fallsfromtrees wrote:In the thirties, the primary source of Helium was gas wells in Texas, and the US wouldn't sell to Germany, so the Hindenberg was forced to use Hydrogen, and hence its destruction at Lakehurst.
I don't know how the Helium was separated out, but it may have been a simple mechanical process.
Helium is extracted from natural gas by a process of liquifying the other gases, which liquify at temperatures higher than that of helium, and recovering the helium in gaseous form (cryogenic process). Basically, this process consisted of compressing and cooling the natural gas as it came in from the pipeline. Hydrocarbons, oxygen, and nitrogen condense under the alternate compression and refrigeration, and can be removed. Carbon dioxide is removed when limewater is sprayed into the incoming gas. The helium that remains as a gas is not affected by the compression and refrigeration that liquifies the other gases, and can be recovered and stored in high-pressure cylinders.
First, the process required removal of carbon dioxide (C02) that made up about 0.7 percent of the intake gas in the CO2 removal units. Carbon dioxide, if not removed, solidified during the super cooling process and plugged the apparatus at less than 600 pounds of pressure per square inch (psi), so the feed gas was scrubbed with a 7 percent solution of caustic soda in the extended system of steel tubing. Water vapor and some hydrocarbons accumulated in this process, but they were removed in the first section of the heat interchangers, also known as heat exchangers, where the gas was then fed.
The remaining gas was sent through the cryogenic process to liquefy all ofthe gases except helium (and traces of nitrogen and neon) to reach 98.2 percent purity. Helium will not liquefy until about minus 452° F, only seven degrees above absolute zero at about minus 459° F. Nitrogen liquefies at about minus 312° F; however, at this early juncture some traces of nitrogen remained in the helium processing technology. Before liquefying the nitrogen, the raw gas entering the plant was run countercurrent and then cooled by residual gas leaving the system after the helium had been removed. Hydrocarbons and most of the nitrogen were removed in this process of liquefaction. These residue gases then returned to the heat interchangers and were vaporized at room temperature, and then passed out of the plant as residue gas, which was sent by pipeline to other locations as fuel. At this stage, the remaining helium-nitrogen mixture (with traces of neon) was "crude helium," or a gas mixture that contained about 50 percent helium. The nitrogen from the initial liquefying process went to the nitrogen interchangers to be used in the cryogenic helium purifying process.
After the first cooling stage, the crude helium was compressed and then sent through a second series of heat exchangers. The crude helium then went to the purifier, or a container, which was surrounded by liquid nitrogen, liquefied by the aid of expander engines in an auxiliary system. In this purification process container, the temperature dropped to approximately minus 312° F under about 2,500 psi. Virtually all of the remaining nitrogen in the crude helium was liquefied and siphoned off, some of which was recovered to be used again to super cool the incoming crude helium. At about 98 percent purity, the processed helium was the highest grade of helium produced in quantity prior to World War II. It was then warmed to atmospheric temperature through interchangers and sent to railroad tank cars and small steel cylinders for transportation.
