Helium Separation Systems

The separation of helium-rich natural gas provides most of the helium used in the U.S. The Bureau of Mines has acted as the agent for the Federal government under the Helium Act of 1947 for the recovery, distribution, and sale of helium because of its importance in missile and space-vehicle applications. This recovery has been augmented in more recent times by a number of industrial process plants. 

The crude helium is purified by compressing the gas to 18.7 MPa, cooling it with the outgoing helium gas, and then sending it to another nitrogenrefrigerated condenser-evaporator or separator. This condenser removes most 

A two-step process is generally used in the laboratory to separate He from He. Because of the small amount of He in a helium gas mixture (ratios 

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Some experimental results for the helium-xenon system are shown in Fig. 25. (The critical temperature of xenon is 16.6°C.) At temperatures several degrees above the critical of xenon, the two phase-compositions are significantly different even at pressures as low as 200 atm. However, to obtain the same degree of separation at higher temperatures, much higher pressures are required. 

Liquid/gaseous detoxification systems, based on hydrogen peroxide, 14 64-65 Liquid-gas separator system, in sulfonation systems, 23 552 Liquid halogen fluorides, 13 128 Liquid heat-transfer media, 12 83 Liquid helium... 

Since helium and neon have boiling points considerably below that of nitrogen, these gases will collect on the nitrogen side of the condenser-reboiler associated with the double-column air separation system. Recovery of these gases is accomplished by periodic venting of a small portion of the gas from the dome of the condenser and transfer to a small condenser-rectifier refrigerated with... 

Microwave absorption measurements were made with a Bruker ER300 ESR spectrometer operated with 100 kHz magnetic field modulation where the derivative of the absorption part of the magnetic susceptibility with respect to magnetic field was detected (dx VdH). Temperature was varied with an Oxford Instruments ESR 900 helium flow system from room temperature to about 6 K. The temperature at the sample position in the flow dewar was calibrated with a separate thermocouple and found to be 2-3 K higher than the Instrumental... 

Excellent performance of the hot gas ducting, of the turbomachinery cooling, of the helium purification system (except the oil aerosole separation), and of the instrumentation and regulation. 

In summary, to obtain similar thermod5mamic efficiency, it appears that nitrogen-based systems will have somewhere around 40% larger volume than helium-based systems. Their capital cost will be higher because of the less optimal thermodynamic properties of nitrogen compared with helium. However, the nitrogen-based Brayton cycle is expected to be less expensive than the equivalent Rankine steam cycle because of the low-pressure steam components and the moisture separator components required for the Rankine cycle. 

Total loss of power supply Evacuation of water entered in the primary system by the water separator of the helium purification system (L)... 

Figure 1.5 Applications of membrane systems. (Source Prism Gas Separation Systems, Monsanto Chemical Co., St. Louis, MO Air Products and Chemicals, Inc., Allentown, PA.) Gaseous components and systems include argon, helium, hydrogen, carbon monoxide/syngas, nitrogen, oxygen, CO,-removal, H,S-removal, dehydration. Capacity for nitrogen recovery is up to 35,000 SCF/hr for 97% purity, and about one-tenth of this for 99+% purity.

A mass spectrometer ionises all gas particles by means of electrons emitted from an incandescent filament. In a next step helium ions are filtered by a (magnetic or electric) separation system and are fed to an ion collector, which is coimected to a sensitive current amplifier that can measure and indicate the extremely tiny electrical current. 

As already discussed above, an ion-separating system (ion spectrometer) is needed for the mass spectrometric detection of helium, which requires high vacuum condition. These systems operate at a total pressure of less than 10 mbar. 

In order to gain some understanding of the nature of the many-body problem in atoms and molecules, let us consider an array of well-separated systems, a Unear array of helium atoms, for example. By weU-separated we mean that the systems are not interacting. For simplicity, let us begin by considering just two weU-separated systems. The total Hamiltonian operator for the supersystem may be written... 

After a double-column air-separation system has been in continuous operation over long periods of time, the effectiveness of the heat transfer in the condenser-reboiler is observed to decrease. This is attributed to the gradual accumulation of neon and helium in the nitrogen, which lowers the partial pressure of the nitrogen so that it will not condense at the condenser design temperature. This problem can be solved by periodically venting some of the accumulated gas from the dome of the condenser either to the atmosphere or to a neon-separation system. 

Fig. 6.33. Neon-recovery subsystem. Crude neon and helium are recovered from the dome of the lower-column condenser in a double-column air separation system.

Helium and Natural-Gas Systems Separation Helium is produced primarily by separation of hehum-rich natural gas. The hemim content of the natural gas from plants operated by the U.S. Bureau of Mines normally has varied from 1 to 2 percent while the nitrogen content of the natural gas has varied from 12 to 80 percent. The remainder of the natural gas is methane, ethane, and heavier hydrocarbons. 

A Bureau of Mines system for the separation of hehum from natural gas is shown in Fig. 11-119. Since the major constituents of natural gas have boiling points very much different from that of helium, a distillation column is not necessary and the separation can be accomphshed with condenser-evaporators. 

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