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1.
This paper aims to develop quantitative insights based on measured deflagration parameters of hybrid mixtures of activated carbon (AC) dust and hydrogen (H2) gas in air. The generated experimental evidence is used to reject the claim of the null hypothesis (H0) that severity of deflagrations of H2/air mixtures always bound the severity of deflagrations of heterogenous combustible mixtures of AC dust/H2/air containing the same H2 concentrations as in the H2/air binaries. The core insights of this investigation show that the maximum deflagration pressure rise (ΔPMAX) and maximum rate of pressure rise ((dP/dt)MAX) of this hybrid mixture are greater than those corresponding to deflagrations of H2/air mixtures for all the dust and H2 concentrations being examined. The deflagration severity indices (KSt and ES) of the hybrid mixture containing 29 mol% H2 are found to be greater than those of the H2/air mixture containing 29 mol% H2. Also, the minimum explosible concentration (MEC) of the hybrid mixture is lower than that of the AC dust in air only. The insights gained should lead to better realization of the severity of a postulated safety-significant accident scenario associated with on-board cryoadsorption H2 storage systems for fuel-cell (FC) powered light-duty vehicles. The identified insights could also be relevant to other industrial processes where combustible dusts are generated in the vicinity of solvent vapors. Moreover, these insights should be useful for supporting quantitative risk assessment (QRA) of on-board H2 storage systems, designing improved safety measures for cryoadsorption H2 storage tanks, and guiding H2 safety standards and transportation regulations.  相似文献   

2.
This study aims to develop a quantitative risk assessment (QRA) framework for on-board hydrogen storage systems in light-duty fuel cell vehicles, with focus on hazards from potential vehicular collision affecting hydride-based hydrogen storage vessels. Sodium aluminum hydride (NaAlH4) has been selected as a representative reversible hydride for hydrogen storage. Functionality of QRA framework is demonstrated by presenting a case study of a postulated vehicle collision (VC) involving the onboard hydrogen storage system. An event tree (ET) model is developed for VC as the accident initiating event. For illustrative purposes, a detailed FT model is developed for hydride dust cloud explosion as part of the accident progress. Phenomenologically-driven ET branch probabilities are estimated based on an experimental program performed for this purpose. Safety-critical basic events (BE) in the FT model are determined using conventional risk importance measures. The Latin Hypercube sampling (LHS) technique has been employed to propagate the aleatory (i.e., stochastic) and epistemic (i.e., phenomenological) uncertainties associated with the probabilistic ET and FT models. Extrapolation of the proposed QRA framework and its core risk-informed insights to other candidate on-board reversible and off-board regenerable hydrogen storage systems could provide better understanding of risk consequences and mitigation options associated with employing this hydrogen-based technology in the transportation sector.  相似文献   

3.
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 (Pex) 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 Pex 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 Pex 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.  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
Currently, China's timber industry is in high demand with the development of real estate. However, there is a certain fire hazard in the production process of wood manufacturing. Once a fire occurs, the fire is violent and the spread is rapid. Therefore, to improve the safety of its production process, ammonium dihydrogen phosphate and magnesium hydroxide were selected to prepare a new composite superfine dry powder, which was denoted as the NH4H2PO4/Mg(OH)2 composite. Furthermore, to figure out dry powders' extinction effect on Class A fire, the wood-crib fire suppression effect of the NH4H2PO4/Mg(OH)2 composite was test, and then compared with that of ultrafine dry powder (UDP) and commercial ABC dry powder (C-ABC) in a 1 m³ chamber. Three parameters of the fire extinguishing process, namely flame extinction time, powder consumption and temperature drop were adopted to measure the fire suppression performance. The results demonstrated that UDP and C-ABC both had a larger flame extinction time and powder consumption than the NH4H2PO4/Mg(OH)2 composite. Besides, a fire (wood cribs) can be extinguished by the NH4H2PO4/Mg(OH)2 composite with the fastest temperature drop and a much-improved toxic gas suppression ability. In short, the NH4H2PO4/Mg(OH)2 composite can better guarantee the safety of the wood processing production process. Moreover, the reasons for performance advantages of the NH4H2PO4/Mg(OH)2 composite were discussed.  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
To accurately predict the development degree of coal spontaneous combustion (CSC), the CSC process was investigated using a programmed high-temperature-heating experimental system, and the variation law of index gas concentration in the holistic process of CSC and oxidation is formulated. Additionally, the accuracy of the experimental system was evaluated using experimental design for thermal analysis, and the correlation between gas index and apparent activation energy was determined using grey correlation analysis. The results indicated the following. In the critical temperature stage (0–100 °C), φ(CO)/φ(CO2) should serve as the main index and C2H4 should serve as the auxiliary index; in the crack-active-speedup temperature stage (100–260 °C), CO and φ(C2H4)/φ(C2H6) should serve as the main index and R1, the Graham index, and φ(C2H4)/φ(CH4) should serve as auxiliary indexes; in the speedup-ignition temperature stage (260–370 °C), R2 and the Graham index should serve as main indexes and φ(CO)/φ(CO2), C2H4, and R1 should serve as auxiliary indexes; in the ignition temperature (370–500 °C), R3 should serve as the main index and R2, the Graham index and C2H4 should serve as auxiliary indexes. Among them, the grey correlation degrees among the Graham index, Grignard fire coefficient, and apparent activation energy were the highest, reaching 0.91.  相似文献   

