Nitrogen supply 1

[supers0nic]

Greetings from Argentina!

My client needs a high purity Nitrogen supply (99.9% or even more). Under normal operation the consumption is less than 10 Nm3/h (5.9 SCFM). Nitrogen needs to be delivered at P=12bar and amb. Temp. Nitrogen Cylinders will be used. I found this type of cylinder:

http://www.praxairdirect.com/PXItem...8&top_category=11502&parent_category_rn=11502

Anybody knows how the pressure in this type of cylinders are regulated? I found some information in the Air Liquide page but I didn't found any detailed information.

When my client's plant shut-downs for maintenance, nitrogen consumption increase up to 100 Nm3/h (59 SCFM). A total volume of 1000 Nm3 (590 SCF) is needed and will be consumed in one week. My idea was to provide this volume by a truck but I'm not sure if it's the best option. As an option Praxair offers a bulk and micro-bulk (on-site storage) to deliver. Any thoughts?

If nitrogen would be provided by truck...I understand that the trailer carries the nitrogen in liquid state. To deliver the Nitrogen in gas state a pumping+evaporator system (provided by the Supplier). Does anybody knows at which conditions (T & P) is the nitrogen finally delivered in gas state? Do I have to include a pressure control valve to maintain the pressure steady for my consumptions? Or does the trailer system maintain the pressure steady (PCV or by other means)?

Thanks in Advance
supers0nic

 

[byronius]

The bottle does not do any of the regulating. It is simply a dumb vessel that is filled and emptied.

The pressure is normally regulated by common pressure reducing regulators that you provide. You can find them from all of the normal regulator providers (Swagelok, Tescom, etc.). I'm sure Praxair has a regulator they are willing to provide with the bottles. I have found the bottle suppliers are normally willing to create panels with mounted instruments/valves to ease usage of their bottles.

The main item of interest is the connection to the N2 cylinders will be a CGA 580 (as called out on their spec sheet there). This is a specific fitting to prevent connections between different types of bottles. In the past when I have used bottles for process connections, I ordered a high pressure stainless steel hose with that CGA 580 fitting welded on one end and normal NPT or flanges on the other. After that, you can connect to whatever you want. You can also get a regulator that mounts directly onto the bottle like what you see in a laboratory. With an inlet and outlet gauge on it, it looks like Mickey Mouse's face. You could also connect to a normal pressure control valve with a high enough pressure rating.

If you need greater volumes, you can go with a 6 or 12 pack which is a combination of bottles mounted together on a steel frame. They are usually joined on the frame with a common manifold and a single outlet. Each bottle has it's own valve though so you can use them one at a time or all lined up at once. This is easily moved with a fork truck if needed. The frame is normally on casters though so it will roll.

If that is not enough volume, you can then move onto a tube trailer. A tube trailer is a trailer made of a number of larger bottles mounted to a rig. Those are still provided as a gas at the same pressures as these bottles. Again, the tube trailer has bottles that are connected and you supply the regulator. The trailer is dropped off and then it's yours to use like the bottles.

If you need even more than that, then you can go to a liquid nitrogen setup on a truck with a heater. When I have done this, you normally give the desired N2 conditions to the supplier and they provide the pressure and temperature control. You will also need a relief valve to protect your equipment. I have seen them provided by the truck also. Bringing in a pumper truck is common practice but not a small deal. Their heater normally involves an open flame and obviously high temperatures. It should be treated with a great deal of respect. They normally also require full time supervision/operation (provided by the supplier).

I always preferred bottles and tube trailers if I could get away with them.

 

[byronius]

Here is an example of a H2 6 pack. They can do it with N2 too (at least in Houston):

http://www.praxairdirect.com/PXItem...Id=11531&langId=-1&storeId=10152&itemID=66809

Here is a tube trailer although it's not obvious what gas that is:

http://www.fibacanning.com/images/dcp_2721.jpg

 

[supers0nic]

wallbyron thank you very much! really useful information!

Do you have a link/PDF with the capacities of the tube trailers? Just to estimate the threshold capacity between the cylinder pack and the tube trailer.

 

[racookpe1978]

If nitrogen would be provided by truck...I understand that the trailer carries the nitrogen in liquid state. To deliver the Nitrogen in gas state a pumping+evaporator system (provided by the Supplier). Does anybody knows at which conditions (T & P) is the nitrogen finally delivered in gas state? Do I have to include a pressure control valve to maintain the pressure steady for my consumptions? Or does the trailer system maintain the pressure steady (PCV or by other means)?

The nitrogen you get out of the pressure regulator will be dry, clean 9per your spec to the supplier) and at a steady pressure as long as the supply is hooked up. For example we hook up GTAW welding machines to a liquid (cryo) Ar tank all the time. After the regulator at the top of the tank, the Ar gets to the welder at a constant pressure, is at near room temperature, and is at the regulated pressure until the cryo bottle goes empty.

So plan a way to exchange the source bottles (cryo container or multiple N2 bank) WITHOUT disconnecting the whole supply set at one time. unless you can completely turn off the N2 at any time (ops or maintenance or shutdown) for a short time.

 

[byronius]

This is what I get from Google when searching for "n2 tube trailer capacity".

http://www.us.airliquidehealthcare.com/wp-content/pdf/gas.pdf