were more effective in inhibiting S Al , whereas the physical effects of nano-SiO 2 were more significant in suppressing F Al . PPAP dramatically reduced the flame propagation velocity, flame temperature, and flame propagation maximum height of S Al as the inhibitor mass fraction increased. The flame temperature, ignition delay time, and flame illumination of F Al could even be considerably changed by nano-SiO 2 . The microscopic and macroscopic suppression mechanisms of PPAP and nano-SiO 2 on different morphology of aluminum powder were proposed. • PPAP displays superior performance in inhibiting spherical aluminum powder. • Flake aluminum powder explosion suppression is more difficult than spherical powder. • Nano-SiO 2 can significantly affects the explosion of flake aluminum powder. • Microscopic and macroscopic suppression mechanisms of PPAP and nano-SiO 2 are studied.

Explosion suppression effect and mechanism analysis of ceramic foam in the horizontal pipe

ABSTRACT Ceramic foams are potential materials for explosion suppression due to their complex three-dimensional porous structure and strong wave absorption capabilities. The ability of ceramic foams to suppress methane/air explosion was investigated in a large-scale horizontal pipe. The factors of pore size and thickness of the ceramic foam were taken into consideration, and the explosion overpressure and explosion energy were compared and discussed collectively. Furthermore, mechanisms for the suppression of ceramic foams were also analyzed. Results indicated that ceramic foam has a good quenching effect on explosions compared to the conditions in an empty pipe. It can effectively decrease the explosion overpressure and explosive energy, thus limiting the flame propagation owing to insufficient fuel supply. The tendency for maximum explosion overpressure and explosion energy varied significantly by changing the thickness and pore size. It is worth noting that the attenuation rate of the maximum overpressure is generally greater than 50%, and the Al2O3 ceramic foam showed a better suppression performance than SiC. Additionally, the inhibitory effect is most obvious at 15 mm-20ppi Al2O3 and 30 mm-30ppi SiC, where the maximum explosion overpressure was reduced to 0.11 MPa and 0.19 MPa. However, the reduction of explosive energy is the combined result of the thickness and size of the pores. Overall, 15 mm Al2O3 and 30 mm SiC were more advantageous in suppressing gas explosions. This work supports the mechanism for preventing and suppressing gas explosions while using ceramic foam, and it might serve as a technological reference for the construction of explosion-proof devices. It is essential to avoid and control explosions in gas pipelines, thereby successfully enhancing the safety guarantee in gas pipeline transportation and engineering applications.

Effect and mechanism of Aluminium hydroxide and Magnesium hydroxide powder on flame suppression of flour explosion

ABSTRACT In order to systematically study the suppression effect of Aluminum hydroxide[Al(OH)3] and Magnesium hydroxide[Mg(OH)2] on the explosion of flour, Hartmann experiment system was used to carry out the explosion flame propagation experiment, and the influence of adding different proportions of Al(OH)3 and Mg(OH)2 powder on the morphology and propagation speed of flour combustion flame was studied. Combined with the thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) curves of Al(OH)3 and Mg(OH)2 powder, the inhibition mechanism of Al(OH)3 and Mg(OH)2 powder on flour explosion was analyzed. The results showed that with the increase of Al(OH)3 and Mg(OH)2, the flame propagation speed gradually decreases. After adding 40%wt Mg(OH)2, when t = 182 ms, the flame reaches the top of the glass tube. When 60 wt% Mg(OH)2 and 60 wt% Al(OH)3 powder were added, the maximum flame propagation velocity of flour decreased from 13.86 m/s to 5.78 m/s and 1.62 m/s, respectively, and Al(OH)3 was superior to Mg(OH)2 in inhibiting flame propagation. Both inhibitors can inhibit flour combustion by adsorption of H and OH radicals.

Study of the Explosion Suppression Mechanism of Different Separate and Explosion-Proof Materials

ABSTRACT The separate and explosion-proof materials (SEPM) is one of the effective means to suppress explosion. The suppression effects of three SEPM on C3H8 explosion were experimentally studied. Based on experiments, explosion product analysis, and numerical simulation, the explosion suppression mechanism was revealed. The experimental results show that the explosion pressure and explosion pressure rise rate significantly decreased after filling with SEPM. The order of explosion suppression upon is iron velvet > aluminum velvet≈mesh extended aluminum alloy (EA). The explosion products are quantitatively analyzed by gas chromatography. After filling with SEPM, the contents of CO and CO2 obviously reduced, and the contents and species of hydrocarbons increased, such as C3H4, i-·C4H10, n-·C4H10, and i-·C5H10. The reaction mechanism of i-·C5H10 was added to the reaction mechanism file of propane. The explosion reaction of propane is numerically simulated by Chemkin-Pro software. The reaction paths of propane forming various explosive products are obtained. Furthermore, the explosion suppression mechanism of SEPM is revealed from physical mechanism and chemical mechanism. It is obtained different SEPM suppress explosion in different ways. These studies are expected to develop a new separate and explosion-proof technology to find more suitable materials in essence.

