1400 - Isimite - Dynamic Simulation of Texas City Refinery Explosion for Safety Studies

8/10/2019 1400 - Isimite - Dynamic Simulation of Texas City Refinery Explosion for Safety Studies

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Dynamic simulation of Texas City

Refinery explosion for safety studies

Joseph Isimite


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Outline

Introduction & background

Previous studies

Simulation approach

Simulation results

Quantitative HAZOP

Conclusion

Questions


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Plant background

30 miles South East of

Houston, TX

Rated capacity of

460,000 bpd of

gasoline

29 oil refining

units and 4

chemical units

covering 1200

acre siteEmploys approx. 1800

employees, plus contractors


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Incident Introduction

Catastrophic failure of

isomerisation units raffinatesplitter

Explosion occurred at 1:20pm on23 March 2005, with subsequentfires

15 deaths, many injuries

financial losses exceeded

US$1.5b


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Previous studies

Woodward & Moosemiller (2005): Baker Risk Report,evaluation of possible event scenarios

Palacin-Linan (2005): PSE, gPROMS model

Manca & Brambilla (2012): Aspen HYSYS simulation

Khan and Amyotte (2007): consequence modelling

Kalantarnia et al. (2010): predictive consequence model

Dynamic simulation of Texas City Refinery explosion for safety studies


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ISOM Unit Description



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Raffinate unit Process Flow Diagram



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Why another Texas City simulation?

Its not new

However, increased legislative oversight, ageing assets,shortage of skilled personnel and prospecting and

production activities in increasingly dangerous terrainrequire fresh thinking in the way dynamic simulators areemployed in oil and gas operations.



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Process simulation

Suitability of Aspen Hysys

Replicate column filling dynamics

2-phase flow of sub-cooled liquid in the blowdown pipe

Dynamic HAZOP



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Process Flowsheet

total liquid volume: 583 m3

35 light HCs lumped into 4 categories: C5-C8

Water and Nitrogen



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Simulation approach

Initial conditions

Transient process variables evolution from 0200am 0120pm

Isothermal temperature regime before 1000am

Model validation with published accident data

Results showColumn filling dynamicsFeed vapourisation dynamicsFeed temperature profile



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Simulation results


0

10

20

30

40

50

60

10 10.5 11 11.5 12 12.5 13 13.5 14 14.5

LiquidLevel

[m]

Time [Hrs]

Column liquid filling dynamics


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0

0.2

0.4

0.6

0.8

1

1.2

10 11 12 13 14

Feedvapourfraction

Time [Hrs]

Feed vapour fraction [1000hrs to 1320hrs]

0

20

40

60

80

100

120

140

10 10.5 11 11.5 12 12.5 13 13.5

Feed

tempe

rature[C]

Time [Hrs]

Feed temperature

Feed vapourisationdynamics

Feed temperaturedynamics


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Dynamic HAZOP

Extrapolation of model for use in dynamic HAZOP studies

Provide a visual representation of quantified level of risks

All four burners lit instead of two



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Dynamic HAZOP feed vapourisation dynamics


-0.2

0

0.2

0.4

0.6

0.8

1

1.2

10 10.5 11 11.5 12 12.5 13 13.5 14

Feedvapourfraction

Time [Hrs]

Actual incident

DynHAZOP


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Conclusions

Additional temperature increase of 43% occurred, leading toa mixed phase feed flow with a vapour fraction of 0.4

Complete vaporisation of the feed takes place at 1230pm

Help secure management buy-in by demonstrating the likelyconsequences

Effective close-out of HAZOP actions

Further investigations of coupled process hazard analysestools



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We do it safely, or not at all.

1400 - Isimite - Dynamic Simulation of Texas City Refinery Explosion for Safety Studies

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