Minimum Ignition Temperature Research Articles

Experimental Study Of Minimum Ignition Temperature Of Spent Coffee Grounds

Abstract The aim of this scientific paper is an analysis of the minimum ignition temperature of dust layer and the minimum ignition temperatures of dust clouds. It could be used to identify the threats in industrial production and civil engineering, on which a layer of combustible dust could occure. Research was performed on spent coffee grounds. Tests were performed according to EN 50281-2-1:2002 Methods for determining the minimum ignition temperatures of dust (Method A). Objective of method A is to determine the minimum temperature at which ignition or decomposition of dust occurs during thermal straining on a hot plate at a constant temperature. The highest minimum smouldering and carbonating temperature of spent coffee grounds for 5 mm high layer was determined at the interval from 280 °C to 310 °C during 600 seconds. Method B is used to determine the minimum ignition temperature of a dust cloud. Minimum ignition temperature of studied dust was determined to 470 °C (air pressure - 50 kPa, sample weight 0.3 g).

마그네슘 부유 분진의 입자 체류시간과 발화온도

본 연구에서는 부유 Mg분진의 최소발화온도(MIT)에 있어서 입자 체류시간이 어떠한 영향을 주는지를 실험자료와 입자속도의 계산결과를 사용하여 조사하였다. 평균입경이 증가하면 Mg분진의 MIT는 증가하는 반면에 입자 체류시간(Residence time)은 지수함수적으로 감소하여 분진의 발화 가능성이 저하되는 요인이 될 수 있음을 계산을 통해 확인할 수 있었다. 또한 온도증가에 의한 입자속도에의 영향은 평균입경이 클수록 미세하지만 증가하는 결과가 얻어졌다. Effects of residence time on the MIT(Minimum Ignition Temperature) in suspended Mg particles are examined by using MIT experimental data and calculation results of terminal velocity. With increasing of the average particle diameter, we were able to identify that MIT of Mg dusts increased and the calculated residence time of particle decreased exponentially. Also, the influence on terminal velocity due to temperature increase increased slightly with increasing of average particle diameter.

Experimental study on the combustion sensitivity parameters and pre-combusted changes in functional groups of lignite coal dust

Sensitivity parameters are critical for safety management and risk assessment of coal dust combustion process. In this paper, in order to evaluate the combustion sensitivity parameters and reveal the mechanism of lignite coal dust, 20L spherical explosion test apparatus and hot surface test apparatus were chosen to test the typical sensitivity parameters of lignite coal dust combustion. Results show that the limiting oxygen concentration of dust clouds (LOCC) was in the range of (13–14) %, and the minimum ignition temperature of dust layer (MITL) was in the range of (280–290) °C, respectively. The functional group variation law before combustion of lignite coal dust was tested by in-situ diffuse reflection Fourier transform infrared spectrometry (FTIR), and the proportions of functional groups in the lignite coal dust were analyzed from 30°C to 290°C. It is demonstrated that in coal dust combustion the key functional groups were CH3/CH2 and OH.

Minimum Ignition Temperature of layer and cloud dust mixtures

The prevention of dust explosions is still a challenge for the process industry. Ignition, in particular, is a phenomenon that is still not completely understood. As a consequence, safety conditions pertaining to ignition suppression are rarely identified to an adequate level. It is well known that, in general, the ignition attitude of a dust depends on several factors, such as the nature of the chemical, the particle size, moisture content, etc., but there is still a lack of knowledge on the effect of the single variables.This paper has the aim of providing data on the Minimum Ignition Temperatures of dust mixtures obtained from a mixing of a combustible dust (flour, lactose, sucrose, sulphur) and an inert dust (limestone, extinguishing powders) as well as from the mixing of two different combustible dusts. Various mixtures with different weight ratios have been tested in a Godbert Greenwald (GG) furnace and on a hot plate in order to measure the effect of mixture composition on the Minimum Ignition Temperature (MITL) of the layer and on the Minimum Ignition Temperature (MITC) of the cloud. In order to further verify the effects of inert dust particle size, inerts sieved to different size ranges have been tested separately. Generally, both MITL and MITC increase as the inert content is increased. MITC is poorly affected by inert particle size when limestone is used. The MITL of pure flour is higher than the MITL of mixtures containing up to 40% of 32–75 μm of limestone. This was probably due to the behaviour of pure flour during the test, which demonstrated strong tendency to produce char, cracks in the layer and detachment from the hot plate.

