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

87

BLEVE Consequences

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.