Liquid Mist Explosions

When a flammable liquid is sprayed as fine droplets into the air, a flammable mixture can result, which may burn or explode. The mist or spray may be formed by condensation of saturated vapors or by mechanical means [40]. As the particle sizes of the liquid become greater than 0.01 mm diameter, the lower flammability limit of the material becomes lower while above 0.01 mm, the LEL is about the same as the vapor. Mechanical engine crankcase explosions of oil mist in air are hazardous, and current practice is to apply explosion relief valves to the crankcase. 

Compressed air system explosions in engines, pipelines, separators, etc., are characteristic of this same type of mist explosion. 

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Liquid mists of ethylene oxide will decompose explosively in the same manner as the vapor. Burning rate increases with decreased droplet size. 

Mist explosions are, of course, dust explosions in which the particles happen to be liquid. Other less common types of detonation involving gaseous oxidants are reviewed in [37], These include wick explosions, foam explosions, and surface explosions. 

Mists are dust clouds in which the particles happen to be liquid. Should that liquid be combustible, even though it is nowhere near its flash-point, explosion is possible [1] [2]. Mist explosions attract increasing study [3]. It is possible that many vapour cloud explosions have had a mist component. The editor surmises that, under appropriate circumstances, evaporation of volatile mist by the heat of a vapour (or mist) explosion might generate a larger pressure pulse than simple thermobaric effects on air. Foams are inverse mists and should show similar explosive potential. 

Chemicals vary in how toxic (poisonous) they are. Toxicity is a chemical properly which causes damage to a tissue, organ or system in the body. A chemical can be a hazard because of its toxicity. How much of a risk the hazard presents depends on the circumstances, e.g. is aityone nearby is the chemical in powder, liquid, mist, vapour or gas form We also talk of risk - how likely is it that the hazard will result in an accident - of something implanned and imwanted occurring. A chemical can also be a hazard in other ways. For example, it may be explosive on its owtt, or it may be explosive when mixed with other chemicals and detonated, for example ANFO, a mixture of arttmonittm nitrate (a fertilizer) and fuel oil. 

Toxic, flammable/explosive, reactive, unstable Liquid, solid (briquette, flake, powder), gas, vapour, ah-borne particulate (including mist, fume, froth, aerosol, dust)... 

Airborne partieulate matter may eomprise liquid (aerosols, mists or fogs) or solids (dust, fumes). Refer to Figure 5.2. Some eauses of dust and aerosol formation are listed in Table 4.3. In either ease dispersion, by spraying or fragmentation, will result in a eonsiderable inerease in the surfaee area of the ehemieal. This inereases the reaetivity, e.g. to render some ehemieals pyrophorie, explosive or prone to spontaneous eombustion it also inereases the ease of entry into the body. The behaviour of an airborne partiele depends upon its size (e.g. equivalent diameter), shape and density. The effeet of partiele diameter on terminal settling veloeity is shown in Table 4.4. As a result ... 

Another advantage is that wet ESPs can collect sticky particles and mists, as well as highly resistive or explosive dusts. The continuous or intermittent washing with a liquid eliminates the reentrainment of particles due to rapping which dry ESPs are subject to. The humid atmosphere that results from the washing in a wet ESP enables them to collect high resistivity particles, absorb gases or cause pollutants to condense, and cools and conditions the gas stream. Liquid particles or aerosols... 

Petroleum and chemical related hazards can arise from the presence of combustible or toxic liquids, gases, mist, or dust in the work environment. Common physical hazards include ambient heat, bums, noise, vibration, sudden pressure changes, radiation, and electric shock. Various external sources, such as chemical, biological, or physical hazards, can cause work related injuries or fatalities. Although all of these hazards are of concern this book primarily concentrates on fire and explosions hazards that can cause catastrophic events. 

Liquids can form explosive atmospheres at temperatures below the flash point appropriate to the pressure in question if agitation is sufficient to form a mist. A destructive instance is reported [21],... 

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