O2 Backup system

[HienN]

Hi all,

We got a new project that we will supply GO2 for a Steel factory. Our factory would be a PSA with the outlet pressure around 25barg.

Customer will use a regulator to regulate the pressure down to 15barg for their application.

Thing is, how is the O2 backup system would be to work at such a high pressure at 15barg? Could we store LO2 with high pressure?

Looking forward to hearing from your experience.

Regards,

Hien

 

[iainuts]

Liquid oxygen can be stored as a liquid below its critical pressure of roughly 49 barg, though I've never seen it stored at that high a pressure. It just isn't economical due to the cost of the tank and problems with filling it.

Typical storage tanks are much lower than that, around 10 to 17 barg, so they may not have sufficient pressure to handle a customer house line at 15 barg. You might also consider a high pressure LOX tank that handles up to around 27 barg, but these tanks require special pumps to fill them so they aren't always the best solution due to cost.

Another option is to have a low pressure storage tank and a liquid pump. This option is often less expensive than the high pressure tank option, but with lower reliability and lower flow capacity.

 

[dcasto]

Most cryogenic tanks I've seen are under 10 barg. Then the trailers that haul it are under 5 barg.

http://www.uigi.com/trailers.html

check out this link

 

[HienN]

Hi all,

Thank you for your useful posts.

I would describe that the oulet GO2 from the PSA is pressurized via a O2 Booster compressor then put into the Buffer tank.

We will also have the backup by storaging LO2. Where we should connect this pipeline to? At the inlet of booster compressor or after it?

I think it should better connect at the inlet of the booster one. But the manufacturer suggested at the outlet. I confirmed but their answer was a silence. God knows!

To reduce one more Booster compressor, I would like to know if I should do it at the inlet?

Is there any better solution to reduce more power for the backup?

Regards,

Hien

 

[iainuts]

Most cryogenic tanks I've seen are under 10 barg.

True, most low pressure tanks are 10 barg but "low pressure" tanks are also found up to 17 barg (250 psig) and can generally be filled without special pumps. They are also typically operated at well below that pressure, making the 15 barg requirement difficult to hit even with these tanks.

 

[iainuts]

To reduce one more Booster compressor, I would like to know if I should do it at the inlet?

Increasing pressure from a conventional low pressure LO2 storage tank to 15 barg using a booster compressor that is already part of your system sounds like a very easy and economical way to go. The only other method I could suggest is to use a reciprocating liquid oxygen pump such as sold by ACD or Cryostar. These pumps are generally lower in capital cost and use much less energy than an ambient temperature booster compressor.

 

[HienN]

Thank you,

This would be summarize as follows:
Use low pressure storage tank, then a reciprocating liquid oxygen pump.
One more problem is: When LO is stored in the tank. As a matter of fact, it would be brought from one of our factory. It would be a very pure LO while customer demand of LO purity is very low at 93%. If we supply by high purity LO, how to charge the customer?

The question comes up is:

1. How the backup system will look like?
2. If I use the liquid pump, do I need more booster compressor?

Although it is not my working range, but I am just so curious about.

It would be highly appreciate your help.

Regards,

Hien

 

[iainuts]

Hi HeinN,

2. If I use the liquid pump, do I need more booster compressor?

I think you have to determine what flow the customer needs, and if it varies, then can the flow be characterized? By that I mean, can you quantify the flow over time for a full period, whatever that cyclic period may be? Generally, we use a cyclic period of one week because most customers shut down over a weekend and if there's no usage, the gas must be either stored or vented.

With the information you have about the customer's usage pattern, you then need to determine how to supply this flow. Do you need to store substantial amounts of gas? Or can the flow be vented when not used because there is no economic advantage to storing?

To provide this gas, what system do you need to provide? Is it just a booster compressor? Or does it also need gas storage at a pressure higher than the customer's need so that variables in flow rate can be accomodated?

Once you calculate how much storage you need for any given compression apparatus, you can determine the most economical means of supplying that gas. I can't tell you what the best means is, that's something you need to determine.

 

[Gator]

You're going to need a high pressure ambient vaporizer for your LOX backup supply. See

http://www.uigi.com/vaporizers.html

 

[HienN]

Thank you all,

For my backup, I would use 02 storage tanks, and 02 liquid pumps, then 02 high pressure vaporizers supplying gas to my customer in emergency case.

I will soon be back here with new topics.

Regards,

Hien

 

[Gator]

I just hope you're going to be very careful with oxygen, especially high pressure! Some of the questions asked seem to be pretty basic (for example, I don't think anyone has mentioned suitable materials for oxygen service, adiabatic compression, special cleaning requirements, and the like), so you might want to hire an expert who has done this before.

Your type of project is usually done (or at least overseen) by the customer installations group of an industrial gas company such as Air Liquide, Praxair, etc. to avoid "unpleasant surprises" since such an event can ruin everyone's otherwise nice day.

 

[HienN]

Hi Gator,

Thank you for your valuable advices.

I have just registered this forum for a month. During the time, I recevied many useful things relating to engineering.

As in your words, special cares should be taken when working with Oxygen.

All the best,

Regards

Hien