Explosion isothermal

It is convenient to calculate a TNT equivalent of a physical explosion to use the military results of Figures 9.1-4 and 5. Baker et al. (1983) give a recipe for the rupture of a gas filled container assuming expansion occurs isothermally and the perfect gas laws apply (equation 9.1-25), where W is... 

Direct fluorinations with elemental fluorine still are not feasible on an industrial scale today they are even problematic when carried out on a laboratory-scale [49-53]. This is caused by the difficulty of sustaining the electrophilic substitution path as the latter demands process conditions, in particular isothermal operation, which can hardly be realized using conventional equipment. As a consequence, uncontrolled additions and polymerizations usually dominate over substitution, in many cases causing large heat release which may even lead to explosions. 

There is a third explosion limit indicated in Figure 4.1 at still higher pressures. This limit is a thermal limit. At these pressures the reaction rate becomes so fast that conditions can no longer remain isothermal. At these pressures the energy liberated by the exothermic chain reaction cannot be transferred to the surroundings at a sufficiently fast rate, so the reaction mixture heats up. This increases the rate of the process and the rate at which energy is liberated so one has a snowballing effect until an explosion occurs. 

Industrial preparation of 4-cyano-3-nitrotoluene by heating the reaction components at around 170°C for 6 h led to an explosion in 1976. Subsequent investigation by DSC showed that the cyano compound in presence of the starting materials exhibited an exotherm at 180°C. After 6 h reaction, this threshold temperature fell to 170°C. Isothermal use of a safety calorimeter showed that a large exotherm occurred dining the first hour of reaction and that, in absence of strong cooling,... 

During evaporation of liquid stibine at — 17°C, a relatively weak and isothermal explosive decomposition may occur. Gaseous stibine at ambient temperature may propagate an explosion from a hot spot on the retaining vessel wall, and it auto-catalytically decomposes, sometimes explosively, at 200°C. 

Four methods are used to estimate the energy of explosion for a pressurized gas Brode s equation, isentropic expansion, isothermal expansion, and thermodynamic availability. Brode s method21 is perhaps the simplest approach. It determines the energy required to raise the pressure of the gas at constant volume from atmospheric pressure to the final gas pressure in the vessel. The resulting expression is... 

By modifying the procedure described above to explode a wire in the water sphere while the system was under compression, they did attain explosions. Measuring the rebound of the cylinder and the loss of aluminum, they could estimate the work produced by the event. Assuming the maximum energy transfer to the water would occur by constant volume heating to the aluminum temperature, foUowed by an isothermal, reversible expansion, they estimated an efficiency of about 25%. Clearly the exploding wire led to an immediate and effective dispersal of the water. 

J.C. Oxley, J.L. Smith and S. Naik, Determination of Urea Nitrate and Guanidine Nitrate Vapour Pressures by Isothermal Thermogravimetry , submitted to Propellants, Explosives, Pyrotechnics. 

One of the simplest calorimetric methods is combustion bomb calorimetry . In essence this involves the direct reaction of a sample material and a gas, such as O or F, within a sealed container and the measurement of the heat which is produced by the reaction. As the heat involved can be very large, and the rate of reaction very fast, the reaction may be explosive, hence the term combustion bomb . The calorimeter must be calibrated so that heat absorbed by the calorimeter is well characterised and the heat necessary to initiate reaction taken into account. The technique has no constraints concerning adiabatic or isothermal conditions hut is severely limited if the amount of reactants are small and/or the heat evolved is small. It is also not particularly suitable for intermetallic compounds where combustion is not part of the process during its formation. Its main use is in materials thermochemistry where it has been used in the determination of enthalpies of formation of carbides, borides, nitrides, etc. 

Effective temperature control of large fixed beds can be difficult because such systems are characterized by a low heat conductivity. Thus in highly exothermic reactions hot spots or moving hot fronts are likely to develop which may ruin the catalyst. In contrast with this, the rapid mixing of solids in fluidized beds allows easily and reliably controlled, practically isothermal, operations. So if operations are to be restricted within a narrow temperature range, either because of the explosive nature of the reaction or because of product distribution considerations, then the fluidized bed is favored. 

H +C>2 - OH+ O, so called because the disappearance of one chain carrier leads to the appearance of two. If chain carriers are produced at a rate faster than they are removed (by chain-breaking or chain-terminating reactions), a branching-chain explosion can occur without any preliminary temperature rise at all (hence "isothermal )... 

