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• Thermokinetic suppression of APP powder on sucrose dust deflagration is researched. • Decomposition products of APP have a composite weakening effect on reaction exotherm. • Crosslinking reaction of PPA catalyzes the formation of more and dense carbon layer. • Suppression mechanisms of sucrose dust deflagration by APP powder is investigated. In this investigation, ammonium polyphosphate (APP) is applied to suppress the deflagration of sucrose dust. Through the systematic research on flame propagation images and temperature, decomposition behavior of powder samples and the compositions of deflagration residue, the suppression performance and mechanism of APP on sucrose deflagration are profoundly summarized. Timing diagrams show that APP contributes to reduce deflagration flame brightness, increases ignition delay time and flame fault area. The minimum inerting concentration of APP for sucrose deflagration is determined to be 8 %. From the collected deflagration flame temperature curves, it is confirmed that APP can delay peak temperature arrival time, weaken temperature fluctuation, and decrease peak values of flame temperature and temperature rising rate. Through the analysis on thermal decomposition of samples and deflagration residue, it is reflected that APP has superior composite suppression effect. It can not only absorb reaction heat, but also decrease deflagration exotherm to improve thermal stability of sucrose particles. Thus, the easily oxidized components in sucrose are protected, and deflagration intensity is effectively weakened. This work provides a new solution for prevention and suppression deflagration of dust waste in sugar industry. [ABSTRACT FROM AUTHOR]

• Influence of wood dust concentration on deflagration parameters was investigated. • Suppression performance of Zr(OH) 4 on dust deflagration was better than that of SiO 2. • Zr(OH) 4 catalyzes the formation of more residuals with smaller crystallite size. • Suppression mechanisms of wood dust deflagration by ultrafine powder were studied. Flame propagation characteristics of wood dust deflagration and suppression mechanism of ultrafine powders are investigated systematically. The deflagration reaction intensity of wood dust increases firstly and then decreases with the increase in dust cloud concentration. This is due to factors such as oxygen supply, positive feedback among flame characteristic parameters. Thus, there is an equivalent dust concentration for greatest deflagration intensity. Nano-sized ultrafine zirconium hydroxide (Zr(OH) 4) and silicon dioxide (SiO 2) powder are introduced to suppress wood dust deflagration at the equivalent concentration. It is found that Zr(OH) 4 has a suppression effect of endothermic decomposition to generate zirconia (ZrO 2), dilution of oxygen and absorption of free radicals; while SiO 2 exerts suppression effect due to its high melting point and heat absorption. The suppression performance of Zr(OH) 4 is better than that of SiO 2. This is because that Zr(OH) 4 and ZrO 2 have a catalytic carbonization effect. It can not only improve thermal stability of wood particles by catalyzing production of high-temperature resistant residuals, but also promote the formation of catalytic sites to reduce crystallite size of carbon layer on wood particles surface, weakening heat and mass transfer between particles. [ABSTRACT FROM AUTHOR]

To ensure the safety of the Al powder/H 2 hybrid system in industrial production, the variation law of H 2 explosion parameters under the environment of Al powder with a concentration of 0–150 g/m3 was investigated in the confined container, and feasible hybrid explosion suppression approaches were explored. The results show that with the increasing concentration of Al powder, the explosion intensity of the hybrid systems exhibited an enhancing trend in all cases. The explosion hazard of the hybrid system was most severe when the concentration of H 2 reached stoichiometry. At 30 % H 2 and 150 g/m3 of Al powder, the maximum explosion pressure (P max) of the hybrid system was almost 2.4 times compared to the pure 30 % H 2 explosion. CO 2 -driven silica/sodium phytate (SiO 2 /PA-Na) suppressed explosions more effectively than N 2 -driven SiO 2 /PA-Na. As the mass fraction of SiO 2 /PA-Na was increased to 50 wt%, the CO 2 -driven solid inhibitors decreased the P max and deflagration index (K st) of the hybrid system by 60.9 % and 90.1 %, respectively, and the delay of the time to peak explosion pressure (T p) was elevated to 306.4 %. Furthermore, it was revealed that the multi-component inhibitors suppressed the Al powder/H 2 hybrid explosion mainly through comprehensive effects such as adsorption of heat, dilution of oxygen, disruption of chain reactions, and isolation reactants. This study contributes to the enrichment of experimental evidence of Al powder/H 2 hybrid explosion and the precise development of efficient explosion prevention technology. • The explosion behavior of H 2 involving five low concentrations of Al powder was explored. • 30 % H 2 mixed with low concentrations of Al powder presented a substantial explosion hazard. • CO 2 -driven SiO 2 /PA-Na exhibited a better suppression effect than N 2 -driven SiO 2 /PA-Na. • The synergistic suppression mechanism of multi-component inhibitors was elucidated. [ABSTRACT FROM AUTHOR]

