We have been processing for a year now and was taught by someone that used NaOH, And we just stayed with with NaOH. I think maybe just because he made soap? We are processing abour 250 Gals. a week. and we are having some trouble passing the 3/27 test whenever we get some wet oil (9000 to 10000 PPM). I try to use only dry oil but it hard to do this all of the time. My question is, would KOH be more forgiving than NaOH when we run into the wet oil? My supply of KaOH is about gone and I was wondering if it would be a good time to switch to KOH. What are the advantages or disadvantages of KOH over NaOH. Thanks for any advice.

The way I understand it, water in the oil will create lots of soap which kills the reaction. Koh soap takes longer to dropout then NaoH soap so you will be no further ahead using KOH for wet oil.
I understand that KOH is a little more tolerant then NaoH for high titrating oils but that has nothing to do with water content.
What you really need is a dewatering setup. A glycerin pretreatment also helps to dry the oil...
Jon

As Jon stated KOH won't help you anymore with wet oil than NaOH does, Personally I prefer NaOH

KOH based glyc usually stays liquid, whereas NaaOH can set solid.
KOH is more expensive than NaOH and you use more of it as well (7g KOH base figure + T, compared to 5g NaOH base figure + T)
KOH is much easier to mix into methanol, than NaOH.
Soap doesn't settle out quite as quick with KOH as it does with NaOH.

I guess my main issue with NaOH is that the glycerin thickens up so much below 60 degrees that it's hard to handle. I tried the 10% water wash for a while but didn't see much inprovement, So I'm thinking that maybe the glycerin pretreatment way might be what I need to try next and thougth that the KOH would be easier to handle? I do need a better way to dewater. Now I just heat and settle and has worked fairly well during the hot summer months but I see cold weather coming and I'm sure it won't work as well then, From what I have read the cold upflow is not the best way for biodiesel? Would a centrifuge be the best route for me? This H2O in oil is a pain, I only have 1 good source for dry oil and the rest of them give me fits. I really appreiciate your help.

Try the glyc pretreat-you will be impressed with the result

if the thickening glyc is your main issue then you will probably prefer KOH, I like the fact that my NaOH glyc sets up solid (especially now that my glyc is well demethed), probably coz I'm poor and it means I can get every last drop of bio out of it! I used to hate seeing the odd half inch or so of bio settling out on top of the glyc before I started demething the whole batch.

We are not recovering our Meth, Will this help or hurt if we pretreat? I've searched alot and i'm confused on how to pretreat? Do you drain the glycerin before you triate? also I've seen where you can dewater with the glycerin, Would the Meth in it help or hurt it to use it to dewater? Also wasn't clear on how to do this. thanks

having the mathanol in the glyc will not hurt glyc pre-treatment of wvo at all, and meth has an affinity to water so probably helps with water removal.

Pretreating with glycerol not only lowers your titration levels, but also gets rid of most of the water as well as dropping out the excess chunky bits. you can use as much glycerol as you want to, ( we have used 200%) you will also recover a lot of the bio left in the glycerol. Titrate the pretreated WVO after letting the glycerol settle out. Also you don't have to worry too much about dropping out all the glycerol before adding your methoxide. Jim.

Pre treatment with glycerol? I'm guessing all that is, is mixing glycerin in oils before processing, let settle and drain off then tirtate and process and ususal? Do you have to heat the mixture or can it be cold?

quote:

Originally posted by BIOMAKER:
Do you have to heat the mixture or can it be cold?

I heat the WVO to the same temperature as I do my reaction at before I add the glycerol, 55 C. I believe that leaving the methanol in the glycerol is better as it also has an affinity water. In fact I now think there is no such thing as too much methanol during the processing of BD, until the final stages.