Minimum Ignition Temperature Research Articles

Experimental Study of the Influence of the Concentration of Organic Water-Coal Fuel Components on the Integral Ignition Characteristics

To enlarge the power raw material base, the processes of stable initiation of combustion of drops of organic watercoal fuels have been investigated. For the main components, we used filter cakes (coal processing waste), anthracite, bituminous and brown coals of brands D and B2, water, and spent machine, turbine, and transformer oils. We have established the influence of concentrations of components on the minimum (limiting) ignition temperatures of organic water-coal fuels and the ignition delay times of drops of fuel components with initial sizes of 0.25–1.5 mm. Investigations were carried out for oxidizer temperatures of 600–1100 K and its velocities of 0.5–5 m/s characteristic of units, aggregates, and large and small power plants. We have determined the characteristic differences of organic water-coal fuel from water-coal fuel and the close laws of the investigated processes for these fuels.

Study on Small Component Thermal Ignition Compliance meeting IEC Standard

With the supplement and revision of IEC standard, the thermal ignition test of small components has been stipulated. Small component ignition test apparatus is testing equipment of intrinsically safe electrical products about thermal ignition. Its research and application is an important link of energy storage components for energy control and temperature control. This paper starts from the analysis of restraining measures of capacitor and inductance energy storage,its system composition, main technical requirements and working principle of small component ignition test apparatus are systematically introduced. Then, the influence of the surface area of heat source in the calibration circuit on the minimum ignition temperature of the mixture of methane and air is demonstrated. From the running situation and the experimental data, the apparatus has the ability to carry out various small components ignition inspection.

Maximum combustion temperature for coal-water slurry containing petrochemicals

This study examines the temperature change of droplets of coal-water slurry containing petrochemicals (CWSP). The slurry consists of coal and oil processing waste. The temperature of oxidant in a modelled combustion chamber is varied between 600 and 1200 K. The initial size (radius) of CWSP droplets varied in the range of 0.5–3 mm. The study identifies typical temperature trends at the center and on the surface of the CWSP droplet. The temperature trends represent the following stages: (i) heating of fuel, (ii) evaporation of water and a liquid combustible component, (iii) thermal decomposition of coal and yield of volatiles, (iv) gas phase ignition of volatiles together with vapor of the combustible liquid, and (v) heterogeneous ignition of carbon and its burnout. Moreover, these trends indicate the maximum combustion temperatures of CWSP that reflect corresponding heat release. The study specifies the parameters which influence the maximum combustion temperature: fuel component composition, properties of components, droplet size, and the oxidant temperature. Finally, the study defines the minimum ignition temperatures and delay times of sustainable combustion initiation that characterize the ignition inertia. The knowledge of influence of these factors will allow one to predict the optimal conditions for the combustion of the CWSP.

Investigation on the ignition, thermal acceleration and characteristic temperatures of coal char combustion

Through using a new thermal analysis model and a method of coal/char combustion, the minimum ignition temperature and minimum ignition heat of three different ranks of pulverized coal char were measured by simultaneous Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) experiments. The results show that the ignition of coal char occurs in the range between the minimum ignition temperature and the inflection-point temperature. The thermal acceleration and its gradient GT increase with increasing heating rate and decrease with increasing coal char rank. The higher the GT of the coal char, the more easily the ignition occurs and more rapidly the burning and burnout occur. The data show that the GT of coal char of SLH lignite is 1.6 times more than that of coal char of ZCY bituminous and JWY anthracite in ignition zone, and 3.4 times in burning zone. The characteristic temperatures increase with increasing temperature of prepared char, heating rate and char rank. Moreover, the Tig,max calculated in DSC experiment is approximately in line with the ignition temperature obtained in the entrained flow reactor, which demonstrates the feasibility of the proposed theory.

