Saturday, December 20, 2014

Abcs Of Oxygen For Energy

By Lucia Weeks


Elemental oxygen occurs predominantly in form of a covalent homodimer on, that is a compound of two O2 atoms and having the empirical formula O2, referred to as molecular oxygen or dioxygen. There is a colorless and odorless gas that is contained in air to 20.942%. It is involved in many combustion and corrosion processes (oxygen for energy).

Almost all living organisms need O2 to live (typically give plants during photosynthesis but more O2 from than they consume). You see him mostly by breathing in air, or by absorption of water (dissolved oxygen). In high concentrations, however, it is toxic to most living things.The metastable, high-energy and reactive allotrope of three O2 atoms (O3) is called ozone. Atomic oxygen, ie O2 in form of free, single O2 atoms, is stable before only under extreme conditions, such as in vacuum of space or in hot stellar atmospheres. However, it has a significant meaning as a reactive intermediate in many reactions of atmospheric chemistry.

Oxygen is not created in primordial nucleosynthesis, but is produced in relatively large amounts in giant stars by helium burning. It is first formed from three helium nuclei 12C (Triple-alpha process), which subsequently merged with another helium nucleus to 16O. 18O is formed by fusion of 4He with a 14N nucleus.

Even in so-called main sequence stars like the sun plays a role in energy oxygen. In CNO cycle (CNO cycle) represents O2 is an intermediate of nuclear reaction in which proton capture by a 12C nucleus, which acts as a catalyst, a 4He nucleus (alpha particle) is produced. In extremely heavy stars occurs in late stage of their development to O2 burning, in which the O2 is used as nuclear fuel for reactions that lead to construction of even heavier nuclei.

With the discovery of O2 its meaning was not clear during combustion. The Frenchman Antoine Lavoisier found in his experiments that during combustion does not escape phlogiston, but O2 is bound. By weighing it demonstrated that a substance after combustion was not easier but harder. This was caused by the additional weight of ingested during the combustion process oxygen.

For O2 recovery after Claude process air by means of compressors to 5-6 bar is compressed, cooled and then removed by first filter of carbon dioxide, humidity, and other gases. The compressed air is cooled by flowing past gases from the process to a temperature near the boiling point. It is then expanded in turbines. A portion of energy used for compression can again be recovered. This is the method -. In contrast to Linde process, in which no energy is recovered - a lot more efficient.

The actual separation of nitrogen and O2 by distillation in two distillation columns with different pressures. The distillation is carried out in counter-current principle, that is by the condensation heat of evaporated gas flows upward, condensed liquid drips down. Since O2 has a higher boiling point than nitrogen, it condenses readily and collects at the bottom so, nitrogen at the top of column.

The separation takes place initially at 5-6 bar in so-called medium pressure column. The resulting oxygen-enriched liquid is then (pressure about 0.5 bar) further separated in low pressure column. Through the liquid O2 of low pressure column, gaseous nitrogen of high pressure column is passed. It liquefies this and heated with the votes condensation heat the liquid. The more volatile nitrogen is discharged and preferably remains purified liquid oxygen. This still contains the noble gases krypton and xenon, which are separated in a separate column.




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