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Chemical Process Safety. Runaway Reactions. Two CSB Videos: Review. Reactive Hazards ( 31 July 2007 ) Runaway: Explosion at T2 Laboratories (19 Dec 2007; video: 22 Sep 2009 ). “167 serious uncontrolled reactions with 108 deaths from 1980 – 2001”. Two CSB Videos: Review. Reactive Hazards: - PowerPoint PPT Presentation
Citation preview
1
Chemical Process SafetyRunaway Reactions
2
Two CSB Videos: Review
1. Reactive Hazards (31 July 2007)2. Runaway: Explosion at T2 Laboratories (19 Dec
2007; video: 22 Sep 2009)
“167 serious uncontrolled reactions with 108 deaths
from 1980 – 2001”
3
Two CSB Videos: Review
1. Reactive Hazards:a) What do you remember about the video?b) Lessons “learned”
4
Two CSB Videos: Review1. Reactive Hazards:
a) 1984 Bhopal• CSB formed & established chemical process
safetyb) Synthron: butyl acrylate (solvents: toluene, cyclohexane)• 1500 gal reactor• HE was used to condense solvent vapors & cool
exothermic reaction• Batch size increased• HE couldn’t remove enough heatc) BP Amoco: HP nylon• Polymerization reactor bypass to 750 gal waste
tank• Overfilled waste tank; no PI or vent • Secondary decomposition reactiond) MFG Chemical: allyl alcohol vapor release• 30 gal test reactor (3rd test significant heat
generation)• Production in 4000 gal reactor (SA/vol ratio: HE
inadequate)e) 1st Chemical Corporation: mono-nitro toluene (MNT)• 145’ distillation tower; MNT left in reboiler• Leaking steam valve• Heated to 450 oF – decomposition reaction
5
Two CSB Videos: Review
1. Reactive Hazards:a) What do you remember about the video?b) Lessons “learned”
6
Two CSB Videos: Review2. Runaway: Explosion at T2 Laboratories:
a) What do you remember about the video?b) Lessons “learned”
Producing a gasoline additive:methylcyclopentadienyl manganese tricarbonyl (MCMT)
Reactor
7
Two CSB Videos: T2 LaboratoriesBrief overview of process steps
• Added to reactor– sodium metal in mineral oil– methylcyclopentadiene dimer– diethylene glycol dimethyl ether (diglyme)
• close the vessel• set pressure to 3.45 bar and heating oil temp to 182.2 C• heating melted sodium that reacted with
methylcyclopentadiene forming sodium methylcyclopentadiene, hydrogen, and heat
• Hydrogen gas was generated• when mix reached 100°C, agitation was shut off• at 150°C hot oil flow stopped• at 180°C cooling was initiated with water admitted
to the reactor jacket. • maintain temperature from the exothermic reaction
via water evaporation.
8
Two CSB Videos: T2 Laboratories
175th batch exploded
Former Reactor Site
9
Figure 2. Control room.*
* From CSB final report; Sep 2009.
10
Figure 4. Injury and business locations.*
* From CSB final report; Sep 2009.
11
Figure 5. Portion of the 3-inch-thick reactor.*
* From CSB final report; Sep 2009.
12
Figure 4. Injury and business locations.*
* From CSB final report; Sep 2009.
13
Two CSB Videos: T2 LaboratoriesCSB Investigation
Runaway exothermic reaction
• Occurred during the first metalation step of the process
• An uncontrollable rise in temperature and resultant pressure lead to the burst of the reactor
• Upon bursting, contents ignited in air• Creating an explosion equivalent of 635 kg (1420 lb)
of TNT exploding from a single point
14
Two CSB Videos: T2 LaboratoriesCSB Investigation
Possible causes for the explosion
Investigation considered:– cross-contamination of the reactor– contamination of raw materials– wrong concentration of raw materials– local concentration of chemical within the reactor– application of excessive heat– insufficient cooling
15
“The CSB determined insufficient cooling to be the only credible cause for this incident, which is consistent with witness statements that the process operator reported a cooling problem shortly before the explosion. The T2 cooling water system lacked design redundancy, making it susceptible to single-point failures including
• water supply valve failing closed or partially closed.• water drain valve failing open or partially open.• failure of the pneumatic system used to open and close the
water valves.• blockage or partial blockage in the water supply piping.• faulty temperature indication.• mineral scale buildup in the cooling system.
