Inhibiting effects of gas–particle mixtures containing CO2, Mg(OH)2 particles,and NH4H2PO4 particles on methane explosion in a 20-L closed vessel

The main risk factors from methane explosion are the associated shock waves, flames, and harmful gases. Inert gases and inhibiting powders are commonly used to prevent and mitigate the damage caused by an explosion. In this study, three inhibitors (inert gas with 8.0 vol% CO₂, 0.25 g/L Mg(OH)₂ particles, and 0.25 g/L NH₄H₂PO₄ particles) were prepared. Their inhibiting effects on methane explosions with various concentrations of methane were tested in a nearly spherical 20-L explosion vessel. Both single-component inhibitors and gas–particle mixtures can substantially suppress methane explosions with varying degrees of success. However, various inhibitors exhibited distinct reaction mechanisms for methane gas, which indicated that their inhibiting effects for methane explosion varied. To alleviate amplitude, the ranking of single-component inhibitors for both explosion pressure (P_ex) and the rate of explosion pressure rise [(dP/dt)_ex] was as follows: CO₂, NH₄H₂PO₄ particles, and Mg(OH)₂ particles. In order of decreasing amplitude, the ranking of gas‒particle mixtures for both P_ex and (dP/dt)_ex was as follows: CO₂–NH₄H₂PO₄ mixture, CO₂‒Mg(OH)₂ mixture, and pure CO₂. Overall, the optimal suppression effect was observed in the system with the CO₂–NH₄H₂PO₄ mixture, which exhibited an eminent synergistic effect on methane explosions. The amplitudes of P_ex with methane concentrations of 7.0, 9.5, and 11.0 vol% decreased by 37.1%, 42.5%, and 98.6%, respectively, when using the CO₂–NH₄H₂PO₄ mixture. In addition, an antagonistic effect was observed with CO₂‒Mg(OH)₂ mixtures because MgO, which was generated by the thermal decomposition of Mg(OH)₂, can chemically react with water vapor and CO₂ to produce basic magnesium carbonate (xMgCO₃·yMg(OH)₂·zH₂O), thereby reducing the CO₂ concentration in a reaction system. This research revealed the inhibiting effects of gas‒particle mixtures (including CO₂, Mg(OH)₂ particles, and NH₄H₂PO₄ particles) on methane explosions and provided primary experimental data.     

Inhibition effects of Al(OH)3 and Mg(OH)2 on Al-Mg alloy dust explosion

To identify a superior explosion suppressant for Al-Mg alloy dust explosion, the inhibition effects of Al(OH)₃ and Mg(OH)₂ powders on Al-Mg alloy explosion were investigated. A flame propagation suppression experiment was carried out using a modified Hartmann tube experimental system, an explosion pressure suppression experiment was carried out using a 20-L spherical explosion experimental system, and the suppression mechanisms of the two kinds of powders on Al-Mg alloy dust explosion were further investigated. The results demonstrate that by increasing the mass percentages of Al(OH)₃ and Mg(OH)₂, the flame height, flame propagation speed and explosion pressure of deflagration can be effectively reduced. When 80% Mg(OH)₂ powder was added, the explosion pressure was reduced to less than 0.1 MPa, and the explosion was restrained. Due to the strong polarity of the surface of Mg(OH)₂, agglomeration easily occurs; hence, when the added quantity is small, the inhibition effect is weaker than that of Al(OH)₃. Because the Mg(OH)₂ decomposition temperature is higher, the same quantity absorbs more heat and exhibits stronger adsorption of free radicals. Therefore, to fully suppress Al-Mg alloy explosion, the suppression effect of Mg(OH)₂ powder is better.     

Experimental and theoretical investigation of dry-water containing phosphoric acid for new fire suppressant

To overcome the shortcomings of phosphorus-containing compounds (PCCs, not widely used) in fire suppression, the dry water powder containing phosphoric acid was analyzed for a new fire suppressant (SiO₂-P). First, the fine conditions (solid-to-liquid ratio, stirring time and stirring speed) were determined to prepare the new powder. The particle size distributions and XPS of SiO₂-P powder were analyzed. The TG tests were conducted to study the decomposition of powder, and there was a major decomposition peak. Second, the extinguishing time of SiO₂-P powder was tested, which showed that the SiO₂-P powder containing phosphorus species could significantly improve the fire suppression ability. In addition, the kinetic parameters of powder decomposition reaction were determined by genetic algorithm based on TG results. Last, based on the decomposition products and kinetic parameters, the burning velocity and mass fraction of free radicals of CH₄/air flame with SiO₂-P powder addition were studied theoretically. The results indicated that SiO₂-P powder had great ability of reducing the burning velocity and scavenging free radicals. Furthermore, the suppression effects were analyzed, which indicated that the cooperation of H₂O and P suppression effect dominated the suppression mechanism and resulted in the good suppression efficiency.     

