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Combining cold upflow and centrifuging

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  • Combining cold upflow and centrifuging

    Depending on what boards you frequent, you all know a little about centrifuges and cold upflow settling. There are folks who swear by both of them for various reasons, but I decided to combine them and I've been getting pretty good results. I'll go into what I did and why in this thread.

    First, about cold upflow-I won't go into a lot of detail here because I didn't come up with it and there are already good articles on it like this one on Frybrid:

    http://www.frybrid.com/forum/showthread.php?t=10361

    Here is a (bad) visual of mine when it was setup at my parents place, sans centrifuge:



    Basically the idea is that you filter at room temperature using very simple methods/components. By constructing a large "funnel" out of a 10 or 15 gallon barrel which sits on top of a 55 gallon drum full of settled oil, you are able to create pressure by filling the top barrel (see link for a diagram which explains it better). Of course, the key with the settled barrel is to keep the PHO, water, crumbs, and junk settled. This is done by inserting a section of pipe into the barrel through the funnel which ensures that all new oil is introduced at the BOTTOM. Again, see the diagram for a clearer picture. Since you continue to add more oil to the funnel which in turn comes out of the pipe at the bottom of the barrel, the pressure forces oil near the top of the barrel out wherever it can. In order to keep the process slow, which keeps the crap settled at the bottom, a simple hose bib or boiler drain is inserted into the opposite bung that the funnel is screwed into. Relatively clean, dry oil which has made its way to the top of the barrel comes out of the valve which is just barely opened, letting only a trickle out.

    Here's a photo of the boiler drain setup which allows oil to move from the settling barrel to the "clean" barrel:



    Some folks combine this method with filters inline, and if it is done SLOWLY enough (I've heard about 10 gallons a day at most) it will ensure that clean, dry, oil comes out. However, 10 gallons a day is a little slow for most people. Also, the filtering becomes tricky because you have to have a filter between the settling barrel and the output barrel, as well as a filter on the final output. John Galt, the author of the above article, uses a hand pump to pump out the finished product through a 5 micron filter.

    Now onto centrifuges-for my rig I've once again copied a design, this time from SunWizard. Links to this design can be found here:

    http://www.burnveg.com/forum/viewtopic.php?t=4

    The object of the heated centrifuge of course is to filter and dewater using the combination of heat and brute force. This is a good method, but it can take a lot of time depending on how wet/dirty the oil is. The difference with centrifuging is that these hours of filtering involve electricity consumption, noise, and risk. Electricity is cheap, but lets face it-like diesel it's just another bill and who likes bills? I've done everything I can to lessen my electric bill and the total draw of my CF rig is about 30 amps-why not lessen the time it runs? As far as noise, this is an issue for some but not others. Centrifuges and pumps are noisy-unless you're an acoustical engineer this a difficult problem to fix. If you filter in a shed away from the house its probably not an issue, but if you filter in an attached garage like I do, it is. It's not a pleasant thing to listen to while trying to watch TV, eat dinner, etc...

    Finally, the risk. I am a firm believer of Murphy's Law. I've done enough wrenching, planning, building, experimenting, etc...in my life to know that anything that can go wrong, will go wrong. Any time you have electricity + heat + pressure + oil, you have the potential for disaster. I would NEVER let my centrifuge run overnight or while I wasn't home. No matter how careful you are you just never know. A leak of hot oil or a burst hose while the rig is left unattended for an extended period of time could be a mess at best and a disaster at worst. God forbid your home burns to the ground as a result of a fire originating with a centrifuge, don't expect your homeowner's insurance to pay. Call me too cautious, I just don't think that a home is something to gamble with. Anyway, the fact that centrifuges shouldn't be left "alone" creates a problem. If you have especially wet or dirty oil, for most folks this limits centrifuging time to the weekend. I started out doing this. I would leave the centrifuge chugging away in the garage while I did yard work/stuff around the house, sticking my head in the garage to check on it periodically. However, that gets old. Plus, we have lives and don't always spend our weekends at home. I wanted to be able to run the centrifuge for an hour or two at most after dinner while I'm milling around the house during the week.