Interviews with employees indicated that T2 ran cooling system components to failure and did not perform preventive maintenance.
* From CSB final report; Sep 2009.
16
Two CSB Videos: Review
2. Runaway: Explosion at T2 Laboratories:a) What do you remember about the video?b) Lessons “learned”
• “T2 did not recognize the runaway reaction hazard associated with the MCMT it was producing.”
Contributing causes:1. “The cooling system employed by T2 was
susceptible to single point failures due to a lack of design redundancy.
2. The MCMT reactor relief system was incapable of relieving the pressure from a runaway reaction.”
17
Two CSB Videos: T2 Observations
• Scaled up from 1 liter to 9300 liter directly• Batch 42 the recipe was increased by 1/3
(testing?)• Periodically experienced problems with cooling• No “backup” cooling system• Used city water supply (minerals?)• Did not recognize and control reactive hazards• No evidence found by CSB that T2 performed a
recommended HAZOP.• There was a need for reactive chemistry testing.
18
CSB Testing on T2 RecipeCSB testing completed with a VSP2 (Vent Sizing Package 2)Adiabatic Calorimeter (116 ml
test cell)
* From CSB final report; Sep 2009.
reaction 1 exotherm
diglyme decomposition
19* From CSB final report; Sep 2009.
20
Follow-up Topics
• Key Findings of CSB investigation:• Cooling discussion• Overpressure• Runaway reactors • Hazard analysis
21* From CSB final report; Sep 2009.
• A second exothermic reaction occurred
• This reaction became uncontrollable around 200°C
• The reaction was the uncontrolled decomposition of diglyme (the solvent used)
• Probably catalyzed by the presence of sodium.
• By the time the rupture disk opened (28.6 bar)
• It was too late• If the rupture disk had opened at 6.2
bar, then no explosion would have occurred
22
Over pressure Wave Profile, 1 Psi=0.07 bar
psi0.017 Bar
0.14 Bar
0.017 Bar1.7 Bar
* From CSB & SACHE module by R. Willey, 2012.
23
Combustion Behavior – Most Hydrocarbons
Slide courtesy of Reed Welker.
Smoke and fire are very visible!
24
Combustion Behavior – Carbon Disulfide
Slide courtesy of Reed Welker.No smoke and fire, but heat release rate just as high.
25
Combustion Behavior – Methane
Methane burns mostly within vessel, flame shoots out of vessel.
26
Combustion Behavior – Dusts
Much of the dust burns outside of the chamber.
27
Definitions - 1
LFL: Lower Flammability LimitBelow LFL, mixture will not burn, it is too lean.
UFL: Upper Flammability LimitAbove UFL, mixture will not burn, it is too
rich.
Defined only for gas mixtures in air.UNITS:
28
Definitions - 2
Flash Point: Temperature above which a liquid produces enough vapor to form an ignitable mixture with air.
Defined only for liquids at 1 atm. pressure.
Auto-Ignition Temperature (AIT): Temperature above which adequate energy is available in the environment to provide an ignition source.
29
Definitions - 3
Limiting Oxygen Concentration (LOC): Oxygen concentration below which combustion is not possible, with any fuel mixture. Expressed as volume % oxygen.
Also called: Minimum Oxygen ConcentrationMax. Safe Oxygen Conc. Others
30
Explosion: A very sudden release of energy resulting in a shock or pressure wave.Shock, Blast or pressure wave: Pressure wave that causes damage.Deflagration: Reaction wave speed < speed of sound.Detonation: Reaction wave speed > speed of sound.Speed of sound in air: 344 m/s, 1129 ft/s at ambient T, P.Deflagrations are the case with explosions involving flammable materials.
Definitions - 4
31
Minimum Ignition Energy (MIE): Smallest energy to initiate combustion.
