Environmental Engineering Reference
In-Depth Information
Explosive
Q
1,2
Q
2
,3
Stable simple
substance of elements
Explosion product
Q
1,3
Fig. 3.3 Hess triangle diagram of explosion heat of explosives
State 3 is formed product from explosion. It can be imagined that there are two
pathways from State 1 to 3. The
first is obtain the explosive from all elements with
the release or absorption of heat Q
1,2
, then the explosive was exploded to release
heat Q
2,3
(explosion heat); another is to generate explosion product directly from
elements with the release of heat Q
1,3
(formation heat of explosion product).
The sum of reaction heat of the system along the
first pathway should be equal to
that along the second pathway, which could be expressed as the following:
Q
1
;
2
þ
Q
2
;
3
¼
Q
1
;
3
Therefore, explosion heat Q
2,3
is:
Q
2
;
3
¼
Q
1
;
3
Q
1
;
2
ð
3
:
13
Þ
where,
Q
1,3
the sum of formation heat of explosion product,
Q
1,2
formation heat of explosive.
Therefore, explosion heat of the explosive is equal to the formation heat of
explosion products subtracted with that of explosive.
According to Eq.
3.5
, explosion ways of explosive, and formation heat values of
explosives and explosion products, the explosion heat of explosive can be calcu-
lated. Based on the explosion reaction, explosion equations close to the real reac-
tions could be
figured out, the formation heat of explosives and explosion products
can be found in the relevant manuals, and formation heat values of some substance
and explosive were listed in Table
3.4
. If the formation heat of explosive is not
known, it can be obtained through the combustion heat experiment or the associated
calculation methods.
For example, PETN with molecular weight of M = 316 and formation heat of
541.28 kJ/mol has the following explosion reaction equation:
CCH
2
ONO
2
ð
Þ
4
!
4H
2
O
þ
3CO
2
þ
2CO
þ
2N
2
þ
Q
v
