Chemists! Is using 50% KOH & 50% NaOH in 2 Stage Process stage 1 OK?

[neisel]

By OK I mean safety wise really. It's not going to blow up or spontaneously combust, is it?

I'm running low on KOH & am wondering if I can stretch it out to last this fuel making season by using 50% NaOH in my first stage instead of 100% KOH.

I use 100% NaOH in Stage 2 as I water wash & am not concerned with the viscosity of the glyc since it gets washed away before it gets even remotely hard.

Presumably the glyc in my 50/50 scenario would be more runny than that produced by straight NaOH & less runny than straight KOH glyc?

[dgs]

 Can non chemists also answer this?

It's fine. I've been doing it for years.

Dissolve the potassium first, then add the Sodium when it's warm, it dissolves quicker.

The glyc is always liqiud except for cold snaps in Winter when it can go partially solid. As you say its more viscous than just using KOH.

[neisel]

I suppose making bio has turned us all into chemists to one degree or another, though I'am a v. amateurish, ignorant, incompetent one.

I went ahead & as you predicted it turned out fine. 145L of WVO consumed 450grms of KOH & 350 of NaOH with 16L of v. meth, followed by S2's 150 grms of NaOH & 4.6L of methanol mixed up a treat. 100% conversion, no explosions, no fires, no soap. Easy peasy.

[nigelb]

Isn't shed alchemy brilliant.

Not so good when it goes wrong but if those episodes are kept to a minimum it's happy days.

[dgs]

 Well done. although I'm a bit puzzled about the % of chems you used noteably methanol in S1.

Presumably your oil was glyc washed.

[neisel]

Yes, it was glyc washed.

What do you find odd about the S1 chem percentages?

[neisel]

Bump!

[dgs]

Hi neisel, sorry, have been busy with various things.

Your total catalyst addition equated to KOH is 7.9gms/litre which is slightly less than base. in other words after your glyc wash there would appear to be no ffa's left in your oil which is unusual.

Average oil that titrates at say 5.0 titrates at about half that when glyc washed.

You only used 11% methanol for S1. Normally 14% is min to get reasonable conversion.

you didn't give us the dropout after S1. Did you leave at least overnight. Did you check dropout after S2.

Are you sure about all your values. I would be lucky to achieve those figures with new oil that I sometimes use.

Just more puzzled than anything .

[neisel]

dgs,

Thanks for coming back to me.

Measured about 2 hours after I turned the machine off at the end of S1, dropout was 10%. S1 was four 8-10 minute bursts of mixing with a 20 minute 'rest' between each burst. My WVO is lightly used & v. clean - no water, no whites, no food. It is taken from the fryer after cooling overnight from operating temperature & is, I think, dry.  When dropout after S2 is not zero it is only maybe 1 or 2%, too little to worry about IME.

I've been doing it like this for for several years now & typically use 20-21L of v. meth to make 145L of BD.

TBH I don't know what an FFA is.

[neisel]

This may sound weird to you actual chemists but what I do is, using the no-tit calculator I tell it I have only 125L of WVO when I actually have 145ish. Methanol @ 16% gives me figures of 16L of meth & 625grms of Sodium or 875grms of Potassium (half those amounts if I' using half NA & half K.)

I suck it in, do the 4 bursts of mixing & fine tune it in S2 after I've seen the dropout.