• Higher for dusts & aerosols than for gases• Many HC gases have MIE ~ 0.25 mJ
Auto-oxidation: slow oxidation and evolution of heat can raise T and lead to combustion. i.e. liquids with low volatility.Adiabatic compression: of a gas generates heat, increases temperature, and can lead to autoignition.Ignition sources: usually numerous and difficult to eliminate. Objective is to identify and eliminate, but not to solely rely on this step to eliminate combustion risk. (Table 6-5; Crowl)
Definitions - 5
32
Typical Values - 1LFL UFL
Methane: 5.3% 15%Propane: 2.2% 9.5%Butane: 1.9% 8.5%Hydrogen: 4.0% 75%
See Appendix B
Flash Point Temp. (deg C)Methanol: 12.2Benzene: -11.1Gasoline: -43
33
Typical Values - 2
AIT (deg. C)Methane: 632Methanol: 574Toluene: 810
LOC (Vol. % Oxygen)Methane: 12%Ethane: 11%Hydrogen: 5%
Great variability in reported AIT values! Use lowest value.
Appendix B
Table 6-2
34
Flammability Relationships
Figure 6-2
35
Aerosol Flammability
Too rich
Too lean
M. Sam Mannan, Texas A&M, Mary Kay O’Conner Process Safety Center
36
Minimum Ignition Energies
What: Energy required to ignite a flammable mixture.Typical Values: (wide variation expected)
Vapors:Dusts:
Dependent on test device --> not a reliable design parameter.Static spark that you can feel: about mJ
Lightning: about 500 megajoules
Table 6-4Or ~ 500,000,000,000 mJ
37
Minimum Ignition Energies
38
Ignition Sources of Major Fires
39
Experimental Determination - Flashpoint
Cleveland Open Cup Method.Closed cup produces a better result - reduces drafts across cup.
Figure 6-3
40
Experimental Determination - Flashpoint
41
Setaflash Flashpoint Device
42
Setaflash Flashpoint Device – Close-up
43
Setaflash Flashpoint Device – Close-up
Window
44
Setaflash Flashpoint Device – Close-up
45
Auto-Ignition Temperature (AIT) Device
46
Auto-Ignition Temperature (AIT) Device
47
0
2
4
6
8
10
0 2 4 6 8 10
Fuel Concentration in air (vol%)
Max
imum
Exp
losi
onP
ress
ure
(bar
g)
LFL UFL
Run experiment at different fuel compositions with air:
Experimental Determination - LFL, UFL
Need a criteria to define limit - use 1 psia pressure increase. Other criteria are used - with different results!
Flammability limits are an empirical artifact of experiment!
See Figure 6-5
48
Experimental Determination: P versus t
0
2
4
6
8
10
0 50 100 150 200 250
Time (ms)
Pres
sure
(bar
-abs
) Pmax
(dP/dt)max
PITI
Ignitor
Final experimental result:
49
Experimental Apparatus
50
Experimental Determination - LFL, UFL
51
Flammability Limit Behavior -1
As temperature increases:UFL increases, LFL decreases--> Flammability range increases
25 251000.75 25 25P
Tc c
CLFL LFL T LFL TH H
2575.025
T
HUFLUFL
cT
:: kcal/mole, heat of combustion
o
c
T CH
Approx. for many hydrocarbons
Equations 6-4, 6-5
52
Flammability Limit Behavior -2
As pressure increases: UFL increasesLFL mostly unaffected
)1(log*6.20 PUFLUFLP
P is pressure in mega-Pascals, absolute
Pressure and temperature effects on flammability limits is poorly understood – estimation methods are poor.
No theoretical basis for this yet!
53
Flammability Limits of MixturesLe Chatelier Rule (1891)
n
i i
imix
LFLy
LFL
1
1
n
i i
imix
UFLy
UFL
1
1
yi on a combustible basis only
n is the number of combustible speciesAssumptions: 1) Product heat capacities constant2) No. of moles of gas constant3) Combustion kinetics of pure species unchanged4) Adiabatic temperature rise the same for all species
Details provided in Process Safety Progress, Summer 2000.
