I'm puzzled by the results of the last couple of batches of biodiesel I have made. I have been using recovered methanol of greater than 95% purity. Instead of 10 gallons of methanol I use 15 gallons of recovered methanol with an extra bit of lye.

Normally with fresh methanol, my reaction requires 10 gallons of methanol and about 4kg of KOH.

I am using the GL process with one step removed (at least in the last couple of batches) of the 5% prewash.

After draining the glycerin, I heat the biodiesel again to recover excess methanol and then put the fuel into storage. The fuel is nice and clear but a little thicker than what I would see with out methanol recovery.

One things for sure, the truck doesn't run too well on it, it surges like there is an air leak in the fuel lines. I've been cutting it with diesel fuel, about 45%, to lessen the surging.

Can one boil off too much methanol and ruin a batch of biodiesel? I would say no, but stranger things have happened.

I've been recovering about 1.5 gallons of methanol from ~45 gallons of methanol. Does that sound about right? I purchased a hydrometer to test the methanol purity and will pick it up tomorrow. I was using my friend's hydrometer to confirm methanol purity.

The only thing I can think of is a post recovery 3/27.
It may nit be perfect, but none the less, some kind of base line.

Did you wash and dry it before pouring it in your truck? Washing and drying the fuel is intended to remove all methanol, unreacted catalyst, soap and other undesirable crud. You can not boil off too much methanol, but if it is your only means of cleaning your bd, you could be leaving several other contminants in it.

TDI,

No, I didn't run the biodiesel through my drywash towers, I needed the fuel to get to work the next morning which I did, but the truck was surging during the drive to work.

I only used about 7 gallons of that batch for use in the truck, the remainder is currently being stored in my 55 gallon fuel drum awaiting a run through the wood chip drywash tower.

I suppose this is what I get for skipping steps and being impatient.

I'm going to venture a wild guess and say that you may have had water in your reclaimed methanol, which led to soap creation during the reaction, which thickens the fuel and may be clogging your filter -- which definitely leads to surging. Not the only option, but one I'd consider looking into.

Cheers, John

John,

Good idea, I'll look into that. I will run the remaining batch of fuel through the wood shavings/dust to further refine.

I think that leaving out the 5% prewash from the process only added to the problems. One thing I have noticed is that after methanol recovery from the biodiesel, it is quite a bit darker, like a dark honey color rather than the light beer appearance that I got before I did the recovery.

there are plenty of folks with GL style processors, including myself, who don't bother with a 5% prewash anymore, we just react until 3/27 pass then demeth and settle soap out and a final filter and into storage drum or vehicle.

quote:

Originally posted by Spencnaz:
I think that leaving out the 5% prewash from the process only added to the problems. One thing I have noticed is that after methanol recovery from the biodiesel, it is quite a bit darker, like a dark honey color rather than the light beer appearance that I got before I did the recovery.

Hmmm... I know that the excess methanol is one thing that helps the glycerine layer quickly separate from the biodiesel layer. If you are de-mething the fuel and the waste layer at the same time, you're effectively stirring up the mixture as the methanol boils out. And since you are reclaiming the methanol, the two layers may not split out as well or as quickly as before.

My guess is that you have a bunch of glycerol in the fuel -- that would explain the darker color as well as the problems with burning it.

I've heard of people saving their glycerine layer for a few batches, and demething it separately from the fuel itself, in part to avoid this kind of issue. Just another thought, only worth what you paid for it!

Cheers, John

Hey John,

I've always drained the glycerin prior to methanol recovery from the biodiesel. But what you say does make a lot of sense if there is still some residual amounts of glycerin in the fuel.

I use my reactor not only for biodiesel manufacture but also methanol recovery from the glycerol byproduct. I may have some cross contamination going on here and haven't really noticed the issues until now.

The remaining biodiesel still in the reactor (about 30 gallons) has been settling since Saturday night. Tomorrow evening, I will drain into a 5 gallon container and see if the fluid lightens in color as it is drained. Also, a 3/27 test sounds like it would be in order.

quote:

If you are de-mething the fuel and the waste layer at the same time, you're effectively stirring up the mixture as the methanol boils out. And since you are reclaiming the methanol, the two layers may not split out as well or as quickly as before.

My guess is that you have a bunch of glycerol in the fuel -- that would explain the darker color as well as the problems with burning it.

The opposite is true, when the methanol is removed the glycerol will drop out WAY faster, like as in completely settled in 10 minutes without the methanol. This is why when using GL's push/pull or Chugs WBD you drain the glycerin immediately after recovery, no settling time is required.
Spencnaz,
It sounds like you are experiencing a back reaction. You can boil off too much methanol if there is still glycerin present, in simple terms without the methanol the biodiesel will react with the glycerin and start to turn back into oil (if I have it all strait). The push/pull relies on neutralizing the caustic with acid and low temps for recovering using vacuum and the WBD also relies on low temps and only recovering to the stoichiometric amount of methanol thus avoiding the back reaction. The fact that your fuel came out darker after recovery is also indicative of a problem...
Before there is anymore speculating you should preform a 3/27...
Jon

quote:

Originally posted by dukegrad98:
I'm going to venture a wild guess and say that you may have had water in your reclaimed methanol, which led to soap creation during the reaction, which thickens the fuel and may be clogging your filter -- which definitely leads to surging. Not the only option, but one I'd consider looking into.

Cheers, John

Not that wild a guess at all- I totally agree with this assessment.

I usually get about 5L of methanol out of a 150L batch of fuel. Then into the settling tank for a 24 hour bubble to remove any residual methanol. Any left over glycerin will drop first with the soap dropping out after. I let it settle further for a day or two and filter to 10 micron. My soap tests usually run 100ppm or less and have had no problems after 2 years in the Benz. I have been using my processor from the start as a methanol still as well and it hasn't caused any dificulties. But then the Benz is very tolerant of fuel quality.

