1. This Project is funded by the European Union Project implemented by Human Dynamics Consortium This project is funded by the European Union Projekat finansira Evropska Unija RELEASE MODELS Antony Thanos Ph.D. Chem. Eng. antony.thanos@gmail.com

2. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Consequence analysis framework Release scenarios Release scenarios Accident type Accident type Event trees Release quantification Release quantification Hazard Identification Release models Consequence results Consequence results Domino effects Limits of consequence analysis Dispersion models Fire, Explosion Models

3. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Release rates models  Essential step as providing one of the main parameters required in Consequence Analysis  General categories of releases based on sources : oReleases from vessels/tanks oReleases from piping oReleases from pools (pool evaporation rates) oReleases from fire events (flue gas dispersion case)

4. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Release rates categories based on physical state of substance to be released  Release of substance stored/handled at liquid state and temperature below normal boiling point (e.g. leak from Diesel tank release)  Release of liquefied gas stored/handled at temperature above normal boiling point (liquefied gas under pressure), e.g. leak of LPG from LPG tank bottom)  Release of liquefied gas stored/handled at liquid state at normal boiling point (refrigerated gas), e.g leak of liquid ammonia from failure of refrigerated tank shell wall  Release of gases (adiabatic expansion at hole), e.g. leak from hydrogen piping

5. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Release rates models  Essential step as providing one of the main parameters required in Consequence Analysis  General categories of releases based on duration : oContinuous (constant/variable flow rate) o“Instantaneous” : Usually refers to catastrophic failures, i.e. release of the whole content of a vessel, tank within short time e.g. 3-5 min

6. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Release rates categories based on physical state of released flow  Liquid  Gas  Two-phase (gas-liquid mixture)

7. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Liquid phase release from tank  Release of substance stored/handled at liquid state and temperature below normal boiling point (e.g. leak from Diesel tank release)  Released substance is expected to form pool in surroundings (no aerosol expected)

8. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Liquid phase release from tank (cont.)  Release driven by pressure difference between pressure in container and atmosphere  Rate is affected by hole size and shape  Model : Bernoulli equation

9. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Liquid phase release from piping  Cd= 0.61-1 oCd=0.61 for hole with rough edges (as for random seizures of tank wall) oCd≈1 hole with smooth edges, Full Bore Rupture (FBR)

10. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Liquid phase release from piping (cont.)  If piping is fed by tank, same approach as for release from tank. oPressure at hole must take into account pressure drop from tank to hole location due to release flow rate (Fanning equation etc.)  If piping is supplied by pump : pressure drop from pump till hole location (normal pressure at hole location) must be taken into account oEspecially important for releases from liquid pipelines with remote pump station

11. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Liquid phase release from piping (cont.)  In case of Full Bore Rupture downstream pump: oRelease rate considered equal to pump flow rate oBetter estimation, if pump performance curves are available (increase of pump flow rate above nominal due to decreased DH at pump discharge). Initial estimation : flow rate appr. 120% of nominal flow rate Conservative approach: assume release point very close to pump oRelease from broken pipe downstream hole is usually ignored…

12. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Liquid phase release and refrigerated gases  Typically, releases of refrigerated gas (storage at normal boiling point) are treated as simple liquid releases oNo severe shear forces are expected at release point oNo significant aerosol formation is expected oSimple pool is formed

13. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Gas phase release  Release from contained gas phase  Example : Release of hydrogen from pressure vessel at discharge of hydrogen compressor  Expansion of gas at hole as pressure is reduced (typically consider as adiabatic), cooling of gas at expansion, as also in tank

14. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Gas phase release (cont.)  For most gases and pressure higher than 1.4 barg, choked flow is established with sonic of supersonic flow at hole  Cd values as for liquid phase releases

15. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Gas phase release (cont.)  When release point is in piping, pressure drop from feeding tank/vessel must be taken into account oEspecially important for releases in long pipelines oConservative approach : release from point close to tank/vessel, equivalent to hole in tank/vessel

16. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Some release points in LPGs 2 in, gas phase to other tanks, compressor to other tanks Supply pipeline from refinery 6 in, liquid phase PSV LIQUID GAS Release from gas phase piping Release from PSV outlet Release from small hole in gas phase

17. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Gas phase release (cont.)  Gas flow expected : oFailures in gas phase piping of liquefied under pressure substance oPressure safety valves of liquefied under pressure substance tanks (e.g. LPGs) o“Small” hole in gas phase of LPG tanks  In case of rather “ big” holes in gas phase ???

18. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporation mechanism in liquefied under pressure tanks

19. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporation mechanism in liquefied under pressure tanks (cont.)  Pressure drops  In order to achieve equilibrium liquid is evaporated.  Evaporation via bubble formation  Bubbles development produce swell (expansion of liquid phase)  Small release hole, small depressurisation, minimal bubble formation, small swell, no effect on released phase  Big hole, rapid depressurisation, increased bubble formation, increased swell, liquid phase expansion may reach release point, 2-phase flow

20. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Some release types in LPGs 2 in, gas phase to other tanks, compressor to other tanks Supply pipeline from refinery 6 in, liquid phase PSV LIQUID GAS Gas release from gas phase piping Gas release from PSV outlet 2-phase release from big hole in gas phase Gas release from small hole in gas phase

