Helium atmosphere

Gas emerges from each expander cooled to -61°C (-77°F). Additional heat exchangers lower the temperature to -84°C (-120°F), at which point all the LNG is removed for delivery. Residue gas, now under reduced pressure, is passed along to the nitrogen rejection unit (NRU) where inert nitrogen is separated and vented into the atmosphere. Helium is also recovered in the NRU. The remaining residue gas is 90% methane. 

In practice, the production of vanadium by aluminothermic reduction is also governed by some other considerations. The reduction has to be carried out under an inert atmosphere (helium or argon) to avoid nitrogen pick-up from the air by vanadium metal. The composition of the oxide-aluminum charge has to be so chosen that the thermit (metal obtained by aluminothermic reduction) contains between 11 and 19% aluminum. This is necessary for the subsequent refining step in the vanadium metal production flowsheet. Pure vanadium pentoxide and pure aluminum are used as the starting materials, and the reduction is conducted in a closed steel bomb as shown in Figure 4.17 (C). 

On completion of the reaction after 10 to 14 hours, the reaction tube is removed from the furnace. The bromine may be frozen at liquid-nitrogen temperature in either bulb A or F, and both A and F are removed by sealing with the hand torch near the bulb E. The remainder of the reaction tube is transferred to the dry-box under an inert atmosphere (helium, nitrogen, or argon) and opened by breaking at the constrictions between bulbs B and E. 

W.F. Libby, Atmospheric helium three and radiocarbon from cosmic radiation, Phys. Rev. 69, 671 672(1946). 

Sano, Y., Wakita, H., Makide, Y., Tominaga, T. (1989) A ten-year decrease in the atmospheric helium isotopic ratio possibly caused by human activity. Geophys. Res. Lett., 16, 1371-4. 

The 3He can be identified based on the background of the atmospheric helium contained in every meteoric groundwater (Chapter 13). 

A major task in the tritium-3He dating method is the identification of 3He based on the background of the atmospheric helium, which has a 3He 4He ratio that varies from one place to another within a wide range of values. 

Torgersen T. (1989) Terrestrial helium degassing fluxes and the atmospheric helium budget implications with respect to the degassing processes of continental crust. Chem. Geol. 79, 1-14. 

Since there appears to be no He sinks in the soil or in the lower levels of the atmosphere, it is more than probable that this noble gas escapes from the upper atmosphere into outer space. It follows from the constant atmospheric level that this sink balances the effect of the sources. When the total atmospheric helium mass is taken into account, as well as the above formation mechanism, the residence time of He is estimated to be approximately 107 years. 

A variety of suggestions has been made to overcome the difficulty [see Hunten (1973) for details]. The most reasonable one appears to be the proposition by Axford (1968) that helium leaves Earth s atmosphere mainly in the ionized state. Ion flow would be most effective in the polar regions where the magnetic field lines are open, but there is some doubt whether the ionization rate is adequate. This question has not yet been resolved, so that our understanding of the atmospheric helium budget remains unsatisfactory. 

Mahoney JJ, Natland JH, White WM, Poreda R, Bloomer SH, Fisher RL, Baxter AN (1989) Isotopic and geochemical provinces of the western Indian Ocean spreading centers. J Geophys Res 94 4033-4052 Mamyrin BA, Tolstikhin IN (1984) Helium Isotopes in Nature. Elsevier. Amsterdam Mamyrin BA, Anufriev GS, Kamenskii IL, Tolstikhin IN (1970) Determination of the isotopic composition of atmospheric helium. Geochem Inti 7 498-505... 

The occurrence of isotopic disequilibrium between coexisting phenocryst pairs. Marty et al. (1994) reported higher He/ He ratios in olivine phenocrysts compared to pyroxene or hornblende for Mt. Etna volcano, an observation that is consistent with addition of late-stage, radiogenic or atmospheric helium. The same effect is seen in arc-related phenocrysts from the Lesser Antilles (Van Soest et al. 2002). 

Helium observed in natural water samples has several sources that may be distinguished by their He/ He ratio. Generally, atmospheric helium with a He/He ratio of 1.384x10 (Clarke et al. 1976) is the major component present in natural waters. Its solubility is a function of the temperature and salinity of the water (Weiss 1971). He is... 

Four decades ago, He of apparent extraterrestrial origin was identified in ocean sediments. Merrihue (1964) observed He/ He ratios in marine sediments roughly 2 orders of magnitude higher than those observed in atmospheric helium and attributed it to the presence of cosmic material. 

Helium contained in ocean sediments can be interpreted as a mixture of helium from two sources, extraterrestrial and terrigeneous helium (Takayanagi and Ozima 1987 Marcantonio et al. 1995). Contributions from an atmospheric helium component have been shown to be negligible (e g., Farley and Patterson 1995). Assuming that the isotopic compositions of both mixing end-members are known, one can easily calculate the amount of extraterrestrial He, using the following equation ... 

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