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Mixtures of dispersed combustible materials (such as gaseous or vaporised fuels, and some dusts) and oxygen in the air will burn only if the fuel concentration lies within well-defined lower and upper bounds determined experimentally, referred to as flammability limits or explosive limits.
The molecule is said to have a positive oxygen balance if it contains more oxygen than is needed and a negative oxygen balance if it contains less oxygen than is needed. [21] The sensitivity, strength, and brisance of an explosive are all somewhat dependent upon oxygen balance and tend to approach their maxima as oxygen balance approaches zero.
For instance, to safely fill a new container or a pressure vessel with flammable gases, the atmosphere of normal air (containing 20.9 volume percent of oxygen) in the vessel would first be flushed (purged) with nitrogen or another non-flammable inert gas, thereby reducing the oxygen concentration inside the container. When the oxygen ...
The original mass of flammable material and the mass of the oxygen consumed (typically from the surrounding air) equals the mass of the flame products (ash, water, carbon dioxide, and other gases). Lavoisier used the experimental fact that some metals gained mass when they burned to support his ideas (because those chemical reactions capture ...
A contact explosive is a chemical substance that explodes violently when it is exposed to a relatively small amount of energy (e.g. friction, pressure, sound, light). Though different contact explosives have varying amounts of energy sensitivity , they are all much more sensitive relative to other kinds of explosives.
Although solid magnesium reacts slowly with oxygen at STP, it is capable of burning in air, generating very high temperatures, and its metal powder may form explosive mixtures with air. Oxygen is present as compounds in the atmosphere in trace quantities in the form of carbon dioxide (CO 2) and oxides of nitrogen (NO x).
The system can be flushed with an inert gas to reduce the concentration of oxygen so that when the flammable gas is admitted, an ignitable mixture cannot form. In NFPA 56, [1] this is known as purge-into-service. In combustion engineering terms, the admission of inert gas dilutes the oxygen below the limiting oxygen concentration.
The inert gas system is used to prevent the atmosphere in cargo tanks or bunkers from coming into the explosive range. [9] Inert gases keep the oxygen content of the tank atmosphere below 5% (on crude carriers, less for product carriers and gas tankers), thus making any air/hydrocarbon gas mixture in the tank too rich (too high a fuel to oxygen ...