21. This Project is funded by the European Union Project implemented by Human Dynamics Consortium 2-phase release  Expected in failures of liquid phase piping and tanks of liquefied under pressure substances  Overview of expansion of substance in pipe

22. This Project is funded by the European Union Project implemented by Human Dynamics Consortium 2-phase release (cont.)  If failure is on tank shell, the expansion of liquid happens totally outside tank  For failures in piping, establishment of liquid/gas equilibrium or not within pipe depends on distance of release point from tank (or other constant pressure point)  For less than 1 m distance of failure point from tank, no equilibrium is established  Consideration of vessel state during depressurisation (flashing/evaporation, liquid phase swell)

23. This Project is funded by the European Union Project implemented by Human Dynamics Consortium 2-phase release (cont.)  Complex models used oQuasi single phase oHomogeneous Equilibrium Models (expanding liquid/gas phase have same velocity) oNon-Homogenous Models (expanding liquid/gas phase have different velocities, phase slip) oFrozen models (expanding liquid/gas phase have same velocity and constant mass ration)

24. This Project is funded by the European Union Project implemented by Human Dynamics Consortium 2-phase release (cont.)  Release is expanding also within ambient air (2- phase jet)

25. This Project is funded by the European Union Project implemented by Human Dynamics Consortium 2-phase release (cont.)  2-phase jet evolution : (cont.) oGas expands and cools (density increase) oLiquid vaporizes and cools (density increase) oAir is entrained and provides heat for evaporation of liquid, air cools with condensation of humidity (density increase) oAfter a time evaporation is completed oEntrainment of air is diminished, gradually, due to less turbulence oHeat from surrounding heats up cloud

26. This Project is funded by the European Union Project implemented by Human Dynamics Consortium 2-phase release (cont.)  2-phase jet is parted from a mix of : oexpanding gas odroplets of liquid vaporising  Aerosol characteristics  Typical example of heavy-gas cloud formation

27. This Project is funded by the European Union Project implemented by Human Dynamics Consortium 2-phase release and pool formation  Formation of pool due to droplets agglomeration (rain-out) depend on : odroplet dimensions, oambient and storage conditions osubstance properties orelease size/location/direction etc.  Rule of thumb : 2 x times the flashing liquid will be airborne (mix of liquid/gas) oPropane : T= 29 °C, rainout estimated to 14 % oButane : T= 29 °C, rainout estimated to 66 %

28. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Example results for release rates  LPG tank, T= 25 C°, 2 in hole at bottom of tank (Aloha) PropaneButane

29. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools  Simple volatile liquid release (e.g. methanol) and pool formation

30. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools (cont.)  Simple volatile liquid pool mechanism oReleased liquid forms pool oHeat provided from/to pool via : ground solar radiation ambient air oEvaporation of pool due to diffusion and convection (wind speed, turbulence) mechanism above pool surface  Similar mechanism for pool of refrigerated gases

31. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools (cont.)  Liquid pool from liquefied under pressure substance release (along with heavy gas formation)  Similar behaviour of pool

32. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools (cont.)  Evaporation rates provided by rather complex models (GASP, LPOOL, SUPERCHEMS) taking into account of all former parameters affecting  Simpler models for low boiling liquids  Significant parameter of pool : pool dimensions (mainly pool area)  Pool formation within bund : pool diameter is equal to bund equivalent diameter

33. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools (cont.)  Unconfined pool : oTheoretically maximum pool diameter is set by balance of release feeding the pool and evaporation rate from pool Evaporation from pool Release to pool

34. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools (cont.)  Unconfined pool : (cont.) oReal life : pool dimensions are restricted by ground characteristics oArea=Volume/Depth oTypical values for assumed depth : o0.5-2 cm (depending on ground type)

35. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools (cont.)  Example results for D p =10 m, depth= 2 cm, T= 25 C°, atmospheric conditions D5 (confined evaporating pool, Aloha) MethanolPropane

36. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Evaporating pools (cont.)  Example results for Methanol tank, D tank =20 m, H tank=20 m, T= 25 C°, atmospheric conditions D5, 2 in hole on tank shell at ground level (unconfined evaporating pool, Aloha)

37. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Literature for Release Models  Lees’ Loss Prevention in the Process Industries, Elsevier Butterworth Heinemann, 3 nd Edition, 2005  Methods for the Calculation of Physical Effects due to Releases of Hazardous Materials (Liquids and Gases), Yellow Book, CPR 14E, VROM, 2005  Guidelines for Chemical Process Quantitative Risk Analysis, CCPS- AICHE, 2000  Guidelines for Consequence Analysis of Chemical Releases, CCPS- AICHE, 1999  Guidelines for Evaluating the Characteristics of Vapour Cloud Explosions, Flash Fires and BLEVEs, CCPS-AICHE, 1994  Safety Report Assessment Guides (SRAGs), Health and Safety Executive, UK

38. This Project is funded by the European Union Project implemented by Human Dynamics Consortium Literature for Release Models (cont.)  Assael M., Kakosimos K., Fires, Explosions, and Toxic Gas Dispersions, CRC Press, 2010 Benchmark Exercise in Major Accident Hazard Analysis, JRC Ispra, 1991  Taylor J., Risk Analysis for Process Plant, Pipelines and Transport, E&FN SPON, 1994  RIVM, Reference Manual Bevi Risk Assessments, 2009  ALOHA, Users Manual, US EPA, 2007  ALOHA Two Day Training Course Instructor's Manual