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Author: Anonymous Article Source: Hits: 30 Updated Time: 2005-11- 25 Score:
During World War II, Hitler's air force kept bombing England with bombs falling from the sky. The owner of a flour mill in England was secretly glad that the bombs did not hit his plant, but almost simultaneously with the fall of the bombs, there was a big explosion in the workshop itself, and the roof flew up into the air, the force of the explosion exceeding the destructive effect of the bombs. At the same time, several other flour mills exploded.
This peculiar explosion cost the mill a lot of money and it is inexplicable, because no bomb fell on the plant, and besides, there is only flour and machinery in the workshop, there is no dynamite class of explosive items.
So, what is the reason for this strange explosion?
It turned out that the bomb explosion due to the air wave lifted the workshop flour dust, so that the flour contained in the air to reach a certain concentration, and met fire after the explosion. The explosives are flour.
Teenage friends may be pursued: flour is not an explosive how it will explode?
We know that the flour mill in the milling machine to process wheat into a very fine and very fine flour, the milling machine to consume electricity and the material being processed to do work, so that the material is crushed. Among them, part of the work done by the crusher is converted into energy, which is stored in the surface of the material particles after being crushed, this part of the energy in physical chemistry is called "surface energy". And, for a certain material, the greater the degree of crushing, that is, the smaller the particles, the greater the surface area, then the greater the surface energy. For example, a 1 kg of silica surface energy of 0.2 joules, which is very small, it is only equivalent to 1 kg of objects lifted 0.02 meters of work done. However, if it is crushed into flour as fine as the dust, its surface energy up to 2.7 × 106 Joule, that is, equivalent to the same heavy object lifted 2700 meters of work done, the surface energy is increased by 10 million times!
As the dust has such a high surface energy, compared with the bulk of the material, it is very easy to physical or chemical changes will release its energy. This is similar to the high water than the low water has excess potential energy, so it has to flow down to the same. Therefore, these usually seem insignificant fine dust once the appropriate conditions, and air fully mixed with the fire, it will rapidly undergo intense combustion reaction, in an instant release of enormous energy, so that a fearful thing - flour explosion also occurred. Not only flour, where easy to burn dust such as cocoa, cork, wood, light rubber, leather, plastics, as well as almost all organic compounds and a variety of inorganic materials such as sulfur, iron, magnesium, cobalt, etc., if these dust in the air to reach a certain concentration, as long as the first encounter with an open flame, even if it is a star fire, but also will cause a furious - -A violent explosion, and sometimes these fine dust explosion is no less than the destructive effect of the bomb. For example, in 1846, Britain's Halway colliery had a big explosion, when the famous scientist Faraday for the British Ministry of the Interior to investigate the explosion of the report had written: "methane mixture of combustion and explosion will set off the presence of all the coal dust in the pit, and make it on fire."
Edited by Zheng Xue