Tony

Ok thanks for all the input. I'll have a look at it again on Thursday or Friday night. I'm working a temp job right now and that cuts into my day time biodiesel pursuits.

If I do indeed have a back reaction, should I just re-react with additional methanol? And yes, a 3/27 test is definitely in order.

The surging is just like when there is air being sucked into the fuel system via a leak. I can see how a soap blockage would cause a similar condition. When diluted with diesel the symptom is less pronounced. It only really happens when the throttle is pressed hard for hills and at freeway speeds when demand is high.

Now that I have a hydrometer to methanol purity testing, I can ascertain if there was water contamination. I'm thinking there was as I remember some persistent drips of cooling water from the recovery condenser getting in the methanol collection bottle.

Spenceaz,
I am gonna jump in here just with my experience. After my 1st demething because I wanted to drywash I ended up with massively clogged filters and surging. What happens is although the glycerin may fall out a little quicker, not WAY faster in my opinion, if you are using KOH you will get soap falling out for several days which is scary and deceiving because you are not sure when its done. This soap is dark ruby red and would make your fuel darker. If you pumped this into your truck and had soap fallout in the tank you are just clogged. Change the filters and run a little dino to clean..

If you drained your glycerin I dont think you have a back reaction because there is nothing to back react with anymore..

Lisa

Spencnaz,
How long are you settling it after demething? and do you filter it after settling it too?

The 5% prewash removes a good bit of the soap, but if you left the prewash out, then drained the glyc and demethed just the bio, maybe you just didn't allow it long enough to settle the soap out, or filter it well enough after settling?

I now recover methanol from the whole batch and with no excess methanol left in bio or glyc the majority of soap drains out with the glyc, and the remaining soap in the bio settles within 12 hours.

Lisa,
I guess you may not have removed all the excess methanol, once all the excess methanol is removed the soap settles out in hours (even if using KOH), if your soap didn't settle out quickly then I suspect there was still some methanol left which was holding onto it.

This message has been edited. Last edited by: Chug,

quote:

What happens is although the glycerin may fall out a little quicker, not WAY faster in my opinion,

Add some demethed glycerin to some demethed biodiesel and try to get it to mix, you will soon change your opinion. This is also well documented in the GL push/pull threads and Chugs WBD threads. The key is to get out ALL of the methanol and then to let it settle for at least a day(using NaoH anyways), even a very small amount of methanol will allow the soap and glycerin to stay in suspension.
If you pumped the bio into your truck without letting it settle you will definitely have soap dropping out in your tank Spence. I have no experience with KOH but many have posted there experiences with it taking much longer to settle out then NaoH...

Even if you did have some back reaction it should not effect the performance of your 6.9, I was postulating on what may have caused the darker colour after demething...
Jon

To recap what I did. I made a 45 gallon batch of fuel with 15 gallons of recovered methanol. The reaction proceeded normally. I mixed the entire tank for 2.5 hours and let it settle for 24 and drained the glycerin.

I don't think I got all the glycerin out as I could see the fluid stream go a little dark and then lighten up as the biodiesel went through.

I heated the biodiesel up to do methanol recovery for about 2 hours (with 240V and 5500W it doesn't take too long). I recovered 1.5 gallons of methanol which is typical thusfar.

I then shut the element down and then filtered some of the still hot biodiesel through my 5 micron filter into one of my clean 5 gallon fuel cans and added it to the truck.

I didn't sawdust filter, I needed the fuel to get to work the next day.

I'm starting to lean towards the soap theory as I checked the fuel lines for leaks and when adding petrodiesel, the problem either dies down or goes away.

A 3/27 test is fully in order for the remaining ~30 gallons that are due to be put through the sawdust/woodchips.

spence

after your method clarification I'm sold on it being soap, but there is an easy way to confirm it is soap, if it is then the remaining 30 gals should have soap settled on the bottom?

Thinking it through, I stand corrected by Jon Heron -- demethed glycerine waste product should settle out faster, that's true. But you still have to give it time to re-settle after you demeth -- boiling it out under vacuum is going to stir a lot of it back up into the upper biodiesel layer. Give it all time to fall out!

And I still think water in the methanol made some soap and goofed up your reaction a bit -- please keep us posted.

Cheers, John

Ok update: I have posted also annotated pictures of the samples and 3/27 test I did tonight.

I tested the methanol stored from the recovery process and they hydrometer shows 90%, so there is some sort of water contamination which I suspect came from a leak at one of the plumbing joints on the condenser, it has since been fixed.

I added the 30 gallons to the sawdust settling drum and noticed something rather alarming. As the biodiesel was coming out of the pump nozzle, a layer of suds not unlike that seen on a head of Guiness was developing on the top of the fluid level. I've not seen this yet in my biodiesel operation. Of course I've not used recovered methanol either.

Gunk at the bottom of the flask after 4 days of sitting:




Results of 3/27 on the fuel right out of the reactor:




Fuel prior to addition to the sawdust column:




Fuel after going through the sawdust column by gravity:




With the input received thus far, I'm leaning very strongly to the assessment that water contaminating the recovered methanol used either ruined this fuel or rendered it marginally useful. Should I just cut this stuff with a large ratio of diesel fuel? I'd hate to let 30 gallons of potential motion lotion go to waste.

Or should I re-react this stuff? It should be noted that the biodiesel clarified greatly after a pass through the sawdust. I didn't have enough pure methanol tonight to do another 3/27 test but will here soon.