7 replies to this topic

[nes13ta]

Hello Gents,

 

The company assigned me to a job where we should store 25% Ammonuim hydroxide in a tank.

 

The tank is SS made and 17.5 cu.mtr. volume. Knowing that Ammonuim hydroxide is brought to our site 

 

in IBC containers and then it should be stored in this tank to be pumped to other tanks to avoid manual 

 

dosing (the way of dosing used currently).

 

The tank operation pressure is  atmospheric pressure. It is served with cooling coil. However, we do not have experience in storing ammonia.

 

So at what conditions ammonia should be kept and what is recommended to avoid lost of vapor and to protect the tank during in/out breathing  .

 

 

Many thanks..

[breizh]

http://www.airgasspe...TechManual.aspx

 

Consider this resource , point 4

 

hope this helps

 

Breizh

[latexman]

And this one:

 

http://www.rmtech.ne...qua Ammonia.htm

 

It lists and shows typical installations that will answer your general questions.

[nes13ta]

Thanks all,

 

But that seems it concerns in transporting ammonia more than store it in our plant.

 

Any operational views? Can be more helpful..

 

We agreed that ammonia should be kept in a cool and tightly closed container. However, would not that affected by charging/discharging ammonia to/from the tank.

 

i.e. how the pressure can be maintained while transporting ammonia , would a pressure relief valve does the job.

 

Knowing that the tank pressure rating is atmospheric pressure .

 

Thank !

[latexman]

Storage and handling is covered - http://www.rmtech.ne...information.htm , but you should realize, most aqueous ammonia storage tanks are not cooled in my experience.  Notice the reference recommends a minimum MAWP of 30 psig for un-cooled aqueous ammonia tanks.

 

It sounds like you will use an existing "atmospheric" storage tank, right?  Does it have any positive pressure rating at all?  If it truly is "name plated" at atmospheric pressure, then how can it modified to a "tightly closed container"?  Any PVRV installed will result in exceeding atmospheric pressure during filling and out breathing.  If tank vapor recycle to iso tank is used, will the iso tank be cooled?  If not, it may arrive on site with a pressure well above atmospheric pressure.  Then, what to do?  Vent it down?  Will the air permit allow that?  To a treatment system?  Is one available?  If not, that's an expensive investment.

 

What temperature will the aqueous ammonia tank be maintained?  When the cooling system is under going maintenance (planned and unplanned), will temporary cooling be provided, will the tank temperature be allowed to be influenced by ambient, or will the aqueous ammonia tank be empty/emptied?  These scenarios need to be addressed by the design, because they will eventually occur.

[breizh]

http://www.google.co...iw=1081&bih=592

 

 

A few more resources 

Breizh

Edited by breizh, 15 April 2013 - 06:40 AM.

[nes13ta]

Dear latexman, Thanks for your helpful points 

 

 unfortunately there is no name  plate on the tank because we bought as a second hand.

 

No pressure test has been done so far on the tank so I consider it to be operated at atmospheric pressure .

 

Considering the tank to be tightly closed  was just an idea raised to solve the problem of ammonia vapor escape. How ever, long atmospheric vent can do the job, doesn't it?

 

Though, the air would be permitted to to get in/out. It is really affected by the ambient temperature 

and in summer it will reach the 50s C

 

The tank temperature would maintained at 25 C, hopefully. Chilled water is passing through the cooling coil all the time.

 

The tank would be normally filled with ammonia. 

[latexman]

Ammonia vapors are classified as TOXIC in my area.  An open, normal vent would not be allowed here.  Since I do not know the regulations in your area, I cannot really answer those questions.  Are you sure your design will be allowed by law there?

 

Besides that, would you want to be a chemical operator in a factory that releases toxic chemicals routinely into the air?  Would you want your son to be a chemical operator in a factory that releases toxic chemicals routinely into the air?  I would not.

 

The bottom line is, I would not use the tank as you have described so far in aqueous ammonia storage service.  A volatile liquid that evolves toxic vapors in an atmospheric tank?  No, no, no, no, no.  At 25C and 25% liquid, the equilibrium vapor is about 96% NH3.  There must be a better way!