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

ABSTRACT In this paper, the TGA-DSC curve of coal powder explosion inhibitors was analyzed. At the same time, the influence of the explosion inhibitor type and mass fraction on the five explosion intensity parameters of pulverized coal Pex,(dp/dt)ex,Kst,t1 , and t2 was explored. The results show that CaCl2 and NH4H2PO4 go through three main stages: dehydration stage, decomposition stage and crystal transformation stage after high-temperature heating. Calcium chloride absorbs heat through the process of water volatilization and crystal transformation to prevent the combustion of pulverized coal. Meanwhile, NH4H2PO4 absorbs heat through decomposition, evaporation and sublimation reactions to prevent the combustion of pulverized coal. For these two explosion inhibitors, the explosion intensity of pulverized coal decreases with the increase of mass fraction. The increase of Al(OH)3 mass fraction basically does not enhance its explosion suppression effect. After adding NH4H2PO4, the maximum decrease of Pex was 32.08%, which was 11.89% and 16.99% higher compared to the addition of CaCl2 and Al(OH)3, respectively. The maximum decrease of (dp/dt)ex was 98.47%, which was 29.45% and 33.38% higher compared to the addition of CaCl2 and Al(OH)3, respectively. Therefore, the order of explosion suppression performance was determined as: NH4H2PO4 > CaCl2 > Al(OH)3.

A comparative study on aluminum dust explosion suppression by powder inhibitors

ABSTRACT An aluminum dust explosion is a major safety hazard that cannot be ignored. It is of great practical significance to investigate explosion flame propagation characteristics and powder inhibition mechanisms of aluminum dust. Based on a self-designed dust explosion experimental system, explosion flame propagation characteristics such as flame shape, temperature and velocity were captured. The effect of aluminum particle size on the flame propagation was explored, and inhibition performances and mechanisms of NaHCO3, CaCO3 and Na2HPO4 on aluminum dust explosion were experimentally and theoretically revealed. The proportion of white bright areas decreased from 17.9% to 7.9%, 8.0% and 8.8% respectively, and the temperature and velocity decreased obviously with powder inhibitors. Especially, NaHCO3 can reduce the maximum flame temperature and maximum flame velocity to 1411°C and 14.27 m/s respectively, and its inhibition performance was optimal. CaCO3 had better performance than Na2HPO4 in suppressing the flame propagation velocity and in delaying the ignition time, and Na2HPO4 was more advantageous in suppressing the explosion flame temperature. It is explained by the mechanism that substances containing Na and P can play an important role in the suppression of gas-phase reactions. The Na cycle (NaO ↔ Na) is effective in scavenging free radicals.

Fire extinguishing and explosion suppression characteristics of explosion suppression system with N2/APP after methane/coal dust explosion

The study aims to examine the suppression performance of an inhibitor after a methane/coal dust explosion. The design of an explosion suppression system included the carrier gas of nitrogen (N2) with an inhibitor of ammonium polyphosphate (APP). The study investigated fire extinguishing and explosion suppression of methane/coal dust by N2/APP in a vertical pipe. Flame propagation characteristics were measured by a high-speed camera, micro-thermocouple, and pressure sensor. The residues after the explosion were characterized chemically by X-ray photoelectron spectroscopy, and the thermal decomposition characteristics of coal dust and APP in the N2 atmosphere were analyzed by synchronous thermal analysis. Experimental results show that the explosion suppression system can effectively hinder the flame propagation of methane/coal dust explosion. The flame height, bottom velocity, and temperature were all weakened significantly. The optimum level of suppressant minimizes the explosion pressure and suppresses the flame significantly. In addition, the fire extinguishing and explosion suppression mechanisms of N2/APP were summarized. The suppression method used in this study blocks the explosion after it occurs rather than preventing it through premixed inerting.