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2015 TIANJIN EXPLOSIONS

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In 2015 a series of explosions occurred at a container storage station at the Port of Tianjin, China, on Wednesday, 12 August 2015, that killed over one hundred people and injured hundreds of firemen and others. The first two explosions happened within 30 seconds of each other at the facility. The second explosion was larger and involved the detonation of about 800 tons of ammonium nitrate. The cause of the explosions was not known at first, but an investigation of the Chinese authorities concluded in February 2016 that an overheated container of dry nitrocellulose was the cause of the initial explosion. Colleagues of the Nanjing University of Science and Technology and BAM worked together to analyze the reasons and the process of that incident based on knowledge about the properties of the involved substances, particularly ammonium nitrate and nitrocellulose, and potential mechanism of initiation and propagation.
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2015 TIANJIN EXPLOSIONS
XU Sen1, LIU Dabin1Klaus-Dieter Wehrstedt2 and Holger Krebs2
1Nanjing University of Science and Technology, Xiao Ling Wei 200, Nanjing,
Jiangsu, China
2Bundesanstalt für Materialforschung und -prüfung (BAM)
Department 2 „Chemical Safety Engineering“
Unter den Eichen 87, 12205 Berlin, Germany
April 11th-12th, 2016
The views expressed in this paper are those of the authors and should not
necessarily be taken to be those of the Nanjing University and BAM.
Introduction
2
A series of explosions that killed over one hundred people and
injured hundreds of others occurred at a container storage
station at the Port of Tianjin on Wednesday, 12 August 2015.
The first two explosions occurred within 30 seconds of each
other at the facility, which is located in the Binhai New Area of
Tianjin, China. The second explosion was far larger and
involved the detonation of about 800 tons of ammonium
nitrate. Fires caused by the initial explosions continued to burn
uncontrolled throughout the weekend, repeatedly causing
secondary explosions, with eight additional explosions
occurring on Saturday, 15 August.
https://en.wikipedia.org/wiki/2015_Tianjin_explosions
IGUS EOS Meeting, April 11th - 12th, 2016, Basle, Switzerland
Wehrstedt et al. 2015 Tianjin Explosions
Introduction
3
The cause of the explosions was not immediately known at
first, but an investigation concluded in February 2016 that
an overheated container of dry nitrocellulose was the cause
of the initial explosion.
As of 12 September 2015, the official casualty report was
173 deaths, 8 missing, and 797 non-fatal injuries.
https://en.wikipedia.org/wiki/2015_Tianjin_explosions
304 buildings, 12,428 cars and 7,533 containers were badly
destroyed.
Environment damage: 320.6 tons of sodium cyanide and a
large amount of other chemicals were dispersed.
IGUS EOS Meeting, April 11th - 12th, 2016, Basle, Switzerland
Wehrstedt et al. 2015 Tianjin Explosions
Beijing
Tianjin
Tianjin port
Ruihai Logistics
© Nanjing University
Accident center
Blast affected area
Earth-quake distance
West: 8.3km
South:8.0km
East: 8.5km
North: 13.3km
Figure 2. Accident site
© Nanjing University
Scenes of destruction
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Explosion crater (the diameter is more than 100m)
Scenes of destruction
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Wehrstedt et al. 2015 Tianjin Explosions
Scenes of destruction
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Tianjin Dongjiang Port Area
Ruihai International Logistics
Satellite picture before the blast
© Nanjing University
Scenes of destruction
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Satellite picture after the blast
© Nanjing University
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Explosion
source
Less than 400 m
Only framework left in
this five floors building
Damage to structures around the explosion source -1
Scenes of destruction
© Nanjing University
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Scenes of destruction
Explosion source
The glasses were shattered and the
security doors were badly destroyed
Damage to structures around the explosion source - 2
© Nanjing University
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Accident Analysis
August 12, 22:51:46: fire, 23:34:06 (~45 min later): the first
explosion, 23:34:37 (~30 sec later): the second explosion.