Potential explosion hazard of carbonaceous nanoparticles: Explosion parameters of selected materials

Following a previous explosion screening study, we have conducted concentration and ignition energy scans on several carbonaceous nanopowders: fullerene, SWCNT, carbon black, MWCNT, graphene, CNF, and graphite. We have measured minimum explosive concentration (MEC), minimum ignition energy (MIE), and minimum ignition temperature (MITcloud) for these materials. The nanocarbons exhibit MEC ~101–102g/m3, comparable to the MEC for coals and for fine particle carbon blacks and graphites. The nanocarbons are confirmed mainly to be in the St-1 explosion class, with fullerene, at KSt~200bar-m/s, borderline St-1/St-2. We estimate MIE~102–103J, an order of magnitude higher than the MIE for coals but an order of magnitude lower than the MIE for fine particle graphites. While the explosion severity of the nanocarbons is comparable to that of the coals, their explosion susceptibility (ease of ignition) is significantly less (i.e., the nanocarbons have higher MIEs than do the coals); by contrast, the nanocarbons exhibit similar explosion severity to the graphites but enhanced explosion susceptibility (i.e., the nanocarbons have lower MIEs than do the graphites). MITcloud>550°C, comparable to that of the coals and carbon blacks.

An exploratory study of explosion potential of dust from torrefied biomass

Torrefaction makes biomass brittle, and as such it is likely to produce more dusts during handling and transportation. So, it could increase the risk of explosion in plant using torrefied biomass. As the torrefaction technology enters commercial market the safety aspect of torrefied wood becomes important. The present paper is one of the first examinations of the question if torrefaction makes the biomass dust more explosive. Effects of torrefaction conditions on two important parameters that define the explosivity of a dust, i.e., minimum ignition temperature (MIT) and minimum explosible concentration (MEC) were studied. Above parameters were measured for Poplar wood before and after torrefaction. Three different particle size distributions of the wood, torrefied at 200, 250 and 300 °C, were tested. Exploratory experiments reported here found negligible effect of torrefaction on measured values of;Deg;ME;Deg;C and MIT of biomass. However, torrefied particles larger than 100 micron showed higher values of MIT than that for raw biomass.

Autoignition and combustion characteristics of kerosene droplets with dilute concentrations of aluminum nanoparticles at elevated temperatures

In this experimental study, we investigated the effects of high ambient temperatures and dilute concentrations of nanoparticles (NPs) on the autoignition and combustion characteristics of kerosene-based nanofluid droplets. An isolated kerosene droplet containing 0.1%, 0.5% or 1.0% by weight of aluminum (Al) NPs suspended on a silicon carbide (SiC) fiber was suddenly exposed to an elevated temperature (in range 400–800°C) at atmospheric pressure (0.1MPa) under normal gravity, and the autoignition and combustion characteristics were examined. The ignition delay time, burning rate constant and combustion characteristics of pure and stabilized kerosene droplets were also observed for comparison. The results indicate that, similar to pure kerosene droplets, the ignition delay time of NP-laden kerosene (n-Al/kerosene) droplets also followed the Arrhenius expression and decreased exponentially with increasing temperature. However, the addition of dilute concentrations of Al NPs to kerosene reduced the ignition delay and lowered the minimum ignition temperature to 600°C, at which pure kerosene droplets of the same initial diameter were not ignited. In contrast to the combustion of pure and stabilized kerosene droplets, the combustion of n-Al/kerosene droplets exhibited disruptive behavior characterized by sudden reductions in the droplet diameter without any prior expansions caused by multiple-time bubble formation and their subsequent rupture at or near the droplet’s surface. This bubble pop-up resulted in droplet trembling and fragmentation and ultimately led to enhancement in gasification, vapor accumulation and envelope flame disturbance. The NPs were also brought out of the droplets through these disruptions. Consequently, the burning time and total combustion time of the droplets were reduced, and almost no residue remained on the fiber following combustion. Thus, the combustion rate of n-Al/kerosene droplets was substantially enhanced compared with pure kerosene droplets at all tested temperatures.

