tank vents & dryers 1

[someguy79]

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?

 

[Duwe6]

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.

 

[someguy79]

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.

 

[chicopee]

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

 

[MJCronin]

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

 

[someguy79]

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.

 

[Duwe6]

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.

 

[someguy79]

Thanks Duwe6,

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