how long to get up to pump up to fixed pressure

[danny200300]

I have a tank 40,000litres filled with nitrogen at 2.5mbar. I have a process that will pump more nitrogen into the system at 64 litres/min and 6bar.
I dont want the pressure to go much over 3mbar. So how long can i keep the pump running?
Can anyone point me in the right direction? I guess there must be regular calculations out there work out how long it would take to pump up to 6bar. I imagine the calculation may need a curve also for the compressibility of the gas. (non europeans : sorry for the units but you get the idea)

Thanks!

 

[TD2K]

I hope you have an engineer around your plant to review your calculations with. You sound like this is out of your field and you should not be doing this on your own.

I'll give you a general approach, you'll have to work through the math for your case as it's not clear whether your 64 litre/sec (for example) is at 6 bar pressure or normal conditions or some other set of conditions.

Work out how much N2 is in 40,000 litres at 2.5 mbar. Then work out how much N2 is needed to bring the tank up to 3 mbar. That gives you how much N2 to add.

How do you add N2 to the tank from the compressor (you use the term pump but pumps are used for liquid, not gas)? I'm concerned when you have a compressor putting out 6 bar into a tank running at a few mbar. Exactly how you are going to do this safely?

 

[danny200300]

Thanks for the concern. I am not on site with my hands on the 'compressor' . This is only conceptual ideas currently. Dont worry this kind of thing is checked and checked for years to come in Nuclear!

The idea is a small suction device (shaped like a gun) to suck up debris inside a vessel, done remotely. The vessel is kept at the low pressure. But the suction device would effectively be adding nitrogen to the vessel i.e. The device is rated at 64litres/min and 6bar.

So from your answer I would work out the additional mass of nitrogen to add, and as it will feed at 64litres per min I can work out that time! Thankyou sounds very logical to me.

From this we can see how long we can operate the device before the tank pressure increases too much.