Warm the BD, then bubble dry air from the bottom and flush dry air through the head space to keep it dry as Rick says.
Which is only a problem if you plan to store the fuel long term. I don't know about you, but I burn it as fast as I can make it. So oxidation is never an issue.
Though it stands to reason that more exposure to air will decrease shelf life I have not heard of a single real world issue with doing so (other then from centrifuging, but that is another story). I bubble dry air through my freshly drained 175F biodiesel overnight to drive off the last trace amounts of methanol and have had no storage issues whatsoever. The bio in my shop furnace tank sits for a year at a time with no issues and my vehicle fuel tote gets topped up routinely after it gets down to about a 1/4 full, going on 6 or 7 years now without any issues in a common rail Duramax, kubota direct injected engine, international 6.9 DI engine, Aero, Riello and an old carlin burner. My new house boiler setup with a standard steel fuel oil tank, that I put 55 gallons of fuel into in February, is now running again flawlessly on the same fuel I added 9 months ago, no smell of paint, just nice clean biodiesel...
I believe leaving the fuel in my vacuum still long enough to get rid of all traces of methanol will oxidize the fuel more then letting the dry air bubble through it overnight while it cools. That is of course while preforming WBD so your mileage may vary with just biodiesel...
Simple schematic for a pump and heater control with a high limit
Sensor for the biodiesel/glycerin layer
The method we use as described above safely dries biodiesel with no oxidation even with long term storage.
So, to answer your question, in our case it would not "be better to buy the plans for Murphys vacuum dehydrator".
If it ain't broke, don't try to fix it.
Reading back over this discussion no one is backing up their theories and methods with measurements. John Galt did mention that a sandy brae or carbide manometer tester would be a good idea but no one has followed up on this. If you want to promote a method we need to know how wet the oil was before drying and how dry after drying.
I live in what is probably the dampest moderate climate in the world. Todays humidity is 92% which is typical of this time of year.
My method is to heat my biodiesel up to 65°C and then bubble air, predried with silica gel, through the fuel. A small fan then evacuates the damp air rising off the surface. The dryer itself consumes about 20 watts and in 6 hours will dry 150 litres ofbiodiesel from 800ppm to 80ppm of water.
Murphy did raise a valid point about the risk of accelerated oxidation using air bubbling but provided the temperature is below 70°C the oxidation is negligible. My biodiesel passes the copper strip corrosion test with an 1A result after drying this way.
Arguing about the merits of your various methods without figures to back them up is pointless.This message has been edited. Last edited by: imakebiodiesel,
I have had several customers present real world testing concerning the oxidation issue and I have extrapolated, by means of data and an educated guess, the following:
1. If you're not doing ASTM testing, then its not a big issue unless your oil has been oxidized to a ridiculous level. In other words, who cares?
2. If you want to pass the ASTM testing, you can use the air exposure technique to dry your incoming wet oil, or use it to dry your washed biodiesel, but not usually both. Of course this depends on a great number of variables but I'm just using what the average biodiesel producer has to deal with for an example.
3. The air exposure technique is not practical in some geological locations. Those in humid areas like some southern states (Georgia, Alabama, Louisiana, Mississippi, etc) have a horrible time using air drying.
My dehydrator system is highly effective but expensive to build. If you don't have the production volume to justify that cost, and if you don't have to pass an ASTM test, than you would probably be much better off using air and/or time to get the water out.
One other thought.. if oxidation is on your mind, find and use a product that helps stabilize the oxidation. I've had many customers use the stuff and it works great.
Hi Callum, hows the weather down under?
Murphy, I wasnt directing my comments at you in my last post,everything I have heard about your equipment has been very good. I was just lamenting the fact that often on this forum, and on others, people promote ideas and methods without any evidence or measured proof of how well they work.
The use of silica gel to dry the air will overcome the problem of ambient humidity just about anywhere. However I would agree that if you both dry the feedstock and the finished product then it would be worth checking the level of oxidation,
There is a DIN standard titration test for oxidation but it is complicated and difficult to do in a home brew situation. The copper strip corrosion test can give some indication if you know how to interpret it. A fuel can fail this test for other reasons and you must rule them out first.
The first is sulphur content but biodiesel contains almost zero sulphur so it is very unlikely that this would cause a fail.
The second is acidic fuel. If the fuel titrates above 0.5ml KOH it will most likely fail.
If these first two conditions are ok then a failed strip test may indicate oxidized fuel.
To do the test polish a strip of copper and hang it inside a saucepan of biodiesel so that the strip is half immersed in the fuel. Heat the fuel to 100°C for 3 hours and compare with the chart.
I use a simple copper penny test to determine if fuel is acidic/corrosive.
Drop a dull penny in a sample; if it gets bright in a few days it's corrosive and likely acidic.
My data comes from customers sending in samples to ASTM testing labs. When it comes to our MM500 plans, I have a lot of contact time with a significant number of clients. Various customers have experienced a few failures here and there and one of the patterns I noticed was a failure on the oxidation test.
When one of my MM500 systems fails an ASTM, I don't really pay too much attention to it other than to reiterate to the folks running the system that cutting corners and not doing a water test or not double checking the titration, etc, is going to come back and bite them..
However, when someone insists that they didn't get lazy or cut corners and they still failed, I start asking lots of questions to hunt the issue down. I get really interested when I see the same failure issue across more than one or two customers. That usually means there is something wrong with the design or with the procedures. Either way, its my responsibility.