Effect of monoammonium phosphate particle size on flame propagation of aluminum dust cloud

The effect of monoammonium phosphate (NH₄H₂PO₄) particles on 5 μm aluminum dust flames is investigated experimentally and computationally. NH4H2PO4 in three particle size is employed to determine the inhibition efficiency on aluminum flame propagation. Flame inhibition mechanism considering both gas and surface chemistry of aluminum particles is developed. Results show that the inhibition effectiveness monotonously increases as NH₄H₂PO₄ particle size is reduced to 25 μm. Flame morphology and flame microstructure change with the addition of different particle size NH₄H₂PO₄. Small NH₄H₂PO₄ particles within the range studied have a greater reduction in average flame propagation compared to the coarser one. Meanwhile, the fine NH₄H₂PO₄ particles almost decompose completely during the penetration of aluminum flame and then undergo a sufficient chemical interaction with the flame. The simulations indicate that the decomposition products of NH₄H₂PO₄ particles obstruct the oxidation of aluminum particles through flame radical consumption. Additionally, the addition of NH₄H₂PO₄ can reduce the vaporization rate and surface reaction rate of aluminum particles.     

复合干粉灭火剂抑制食用油火的试验研究

为改善普通碳酸氢钠干粉灭火剂(BC干粉)抑制食用油火时抗复燃性较差的不足,选择聚磷酸铵、溴化钾和一水合草酸钾作为添加剂,与普通BC干粉灭火剂混合配制成复合干粉灭火剂。通过全尺度模拟试验研究各种复合粉体对食用油火的灭火效果及其抗复燃性能。结果证明,普通BC干粉与一水合草酸钾复配而成的复合粉体针对食用油火的灭火效果和抗复燃性能在几种粉体中最佳。根据试验数据和各粉体的理化特性,对4种粉体的灭火效果差异作了详细的分析和讨论。     

Experimental and theoretical investigations for mitigating NaAlH4 reactivity risks during postulated accident scenarios involving exposure to air or water

Experimental and theoretical studies were conducted to investigate the pyrophoricity and water-reactivity risks associated with employing sodium alanate (NaAlH₄) complex metal hydride in on-board vehicular hydrogen (H₂) storage systems. The ignition and explosivity of NaAlH₄ upon exposure to oxidizers in air or water were attributed to the spontaneous formation of stable hydroperoxyl intermediates on the NaAlH₄ surface and/or H₂ production, as well as the large driving force for NaAlH₄ conversion to favorable hydroxide products predicted by atomic and thermodynamic modeling. The major products from NaAlH₄ exposure to air: NaAl(OH)₄, gibbsite and bayerite Al(OH)₃, and Na₂CO₃ observed by XRD, were identified to be formed by surface-controlled reactions. The reactivity risks were significantly minimized, without compromising de-/re-hydrogenation cyclability, by compacting NaAlH₄ powder into wafers to reduce the available surface area. These core findings are of significance to risk mitigation and H₂ safety code and standard development for the safe use of NaAlH₄ for on-board H₂ storage in light-duty vehicles.     

Efficiency characterization of fire extinguishing compound superfine powder containing Mg(OH)2

To improve the fire extinguishing efficiency of existing dry powders, a new type of superfine dry powder was prepared using magnesium hydroxide as an additive. In our study, a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to analyze the thermal decomposition of the synthesized powders. The temperature of thermal decomposition, weight loss, and other thermodynamic parameters of the fire extinguishing powders were analyzed to explain the performance advantages of the compound superfine powder. Through a small-scale fire experiment, the physical parameters of the extinguishing process—such as extinguish time, powder dosage, smoke concentration, and minimum extinguishing concentration—were quantified for the suppression of a diesel fire using the different powders; these parameters were used to evaluate the fire extinguishing capacity and toxic gas suppression ability of the powders. TGA demonstrated that the compound superfine powder decomposed more quickly and its thermal decomposition process was much shorter than those of the other powders. The DSC data indicated that the compound superfine powder could decrease the characteristic temperature at each stage and thus the powder absorbed the flame's heat more quickly and suppressed flame propagation. The fire extinguishing test demonstrated that the consumption of the three types of fire extinguishing powder decreased with an increase in the driving pressure, and the order of powder dosage was as follows: commercial dry powder > superfine powder > compound superfine powder. Similarly, the order of minimum extinguishing concentration was as follows: commercial dry powder > superfine powder > compound superfine powder. Furthermore, the compound superfine powder exhibited a greater capacity for controlling toxic and harmful gas emissions.     

