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A BATCH POLYSTYRENE REACTOR RUNAWAY:

A CASE HISTORYBY

RONALD J. WILLEY, PhD. PE.NORTHEASTERN UNIVERSITY

PREPARED FOR SACHEA PRODUCT OF THE CCPS-AICHE

NEW YORK, NEW YORK 2000

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PROVINCE OF QUEBECCANADA

ISLE OF MONTREAL

LASALLE

LACHINECANAL

ST. LAWRENCE RIVER

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BUILDING #2 POLYSTYRENE

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THE ACCIDENT

 

OCTOBER 13, 1966

 

LATE EVENING

 

INITIAL EVENT

STYRENE VAPOR COMBUSTION

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BACKGROUND

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ST. PATRICK STREET

SUBSTATION

SUBSTATION

21MFGUNIT

19MFGBLDG

22MFG UNIT

11STORAGE

12MAIN OFFICE

25MFGBLDG

20WASTE TREATMENT

PLANT

12RESEARCHBLDG

GUARDHOUSE

GARAGE10

2POLYSTYRENE

PUMPHOUSE

STORAGETANKS

3STORAGE

8SERVICES

BLDG

6STEAMPLANT

5MFG BLDG

4MFG BLDG

PLANTNORTH

MERSIZETANKS

SITEOF

ACCIDENT

RAILROADTRACKS

RAILROADTRACKS

100 FT

7MFGBLDG

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5POLYMERIZATION REACTORS

IN THE BUILDING

2 REACTORS WERE USED FOR THE PROCESS DESCRIBED

BELOW

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PHYSICAL PROPERTIES OF STYRENE

·     MOLECULAR WEIGHT 104.5·       BOILING POINT 145C·       FREEZING POINT -30.6C·       FLASH POINT 31C·       AUTOIGNITION TEMPERATURE 490C

CH=CH2

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ADDITIONAL PROPERTIES OF STYRENE

FLAMMABLE LIMITS IN AIR (VOL%) 1.1 TO 6.1OSHA PEL 50 PPMWILL POLYMERIZE AT ROOM TEMPERATURE IF UNINHIBITEDHEAT OF POLYMERIZATION 74.5 MJ/KMOLCP, HEAT CAPACITY 1.69 J/G

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Vapor Pressure - Temperature for Styrene and Water

0

10

20

30

40

50

60

70

80

30 40 50 60 70 80 90 100 110 120 130 140 150

Temperature (ºC)

Pre

ssu

re (

psi

a) waterstyrene

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ARRHENIUS EQUATION

k Rate constantA Pre-exponential constantEa Activation energyR Gas ConstantT Absolute temperature

RT

EexpAk a

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RUNAWAY REACTIONS

0

200

400

600

800

1000

1200

1400

1600

1800

0 50 100 150 200

TEMPERATURE,°C

RA

TE

OF

HE

AT

RE

MO

VE

D O

R

AD

DE

D

HEAT GENERATED BY EXOTHERMIC REACTION

MAXIMUM HEAT REMOVED BY HEAT TRANSFER

POINT OF NO RETURN

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EQUATIONS TO PREDICT TIME, t, TO RUNAWAY

 

a is a proportionality constant

T1 is the initial temperature

12 aTexpKt

)c(contents)of(mass

reaction)ofheatreactant)( (massK

p2

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ADIABATIC TEMPERATURE RISE OF CATALYZED STYRENE (HYPOTHETICAL EXAMPLE) from Boyle

0.1

1

10

100

100 150 200

BATCH TEMPERATURE, oC

TIM

E,

t, M

INU

TE

S

At ~130oC, 10 MIN TO RUNAWAY

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STYRENE POLYMERIZATION METHODS

ANIONIC POLYMERIZATIONCATIONIC POLYMERIZATION

FREE RADICAL POLYMERIZATIONZIEGLER NATTA POLYMERIZATION

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FREE RADICAL POLYMERIZATION

CH=CH2

+ R .

CH-CH R2

.INITIATION

PROPAGATION

R.

CH-CH R2

.

.

n

+

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STYRENE TO POLYSTYRENE BATCH PROCESS

1. LOAD THE REACTOR WITH STYRENE2. ADD POLYMERIZATION CATALYST3. HEAT TO 95°C4. HOLD FOR 2 TO 8 HOURS

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STYRENE TO POLYSTYRENE BATCH PROCESS CONTINUED

5. TRANSFER TO FORMING UNIT AT ABOUT 75% CONVERSION6. OPEN FORMING UNIT AFTER FULL CONVERSION. REMOVE PS BLOCK7. CRUSH PS BLOCK8. TRANSFER SOLIDS TO EXTRUDER

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SIMPLIFIED SCHEMATIC FOR TEMPERATURE CONTROL ON JACKETED VESSELS

WATER FOR

COOLING

STEAM FOR HEATING

JACKET

Temperature TC

BATCH REACTOR

TO DRAIN

TC sensor

Air to Open

sensor

Air to Close

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BatchPolystyreneReactor Train

