Explosion explosive conditions

The fuels consumed in the fire were treated wood, penta, and creosote (coal tars). Both are considered combustible liquids, with flash points above 160° F (CC). Vapor conditions within the headspaces of tanks can, however, reach explosive conditions, and the introduction of an ignition source resulted in spontaneous combustion. Under ideal conditions, creosote burns similar to crude oil, and in standard lab burn tests, has an average burn rate of 4 mm/min. There is no data on the burn rate of penta however, its vapors would have likely burned at much slower rates and a series of complex chemical transformations would have occurred. 

Small vertical vessels may be supported by angle support legs, as shown in Figure 12-11. Larger vertical vessels are generally supported by a skirt support, as shown in Figure 12-12. At least two (2) vent holes, 180" apart, should be provided at the uppermost location in the. skirt to prevent the accumulation of gas, which may create explosive conditions. Horizontal vessels are generally supported by a pair of saddle type supports. 

Establish actual relieving pressure (and corresponding temperature) from Figure 7-7A (at 110% of set pressure for non-fire and non-explosive conditions). Explosive conditions may require total separate evaluation of the set pressure never above the MAWP), which should be lower or staged or, most likely, will not be satisfied by a standard SRV due to the extreme rapid response needed. 

Often the process may have conditions that control the flexibility of compression equipment selection. These might include limiting temperatures before polymer formation, chemical reaction, excess heat for lubrication materials, explosive conditions greater than a certain temperature, etc. 

J. Pressure ventilated large induction or synchronous motors A Pressure Ventilated motor requires a closed pressure system to force filtered air or nitrogen into the motor casing (housing) to avoid corrosive or explosive conditions internally. Constance reference 56 describes some of the details of such a system also see Ecker et al. [69]. 

GP 2[ [R 2[ Safe operation under explosive conditions using pure oxygen was demonstrated in a steel multi-plate-stack micro reactor (e.g. 3 vol.-% ethylene, 50 vol.-% oxygen, balance nitrogen 5 bar 4 1 h 277 °C) ]4, 26,40]. The cross-sections of the various micro channels employed were from 500 x 50 pm to 500 x 90 pm. ... 

The necessity of avoiding potentially explosive conditions requires that the mole percent naphthalene in the feed be kept below 1%. It is suggested that preliminary design calculations be based on a feed composition of 0.75 mole percent naphthalene (remainder air). 

The interstellar medium is thus a chemically diverse medium fed nearly all of the chemical elements by supernova explosions. Conditions in the interstellar medium produce a cocktail of molecules that ultimately find themselves back on the surface of planets during the formation of the new star and solar system. Does the interstellar medium seed life with molecules from space The nature of interstellar medium chemistry might then add credibility to the formation of life in many places within the Universe and act as a panspermia model for the origins of life. 

Venting element That part of vent area device that covers the vent area and opens under explosion conditions. 

Trenches were constructed using conventional earthmoving equipment. During construction, air monitoring was continued to assure that explosive conditions were not present. However, odors persisted from the freshly excavated soils but disappeared within a few days. Operation of this trench system continues throughout frost-free seasons and has proved very successful. Initially, approximately 5 bar-... 

The question to be considered is what value of a is necessary for the system to be explosive. This explosive condition is determined by the rate of formation of a major product, and P (products) from reaction (3.3) is the obvious selection for purposes here. Thus... 

The essential feature of the initiation step is to provide a radical for the chain system and, as discussed in the previous section, the actual initiation step is not important in determining the explosive condition, nor is it important in determining the products formed. Either reaction (3.14) or (3.16) provides an H radical that develops a radical pool of OH, O, and H by the chain reactions... 

There is, of course, a chemical effect in carbon monoxide flames. This point was mentioned in the discussion of carbon monoxide explosion limits. Studies have shown that CO flame velocities increase appreciably when small amounts of hydrogen, hydrogen-containing fuels, or water are added. For 45% CO in air, the flame velocity passes through a maximum after approximately 5% by volume of water has been added. At this point, the flame velocity is 2.1 times the value with 0.7% H20 added. After the 5% maximum is attained a dilution effect begins to cause a decrease in flame speed. The effect and the maximum arise because a sufficient steady-state concentration of OH radicals must be established for the most effective explosive condition. 

