Environmental Engineering Reference
In-Depth Information
The heat released in this reaction is enough to raise the temperature of products
at 3,000
C while Fe and Al
2
O
3
are liquids now. No gas is produced in this reaction,
and it is nonexplosive.
In certain conditions, rapid and exothermic reactions without gas production also
lead to explosion. E.g., reactions of well-grounded thermite reactants in the air
make the nearby air heated and expand, and then explode. This explosion comes
from the heated air, not the reaction of thermites. Sometimes the amount of gases
reduces rather than increase, especially the explosive reaction of gas reactants. The
explosion of detonation gas is listed below.
°
2H
2
þ
O
2
¼
2H
2
O
þ
481
:
68 kJ
In above reaction, 1/3 amount of gases is cut off. The rapidity and exothermicity
make up the reduction of gas amount. The volume of gases increases rapidly under
high temperature. If the volume is maintained, the pressure reaches more than
10 atm within an extreme short time. This is the key feature of detonation gases.
In summary, exothermicity, rapidity, and gas productions are key features of
explosive reactions. Exothermicity of reactions supplies the initiating energy for
explosion. Rapidity is the must condition which helps to con
ne the limited energy
into small space, while produced gases are media of energy conversion. Explosion
power has close relationship with exothermicity, rapidity, and gas productions.
Exothermicity helps heat explosive to a relative high temperature, which increases
the reaction speed and makes the reaction reach rapidity. In addition, the released
energy dramatically increases the temperature and promotes the conversion of
reaction products into gas state.
The chemical structures and physical states of explosive determine whether they
explode or not. But, to some degree, different explosives are different in amount of
released energy, reaction speeds, and gas productions. In general, explosion reac-
tions must have the three key features: exothermicity, rapidity, and gas productions.
This is applied for all explosions.
2.2 The Explosion Changing of Liquid Explosive Materials
Liquid explosives are noncompressible, and are different from condensed explo-
sives. In the explosion, liquid explosives should be gasi
first, later ignited. Once
this abnormal combustion reaction becomes normal one, self-sustaining spread
detonation follows. The explosion changes of liquid explosives have two classic
forms: combustion and detonation.
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