When a pulse cleaning event occurs, a suspended cloud of combustible dust is present in high concentration within the collector. Though some incidents involve a single explosion, it is more common for a series of deflagrations to occur. The initial explosion can dislodge ignitable dust hidden on overhead surfaces or other areas over a large ...
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Coal dust explosions in underground coal mines are prevented by generous application of rock dust (usually limestone). If an explosion should occur, the rock dust …
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A positive feedback loop can be established during dust explosion propagation in long ducts or galleries, by which the flame can accelerate to very high speeds and even transit to detonation. Fig. 13 gives an example where a coal dust explosion along an experimental gallery accelerated to a quasi-steady state flame speed of more than 1000 m/s.
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Conditions Required for Dust Explosions to Occur. Six conditions must exist simultaneously and in one location for a dust explosion to occur: 1. The dust must be combustible (as far as dust clouds are concerned, the terms "combustible," "flammable," and "explosible" all have the same meaning and could be used interchangeably).
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A dust explosion is caused by a quick release of a large amount of energy due to the combustion of a particulate material of small size. Given the fact that > 50% of the solids processed in chemical and allied process engineering applications are combustible to some extent, accompanied by a rapid increase in pressure due to confinement, dust explosions pose a …
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(a) Illustrates that a 1 mm thick dust layer of a dust of bulk density 500 kg/m 3 will, as (b) illustrates, generate a cloud of average concentration 100 g/m 3, if dispersed in a room of 5 m height.
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Unlike dust explosions in traditional industrial systems [13], [14], [15], dust explosion in tokamak devices has the following characteristics: (1) Micro-sized tungsten powder is one of the main composition of dust in future fusion reactors and its physical and chemical properties is quite different from the materials used in the existing study.For instance, the tungsten is a very …
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The criterion for indicating an explosion was the propagation of flame away from the ignition source. If an explosion occurred, the dust concentration was reduced and testing was continued with different dispersing pressures (40–50 lb /in 2), until no flame was observed in ten tests at the same dust concentration.The next higher concentration tested was taken as the …
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pressure rise may cause an explosion. These five factors (oxygen, heat, fuel, dispersion, and confinement) are known as the "Dust Explosion Pentagon". If one element of the pentagon is missing, an explosion cannot occur. Catastrophic Secondary Explosions An initial (primary) explosion in processing equipment or in an area where fugitive ...
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The key to avoiding a dust explosion is removing one of the five contributors so that an explosion cannot occur. Due to the nature of storing, transporting, or using a huge range of industrial powders in large vessels where oxygen is present, removal of most of the 5 factors in the "Dust Explosion Pentagon" is not possible.
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However, it is important to note that lime dust can react violently with water, releasing heat that can potentially ignite combustible materials. While it is not combustible or …
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Limestone powder, known as rock dust, is spread throughout the mine workings on a regular basis. This rock dust serves to inert the coal dust when applied in the proper proportion. When explosions do occur, the dispersed limestone powder absorbs the heat generated from the explosion and will either stop the chain reaction or reduce the ...
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Explained: It doesn't take much dust to give rise to and sustain an explosion. Even a small, localized dust cloud (for example in a drum filling operation) can result in an explosion if it …
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Although the coal dust concentration within the Exhaust Gas Recycling Pipe gradually decreased with the diminishing Stack effect, by the time of the first explosion, the conditions inside the piping had met the essential criteria for a dust explosion: a high-temperature heat source, a combustible coal dust cloud at a certain concentration, an ...
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When explosions do occur, the dispersed limestone powder absorbs the heat generated from the explosion and will either stop the chain reaction or reduce the intensity of …
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Limestone dust is more effective coal dust explosion suppressant than dolomite dust. Rock dust inertant is commonly used for prevention and suppression of coal dust …
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One of the first recorded accounts of a dust explosion was written by Count Morozzo 2 in 1795, and gave a detailed account of an explosion in a flour warehouse in Turin, Italy (as described by Piccinini 3 and Eckhoff 4).In 1845, Faraday and Lyell 5 elucidated the key role of coal dust in the devastating explosion in the Haswell (UK) coal mine the previous year. 6 Fast …
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"A place in which an explosive dust atmosphere, in the form of a cloud of dust in air, is likely to occur in normal operation occasionally". Zone 22 "A place in which an explosive dust atmosphere, in the form of a cloud of dust in air, is not likely to occur in normal operation but, if it does occur, will persist for a short period only."
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Conditions for an Explosion A dust cloud of any flammable material will explode where: 1 the concentration of dust in air falls within the explosive limits, and 2 a source of ignition of the required energy for that dust cloud is present. Conversely, an explosion can be prevented if one, or preferably both, of these conditions are avoided.
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Dust explosions are a common hazard in many industrial environments where dispersed powder or other types of combustible materials are present within a confined space. Understanding dust explosions is a key step when creating better health and safety practices at your plant to prevent a serious accident from occurring.
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The minimum explosible concentration (MEC) in the air atmosphere at the boundary between an explosion and no explosion in a dust cloud, has been investigated for several particle sizes of oil shale and for mixtures of oil shale and inert powder of different particle size. Limestone, stone dust and coarse particle size of oil shale were used as inert materials.
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However, the effect of σ D and dust concentration on τ 1 and τ 2 becomes weak for the higher coal dust clouds (> 250 g/m 3). Results indicated that the evaluation of coal dust explosion hazard should be considered in terms of not only dust concentration, but also particle size (D 50) and size dispersity (σ D).
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Below this right concentration, the mixture is too lean to explode; above it, the mixture is too rich. Dust Cloud Flammability Limits: These limits define the range of dust concentrations in which an explosion can occur. The …
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Only dust deposition affected by the shock waves can form a high concentration of suspended dust. Therefore, for the explosion limit of combustible dust, only the lower limit of the
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4. Oxygen concentration Influence of the concentration of oxygen on the risk to experience a dust explosion. Referring to the explosion pentagon, the presence of air, and thus oxygen, is required to trigger the explosion. A lack of oxygen can actually inhibit the explosion risk.
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In some situations the residual risk of a sugar dust explosion is too high, ... ing the presence of dust. If the dust concentration can always be kept. ... an explosion should occur inside.
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In the preceding introductory section, reference was made to the issue of dust explosion risk and how this concept is composed of two components—likelihood of occurrence and severity of consequences. The term inerting arises when focusing on preventing the occurrence of a dust explosion. In the present context, use of an inert dust in sufficient amount …
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The earliest recorded dust explosion was at Giacomelli's Bakery in Turin, Italy in 1785 where flour dust generated during normal operations came into contact with a mounted lamp. ... Dust explosions occur when a dispersed combustible material is present in high enough concentration; therefore an explosion hazard exists when dusts are produced ...
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