Vapor-phase explosion examples

A significant challenge in using vibrational spectroscopy for explosive detection (especially in the vapor phase) arises because of the combination of low vapor pressures and relatively low cross-section for absorption in the IR and the low scattering cross-section for Raman spectroscopy. For example, typical peak absorption cross-sections, a, for the NOz stretching modes are near 1 x 106 cm2/mole in the IR (for comparison, peak UV absorption cross-sections for TNT approach 50 x 106 cm2/mole). For Raman spectroscopy, scattering cross-sections in the UV may approach 1 x 10 2 cm2/mole [3,7],... 

In many CVD processes, toxic, explosive, and corrosive materials are produced as one component of the vapor phase reaction co-product. In order to remove them prior to atmospheric venting, scrubbers are employed, which must be appropriate for the process used. For example, halides frequently are neutralized in a water scrubber. Carbon monoxide and hydrogen often are burnt. Arsine generally is removed by heating the exhaust gas in a cracking furnace. Charcoal canisters often are used to absorb vapor phase species. Sulfur has been employed to getter thallium. Very fine particle filters also are used to catch a diversity of solids entrained within the exhaust stream. 

The thermal dissociation of N4H4 is frequently mistaken for sublimation. It has been reported with a note of surprise, for example, that the salt explodes when heated in a sealed system, but not in open air [303,304]. These explosions stem from a pressure build-up of free HN3 in the vapor phase (see hydrogen... 

The theory of detonation is applied to the liquid-vapor phase transition in superheated fluids. It is shown that such detonations are always we detonations, characterized by supersonic flow of the shocked region. The detonation state is therefore determined by the transport properties— the viscosity and reaction rate— rather than by the boundary conditions. A numerical example is presented using the Van der Waals equation of state with parameters api opriate for water superheated approximately 100 degrees at a pressure of 5 bars. Detonation pressures of the order of 100 bars and explosion energies of the order of 10 J/Kg are predicted for this example. 

Flammable liquids Flammable liquids are mostly hydrocarbon compounds, for example, petroleum spirit. At room temperature some of these can even change into the vapor phase in sufficient quantities to form an explosive atmosphere near the surface. Many other liquids can form such an atmosphere near the surface at increased temperatures. So, the flashpoint discussed in Clause 3.1.1 is... 

Events of this nature have been described by various terms, e.g., rapid phase transitions (RPTs), vapor explosions, explosive boiling, thermal explosions, and fuel-coolant interactions (FCIs). They have been reported in a number of industrial operations, e.g., when water contacts molten metal, molten salts, or cryogenic liquids such as liquefied natural gas (LNG). In the first two examples noted above, water is the more volatile liquid and explosively boils whereas, in the last example, the cryogenic liquid plays the role of the volatile boiling liquid and water is then the hot fluid. 

Explosive boiling is certainly not the normal event to occur when liquids are heated. Thus, the very rapid vaporization process must be explained by theories other than standard equilibrium models. For example, if two liquids are brought into contact, and one is relatively nonvolatile but at a temperature significantly above the boiling point of the second liquid, an explosive rapid-phase transition sometimes results. Various models have been proposed to describe such transitions. None has been... 

If hazardous materials must be used and unsafe enviromnents exist, limit the potential for leakage use finned tube heat exchangers for vaporization on the shell side. Develop special procedures during the startup phase, when conditions go through the explosive limits. Measure key variables to trigger safety measures for example, for reactors, include instrumentation to detect temperature runaways. For example, AlChE/CCPS (1995) recommends tPT/df >0 and d (T eacior- Tcooiant)/dt >... 

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