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A small electric flash evaporator to dewater WVO.
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[quote]Vacuum dewatering -- (snip)The "energy from someplace" is a problem with these vacuum units. You can only make 15 pounds of vacuum max and it still takes almost as much energy to flash off the steam, it just burst into vapor at a bit lower temp. One of the problems is that because the oil is not pressurized you can only heat it to 212 degrees before the water boils, the boiling eats up any further heat you put into it so you can not superheat the oil and get the flash off energy from the extra heat directly.

--if the 212 degree oil is sprayed into a vacuum, it is effectively superheated (heated above the boiling temperature FOR THAT PRESSURE) and will flash off more water. More complexity, sigh.
---heat exchangers (fphx discussed elsewhere, for example, or the copper tube-in-tube type like I use for the Bird Waterer) recycles about half the heat needed to raise the oil temperature from room temp to 212, but not the sensible needed heat to boil water. given infinite time and budget I'd build a small vacuum spray drying chamber.

Tim: As it is, I'm spending about 0.7 cents per gallon to dry my svo oil (in warm weather, twice that in cold weather), at 3.4 cents per kwh, but it's a slow process, only moving between 1-2 gph. Filters account for another 8-14 cents per gallon, if anyone cares.

Cheers,
JohnO
 
Location: Moses Lake, WA, USA | Registered: August 15, 2001Reply With QuoteReport This Post
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Wow.... 3.4 cents per kwh? I'm jealous! I live in a loft above my office/shop and pay commercial rates, currently about 13.5 cents kwh! Residential in Louisiana is probably around 8 cents.

As for these airless sprayers, if they are like pressure washers they will not handle high temperatures. The valves and related hardware may be plastic. Pressure washers cannot handle above 140 degrees. F.

If the boiling point of water is reduced under vacuum, doesn't it stand to reason that it will be elevated under pressure. Anyone know the boiling point of water at 150 psi, 2000psi, 3000psi?

Keep in mind, too, that the effective flashpoint of a combustible material (i.e. WVO)is drastically reduced by atomization. At the OSHA Institute, they demonstrated this by spraying some perfume through the flame of a lighter. Poof!

So, pressurizing the WVO may be narrowing the gap between the boiling point of water and the flashpoint of oil. Just something to consider from a safety nut.

One question about the steam released from the oil... how do you prevent it from settling back into the oil? Do you have a fan to push the steam vapors away? Around here (Louisiana) many chemicals suck in the water from the air, not just KOH and NaOH powders but many liquids.

I'm very interested in this approach so please understand these are only points to consider, not at all criticisms.

Todd T


2002 F-250, 7.3l on WVO since '04
'82 VW Rabbit diesel 1.6l na
'83 GMC 6.2l Class C RV
'85 F-350, 6.9l flat bed
'85 E-350, 6.9l cube van
2 Mercedes 300SD's
3 Chinese Changfa-style diesel generators- 12kw, 8kw & 7.5kw
Mitsubishi 3 cyl diesel generator/light tower
Kubota 2 cyl. diesel, water cooled air compressor
Onan 12.5kw air-cooled diesel genset
I run my company entirely on renewable energy including electricity from generators running on biofuels.

 
Location: El Dorado, Ark | Registered: July 04, 2004Reply With QuoteReport This Post
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the steam released from the oil... how do you prevent it from settling back into the oil?

The oil and the spray chamber need to be above the boiling temperature of water, so that the water can only exist there as vapor. The oil of course will be liquid, so it will run back down to the bottom, while the water vapor can be sucked away as a gas. This is essentially a destillation process.
 
Location: Moses Lake, WA, USA | Registered: August 15, 2001Reply With QuoteReport This Post
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Johno -- OOps, You are correct, the water will be superheated a bit based on what vacuum you can draw in the tank. My steam pressure table shows that if you pull the tank down to about 15 inches (7.3 pounds pressure absolute) the flash temp will be about 179 deg f, If you could somehow get the pressure down to about one pounds absolute the temp would be at about 100 deg f. Since the water can never be more than 212 deg f entering the tank and a practical vacuum will be closer to 15-18 inches that gives you an excess of maybe 35-40 degrees f to draw on for flashing off water, a bit more limited than I would like depending on the water content of the oil. Sounds like this may be the limiting factor on how much oil each of these vacuum dewatering units will be able to handle in one pass, not a problem really, just add extra units until you get to the flow rate you want.
Pulling a high vacuum sounds like the thing to do but It is almost impossible with cheap equipment even on a sealed tank let alone one that has a continuous vapor releasing inflow of oil at a reasonable flowrate of even a couple G/H. There is also the problem of removing the water vapor before it has a chance to re-condense inside the tank, I think this will take more than relying on the vac pump to pull it out, I have to flush it out with additional crossflow air.
I must admit that I have not given this approach nearly enough thought so I could easily be missing something crucial.

