Waterwashing!

[Islebio]

Hi,

With great reluctance i am starting to look at water washing. I have a JL processor with condenser to lift and recapture methanol through demeth. I bubble for 15 - 20 hours in settling tank , leave to settle at least a week, run through a dry media tower ( Ecopure) but i still can't seem to get a clear pass on a 50/50 test.

I have tried the in processor water wash with acid but emulsion still forms so am looking to try the traditional methods of water washing. I have tried a mist spray ( not that fine as i would like it ) but this has also ended in an emulsion. How do i water wash correctly?

Many thanks

Rod

[dgs]

There are so many variables to water washing it is difficult to advise within 1 reply, but I will give you some do's and dont's based on personal experiance.

Do use the 5% prewash method (I don't actually use this as stated but use my variation of it)

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

What you are really trying to do using this method is create a rough 50/50 mix of glycerol/water in the mix. Because my S2 is really small (0.5mls d/o after S1) I make a guess at the amount of glycerol in the mix after S2 which is usually 3 litres, so I simply add 3 litres of water before mixing. Then, don't just let the glycerol/water layer drop, you need to gently bubble overnight, the action of the bubbles releases the glyc/soap/water from the bio. Doing this and then leaving a few hours to settle will leave your soap level very low, like 300ppm.

No need to piddle around with little bubbles or misting, if the soap is low eg <400ppm after the pre-wash you won't/can't make an emulsion.

You must wash in an agressive way either with your pump or use a compressor to really churn up the water/bio

Wash as many times as you need until you get clear wash water, then your shake up test will be perfect.

Try not to use acid, it produces ffa's from the soap and encourages the monoglycerides to stay in the biodiesel. ( mono's are always present, they form a small emulsified layer between the bio and water, it's best to remove this layer)

[Islebio]

Hi,

Many thanks for that. Will try this. Keeping glyc in after stage 2, adding equal amount of water then bubbling over night. My bubbling?settling tank is quite aggressive, with a big pump should i be using a smaller one that makes small bubbles like a fish tank pump?Is there a set up you would recommend? I take it the soap, water and glyc drop out in the settling process after the bubbling?. I am planning doing the second wash in the processor.

Once you have waterwashed and tested does you bio look clear or is it always going to be slightly hazy?

Thanks for your reply

Rod

[Islebio]

Hi,

Also am i able to recover my methanol through demeth, then start the water prewash?

Thanks

[Islebio]

Hi,

And your post says you keep the stage 2 glyc in, but the wiki page says i should re-introduce the glyc i took off in Stage 1?

many thanks

Rod

[RichardP]

I've never done meth recovery, but can't see an issue with recovering the meth then starting the wash process.

Re the glyc, just leave the stage 2 glyc in, I've never seen the point in putting any stage 1 glyc back in and never found the need to.

No need to piddle around with little bubbles or misting, if the soap is low eg <400ppm after the pre-wash you won't/can't make an emulsion.
You must wash in an agressive way either with your pump or use a compressor to really churn up the water/bio

I wouldn't agree with this statement, I know it's from personal experience and this is how you do it Dave, but there's more ways to skin a cat.

Unless you do a soap test after the prewash, you're not going to know the soap ppm. Not everyone has the kit to do the tests, or want to for that matter.
You do not have to wash in an aggressive way, it's one way, but not the only way. I did all the aggressive pump washing thing some years ago,  it was a lot more hands on time than gently bubbling, which gives as clean a bio as pump washing does. Indeed, I found that gently bubble washed bio is a lot quicker/easier to dry than pump washed (unless I gave the pump washed bio a 2hour gentle bubble the settle at the end).

[dgs]

I've never done meth recovery, but can't see an issue with recovering the meth then starting the wash process.

Re the glyc, just leave the stage 2 glyc in, I've never seen the point in putting any stage 1 glyc back in and never found the need to.

No need to piddle around with little bubbles or misting, if the soap is low eg <400ppm after the pre-wash you won't/can't make an emulsion.
You must wash in an agressive way either with your pump or use a compressor to really churn up the water/bio

I wouldn't agree with this statement, I know it's from personal experience and this is how you do it Dave, but there's more ways to skin a cat.

Unless you do a soap test after the prewash, you're not going to know the soap ppm. Not everyone has the kit to do the tests, or want to for that matter.
You do not have to wash in an aggressive way, it's one way, but not the only way. I did all the aggressive pump washing thing some years ago,  it was a lot more hands on time than gently bubbling, which gives as clean a bio as pump washing does. Indeed, I found that gently bubble washed bio is a lot quicker/easier to dry than pump washed (unless I gave the pump washed bio a 2hour gentle bubble the settle at the end).

You only need to do a soap test every now and again if you adopt the same proceedure with every batch, but using this method the soap is approx 50% of that if just de-mething.

If the water level after w/washing agressively is much above the saturation point (@1000ppm) then just leaving it to settle for a while will see the excess water sink to the bottom.

Richard, the reason I like the agressive wash is that I've seen some w/washed bio, done in a meek and mild way that still has small amounts of glyc dropping when dried. Have you ever pump washed a bubbled batch to see if the wash water is still clear.

Rod, yes de-mething then washing should be OK. My bio is clear and bright and is <300ppm water (although I don't check every batch) I also magnesol treat it then leave it to bleach in the sun, it looks like kerosene.

[RichardP]

Dave, yes I have done a pump wash after a bubble wash some years ago when I was seeing what method was best, with the least hands on time. Nigel did some soap tests for me and the soap level did reduce, but only from about 18ppmto about 12ppm as I remember.
As for glyc still dropping out after bubble washing, I've never seen anything drop out in my bio, and I don't aggressively bubble, it's about a 5lpm air pump.

The point I was making here was that there is more than one method of water washing that will give very low soap levels, I think the last test I did came out around 6ppm. I found with pump washing I was spending more hands on time with the washing, and settling out the water was taking a long time. With bubbling I can put the air pump on a timer and come back to it hours later and drop the settled water, 10 minutes later the next wash is on the go, and off I go.

[dgs]

Thanks Richard, I certainly agree that pump/compressor washing requires more hands on time than bubbling.

[Islebio]

Hi,

Thanks very much for the replies. I have tried the 5% prewash, with glyc and water, but still seem to be getting an emulsion. I am bubbling to see what happens, does anyone have any guidance as to the correct bubbling equipment/technique. I currently use quite a powerful air pump with a home made ring that i lower down into the bottom of the drum that i made out of copper pipe. Do folk use some kind of bubble stone or something?.

Forever onwards.

Rod

[dgs]

Rod, you shouldn't get an emulsion if the ratio's of glyc and water are about 50/50, this ratio will absorb most of the soap leaving the bio at a soap level where you can wash how you want without creating an emulsion.

I use an air distributor which is sort of like a copper tube with holes with a 600 lph pump.

Is your emulsion forming after the 5% prewash when you are water washing and is the whole volume emulsified or is the emulsion a layer between the water and the wet bio. If the latter then it is due to the monoglycerides left in the bio that are emulsifying with water.

[neisel]

I water wash & do a pre-wash with the 2nd stage glyc still in, though sometimes if I get a very good conversion on the 1st stage there is only a litre or two of glyc.

I've found the amount of water I add makes no difference - 5%, 7%, 10% or what have you -  to whether an emulsion develops, the only thing that affects that is the speed with which I introduce the water. Slow is good, too fast & I'll get an emulsion.

After the pre-wash & the first proper, slowly administered water wash I just chuck 18 - 20 litres of water into the top of the machine & never get an emulsion.