Ignition Temperature Of Layer Research Articles

Biomass inertization to increase minimum ignition temperature

In the past years, the use of biomass has significantly increased and, therefore, so has the number of accidents related to its storage, transport, and use. To prevent these accidents, it is essential to properly know their flammability and explosion characteristics so their behaviour can be addressed as a first stop for preventing accidents. The present work studies the inertization with solid inerts of biomass layers and clouds (biomass powder suspended in air) as a possible solution to reduce their ignition tendency. To do so, two biomass samples were studied: wood pellets and dried sewage sludge; mixed with two different inert materials: recycled glass and sodium bicarbonate. In particular, the inert materials were mixed with biomass at three different concentrations (30%, 50% and 70%) and the ignition of the mixtures was studied, determining the minimum ignition temperature of layer and cloud (MITL and MITC) for each mixture, and detecting the needed concentration for avoiding the ignition. Additionally, samples were tested using TGA and DSC techniques to analyse their thermal behaviour and to determine the influence that the inert material has in the energetic power of the biofuel.Different behaviours were observed depending on the different inert materials, showing that not only the amount of inert added is important but also its physico-chemical properties. If the results for a layer and a cloud are compared, it was noticed that inertization effect differs between biomass and test. Regarding TGA and DSC results, it was concluded that smaller percentages of inert material should be considered, as they substantially modify the energetic value.

Flammability and explosion characteristics of softwood dust

In technical terms, wood is a natural composite material with a polymer matrix, reinforced with fibres made of uniaxially oriented longitudinal cells. Due to the ease of obtaining and relatively low technological requirements related to its processing, wood is a common material used for various types of construction materials. An experimental investigation was carried out to determine the evolution of the ignition sensitivity and the explosion of three types of softwood dusts. Two of those dusts come from conifers and one from a deciduous tree. Complete fire characteristic requires several parameters describing wood dust behaviour under fire conditions including heat release rate (HRR), ignition time, or fire growth index. To determine those parameters, a cone calorimeter was used. Explosion characteristic was tested for representative wood as a dust sample in 20-L spherical vessel. Minimum ignition energy (MIE) was tested on MINOR II apparatus, which is a modified Hartman’s tube. Minimum ignition temperatures were tested with the use of layer ignition temperature apparatus and Godbert–Greenwald apparatus for minimum ignition temperature of a dust layer and dust cloud (MIT), respectively. Dust with the highest KST value, lowest MIE in the widest concentration range, and lowest MIT was pine wood dust. It also shows the shortest ignition time and a timespan between ignition and HRR peak.

An experimental study of mitigation of fire hazards of flash powder by adding mono ammonium phosphate as a solid inertant for explosive waste disposal in firework industries.

In firework industries, flash powder (FP) is a highly inflammable chemical mixture, which contains aluminum, sulfur, and potassium nitrate which is used for crackers manufacturing. During manufacturing, daily collected wastes shall be burnt in the open pit. This not only leads to pollution but also causes accidents. Here, a novel method had recommended that an inert substance was added to the FP to convert it to non-flammable. Mono-ammonium phosphate (MAP) is a fire-extinguishing agent and also used as fertilizer was considered. Layer ignition temperature, friction and impact sensitivity, plant growth test, and decomposition test were conducted for the MAP-mixed FP. It has been concluded that 50% MAP-mixed FP is having no mechanical sensitivity and a higher minimum ignition temperature. Seventy-five percent of mixed FP did not decompose in all weather conditions. From the soil test, it was found that soil macronutrients had been increased and ensured for safe landfilling.

Analysis of the chosen thermal and flammability parameters of dried sewage dust

The hazardous sludge disposal process in the form of landfills requires the determination inter alia of the flammable and explosion properties of dried sewage sludge dust, which has the ability to ignite and spontaneously combust when stored in silos. At a constant furnace surface temperature, the minimum ignition temperature of the sludge dust layer with a layer thickness of 5 mm is 270 °C, and for a layer thickness of 12.5 mm it is 250 °C. Two selected fire extinguishing powders for Class A, B, C and D fires were used in the study to determine the possibility of reducing the susceptibility of dried wastewater to ignition from heated surface, self-ignition and explosion parameters. The most effective extinguishing powder was ABC Favorit, which increased the value of the minimum ignition temperature of the layer (5 mm thick) to 360 °C and the spontaneous ignition temperature of the sludge with this powder increased by 22 °C at 169.6 cm3 in comparison to the sludge without extinguishing powder, respectively. The lowest self-ignition temperature of 136 °C was recorded for the largest tested volume (169.6 cm3) for dried sewage dust without any fire extinguishing powders. The biggest values of pmax and (dp/dt)max dried sewage dust were recorded 4.8 bar and 113 bar/s respectively. By analysing the obtained test results, it can be assumed that dried sewage dust is a combustible material with properties similar to biomass.

The effects of phosphorus-free inhibitors on the ignition of lycopodium dust

The minimum ignition temperature of dust suspension (MIT) and the hot surface ignition temperature of the dust layer (LIT) are essential safety parameters for the process industry. However, the knowledge of the ignition behavior when solid mixtures of flammable fuels and phosphorous-free inhibitors are considered is still scarce and further experimental and theoretical analyses are requested. In this work, the ignition temperature of phosphorous-free inhibitors (coal fly ash and calcium carbonate) mixed with lycopodium dust have been studied in terms of LIT analysis (hot plate thickness: 5 mm, 12.5 mm and 15 mm), and by the Godbert-Greenwald test for the MIT. Both coal fly ash and calcium carbonate have been tested at different concentrations and particle sizes.Results show that the effects of the inhibitor can be counter-productive when layer ignition temperature is considered even if the minimum ignition temperature of the dust suspension shows a positive effect from the safety point of view. This behavior has been analyzed in the terms of thermal conductivity and diffusivity of the mixture, by using Maxwell's equation for two-phase solid mixtures. Standard empirical correlations for the ignition temperature of solid mixtures have been also tested, showing their weakness in reproducing mixture behavior.

