Minimum Ignition Temperature Research Articles

Explosion mechanism of aluminum powder mixed with low-concentration hydrogen

This paper examines dust explosion characteristics and mechanisms for aluminum powder (Alp) in four different low-concentration hydrogen environments (0%, 1%, 2%, and 4 vol%). The aluminum powder's combustion characteristics were determined and the minimum ignition temperature and minimum ignition energy were found to be 690 °C and 45 mJ, respectively. A 20-L apparatus was used to evaluate how the explosive characteristics varied under different hydrogen concentrations. The explosion pressure generated by 4 vol% H2 was ca. 8.3% stronger than an explosion in the air, and the explosion pressure rise rate showed an increase of 48%. In addition, the time to maximum rate of pressure rise was shortened in the mixed Alp/hydrogen experiment. The experimental residues were observed, and from this it was inferred that the explosion mechanism changed when a low concentration of H2 was present.

Research on law and mechanism of dust explosion in bag type dust collector

The bag type dust collector will accumulate dust during long-term operation, and the high temperature during operation will cause dust explosion. In this paper, with the dust removal system involved in the “8·2” Kunshan dust explosion accident taken as the research background, the minimum ignition temperature and lower explosion limit experiments are carried out on aluminum powder with different particle sizes (10–60 μm) by using the lowest ignition temperature test device and the 20 L near-spherical explosive device. The dust concentration distribution and temperature field in the bag type dust collector are analyzed through the CFD-FLUENT software. Through the analysis of the experimental results, it is found that when the particle size of aluminum powder is 19 μm, the minimum ignition temperature is 585 °C, and the lower explosion limit of concentration is 0.04 kg/m3. The simulation results indicate that the dust particles gather in the dust collecting bucket, and the aluminothermic reaction occurs in the dust collecting bucket. The temperature of the upper and right parts in the dust collecting bucket is above 600 °C, which exceeds the minimum ignition temperature. At the interface between the dust hopper and the dust collecting bucket, the concentration of aluminum powder reaches 0.126 kg/m3, which exceeds the lower explosion limit of aluminum powder.

Experimental analysis and data-driven machine learning modelling of the minimum ignition temperature (MIT) of aluminium dust

The industrial sector continues to face difficulties in preventing dust explosions. Ignition, in particular, is a phenomenon that has yet to be fully comprehended. As a result, safety conditions pertaining to ignition control are rarely assessed to an adequate level. It is generally recognised that the ignition behaviour of combustible dust is influenced by a variety of parameters, including the chemical composition, particle size, moisture content, dispersion pressure, the concentration of dust and so on, but there is still a lack of understanding regarding the simultaneous effect of multiple influential variables. This article aims to provide data on the minimum ignition temperatures of combustible dust using aluminium dust. The minimum ignition temperatures (MITs) were evaluated in a Godbert-Greenwald (GG) furnace with synergistic effects of dispersion pressure and concentrations for two distinct particle size ranges. Based on the statistical nature of the dust explosions and controlling parameters, this study uses data-driven modelling approaches. The experimental data has been divided into the training set and testing set in the proportion of 85% (for training) and 15% (for testing) respectively. A machine learning artificial neural network approach with Levenberg-Marquardt algorithm is implemented to obtain the predictive model for MIT of aluminium dust for both the particle size ranges (100–63 µm, 50–32 µm). The resultant model was obtained with acceptable accuracy in terms of both the training and test data sets. Besides, a statistical surface fit approach has also been adopted to model the MIT to obtain the correlations. It was found that the predictive accuracy is significantly higher for the developed ANN model than the surface fitting based on the minimum values of AIC (Akaike Information Criterion) and BIC (Bayesian Information Criterion). The assessment of the MIT for combustible dust is crucial in preventing the ignition and subsequent dust explosion. If a sufficiently accurate estimate of MIT is available then the temperature of the surrounding equipment in the process industries can be controlled well below that particular value.

Mild ignition and flame trajectory of horizontal transformer insulating oil spray by hot surface with different angles

In this study, a hot surface of 0°, 45° and 90° was used as the ignition source for mild ignition experiments of large-scale horizontal transformer insulating oil spray. Combined with the principle of spray impinging, it was found that during ignition, the angle of hot surface affects the heat transfer from hot surface to oil droplets and vapor, and the minimum ignition temperature and time to ignition increase with increasing angle. There exists an inverse exponential correlation of time to ignition and ignition temperature. After ignition, the deceleration effect caused by the hot surface dragging spray reduces the flame projection length and leads to different trajectories. The deceleration effect can be modelled using the effective initial velocity of spray derived from the reduced axial velocity at the hot surface location. The predicted flame trajectories considering the deceleration effect presents a good agreement with the experimental records.

