Cold Processing

[Guest Close David]

After reading some wide and varied info on bio, I'm wondering if it is possible to make bio without heating the oil first?

If say the conversion was attempted on fully liquid oil at a reasonable temp, say 20oC, and the mixing time was extended to say 3,4, ? Hours, could reasonable yields and overall decent quality of bio be made?

Does heating the oil just allow for a faster reaction or dose it allow other phenomena to take place?

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

Re: Cold Processing

Hello David

I have performed tests which showed that you can make just as good biodiesel whether it is cold or hot provided your oil remains a liquid and you mix for the correct amount of time.
For every 10deg C the reaction temp is decreased reaction time doubles.


50deg C= 1 hour reaction time
40deg C= 2 hours
30deg C= 4 hours
20deg C= 8 hours.

Tilly

[Guest Close David]

Re: Cold Processing

Thanks Tilly.
Lack of heat certainly slows things down!
With these extended reaction times, have you found the mixing needs to be constant or could it be done intermittently, say every 5 or 15 minutes?

Another question for you....

Will longer mixing times allow less meth, Koh or both to used and still produce decent bio?

I read someone was using less chemistry and increasing the mixing time to compensate but I am wondering if this will still allow a proper conversion to take place?

My best guess is that it may be possible to use less meth as it is recoverable from the glycerin in a more or less pure form and therefore not " consumed" as such, but I'm not sure if the koh could be reduced in the same way?
From what I have come to understand, the koh is not in the converted bio so it still must be in the glycerin but I do not know if it is changed into another compound or it is just mixed in with the other reaction byproducts?

How close are my guesses?

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

Re: Cold Processing

Hello David

Tests have shown that intermittant mixing is fine, once every 10 or 15 minutes to mix all the glycerine back into the biodiesel.

You said:
"Will longer mixing times allow less meth, Koh or both to used and still produce decent bio?"
None of the tests I have performed nor any other tests I have seen suggests this is possible.

You said:
"I read someone was using less chemistry and increasing the mixing time to compensate but I am wondering if this will still allow a proper conversion to take place?"
There is a lot of inaccurate information posted on the forum about biodiesel production.

You said:
"My best guess is that it may be possible to use less meth as it is recoverable from the glycerin in a more or less pure form and therefore not " consumed" as such, but I'm not sure if the koh could be reduced in the same way?"
I have never performed a test that showed you could get away with using less methanol. Tests I have performed showed that If you have low titration oil, you can perform a 2 stage Base/Base procedure and save about 1g NaOH per litre oil reacted and achieve about the same results as the single stage method.

Tilly

[Guest Close David]

Re: Cold Processing

You said:
"I read someone was using less chemistry and increasing the mixing time to compensate but I am wondering if this will still allow a proper conversion to take place?"
There is a lot of inaccurate information posted on the forum about biodiesel production.

Yep, That's why I took the opportunity to ask someone who would know the correct answer.

Thank You again.

[chookshed Biofuels Forum Newbie Find all posts View Profile Close chookshed]

Re: Cold Processing

In regard to less methanol:

Chemical reactions, if based on the exact amounts required to just get the job done will stop when they reach equilibrium. This equilibrium state usually means your reaction only progressess some of the way, ie you have a balance of reagents and products.

You can push the reaction to completion, use all the oil in two ways:

Either take the products away from the "system"
or
Have a large excess of one of the reagents; in our reaction this is methanol.

I hope this helps

Steve

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

Re: Cold Processing

Hi All
This may also be of help as well
Published information on the rate of the reaction shows that there are three key stages in the overall reaction, which take time based on temperature as well as pressure
The ratios of converting oil's or triglycerides into methyl esters for biodiesel is a relationship based on exact amounts of oil and another material usually an alcohol, the ideal of course is what can be calculated rather than what is done in practice
The process is also known as alcoholysis
We use methanol, in our case the molar ratio is known to be about 6;1 Any other alcohol that may be used will have a different molar ratio,
These ratios are fairly well "fixed" using a common term "not a scientific one"
So in any transesterification process we will be faced with these three steps that take place in the reactor

1. Mixing the methanol/methoxide with the oil,

2. A fairly rapid reaction to about 80% conversion which needs sufficient methanol but not an excess,

3. A slow reaction to about 87% conversion at equilibrium which can be pushed to maybe 97% conversion if sufficient excess methanol is present.