August 14, 16:40: the fire was extinguished.
According to the on-site staffs, the video, the trace evidences,
and the destruction and displacement characteristics of the
containers, the central area of the dangerous goods container
storage station was identified as the initial fire point.
No electrical equipment at the fire site; cable, lighthouse (road
lamp) and video surveillance are normally. So we can rule out
the possibility of electrical lines and equipment factors causing
the fire.
Meanwhile, no lightning weather; no vehicles. So we can
exclude the fire legacy, lightning, vehicles and other external
factors.
The Ministry of Public Security: no terroristic attack.
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Accident Analysis
There were 72 different dangerous goods in the warehouse,
including Classes 2, 3, 4, 5, 6, 8 and other common goods.
1Class 2: 2 kinds of gases, non-combustible;
2Class 3: 10 liquids, no spontaneous combustion or self-heating
characteristics;
3Class 5: 5 oxidizing substances: no spontaneous combustion
or self-heating characteristics;
4Class 6: 12 toxic substances;
5Class 8: 8 kinds of corrosive substances,
6) 27 kinds of common goods, no spontaneous combustion or
self-heating characteristics;
7Class 4: 8 dangerous goods, and the dry
nitrocellulose have spontaneous combustion characteristics.
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Accident Analysis
Lists of the goods in the warehouse (selection)
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Accident Analysis
Lists of the goods in the warehouse (selection)
ΣNC 48.17 tons (11.1 t NC, wetted,
15.2 t NC solution, 21.87 t NC chips -
not in the list and not specified!) NC
chips normally phlegmatized with 20 %
plasticizer. The difference between NC
and NC-Chips is the type of phlegmatizer
used (alcohol or plasticizer).
16
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Accident Analysis – Nitrocellulose (NC)
Production process (Hengshui Neweastern Chemical Industry Co.,Ltd.):
Alcohol was used as wetting agent, and the NC (N ≤ 12.3 %) was
packed in plastic bags. The bags were sealed only by a packing rope,
loaded inside fiber drums.
According to the employees of Ruihai Company, there exist the rough
operation in loading or unloading, the packing of the nitrocellulose was
destroyed, and the nitrocellulose scattered (what really happens
Over and over again).
The experimental data indicated that: A) if the packing was destroyed,
the wetting agent (alcohol) will volatilize in 2 hours under 50°C, and
the dry NC decomposes at 40 °C, a serious reaction and mass loss at
174 °C, spontaneous combustion and releasing lots of heat; B) under
adiabatic condition, an exothermic reaction happened at 35 °C, and a
violent combustion at 150 °C;
On the day, the highest temperature was 36 °C, an experiment showed
that the temperature in a container is up to 65 °C when the ambient
temperature is 35 °C.
Information and data of the Chinese co-authors
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Accident Analysis – Nitrocellulose (NC)
Production process (Hengshui Neweastern Chemical Industry Co.,Ltd.):
Alcohol was used as wetting agent, and the NC (N ≤ 12.3 %) was
packed in plastic bags. The bags were sealed only by a packing rope,
loaded inside fiber drums.
According to the employees of Ruihai Company, there exist the rough
operation in loading or unloading, the packing of the nitrocellulose was
destroyed, and the nitrocellulose scattered (what really happens
Over and over again).
The experimental data indicated that: A) if the packing was destroyed,
the wetting agent (alcohol) will volatilize in 2 hours under 50°C, and
the dry NC decomposes at 40 °C, a serious reaction and mass loss at
174 °C, spontaneous combustion and releasing lots of heat; B) under
adiabatic condition, an exothermic reaction happened at 35 °C, and a
violent combustion at 150 °C;
On the day, the highest temperature was 36 °C, an experiment showed
that the temperature in a container is up to 65 °C when the ambient
temperature is 35 °C.