54
Flammability Limits - Le Chatelier
LeChatelier’s rule shows that the LFL can be approximated by:
*
100p
c
C TLFLh
Where Cp is the product heat capacity, is the adiabatic temperature rise, and is the heat of combustion. 1200 K is frequently used as the adiabatic temperature rise at the flammability limit.A similar expressions is written for the UFL.
*Tch
55
Flammability Limits of Mixtures
From this equation, a plot of the flammability limit vs. 1/(Heat of Combustion) should yield a straight line if Le Chatelier’s rule is valid. If this is done, one finds that:Le Chatelier’s rule works better at the lower flammability limit than the upper flammability limit.Assumptions are more valid at LFL.
*
100p
c
C TLFLh
56
Lower Flammability Limit and Heat of Combustion
LFLN Comp. = 5327.4[1/hc]R2 = 0.9478
LFLHC Comp. = 4569.1[1/hc]R2 = 0.8849
LFLOxy. Comp. = 5030.7[1/hc]R2 = 0.9338
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014
1/hc [kJ/mole]-1
LFL
[Vol
% F
uel i
n ai
r]
Hydrocarbons
Oxygen Compounds
Nitrogen Compounds
Sulfur Compounds
Linear (NitrogenCompounds)Linear (Hydrocarbons)
Linear (OxygenCompounds)
57
Upper Flammability Limit and Heat of Combustion
0
20
40
60
80
100
0.000 0.001 0.001 0.002 0.0021/(-hc) [kJ/mol]-1
UFL
[vol
. % fu
el in
air
]
HydrocarbonsOxygen CompoundsNitrogen CompoundsSulfur Compounds
58
Estimating FlammabilityJones equation where
the stoichiometric concentration, Cst, is vol% fuel in fuel plus air.
From the general combustion equation,
CmHxOy + zO2 = mCO2 + x/2 H2O
It follows that z = m + x/4 – y/2, where z has the units of moles O2/mole fuelTherefore,
The Jones equation can now be converted to
LFL = 0.55Cst UFL = 3.50Cst
21.01
100
21.011
100
1
1001002
zfuelmolesOmoles
fuelmolesairmoles
Xairmolesfuelmoles
fuelmolesCst
138.219.176.4)100(50.3
yxmUFL
138.219.176.4)100(55.0
yxmLFL
59
Estimating Flammability
Suzuki and Koide correlation
where:LFL and UFL are the lower and upper flammability limits (vol% fuel in air), respectively, and
is the heat of combustion for the fuel (in 103 kJ/mol)
NOTE that the accuracy of this and Jones methods are modest.
5.23567.030.6 2 cc HHUFL
80.10538.0569.042.3 2
ccc
HHH
LFL
∆Hc
60
LOC limiting oxygen conc. [vol% O2]
Typically 8 - 10%
Estimating LOC
(1)Fuel + (z) Oxygen --> Products
• Concentration required to generate enough energy to propagate flame
• Reduce O2 concentration below LOC to prevent the fire/explosion • If data for LOC is not available, estimate using the stoichiometry of the
combustion process and the LFLFor example, the stoichiometry for butane:
The LFL for butane is 1.9% by volume, therefore from stoichiometry
By substitution, we obtain,
OHCOOHC 222104 545.6
fuelmolesOmolesLFL
fuelmolesOmoles
molestotalfuelmolesLOC 22
22 %4.12
0.15.69.1 Ovol
fuelmolesOmoles
molestotalfuelmolesLOC
61
LOC’s for Various Substances
62
Flammability Diagram
20 40 60 80 100
Nitrogen0
100
20
40
60
80
Oxyg
en
100
80
60
40
20
0
Fuel
Stoichiom etric line
FlammabilityZone
LFL
UFL
MOC
A
Upper limit inpure oxygen
Lower limit inpure oxygen
Air Line
63
Flammability Diagram
Useful for:• Determining if a mixture is flammable.• Required for control and prevention of flammable
mixtures
Problems:• Only limited experimental data available.• Depends on chemical species.• Function of temperature and pressure.
Flammability diagram can be approximated.
