Helium production

Relatively new methods for separating helium from natural gas use pressure swing adsorption (PSA) processes to recover helium at better than 99.99% purity. This type of process is probably less costiy for the production of gaseous helium but might be uneconomical for liquefied helium production. The PSA process is widely used to produce specification pure helium from 85+% cmde helium in conjunction with cryogenic enrichment of the ca 50% helium raffinate. 

Ernest Rutherford, however, used the alpha decay of uranium, which produces helium, to estimate the ages of several uranium ores in 1906. By measuring the ratio of helium to uranium and the current rate of helium production (that is, the current decay rate of uranium), he deduced that the minerals were at least 440 million years old. All this was, of course, before anyone knew anything about isotopes. 

The production rate of the radiogenic helium in each of these decay series is determined by the respective half-lives, and the overall helium production per unit rock is determined by the concentration of uranium and thorium in the rock (common rocks containing uranium and thorium in parts per million (ppm) concentrations). 

Hydrogen burning and helium production. Hydrogen burns in the core of a star to form 4He through either the proton-proton chain reaction, which takes place at 5 X 106 K or at higher temperatures (> 20 X 106 K) through the carbon cycle (the C-N-O cycle) in which carbon acts as a nuclear catalyst in the production of He. This process is also known as the quiescent burning phase of a star and is a slow process which takes billions of years and covers much of the life of a star. Our sun is currently in this phase. 

As shown in Fig. 20.4-3, this added effect can improve helium selectivity relative to methane by a factor of 1.73. At the same time, a factor of 2.0 loss in helium solubility and a factor of2.S [eduction in heiium diffusivjty due to the crystallinity produces a 5,6-fold reduction in helium productivity relative to the hypothetical amorphous film case. Interestingly, the effects of chain restriction on different sizes of peaetranls ware found by Michaels to be effective only for rubbery materials, not glassy ones. A logical explanation for this fact was ndvanced in terms of the already low mobility of chain segments in the glass compared to the rubbery stale ... 

The total production rate of helium cannot be much higher. As was pointed out by Nicolet (1957), the heat flow of Earth places a limit on the rate of helium production. If the heat originates entirely from the decay of uranium and thorium, an average heat flow of 3x 103 J/m2 s would correspond to a helium production rate of 3.5 x 106 kg/yr. Clearly, these values are quite... 

Radium-224 is radioactive and decays by emitting an a-particle. (a) Write an equation for this process, (b) The decay of radium-224 produces helium gas. Rutherford and Geiger determined that a-particles were emitted from ggRa at a rate of 7.65 x lO s moU, and that this corresponded to a rate of helium production of... 

TABLE 17.2. The CNO cycle for helium production about 10% of the solar energy... 

Crude helium product contains at least 65 mol% helium, a maximum of 1 mol% methane,... 

Like hydrogen, hehum has high selectivity against most other components present in its mixtures for a wide variety of polymers. The primary source of hehum is natural gas reservoirs usually in concentrations below 1%. Considering that the low concentrations translate to low partial pressures, it can be seen that membranes find hmited appHcation in helium production since multiple stages would be required to reach even crude helium purity levels. 

Helium Refrigeration (1) 41 Helium Production Process (1) 171 Hydrogen-Helium Liquefier (2) 8 Gas Chromatography as Applied to the Industrial Separation of Neon from Nitrogen and Helium (2) 197 Helium Heat Rectifiers and a Simple Magnetic Refrigerator (2) 220 A Liquid Helium Bubble Chamber (2) 330 Economic and Other Aspects of the Distribution of Navy Helium in Liquid Form (3) 114... 

An early confirmation for the correlation of excess heat and helium production in the Pd/D system was reported by McKubre and coworkers at SRI [9]. Several different experiments, using three different calorimetric methods, gave a strong time correlation between the rates of heat and helium production [9]. The production of helium-4 was also observed in sealed cells containing a Pd-C catalyst and D2 gas where the helium increase exceeded the amount of helium-4 in room air [39]. There are a number of other reports of helium4 production in Pd/D systems [3], including those of Gozzi in Italy [40], DeNinno in Italy [40], and Arata in Japan [41]. 

Bush, B.F., Lagowski, J.J., Miles, M.H. and Ostrom, G.S. (1991) Helium production during the electrolysis of DjO in cold fusion experiments. Journal of Electroanalytical Chemistry, 304, 271-278. 

MUes, M.H., Hollins, R.A., Bush, B.F. et al. (1993) Correlation of excess enthalpy and helium production during DjO and HjO electrolysis using palladium cathodes. Journal of Electroanalytical Chemistry, 346, 99-117. 

Helium embrittlement is another structural material damage mechanism. Helium is produced in (n,a ) reactions. Trace quantities of boron and nitrogen in structural materials can make a significant contribution to the helium production. Consideration must also be given to (n,a) reactions in isotopes which are formed as a consequence of irradiation for example Ni-58 (n,y) Ni-59 (n,a)... 

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