PPH (potassium polyacrylate & hectorite) composite materials – A new fire accident emergency method for thermal protection of adjacent tanks

When a chemical tank fire happens in a storage area, it is very important to protect adjacent tanks so as to decrease fire accident losses. In this paper, a new thermal protection method was put forward based on a PPH (potassium polyacrylate & hectorite) thermal insulation composite material spraying on an adjacent tank under fire. Firstly, the PPH material was prepared successfully by a polymerization reaction of potassium acrylate, hectorite, NaHSO₃ and (NH₄)₂S₂O₈. Secondly, thermal insulation performance of the PPH material was characterized by heat transfer process at high incident heat flux using cone calorimeter. The results show that thermal insulation performance of the PPH material is affected by a content change of (NH₄)₂S₂O₈, NaHSO₃ and hectorite in formulations. The content of (NH₄)₂S₂O₈ 0.14 wt%, NaHSO₃ 1.38 wt% and hectorite 1.4 wt% was an optimum formulation ratio to obtain best thermal insulation performance. Finally, possible thermal insulation mechanisms of the PPH material were presented using SEM, TG and TG-IR techniques. One of the thermal insulation mechanisms is the incident heat flux absorbed by water evaporation from the PPH material. Another is the thermal protection of the char formed from the PPH material at high incident thermal radiation, which can prevent heat and mass transfer.     

Inerting characteristics of ultrafine Mg(OH)2 on starch dust explosion flame propagation

Experiments on the flame propagation of starch dust explosion with the participation of ultrafine Mg(OH)₂ in a vertical duct were conducted to reveal the inerting evolution of explosion processes. Combining the dynamic behaviors of flame propagation, the formation law of gaseous combustion products, and the heat dissipation features of solid inert particles, the inerting mechanism of explosion flame propagation is discussed. Results indicate that the ultrafine of Mg(OH)₂ powders can cause the agglomeration of suspended dust clouds, which makes the flame combustion reaction zone fragmented and forms multiple small flame regions. The flame reaction zone presents non-homogeneous insufficient combustion, which leads to the obstruction of the explosion flame propagation process and the obvious pulsation propagation phenomenon. As the proportion of ultrafine Mg(OH)₂ increases, flame speed, flame luminescence intensity, flame temperature and deflagration pressure all show different degrees of inerting behavior. The addition of ultrafine Mg(OH)₂ not only causes partial inerting on the explosion flame, but also the heat dissipation of solid inert particles affects the acceleration of its propagation. The explosion flame propagation is inhibited by the synergistic effect of inert gas-solid phase, which attenuates the risk of starch explosion. The gas-solid synergistic inerting mechanism of starch explosion flame propagation by ultrafine Mg(OH)₂ is further revealed.     

磷酸铵盐亚纳米粉体灭火性能实验研究

使用溶剂-非溶剂法制备了粒径达到亚纳米量级（300nm-500mm）的磷酸铵盐灭火剂,建立了1．2m×1．2m×1．2m的小尺度灭火实验平台,开展了灭油池火和木垛火的全淹没灭火实验,对磷酸铵盐亚纳米粉体的灭火性能进行了研究,并与普通磷酸铵盐粉体的灭火性能进行了比较。实验结果显示磷酸铵盐亚纳米粉体的灭火性能要明显高于普通粉体,并且在低压下就可以获得很好的灭火果。工作压力的增加会缩短粉体的灭火时间,但是对于磷酸铵盐亚纳米粉体灭木垛火的情况,由于灭火时间相差示大,反而会导致灭火剂用量增加。     

Synthesis and adsorption studies of NiO nanoparticles in the presence of H2acacen ligand,for removing Rhodamine B in wastewater treatment

