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tank vents & dryers

tank vents & dryers

tank vents & dryers

(OP)
I need to get a vent system for a diesel tank figured out. It's approx 300,000 gal of 5% biodiesel. The fuel is expected to sit unused for long periods of time.

The tank is 40' dia & 32' high shell. The tank will be located in a coastal marine environment.

The tank is being designed for 2.5 psig / -2 in-WC (vacuum). It's starting to look like a conservation vent and blowoff vent might do the job.

I'm worried that the conservation vent will still let in considerable moisture.

Is a desiccant vent a good idea for this?
Would a desiccant stop the ingress of salts to the tank?

RE: tank vents & dryers

I would slightly slope the floor to a sump about 2-feet deep and 3-ft in diameter.  Slope can be as little as 1/8-inch per foot, assuming the tank floor is 'shingled' to allow easy flow to the sump.  Draw off water/diesel every week or three until you can establish a pattern, then draw off based on your established pattern.

RE: tank vents & dryers

(OP)
Yes, a floor level water draw-off is designed into this tank. My major concern is degrading fuel quality. The addition of water in a marine environment may include the addition of salts.

The total sodium and potassium allowed in the fuel is 1 ppmw.
The fuel has 5% biodiesel which is hygroscopic. I'm still looking into what the limitations on this phenomenon are. If you have good resources/references for this, please let me know.

Nomally, a water wash of the fuel would remove the salts very effectively, but I can't say that for sure with the biodiesel.

I realize the chemistry involved here may be more appropriate for another forum.

If someone has experience with this type of storage situation, I thought this might be the place to ask.

Consequently, I wonder whether eliminating the water from air entering the tank will be a reasonable and effective way to deal with this concern.

RE: tank vents & dryers

I was told that additives are used for heating fuel oil, have you checked into additives for diesel fuel?

RE: tank vents & dryers

someguy.....

Google still works realllly, really well...!!

https://www.pindellengineering.com/H2Out_Filter_Home.html

Try the search terms "vent" "biodiesel" and "tank"

Have you calculated your vent massflow rate yet ?

This, of course, affects your device size and selection

Please complete this thread and let us know of your final size and selection

   

RE: tank vents & dryers

(OP)
Yes, Google still works. Snarky comments are not helpful, nor are links to equipment that's woefully unsuited to the service described.

I've been in contact with various manufacturers of desiccant beds. I was hoping someone on this forum who has had real life experience with similar equipment would comment.

The problem isn't the existence or availability of desiccant beds. It's just that I can't find information on anything this size.

At this point, I'm moving away from this option. It's not looking very promising. I do not like the idea of putting an extra 1000 lb of media inside a vertical tank, on top of another tank, in an earthquake zone, where the benefits are not clear, and the equipment doesn't seem very common.

RE: tank vents & dryers

If the contents of your tank are going to be il long-term storage, a standard Conservation Vent w/Flame Arrestor will work fine.  The tank only breaths when you pump in or out.

You can put a nitrogen or argon blanket on the tank when your are [infrequently] pumping out, at gas flowrate that gives you at net positive pressure -- no intake of moist air.

RE: tank vents & dryers

(OP)
Thanks Duwe6,

I hadn't thought of using N2 blanket as a method of moisture control.  

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