Minimum Ignition Temperature of Hybrid Mixtures

Minimum Ignition Temperature of Hybrid Mixtures

Experimental study on thermal runaway of sodium nitrate-containing hazardous waste during thermal treatment

Sodium nitrate-containing organic solid waste (NaNO3-OSW) has been classified as hazardous waste because it engendered severe fire and explosion risk, while large amounts of NaNO3-OSWs were generated during the metal recovery process from e-waste recently. This study aims to characterize thermal runaway behavior and reaction mechanism of NaNO3-OSW via theoretical and experimental analysis. Component characterization results show that this waste contains 23.3% wt. NaNO3, mixed with 11.8% wt. ascorbic acid, 47.2% wt. dehydroascorbic acid, and 17.7% wt. polyvinylpyrrolidone. Thermal risk assessment could provide guidance on the kind of safety measurements. Results present that this waste is thermal sensitive with high deflagration potential while its minimum ignition temperature is 290 ℃, and the maximum explosion pressure is 0.51 MPa. The predicted self-accelerating decomposition temperature is 148.3 ℃ for a standard 50 kg package. Combustion behavior characterization could offer insights into the realization of essential safety during disposal. Results reveal that the self-redox reaction between organic compounds and NaNO3 has occurred in the temperature range of 276–405 ℃. The reaction mechanism suggests that the catalytic decomposition of ascorbic acid by melting NaNO3 is the crucial factor that results in intense combustion. The findings of this study provide practical insights into the in-situ disposal of this waste by removing organic compounds at low temperatures.

Study on the characteristics and influencing factors of micron/nano carbon material dust explosions

Because of the wide range of applications of lithium ion batteries, the combustible and explosive carbon material dust of a negative electrode material requires additional attention. Few explosion test data of carbon material dust are available. In this paper, the thermodynamic and explosion parameters of allotropes of carbon dust and the same type of carbon material dust with different particle size distributions were determined. The results showed that the explosion pressure of micron/nano carbon material dust ranged from 0.4 to 0.7 MPa; the maximum deflagration index Kst ranged from 4 to 10 MPa · m/s; and the minimum ignition temperature was approximately 600 °C. The proportion of the small dust particles was an important factor that caused a change in the initial oxidation weight loss temperature and apparent activation energy of the same type of carbon dust. The variation trend among the initial oxidation weight loss temperature, apparent activation energy and particle size distribution of different carbon dust materials was not obvious, and mainly depended on the difference in molecular structures. Different molecular structures resulted in different apparent activation energies of the carbon allotropes. The apparent activation energy played a leading role in the change in the dust deflagration index. The smaller the apparent activation energy was, the smaller the energy required for carbon-carbon chemical bond breaking. The faster the carbon-carbon bond-breaking rate was, the larger the deflagration index. The dust particle size distribution, specific surface area and other characteristics had little influence on the deflagration index. Furthermore, the apparent activation energy had a greater impact on the deflagration index than the explosion pressure. The dust explosion pressure was mainly limited by oxygen in the test equipment, and its maximum value remained relatively constant. The minimum ignition temperature of dust clouds decreased with decreasing activation energy and increasing pre-exponential factor. The lower the initial oxidation weight loss temperature was, the lower the measured dust cloud minimum ignition temperature.

High energy density renewable fuels based on multicyclic sesquiterpene: Synthesis and performance

Considering the global carbon emissions and ambition of carbon neutrality, renewable fuels synthesized from biomass have great application prospects. Herein we adopted hydrogenation and cyclopropanation to synthesize four biofuels using α-cedrene and longifolene as feedstocks. Specifically, the modified Simmons-Smith method was used to synthesize cyclopropanated biofuels with a yield greater than 80% under the optimized conditions. The as-prepared biofuels possess the density of 0.925–0.965 g/mL, and the volumetric energy of 39.45–41.51 MJ/L. Additionally, the minimum ignition temperature and ignition delay time of the synthesized biofuels are shortened by 46–108 °C and 27.0–71.4%, respectively, compared with the widely used JP-10 fuel. The synthesized sesquiterpene-based biofuels have good potential to as alternative of high energy density fossil fuels like JP-10.

