Washing

[Michael David Junior Member Find all posts View Profile Close Michael David]

I have made several 1liter batches Dr Pepper style & have found it takes a large number of washes to clean (8-10) does it take this many washes when people do large quantities? or am I missing something?
I took one of my 1Liter test batches & tested it by adding 1ml of biodiesel to 27mls of methanol & mixed. After what seemed a couple of minutes I was left with what appeared to be a liquid with a slight tinge (yellow) only very slight though & a minute amount of sediment on the bottom. Is this ok to use?
My second test as above on a different batch gave the same colour but with no sediment. Obviously this is better.
When do I know I can pour it into my tank without the fear of damaging my vehicle?
Back to washing is it better to wash with cold warm or hot water?

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Washing

Hello Michael, some thoughts on washing

The World Famous Dr Pepper Wasn Technique (Pat Pend) is not indicative of what normally occures with larger batches.

Tests have shown that if you perform the 5% water/Glycerine wash at the end of the reaction 64% of the soap is removed compared to not doing the 5% water /Glycerine wash.
Experience shows that the longer you allow the glycerine to settle out before commencing the wash, the less washing that is required in every situation.

I considered the wash finished when the biodiesel showed definate signs of darkening within 1- 2 hours of turning the wash off.
If it did not noticably darken or there were light and dark streaks in the top of the biodiesel this required another wash.

I found that if I did the 5% water/Glycerine wash and allowed it to settle over night, it required 3 mist washes of about 40 litres water per wash sprayed over 140 litres Biodiesel to reach this point.

I did not worry about clearness or pH of the wash water.

Tilly

[Aussie1 Biofuels Forum Newbie Find all posts View Profile Close Aussie1]

Re: Washing

Michael, I am in a similar position as you (see post "Is PH of 8.00 ok?"). I have only made the one batch though using new canola oil with six washes. I did the "Jan Warnqvist's Conversion Test" this morning with the assistance of our head chemist. I used 3mls of BD to 27mls of methanol and my test came out cloudy. The chemist played around with things (re washing etc) and came to the conclusion that owing to an amount of soap in the results that I did not do a full conversion or had not fully washed the BD. He also checked the Ph of the wash water (after washing) to determine if I had used too much caustic soda, the Ph was 7.88 which apparently is ok. He also agreed with Tilly by saying that testing the Ph of BD itself is a waste of time. I told him that some members do not wash there BD and he said that the soap from the caustic soda would probably be very slightly abrasive HOWEVER the amount of abrasion would be so minute you would probably not notice the effect over the life of the motor. In reality I guess you would need to drive two similar vehicles in the same environment, one use BD and the other PD over a few thousand kilometers to get a result.
My next test batch I'll will be using WVO. Aussie1.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Washing

Hello Aussie1

With all due respect to your chemist, I do not think he/she is fully aware of what is going on in the reaction.

Checking the pH of your wash water will tell you nothing about whether you used too much NaOH or not.
The amount of soap left in the biodiesel is not an indication of how far the reaction has gone.

There is a side reaction going on during the main reaction that consumes NaOH by converting biodiesel and Veggie oil into soap.
Tests have shown that for all practical purposes, by the time you do the wash there will be no NaOH left in the Biodiesel.
This is why the reaction stops if you do not have enough extra NaOH present even though you have not achieved high conversion. The NaoH that is catalysing the biodiesel reaction is all consumed in this side reaction making soap.
If this side reaction were not consuming NaOH, you would eventually achieve high conversion even if you used less NaOH. This is not what happens, the reaction stops after about an hour at 50deg C no matter what the conversion is.

Tests have shown that in order to obtain ASTM conversion you need to include extra NaOH in the reaction and by so doing you end up making more soap than if you only make a lower conversion biodiesel.
This results in MORE soap and LESS yield in a high conversion batch of biodiesel.

The very small amount of NaOH that might make it's way into the washer will, for all practical purposes, be removed in the first wash because of NaOH's much stronger attraction to water than biodiesel.
pH testing will tell you NOTHING about conversion.
To check for conversion requires GC testing, or in a pinch viscosity testing if done properly is very informative. The Warnqvest Conversion Test and the World Famous Dr Pepper ASTM Reprocess Technique (Pat Pend) are good quick backyard indicators but that is all they are, they are only indicators.

