Systems and methods are provided for recovering helium from a feed comprising helium, carbon dioxide, and at least one of nitrogen and methane. The feed is separated in a first separator to form helium-enriched stream and a CO.sub.2-enriched stream. The helium-enriched stream is separated in a pressure swing adsorption unit to form a helium-rich product stream and a helium-lean stream. At least a portion of the helium-lean stream is recycled to the first separator with the feed. In some embodiments, a membrane separation unit is used to enhance helium recovery.

A system and method for removing nitrogen and producing a high pressure methane product stream from natural gas feed streams having wide variations in nitrogen and methane content are disclosed. Optional add-on systems may be incorporated into the nitrogen and methane separation to produce an NGL sales stream to reduce excess hydrocarbons in the nitrogen vent stream, or to recover helium. The system and method of the invention are particularly suitable for use with feed streams in excess of 50 MMSCFD and up to 300 MMSCFD and containing up to 100 ppm carbon dioxide. Typical power requirements for compressing the methane product stream to produce a suitably high pressure stream for sale are reduced according to the systems and methods of the invention.

An apparatus and method for mitigating the shock front of a rocket or aerospace plane flying at hypersonic speeds while simultaneously distilling liquid chemical elements from the ambient air. The ensuing supercool/chilled air that is rendered as a consequence of supercooling may hence be compressed, regeneratively intercooled & flashed into liquid air. By means of extension, liquid air may be rendered as a direct result of said supercooling throughout the hypersonic regime into space. Also described are the details of an isentropically expanded hypersonic stochastic switch (a singularity), which is mainly achieved via the addition of a high pressure supersonic isentropic expansion nozzle whereby a continuous flow continuum is transformed into a stochastic flux.

Disclosed is a method for purifying a main gas, in particular helium, from a source gas stream comprising the main gas, a main impurity, in particular nitrogen, and optionally another, secondary impurity, in particular oxygen, the method comprising a step of partial condensation of the gas stream in order to extract therefrom impurities in liquid form, in particular the main impurity, and to produce a gas stream enriched with main gas, characterized in that the method comprises, before the partial condensation step, a step of injecting into the gas stream a compound in which the main impurity of the gas to be treated is soluble and having a saturation vapor pressure lower than the saturation vapor pressure of the main impurity.

The present invention relates to a cryogenic process to produce crude helium from pretreated natural gas. The pretreated natural gas is processed in two flash stages using the helium free process stream as a stripping agent, and a distillation column with the identified operating conditions and process scheme to ensure 100% helium recovery with reduced capital and operating cost for producing the crude helium. The integration of the cryogenic process with the already known purification system to produce pure helium is demonstrated to ensure high helium recovery in a hybrid process.