10.
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.  相似文献   

11.
Deposition of combustible dust on a hot surface is a hidden danger of fire. In this work, polymethylmethacrylate (PMMA) dust was selected to analyse the influence of dust layer diameter, dust particle size and dust layer thickness on the ignition characteristics of PMMA dust layer. Critical heating temperatures and ignition time had been measured. The STA-GC/MS-FTIR analysis was used to determine that the main products of PMMA pyrolysis were MMA, CO, CO2, and C2H4, of which CO and C2H4 were transported to the ambient to cause gas phase combustion on the surface of the dust layer. For 10 mm thick dust layer, the critical heating temperatures of 5 μm PMMA, 100 nm PMMA, and 30 μm PMMA were 300 °C, 330 °C, and 320 °C. As the thickness of the dust layer increased, the gas transport path became longer, the critical heating temperature and ignition time increased. The characteristic particle size (D [3,2]) was utilized to represent the true particle size, and the ignition time increased with the increase of the characteristic particle size. The increase in the diameter of the dust layer had a slight effect on the temperature history and ignition time of the dust layer.  相似文献   

12.
To achieve the rapid prediction of minimum ignition energy (MIE) for premixed gases with wide-span equivalence ratios, a theoretical model is developed based on the proposed idea of flame propagation layer by layer. The validity and high accuracy of this model in predicting MIE have been corroborated against experimental data (from literature) and traditional models. In comparison, this model is mainly applicable to uniform premixed flammable mixtures, and the ignition source needs to be regarded as a punctiform energy source. Nevertheless, this model can exhibit higher accuracy (up to 90%) than traditional models when applied to premixed gases with wide-span equivalence ratios, such as C3H8-air mixtures with 0.7–1.5 equivalence ratios, CH4-air mixtures with 0.7–1.25 equivalence ratios, H2-air mixtures with 0.6–3.15 equivalence ratios et al. Further, the model parameters have been pre-determined using a 20 L spherical closed explosion setup with a high-speed camera, and then the MIE of common flammable gases (CH4, C2H6, C3H8, C4H10, C2H4, C3H6, C2H2, C3H4, C2H6O, CO and H2) under stoichiometric or wide-span equivalence ratios has been calculated. Eventually, the influences of model parameters on MIE have been discussed. Results show that MIE is the sum of the energy required for flame propagation during ignition. The increase in exothermic and heat transfer efficiency for fuel molecules can reduce MIE, whereas prolonging the flame induction period can increase MIE.  相似文献   

13.
In this study, experimental determination and modelling investigations for the explosion regions of 1,3-dioxolane/inert gas/N2O and 1,3-dioxolane/inert gas/air mixtures were carried out and compared. The experimental measurements were carried out at 338 K and atmospheric pressure according to EN1839 method T using the inert gases N2, CO2, He and Ar. The results showed that the ratio of the lower explosion limit in N2O (LELN2O) to the lower explosion limit in air (LELair) is 0.52 and the ratio of the maximum oxygen content in air (MOCair) to the limiting oxidizer fraction in nitrous oxide (LOFN2O) is 0.36 ± 0.02 independent of the inert gas. When comparing the inert gas amount at the apex based on the pure oxidizing component, which is O2 in case of air, N2O-containing mixtures need less inert gas to reach the limiting oxidizer quantity whereas the efficiency of inert gases is in the same order. The coefficients of nitrogen equivalency however were found to differ to some extent. The explosion regions of 1,3-dioxolane/inert gas/oxidizer mixtures were modelled using the calculated adiabatic flame temperature profile (CAFTP) method as well as corrected adiabatic flame temperatures. The results indicate good agreement with experimental data for CO2, N2 and Ar- containing mixtures. The noticeable deviations that occur when He is the inert gas are due to the lacking transport data of that mixture.  相似文献   

