Detonation interactions

Section IV combines the thermochemistry from Section II with the shock behavior of Section III to describe detonation (reactive shock waves). This section begins with simple ideal detonation theory and then goes on to quantitative calculations of detonation interactions at interfaces with other materials, and then deals with nonideal effects, those that cannot be predicted by ideal theory, such as the effects of size and geometry. 

The reactive fluid dynamics of a detonation interaction with a matrix of metal particles was performed in reference 36 to determine the nature of the observed nonideal behavior. 

Nitrogen Triiodide, NI3, mw 394.77, N 3.5% a black powd, detons when dry, exposed to light, or an elec spark (Refs 8 10) Qf 35kcal/mole (Ref 7). It is formed by the interaction of free 1 or I3" on liq, gaseous, or aq ammonia (Refs 1, 8 10). N triiodide forms a series of solvates with excess ammonia NI3.NH3) bright red needles, explds when dry (Ref 2). 

Transition to detonation caused by instabilities near the flame front, the flame interactions with a shock wave, another flame or a wall, or the explosion of a previously quenched pocket of combustible gas... 

Transition to detonation in charmels without obstacles was recently successfully simulated numerically [11,12]. In these simulations, it was shown that shock compression of the unreacted mixture forms the hot spots resulting from shock-shock, shock-wall, and shock-vortex interactions. The hot spots contain temperature gradients that produce spontaneous reaction waves and detonations. 

In the 1950s, the more descriptive schlieren records of the interactions between pressure waves and deflagration fronts were obtained [16-18], and Oppenheim [9] introduced the hypothesis of the "explosion in the explosion" (of the detonating mixture) occurring in the regime of accelerating flame to explain the sudden change in the velocity of the combustion wave observed in the experiments. 

Phosphorus trichloride detonates in contact with nitric acid. The same may occur during the highly exothermic interaction between this chloride and sodium peroxide. 

If the interaction takes place in a closed container, it can detonate. 

The interaction of disulphide with oxygen can be very dangerous. This compound has a very low self-ignition temperature (see tables in Part Three). When rust is present it can cause the mixture to detonate by catalysing the oxidation reaction. 

Detonation occurs during the reaction of molten aluminium with ammonium peroxodisulphate in the presence of water. However, since the temperature is above 75°C, the presence of water is sufficient to decompose it and the water/molten aluminium interaction has aiready been mentioned as being explosive. 

Chlorates and perchlorates react violently with metals when they are exposed to heat (the salt is then in molten state), a flame, a spark, friction or impact. The ignition often involves very spectacular blinding flames. The mixtures can detonate the conditions of the reaction depend on how the interaction is... 

Finally, there was a detonation caused by the interaction of molten calcium with asbestos cement (complex silicate). 

There was a surprising fatal accident during which an iron container with magnesium chloride (probably moist) detonated. It was thought that the magnesium salt had catalysed the interaction between the metal and water. 

Finally, an accident involved an active carbon filter, which contained potassium iodide and through which gas containing ozone was passing. The detonation of the filter was explained by ozone oxidising iodide into iodate and by the iodate interacting to produce an explosion with the active carbon (see the effect of iodates on metalloids above). 

In the same way, the detonation of moist trichloroethylene, which had been stored in a metal container, was explained by the hydrogen chloride formed. In this case it is possible to suggest another cause, which would involve iron trichloride forming by the interaction of hydrogen chloride with rust traces, and the catalysis by this salt of a polymerisation or degradation of the chlorinated derivative (see the similar case of aluminium chloride on p.281). 

Chloroform or bromoform/nitromethane mixtures can detonate very easily. This interaction has to be connected with the one described on p.297 that involved the CH3N02/CH2CI2 system, which by analogy could have been a factor in the accident described. 

The interaction of a sodium or calcium hypochlorite or phosphorus penta-chloride with urea causes a violent detonation, that has been put down to the decomposition of the nitrogen trichloride formed. 

Turbulence is required for the flame front to accelerate to the speeds required for a VCE otherwise, a flash fire will result. This turbulence is typically formed by the interaction between the flame front and obstacles such as process structures or equipment. Turbulence also results from material released explosively or via pressure jets. The blast effects produced by VCEs can vary greatly and are strongly dependent on flame speed. In most cases, the mode of flame propagation is deflagration. Under extraordinary conditions, a detonation with more severe blast effects might occur. In the absence of turbulence, under laminar or near-laminar conditions, flame speeds are too low to produce significant blast overpressure. In such a case, the cloud will merely bum as a flash fire. 

Interaction to produce 3,5-dimethyl-4-bis(trifluoroacetoxy)iodoisoxazole yields a detonable by-product, believed to be iodine pentaoxide contaminated with organic material. 

Mercury fulminate, readily formed by interaction of mercury(II) nitrate, nitric acid and ethanol, is endothermic (AH°f (s) +267.7 kJ/mol, 0.94 kJ/g) and was a very widely used detonator. It may be initiated when dry by flame, heat, impact, friction or intense radiation. Contact with sulfuric acid causes explosion [1], The effects of impurities on the preparation and decomposition of the salt have been described [2],... 

Interaction in THF gives 2,4-dinitrophenol and ammonia, and on one occasion a violent detonation occurred potassium dinitrophenoxide may have been involved. See Sodium 2,4-dinitrophenoxide See other n-o compounds, polynitroaryl compounds... 

The peroxyhypochlorite is especially reactive, and the fluoroperoxy compounds produced by its interaction with haloalkenes can detonate when subjected to thermal or mechanical shock. However, no explosions were experienced dining this work. 

---