Study of Parameters and Theory of Sucrose Dust Explosion

To investigate the parameters of sucrose dust explosion, the minimum ignition energy (MIE) and minimum ignition temperature (MIT) were evaluated. The experiments tested the MIE of sucrose dust under different conditions of dust quantity, ignition delay time (IDT), and powder injection pressure (PIP). The experiments tested the MIT of different particle sizes. The results demonstrate that the MIE of sucrose powder under three conditions was an open-up quadratic polynomial. When the dust quantity, the IDT, and PIP were 0.5 g (417 g/m3), 90 ms, and 150 kPa, respectively, the MIE was 58.9 mJ, 62.6 mJ, and 52.4 mJ. The MIT was positively correlated with the particle size of sucrose dust, and the MIT was 340 °C. At the molecular level, the “O–H” bonds of the sucrose molecule hydroxyl groups were broken by the discharge of electrodes or high temperature to generate H2. The combustion of H2 caused the explosion to spread to the surrounding sucrose dust and made the deposited dust rise, forming an interlocking explosion. The explosion would not stop until the dust concentration dropped below the lowest explosion limit. The results of this study can provide guidance for sucrose enterprises to prevent dust explosion accidents.

Fire Parameters of Spruce (Picea abies Karst. (L.)) Dust Layer from Different Wood Technologies Slovak Case Study

The issue of the formation of wood dust particles in the work environment is still an actual topic in terms of its impact on employee health and the risk of fire or explosion in a woodworking operation. This article deals with the characteristics of spruce dust (Picea abies Karst. (L.)), which was taken from several types of wood technology. Experimental samples of spruce dust were taken from four types of sawing technologies, including grinding, briquetting and from the suction device container. The physical parameters of the samples taken were monitored and the particle size analysis was determined. The granulometric composition of the samples is significantly different. The sample of spruce wood dust from sawing has the most numerous fraction (250 µm), while the sample from grinding has the most numerous fraction 63–250 µm (87%).The aim of the paper was to monitor the minimum ignition temperature of the settled spruce dust layer and to look for a significant dependence of the minimum ignition temperature and ignition time on the type of spruce dust sample. A significant dependence was not confirmed. Significant moisture dependence of the samples was confirmed; the highest humidity was observed in the container, the lowest in sawing.

Effects of potassium additives on the combustion behavior of chrysanthemum biochar blended with graphite carbon as a heating source for heat-not-burn tobacco.

Heat-not-burn tobacco with an external heating source is a cleaner alternative to conventional cigarettes due to its lower emission of nicotine, CO and tar in the smoke, and the co-combustion of the composite carbon source (chrysanthemum biochar blended with graphite carbon) is a promising carbon heating source for a heat-not-burn tobacco product. This work has investigated the effect of the blending ratio of the graphite carbon on the co-combustion characteristics (i.e., the minimum ignition temperature, the burnout temperature, etc.) of the composite carbon source, as well as the effect of K2CO3 on the co-combustion behaviors. The results indicate that the minimum ignition temperature is mainly controlled by the ignition of the biochar while the burnout temperature is dominated by that of the graphite. The minimum ignition temperature of the carbon mixture is decreased by only 2–17 °C with K2CO3 because the ignition temperature of the biochar is difficult to reduce further by adding K2CO3. Simultaneously, the burnout temperature can be reduced by 30–60 °C since the graphite firing can be significantly improved by the presence of K2CO3. Moreover, the promotion effect of K2CO3 on the co-firing process is not always proportional to the addition amount of the catalyst, especially when the mass fraction of the graphite exceeds the threshold value of 30% based on the observation of the activation energies from the third-order kinetic model analysis.

Stanovenie teploty vznietenia sena pre účely posudzovania rizík v stredných a malých poľnohospodárskych podnikoch

Hot surfaces are an integral part of the technological processes of agricultural crop processing. Hot surfaces' temperature, at critical points, may exceed their minimum ignition temperature. The article aims to experimentally monitor the behaviour of hay in the event of its exposure to radiant heat. The mentioned model is implemented using a hot-plate device. The hot plate has a defined temperature-time curve. Based on the temperature-time curve, the hot surface´s temperature is determined as the minimum ignition temperature of the examined hay sample. At the same time, the temperatures inside the tested material were monitored. The heterogeneity of these samples significantly affected the nature of thermal degradation of biomass samples. The hay ignition temperature (406 ° C) can serve as a tool to assess the risk of fire.

Experimental study on the ignition characteristics of leaking RP-3 aviation kerosene on a horizontal hot wall

The accidental ignition of liquid fuels is an industrial safety concern due to the storage and transport of pressurized flammable liquids near components at elevated temperatures. In this work, the ignition process of leaked RP-3 aviation kerosene on the surface of the high temperature heat meter was studied experimentally and the critical temperature of the 50% ignition probability was obtained by the statistical method. The ignition process of fuel on horizontal hot wall was analysed by using the ignition video shot by high-speed camera, and the fuel steam plume model of the minimum hot surface ignition temperature for spilled fuel was established, which provided a theoretical basis for quantitative research on the ignition characteristics of leaking fuel on the hot surface. It shows that the temperature field and spatial concentration distribution produced by oil evaporation are time-varying and helpful for engine room fire protection. This study complements the related content of the fuel ignition mechanism on hot wall, at the same time, and provides fundamental understanding of the physical phenomena involved in the thermal ignition of impinging sprays in different regimes toward the goal of improved industrial safety.

