6 replies to this topic

[populas]

Dear community,

 

I am struggling on the web to find a code or a norm stating officially how to choose the type of ammonia storage tank in function of the capacity required.

I have found some good reports saying roughly the following ;

• < 500 t : cylindrical tank under pressure --> pressurized storage
• between 500 and 3000 t : spherical tank under pressure --> semi-refrigerated tanks
• > 3000 t : storage at atmospheric pressure at a temperature of -33°C --> fully refrigerated storage in large tanks

Is there an API or EN code saying the same?

From your experience, do you agree with the above?

Why couldn't we build a big pressurised sphere for a 5000 t storage?

 

Thank you for your help

[Art Montemayor]

Populas:

 

Nobody is going to make the decision that rightly falls on your shoulders.  There is no such thing as a "code", "best practice", or "norm" that dictates or even suggests what type and size of ammonia tank you should design and build for YOUR application.  That's a step and a decision that falls on you.

 

What every owner does is to commission an economic and engineering study based on the scope of the project or need and goes on from there.  The results of the study should reflect all the needs and requirements of the owner and clearly show the advantages and return on investment of the selected storage facility.  Without being in your shoes and knowing ALL the basic data as well as your scope of work, location, economics, cash flow, cost of capital, etc., etc., our members can only generalize.  If guess work and generalities are OK, then that's what our members can contribute.  Your table seem to be OK to me, considering what I know about your application and situation.

[fallah]

 

Why couldn't we build a big pressurised sphere for a 5000 t storage?

 

 

populas,

 

In addition to valuable explanations of Art, the criteria in your table for storage tank type selection looks like to be logical to me as well.

 

About the limitations building pressurized spherical tank, as stated in "Chemical Engineering, Process Design and Economics, 2nd ed., PP, 2004" a typical maximum size of 8000 m3 is to be considered for spherical storage vessels mostly due to economical reasons...
 

[latexman]

https://www.osha.gov...DARDS&p_id=9757

 

Populas, in no way does this answer your question, but it is a good reference for one working on an anhydrous ammonia storage tank anywhere in the world.  In the U.S., it happens to be law.

Edited by latexman, 01 May 2015 - 06:59 AM.

[populas]

Art, fallah, latexman, many thanks for sharing your valuable experience.

 

You are right, there is no such "code" to choose the right ammonia storage tank and it depends on so many parameters (Art, you summarised them well). This needs to be rightly studied with the client before going on. It seems the economic parameter is the most important and drove the "standard" selection list which is widely spread in many reports on the web.

[jdev]

As Art has advised each project requires specific economic analysis and evaluation. Having said that  I have seen atmospheric refrigerated storage applied for capacities 5000 t and above. The max capacity of pressurized storage ( Horton Sphere) that I have seen is 3500 t

 

Jayadev

[Faisal Ghafoor]

After going for atmospheric refrigerated tank, the next question would be which type 1) single wall 2) double wall 3) double wall full containment etc. is the best to use. QRA study also limits the choice and depending on the consequences, one has to select the specific as per API guidelines. Vertical roof mounted pumps or horizontal pump with side nozzle is also a big question / decision to be made. 

 

My question is the intank valve specified in API, should it be inside the inner tank in double wall full containment tank or should it be in annulus space. I have seen one Maraldi tank full containment type with valve in annulus space and I doubt it satisfies in-tank valve requirement as specified in API 625.