Minimum Ignition Temperature of Dusts, Gases, and Solvents Hybrid Mixtures

ABSTRACTInvestigation of the ignition behavior (minimum ignition temperature [MIT]) of dusts, gases, or solvents and their mixtures has been undertaken by performing a series of tests in the modified Godbert–Greenwald furnace. Four flammable gases (methane, propane, ethanol, and isopropanol) as well as three combustible dusts (starch, lycopodium, and toner) were used as materials. For the dusts alone test, the experimental protocol was in accordance with the European standard EN 50281-2-1, whereas for the gases, solvent vapors, and mixtures of these with the dusts, this protocol had to be modified slightly. The experimental results demonstrate the significant decrease of the MIT of either gas, solvent, or dust and an increase in the explosion likelihood when a small amount dust, which is either below the minimum explosion concentration or not ignitable itself at the given temperature, are admixed with gas or solvent and vice versa. For example, the MIT of methane decrease from 600°C to 585°C when a small amount of starch was added. This hybrid MIT further decreased to 490°C when a third component (ethanol) was added. The same effect was noticed when a small amount of gas was added to a dust; for example, toner with a MIT of 460°C decreases to 450°C when a small amount of ethanol was added, which further decreased to 430°C when a third component (propane) was added. The result also confirm that an explosion is possible for a process or a system where hybrid mixtures are generated even if the temperature is below the MIT of a single substance and, hence, the MIT of hybrid mixtures cannot be predicted by simply overlapping the effects of the single dust, gas, or solvent.

Experimental determination of dust cloud combustion parameters of α-AlH3 powder in its charged and fully discharged states for H2 storage applications

This study discusses results of an experimental program for determination of dust cloud combustion parameters of charged and fully discharged states of metastable alane (aluminum hydride, α-AlH3 polymorph) powder in air. The measured characterization parameters include: maximum deflagration pressure rise (ΔPMAX), maximum rate of pressure rise (dP/dt)MAX, minimum ignition temperature (TC), minimum explosible concentration (MEC), and minimum ignition energy (MIE). These measured values are used for calculating the associated explosion severity (ES) index, and volume-normalized maximum rate of pressure rise (KSt). The experimental results show values of MEC and TC of fully discharged alane to be greater than those of the charged alane but measured MIE values are about the same. Moreover, the results show higher reactivity of fully discharged alane dust cloud in air compared to its charged state. For example, ES and KSt of discharged alane dust cloud in air are about 300% and 35% greater, respectively, than ES and KSt of charged alane dust. The higher air reactivity of fully-discharged (primarily Al powder) dust cloud compared to its charged state can be attributed to the higher surface energy (J/m2) of Al compared to that of α-AlH3. These experimental insights have safety implications in postulated risk scenarios involving light-duty vehicles powered by PEM fuel cells. The core insights and critical data provided by this contribution are useful for supporting development and promulgation of hydrogen safety standards and augmenting property databases of hydrogen storage materials.

Numerical study on the ignition behavior of coal dust layers in air and O2/CO2 atmospheres

Understanding the fundamental basis of coal dust layers ignition behavior is of interest for the mitigation of industrial fires and explosions. This paper develops a 2D numerical method to investigate the self-ignition of coal dust layers with an emphasis on the roles of the oxygen mole fraction and diluent gas. A global one-step 2nd-order reaction kinetic model considering both coal density and oxygen density is used to estimate the reaction rate of self-heating process until ignition. In addition, the overall heat transfer coefficient is evaluated based on a steady state method and the kinetic parameters are estimated by fitting experimental and numerical temperature evolution figures. This model has been found to be valid to predict the transient temperature and concentration profiles until ignition. The numerical results of the minimum ignition temperature of dust layers (MITL) are in close agreement with experimental observations. The ignition delay time and the most sensitive ignition position (MSIP) of dust layer are found to vary with varying ambient gas conditions, hot plate temperatures and ambient temperatures using the verified model. The model provides a satisfactory explanation for the dependence of ignition characteristics of coal dust layer in oxygen-enriched oxy-fuel atmospheres.

Effects of differential diffusion on ignition of stoichiometric hydrogen-air by moving hot spheres

Studying thermal ignition mechanisms is a key step for evaluating many ignition hazards. In the present work, two-dimensional simulations with detailed chemistry are used to study the effect of differential diffusion on the prediction of ignition thresholds of a stoichiometric hydrogen-air mixture by moving hot spheres. Numerical experiments showed an increase of 40 K in the minimum ignition temperature required for ignition when diffusion of species at different rates is taken into account. Detailed analysis of the species profiles at the ignition location and a sensitivity study of the system to the diffusivity of H2 and H revealed the key role played by the diffusion of H atoms in preventing ignition to take place at temperatures below 1000 K.