Heat exchanger -- I have a 12 foot coil of 3/16 inch steel brakeline ready to make up and add below the hot oil inside the flash tank, intend to get to this sometime in the near future. I am hoping I can preheat the oil to simething close to the 180-230 degrees that is the temp of the oil exiting the flash tank, won't reach this but will be interesting to see what the inflow oil reaches and how much it cools the exiting dry oil? With 1/2 gallon of hot oil in the tank and the small amount of oil flowing through the 3/16 inch tube I hope both oiles will at least reach equilibrium without cooling the oil in the tank down to a point that I get water vapor condensing back into it ? If that happens I will have to run both oils through an added exchanger outside the tank.

OK - our energy use is about the same to dewater except I use about the same energy no matter what the season.

I wish I had that low of an electric rate, one of the benefits of being close to hydroelectric I suspect, my 1.5 cents/G is based on my 7 cents/KW rate.

Todd T -- Airless sprayers -- The reasons you state are why I added the "once tweeked" caviat in my above posts. The big spray unit I saw was pushing warm (band heaters on 55 gallon drums) polyurethane 2-part chemicals up to 2 big spray guns applying foam over the top of a roof. I'm sire the adequate pump units exist but may not be affordable for our needs ?

Boiling point of pressurized water -- At 150 pounds it is 365.9 deg f., at 1000 pounds it is 546.4 deg f. that is high as my steam pressure table goes.

This is the reason I decided on 300 degrees and 150 pounds for my heater pipe, no boiling but a good bit of excess heat above the 212 deg f ambient pressure boiling point so there is adequate heat to flash off even a lot of water.

-- (OK -I could not pass this up) Based on the above analogy, this flash technique is no more dangerous than spraying perfume .. Just stay away from a flame. I can accept that.

Flash temp of vegoil-- Forget exactly what the flash point of veg is but it is up above 350 deg f, (auto-ignition requires oil to be a LOT hotter still) this gives a bit of a margine from the 300 deg heat. From reading about igniting a spray of vegoil (on the altfuelfurnace site and others) It seems to actually take even more energy than it would seem to actually GET ignition. There also has to be an ignition source, by flashing the oil inside a tank this problem is reduced considerably. Was and still is a bit of concern but no problems yet. The tank is not totaly sealed, it has two 1 inch diameter openings (crossflow air in/out) in the 5 inch diameter tank so the pressure should be released through these two openings, would sure scare hell out of me though.

Temp of oil in flash tank -- Measuring the temp of the oil as it exits the tank it will vary between 180 deg if a lot of water has just been flashed off - up to around 230 degrees with the normal amount of water being flashed off. This seems to be acceptable as water testing the oil exiting the flash tank shows NO water and also testing the oil from the very bottom of the tank after drying 30-40 gallons of oil also shows NO water. I do drain the first cold start-up oil out of the tank before continuing as I did find just a drop or two of free water in the tank on one occasion, this start-up oil goes back into the wet-oil feed tank to insure it gets dewatered.

Oil spray -- I don't actually "spray" the oil out of the oriface, it exits the oriface as a solid stream and then this stream bashes into a solid steel plate about 3 inches below the oriface. This reduces the oil vapor produced over an actual spray by a bit and still releases all the water.

Vapor removal -- There is a small up-and-across airflow of outside air through the flash tank, this seems to be required to move all the vapor out of the tank or you may get some re-condensing of water into the tanks pool of oil. This is what happened when I found a bit of water in the oil, the crossflow had stopped due to problems described earlier with using compressed air and a single stage pressure regulator to supply the air. I will try using a small 12 volt DC blower unit tomorrow to produce the crossflow ? A blower should produce a more steady flow of air and also the air will be from ambiant air so should be a bit dryer than the air from the air compressor.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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I bought this small blower from Surplus Center for about $10. It works nicely connected to a 1-inch pipe adapter, made by brazing a large washer to a pipe nipple. The blower has a mounting flange with three holes, so it was easy to bolt to the washer. I've used it to dry oil in my sealed BD processor by keeping a steady stream of fresh air moving over the top of the warm circulating oil. It should work to do the same for your spray dryer setup.

