Environmental Engineering Reference
In-Depth Information
several to more than 10 min. However, the explosion of nitroglycerine
finishes
within 1/100
1,000 times faster than
the combustion of general fuels. Both explosion and combustion reactions release a
lot of heat and large volume of stable gas
1/1000000 s. Explosion reaction is about 100
-
-
finally. Combustion reacts slowly. There is
enough time for gas transportation, and no high-pressure space forms. While the
rapidity of explosion limits the expansion of gas products, the energy is con
ned to
the original volume of explosive materials, and the energy density is extremely high.
The as-prepared high-temperature and high-pressure gas products let explosion
powerful and damaging. For example, the energy released by one-kilogram explo-
sive materials equals the electricity that a 1,000 W motor needs to work for an hour.
C
þ
O
2
¼
CO
2
þ
394
:
55 kJ
This reaction is familiar for most of us. The combustion of coal in air releases
large amount of heat and gas production. But coal combustion is not explosion.
Only when oxygen diffuses onto the surface of coal, combustion reacts. This
process is very slow. And the produced energy and gas diffuse into the atmosphere
gradually. The space of energy is open. Neither high temperature nor high pressure
is created. There is no mechanical interaction with the environment. If coal powders
with
*
200 nm diameters are obtained by grinding, and suspended in the air, violent
explosion takes place after a
flash. Explosive power increases following that the
diameters of powders become smaller. The main reason is that the dramatic increase
in surface area per unit weight and complete contact of surface with oxygen results
in rapid combustion reaction.
fl
2.1.3 Gas Products in Explosion of Liquid Explosives
Explosions of liquid explosives affect the nearby media using the speedy expansion
of high-temperature and high-pressure gases. Immediate release of large amount of
gas is one of the key features in explosion reactions. Explosion of nitromethane
(1 L, 1,140 g) produces
1,464 L (std) gas and explosion of isopropyl nitrate (1 L,
*
1,040 g) generates
1,551 L gases. While in explosion, TNT (1 L, 1,600 g) begets
1,656 L gas production. Because of exothermic and rapid reactions of explosions,
huge amount of gas production limited in the original little space is heated to
extreme high temperature. High-temperature and high-pressure gases violently
affect the environment in mechanical work.
There are other materials, whose reactions are rapid and release a lot of energy/
heat at the same time. However, the reactions do not generate gas productions.
These materials are not explosives. Take thermite reaction as an example,
*
2Al
þ
Fe
2
O
3
¼
Al
2
O
3
þ
2Fe
þ
828
:
4kJ