Thermal behaviour of organic solid recovered fuels (SRF)

The determination of the safety conditions in the storage and handling of solid recovered fuels (SRFs) was evaluated in order to avoid the presence of explosive atmospheres. Ten SRF samples were selected from different solid waste streams and collected in different seasons and different locations in Spain.Four different testing methodologies for characterizing the SRF dusts were carried out in order to determine thermal susceptibility and flammability. By means of thermogravimetric techniques, differential scanning calorimetry, minimum ignition energy and minimum ignition temperature on a cloud tests it has been possible to analyse the thermal susceptibility and ignition sensibility of SRFs. A prediction of the self-ignition risk level has been also obtained by a graphical method thanks to the data obtained.

Estimation of Thermal and Kinetic Parameters of Sugarcane Bagasse and Cotton Stalks Dust Layers from Hot Surface Ignition Tests

ABSTRACTA method to estimate thermal and kinetic parameters of sugarcane bagasse and cotton stalks subject to thermal runaway is presented using the standard and modified ASTM E2021 hot surface ignition test apparatus. These parameters include thermal conductivity (k), activation energy (E), and coupled term (QA). Experimental tests are used to determine the minimum hot surface temperature for dust ignition, ignition temperature of the dust itself, and ignition times. Four different dust layer thicknesses: 6.4 mm, 12.7 mm, 19.1 mm, and 25.4 mm, are tested for each material and their E and (QA) values are calculated by a widely known multiple test method. The average value of estimated k is 0.08 W/m.K and 0.068 W/m.K for sugarcane bagasse and cotton stalks, respectively. For sugarcane bagasse, the activation energy ranges from 178.7 kJ/mol to 181.3 kJ/mol and the corresponding value of (QA) is 3.5 × 106 for this range. For cotton stalks, the activation energy ranges from 147 kJ/mol to 149.8 kJ/mol and the corresponding value of (QA) is 10 × for this range. Results also showed that as the dust layer thickness increases, the minimum hot plate ignition temperature () decreases and the ignition time () increases. Different photographs for ignition of dusts are presented and discussed. Gas emissions during ignition are measured and discussed.

A Study on the Flash Point and Spontaneous Ignition Determination of Diethylene Glycol

This study investigates the main factors of fire prevention, such as spontaneous ignition and flash point, while using Diehylene Glycol (DEG) as the antifreeze for automobile and industrial machines. Our results show the flash point of 142℃ and the minimum ignition temperature of 388℃ in the range of 130㎕ ～ 150㎕. By increasing temperature to ignite in 1 second, an instantaneous ignition temperature of the sample is 569℃ in the sample amount of 140㎕.

Lower explosion limit/minimum explosible concentration testing for hybrid mixtures in the Godbert-Greenwald furnace

Experimental investigations of the lower explosion limits (LEL) of three-component hybrid mixtures of six combustible dusts, three gases, and four solvents were performed in the modified Godbert-Greenwald furnace. The test protocol was in accordance with European standard EN 50281-2-1 which is originally used to determine the minimum ignition temperature of dusts. Modification was done on the equipment to test for the explosion limits for dusts, gases, solvents, and hybrid mixtures. In order to prove the validity of our experimental procedure, the LEL for pure gases were initially tested and the results were compared with values found in literature obtained from the standard procedure which show very good agreement. The experimental results demonstrated a significant decrease of the explosion limits of gas, solvent, or dust and an increase in the likelihood of explosion when a small amount of dust was mixed with gas or solvent and vice versa. For example, the minimum explosible concentration (MEC) of high density polyethylene (HDPE) of 174 g/m3 decreased to 130 g/m3 upon addition of methane the concentration of which itself was below the LEL. The MEC of HDPE further decreased to 65 g/m3 when a nonexplosible concentration of hexane was added. © 2016 American Institute of Chemical Engineers Process Saf Prog 36: 81–94, 2017

Experimental investigation of the minimum auto-ignition temperature (MAIT) of the coal dust layer in a hot and humid environment

