Cutting down the amount of methanol used (on the 2 stage reaction)

[Head Womble]

I do 200L batches and add 25L meths + 1000g NaOH on the first stage,
then only 20% meths for the amount of dropout in the second stage,
I normally get around 2.5ml dropout, so around 50L left to convert,
that's around 35L of fresh meths + what ever is left after gly prewash.


As to how much meths stays in the gly when prewashing,
all I can say is the gly is very thick and gloupy when it's drained,
but runny enough to be sucked in via venturi to start with.

Mark I know you like to experiment..

Would you try 30 Litres in stage one and then 5 in stage 2. ?       Same total but I think you may stretch to 85 % maybe a touch more conversion from stage 1.   Just a gut feeling that stage 1 may be stalling due to the amount of Meth.

I used to use 32L in the first stage, 25L with the NaOH and then 7L after (I mix the methoxide in 25L drum so it's easier),
one day I forgot to add the extra 7L and didn't notice any difference, so I just carried on with only 25L.

[Carrington]

Hi all
Going on my experience the bio production uses 12.5-14% total batch volume meth depending on oil used, the bio holds on to between 2-3 % tbv
So on a 100L batch of oil + 20L meth

S1
80% meth = 16L
Meth used = 10L
Meth in bio about 2L
Meth in Glyc about 4L

If it was me I would try with just 20% meth to start with but I would make sure I have some good clean Glyc from earlier batch to mix in after reaction or the Glyc produced may settle.

This way a small % reduction in s2 works out to be much more the if the remaining meth is only 20% tbv.

Paul

For your s1 do you use 80% catalyst based on titration?

Interesting that only 10% is used in the reaction for your s1 (presumably measured by doing a 10/90?)

Hi Tony
My description is a bit confusing (sorry )
It was mainly to say that although there is meth in the Glyc there isn't as much as people think as most of it does get used in the reaction.

Will have another go at a explanation when I have a bit more time.

Paul

[julesandtash]

Do either of you WBD or recover any Methanol ?

No, I dont recover any methanol at all. I reused the glycerol for glyc wash (which gets some of it back) but water wash the bio (using the titrated in-processor method) so dont get anything back from the bio. That is why I try to minimise the amount I use in the first place.

[Head Womble]

I do 200L batches and add 25L meths + 1000g NaOH on the first stage,
then only 20% meths for the amount of dropout in the second stage,
I normally get around 2.5ml dropout, so around 50L left to convert,
that's around 35L of fresh meths + what ever is left after gly prewash.


As to how much meths stays in the gly when prewashing,
all I can say is the gly is very thick and gloupy when it's drained,
but runny enough to be sucked in via venturi to start with.

Mark I know you like to experiment..

Would you try 30 Litres in stage one and then 5 in stage 2. ?       Same total but I think you may stretch to 85 % maybe a touch more conversion from stage 1.   Just a gut feeling that stage 1 may be stalling due to the amount of Meth.

I used to use 32L in the first stage, 25L with the NaOH and then 7L after (I mix the methoxide in 25L drum so it's easier),
one day I forgot to add the extra 7L and didn't notice any difference, so I just carried on with only 25L.

Steve, to follow up on this, I have recently started using 25L of meth and 800g of NaOH in my first stage,
so I may not be adding the 30L of meths but I have reduced to catalyst,
this has so far reduced the total NaH used on average,
so yes you were right, the reaction did seem to stall due to the unbalance of chemicals.

[Dickjotec]

Here's a thought, if s1 at 12.5% stalls due to lack of Meth, presumably there is no point in re-introducing that Glyc back for WBD?  Might reduce process costs for those that WBD.

By no means conclusive but on the last 2 batches I did using acetone. The first was just a bio demeth without the second stage drained, the second a WBD and there was little difference in the meth recovered.

160L batches 25l 800g NaOH stage 1

Dick