Final Reaction Mass Decomposition
Christian
Christian Pasturenzi
Pasturenzi
[email protected]
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1
Synthesis reaction - Nitration
The desired reaction is a nitration
An organic substrate is added to sulphonitric mixture at 0 °C
At the end of addition there’s the product isolation and
purification
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2
The problem
The reaction was in scaling up phase from lab scale to plant
scale
At the end of a batch in pilot reactor, a sample of reaction
mass was taken and analyzed to determine the conversion
The synthesis was complete
After analysis the sample remained in quality control lab at
room temperature
48 hours after nitrous fumes were observed in the sample
container
The container was pressurized
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3
Custom synthesis (no communication)
The reaction was a custom synthesis
After some questions the customer said:
“Sometimes it happens to us”
“Sometimes the cap jumps”
“Two or three times the container exploded ”
!!
The customer didn't say anything before
!!
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4
Synthesis reaction
Reaction Enthalpy = -120 kJ/kg (normalized to reaction mass)
Adiabatic temperature rise = 80 °C
MTSR* = 0 + 80 = 80 °C
All these data were known in Company
but
they didn’t know anything about the thermal stability of the
final reaction mass
*Maximum Temperature attainable by the Synthesis Reaction
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5
Thermal stability test
After the near-miss the Company decided to investigate
the thermal stability of the final reaction mass
ARC test
Isoageing at room temperature (30 °C)
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Isoageing at 30 °C – T, P Vs. t
Temperature and Pressure Vs. Time Plot
175
40
150
exotherm
100
20
75
Pressure (bar)
Temperature (°C)
30
125
isoageing
50
10
25
0
0
100
200
300
400
500
600
700
800
900
0
1000
Time (Minutes)
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Isoageing at 30 °C - SHR
Self Heat Rate Vs. Temperature Plot
1000
550 °C/min
Self Heat Rate (°C/min)
100
10
1
0.1
0.01
0.001
0
50
100
150
200
Temperature (°C)
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Isoageing at 30 °C - Prate
Pressure Rate Vs. Temperature Plot
1000
600 bar/min
Pressure rate (bar/min)
100
10
1
0.1
0.01
0.001
0
50
100
150
200
Temperature (°C)
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Isoageing at 30 °C - TMR
TMR
Temperature (°C)
100
80
60
TMR
40
TMR cor
20
60 min
0
1000.000
100.000
10.000
1.000
0.100
0.010
0.001
Log Time (min)
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Isoageing at 30 °C - Results
Maximum Self Heating Rate (Φ corrected) = 1800 °C/min
Adiabatic Temperature Rise (Φ corrected) = 400 °C/min
Tmax = 430 °C
Pmax = 35 bar (fill level 0.3 g/ml)
TMR (33 °C) = 60 min
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11
Conclusion
The reaction mass decomposes at room temperature
Isolation and purification have to be done immediately
after the reaction
The Customer knew it, but he didn’t say anything
The Company studied the synthesis reaction but not the
thermal stability of the final mixture
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