14.
Coal-mine gas disaster is one of the most serious coal-mine disasters in China. The main component of coal-mine gas, methane is chemically stable and very difficult to be degraded by conventional methods. Hydroxyl radical (OH), due to strong oxidizing ability and high electro-negativity, is the primary degradation source of atmospheric methane. In the present study, methane degradation using hydroxyl radicals generated by Fenton’s reagent, Fe2+/H2O2, has been carried out in the self-designed bubbling reactor. The effects of H2O2 concentration, dosage of FeSO4·7H2O and initial pH value on methane removal efficiency were investigated respectively. It has been found that the optimal reaction conditions were 100 mM of hydrogen peroxide, 2.00 mM of ferrous ion and initial pH value of 2.5. Under optimal conditions, the removal efficiency of methane reached 25% after 30 min. The preliminary experimental results unambiguously demonstrate that the degradation of methane using hydroxyl radicals generated by Fenton’s reagent is feasible.  相似文献   

15.
To reduce costs, high-purity chemical suppliers wash and reuse HDPE containers collected from users. To determine the lifetime of a container, the appearance of that container and the manufacturer's recommendations for its lifetime are generally considered. Guidelines for determining the lifetime of an HDPE container have not been clearly defined. The lack of these specifications may result in the leakage of high-purity chemicals in the storage, transportation and use of HDPE containers. To understand the effects of using high-purity chemicals (sulfuric acid (H2SO4) and nitric acid (HNO3)) on HDPE, this study revealed its effects by mechanical and thermal performance tests. According to the mechanical properties test results, the ductility and tensile strength of HDPE soaked H2SO4 and HNO3 decreased. HDPE immersed in HNO3 exhibited the lowest thermal stability by thermal performance testing. In summary, the degradation of HDPE is affected by storage conditions. For this study, HDPE only needs 60 days of immersion in HNO3, and its ductility and tensile strength will decline obviously. This study shows that when these containers are used for long-term storage of high purity chemicals, the mechanical properties (including ductility, ductility, and tensile strength) of HDPE containers tend to decrease. To decrease accidental leakage of chemicals due to aging of HDPE, comprehensive and approved regulations should be established for the loading, transport, and storage of HDPE containers.  相似文献   

16.
Explosion indices and explosion behaviour of Al dust/H2/air mixtures were studied using standard 20 l sphere. The study was motivated by an explosion hazard occurring at some accidental scenarios considered now in ITER design (International Thermonuclear Experimental Reactor). During Loss-of-Vacuum or Loss-of-Coolant Accidents (LOCA/LOVA) it is possible to form inside the ITER vacuum vessel an explosible atmosphere containing fine Be or W dusts and hydrogen. To approach the Be/H2 explosion problem, Be dust is substituted in this study by aluminium, because of high toxicity of Be dusts. The tested dust concentrations were 100, 200, 400, 800, and 1200 g/m3; hydrogen concentrations varied from 8 to 20 vol. % with 2% step. The mixtures were ignited by a weak electric spark. Pressure evolutions were recorded during the mixture explosions. In addition, the gaseous compositions of the combustion products were measured by a quadruple mass-spectrometer. The dust was involved in the explosion process at all hydrogen and dust concentrations even at the combination ‘8%/100 g/m3’. In all the other tests the explosion overpressures and the pressure rise rates were noticeably higher than those relevant to pure H2/air mixtures and pure Al dust/air mixtures. At lower hybrid fuel concentrations the mixture exploded in two steps: first hydrogen explosion followed by a clearly separated Al dust explosion. With rising concentrations, the two-phase explosion regime transits to a single-phase regime where the two fuel components exploded together as a single fuel. In this regime both the hybrid explosion pressures and pressure rise rates are higher than either H2 or Al ones. The two fuels compete for the oxygen; the higher the dust concentration, the more part of O2 it consumes (and the more H2 remains in the combustion products). The test results are used to support DUST3D CFD code developed at KIT to model LOCA or LOVA scenarios in ITER.  相似文献   