This is for the single stage Base method.

If you do not put acid in the wash the pH of the wash water will be above 7 because of the soap in the biodiesel, not the NaOH. Every time you wash the biodiesel a bit more soap is removed and the pH drops.

Tilly

[Aussie1 Biofuels Forum Newbie Find all posts View Profile Close Aussie1]

Re: Washing

Hello Tilly,

Thanks for the informative reply. I'll pass it on to "him". He said to me that he was not familiar with the process however he did draw a diagram using chemical symbols that baffled me. He also said that he looks forward to using some in his diesel Landcriuser once I get under way. I only ran my (750ml) reaction at 55c for a few minutes; maybe that was a mistake?
Sorry for stealing your post Michael. Aussie1.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Washing

Hello Aussie1

The vast majority of the reaction occures fairly quickly, within a few seconds/minutes. During this time violent aggitation insures a good initial mixing and a good initial reaction.
If you do the reaction in a Dr Pepper bottle you will see the contents of the bottle first increase in viscosity and then suddenly decrease in viscosity.
Violent mixing is no longer required once the decrease in viscosity occures.
However, tests have shown that at 50deg C it takes about an hour for the reaction to go as far as it can go for the amount of chemicals used.
Once the glycerine starts to precipitate out, the NaOH and Methanol are more strongly attracted to the glycerine than they are to the oil in the reaction.
If you allow the glycerine to settle out, the chemicals are removed from the reaction zone and the reaction is cut short.
To achieve as full a reaction as possible it is necessary to keep the glycerine which contains the chemicals mixed into the oil.
This does not need to be violent mixing, and in fact tests have shown that mixing for a minute every 10- 15 minutes over the hour or continual gentle mixing is all that is required to achieve as high a conversion as possible with refrence to the amount of chemicals used.

Tilly

[Michael David Junior Member Find all posts View Profile Close Michael David]

Re: Washing

Hi guys, I have no problem with others coming in this for me is a learning experience & the more information I get the better - so thanks.
Tilly, thanks for you response - more questions.
1. Will 5% wash at the end of the reaction work on the Dr Pepper 1 liter batches.
2. Which is best for Pre wash hot or cold water?
3. On the rest of the washes which is best hot or cold?
4. From your experience what is the optimum amount of time to let the biodiesel settle before starting your washing?
5. I'm now planning to mix in a 250 Litre hot water system & drain the Glycerine from the bottom of the tank then proceed with the washing & again drain from the bottom of the tank. When washing finished reheat the biodiesel to boil off some of the water then pump into a 44 gal drum & let sit for a couple of weeks to settle. Do you see any problems with this?
Thanks again Guys Regards Michael

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Washing

Hello Michael

1. yes, the 5% water/Glycerine wash at the end of the reaction works fine with the Dr Pepper method.

2. I doubt that temp is terriably important for the pre-wash. If in doubt use a bit more water. This procedure originally was performed with 15% water, but Neutral did some tests that showed after 5% there was no further benefit.
The original reason for performing this procedure was because it improves yield slightly, not because it makes washing quicker.

3. Hot water is probably better/quicker, but unless you have free heating, hot water also costs money. I have never actually performed any tests.

4. Settling overnight is fine. However, the longer it settles the less washing that is required.

5. I am not sure what re-heating after washing while in the reactor will accomplish.
If you are going to leave it settle for a couple of weeks I would do that before the wash, not after it.
After the biodiesel is washed there is virtually nothing in it except water. Once the biodiese is crystal clear at the lowest temperature it is likely to experience it is ready to use. This may be a day or 3 after the last wash.

Tilly

[Milhouse Junior Member Find all posts View Profile Close Milhouse]

Re: Washing

Whilst on the topic of washing, can any water be used for this? I have a ;arge rainwater tank that happens to right next to my BD "petrol station" and it would be easier to hook into this (and cheaper and better for the environment) than a normal tap. Is this ok? It only has a small particle filter (flyscreen) that stops big bits of gunk.

Thanks

Milhouse

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Washing

Hello Milhouse

It should be OK to wash with.
Soft water does have a greater tendency to form emulsions than hard water.

Tilly