Dust cloud combustion characterization of a mixture of LiBH4 destabilized with MgH2 for reversible H2 storage in mobile applications

This study discusses results of an experimental program to determine dust cloud combustion characteristics of 2LiBH4 + MgH2 binary system in air. The determined parameters of hydrided and partially-dehydrided states of this system include: maximum deflagration pressure rise (PMAX), maximum rate of pressure rise (dP/dt)MAX, minimum ignition temperature (TC), minimum explosible concentration (MEC), minimum ignition energy (MIE), and explosion severity index (KSt). Impact of dust particle size on the measured parameters is evaluated for the partially-dehydrided state. For dust of same mean particle size, results show the hydrided state to be more explosible in air compared to its partially-dehydrided state. Moreover, MIE of the partially-dehydrided mixture is identified in the test with lowest ignition delay time (IDT) and highest dust cloud concentration (DC). Taguchi's mixed-levels design of experiments (DoE) methodology is employed to calculate dust's MIE response surface as a function of DC and IDT. The one-at-a-time effect and interaction effect between DC and IDT on dust MIE are determined. The core insights of this contribution are useful for quantifying risks in mobile and stationary H2 storage applications, informing H2 safety standards, and augmenting property databases of H2 storage materials.

Hazards of Explosibility Dust from Wood Pellets

The main purpose of this publication is to determine minimal ignition temperature of dust cloud. The flammable and explosive dust is formed during the production, transport, storage and usage of the wood pallets. The examined samples in experimental part of the work were made from different kind of pallets. Contribution deals with analysis of fire and explosion hazards of dust particles generated during transportation and handling of wood pellets. Minimum ignition temperature of dust cloud were performed according to STN EN 50281-2-1. In terms of forensic approach, by using of selected methods, the conditions in which initiation and explosion of dust can be occurred were simulated the exposibility for wood pellets dust was tested under different condition using various pressures and various weight to samples. Defining the conditions in which the risk of formation of dangerous situation exists, helps to predict the fire and explosion in the premises where the pellets are used.

Study on Ignition Time of Radiation Cargo in Irradiation Room under Stuck Radioactive Sources

Ignition temperatures of common radiation cargo in irradiation room were measured through the experiments, minimum ignition temperature is 210 °C. In order to discuss the temperature variation and temperature field under stuck radioactive sources, the fire scenario was presented and simulated by FDS. The results show that temperatures rise rapidly when stuck radioactive source broke out within an hour. As the growth of the time, temperatures in irradiation room are rising, but the rising rate is slowing. The temperature field in the irradiation room tends to be the same after three hours. The stuck radioactive source occurred after 2.4 days later, local temperatures can reach 210 °C, and radiation cargo may be ignited.

Minimum ignition temperature of nano and micro Ti powder clouds in the presence of inert nano TiO2 powder

Minimum ignition temperature (MIT) of micro Ti powder increased gradually with increases in nano-sized TiO2 employed as an inertant. Solid TiO2 inertant significantly reduced ignition hazard of micro Ti powder in contact with hot surfaces. The MIT of nano Ti powder remained low (583K), however, even with 90% TiO2. The MIT of micro Ti powder, when mixed with nano Ti powder at concentrations as low as 10%, decreased so dramatically that its application as a solid fuel may be possible. A simple MIT model was proposed for aggregate particle size estimation and better understanding of the inerting effect of nano TiO2 on MIT. Estimated particle size was 1.46–1.51μm larger than that in the 20-L sphere due to poor dispersion in the BAM oven. Calculated MITs were lower than corresponding empirically determined values for micro Ti powder because nano-sized TiO2 coated the micro Ti powder, thereby decreasing its reaction kinetics. In the case of nano Ti powder, nano-sized TiO2 facilitated dispersion of nano Ti powder which resulted in a calculated MIT that was greater than the experimentally determined value.

Experimental investigation of the influence of inert solids on ignition sensitivity of organic powders

This work presents the results of the experimental characterization of the ignition sensitivity of solid inertant/combustible powders mixtures. Three inert solids (alumina, Kieselguhr, aerosil) and eleven organic powders have been considered and the following parameters have been determined: (1) the minimum ignition energy, (2) the minimum ignition temperature in cloud and (3) the minimum ignition temperature in 5mm layer. The effects of the addition of inert solids are described and a simple model is proposed to represent the experimental results.Generally, increasing inert solid content in a powder leads to a higher minimum ignition energy as well as a higher minimum ignition temperatures in cloud and in layer. In some cases, the flammability is influenced above a threshold concentration value, which can be quite high (up to 85wt.%). Indeed, the proposed model shows a zone below the minimum ignition concentration (MIC), which does not enable an efficient or safe inerting: either the admixed inert solid does not provide a sufficient effect, or it can even facilitate the ignition of the dust by notably improving its dispersability.The influence of key parameters such as the thermal conductivity or optical properties on the efficiency of the inerting by admixed solid need to be further assessed in a future work in view to better understand the mechanisms involved and to extend the scope to other types of oxidizable materials.

