Chemistry Reference
In-Depth Information
Fig. 11.19
Plot of the rate of
heat evolution against the
temperature for h/c H
2
O
2
samples with TSI = 14 (
1
)
and30(
2
)at
P
∞
= 0
.
1MPa
J/(cm s)
TSI
TSI
16
12
8
the theory presented in Sect. 10.4, kinetic data on homogeneous decomposition and
the expression for the vapor pressure
P
H
2
O
2
10
5
exp(
575
/
T
)MPa[8]. This
value for the critical parameter is significantly lower than that indicated for the ex-
perimental setup used. At higher pressures (
P
∞
≥
= 0
.
8
×
−
sv
1 MPa), both self-heating modes
were observed, which is characteristic of regular (nonvolatile) systems prone to
thermal explosion. However, in contrast to regular systems, the maximum value of
h/c H
2
O
2
warm-up measured with a thermocouple under above-critical conditions
was quite high (3-5 times higher than that estimated using the Semenov theory:
R
T
0
/
E
). In this case, the maximum liquid temperature was lower than the theo-
retical “adiabatic” temperature,
T
ad
. It was found from the thermograms that the
decomposition of h/c H
2
O
2
occurs in the flameless flash mode. After reaching its
maximum (“non-Semenov”) value, the warm-up rapidly drops. As the pressure in-
creases further (
P
∞
≥
1
.
5 MPa), the warm-up of the liquid under above-critical con-
ditions is accompanied by self-inflammation of the vapor. The process occurring
under above-critical conditions is characterized by relatively poor reproducibility.
This is because it is impossible to keep the conditions for heat and mass transfer
in the gas phase above the vigorously decomposing liquid constant. Since the uni-
formity of the temperature in the liquid phase is ensured by its active mixing with
rising oxygen bubbles, the approximation Bi
1 used to calculate the critical con-
ditions is quite correct. The corresponding experimental and theoretical data are in
satisfactory agreement (Table 11.3).
Table 11.3
Comparison of theoretical and experimental parameters of the thermal explosion of
h/c H
2
O
2
(
10
3
,
T
c
0
,K
α
S
/
V
)
×
P
∞
,MPa
Δ
T
cr
,K
Δ
T
st
,K
Jcm
−
3
s
−
1
deg
−
1
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
7.5
1.1
420
422
17.0
20.5
93
64
9.2
1.6
427
429
17.5
18.6
132
Vapor inflammation
12.9
1.7
433
434
18.0
19.0
140
Vapor inflammation