64
Flammability Diagram
(1) Fuel + (z) Oxygen ---> Products
Fuel
Oxyg
en
Nitrogen
0
1000
1001000
Flammable
UFL
LFL
Stoichiometric100*
1
zz
CH4 + 2 O2 --> Products
z = 2
*1001zz
65
Drawing an Approximate Diagram
1. Draw LFL and UFL on air line (%Fuel in air).2. Draw stoichiometric line from combustion equation.3. Plot intersection of LOC with stoichiometric line.4. Draw LFL and UFL in pure oxygen, if known (% fuel in pure oxygen).5. Connect the dots to get approximate diagram.
66
ExampleMethane: LFL: 5.3% fuel in air UFL: 15% fuel in air LOC: 12% oxygenCH4 + 2 O2 --> CO2 + 2 H2O
--> z = 2
7.66100*32100*
1
zz
Pure Oxygen: LFL: 5.1% fuel in oxygen UFL: 61% fuel in oxygen
% oxygen
67
Flammability Diagram - Example
FuelOx
ygen
Nitrogen 0
1000
1001000
66.7% O2 Stoichiometric UFL = 15% fuel
LFL = 5.3% fuel
LOC = 12% oxygen
61% Methane
5.1% Methane
68
Flammability Zone
00
0
100100
20
20
40
40
40 60
60
60
80
Methane
Nitrogen80
80
20
100
Oxyg
en
Stoichiometric Line
Air Line
Non-FlammableFlammableTransition Boundary
69
Flammability Zone
00
0
100100
20
20
40
40
40 60
60
60
80
Nitrogen80
80
20
100
Oxyg
en Air Line
Ethylene
Stoichiometric Line
Transition BoundaryFlammableNon-Flammable
70
Removal of Vessel from Service
71
Explosions - Definitions
Explosion: A very sudden release of energy resulting in a shock or pressure wave.Shock, Blast or pressure wave: Pressure wave that causes damage.Deflagration: Reaction wave speed < speed of sound.Detonation: Reaction wave speed > speed of sound.Speed of sound in air: 344 m/s, 1129 ft/s at ambient T, P.Deflagrations are the case with explosions involving flammable materials.
72
Explosions
• Rapid release of energy • Damage due to dissipation of energy in the form of
pressure wave, projectiles, sound, radiation, etc• Reaction front moves out from ignition source
preceded by shock wave or pressure front. Once combustible material consumed, reaction front terminates, but pressure wave continues.
• Shock wave (results from abrupt pressure change) and is associated with highly explosive materials
• Most damage due to blast wave (shock / pressure wave followed by wind)
73
Detonations
• Energy releases short, < 1 ms, associated with abrupt rise in P
• Shock and reaction front > speed of sound• Reaction front provides energy to shock wave and
drives it at sonic or greater speeds • P of shock wave: ~ 10 - 100 atm.
74
Deflagrations
• Energy release longer than detonation ~ 0.3 s, • Pressure front = speed of sound; reaction front
behind at < speed of sound• Mechanism: turbulent diffusion, mass transfer
limited• P of wave: ~ a few atmospheres• Can evolve, especially in pipes but not open spaces,
to a detonation due to adiabatic compression and heating leading to pressure rise
75
Comparison of Behavior
Reacted gases
Unreacted gases
Deflagration:
Detonation:
Pressure WaveReaction / Flame Front
Ignition
Ignition
Reaction front moves at less than speed of sound.Pressure wave moves away from reaction front at speed of sound.
Reaction front moves greater than speed of sound.Pressure wave is slightly ahead of reaction front moving at same speed.
X
X
76
Comparison of Behavior
Reacted gases
Unreacted gases
Deflagration:
Detonation:
Pressure WaveReaction / Flame Front
Ignition
Ignition
P
Distance
P
Distance
Shock Front
77
Comparison of Behavior
Detonation
Deflagration
Localized DamageNo wall thinningLots of pieces
Damage all overWall thinningA few pieces
78
Confined ExplosionsOccurs in process or building. Almost all of the thermodynamic energy ends up in the pressure wave.
