Liquid Nitrogen Storage and Distribution

[EmmanuelTop]

Greetings from Equatorial Guinea,

I need some information about liquid Nitrogen systems - particularly the details about liquid Nitrogen storage conditions (pressure, temperature) and connection with the existing (gaseous) Nitrogen distribution system. Some tips on liquid Nitrogen storage tank and vaporizer design would be very much appreciated.

We are planning to purchase Nitrogen liquefaction skid and provide storage tank for cryogenic liquid, that will be used for equipment purging during plant shutdowns. The plant operates 3 PSA units for Nitrogen production which is sufficient for normal operation, but the available quantity of Nitrogen is not sufficient for purging during plant S/D - or better to say it causes very extended purging time which causes loss of production. On the other hand, during normal operation PSA units always have an extra/unused Nitrogen production capacity, and our idea was to take this extra production of N2, liquefy it, store it and keep it under cryogenic conditions so as to have a separate supply of N2 when the plant is shutdown. This would reduce the timeframe required for equipment purge due to availability of higher quantities of N2.

What are the "usual" liquid N2 storage conditions, and how this system is connected with the existing (PSA discharge) plant Nitrogen distribution system? Also, is there any recommended manufacturer of these skids?

Best regards,

 

[Compositepro]

I would suggest that you get a truckload of liquid nitrogen when you need extra nitrogen for shutdowns.

 

[EmmanuelTop]

That is not possible. The plant is in remote location
(Bioko Island) and there's no external supply of Nitrogen. As a matter of fact, there is nothing on this island...

 

[unclesyd]

Ask your supplier to set setup storage facilities at your site. We did this for years where the supplier installed and maintained the storage tanks on our site. All our tanks had self contained vaporizers, air, the size was based on our demand for particular N2 flow.

Here is some literature from Taylor Wharton on their tanks which are very similar to most LN2 storage tanks. Again you supplier should provide all this information.

http://www.taylorwharton.com/assets...Storage_Tanks_-_1500_through_15000_gallon.pdf

http://www.taylorwharton.com/default.aspx?pageid=113

 

[MJCronin]

Emmanuel...

For chemical plants in most developed areas, Nitrogen is contracted out as a utility service. PRAXAIR and AIR LIQUIDE are major players in this area.

These firms will install "islands of equipment" (including tanks vaporizers and metering equipment)for compressed gaseous supply to the plant's distribution system. Contracts are typically multi-year.

Process plant owners like this arangemnent because 1) costs are competitive and well known 2) equipment maintenance is by others 3) there are financial penalties for service interuptions.

Your situation seems geographically unique....

Who is it that will supply the liquid nitrogen, but does not offer the rest of the system as part of the contract ?

Is there some type of secret process involved that puts you in such a remote location and makes nitrogen delivery difficult ?

My thoughts only....

-MJC

 

[EmmanuelTop]

MJC,

There's no company in the vicinity of Bioko Island that can supply us with liquid N2. Our idea is to process excess N2 production from PSA units, liquefy it, store it, and use it when required (plant shutdown).

Looking from that point of view, what we do need is:

- N2 liquefaction and storage system, at pressure slightly higher than the existing gaseous N2 distribution system (8.5 barg)
- Vaporizer

How the boil-off vapors from LN2 storage tank are usually handled? Recycled to liquefaction package, or vented to atmosphere?

Thanks,

 

[mbt22]

How much nitrogen do you need? Would a compressor and higher pressure gas storage vessel be a more economical option than a liquefaction plant?

An LP liquid store feels somewhat safer than an HP reservoir, but I would think things would even out once you factor in the complexity of liquefaction and higher risk of something going wrong.

Matt

 

[StoneCold]

EmanualTop
I think that compressing N2 and storing it at high pressure would be an easier operation than liquification.
But I did think of something else. What if you used combustion exhaust. It would have a low O2 content and you could create it and compress it at will. Maybe someone else will shoot this down, who actually knows something about it, but on the surface it seems like a good way to produce a large stream of lean O2 gas for purging.

Regards
StoneCold

 

[Compositepro]

Inert gas generators that burn natural gas or propane to produce low oxygen gas have been round a long time. Can your process tolerate CO2 mixed with nitrogen?

 

[EmmanuelTop]

It's an LNG complex consisting of Amine unit, Mol Sieve dehydration unit, and the Liquefaction Unit (ConocoPhillips optimized cascade process).

 

[abcmex]

To liquify and store N2 is a feasible task. If you want to design it yourself, well good luck.

If you want a straigth forward solution perhaps you should contact the usual suspects in the liquid nitrogen scene (Liquid Air, Praxair, Linde ect). they have standarized solutions which can be adapted for operation around the world.

There are two decisive informations that are still missing from you:
how much Nitrogen do you need (Nm3/h and duration in hours)?
how many times a year does this event happend?

perhaps you need nitrogen gas membran based generator

http://www.domnickhunter.com/news/351

rgs

 

[ZGZtanker]

Another possible supplier:

http://www.oxymat.dk/

Best regards

 

[drsmiranda]

Another possible supplier:

http://www.sysadvance.com

Best regards

 

[dcasto]

google portable LIN plants and you get this

http://pacificconsolidatedindustries.com/index.php?option=com_content&view=article&id=122&Itemid=158