Ventilation Air Methane (VAM) abatement technology is recognized as a promising and value adding technique for reducing fugitive methane emissions, however, it also increases the potential fire and explosion risks of overheated coal dust. To eliminate these risks from the abatement systems it is necessary to determine the critical combustion characteristics of the minimum auto ignition temperature (MAIT) for a coal dust layer.This study investigates the auto-ignition behavior of coal dust layers in a humid environment with Relative Humidity (RH) >80%. The MAIT of four different coal dust samples (Australian coal) with particle sizes below 212μm and dust layer thicknesses of 5, 12 and 15mm were measured using a dust layer auto ignition temperature apparatus in accordance with the ASTM E2021 standard.It was concluded that the MAIT of the coal dust layer significantly decreases with decreasing particle size. The MAIT for the coal samples with a smaller D50 size were observed to be lower in comparison with samples with a larger D50 size. The dust layer thickness was shown to significantly impact on the MAIT. The MAIT increased proportionally with the increasing thickness of the coal dust layer. The effect of the coal dust moisture content and humidity on the MAIT for compacted dust layers was noticeable, whereas, this effect was less important with loose dust layers. In addition, this work investigated and compared the MAIT for a typical coal dust sample based on the existing ASTM and International Electrotechnical Commission (IEC) standard procedures for ignition of coal dust layers.

Experimental investigations of the minimum ignition energy and the minimum ignition temperature of inert and combustible dust cloud mixtures

The risks associated with dust explosions still exist in industries that either process or handle combustible dust. This explosion risk could be prevented or mitigated by applying the principle of inherent safety (moderation). This is achieved by adding an inert material to a highly combustible material in order to decrease the ignition sensitivity of the combustible dust. The presented paper deals with the experimental investigation of the influence of adding an inert dust on the minimum ignition energy and the minimum ignition temperature of the combustible/inert dust mixtures. The experimental investigation was done in two laboratory scale equipment: the Hartmann apparatus and the Godbert-Greenwald furnace for the minimum ignition energy and the minimum ignition temperature test respectively. This was achieved by mixing various amounts of three inert materials (magnesium oxide, ammonium sulphate and sand) and six combustible dusts (brown coal, lycopodium, toner, niacin, corn starch and high density polyethylene). Generally, increasing the inert materials concentration increases the minimum ignition energy as well as the minimum ignition temperatures until a threshold is reached where no ignition was obtained. The permissible range for the inert mixture to minimize the ignition risk lies between 60 to 80%.

Experimental study on the minimum ignition temperature of coal dust clouds in oxy-fuel combustion atmospheres

BAM furnace apparatus tests were conducted to investigate the minimum ignition temperature of coal dusts (MITC) in O2/CO2 atmospheres with an O2 mole fraction from 20 to 50%. Three coal dusts: Indonesian Sebuku coal, Pittsburgh No.8 coal and South African coal were tested. Experimental results showed that the dust explosion risk increases significantly with increasing O2 mole fraction by reducing the minimum ignition temperature for the three tested coal dust clouds dramatically (even by 100°C). Compared with conventional combustion, the inhibiting effect of CO2 was found to be comparatively large in dust clouds, particularly for the coal dusts with high volatile content. The retardation effect of the moisture content on the ignition of dust clouds was also found to be pronounced. In addition, a modified steady-state mathematical model based on heterogeneous reaction was proposed to interpret the observed experimental phenomena and to estimate the ignition mechanism of coal dust clouds under minimum ignition temperature conditions. The analysis revealed that heterogeneous ignition dominates the ignition mechanism for sub-/bituminous coal dusts under minimum ignition temperature conditions, but the decrease of coal maturity facilitates homogeneous ignition. These results improve our understanding of the ignition behaviour and the explosion risk of coal dust clouds in oxy-fuel combustion atmospheres.

Ignition characteristics of metal dusts generated during machining operations in the presence of calcium carbonate

Metal dust explosions in machining industries have caused large losses in recent years. In order to evaluate and control the ignition likelihood of metal dusts generated during machining operations, it is necessary to determine the ignition characteristics such as minimum ignition energy (MIE) and minimum ignition temperature (MIT). The aim of this paper is to investigate the inerting effect of calcium carbonate (CaCO3) on these ignition characteristics. Six kinds of typical metal dusts and two kinds of pure atomized metal powders were used to determine the MIE and MIT of dust cloud in the presence of CaCO3. To provide a practical guidance for metal dust explosion prevention, the recommended percentage of CaCO3 were discussed based on the inerting effect.

