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From Wikipedia

Air separation

An air separation plant separates atmospheric air into its primary components, typically nitrogen and oxygen sometimes also argon and rarely other inert gases. There are various technologies that are used for the separation process, the most common is via cryogenic distillation. This process was pioneered by Dr. Carl von Linde in the early 20th century and is still used today to produce high purity gases. In addition to the cryogenic distillation method there are other methods such as Membrane, Pressure Swing Adsorption (PSA) and Vacuum Pressure Swing Adsorption (VPSA), which are typically used to separate a single component, such as oxygen, from ordinary air.

The Cryogenic Process

The separation of air into its constituent parts at high purity requires a cryogenicdistillation process. To achieve the low distillation temperatures a modern Air Separation Unit requires a refrigeration cycle, and the cold equipment has to be kept within an insulated enclosure (commonly called a "cold box"). The cooling of the gases requires a large amount of energy to drive an air compressor to make this refrigeration cycle work. The air also has to be "clean" enough for cryogenic distillation, since water and carbon dioxide as well as other minor constituents of air can freeze in the cryogenic equipment.

The process has the following main features:


Atmospheric air is pre-filtered (to remove dust), and compressed to a pressure typically between 5 and 10 bar. Since the compressor heats up the air, it is cooled again in a heat exchanger to ambient temperatures. This can also achieve the removal of some ambient moisture.


The process air is generally passed through a molecular sieve bed, which removes any remaining water vapour, as well as carbon dioxide, which would freeze in the cryogenic equipment. The molecular sieve is often designed to remove any gaseous hydrocarbons from the air, since these can be a problem in the subsequent air distillation.

Cooling & Distillation

Process air is passed through an integrated heat exchanger (usually a plate fin heat exchanger) and cooled against product (and waste) cryogenic streams. The air is then cool enough to be distilled in a distillation column. The formation of liquid air in the cryogenic equipment requires some refrigeration and liquid is usually formed by Joule Thomson expansion of air across a valve or through an Expander, (a reverse compressor). The air is distilled in at least one and often two distillation columns, depending on the products required. Cryogenic air separation units are built to provide one or both of nitrogen and oxygen although argon is also often produced. Liquid nitrogen "LIN", Liquid oxygen "LOX" and liquid argon can be produced if sufficient refrigeration is provided for in the design. Finally the product gases are warmed against the incoming air to ambient temperatures.

Product supply and storage

The air gases are sometimes supplied by pipeline to large industrial users adjacent to or nearby to the production plant or stored as liquid. Unless a viable pipeline system exists, long distance transportation of products is usually done as a liquid product for large quantities or as dewar flasks or gas cylinders for small quantities.

In addition to oxygen, nitrogen and argon; rarely other gas products may be produced - the only viable sources of neon, krypton and xenon are from the distillation of air.

From Yahoo Answers


Answers:1. the air will have to be made into a liquid through cooling and compression 2. the liquid is put into a conical flask (which is attached to the fractionating column) and heated 3. when the boiling point of oxygen (or nitrogen, whichever has the lower boiling point) is attained, the the oxgyen vapours will rise up and pass through the fractionating column 4. the vapoours will travel through the condenser next, and the cool, circulating water surrounding the condenser will cause the vapours to become liquid again 5. now that liquid is collected. 6. in the same way, the other gas is collected make sure you know the boiling points of nitrogen and oxygen. whichever has the lower bp. will be distilled across first.

Question:What is the chemical and physical difference between liquid nitrogen and nitrogen? And how would one go about converting one to another?

Answers:Chemical difference ...None. Physical difference...A liquid separated from liquefied air at -196 C. Vaporises (Boils Off) to its natural gaseous state at this temperature and Atmospheric pressure. It soon gains the temperature of the atmosphere as a gas while the liquid stays at -196 C while boiling.. Very briefly, the Liquefaction of Air process requires the Compression and Cooling of Clean, dry air by a series of these processes until the air changes to liquid at its Critical Temperature and Pressure of -149 C and 35 atm. The liquid air is then Fractionally Distilled to separate Nitrogen at -196 C and Oxygen at -183 C, at atmospheric pressure. The other gases contained in the atmosphere can also be separated in this way as required.

Question:Combustion of a 2.18 g sample burns in excess oxygen yields 3.94 g of CO2 and 1.89 g of H2O. A separate experiment shows that a 1.23 g sample contains 0.235 g of N. Calculate the moles of C in the sample. [Please explain the process. Best Answer AND Explaination will get Best Answer.]

Answers:moles CO2 = 3.94 g / 44.009 g/mol=0.0895 mass C = 0.0895 x 12.011 g/mol=1.07 g moles H = 1.89 x 2 / 18.02 g/mol=0.210 mass H = 0.210 x 1.008 g/mol=0.212 g mass N in 2.18 g = 0.235 x 2.18/ 1.23 =0.417 g moles N = 0.417 / 14.0067 g/mol= 0.0297 mass O = 2.18 - ( 1.07 + 0.212 + 0.417)=0.481 g moles O = 0.481 g / 15.999 g/mol=0.0301 C 0.0895 H 0.210 N 0.0297 O 0.0301 divide by the smallest C3 H 7 N O = empirical formula

Question:a, both gases have too low of solubility's b, fractional dis. won't work any time. c, their boiling points are too far below room temp d, their densities are almost the same as room air PLEASE HELP! Why c as the answer? I meant nitrogen and oxygen from air :)

Answers:Correct answer: c (boiling points are too low) a: As you know nitrogen and oxygen mix with each other freely. Air is a homogeneous mixture, isn't it? Both gases are soluble in each other without any problem. Also think about whether solubility is a requirement for distillation in the first place? b: This is a nonsense sentence. c: Have you ever seen air condensing? Water can condense from moist air, but the air itself? Is air consensing in a deep freezer? No. You see that the temperature to condense air must be really, really low. Interestingly enough, air actually is distilled at very low temperatures to gain noble gases and to separate nitrogen and oxygen. d: What has density to do with destillation? Nothing. Generally, even if you do not know the answer to such a question, try to think about which properties have to do with the title question at all. In this case solubility and density are just independent and b) is pure non-sense.

From Youtube

HVAC Oxygen, Acetylene and Nitrogen tanks and Regulators :I demonstrate how to hook-up the regulators on an oxygen, acetylene and nitrogen tanks to get them ready to braze. The guy in my intro that wears the pink shirt and wig is edbassmaster. You can check him out at: www.youtube.com The music was played and composed by Champagne Millionaire. You can check him out at: profile.myspace.com