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Chemical Hazards in the Process Industry

Chemical Hazards in the Process Industry.

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Chemical Hazards in the Process Industry

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  1. Chemical Hazards in the Process Industry SAND No. 2011-0720P Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000

  2. Overview of Presentation Definition of process hazard Types of hazards and potential consequences Approaches and methods for systematically identifying process hazards Sources of chemical hazard data Discussions Resources Summary

  3. Key acronyms BLEVE = boiling-liquid-expanding-vapor explosion VCE = vapor cloud explosion LFL = lower flammable limit UFL = upper flammable limit LOC = limiting oxygen concentration AIT = auto ignition temperature DHS = Department of Homeland Security (USA) MOC = minimum oxygen concentration MSOC = maximum safe oxygen concentration MIE = minimum ignition energy TNT = trinitrotoluene CCPS = Center for Chemical Process Safety CAMEO = computer-aided management of emergency operations NIOSH = National Institutes of Occupational Safety and Health NOAA = National Oceanic and Atmospheric Administration

  4. “Process hazard” defined Types of hazards and potential consequences Approaches and methods for systematically identifying process hazards Chemical hazard data Identification of Hazards and Potential Consequences US Chemical Safety Board

  5. Process hazard definition Presence of a stored or connected material or energy with inherent characteristics having the potential for causing loss or harm.

  6. “Process hazard” defined Types of hazards and potential consequences Identification of Hazards and Potential Consequences US Chemical Safety Board

  7. Toxicity and corrosivity hazards Asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards These are not mutually exclusive categories. Types of Process Hazards and Potential Consequences

  8. Toxicity and corrosivity hazards Simple asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards Types of Process Hazards and Potential Consequences

  9. Toxicity/corrosivity hazards

  10. Toxicity/corrosivity hazards

  11. Toxicity and corrosivity hazards Asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards Types of Process Hazards and Potential Consequences

  12. Asphyxiation hazards • An asphyxiant is a gas that can cause unconsciousness or death by suffocation (asphyxiation). • Chemical asphyxiants chemically interfere with the body’s ability to take up and transport oxygen • Physical asphyxiants displace oxygen in the environment • Simple asphyxiants have no other health effects • Most simple asphyxiants are colorless and odorless.

  13. Common industry asphyxiant: Nitrogen Other simple asphyxiants: Hydrogen Argon, helium, neon Hydrocarbon gases (for example: methane, ethane, ethylene, acetylene, propane, propylene, butane, butylene) Carbon dioxide Asphyxiation hazards

  14. Asphyxiation hazards

  15. Toxicity and corrosivity hazards Asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards Types of Process Hazards and Potential Consequences

  16. Combustion hazards Oxidant Fuel Ignition Source

  17. Combustion hazards

  18. Some definitions

  19. Some definitions Reference: Johnson et al. 2003

  20. Combustion hazards

  21. Combustion hazards

  22. Flammability limits • LFL Lower flammability limit • Below LFL, mixture will not burn, it is too lean. • UFL Upper flammability limit • Above UFL, mixture will not burn, it is too rich. • Defined only for gas mixtures in air • Both UFL and LFL defined as volume % fuel in air

  23. Flash point Flash Point Temperature above which a liquid produces enough vapor to form an ignitable mixture with air (Defined only for liquids at atmospheric pressure)

  24. Example values LFLUFL Methane 5% 15% Propane 2.1% 9.5% Butane 1.6% 8.4% Hydrogen 4.0% 75% Flash point Methanol 12.2 °C Benzene -11.1 °C Gasoline -40 °C Styrene 30.5 °C

  25. Limiting oxygen concentration Limiting oxygen concentration (LOC): Oxygen concentration below which combustion is not possible, with any fuel mixture, expressed as volume % oxygen. Also called: Minimum Oxygen Concentration (MOC) Max. Safe Oxygen Concentration (MSOC) Examples: LOC (volume % oxygen) Methane 12% Ethane 11% Hydrogen 5%

  26. Design Criteria 1.Avoid flammable mixtures 2.Eliminate ignition sources

  27. Inerting and purging Purpose: To reduce the oxygen or fuel concentration to below a target value using an inert gas (for example: nitrogen, carbon dioxide) For example reduce oxygen concentration to < LOC

  28. Vacuum Purge - evacuate and replace with inert Pressure Purge - pressurize with inert, then relieve pressure Sweep Purge - continuous flow of inert Siphon Purge - fill with liquid, then drain and replace liquid with inert Combined - pressure and vacuum purge; others Inerting and purging options See Chapter 7 of Crowl and Louvar for details

  29. Flammability diagram Upper limit in 100 pure oxygen Air Line 20 80 Flammability OBJECTIVE: Stay out of Flammability Zone! A Zone n e F g 40 60 u y e x l O 60 40 Lower limit in S t o i c h pure oxygen i o m e t r i c l i n 80 20 e UFL MOC 100 0 LFL 0 20 40 60 80 100 Nitrogen

  30. Ignition sources Obvious (for example: flames, welding, hot surfaces) Spontaneous ignition at moderate temperatures Electrical sources Powered equipment Static electricity Stray currents Radio-frequency pickup Lightning Chemical Sources Catalytic materials Pyrophoric materials Thermite reactions Unstable chemical species formed in system • Physical sources • Adiabatic compression • Heat of adsorption • Friction • Impact

  31. Minimum ignition energy • Typical values: (wide variation expected) • Vapors 0.25 mJ • Dusts about 10 mJ • Dependent on test device, so not a reliable design parameter • Static spark that you can feel: about 20 mJ

  32. Autoignition temperature Autoignition Temperature (AIT):Temperature above which adequate energy is available from the environment to start a self-sustaining combustion reaction. AIT (°C) Methane 632 Ethane 472 1-Pentene 273 Toluene 810 Acetaldehyde 185 There is great variability in reported AIT values! Use lowest reported value. See Appendix B of Crowl and Louvar 2002 for a table of AITs

  33. Identify ignition sources Continuous ignition sources: for example fired equipment Potential/intermittent ignition sources: for example traffic Identify what could be ignited Flammable atmospheres Potentially flammable atmospheres Likely leak/release locations Avenues to unexpected locations: drains, sumps Analyze for adequate control Ignition source control

  34. DISCUSSION Which of these two design criteria can be more easily and reliably attained? 1.Avoid flammable mixtures 2.Eliminate ignition sources

  35. Toxicity and corrosivity hazards Asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards Types of Process Hazards and Potential Consequences

  36. Detonation hazards

  37. Detonation hazards

  38. Some definitions

  39. Deflagration: P Ignition Detonation: Distance Ignition Shock Front P Reacted gases Reaction / Flame Front Pressure Wave Unreacted gases Distance Deflagration vs. Detonation

  40. Toxicity and corrosivity hazards Asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards Types of Process Hazards and Potential Consequences

  41. Chemical reactivity hazards

  42. Chemical reactivity hazards

  43. Toxicity and corrosivity hazards Asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards Types of Process Hazards and Potential Consequences

  44. Rapid phase transition hazards

  45. Rapid phase transition hazards

  46. Toxicity and corrosivity hazards Asphyxiation hazards Combustion hazards Detonation hazards Chemical reactivity hazards Rapid phase transition hazards (BLEVEs) Bursting vessel explosion hazards Other physical hazards Types of Process Hazards and Potential Consequences

  47. Bursting vessel explosion hazards

  48. Bursting vessel explosion hazards

  49. Bursting vessel explosion hazards One equation used for calculating blast energy:

  50. Bursting vessel explosion hazards Another equation used for calculating blast energy:

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