Such reactions have been used to explain the three limits found in some oxidation reactions, such as those of hydrogen or of carbon monoxide with oxygen, with an "explosion peninsula between the lower and the second limit. However, the phenomenon of the explosion limit itself is not a criterion for a choice between the critical reaction rate of the thermal theory and the critical chain-branching coefficient of the isothermal-chain-reaction theory (See Ref). For exothermic reactions, the temperature rise of the reacting system due to the heat evolved accelerates the reaction rate. In view of the subsequent modification of the Arrhenius factor during the development of the reaction, the evolution of the system is quite similar to that of the branched-chain reactions, even if the system obeys a simple kinetic law. It is necessary in each individual case to determine the reaction mechanism from the whole... 

In the latter units "impetus is numerically equal to the volume that unit weight of the explosion products, if ideal gases, would occupy on isothermal expansion at (Tv) to a pressure of 1 atm. The "work done in this expansion would depend on the conditions. Work done would equal impetus only if the expansion were against an external pressure of 1 atm thruout Refs 1) Dunkle s Syllabus (1957-1958), p 257 2) Dunkle,private communication,... 

Detonation (Explosion, Deflagration and Decomposition), Thermal Theories and Thermochemistry of. Cook (Ref 8) discusses both isothermal and adiabatic decompositions... 

Under isothermal decomposition, he states that it is difficult to maintain isothermal conditions in such strongly exothermic reactions as are involved in the thermal decomposition of explosives owing to their tendency for selfheating. One is also concerned with. the elimination (or minimization) of temperature transients in bringing the sample to the predetermined temp of the experiment. After a brief description of experiments of A.J.B. Robertson and of A.D. Yoffe, conducted in England, the quartz spring apparatus designed by M.A. Cook ... 

The isothermal method for such expls as PETN, RDX, NG and Tetryl is complicated by autocatalysis to such an extent that one cannot determine the intrinsic (pure explosive) decompn rate from the logw vs t curves and their change with temperature. Hence, the results obtd by the adiabatic(sensitivity) methods may be more reliable from this viewpoint (Ref 8, p 177)... 

The vacuum stability test (VST) is considered the most acceptable test for measuring stability and compatibility of explosives, worldwide. This is an empirical test in which rate of gas evolution is measured under isothermal conditions and a limit of 01 cm3 of gas per gram of an explosive is set for explosives heated at 120°C (150°C for RDX) for 40h (25h for PETN). A similar test but at somewhat lower temperatures, is used to assess compatibility of an explosive with other explosives or with non-explosive materials such as binders (polymers), plasticizers etc. 

Isothermal DSC was used to determine the kinetic parameters for thermal decomposition of 2,4,6-TNT and it was found that molten TNT shows a temperature-dependent explosion delay prior to its exothermic decomposition. The rate constant of exothermic decomposition and activation energies of explosion delay and exothermic decomposition were also reported [42]. Similarly, House and Zack... 

Recovery of solvent by isothermal compression. This method was proposed by Claude [14]. It was applied to the recovery of alcohol containing camphor which escapes during the manufacture of celluloid. With alcohol and ether this process entails compressing the vapours to 7 atm, thus causing the condensation of the alcohol and after that rapidly expanding them. Ether is condensed by intensive cooling. The necessary plant was very expensive and there was risk of explosion when the mixture of the air with alcohol and ether was compressed too rapidly. It never attained wide application. 

All explosives undergo thermal decomposition at temperatures far below those at which explosions take place. These reactions are important in determining the stability and shelf life of the explosive, The reactions also provide useful information on the susceptibility of explosives to heat. The kinetic data are normally determined under isothermal condi-... 

I he occurrence of a spontaneous explosion in a chemically reacting system is a complicated process. However, the events that lead to explosion can be characterized as being either of a branching chain or of a thermal nature. Branching-chain explosions occur in systems that react by a chain mechanism, the details of which allow the chain carrier concentration, and hence, the over-all reaction rate to increase without limit, even under isothermal conditions. Such a condition is possible only if one or more of the steps in the reaction chain results in a multiplication of chain carriers—i.c., X + A — Y + Z + , where X, F, and Z arc chain carriers. 

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