Assessment of explosion risk for wood dust in a ventilation-dust separation installation, by determining the concentration of total dust in suspension inside of the installation

Most of combustible dusts present both fire and explosion hazard. Explosion may occur at certain concentrations of dust mixed with air and in the presence of an ignition source. The threat posed by this real danger was confirmed by the events that took place in economic units such as: feed factories, wood products, textile industry, steel, etc. Among the parameters of explosiveness of combustible dust, which can cause an explosion, we mention: maximum explosion pressure, lower explosion limit, explosive index, minimum ignition energy, electrical resistivity of dust, minimum ignition temperature of dust layer and cloud, particle size and concentration of dust in suspension. The current paper presents the results of determinations of combustible wood dust concentrations, performed at an important economic unit, manufacturing veneer and wood panels, at a dusting ventilation installation composed of fan, cyclone and textile filter. These determinations were made in the pipe connecting the fan and the bag filter, to assess possible danger of explosion in the pipe, by relating the measured concentration to the lower explosion limit (concentration of wood dust).

Enhanced low-temperature stable combustion of hydrocarbon with suppressing the Leidenfrost effect

Low-temperature stable combustion of liquid hydrocarbons helps improve energy efficiency and alleviate environmental pollution. However, when hydrocarbons (mainly saturated ones) are used as aircraft fuel, they show a long ignition delay time (IDT) and high ignition temperature as a result of Leidenfrost effect and chemical inertness of the CH bond. In especial, the insulated fuel vapor film due to the Leidenfrost effect that inhibits the heat transfer efficiency in the wide Leidenfrost region is unfavorable. Herein, we first propose a strategy that combines low-temperature self-oxidation and enhanced heat conduction to achieve low-temperature stable combustion of hydrocarbon while suppressing the Leidenfrost effect. Specifically, moderately reactive organometallic compound methoxydiethylborane (MDEB) with special radicals and silver nanoparticles (Ag NPs) with high thermal conductivity are preferred as fuel modifiers. By thermodynamic calculation, the heat released by the self-oxidation of MDEB is two orders of magnitude higher than the evaporation latent heat of n-decane, suggesting the applicability of energy conversion supported by enhancing fuel reactivity in suppressing the Leidenfrost effect. Ignition experiment results show that the negative temperature dependence associated with the Leidenfrost effect is eliminated under the specific fuel composition. Encouragingly, compared with n-decane, the IDT of MDEB/Ag/n-decane hybrid fuel is reduced from 4027 to ∼10 ms at a surface temperature of 600 °C. Comparing the ignition of MDEB/Ag/n-decane and MDEB/n-decane hybrid fuels at same temperatures, the influence of Ag NPs on IDT is highlighted by its significant decrease (∼28%). The minimum ignition temperature of n-decane-based hybrid fuel decreases to 112 °C, which is 508 °C lower than that of n-decane. These two ignition characteristic values are the low limit of saturated hydrocarbons to date. Our results thus provide a promising tool for enhancing the low-temperature ignition reliability and combustion stability of liquid hydrocarbons, which potentially decreases the pollution from the low temperature combustion.

Influence of anode temperature on ignition performance of the IRIT4-2D iodine-fueled radio frequency ion thruster

This paper reports the ignition performance of the iodine-fueled radio frequency (RF) ion thruster (IRIT) at different anode temperatures (). The experimental results show that the anode temperature plays important role on the ignition process of the IRIT. There were two characteristic temperatures related to the anode: the minimum ignition temperature () and the stable ignition temperature (), which were much lower than the pipeline temperature and the storage tank temperature. At < it failed to discharge. When ≤ < it was ignited with dramatical oscillations. At ≥ the discharge was stable in a large anode temperature range. The analysis showed that the different discharge phenomena at different anode temperatures were attributed to the change of iodine flow rate during the process of the iodine deposition-clogging and sublimation-clearing inside the thruster. The research helps improve the preheating design of the iodine-fueled electric thruster.

The Fire and Explosion Hazard of Coloured Powders Used during the Holi Festival.

