Gas separation

As gas separation , the technique is called, various gases, for example by using membranes to separate or due to their physical properties (boiling point / mass).

Linde process

In the Linde process , a gas mixture is pressurized, cooled and relaxed, and this often until the individual fractions liquefy, sorted according to their boiling point. The Linde process for gas liquefaction requires a positive Joule-Thomson coefficient . Gases such as He must be pre-cooled below the inversion temperature .

Membrane process

Here, gases are separated by membranes due to their size and / or their affinity . The purity that can be achieved with oxygen - nitrogen separation via membranes does not reach the purity of the cryogenic Linde process. If a lower purity or even only the enrichment of one component - for example oxygen in the breath - is sufficient, the membrane process represents an energy and cost-saving alternative. For example, a purity of 99.5% for nitrogen is often sufficient, and it is currently estimated 30% of the nitrogen requirement covered by the membrane technology. Membranes are also used in the separation of carbon dioxide and nitrogen / hydrogen . Membranes made of multiblock copolymers consisting of polyethylene glycol (PEG) and polyamide (PA) are easily and quickly permeable to carbon dioxide, while they have only a very low permeability to nitrogen and hydrogen. These recently developed membranes could be used in the so-called “emission-free power plant”.

Gas centrifuges

Gas centrifuges separate gases with the help of centripetal force based on their mass differences.

Gas chromatograph

In the gas chromatograph , gases from a sample are separated by absorption / desorption on a carrier material through which the gas flows, in order to be analyzed sequentially at the end of the column.

Pressure swing adsorption

Pressure swing adsorption (PSA - pressure swing adsoption) in a pair of pressure vessels with a granular molecular sieve as an adsorbent is used, for example, for air separation.

application areas

Fuel cell
Hydrogen separation for energy generation
Purification of biogases , landfill gases and natural gas (separation of CO ₂ ; H ₂ S and silanes )
Nitrogen oxide reduction through nitrogen enrichment (RWTH Aachen)
Membrane process: nitrogen generators , such as those used for the HPLC-MS coupling, work according to this principle.

literature

R. Prasad, F. Notaro, DR Journal of Membrane Science , 62, 225 (1994)