Acetylene material factor

Exact design criteria on equipment for handling acetylene is not readily available because of the great number of factors involved. However, recommendations have been made concerning the equipment, piping, compressors, flash arresters, and proper materials (69,92—94). 

The equivalent charge weight of TNT is calculated on the basis of the entire cloud content. FMRC recommends that a material-dependent yield factor be applied. Three types of material are distinguished Class I (relatively nonreactive materials such as propane, butane, and ordinary flammable liquids) Class II (moderately reactive materials such as ethylene, diethyl ether, and acrolein) and Class III (highly reactive materials such as acetylene). These classes were developed based on the work of Lewis (1980). Energy-based TNT equivalencies assigned to these classes are as follows ... 

A great many materials have been used as catalyst supports in hydrogena-tion, but most of these catalyst have been in a quest for an improved system. The majority of catalyst supports are some form of carbon, alumina, or silica-alumina. Supports such as calcium carbonate or barium sulfate may give better yields of B in reactions of the type A- B- C, exemplified by acetylenes- cjs-olefins, apparently owing to a weaker adsorption of the intermediate B. Large-pore supports that allow ready escape of B may give better selectivities than smaller-pore supports, but other factors may influence selectivity as well. 

Chen et al. [70] suggested that temperature gradients may have been responsible for the more than 90 % selectivity of the formation of acetylene from methane in a microwave heated activated carbon bed. The authors believed that the highly nonisothermal nature of the packed bed might allow reaction intermediates formed on the surface to desorb into a relatively cool gas stream where they are transformed via a different reaction pathway than in a conventional isothermal reactor. The results indicated that temperature gradients were approximately 20 K. The nonisothermal nature of this packed bed resulted in an apparent rate enhancement and altered the activation energy and pre-exponential factor [94]. Formation of hot spots was modeled by calculation and, in the case of solid materials, studied by several authors [105-108],... 

The explosion efficiency is one of the major problems in the equivalency method. The explosion efficiency is used to adjust the estimate for a number of factors, including incomplete mixing with air of the combustible material and incomplete conversion of the thermal energy to mechanical energy. The explosion efficiency is empirical, with most flammable cloud estimates varying between 1 % and 10%, as reported by a number of sources. Others have reported 5%, 10%, and 15% for flammable clouds of propane, diethyl ether, and acetylene, respectively. Explosion efficiencies can also be defined for solid materials, such as ammonium nitrate. 

An extensive computational analysis expanded the range of the c-d distances for reactive cyclic enediynes to 2.9-3.4 A.38 By comparing unsubstituted enediynes with dialkyl-substituted enediynes, it was found that the activation enthalpy is dependent on factors other than the c-d distance and that reactivity hinges on a subtle interplay of steric and electronic effects that accompany distortion caused by incorporation into a macrocycle. For example, since alkyl substituents stabilize acetylenic bonds to a greater extend than olefinic bonds,39 such substituents stabilize the starting material, thus increasing both the activation barrier and the reaction endothermicity. 

Materials like acetylene may decompose under the appropriate conditions with a fairly large liberation of energy. Determine the temperature and pressure attained in a closed spherical container when acetylene, initially at 25°C and 10 atm, rapidly decomposes to carbon and hydrogen after accidentally being subjected to an electrical spark. What thickness of carbon steel would have been required to contain the decomposition reaction if no relief valve had been available to relieve the pressure buildup (Assume that a safety factor of 4 has been used in the thickness calculation.)... 

The discovery that exposure to exogenous chemicals could lead to cancer in humans was first made in the late 18th century, when Percival Pott demonstrated the relationship between cancer of the scrotum and the occupation of chimney sweepers exposed to coal tar/soot. Other examples noted later were scrotal cancers in cotton spinners exposed to unrefined mineral oils, and cancers of the urinary bladder in men who worked in textile dye and rubber industries due to their exposure to certain aromatic amines used as antioxidants. Experimental induction of cancer by chemicals was first reported in detail by Yamagiwa and Ichikawa in 1918, when repeated application of coal tar to the ear of rabbits resulted in skin carcinomas. Over the next few years, Kennaway and Leitch confirmed this finding and demonstrated similar effects in mice and rabbits from the application of soot extracts, other types of tar (e.g., acetylene or isoprene), and some heated mineral oils. These researchers also observed skin irritation sometimes accompanied by ulcers at the site of application of the test material. Irritation was thought to be an important factor in skin tumor development. However, not all irritants (e.g., acridine) induced skin cancer in mice and conversely, some purified chemicals isolated from these crude materials... 

In acetylene engineering - and especially in the generation of acetylene from carbide as well as in supply engineering - the possibihty of generating acetylide is an important factor when selecting the material for the equipment. The formation of acetylides is not only possible in saline solutions in laboratory experiments but it also occurs when moist crude acetylene comes into contact with metallic silver or copper surfaces. Corrosion products encourage acetylide formation on copper surfaces. 

A further development in GDL manufacture was the introduction of a micro porous hydrophobic layer applied to one side of the carbon backing which faced the catalyst layer (Lister and McLean, 2004 Song et al., 2001). This layer typically consisted of PTFE and carbon black. Carbon black imparts good electrical properties and improves the gas transport to the catalyst layer. The type of carbon powder used also impacts the cell performance. Antolini et al. (2002) investigated two different carbon powders (oil furnace carbon black and acetylene black) and reported that acetylene black gave better cell performance than oil furnace carbon black. Carbon is a critical material in fuel cells since it has the necessary properties of electrical conductivity, corrosion resistance, surface properties and low cost factors which could make an inexpensive fuel cell a reality. Carbon is a nonmetallic substance with a wide range of crystalline and amorphous... 

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