Cubic Law:
Ki Deflagration index (bar-m/s) G gasSt dust (Staub)
Deflagration index:Measure of explosion robustness, higher value means more robust.Depends on experimental conditions.Not a fundamental property.
dPdt
maxV1/3 KG
dPdt
maxV1/3 KSt
79
Deflagration Indexes
80
Deflagration Indexes
81
Data: Max. P and KG
0
20
40
60
80
100
120
140
160
0
2
4
6
8
10
12
0 20 40 60 80 100 120 140 160 180
Pres
sure
(psi
a) .
Pres
sure
(bar
) .
Time (ms)
Stable Combustion Pressure
P = 7.6 bar
t = 24 ms
KG = V1/3 [dP/dt]maxKG = (0.02m3)1/3(316.7 bar/sec)
82
Damage Estimates from Overpressure
Table 6-9; Crowl
83
Dust Explosions
• Finely divided combustible solids dispersed in air encounter an ignition source
• Examples: flour milling, grain storage, coal mining, etc• Initial dust explosion produces secondary explosions• Conditions for explosion: a) particles < certain size for ignition & propagation b) particle loading between certain limits
c) dispersion in air fairly uniform for propagation
84
Occur in the open. Only 2 to 10% of thermodynamic energy ends up in pressure wave. Use for this class:
Unconfined Explosions
Prevention
VCE: Vapor Cloud Explosion- sudden release flammable vapor- dispersion and mixing with air- ignition vapor cloud Flixborough
- smaller inventories- milder process conditions- incipient leak detection- automated block valves
85
BLEVEBLEVE: Boiling Liquid Expanding Vapor Explosion
- Release large amount of superheated liquid after vessel rupture (e.g. fire)
• BLEVE: Explosive vaporization of a liquid at a temperature above its normal boiling point caused by container rupture. Ex: from external fire
• If liquid is flammable, a VCE can result• Boiling liquid can behave as rocket fuel, propelling vessel
fragments• Fraction of liquid vaporized from Chapter 4, To > Tb
86
BLEVE
Liquid
Vapor
Vessel with liquid stored below its normal boiling pointBelow liquid level –
Above liquid level –
Effects: Blast + thermal
88
Mechanical Explosions
Rupture of vessel containing an inert gas at high pressure.
PP
PPTRW E
Ege 1ln
Where: We is the energy of explosion, P is abs. gas pressure in vessel, PE is abs. ambient pressure, T is abs. temperature.
Max. Mechanical Energy
Eqn. 6-31
89
Batch Reactor Explosion Consequences
90
Overpressures
Blast Origin
Blast wavePI
PI
Side-on Overpressure
Direct-on Overpressure
91
Pres
sure
Distance from explosion origin
Ambient pressure
Peak overpressure
Shock front
Direction of movementExplosionorigin
P
P
o
a
Peak Side-on Overpressures
92
Peak Side-on OverpressuresO
verp
ress
ure
Distance
t
t
t
t
tt
1
2
3
4
5
6
Explosion Origin
Direction of movement
93
Consequences of Explosions: Table 6-9
Peak Side-on Overpressure(psig) Consequence
0.03 Large glass panes shatter0.15 Typical glass failure0.7 Minor house damage1.0 Partial house demolition3 Steel frame building distorted> 15 100% fatalities
3 psig: Hazard zone for fatalities due to structure collapse.
P
Distance
94
P
Distance
95
TNT Equivalency Method
Scaled distance 3/1TNT
e mrz
a
os p
pp
96
P
Distance
97
TNT Equivalency for VCEs
Where: mTNT is the equivalent mass of TNT
is the explosion efficiencym is the total mass of fuelEc is the heat of combustion
ETNT is the heat of combustion for TNT
(1120 cal/gm = 4686 kJ/kg = 2016 BTU/lb)
TNTofmassEnergyFuelinEnergyTotalmTNT /
TNT
c
EmE
98
TNT Equiv. - Explosion Efficiency
TNT
cTNT E
mEm
1 for confined explosion0.02 to 0.10 for unconfined explosion
Use a default value of unless other information is available.
