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Ethylene plant safety

Transcript of Cracker safety

SAFETY IN NAPHTHA CRACKER By Kushal chaudhuriSAFETY IN NAPHTHA CRACKER

ETHYLENE CRACKERS IN INDIANaphtha CrackersPlant/location HAZIRA/RIL BARODA/RIL(ex-IPCL) HALDIA/HPL PANIPAT/IOCL Capacity in 000TPA. 750 170 550 800

Gas CrackersPlant/location NAGOTHANE/RIL(ex-IPCL) GANDHAR/RIL(ex-IPCL) PATA/GAIL Capacity in 000TPA. 400 400 400

Upcoming Dual CrackersPlant/location OPAL(ONGC Petro Additions Ltd.) Capacity in 000TPA. 1100

BCPL(Brahmaputra Valleys Cracker Petrochemical Ltd.)

2220

IOCL NAPHTHA CRACKER & ASSOCIATED UNITSPlant Capacity, TMTPA Mode Technology / Licensor CBI Lummus, USA

NCU & AU

800

Steam Cracking

TMTPAC4HU PGHU BEU 142 541 168

LicensorCBI Lummus, CBI Lummus GTC,USA

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TYPICAL FLOW DIAGRAM OF NAPHTHA CRACKER UNIT

Recycle furnace

GENERIC PROCESS SAFETY DESIGN ISSUES IN NAPHTHA CRACKER UNIT

Emergency Remote Isolation of Flammable Inventories Emergency Remote Equipment Depressurization

267 class-6 remote isolation valve ( XV ) provided through out NCU & AU

Heat Exchanger Overpressure Protection external fire, thermal expansion, blocked outlet, and tube ruptureprovision of safety interlock Systems with suitable redundancy

To prevent major process operating upsets from threatening the physical integrity of process equipment usually by mitigating the extent of pressure and/or temperature deviations. To protect against temperature excursions outside of the mechanical design envelope of process equipment SIL-3 interlock system provided for flare load mitigation

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GENERIC PROCESS SAFETY DESIGN ISSUES IN NAPHTHA CRACKER UNIT

Two independent effluent relief systems have been provided for handling effluent relief vapors:

cold dry flare system for handling liquid /vapor below 4C wet flare system for handling liquid /vapor above 4C Separate liquid vaporiser & superheater provided in the dry flare system

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CASE STUDY OF FLARE HEADER FAILURE

A low temperature alarm sounded as the overhead line temperature fell to 0 F, and the thermocouple went bad. at a value of -13 F With the cold flare drum overhead line running below its minimum design temperature of -10 F, the pipe ruptured resulting in loss of hydrocarbon containment The hydrocarbon released found an ignition source, resulting in an explosion and fire7

PROCESS HAZARDS AND SAFETY SYSTEMS8

PROCESS HAZARDS AND SAFETY SYSTEMS IN PYROLYSIS FURNACE

Firebox explosions during lighting of burners Light up procedures must be followed Over temperature in furnace convection & radiation section

Excessive firing rate Partial trip provided at loss of feed Low or no flow rate in selected coils Minimum lock provided in dilution steam supply direct injection of medium pressure steam provided

Over temperature protection in TLE / steam superheat coil

Minimum lock provided at BFW feed C/V Furnace trip provided at low flow of BFW / Low level at steam drum9

PROCESS HAZARDS AND SAFETY SYSTEMS IN PYROLYSIS FURNACE

Switch to backup fuel can cause a rapid increase in firing causing over heating of the coil

Wobbe Meter provided in fuel gas system to cater the situationPosition where thermowell broke

Fire from coil outlet due to thermowell erosion Rotation of thermowell after 3 decoking cycle is recommended

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PROCESS HAZARDS AND SAFETY SYSTEMS IN PYROLYSIS FURNACE

TLV/DV system provided along with mechanical link To prevent hydrocarbon backup to firebox by maintaining sufficient back pressure

allows the heater to be isolated in the unlikely event of a heater radiant coil rupture To protect the overpressurization of radian coils & TLE tubes

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PROCESS HAZARDS AND SAFETY SYSTEMS IN HYDROGENATION REACTORS

Hazard for runway reaction due to excess hydrogenation & polymerization reaction

Emergency shut down valve provided for immediate hydrogen cutoff & releasing the inventory to flare

Provision for immediate nitrogen purge in all the reactors to cool down the reactors Auto cutting provision provided in liquid recycle standby pumps in case of liquid /Mixed phase hydrogenation rectors

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PROCESS HAZARDS AND SAFETY SYSTEMS IN CHILLING TRAIN

Lowest temperature handled in cold box is -165 C Piping and vessels in Coldbox are made of aluminum Internally insulated with loosePerlite (very high insulating value)Over chilling of the cold box outlet piping due to loss of heating media

interlocks are provided to isolate the subject piping with two out of three voting logic for protecting possible embrittlement

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PROCESS HAZARDS AND SAFETY SYSTEMS IN CHILLING TRAIN

Cold box under slight positive nitrogen pressure

Keeps air and moisture out of cold box Nitrogen minimizes hydrocarbon accumulation if a small leak

Nitrogen vent monitored hydrocarbon presence

for

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TYPICAL SAFETY ISSUES IN COLD BOX

Potential Acetylene FreezingPotential Nitrogen Oxides Freezing Potential Benzene Freezing Potential Mercury Embrittlement

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PROCESS HAZARDS AND SAFETY SYSTEMS IN COLD SERVICE LIQUID VALVE

One side of the seat is drilled to relieve pressure as liquid vaporizes.Typically and arrow on body showing direction of relief. CAUTION

Arrow is in the direction of vent

Drill Gate

Must be installed correctly Arrow is NOT direction of flow

Arrow is in the direction of vent

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PROCESS HAZARDS AND SAFETY SYSTEMS IN GASOLINE FRACTIONATOR

Low pressure rating Not designed for TLE outlet temperatures

Furnaces trip provided at high if Quench fittings outlet temperature

Pyrophoric material deposits on Trays & Packing's

Special precautions required for man entry during shut down

Pool Fire potential if a leak

Caution: No PSV for overpressure protection

When items are off line and isolated administrative

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SAFETY CONCERN IN DEPROPANISER & PROPYLENE SPLITTER

Potential concentration of MAPD above 70% is dangerous forms explosive mixture

Avoid excessively good fractionation In DePropaniser Likely if design reflux flow is maintained at reduced plant capacity. Reflux should always be reduced in proportion to the tower feeds. C4s in overhead is evidence that MAPD is not conc18

GENERAL SAFETY ISSUES IN EHTYLENE PLANT

Injuries Hot Water Steam Catastrophic Failures Furnace light off

Over chilling Equipment due to

Adding liquid before pressuring Depressuring before removing liquid

Inadequate vent capacity Non engineered changes Not following good operating practices/procedures

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THANK YOU20

TLV/DV CHANGEOVER

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