Chemical explosions vapor-phase

Potential explosion phenomena include vapor cloud explosions (VCEs), confined explosions, condensed-phase explosions, exothermic chemical reactions, boiling liquid expanding vapor explosions (BLEVEs), and pressure-volume (PV) ruptures. Potential fire phenomena include flash fires, pool fires, jet fires, and fireballs. Guidelines for evaluating the characteristics of VCEs, BLEVEs, and flash fires are provided in another CCPS publication (Ref. 5). The basic principles from Reference 5 for evaluating characteristics of these phenomena are briefly summarized in this appendix. In addition, the basic principles for evaluating characteristics of the other explosion and fire phenomena listed above are briefly summarized, and references for detailed evaluation of characteristics are provided. 

Nitromethane is an oily liquid with a strong odor. It is highly flammable, and has a melting point of -29 Celsius with a boiling point of 101 Celsius. Nitromethane is not very soluble in water, but is soluble in alcohol, ether, and DMF. It can form explosive salts with sodium, which ignite in contact with water. Nitromethane is used in liquid rocket fuels, and is produced on an industrial scale from vapor-phase oxidation of propane with nitric acid vapor. Nitromethane can be prepared on a laboratory scale by mixing sodium nitrite with sodium chloroacetate. Nitromethane is widely available commercial chemical. 

PERSONAL PROTECTION wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls use chemical safety goggles and/or full face shield where splashing is possible appropriate respirators are needed in areas where exposure would be above the permissible exposure level (PEL) in high vapor concentrations, wear self-contained breathing apparatus dust/mist pre-filter should be used for the particulate phase since this compound possibly exists in both particulate and vapor phase use a closed system, ventilation, and explosion-proof electrical equipment above 25°C maintain eyewash fountains and quick-drench facilities in immediate work area,... 

Solution pressurizers. Solution steam pressurizers must satisfy rather strict chemical criteria. Stainless-steel surfaces in contact with solutions must not exceed temperatures at which heavy-li(juid-phasc. solutions form, giving rise to rapid corrosion [20]. Undesirable reduction of uranium must be avoided by the presence of some dissolved oxygen. Undesirable hydrolysis of uranyl ion must be avoided by control of the chemistry and temperature in pressurizer solutions [21]. The vapor-phase concentration of deuterium should be maintained below the explosive limit. One solution to these problems, used in the HRE-2, is the generation of steam from distilled water rather than from fuel solution. Another solution is the boiling of solutions in corrosion-resistant titanium. A third solution is the use of fission-product heating rather than external heating to reach the desired temperature. 

Additional events of concern that may or may not involve flammable or combustible materials are condensed-phase explosions, uncontrolled chemical reactions, boiling liquid expanding vapor explosions (BLEVEs),... 

Figure 6-24 Sachs-scaled overpressure and Sachs-scaled positive-phase duration for the TNO multi-energy blast model. Source Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires, and BLEVEs (New York American Institute of Chemical Engineers, 1994) used by permission.

Ion mobility spectrometry (IMS) is an instrumental method where sample vapors are ionized and gaseous ions derived from a sample are characterized for speed of movement as a swarm in an electric field [1], The steps for both ion formation and ion characterization occur in most analytical mobility spectrometers at ambient pressure in a purified air atmosphere, and one attraction of this method is the simplicity of instrumentation without vacuum systems as found in mass spectrometers. Another attraction with this method is the chemical information gleaned from an IMS measurement including quantitative information, often with low limits of detection [2 1], and structural information or classification by chemical family [5,6], Much of the value with a mobility spectrometer is the selectivity of response that is associated with gas-phase chemical reactions in air at ambient pressure where substance can be preferentially ionized and detected while matrix interferences can be eliminated or suppressed. In 2004, over 20000 IMS-based analyzers such as those shown in Fig. 1 are placed at airports and other sensitive locations worldwide as commercially available instruments for the determination of explosives at trace concentration [7],... 

Quantitative response curves for the nitrobenzenes and nitrotoluenes were obtained for a continuous vapor stream of chemical in air and the plots extended from 0.1 to 100 ppb with an anticipated systematic error from surface adsorption at low vapor concentrations. At the high concentrations, the curves begin to flatten as seen with all IMS and DMS response owing to saturation of the ion source region, a complication in all uses of gas-phase ion chemistry with sources at ambient pressure. Detection limits from the micro-fabricated DMS analyzer were suggestive of suitable analytical performance for a trace explosives detector [57],... 

EXPLOSION and FIRE CONCERNS flammable gas NFPA rating Health 3, Flammability 4, Reactivity 3 volatile flammable liquid below room temperature polymerizes violently on contact with ammonia, alkali hydroxides, amines, metallic potassium, acids, aluminum chloride, iron (III) chloride, tin (IV) chloride, aluminum oxide, iron oxide, and rust reacts explosively with glycerol at 200°C vapor forms explosive mixtures with air vapors may travel to an Ignition source and flash back incompatible with bases, alcohols, air, copper, trimethyl amine, magnesium perchlorate, mercaptans, alkane thiols, bromoethane, and others explosive decomposition may occur in vapor or liquid phases use water spray, dry chemical, foam, or carbon dioxide for firefighting purposes. 

---