Recommended
More Related Content
Similar to Case analysis and hazard discussion in case of Advanced chemical fire.pdf
Similar to Case analysis and hazard discussion in case of Advanced chemical fire.pdf (20)
Recently uploaded
Recently uploaded (20)
Case analysis and hazard discussion in case of Advanced chemical fire.pdf
- 1. Advanced Chemical Fires Kazunori Kuwana Topic 8, Ignition and ignition sources II (November 3, 2023)
- 2. Temperature and pressure effects on MIE Babrauskas (2014) Acetylene Hydrogen Carbon disulfide A category-II hazardous material (special inflammable materials)
- 3. Ignition by a hot surface Temperatures needed to ignite various gas/air mixtures using a 1-mm Nichrome wire Babrauskas (2014)
- 4. Ignition by a hot surface Imamura et al. (2021)
- 5. Ignition by a hot surface Babrauskas (2014)
- 6. A criterion for hot-surface ignition In no-ignition cases, the gas temperature is lower than the wall (hot-surface) temperature. In ignition cases, the maximum temperature exists in the gas phase. Under the critical ignition condition, the temperature gradient at the wall is equal to zero. Babrauskas (2014)
- 8. Smoldering-to-flaming transition O2/N2 To data logger 18 mm K-type thermocouple Glass beads Sintered metal element Moxa rod Quartz tube Moxibustion in Chinese medicine Moxa rod
- 9. Smoldering-to-flaming transition Temperature [K] 20 mm Char 1200 900 600 300 Fresh fuel A half-cut sample (𝑌 , = 0.23) Char Fresh fuel 𝑇, 𝑌 𝑇 𝑇 𝑇 𝑥 Gas phase 𝑣 (spread velocity) Pyrolysis front 𝑥 𝑥 𝑇 𝑌 𝑌 , 𝑢 , Char surface 𝑥 0
- 10. Smoldering-to-flaming transition 0 2 4 6 8 300 600 900 1200 1500 0 0.1 0.2 0.3 0.4 0.5 T (upper solution) T [K] T (lower solution) Y G , Y O YO x [mm] YG In smoldering cases, the gas-phase temperature is lower than the smoldering temperature. In flaming cases, the maximum temperature exists in the gas phase. Under the critical transition condition, the temperature gradient at the smoldering surface is equal to zero.
- 11. MIE for alkane-series hydrocarbons Babrauskas (2014) For industrial operations where flammable vapors may be present, any charge accumulation exceeding 0.1 mJ is considered dangerous. Static charges of this magnitude are easily generated̶for example, the static buildup by walking across a carpet averages about 20 mJ.
- 15. Self-service stations and hold-open latches • In Japan, hold-open clips on gas pumps are not allowed for self-service stations. • The customer always holds the nozzle; static electricity on the human body can be removed.
- 16. Static electricity as an ignition source Charge generation Charge accumulation Electrostatic discharge Ignition
- 17. Charge generation & accumulation When two materials touch, the electrons move from one surface to the other across the interface. Upon separation, more electrons remain on one material, which becomes negatively charged, while the other is positively charged. When both materials are good conductors, electrons can move quickly across the interface; hence, the charge buildup due to separation is small. When one or both of the materials are insulators or poor conductors, electrons may be trapped on one of them, resulting in charge accumulation.
- 18. Charge accumulation: household examples • Walking on a rug • Placing different materials in a tumble dryer • Removing a sweater • Combing hair https://commons.wikimedia.org/wiki/File:Static_on_the_playground_(48616367).jpg
- 19. Charge accumulation: industrial examples • Pumping a nonconductive liquid through a pipe • Mixing immiscible liquids • Sedimentation Metal pipe Petroleum liquid flow ー ー ー ー ー ー ー ー ー ー ー ー ＋ ＋ ＋ ＋ ＋ ＋ ＋ ＋ ＋ Water ＋ ＋ ＋ ＋ ＋ ＋ ＋ ー ー ー ー Gravity Oil
- 20. Static charge generation Solids Liquids Contact and separation Fluctuations in charge distribution Electrostatic induction and others • Frictional charging • Peeling charging • Rolling charging • Crushing charging • Frozen charging • Induction charging • Streaming charging • Sedimentation charging • Bubbling charging • Stirring charging • Dividing charging • Splash charging • Ejection charging • Induction charging From Prof. Matsubaraʼs lecture note Static electricity is generated no matter what we do! Whether it accumulates or not is the problem.
- 21. Electrification by induction ＋ ＋ ＋ ＋ ＋ ＋ ＋ ＋ ＋ ＋ Charged insulator ＋ ＋ ＋ ＋ ＋ ー ー ー ー ー Induction Grounded metal Spark
- 22. Electrostatic discharge • A charged object can be discharged to the ground or an oppositely charged object when the field intensity exceeds 3 MV/m (the breakdown voltage of air) or when the surface reaches a maximum charge density of 7×10−5 coulombs/m2. • The discharge can occur in six mechanisms: (1) spark, (2) propagating brush, (3) conical pile, (4) brush, (5) lightning-like, and (6) corona discharges.
- 23. Crowl and Louvar (2019) Discharge between two metallic objects (from a single point to a single point) From a grounded conductor to a charged insulator backed by a conductor A brush-type discharge that occurs at the conical surface of a pile of powder Less intense than a point-to-point spark discharge
- 24. Crowl and Louvar (2019) Air has undergone an electrical breakdown, allowing charge to leak off the conductor into the air continuously. A slow, diffuse discharge.
- 25. Crowl and Louvar (2019)
- 27. Case study: An explosion caused by static electricity in a propylene plant Chou et al., Process Safety and Environmental Protection 97 (2015) 116-121 A 2010 fire/explosion that occurred at a polypropylene (PP) and copper- clad laminate (CCL) high-tech plant in Taiwan was investigated. One person was killed, and five were injured.
- 30. The air pump (solenoid valve) to deliver acetone to Plant 1 failed, resulting in an acetone shortage in the storage tank of Plant 1. An engineer wrongfully removed the solenoid valve for delivering acetone to Plant 2 to force the delivery of acetone. The pump lost automatic control, causing a high volume of acetone to be delivered to the tank on the third floor of Plant 2, resulting in the overflow of acetone. The PP manufacturing process generates static electricity. Various processes, such as production, packaging, and processing, likely produce static electricity in a workplace.