Liquid nitrogen (N2) represents itself transparent liquid, from slightly smaller, than at water, density. In this state nitrogen has exclusively low temperature (near – 196 degrees). How it is possible to receive liquid nitrogen?
Instruction
1. As liquid nitrogen at contact with air and heating very quickly evaporates, sharply increasing in volume, it is stored in special conditions: or in special low-temperature tanks, at elevated pressure, or in "vessels of the Dewar".
2. Now the cryogenic method, that is a way of deep cooling of air is used. It is applied as commercially, and in laboratory.
3. The key moment – obtaining very low temperatures necessary for air liquefaction. Here it is possible to use three methods: - Using the low-boiling liquids, at their evaporation, they absorb a large amount of heat at the expense of what air is strongly cooled. - By a drosselirovaniye (effect of Joule Thompson).-Putem adiabatic expansion of gas.
4. The first two methods are most widespread. When using of the low-boiling liquids, several coolants which are picked up so that liquefaction of one happened due to evaporation of another are consistently applied. The method is very effective, but is structurally difficult.
5. The second method demands preliminary strong compression of air (to 200 – 250 bars). It is widely used, despite low efficiency of such installations.