Environmental Engineering Reference
In-Depth Information
can greatly increase the explosion energy and the following secondary reactions
enhanced the effect of released heat, it has been used relatively widely in military
explosives and industrial explosives.
Metal element not only can capture the oxygen in carbon oxides and water, but
also generate the corresponding metal nitride with nitrogen gas in the explosion
products, such as,
þ
N 2 !
MgN 2 þ
:
Mg
463
17 kJ
=
mol
Al
þ
0
:
5N 2 !
AlN
þ
241 kJ
=
mol
:
It can be found that these reactions are highly exothermic reactions, thus to
increase the explosion heat.
3.2.2 Explosion Formation Heat of Explosive
The calculation of explosion heat of explosive involves its formation heat, there-
fore, its explosion heat not only depends on element composition of the explosive,
but also has a great relationship with its formation heat.
Formation heat is expressed with
D H f or Q f usually and their relationship is
D H f ¼ Q f , with unit of kJ/mol.
Formation heat is a basic parameter in the thermochemical calculation, which
can be calculated from combustion heat of a compound according to Hess
s law.
The measurement accuracy of combustion heat has reached a very high level. In the
design of a new explosive, in order to know its explosion properties and thermo-
chemical properties, its formation heat can be calculated
'
first, which is necessary to
design and decide the formulation of explosive.
Electron transfer method is the basic method to calculate the combustion heat,
which can also be used to calculate the formation heat. Assumed that the designed
explosive or organic material is an aliphatic n-alkane, wherein one or more
hydrogen atoms have been substituted with other atoms or atom group. Thus, its
combustion is the transferring process of electrons from carbon and hydrogen atoms
to oxygen atoms. It was found in experiments that, when the electron of 1 mol of
atom is transferred to oxygen atom under constant pressure to 1 mol of atom, the
substance will release 108.99 kJ of heat.
When any substituent is introduced in hydrocarbon molecules to saturate double
bond or triple bond, the electronic structure of molecule will be changed, thus the
thermal effect of electron transfer of 1 mol atom will have some change. According to
the impact of change in molecule structure, the explosion heat of explosive can be
calculated based on the corresponding corrected thermochemical data of some groups
and the corrected data are listed in Table 3.9 . The combustion heat of C a H b O c N d
compounds under constant pressure can be calculated as the following equation:
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