Sicherheitstechnik

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Safety Engineering Environmental Protection
Topic Strong exothermic reactions and explosions
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Strong exothermal reactions that can lead to an
explosion
What is an explosion ?
How do explosions occur?
How can reactions be carried out more quickly ?
In what other ways can explosions take place ?
How can explosions be avoided ?
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Definition of an Explosion An explosion is a
spontaneous exothermal reaction that is caused
because a gas needs to expand. This explosion
occurs in fractions of a second.
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How do explosions happen ? An explosion can
occur if an explosive substance or compound
disintegrates due to a fast exothermal reaction.
During this reaction energy is released in the
form of heat, light and volume expansion of
gases.
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To start this kind of reaction activation energy
is necessary. This energy depends on the
substances involved so sometimes even a small
spark is sufficient to trigger an explosion.
Example of a dust explosion
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How can explosions be caused? Explosions not
only take place in the field of chemistry, they
can also occur in physical areas, for example,
when explosions are caused by over-pressure.
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• An example of a semi-physical explosion
• Dust creates pressure when burnt
• The outer packaging of the dust explodes due to
• the pressure of the dust inside
• The sudden pressure creates sound and pressure
• waves

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With this experiment we want to demonstrate the
power behind an explosion that occurs using only
a small amount of explosive dust. The powder is
packed in several layers of cardboard and is
ignited using an electrical source of
ignition. For reasons of safety we will not go
into exact details of the experiment, for
example, how to set up the apparatus and the name
of the dust.
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The experiment was carried out on a site that was
specially prepared for the experiment and
sufficient safety distances were complied with!
Important Do not attempt to copy this
experiment!!! We do not accept any
responsibility for accidents that occur as a
result!!!
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! WARNING !
Do not carry out the experiment yourself !
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Video
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For this demonstration only 44 g of the dust were
needed that were ignited using an electrical
source of ignition. To demonstrate the pressure
wave we used flexible objects placed around the
explosives. Unfortunately, the desired effect
is not easy to see due to the strong development
of smoke.
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• How is a reaction accelerated ?
• Temperature
• Changes in the surrounding air pressure
• Catalysts

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• How can explosions be avoided ?
• Correct storage and working practice when dealing
  with explosive substances
• Keep explosive substances away from sources of
  ignition (avoid static charges)
• When working with closed system make sure there
  is a pressure balance and watch the temperature
• Pay attention to the explosion limit

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• On the 6th February 1979 a small fire at a mill
  in Bremen caused a catastrophe
• 14 fatalities
• 17 injured
• Damage caused amounted to over 50 Mio
• Euros

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Photos of the exploded mill
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The problem was that flour dust was blown around
in a chain reaction and then exploded.
This was the most serious flour dust explosion
ever recorded in the German Federal Republic.
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