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防爆基（jī）礎（chǔ）知識：
可燃（rán）性氣體和蒸氣的爆炸特性
可燃（rán）性氣體和蒸氣的爆炸特性
1.燃燒和爆炸產生的條件
燃燒是人們十分熟（shú）悉（xī）的一（yī）種自然現象，它是一種氧化（huà）反應，氧化反應放出熱量（liàng），當反應放出的熱量（liàng）使反應介質溫度（dù）升高到一定程（chéng）度時，可以形成可見的火焰。
可控條件下的燃燒和爆炸可為（wéi）人類服務。
失控的燃燒和爆炸能造成人員傷亡和財產損失。
可燃性物質（zhì）例如氫氣、乙炔、甲烷（wán）等可燃性氣（qì）體，汽（qì）油（yóu）、柴油、苯等可燃性液體以及煤塵和棉花纖維（wéi）等可燃性粉塵纖維等能夠形成燃（rán）燒或爆炸。但是，形成燃燒和（hé）爆炸必須具備一定條件（jiàn）。
下述條（tiáo）件在時間（jiān）和空間上相遇（yù），才會（huì）產生燃燒或爆炸：
燃燒劑，例如氫氣，汽油等；
氧化劑，例如氧氣，空氣等（děng）；
點燃源，例如明火，火花，電弧，高溫表麵等。
上（shàng）述條件被稱（chēng）為形成燃燒和爆（bào）炸的三要素。
工程上采（cǎi）取措施，防（fáng）止三要素同時存在，防止出現火災和爆炸（zhà）危險。
2.可燃性氣體（tǐ）和蒸氣的安全參數（shù）：
可燃性氣體和蒸（zhēng）氣在點燃和爆炸（zhà）的過程中有許多理化（huà）參數，與防爆安全有直接關係的有以下幾個：
爆炸界限----可燃性氣體或蒸氣與空氣的混合物隻有在某個濃度範圍內才（cái）能爆炸（燃燒），超出此範圍就不（bú）會被點燃，這一範圍的最高點和最低點分別稱（chēng）為爆炸上限和爆炸（zhà）下限。
爆炸界限（xiàn）常用可燃性物（wù）質在可燃性混合物中（zhōng）的體（tǐ）積（jī）百分比（濃度）表示，例如，甲烷的爆（bào）炸下限是5。0%（體積比），爆（bào）炸上限是15%（體積比）。可燃性物質的（de）濃度低於爆炸下限的混（hún）合物可以稱作“過稀”，濃度高（gāo）於爆炸上限（xiàn）可以
稱作“過濃”，過濃或過稀的混合物不能形成爆炸或燃燒。工程上采用通風的方法降低環境中可燃性物質的濃度，以便（biàn）避免爆炸危險。當（dāng）環境中的可燃性物質的濃度（dù）低於爆炸下限的25%時，可認為該（gāi）環境是安全的。
Explosive properties of flammable gases and vapors
1. Conditions for combustion and explosion
Combustion is a natural phenomenon that people are very familiar with. It is an oxidation reaction that emits heat. When the heat released by the reaction raises the temperature of the reaction medium to a certain degree, a visible flame can be formed.
Combustion and explosion under controlled conditions can serve human beings.
Uncontrolled combustion and explosion can cause casualties and property damage.
Combustible substances such as hydrogen, acetylene, methane and other flammable gases, flammable liquids such as gasoline, diesel, benzene, and flammable dust fibers such as coal dust and cotton fibers can form combustion or explosion. However, certain conditions must be met for the formation of combustion and explosion.
The following conditions will meet in time and space before they will burn or explode:
Combustion agent, such as hydrogen, gasoline, etc .;
Oxidizing agents, such as oxygen, air, etc .;
Ignite sources, such as open flames, sparks, arcs, hot surfaces, etc.
The above conditions are referred to as the formation of three elements of combustion and explosion.
Take engineering measures to prevent the three elements from coexisting and prevent fire and explosion hazards.
2. Safety parameters of flammable gas and vapor:
Flammable gases and vapors have many physical and chemical parameters during ignition and explosion. The following are directly related to explosion-proof safety:
Explosion limit-the mixture of flammable gas or vapor and air can only explode (burn) within a certain concentration range, and beyond this range it will not be ignited. The highest and lowest points in this range are called explosions, respectively Upper limit and lower explosive limit.
The explosion limit is usually expressed as the volume percentage (concentration) of flammable substances in the flammable mixture. For example, the lower explosion limit of methane is 5.0% (volume ratio) and the upper explosion limit is 15% (volume ratio). Mixtures with flammable substances whose concentration is lower than the lower explosive limit can be called "excessively diluted", and those whose concentration is higher than the upper explosive limit can be
Known as "excessive concentration", a mixture that is too rich or too thin cannot form an explosion or burn. The project uses ventilation to reduce the concentration of flammable substances in the environment in order to avoid the risk of explosion. When the concentration of flammable substances in the environment is less than 25% of the lower explosion limit, the environment may be considered safe.
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