Self-Ignition Behaviour of Growing Dust Layers (original) (raw)
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Procedia Engineering, 2012
The paper presents an analysis of the minimum ignition temperature of dust layer and the minimum ignition temperatures of dust clouds. Tests have been performed for selected dusts: hop, lemon balm, nettle, senna fruit, valerian, buckwheat, barley, semolina, cornflakes, oatmeal, rice flakes, flour, malt, beech, dried carrot, corn starch and sunflower husk. Tests have been performed in accordance with EN 50281-2-1. Method A consists in determining the minimum temperature at which ignition occurs of dust and/or its decomposition on a hot plate at a constant temperature. The study is used to identify the threats from industrial equipment and construction, which while working have hot surfaces, on which can create a layer of combustible dust. Method B is used for determining the minimum ignition temperature of a dust cloud or other particulate solids. Method B is complementary to the method A. It is used in relation to industrial equipment, inside which dust may exist in the form of short-term cloud.
Modeling of Dust Explosion in the Industrial Spray Dryer, Drying Technology
Standard ANSYS FLUENT software was used to model a dust explosion inside a counter current spray-drying tower by replacing the dust with a flammable gas-air mixture. Two sets of computational fluid dynamics (CFD) calculations for a dust explosion in the tower were carried out at a uniform gas concentration and variable concentration in the dryer, which reflect the distribution of wet and dry powder zones in the spray dryer. The CFD calculation showed that a dust explosion developed from the ignition point mostly to the upper part of the tower. The temperature, velocity, and reaction profiles followed the same upward pattern. Results of the calculations allowed us to determine the position and parameters of venting devices that should be installed to minimize the risk of damage to the dryer construction.
Smoldering combustion of dust layer on hot surface
Journal of Loss Prevention in The Process Industries, 2000
The critical temperature as well as the critical flux for ignition of a dust layer of cornflour and a mixture of wheatflour and cornflour (80% wheatflour+20% cornflour) on a hot plate have been determined. The moulded sample was cylindrical in shape and of different heights and diameters. The particle size of dusts ranged between 63 µm to 150 µm. The temperature-time histories for self-heating without ignition and with ignition are offered, showing the critical boundaries between them. Also the times to ignition for each dust, showing the effect of sample size on their values, are determined. Certain experimental correlations which relate to times to ignition, as well as the critical temperature for ignition and thermal and geometrical dimensions of sample are presented.
Hot Surface Ignition Temperature of Dust Layers with and without Combustible Additives
2006
An accumulated combustible dust layer on some hot process equipment such as dryers or hot bearings can be ignited and result in fires when the hot surface temperature is sufficiently high. The ASTM E 2021 test procedure is often used to determine the Hot Surface Minimum Ignition Temperature for a half inch deep layer of a particular dust material. This test procedure was used in this thesis to study possible effects of combustible liquid (such as lubricating oil) and powder additives in the dust layer as well as air flow effects. The following combustible dusts were used: paper dust from a printing press, Arabic gum powder, Pittsburgh seam coal, and brass powder. To develop an improved understanding of the heat transfer, and oxygen mass transfer phenomena occurring in the dust layer, additional instrumentation such as a second thermocouple in the dust layer, an oxygen analyzer and gas sampling line, and an air velocity probe were used in at least some tests. Hot Surface Minimum Igni...
Journal of Hazardous Materials, 2010
Agricultural products stored in silos, and their dusts, can undergo oxidation and self-heating, increasing the risk of self-ignition and therefore of fires and explosions. The aim of the present work was to determine the thermal susceptibility (as reflected by the Maciejasz index, the temperature of the emission of flammable volatile substances and the combined information provided by the apparent activation energy and the oxidation temperature) of icing sugar, bread-making flour, maize, wheat, barley, alfalfa, and soybean dusts, using experimental methods for the characterisation of different types of coal (no standardised procedure exists for characterising the thermal susceptibility of either coal or agricultural products). In addition, the thermal stability of wheat, i.e., the risk of self-ignition determined as a function of sample volume, ignition temperature and storage time, was determined using the methods outlined in standard EN 15188:2007. The advantages and drawbacks of the different methods used are discussed.
Ignition behavior of dusts: Meaning and interpretation
Process Safety Progress, 1995
The minimum ignition energy and minimum ignition temperature of dust-airmixtures are important technical safety indices. They are used for the assessment of the efficacy of the ignition sources expected in dust-air mixtures. First of all, the test apparatus and the determination procedures are introduced, including the signifcant parameters on the mentioned indices. Finally, the correlations are described between-the minimum ignition energy and the efficacy of electrostatic sparks,-the minimum ignition energy and the minimum ignition temperature and the mechanically generated sparks on the on hand, the limiting oxygen concentration and the limiting gap width of combustible dusts on the other hand,-the minimum ignition temperature and hot steel surfaces (mechanically generated hot surfaces) or glowing particle nests surfaces. no ignition < MIE < ignition
Self-ignition temperature of the dust accumulations for sunflower and wood powders
MATEC Web of Conferences
Spontaneous combustion is a phenomenon that results from the heating of combustible organic powders by slow oxidation and which occurs through the air passage (created by an air depression) through the mass of dust. The oxidation phenomenon of combustible powders represents their reaction with atmospheric oxygen resulting in products of carbon dioxide, carbon oxide, water and other gases whose content depends on the temperature at which the oxidation takes place. The self-ignition of combustible dusts depends on their chemical composition, the properties of component substances, on the particle size and geometry of the material mass and, last but not least, on the temperature of the environment. Due to global worries of sustainability in construction engineering the trend is to use ecofriendly organic waste to various purposes as in construction materials. The challenge is that by using this kind of materials one should ensure the safety related to the process of such organic materi...
Determination of Fire and Explosion Characteristics of Dust
TRANSACTIONS of the VŠB – Technical University of Ostrava, Safety Engineering Series, 2016
The aim of this paper is to approximate danger of dust clouds normally occur by determining their explosion characteristics. Nowadays, dusty environment is phenomenon in the industry. In general, about 70% of dust produced is explosive. Dust reduction in companies is the main purpose of the national and European legislative. Early identification and characterization of dust in companies may reduce the risk of explosion. It could be used to identify hazards in industrial production where an explosive dust is produced. For this purpose several standards for identification and characterization of explosion characteristics of industrial dust are being used.