Experimental Analysis of Minimum Ignition Temperature of Dust Cloud Obtained from Thermally Modified Spruce Wood

This article deals with study of minimum ignition temperature (MIT) of thermally modified spruce dust. Dust of several species of spruce was mixed, sieved, dried and subjected to Thermo-S temperature programme. Samples of dust (200 250 μm) were tested in Goldbert-Greenwald furnace apparatus for determination of the MIT of dust clouds. The influence of air pressure and sample weight to the MIT was studied. The results show that the MIT of thermally modified spruce dust gradually decreases as the sample weight and air pressure rise. The lowest value of MIT (470 °C) was measured, when the air pressure was 50 kPa and the sample weight 0,5 g. To reach even lower values of MIT (˂468 °C), the air pressure should gradually rise to approx. 42 46 kPa and the weight of dust sample should be approx. 0,46 0,53 g.

Study on Fire Risk Assessment on Irradiation Room under Stuck Radioactive Sources

Ignition temperatures of common radiation cargo in irradiation room were measured through the experiment, minimum ignition temperature is 210 °C. In order to discuss the temperature variation under stuck radioactive sources, two fire scenarios were presented and simulated by FDS. The results show that temperatures rise rapidly when stuck radioactive sources broke out within an hour. As the growth of the time, temperatures in irradiation room are rising, but the rising rate is slowing. In fire scenario A and B, the incidents of stuck radioactive sources occur in 9 days, 4 days later, local temperatures can reach 210 °C, and radiation cargo may be ignited. The results of the research can provide reference for fire risk judgment and assessment in irradiation room.

Study on Fire Risk Assessment on Round Irradiation Room of Stacking under Stuck Radioactive Sources

The typical 60Co round irradiation room of stacking has been taken as a research subject. Ignition temperatures of common radiation cargo were measured through the experiments, minimum ignition temperature is 210 °C. In order to discuss the temperature variation and temperature field under stuck radioactive sources, the fire scenario was presented and simulated by FDS. The results show that temperatures rise rapidly when stuck radioactive source broke out within an hour. As the growth of the time, temperatures in irradiation room are rising, but the rising rate is slowing. The temperature field in the irradiation room tends to be the same after two hours. The stuck radioactive source occurred after 7.2 days later, local temperatures can reach 210 °C, and radiation cargo may be ignited.

Influence of liquid and vapourized solvents on explosibility of pharmaceutical excipient dusts

Hybrid mixtures of a combustible dust and flammable gas are found in many industrial processes. Such fuel systems are often encountered in the pharmaceutical industry when excipient (nonpharmaceutically active ingredient) powders undergo transfer in either a dry or solvent prewetted state into an environment possibly containing a flammable gas.The research described in this article simulated the conditions of the above scenarios with microcrystalline cellulose and lactose as excipients, and methanol, ethanol, and isopropanol as solvents. Standardized dust explosibility test equipment (Siwek 20‐L explosion chamber, MIKE 3 apparatus, and BAM oven) and ASTM test protocols were used to determine the following explosibility parameters: maximum explosion pressure (Pmax), volume‐normalized maximum rate of pressure rise (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE), and minimum ignition temperature (MIT).The experimental results demonstrate the significant enhancements in explosion likelihood and explosion severity brought about by solvent admixture in either mode. The extent of solvent influence was found to be specific to the given excipient and method of solvent addition. Solvent burning velocity considerations help to account for some of the experimental observations but for others, a more rigorous evaluation of solvent and excipient physical property data is needed. © 2014 American Institute of Chemical Engineers Process Saf Prog 33: 374–379, 2014

A model to assess dust explosion occurrence probability

Dust handling poses a potential explosion hazard in many industrial facilities. The consequences of a dust explosion are often severe and similar to a gas explosion; however, its occurrence is conditional to the presence of five elements: combustible dust, ignition source, oxidant, mixing and confinement. Dust explosion researchers have conducted experiments to study the characteristics of these elements and generate data on explosibility. These experiments are often costly but the generated data has a significant scope in estimating the probability of a dust explosion occurrence. This paper attempts to use existing information (experimental data) to develop a predictive model to assess the probability of a dust explosion occurrence in a given environment. The pro-posed model considers six key parameters of a dust explosion: dust particle diameter (PD), minimum ignition energy (MIE), minimum explosible concentration (MEC), minimum ignition temperature (MIT), limiting oxygen concentration (LOC) and explosion pressure (Pmax). A conditional probabilistic approach has been developed and embedded in the proposed model to generate a nomograph for assessing dust explosion occurrence. The generated nomograph provides a quick assessment technique to map the occurrence probability of a dust explosion for a given environment defined with the six parameters.

