25% Aqueos Ammonia Storage Tank 2

How about an atmospheric tank based on API 620 and without scrubber?

bif, I have arrived into UK 2 years ago, so recently I was looking for something similar.

First, you can read the CIRIA's ( C598 - "Chemical storage tank systems - good practice: Guidance on design, manufacture,installation, operation, inspection and maintenance" publication, this will give you overall principles.
From my practice in other countries: yes, atmospheric tank with water scrubber on it is popular solution.
You can order specialized scrubbers dedicated to the tank (if not whole system) from i.e. KTS Szczecin or Weber Kunstofftechnik (sorry, but I don't know the UK suppliers yet).
Hope it will help.

You can search on but you may find the focus is on anhydrous ammonia. However, you will then pick up on all the regulations.

Steve Jones
Materials & Corrosion Engineer

This is my personal, professional opinion. The partial pressure of NH3 over the aqueous solution is too high and the odor threshold of NH3 is too low to use an atmospheric or API tank that has no cooling capability. The partial pressure of NH3 at 100 F from a 25 wt. % solution is 15 psia by itself. This means at atmospheric pressure the solution will be boiling off the NH3! I think the odor threshold of NH3 is 5 ppm. The high partial pressure/low odor threshold combination coupled with an API tank will plague the plant with odor issues the entire life of the facility! Do yourself and others a favor and build a robust tank and system.

Good luck,
Latexman

absolutely what latexman said!

we used to make the 29.6% stuff and the original tank was installed in the 50's. we combined the vapor spaces, added a conservation vent valve and a scrubber.

you can greatly minimize the vapors if the truck has a pump and a vapor return line when unloading. then the vapor space in your tank is vented back to the truck.

but to do this, you need a tank that can take some pressure. even if you wanted to avoid a ASME tank, something with a 14 psig MAWP might give you enough driving force to return the fumes to the truck.

when we loaded trucks, we vented them back to our tank. most of our emissions came during the reaction/blending step to make the solution.

good luck,

ben

To all..

You are on the right track when you conclude that an atmospheric tank is not acceptable because of vapor pressure and noxious emissions.

In the USA, the suppliers of aqueous ammonia suggest a horizontal axis tank, designed as an ASME pressure vessel with a MAWP of 25 PSIG. Other tank features, such as delivery tank supply and equalizing lines should be included. The tank should be sized to hold 2-3 tanker loads. 12,000 gallons is a popular size

The Tanner company has published some excellent guidelines.


Hope that this helps...

Please compete this thread and tell us of your final decision......


-MJC

MJC,

good info! i have been away from the ammonia business since 98 and knew some folks at LaRoche.

a couple of observations though:

1) Truck unloading Pump Method "B" is my basic preference and I would add a check valve going into the tank. a mistake at the truck or a failed hose should not cause flow from the tank.

2) i am not a fan of pressure to unload since DOT does not allow for trucks to leave with pressure and they would typically vent off pressure and cause release of ammonia fumes.

3) i am also not a fan of combined conservation vent valves. the 25 psig tank would allow quite a high pressure PSV or rupture disc. they noted the vacuum protection should be minimally set at 2-4 oz of vacuum. i would likely go further to try and minimize any air into the tank.

3) carbon steel is likely the least expensive option but you best be aware of what it takes to passivate the tank and what your quality requirements are for your process. if you need "water white" color purity, you should ask what you will do if you need to work on the tank and it needs to be repassivated.

we would use TSP (tri sodium phosphate) solution to pre-passivate the tank and then the first batch we made in our mild carbon steel tanks would still have some color for the first batch or two. since we were a complete ammonia, urea, nitric acid UAN facility, we were able to use it internally and make fresh batches that were water white.

good luck! and please update the thread.