During the world-famous Holi festival, people throw and smear each other with a colored powder (Holi color, Holi powder, Gulal powder). Until now, adverse health and environmental effects (skin and eye irritation, air pollution, and respiratory problems) have been described in the available literature. However, the literature lacks data on the flammable and explosive properties of these powders during mass events, despite the fact that burns, fires, and explosions during the Holi festival have taken place many times. The aim of the article is to present the fire and explosion parameters of three currently used Holi dust and cornflour dust types as reference dust. The minimum ignition temperature of the dust layer and dust cloud, the maximum explosion pressure and its maximum rate of growth over time, the lower explosion limit, the limit of oxygen concentration, and the minimum ignition energy were determined. Tests confirmed that the currently available Holi powders should be classified as flammable dusts and low-explosive dusts. The likelihood of a fire or explosion during mass incidents involving a Holi dust-air mixture is high.

Insight into the dust explosion hazard of pharmaceutical powders in the presence of flow aids

Coating of nanoscale flow aids is widely used in pharmaceutical applications to increase the flowability of cohesive powders. For combustible pharmaceutical active ingredients and excipients, it is unclear whether increased flowability affects the dust explosion hazard. In this work, acetaminophen (APAP) and microcrystalline cellulose (MCC) were studied with and without a coating of silica nanoparticles. A full set of explosion parameters for the pure materials and their flow-improved mixtures was determined in accordance with ASTM standards. The results show that parameters including minimum ignition temperature, minimum explosible concentration, and maximum explosion pressure were independent of powder flow properties, while the presence of flow aids led to significantly lower minimum ignition energy values for both APAP and MCC, and a slightly higher maximum rate of pressure rise for APAP. The connection between dust flowability and the dust explosion hazard is discussed with respect to these experimental results.

Influence of Volatile Content on the Explosion Characteristics of Coal Dust.

To study the influence of different volatile contents on the explosion characteristics of coal dust, the volatile content in coal dust was controlled under different final temperatures of pyrolysis. The maximum explosion pressure, maximum pressure rising rate, and explosion index were used to characterize the pressure behavior, the pressure ratio to characterize the explosibility, and the minimum ignition temperature of the coal dust cloud to characterize the sensitive characteristics. A 20 L of nearly spherical coal dust explosion parameter measuring device and a dust cloud minimum ignition temperature measuring device were used to study the influence of the explosion characteristics of dust with different volatile contents prepared under different pyrolysis temperature conditions. The results showed that the volatile matter content in lignite dust has little effect on the maximum explosion pressure, with an average change rate of 5.435%. When the volatile content was reduced from 45.4 to 2.45%, the maximum explosion pressure rise rate dropped by 65.976%. The explosion index of the experimental sample was in the range of 0–1.6, with weak explosion characteristics; the lower the volatile content, the weaker the explosion intensity. When the volatile content was only 2.45%, the pressure ratio was still greater than 2, that is, the dust was still explosive. When the volatile content in lignite was reduced from 45.4 to 18.21%, the lowest ignition temperature of the dust cloud was consistently 490 °C. At this stage, the contents of H2, CO, CH4, CO2, and other precipitated dases were low. When the volatile content was reduced from 18.21 to 2.45%, the precipitated volatile gas increased rapidly, the remaining precipitated gas content decreased, and the dust could not be easily ignited. The experimental results lay the foundation for studying the influence mechanism of volatile matter in coal dust on the explosion characteristics.

Characteristics of self–ignition and smoldering of coal dust layer under inclination conditions

In many actual industrial scenes, the coal body and coal dust are not always in the tiled state, but in the inclined situation. A two – dimensional transient numerical model of coal oxidation reaction was established to study the self–ignition and smoldering characteristics of coal dust layers in the presence of inclination angle. The effects of gravity and thermal buoyancy were considered to solve the coupling problem of coal oxidation reaction and air flow. The results show that the growth coefficients of minimum ignition temperature of coal dust with thicknesses of 6.4 mm, 12.7 mm, 19.1 mm and 25.4 mm are 0.117 °C/°, 0.0467 °C/°, 0.033 °C/° and 0.033 °C/°, respectively. With the increase of hot plate temperature, the inclination of coal dust can greatly shorten the ignition delay time (IDT). The ΔIDT of coal dust inclination of 60° is 128 s/°C greater than that of 0°. The movement of high temperature point of coal dust in self–heating development stage is from the inside to the outside, and that in decaying stage is from the outside to the inside. In addition, some interesting phenomena in the process of coal self–ignition and smoldering have also been found. The influence of coal dust inclination on its self–heating is mainly reflected in the location of high temperature points and the spread of smoldering. This study is helpful to understand the characteristics of coal dust self–ignition and smoldering spread in inclined situation, and can guide the prevention of coal dust self–ignition.