There's nothing about the GL method that should change most of the parameters above, except:

-flash point
-sulfated ash, which you guys didn't do.

Flash point is an indirect test for methanol, and sulfated ash is an indirect test for soap. None of the other tests above have anything to do with methanol or soap removal, so they only show that you made good conversion biodiesel out of a certain feedstock (congratulations on the good conversion)

Rancimat isn't generally done routinely yet.

girl mark,
By "done routinely" do you mean by homebrewers? Because for me here in Ohio, I have to have it done as part of the new ASTM requirements.

-Dave

GL process does not rely solely on boiling or high temp distillation for methanol removal. He achieves removal also by simple evaporation/condensation at lower than methanol boiling temps due to the air movement over the surface. (BTW-- I see plenty of methanol collecting on the inside of my hoses while draining my newly reacted batches at 40 deg C)

Has anyone any data that addresses the relative damage in terms of increased susceptibility to oxidation of the BD when exposed to the air with and w/o being heated past the boiling point of methanol ?

ReM

quote:

Originally posted by OU_Dave:
Was any Rancimat testing ever done on that procedure? ---snip---), but I've had oxidation stability issues

My apologies for going off topic here--

Do you use any antioxidant additives ? Have you found a source for any that are affordable for small scale brewers ? There are posts here that address this but I have yet to find a source that doesn't increase my cost of production by at least 25%.

Tnx,

ReM

I haven't started using any as of yet, but probably will soon. I'll let you know. If I can get a cheaper price by buying bulk, I'll see what I can do if small brewers are interested in it as far as price break with my bulk discount.

Dave

Hi ReM,

Try this link

Or this link

Interesting info, but not cheap!

Nature's anti-oxidant for oils is vitamin E.

To act as an efficient antioxidant in biodiesel requires approximately 0.1% volume of vitamin E, or 1ml per litre of biodiesel, approx.

If you buy vitamin E oil, check how much is actually vitamin E, as most off the shelf vit E consists of very little vitamin E in a lot of carrier oil.

You may see the potency of vitamin E expressed in IU (international units).

1 IU of Vitamin E is the equivalent of about 0.7 mg

As an example, in this link you'd get 32000 IU or approx 21g of vitamin E, enough to treat 21 litres of completely anti-oxidant free biodiesel. Buying vitamin E in this small volume, and from a health food store, is clearly too expensive to be sensible.

Most biodiesel will have some natural vitamin E in it anyway, if reasonably fresh. The vitamin E will sacrifice itself to oxidisation first, so will become less and less with time, so if you are storing biodiesel for long periods you may need to re-dose.

Hope that helps.

quote:

Most biodiesel will have some natural vitamin E in it anyway, if reasonably fresh

My understanding was that biodiesel made from used cooking oil has little or no vitamin E because it is destroyed by the high temperatures endured in the fryers. Virgin oil would however contain Vitimin E.

ReM suggests that the GL process removes methanol by evaporation at less than the boiling point of methanol. That is however not the case - Graham advocates heating to 90*C - see here and look at step 10.

I have felt for some time that the GL process might increase oxidation. The distillation process uses high temperatures and exposes the biodiesel to copious amounts of air for some hours - precisely the accelerated oxidation conditions used by the Rancimat test. A Rancimat test on finished fuel would be the only way to tell for sure. On the positive side, it ought to be easy to prevent oxidation if it is an issue - either dose with antioxidant before methanol removal, or perform the removal under an inert gas - the latter I think Graham did himself propose.

Cheers

Nick

To remind everyone,

oxidation by itself isn't the worst condition for fuel to be in. For one thing, cetane goes up temporarily when you do this.

I believe that the problem is that oxidation is likely to cause further breakdown in the fuel. This would be higher viscosity due to polymerisation, and other forms of degradation that can lead to higher acid value due to FFA and water-soluble acid formation. However, the Rancimat and other tests don't predict when this may or may not happen, they just tell you that the fuel is oxidized.

