HAZOP ANALYSIS ON ETHYLENE OXIDE REACTOR (R100) The Ethylene Oxide reactor converts ethylene to ethylene oxide using oxygen and a sliver catalyst. The operating temperature of the reactor is 280 o C and operating pressure is 8 atm. Ethylene oxide is very dangerous, carcinogenic, flammable and explosive. hen it reaches its decomposition temperature of approximately !00 o C, a very deadly explosion may occur.
Figure 1: Simple Diagram Diagram Showing Showing Ethylene Ethylene Oxide Reactor Reactor Streams Streams
"#$ %"ac&%flo' $revention ()on%*eturn +alve +alve Oxygen and ethylene is combined and forms the feed stream. Oxygen inlet concentration and ethylene inlet concentration is dependent on the oxygen and ethylene supply respectively as sho'n in the diagram. The combined feed rate, feed compositions and coolant streams 'ill be analysed. The reactor products stream only needs a non%return valve to prevent bac&flo' of reactor products to the reactor.
Deviations
Property
Possible Causes
Possible Consequences
(Guide Words)
)o
Oy*en Inlet
COMBI!D "!!D #O #$! R!%C#OR (R&') Control valve Technological Technological $roblem. • •
Concentration
failure.
Ethylene Oxide Conversion (EO is 0.
-ore
Oy*en Inlet
•
Concentration
Control valve
•
failed to close
Thermal runa'ay effect (*eactor Temperature Temperature ncrease and possible explosion due to Ethylene Oxide decomposition.
/ess
Oy*en Inlet
Other Than
Concentration Oy*en Inlet
•
Control valve
•
failed to open rong reagent
Concentration
or ra' material.
•
Technological Technological $roblem and
•
Conversion is too lo'. +essel *upture #ormation of undesirable
•
•
$roducts. ecreased conversion Technological Technological $roblem in
•
*eactor Technological Technological $roblem and
•
1s ell 1s
Oy*en Inlet
•
mpurities in
•
ra' material Ethylene
Concentration
)o
!t+ylene Inlet Concentration
pipeline may be •
conversion is ero.
clogged. Control valve failure.
-ore
!t+ylene Inlet Concentration
•
Control valve
•
failed to close
1 very high 't. 3 of ethylene may form explosive mixtures
•
of hydrocarbon and oxygen. /o' selectivity.
/ess
!t+ylene Inlet
Other Than
Concentration !t+ylene Inlet
•
Control valve
•
failed to open rong reagent
Concentration
or ra' material.
•
Technological Technological $roblem and
•
Conversion is too lo' +essel *upture #ormation of undesirable
•
•
$roducts. ecreased conversion Technological Technological $roblem in
•
*eactor /oss of feed to reaction section
•
1s ell 1s
!t+ylene Inlet
)o
Concentration "lo,
•
mpurities in
•
ra' material #lo' Controller
•
failure. /ine fracture. /ine bloc&age.
•
#lo' Controller
•
failed to close /o' flo'
•
-ore
"lo,
and no output
• •
ncreased EO Conversion. 4igh concentrations of ethylene oxide and oxygen
controller valve
leading to explosive mixtures.
bypass failed to /ess 1s ell 1s
"lo, "lo,
•
close. #lo' Controller
•
/ess EO Conversion
•
failed to open ater
•
Out of spec. supply
Contamination mpurities rong #eed
• •
ecreased conversion. ncreased formation of
•
undesirable products This may form explosive
•
Other Than
"lo,
•
elivered *everse
"lo,
•
$ump failure, non%return valve
mixtures since ethylene is
failure,
flammable and explosive in the
•
-ore
#emperature
•
•
Over%
presence of high levels of
pressurisation of
oxygen.
reactor. Temperature
•
O2 concentrations increases
Controller
and forms potential explosive
#ailure. External #ire.
mixture of hydrocarbons and •
oxygen. ecreased conversion and
•
selectivity. ncreased *eaction Temperature Temperature leading to runa'ay effect.
/ess
#emperature
•
Temperature Controller
• •
ecreased 5electivity. /o' $ressure.
#ailure
4igher
COO-IG (COO-%#) .#R!%M P%..IG #$RO/G$ R!%C#OR ( Inlet and Outlet Cooling 'ater Thermal runa'ay effect and • • #emperature
valve
possible explosion
malfunction or /o'er
Inlet and Outlet
•
#emperature
failure. Control valve
•
failure, operator
The temperature of the reactor may become very cool
fails to ta&e action on alarm
)o
"lo,
•
Cooling 'ater valve or flo' controller
•
malfunction. Cooling 'ater service failure.
