Salt drying

Collecting, filtering and dewatering of WVO SVO vegetable oil. For Biodiesel producers too.

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Salt drying

Postby Burbarian » Mon Aug 25, 2008 1:57 pm

Came across this:

http://www.pall.com/Aerospace_3255.asp

This part is of interest:
"Salt driers can remove dissolved water where coalescers may only remove free or suspended water."

Note this is for dewatering jet fuel in a refinery down to 6ppm (acceptable biodiesel water content is 500ppm).

With salt being $4 per 50# bag this seems to be a low energy input, low cost dewatering method.

I figure something like a slightly tilted/angled and covered horse trough filled with salt. Prefiltered WVO enters on one end, slowly flows to the other end through the salt, and is taken off the top at the far end. Meanwhile, accumulated brine can be taken off the bottom of the trough via a drain valve. With choked gravity feed input and passive output through a 1 micron absolute filter into a storage drum, the entire thing could be set up and pretty much forgotten. For a small setup in a shed, it could continuously dewater say a gallon an hour, 24 hours a day. Get half a 275 gallon tote of filtered and dewatered oil every week. Just pump the finished oil into storage and top off the elevated input tote with more WVO. Perhaps an hour's work a week for ~150 gallons of processed oil. Using a brain-dead-simple and dirt-cheap setup that requires no electricity and negligible attention.

Of course, come winter time the setup could be insulated and heated. But in an already insulated and heated workshop, even that would be unnecessary.

As always, comments, criticism and ridicule welcomed.
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Postby biovindiesel » Mon Aug 25, 2008 2:17 pm

Maybe add in some upflow settling for the oil input on one side, brine drain and clean oil sift on the other. A wood-fired boiler could be used to precipitate the used brine back into usable salt.

I like my Dieselcraft though.
~Cv
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Postby SunWizard » Mon Aug 25, 2008 4:52 pm

Some have been experimenting with salt for dewatering. A problem I see is the hot pan test quits working due to high salt content in suspended water, so you wouldn't know if you have got the water out. Salty suspended water that you don't get completely out could be very corrosive.
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Postby Burbarian » Mon Aug 25, 2008 5:18 pm

SunWizard wrote:Some have been experimenting with salt for dewatering. A problem I see is the hot pan test quits working due to high salt content in suspended water, so you wouldn't know if you have got the water out. Salty suspended water that you don't get completely out could be very corrosive.


Excellent point. I will have to do some hot pan experiments using oil deliberately infused with a drop of salt saturated water in it, thoroughly shaken. From the Mechanical Engineers Handbook, the boiling-point of saturated brine under one atmosphere is 226° F. Brine suspended in oil might behave differently.
1987 GMC Suburban 6.2L V8 IDI
1985 Merc 300TD
1968 CAT D4D 3304 dozer
1971 Waldon 4100 loader
1981 IHI 30F excavator
1995 Changfa 195 w/ ST 10kw genset
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Postby Burbarian » Mon Aug 25, 2008 8:49 pm

biovindiesel wrote:Maybe add in some upflow settling for the oil input on one side, brine drain and clean oil sift on the other. A wood-fired boiler could be used to precipitate the used brine back into usable salt.

I like my Dieselcraft though.


Indeed. Perhaps upflow drums at both ends. The first one to minimize loading of the prefilter and salt dryer, and the 2nd to segregate the output. Any residual saltwater should stay at the bottom of the 2nd upflow drum considering the density differential with dry oil. Take off the top and it should be bone dry. The ability to remove even dissolved water is a very attractive target.

Quick test of saltwater in oil with a hot pan at 350F, sizzle and pop. But a bit strange. Bubbles zigzagged across the pan instead of staying still. No discernable residue, so any precipitated salt appears to be microscopic on the water's boil-off.
1987 GMC Suburban 6.2L V8 IDI
1985 Merc 300TD
1968 CAT D4D 3304 dozer
1971 Waldon 4100 loader
1981 IHI 30F excavator
1995 Changfa 195 w/ ST 10kw genset
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Joined: Wed Mar 05, 2008 12:14 pm
Location: Vermont


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