Cost efficient NiO nanoparticles were synthesized by hydrothermal production of nano-scale Ni(OH)₂, using Ni(NO₃)₂·6H₂O and NaOH as precursors, in the presence of H₂acacen ligand, followed by calcinations of the produced Ni(OH)₂. Prepared samples were then characterized using X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectra, Brunauer–Emmet–Teller (BET) and transmission electron microscopy (TEM). BET analysis revealed high surface area for pure nano sized NiO, averaging 176.56 m²/g and confirming its application as an efficient adsorbent. Experimental studies for Rhodamine B (RB) removal from aqueous solutions in batch systems revealed that the adsorption equilibrium was best represented by Langmuir isotherm, with the maximum monolayer capacity of 111 mg/g for RB. The kinetic data was well described by a pseudo-second-order kinetic model, having intraparticle diffusion model as a rate limiting step.     

The effect of Mg(BH4)2 on the energy characteristics of RDX based aluminized explosives

This paper mainly discusses the effect of Mg(BH₄)₂ on RDX-based aluminized explosives' energy characteristics. RDX/Mg(BH₄)₂, RDX/Al/Mg(BH₄)₂, RDX/AP/Al/Mg(BH₄)₂ mixed explosives were prepared by molding power method. The influence of energy storage materials on the performance of mixed explosives was discussed by adjusting the proportion of Mg(BH₄)₂. The impact sensitivity, friction sensitivity, detonation heat experiment, and XPS experiment were carried out for the mixed explosive. The mechanical sensitivity, energy characteristics, and the products after the explosion of the mixed explosive were analyzed. Through the above experiments, it is concluded that Mg(BH₄)₂ can effectively improve the energy characteristics of RDX, but its safety will become worse after being prepared by a simple mixing method, and the use of the molding power method can effectively reduce the sensitivity. As the mass fraction of Mg(BH₄)₂ increases and Al decreases, the detonation heat of explosives decreases gradually. Mg(BH₄)₂ made the oxygen balance of mixed explosives more negative has been considered as a potential reason. Analysis of the detonation heat solid products by XPS found that, unlike our expected results, the product contained a large amount of low calorific value of B₂O₂ instead of B₂O₃, which may be a crucial reason. This paper provides a reference for the application of Mg(BH₄)₂ in energetic materials and is of great significance for the development and application of new materials in energetic materials.     

Renewable biomass gel reinforced core-shell dry water material as novel fire extinguishing agent

This work explores the feasibility of using chitosan (CS)-sodium alginate (SA) crosslinking gel to reinforce dry water (DW) composites. The stability and fire extinguishing efficiency of the DW powder are investigated. Compared to ordinary DW material, water loss rate of the modified DW composite is decreased, and its pressure resistance and stability are significantly increased. Moreover, it possesses higher fire extinguishing efficiency than conventional dry powder. Fire extinguishing mechanism and gel formation mechanism are proposed. The improvement in stability has great significance for the storage and transportation of DW materials. These results demonstrate the ability to create a fully green and renewable crosslinking gel capable of endowing high stability to DW material. This work provides a novel solution to improve the stability of DW materials, which will have great application prospect in fire suppression of some flammable hazardous chemicals.     

Effect of solvent on the hydrothermal liquefaction of macro algae Ulva fasciata

Hydrothermal liquefaction is an attractive approach for the conversion of aquatic biomass like algae as it does not require the energy intensive drying steps. The objective of the study is to understand the effect of various solvents (H₂O, CH₃OH and C₂H₅OH) on product distribution and nature of products of hydrothermal liquefaction of macro algae Ulva fasciata (MAUF). Hydrothermal liquefaction of MAUF was performed using subcritical H₂O (300 °C) as well as supercritical organic solvents CH₃OH and C₂H₅OH (300 °C). The use of alcoholic solvents significantly increased the bio-oil yield. The bio-oil yield was 44% and 40% in case of liquefaction with CH₃OH and C₂H₅OH respectively whereas the bio-oil yield was 11% with H₂O. Use of alcoholic solvents converted the acids obtained in bio-oil to the corresponding methyl and ethyl esters. ¹H NMR data showed that use of alcoholic solvents (C₂H₅OH and CH₃OH) increased aliphatic content of bio-oil1 (ether/methanol/ethanol fraction). FTIR and SEM results showed the difference in the bio residue obtained using alcoholic solvents and H₂O. The results showed that liquefaction with supercritical alcohols is an effective way to produce functional hydrocarbons for chemical feedstock.     

