Environmental Engineering Reference
In-Depth Information
Table 2.12 Toxic gas amount of explosion of ammonium nitrate
Ingredient (%)
Oxygen balance (%)
Toxic gas (L/kg)
CO Equivalent a
TNT
NH 4 NO 3
KNO 3
CO
NO x
37.6
62.4
15.3
125
2.7
142.6
-
22
78
0.7
30.4
5.5
66
-
17.6
82.4
-
+3.5
20
13.3
106.5
17.6
62.4
20
+7.4
16.6
5.3
51.1
a The conversion factor of NO x to CO is 6.5
gases. Besides, addition of materials with catalytic activity (e.g., alkaline nitrate
KNO 3 ) helps to signi
cantly lower the nitrogen oxide amount of explosion prod-
ucts from ammonium nitrate explosives. Take pentaerythritol
trinitrate as an
example. Its oxygen balance is
34.49 %, and its detonation reactions are not
complete. The reaction equation is below.
C 5 H 9 N 3 O 9 !
CO 2 þ
CO
þ
H 2 O
þ
N 2 þ
NO
Whether the detonation reactions are complete or not is indirectly estimated from
detonation parameters (e.g., detonation rate, brisance, etc.). If the processing time of
trihydroxy methyl nitro methane is different, the measured brisance value is also
different.
The compositions of liquid explosives are the main factors to produce toxic
products. And the oxygen balance of liquid explosives is the determinant of toxic
product amount. When the oxygen balance of explosives is zero, the explosion
products are almost all H 2 O, N 2 , and CO 2 . When the oxygen balance of explosives
is positive, the excess oxygen oxidizes the nitrogen into nitrogen oxides, or con-
verts to free oxygen, which increases the toxic ingredients. The main toxic ingre-
dients are NO and NO 2 /N 2 O 4 , while NO 2 /N 2 O 4 and N 2 O 3 are the oxidization
products of NO. When the oxygen balance of explosives is negative, carbon cannot
be completely oxidized, which results in the production of CO gas. More the
negative oxygen balance, more is the CO gas. Under certain conditions, the oxygen
in the surrounding media affects the explosion. More oxygen, oxygen balance is
positive. Less oxygen, oxygen balance is negative. To make the explosion reaction
complete, it needs zero oxygen balance. This effect is especially obvious for the
explosions under water.
Take solid explosives as an example to explain the in
uence of toxic gases by
oxygen balance in explosion. Table 2.12 lists the experimental data of toxic gases
released from explosion of ammonium nitrate mixtures.
The reactions of hydrogen and metal with oxygen are faster than the oxidation of
carbon. For explosives, with the same amount of oxygen, if the ratio of carbon to
hydrogen or carbon to metal is bigger, more CO is produced.
There are other factors for the production of toxic/poisonous composition/
compounds. Imperfect explosion condition, noncomplete detonation, or blasting of
explosive leads to production of large amount of NO 2 . The posttreatment of
fl
Search WWH ::




Custom Search