6 replies to this topic

[nes13ta]

Hello gents,

In polymer plant in some batches ammonia 25% to be added for cetain purposes
the current sitiuation is adding it manually which is not safe.
installing a tank would be a suggested solution. the issue is what material to be used rather than SS since it is costly, to be applicable for ammonia.
new ideas are welcomed.

Thanx

[breizh]

Hi ,
Based on my experience , let you consider SS 304 and add load cells or use a mass flow meter for adjustment .
Breizh

[nes13ta]

Hi,
Thanx for that but what i need is about 10 ton tank and that would cost a lot if SS is used.
Dont you think that a tank made fron fiber or similar would be suitable for ammonia??

Thanx a lot,,,

[ankur2061]

nes 13ta,

Aqueous ammonia (ammonia solution) can be stored in carbon steel tanks as per the link provided below:

http://www.tannerind...en-aqua-amm.pdf

Regards,
Ankur.

[breizh]

Hi ,
It's not only a question of cost . You need to put the money where it is necessary , especially if you are thinking Polymers and latex .

Probably Latexman will follow this post .

Breizh

[latexman]

We try to purchase 30% aqueous ammonia for our plants. Sometimes, local supply situation reduces this to 25%, like you use. So, I am familiar with the application.

What location are you interested in? This may be important, because aqueous ammonia is somewhat volatile. It is much worse in summer months as you can imagine. If the vapors are not contained, the concentration degrades with time. AND, your plant has an odor and exposure problem! This pH modifier inconsistency will impact your product consistency (pH, solids, etc.) We do not want to design these problems into our project, so we require 100% containment. Therefore, in summer months a pressure vessel is required. For some guidance you should look here:

http://www.rmtech.ne...information.htm

Look at the aqueous ammonia storage and handling booklet. They recommend a 30 psig MAWP. From an economic long term cost of ownership point of view, this means a CS or SS pressure vessel (> 15 psig).

Do any of your products have food or pharmacutical applications? If so, CS may not be an option due to sanitary reasons.

Are colorants a problem in your products? If so, aqueous ammonia in CS may not be an option.

We had some CS aqueous ammonia tanks from old projects. It can work, but you may need to inert the tank with, say, nitrogen, to stop colorant formation. New projects we use SS. Old CS tanks get replaced with SS as time and money permits.

[kkala]

Thanks, latexman, for the really useful information about the material of aqueous ammonia tanks. Perry's (5th edition, Materials of construction) corrosion data of aqueous ammonia on carbon or stainless steel does not seem clear (*). But the concern seems to be about downstream product contamination, not destruction of tank itself. Plants producing polymers usually require raw materials of high purity; I wonder whether this could exclude carbon steel drum in the specific case.
Two notes might be of interest.
1. 30 psig vessel of GRP seems possible in theory (**), ( http://www.ifs-frp....sCorrResis.pdf - Pressure applications - p. 144). But in 1979 a 150 m3 atmospheric tank of GRP was more expensive than a carbon steel tank cladded with stainless steel. I do not know the development of GRP, yet we thought of them only in case that corrosion did not permit commercial stainless steels.
2. Probably a cladded tank as above could be a cheaper option. Phosphoric acid tanks and decanters were constructed so, successfully (capacity 400 - 2500 m3).



(*) Info also on http://www.eng-tips...cfm?qid=273391 .
(**) GRP coatings or PVC did not seem to be attacked by aqueous ammonia (1979), but corrosion resistance and proper material can be advised by Supplier.

Edited by kkala, 29 April 2012 - 11:15 AM.