Drug powder explosions pose a potential threat to the process safety of pharmaceutical companies in the processing and storage of products. To explore a reasonable and efficient technology to prevent and mitigate the explosion of combustible drug dust, an experimental system of vertical combustion pipeline equipped with a partial suppression device was built, and the performance of N 2 and CO 2 loaded with hydrophobic SiO 2 encapsulated SiO 2 gel (HSESG) respectively to synergistically suppress the explosion of acetaminophen powder was investigated. The results demonstrated that N 2 /HSESG and CO 2 /HSESG were effective in reducing the flame average velocity (V avg), maximum velocity (V max), velocity to the top of the pipe (V top), and maximum flame temperature (T max). N 2 loaded with 60 wt% HSESG reduced the V max , V avg , and V top of the explosion flame by 68.1%, 66.7%, and 81.3%, respectively, and T max by 58.7%. Acetaminophen dust explosion could be completely suppressed by CO 2 /40 wt% HSESG with 83.7%, 73.0%, and 85.7% decrease in V max , V avg, and V top values, respectively, and 80.7% decline in T max. The results of thermal decomposition tests and residues characterization indicated that the partial suppression of N 2 /HSESG and CO 2 /HSESG was mainly accomplished through the synergistic interaction among thermodynamic, kinetic, and non-homogeneous chemical effects. Subsequently, the reason for the more pronounced suppression effect under the impact of CO 2 /HSESG was further explained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Active suppression of N 2 driven APP was used to suppression compound explosion. • Loading of N 2 /APP increased turbulent intensity which is a key factor of suppression. • Flame characteristics and flame acceleration were weakened by active suppression. • Explosion pressure surge occur in the early stage but it does not occur in later stage. • Turbulent, physical and chemical effects together suppressed the compound explosion. This study develops an active suppression system for N 2 driven APP (ammonium polyphosphate) to evaluate its efficacy in fire and explosion suppression during the early and late stages of methane/coal dust explosions. Particle Image Velocimetry (PIV) was employed to characterize the turbulent state of the supplementary flow field introduced into the pipe. High-speed photography, micro-thermocouples, and pressure sensors were utilized to record the propagation characteristics and dynamic parameters of explosion flames. The experimental results indicate that introducing N 2 /APP modifies the turbulent state within the pipe, and the turbulence intensity escalates in correlation with the increase in APP mass. This factor is critical for both fire and explosion suppression. The explosion suppression system significantly impedes the flame propagation path, weakens the compound flame characteristics, and inhibits the flame acceleration. When the explosion suppression system is applied to the early stage of an explosion, there is a surge in explosion pressure; however, this does not occur during the later stage. The combined effects of the turbulence generated by the explosion suppression system and the physical and chemical suppression of the suppression medium under thermal action collectively suppress methane/coal dust compound explosions and prevent the expansion of explosion accidents. [ABSTRACT FROM AUTHOR]

[Display omitted] To reveal the suppression characteristics of methane/coal dust deflagration flame propagation by the flue gas loading in local zones. The suppression experiments of flue gas layer (CO 2 and fly ash) with different thicknesses and fly ash concentrations were conducted in semi-open vertical combustion pipe. The flue gas layer was produced by self-designed flue gas layer generator. Flame propagation characteristics which including the flame image, velocity, the ion current and temperature were recorded by the high-speed photography, the ion current probe and the thermocouple. The residues after coal dust deflagration were characterized by FTIR (Fourier transform infrared spectroscopy). The results show that the flue gas layer has a significant suppression on deflagration flame propagation. With the increasing of flue gas layer thickness and fly ash concentration, the flame velocity, height, temperature and the ion current gradually decreases, and the suppression effect was enhanced. The asphyxiation of CO 2 , heat absorption and insulation of fly ash were mainly methods for the suppression of coal dust deflagration flame. [ABSTRACT FROM AUTHOR]