The first failures (not related to ASTM) was a rash of reports that folks where getting sludge buildup in filters and tanks. This was solved by making sure that petrol and bio were never mixed together without being filtered right after the mixing. It was a polarity issue that was discovered by people far smarter in chemistry than I.
The second failure was the oxidation stability of the fuel. It was by luck that I realized that producers with new or very low titrating oil, or folks using my dehydrator systems didn't ever fail oxidation tests.
When I started telling customers that you can not air-dry on both sides of the process, the oxidation failures went away.
Hope that helps,
I think that explains your findings perfectly and since your recommendations are based on ASTM results they are exactly the kind of information we can rely on.
Going off topic slightly, I mix 5% petrol or naphtha to my biodiesel throughout the winter months. I normally dose the petrol directly into my vehicle tank after I fill up with biodiesel. Would it be better to dose the whole batch in the processor and then filter to 10 microns before filling the vehicle?
John Galts penny test seems to be the opposite to the strip test but its not really. If fuel is corrosive it will etch the tarnish off the coin and then leave a 2A or 2B result on the surface.
Bear in mind that corrosive is not necessarily acidic. The acid number titration is a better way to determine acidity.
Ive never tried the penny test so I cant comment on it. The most common reason for a strip test failure is sulphur so yes Rick is right it is rare for biodiesel to fail but I have had a couple of 2A results with biodiesel that had an acid number of 1.5 - 2 ml KOH. ( I drywash so I always check my acid number.)
I mix kerosene/naptha [stale JP4] with the biodiesel in a barrel. As the temperature cools the HMPEs settle out and the 5 micron final filter keeps them out of the vehicle tank. Adding the JP4 also makes it much easier to pump thru the filter when cold.
My reasoning is if it etches the tarnish off copper then I don't want it in the truck's fuel system. I've been doing this way before I heard about the ASTM copper test. One could use a bright penny if so inclined, or one of each.
I've done the copper penny trick and the tarnish does disappear, also noted is a green tinge in the biodiesel sample. In my heated uvo holding tank the tarnish is gone from the copper hot water lines that sit in the oil. I suspect this is caused,in the uvo tank by high titrating oil (acidic) but unsure the reason this also happens on occasion with the biodiesel.
" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
Don't know. Customers don't always contact me until there is a problem they can't figure out. Once they do contact me, I usually get a large influx of information for which I must sort though to find what is and isn't relevant. Most folks who make fuel don't care about all the issues we in this forum discuss. They don't know, they don't want to know.. they just want fuel.
Unexpected oxidation failures =yes
I wouldn't know. If there wasn't a problem, I wouldn't be contacted.
New or Used, storage conditions, and Titration was all I asked about. Didn't care what kind of vegetable it came from.
I wouldn't characterized it as constant. More like predisposed.
Titration varied but problems were hit and miss above 4 KOH on average. (if I recall correctly) I think storage conditions had a lot to do with it also.
I don't know.
I don't know, people don't normally report non-problems.
Sorry my info is limited. My customers are not under my constant watch and control. My information comes only from the problems because most folks don't call me to report that my system is working like I said it would. When I am diagnosing an issue, I usually don't get to reference all the successes, only the failures.
Hope that helps,
You should probably ask your oxidation questions to others here in the forum. I have my circle of knowledge that can be really helpful but chemistry is not in that circle.
My knowledge of the oxidation issue is limited to this: The more you limit the oils exposure to air, the better.
How much, how far, how fast and how often are questions that should be directed to those in this forum with far more knowledge of the chemistry than me.
Now, if you have a pump issue or if you need to build a robot or heat or cool something, I may be of more help...
Oops.. just saw this....
I didn't think they were directed at me but that doesn't mean your comment was any less valid.
This forum isn't that bad at all for that.. but there are other forums with members who seem to think the laws of physics don't apply to them... My absolute favorite of all time is the electrolysis contraptions they put on cars claiming the hydrogen increases fuel mileage. Its some of the best BS I have ever seen.
Ok. back to our regularly scheduled program......
If you can keep the Epsom salts away from the glycerin you can reused the Epsom salts over and over again. To remove the oil from the Epsom salt I believe if you use a little water. The water can only adsorb so much Epsom salt. Once the water Adsorbs all the Epsom salt it can it will just float on top of your Epsom salt. Heat it. The oil or biodiesel will float to the top of the water. Pour off the water and oil or biodiesel. Save the water for next batch of Epsom salt you need to clean. Than bake dry the Epsom salt that was on the bottom. Dont try to boil the water and Epsom salt mix. This takes a lot of energy and you can reuse this water to remove oil from another batch of Epsom salt. Since its already saturated with Epsom salt it wont adsorb anymore of your Epsom salt in all the following batches you clean.
To remove glycerin from Epson Salt you will need a good vacuum and heat. This will remove the glycerin without burning it into the Epson salt.This message has been edited. Last edited by: Samuel,
Biodiesel for cleaner air and fuel independence!
I see no reason why waste glycerol cant be used to dry biodiesel. The Soaps can be remove from the waste glycerol by using controlled acid mix. Afterwards the waste glycerol can be heated or bubbled dried. I am thinking 100 gallons of waste dried glycerol can remove water from 2000 gallons of biodiesel. And it is so easy to just mix and let settle out.
Glycerol can be heated at least to 350F without decomposing so removing water from Glycerol should be very easy.
If anyone knows good reason not to use Glycerol to dry oil or biodiesel please educate me.
Biodiesel for cleaner air and fuel independence!