10 replies to this topic

[zasa3]

Hi,

This is my first query in this forum

I work at urea complex company and I want to calculate vapor flowrate of ammonia storage in different operational conditions ( using cold or warm ammonia in urea plant). Is there any procedure for these calculations? Our storage has two roofs and doublewalls and is at atmospheric pressure. There is a pressure reduction in vapor outlet.

Thanks in advance

[breizh]

Zasa3 ,

To get a "good " answer to your query  can you provide more info about the storage tanks with a sketch , a PID will be great ?  

What do you mean by procedure to perform calculation?

 

Thanks for your reply.

 

Breizh 

[zasa3]

I enclose operational and disign information and P&ID of ammonia storage.

Attached Files

•  Ammonia storage.pdf   122.23KB   190 downloads
•  P&ID.pdf   231.47KB   179 downloads

Edited by zasa3, 20 May 2013 - 04:28 AM.

[breizh]

To me your query is unclear , let see how others understand it .

I've attached a link about equilibrium liquid-gas NH3 to support :

 http://encyclopedia....orPressureGraph

 

Hope this helps

 

Breizh

[zasa3]

Ammonia enter to storage at  subcooled condition. but we have vapor formation thet return to ammonia unit. I want to know what factors have an impact on vapor formation and How can I calculate this value?

[breizh]

Zasa3,

It might be interesting for you to read this post :

http://www.refrigera...rage-of-Ammonia

 

Hope this helps

Breizh

Edited by breizh, 21 May 2013 - 01:14 AM.

[zasa3]

We have an innage stream at different flow during different conditions.I want to know how  amount of flow affect on vapor formation.( This stream enters at tank temp)

[Satyajit]

Dear Zasa,

                     I  can help you if you provide stream flow rate, pressure and temperature. You also can look into ammonia VLE diagram to claculate the vapor generation rate. It can be easily calculated in aspen too.

Please consider following factors to calculate vapor generated in the tank:

1. About 15% of the total incoming streams flashed to vapour when flashed into the tank.

2.About 0.04% boil off rate ( 0.04% of total ammonia in the tank per day).

 

Hope, you will be to start doing some calculation.

Kind regards,

Satyajit

[Art Montemayor]

The subject of Atmospheric Ammonia (and LPGs) storage and the calculations required to determine the re-compression & refrigeration duty required has been treated, debated, discussed, and expounded in our Forums since I've been a member - and that is a very long time.  A lot of this information is to be found in our archives and these are available through the use of our SEARCH engine.   Use this engine to find all the information already discussed and uploaded.  It is there for you and your benefit - but YOU have to do the effort of searching for it, not us.

 

As an example of the type and quality of the calculations and information I've uploaded for everyone on the Forum, I'm attaching a copy of an Excel file I did for one student with a hard head who finally saw the light - after 3 revisions.

 

 Ammonia Multi-EvaporatorsRev3.xlsx   845.91KB   182 downloads

 

[zasa3]

Thanks for your answers.

The ammonia storage work at a little below saturation condition. I simulated storage in hysys but it didn't produce any vapor.After that I did flash calculation using flash equations too. but vapor fraction has a negativevalue because of subcooled condition.

[zasa3]

I think heat transfer between storage tank and ambient can be cause of vapor formation. at design condition( ambient Temp:40degC) vapor formation in tank is between 2.3-17% of inlet flow.  inlet Flow varies between 3771-51429 Kg/hr. There is a different Temperature in tank at any elevation. How can I compute this profile?

Can anyone tell me about approximate overall heat transfer from tank to ambient?

Edited by zasa3, 28 May 2013 - 11:11 PM.