Information and data of the Chinese co-authors
BAM: Under these conditions the alcohol
evaporates and an explosive atmosphere
exists which may lead to an explosion if an
ignition source is present or a self-ignition may
occur. This scenario could be the start of the
explosion disaster (?).
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Accident Analysis – Nitrocellulose (NC)
At the same time, there were 48.17 tons of NC, NC chips and NC
solutions in accident region (about 5-6 containers - 2 with chips,
1 with solution, 2-3 with NC, wetted). Thus, the NC was identified as
the initial ignition substance.
Pictures sent by Chinese colleagues.
One typical
sample of NC.
© Nanjing University
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Accident Analysis – Nitrocellulose (NC)
NC in bags
and fibre
drums.
Pictures sent by Chinese colleagues.
© Nanjing University
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Accident Analysis – Nitrocellulose (NC)
Drums in a
container.
Pictures sent by Chinese colleagues.
© Nanjing University
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Accident Analysis – Ammonium nitrate (AN)
The small packaging(25kg/bag) of AN in container. There are about 23,000 kg
AN in a 20-foot container
Pictures sent by Chinese colleagues.
© Nanjing University
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The large packages (1,000kg/bag) of AN in a container. There are about
20,000kg AN in a 20-foot container.
Pictures sent by Chinese colleagues.
Accident Analysis – Ammonium nitrate (AN)
© Nanjing University
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Accident Analysis – Possible Process of
the Accident
A large storage area was involved in fire (45 min before first explosion,
height of flame > 100 m), containers stood at close quarters (about
20 m between NC and AN).
Volatilization of alcohol led to dry NC.
An exothermic reaction and spontaneous combustion happened under
high temperature condition (the temperature of NC containers
> 60 °C, heating by sunshine, or higher by the above-mentioned fire).
The flame spread and a possible deflagration-to-detonation transition to
neighboring ammonium nitrate (pure, 800 tons) containers (40!), which
stood close to other containers and led to two large blasts.
According to the simulation result of the State Key Laboratory of
Explosion Science and Technology, the first explosion energy was
equivalent to about 15 tons of TNT, the second explosion was equivalent
to about 430 tons of TNT. Consideration many small-scale explosions,
the total energy was equivalent to about 450 tons of TNT.
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Accident Analysis – First Assumption
The time lag between detonations of NC and AN should be assumed to
be
- in case of thermal impact (flame, fire engulfment, radiation) > 20 min,
- in case of propagation (explosion, detonation) by fragments, shock
pressure, fireball, etc., a few seconds.
This agrees formally with the described time lag of 30 seconds between the
two major explosions (detonations).
The assumed TNT equivalent for 15 tons (first explosion) correlates well
with detonation of about 15 tons NC (TNT equivalent of 1 if all NCs have
a mass explosive hazard). The TNT equivalent for the second explosion
(450 tons AN) correlates with the 800 tons of AN provided an efficiency
of about 50 % in case of a high impact detonation (from NC). This would
confirm the involved masses and the order of events.
The fire before the explosions could be the reason for the accelerate
evaporation of alcohol and decomposition of NC as well as for the
thermal sensitization of AN.
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Accident Analysis – Second Assumption
The fire led to decomposition and burning (and partial explosions of NC)
in containers.
Both effects have influenced the stability of a smaller amount of AN. A
deflagration started leading to a deflagration-to-detonation transition
(first explosion/detonation, 15 tons TNT equivalent).
The detonation of one (?) AN container led to a second more severe
detonation of the larger amount of AN (430 to 450 tons TNT equivalent).
Currently no evidence exists for these assumptions. After intensive
discussions the authors rather favor the second assumption/theory.
The IGUS EOS colleagues are invited to give comments and/or to
review the argumentation.
26
We sympathize with firefighters and others
who died in the Tianjin explosion!
IGUS EOS Meeting, April 11th - 12th, 2016, Basle, Switzerland
Wehrstedt et al. 2015 Tianjin Explosions
© Washington Post
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