Homebrewers have obviously been oxidizing their fuel for years without obvious vehicle problems resulting. The likely explanation is that we don't tend to keep fuel in storage very long, and it tends to get used up before anything too strange happens to it because we make small batches.



Mark

quote:

Originally posted by Twenty4Seven:
. . . the GL process might increase oxidation. The distillation process uses high temperatures and exposes the biodiesel to copious amounts of air for some hours. . . .

The GL process includes an open vent to the atmosphere, but the presence of the vent does not expose the BD to copious amounts of air.

The "air" that is drawn by the venturi from above the condensed methanol is mostly oxygen depleted and 100% saturated with methanol vapors. The "same air" is recirculated from the reactor, where the "air" is resaturated with methanol, to the condenser, where some, but not all of the methanol vapors are condensed, and back to the reactor, etc, etc.

The oxygen in the first volume of air would be consumed in the oxidation reaction, but the total amount of material oxidized would be limited to the amount of oxygen originally present in the air in the headspaces of the reactor and the condensate tank. The design of the system limits oxygen replenishment.

yeah, that's an absolutely brilliant discovery. Anyone done this with argon/CO2 or some other inert gas yet?
Mark

quote:

Originally posted by producer:

The oxygen in the first volume of air would be consumed in the oxidation reaction, but the total amount of material oxidized would be limited to the amount of oxygen originally present in the air in the headspaces of the reactor and the condensate tank. The design of the system limits oxygen replenishment.

Not sure I entirely agree with that. As the oxygen is removed by oxidation, it has to be replaced by something to maintain the same pressure in the tank. It has to be air drawn in from the vent. Thus, fresh air (and fresh oxygen) is drawn into the stream throughout the process. The effect may be mitigated to some degree in the early stages of methanol removal by the methanol vapour itself - but as the prosess progresses, the vapour concentration will reduce and therefore oxidation will increase...... perhaps? Also, as you distill out the methanol, the total volume in the tank goes down - this has to be replaced by air from the vent.

Please don't misunderstand me, I use the GL process and think it's the best thing since sliced bread (what was the best thing before sliced bread?) but I still think there is an issue here that is at least worth investigating.

Nick

quote:

Originally posted by Twenty4Seven:
. . . As the oxygen is removed by oxidation, it has to be replaced by something to maintain the same pressure in the tank. It has to be air drawn in from the vent. Thus, fresh air (and fresh oxygen) is drawn into the stream throughout the process. . .

Agreed. But, the only volume that must be replaced is the volume of oxygen in the air, or about 20% of the initial reactor and recovery tank headspace. The amount of volume to be replaced is a small increment of the original volume, not an order of magnitude.

quote:

Originally posted by Twenty4Seven:
as you distill out the methanol, the total volume in the tank goes down

Doesn't the volume in the methanol recovery tank increase at the same rate as the decrease in the volume of the reactor, temperature issues excluded?

Producer

Yes, you're quite right on the second point - I missed that.

On the first point, what you're saying is that the 20% removed by oxidation is replaced by air which is itself just 20% oxygen meaning that only 4% oxygen in total remains and so on, until the oxygen is almost totaly depleted? Sounds plausible.

Nick

quote:

Originally posted by Twenty4Seven:
---snip---
ReM suggests that the GL process removes methanol by evaporation at less than the boiling point of methanol. That is however not the case - Graham advocates heating to 90*C - see

---snip---

Nick

Please note the words "solely" and "also" in my referenced post--

My point, apparently not made well is that, although it may take longer, methanol can be separated from BD or glycerol at temperatures below its boiling point.

Graham-- any comment on this ?

I like the oxygen depletion theory-- would be interesting to use another gas as gm suggests.



Tnx,

ReM

quote:

Originally posted by ReM:
. . . methanol can be separated from BD or glycerol at temperatures below its boiling point.

In the open air methanol, even water, will evaporate at almost any temperature, given enough time. That's because the molecular concentration of methanol, or water, in the air covering the liquid is, virtually, zero.

