A/E Question

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

Morning all....I've made a 20 l batch using ae and cant quite pass 3/27 ie 6% unreacted.

Started with 25 ml 98% acid into reactor ( didnt decontaminate the reactor of base leftovers !!!! ) then mixed in 2 l meth.mix on and off( mostly on as pump warms as well ) for 3 hrs temps between 65 and 55 deg c. T at 9.5 to start-got down to 6.5.

Tried to drain a little black yuck but nothing to be found on the bottom ( did a 1 L batch and got 6 % as well) so went to base with 140 g naoh and 2 L meth. ( figured Id do a base base) got 6 % unreacted
Added another 20g naoh and 400 ml meth. Didnt shift it much at all.

thoughts.............
Water eating up the meth?
My pump turns that batch over every 20 sec..sooo over processing ??
open top 44 pretty well sealed ( cant see escaping vapors at 65 c )
I drained the contents last night to prevent glyc blockages ( found a LITTLE white liquid but not much )

got 19 L "bio" +1.5 L solid glyc this morning... ( some fluid missing???...20 L oil +4 nearly 5 L meth ? )

If Id been up to it last night I may have tried putting the bio and half the glyc + .75 l new meth back in THEN tried another 20 g naoh and 0.5 L meth to get to completion

Any thoughts people?
Also..do you believe the titration 100% and mix accordingly or add a little more for good measure?

Cheers

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

Re: A/E Question

Hi Farmerpete,
Just a few thoughts.
You reacted 20 litres of WVO and got the titration down to 6.5 in the AE stage.
That means that the NaOH required is (6.5+ 5)=11.5g X 20= 230g total NaOH if you performed a single stage.
You used a total of 140g NaOH in the Base/Base?
Then you added 20g NaOH in the reprocess for a total of 160g NaOH.

I think you are short on NaOH in the reaction

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

Re: A/E Question

Hi Farmerpete,
Some more thoughts.
Did you actually measure the output of your pump or are you just going by the rated output. Pump tests people have performed with biodiesel reactors have shown a pumping rate less than that rated on the pump.
However it sounds like you have a very strong pump and that should not be a problem.
I have never seen "overprocessing" demonstrated so I do not think that is a concern.

When you do AE, the times involved are so long that you need to have a tignt reactor. Just an open vent pipe leading up and outside. Otherwise, At the temperatures you are holding the reaction at for hours and hours evaporation will be happening and you will not see it.

When you do a reprocess never leave any glycerine in the reactor. It will act like a big sponge and soak up a good portion of the methanol you added in the reprocess.

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

Re: A/E Question

Cheers Tilly...

just so I'm not guessing, the 6.5 in the (6.5+5) comes from the final t of the ae stage before i went to base? Somehow I decided 5+1.5 or round up to 2 =7 g per l oil. I should have sat tight and given the acid more time to do its job

I remember reading (somewhere ) it would be better to do a solid 1 stage base with plenty of naoh and meth ,that to do a 1st stage base that just got a break then doing another base to finish. (something about the water creating process and its retarding the reaction ?

Also....If I did do a second base reaction how would you have proceeded from the point in my process where I did the 3/27 and had 6-7% drop out ?

Any thoughts on adding an amount (how much ) of acid to oil to use it to attract water and pull it to the bottom of my storage shuttle...1000l ?



thanks Poiter

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

Re: A/E Question

Just a few quick thoughts.
Yes, the 6.5 came from the final titration of the AE stage. You still need to then add the "Base" amount of 5 into the reaction.
If you had continued running your AE stage there is a good chance the titration would have continued to fall.
My AE experience is limited to some testing I did 5 or 6 years ago.
When you turn the mixer off the reaction pretty much comes to a halt.

It depends on what you want to achieve as to what procedure you should use.
Even though my oil titrates less than 2 I still do a 2 stage Base/Base procedure. My concern is to reduce Methanol use so I do a different type of 2 stage base method than most people.
I also do not worry about 3/27 testing because my engine does not require very high conversion biodiesel.
I do not know what 2 stage procedure you would do.

[WesleyB Donating Member Find all posts View Profile Close WesleyB]

Re: A/E Question

25 ml of sulfuric acid neutralizes about 37.5 grams NaOH, into sodium sulfate. So you had 120 grams left of NaOH to act as catalyst for about 20 liters vegetable oil. If your titration was 6.5 and the base amount of NaOH to use as catalyst is 5 grams per litre, Then it seems you're light on NaOH, to me. I have done AE successfully a few times in test batch amounts. I heat it with the methanol/sulfuric acid, overnight, not just three hours. But the AE process I did was on a small lab scale. Thanks

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

Re: A/E Question

Just a reminder,
The sulfuric acid is included in the 6.5 titration number.

[WesleyB Donating Member Find all posts View Profile Close WesleyB]

Re: A/E Question

Thanks Tilley about that reminder. About the volume of the product in question, for corn oil, 20 litres of oil makes about 21.6 litres of biodiesel for a 100% reaction and about 1.3 liters of glycerine plus methanol in the glycerine layer and methanol in the biodiesel layer. I'm confused why only 19 litres biodiesel product. Was there a spill. Do you measure the density of the biodiesel product? I get 0.845 grams per millilitre for biodiesel, but I've found on the internet density for biodiesel should be0.87 to 0.88 grams per millilitre. Thanks

[WesleyB Donating Member Find all posts View Profile Close WesleyB]

Re: A/E Question

If the density of the pure product biodiesel is 0.88 grams per millilitre then ideally on paper calculations for 100% transesterification reaction the volume of methyl biodiesel product for 20 litres of corn oil should be 20.9 litres. The volume of product should be larger than the volume of starting material. I've only figured it for corn oil but it should be true for other types of vegetable oil also. Formation of soap is a complicating factor in calculating. Thanks