1 / 43

The Wily Coyote Lecture Fires and Explosions

The Wily Coyote Lecture Fires and Explosions. CME 470. Caution!. Fire vs. Explosion. Fires: release energy slowly Explosions: rapid release of energy. Fire or Explosion?. Fire Triangle. Fuels Solids: plastic, wood dust fiber, metal particles Liquids: gasoline, acetone, ether, pentane

gary
Télécharger la présentation

The Wily Coyote Lecture Fires and Explosions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Wily Coyote LectureFires and Explosions CME 470 Eric Grulke. fires & explosions. CME 470

  2. Caution! Eric Grulke. fires & explosions. CME 470

  3. Fire vs. Explosion • Fires: release energy slowly • Explosions: rapid release of energy Eric Grulke. fires & explosions. CME 470

  4. Fire or Explosion? Eric Grulke. fires & explosions. CME 470

  5. Fire Triangle • Fuels • Solids: plastic, wood dust fiber, metal particles • Liquids: gasoline, acetone, ether, pentane • Vapors: acetylene, propane, CO, H2 • Oxidizers • Solids: metal peroxides, ammonium nitrate • Liquids: H2O2, nitric acid, perchloric acid • Vapors: O2, F2, Cl2 • Ignition sources • Sparks • Flames • Static electricity • heat Eric Grulke. fires & explosions. CME 470

  6. The Fire Triangle Eric Grulke. fires & explosions. CME 470

  7. Definitions • Combustion: chemical reaction in which fuel combines with oxidant and releases energy • Ignition: start of the burning process • Autoignition temperature: T such that mixture can self-ignite • Flash Point: lowest temperature at which the liquid will volatilize enough vapor to form an ignitable mixture Eric Grulke. fires & explosions. CME 470

  8. Definitions • Fire point: lowest T at which vapor above a liquid will burn • Flammability limits: burning occurs between LFL and UFL (LEL and UEL) • Explosion: rapid expansion of gases with fast pressure or shock wave • Mechanical Explosion: explosion due to vessel failure, high pressure non-reactive gas Eric Grulke. fires & explosions. CME 470

  9. Definitions • Deflagration: explosion with shock wave moving at a speed lower than speed of sound • Detonation: explosion with shock wave moving faster than speed of sound • Confined explosion: explosion inside vessel or building • Unconfined explosion: flammable gas spill Eric Grulke. fires & explosions. CME 470

  10. Definitions • Boiling liquid expanding vapor explosion (BLEVE): vessel containing liquid at T>Tb ; explosive vaporization of vessel contents • Dust explosion: rapid combustion of fine particles • Shock wave: pressure wave moving through a gas • Overpressure: P as f(shock wave) Eric Grulke. fires & explosions. CME 470

  11. Flammability Characteristics of Liquids and Gases • Liquids – use flash point temperature to characterize the fire and explosion hazards • FPT – determined in open-cup apparatus; open flame over liquid which is heated; closed-cup apparatus gives lower T Eric Grulke. fires & explosions. CME 470

  12. Flammability Characteristics of Liquids and Gases Eric Grulke. fires & explosions. CME 470

  13. Flammability Characteristics of Liquids and Gases Eric Grulke. fires & explosions. CME 470

  14. Flash Point • FP’s are tabulated • Multicomponent mixtures: one component is flammability and its characteristics are known • Estimate is based on the partial pressure of the flammable component K. Satyanarayana, P. G. Rao, Improved equation to estimate flash points of organic compounds, J. Hazardous Materials, 32, 81-85 (1992). Coefficients tabulated for chemical groups. Eric Grulke. fires & explosions. CME 470

  15. Example 6-1. Flash point of MeOH solution Eric Grulke. fires & explosions. CME 470

  16. Saturation Vapor Pressure for Methanol Eric Grulke. fires & explosions. CME 470

  17. Concentration of Flammable Gas (vol%) Eric Grulke. fires & explosions. CME 470

  18. Vapor Flammability • LFLs and UFLs can be computed for mixtures using an equation by Le Chatelier Eric Grulke. fires & explosions. CME 470

  19. LFL = f(T, P) Eric Grulke. fires & explosions. CME 470

  20. Estimating LFL, UFL Cst is the volume % fuel in fuel plus air Eric Grulke. fires & explosions. CME 470

  21. Minimum Oxygen Concentration • LFL is based on fuel in air • A minimum oxygen level is needed to propagate a flame • Below the MOC, the flame cannot generate enough energy to heat the mixture for self-propagation • MOC is estimated using the stoichoimetry of the combustion and the LFL Eric Grulke. fires & explosions. CME 470