Imagesmall_blower.jpg (23 Kb, 120 downloads)
 
Location: Moses Lake, WA, USA | Registered: August 15, 2001Reply With QuoteReport This Post
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I dried 20 gallon of oil today using the small 12 volt blower (picture in an above post) instead of an air compressor to produce the vapor removing cross-flow air, worked great. This elimimated the agrivation of having to constantly fiddle with the air compressor secondary air regulator and it saves a bunch of electricity as the blower draws less than 1/2 amp at 12 volt DC.

I have been bidding on what I think will be the perfect blowers for this use when running on 110 volt AC power but have not yet won any of the Ebay sales (yes, i'm cheap). these are "Master Appliance" brand industrial heat guns, I will toss the handle and the heating element and use just the fan housing. They are cast aluminum units with metal squirl-cage blowers (my 12 volt blower has a plastic fan) and are repairable. These have 110 volt AC brush-type motors so there speed can be controled with a simple and cheap 600 watt incandescent light dimmer.

johno -- I can not see the motor on your fan, does it have brushes or is it an induction motor ?

Nothing wrong with an induction motor but there speed can not be controled directly with a dimmer. The amount of air that any blower moves can easily be controled by somewhat blocking the air inlet opening but I would rather control the speed a bit more directly by slowing the motor, slowing the motor reduces both noise and vibration, blocking the inlet actually speeds the motor up because the motor does not have to work as hard when moving less air.

Flashing cold oil -- I did a couple crude tests before fiering up the heater in the unit. I pushed cold oil through at first 150 pounds pressure than I maxed out the pump at 180 pounds pressure. Both these were putting out steam but not as much as was output once the heater was up to temp. I have samples of these and the wet oil but have not yet water-tested them.

This cold oil test DID CLOG the oriface though, looked like the pressure pushed some semi-solid oil through the filter and it clumped up and clogged the 18/000 oriface. This is the first time I have clogged the actual oriface in several hundred gallons of oil so this is going to be something to consider if trying to use this unit cold. Actually, the oil was not "cold" really. I had the tank heaters on due to mid-50's nights so the oil was actually around 100 deg f. but it must still have had at least a tiny bit of very high meltpoint solidified fats on the bottom of the barrel ?
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post



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This cold oil test DID CLOG ...


Oops! Sorry I suggested it. Were you able to clean your orifice/filter okay?


Brian

2000 Jetta TDI
1982 Mercedes 300D Turbo
1986 Isuzu P'up (NA)
1985 Mercedes 300D Turbo
75/25 WVO/D2 for warm weather
50/50 WVO/D2 for cold weather
Uniqueness is a treasure not to be buried. - Laurence Martel
 
Location: High Point, NC | Registered: May 04, 2006Reply With QuoteReport This Post
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No problem cleaning, The entire filter/oriface assembly is quickley removably by removing 3 wing nuts. I did not find much of anything in the filter and it was not clogged but there was a pinhead sized ball of what looked like white fat covering the oriface, a blast of compressed air cleared that.

I will do more testing using no or at least less heat, would be nice if it can be done reliably ?
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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Whew, ok!

Well, I got my Watlow PID controllers; they're purdy smart. After about 5-10 minutes, the temp is exactly what I set it on and it does not fluctuate like it did with the thermostat. I mean it doesn't fluctate at all that I can tell. I am so impressed!

I'm planning to put one on my biodiesel processor next, but I need another thermocouple. Actually, I need two more because the one I'm using now, I robbed from my multimeter and it was nice being able to spot-check temps easily.


Brian

2000 Jetta TDI
1982 Mercedes 300D Turbo
1986 Isuzu P'up (NA)
1985 Mercedes 300D Turbo
75/25 WVO/D2 for warm weather
50/50 WVO/D2 for cold weather
Uniqueness is a treasure not to be buried. - Laurence Martel
 
Location: High Point, NC | Registered: May 04, 2006Reply With QuoteReport This Post
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How much was your PID and where - I just priced one new for a theoretical project and it was something like $384 at McMaster. johnO and mtushmoo were talking about $30 on eBay at various times.
 
Location: Pittsboro, North Carolina | Registered: March 07, 2001Reply With QuoteReport This Post
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Dried another 15 gallon of oil yesterday, took all of about 5 minutes to fire up the flash unit and start dewatering, getting more usable all the time. The small crossflow air blower works great.