Inhibiting effect of inhibitors on ignition sensitivity of wood dust

Wood products are easy to produce dust in the production and processing process, and have a serious explosion risk. In order to improve the safety of wood products production, the inhibiting effects of magnesium hydroxide (MTH), SiO₂, melamine polyphosphate (MPP) on the minimum ignition energy (MIE) and minimum ignition temperature (MIT) of wood dust were experimentally studied. The results showed that the inhibiting effects of inhibitors on the MIE of wood dust show the order of MPP > SiO₂>MTH. The order of the inhibiting effects on the MIT of wood dust was MPP > MTH > SiO_2. When 10% MPP was added to wood dust, the time when the flame appears (T_appear) and the time when the flame reaches the top of the glass tube (T_top) obviously rose to 80, 140 ms. Therefore, MPP had the best inhibiting effect on the ignition sensitivity of wood dust.According to thermogravimetry (TG), differential scanning calorimetry (DSC) tests, the introduction of MPP leaded to lower maximum mass loss rate (MMLR), higher temperature corresponding to mass loss of 90% (T_0.1), residual mass and heat absorption. In addition, thermogravimetric analysis/infrared spectrometry (TG-IR) results showed that MPP produced H₂O (g) and NH₃ (g) during the thermal decomposition process, which diluted the oxygen.     

Experimental investigation on extinguishing performance of a novel nanocomposite for gaseous fires

A novel nanocomposite was synthesized by incorporating three different types of flame-retardants and its extinguishing performance was tested for gaseous fires. The nanocomposite consists of the inorganic magnesium hydroxide (MH) nanoparticles as the dominant component, the nitrogen-based melamine cyanurate (MCA), and the phosphorus-based ODOPB. The wet mixing, dry mixing, and ultrasonic agitation were employed in the preparation process to enhance the homogeneity of the nanocomposite. The prepared powders were characterized using a series of analytical instruments including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravity analyzer (TGA), and differential scanning calorimeter (DSC). The efficiency of various samples in extinguishing gaseous fires was investigated in a lab-scale extinguishing system. The fire extinguishing tests indicated that the nanocomposite is considerably more effective in fire extinguishing than other powders in terms of extinction time and agent mass consumed. The fire extinction time of nanocomposite was 45.2% shorter than that of commercial ABC-MAP powder. Furthermore, the consumed amount of nanocomposite was 63.2% less than that of commercial powder. In addition, the order of extinguishing mass concentrations was as follows: the novel nanocomposite (103.7 g/m³) < MH/MCA (148.1 g/m³) < MH/ODOPB (155.6 g/m³) < MH (170.4 g/m³) < commercial ABC powder (281.5 g/m³) < MCA/ODOPB (384.1 g/m³). The fire suppression mechanisms of the nanocomposite were also discussed. It was inferred that the extinguishing mechanism of nanocomposite comprised of simultaneous chemical and physical inhibition actions involving chemical inhibition action, cooling action, and asphyxiation action. This study provides a promising attempt to gain benefits from the striking features of nanotechnology and flame-retardants in extinguishing gaseous fires.     

Inhibiting effects by Fe2O3 on combustion and explosion characteristics of ABS resin

The global increase in the use of, and reliance on, plastics has prompted the demand for acrylonitrile-butadiene-styrene (ABS) resin in various fields. With this increased requirement, numerous failures have occurred in the ABS process. Those incidents, resulting from electrostatic discharge, powder accumulation, heat accumulation, construction sparks, and plant fires, have caused dust fire and explosions.In this study, the ABS resin was gleaned from the site and tested for its explosion parameters, including minimum ignition temperature of dust cloud (MIT_C), minimum ignition energy (MIE), and minimum explosion concentration (MEC). To improve loss prevention in the manufacturing process, ferric oxide (Fe₂O₃) as an inert additive was added in the ABS powder. According to the MIE test, Fe₂O₃ has an apparent inhibiting effect on dust explosion for the ABS dust. With the proportion of Fe₂O₃ increased from 25 to 50 mass% in ABS, the MIE increased from 67 to 540 mJ. The explosion tests via 20-L apparatus indicated that Fe₂O₃ mixed with ABS could not increase the MEC significantly. However, the explosion pressure dropped by increasing in the ratio of Fe₂O₃ in ABS. This inerting strategy of ABS was deemed to substantially lessen the probability and severity of fire and explosion.     