Flake aluminum powder (F Al), due to its larger specific surface area and higher reactivity, posing a potential threat to the process safety of involved enterprises. To mitigate the explosion caused during the production of F Al , a green composite inhibitor, Sep@CS@PA-Na, was successfully prepared in the aqueous phase using microencapsulation technology with sepiolite (Sep), chitosan (CS), and sodium phytate (PA-Na) as raw materials. The suppression of F Al explosions in a vertical combustion duct system by inhibitors with different inerting ratios (α) was investigated. The results showed that after adding Sep@CS@PA-Na with an α of 0.75, the maximum flame propagation velocity (V max), the average flame velocity (V avg), and the velocity of the flame reaching the pipeline top (V top) decreased by 79.6%, 75.1%, and 86.2%, respectively, and the reduction of the maximum flame front pressure (P max) and the maximum flame pressure rise rate ((d P/ d t) max) were 90.4% and 89.8%, respectively, and the peak temperature (T p) dropped to 505°C. Combined with TG-DSC and explosion product analysis, Sep@CS@PA-Na possessed both gas-phase reaction and surface reaction suppression functions, which were mainly reflected in the dilution effect, quenching effect, and barrier effect. This work will provide technical support for the emergency prevention and control of energetic metal dust explosions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A core–shell composite (FA-2@Mg(OH) 2) is synthesized by the heterogeneous nucleation method. • The modified fly ash greatly improves the interfacial compatibility with Mg(OH) 2 substrate. • The suppression effects of FA-2@Mg(OH) 2 on the explosion flame and pressure of Al-Mg alloy dust is explored. • FA-2@Mg(OH) 2 shows excellent capability owing to the multiple suppression effect embodied in the unique structure. Dust explosions caused by energetic metals pose a significant risk to process industries, making it crucial to develop high-performance explosion inhibitors. In this study, the modified power plant solid waste fly ash (FA) was confirmed as a raw material for the preparation of core–shell inhibitors to efficiently suppress dust explosion of Al-Mg alloy. The interfacial compatibility of FA was dramatically improved by using alkali hydrothermal modification and organic modification. It formed a well-coated nano-Mg(OH) 2 cladding layer on the surface of modified FA by the heterogeneous nucleation method. In a vertical combustion pipe and a 20 L spherical explosion device, the suppression effect of this novel core–shell inhibitor (FA-2@Mg(OH) 2) was investigated. The experimental results showed that the addition of 60 wt% of FA-2@Mg(OH) 2 reduced the maximum flame velocity (V max), velocity to the top of the pipe (V top), and average pulsation degree (V ap) by 87.9 %, 92.5 %, and 87.7 %, respectively, and the peak flame temperature (T p) declined to 298 °C. The maximum explosion pressure (P max) and the maximum explosion pressure rise rate ((dp / dt) max) were reduced by 86.1 % and 92.9 %, respectively. Combining the analysis results of SEM, EDS, XRD, and TG-DSC, the suppression mechanism of FA-2@Mg(OH) 2 was explained in depth, mainly from the heat absorption, coating effect, gas dilution, and radical adsorption. This work not only sheds new light on the design of dust explosion suppression functional materials but also broadens the application of industrial solid waste FA. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel inhibitor was synthesized by supramolecular self-assembly. • This inhibitor exhibits a prolonged suppression effect on CH 4 /H 2 /air explosion. • A comprehensive inhibition mechanism is revealed. • By virtue of lotus leaf-like appearance, the hydrophilicity of inhibitors is weakened. A novel inhibitor of PA-MEL@NH 2 -Al 2 O 3 was synthesized by using supramolecular self-assembly technique with phytic acid (PA) and melamine (MEL) as the building blocks. Bauxite is a kind of mining waste, which is abundant in Al 2 O 3 and is used as loading matrix. By right of lotus leaf-like structure, the hygroscopicity of PA-MEL@NH 2 -Al 2 O 3 is greatly weakened. The feasibility of inhibiting CH 4 /H 2 /air explosion by different concentrations of PA-MEL@NH 2 -Al 2 O 3 was explored in a 20 L Spherical explosive vessel. The optimum inhibitory effect is obtained when the concentration is 0.25 g/L. The maximum pressure (P max) and maximum pressure rise rate ((dP/dt) max) decrease by 52.41 % and 83.50 % respectively. The induction time and the time to maximum pressure are prolonged to 193 and 400 ms, respectively. The synergistic inhibition mechanism of physics and chemistry is illustrated in the analysis of post-explosion residues. This work provides an efficient and promising approach for the suppression of CH 4 /H 2 /air explosion by synthesizing the prolonged action inhibitor with a lotus leaf-like structure. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • 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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Suppression of methane/coal dust deflagration by Al(OH) 3 were investigated. • Al(OH) 3 with higher mass fraction has better suppression effect. • The thermal decomposition process of coal dust was suppressed by Al(OH) 3. • Suppression mechanisms of Al(OH) 3 on flame propagation were revealed. In order to investigate the suppression effect of Al(OH) 3 on the flame characteristics of methane/coal dust deflagration. The experiments of methane/coal dust deflagration under Al(OH) 3 with different mass fractions were conducted by a vertical combustion pipe, and the thermal decomposition of the experimental materials were characterized by simultaneous thermal analyzer. The suppression mechanisms of Al(OH) 3 on methane/coal dust deflagration were summarized. The results showed that the flame characteristic parameters of methane/coal dust deflagration decreased with the increasing of Al(OH) 3 mass fraction. The flame temperature and speed were reduced significantly at 100% Al(OH) 3. Al(OH) 3 hindered the thermal decomposition of coal dust by making the thermal decomposition of coal dust ended in advance, reducing the weight loss rate, and decreasing the maximum heat flow rate and heat release. Al(OH) 3 played the function of cooling, heat insulation, and dilution of combustible concentration, and Al(OH) 3 also adsorbed the chemical molecule produced by the thermal decomposition of coal dust, thus suppressed the methane/coal dust deflagration. [ABSTRACT FROM AUTHOR]