Analysis of minimum ignition temperature of pellet dust layer and cloud due to adding BC and ABC fire extinguishing powders

The paper describes the impact of adding fire extinguishing powders acting based on oxygen or flame on values of minimum ignition temperatures of the layer and cloud of pellet dust, and as a consequence the impact or lack of impact on values of maximum admissible temperature on external surfaces of electrical appliances working in their atmospheres. Tests were conducted of the minimum ignition temperature of layer and cloud of the agro armakow pellet dust and the agro jesień pellet dust, with and without additives of fire extinguishing powders BC Jet, BC LB2, ABC 90 and Ogniotex 103 at concentrations ranging from 5 to 70% by weight of powder contents in the mixture. Based on obtained test results it has been ascertained that type ABC powders appear to be much more effective than those type BC, because they have a much bigger impact on increasing the minimum ignition temperature of the layer and the cloud of analysed dust types. Adding only 15% of ABC 90 extinguishing powder to the agro jesień pellet has caused an increase in the minimum ignition temperature of dust layer by 80°C. The BC LB2 powder with agro armakow pellet dust has not been found to cause any changes, even at its concentration as high as 70%. The most optimum additive of powder to the biomass dust was 10% by weight of ABC powder in the mixture. At this concentration the highest increase was recorded in the maximum admissible temperature on the outer surface of electrical appliances from 235°C to 273°C.

Analysis of susceptibility of inflammable tobacco products dust to ignition from a heated surface

In the article was described combustible properties of tobacco product dust. Those properties decide about fire and explosion hazard for dust in layer and in cloud according to PN-EN 50281-2-1:2002 and PN-EN ISO/IEC 80079-20-2. There were determined protection against fire and explosion requirements of buildings structural elements and appliances used in space where dust accumulates. The article also consists safety requirements of using appliances in explosion hazard areas according to PN-EN 60079-14:2014. In the article are presented results of minimal ignition temperature of layer (MITL) and minimal ignition temperature of cloud dust (MTCD) as a function of dust layer thickness of chosen tobacco product and values of maximum acceptable surface temperature (MAST) of machines operating in the presence of dust cloud and chosen dust layer with thickness of 5 and 12.5mm.

Analysis of susceptibility to ignition of dust layer and dust cloud of selected hardened unsaturated polyester resins

In the article there were described combustible properties of selected dust types formed of plastic materials. Those properties decide on fire and explosion hazard for dust in layer and in cloud, according to PN-EN 50281-2-1:2002. The article also consists of safety requirements concerning using appliances in explosion hazard areas, according to PN-EN 50281-1-2:2002. In the article there are presented results of investigations on minimal ignition temperature of layer (MITL) and minimal ignition temperature of dust cloud (MITDC) as a function of dust layer thickness of chosen industry dust with different addition of modification and values of maximum acceptable surface temperature (MAST) of machines operating in the presence of dust cloud and chosen dust layer with thickness of 5 and 12.5 mm.

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.

Effect of Inerts on Layer Ignition Temperatures of Coal Dust

An experimental study into the hot surface ignition of coal dust layers has been conducted. Two coals were examined: Prince coal from the Cape Breton Development Corporation and Pittsburgh coal from the United States Bureau of Mines. The effect of admixed inerts (dolomite and limestone) on the dust layer ignition temperature has been analyzed using a steady-state thermal explosion model. The analytical procedure used for evaluating the ignition temperature of a dust layer, heated from below and losing heat from its upper surface by convection, is an extension of the thermal explosion model of Thomas (Ref. [8]); namely, that of Thomas and Bowes (Ref. [15]). To commission the hot plate apparatus and validate the model predictions, a series of experiments were undertaken using sodium dithionite. This material is known to exhibit self-heating and there have been previous layer ignition temperature studies with which to compare results. It was demonstrated that an adequate estimate of the critical ignition temperature may be readily obtained by this analytical method. Furthermore, computed values of the critical ignition parameters for layers of coal dust admixed with inerts, accounting for changes in thermal conductivity, were in reasonable agreement with experimentally determined values.

Hot‐surface ignition temperatures of dust layers

AbstractMinimum dust layer ignition temperatures on a hot surface were determined for several dusts, using a test procedure recommended by the National Academy of Sciences. The dusts included coal, three oil shales, lycopodium spores, corn starch, grain and brass powder. For a few of the dusts the effects of particle size and layer thickness on the minimum ignition temperatures were examined. Test results were repeatable and reliable for the fuels, the lycopodium and the brass powder. The minimum hot‐surface ignition temperatures of 12.7‐mm thick layers of these dusts ranged from 160°C for brass to 290°C for 20‐gal ton−1 oil shale. Flaming combustion was observed only with the brass powder. The minimum ignition temperatures decreased with thicker layers and with smaller particle sizes. Some difficulties were encountered with the corn starch and grain dusts. During heating, the starch charred and expanded; the grain dust swelled and distorted. The test was found acceptable for the purpose of determining the minimum layer ignition temperature of a variety of dusts. To prevent fire hazards due to smoldering or flaming dust layers the temperatures of surfaces on which combustible dusts accumulate should be lower than the minimum hot‐surface ignition temperatures of the dusts.