  22. Minimum Ignition Energies Eric Grulke. fires & explosions. CME 470

  23. Ignition Sources of Major Fires Eric Grulke. fires & explosions. CME 470

  24. Reaction and Pressure Fronts Propagating Through a Pipe Eric Grulke. fires & explosions. CME 470

  25. Test Apparatus for Acquiring Vapor Explosion Data Eric Grulke. fires & explosions. CME 470

  26. Typical Pressure Versus Time Data Obtained from Explosivity Apparatus Eric Grulke. fires & explosions. CME 470

  27. Pressure Rate and Maximum Explosion Pressure as a Function of Vapor Concentration Eric Grulke. fires & explosions. CME 470

  28. Typical Explosion Data Exhibiting the Cubic Law Eric Grulke. fires & explosions. CME 470

  29. Average Kg Values for Selected Gases Eric Grulke. fires & explosions. CME 470

  30. Average KSt Values for Selected Dusts Eric Grulke. fires & explosions. CME 470

  31. Effect of Initial Pressure on Maximum Explosion Pressure and Rate Eric Grulke. fires & explosions. CME 470

  32. Explosion Data for Propane Showing Peaks Indicative of the Onset of Detonation Eric Grulke. fires & explosions. CME 470

  33. Damage Produced by Overpressure Eric Grulke. fires & explosions. CME 470

  34. Correlation Between Overpressure and Scaled Distance, English Engineering Units Eric Grulke. fires & explosions. CME 470

  35. Correlation Between Overpressure and Scaled Distance, SI Units Eric Grulke. fires & explosions. CME 470

  36. Maximum Horizontal Range of Blast Fragments Eric Grulke. fires & explosions. CME 470

  37. Images from Wikipedia.org Case study: TNT Eric Grulke. fires & explosions. CME 470

  38. 2,4,6-trinitrotoluene CAS Reg # 118-96-7 Formula: C7H5N3O6 Fw = 227.13 kg/kmol Names: TNT, Trotyl, Triton, … Density: 1654 kg/m3 Melting point: 80.35 C; boiling point: 295 C (decomposition) Solubility: 0.13g/L in water; soluble in ether, acetone, benzene, pyridine EU classification: explosive (E), toxic (T), environmental hazard (N) NFPA 704 Trinitrotoluene Eric Grulke. fires & explosions. CME 470

  39. background • Common explosive with convenient handling properties • C6H2(NO2)3CH3 • Standard measure of explosive strength • Synthesis:multi-step process. Nitration of toluene (nitric + sulfuric acid) to MNT/separation/nitration to DNT then nitration to TNT in anhydrous mixtures of nitric acid + oleum. NOX in feed nitric acid must be controlled to prevent oxidation of methyl group. • Stabilization: aqeous sodium sulfite to remove less stable isomers and other byproducts. Rinse water is a significant pollutant. Eric Grulke. fires & explosions. CME 470

  40. applications • Common explosive for military and industrial applications • Low sensitivity to shock & friction; ignition temperature is well above the melting point • Does not sorb water, relatively stable. • Block sizes: 0.25, 0.5 and 1 kg. • Synergistic blends with other exposives Eric Grulke. fires & explosions. CME 470

  41. Explosive characteristics • Explosives decompose to elements, stable molecules (mostly) without the aid of external oxidizing agents. • Exothermic, high activation energy • Carbon is a product, leading to sooty appearance of explosions • Ignition with a high velociy initiator or by concussion • Reference point – Figure of Insensitivity • The Figure of Insensitiveness is determined from impact testing, typically using a drop-weight tower. In this test, a small sample of the explosive is placed on a small steel anvil which is slotted into a recess in the base of the drop tower. A cylindrical, 1 kilogram steel weight (mounted inside a tube to accurately guide its descent to the impact point in the centre of the anvil) is then dropped onto the test specimen from a measured height. The specimen is monitored both during and after this process to determine whether initiation occurs. This test is repeated many times, varying the drop height according to a prescribed method. Various heights are used, starting with a small distance (e.g. 10 cm) and then progressively increasing it to as high as 3 metres. The series of drop heights and whether initiation occurred are analysed statistically to determine the drop height which has a 50% likelihood of initiating the explosives. The intention of these tests is to develop safety policies/rules which will govern the design, manufacturing, handling and storage of the explosive and any munitions containing it. Eric Grulke. fires & explosions. CME 470

  42. Energy content • 4.6 megajoules/kg (energy density) • Nuclear weapons are measured in megatons of TNT • Gunpowder: 3 MJ/kg • Dynamite: 7.5 MJ/kg • Gasoline: 47.2 MJ/kg (gas+O2=10.4 MJ/kg) Eric Grulke. fires & explosions. CME 470

  43. 500 ton TNT explosion, 1965, wikipedia.org Note white blast wave at water surface and condensate cloud caused by shock wave. Eric Grulke. fires & explosions. CME 470

More Related