Originally posted by AZBiodsl: jehu if you don't do a soap test after your wood towers how can you know its taking out the soap? Unless the soap falls out of solution and begins to clump together the sawdust won't take out the soap
I am not a scientist or a chemist either, but after filtering over 1/2 million gallons of bio I have drawn a few conclusions.
1:Sawdust chips work, they DO remove soap. Life is dependant on the ppm of soap in the bio going into the sawdust. Many, many soap test over the last year and a half have shown this. I like to see soap numbers in the 500ppm range or less before the filters.
2:Methanol left in the fuel greatly reduces the soap removal properties of the dust. For the first several hundred gallons you want see this with the soap test, your results will look good.(volumn will be dependant on cubic feet of dust used) As the wood chips are used and soak up more and more methanol your soap numbers will start to rise. From experience and many test if the fuel is demethed I can filter several thousand gallon before soap numbers get to high, but if the fuel is NOT demethed I was lucky to get 1000 gallon before failing soap test.
3:The amount of methanol removed by the sawdust is negligible, you will definately not pass ASTM flashpoint this way.
I used to homebrew thanks to all the info I got from this forum (avid reader not a poster). I made 30 gal batches, If I were using a 55 gallon drum for a sawdust filter, making 1 to 2 batches per/week it would probably take several months for the above results to showup. I can see where people would say it doesnt make any difference if you demeth before or after, most people probably change there chips more often than this.
I can also see where people doing like Jehu are not having problems. The methanol laden fuel is filtered through the sawdust and removes gross soap level. The methanol that is still present in the fuel holds the rest of the soap in solution. The fuel is probably being used fairly quickly and doesnt sit for long periods of time where the methanol could evaporate and let the rest of the soaps fallout. Burning soap is another story. You dont know your soap ppm without testing.
Or......The saw dust is being changed often enough that soap ppm is staying low enough that soap is not a problem.
Bottom line...If the fuel you make works for you and you are happy with it Great!
Overworked, thanks for the info regarding methanol reduction of sawdust life. I dont demeth. The sawdust is free so whenever I get cloudiness in the shakeup test I change it. Ive never had a problem with my biodiesel since using sawdust. I agree entirely with your statement - "Bottom line...If the fuel you make works for you and you are happy with it Great!". Thats the only rule I work to too.
it is puzzle for me that why i fail shake em up test i get cloudy water my bio is crystal clear and i have done about 500L so far.i have 200L barrel full of saw dust /chip wood.last time i filter the same bio twice and the water test was much cleaner but had some cloudy sort of bubble between bio and water any explanation please
i though the first batch or two has only resin and after that it gets clear?could it be that i am using too much koh?i have just find out that my meter was showing 8L less so when i was doing 100L oil in fact i had 92L in my tank and i was taking koh for 100L so approx i was putting 68G more than usual
It isn difficult to do a soap titration. How anyone can consistently dry wash biodiesel (succesfully) WITHOUT testing for soap is a mystery to me. The risks are so high (ruin your resin, create off spec fuel) that I don't understand why anyone would argue that this simple testing is unnecessary.
A layer that sits between biodiesel and water in the shake-up test -ie is insoluble in both - is resin. It cant be soap.
A few weeks ago my isoprop turned acidic and I was adding 200g too much NaOH to my 100L batch, and altho it obviously produced too much soap it made no difference to the shake-up test and the finished biodiesel, so I wouldnt worry about it.
I dont do soap titrations BTW. If the shake-up test is clear thats good enough for me.
All the resin comes out with the first batch of biodiesel, if its gravity filtered and not pumped or circulated. The resin will fall out of the fuel naturally after two or three days, but in the meantime another batch can be sent thru the sawdust which should be resin free. The sawdust lasts so long (if its in a lrage enough volume) that this is a minor inconvenience for something which is so cheap (free even) and effective.
i have done some tests with ASTM 6584 before and after wood chips, as of right now the preliminary results show that the sawdust will take out the glycerin. I have data to back up this claim. However I am waiting to reproduce my results in a less biased manner before i am positive. BUT i would say the chances of reproducibilty is good.
RolfQuo Biodiesel, mid sized commercial producer, uses wood chips exclusively to filter their fuel. It is tested several times during the process. The soap removal numbers are quite impressive. I did an interview with them (in the sig line) where some of these issues were brought up.
*residual glycerin by the way. from the numbers i have seen it can take it from a couple one hundredths of a percent out of spec on free glycerin to in spec. But again i need to repeat this a bit more.
I looked at buying/purchasing a dry washing tower and the cost was horrendous, £898. I sat and thought and the ideal home made solution is the old fashioned fire extinguisher. The old water version with the big brass twisty thing at the top. Remember hit the top and the water rushes out. The design is spot on; the vessel is pressurised, it has an out let which has brass fittings with a feed from the bottom. Make a hole on the opposite side and that is the out let. Brass fittings work well. The Eco2pure sits in the bottom circa 1.5 kg and then a pump is fashioned to flush it through. The hard part is to get a filter on the outlet side..........I am still working on this, I think an inline with 75 micron washable affair, £29.99 with 2 filters (Ebay). Tried it with out the inline filter through a filtakleen bio-diesel filter with 1 micron filter (found in a scrapyard) witha new filter from Luton. Found bits in the polishing pot so need the inline bit. This so far cost me £19.00 inc delivery for the polisher filter and Eco2pure £70 inc VAT and delivery. I am now building a oak sawdust filter system for pre tower and polish any advice gratefully. Good news my neighbour is a bespoke carpenter with gallons of superdry sawdust and ..............its oak
3:The amount of methanol removed by the sawdust is negligible, you will definitely not pass ASTM flash-point this way.
My experience differs. The sawdust works because it removes the methanol thus precipitating the soap which is then depth filtered out by the same sawdust. If this did not happen it would be impossible to get zero soap content using the method as residual methanol would always hold a significant portion of soap in the bio which would then be detected by the testing method used in the particular instance. It is a fact that zero soap content has been achieved with the method and been tested and shown to work by a reputable university laboratory. Thus methanol has to be removed. Logic and lab testing aside it is my observation that this happens also.
mathematical elegance -- desired result achieved with minimal complication
Location: Manchester UK | Registered: June 03, 2003
Ok guys, How is it going here with the dry washing? No comments for months. I have been waiting for you guys to get this dry washing down to a science so that I could implement it without have to go through a bunch of trial and error.
I have been "dry washing" for a couple years now. Once the biodiesel is transferred leaving the settled glycerine behind is it then circulated and demethed.
A settling period of at least a few days gets the suspended soaps to fall out and what is not immediately removed by gravity is taken out by the 200L drum of hard wood chips followed by a lead /lag resin tower set up and final polished using a 2 micron CAT fuel can.
My fuel has frozen and thawed several times over winters and there has been absolutely NO fall out. It test zero PPM soaps in the lab.