Inerting effect of CaCO3 powder on flame spread of wood dust layer

The effect of CaCO₃ powder, a typical inert dust, on the flame spread characteristics of wood dust layers was studied using an experimental device to understand the ignition characteristics of and develop inert explosion-proof technology for deposited wood dust. The results showed that the flame spread velocity (FSV) of the mixed dust layer was affected by the dispersion effect of CaCO₃ powder and physical heat absorption. As the CaCO₃ powder mass fraction increased, the FSV of the dust layer first increased and then decreased, reaching a peak at a 50% mass fraction. Moreover, the front-end temperature of the flame gradually decreased, and the red spark faded. The combustion reaction of the mixed dust layer could be more completed, and the colour of the combustion residue changed from charcoal black to charcoal grey. The coupling effect of the initial temperature and wind speed can promote an increase in the FSV in the mixed dust layer. The Gauss–Amp model of the FSV of the wood dust layer and mass fraction of CaCO₃ powder showed that the peak of the FSV occurred when the mass fraction of CaCO₃ powder was between 40 and 50%. Thus, a good inerting and explosion-proof effect can be achieved by using CaCO₃ powder with a mass fraction of more than 50%; it can improve the whole inerting process. Inert explosion-proof technology should be considered when assessing fire and explosion risk of dust in real process industry situations.     

Low-dose irradiation by electron beam for the treatment of high-SOx flue gas on a semi-pilot scale—Consideration of by-product quality and approach to clean technology

Attention has been focused on the treatment of lignite-fired flue gas in order to use lignite in an environmentally friendly way – (i) low-CO₂ emission, (ii) production of a valuable by-product, (iii) no discharge of wastewater, (iv) direct removal of SO₃ (strong toxicity), and (v) treatment of high SO₂ concentration. Based on these criteria, electron beam irradiation with ammonia injection was tested on a semi-pilot scale: 800 Nm³ h^?1 flow rate, 5500 ppm SO₂, 70 ppm NO_x, 22% flue gas moisture, and 75–80 °C at the reactor outlet.As an energy-saving measure, a low dose (5 kGy) of irradiation was applied: the problem lay in the by-product quality. It is considered that (NH₄)₂SO₃ and NH₄HSO₃ produced by thermal reactions are oxidized to form (NH₄)₂SO₄ (fertilizer) by an electron beam. However, not all reactions were complete because the by-product contained small amounts of H₂SO₄ and NH₂SO₃NH₄ (herbicide), so a vegetable pot test was performed to study the by-product quality: no adverse effect was observed. It is inferred from the pot test that slightly acidic soil may protect vegetables from disease and a small amount of NH₂SO₃NH₄ probably affects woody species and not herbaceous species.It is concluded that the electron beam system is noted as a multi-component pollution control process (removal of NO_x, SO₃, SO₂ and dioxins) and this system will contribute to environmentally friendly use of lignite as well as agricultural productivity via fertilizer supply.     

Suppression of different functional group modified powders on 9.5% CH4-air explosion and molecular simulation mechanism

Thiol and urea functionalized montmorillonite powders were successfully prepared by silane coupling agent treatments in this work. The pyrolysis characteristics, surface functional groups, and distribution of particle size of untreated montmorillonite powders (Mt), the hydroxyl functionalized montmorillonite (O–Mt), the urea functionalized montmorillonite (N–Mt), and the thiol functionalized montmorillonite (S–Mt), which was derived from the previous research, were respectively characterized by utilizing the thermogravimetric differential scanning calorimetry, Fourier transform infrared spectroscopy, as well as the laser particle analyzer. The suppression effect of the S–Mt, O–Mt, Mt, and N–Mt on a 9.5% CH₄ explosion was tested in the duct system (5 L). The obtained results indicated that N–Mt and O–Mt exhibited a better explosion suppression effect than Mt and S–Mt at the same mass concentration. Additionally, the methane/air explosion suppression mechanism of these powders could be explained by molecular simulation results that indicated the negatively electrophilic potential regions exist on the surface of O–Mt and N–Mt. Moreover, NH₄∙、 NCO∙ and ∙OH radicals, which can interrupt explosive chain reactions, were easily generated by N–Mt and O–Mt.