Ethylene-air mixtures

An ethylene compressor was shut down for maintenance and correctly isolated by slip-plates. When repairs were complete, the slip-plates were removed before the machine was tried out. During the tryout, some ethylene leaked through the closed isolation valves into the machine. The ethylene/air mixture was ignited, either by a hot spot in the machine or by copper acetylide on the copper valve gaskets. The compressor was severely damaged. 

Bjorklnnd et al. (1982) report experimental results on the evalnation of a single 30-mesh gauze screen and a dual 20-mesh gauze screen flame arresters using propane-air and ethylene-air mixtures. The test results are as follows ... 

Van Wingerden and Zeeuwen (1983) demonstrated increases in flame speeds of methane, propane, ethylene, and acetylene by deploying an array of cylindrical obstacles between two plates (Table 4.3). They showed that laminar flame speed can be used as a scaling parameter for reactivity. Van Wingerden (1984) further investigated the effect of pipe-rack obstacle arrays between two plates. Ignition of an ethylene-air mixture at one edge of the apparatus resulted in a flame speed of 420 m/s and a maximum pressure of 0.7 bar. 

Brossard, J., D. Desbordes, N. Difabio, J. L. Gamier, A. Lannoy, J. C. Leyer, J. Perrot, and J. P. Saint-Cloud. 1985. Truly unconflned deflagrations of ethylene-air mixtures. Paper presented at the 10th Int. Coll, on Dynamics of Explosions and Reactive Systems. Berkeley, California. 

Analysis had shown that the fuel behaved like ethylene-air mixture and the cloud could be so large that it could fill the whole calculation domain up to about 20 m high. The ethylene-air gas cloud was assumed to be a homogeneous stoichiometric mixture with the shape of a box. The following two cloud assumptions were chosen ... 

The solubility of ethylene in freshly prepared polyethylene, and its diffusion out of the latter were studied in relation to the formation of explosive ethylene-air mixtures in storage. Explosive mixtures may be formed, because the solubility of ethylene in its polymer (e.g. 1130 ppm w/w at 30°C) considerably exceeds the concentration (30 ppm at 30°C) necessary to exceed the lower explosive limit above the gas-containing polymer in closed storage, and the diffusion coefficient is also 30% higher than for aged polymer samples. 

Calculate the detonation velocity of an ethylene-air mixture at an equiva-... 

Silver is used in the form of porous pellets or, more often, supported on an inert carrier with wide pores (e.g., corundum). Commercially, the reaction is performed with ethylene-oxygen and ethylene-air mixtures at about 250°C, 10-25 atm and time of contact of the order of 1 sec. Higher pressures facilitate the subsequent separation of ethylene oxide from the exit gas mixture. Small amounts of some elements are added to silver this increases the selectivity [i.e., the fraction of ethylene converted according to (218) in the total amount of ethylene converted]. 

Caton, J.A. Heterogeneous catalysis of lean ethylene/air mixtures by platinum coated wire screens. American Society of Mechanical Engineers. Paper No. 76-WA/GT-2, 1976. 

The inflammability limits for ethylene-air mixtures have been found by White31 to be ... 

Figure 3.10 summarizes the successful and unsuccessful test conditions for which detonation transmission occurred for the ethylene-air mixtures. 

Figure 11—36. Explosion limits (1 s isochrone) in ethylene-air mixture as a function of vibrational temperature of nitrogen molecules.

Figure T. Computed induction lengths for ethylene-air mixtures showing the effects of addition of selected inhibitors. Also shown is the predicted rich limit for the propagation of detonation in a linear tube, based on the data without inhibitors present of Borisov and Loban (2T).

Gordon L. Dugger and Sheldon Heimel, Flame Speeds of Methane-Air, Propane-Air, and Ethylene-Air Mixtures at Low Initial Temperatures, Nat. Advisory Committee for Aeronautics TN 2624, Washington, D.C., February 1952, 25 pp. 

The same data permit the computation of the progress of these concentrations as a consequence of a flash evaporation at distances of 100 and 500 m from the emission source (Figure 7.27). Due to the rate of dispersion of the very rapidly released amount of ethylene, the ethylene/air mixture would remain ignitable for approximately 350 s at a distance of 500 m from the emission source, i.e., the lower ignition threshold would have been exceeded and the upper level would not yet have been reached. 

At a point approximately 100 m from the source, a cloud of ethylene/air mixture would pass by for 200 s, where it would be ignitable for only 100 s. 

Under neutral turbulence conditions in the atmosphere and a wind velocity of 3 m/s, the area in which a flammable ethylene/air mixture must be expected will be reduced to approximately 1/6 km with a maximum height of 100 m (Figure 7,28). At 100 m from the emission source, the passing mixture would still be flammable during approximately 40 s, and at 500 m during approximately 60 s (Figure 7.29). 

The oxidation of ethylene in air on a Pt wire is a good example by which to demonstrate the ignition behavior of exothermic catalytic reactions. The experiment was conducted as follows (Table 4.5.4). A coil consisting of a thin Pt-wire is placed in a tubular reactor. Then an ethylene-air mixture of constant temperature and pressure (303 K, 1 bar) is fed into the tubular reactor. The wire is now electrically heated until ignition (jump in temperature) occurs. The current and the voltage is measured and, thus, also the temperature of the wire as the electrical resistance depends on temperature. 

Fig. 5.16 Experimental data and computed 2o uncertainty bands for the laminar flame speed of ethylene-air mixtures at p = l atm. Reproduced from Sheen et al. (2009) with permission from Elsevier...

Fig. 4.15 The upper concentration limit for hydrogen + ethylene + air mixture versus the hydrogen concentration in the fuel at 21°C and 350°C, t = 10 min the solid cwve - calculation by the Le-Chatelier law...

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