99
Other Methods
Other methods are based on degree of congestion or confinement. Basis is that confinement leads to turbulence which increases the burning velocity.
• TNO Multi-Energy Model (see pages 271-274)
• Baker - Strehlow ModelBoth produce essentially the same answer.Need much more information, i.e. confinement info.
100
TNT Equivalency Procedure
1. Determine total mass of fuel involved.2. Estimate explosion efficiency.3. Look up energy of explosion (See Appendix B in text).4. Apply Equation 6-24 to determine mTNT.
5. Determine scaled distance.6. Use Figure 6-23 or Equation 6-23 to determine overpressure.7. Use Table 6-9 to estimate damage.
Problem: Determine consequences at a specified location from an explosion.
3/1TNTmrz
101
TNT Equivalency Procedure
The problem with the application of this approach to exploding vapor is that:
Overpressure curve developed from detonation data, i.e. TNT, and flammable vapor explodes as a deflagration.
The TNT method applied to vapor explosions tends to underpredict overpressures at some distance from the explosion, and over-predicts the overpressures near the explosion.
P
Distance
P
Distance
Shock Front
DetonationDeflagration
102
ExampleDetermine the energy of explosion for 1 lb of n-butane? What is the TNT equivalent? Use an explosion efficiency of 2%.
02.0,exp
142,1158100021.646
21.646)1.4()636.54(5)26.94(4
542
13
10422tanRePr
222104
efficiencyanhaslosiontheBut
gcal
ggmoleX
kcalcalX
gmolekcalGor
gmolekcalGGG
OHCOOHC
HCOHCOtsac
of
oducts
of
103
Example
TNTkgTNTg
TNTgcalcalm
callblbg
gcalG
TNT
available
093.033.901120
169,101
169,10102.0*1*454*142,11
104
Example
0 5 10 15 20 25 30 350
1
10
100
1 lb n-butane overpressure vs distance
r (distance from explosion) [m]
Po (o
verp
ress
ure)
[psi]
105
TWA - 800: July 17, 1996
106
TWA - 800: July 17, 1996
107
Example
Determine equivalent TNT mass for TWA 800 explosion.Assume: 18,000 gallon fuel tank, P = 12.9 psia, T = 120 F, Concentration of fuel = 1%, Energy of explosion for jet fuel = 18,850 BTU/lb, M = 160.Mass of fuel in vapor:
3
3 o o
(12.9 psia)(18,000 gal)(0.1337 ft / gal)(10.731 psia ft / lb-mole R)(580 R)
= 4.99 lb-moles total
totalg
PVnR T
108
Example
(1)(7.98 lb)(18,850 BTU/lb)2076 BTU/lb TNT
= 74 lb of TNT
cTNT
TNT
mEmE
Moles of fuel = (0.01)(4.99 lb-moles) = 0.0499 lb-moles = 7.98 lb of fuel
Assume 100% efficiency (confined explosion).
109
Questions?
110
Flammability Diagram - 3
Air line always extends
FROM: Fuel: 0%, Oxygen: 21% Nitrogen: 79%
TO: Fuel: 100%, Oxygen: 0%, Nitrogen: 0%
Equation for this line:
Fuel = -(100/79) Nitrogen + 100
111
Fuel/Air ExplosiveCBU-72 / BLU-73/B Fuel/Air Explosive (FAE)The the 550-pound CBU-72 cluster bomb contains three submunitions known as fuel/air explosive (FAE). The submunitions weigh approximately 100 pounds and contain 75 pounds of ethylene oxide with air-burst fuzing set for 30 feet. An aerosol cloud approximately 60 feet in diameter and 8 feet thick is created and ignited by an embedded detonator to produce an explosion. This cluster munition is effective against minefields, armored vehicles, aircraft parked in the open, and bunkers. During Desert Storm the Marine Corps dropped all 254 CBU-72s, primarily from A-6Es, against mine fields and personnel in trenches. Some secondary explosions were noted when it was used as a mine clearer; however, FAE was primarily useful as a psychological weapon. Second-generation FAE weapons were developed from the FAE I type devices (CBU-55/72) used in Vietnam.