[Display omitted] • The width of inerting zone (N 2 -Fly ash) was determined by theoretical calculation. • The suppression of local whole-inerting on the flame propagation was investigated. • The attenuation amplitude of flame velocity was aggravated by inerting zone. • The working conditions of significantly hindered flame propagation were discovered. • Hindrance and suppression mechanisms of inerting zone on the flame were summarized. To investigate the suppression of local whole-inerting on the flame propagation of methane/coal dust deflagration. N 2 was used as the loading gas to dispersed the fly ash into a fixed zone of the pipe and thus form local whole-inerting zone (contained N 2 -Fly ash), and the widths of inerting zone were determined by theoretical calculation. The deflagration experiments under different concentrations of fly ash in inerting zone and different widths of inerting zone were conducted by using vertical combustion pipe. Results indicate that the flame maximum height, bottom velocity and temperature of methane/coal dust deflagration were decreased obviously with the fly ash concentration and inerting zone width increased. The inerting zone aggravated the attenuation amplitude of flame velocity at deceleration period, and the velocity difference (Δ v) between the maximum velocity and the bottom velocity was increased obviously. These combinations (concentration, width) can suppress significantly the deflagration flame propagation: (100 g/m3, 30 cm), (200 g/m3, 25 cm), (300 g/m3, 25 cm), (400 g/m3, 25 cm), (500 g/m3, 20 cm) and (600 g/m3, 15 cm). The inerting zone can suffocate the deflagration flame, and contained N 2 and fly ash which can hinder the coal decomposition and the combustion reaction through dilution effect, heat absorption, heat insulation and free radicals consumption, so that deflagration reaction and flame propagation were weakened. [ABSTRACT FROM AUTHOR]

[Display omitted] • Suppression characteristics of compound deflagration by ABC powder were investigated. • 30% ABC powder can effectively suppress the compound deflagration flame propagation. • Combination of free radicals and intermediates is the main way of explosion suppression. • Suppression mechanism of ABC powder were discussed systematically. ABC powder was widely used at the places of fire extinguishing and explosion suppression due to its excellent suppression performance. In order to investigate the suppression characteristics and mechanism of ABC powder on methane/coal dust compound deflagration flame. A vertical combustion pipe was built to conduct the deflagration experiment of methane/coal dust/ABC powder. The thermal decomposition of coal dust/ABC powder was studied by simultaneous thermal analyzer. The chemical bonds and surface functional groups of the deflagration residue were characterized, and the suppression mechanism of ABC powder was summarized. The experimental results show that the addition of ABC powder increased the initial temperature of coal dust thermal decomposition, which reduced significantly the thermal decomposition rate, heat release and maximum heat flow. The existence of ABC powder weakened significantly the deflagration characteristics of methane/coal dust. The methane/coal dust deflagration was suppressed effectively under 30% ABC powder. The deflagration reaction can be destroyed by physical effects such as heat absorption, heat insulation, dilution of combustible and oxygen concentration, as well as the chemical action of the intermediate which produced by the thermal decomposition of ABC powder on the adsorption of free radicals which maintain the chain reaction. [ABSTRACT FROM AUTHOR]