In a G/L type reactor the vapor above the biodiesel is saturated with methanol. Therefore, you must increase the temperature of the biodiesel above the boiling point of the methanol or more methanol will not evaporate.

If heat is not added to the reaction, then an equilibrium will be reached. If equilibrium is reached, then methanol vapors will simply pass back and forth between the condenser and the reactor with no more vapors evaporating/boiling from the biodiesel and no more methanol condensing in the condenser.

Hi Producer--

quote:

Originally posted by producer:

quote:

Originally posted by ReM:
. . . methanol can be separated from BD or glycerol at temperatures below its boiling point.

In the open air methanol, even water, will evaporate at almost any temperature, given enough time. That's because the molecular concentration of methanol, or water, in the air covering the liquid is, virtually, zero.

In a G/L type reactor the vapor above the biodiesel is saturated with methanol. Therefore, you must increase the temperature of the biodiesel above the boiling point of the methanol or more methanol will not evaporate.

If heat is not added to the reaction, then an equilibrium will be reached. If equilibrium is reached, then methanol vapors will simply pass back and forth between the condenser and the reactor with no more vapors evaporating/boiling from the biodiesel and no more methanol condensing in the condenser.

Tnx for the explanation--- Sounds reasonable--

Is not the methanol being removed from the air when it condenses and runs in liquid form into the recovery container thus leaving the air below saturation again ??

ReM

quote:

Is not the methanol being removed from the air when it condenses and runs in liquid form into the recovery container thus leaving the air below saturation again ??

Yes, I agree. The recirculation of vapour through the venturi does it. It's a bit like clothes drying on a line - they dry well enough without the surrounding air being anywhere near the boiling point of water. I'm sure that Graham will be able to offer a more scientific explanation involving the vapour pressure of methanol

Cheers

Nick

Evaporation and condensation of methanol in a GL designed processor occur differently than in the open air.

Evaporation of methanol in the open air occurs because the air has an infinite capacity to move methanol vapor molecules away from the methanol source. The G/L processor/condenser is a closed system so has a very, very limited capacity to remove methanol vapors from the source.

Operation of GL's system is based on the different methanol saturation levels in air at different temperatures.

The biodiesel in the reactor, and the reactor headspace, must operate at a higher temperature than the "headspace" around the condenser.

For example, assume (I don't know the exact numbers, but these assumptions work to highlight the concept) the methanol saturation level in air at 90 deg C is 2 parts in 10 parts and is 1 part in 10 parts at 30 deg C. Also assume the operating temperature of the biodiesel is 90 deg C and for the condenser is 30 deg C.

As the air circulates through the reactor it picks up 2 parts of methanol. The air loses 1 part of methanol as it passes through the condenser. Note, the air is still saturated with methanol vapor, but at a temperature lower than in the reactor. The methanol concentration in the biodiesel continually reduces until an equilibrium of about 1 part of methanol in 10 parts of air is achieved. Any further reduction of methanol can not occur until some condition is changed. The operating temperature of the biodiesel can be increased or the temperature in the condenser can be reduced. Either will result in more methanol recovery. But, the maximum methanol recovery will be based on the methanol saturation limit at the operating temperature inside the condenser.

I modified my system with an additional valve not shown in GL's plans (which I used as my guide). The valve opens to the atmosphere and is located between the condenser and the reactor. I open the valve and pull fresh air into the system right at the end of the methanol recovery cycle when, virtually, no more methanol is being captured. The movement of the unsaturated air into the reactor headspace picks up methanol vapor. This air then passes through the condenser and out the vent line to the outside atmosphere. This allows me to achieve very, very low levels of methanol in the biodiesel. This is done only at the very end of the cycle to limit the amount of air (oxygen) introduced into the system.

Very clever....

quote:

Originally posted by girl mark:
yeah, that's an absolutely brilliant discovery. Anyone done this with argon/CO2 or some other inert gas yet?
Mark

I would recommend nitrogen as it's commonly used in aircraft to 'inert' the tanks from explosion risk. I currently inject my large fuel storage tank with nitrogen from a welding bottle to displace any air that is in the tank.