1st try at 7% pre-wash. 1 question.

[neisel]

Fed up with water washing taking as long as the conversion process, I'm going to give the 7% pre-wash process a go.

The process I use currently is 80 /20 2 stage no tit, KOH, water wash, spray dry. It works well but most times I'm doing too many water washes for my liking, sometimes 7 or 8 or 9, which is a PITA.

Unless I've read it wrong, peeps seem to be doing this 7% pre-wash by removing the glyc after 2nd stage full conversion, adding it back & then adding 7% water.

The 1 question is this.

After the 2nd stage is done, the oil left to settle, tested & I have 100% conversion can I just leave the glyc from the 2nd stage in (& or add from the first stage glyc to bring it up to 6-7 litres as needed), turn the processor back on & venturi in my 7% of hot water?

Has anyone tried mixing the glyc with the water outside the processor & dosing it back by venturi?

[Chug]

You can add the 1st stage glyc back and add 7% water, or some folks just leave 2nd stage glyc and add a bit less water.

Not tried mixing the glyc with water first but it mixes readily so it shouldn't be a problem, try it and report back.

[Julian]

I've not heard of anyone doing that either, so as chug says, give it a go.

You could if you have a condenser, recover usable methanol, by adding back the first stage glycerin and then recover methanol in the normal way.  When that's finished move onto the 7% water wash ... no possibility of contaminated methanol that way.

In my process, I then do an acid pump wash followed by one or two pump washes all of about 5%, checking that the pH of the wash water, finishing with drying with the venturi and condenser.

[neisel]

I don't introduce any acid, acetone or anything else.

Would that change anything for me using the 7% wash?

[willbuild]

I have also been doing the acid wash and followed by 5% water washes on my last two batches and it works well for me.
I dont  remove 2nd stage glyc, i add back in 1st stage (de meth opitnal) then a 5% (of wvo volume) water wash, then settle and drain.

[Julian]

I don't introduce any acid, acetone or anything else.

Would that change anything for me using the 7% wash?

The idea of the acid wash is to neutralise the soap in one wash, so in theory it should cut down the number of washes you need to do.  There's info on the wiki, here ...

http://www.biopowered.co.uk/wiki/Water_washing_titrated_acid_method

[neisel]

I don't have any way to calculate how much acid to add.

I do have some 36% hydrochloric acid. It'll be about 135 litres of BD, add 100ml to the 7% water, venturi in, keep fingers crossed or

[Julian]

There is a rule of thumb which Carington came up with, which is multiply the amount of NaOH use in the reaction in grams, by 0.12 to give you the ml of concentrated acid circa (95%+).

For KOH and other acid strengths you can mathematically adjust the result.

[willbuild]

what would the calculation be if using vinegar?

[neisel]

Julian,

Do you think no acid would result in an emulsion?

[Julian]

You're asking the wrong person ... one of my very few talents is emulsion creation!

I know many people have pumped washed without acid and it's worked out fine for them.  Give it a go ... what's the worst that can happen?

There are lots of ways of breaking an emulsion ... ask me how I know!

[neisel]

I'll give it a go & report back.

[willbuild]

There is a rule of thumb which Carington came up with, which is multiply the amount of NaOH use in the reaction in grams, by 0.12 to give you the ml of concentrated acid circa (95%+).

For KOH and other acid strengths you can mathematically adjust the result.

So am i right in saying that, if my vinegar is 4.25 acidity the multiplier would be 2.4 as to 0.12 for concerated acid?

[neisel]

Well, so far so good.

I had a cloudy 100% conversion after stage 1 - 148 litres of very nice WVO, 20 litres virgin meth & 978 grms of KOH processed for about 90 mins & left to settle for 65. Forgot to mention in the opening post that I glyc washed this before adding any chemicals.

Dropped out 11 or 12 litres of glyc leaving 5 or 6 or 7, added 10 litres of very hot water with a splash of hydrochloric acid by venturi & no emulsion! For the first 20 seconds or so it looked like I was poaching eggs but that went away almost instantly & now I've got a sort of milky coffee coloured concoction circulating with no emulsion lumps.

I'll give it an hour & another hour to settle & then start pump washing. It'll be interesting to see if it does require fewer water washes.

Ideally I'd like to be able make a batch in 1 day.

[Julian]

There is a rule of thumb which Carington came up with, which is multiply the amount of NaOH use in the reaction in grams, by 0.12 to give you the ml of concentrated acid circa (95%+).

For KOH and other acid strengths you can mathematically adjust the result.

So am i right in saying that, if my vinegar is 4.25 acidity the multiplier would be 2.4 as to 0.12 for concerated acid?

Sums have never been my strong point, but I make it 2.82.  I don't think it's reall that critical.