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Emergency Relief

Emergency Relief. Gary Van Sciver September 16, 2008 ·         . Gary Van Sciver. Process Engineer – 8 years Risk Analyst – 22 years ETC – 2 ½ years. Presentation Overview. Terminology (ERS). E mergency R elief S ystem. 1. Normal Vent.

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Emergency Relief

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  1. Emergency Relief Gary Van Sciver September 16, 2008 ·         

  2. Gary Van Sciver Process Engineer – 8 years Risk Analyst – 22 years ETC – 2 ½ years

  3. Presentation Overview

  4. Terminology (ERS) Emergency Relief System

  5. 1. Normal Vent

  6. What is the difference between the normal vent & the emergency vent?

  7. What are the differences? (between the normal & emergency vents) • No blocking devices in ERS • No flame arresters in ERS • ERS usually bigger • Normal vent also handles vacuum • Pollution abatement for normal vent • Normal vent opens first • Manifolding for normal vent .

  8. VPRV (conservation vent)

  9. VPRV(vacuum pressure relief valve)

  10. Manifolds One pollution abatement device will normally handle the discharge of multiple vessels

  11. VPRV(vacuum pressure relief valve)

  12. Storage Tank Under Vacuum

  13. Plastic Bag Over Vent

  14. 2. Design Basis

  15. Upset Scenario... Series of events leading to high vessel pressure

  16. What do we want the ERS to protect against?...

  17. Concept Sciences 1999 Allentown, PA 5 fatalities hydroxylamine

  18. Concept Sciences • The plant was designed to concentrate hydroxylamine (HA) up to 50% • HA is known to be explosive above 70% concentration • Due to startup problems, the actual concentration was 86% HA .

  19. Concept Sciences

  20. Flammable Discharge

  21. BP - 2005 Texas City, Texas 15 fatalities Vapor cloud explosion of hexane/heptane (44ºC) 7700 gallons released < 2 minutes from 35 m height

  22. BP - 2005 Tower – 170 feet tall Blowdown drum – 115 feet tall

  23. BP - 2005 Truck parked, but idling about 25 feet from blowdown drum Eyewitness saw engine over-revving and backfiring sparks

  24. BP - 2005

  25. Toxic Discharge

  26. Bhopal - 1984 >2000 off-site fatalities due to toxic relief valve discharge

  27. Bhopal

  28. Bhopal1984 • Relief valve on an MIC storage tank lifted in the middle of the night releasing 80,000 lbs • >2,000 people died within a short period • ~30,000 people were permanently or totally disabled • MIC reacted with water, source of contamination uncertain • Incident had long-term ramifications for Union Carbide and the chemical industry as a whole.

  29. Bhopal - 1984

  30. Design Basis Procedure 1. Identification   2. Sizing 3. Selection

  31. How do we identify upsets?

  32. 2 important upsets

  33. Fire Exposure

  34. Runaway reaction

  35. Some other non-reactive upsets

  36. Excessive heating(steam valve failures, coil leaks)

  37. Pressurized liquid addition

  38. Pressurized gas addition(line blowing, pressure transfers, pads or purges)

  39. Some reactive upsets

  40. Inadequate cooling

  41. Inadequate heat sink

  42. Excessive reactant

  43. Poor reactivity

  44. Design Basis Procedure 1. Identification   2. Sizing

  45. Sizing vents is straightforward but we do need kinetics data for reactive scenarios

  46. Types of runaway reaction • Vapor Pressure • Gas Generating.

  47. Vapor PressureRunaway Reaction • Pressure related to temperature • Control temperature by evaporative cooling.

  48. Emulsion Runaway • 1995, one-shot emulsion process • Water charging system failed • New operator being trained, batch not stopped • 2,000-gallon, 120-psig reactor • Broke 35-psig, 18-inch rupture disk • ~1200 lbs ethyl acrylate released.

  49. Emulsion Runaway

  50. Emulsion Runaway Odor complaints 13 miles away in Karlsruhe, Germany

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