Environmental Engineering Reference
In-Depth Information
Therefore, the explosion heat of PTEN can be calculated according to the tri-
angle graph of PTEN explosion heat as Q
2
;
3
¼
Q
1
;
3
Q
1
;
2
.
As listed in Table
3.4
, formation heats of H
2
O, CO
2
, CO, and N
2
are 241.75,
395.43, and 112.47 kJ/mol and 0, respectively.
So, we can obtain Q
2
;
3
¼
4
241
:
75
þ
3
395
:
43
þ
2
112
:
47
541
:
28
¼
1836
:
95 kJ
=
mol where the used formation heat are the constant-pressure heat effect
at 18
°
C; therefore, the calculated heat is the constant-pressure thermal effect Qpat
°
18
C. However, the explosion heat should be constant-volume thermal effect Qv,
which should be corrected in accordance with Eq.
3.11
(Qv=Qp + 0.577n), where
n = 4 + 3 + 2 + 2 = 11 mol.
Therefore, explosion heat of PTEN is:
Q
v
¼
439
:
04
þ
0
:
577
11
¼
1863
:
55 kJ
=
mol
or
Q
v
¼
1863
:
55
1000
=
316
¼
5897
:
31 J
=
g
According to Kirchhoff Law, formation heats of material with different reference
temperature (15, 18, 25
C) are different. But, in engineering calculations, the
calculation error caused by different reference temperature is relatively small, so,
generally, the further correction is not needed.
For example, the calculation of explosion heat of explosive Amatol 80/20 is the
following. Its explosion reaction equation is,
°
:
35NH
4
NO
3
þ
ð
Þ
3
!
7CO
2
þ
:
þ
:
85N
2
þ
:
425O
2
þ
Q
v
11
C
7
H
5
NO
2
25
2H
2
O
12
0
As listed in Table
3.4
, formation heat values of ammonium nitrate and TNT are
365.5 and 73.22 kJ/mol, respectively.
According to the triangle diagram, we can obtain:
Q
2
;
3
¼
Q
1
;
3
Q
1
;
2
¼
:
þ
:
:
ð
:
:
þ
:
Þ
7
94
51
25
2
57
78
11
35
87
36
17
5
¼
:
:
¼
:
2117
63
1009
04
4638
41 kJ
which can be turned into constant-volume thermal effect Q
v
as:
Q
v
¼
1108
:
58
þ
0
:
577
ð
7
þ
25
:
2
þ
12
:
85
þ
0
:
425
Þ
¼
:
þ
:
¼
:
:
1108
59
26
29
4748
34 kJ
This value is the constant-volume explosion thermal effect of a mixture of
ammonium nitrate (11.35 mol) and TNT (1 mol).
