Liquid Nitrogen?

Question

Can LN2 be kept in a pressurized system and maintain liquid form indefinitely or for a long time? How long? Would pressure build if it was in a sealed pressurized system absorbing heat? Can you use a pressure release valve to maintain a certain pressure and slow the process of LN2 becoming Hydrogen? How long would it take for 1 litre of LN2 to become gas in a open system? How long in a pressurized system with a release valve? If you used LN2 to absorb heat can you slow it from becoming a gas without a compressor?

Thanks in advance.

"Can you use a pressure release valve to maintain a certain pressure and slow the process of LN2 becoming Hydrogen?" sorry I meant Nitrogen gas, not Hydrogen.

Answer 1

In practice, no. The dewar flasks used to contain cryogenic liquids are made of glass containing a vacuum. They are designed to minimize heat transfer, not to withstand pressure. They always have a relief valve so the pressure does not build up.

The best way to maximize the lifetime of a supply of liquid nitrogen is to use a high quality dewar flask, minimize the number of openings, and keep a large quantity. I doubt anyone bothers with special effort to regenerate it locally, since it's cheaper to just buy more. It's economical to produce in large quantity.

Answer 2

Nitrogen, like LNG (Liquefied Natural Gas) can be maintained at just above atmospheric pressure in specially insulated storage vessels for as long as needed..some small losses are incurred due to some boil-off depending on how long they are stored for.

The boil-off maintains the liquid state (-196°C for nitrogen and -150°C for LNG).
The boil off of N2 goes to atmosphere by pressure regulation, the LNG boil off goes to a fuel or flare system also by pressure regulation. Pressure relief valves are also fitted set at about 1½ times the operating pressure.