GM -- Search Ebay for "temperature controls" or veriations. There are usually a couple dozen or more of veious manufactrers listed, usually sell for under $50.00 for a single input unit, some have the temp probe, some not. Most are sold WITHOUT the nescicary contactor or solid state relay that is needed to switch the actual high powered heater unit, these will cost an additional 30-40 dollars per heating unit being controled.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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A CAUTION, Maybe -- I have seen this several times now with oil that has passed through the flash unit, I kept telling myself it was caused due to some other reason like flaking paint sealent inside the jerry cans.

It seems that the high heat/pressure is causing something wierd to coagulate out of the oil when the oil cools. I usually find a clump of "stuff" in the bottom of each 5 gallon jerry can that I am storing the dryed flashed oil in. Once the oil cools I am finding a clump of coagulated plasticized type stuff in the bottom of the cans, not a lot, a bit of stuff about the size and shape of your index finger only about 1/16 inch or less thick, seems to only be one piece of this stuff to each 5 gallon can. I seems that this stuff is attracted to itself and clumps up into one long chunk rather than floating loosly around in the can. It is coming from the oil as I am now making an effort to flush out the cans before filling them. It can not be passing through into the flash unit as a solid or it would have been caught during the 30 passes through my filter tank or in the 90 micron hydraulic filter just prior to the flash tank oriface, or it probably would have even clogged my 18/1000 inch oriface ? Don't know what it is but by clumping it is easily screened out when pouring the oil through a piece of windowscreen inside a funnel. I have NOT plugged and vehicle filters in several months so the window screen seems to be keeping it from getting into the vehicle tank.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post



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Polymerisation is caused when oil is heated and exposed to oxygen. Spraying hot oil in the air is asking for polymerisation.
 
Location: Perth W.Australia | Registered: August 10, 2001Reply With QuoteReport This Post
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Originally posted by Tony from West Oz (The Wizard of Oz):
Polymerisation is caused when oil is heated and exposed to oxygen. Spraying hot oil in the air is asking for polymerisation.
This might end up being a good thing Tony and Tim. Maybe this process is allowing the the easy to polymerize stuff to get polymerized. Would think that this is good cause now you get to remove this easy polymerizing stuff before it even goes into a fuel tank.


_________________________
If you believe you can't YOUR RIGHT;

But equally so.... if you believe you can, YOUR RIGHT as well.
 
Location: North Tx | Registered: November 23, 2002Reply With QuoteReport This Post
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I like the flash evaporation method of drying wvo, except for one little problem. When you flash the water out, it will be pure water: therefore any dissolved (e.g. salts) or suspended (e.g. food bits) contaminants will not be removed by this process. The suspended solids are easy enough to filter out, but what happens to the salts, acids and bases?


Mahalo and Aloha,
Steven L. Pike, Naval Architect/Marine Engineer, USCG Licensed First Assistant Engineer
"Sustained superior performance through continuous incremental improvement."
 
Location: White Plains, NY USA | Registered: February 16, 2004Reply With QuoteReport This Post
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Red Pike -- I try to reduce the "concentrating" problem by first water washing to remove the water soluable acids, salts, sugar, soy sauce etc, acid neutrilizing by adding Baking soda in the wash water, then do crud/soap settling followed by extensive filtering (at least 30 passes through 4 progressivly finer filters, the last being 5 micron).

The entire procedure is described in this discussion.

Polymerisation -- May be polymerization taking place, sure happens quick as the "stuff" is found after only a few hours of cooling of the hot dewatered oil. I think I prefere it to drop out of the oil before I use it for fuel.

Over the winter I have noticed that the oil that was passed through the flash evaporator stays liquid far below the oil that was only settled and filtered. I burn 5 gallon jerry cans of oil for additional heat from my wood stove during the winter. Settled-only oil will turn almost completely solid (may be very thick and creamy but porable) by about freezing, the flash dried oil was still sloshing freely in the cans at 15 deg f. I don't know the reason for this, it may be that by removing ALL the water there was no water to turn to ice crystals in the below freezing temps (think "slushie).
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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I did the water content "hot frypan bubble test" on the recent "cold flashed" (100 deg f) oil. The wet oil made a lot of 1/16 inch bubbles about 1/8 inch apart all over the bottom of the pan and even had a couple of small pops. The oil that was flashed cold at 150 pounds had NO pops and the bubbles were a bit smaller and spaced 3/16 to a quarter inch apart over the entire pan, the oil that was cold flashed at 180 pounds had even Less bubbles, no pops and the bubbles were 1/32 in size and only covered the area of the pan directly above the flame of my gas kitchen stove. -so- it looks like water WILL flash off of 100 deg f. oil and the higher the pressure the more water will be released. The 180 pound flashed oil was still a bit wetter than I would have wanted but I would have used it in a pinch. May not take all that much higher pressure to do cold dewatering ?