Belles prediction of the limits of detonability takes the following course. He deals with the hydrogen-oxygen case. Initially, the chemical kinetic conditions for branched-chain explosion in this system are defined in terms of the temperature, pressure, and mixture composition. The standard shock wave equations are used to express, for a given mixture, the temperature and pressure of the shocked gas before reaction is established (condition 1 ). The shock Mach number (M) is determined from the detonation velocity. These results are then combined with the explosion condition in terms of M and the mixture composition in order to specify the critical shock strengths for explosion. The mixtures are then examined to determine whether they can support the shock strength necessary for explosion. Some cannot, and these define the limit. 

The set of reactions that determine the explosion condition of the hydrogen-oxygen system is essentially... 

From Eq. (5.46) it is apparent that many combinations of pressure and temperature will satisfy the explosive condition. However, if the condition is specified that the ignition of the deflagration state must come from the shock wave, Belles argues that only one Mach number will satisfy the explosive condition. This Mach number, called the critical Mach number, is found by substituting Eqs. (5.47) and (5.48) into Eq. (5.46) to give... 

Questions have been raised about this approach to calculating detonation limits, and some believe that the general agreement between experiments and the theory as shown in Table 5.6 is fortuitous. One of the criticisms is that a given Mach number specifies a particular temperature and a pressure behind the shock. The expression representing the explosive condition also specifies a particular pressure and temperature. It is unlikely that there would be a direct correspondence of the two conditions from the different shock and explosion relationships. Equation (5.49) must give a unique result for the initial conditions because of the manner in which it was developed. 

If the initial pressure is increased to some value P2, the heat release curve shifts to higher values, which are proportional to P" (or p"). The assumption is made that h is not affected by this pressure increase. The value of P2 is selected so that the ql becomes tangent to the qr curve at some point c. If the value of h is lowered, qr is everywhere greater than ql and all initial temperatures give explosive conditions. It is therefore obvious that when the ifo line is tangent to the qr curve, the critical condition for mixture self-ignition exists. 

Up to now, the search for an astrophysical site that could sustain the r process has not brought much success, but it is certainly not for want of imagination. Mergers between two neutron stars or a neutron star and a black hole have even appeared on the list. Notwithstanding, the favourite potential site remains the supernova. However, despite a long inquiry into the matter, we are still unable to put forward a detailed mechanism to show how it would operate. Calculations with the r process in explosive conditions are notoriously difficult, but they are being pursued with courage and determination. 

Apin et al (Ref 4), in a calorimetric investigation of mixtures of Hydrazine Azide with several metallic elements found that an explosion resulted with the formation of NH3. The amount of NH3 depended on the explosion conditions. The limiting conditions were either N21VHN3 >2 AHj +2 AN2 or 1 2/3NH3 + 1 2/3N2... 

This reaction is highly exothermic. If the heat of the reaction is not conducted thru the walls of a closed container at a rate capable of maintaining an equilibrium temperature, an increase in pressure results with an increase in reaction rate, leading to explosive conditions. Acid salts, such as stannic chloride and zinc chloride, and bases, such as alkali metal hydroxides, either solid or in aqueous solution, and tertiary amines are all effective catalysts. It is, therefore, imperative that the concentration of such contaminants be kept at a minimum when transporting or storing sizeable quantities of ethylene oxide Accdg to Hess Tilton (Ref 16), a 90% decompn takes place if 100% vapor of EtnO in a closed container is. initiated with MF. There is no upper limit of EtnO in air (the previously reported value of 80% was in error), but the lower expl limit is 3% (Ref 17, p 87)... 

Explosive Conditioning. Mentioned, but not described, under Explosive Fabrication of Metals... 

Carbon tetrachloride represents an example of the change to petroleum raw materials in this field. The traditional source of this widely used product has been the chlorination of carbon disulfide, either directly or through the use of sulfur dichloride. Military requirements in World War II caused an increase in demand, and in addition to expansion of the older operations, a new process (28) was introduced in 1943 it involved direct chlorination of methane at 400° to 500° C. and essentially atmospheric pressure. This apparently straight-forward substitution of halogen for hydrogen in the simplest paraffin hydrocarbon was still a difficult technical accomplishment, requiring special reactor construction to avoid explosive conditions. There is also the fact that disposal of by-product hydrochloric acid is necessary here, though this does not enter the carbon disulfide picture. That these problems have been settled successfully is indicated by the report (82) that the chlorination of methane is the predominant process in use in the United States today, and it is estimated that more than 100,000,000 pounds of carbon tetrachloride were so produced last year. 

This equation has been numerically integrated by Rice and his associates (4 ). The results of their rather tedious calculations are in good agreement with the experimental data which they have obtained for azomethane and ethyl azide explosions. These calculations, together with the measured induction periods and explosion conditions, allowed these authors to make reasonable estimates of ( , the heat of reaction. 

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