How should a liquid nitrogen unit be designed to serve as a source for instrument air and purge gas?
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There is a small unit with a limited number of instruments; no compressor unit (instrument air) is planned to be installed, and liquid nitrogen will be used instead. But I haven’t designed this before; I would like some advice on how to design it, especially regarding how to achieve vaporization and what to do with the high pressure of the instrument air, as well as how to control it! ! Thank you!
Contact the liquid nitrogen manufacturer; they might be able to provide a complete set. You just need to specify the requirements – the volume of gas and the pressure – and they’ll prepare everything for you, right?/
By the way, you still need to perform purging, right? Then you’ll have to calculate the purging time, the amount of gas used for purging, the capacity of the tank used in each operation, as well as the fact that the purging pressure is different from the pressure required for the instruments
Reply to 2# 100baomihua Thank you! ! The control is handled by the manufacturer@@@
Reply to 4# yechenlin1818: Of course, that’s possible. But you need to explain the situation in detail and clarify your requirements
This post was last edited by wl0302 on 2011-2-14 at 13:38. It’s better to use compressed air; in environments with poor ventilation, nitrogen leaks can be fatal due to asphyxiation
If liquefied nitrogen is used, the cost will increase as well; it’s definitely higher than that of compressors
Liquid nitrogen can only be used as instrument air in case of an accident; under normal conditions, air must be used.
For example, in the case of a gas storage tank with a capacity of 30 cubic meters, plus the pipes and air heat exchanger coils, the total volume is 31 cubic meters. To maintain a pressure of 8 kilograms at an atmospheric temperature of 20 degrees, it’s possible to calculate how much liquid nitrogen is needed to achieve this pressure. A flow meter is required to measure the amount of gas used, and the flow rate of liquid nitrogen is determined based on the temperature and pressure values; this value is then used as input for the variable-frequency piston pump to keep the pressure in the storage tank constant. The next step is to calculate the area of the air heat exchanger, so that the liquid nitrogen can be vaporized and heated to a temperature close to that of the surrounding environment. There should be a certain margin of safety, and an axial flow fan can be used to blow air over the heat exchanger coils to prevent frosting. Of course, a safety valve is also necessary to prevent overpressure. . . Is this okay?