    How to get clean dry oil in one hour from your centrifuge? Use cold upflow as your "pre-filter." With my method I forgo any real "filtering" in the cold upflow portion of the setup. Here are the steps laid out in order of what happens in the cold upflow setup:

    1. Pour oil into "funnel" barrel - My funnel barrel consists of an upturned 15 gallon barrel with the bottom cut out so that a 5 gallon spackle bucket can be sleeved into it. The fit must be tight so that the top rim of the bucket acts as a "stop," suspending the bucket in the barrel. I used a 1" hole saw to drill holes in the bucket which serves to support the t-shirt pre-filter ($0.05-0.10 a piece at the local Goodwill store/church rummage sale).

    Here is a photo of the bucket with t-shirt: (A 12" HVAC duct clamp works great to keep the t-shirt from falling in)



    2. Let gravity do the work - Since you've already allowed the full bottom drum to settle for a week, and the boiler drain is closed so that oil trickles out at a rate of about 1-1.5 GPH, the oil you dumped will slowly make its way to the bottom of the settling barrel via the pipe inserted through the bung (see John's diagram on Frybrid), where it will push on oil already in there. The cleanest, driest oil will rise to the top and exit via the boiler drain into the "clean" barrel. I say "clean" because it's only part way there.

    3. Pump into centrifuge barrel via hand pump - Get yourself a good Blackmer hand pump which you'll use to transfer oil from the "clean" barrel in to the final stage, which is the centrifuge barrel. I don't have pictures of the adapter I made in order to screw the pump into the barrel, but I'll post them soon. It's a very simple thing which can be made from $10 worth of PVC and black pipe fittings/pipe. Basically what you want is to have it so that the pump screws into the barrel so that it's stable and easy to crank. Also, you want to have a pickup tube inside the barrel that will only pickup oil 10" from the bottom. This way, by letting the "clean" barrel settle for a day before you move the "clean" oil to the final stage, you can ensure that the wettest stuff is remaining on the bottom of the barrel.

    4. Run centrifuge - At this point you are centrifuging oil that is much cleaner and drier than when you picked it up, but still not ready to be used as fuel. At this point it is entirely possible to run the centrifuge for 2 hours MAXIMUM and obtain oil that is bone dry, and filtered to 1/10 of a micron. Essentially you're using the centrifuge to "polish" the oil. The heavy lifting is done by the t-shirt pre-filter, and gravity.

    Pictured here is my centrifuge rig in my new house, sans cold upflow:



    To the right of the black barrel you can see a white poly barrel against the wall. This is now my settling barrel. I'll post pictures of the whole setup soon.

    I have used both the hot pan test and the "weigh-heat-weigh" method to test this and the oil is dry as can be. As for filtration, I guess the life of my Donaldson will be the final judge, but after using cold upflow to pre-filter my oil I experimented by running my centrifuge for 5 hours straight, which resulted in a film less than 1/16" thick on the inside of the rotor. This was using oil that typically will deposit a 1/4" of crap in 2 hours when filtered through a t-shirt directly into the centrifuge barrel. Now, could there be some crap still in the oil since I'm only running for 2 (sometimes 1) hours? Of course, but I've added a final step which should negate that. On the outlet that my fill hose is connected to I've plumbed in a Goldenrod 10 micron water block filter (the one with the amber plastic housing)-this serves two functions. First, it will catch anything that centrifuging misses, thus extending the life of the Donaldson filter. Second, though the water block filter will not SEPARATE water from the oil, IF in fact there is a "problem" amount of water in it for some reason (however unlikely), it will clog, signifying that there is a problem somewhere. I think of it like a shear pin in a snowblower. If you hit a large rock, the shear pin will break, causing the snowblower to stop working, but it protects against any further damage.

    I encourage you guys to try it, hack it, improve upon it, etc... After all that's the beauty of this whole free exchange of information. I wouldn't know 1/10 of what I know about WVO as fuel had it not been for webforums like this. The whole point of this was to remove a little more of the "job" aspect of all of this because let's face it-"free" oil is not really free. However, the less time you need to devote to it, the more "free" it becomes.
    Last edited by powerstroke73L; 09-11-2008, 08:34 AM.
    Currently dieselless!
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