•
*una'ay effect and possible explosion
-ore
/ess
"lo,
"lo,
•
• •
•
Control valve
•
The reactor becomes very cool
failure, operator
and reactant concentration
fails to ta&e
builds up and potential
action on alarm.
runa'ay effect on heating.
$ipe /ea&age. Temporary
•
Temperature Temperature of process fluid
ater 5ource
•
remains constant or increases Thermal runa'ay effect
•
/ess Cooling, $otential
#ailure. $artially clogged cooling line.
$art of
"lo,
•
$artially clogged cooling
1s ell 1s
"lo,
•
line. Contamination
runa'ay effect. •
ecreased Conversion.
•
/ess cooling, runa'ay effect
($resence of *eactor product in *everse
"lo,
•
cooling tubes #ailure of 'ater source or high bac&pressure resulting in bac&'ard flo'
and explosion
-ore
#emperature
R!%C#OR PROD/C#. -!%0IG #$! R!%C#OR (R&') Temperature O2 concentrations increases • •
• •
Controller
and forms potential explosive
#ailure. External #ire. 4igh *eaction
mixture of hydrocarbons and •
Temperature.
oxygen. ncreased Ethylene Oxide Temperature Temperature leading to runa'ay effect.
/ess
#emperature
•
Temperature
•
/o' *eactor $ressure.
Controller )o
"lo,
•
• •
•
#ailure #lo' Controller
•
failure. /ine fracture. #ull /ine
)o production of ethylene oxide.
bloc&age. rong Catalyst or Catalyst is fully consumed.
-ore
"lo,
•
#eed #lo'
•
-ore production of ethylene
•
oxide. 4igh concentrations of
Controller failed •
to close. /o' feed flo'
ethylene oxide and oxygen
controller valve
leading to explosive mixtures.
bypass failed to /ess
"lo,
•
close. #eed #lo'
•
Controller failed 1s ell 1s
"lo,
•
•
Other Than
"lo,
•
to open ater Contamination mpurities rong #eed
oxide. •
Out of spec. supply to the reactor.
•
ecreased Ethylene oxide
•
production. 5tream may contain a large
elivered to the *eactor
/ess production of Ethylene
amount of undesirable *everse
"lo,
•
•
$ump failure,
•
products. This may form explosive
non%return valve
mixtures since ethylene is
failure, Over%
flammable and explosive in the presence of high levels of
pressurisation of
oxygen.
reactor.
-ore
Reactor Pressure
OP!R%#IG CODI#IO. O" R!%C#OR (R&') ncreased steam *educed 6ield. • • #ormation of undesirable • flo' rate. *elief valve • products. evelopment of Temperature Temperature • fails closed. 7radients 'ith localied hot
spots leading to impairment of the catalyst to produce
/ess
Reactor Pressure
•
*elease valve
•
fails open. #illing hose
•
ethylene oxide. +essel overpressure or rupture.
•
ecreased Conversion.
•
O2 concentrations increases
ruptures.
-ore
#emperature
•
•
Temperature Controller
and forms potential explosive
#ailure. External #ire.
mixture of hydrocarbons and oxygen.
•
ecreased conversion and
•
selectivity. ncreased *eaction Temperature Temperature leading to
/ess
#emperature
•
Temperature Controller #ailure
• •
runa'ay effect. ecreased 5electivity. /o' $ressure.
Thermal runa'ay 1n exothermic reaction can lead to thermal runa'ay, 'hich begins 'hen the heat produced by the reaction exceeds the heat removed. The surplus heat heat raises the temperature of the reaction mass, 'hich causes the rate of reaction to increase. This in turn accelerates the rate of heat production. Thermal runa'ay can occur because, as the temperature increases, the rate at 'hich heat is removed increases linearly but the rate at 'hich heat is produced increases exponentially. Once control of the reaction is lost, temperature can rise rapidly leaving little time for correction. The reaction vessel may be at ris& from over%pressurisation due to violent boiling or rapid gas generation. Executive temperatures may initiate secondary, more haardous runa'ays or decompositions. 1n over%pressure may result in the plant failing catastrophically resulting in blast or missile damage. 1 release of flammable materials from the process could result in a fire or an explosion in the 'or&room. 4ot liuors and toxic materials may contaminate the 'or&place or generate a toxic cloud that may spread off%site. There can be serious ris& of in9uries, even death, to plant operators, and the general public and the local environment may be harmed. 1t best, a runa'ay cause loss and disruption of production, at 'orst it has the potential for a ma9or accident.
