Ignition, vapor explosions

On March 26, 1980, a power shovel was relocating a tank containing 1500 I (750 kg 1650 lb) liquid propane. During maneuvering, the tank fell from the shovel a portion of its contents was releas as a result. After a delay of 30 seconds, the ensuing vapor cloud was ignited. The explosion caused substantial blast and fire damage. There were no casualties. 

On January 4, 1966, at Feyzin refinery in France, a leak from a propane storage sphere ignited. The fire burned around the vessel and led to boiling liquid expanding vapor explosions. The accident caused eighteen deaths and eighty-one injuries. 

The explosion hazard of a vapor cloud can be quantifled in terms of its explosive power after ignition. The explosive power of a vapor cloud can be expressed as an equivalent explosive charge (TNT or fuel-air) whose blast characteristics, that is, the distribution of blast-wave properties in the charge s vicinity, are known. 

The subscript in vessel is for the reactor or building. The subscript experimental applies to data determined in the laboratory using either the vapor or dust explosion apparatus. Equation 6-20 allows the experimental results from the dust and vapor explosion apparatus to be applied to determining the explosive behavior of materials in buildings and process vessels. This is discussed in more detail in chapter 9. The constants KG and KSt are not physical properties of the material because they are dependent on (1) the composition of the mixture, (2) the mixing within the vessel, (3) the shape of the reaction vessel, and (4) the energy of the ignition source. It is therefore necessary to run the experiments as close as possible to the actual conditions under consideration. 

Vibration from a bad pump bearing caused a pump seal to fail in a cumene section of a phenol acetone unit. The released flammable liquids and vapors ignited. An explosion ruptured other process pipes, adding fuel to the original fire. Damage to the plant exceeded 23 million. 

Sizing of vent areas The empirical equation (23-12) can be used to calculate the required vent area for flammable gas or solvent vapor explosions. The equation is valid for flammable gas-air mixtures which have been ignited in a quiescent state (nonturbulent) with an ignition source of E = 10 J. 

Lower explosive limit The minimum concentration (vol % in air) of a flammable gas or vapor required for ignition or explosion to occur in the presence of anignition source (see also Flash point). 

It has been reported that serious explosions may occur when impure tetrahydrofuran is treated with solid potassium hydroxide or with concentrated aqueous potassium hydroxide, as has been recommended widely for the purification of tetrahydrofuran see Org. Syntheses, Coll. Vol. 4,474, 792 (1963) Vol. 40,94 (1960). There is evidence that the presence of peroxides in the tetrahydrofuran being purified was causal. It is strongly recommended, therefore, that this method not be used to dry tetrahydrofuran, if the presence of peroxides is indicated by a qualitative or quantitative test with acidic aqueous iodide solution. Traces of peroxide can be removed by treatment with cuprous chloride sec Org. Syntheses, 46, 57 (1965). The safety of this operation should be checked first on a small scale (1-5 ml.). It is recommended that tetrahydrofuran containing larger than trace amounts of peroxides be discarded by flushing down a drain with tap water. It must be kept in mind that mixtures of tetrahydrofuran vapor and air are easily ignitable and explosive purification is best carried out in a hood which is well exhausted and which does not contain an ignition source... 

The PH3 molecule is pyramidal with an HPH angle of 93.7°. Phosphine, when pure, is not spontaneously flammable, but often inflames owing to traces of P2Ht or P4 vapor. It is readily oxidized by air when ignited, and explosive mixtures may be formed. It is also exceedingly poisonous. Unlike NH3, it is not associated in the liquid state and it is only sparingly soluble in water pH measurements show that the solutions are neither basic nor acidic—the acid constant is 10-29 and the base constant 10-26. 

Mutation data reported. Reacts with moisture to form sulfuric acid. Mixtures with calcium hypochlorite + starch + sodium carbonate explode when compressed. Violent reaction with acetic anhydride + ethanol may lead to ignition and a vapor explosion. Incompatible with calcium hypochlorite. When heated to decomposition it emits toxic fumes of SO and Na20. See also SULFATES. 

Acetylaminofluorene can be easily ignited by heat, sparks, or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They can spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapor explosion hazard exists indoors, outdoors, or in sewers. 

Flammable Vapor Explosions This can be a problem for products wetted by flammable solvents if the solvent concentration exceeds 0.2% v/v in the vapor phase. The ignition energy of vapor-air mixtures is lower (< 1 mJ) than that of dust-air suspensions. Many of these values are available in the literature, but testing may sometimes be required. 

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