The first mixing constraint can produce a "lag-time" while methanol and oil are pushed into contact.
To speed up this process, stirring is required within the reactor.
Not much mixing is needed if the methanol is squirted into the hot oil through small holes at the bottom of the reactor vessel
This can be done with an old shower head mounted face up, internally of course, at the bottom of the reactor vessel the methanol pumped in from a hand or a mechanical pump
A 12 volt automotive type fuel pump from a fuel injected car with the appropriate delivery rate for the size of the batch being made would suffice
The solubility of methanol in oil rises rapidly as the boiling point of methanol is approached
If the oil happens to be a bit above the boiling point of methanol (64.8 deg C ), the hydrostatic pressure in a tall and narrow reactor keeps the methanol liquid up to about 70 deg C
This means the weight of the oil itself creates a pressure at the bottom of the vessel
The second stage, which is fairly rapid, produces the peak concentrations of di-glycerides and mono-glycerides within about 10 minutes.
If we use the 6:1 molar ratio (25% v/v), there is no great advantage to dumping the methanol in one big addition.
There is a good chance that some of it will by-pass the oil, something to be avoided
The third stage of the reaction is the slowest of the three and takes up to 40 minutes at 60 deg C
This stage requires excess methanol so, ideally, all the methanol should have been fed into the reactor after about 15 minutes
The point is if we are to get the maximum conversion of oil into biodiesel the feed rate of the methanol should be adjusted to the above parameters
Conversion rates of oil up to 98.5% are achieved quite easily using this approach given a very low FFA content in the initial material
Stirring of the mixture can be and should be minimised after all the methanol has been injected so as to help with the glycerin "fall out"
Finally,
This thread talks about cold oil and less chemicals to be used in the process, if one can make decent "bio" under those conditions
I suppose the answer would have to be a yes, if we are to ignore time as well as the conversion rate as well as the final result in so far as quantity of usable product
Cheers
Chris

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

Re: Cold Processing

Hello Mark,
I see what you have posted comes from Dr Michael Allen's "Deepthort 100B Posting" On JtF.

I do question some of his information.
The reaction timeline is a case in point. I have never seen this information posted anywhere else.
Mike Jureidini who is/was a consultant to SAFF's commercial biodiesel production venture posted to the Infopop Forum that their reactor achieved 99% conversion to esters in 10 seconds. If this is the case, it is apparently due mainly to the violent mixing involved.

Neutral (PhD Chemistry) did a test that showed the temperature of the reaction could be taken to 70deg C before reflux began to occur and was not because of hydrostatic pressure. This whole thread is interesting.
As a side note, At 70deg C the reaction is complete in about 15 minutes using normal home production procedures.

Dr Allen's advice that "Stirring of the mixture can be and should be minimised after all the methanol has been injected so as to help with the glycerin "fall out" also goes against tests results. Almost all of the methanol/NaOH is in the glycerine. If the glycerine is allowed to settle out of the reaction zone it takes the methanol and NaOH with it and the reaction is cut short.
While it is true that once the methanol/NaOH has all been introduced into the reactor and thoroughly/violently mixed it is no longer necessary to continue mixing violently, it is necessary to mix so that the glycerine is not allowed to settle out.

Neutral has achieved a conversion of 99.89% using 260ml methanol and 13.85g KOH in a litre of new oil

Tilly

[Maxwell Member Find all posts View Profile Close Maxwell]

Re: Cold Processing

Do we need to have such a complete reaction?
We know that we can run SVO in our vehicles with modifications.
What we need to know is how much methanol/NaOH we need to eliminate the need to modify the vehicle to be used.
Cheers
Maxwell