StyreneStorage

TankGravity Feed

2400 gallon Batch Reactor

Forming Unit

Grinder

6" Dump Line toCatch Tank

Valve

BlankFlange

RuptureDisk

SightGlass

To Roof

2nd floor

1st floorReactorJacket

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THE RELIEF SYSTEM

RUPTUREDISC

SIGHTGLASS

TOROOF

REACTOR INSIDE BUILDING

OUTSIDE

BUILDING

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TIME LINE EARLY IN THE DAY OF EXPLOSION

TIME NOTE2:30 POLYMER A PRODUCED19:30 STARTED POLYMER B BATCH19:30 LOADED MATERIAL19:40 STARTED HEATING21:15 HEATED TO 92°C

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TIME LINE BEFORE EXPLOSION

TIME TEMP,C NOTE21:15 9221:45 110 R.O. (REACTOR OPER.) IN CANTEEN21:51 11521:55 11922:00 126 R.O. RETURNED FROM CANTEEN

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TIME LINE MINUTES BEFORE EXPLOSIONTIME TEMP,C NOTE22:02 130 R.O. CHECKS IN22:03 132 R.O. ORDERS DUMP22:04 137 3 MEN ATTEMPT DUMP22:07 170 R.O. ORDERS 3 BOLTS ON FLANGE22:08 R.O. ORDERS EVACUATION

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??HOW DID STYRENE FOG ENTER

THE INTERNAL BUILDING??

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INVESTIGATIONCOMPARISON/CONTRAST OF

TWO REACTORS

ITEM REACTOR 1 REACTOR 2

(THE OTHER) (THE SUSPECT)

RUPTURE DISC INTACT RUPTUREDMANWAY INTACT INTACTDUMP VALVE CLOSED 1/4 OPENSIGHT GLASS INTACT MISSINGANSWER: FAILED SIGHT GLASS

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Ignition Source

CourtesyProf. Chuck Sheppard,Univ. of Tulsa

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A CONFINED SPACE EXPLOSION

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EXTENT OF EXPLOSION

11 PEOPLE KILLED130 TON CAR OF VINYL

CHLORIDE TIPPED OVERGUARDHOUSE DESTROYED

BRICKS FOUND 400 FEET AWAY

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TNT EQUIVALENT

BASED ON THE ESTIMATED OVERPRESSURES AND AMOUNT OF STYRENE RELEASED BEFORE THE

INITIAL COMBUSTION

THE COMBUSTION WAS AS IF 6.6 TONS OF TNT

EXPLODED AT ONCE

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FIRE PROTECTION SYSTEMS

SPRINKLER SYSTEMSFIRE WATER PUMPS

FIRE RATED WALLS AND BARRIERS

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BROKEN SPRINKLER MAIN

REMAINS OF POLYMERIZATION BUILDING

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PROPERTY DAMAGE SUMMARY

POLYSTYRENE BUILDING DESTROYED

BUILDINGS 1,4,5,8,&12 SUFFERED FIRE AND WATER

DAMAGEPUMP HOUSE DESTROYEDSEVERAL AUTOMOBILES

DAMAGED

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INVESTIGATIONSEARCH FOR THE ROOT CAUSE

PRINCIPAL CAUSE – RUNAWAY REACTION CAUSED A PRESSURE

BUILDUP INSIDE A REACTOR THAT SUBSEQUENTLY RELIEVED.

ALL MATERIAL RELIEVED SHOULD HAVE EXITED BUILDING THROUGH

ROOF VENT.

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TESTIMONY

STYRENE VAPOR INSIDE PS BUILDING

WHY?FAILED SIGHT GLASS ABOVE

RUPTURE DISK

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POSSIBLE IGNITION SOURCE

ARCING MOTOR?HOT SURFACES?

ELECTROSTATIC DISCHARGE?

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WHY DID THE REACTION RUN AWAY?

WRONG CAM ON THE RECORDER?

ORTHE PENS STUCK?

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LESSONS LEARNED

MAINTAIN CRITICAL PROCESS EQUIPMENTINSTALL AUDIBLE ALARMSCENTRALIZE CONTROL OF BATCH OPERATIONSELIMINATE SIGHT GLASS VIEWPORTS FROM RELIEF LINESHAVE SEMI-AUTOMATED DISCHARGE SYSTEMS (REMOTE DUMP VALVE)

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BROADER LESSONS LEARNED

USE DOW FIRE AND EXPLOSION INDEX FOR SPACING OF PROCESS EQUIPMENT STORAGE TANKS, AND TANK CARKEEP UPDATED DISASTER CONTROL PLANS

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OTHER LESSONS LEARNED

REDUNDANT PROCESS CONTROL EQUIPMENT

LOCATION OF EMERGENCY POWER AND FIRE PROTECTION

FAIL SAFE VALVES ON STORAGE TANKS

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ACKNOWLEDGEMENT

DR. WALT HOWARDLASALLE FIRE DEPARTMENT

MR. ROBERT GUERARDMR. JOHN PAUL LACOURSIERE

SACHE COMMITTEE