Minimum temperatures for sustainable ignition of coal water slurry containing petrochemicals

This paper presents the conditions and characteristics of the sustainable ignition of coal water slurry (CWS) containing petrochemicals in the air flow. This study may be useful to expand the raw material base for the power industry and the effective recycling of low-grade wastes from coal and oil processing. We use an experimental setup to investigate the ignition of slurry droplets with the radius from 0.5 mm to 1.5 mm when heating in the air flow with the temperature of 500–900 K and rate of 0.5–5 m/s. The present paper also studies necessary and sufficient conditions for the ignition of the different slurry compositions. We reveal the minimum ignition temperatures of slurry droplets in air flow. In addition, we show that these temperatures can be significantly less than the temperatures in combustion chambers of power plants (as a rule, higher than 900 K). Furthermore, we determine the times of ignition delay and complete combustion for slurry droplets, as well as the influence of the air flow temperature and rate, droplet sizes, and slurry composition on these times. Research results show that combustion initiation conditions and characteristics of fuel compositions can vary within wide ranges. This effect contributes to using CWS containing petrochemicals in power engineering, chemical, petrochemical, and transportation industries.

알루미늄 나노 및 마이크로 입자의 열분해 위험성

Aluminum dusts, from micro to nano-scale, are widely used in various applications such as propulsion and pyrotechnic compounds because of high burning rate. In this study, the pyrolysis hazard of aluminum dusts with different median size (sized by 70 nm, 100 nm, , ) were investigated experimentally. The thermal decomposition characteristics of aluminum dusts with the variation of heating rate were investigated using TGA (Thermo gravimetric analysis) and was estimated the minimum ignition temperature from temperature of weight gain in nano and micro-sized aluminum dusts with different diameter. In the same condition of heating rate, the temperature of weight gain in aluminum dust layers increased with increasing of particle size and increased with increasing of heating rates in air. From the results, it was estimated that the pyrolysis hazard of aluminum dusts decrease with increasing of mean diameter.

Models to estimate the minimum ignition temperature of dusts and hybrid mixtures

The minimum ignition temperatures (MIT) of hybrid mixtures have been investigated by performing several series of tests in a modified Godbert–Greenwald furnace. Five dusts as well as three perfect gases and three real were used in different combinations as test samples. Further, seven mathematical models for prediction of the MIT of dust/air mixtures were presented of which three were chosen for deeper study and comparison with the experimental results based on the availability of the input quantities needed and their applicability. Additionally, two alternative models were proposed to calculate the MIT of hybrid mixtures and were validated against the experimental results. A significant decrease of the minimum ignition temperature of either the gas or the vapor as well as an increase in the explosion likelihood could be observed when a small amount of dust which was either below its minimum explosible concentration or not ignitable itself at that particular temperature was mixed with the gas. The various models developed by Cassel, Krishma and Mitsui to predict the MIT of dust were in good agreement with the experimental results as well as the two models proposed to predict the MIT of hybrid mixtures were also in agreement with the experimental value.

Experimental investigation on the minimum ignition temperature of hybrid mixtures of dusts and gases or solvents

Investigations on the minimum ignition temperatures (MIT) of hybrid mixtures of dusts with gases or solvents were performed in the modified Godbert–Greenwald (GG) furnace. Five combustible dusts and six flammable gases (three ideal and three real) were used. The test protocol was according to EN 50281-2-1 for dust–air mixtures whereas in the case of gases, solvents and hybrid mixtures this standard was used with slight modification. The experimental results demonstrated a significant decrease of the MIT of gas, solvent or dust and an increase in the likelihood of explosion when a small amount of dust, which was either below the minimum explosion concentration or not ignitable by itself, was mixed with gas and vice versa. For example, the MIT of toluene decreased from 540°C to 455°C when small amount of lycopodium was added. It was also confirmed that a hybrid mixture explosion is possible even when both dust and vapour or gas concentrations are respectively lower than their minimum explosion concentration (MEC) and lower explosion limit (LEL). Another example is CN4, the MEC of which of 304g/m3 decreased to 37g/m3 when propane was added, even though the concentrations of the gas was below its LEL.