I will keep an eye out for some schedule 80 pipe and a hydraulic pump and see how even higher pressure works, may be a while before I get to do this testing but I think it might be worth the effort.

I will do more cold tests and lower-than-300-degree f tests with the existing unit each time I set it up to dewater.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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filtering:
Tim, if your 50% assumption is true, then after 10 passes you've already reached 99.9% filtration. (If it's any higher than 61% per pass, then 3 passes will reach maximum filtration.) So, you may be able to cut your filtration time by 67% (or more) and achieve the same level.

"cold" flashing:
This sounds very promising for reducing the waste energy. Especially with the use of the "airless" paint sprayers. I don't have access to our landfill, so my options for experimentation are limited. (Our landfill doesn't allow the public inside.)


Brian

2000 Jetta TDI
1982 Mercedes 300D Turbo
1986 Isuzu P'up (NA)
1985 Mercedes 300D Turbo
75/25 WVO/D2 for warm weather
50/50 WVO/D2 for cold weather
Uniqueness is a treasure not to be buried. - Laurence Martel
 
Location: High Point, NC | Registered: May 04, 2006Reply With QuoteReport This Post



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This is a link to a 3 page pdf found on the "Filter Manufacturers Council" webpage explaining there basic description of the terms "absolute" and "nominal" as they relate to filters. I found info on several water cartridge filter manufacturers web pages saying they consided 40% for each pass to be "nominal", didn't keep the links.

30 passes through the filters, can't hurt -- Yes, this is definatly overkill but this circulation is done without the need for me being present. I have a new barrel of oil settled and ready for filtering every 3-4 days so I just let the pump run until I am ready to drain and refill the filter barrel, just easier.

Electricity cost -- the small Shurflo RV pump draws 6 amps at 12 volts, amounts to 72 watts/Hour (1.75KW/day) costs me right at 12 cents per 24 hour period for the electricity. 36 cents to insure 40 gallons of well filtered oil is acceptable.

Cold flashing -- Yes, this would make it a very practical method of dewatering on a moving vehicle. It only takes me 6 amps to power the 12 volt DC motor turning the 180 pound pressure pump, this is a LOT less than the nearly 100 amps of 12 volts needed to power a 12 volt 600 watt water heater elements that would oterwise be needed to dewater even 4 G/H of oil. If the 180 pound oil water content is progressive with adding pressure it wouuld seem 300 pounds will be more than adaquate for cold dewatering ? this might require 15-20 amps to power the pump but it is a doable amount from a vehicle alternator. More testing will tell. By doubling the pressure from 150 to 300 pounds the same sized orifice will flow 50% more oil so my current 5 G/H 18/1000 orifice would flow about 7.5 G/H at this higher pressure, this would be about twice the amount that my Cummins uses per hour even worst case.

I am a bit heasitent to put 300 pounds of pressure on standard schedule 40 water pipe so I will need to build a much stronger test setup before I can attempt this, may simply screw an oriface into/onto a standard 1/4 inch high pressure hydraulic hose for the first tests. I have a tiny .o5 cubic inch/rev hydraulic pump to make the pressure.

Landfill ? - I don't have access to this either, the trash collection folks deliver my crud cubees to it for me. I do have a local SALVAGE (junk) yard, everyplace does, this is my primary shopping place.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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Tim,
You wrote
quote:
Yes, this would make it a very practical method of dewatering on a moving vehicle. It only takes me 6 amps to power the 12 volt DC motor turning the 180 pound pressure pump, this is a LOT less than the nearly 100 amps of 12 volts needed to power a 12 volt 600 watt water heater elements that would oterwise be needed to dewater even 4 G/H of oil.

If the vehicle engine coolant was used, ther would not be a need for that level of power to be used heating the oil. If 80°C is not hot enough, you could add more heat using exhaust heat or electric heat to make up the difference.

Keep up thegood work.
Tony
 
Location: Perth W.Australia | Registered: August 10, 2001Reply With QuoteReport This Post
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