Self ignition of layers of metal powder mixtures

The availability of models that predict the thermal stability and spontaneous ignition of metal powders is of great importance to the nuclear industry and powder handling systems in general. The present paper describes the application of a previously published two-dimensional axisymmetric model to the ignition characteristics of zirconium (Zr), tantalum (Ta) and Zr/Ta deposits on a hot surface. Their minimum ignition temperatures and oxidation behavior were investigated by validating the model against extensive experimental data. A nonlinear increase of the minimum ignition temperature was observed for Zr/Ta layers as a function of Zr content. The more reactive material, Zr, determines the thermal sensitivity of Zr/Ta mixtures, even when the Zr content is as low as 30wt.%. The model successfully predicts the ignition sensitivity of such mixtures with average deviations of ±4% for Ta loads amounting to less than 80wt.%. Three main aspects have been highlighted by SEM observations and XRD analyses: i) the diffusion of oxygen through the upper layers is the rate limiting step of the combustion reaction, ii) mechanical stresses are important for tantalum oxide layers and modify oxygen diffusion, and iii) due to lack of oxygen at the bottom of dust deposits, nitration reactions occur.

Experimental Analysis of Minimum Ignition Temperature of Coal Dust Layers in Oxy-fuel Combustion Atmospheres

An experimental investigation into the hot surface ignition of coal dust layers has been undertaken in oxy-fuel combustion atmospheres, with the oxygen mole fractions in the range of 21-50 vol. % (21%, 30%, 40% and 50%). Three coals were used to determine the minimum layer ignition temperature (MLIT) with a hot surface ignition apparatus according to the European EN50281-2-1 norm. In addition, thermal and kinetic parameters were also determined. Layer thicknesses of 5, 12.5, 15, 20 and 30mm were investigated. Firstly, 5 and 12.5mm thick coal dust layers were used to investigate the influence of the oxygen mole fraction on the MLIT, and the steady state dust layer temperature profile of a 30mm thick coal dust layer was used to estimate the thermal conductivity (k) at a low hot surface temperature. Secondly, the South African coal was used in this study to determine the kinetic parameters on the basis of the Frank-Kamenetskii theory. Results show that oxygen concentration has a significant influence on the MILT, (i.e., MLIT decreases with increasing oxygen concentration). It also shows that replacing N2 in the combustion air with CO2 a small increase of the MLIT will occur. The estimated k of the coal dust samples is respectively 0.1, 0.11 and 0.1 W·m-1·K-1 for South African coal, Sebuku coal and Pittsburgh coal. The region of the kinetic parameters of South African coal changes when there is a shift in the test from air to oxy-fuel combustion atmospheres,which means that the reaction mechanism of self-heating or ignition changed somewhat.

Research on Explosion Characteristics of Sulfur Dust and Risk Control of the Explosion

As dust explosion is a major risk factor threating the safety of sulfur production, evaluating and controlling the hazards of sulfur dust produced in the wet process are very important. Several characteristic parameters including minimum ignition temperature, minimum ignition energy, lower explosive limit, maximum explosion pressure, explosion index, limit oxygen concentration of sulfur dust were determined and investigated by the experimental device such as hot plate, Godbert-Greenwald furnace, Hartmann tube, 20L spherical container of explosive testing. The experimental results indicated the influence rules of particle size, water content and concentration on the explosion characteristics of sulfur dust. The results showed that sulfur dust could be lighted easily and had high explosibility. The explosion risk and strength of sulfur dust decreased with the increase of the particle size. The minimum ignition energy and the minimum ignition temperature increased as the water content increased. The maximum explosion pressure and the explosion index rose at first and went down latter as the dust concentration increases. Prevention and control measures of sulfur dust explosion, from two aspects of building control and process control, were proposed for production, storage and transportation process of sulfur produced in the wet process.