17.
As a commonly used initiator for polyethylene, tert-butyl peroxide 3,5,5-trimethylhexanoate (TBPTMH), with the molecular formula of C13H26O3, is more likely to decompose and cause fires and explosions. Understanding the thermal risks of TBPTMH mixed with common metal ions, potentially in containers and pipes, is important. In this work, by using differential scanning calorimetry (DSC) and Phi-Tec adiabatic calorimetry, the effects of CuCl2, FeCl3, CuBr2, and FeBr3 on the thermal decomposition of TBPTMH were investigated. Adiabatic kinetic analysis was performed and the apparent activation energy (Ea) was calculated by thermodynamic analysis. Time to maximum rise under adiabatic conditions (TMRad) and the self-accelerating decomposition temperature (SADT) under different packing qualities were reckoned. It was found that the thermal risk of TBPTMH was increased while mixing these metal ions, especially CuBr2. To ensure the safety of the substance in process industry, the temperature of TBPTMH in the presence of metal should be governed below 39.48 °C. This work was expected to provide some guidance for improving the process safety of TBPTMH.  相似文献   

18.
The purpose of this study was to develop a model for an integrated estimation of the functional state of the human organism (FSHO) and an integral estimation of physical factors (PF) for hygienic rating. Tests were performed twice with 3 men in 0.7-clo clothing during 4-hr mental work with 9 combinations of 4 PF: wideband noise (55–83 dB(A)), whole-body vibration (6 Hz, az = 0.2–1.8 ms?2), air temperature (18–30 °C), and illumination (1, 3, 5 lx). Thermoregulatory, cardiovascular, and psychophysiological reactions and temporary threshold of hearing (TTS2) shifts were studied. For the integral estimation of PF influence on FSHO the model F(y1, y2, ... ym) = f(x1, x2, ... xn) was used, relating both FSHO and PF sets. The most important physiological parameters in creating FSHO are defined and the contribution of individual parameters of FSHO and PF is found.  相似文献   

19.
The influence of additives of various chemical natures (CH4, N2, CO2, and steam) at a laminar burning velocity Su of hydrogen in air has been studied by numerical modelling of a flat flame propagation in a gaseous mixture. It was found that the additives of methane to hydrogen–air mixtures cause as a rule monotonic reduction in the Su value with the exception of very lean mixtures (fuel equivalence ratio ? = 0.4), for which a dependence of the laminar burning velocity on the additive's concentration has a maximum. In the case of the chemically inert additives (N2, CO2, H2O) the laminar burning velocity of rich near-limit hydrogen–air flames drops monotonically with an increase in the additive's content, but no more than 1.5 times, and the adiabatic flame temperature changes slowly in this case. In the case of methane as the additive, the laminar burning velocity is diminished approximately 5 times with an increase in the adiabatic flame temperature from 1200 to 2100 K. Deviations from the known empirical rule of the approximate constancy of the laminar burning velocity for near-limit flames are shown.  相似文献   

20.
The objective of this study is to obtain information about the thermal decomposition behaviors of hydrazine (N2H4) caused by metals, using differential scanning calorimeter (DSC) and SuperCRC. The DSC measurements revealed that the exothermic reactions of N2H4 were caused by the reaction conditions such as the type of cells; the TDSC with a gold pan is 485.2 K and that with a glass capillary is 620.5 K. Besides, the activation energy of the thermal decomposition of N2H4, calculated from the Kissinger and Ozawa methods, were found to be about 38±2 kJ mol−1 in the gold pan and 141±8 kJ mol−1 in the glass capillary. Moreover, a heat flow profile was observed with SuperCRC during the mixing of N2H4 and the metal ion solution at 298 K. The maximum heat flow was related to the metal ion oxidative characters. The higher oxidative characters would provide a faster acceleration for the exothermic behavior than the lower oxidative ions. Based on this study, Mn(VII) and Cr(VI) were considered to exhibit strongly oxidative characteristics during mixing with N2H4.  相似文献   

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