Multiple problems

[Milhouse Junior Member Find all posts View Profile Close Milhouse]

I have just made my second batch of BD and I ran into some problems. I mixed the batch in the reactor for about 50 minutes and the reactor became very warm to the touch. The batch temperature raised to about 60 degrees C. I let it all settle overnight and today I drained off the Glycerine. The glycerine was very runny compared to my last batch. It was only a little thicker than water, however was still very dark in colour.

I pumped it all to the wash tank and washed it for 1hr 50 minutes by the bubble wash method. The wash tank became warm to the touch and there was a large amount of foam on top of the tank. I took a test sample of the BD and it was quite cloudy, however was a nice honey colour. There was a amount of cream coloured gunk floating on top of the BD (I assume this is soap)

My questions are:
1. Why was the glycerine so runny, isnt it meant to be fairly thick?
2. Why did the wash tank become hot and foam up?
3. Why is the BD cloudy? I washed the first batch twice (1 x 2hr and 1 x 10 hr) and it cleared fairly quickly. This stuff stays cloudy

I was thinking that I may have put too much catalyst into the mix and the heat in the wash tank was the mix still reacting.....

Thanks
Greg

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Multiple problems

Hello Greg

There are lots of possible reasons for what you have described.
Be very specific about everything you did.

[Guest Close David]

Re: Multiple problems

If you have an appleseed type reactor made from an old water heater it will be insulated to keep as much heat from leaking out as possible. Even with the plumbing radiating and leeching an amout of heat, I still wouldn't think the temp of the BD would drop from 60 to anything below 40 just over night. The bigger your reactor and batch volume, the more stored energy you have.

You won't notice the heat of the mixture in an insulated vessel like a water heater but you sure will in an uninsulated drum which the heat can radiate straight out of!

[Milhouse Junior Member Find all posts View Profile Close Milhouse]

Re: Multiple problems

I have cleaned this batch up a fair bit simply by heating and allowing to settle. I also did another wash. It appears as though there is very small water molecules suspended in the BD which is causing it to be cloudy.

I reread the Collaborative BD tutorial website and they offered water in the feedstock as a problem. I have noticed that there is some water in the oil that I am using. I have tried to prevent this from going into my settling/heating tank and I always preheat the oil before using and allow it to stand overnight so as to allow the crud to drop out.

Does water in the raw oil make unwashed BD cloudy or is it another problem?

Is there any way that I can clear the BD without waiting weeks for it to settle out and wasting heaps.

Thanks again
Greg

[quesoburgesa Senior Member Find all posts View Profile Close quesoburgesa]

Re: Multiple problems

Hi Greg,

Water in the oil will prevent a complete reaction (I believe Tilly has said >1% water will cause problems), and will, to my knowledge, result in extremely soapy biodiesel. I believe this is because the catalyst has not reacted with the methanol, so it has stayed suspended in the oil. The resulting biodiesel is difficult to wash, with an increased risk of emulsion.

When I make mine, I always heat my oil up to 110 deg+ and get all the water out of it. I'm not sure that heating it up to low temperatures, and letting it settle is sufficient, as perhaps some of the water remains in suspension.

If I'm incorrect about any of the above, hopefully someone will correct me.

Justin

[Milhouse Junior Member Find all posts View Profile Close Milhouse]

Re: Multiple problems

Hi Greg,

Water in the oil will prevent a complete reaction (I believe Tilly has said >1% water will cause problems), and will, to my knowledge, result in extremely soapy biodiesel. I believe this is because the catalyst has not reacted with the methanol, so it has stayed suspended in the oil. The resulting biodiesel is difficult to wash, with an increased risk of emulsion.

When I make mine, I always heat my oil up to 110 deg+ and get all the water out of it. I'm not sure that heating it up to low temperatures, and letting it settle is sufficient, as perhaps some of the water remains in suspension.

If I'm incorrect about any of the above, hopefully someone will correct me.

Justin

I think you are correct. The oil I have been getting is pretty bad quality and has a fair amount of water. I have tried to keep most of it out, but when I try to heat it you can really hear it crackle.

I have started to treat all my oil with glis cause I read on this forum that mixing glis with WVO will help remove some water before it is processed by allowing it to settle out. I am also heating my oil to about 70 and leaving the lid off to aid evaporationl

I have narrowed down most of my problems to water in the oil. I just got a bucket and a half of soap out of my last batch but I never had this problem when I was using oil of better quality.

Maybe I need to change suppliers... I am starting to mix tallow with my mix and it seems to be a little easier to process with less problems apart from the higher gel point than normal Bio.

Thanks again
Greg

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Multiple problems

I have posted before about the problems caused by water in your feedstock oil.

It is possible to dry the oil by adding some biodiesel byproduct to the oil after most of the water has settled out and been drained.

Stirring approximately 10% (of the oil volume) of byproduct into the oil will cause the residual water to be taken into the byproduct layer.
After settling, the oil will be significantly cleaner and can be decanted from the soap + wet byproduct layer.
Note: Soap production will occur if there is residual caustic in the byproduct.

If the oil has minimal water content, the soap produced will be a minor amount and will not affect the amount of oil available for processing. Excessive water content will cause significant soap production, so please ensure that the oil is well settled before using this process.

While it is possible to neutraise the caustic in the byproduct using acid, I have not tried using neutralised byproduct for this purpose.



Pretreatment of Dry Oil

NOTE: The byproduct contains all of the "catalyst amount" of the caustic added to the methanol, and about 1/2 of the methanol added to the oil in the batch from which the byproduct was obtained. Thus, using 5g/L NaOH as the Catalyst amount, with 22% methanol and with a 20% byproduct layer, there will be approx 25g of caustic and 500 ml of methanol in each litre of the byproduct. This should be enough to react up to 2.5 litres of DRY oil having a titration of 5 g/L.

Has anyone tried this pretreatment?
Did you test your results? What were the outcomes?

[fantom Member Find all posts View Profile Close fantom]

Re: Multiple problems

hi Tony you said:-
Pretreatment of Dry Oil

NOTE: The byproduct contains all of the "catalyst amount" of the caustic added to the methanol, and about 1/2 of the methanol added to the oil in the batch from which the byproduct was obtained. Thus, using 5g/L NaOH as the Catalyst amount, with 22% methanol and with a 20% byproduct layer, there will be approx 25g of caustic and 500 ml of methanol in each litre of the byproduct. This should be enough to react up to 2.5 litres of DRY oil having a titration of 5 g/L.

Tony I can't see how there can be 500ml per litre of glis. I'd say it would be more like 250ml as I am getting about 25-30% methanol recovered from the volume of glis. I use 22% methanol in my bd reaction. And 25g of caustic in each litre of glis? sorry but this just does not add up, as most of the causic is used up in the reaction. certainly can't be if ya only start with 5g per litre of methanol.
Tony please feel free to correct me if I am wrong.

Cheers Fantom